Category Archives: Detoxification


Specific Chemical Compounds in Citrus Peels Demonstrates Potential Promise in Cancer Prevention

Citrus is a genus of flowering trees and shrubs in the rue family, Rutaceae. Citrus trees and shrubs produce citrus fruits, which include the five different common varieties:

  • Grapefruit
  • Lemon
  • Lime
  • Orange
  • Tangerine

Within each of these common varieties are a number of species. 

List of Citrus Fruits

Citrus peels are very rich in phenolic compounds, such as phenolic acids, flavonoids, limonoids, as wells as carotenoids.  The main source of polyphenols are contained in the citrus peels.  1    A specific class of flavones exist almost ubiquitously in citrus plants named polymethoxylated flavones (PMFs).  These main polymethoxylated flavones in citrus include:

  • nobiletin
  • tangeretin
  • sinesetin
  • 3,5,6,7,8,3′,4′-heptamethoxyflavone
  • 3,5,6,7,3′,4′-hexamethoxyflavone

Six PMFs and three major 5-demethoxyflavones can be extracted from a variety of citrus peels.  2  Accumulative in vitro and in vivo studies indicate protective effects of polymethoxyflavones (PMFs) against the occurrence of cancer. PMFs inhibit carcinogenesis by the following mechanisms:  3

  • blocking the metastasis cascade
  • inhibition of cancer cell mobility in circulatory systems
  • inducing apoptosis
  • antiangiogenesis

Citrus peels also have an abundant source of polyhydroxyl flavonoids (PHFs) which include:

  • hesperidin
  • neohesperidin
  • naringin

Less studied but equally important are the limonoid glucosides, a class of furan-containing triterpenes.  Up to 53 limonoids have been identified and characterized, yet the most important limonoids that are subject to anticancer research include:

  • limonin
  • nomilin
  • nomilinic acid

The anti-cancer activity of citrus peel flavonoids has been studied on several animal models.  The various cancers that have been studied with citrus peel flavonoids include, among others:  4

  • colon cancer
  • lung cancer
  • liver cancer
  • prostate cancer
  • skin cancer

Citrus peels, in addition to cancer prevention and intervention, exhibit other biological functions with various disease states:  5

  • antiatherogenic
  • antimicrobial
  • antithrombotic
  • cardioprotective
  • delayed onset of Alzheimer’s disease  6 
  • hypolipidemia  7 
  • inflammation inhibition  8 
  • neuroprotective  9
  • regulation of metabolic syndrome  10

The Tabs below lists the individual citrus fruit chemical compounds:

Individual Citrus Fruit Chemical Compounds

  • Lycopene
  • Beta-Carotene
  • Bergamottin
  • Bergapten
  • Bergaptol
  • Limonin
  • Nomilin
  • Nomilinic acid
Organic Acids:
  • Citric Acid
  • Glycyrrhetinic Acid
  • Naringin
  • Naringenin
  • Quercetin
  • Rutin
  • Kaempferol
  • Hesperidin
  • Eriocitrin
  • Nobiletin
  • Tangeritin
  • Diosmin
  • Citral
  • Beta-Carotene
  • Cryptoxanthin
  • Limonin
  • Nomilin
  • Nomilinic acid
Organic Acids:
  • Citric Acid
  • P-Coumaric Acid
  • Sinapic Acid
  • Diosmin
  • Eriocitrin
  • Didymin
  • Hesperidin
  • Rutin
  • Limonene
  • Citronellal
  • Citral
  • Limonin
  • Nomilin
  • Nomilinic acid
  • Eriocitrin
  • Hesperidin
  • Citral
  • Synephrine
  • Hordenine
  • Octopamine
  • N-Methyltyramine
  • Tyramine
  • Alpha-Carotene
  • Beta-Carotene
  • Zeaxanthin
  • Lutein
  • Cryptoxanthin
  • Limonin
  • Nomilin
  • Nomilinic acid
Organic Acids:
  • Citric Acid
  • Anthocyanidins
  • Cyanidin
  • Dephinidin
  • Tangeretin
  • Hesperidin
  • Limonene
  • Citral
* These Alkaloids and Amines are found primarily in the peel of Oranges.
  • Synephrine
  • Beta-Carotene
  • Lutein
  • Zeaxanthin
  • Limonin
  • Nomilin
  • Nomilinic acid
Organic Acids:
  • Citric Acid
  • Nobiletin
  • Tangeretin
  • Hesperidin
  • Limonene
  • Carvone

The Table below lists the 7 groups of chemical compounds found in each of the 5 varieties of citrus.

Chemical Compounds Found in Common Citrus Fruits

Chemical CompoundGrapefruitLemonLimeOrangeTangerine
Organic AcidsXXX

This Table specifically excludes the following chemicals found in citrus fruits: carbohydrates, minerals, vitamins, amino acids, enzymes.

The Table below lists the individual chemical compounds in each of the 5 varieties of citrus.

Individual Chemical Compounds in Common Citrus Fruits

Chemical CompoundsGrapefruitLemonLimeOrangeTangerineTotals
Nomilinic acidXXXXX5
Organic Acids:
Citric AcidXXXX4
Glycyrrhetinic AcidX1
P-Coumaric AcidX1
Sinapic AcidX1

The Tabs below lists the specific chemical compounds within each chemical group that show evidence of cancer prevention.

Specific Chemical Compounds in Citrus Fruit that May Show Promise for Cancer Prevention

  • Alpha-Carotene
  • Cryptoxanthin
  • Lutein
  • Lycopene
  • Zeaxanthin
  • Limonin
  • Nomilin
  • Nomilinic acid
  • P-Coumaric Acid
  • Anthocyanidins
  • Cyanidin
  • Didymin
  • Diosmin
  • Hesperidin
  • Kaempferol
  • Naringenin
  • Naringin
  • Nobiletin
  • Quercetin
  • Rutin
  • Tangeritin
  • Limonene

The Tabs below lists the published Abstracts and links to various studies within the 5 carotenoids.

Anticancer Properties of Citrus Peel Carotenoids


Bladder cancer
We examined the associations between plasma micronutrients and bladder cancer risk, and evaluated the combined effects of carotenoid and cigarette smoke. Our results show protective effects of carotenoids on bladder cancer. They suggest that bladder cancer may be a preventable disease through nutritional intervention, especially in smokers.1
Breast cancer
An inverse association was observed among premenopausal women was for high levels of vitamin A (OR: 0.82, 95%CI: 0.68–0.98, p for trend = 0.01), β-carotene (OR: 0.81, 95% CI 0.68–0.98, p for trend = 0.009), α-carotene (OR: 0.82, 95% CI: 0.68–0.98, p for trend = 0.07), and lutein/zeaxanthin (OR: 0.83, 95% CI 0.68 – 0.99, p for trend = 0.02). An inverse association was not observed among postmenopausal women. Among premenopausal women who reported ever smoking, these results were stronger than among never smokers, although tests for interaction were not statistically significant. Results from this study are comparable to previous prospective studies and suggest that a high consumption of carotenoids may reduce the risk of pre but not post menopausal breast cancer, particularly among smokers.2
Cervical cancer
The mean serum levels of total carotenoids, alpha-carotene, beta-carotene, cryptoxanthin, and lycopene were lower among cases than they were among controls. These findings are suggestive of a protective role for total carotenoids, alpha-carotene and beta-carotene in cervical carcinogenesis and possibly for cryptoxanthin and lycopene as well.3
Colon cancer
To investigate associations between plasma carotenoids, alpha-tocopherol and retinol with colorectal adenomas risk, we measured concentrations in 224 asymptomatic colorectal adenoma cases and 230 population-based controls matched for age and sex. Our findings suggest a protective effect of carotenoids against the development of colorectal adenomas.4
Laryngeal cancer
Significant inverse relations emerged between laryngeal cancer risk and intake of vitamin C (OR = 0.2, for the highest versus the lowest intake quintile; 95% CI: 0.2–0.4), β-carotene (OR = 0.2; 95% CI: 0.2–0.4), α-carotene (OR = 0.3; 95% CI: 0.2–0.5)5
Liver cancer
Potent preventive action of alpha-carotene against carcinogenesis: spontaneous liver carcinogenesis and promoting stage of lung and skin carcinogenesis in mice are suppressed more effectively by alpha-carotene than by beta-carotene6
Lung cancer
After adjusting for smoking and other covariates, no association was found with lung cancer risk for dietary lycopene or beta-cryptoxanthin intake, whereas dose-dependent inverse associations of comparable magnitude were found for dietary beta-carotene, alpha-carotene, and lutein.7
Analysis by flow cytometry indicated that when GOTO cells were exposed to alpha-carotene, they were arrested in the G0-G1 phase of their cell cycle. However, as the level of the N-myc messenger RNA was recovering, these cells resumed normal cycling. These results indicate that the reduction in the level of the N-myc messenger RNA caused by alpha-carotene is closely linked with G0-G1 arrest.8
Prostate cancer
The adjusted odds ratio for the highest quartiles compared with the lowest were 0.18 (95% CI: 0.08-0.41) for lycopene, 0.43 (95% CI: 0.21-0.85) for α-carotene, 0.34 (95% CI: 0.17-0.69) for β-carotene, 0.15 (95% CI: 0.06-0.34) for α-cryptoxanthin and 0.02 (95% CI: 0.01-0.10) for lutein and zeaxanthin. The dose response relationships were also significant, suggesting that intake of lycopene and other carotenoid rich vegetables and fruits may associate with a reduced risk of prostate cancer.9
Skin cancer
Alpha-carotene was found to have a stronger effect than beta-carotene in suppressing the promoting activity of 12-O-tetradecanoylphorbol-13-acetate on skin carcinogenesis in 7,12-dimethylbenz[a]anthracene-initiated mice.10


Breast cancer
Results of this study suggest that the carotenoids beta-cryptoxanthin, lycopene, and lutein/zeaxanthin may protect against breast cancer.1
Cervical cancer
Cryptoxanthin was significantly associated with a lower risk of cervical cancer when examined as a continuous variable. Retinol, lutein, alpha- and gamma-tocopherol, and selenium were not related to cervical cancer risk. Smoking was also strongly associated with cervical cancer. These findings are suggestive of a protective role for total carotenoids, alpha-carotene and beta-carotene in cervical carcinogenesis and possibly for cryptoxanthin and lycopene as well.2
Lung cancer
β-Cryptoxanthin suppresses the growth of immortalized human bronchial epithelial cells and non-small-cell lung cancer cells and up-regulates retinoic acid receptor β expression3
The associations observed in our study suggest that the influence of some antioxidants on survival following a diagnosis of malignant glioma are inconsistent and vary by histology group. Further research in a large sample of glioma patients is needed to confirm/refute our results.4
Prostate cancer
The prostate cancer risk declined with increasing consumption of lycopene, alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein and zeaxanthin. Intake of tomatoes, pumpkin, spinach, watermelon and citrus fruits were also inversely associated with the prostate cancer risk. The adjusted odds ratios for the highest versus the lowest quartiles of intake were 0.18 (95% CI: 0.08-0.41) for lycopene, 0.43 (95% CI: 0.21-0.85) for alpha-carotene, 0.34 (95% CI: 0.17-0.69) for beta-carotene, 0.15 (95% CI: 0.06-0.34) for beta-cryptoxanthin and 0.02 (95% CI: 0.01-0.10) for lutein and zeaxanthin. 5


Bladder cancer
Our results show protective effects of carotenoids on bladder cancer. They suggest that bladder cancer may be a preventable disease through nutritional intervention, especially in smokers.1
Breast cancer
An inverse association was observed among premenopausal women was for high levels of vitamin A (OR: 0.82, 95%CI: 0.68–0.98, p for trend = 0.01), β-carotene (OR: 0.81, 95% CI 0.68–0.98, p for trend = 0.009), α-carotene (OR: 0.82, 95% CI: 0.68–0.98, p for trend = 0.07), and lutein/zeaxanthin (OR: 0.83, 95% CI 0.68 – 0.99, p for trend = 0.02).2
Colon cancer
Lutein was inversely associated with colon cancer in both men and women [odds ratio (OR) for upper quintile of intake relative to lowest quintile of intake: 0.83; 95% CI: 0.66, 1.04; P = 0.04 for linear trend]. The greatest inverse association was observed among subjects in whom colon cancer was diagnosed when they were young (OR: 0.66; 95% CI: 0.48, 0.92; P = 0.02 for linear trend) and among those with tumors located in the proximal segment of the colon (OR: 0.65; 95% CI: 0.51, 0.91; P 3
Liver cancer
Lutein presented inhibitory actions during promotion but not initiation of hepatocarcinogenesis, being classified as a suppressing agent. This reinforces lutein as a potential agent for liver cancer chemoprevention.4
Lung cancer
Protective effects on lung cancer incidence were found for lutein + zeaxanthin, beta-cryptoxanthin, folate, and vitamin C. Other carotenoids (alpha-carotene, beta-carotene, and lycopene) and vitamin E did not show significant associations.5
(Non-Hodgkin’s) Lymphomas
Higher intakes of vegetables, lutein and zeaxanthin, and zinc are associated with a lower non-Hodgkin lymphoma (NHL) risk.6
Ovarian cancer
Micronutrients, specifically ss-carotene, lycopene, zeaxanthin, lutein, retinol, alpha-tocopherol, and gamma-tocopherol, may play a role in reducing the risk of ovarian cancer.7
Prostate cancer
Results demonstrated that both lycopene, in an alpha -cyclodextrin water soluble carrier, and lutein inhibited malignant AT3 cells in a concentration and time-dependent manner. 8
Skin cancer
The results of the photocarcinogenesis experiment were increased tumor-free survival time, reduced tumor multiplicity and total tumor volume in lutein/zeaxanthin-treated mice in comparison with control irradiated animals fed the standard diet. These data demonstrate that dietary lutein/zeaxanthin supplementation protects the skin against UVB-induced photoaging and photocarcinogenesis.9


Breast cancer
The inhibition of cell growth by lycopene was accompanied by slow down of cell-cycle progression from G1 to S phase. Moreover, the carotenoids inhibited estrogen-induced transactivation of ERE that was mediated by both estrogen receptors (ERs) ERalpha and ERbeta. The possibility that this inhibition results from competition of carotenoid-activated transcription systems on a limited pool of shared coactivators with the ERE transcription system was tested.1
Cervical cancer
 Increasing concentrations of serum lycopene were negatively associated with CIN1, CIN3 and cancer, with odds ratios (OR) (95% CI) for the highest compared to the lowest tertile of 0.53 (0.27-1.00, p for trend = 0.05), 0.48 (0.22-1.04, p for trend = 0.05) and 0.18 (0.06-0.52, p for trend = 0.002), respectively, after adjusting for confounding variables and HPV status.2
Colon cancer
Lycopene treatment suppressed Akt activation and non-phosphorylated beta-catenin protein level in human colon cancer cells. Immunocytochemical results indicated that lycopene increased the phosphorylated form of beta-catenin proteins. These effects were also associated with reduced promoter activity and protein expression of cyclin D1. Furthermore, lycopene significantly increased nuclear cyclin-dependent kinase inhibitor p27(kip)abundance and inhibited phosphorylation of the retinoblastoma tumor suppressor protein in human colon cancer cells.3
Endometrial cancer
In contrast to cancer cells, human fibroblasts were less sensitive to lycopene, and the cells gradually escaped growth inhibition over time. In addition to its inhibitory effect on basal endometrial cancer cell proliferation, lycopene also suppressed insulin-like growth factor-I-stimulated growth. Insulin-like growth factors are major autocrine/paracrine regulators of mammary and endometrial cancer cell growth. Therefore, lycopene interference in this major autocrine/paracrine system may open new avenues for research on the role of lycopene in the regulation of endometrial cancer and other tumors.4
Esophageal cancer
This review of previous epidemiological studies found that high blood lycopene levels are associated with a reduced risk of esophageal cancer.5
Addition of nutrition supplements such as lycopene may have potential therapeutic benefit in the adjuvant management of high-grade gliomas.6
Liver cancer
The invasion of SK-Hep1 cells treated with lycopene was significantly reduced to 28.3% and 61.9% of the control levels at 5 microM and 10 microM lycopene, respectively (P 7
The combination of low concentrations of lycopene with 1,25-dihydroxyvitamin D3 exhibited a synergistic effect on cell proliferation and differentiation and an additive effect on cell cycle progression. Such synergistic antiproliferative and differentiating effects of lycopene and other compounds found in the diet and in plasma may suggest the inclusion of the carotenoid in the diet as a cancer-preventive measure.8
Lung cancer
In conclusion, lycopene may mediate its protective effects against smoke-induced lung carcinogenesis in ferrets through up-regulating IGFBP-3 and down-regulating phosphorylation of BAD, which promote apoptosis and inhibit cell proliferation.9
Mouth cancer
The results of the present study further support the hypothesis that carotenoids in general, and lycopene in particular, may be effective anticarcinogenic agents in oral carcinogenesis.10
Ovarian cancer
Micronutrients, specifically ss-carotene, lycopene, zeaxanthin, lutein, retinol, alpha-tocopherol, and gamma-tocopherol, may play a role in reducing the risk of ovarian cancer.11
Pancreatic cancer
After adjustment for age, province, BMI, smoking, educational attainment, dietary folate, and total energy intake, lycopene, provided mainly by tomatoes, was associated with a 31% reduction in pancreatic cancer risk among men [odds ratio (OR) = 0.69; 95% CI: 0.46-0.96; P = 0.026 for trend] when comparing the highest and lowest quartiles of intake. Both beta-carotene (OR = 0.57; 95% CI: 0.32-0.99; P = 0.016 for trend) and total carotenoids (OR = 0.58; 95% CI: 0.34-1.00; P = 0.02 for trend) were associated with a significantly reduced risk among those who never smoked. The results of this study suggest that a diet rich in tomatoes and tomato-based products with high lycopene content may help reduce pancreatic cancer risk.12
Prostate cancer
We report the inhibitory effect(s) of lycopene in primary prostate epithelial cell (PEC) cultures, and the results of a pilot phase II clinical study investigating whole-tomato lycopene supplementation on the behavior of established CaP, demonstrating a significant and maintained effect on prostate-specific antigen velocity over 1 year.13


Breast cancer
Carotenoids could inhibit the proliferation of human beast cancer MCF-7 cell line in vitro and the action of carotenoids may be worked through different pathways.1
Lung cancer
Inverse associations with carotenes, lutein + zeaxanthin, and beta-cryptoxanthin seemed to be limited to small cell and squamous cell carcinomas. Only folate and vitamin C intake appeared to be inversely related to small cell and squamous cell carcinomas and adenocarcinomas. Folate, vitamin C, and beta-cryptoxanthin might be better protective agents against lung cancer in smokers than alpha-carotene, beta-carotene, lutein + zeaxanthin, and lycopene.2
Zeaxanthin strongly induced apoptosis in neuroblastoma cells. Consistent with this finding, zeaxanthin did not inhibit LOX activity. Zeaxanthin is a remarkable dietary factor that is able to induce apoptosis in neuroblastoma cells while being able to prevent apoptosis in healthy cells.3

The Tabs below lists the published Abstracts and links to various studies within the 3 limonoids.

Anticancer Properties of Citrus Peel Limonoids


Colon Cancer
The current study was an attempt to elucidate the mechanism of human colon cancer cell proliferation inhibition by limonin and limonin glucoside (LG) isolated from seeds of Citrus reticulata. Results of the current study provide compelling evidence on the induction of mitochondria mediated intrinsic apoptosis by both limonin and LG in cultured SW480 cells for the first time.1


Inhibits tumor-specific angiogenesis
These data clearly demonstrate the antiangiogenic potential of nomilin by downregulating the activation of MMPs, production of VEGF, NO and proinflammatory cytokines as well as upregulating IL-2 and TIMP.1
Inhibits chemical-induced carcinogenesis
Limonin and nomilin, two of the most abundant limonoids, have been found to inhibit chemical-induced carcinogenesis. Both compounds are inducers of glutathione S-transferase, a major detoxifying enzyme system. The increased enzyme activity was correlated with the ability of these compounds to inhibit carcinogenesis.2
Nomilin is a triterpenoid present in common edible citrus fruits with putative anticancer properties. In this study, the authors investigated the antimetastatic potential of nomilin and its possible mechanism of action. Metastasis was induced in C57BL/6 mice through the lateral tail vein using highly metastatic B16F-10 melanoma cells. Administration of nomilin inhibited tumor nodule formation in the lungs (68%) and markedly increased the survival rate of the metastatic tumor-bearing animals. 3

Nomilinic acid

Induces apoptosis
No significant effects were observed on growth of the other cancer cell lines treated with the four individual limonoids at 100 micrograms/ml. At 100 micrograms/ml, the limonoid glucoside mixture demonstrated a partial inhibitory effect on SKOV-3 cancer cells. With use of flow cytometry, it was found that all the limonoid samples could induce apoptosis in MCF-7 cells at relatively high concentrations (100 micrograms/ml). 1
Breast cancer
Although most of the limonoids showed anti-aromatase activity, the inhibition of proliferation was not related to the anti-aromatase activity. On the other hand, the anti-proliferative activity was significantly correlated with caspase-7 activation by limonoids. Our findings indicated that the citrus limonoids may have potential for the prevention of estrogen-responsive breast cancer (MCF-7) via caspase-7 dependent pathways.2
We conclude that citrus limonoid glucosides are toxic to SH-SY5Y cancer cells. Cytotoxicity is exerted through apoptosis by an as yet unknown mechanism of induction. Individual limonoid glucosides differ in efficacy as anticancer agents, and this difference may reside in structural variations in the A ring of the limonoid molecule.3

The Table below lists the published Abstract and links to the studies on P-Coumaric acid.

P-Coumaric Acid

Colon cancer
We demonstrate that two hydroxycinnamic acids, (E )-ferulic acid and (E )-p-coumaric acid, have the ability to protect against oxidative stress and genotoxicity in cultured mammalian cells. They also show the ability to reduce the activity of the xenobiotic metabolising enzyme, cytochrome P450 1A, and downregulate the expression of the cyclooxygenase-2 enzyme. At equitoxic doses, their activities are equal to or superior to that of the known anticarcinogen, curcumin. The hydroxycinnamic acids are both important components of plant cell walls in certain plant foods. It is known that the action of microbial hydroxycinnamoyl esterases can lead to the release of hydroxycinnamic acids from ester-linkages to cell wall polysaccharides into the human colon. 1
Results depicted that p-Coumaric acid inhibited the growth of colon cancer cells by inducing apoptosis through ROS-mitochondrial pathway.2

The Table below lists the published Abstracts and links to the various studies on Limonene.


Breast Cancer
The blocking chemopreventive effects of limonene and other monoterpenes during the initiation phase of mammary carcinogenesis are due to the induction of Phase II carcinogen-metabolizing enzymes, resulting in carcinogen detoxification. The post-initiation phase chemopreventive and chemotherapeutic activities of monoterpenes may be due to the induction of tumor cell apoptosis, tumor redifferentiation, and/or inhibition of the post-translational isoprenylation of cell growth-regulating proteins.1
Colon Cancer
Diet-cancer and diet-cardiovascular disease interrelationships may be explained by the mevalonate-suppressive action of isoprenoid end products of plant secondary metabolism. Assorted monoterpenes, sesquiterpenes, carotenoids and tocotrienols posttranscriptionally down regulate 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, a key activity in the sterologenic pathway. 2
The results showed that D-limonene (D-L) inhibited HL-60 and K562 cell growth in a dose- and time-dependent manner with the IC50 of 0.75 mmol/L similarly, D-L induced apoptosis of HL-60 and K562 cells, and expression of bcl-2 gene was down regulated by D-L in a concentration-dependent manner in HL-60 cells.3
Liver Cancer
Monoterpenes are nonnutritive dietary components found in the essential oils of citrus fruits and other plants. A number of these dietary monoterpenes have antitumor activity. For example, d-limonene, which comprises >90% of orange peel oil, has chemopreventive activity against rodent mammary, skin, liver, lung and forestomach cancers. 4
Lung Cancer
D-limonene given p.o. 1 h prior to NNK administered i.p. again showed pronounced inhibition of pulmonary adenoma formation. This study provides additional data demonstrating that non-nutrient constituents of the diet can inhibit carcinogen-induced neoplasia when administered at a short time interval prior to carcinogen challenge.5
Results showed that limonene exhibited antiproliferative action on tumoral lymphocytes exerting a decrease in cell viability that was related to apoptosis induction and to the increase in NO levels at long incubation times. At short times and depending on its concentration, limonene arrested cells in different phases of the cell cycle, related to NO production.6
Skin Cancer
Monoterpenes are nonnutritive dietary components found in the essential oils of citrus fruits and other plants. A number of these dietary monoterpenes have antitumor activity. For example, d-limonene, which comprises >90% of orange peel oil, has chemopreventive activity against rodent mammary, skin, liver, lung and forestomach cancers.7
Squamous Cell Carcinoma
This is the first study to explore the relationship between citrus peel consumption and human cancers. Our results show that peel consumption, the major source of dietary d-limonene, is not uncommon and may have a potential protective effect in relation to skin squamous cell carcinoma (SCC). 8
Stomach Cancer
D-limonene has antiangiogenic and proapoptotic effects on gastric cancer, thereby inhibits tumor growth and metastasis. Combination of d-limonene with cytotoxic agents may be more effective.9

The Table below lists the published Abstract and link to the studies on Limonin.


Colon Cancer
The current study was an attempt to elucidate the mechanism of human colon cancer cell proliferation inhibition by limonin and limonin glucoside (LG) isolated from seeds of Citrus reticulata. Results of the current study provide compelling evidence on the induction of mitochondria mediated intrinsic apoptosis by both limonin and LG in cultured SW480 cells for the first time.1

The Tabs below lists the published Abstracts and links to various studies within the 6 polyphenols of citrus peels.  (Part 1 of 2)

Anticancer Properties of Citrus Peel Polyphenols (Part 1 of 2)


Breast cancer
At 200 μg/mL, cyanidin, delphinidin and petunidin inhibited the breast cancer cell growth by 47, 66 and 53%, respectively. This is the first report of tumor cell proliferation inhibitory activity by anthocyanidins.1
Non-Hodgkin lymphoma
Higher intakes of flavonols, epicatechins, anthocyanidins, and proanthocyanidins were each significantly associated with decreased NHL risk. Similar patterns of risk were observed for the major NHL subtypes--diffuse large B-cell lymphoma (n = 167) and follicular lymphoma (n = 146). A higher intake of flavonoids, dietary components with several putative anticarcinogenic activities, may be associated with lower NHL risk.2


Colon cancer
Anthocyanins and cyanidin also reduced cell growth of human colon cancer cell lines HT 29 and HCT 116. The IC(50) of anthocyanins and cyanidin was 780 and 63 microM for HT 29 cells, respectively and 285 and 85 microM for HCT 116 cells, respectively. These results suggest that tart cherry anthocyanins and cyanidin may reduce the risk of colon cancer.1
These results indicate that cyanidin-3-rutinoside has the potential to be used in leukemia therapy with the advantages of being widely available and selective against tumors.2


Lung cancer
Importantly, a novel chemotherapeutic agent for the treatment of non-small-cell lung cancer, and is supported by animal studies which have shown didymin delay the tumor growth in nude mice. Our study reports here for the first time that the activity of the Fas/Fas ligand apoptotic system may participate in the antiproliferative activity of didymin in A549 and H460 cells.1


Bladder cancer
The chemopreventive effects of 2 flavonoids (diosmin and hesperidin) on N-butyl-N-(4-hydroxybutyl)nitrosamine (OH-BBN)-induced urinary-bladder carcinogenesis were examined in male ICR mice.  Feeding of the test compounds, singly or in combination, during both phases caused a significant reduction in the frequency of bladder carcinoma and preneoplasia. Dietary administration of these compounds significantly decreased the AgNOR count and the BUdR-labeling index of various bladder lesions. These findings suggest that the flavonoids diosmin and hesperidin, individually and in combination, are effective in inhibiting chemical carcinogenesis of the bladder, and that such inhibition might be partly related to suppression of cell proliferation.1
Colon cancer
These results indicate that diosmin and hesperidin, both alone and in combination, act as a chemopreventive agent against colon carcinogenesis, and such effects may be partly due to suppression of cell proliferation in the colonic crypts, although precise mechanisms should be clarified.2
Esophageal cancer
These findings suggest that diosmin and hesperidin supplementation, individually or in combination, is effective in inhibiting the development of oesophageal cancer induced by MNAN when given during the initiation phase, and such inhibition might be related to suppression of increased cell proliferation caused by MNAN in the oesophageal mucosa.3
Mouth cancer
Diosmin, the 7-rutinoside of diosmetin, surprisingly, was more potent and effective than diosmetin. In contrast, quercitrin, the 3-rhamnoside of quercetin, showed no effect and only minimal cellular uptake and no hydrolysis. In summary, dietary flavonoid glycosides may exert cellular effects in the oral cavity, but this varies greatly with the nature of the glycoside.4


Bladder cancer
Dietary administration of these compounds significantly decreased the AgNOR count and the BUdR-labeling index of various bladder lesions. These findings suggest that the flavonoids diosmin and hesperidin, individually and in combination, are effective in inhibiting chemical carcinogenesis of the bladder, and that such inhibition might be partly related to suppression of cell proliferation.1
Breast cancer
Two citrus flavonoids, hesperetin and naringenin, are found in orange and grapefruit, respectively. An experimental study has shown that citrus flavonoids are effective inhibitors of human breast cancer cell proliferation in vitro, especially when paired with quercetin, widely distributed in other foods2
Cervical cancer
This study shows that hesperetin exhibits a potential anticancer activity against human cervical cancer cell lines in vitro through the reduction in cell viability and the induction of apoptosis. Altogether, these data sustain our contention that hesperetin has anticancer properties and merits further investigation as a potential therapeutic agent.3
Colon cancer
Inhibition of Colonic Aberrant Crypt Formation by the Dietary Flavonoids (+)-Catechin and Hesperidin4
Esophageal cancer
These findings suggest that diosmin and hesperidin supplementation, individually or in combination, is effective in inhibiting the development of oesophageal cancer induced by MNAN when given during the initiation phase, and such inhibition might be related to suppression of increased cell proliferation caused by MNAN in the oesophageal mucosa.5
The apoptotic activity of CME was significantly attenuated by Akt augmentation. In conclusion, this study suggested that Citrus aurantium L. (CMEs) should induce caspase-dependent apoptosis at least in part through Akt inhibition, providing evidence that CMEs have anticancer activity on human leukemia cells.6
Lung cancer
Hesperidin (25 mg/kg body weight) supplementation effectively counteracted all the above changes and restored cellular normalcy, indicating its protective role during B(a)P-induced lung cancer.7
Mouth cancer
These findings suggest that supplementation with the flavonoids diosmin and hesperidin, individually and in combination, is effective in inhibiting the development of oral neoplasms induced by 4-NQO, and such inhibition might be related to suppression of increased cell proliferation caused by 4-NQO in the oral mucosa.8
Prostate cancer
t is concluded that hesperidin can inhibit the proliferation of breast cancer cells through mechanisms other than antimitosis and it is suggested that hesperidin be further investigated for the possible interaction with androgenic receptors and involvement in signaling pathway after receptor binding in prostate cancer cells through future research.9


Breast cancer
This paper also presents in vivo data of primary breast cancer prevention by individual compounds and whole berries. Finally, a possible role for berries and berry compounds in the prevention of breast cancer and a perspective on the areas that require further research are presented. 1
Glioblastoma Multiforme
Importantly, kaempferol potentiated the toxic effect of chemotherapeutic agent doxorubicin by amplifying ROS toxicity and decreasing the efflux of doxorubicin. Because the toxic effect of both kaempferol and doxorubicin was amplified when used in combination, this study raises the possibility of combinatorial therapy whose basis constitutes enhancing redox perturbation as a strategy to kill glioma cells.2
Some simple and polyphenols found in honey, namely, caffeic acid (CA), caffeic acid phenyl esters (CAPE), Chrysin (CR), Galangin (GA), Quercetin (QU), Kaempferol (KP), Acacetin (AC), Pinocembrin (PC), Pinobanksin (PB), and Apigenin (AP), have evolved as promising pharmacological agents in treatment of cancer. In this review, we reviewed the antiproliferative and molecular mechanisms of honey and above-mentioned polyphenols in various cancer cell lines.3
Lung cancer
Certain flavonoid compounds, including epicatechin, catechin, quercetin, and kaempferol, were associated inversely with lung cancer among tobacco smokers, but not among nonsmokers. Further studies of these associations may be warranted.4
Ovarian cancer
Recent studies further indicate that apigenin, genistein, kaempferol, luteolin, and quercetin potently inhibit VEGF production and suppress ovarian cancer cell metastasis in vitro. Lastly, oridonin and wogonin were suggested to suppress ovarian CSCs as is reflected by down-regulation of the surface marker EpCAM. Unlike NSAIDS (non-steroid anti-inflammatory drugs), well documented clinical data for phyto-active compounds are lacking. In order to evaluate objectively the potential benefit of these compounds in the treatment of ovarian cancer, strategically designed, large scale studies are warranted.5
Pancreatic cancer
Total flavonols, quercetin, kaempferol, and myricetin were all associated with a significant inverse trend among current smokers (relative risks for the highest vs. lowest quartile = 0.41, 0.55, 0.27, 0.55, respectively) but not never or former smokers. This study provides evidence for a preventive effect of flavonols on pancreatic cancer, particularly for current smokers.6
Stomach cancer
A case controlled study found that “consumption of kaempferol-containing foods was associated with a reduced gastric cancer risk”7

The Tabs below lists the published Abstracts and links to various studies within the 6 polyphenols of citrus peels.  (Part 2 of 2)

Anticancer Properties of Citrus Peel Polyphenols (Part 2 of 2)


Breast cancer
Collectively, our findings suggest that naringenin inhibits the proliferation of MCF-7 cells via impaired glucose uptake. Because a physiologically attainable dose of 10 µM naringenin reduced insulin-stimulated glucose uptake by nearly 25% and also reduced cell proliferation, naringenin may possess therapeutic potential as an anti-proliferative agent.1
Colon cancer
The ability of dietary apigenin and naringenin to reduce HMACF, lower proliferation (naringenin only) and increase apoptosis may contribute toward colon cancer prevention. However, these effects were not due to mitigation of iNOS and COX-2 protein levels at the ACF stage of colon cancer.2
everal polyphenolic compounds were tested for the inhibition of lung metastasis induced by B16F10 melanoma cells in mice. Oral administration of polyphenols such as curcumin and catechin at concentrations of 200 nmol/kg body weight were found to inhibit the lung metastasis maximally as seen by the reduction in the number of lung tumor nodules (80%). Other polyphenols which inhibited the lung tumor nodule formation were rutin (71.2%), epicatechin (61%), naringin (27.2%) and naringenin (26.1%). 3
Prostate cancer
As part of a systematic study of the effects of phytochemicals beyond antioxidation on cancer prevention, we investigated whether naringenin (NR), a citrus flavonoid, stimulates DNA repair following oxidative damage in LNCaP human prostate cancer cells. In conclusion, the cancer-preventive effects of citrus fruits demonstrated in epidemiological studies may be due in part to stimulation of DNA repair by NR, which by stimulating BER processes may prevent mutagenic changes in prostate cancer cells.4


Breast cancer
Two citrus flavonoids, hesperetin and naringenin, found in oranges and grapefruit, respectively, and four noncitrus flavonoids, baicalein, galangin, genistein, and quercetin, were tested singly and in one-to-one combinations for their effects on proliferation and growth of a human breast carcinoma cell line, MDA-MB-435 These experiments provide evidence of anticancer properties of orange juice and indicate that citrus flavonoids are effective inhibitors of human breast cancer cell proliferation in vitro, especially when paired with quercetin, which is widely distributed in other foods.  1
Lung cancer
To investigate the possible relationship between intake of flavonoids-powerful dietary antioxidants that may also inhibit P450 enzymes-and lung cancer risk, we conducted a population-based, case-control study in Hawaii. If replicated, particularly in prospective studies, these findings would suggest that foods rich in certain flavonoids may protect against certain forms of lung cancer and that decreased bioactivation of carcinogens by inhibition of CYP1A1 should be explored as underlying mechanisms.2
Oral administration of polyphenols such as curcumin and catechin at concentrations of 200 nmol/kg body weight were found to inhibit the lung metastasis maximally as seen by the reduction in the number of lung tumor nodules (80%). Other polyphenols which inhibited the lung tumor nodule formation were rutin (71.2%), epicatechin (61%), naringin (27.2%) and naringenin (26.1%). 3
Mouth cancer
The results with naringin and naringenin show that both of these flavonoids significantly lowered tumor number [5.00 (control group), 2.53 (naringin group), and 3.25 (naringenin group)]. Naringin also significantly reduced tumor burden [269 mm(3)(control group) and 77.1 mm(3)(naringin group)]. The data suggest that naringin and naringenin, 2 flavonoids found in high concentrations in grapefruit, may be able to inhibit the development of cancer.4


Colon cancer
Nobiletin (NOB), a citrus flavonoid, was given in the diet (100 p.p.m) for 17 weeks. Thereafter, the incidence and number of colon tumors and serum concentration of adipocytokines were determined at the end of week 20. The serum leptin level in AOM/DSS-treated mice was six times higher than that in untreated mice, whereas there were no significant differences in the levels of triglycerides, adiponectin and interleukin-6. 1
In vitro effects of medicinal plant extracts from the pericarpium of Citrus reticulata (cv Jiao Gan) (PCRJ) on the growth and differentiation of a recently characterized murine myeloid leukemic cell clone WEHI 3B (JCS) were investigated. The survival rate of mice receiving PCRJ treated JCS tumour cells was also increased. Using 1H-NMR, 13C-NMR, and GC/MS, two active components isolated from PCRJ were identified as nobiletin and tangeretin.2
Liver cancer
Dietary phytochemicals can inhibit the development of certain types of tumors. We here investigated the effects of nobiletin (Nob), garcinol (Gar), auraptene (Aur), beta-cryptoxanthin- and hesperidine-rich pulp (CHRP) and 1,1'-acetoxychavicol acetate (ACA) on hepatocarcinogenesis in a rat medium-term liver bioassay, and also examined their influence on cell proliferation, cell cycle kinetics, apoptosis and cell invasion of rat and human hepatocellular carcinoma (HCC) cells, MH1C1 and HepG2, respectively.3
Lung cancer
Furthermore, Nobiletin had overt inhibitory effect on the tumor growth in nude mice model was observed in vivo. Taken together, these results suggest that Nobiletin could induce p53-mediated cell cycle arrest and apoptosis via modulated the Bax:Bcl-2 protein ratio, is effective as a potent antitumor agent on lung tumors.4
Prostate cancer
A further experiment demonstrated that growth of androgen sensitive LNCaP and androgen insensitive DU145 and PC3 human prostate cancer cells, was suppressed by both nobiletin and to a lesser extent auraptene in a dose-dependent manner, with significant increase in apoptosis. In conclusion, these compounds, particularly nobiletin, may be valuable for prostate cancer prevention.5
Squamous Cell Carcinoma
Tangeretin and nobiletin markedly inhibited the proliferation of a squamous cell carcinoma (HTB 43) and a gliosarcoma (9L) cell line at 2-8 micrograms/ml concentrations. 6
Stomach cancer
Although the effective dose and administration route of nobiletin require further investigation, our study represents a potential successful linking of this compound with the treatment of gastric cancer.7


Breast cancer
There has been considerable evidence recently demonstrating the anti-tumour effects of flavonols. Quercetin, an ubiquitous bioactive flavonol, inhibits cells proliferation, induces cell cycle arrest and apoptosis in different cancer cell types. Taken together, these findings suggest that quercetin results in human breast cancer MDA-MB-231 cell death through mitochondrial- and caspase-3-dependent pathways.1
Cervical cancer
Quercetin showed a marked inhibitive effect on U14 growth, and its antitumor mechanism may be associated with inhibiting the angiogenesis and inducing apoptosis.2
Colon cancer
In conclusion, quercetin, but not rutin, at a high dose reduced colorectal carcinogenesis in AOM-treated rats, which was not reflected by changes in ACF-parameters. The lack of protection by rutin is probably due to its low bioavailability.3
Endometrial cancer
This study suggests a reduction in endometrial cancer risk with quercetin intake and with isoflavone intake in lean women.4
Esophageal cancer
The results of MTT assay showed that flavones (luteolin, apigenin, chrysin) and flavonols (quercetin, kaempferol, myricetin) were all able to induce cytotoxicity in OE33 cells in a dose- and time-dependent manner, and the cytotoxic potency of these compounds was in the order of quercetin > luteolin > chrysin > kaempferol > apigenin > myricetin. 5
Quercetin exposure resulted in proteasomal degradation of survivin. TRAIL-quercetin–induced apoptosis was markedly reduced by overexpression of survivin. In addition, upon treatment with quercetin, downregulation of survivin was also regulated by the Akt pathway. Taken together, the results of the present study suggest that quercetin sensitizes glioma cells to death-receptor–mediated apoptosis by suppression of inhibitor of the apoptosis protein survivin.6
Kidney cancer
These results suggest that the flavonoid quercetin may prevent renal cell cancer among male smokers. The possible risk associated with fish intake warrants further investigation before conclusions may be drawn.7
Laryngeal cancer
Quercetin could effectively inhibit the proliferation of Hep-2 cells and its mechanism is probably related to the apoptosis.8
It is concluded that the quercetin and kaempferol have significant anti-leukemia effect in vitro. Furthermore the apoptosis-inducing effect of quercetin is stronger than that of kaempferol, both of which induce apoptosis of HL-60 cells through depressing cell growth, arresting cell cycle and inhibiting expression of survivin.9
Liver cancer
Quercetin, a dietary flavonoid, has been shown to possess anticarcinogenic properties, but the precise molecular mechanisms of action are not thoroughly elucidated. The aim of this study was to investigate the regulatory effect of quercetin (50 microM) on two main transcription factors (NF-kappa B and AP-1) related to survival/proliferation pathways in a human hepatoma cell line (HepG2) over time. Quercetin induced a significant time-dependent inactivation of the NF-kappa B pathway consistent with a downregulation of the NF-kappa B binding activity (from 15 min onward).10
Lung cancer
Lung cancer was associated inversely with the consumption of epicatechin (in 10 mg per day increment: OR, 0.64; 95% CL, 0.46-0.88), catechin (4 mg per day increment: OR, 0.49; 95% CL, 0.35-0.70), quercetin (9 mg per day increment: OR, 0.65; 95% CL, 0.44-0.95), and kaempferol (2 mg per day increment: OR, 0.68; 95% CL, 0.51-0.90) among tobacco smokers.11
In this paper, the DNA protective free radical scavenging potential of quercetin (QU) and luteolin (LU) against H2O2 and their clastogenic effect alone and in combination with melphalan (MH) were investigated in human melanoma HMB-2 cells. Results are correlated to their structural arrangement and organization of the hydroxyl groups.12
Mouth cancer
In conclusion, our data support a view that quercetin initially induces a stress response, resulting in necrosis of these oral epithelial cells. Prolonged exposure of the surviving cells to quercetin causes apoptosis, presumably mediated by inhibition of TS protein.13
Ovarian cancer
It has been demonstrated that the flavonoid quercetin (3,3',4',5-7-pentahydroxyflavone) (Q) inhibits the growth of several cancer cell lines and that the antiproliferative activity of this substance is mediated by a so-called type II estrogen binding site (type II EBS). Since both rutin and hesperidin do not bind to type II EBS it can be hypothesized that Q synergizes with CDDP by acting through an interaction with these binding sites.14
Pancreatic cancer
Our studies aimed at evaluation of antiproliferative and pro-apoptotic effects of quercetin alone and in combinations with daunorubicin on cells of human pancreatic carcinoma lines. Our data demonstrated that quercetin exerted cytotoxic action on cells of the both neoplastic cell lines in concentration-dependent manner. In the case of EPP85-181RDB cell line, quercetin seemed to sensitize resistant cells to daunorubicin.15
Prostate cancer
Taken together, as shown by the issues of the current study, the manifold inhibitory effects of quercetin on PC-3 cells may introduce quercetin as an efficacious anticancer agent in order to be used in the future nutritional transcriptomic investigations and multi-target therapy to overcome the therapeutic impediments against prostate cancer.16
Squamous Cell Carcinoma
We examined the effects of flavone and two polyhydroxylated plant flavonoids (quercetin and fisetin), either singly or in combination with ascorbic acid, on the growth of a human squamous cell carcinoma cell line (HTB 43) in vitro. Fisetin and quercetin significantly impaired cell growth in the presence of ascorbic acid. 17
Stomach cancer
Cells were divided into the control group and the quercetin (Que)-treated group. Que significantly decreased the expression of VEGF-C and VEGFR-3 at 40 mumol/L compared with the control group after 48 h (P18


Colon cancer
The dietary effect of monoglucosyl-rutin (M-R), a flavonoid, on azoxymethane (AOM)-induced colon carcinogenesis was investigated in two experiments with 5 week old, F344 male rats. At the termination of the experiment (40 weeks after the start), groups 2-5 had significantly smaller numbers of positive cells with anti-proliferating cell nuclea antigen (PCNA) antibody than group 1. Furthermore, group 5 treated with 500ppm M-R for 36 weeks demonstrated tendencies for decrease in the incidence and multiplicity of colon tumors. These data suggest that M-R has the potential to inhibit AOM-induced colon carcinogenesis.1
During the post-initiation phase aspirin, calcium glucarate, ketoprofen, piroxicam, 9-cis-retinoic acid, retinol and rutin inhibited the outgrowth of ACF into multiple crypt clusters. Based on these data, certain phytochemicals, antihistamines, non-steroidal anti-inflammatory drugs and retinoids show unique preclinical promise for chemoprevention of colon cancer, with the latter two drug classes particularly effective in the post-initiation phase of carcinogenesis.2
Consequent to the inhibition of the lung tumor nodules, the life span of animals treated with polyphenols was also found to be increased. Curcumin (143.85%), catechin (80.81%) and rutin (63.59%) had maximal increase in life span. The results indicate a possible use of these compounds in arresting the metastatic growth of tumor cells.3


Breast cancer
Tangeretin is a methoxyflavone from citrus fruits, which inhibits growth of human mammary cancer cells and cytolysis by natural killer cells. Attempting to unravel the flavonoid's action mechanism, the authors found that it inhibited extracellular-signal-regulated kinases 1/2 (ERK1/2) phosphorylation in a dose- and time-dependent way. In human T47D mammary cancer cells this inhibition was optimally observed after priming with estradiol. 1
Colon cancer
Tangeretin and nobiletin are citrus flavonoids that are among the most effective at inhibiting cancer cell growth in vitro and in vivo. The antiproliferative activity of tangeretin and nobiletin was investigated in human breast cancer cell lines MDA-MB-435 and MCF-7 and human colon cancer line HT-29. Thus, tangeretin and nobiletin could be effective cytostatic anticancer agents. Inhibition of proliferation of human cancers without inducing cell death may be advantageous in treating tumors as it would restrict proliferation in a manner less likely to induce cytotoxicity and death in normal, non-tumor tissues.2
Tangeretin showed no cytotoxicity against either HL-60 cells or mitogen-activated PBMCs even at high concentration (27 microM) as determined by a dye exclusion test. Moreover, the flavonoid was less effective on growth of human T-lymphocytic leukaemia MOLT-4 cells or on blastogenesis of PBMCs. These results suggest that tangeretin inhibits growth of HL-60 cells in vitro, partially through induction of apoptosis, without causing serious side-effects on immune cells.3
Tangeretin was the most effective of the flavonoids in inhibiting B16F10 and SK-MEL-1 cell growth, showing a clear dose-response curve after 72 h. These results suggest that the absence of the C2-C3 double bond on hydroxylated flavonoids results in a loss of effect on both the cell lines, while the higher activity of tangeretin compared with 7,3'-dimethylhesperetin suggests that the presence of at least three adjacent methoxyl groups confers a more potent antiproliferative effect.4
Squamous Cell Carcinoma
 We investigated the antiproliferative effect of two polyhydroxylated (quercetin and taxifolin) and two polymethoxylated (nobiletin and tangeretin) flavonoids against three cell lines in tissue culture. Tangeretin and nobiletin markedly inhibited the proliferation of a squamous cell carcinoma (HTB 43) and a gliosarcoma (9L) cell line at 2-8 micrograms/ml concentrations. 2

A number of different varieties of citrus has been used in the numerous studies of citrus peel extracts.  A list of the most commonly used varieties are as follows:

  • Mandarin orange (Citrus reticulata)
  • Satsuma Mandarin (Citrus unshiu)

The Chinese have been using Chenpi or chen pi (Chinese: 陈皮, pinyin: chénpí) as a traditional seasoning in Chinese cooking and traditional medicine.  Chen pi is a sun dried tangerine (mandarin).  Some Chen pi is made from the mandarin orange (Citrus reticulata ‘Blanco’) and bitter orange (C. aurantium).  11

Chen pi contains a high content of 5-demethylated polymethoxyflavones (5-OH PMFs).  12  Oral administration of 0.25 and 0.5% chenpi extract in food over 15 weeks markedly prevented HFD-induced obesity, hepatic steatosis, and diabetic symptoms.  13

The varieties of citrus that are good candidates for citrus peel powder are the following:

  • Bitter Orange  (Citrus aurantium)
  • Sweet Orange (Citrus sinensis L. Osbeck)
  • Mandarin (Chinese) Tangerine  (Citrus reticulata)
  • Satsuma Mandarin  (Citru unshiu)
  • Chinese Honey Orange (Ponkan)  (Citrus poonensis)
  • Yuzu (Citrus ichangensis × C. reticulata)
  • Grapefruit  (Citrus paradisi)
  • Meyer Lemon (Citrus × meyeri)

When consuming citrus peel from any of the above varieties, it is important to choose the organic variety only.  Citrus fruits can be heavily sprayed with pesticides which tend to concentrate on the outer peel.  The fruit should be washed prior to using the peel, whether raw (zest) or dried and ground into citrus peel powder. 

Raw citrus peel (zest) can be used in salads, yogurt, tea, added to smoothies, stews, vegetable dishes as well as added to fish as a garnish.  The dried and grounded citrus peel powder can be added to smoothies and soups.

Images of various citrus fruits used for citrus peel and citrus peel powder:

  • Bitter Orange (Citrus aurantium)

How to Make Pure Orange Peel Powder at Home

Cover Photo from Nan Products

Support and Enhancement of Phase II Detoxification Pathways Using Foods, Food-Derived Components and Nutrients

Phase II Detoxification Pathways

There are 6 Phase II detoxification pathways in the body.  Each conjugation pathway serves a specific purpose of detoxifying certain toxins and requires specific nutrients to function.  These 6 detoxification pathways include:

  • Glutathione conjugation
  • Methylation
  • Sulfation
  • Acylation/Glycation
  • Acetylation
  • Glucuronidation

These 6 conjugation pathways are found primarily in the liver and in various other locations within the body:

Locations of Phase 2 Conjugation

Conjugation System Location in Body
Acylation/Glycation conjugation liver, kidney
Glutathione conjugation liver, kidney
Glucuronidation liver, kidney, intestine, lung, skin, prostate,
Acetylation liver, lung, spleen, gastric mucosa, RBCs,
Sulfation liver, kidney, intestine
Methylation liver, kidney, lung,

Source:  Liston HL, Markowitz JS, DeVane CL, (October 2001). “Drug glucuronidation in clinical psychopharmacology”. J Clin Psychopharmacol 21 (5): 500–15.doi:10.1097/00004714-200110000-00008. PMID 11593076

Phase II Conjugation Enzymes

After a toxin (xenobiotic) has gone through the process of becoming hydrophilic (water-soluble) through reactions overseen by Phase I enzymes, its intermediate molecules are then conjugated with endogenous hydrophilic enzymes.  These endogenous enzymes include:  1

  • glucuronic acid (glucuronyl transferases)
  • sulfate (sulfotransferases)
  • glutathione (glutathione transferases)
  • amino acids (amino acid transferases)
  • acetyl group (N-acetyl transferases)
  • methyl group (N- and O-methyltransferases)

These enzymatic reactions result in an increase in the hydrophilicity of the metabolite leading to enhanced excretion in the bile and/or urine.

The modulation of phase II enzymes by food-based bioactive compounds can support and enhance the Phase II process, especially when there are issues with:

  • genetic polymorphisms that inhibnit Phase II
  • high toxic burden due to chronic exposure to environmental pollutants
  • overactive Phase I activity
  • hormonal imbalance

Each of the 6 Phase II pathways are supported and enhanced by various foods, food-derived components and nutrients.

Amino Acid Conjugation:  Acylation/Glycation

In acylation/glycation, toxins are attached to amino acids, especially glycine. A low protein diet can inhibit acylation/gylcation.  Acylation/glycation detoxifies compounds like benzoate, aspirin and toluene (a widely used industrial solvent).



Glucuronic acid is a metabolite of glucose that can be attached to toxins. This pathway is used as a back-up for sulfation or acylation/glycination. It is used to eliminate chemical and bacterial toxins, excess steroidal hormones (like estrogen), toxins from fungal infections and a variety of chemical toxins such as nitrosamines, aromatic amines, alcohols and phenols.


Glutathione Conjugation

Attaching toxins to glutathione helps to detoxify and eliminate poisons in the liver, lungs, intestines and kidneys. Glutathione helps the body get rid of a wide variety of chemical compounds including aromatic disulphides, paththalene and anthracene.




Methylation attaches toxins to the amino acid methionine. This process occurs in every cell of the body and helps the body get rid of excess hormones and neurotransmitters, including steroidal hormones like estrogen, adrenaline, dopamine, melatonin, histamine and serotonin. It also helps eliminate homecysteine, a compound associated with increased risk of heart disease. A variety of chemicals (amines, phenols, etc.) are also eliminated through methylation.



Sulfation eliminates toxins by attaching them to sulphate. This is the principle pathway for eliminating excess neurotransmitters, several drugs (including acetaminophen, some food additives and toxins from intestinal bacteria. It also removes many forms of environmental toxins. Reduced sulfation may be involved in Parkinson’s disease, Alzheimer’s disease and other nervous system disorders and in environmental illness.



Acetylation involves attaching acetyl co-A to toxins for elimination. People who are chemically sensitive are usually slow acetylators. Slow acetylation enhances the toxicity of drugs because it prolongs their life span in the body. Acetylation is used to eliminate excess histamine, serotonin, sulfa drugs, PABA and chemicals like sulphur amides and hydranzines.


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Glutathione conjugation (page 1)

Glutathione conjugation  (page 2)






Maximizing The Sulforaphane Content of Broccoli and Broccoli Sprouts


Glucosinolates are natural components of many pungent plants that occur as secondary metabolites of most of the Brassicales family, or the cruciferous vegetables.   When these vegetables are chewed, a pungent taste arises due to the breakdown products of glucosinolates.

Each vegetable, sprout and seed usually contains more than one glucosinolate.  However, certain vegetables, sprouts and seeds may contain a predominant amount of one glucosinolate.  An example is the following:

  • Broccoli and broccoli sprouts contain large amounts of glucoraphanin
  • Mustard seeds and Brussel sprouts contain a large amount of Sinigrin
  • Garden cress and cabbage contain a large amount of glucotropaeolin
  • Watercress contains a large amount of gluconasturtiin

The total number of documented glucosinolates from nature can be estimated to around 132, as of 2011.  1  For purposes of this article, we will focus on the 4 most important glucosinolates and the ones that have been the subject of the majority of medical research.  These 4 glucosinolates include:

  • Gluconasturtiin
  • Glucoraphanin
  • Glucotropaeolin
  • Sinigrin

Gluconasturtiin, also known as phenethylglucosinolate, is a widely distributed glucosinolate in cruciferous vegetables.  The name is derived from it occurrence in watercress which has the botanical name Nasturtium officinale.

Glucoraphanin is a glucosinolate distributed in broccoli, Brussel sprouts, cabbage and cauliflower.  It is also found in large amounts in young sprouts of cruciferous vegetables, like broccoli sprouts.

Glucotropaeolin is a phytochemical from Tropaeolum majus, which is commonly known as garden nasturtium, Indian cress or monks cress.  It is also found in cabbage.

Sinigrin is widely distributed in the plants of the Brassicaceae such as Brussel sprouts, broccoli, horseradish and black mustard seeds.


Each of the vegetables, sprouts and seeds contain the enzyme myrosinase, which is activated when the vegetable, sprout or seeds is damaged (chopped or chewed) in the presence of water.  The glucosinolate converts to an isothiocyanate (or thiocyanate) through the enzymatic activity of myrosinase.  These isothiocyanates are the defensive substances of the plant.

Thus glucosinolates are the precursors to isothiocyanates through the breakdown of the enzyme myrosinase.  Myrosinase activity on the glucosinolate also continues in the gastrointestinal tract through intestinal bacteria which allows for some further formation and absorption of isothiocyanates. 2

Image result for glucosinolates myrosinase pathway

Figure 1:  Glucosinolates Hydrolysis by Myrosinase  (Source:  Linus Pauling Institute – Isothiocyanates)


Sulforaphane is obtained from cruciferous vegetables such as broccoli, broccoli sprouts, Brussels sprouts, and cabbages. It is produced when the enzyme myrosinase transforms glucoraphanin into sulforaphane upon damage to the plant (such as from chewing), which allows the two compounds to mix and react.

When the enzyme myrosinase acts on glucoraphanin, an unstable intermediate is produced.  This unstable intermediate is then acted on by a protein called epithiospecifier protein (ESP) to produce sulforaphane or sulforaphane nitrile.

If epithiospecifier protein (ESP) is abundant in the plant and is active, it will convert this unstable intermediate to a sulforaphane nitrile.  This sulforaphane nitrile has no anti-cancer activity.  3 

If epithiospecifier protein (ESP) is not abundant and is low-active, then it will convert this unstable intermediate into sulforaphane.  Sulforaphane has anti-cancer activity.  4

Image result for sulforaphane nitrile

Figure 2.  ESP converts into sulforaphane and sulforaphane nitrile  (Source

Decreasing Epithiospecifier Protein Activity

A research paper entitled “Heating decreases epithiospecifier protein activity and increases sulforaphane formation in broccoli”, published in Phytochemistry in 2004, examined the effects of heating broccoli florets and sprouts on sulforaphane and sulforaphane nitrile formation, to determine if broccoli contains ESP activity, then to correlate heat-dependent changes in ESP activity, sulforaphane content and bioactivity, as measured by induction of the phase II detoxification enzyme quinone reductase (QR) in cell culture.  5

Researchers experimented with cooking broccoli at different temperatures and at different times periods.  They then measured the point at which the epithiospecifier protein is destroyed. 

What they learned was that they only had to heat the broccoli for a short time in order to destroy the epithiospecifier protein thus yielding more sulforaphane and little to no sulforaphane nitrile.

Specifically, to maximize the sulforaphane in broccoli, they found that heating it for 10 minutes at 140 degrees Fahrenheit (60 degrees Celsius).  This can translate to steaming broccoli lightly for about 3 to 4 minutes.

When they heated the broccoli for 10 minutes at 158 degrees Fahrenheit (70 degrees Celsius) it not only destroyed the epithiospecifier protein but also the sulforaphane content. 

Broccoli sprouts

Broccoli sprouts are germinated from broccoli seeds for about 3 days minimum and 5 days maximum. 

Image result for broccoli sprouts

Figure 3.  Broccoli sprouts

Broccoli sprouts that are 3 days old have very concentrated sources of glucoraphanin.  It is estimated that broccoli sprouts have 10 to 100 times more glucoraphanin by weight than mature broccoli plants.  6

Three-day-old broccoli sprouts have been shown to be highly effective in reducing the incidence, multiplicity, and rate of development of mammary tumors in dimethylbenz(a)anthracene-treated rats.  7  Small quantities of crucifer sprouts may protect against the risk of cancer as effectively as much larger quantities of mature vegetables of the same variety.

The activity of the epithiospecifier protein (ESP) in broccoli sprouts fluctuates based on the number of days the sprouts have grown.  8

ESP activity increases up to day 2 after germination before decreasing again to seed activity levels at day 5.

Thus, the optimal amount of days to grow broccoli sprouts is probably 5 days since the amount of glucoraphanin in broccoli seeds remains more or less constant as those seeds germinate and grow into mature plants.  9

When the researchers heated broccoli sprouts for 10 minutes at 158 degrees Fahrenheit (70 degrees Celsius) in water, it minimized the epithiospecifier protein and maximized the sulforaphane content.

Heating broccoli sprouts in water under these exact specifications will increase the sulforaphane content for maximum anti-cancer benefit.

Compare the technique of heating broccoli sprouts in water with the study from China where they increased the sulforaphane yield by freezing the broccoli sprouts:

An example of heating broccoli sprouts in water using the specifications of the researchers can be viewed in the experiment conducted by Dr. Rhonda Patrick:

Rice Bran Fiber found to bind effectively to toxic Polychlorinated Biphenyls (PCBs) more than other tested natural substances

A polychlorinated biphenyl (PCB) is an organic chlorine compound that were used as lubricants and coolants in transformers, capacitors, and electronic equipment because of a high resistance to heat.

Unfortunately PCBs do not break down in the environment and bio-accumulate in animals and humans due to it being a very stable compound. 

As a result, and because of PCBs’ environmental toxicity and classification as a persistent organic pollutant, PCB production was banned from use in the US in 1979 by the Environmental Protection Agency (EPA). However, due to the persistence of PCBs in the environment, PCBs continue to leach into soil and groundwater from hazardous waste sites and landfills.

Humans are exposed to PCBs through our food chain by eating fish, meat and dairy products.  PCB’s are fat soluble and are not excreted by the body but instead are stored in fat cells, resulting in accumulations of PCBs over a lifetime.  This long term bio-accumulation increases a person’s body burden of PCBs.

A number of symptoms in humans of PCB exposure have been identified:

  • Severe acne
  • Rash
  • Eye irritation
  • Liver damage
  • Weakened immune system
  • Chemical sensitivity
  • Allergies
  • Obesity
  • Fatigue
  • Certain cancers
  • Developmental disorders


You can test for PCBs in your blood from Genova Diagnostics (GDX):

Polychlorinated Biphenyls (PCBs) Profile

A study published in the Journal Of Nutritional Biochemistry in January 2005 found that rice bran flour (RBF) was effective in binding and accelerating the fecal excretion of polycyclic biphenyl (PCBs), polychlorinated dibenzofurans (PCDFs), polychlorinated-p-dioxines (PCDDs) and various mutagens and carcinogens.  RBFs binding effects were related to its high lignan content.  1

Other dietary fibers were testing and compared to RBF.  These other dietary fibers included:

  • corn
  • wheat bran
  • spinach
  • Hijiki (a kind of seaweed)
  • sweet potatoes
  • burdock fibers

The binding effects to RBF and pulp lignin were obtained at ratios of over 90%, while corn fiber and cellulose were at ratios of 4-30%.

It was also found that RBF was capable of binding even conjugates containing mutagens such as glucuronides and sulfates, as well as metabolites in urine.  

Freezing Broccoli Sprouts Increases Sulforaphane Yield

Three-day old broccoli sprouts are concentrated sources of glucoraphanin, which is the precursor to sulforaphane.  Fresh broccoli sprouts contain 10 to 100 times more glucoraphanin by weight than mature broccoli plants. 1  Fresh broccoli sprouts can contain at least 73 mg of glucoraphanin (also called sulforaphane glucosinolate) per 1-oz serving.

A study from 2015 published in the journal RSC Advances by researchers from the College of Food Science and Technology, Nanjing Agricultural University, Nanjing, People’s Republic of China and the College of Food Science and Engineering, Qingdao Agricultural University, Qingdao, People’s Republic of China, investigated whether freezing broccoli sprouts would have an effect on glucoraphanin and ascorbic acid content, myrosinase activity, sulforaphane and sulforaphane nitrile formation.  2

The researchers froze broccoli sprouts at −20 °C (DF-20), −40 °C (DF-40) and −80 °C (DF-80) or stored at −20 °C (LN-20), −40 °C (LN-40) and −80 °C (LN-80) after being frozen in liquid nitrogen for 5 min or always frozen in liquid nitrogen (LN).

The results showed the following:

  • glucoraphanin content was not significantly affected by freezing
  • myrosinase activity was enhanced
  • sulforaphane yield  was increased by 1.54–2.11 fold
  • sulforaphane nitrile formation decreased
  • ascorbic acid content was decreased

By freezing fresh broccoli sprouts, sulforaphane can be increased by on average 1.825 times its original value when fresh and not frozen. 

Eating frozen broccoli sprouts may not be very appetizing.  Instead it is recommended to use the frozen broccoli sprouts in a smoothie.  Make sure you use the broccoli sprouts straight from the freezer and do not allow them to thaw.  

Increasing Nrf2: A Master Regulator of the Aging Process

Nuclear factor (erythroid-derived 2)-like 2, also known as NFE2L2 or Nrf2, is a transcription factor. The Nrf2 pathway is “the primary cellular defense against the cytotoxic effects of oxidative stress.”

Activation of Nrf2 results in the induction of many cytoprotective proteins. These include, but are not limited to, the following:

  • NAD(P)H quinone oxidoreductase 1 (Nqo1)
  • Glutamate-cysteine ligase, catalytic (Gclc) and glutamate-cysteine ligase, modifier (GCLM)
  • Heme oxygenase-1 (HMOX1, HO-1)
  • The glutathione S-transferase (GST) family
  • The UDP-glucuronosyltransferase (UGT) family
  • Multidrug resistance-associated proteins (Mrps)

A wide variety of dietary components have been shown in vitro or cell culture to activate Nrf2 and directly increase activity of phase II enzymes; these include:

  • epigallocatechin gallate (EGCG)
  • resveratrol
  • curcumin and its metabolite tetrahydrocurcumin, which has greater phase II activity
  • cinnamaldehyde
  • caffeic acid phenyethyl ester
  • alpha lipoic acid
  • alpha tocopherol
  • lycopene
  • apple polyphenols (chlorogenic acid and phloridzin)
  • gingko biloba
  • chalcone
  • capsaicin
  • hydroxytyrosol from olives
  • allyl sulfides from garlic
  • chlorophyllin
  • xanthohumols from hops

The beneficial effects of these phytochemicals have been demonstrated in numerous animal and human studies, particularly their chemopreventative and antioxidant abilities; these effects may be explained by their indirect stimulation of antioxidant enzyme production and phase II detoxification through Nrf2 signaling. (Source: Life Extension)


Yuan JH, Li YQ, Yang XY. Inhibition of epigallocatechin gallate on or- thotopic colon cancer by upregulating the Nrf2-UGT1A signal path- way in nude mice. Pharmacology 2007; 80: 269 – 78

Hsieh TC, Lu X, Wang Z, Wu JM. Induction of quinone reductase NQO1 by resveratrol in human K562 cells involves the antioxidant response element ARE and is accompanied by nuclear translocation of tran-scription factor Nrf2. Med Chem 2006; 2: 275 – 85

Nayak S and Sashidhar RB. Metabolic intervention of aflatoxin B1 toxicity by curcumin. J Ethnopharmacol 2010;127 (3) : 641-4

Osawa T. Nephroprotective and hepatoprotective effects of curcuminoids. Adv Exp Med Biol 2007;595 : 407-23

Liao BC, Hsieh CW, Liu YC, Tzeng TT, Sun YW, Wung BS. Cinnamaldehyde inhibits the tumor necrosis factor-alpha-induced expression of cell adhesion molecules in endothelial cells by suppressing NF-kap- paB activation: Effects upon IkappaB and Nrf2. Toxicol Appl Pharmacol 2008; 229: 161 – 71

Lii CK, Liu KL, Cheng YP et al. Sulforaphane and alpha-lipoic acid upregulate the expression of the pi class of glutathione S-transferase through c-jun and Nrf2 activation. J Nutrition 2010;140 (5) : 885-92

Feng Z, Liu Z, Li X, et al. α-Tocopherol is an effective Phase II enzyme inducer: protective effects on acrolein-induced oxidative stress and mitochondrial dysfunction in human retinal pigment epithelial cells. J Nutr Biochem 2010;21 (12) : 1222-31

Wang H and Leung LK. The carotenoid lycopene differentially regulates phase I and II enzymes in dimethylbenz[a]anthracene-induced MCF-7 cells. Nutrition 2010;26 (11-12) : 1181-7

Veeriah S, Miene C, Habermann N et al. Apple polyphenols modulate expression of selected genes related to toxicological defence and stress response in human colon adenoma cells. Int J Cancer 2008;122 (12) : 2647-55

Liu XP, Goldring CE, Wang HY, Copple IM, Kitteringham NR, Park BK. Extract of Ginkgo biloba induces glutathione-S-transferase subunit-P1 in vitro. Phytomedicine 2009; 16(5):451–455

Liu YC, Hsieh CW, Wu CC, Wung BS. Chalcone inhibits the activation of NF-kappaB and STAT3 in endothelial cells via endogenous electrophile. Life Sci 2007; 80: 1420 – 30

Joung EJ, Li MH, Lee HG, Somparn N, Jung YS, Na HK et al. Capsaicin in- duces heme oxygenase-1 expression in HepG2 cells via activation of PI3K-Nrf2 signaling: NAD(P)H:quinone oxidoreductase as a potential target. Antioxid Redox Signal 2007; 9: 2087 – 98

Zhu L, Liu Z, Feng Z et al. Hydroxytyrosol protects against oxidative damage by simultaneous activation of mitochondrial biogenesis and phase II detoxifying enzyme systems in retinal pigment epithelial cells. J Nutr Biochem 2010;21 (11) : 1089-98

Gong P, Hu B, Cederbaum AI. Diallyl sulfide induces heme oxygenase-1 through MAPK pathway. Arch Biochem Biophys 2004; 432: 252 – 60

Zhang Y, Guan L, Wang X, Wen T, Xing J, Zhao J. Protection of chloro- phyllin against oxidative damage by inducing HO-1 and NQO1 ex- pression mediated by PI3K/Akt and Nrf2. Free Radic Res 2008; 42: 362–71

Dietz BM, Kang YH, Liu G et al. Xanthohumol isolated from Humulus lupulus Inhibits menadione-induced DNA damage through induction of quinone reductase. Chem Res Toxicol 2005;18 (8) : 1296-305

Surh YJ, Kundu JK, Na HK. Nrf2 as a master redox switch in turning on the cellular signaling involved in the induction of cytoprotective genes by some chemopreventive phytochemicals. Planta Med 2008;74 (13) : 1526-39

Informational Reference:  

Free E-Book: The Health and Medicinal Benefits of Ashitaba

Ashitaba, which is the common name used in Japan, is botanically known as Angelica keiskei or Angelica Keiskei Koidzumi. The English translation of the Japanese word “Ashitaba” (アシタバ or 明日葉) is “Tomorrow’s Leaf”. Ashita means ‘tomorrow and ba means ‘leaf.’ The name stems from the plant’s ability to quickly regenerate new leaves after taking cuttings. This give an indication of its potential for longevity of life.


Ashitaba plant

There are two separate substances (products) that are derived from the Ashitaba plant.

The first is the hot-air dried powder of Ashitaba from the leaves and stems. The color of this powder is bright green. The leaves of the Ashitaba plant contain approximately 0.25% to 0.35% chalcones.

The second is the powder made from the unique yellow sap which is collected from the Ashitaba’s stem. It is commonly called Ashitaba Chalcone Powder which consists up to 8% chalcones. The color of Ashitaba Chalcone Powder is bright yellow and is a fat-soluble substance.

Although the green Ashitaba powder from the leaves and stems provide nutritional and health benefits, it is the Ashitaba Chalcone Powder (bright yellow powder from the sap of the stem) that is the Chalconoids are natural phenols related to chalcone. They form the central core for a variety of important biological compounds.


Chalcone sap from Ashitaba stem

Chalcones are the active factors in Angelica Keiskei Koidzumi. At least 20 chalcones have been identified in Angelica Keiskei.

Ashitaba contains a thick, sticky yellow sap, which is not found in other celery plants, and are unique to this strain of angelica. This yellowish element in Ashitaba contain the chalconoids.


Download the Free E-Book (PDF): The Health and Medicinal Benefits of Ashitaba

Left-click to download into new window, then right-click (in new window) to save as PDF file.

The Detoxification and Biotransformation System in the Human Body

Detoxification Pathways

There are 6 main detoxification organs or systems in the human body:

  • Liver (processes and packages toxins) (70% of detoxification)
  • Lungs (gas exchange of oxygen and carbon dioxide)
  • Gastrointestinal Tract (excretes waste)
  • Skin (sweat)
  • Kidneys (urination)
  • Endothelial cells of the blood brain barrier

The intestines, liver and kidneys are the primary organs of detoxification.

Biotransformation enzymes exist in the smooth endoplasmic reticulum, cystosol (intracellular fluid) and to a lesser degree in the membranes of the mitochondria, nuclei and lysosomes (small spherical organelles) of the liver’s hepatocytes. The kidneys and lungs are the next major biotransformation sites, but only at 10 – 30% of the livers capacity. The skin, nasal mucosa and intestinal mucosa also have some biotransformation capacity.

Other sites of detoxification metabolism include epithelial cells of the gastrointestinal tract, lungs, kidneys, and the skin. These sites are usually responsible for localized toxicity reactions.

Once an unwanted compound has been completely bio transformed and removed from the cell, it will then be eliminated from the body via – kidneys, bowels, breath, sweat, saliva or hair – completing the detoxification process.

Toxins that the body is unable to eliminate build up in the tissues and typically stored in the adipose (fat) tissue.

Liver Detoxification

Almost 2 quarts of blood pass through the liver every minute for detoxification. Filtration of toxins is absolutely critical for the blood from the intestines because it is loaded with bacteria, endotoxins, antigens – and tight body complexes, and various other toxic substances.


Figure 1:  Detoxification pathways

Intermediary Metabolites  and Pathological Detoxifiers

The transformation of xenobiotics into more chemically active toxins can cause several problems. A significant side effect of all this metabolic activity is the production of free radicals as xenobiotics are transformed by phase 1. Without adequate free radical defenses, every time the liver neutralizing toxins, it is damaged by the free radicals that are produced.

The most important antioxidant for neutralizing free radicals produced by phase 1 byproducts is glutathione. In the process of neutralizing free radicals glutathione is oxidized to glutathione disulfide. Glutathione is required for one of the phase 2 detoxification processes namely glutathione conjugation. When high levels of toxic exposure produces so many free radicals from phase 1, all of glutathione is used up, and glutathione conjugation stops working.

Another potential problem occurs because the toxins transformed into intermediary metabolites by phase 1 can be more toxic than the original toxin. Unless these intermediary metabolites are quickly removed from the body by phase 2 detoxification pathways, they can cause widespread problems. Therefore, the rate at which phase 1 produces intermediary metabolites must be balanced by the rate at which phase 2 finishes the process. Unfortunately, some people have a very active phase 1 detoxification system but very slow phase 2 enzymes. These people are described as “pathological detoxifiers” because they’re over active phase 1 results in a buildup of more harmful intermediate products, which phase 2 cannot detoxify quickly enough. The end result is that these people suffer severe toxic reaction to environmental poisons.

Gastrointestinal Tract Detoxification

About 25% of detoxification occurs within the cells lining the intestines, the remainder occurs in the liver.

Most literature on detoxification refers to liver enzymes, as the liver is the site of the majority of detoxification activity for both endogenous and exogenous compounds. However, the first contact the body makes with the majority of xenobiotics is the gastrointestinal tract. the gastrointestinal tract is the second major site in the body for detoxification. Detoxification enzymes such as Cyp3A4 and the antiporter  activities have been found in high concentrations at the tip of villi in the intestine.

Adequate first pass metabolism of xenobiotics by the gastrointestinal tract requires integrity of the gut mucosa. Compromised barrier function of the mucosa will easily allow xenobiotics to transit into the circulation without opportunity for detoxification. Therefore, support for healthy gut mucosa is instrumental in decreasing toxic load.

The gastrointestinal tract influences detoxification in several other ways. Gut microflora can produce compounds that either induce or inhibit detoxification activities.

Pathogenic bacteria can produce toxins that can enter circulation and increase toxic load.

Detoxification through the intestinal tract is enhanced by fasting, mono, high fiber and mucus-less diets, ingestion of substances such as charcoal, mud and grasses, and in some cases by the use of cathartics that either lubricate, increase fluidity, add bulk or stimulate peristaltic motion.

Gastrointestinal health and gut permeability also play a role in detoxification. Increased gut permeability allows for increased absorption of xenobiotics and toxins, which are processed and removed by the liver, thus increasing the demands on the liver detoxification system. Impaired gastrointestinal integrity can be improved via dietary support as well as prebiotics and probiotics.

Fiber is particularly important for supporting detoxification. Dietary fibers bind not only carcinogens, bile acids, and other potentially toxic agents, it also promotes a faster transit time and therefore less opportunity for toxin interaction with the intestinal lining and reabsorption. In addition, increased fiber intake helps positively balance the intestinal microflora, which minimizes endotoxin production from pathogenic bacteria.

Brain Detoxification: The Glymphatic System

The cytochrome P450 enzyme system is found in other parts of the body, especially the brain cells.

The glymphatic system (or glymphatic clearance pathway) is a functional waste clearance pathway for the mammalian central nervous system (CNS). The brain is not part of the body’s lymphatic system which is responsible for removing extracellular proteins, excess fluid, and metabolic waste products from peripheral tissues.

Glymphatic flow answers the long standing question of how the sensitive neural tissue of the CNS functions in the absence of a conventional lymphatic circulation. The pathway consists of a para-arterial influx route for cerebrospinal fluid (CSF) to enter the brain parenchyma, coupled to a clearance mechanism for the removal of interstitial fluid (ISF) and extracellular solutes from the interstitial compartments of the brain and spinal cord. Exchange of solutes between the CSF and the ISF is driven by arterial pulsation and regulated during sleep by the expansion and contraction of brain extracellular space.

Clearance of soluble proteins, waste products, and excess extracellular fluid is accomplished through convective bulk flow of the ISF, facilitated by astrocytic aquaporin 4 (AQP4) water channels.


Figure 2:  Mammalian Gymphatic System

A publication by L. Xie and colleagues in 2013 explored the efficiency of the glymphatic system during slow wave sleep and provided the first direct evidence that the clearance of interstitial waste products increases during the resting state. Xia and Nedergaard demonstrated that the changes in efficiency of CSF–ISF exchange between the awake and sleeping brain were caused by expansion and contraction of the extracellular space, which increased by ~60% in the sleeping brain to promote clearance of interstitial wastes such as amyloid beta.

During the night, we experience sleep cycles that average about 90 minutes. In the first half of the night we cycle through all of the stages, N1, N2, N3, and REM sleep. Slow wave sleep or delta sleep is N3. We start at N1 and go deeper into N2, then deeper into N3, the stage where brain cleansing occurs. In the second half of the night, REM sleep increases and alternates with N1 and N2 sleep, so it appears most of the cleanup is done in the first half of the night.

The interstitial space makes up about 20% of the brain volume but that fraction varies over the course of the day and night. During sleep this space increases by up to 60% in volume. This flushing of the glymphatic system removed waste metabolic products that are potentially neurotoxins. These products include β-amyloid proteins which are strongly suspected to play a part in Alzheimer’s Disease.

This is a two part process:

  • 1. After the brain cells shrink 60 %  cerebral spinal fluid is pumped through the brain’s tissue, then 
  • 2. The waste is flushed back into the circulatory system where it enters the blood circulation system and goes to the liver

Cerebral spinal fluid quickly flows into the space, aided by the pulse of the arteries. It mixes with the interstitial fluid and washes the waste toward the veins and carries it to the liver. This process occurs during slow wave sleep, the deepest sleep.

Another startling finding was that the cells in the brain “shrink” by 60 percent during sleep. This contraction creates more space between the cells and allows CSF to wash more freely through the brain tissue. In contrast, when awake the brain’s cells are closer together, restricting the flow of CSF. 

The researchers observed that a hormone called noradrenaline is less active in sleep. This neurotransmitter is known to be released in bursts when brain needs to become alert, typically in response to fear or other external stimulus. The researchers speculate that noradrenaline may serve as a “master regulator” controlling the contraction and expansion of the brain’s cells during sleep-wake cycles.

Using these techniques, researchers were able to observe in mice – whose brains are remarkably similar to humans – what amounts to a plumbing system that piggybacks on the brain’s blood vessels and pumps cerebral spinal fluid (CSF) through the brain’s tissue, flushing waste back into the circulatory system where it eventually makes its way to the general blood circulation system and, ultimately, the liver.

Skin Detoxification

Detoxification through the skin is facilitated by the promotion of sweating. This can be accomplished by ingesting sudorific (diaphoretic) herbs like ginger, mustard and cayenne, either by themselves or in conjunction with fasting, saunas, baths and sweats.

Packs of clay, mud, salt, charcoal, seaweed, volcanic ash and castor oil have also proven useful in increasing the elimination of toxins through the skin.

Physiological Factors that Affect Detoxification

There are various physiological and pathological factors that affect the detoxification process. Physiological factors that can influence detoxification include:

  • Age
  • Genetic Factors
    • Polymorphisms (SNPs)  


The activity of phase I detoxification enzymes decreases in old age. Aging also decreases blood flow through the liver, further aggravating the problem. Lack of the physical activity necessary for good circulation, combined with the poor nutrition commonly seen in the elderly; add up to a significant impairment of detoxification capacity, which is typically found in aging individuals.

Genetic Factors

Biochemical individuality is a simple concept that states all humans differ biochemically from others. And that biochemical individuality directly affects the degree to which a chemical compound is bio-transformed from person to person. Some of the factors that determine a person’s level of biochemical individuality and therefore biotransformation capacity are:

The structure, amount of or complete lack of a specific biotransformation enzyme may differ among individuals and this can give rise to differences in rates of biotransformation.  Genetic differences in the ability of an individual to metabolize xenobiotics are related to the presence of different versions of the gene encoding that activity, or genetic polymorphism.

A Single Nucleotide Polymorphism, also known as Simple Nucleotide Polymorphism, is a DNA sequence variation occurring commonly within a population (e.g. 1%) in which a single nucleotide — A, T, C or G — in the genome (or other shared sequence) differs between members of a biological species or paired chromosomes.

Polymorphisms (SNPs) in the genes coding for a particular enzyme can increase or, more commonly, decrease the activity of that enzyme. Both increased and decreased activity may be harmful. As mentioned above, increased Phase I clearance without increased clearance in Phase II can lead to the formation of toxic intermediates that may be more toxic than the original toxin. Decreased Phase I clearance will cause toxic accumulation in the body.

Genova Diagnostics offers a comprehensive test of the Polymorphism (SNPs) in its DetoxiGenomic(TM) Profile. 

Click the link to view a Sample Report


Amino Acid Conjugation Pathway in Metabolic Detoxification: Glycine is the Main Amino Acid

Phase 1 Biotransformation Process

The primary function of the Phase I biotransformation process is to either:

  • Biotransform a toxic lipophilic compound directly to a more hydrophilic compound so it can be directly excreted in the kidneys (e.g. caffeine). Though, Phase I usually results in only a small amount of direct hydrophilicity and excretion
  • The bulk of Phase I enzymatic activity takes place in the form of altering unwanted compounds in a way as to either expose or introduce a functional group. Functional groups such as: Carboxyl group (–COOH), hydroxyl group (– OH), amino group (-NH2), or sulfhydryl group/thiol (-SH)

In the Phase 1 detoxification process a toxic chemical is converted into a less harmful chemical through various chemical reactions.  Phase 1 is essentially responsible for breaking fat-soluble toxins down and then sending the raw materials to Phase 2 detoxification process.  Phase 2 is the addition or conjugation phase where new substances are added/conjugated to the toxic metabolites produced in Phase 1 in order to make them easier to transport, more stable and/or more functional for the body.

Phase 2 Conjugation Pathways

There are 6 Conjugation Pathways in the human body and they include:

  • Sulphation (sulfation) pathway
  • Glucoronidation pathway
  • Glutathione conjugation pathway
  • Acetylation pathway
  • Methylation (& Sulfoxidation) pathway
  • Amino Acid conjugation pathway (glycine, cysteine, glutamine, methionine, taurine, glutamic acid and aspartic acid)

These 6 conjugation pathways occur in different organs of the body.  The locations of the Phase 2 conjugation pathways are listed in Table 1.

  Table 1 Locations of Phase 2 Conjugation Systems

Conjugation System

Location in Body

Glycine conjugation

liver, kidney

Glutathione conjugation

liver, kidney


liver, kidney, intestine, lung, skin, prostate, brain


liver, lung, spleen, gastric mucosa, RBCs, lymphocytes


liver, kidney, intestine


liver, kidney, lung, CNS

(Source:   Liston HL, Markowitz JS, DeVane CL (October 2001). “Drug glucuronidation in clinical psychopharmacology”. J Clin Psychopharmacol 21 (5): 500–15.)

Amino Acid Conjugation Pathway

The Amino Acid conjugation pathway is less utilized by the body, yet is still a very important conjugation pathway. 

The conjugation of toxins with amino acids occurs in this pathway. The amino acids commonly used in this pathway include:

  • Glycine
  • Taurine
  • Glutamine

but arginine, and ornithine are also used.


Figure 1:  Amino acid conjugation pathways

(Source:  Wikipathways)

The Amino Acid Conjugation Pathway often includes the Acylation Pathway.  Acylation uses acyl CO-A with the amino acids glycine, glutamine and taurine. Conjugation of bile acids in the liver with glycine or taurine is essential for the efficient removal of these potentially toxic compounds.  

The main amino acid in the Amino Acid Conjugation Pathway is glycine.  Glycine is the smallest of the 20 amino acids commonly found in proteins.  Glycine is a colorless, sweet-tasting crystalline solid. It is unique among the proteinogenic amino acids in that it is achiral. It can fit into hydrophilic or hydrophobic environments, due to its minimal side chain of only one hydrogen atom.

Since it plays such an important role in the Amino Acid Conjugation Pathway, it is also known as the Glycination Pathway.  Salicylates and benzoate are detoxified primarily through glycination. Benzoate is present in many food substances and is widely used as a food preservative.

In humans, there is a wide variation that exist in the activity of the glycine conjugation, which is primarily due not only to genetic variations, but also to the availability of glycine in the diet.

High-protein rich foods should be consumed in the diet to ensure that the amino acid conjugation is functioning properly.  There are a number of natural substances that induce the

Amino Acid Conjugation Pathway and act as co-factors in the conjugation process.  These substances are listed in Table 2. 

Table 2 Natural Substances that Induce the Amino Acid Conjugation Pathway













B Complex Vitamins (particularly

Vitamin B3 and Vitamin B6)

Amino Acids













Life Extension – Glycine (Capsules)

NOW – Glycine (Powder)

Cover Photo Source:  Perfect Health Diet

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Detoxifying Heterocyclic aromatic amines (HCAs) and Polycyclic aromatic hydrocarbons (PAHs) with Chlorella vulgaris

Heterocyclic aromatic amines (HAAs) and polycyclic aromatic hydrocarbons (PAHs) have been identified by scientific research as carcinogenic chemicals in the diet. 

Heterocyclic aromatic amines (HAAs)

Heterocyclic aromatic amines are a group of 20 chemical compounds formed during cooking. They are found in meats that are cooked to the well done stage, in pan drippings, and in meat surfaces that show a crispy brown crust.

Related image

Epidemiological studies show associations between intakes of heterocyclic aromatic amines and cancers of the:

  • colon
  • rectum
  • breast
  • prostate
  • pancreas
  • lung
  • stomach
  • esophagus

The U.S. Department of Health and Human Services Public Health Service labeled several heterocyclic aromatic amines as likely to be carcinogenic to humans in its most recent Report on Carcinogens.  1 

The most common types of Heterocyclic Aromatic Amines (HAAs) include:

  • 4,8-DiMelQx 2-Amino-3,4,8-Trimethylimidazo [4,5-f]Quinoxaline
  • 8-MelQx 2-Amino-3,8-Dimethylimidazo [4,5-f]Quinoxaline
  • IQ 2-Amino-3-Methylimidazo [4,5-f]Quinoline
  • MelQ 2-Amino-3,4-Dimethylimidazo [4,5-f]Quinoline
  • PhIP 2-Amino-1-Methyl-6-Phenylimidazo [4,5,b]Pyridine
  • TMIP 2-Amino-N,N,N-Trimethylimidazopyridine

HAAs form when Amino Acids and Creatine present in muscle Meats react at high temperatures (above 100° C). Temperature is the most important factor in formation of HAAs. Frying, Grilling, and Barbecuing produce the largest amounts of HAAs because the Meats are cooked at very high temperatures. Roasting and Baking are done at lower temperatures, so lower levels of HAAs are likely. Microwaving, Stewing, Boiling, or Poaching are done at or below 100° and cooking at this low temperature creates negligible amounts of HAAs.

Polycyclic aromatic hydrocarbons (PAHs)

Polynuclear aromatic hydrocarbons (PAH) are potent atmospheric pollutants. Some compounds have been identified as carcinogenic, mutagenic, and teratogenic.

Image result for polycyclic aromatic hydrocarbons

The EPA has classified seven PAH compounds as probable human carcinogens:

  • benz[a]anthracene,
  • benzo[a]pyrene,
  • benzo[b]fluoranthene,
  • benzo[k]fluoranthene,
  • chrysene,
  • dibenz(a,h)anthracene, and
  • indeno(1,2,3-cd)pyrene

The source of PAH’s include:

  • Car exhaust
  • The smoke generated by various cooking methods
    • High heat grilling
    • Barbequing
    • Smoked foods (meats, fish,etc.)
  • Tobacco smoke

Detoxifying Heterocyclic aromatic amines (HAAs) and Polycyclic aromatic hydrocarbons (PAHs) with Chlorella vulgaris

A randomized, double blind, placebo-controlled crossover study from January 2015 assessed the ability of Chlorella vulgaris to detoxify carcinogenic HAAs and PAHs.   Researchers analyzed urine specimens of 6 females with ages around 27 years for 2 weeks.  Urine specimens showed high levels of three HAAs, specifically:  2

  • MeIQx                 323.36±220.11ng/L
  • PhIP                    351.59±254.93ng/L
  • IQx-8-COOH       130.85±83.22ng/L

Consumption of Chlorella vulgaris significantly reduced urinary levels of MeIQx:

  • Before    430±226.86pg/mL
  • After       174.45±101.65pg/mL

Urinary levels of PhIP or IQx-8-COOH, a major metabolite of MeIQx, were not changed by chlorella supplementation.