Monthly Archives: September 2017

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Bifidobacterium in the Gut Microbiota Declines in the Aging Adult: Guidance on How to Repopulate and Increase Bifidobacterium in the Gastrointestinal Tract

Human Health Depends on a Beneficial and Diverse Gut Microbiota

In order to establish and maintain the health of the host, the intestinal microbiota in general and bifidobacterium in particular are very important.

Regardless of age, studies have determined that human health depends greatly on a beneficial gut microbiota.  1  One study from 2006 called the gut microbiota as the “forgotten organ.”  2 

The aging process can alter and affect the composition and functions of bacterial species in the gut microbiota.   A major consequence of the aging process, coupled with poor eating habits, extended use of antibiotics and stress is a loss of diversity in the gut microbiota.  In general a high diversity of gut organisms has been associated with states of relatively good health, while low diversity has been associated with states of disease or chronic dysfunction.  3 4

At the later stages of life the microbiota composition becomes less diverse, with a higher Bacteroides to Firmicutes ratio, an increase in Proteobacteria and decrease in Bifidobacterium.  5 

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Human microbiota: onset and shaping through life stages and perturbations. The graph provides a global overview of the relative abundance of key phyla of the human microbiota composition in different stages of life. Measured by either 16S RNA or metagenomic approaches (DNA). Data arriving from: Babies breast- and formula-fed (Schwartz et al., 2012), baby solid food (Koenig et al., 2011), toddler antibiotic treatment (Koenig et al., 2011), toddler healthy or malnourished (Monira et al., 2011), adult, elderly, and centenarian healthy (Biagi et al., 2010), and adult obese (Zhang et al., 2009).  Source:  The function of our microbiota: who is out there and what do they do?

The microbiota acclimates changes during the aging process as illustrated in the diagram below:

Development of human gut microbiota from prenatal to elderly. It is believed that infants are born with a sterile gastrointestinal track. During birth, the infant gut is exposed to microbes from the mother’s reproductive tract and environment and the gut microbiota starts colonizing. Up to the first two years of life, the composition of the gut microbiota often varies. After two years, when children are started to eat solid food (e.g. fibers and complex carbohydrates), the gut microbiota becomes more diverse and stable. In old age, the gut microbiota alters drastically and shows less diversity compared to younger age.

Development of human gut microbiota from prenatal to elderly. It is believed that infants are born with a sterile gastrointestinal track. During birth, the infant gut is exposed to microbes from the mother’s reproductive tract and environment and the gut microbiota starts colonizing. Up to the first two years of life, the composition of the gut microbiota often varies. After two years, when children are started to eat solid food (e.g. fibers and complex carbohydrates), the gut microbiota becomes more diverse and stable. In old age, the gut microbiota alters drastically and shows less diversity compared to younger age.  Source: Human gut microbiota and healthy aging: Recent developments and future prospective

Diversity Association is a proxy measure of gut biodiversity, which is defined as the number and abundance of distinct types of organisms present in the gut.  6  

The Diversity Association (DA) graphic is a global biomarker of overall gut health status and serves as a proxy measure of gut biodiversity. Specifically, the Diversity Association graphic represents the results of a proprietary algorithm based on selected commensal targets that appear to correlate with gut health status.

Diversity Association is graphically represented on a vertical ascending scale reflecting lower to higher overall diversity. In the gut, higher diversity is associated with gut health.

  • A Diversity Association indicator in the lower half of the graphical bar indicates a high likelihood that a patient’s gut is not healthy
  • A Diversity Association in the upper quartile of the graphical bar indicates high likelihood that a patient’s gut is healthy

The clinical utility of the Diversity Association is based on a growing body of research demonstrating that lower gut diversity is associated with clinical disease. As such, therapeutic interventions to restore gut balance (including dietary manipulation, prebiotics and/or probiotics, as well as other clinical strategies to heal the gut) are consistent with emerging clinical science on biodiversity.   7

 

Example of Diversity Association from Genova Diagnostics:

GI Effects® Comprehensive Profile – Stool

The prevalence of intestinal dysbiosis is the loss of microbiota diversity (LOMD).  8   This loss of microbiota diversity is in part due to the modern Western lifestyle.  9 

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Associative links between Western lifestyle, Human conditions, and loss of microbial diversity (LOMD). On one hand, most of the Human diseases affecting westernized countries are associated with LOMD and on the other hand, some western lifestyle patterns cause LOMD. Then, LOMD appears to play a central role linking western lifestyle and western chronic human conditions.  *LOMD not assessed.  Source:  Gut Microbiota Diversity and Human Diseases: Should We Reintroduce Key Predators in Our Ecosystem?

Bifidobacterium is Critical to a Healthy Gut Microbiota

The most frequently observed intestinal microbiota alteration is the aberrant number or composition of bifidobacteria in the gut microbiota.  The population of bifidobacteria plays a very important role in intestinal homeostasis. 10

The NCBI data base, as of April 2016, holds 254 publicly available bifidobacterial genome sequences, of which sixty one represent complete genome sequences.  11  The Table below lists all the completely sequenced bifidobacterial genomes:  12

Table 1. Summary of all completely sequenced bifidobacterial genomes

A study from 2014 identified the most abundant bifidobacterial species present in the human gut, being represented by:  13

  • B. longum
  • B. pseudolongum
  • B. animalis subsp. lactis
  • B. adolescentis
  • B. bifidum
  • B. pseudocatenulatum
  • B. breve

Studies agree that the most abundant species of bifidobacteria is B. longum.  14  In adults, some studies have identified higher levels of B. adolescentis and B. catenulatum15  

The intestines of healthy breast fed infants are dominated by bifidobacterium. During the first three years of life, the fecal microbiota then gradually develops into the microbiota of adults. 

The strains commonly dominant in infants include:  16  17

  • B. longum
  • B. breve
  • B. bifidum subsp. infantis

However, by adulthood, bifidobacteria is lower but relatively stable and account for 10-20% of intestinal bacteria. 18  The presence of different species of bifidobacteria changes with age, from childhood to old age.

The strains commonly dominant in adults include:

  • B. catenulatum
  • B. adolescentis
  • B. longum

The intestinal flora then begins to again show changes during the transition from middle age to old age.  In old age (starting roughly at age 55), bifidobacterium decrease considerably.  19  20  The reported decline in bifidobacteria population with aging was accompanied by a decrease in species diversity.

FIGURE 1. At birth levels of bifidobacteria are found to be at their highest. In cases of natural childbirth the numbers are highest at birth. In contrast, they are lower in C sectioned babies. Various diseases such as obesity, diabetes and allergies have been associated with lower numbers of bifidobacteria at various stages of life. When weaned onto solid foods diet is more of an intervening factor and an adult-like (stable) microbiota develops. In this figure the authors hypothesize with regard to the relative abundance of bifidobacteria present at each stage of the life cycle, based on the literature cited in the following review by Voreades et al. (2014).  Source:  Gut Bifidobacteria Populations in Human Health and Aging

Certain research demonstrates that the decline in bifidobacteria in old age is associated with the reduction in adhesion to the intestinal mucosa.  21  However, an extrinsic factor, which is the extended use of antibiotics, may indirectly affect the bifidobacteria composition drastically. 22 

The Table below shows the distribution of the most abundant bifidobacterium species in the intestinal microbiota at different stages of life analyzed using different techniques:

Source: Gut Bifidobacteria Populations in Human Health and Aging

The three diagrams/figures below illustrate the fact that the intestinal flora begins to change during the transition from middle age to old age, with a reduction in the bifidobacterium. This reduction in the bifidobacterium has been claimed to be from the effect that aging of physiologic function in the host has on the intestinal bacterial microbiota; and due to this result can further accelerate the aging process.  23

Intestinal Flora and Age

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Changes in the fecal microbiota with increasing age.  Source:  Establishment of Intestinal Bacteriology

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Evolution of some representatives of the intestinal microbiota accordingly to age  Source:  Intestinal microbiota in health and disease: Role of bifidobacteria in gut homeostasis

Researchers have identified differences in the predominant bifidobacterium species or biotypes in different age groups of humans.  24

The Table below shows the frequency of occurrence of species and biotypes of bifidobacteria in feces of various age groups of humans:

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Source:  Establishment of Intestinal Bacteriology

Reduction in Bifidobacterium and Its Link to Various Diseases

Alterations in number and composition of the populations of bifidobacteria is one of the most frequent features present in various diseases.  This loss and reduction of bifidobacteria is called bifidobacterial dysbiosis.

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Bifidobacterial dysbiosis and its relationship with diseases: A target for probiotic intervention. IBD: Inflammatory bowel disease; IBS: Irritable bowel syndrome.   Source:  Intestinal microbiota in health and disease: Role of bifidobacteria in gut homeostasis

Bifidobacteria dysbiosis has been shown to lead to or be a cause of the following disease states:

  • allergy 25
  • atherosclerosis 26  27
  • atopic disease  28  29 
  • autism 30
  • celiac disease  31  32
  • colorectal cancer  33
  • diabetes – type 1 and type 2 34  35  36
  • inflammatory bowel disease 37  38  39
  • intestinal inflammation 40
  • irritable bowel syndrome 41  42  43  44
  • obesity 45  46

The Multiple Benefits of Bifidobacterium

Bifidobacterium has been studied extensively for its multiple benefits on human physiology.  Among the many benefits of bifidobacterium, the important ones include:

  • Bifidobacteria produces a number of potentially health promoting metabolites including:
    • short chain fatty acid acetic acid  47
    • conjugated linoleic acid  48 
    • bacteriocins  (Bacteriocins are an abundant and diverse group of ribosomally synthesized antimicrobial peptides)  49  
  • Bifidobacteria produce lactic acid (lactate) 50  51
  • Bifidobacteria detoxifies toxic substances
    • Bifidobacteria may lower blood ammonia levels  52
    • Bifidobacteria may reduce levels of beta-glucuronidase (activates various carcinogens and mutagens)  53 
    • Bifidobacteria may facilitate the detoxification and excretion of mercury 54
  • Bifidobacteria produce and synthesize B vitamins 55  56
  • Bifidobacteria do not produce the short-chain fatty acid butyrate directly, they do produce lactate that may be transformed in butyrate  57
  • Abundance  of bifidobacterium is associated with higher bacterial gene richness in the gut  58

Repopulating and Increasing Bifidobacterium in the Gastrointestinal Tract

As has been established, the colonic microbiota undergoes certain age related changes that may affect health. Above the age of 55-65 years, populations of bifidobacteria are known to decrease markedly.  59  It is important for persons at or above this age range to be proactive in replacing the lost bifidobacterium and to increase the population of bifidobacterium in the gastrointestinal tract. 

There are three ways in which to increase the population of bifidobacterium in the gastrointestinal tract.  These include:

  • Bifidogenic Factor
  • Bifidobacterium in food
  • Bifidobacterium in supplements (probiotics)

Bifidogenic Factor

A bifidogenic factor, also known as bifidus factor, is a compound that specifically enhances the growth of bifidobacteria in the gastrointestinal tract.  Most of the products available as bifidogenic factors consist of fibers and are known as prebiotics.  Fibrous substrates act as prebiotics for developing a beneficial gut microbiota.

It has been determined that elderly people consume low amounts of fibers which causes a negative impact on gut microbiota diversity.  60   

The following fibers are known to act as bifidogenic factors thus stimulating the growth of bifidobacteria:

  • Amylose  61
  • Apple Pectin  62
  • Fructo-oligosaccharides  63
  • Galactooligosaccharides  64
  • Gum Arabic  65
  • Inulin  66
  • Isomalto-oligosaccharide  67
  • Lactulose  68
  • Larch Arabinogalactan  69
  • Mannooligosaccharides 70
  • Resistant starch 71
  • Transgalactosylatedoligosaccharides  72
  • Xylooligosaccharides  73

In a study from 2010, done with human subjects, resistant starch showed significant growth of bifidobacteria in the gastrointestinal tract.  74  Resistant starch is starch and starch degradation products that avoid digestion in the small intestine and are fermented in the large intestine by beneficial bacteria.  Resistant starch occurs naturally in various foods.  The Table below list those foods in which resistant starch naturally occurs:

Examples of naturally occurring resistant starch*
Food Serving size Resistant starch
(grams)
Banana flour, from green bananas 1/4 cup, uncooked 10.5-13.2
Banana, raw, slightly green 1 medium, peeled 4.7
High amylose RS2 corn resistant starch 1 tablespoon (9.5 g) 4.5
Oats, rolled 1/4 cup, uncooked 4.4
Green peas, frozen 1 cup, cooked 4.0
White beans 1/2 cup, cooked 3.7
Lentils 1/2 cup cooked 2.5
Cold pasta 1 cup 1.9
Pearl barley 1/2 cup cooked 1.6
Cold potato 1/2″ diameter 0.6 – 0.8
Oatmeal 1 cup cooked 0.5

Source:  Wikipedia – Resistant Starch

Another bifidogenic factor, other than a specific fiber, is actually a beneficial bacteria found in the human gastrointestinal tract, called propionibacterium freudenreichii.  Propionibacterium freudenreichii produces a Bifidogenic Growth Stimulator (BGS) named ACNQ which selectively enhances the utilization of oligosaccharides by bifidobacteria.  75

Bifidobacterium in Food

Foods rich in bifidobacteria are not widespread and mostly include fermented dairy products.  The most common fermented dairy products that contain bifidobacteria include:

  • Yogurt (Cow and goat milk)
  • Kefir (Cow and goat milk)
  • Lassi (yogurt drink from the Indian subcontinent)

The Table below lists the various bifidobacterium strains found in each of the three fermented dairy products:

Bacteria

Yogurt

Kefir

Lassi

B. bifidus

X

X

 

B. animalis

X

 

 

B. animalis BB-12

 

X

 

B. lactis

 

X

X

B. lactis BB-12

X

 

 

B. breve

 

X

X

B. longum

 

X

X

B. regularis

X

 

 

Propionibacterium freudenreichii

 

 

X

Note:  Not all the commercially available products may contain all the listed bifidobacteria strains

Bifidobacterium in Supplements (Probiotics)

Other than the three fermented dairy products, no other foods contain bifidobacterium in any great quantities.  It therefore may be necessary to supplement with a combination of bifidobacterial strains in the form of a probiotic supplement in order to increase the gastrointestinal tract with bifidobacterium.

Consuming probiotic supplements that contain bifidobacteria can be very beneficial and efficient in obtaining proper quantities of bifidobacteria.  There are probiotic products that specifically contain only bifidobacteria strains and others that contain mixtures of bifidobacteria strains and lactobacillus strains.

Some of the more common strains of bifidobacterium species and strains found in probiotic products include:

  • B. adolescentis
  • B. animalis
  • B. bifidum
  • B. breve
  • B. infantis
  • B. lactis
  • B. lactis DN-173 010
  • B. lactis DR10
  • B. lactis HN019
  • B. longum
  • Bifantis
  • Bifidus DR10
  • Bifidus Regularis
  • HOWARU Bifido

Colon's friendly bifidobacteria population decreases from the age of 50

Bifidobacteria Levels Decline With Age How To Replace Bifidobacteria

Cover image credits from www.sott.net

The Multiple Health Benefits of Tributyrin, a Triglyceride Form of Butyrate

Short-Chain Fatty Acids

A considerable amount of scientific interest has been focused on short chain fatty acids (SCFAs) for improving colonic and systemic health, and specifically reducing the risk of inflammatory diseases, diabetes, and cardiovascular disease.

Researchers have shown that SCFAs have distinct physiological effects:  1

  • they contribute to shaping the gut environment
  • they influence the physiology of the colon
  • they can be used as energy sources by host cells and the intestinal microbiota 
  • they also participate in different host-signaling mechanisms

Prebiotics, which consist of primarily dietary carbohydrates such as resistant starch and dietary fibers, are the substrates in the large intestine for fermentation that produce SCFAs.  The other source of SCFA, although in smaller amounts than dietary carbohydrates, are amino acids.  Three amino acids:

  • valine
  • leucine
  • isoleucine

obtained from protein breakdown can be converted into isobutyrate, isovalerate, and 2-methyl butyrate, known as branched-chain SCFAs (BSCFAs), which contribute very little (5%) to total SCFA production.  2

There are seven short-chain fatty acids that are produced by the large intestine through the fermentation of dietary fiber and resistant starch.  Of these seven short-chain fatty acids, three of them are the most important and common:

  • acetate
  • propionate
  • butyrate

These three represent about 90–95% of the SCFA present in the colon.  The rate and amount of SCFA production depends on the species and amounts of microflora present in the colon, the substrate source and gut transit time.

Butyrate is the major energy source for colonocytes. Propionate is largely taken up by the liver. Acetate enters the peripheral circulation to be metabolized by peripheral tissues and is the principal SCFA in the colon, and after absorption it has been shown to increase cholesterol synthesis.

Image result for Short-Chain Fatty Acids

Figure 1.  Fibers, specific oligosaccharides and resistant starch reach the colon intact, where they induce shifts in the composition and function of intestinal bacteria (shifts indicated by different colors). Intestinal bacteria use these compounds as substrates for the production of the short-chain fatty acids acetate, propionate and butyrate. These microbial metabolites are taken up by intestinal epithelial cells called enterocytes. Butyrate mainly feeds the enterocytes, whereas acetate and propionate reach the liver by the portal vein.  (Source:  You are what you eat,  Nature Biotechnology  32, 243–245 (2014) doi:10.1038/nbt.2845)

Butyrate (Butyric Acid)

The most important short-chain fatty acid is butyrate.

Butyrate is a primary energy source for colonic cells.  3 4   Butyrate also has demonstrated anti-inflammatory properties.  5  Butyrate may also have a role in preventing certain types of colitis. A diet low in resistant starch and fiber, which will result in a low production of SCFAs in the colon, may explain the high occurrence of colonic disorders seen in the Western civilization.  6

Studies have demonstrated that butyrate has anti-carcinogenic properties:

  • It inhibits the growth and proliferation of tumor cell lines in vitro.  7
  • It induces differentiation of tumor cells, producing a phenotype similar to that of the normal mature cell.  8
  • It induces apoptosis or programmed cell death of human colorectal cancer cells.  9 10
  • It inhibits angiogenesis by inactivating Sp1 transcription factor activity and down regulating VEGF gene expression. 11

Butyrate has been studied for its role in nourishing the colonic mucosa and in the prevention of cancer of the colon, by promoting cell differentiation, cell-cycle arrest and apoptosis of transformed colonocytes; inhibiting the enzyme histone deacetylase and decreasing the transformation of primary to secondary bile acids as a result of colonic acidification.

Therefore, a greater increase in SCFA production and potentially a greater delivery of SCFA, specifically butyrate, to the distal colon may result in a protective effect.   12

Butyrate is mainly taken up by the colon epithelial cells, only small amounts reach the portal vein and the systemic circulation.  The primary beneficial effects of butyrate occurs at the intestinal level, yet there are additional benefits at the extra intestinal level:

Intestinal effects

  • Is the preferred energy source for the colon epithelial cells
  • Decreases the pH of the colon (which decreases bile salt solubility, increases mineral absorption, decreases ammonia absorption, and inhibits growth of pathogens)
  • Stimulates proliferation of normal colon epithelial cells
  • Prevents proliferation and induces apoptosis of colorectal cancer cells
  • Affects gene expression of colon epithelial cells
  • Plays a protective role against colon cancer and colitis
  • Improves the gut barrier function by stimulation of the formation of mucin, antimicrobial peptides, and tight-junction proteins
  • Interacts with the immune system and regulates immune function
  • Has anti-inflammatory effects
  • Stimulates the absorption of water and sodium
  • Reduces oxidative stress in the colon
  • Assists in ion absorption
  • Assists in proper intestinal motility
  • Induces cell cycle arrest, differentiation, and apoptosis in colon cancer cells

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Figure 2.  The multiple effects of butyrate at the intestinal level.  (Source:  Potential beneficial effects of butyrate in intestinal and extra intestinal diseases)

Extra intestinal effects  13

  • Insulin sensitivity
  • Cholesterol synthesis
  • Energy expenditure
  • Ammonia scavenger
  • Stimulation of β-oxidation of very long chain fatty acids and peroxisome proliferation
  • CFTR function
  • Neurogenesis
  • HbF production

Tributyrin

The major problem with butyrate is achieving high concentrations in the blood. Butyrate is metabolized rapidly as soon as it enters the enteroocytes via its active transport system, and its plasma concentrations are far below those required to exert its antiproliferative/differentiating actions.  14 

An alternative and more advantageous form of butyric acid is the triglycerine form called Tributyrin, also known as glyceryl tributyrate. Tributyrin is a triglyceride containing 3 molecules of butyric acid which are bound by a glycerol molecule. 

Tributyrin is naturally present in butter in trace amounts.  However, it is not recommended to consume butter as a means to obtain therapeutic amounts of tributyrin.  There is no point to recommend consuming butter to someone if the intention is to increase butyric acid consumption.

As an alternative to consuming butter, tributyrin can now be consumed in the form of a supplement or a food additive and can provide considerable amounts of butyrate to the intestine in addition to the endogenous production of SCFAs (butyrate) from the fermentation of dietary fibers.

Tributyrin is known to overcome the pharmacokinetic drawbacks of butyrate.  Because it is rapidly absorbed and chemically stable in plasma, tributyrin diffuses through biological membranes and is metabolized by intracellular lipases, releasing therapeutically effective butyrate over time directly into the cell. 

Ball-and-stick model of the butyrin molecule

Figure 3.  Ball-and-stick model of the tributyrin molecule, the triglyceride of butyric acid.  Source:  By Jynto (talk) – Own workThis chemical image was created with Discovery Studio Visualizer., CC0, https://commons.wikimedia.org/w/index.php?curid=20234384

The technique of attaching butyrate to a glycerol molecule turns the new molecule (tributyrin) into a fat. The attachment of a glycerol molecule to 3 butyric acid molecules is through an ester bond which can only be broken by a specific enzyme called pancreatic lipase.  

Pancreatic lipase is secreted from the pancreas into the small intestine (duodenum) and not in the stomach.  Because of this, tributyrin stays intact in the stomach but once it reaches the small intestine (duodenum), the 3 butyric acid molecules are released by the pancreatic lipase enzyme. 

After the pancreatic lipase action, two free butyric acid molecules and one monobutyrin molecule are formed where they are used in the intestine and taken up by the enterocytes. After transportation through the portal vein they are metabolized in the liver. 

chem formula

Figure 4.  Ester bond of glycerol and 3 butyric acid molecules.  (Source: Bioremediation of Fats and Oils)

The tributyrin form of butyrate ensures high bioavailability of butyrate in all the sections of the small intestine.  Because tributyrin is a delayed release source of butyrate, it achieves more sustained plasma levels. 

According the the U.S. Federal Drug Administration (FDA), tributyrin is a food substance affirmed as Generally Recognized As Safe (GRAS).  15

Multiple Health Benefits of Tributyrin 

Specific studies on tributyrin have demonstrated multiple benefits in a number of disease conditions by releasing therapeutically effective butyrate over time directly into the cell.  The advantage with tributyrin is that it has all the health benefits of butyrate, as evidenced above, as well as its own specific targeted health benefits.

Some of the more important and specific health benefits of tributyrin include:

  • Anticarcinogenic potential
    • Colon cancer
    • Leukemia
    • Melanoma
    • Liver cancer (apoptosis)
  • Alzheimer’s disease and Dementia
  • Antibiotic-associated diarrhea (AAD)
  • Lipopolysaccharide (LPS)-induced liver injury
  • Inflammation

Anticarcinogenic potential

In vitro and in vivo studies have shown that tributyrin acts on multiple anticancer cellular and molecular targets without affecting non-cancerous cells. The mechanisms of action of tributyrin as a anticarcinogenic agent include:  16

  • the induction of apoptosis
  • cell differentiation
  • the modulation of epigenetic mechanisms

Due to the minimum toxicity profile of tributyrin, it is an excellent candidate for combination therapy with other agents for the control of cancer. 

Colon cancer

Tributyrin was shown to be more potent in inhibiting growth and inducing cell differentiation than natural butyrate on growth, differentiation and vitamin D receptor expression in Caco-2 cells, a human colon cancer cell line.  17

Tributyrin provides a useful therapeutic approach in chemoprevention and treatment of colorectal cancer.   

In another in vitro study, tributyrin showed potent antiproliferative, proapoptotic and differentiation-inducing effects in neoplastic cells.  18

Leukemia

In this study monobutyrin (MB) and tributyrin (TB) were studied in vitro for their effects on inducing differentiation of human myeloid leukemia HL60 cells and murine erythroleukemia cells. On a molar basis TB was about 4-fold more potent than either BA or MB for inducing differentiation of HL60 cells. BA, MB, or TB induced erythroid differentiation of murine erythroleukemia cells.  19

Melanoma

A study from February 2011 sought to investigate a possibility to develop tributyrin emulsion as a potent anti-cancer agent against melanoma. Tributyrin emulsion was more potent than butyrate in inhibiting the growth of B16-F10 melanoma cells. Accumulation of cells at sub G(0)/G(1) phase and the DNA fragmentation induced by tributyrin emulsion treatment revealed that tributyrin emulsion inhibited the growth of B16-F10 cells by inducing apoptosis. Treatment with tributyrin emulsion suppressed the colony formation of melanoma cells in a dose-dependent manner.  20

The data from this study suggests that tributyrin emulsion may be developed as a potent anti-cancer agent against melanoma.

Liver cancer

Researchers in this study from November 1999 investigated whether butyrate could induce apoptosis in transformed human liver (Hep G2) cells. Hep G2 cells treated with butyrate displayed acetylated histones, increased DNA fragmentation and morphological features consistent with apoptosis. 

They also investigated whether butyrate present in tributyrin, a triacylglycerol more compatible for inclusion into colloidal lipid structures than butyrate, could also induce apoptosis in Hep G2 cells.

Tributyrin induced DNA fragmentation and morphological features characteristic of apoptotic cells in Hep G2 cells.

These results are a significant advance towards delivering butyrate via colloidal lipid particles to cancerous sites in vivo. This study showed that butyrate and tributyrin are potent apoptotic agents. 21

Alzheimer’s disease and Dementia

Recent research at MIT has determined that, in rodent models of Alzheimer’s dementia, the negative impact of amyloid beta exposure on neuronal function and new memory formation results largely from increased neuronal expression of an enzyme known as HDAC2 (histone deacetylase 2).

A study from March 2004 showed that tributyrin may have the most practical potential to inhibit HDAC by blunting microglial activation. Tributyrin is anti-inflammatory in primary, brain-derived microglial cells.  A blunting of microglial cytokine production might in itself have a favorable impact on progression of Alzheimer’s.  22  23  

Antibiotic-associated diarrhea (AAD)

In a recent study from November 2014, researchers hypothesized that antibiotic-induced changes in gut microbiota reduce butyrate production, varying genes involved with gut barrier integrity and water and electrolyte absorption, lending to AAD, and that simultaneous supplementation with the probiotic Lactobacillus GG  and/or tributyrin would prevent these changes.

Optimizing intestinal health with Lactobacillus GG and/or tributyrin may offer a preventative therapy for AAD.  24  Lipopolysaccharide (LPS)-induced liver injury

In this study from April 2015, researchers elucidated the protective effect of oral administration of tributyrin against LPS-mediated lipid metabolism disorder in rats.  Tributyrin suppresses lipopolysaccharide (LPS)-induced liver injury through attenuating nuclear factor-κB activity with an increased hepatoportal butyrate level.  25

Inflammation

Another study from May 2015 was carried out to investigate the effects of tributyrin (TB) on the growth performance, pro-inflammatory cytokines, intestinal morphology, energy status, disaccharidase activity, and antioxidative capacity of broilers challenged with lipopolysaccharide (LPS).

Taken together, these results suggest that the TB supplementation was able to reduce the release of pro-inflammatory cytokines and improve the energy status and anti-oxidative capacity in the small intestine of LPS-challenged broilers.  26

ELiE Health Solutions

Tributyrin is now available for purchase by consumers and professionals directly from ELiE Health Solutions as a product called BUTYCAPS.

ELiE Health Solutions, based in Sevilla, Spain, was formed through a project based on the science of the microbiota and probiotics.

ELiE Health Solutions is named after Elie Metchnikoff, famed microbiologist and the recipient of the 1908 Nobel Price in Physiology. A century ago he proposed the benefit of acid lactic bacteria to the human host and their role in health and longevity.

David Manrique, a pharmacist with ELiE Health Solutions describes the challenges of finding a more bio-available form of butyric acid:

“The challenge was to find a chemical form of enteric release of butyric acid, and also to ensure microencapsulated as slowly and delayed release possible. It has been a great innovative effort, but we are very satisfied with the results.”  27 

ELiE Health Solutions was successful in developing a delayed release form of butyric acid (tributyrin) using microencapsulation technology in their product BUTYCAPS.  The microencapsulation technology of BUTYCAPS allows a slower and gradual release along the intestine. 

BUTYCAPS contains 900 mg of Tributyrin equivalent to 787 mg of butyric acid in each sachet. Each box contains 30 sachets.  BUTYCAPS are non-chewable granules.

170126_3dbutycaps

Figure 5.  BUTYCAPS product from ELiE Health Solutions

BUTYCAPS can be purchased directly from ELiE Health Solutions. 

Figure 6.  Formulation process of microencapsulated tributyrin. (Source:  ELiE Health Solutions)

Resources:

Purchase BUTYCAPS

Cover photo:  Enterocytes were butyrate is taken up in the intestine (Source)

Exogenous Glycation: How Many Glycotoxins are You Consuming in Your Diet?

When sugars are cooked with proteins or fat at temperatures over 120°C (~248°F) or at lower temperatures for longer cooking times, a molecule known as advanced glycation end products (AGE) is formed. This AGE is known as exogenous gylcation, as opposed to endogenous glycation, which is created inside the body by metabolic processes.

These orally absorbed reactive glycation products are also known as “glycotoxins” or dietary AGE products (dAGE). The dAGE products are known to contribute to increased oxidant stress and inflammation, and may result in diabetes and cardiovascular disease.

An article that appeared in the Annals of the New York Academy of Sciences in 2006 by Helen Vlassara entitled: Advanced glycation in health and disease: role of the modern environment, demonstrated that there is evidence from animal studies that point to AGE restriction as an effective means for extending median life span, similar to that previously shown by marked caloric restriction. The authors conclusion is quite definitive:

“We conclude that excessive AGE consumption, in the current dietary/social structure, represents an independent factor for inappropriate oxidant stress responses, which may promote the premature expression of complex diseases associated with adult life, such as diabetes and cardiovascular disease.”

(Source: Advanced glycation in health and disease: role of the modern environment.)

Most, if not all, processed foods has some measure of dAGE. Food manufactures will add sugar to their products to enhance the browning effect, thus contributing to the addition of dAGE’s. Any food that is caramelized and browned contains dAGE’s.

The Journal of the Academy of Nutrition and Dietetics published a very interesting Table listing the advanced glycation end product (AGE) content of 549 foods, based on carboxymethyllysine content.

View Table

The method of cooking is also crucial to the production of exogenous AGE’s. Specifically, grilling, broiling, searing, roasting, and frying produce and accelerate new AGE formation in food.

Animal-derived foods that are high in fat and protein have been shown to have higher AGE products and especially after cooking these animal products using the methods described above. Carbohydrate-rich foods such as vegetables, fruits, whole grains, contain relatively few AGEs, even after cooking.

In the August 2004 Journal of the American Dietary Association an article entitled: Advanced glycoxidation end products in commonly consumed foods, listed some interesting results regarding the dAGE content of certain food and the highest dAGE for each cooking method:

“Foods of the fat group showed the highest amount of AGE content with a mean of 100+/-19 kU/g. High values were also observed for the meat and meat-substitute group, 43+/-7 kU/g. The carbohydrate group contained the lowest values of AGEs, 3.4+/-1.8 kU/g. The amount of AGEs present in all food categories was related to cooking temperature, length of cooking time, and presence of moisture. Broiling (225 degrees C) and frying (177 degrees C) resulted in the highest levels of AGEs, followed by roasting (177 degrees C) and boiling (100 degrees C).”

(Source: Advanced glycoxidation end products in commonly consumed foods.)


References:

Orally absorbed reactive glycation products (glycotoxins): An environmental risk factor in diabetic nephropathy

Advanced Glycation End Products in Foods and a Practical Guide to Their Reduction in the Diet

Advanced glycation in health and disease: role of the modern environment.

Advanced glycoxidation end products in commonly consumed foods.

Live Longer By Changing How You Cook! By William Faloon Life Extension Magazine August 2015


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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

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

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
Alkaloids:
HordenineX1
SynephrineXX2
Amines:
OctopamineX1
N-MethyltyramineX1
TyramineX1
Carotenoids:
Alpha-CaroteneX1
Beta-CaroteneXXXX4
CryptoxanthinXX2
LuteinXX2
LycopeneX1
ZeaxanthinXX2
Furocoumarins:
BergamottinX1
BergaptenX1
BergaptolX1
Limonoids
LimoninXXXXX5
NomilinXXXXX5
Nomilinic acidXXXXX5
Organic Acids:
Citric AcidXXXX4
Glycyrrhetinic AcidX1
P-Coumaric AcidX1
Sinapic AcidX1
Polyphenols:
AnthocyanidinsX1
CyanidinX1
DephinidinX1
DidyminX1
DiosminXX2
EriocitrinXXX3
HesperidinXXXX4
KaempferolX1
NaringeninX1
NaringinX1
NobiletinX1
QuercetinX1
RutinXX2
TangeritinXXX3
Terpenoids:
CarvoneX1
CitralXXXX4
CitronellalX1
LimoneneXXX3

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
Limonoids
  • 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

Alpha-Carotene

CancerAbstractReference
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
Neuroblastoma
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

Cryptoxanthin

CancerAbstractReference
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
Neuroblastoma
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

Lutein

CancerAbstractReference
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

Lycopene

CancerAbstractReference
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
Gliomas
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
Leukemia
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

Zeaxanthin

CancerAbstractReference
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
Neuroblastoma
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

Limonin

CancerAbstractReference
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

Nomilin

CancerAbstractReference
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
Melanoma
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

CancerAbstractReference
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
Neuroblastoma
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

CancerAbstractReference
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.

Limonene

CancerAbstractReference
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
Leukemia
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
Lymphomas
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.

Limonin

CancerAbstractReference
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)

Anthocyanidins

CancerAbstractReference
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

Cyanidin

CancerAbstractReference
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
Leukemia
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

Didymin

CancerAbstractReference
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

Diosmin

CancerAbstractReference
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

Hesperidin

CancerAbstractReference
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
Leukemia
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

Kaempferol

CancerAbstractReference
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
Leukemia
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)

Naringenin

CancerAbstractReference
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
Melanoma
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

Naringin

CancerAbstractReference
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
Melanoma
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

Nobiletin

CancerAbstractReference
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
Leukemia
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

Quercetin

CancerAbstractReference
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
Gliomas
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
Leukemia
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
Melanoma
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

Rutin

CancerAbstractReference
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
Melanoma
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

Tangeritin

CancerAbstractReference
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
Leukemia
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
Melanoma
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