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Benefits of quercetin?
http://www.raysahelian.com/quercetin.html
quote:
Benefit of Quercetin
Quercetin is a powerful antioxidant. Potential quercetin benefits that are still being discovered. Here's a summary of some of the quercetin benefit research.
Quercetin and Allergy
I have not come across any good human studies evaluating the role of allergy and quercetin supplements. However, quercetin, as a flavonoid, has been shown in lab studies to have blunt the effects of IgE mediated reactions and perhaps have anti histamine effects There are several nutrients and herbs, in addition to quercetin, that have had some research in terms of their influence on allergy, these include Urtica dioica, bromelain, acetylcysteine, and vitamin C.
Quercetin and Cancer
Quercetin has anti-tumor potential in laboratory studies, and has potential to be useful in various cancers including pancreatic cancer, however human trials are difficult to find.
Queretin and Heart disease
Quercetin may benefit in heart disease. Quercetin inhibits the proliferation and migration of aortic smooth muscle cells, inhibits platelet aggregation, along with inhibition of mitogen-activated protein kinase phosphorylation. These findings provide new insights and a rationale for the potential benefit of quercetin in the prevention of cardiovascular diseases.
Ingestion of onion soup high in quercetin inhibits platelet aggregation and essential components of the collagen-stimulated platelet activation pathway in man: a pilot study.
Br J Nutr. 2006 Sep;96(3):482-8. School of Animal and Microbial Sciences, University of Reading, Whiteknights, Reading, Berkshire, RG6 6AL, UK.
Epidemiological data suggest that those who consume a diet rich in quercetin -containing foods may have a reduced risk of cardiovascular disease. Furthermore, in vitro and ex vivo studies have observed the inhibition of collagen-induced platelet activation by quercetin. The aim of the present study was to investigate the possible inhibitory effects of quercetin ingestion from a dietary source on collagen-stimulated platelet aggregation and signalling. A double-blind randomised cross-over pilot study was undertaken. Subjects ingested a soup containing either a high or a low amount of quercetin. Plasma quercetin concentrations and platelet aggregation and signalling were assessed after soup ingestion. The high- quercetin soup contained 69 mg total quercetin compared with the low- quercetin soup containing 5 mg total quercetin. Plasma quercetin concentrations were significantly higher after high- quercetin soup ingestion than after low- quercetin soup ingestion. Collagen-stimulated (0.5 mug/ml) platelet aggregation was inhibited after ingestion of the high- quercetin soup in a time-dependent manner. Collagen-stimulated tyrosine phosphorylation of a key component of the collagen-signalling pathway via glycoprotein VI, Syk, was significantly inhibited by ingestion of the high- quercetin soup. In conclusion, the ingestion of quercetin from a dietary source of onion soup could inhibit some aspects of collagen-stimulated platelet aggregation and signalling ex vivo. This further substantiates the epidemiological data suggesting that those who preferentially consume high amounts of quercetin -containing foods have a reduced risk of thrombosis and potential cardiovascular disease risk.
Kidney Disease
Quercetin reduces damage to kidneys in rats given a toxin or a chemotherapy drug such as cisplatin.
Quercetin and Liver
The liver of rats given toxins was much better protected when they were pre-treated with quercetin.
Brain tissue and Schizophrenia
Quercetin has potential for the treatment of neuroleptic-induced extrapyramidal side effects, such as from haloperidol. Quercetin also is a powerful antioxidant that may protect brain cells from damage.
Quercetin and viral illness
Quercetin, a naturally occurring, powerful antioxidant found in red grapes, red wine, red apples, green tea and broccoli, appears to be one of the first plant compound proven in a double-blind, randomized, placebo-controlled clinical trial to reduce susceptibility to viral illnesses. Dr. David Nieman, a professor at Appalachian State University was the researcher and presented his findings at the southeastern regional meeting of the American College of Sports Medicine in Charlotte, N.C. Participants in the study -- long-distance cyclists -- ingested 1,000 milligrams of pure quercetin, combined with vitamin C and niacin.
Quercetin Side Effects
At this time quercetin side effects have not been reported in the medical literature. I have personally taken 3 capsules of quercetin and bromelain for 3 days in a row without side effects. Quercetin side effects with long term supplementation over several years is not known.
Food Content of Flavonoids
The average U.S. adult eating a normal, healthy diet consumes about 25 to 50 milligrams of quercetin a day. Studies were conducted on the flavonoids (myricetin, quercetin, kaempferol, luteolin, and apigenin) contents of 62 edible tropical plants. The highest total flavonoids content was in onion leaves ( 1497 mg/kg quercetin, 391 mg/kg luteolin, and 832 mg/kg kaempferol ), followed by Semambu leaves (2041.0 mg/kg), bird chili (1663.0 mg/kg), black tea (1491.0 mg/kg), papaya shoots (1264 mg/kg), and guava (1128 mg/kg). The major flavonoid in these plant extracts is quercetin, followed by myricetin and kaempferol. Luteolin could be detected only in broccoli (74 mg/kg dry weight), green chili (33.0 mg/kg), bird chili (1035.0 mg/kg), onion leaves (391.0 mg/kg), belimbi fruit (202.0 mg/kg), belimbi leaves (464.5 mg/kg), French bean (11.0 mg/kg), carrot (37.5 mg/kg), white radish (9.0 mg/kg), local celery (80.5 mg/kg), limau purut leaves (30.5 mg/kg), and dried asam gelugur (107.5 mg/kg). Apigenin was found only in Chinese cabbage (187.0 mg/kg), bell pepper (272.0 mg/kg), garlic (217.0 mg/kg), belimbi fruit (458.0 mg/kg), French peas (176.0 mg/kg), snake gourd (42.4 mg/kg), guava (579.0 mg/kg), wolfberry leaves (547.0 mg/kg), local celery (338.5 mg/kg), daun turi (39.5 mg/kg), and kadok (34.5 mg/kg). In vegetables, quercetin glycosides predominate, but glycosides of kaempferol, luteolin, and apigenin are also present. Fruits contain almost exclusively quercetin glycosides, whereas kaempferol and myricetin glycosides are found only in trace quantities.
Quercetin Research Update
Quercetin exerts antihypertensive effects and reduces left ventricular hypertrophy, endothelial dysfunction, and the plasma and hepatic oxidative status in spontaneously hypertensive rats.
Antimutagenic and antioxidant/prooxidant activity of quercetin.
Indian J Exp Biol. 2005 Jan;43(1):61-7.
The present study has been performed to evaluate the antimutagenic activity of quercetin, ascorbic acid and their combination against an oxidative mutagen. An effort was also made to correlate this activity to the in vitro antioxidant activity of these agents. Antimutagenicity testing was done in Ames Salmonella Assay system using Salmonella typhimurium TA102 against t-butylhydroperoxide as an oxidative mutagen. In vitro antioxidant scavenging activity was tested for DPPH free radical, superoxide anion, hydrogen peroxide and hydroxyl radical in their specific test systems. Quercetin and ascorbic acid showed significant effect. Quercetin when combined with ascorbic acid showed an increase in the antimutagenic activity. In vitro antioxidant activity of quercetin was better than ascorbic acid in all the test systems used. The study indicated that the antimutagenic activity of quercetin was not solely accountable by its antioxidant nature. However, in vitro free radical scavenging activity of quercetin correlated well with the antimutagenic activity.
Content of the flavonols quercetin, myricetin, and kaempferol in 25 edible berries.
J Agric Food Chem. 1999 Jun;47(6):2274-9.
The amounts of quercetin, myricetin, and kaempferol aglycons in 25 edible berries were analyzed by an optimized RP-HPLC method with UV detection and identified with diode array and electrospray ionization mass spectrometry detection. Sixteen species of cultivated berries and nine species of wild berries were collected in Finland in 1997. Quercetin was found in all berries, the contents being highest in bog whortleberry (158 mg/kg, fresh weight), lingonberry (74 and 146 mg/kg), cranberry (83 and 121 mg/kg), chokeberry (89 mg/kg), sweet rowan (85 mg/kg), rowanberry (63 mg/kg), sea buckthorn berry (62 mg/kg), and crowberry (53 and 56 mg/kg). Amounts between 14 and 142 mg/kg of myricetin were detected in cranberry, black currant, crowberry, bog whortleberry, blueberries, and bilberry. Kaempferol was detected only in gooseberries (16 and 19 mg/kg) and strawberries (5 and 8 mg/kg). Total contents of these flavonols (100-263 mg/kg) in cranberry, bog whortleberry, lingonberry, black currant, and crowberry were higher than those in the commonly consumed fruits or vegetables, except for onion, kale, and broccoli.
An apple a day really does keep the doctor away, thanks to strong antioxidants that fight cell damage. Rat brain cells exposed to the antioxidant quercetin resisted damage much better than those not treated, a team at Cornell University in New York found. The researchers say their study adds strength to the theory that the risk of developing Alzheimer's and similar brain diseases might be reduced by eating plenty of fresh fruits and vegetables. Writing in the December 1st issue of the Journal of Agricultural and Food Chemistry, the Cornell team said they soaked rat brain cells in either quercetin or vitamin C -- another potent antioxidant. The cells were then exposed to hydrogen peroxide to mimic the type of oxidative cell damage that is believed to occur with Alzheimer's disease. Brain cells that were treated with quercetin had significantly less damage than the cells treated with vitamin C and cells that were not treated with antioxidants.
Immunomodulatory and antimetastatic action of propolis and related polyphenolic compounds.
J Ethnopharmacol. 2004 Oct;94(2-3):307-315.
The effect of polyphenolic compounds isolated from propolis and propolis itself was investigated on the growth and metastatic potential of a transplantable mammary carcinoma (MCa) of CBA mouse. A water-soluble derivative of proplis, caffeic acid (CA), caffeic acid phenethyl ester (CAPE) and quercetin were given to mice before tumor cells inoculation. Tested compounds significantly decreased the number of tumor nodules in the lung. According to the results obtained the antitumor activity of tested compounds can be related to the immunomodulatory properties of the compounds, their cytotoxicity to tumor cells, and their capacity to induce apoptosis and necrosis. The experimental data support that propolis, CA, CAPE and quercetin could be potentially useful in the control of tumor growth in experimental models.
Studies on the protective effects of caffeic acid and quercetin on chemical-induced hepatotoxicity in rodents.
Phytomedicine. 2004 Jul;11(5):424-30.
Caffeic acid and quercetin, the well-known phenolic compounds widely present in the plant kingdom, were investigated for their possible protective effects against paracetamol and CCl4-induced hepatic damage. Paracetamol at the oral dose of 1 g/kg produced 100% mortality in mice while pretreatment of separate groups of animals with caffeic acid and quercetin reduced the death rate to 20% and 30%, respectively. Oral administration of sub-lethal dose of paracetamol produced liver damage in rats as manifested by the significant rise in serum levels of aminotransferases (aspartate transaminase (AST) and alanine transaminase (ALT)) compared to respective control values. The serum enzyme values were significantly lowered on pretreatment of rats with either caffeic acid or quercetin. Similarly, the hepatotoxic dose of CCl4 also raised significantly the serum AST and ALT levels as compared to control values. The same dose of the caffeic acid and quercetin was able to prevent CCl4-induced rise in serum enzymes. Caffeic acid and quercetin also prevented the CCl4-induced prolongation in pentobarbital sleeping time confirming their hepatoprotectivity. These results indicate that caffeic acid and quercetin exhibited hepatoprotective activity possibly through multiple mechanisms.
Reduction of rat prostate weight by combined quercetin - finasteride treatment is associated with cell cycle deregulation.
J Endocrinol. 2004 Jun;181(3):493-507.
Benign prostate hyperplasia and prostate cancer are major public health problems. We report herein that daily treatment of male rats with 50, 100 or 150 mg quercetin per kg body weight. Concomitantly, serum testosterone levels were increased by 1.79-, 1.83- and 3.48-fold, while serum dihydrotestosterone (DHT) levels were 125%, 92% and 73% of the control. A slight increase in prostate weight coupled with dilated prostate lumens full of secretory materials were observed. Finasteride alone caused a significant decrease in serum DHT level and prostate weight. Co-administration of quercetin with finasteride prevented the finasteride-induced decrease in serum DHT levels but significantly enhanced the reduction in wet prostate weight, which was reduced by 26.9% in finasteride-treated animals to 31.8%, 40.0% and 48.2% after finasteride given together with the three doses of quercetin. The combined treatment altered cell cycle-regulated proteins in a wide spectrum. In conclusion, quercetin - finasteride treatments caused wide cell cycle deregulation in rat prostates, which, in turn, decreased the proliferation rate, changed the secretion activities of epithelial cells and resulted in a marked reduction in wet prostate weight. The results suggest that quercetin synergizes with finasteride to reduce the wet prostate weight through a cell cycle-related pathway, which may be androgen independent.
Quercetin, a bioflavonoid, reverses haloperidol-induced catalepsy.
Methods Find Exp Clin Pharmacol. 2004 Jun;26(5):323-6.
Neuroleptics are extensively used in the treatment of schizophrenia and other affective disorders. Unfortunately their use is often associated with distressing side effects involving the extrapyramidal tract, such as Parkinsonism and tardive dyskinesia. Neuroleptic-induced catalepsy has long been used as a model for extrapyramidal side effects such as Parkinsonian-like bradykinesia associated with antipsychotic use in humans. In the present study, haloperidol was administered to mice to induce catalepsy. Pretreatment with quercetin dose-dependently reduced the catalepsy score in haloperidol-treated animals. The findings of the present study strongly suggest that quercetin can be screened as a potential drug candidate or as an adjuvant for the treatment of neuroleptic-induced extrapyramidal side effects.
Quercetin, a bioflavonoid, attenuates ferric nitrilotriacetate-induced oxidative renal injury in rats.
Drug Chem Toxicol. 2004 May;27(2):145-56.
An iron chelate, ferric nitrilotriacetate (Fe-NTA), induces acute proximal tubular necrosis as a consequence of lipid peroxidation and oxidative tissue damage, that eventually leads to high incidence of renal adenocarcinomas in rodents. This study was designed to investigate the effect of quercetin, a bioflavonoid with antioxidant potential, on Fe-NTA-induced nephrotoxicity in rats. One hour after a single intraperitoneal (i.p.) injection of Fe-NT, a marked deterioration of renal architecture and renal function was observed. Pretreatment of animals with quercetin 30 minutes before Fe-NTA administration markedly attenuated renal dysfunction, morphological alterations, and restored the depleted renal antioxidant enzymes. These results clearly demonstrate the role of oxidative stress and its relation to renal dysfunction, and suggest a protective effect of quercetin on Fe-NTA-induced nephrotoxicity in rats.
Quercetin protects against linoleic acid-induced porcine endothelial cell dysfunction.
J Nutr. 2004 Apr;134(4):771-5.
Consumption of plant phenolics, such as quercetin, may be associated with decreased risk of cardiovascular disease by stabilizing and protecting vascular endothelial cells against oxidative and proinflammatory insults. The present study focused on the effect of quercetin on linoleic acid-induced oxidative stress. Porcine pulmonary-arterial endothelial cells were activated with linoleic acid in the presence or absence of quercetin. Oxidative stress was markedly induced by endothelial cell exposure to linoleic acid and diminished by treatment with quercetin. Quercetin reduced linoleic acid-mediated binding activity of NF-kappaB and AP-1 and mRNA levels of inflammatory genes such as interleukin-6 (IL-6) and vascular cell adhesion molecule-1 (VCAM-1). Cotreatment of linoleic acid plus quercetin or vitamin E also decreased linoleic acid-induced binding activity of PPARgamma. These data suggest that quercetin has potent antioxidative and anti-inflammatory properties and protects endothelial cells against linoleic acid-mediated cell dysfunction.
Consumption of black currants, lingonberries and bilberries increases serum quercetin concentrations.
Eur J Clin Nutr. 2003 Jan;57(1):37-42.
To study serum quercetin concentrations of subjects consuming berries or habitual Finnish diets. Forty healthy men (age 60 y). Twenty subjects consumed 100 g/day of berries (black currants, lingonberries and bilberries) for 8 weeks. Twenty subjects consuming their habitual diets served as controls. Fasting blood samples were obtained 2 weeks prior to the study, at baseline, and at 2, 4 and 8 weeks. Intake of quercetin was assessed from 3 day food records collected at baseline and at 8 weeks. RESULTS: The serum quercetin concentrations were significantly higher in the subjects consuming berries compared to the control group. During the berry consumption period the mean serum concentrations of quercetin ranged between 21.4 and 25.3 micro g/l in the berry group, which was 32-51% higher compared with the control group. According to 3 day food records, there was no difference in quercetin intake at baseline, but at 8 weeks the intake was 12.3+/-1.4 mg/day in the berry group and 5.8+/-0.6 mg/day in the control group. CONCLUSIONS: The results indicate that the berries used in this study are a good source of bioavailable quercetin.
Plant compounds may curb cancer growth
Several studies have shown that a group of antioxidant compounds found in grapes, green tea, soybeans and wine may lower the risk of a range of cancers, but exactly how these powerful compounds work has remained unclear. Now, researchers report that a plant-derived polyphenol can slow the growth of pancreatic cancer cells in mice and curb the spread of cells by triggering a series or reactions that causes the cells to self-destruct, a process known as apoptosis. In the study, the researchers investigated the effects of quercetin -- a type of antioxidant polyphenol commonly found in apples -- in mice given injections of human pancreatic cells. The mice used in the study are a specially bred strain that lacks an immune system, so that they quickly grow tumors when cancer cells are injected. Quercetin caused apoptosis, decreased the growth of the main tumor and inhibited the spread of malignant cells, the researchers report. Mice treated with quercetin survived for about 75 days, compared with 67 days in mice not given the compound. Genistein, another type of polyphenol compound found in soy, also prevented the spread of cells and inhibited the growth of the primary tumor in mice while resveratrol, found in wine and grapes, caused apoptosis in laboratory-grown cells, according to the report.
SOURCE: International Journal of Cancer 2002:98;761-769.
Effects of chronic quercetin treatment on antioxidant defense system and oxidative status of deoxycorticosterone acetate-salt-hypertensive rats.
Mol Cell Biochem. 2004 Apr;259(1-2):91-9.
We investigated the potential of chronic administration of an oral daily dose of the dietary flavonoid quercetin to prevent hypertension and oxidative stress induced by deoxycorticosterone acetate in rats. In conclusion, quercetin shows both antihypertensive and antioxidant properties in this model of mineralocorticoid hypertension, while verapamil exhibits only antihypertensive effects.
Protective Effect of Quercetin on the Evolution of Cisplatin-Induced Acute Tubular Necrosis.
Kidney Blood Press Res. 2004 Apr 30;27(3):148-158.
The mechanism of cisplatin-induced nephrotoxicity is unknown, but has been associated with renal lipid peroxidation. The bioflavonoid quercetin may be a potential alternative to reduce cisplatin-induced nephrotoxicity. The aim of this study was to evaluate the effect of quercetin on the evolution of cisplatin-induced acute tubular necrosis. Methods: One hundred and three male Wistar rats were injected with cisplatin 43 of them received quercetin (50 mg/kg, by gavage) before cisplatin injection. Cisplatin-treated rats presented a transitory increase in plasma creatinine levels, tubular cell necrosis and increased immunostaining for vimentin, alpha-SM-actin, fibronectin, ED1, NF-kappaB, and p-JNK in the renal cortex and outer medulla. These alterations were less intense in animals treated with quercetin. Conclusion: Quercetin treatment attenuated the functional, histological and immunohistochemical alterations induced by cisplatin.
Consumption of black currants, lingonberries and bilberries increases serum quercetin concentrations.
Eur J Clin Nutr. 2003 Jan;57(1):37-42.
To study serum quercetin concentrations of subjects consuming berries or habitual Finnish diets. DESIGN: Randomized parallel dietary intervention. Forty healthy men (age 60 y). INTERVENTION: Twenty subjects consumed 100 g/day of berries (black currants, lingonberries and bilberries) for 8 weeks. Twenty subjects consuming their habitual diets served as controls. Fasting blood samples were obtained 2 weeks prior to the study, at baseline, and at 2, 4 and 8 weeks. Intake of quercetin was assessed from 3 day food records collected at baseline and at 8 weeks. RESULTS: The serum quercetin concentrations were significantly higher in the subjects consuming berries compared to the control group. During the berry consumption period the mean serum concentrations of quercetin ranged between 21.4 and 25.3 micro g/l in the berry group, which was 32-51% higher compared with the control group. According to 3 day food records, there was no difference in quercetin intake at baseline, but at 8 weeks the intake was 12.3 mg/day in the berry group and 5.8+/-0.6 mg/day in the control group. CONCLUSIONS: The results indicate that the berries used in this study are a good source of bioavailable quercetin.
http://www.raysahelian.com/quercetin.html
quote:
Benefit of Quercetin
Quercetin is a powerful antioxidant. Potential quercetin benefits that are still being discovered. Here's a summary of some of the quercetin benefit research.
Quercetin and Allergy
I have not come across any good human studies evaluating the role of allergy and quercetin supplements. However, quercetin, as a flavonoid, has been shown in lab studies to have blunt the effects of IgE mediated reactions and perhaps have anti histamine effects There are several nutrients and herbs, in addition to quercetin, that have had some research in terms of their influence on allergy, these include Urtica dioica, bromelain, acetylcysteine, and vitamin C.
Quercetin and Cancer
Quercetin has anti-tumor potential in laboratory studies, and has potential to be useful in various cancers including pancreatic cancer, however human trials are difficult to find.
Queretin and Heart disease
Quercetin may benefit in heart disease. Quercetin inhibits the proliferation and migration of aortic smooth muscle cells, inhibits platelet aggregation, along with inhibition of mitogen-activated protein kinase phosphorylation. These findings provide new insights and a rationale for the potential benefit of quercetin in the prevention of cardiovascular diseases.
Ingestion of onion soup high in quercetin inhibits platelet aggregation and essential components of the collagen-stimulated platelet activation pathway in man: a pilot study.
Br J Nutr. 2006 Sep;96(3):482-8. School of Animal and Microbial Sciences, University of Reading, Whiteknights, Reading, Berkshire, RG6 6AL, UK.
Epidemiological data suggest that those who consume a diet rich in quercetin -containing foods may have a reduced risk of cardiovascular disease. Furthermore, in vitro and ex vivo studies have observed the inhibition of collagen-induced platelet activation by quercetin. The aim of the present study was to investigate the possible inhibitory effects of quercetin ingestion from a dietary source on collagen-stimulated platelet aggregation and signalling. A double-blind randomised cross-over pilot study was undertaken. Subjects ingested a soup containing either a high or a low amount of quercetin. Plasma quercetin concentrations and platelet aggregation and signalling were assessed after soup ingestion. The high- quercetin soup contained 69 mg total quercetin compared with the low- quercetin soup containing 5 mg total quercetin. Plasma quercetin concentrations were significantly higher after high- quercetin soup ingestion than after low- quercetin soup ingestion. Collagen-stimulated (0.5 mug/ml) platelet aggregation was inhibited after ingestion of the high- quercetin soup in a time-dependent manner. Collagen-stimulated tyrosine phosphorylation of a key component of the collagen-signalling pathway via glycoprotein VI, Syk, was significantly inhibited by ingestion of the high- quercetin soup. In conclusion, the ingestion of quercetin from a dietary source of onion soup could inhibit some aspects of collagen-stimulated platelet aggregation and signalling ex vivo. This further substantiates the epidemiological data suggesting that those who preferentially consume high amounts of quercetin -containing foods have a reduced risk of thrombosis and potential cardiovascular disease risk.
Kidney Disease
Quercetin reduces damage to kidneys in rats given a toxin or a chemotherapy drug such as cisplatin.
Quercetin and Liver
The liver of rats given toxins was much better protected when they were pre-treated with quercetin.
Brain tissue and Schizophrenia
Quercetin has potential for the treatment of neuroleptic-induced extrapyramidal side effects, such as from haloperidol. Quercetin also is a powerful antioxidant that may protect brain cells from damage.
Quercetin and viral illness
Quercetin, a naturally occurring, powerful antioxidant found in red grapes, red wine, red apples, green tea and broccoli, appears to be one of the first plant compound proven in a double-blind, randomized, placebo-controlled clinical trial to reduce susceptibility to viral illnesses. Dr. David Nieman, a professor at Appalachian State University was the researcher and presented his findings at the southeastern regional meeting of the American College of Sports Medicine in Charlotte, N.C. Participants in the study -- long-distance cyclists -- ingested 1,000 milligrams of pure quercetin, combined with vitamin C and niacin.
Quercetin Side Effects
At this time quercetin side effects have not been reported in the medical literature. I have personally taken 3 capsules of quercetin and bromelain for 3 days in a row without side effects. Quercetin side effects with long term supplementation over several years is not known.
Food Content of Flavonoids
The average U.S. adult eating a normal, healthy diet consumes about 25 to 50 milligrams of quercetin a day. Studies were conducted on the flavonoids (myricetin, quercetin, kaempferol, luteolin, and apigenin) contents of 62 edible tropical plants. The highest total flavonoids content was in onion leaves ( 1497 mg/kg quercetin, 391 mg/kg luteolin, and 832 mg/kg kaempferol ), followed by Semambu leaves (2041.0 mg/kg), bird chili (1663.0 mg/kg), black tea (1491.0 mg/kg), papaya shoots (1264 mg/kg), and guava (1128 mg/kg). The major flavonoid in these plant extracts is quercetin, followed by myricetin and kaempferol. Luteolin could be detected only in broccoli (74 mg/kg dry weight), green chili (33.0 mg/kg), bird chili (1035.0 mg/kg), onion leaves (391.0 mg/kg), belimbi fruit (202.0 mg/kg), belimbi leaves (464.5 mg/kg), French bean (11.0 mg/kg), carrot (37.5 mg/kg), white radish (9.0 mg/kg), local celery (80.5 mg/kg), limau purut leaves (30.5 mg/kg), and dried asam gelugur (107.5 mg/kg). Apigenin was found only in Chinese cabbage (187.0 mg/kg), bell pepper (272.0 mg/kg), garlic (217.0 mg/kg), belimbi fruit (458.0 mg/kg), French peas (176.0 mg/kg), snake gourd (42.4 mg/kg), guava (579.0 mg/kg), wolfberry leaves (547.0 mg/kg), local celery (338.5 mg/kg), daun turi (39.5 mg/kg), and kadok (34.5 mg/kg). In vegetables, quercetin glycosides predominate, but glycosides of kaempferol, luteolin, and apigenin are also present. Fruits contain almost exclusively quercetin glycosides, whereas kaempferol and myricetin glycosides are found only in trace quantities.
Quercetin Research Update
Quercetin exerts antihypertensive effects and reduces left ventricular hypertrophy, endothelial dysfunction, and the plasma and hepatic oxidative status in spontaneously hypertensive rats.
Antimutagenic and antioxidant/prooxidant activity of quercetin.
Indian J Exp Biol. 2005 Jan;43(1):61-7.
The present study has been performed to evaluate the antimutagenic activity of quercetin, ascorbic acid and their combination against an oxidative mutagen. An effort was also made to correlate this activity to the in vitro antioxidant activity of these agents. Antimutagenicity testing was done in Ames Salmonella Assay system using Salmonella typhimurium TA102 against t-butylhydroperoxide as an oxidative mutagen. In vitro antioxidant scavenging activity was tested for DPPH free radical, superoxide anion, hydrogen peroxide and hydroxyl radical in their specific test systems. Quercetin and ascorbic acid showed significant effect. Quercetin when combined with ascorbic acid showed an increase in the antimutagenic activity. In vitro antioxidant activity of quercetin was better than ascorbic acid in all the test systems used. The study indicated that the antimutagenic activity of quercetin was not solely accountable by its antioxidant nature. However, in vitro free radical scavenging activity of quercetin correlated well with the antimutagenic activity.
Content of the flavonols quercetin, myricetin, and kaempferol in 25 edible berries.
J Agric Food Chem. 1999 Jun;47(6):2274-9.
The amounts of quercetin, myricetin, and kaempferol aglycons in 25 edible berries were analyzed by an optimized RP-HPLC method with UV detection and identified with diode array and electrospray ionization mass spectrometry detection. Sixteen species of cultivated berries and nine species of wild berries were collected in Finland in 1997. Quercetin was found in all berries, the contents being highest in bog whortleberry (158 mg/kg, fresh weight), lingonberry (74 and 146 mg/kg), cranberry (83 and 121 mg/kg), chokeberry (89 mg/kg), sweet rowan (85 mg/kg), rowanberry (63 mg/kg), sea buckthorn berry (62 mg/kg), and crowberry (53 and 56 mg/kg). Amounts between 14 and 142 mg/kg of myricetin were detected in cranberry, black currant, crowberry, bog whortleberry, blueberries, and bilberry. Kaempferol was detected only in gooseberries (16 and 19 mg/kg) and strawberries (5 and 8 mg/kg). Total contents of these flavonols (100-263 mg/kg) in cranberry, bog whortleberry, lingonberry, black currant, and crowberry were higher than those in the commonly consumed fruits or vegetables, except for onion, kale, and broccoli.
An apple a day really does keep the doctor away, thanks to strong antioxidants that fight cell damage. Rat brain cells exposed to the antioxidant quercetin resisted damage much better than those not treated, a team at Cornell University in New York found. The researchers say their study adds strength to the theory that the risk of developing Alzheimer's and similar brain diseases might be reduced by eating plenty of fresh fruits and vegetables. Writing in the December 1st issue of the Journal of Agricultural and Food Chemistry, the Cornell team said they soaked rat brain cells in either quercetin or vitamin C -- another potent antioxidant. The cells were then exposed to hydrogen peroxide to mimic the type of oxidative cell damage that is believed to occur with Alzheimer's disease. Brain cells that were treated with quercetin had significantly less damage than the cells treated with vitamin C and cells that were not treated with antioxidants.
Immunomodulatory and antimetastatic action of propolis and related polyphenolic compounds.
J Ethnopharmacol. 2004 Oct;94(2-3):307-315.
The effect of polyphenolic compounds isolated from propolis and propolis itself was investigated on the growth and metastatic potential of a transplantable mammary carcinoma (MCa) of CBA mouse. A water-soluble derivative of proplis, caffeic acid (CA), caffeic acid phenethyl ester (CAPE) and quercetin were given to mice before tumor cells inoculation. Tested compounds significantly decreased the number of tumor nodules in the lung. According to the results obtained the antitumor activity of tested compounds can be related to the immunomodulatory properties of the compounds, their cytotoxicity to tumor cells, and their capacity to induce apoptosis and necrosis. The experimental data support that propolis, CA, CAPE and quercetin could be potentially useful in the control of tumor growth in experimental models.
Studies on the protective effects of caffeic acid and quercetin on chemical-induced hepatotoxicity in rodents.
Phytomedicine. 2004 Jul;11(5):424-30.
Caffeic acid and quercetin, the well-known phenolic compounds widely present in the plant kingdom, were investigated for their possible protective effects against paracetamol and CCl4-induced hepatic damage. Paracetamol at the oral dose of 1 g/kg produced 100% mortality in mice while pretreatment of separate groups of animals with caffeic acid and quercetin reduced the death rate to 20% and 30%, respectively. Oral administration of sub-lethal dose of paracetamol produced liver damage in rats as manifested by the significant rise in serum levels of aminotransferases (aspartate transaminase (AST) and alanine transaminase (ALT)) compared to respective control values. The serum enzyme values were significantly lowered on pretreatment of rats with either caffeic acid or quercetin. Similarly, the hepatotoxic dose of CCl4 also raised significantly the serum AST and ALT levels as compared to control values. The same dose of the caffeic acid and quercetin was able to prevent CCl4-induced rise in serum enzymes. Caffeic acid and quercetin also prevented the CCl4-induced prolongation in pentobarbital sleeping time confirming their hepatoprotectivity. These results indicate that caffeic acid and quercetin exhibited hepatoprotective activity possibly through multiple mechanisms.
Reduction of rat prostate weight by combined quercetin - finasteride treatment is associated with cell cycle deregulation.
J Endocrinol. 2004 Jun;181(3):493-507.
Benign prostate hyperplasia and prostate cancer are major public health problems. We report herein that daily treatment of male rats with 50, 100 or 150 mg quercetin per kg body weight. Concomitantly, serum testosterone levels were increased by 1.79-, 1.83- and 3.48-fold, while serum dihydrotestosterone (DHT) levels were 125%, 92% and 73% of the control. A slight increase in prostate weight coupled with dilated prostate lumens full of secretory materials were observed. Finasteride alone caused a significant decrease in serum DHT level and prostate weight. Co-administration of quercetin with finasteride prevented the finasteride-induced decrease in serum DHT levels but significantly enhanced the reduction in wet prostate weight, which was reduced by 26.9% in finasteride-treated animals to 31.8%, 40.0% and 48.2% after finasteride given together with the three doses of quercetin. The combined treatment altered cell cycle-regulated proteins in a wide spectrum. In conclusion, quercetin - finasteride treatments caused wide cell cycle deregulation in rat prostates, which, in turn, decreased the proliferation rate, changed the secretion activities of epithelial cells and resulted in a marked reduction in wet prostate weight. The results suggest that quercetin synergizes with finasteride to reduce the wet prostate weight through a cell cycle-related pathway, which may be androgen independent.
Quercetin, a bioflavonoid, reverses haloperidol-induced catalepsy.
Methods Find Exp Clin Pharmacol. 2004 Jun;26(5):323-6.
Neuroleptics are extensively used in the treatment of schizophrenia and other affective disorders. Unfortunately their use is often associated with distressing side effects involving the extrapyramidal tract, such as Parkinsonism and tardive dyskinesia. Neuroleptic-induced catalepsy has long been used as a model for extrapyramidal side effects such as Parkinsonian-like bradykinesia associated with antipsychotic use in humans. In the present study, haloperidol was administered to mice to induce catalepsy. Pretreatment with quercetin dose-dependently reduced the catalepsy score in haloperidol-treated animals. The findings of the present study strongly suggest that quercetin can be screened as a potential drug candidate or as an adjuvant for the treatment of neuroleptic-induced extrapyramidal side effects.
Quercetin, a bioflavonoid, attenuates ferric nitrilotriacetate-induced oxidative renal injury in rats.
Drug Chem Toxicol. 2004 May;27(2):145-56.
An iron chelate, ferric nitrilotriacetate (Fe-NTA), induces acute proximal tubular necrosis as a consequence of lipid peroxidation and oxidative tissue damage, that eventually leads to high incidence of renal adenocarcinomas in rodents. This study was designed to investigate the effect of quercetin, a bioflavonoid with antioxidant potential, on Fe-NTA-induced nephrotoxicity in rats. One hour after a single intraperitoneal (i.p.) injection of Fe-NT, a marked deterioration of renal architecture and renal function was observed. Pretreatment of animals with quercetin 30 minutes before Fe-NTA administration markedly attenuated renal dysfunction, morphological alterations, and restored the depleted renal antioxidant enzymes. These results clearly demonstrate the role of oxidative stress and its relation to renal dysfunction, and suggest a protective effect of quercetin on Fe-NTA-induced nephrotoxicity in rats.
Quercetin protects against linoleic acid-induced porcine endothelial cell dysfunction.
J Nutr. 2004 Apr;134(4):771-5.
Consumption of plant phenolics, such as quercetin, may be associated with decreased risk of cardiovascular disease by stabilizing and protecting vascular endothelial cells against oxidative and proinflammatory insults. The present study focused on the effect of quercetin on linoleic acid-induced oxidative stress. Porcine pulmonary-arterial endothelial cells were activated with linoleic acid in the presence or absence of quercetin. Oxidative stress was markedly induced by endothelial cell exposure to linoleic acid and diminished by treatment with quercetin. Quercetin reduced linoleic acid-mediated binding activity of NF-kappaB and AP-1 and mRNA levels of inflammatory genes such as interleukin-6 (IL-6) and vascular cell adhesion molecule-1 (VCAM-1). Cotreatment of linoleic acid plus quercetin or vitamin E also decreased linoleic acid-induced binding activity of PPARgamma. These data suggest that quercetin has potent antioxidative and anti-inflammatory properties and protects endothelial cells against linoleic acid-mediated cell dysfunction.
Consumption of black currants, lingonberries and bilberries increases serum quercetin concentrations.
Eur J Clin Nutr. 2003 Jan;57(1):37-42.
To study serum quercetin concentrations of subjects consuming berries or habitual Finnish diets. Forty healthy men (age 60 y). Twenty subjects consumed 100 g/day of berries (black currants, lingonberries and bilberries) for 8 weeks. Twenty subjects consuming their habitual diets served as controls. Fasting blood samples were obtained 2 weeks prior to the study, at baseline, and at 2, 4 and 8 weeks. Intake of quercetin was assessed from 3 day food records collected at baseline and at 8 weeks. RESULTS: The serum quercetin concentrations were significantly higher in the subjects consuming berries compared to the control group. During the berry consumption period the mean serum concentrations of quercetin ranged between 21.4 and 25.3 micro g/l in the berry group, which was 32-51% higher compared with the control group. According to 3 day food records, there was no difference in quercetin intake at baseline, but at 8 weeks the intake was 12.3+/-1.4 mg/day in the berry group and 5.8+/-0.6 mg/day in the control group. CONCLUSIONS: The results indicate that the berries used in this study are a good source of bioavailable quercetin.
Plant compounds may curb cancer growth
Several studies have shown that a group of antioxidant compounds found in grapes, green tea, soybeans and wine may lower the risk of a range of cancers, but exactly how these powerful compounds work has remained unclear. Now, researchers report that a plant-derived polyphenol can slow the growth of pancreatic cancer cells in mice and curb the spread of cells by triggering a series or reactions that causes the cells to self-destruct, a process known as apoptosis. In the study, the researchers investigated the effects of quercetin -- a type of antioxidant polyphenol commonly found in apples -- in mice given injections of human pancreatic cells. The mice used in the study are a specially bred strain that lacks an immune system, so that they quickly grow tumors when cancer cells are injected. Quercetin caused apoptosis, decreased the growth of the main tumor and inhibited the spread of malignant cells, the researchers report. Mice treated with quercetin survived for about 75 days, compared with 67 days in mice not given the compound. Genistein, another type of polyphenol compound found in soy, also prevented the spread of cells and inhibited the growth of the primary tumor in mice while resveratrol, found in wine and grapes, caused apoptosis in laboratory-grown cells, according to the report.
SOURCE: International Journal of Cancer 2002:98;761-769.
Effects of chronic quercetin treatment on antioxidant defense system and oxidative status of deoxycorticosterone acetate-salt-hypertensive rats.
Mol Cell Biochem. 2004 Apr;259(1-2):91-9.
We investigated the potential of chronic administration of an oral daily dose of the dietary flavonoid quercetin to prevent hypertension and oxidative stress induced by deoxycorticosterone acetate in rats. In conclusion, quercetin shows both antihypertensive and antioxidant properties in this model of mineralocorticoid hypertension, while verapamil exhibits only antihypertensive effects.
Protective Effect of Quercetin on the Evolution of Cisplatin-Induced Acute Tubular Necrosis.
Kidney Blood Press Res. 2004 Apr 30;27(3):148-158.
The mechanism of cisplatin-induced nephrotoxicity is unknown, but has been associated with renal lipid peroxidation. The bioflavonoid quercetin may be a potential alternative to reduce cisplatin-induced nephrotoxicity. The aim of this study was to evaluate the effect of quercetin on the evolution of cisplatin-induced acute tubular necrosis. Methods: One hundred and three male Wistar rats were injected with cisplatin 43 of them received quercetin (50 mg/kg, by gavage) before cisplatin injection. Cisplatin-treated rats presented a transitory increase in plasma creatinine levels, tubular cell necrosis and increased immunostaining for vimentin, alpha-SM-actin, fibronectin, ED1, NF-kappaB, and p-JNK in the renal cortex and outer medulla. These alterations were less intense in animals treated with quercetin. Conclusion: Quercetin treatment attenuated the functional, histological and immunohistochemical alterations induced by cisplatin.
Consumption of black currants, lingonberries and bilberries increases serum quercetin concentrations.
Eur J Clin Nutr. 2003 Jan;57(1):37-42.
To study serum quercetin concentrations of subjects consuming berries or habitual Finnish diets. DESIGN: Randomized parallel dietary intervention. Forty healthy men (age 60 y). INTERVENTION: Twenty subjects consumed 100 g/day of berries (black currants, lingonberries and bilberries) for 8 weeks. Twenty subjects consuming their habitual diets served as controls. Fasting blood samples were obtained 2 weeks prior to the study, at baseline, and at 2, 4 and 8 weeks. Intake of quercetin was assessed from 3 day food records collected at baseline and at 8 weeks. RESULTS: The serum quercetin concentrations were significantly higher in the subjects consuming berries compared to the control group. During the berry consumption period the mean serum concentrations of quercetin ranged between 21.4 and 25.3 micro g/l in the berry group, which was 32-51% higher compared with the control group. According to 3 day food records, there was no difference in quercetin intake at baseline, but at 8 weeks the intake was 12.3 mg/day in the berry group and 5.8+/-0.6 mg/day in the control group. CONCLUSIONS: The results indicate that the berries used in this study are a good source of bioavailable quercetin.
