Functional Foods and Nutraceuticals. Kempherol, Quercetin, and resveratrol. Dr. K. Bhaskarachary. Description of Module

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1 Component I (A) Role Name Affiliation Principal Investigator Dr. Sheela Ramachandran Avinashilingam Institute for Home Science and Higher Education for Women, Coimbatore. Co-Principal Investigators Dr. S.Kowsalya Dr.M.Sylvia Subapriya Dr.G. Bagyalakshmi Mrs.E.Indira Avinashilingam Institute for Home Science and Higher Education for Women, Coimbatore. Paper Coordinator Dr. S. Thilakavathy Avinashilingam Institute for Home Science and Higher Education for Women, Coimbatore. Content Writer Senior Research Officer Dept. Food Chemistry National Institute of Nutrition Jamai Osmania, Hyderabad Content Reviewer Senior Research Officer Dept. Food Chemistry National Institute of Nutrition Jamai Osmania, Hyderabad Language Editor Senior Research Officer Dept. Food Chemistry National Institute of Nutrition Jamai Osmania, Hyderabad Component-I (B) Description of Module Items Subject Name Paper Name Module Name Module ID Pre-requisites Description of Module Foods and Nutrition Functional Foods and Nutraceuticals Kempherol, Quercetin, and resveratrol F11FN15 Pro-oxidant and mutagenic effects of Quercetin, Kempherol and resveratrol Objectives To know the rich sources, metabolism, bioavailability and health benefits of Quercetin, Kempherol and resveratrol Keywords Quercetin, Kempherol, resveratrol, flavonoid glycosides, glucoside, glucuronidation, radio activity, carcinogen activating genes and enzymes 1

2 and carcinogen detoxification. Introduction There has been a great deal of interest in the potential health benefits of flavonoids and phenolic compounds present in fruits and vegetables. The biological effects of these compounds, as shown by numerous in vitro and animal studies, suggest that they may be protective against cancer, cardiovascular, inflammatory and other diseases. Several in vitro studies have also suggested pro-oxidant and mutagenic effects. Although there have been great strides in understanding the occurrence, bio-availability and activities of these compounds, relatively little is known of their in vivo effects in humans. Quercetin and kaempferol are widely distributed flavonols found, typically as glycosides, in many fruits and vegetables. Resveratrol, present in red wine, has received particular attention for its potential role in preventing cardiovascular disease. Objectives After completing this module, the learner will be able to know the rich sources, metabolism, bioavailability and health benefits of quercetin know the rich sources, metabolism, bioavailability and health benefits of kaempferol know the rich sources, metabolism, bioavailability and health benefits of resveratrol Quercetin Quercetin is a typical flavonoid ubiquitously present in fruits and vegetables, and its antioxidant effect is implied to be helpful for human health. Quercetin has been proposed to have antiatherogenic, anti-inflammatory, and anti-hypertensive properties leading to the beneficial effects against cardiovascular diseases. Food Sources The edible portion of some foodstuffs has an unusually high concentration of quercetin. High concentration of quercetin is present in onions ( mg/kg), kale (110 mg/kg), french beans 2

3 (32~,5 mg/kg), broccoli (30 mg/kg), lettuce (14 mg/kg) and tomatoes (8 mg/kg). Among the fruit examined, the quercetin concentration averaged 15 mg/kg, with apples having the highest concentration (21-72 mg/kg). The quercetin concentration in beverages such as beer, coffee, chocolate milk and white wine were below 1 mg/litre. By contrast, the quercetin concentration in red wine ranged from 4 to 16 mg/litre, while grape juice contained 7-9 mg/litre. Fruit juices other than lemon (7 mg/litre) and tomato (13 mg/litre) contained below 5mg/litre quercetin. Tea infusions were the highest, ranging in quercetin concentration from 10 to 25mg/litre. Since approximately 5% of the flavonoids consumed exist as quercetin. Daily consumption of at least 50 mg quercetin was a reasonable assumption for the American diet; however, a report from the National Toxicology Program suggested a more conservative estimate of 25 mg/day/person. Health Benefits The antidengue virus properties of quercetin, hesperetin, naringin, and daidzein at different stages of DENV-2 (dengue virus type-2) infection and replication cycle were analysed. Quercetin was found to be most effective against DENV-2 in Vero cells. Many flavonoids, namely, dihydroquercetin, dihydrofisetin, leucocyanidin, pelargonidin chloride, and catechin, show activity against several types of virus including HSV, respiratory syncytial virus, polio virus and Sindbis virus. Inhibition of viral polymerase and binding of viral nucleic acid or viral capsid proteins have been proposed as antiviral mechanisms of action. Absorption of Quercetin The absorption of quercetin from regular foods in man was studied in ileostomy subjects who lack a colon with the bacterial flora. These subjects were chosen to circumvent the problem of microbial degradation. Absorption of the quercetin glycosides from onions (52%) was far better than that of the pure aglycone (24%). Absorption of pure rutin (quercetin-3-orhamnosylglucoside), a major glycoside in tea, was 17%. Thus some glycosides can be absorbed in man as such without prior hydrolysis by microorganisms. Recent studies, however, indicate that flavonoid glycosides can be absorbed without hydrolysis. Thus, absorption of pure quercetin was lower than that of quercetin glycosides present in onion and evidence for flavonoid glycosides being present in human plasma has been reported. Bioavailability and Pharmacokinetics of Quercetin The bioavailability of quercetin glycosides should be clarified, because dietary quercetin is mostly present as its glycoside form. Although quercetin glycosides are subject to deglycosidation by enterobacteria for the absorption at large intestine, small intestine acts as an 3

4 effective absorption site for glucose-bound glycosides (quercertin glucosides). This is because small intestinal cells possess a glucoside-hydrolyzing activity and their glucose transport system is capable of participating in the glucoside absorption. A study using a cultured cell model for intestinal absorption explains that the hydrolysis of the glucosides accelerates their absorption in the small intestine. Small intestine is also recognized as the site for metabolic conversion of quercetin and other flavonoids as it possesses enzymatic activity of glucuronidation and sulfation. Modulation of the intestinal absorption and metabolism may be beneficial for regulating the biological effects of dietary quercetin. Most flavonoids enter the diet as glycosides, with quercetrin and rutin as the most common flavonoids glycosides consumed. The hydrophdic nature of glycosides and their relative high molecular weight precludes absorption in the small intestine. Furthermore, flavonoid flglycosides resist intestinal hydrolases; consequently, flavonoid glycosides can pass unaltered into the large intestine. The resident microflora of the bowel produce glycosidases capable of releasing the aglycone from its sugar. In addition, the resident microftora can cleave the pyrone ring (ring C) producing phenyl acetic and phenyl propionic acids and other derivatives. But since glycosidase activity proceeds at a faster rate than ring cleavage, the intact flavonoid aglycone can persist in the large intestine with the clear potential for absorption. These anticipated results were verified in human and animal studies. In human trials, orally administered rutin (quercetin rutinoside) and quercetin were not found in the urine (or plasma in an unaltered form even at doses of mg/kg body weight. However, 53% of the orally administered dose was recovered as the aglycone in faeces but only within the first 3 days. It was assumed that the remainder of the quercetin underwent microbial degradation in the lower bowel. In animal studies, the metabolite, phenyl acetic acid, was found in urine after the oral administration of quercetin. In a more definitive study, 14C-labelled quercetin was administered orally to rats which were killed after 12 hr. Only 80% of the administered radioactivity was recovered, with the major portion (44%) of the radioactivity found in the intestinal contents (primarily the lower bowel). Of the remaining radioactivity, 15% was respired, 12% was found in lung tissue, 3% in the wall of the large intestine, less than 1% in blood, kidney and gastric wall, and only 4% in the urine, but not as quercetin. Radioactivity was not detected in the liver, spleen, heart and brain. Apparently free flavonoids do not persist in the general circulation or the enterohepatic circulation after ingestion. 4

5 Dietary flavonols glycosides showed very rapid to very slow absorption in man; times to reach peak concentrations (T max ) were between, 0.5 and 9h. The bioavailability of quercetin glucosides from onion was superior to that of various quercetin glycosides from apples (30%) and of pure quercetin rutinoside (30%). Onions contain mainly quercetin β-glucosides, whilst apples contain a mixture of quercetin-β-galactosides and quercetin-β-xylosides, whereas quercetin is bound to a disaccharide in rutin. These data suggested that the sugar moiety of quercetin glycosides is an important determinant of their absorption and bioavilability. Onions contain mainly quercetin-β-glucosides and quercetin- β-xylosides, whereas quercetin is bound to a disaccharide in rutin. These data suggested that the sugar moiety opf quercetin glycosides is ana important determinant of their absorption and bioavailability. The effect of the sugar moiety on the absorption of quercetin was confirmed when pure quercetin- β-glucoside or pure quercetinβ-rutinoside. Kaempferol The accumulation of flavonols such as kaempferol and its glycosides is induced by both wounding and pollination in petunia stigmas and appears to be required for normal pollen development in plants. Anthocyanins and flavones increase in response to high visible light levels, and it is thought that these compounds help attenuate the amount of light reaching the photosynthetic cells. UV irradiation induces flavonoids (particularly kaempferol derivatives) and sinapate esters in Arabidopsis and isoflavonoids and psoralens in other species. These UVabsorbing compounds are thought to provide a means of protection against UV-B damage and subsequent cell death by protecting DNA from dimerization and breakage. Food Sources Kaempferol (3,5,7-trihydroxy-2-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) is a flavonoid found in many edible plants (e.g. tea, broccoli, cabbage, kale, beans, endive, leek, tomato, strawberries and grapes) and in plants or botanical products commonly used in traditional medicine (e.g. Ginkgo biloba, Tilia spp, Equisetum spp, Moringa oleifera, Sophora japonica and propolis). Some epidemiological studies have found a positive association between the consumption of foods containing kaempferol and a reduced risk of developing several disorders such as cancer and cardiovascular diseases. Numerous preclinical studies have shown that kaempferol and some glycosides of kaempferol have a wide range of pharmacological activities, 5

6 including antioxidant, anti-inflammatory, antimicrobial, anticancer, cardioprotective, neuroprotective, antidiabetic, anti-osteoporotic, estrogenic/antiestrogenic, anxiolytic, analgesic and antiallergic activities. Health benefits Like other flavonoids, kaempferol has a diphenylpropane structure and is synthesized by condensation of 4-coumaroyl-CoA with three molecules of malonyl- CoA. This reaction, catalyzed by the enzyme chalcone synthase, results in the formation of the flavonoid naringenin chalcone. This chalcone is transformed into the flavanone naringenin by the enzyme chalcone isomerase, which catalyzes the closure of the C3 ring. The enzyme flavanone 3- dioxygenase introduces a hydroxyl group in naringenin at C3 to form dihydrokaempferol. Finally, the enzyme flavonol synthase introduces a double bond in dihydrokaempferol at C2-C3 to produce kaempferol. Because the enzymes involved in the biosynthesis of kaempferol are relatively common in the plant kingdom, it is not surprising that this flavonoid is widely distributed in plants. Sugars such as glucose, rhamnose, galactose and rutinose are usually bound to kaempferol to form glycosides. Some glycosides of kaempferol are very common in nature (e.g. kaempferol-3-o-glucoside, also called astragalin), because their biosynthesis only requires additional enzymes that are widespread in the plant kingdom (e.g. flavonol 3-Oglucosyltransferase. The enzymes involved in the biosynthesis of some other kaempferol glycosides are more restricted in nature and, therefore, these glycosides will only be synthesized by plant species with the genetic information required to code for such enzymes. For instance, kaempferol-3-(p-coumaroyltriglucoside) is not widelydistributed in plants, as its biosynthesis requires the presence of three additional enzymes that are not widespread: flavonol-3-oglucoside glucosyltransferase, flavonol-3-o-diglycoside glucosyltransferase and flavonol-3-otriglucoside p-coumaroyltransferase. Kaempferol (3, 4, 5, 7-tetrahydroxyflavone) is a flavonoid that is widely distributed in onion, kale, endive and tea. It has been shown to exhibit cancer chemopreventive efficacy against many types of cancers including hepatocellular carcinoma, breast, lung and prostate. The estimate of human intake of all flavonoids was a few hundred milligrams to 650 mg/d. Total average intake of flavonols (quercetin, myricetin, and kaempferol) and flavones (luteolin and apigenin), major flavonoids in human diet, was estimated at 23 mg/d, of which quercetin contributed ~70%, kaempferol 17%, myricetin 6%, luteolin 4%, and apigenin 3%. The total intake of flavonoids (quercetin, myricetin, kaempferol, luteolin, and ficetin) was inversely associated with the LDL cholesterol and plasma total cholesterol concentrations. 6

7 Possible mechanisms of chemoprevention by Kaempferol include inhibition of a carcinogen activating genes and enzymes, enhancing carcinogen detoxification by inducing the phase II detoxifying genes and enzymes. It has ability to scavenge free radicals and modulate several signaling pathways leading ultimately to cancer cell apoptosis. Endive (Cichorium endivia L.) (an edible Mediterranean plant, the bitter leaves of which may be used in salads) is a rich source of kaempferol, containing up to 246mg kaempferol per kg fresh weight. Further, the majority of the kaempferol in endive is present as an uronic acid conjugate (kaempferol-3-glucuronide) rather than a glycoside; nothing is known about the absorption of glucuronosyl flavonoid conjugates, which also enter the gut via the bile duct after metabolism in the liver (ie enterohepatic circulation). Epidemiological data suggest that a high intake of kaempferol-containing foods may reduce the risk of developing several types of cancers (e.g. lung, gastric, pancreatic and ovarian cancer) and cardiovascular diseases. But the relatively low number of studies and the possible presence of other bioactive constituents in kaempferol containing foods (e.g. vitamins, minerals and other phytochemicals) make these data insufficient to draw any conclusion regarding the possible protective effect of kaempferol in these diseases. Pharmacokinetics of Kaempferol The pharmacokinetics of kaempferol has been studied in vitro and in vivo, both in rats and humans. An overview of the pharmacokinetics of kaempferol is illustrated in Fig. (1). Flavonols such as kaempferol are commonly ingested as glycosides. It is recognized that the high polarity of glycosides hinders their absorption, whereas the intermediate polarity of aglycones facilitates it. Although this suggests that the absorption of glycosides needs the previous hydrolysis to absorbable aglycones, studies have shown that glycosides can be absorbed without hydrolysis. 7

8 Fig. (1). Overview of the pharmacokinetics of kaempferol (see text for details). K: kaempferol; KG: kaempferol glycosides; KCF: kaempferol conjugated forms; PA: phenolic acids; A: absorption, M: metabolism; E: excretion Like other flavonoids, kaempferol is mainly absorbed in the small intestine. The lipophilicity of kaempferol facilitates its absorption by passive diffusion, but evidence suggests that it can also be absorbed by facilitated diffusion or active transport. Kaempferol can be metabolized in the small intestine (to glucuronides and sulfoconjugates) by intestinal conjugation enzymes. Like other flavonoids, kaempferol glycosides and kaempferol are extensively metabolized by the colon microflora. The colonic bacteria can both hydrolyze the glycosides to aglycones and break the C3 ring of aglycones to form simple phenolic compounds such as 4-hydroxyphenylacetic acid, phloroglucinol and 4- methylphenol, which can either be absorbed or excreted in feces. After absorption, kaempferol is extensively metabolized in the liver to form glucurono- and sulfo-conjugated forms. These conjugated forms of kaempferol, some phenolic compounds produced by the colon microflora, kaempferol and some kaempferol glycosides can reach systemic circulation and tissues and are then excreted in urine. The percentage of kaempferol 8

9 excreted in urine has been found to be 1.9% and 2.5% of the total amount of kaempferol ingested. Metabolism of Kaempferol The metabolism of the flavonoids quercetin and kaempferol by rat hepatocytes was investigated using liquid chromatography coupled with electrospray mass spectrometry (LC-ESI MS). Quercetin and kaempferol are extensively metabolized by microsomes expressing a human form (UGT1A9) of the enzyme UDP-glucuronosyltransferase. Kaempferol is absorbed more efficiently than quercetin in humans even at low oral doses. The predominant form in plasma is a 3-glucuronide conjugate, and interindividual variation in absorption and excretion is low, suggesting that urinary kaempferol could be used as a biomarker for exposure. Also study supports that the metabolism of kaempferol glycosides was prompted by the co-administration with rutin. Resveratrol The most important dietary source of resveratrol is red wine, and it is often postulated to be an important factor in the French Paradox, a term coined to describe the observation that the French population has a very low incidence of cardiovascular disease, despite a diet high in saturated fats. In the intervening years, this molecule has received considerable attention for its antiinflammatory, anti-tumorigenic, and anti-oxidant properties, as well as its ability to increase lifespan in lower organisms and improve general health in mammals. Food Sources Resveratrol (3, 5, 40-trihydroxystilbene) is a polyphenol found in grapes (Vitis vinifera), a variety of berries, peanuts, and medicinal plants, such as Japanese knotweed (Polygonumcuspidatum), purple grapes, blueberries, mulberries, cranberries, rhubarb, peanuts, groundnuts and pines. Grapes are probably the most important source of resveratrol for humans, since the compound is also found in one of the end products of grapes: wine. Resveratrol was first detected in grapevines (Vitis vinifera) in 1976, and afterwards in wine in In grapes, especially when infected with Botrytis cinerea, resveratrol is synthesized almost entirely in the skin and its content is maximum just before the grapes reach maturity. Therefore, resveratrol highest concentration is in the skin and seeds of grapes ( μg per gram, corresponding to 5 10% of their biomass). Health benefits 9

10 Resveratrol has multiple mechanisms of action that may be related to its health benefits. Similar to most polyphenols, resveratrol has intrinsic anti-oxidant capacity, but it also induces the expression of a number of anti-oxidant enzymes, making it difficult to decipher the precise contribution of each mechanism to an overall reduction in oxidative stress. Resveratrol further interacts with a large number of receptors, kinases, and other enzymes that could plausibly make major contributions to its biological effects. In vivo, resveratrol treatment stimulates the activities of sirtuin 1 (SIRT1) and adenosine monophosphate activated protein kinase (AMPK), both of which influence the regulation of metabolism in multiple tissues. The search for novel and effective cancer chemopreventive agents has led to the identification of various naturally occurring compounds one of which is resveratrol (trans-3,4,5- trihydroxystilbene), a phytoalexin derived from the skin of grapes and other fruits. Resveratrol is known to have potent anti-inflammatory and antioxidant effects and to inhibit platelet aggregation and the growth of a variety of cancer cells. Its potential chemopreventive and chemotherapeutic activities have been demonstrated in all three stages of carcinogenesis (initiation, promotion, and progression), in both chemically and UVB-induced skin carcinogenesis in mice, as well as in various murine models of human cancers. Evidence from numerous in vitro and in vivo studies has confirmed its ability to modulate various targets and signaling pathways. Resveratrol, known to be abundantly present in red wine, compared to white wine, beer, or spirits, has been demonstrated to elicit a broad spectrum of biological responses in in vitro and in animal studies, including effects that are compatible with the cardioprotective roles proposed for red wine. Bioavailability A number of studies have demonstrated that resveratrol and other polyphenols have very low bioavailability, leading to concern that many of the beneficial effects observed in either cells or biochemical assays may not be achievable in humans due to rapid metabolism. The absorption and metabolism of resveratrol appear to be broadly similar to that of other polyphenols such as quercetin and catechin, although a number of factors may influence the pharmacokinetics of each. Further studies are needed to compare maximum or average concentrations of resveratrol (Cmax or Cavg, respectively) in human plasma or tissue with the concentrations necessary for achieving physiological benefit in animal and in vitro models. There is evidence that resveratrol and its metabolites accumulate within human cells in vivo in a tissue-specific manner and this is highly dependent on the dosage. Following either 0.5 or 1 10

11 g/day of resveratrol administration to 20 prostate and colon cancer patients for 8 days, normal prostate tissue contained resveratrol metabolites but no free resveratrol. Conversely, normal colonic tissue had considerably more trans-resveratrol ( nmol/g) than metabolites for the 1 g/day group, whereas the 0.5 g/day had much lower concentrations ( nmol/g). Despite these differences, it is uncertain if the optimal resveratrol concentration and metabolite profile differs in other tissues and further research is needed in this area. The wide variability in tissue concentration observed is consistent with that of the plasma, further emphasizing inter individual differences in bioavailability. Conclusion Flavonols and flavones are flavonoids widely distributed in the plant kingdom. Epidemiological studies have found a positive association between the consumption of kaempferol, quercetin and resveratrol containing foods and a reduced risk of developing cardiovascular diseases and some types of cancer. Numerous in vitro and some animal studies support a role of kaempferol, quercetin and resveratrol in the prevention and/or treatment of these and other diseases, such as neurodegenerative diseases, infectious diseases, diabetes, osteoporosis, anxiety, allergies, inflammation and pain. However, many of these studies have been conducted at doses higher than those documented in humans and, therefore, it is difficult to predict from these results the effects of kaempferol, quercetin, resveratrol and intake on the prevention of these diseases. Additional animal and human studies and clinical trials are needed to better understand the possible health effects of kaempferol, quercetin and resveratrol and to further evaluate its potential as a new drug. 11