What other names is Quercetin known by?

3,3',4'5,7-Penthydroxyflavone, Bioflavonoid, Bioflavonoid Complex, Bioflavonoid Concentrate, Bioflavonoid Extract, Bioflavonoïde, Bioflavonoïde de Citron, Bioflavonoïdes de Citron, Citrus Bioflavones, Citrus Bioflavonoid, Citrus Bioflavonoids, Citrus Bioflavonoid Extract, Citrus Flavones, Citrus Flavonoids, Complexe de Bioflavonoïde, Concentré de Bioflavonoïde, Extrait de Bioflavonoïde, Extrait de Bioflavonoïdes de Citron, Flavones de Citron, Flavonoid, Flavonoïde, Meletin, Mélétine, Quercetina, Quercétine, Sophretin, Sophrétine.

What is Quercetin?

Quercetin is a plant pigment (flavonoid). It is found in many plants and foods, such as red wine, onions, green tea, apples, berries, Ginkgo biloba, St. John's wort, American elder, and others. Buckwheat tea has a large amount of quercetin. People use quercetin as a medicine.

Quercetin is used for treating conditions of the heart and blood vessels including “hardening of the arteries” (atherosclerosis), high cholesterol, heart disease, and circulation problems. It is also used for diabetes, cataracts, hay fever, peptic ulcer, schizophrenia, inflammation, asthma, gout, viral infections, chronic fatigue syndrome (CFS), preventing cancer, and for treating chronic infections of the prostate. Quercetin is also used to increase endurance and improve athletic performance.

Possibly Effective for...

  • Prostate pain and swelling (inflammation). Taking quercetin by mouth seems to reduce pain and improve quality of life, but doesn't seem to help urination problems in men with ongoing prostate problems that aren't due to infection.


Vitamin D Deficiency: How Much Vitamin D Is Enough? See Slideshow

Insufficient Evidence to Rate Effectiveness for...

  • Heart disease. Some research suggests that eating foods rich in quercetin, such as tea, onions and apples, can reduce the risk of heart disease-related death in elderly men. However, other early research suggests that taking a daily quercetin supplement does not improve heart disease risk factors.
  • High cholesterol. Short-term use of quercetin supplements does not seem to lower “bad cholesterol” (low-density lipoprotein (LDL) cholesterol), lower total cholesterol, or raise “good cholesterol” (high-density lipoprotein (HDL) cholesterol).
  • High blood pressure. Some research suggest that 365mg of quercetin aglycone twice daily produces a small (5-7 mmHg) decrease in blood pressure in people with untreated, mild high blood pressure. It's not known yet how important this is.
  • Exercise-induced respiratory infections. Developing research shows that taking 500 mg of quercetin twice daily for 3 weeks before, and continuing during 3 days of extended, intense cycling reduces the number of upper respiratory infections in the 14 days following the heavy exercise.
  • Kidney transplantation. Some research suggests that a combination of 20 mg of quercetin and 480 mg of curcumin taken once or twice daily, starting within 24 hours of kidney transplantation and continuing for one month, in combination with anti-rejection drugs, improves early function of the transplanted kidney.
  • Lung cancer. Some research suggests that consuming high amounts of quercetin in the diet might reduce the chance of developing lung cancer, especially in men who smoke.
  • Ovarian cancer. One study found no link between quercetin intake from the diet and the chance of ovarian cancer.
  • Pancreatic cancer. Some research suggests that eating high amounts of quercetin in the diet might reduce the chance of developing pancreatic cancer, especially in men who smoke.
  • Exercise performance.
  • “Hardening of the arteries” (atherosclerosis).
  • Diabetes.
  • Cataracts.
  • Hay fever (allergic rhinitis).
  • Stomach and intestinal ulcers.
  • Schizophrenia.
  • Pain and swelling (inflammation).
  • Asthma.
  • Gout.
  • Viral infections.
  • Chronic fatigue syndrome (CFS).
  • Cancer.
  • Other conditions.
More evidence is needed to rate quercetin for these uses.

How does Quercetin work?

Quercetin has antioxidant and anti-inflammatory effects which might help reduce prostate inflammation.

Are there safety concerns?

Quercetin is POSSIBLY SAFE for most people when taken by mouth short-term. Quercetin has been safely used in amounts up to 500 mg twice daily for 12 weeks. It is not known if longer-term use or larger amounts are safe.

Quercetin can cause headache and tingling of the arms and legs. Very high doses might cause kidney damage.

When given intravenously (by IV) in appropriate amounts (less than 722 mg), quercetin is POSSIBLY SAFE. But larger amounts given by IV are POSSIBLY UNSAFE. There have been reports of kidney damage at higher doses.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Not enough is known about the use of quercetin during pregnancy and breast-feeding. Stay on the safe side and avoid use.

Are there any interactions with medications?

Antibiotics (Quinolone antibiotics)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.

Taking quercetin along with some antibiotics might decrease the effectiveness of some antibiotics. Some scientists think that quercetin might prevent some antibiotics from killing bacteria. But it's too soon to know if this is a big concern.

Quinolone antibiotics include ciprofloxacin (Cipro), levofloxacin (Levaquin), ofloxacin (Floxin), moxifloxacin (Avelox), gatifloxacin (Tequin), and others.

Cyclosporine (Neoral, Sandimmune)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.

A small study in healthy volunteers shows that giving quercetin before cyclosporine increases blood levels of the cyclosporine and lengthens the time it remains in the body.

Medications changed by the liver (Cytochrome P450 2C8 (CYP2C8) substrates)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.

Some medications are changed and broken down by the liver. Quercetin might decrease how quickly the liver breaks down some medications. Taking quercetin along with some medications that are broken down by the liver can increase the effects and side effects of these medications. Before taking quercetin, talk with your healthcare provider if you take any medications that are changed by the liver.

Some medications that are changed by the liver include paclitaxel (Taxol), rosiglitazone (Avandia), amiodarone (Cordarone), docetaxel (Taxotere), tretinoins, repaglinide (Prandin), verapamil (Calan, Isoptin, Verelan, etc.), and others.

Medications changed by the liver (Cytochrome P450 2C9 (CYP2C9) substrates)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.

Some medications are changed and broken down by the liver. Quercetin might decrease how quickly the liver breaks down some medications. Taking quercetin along with some medications that are broken down by the liver can increase the effects and side effects of these medications. Before taking quercetin, talk with your healthcare provider if you take any medications that are changed by the liver.

Some medications that are changed by the liver include celecoxib (Celebrex), diclofenac (Voltaren), fluvastatin (Lescol), glipizide (Glucotrol), ibuprofen (Advil, Motrin), irbesartan (Avapro), losartan (Cozaar), phenytoin (Dilantin), piroxicam (Feldene), tamoxifen (Nolvadex), tolbutamide (Tolinase), torsemide (Demadex), and warfarin (Coumadin).

Medications changed by the liver (Cytochrome P450 2D6 (CYP2D6) substrates)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.

Some medications are changed and broken down by the liver. Quercetin might decrease how quickly the liver breaks down some medications. Taking quercetin along with some medications that are broken down by the liver can increase the effects and side effects of these medications. Before taking quercetin, talk with your healthcare provider if you take any medications that are changed by the liver.

Some drugs that are changed by the liver include amitriptyline (Elavil), codeine, flecainide (Tambocor), haloperidol (Haldol), imipramine (Tofranil), metoprolol (Lopressor, Toprol XL), ondansetron (Zofran), paroxetine (Paxil), risperidone (Risperdal), tramadol (Ultram), venlafaxine (Effexor), and others.

Medications changed by the liver (Cytochrome P450 3A4 (CYP3A4) substrates)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.

Some medications are changed and broken down by the liver. Quercetin might decrease how quickly the liver breaks down some medications. Taking quercetin along with some medications that are broken down by the liver can increase the effects and side effects of these medications. Before taking quercetin, talk with your healthcare provider if you take any medications that are changed by the liver.

Some drugs that are changed by the liver include calcium channel blockers (diltiazem, nicardipine, verapamil), chemotherapeutic agents (etoposide, paclitaxel, vinblastine, vincristine, vindesine), antifungals (ketoconazole, itraconazole), glucocorticoids, alfentanil (Alfenta), fentanyl (Sublimaze), losartan (Cozaar), fluoxetine (Prozac), midazolam (Versed), omeprazole (Prilosec), lansoprazole (Prevacid), ondansetron (Zofran), propranolol (Inderal), fexofenadine (Allegra), amitriptyline (Elavil), amiodarone (Cordarone), citalopram (Celexa), sertraline (Zoloft), and numerous others.

Medications for high blood pressure (Antihypertensive drugs)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.

Quercetin seems to decrease blood pressure. Taking quercetin along with medications for high blood pressure might cause your blood pressure to go too low.

Some medications for high blood pressure include captopril (Capoten), enalapril (Vasotec), losartan (Cozaar), valsartan (Diovan), diltiazem (Cardizem), Amlodipine (Norvasc), hydrochlorothiazide (HydroDIURIL), furosemide (Lasix), and many others.

Medications moved by pumps in cells (P-Glycoprotein substrates)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.

Quercetin might affect the way certain medications are processed by the body. Quercetin might make these medications easier for the body to use and make them last longer in the body.

Some of the drugs that may be affected in these ways by quercetin include paclitaxel, diltiazem, cyclosporine, saquinavir, digoxin, cancer drugs (etoposide, vinblastine, vincristine, vindesine), antifungals (ketoconazole, itraconazole), protease inhibitors (amprenavir, indinavir, nelfinavir), H2 antagonists (cimetidine, ranitidine), verapamil, corticosteroids, erythromycin, fexofenadine (Allegra), loperamide (Imodium), quinidine, and others.

Warfarin (Coumadin)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.

A small test tube study shows that quercetin might increase the effects that warfarin has on the body. Taking quercetin and warfarin together might increase the chance of side effects of warfarin such as bruising and bleeding.

Dosing considerations for Quercetin.

The following dose has been studied in scientific research:


  • For prostate pain and swelling (prostatitis): 500 mg twice daily.



Next to red peppers, you can get the most vitamin C from ________________. See Answer

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).

FDA Logo

Report Problems to the Food and Drug Administration

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

Health Solutions From Our Sponsors

Reviewed on 9/17/2019

Alexandrakis, M., Letourneau, R., Kempuraj, D., Kandere-Grzybowska, K., Huang, M., Christodoulou, S., Boucher, W., Seretakis, D., and Theoharides, T. C. Flavones inhibit proliferation and increase mediator content in human leukemic mast cells (HMC-1). Eur.J Haematol. 2003;71(6):448-454. View abstract.

Beatty, E. R., O'Reilly, J. D., England, T. G., McAnlis, G. T., Young, I. S., Geissler, C. A., Sanders, T. A., and Wiseman, H. Effect of dietary quercetin on oxidative DNA damage in healthy human subjects. Br J Nutr 2000;84(6):919-925. View abstract.

Bischoff, S. C. Quercetin: potentials in the prevention and therapy of disease. Curr.Opin.Clin Nutr Metab Care 2008;11(6):733-740. View abstract.

Blanco-Colio, L. M., Valderrama, M., Alvarez-Sala, L. A., Bustos, C., Ortego, M., Hernandez-Presa, M. A., Cancelas, P., Gomez-Gerique, J., Millan, J., and Egido, J. Red wine intake prevents nuclear factor-kappaB activation in peripheral blood mononuclear cells of healthy volunteers during postprandial lipemia. Circulation 8-29-2000;102(9):1020-1026. View abstract.

Boots, A. W., Haenen, G. R., and Bast, A. Health effects of quercetin: from antioxidant to nutraceutical. Eur.J Pharmacol 5-13-2008;585(2-3):325-337. View abstract.

Boulton, D. W., Walle, U. K., and Walle, T. Extensive binding of the bioflavonoid quercetin to human plasma proteins. J.Pharm.Pharmacol. 1998;50(2):243-249. View abstract.

Brevik, A., Rasmussen, S. E., Drevon, C. A., and Andersen, L. F. Urinary excretion of flavonoids reflects even small changes in the dietary intake of fruits and vegetables. Cancer Epidemiol.Biomarkers Prev. 2004;13(5):843-849. View abstract.

Castillo, M. H., Perkins, E., Campbell, J. H., Doerr, R., Hassett, J. M., Kandaswami, C., and Middleton E Jr. The effects of the bioflavonoid quercetin on squamous cell carcinoma of head and neck origin. Am.J.Surg. 1989;158(4):351-355. View abstract.

Chopra, M., Fitzsimons, P. E., Strain, J. J., Thurnham, D. I., and Howard, A. N. Nonalcoholic red wine extract and quercetin inhibit LDL oxidation without affecting plasma antioxidant vitamin and carotenoid concentrations. Clin.Chem. 2000;46(8 Pt 1):1162-1170. View abstract.

Crespy, V., Morand, C., Manach, C., Besson, C., Demigne, C., and Remesy, C. Part of quercetin absorbed in the small intestine is conjugated and further secreted in the intestinal lumen. Am J Physiol 1999;277(1 Pt 1):G120-G126. View abstract.

Cross, H. J., Tilby, M., Chipman, J. K., Ferry, D. R., and Gescher, A. Effect of quercetin on the genotoxic potential of cisplatin. Int J Cancer 5-3-1996;66(3):404-408. View abstract.

Czekalla, J., Gastpar, M., Hubner, W. D., and Jager, D. The effect of hypericum extract on cardiac conduction as seen in the electrocardiogram compared to that of imipramine. Pharmacopsychiatry 1997;30 Suppl 2:86-88. View abstract.

de Vries, J. H., Hollman, P. C., Meyboom, S., Buysman, M. N., Zock, P. L., van Staveren, W. A., and Katan, M. B. Plasma concentrations and urinary excretion of the antioxidant flavonols quercetin and kaempferol as biomarkers for dietary intake. Am.J Clin Nutr. 1998;68(1):60-65. View abstract.

Dhar, N. B. and Shoskes, D. A. New therapies in chronic prostatitis. Curr.Urol.Rep. 2007;8(4):313-318. View abstract.

Egert, S., Wolffram, S., Bosy-Westphal, A., Boesch-Saadatmandi, C., Wagner, A. E., Frank, J., Rimbach, G., and Mueller, M. J. Daily quercetin supplementation dose-dependently increases plasma quercetin concentrations in healthy humans. J Nutr 2008;138(9):1615-1621. View abstract.

Elattar, T. M. and Virji, A. S. The inhibitory effect of curcumin, genistein, quercetin and cisplatin on the growth of oral cancer cells in vitro. Anticancer Res 2000;20(3A):1733-1738. View abstract.

Erlund, I., Alfthan, G., Maenpaa, J., and Aro, A. Tea and coronary heart disease: the flavonoid quercetin is more bioavailable from rutin in women than in men. Arch.Intern.Med. 8-13-2001;161(15):1919-1920. View abstract.

Ferrandina, G., Almadori, G., Maggiano, N., Lanza, P., Ferlini, C., Cattani, P., Piantelli, M., Scambia, G., and Ranelletti, F. O. Growth-inhibitory effect of tamoxifen and quercetin and presence of type II estrogen binding sites in human laryngeal cancer cell lines and primary laryngeal tumors. Int.J.Cancer 8-31-1998;77(5):747-754. View abstract.

Formica, J. V. and Regelson, W. Review of the biology of Quercetin and related bioflavonoids. Food Chem.Toxicol. 1995;33(12):1061-1080. View abstract.

Franke, A. A., Custer, L. J., Wilkens, L. R., Le Marchand, L. L., Nomura, A. M., Goodman, M. T., and Kolonel, L. N. Liquid chromatographic-photodiode array mass spectrometric analysis of dietary phytoestrogens from human urine and blood. J Chromatogr B Analyt.Technol.Biomed Life Sci 9-25-2002;777(1-2):45-59. View abstract.

Graefe, E. U., Wittig, J., Mueller, S., Riethling, A. K., Uehleke, B., Drewelow, B., Pforte, H., Jacobasch, G., Derendorf, H., and Veit, M. Pharmacokinetics and bioavailability of quercetin glycosides in humans. J Clin.Pharmacol. 2001;41(5):492-499. View abstract.

Gugler, R., Leschik, M., and Dengler, H. J. Disposition of quercetin in man after single oral and intravenous doses. Eur.J.Clin.Pharmacol. 12-19-1975;9(2-3):229-234. View abstract.

Hanninen, Kaartinen, K., Rauma, A. L., Nenonen, M., Torronen, R., Hakkinen, A. S., Adlercreutz, H., and Laakso, J. Antioxidants in vegan diet and rheumatic disorders. Toxicology 11-30-2000;155(1-3):45-53. View abstract.

Hänsgen, K. D., Vesper, J., and Ploch, M. Multicenter double-blind study examining the antidepressant effectiveness of the hypericum extract LI 160. J Geriatr.Psychiatry Neurol. 1994;7 Suppl 1:S15-S18. View abstract.

Havsteen, B. Flavonoids, a class of natural products of high pharmacological potency. Biochem.Pharmacol 4-1-1983;32(7):1141-1148. View abstract.

Hayashi, A., Gillen, A. C., and Lott, J. R. Effects of daily oral administration of quercetin chalcone and modified citrus pectin on implanted colon-25 tumor growth in Balb-c mice. Altern Med Rev 2000;5(6):546-552. View abstract.

Hayek, T., Fuhrman, B., Vaya, J., Rosenblat, M., Belinky, P., Coleman, R., Elis, A., and Aviram, M. Reduced progression of atherosclerosis in apolipoprotein E-deficient mice following consumption of red wine, or its polyphenols quercetin or catechin, is associated with reduced susceptibility of LDL to oxidation and aggregation. Arterioscler.Thromb.Vasc.Biol 1997;17(11):2744-2752. View abstract.

Hertog, M. G., Feskens, E. J., Hollman, P. C., Katan, M. B., and Kromhout, D. Dietary flavonoids and cancer risk in the Zutphen Elderly Study. Nutr Cancer 1994;22(2):175-184. View abstract.

Hoffman, R., Graham, L., and Newlands, E. S. Enhanced anti-proliferative action of busulphan by quercetin on the human leukaemia cell line K562. Br.J.Cancer 1989;59(3):347-348. View abstract.

Hollman, P. C., de Vries, J. H., van Leeuwen, S. D., Mengelers, M. J., and Katan, M. B. Absorption of dietary quercetin glycosides and quercetin in healthy ileostomy volunteers. Am.J.Clin.Nutr. 1995;62(6):1276-1282. View abstract.

Hollman, P. C., van Trijp, J. M., Buysman, M. N., van der Gaag, M. S., Mengelers, M. J., de Vries, J. H., and Katan, M. B. Relative bioavailability of the antioxidant flavonoid quercetin from various foods in man. FEBS Lett. 11-24-1997;418(1-2):152-156. View abstract.

Hollman, P. C., van Trijp, J. M., Mengelers, M. J., de Vries, J. H., and Katan, M. B. Bioavailability of the dietary antioxidant flavonol quercetin in man. Cancer Lett. 3-19-1997;114(1-2):139-140. View abstract.

Hollman, PC, Bijsman, MN, van Gameren, Y, Cnossen, EP, de Vries, JH, and Katan, MB. The sugar moiety is a major determinant of the absorption of dietary flavonoid glycosides in man. Free Radic.Res. 1999;31(6):569-573.

Kang, L. P., Qi, L. H., Zhang, J. P., Shi, N., Zhang, M., Wu, T. M., and Chen, J. Effect of genistein and quercetin on proliferation, collagen synthesis, and type I procollagen mRNA levels of rat hepatic stellate cells. Acta Pharmacol.Sin. 2001;22(9):793-796. View abstract.

Kasper, S. Treatment of seasonal affective disorder (SAD) with hypericum extract. Pharmacopsychiatry 1997;30 Suppl 2:89-93. View abstract.

Katske, F., Shoskes, D. A., Sender, M., Poliakin, R., Gagliano, K., and Rajfer, J. Treatment of interstitial cystitis with a quercetin supplement. Tech.Urol. 2001;7(1):44-46. View abstract.

Kaul, T. N., Middleton E Jr, and Ogra, P. L. Antiviral effect of flavonoids on human viruses. J.Med.Virol. 1985;15(1):71-79. View abstract.

Keinzler, JL, Sallin, D, Schifflers, MH, and Ghika A. Phamokinetics of mono-3'-and mono-4'-0-(beta-hydroxyethyl)-rutoside derivatives, after single doses of Venoruton powder in healthy volunteers. Eur.J.Clin.Pharmacol. 2002;58(6):395-402.

Kiesewetter, H, Koscielny, J, Kalus, U, Vix, JM, Peil, H, Petrini, O, van Toor, BS, and de Mey, C. Efficacy of orally administered extract of red vine leaf AS 195 (folia vitis viniferae) in chronic venous insufficiency (stages I-II). A randomized, double-blind, placebo-controlled trial. Arzineimittelforschung 2000;50(2):109-117.

Lamson, D. W. and Brignall, M. S. Antioxidants and cancer, part 3: quercetin. Altern.Med.Rev. 2000;5(3):196-208. View abstract.

Lin, C. M., Chen, C. S., Chen, C. T., Liang, Y. C., and Lin, J. K. Molecular modeling of flavonoids that inhibits xanthine oxidase. Biochem.Biophys.Res Commun. 5-31-2002;294(1):167-172. View abstract.

Loke, W. M., Hodgson, J. M., Proudfoot, J. M., McKinley, A. J., Puddey, I. B., and Croft, K. D. Pure dietary flavonoids quercetin and (-)-epicatechin augment nitric oxide products and reduce endothelin-1 acutely in healthy men. Am J Clin Nutr 2008;88(4):1018-1025. View abstract.

Lozoya, X., Reyes-Morales, H., Chavez-Soto, M. A., Martinez-Garcia, Mdel C., Soto-Gonzalez, Y., and Doubova, S. V. Intestinal anti-spasmodic effect of a phytodrug of Psidium guajava folia in the treatment of acute diarrheic disease. J Ethnopharmacol 2002;83(1-2):19-24. View abstract.

Makita, H., Tanaka, T., Fujitsuka, H., Tatematsu, N., Satoh, K., Hara, A., and Mori, H. Chemoprevention of 4-nitroquinoline 1-oxide-induced rat oral carcinogenesis by the dietary flavonoids chalcone, 2-hydroxychalcone, and quercetin. Cancer Res 11-1-1996;56(21):4904-4909. View abstract.

Mayer, B., Schumacher, M., Brandstatter, H., Wagner, F. S., and Hermetter, A. High-throughput fluorescence screening of antioxidative capacity in human serum. Anal.Biochem 10-15-2001;297(2):144-153. View abstract.

McAnulty, S. R., McAnulty, L. S., Nieman, D. C., Quindry, J. C., Hosick, P. A., Hudson, M. H., Still, L., Henson, D. A., Milne, G. L., Morrow, J. D., Dumke, C. L., Utter, A. C., Triplett, N. T., and Dibarnardi, A. Chronic quercetin ingestion and exercise-induced oxidative damage and inflammation. Appl.Physiol Nutr Metab 2008;33(2):254-262. View abstract.

Morrow, D. M., Fitzsimmons, P. E., Chopra, M., and McGlynn, H. Dietary supplementation with the anti-tumour promoter quercetin: its effects on matrix metalloproteinase gene regulation. Mutat.Res. 9-1-2001;480-481:269-276. View abstract.

Mueller, B. M. St. John's Wort for depressive disorders: results of an outpatient study with the Hypericum preparation HYP 811. Adv.Ther. 1998;15(2):109-116. View abstract.

Mulholland, P. J., Ferry, D. R., Anderson, D., Hussain, S. A., Young, A. M., Cook, J. E., Hodgkin, E., Seymour, L. W., and Kerr, D. J. Pre-clinical and clinical study of QC12, a water-soluble, pro-drug of quercetin. Ann.Oncol. 2001;12(2):245-248. View abstract.

Murakami, A., Ashida, H., and Terao, J. Multitargeted cancer prevention by quercetin. Cancer Lett. 10-8-2008;269(2):315-325. View abstract.

Negre-Salvayre, A. and Salvayre, R. Quercetin prevents the cytotoxicity of oxidized LDL on lymphoid cell lines. Free Radic.Biol.Med. 1992;12(2):101-106. View abstract.

Nieman, D. C. Immunonutrition support for athletes. Nutr.Rev. 2008;66(6):310-320. View abstract.

Noroozi, M., Burns, J., Crozier, A., Kelly, I. E., and Lean, M. E. Prediction of dietary flavonol consumption from fasting plasma concentration or urinary excretion. Eur J Clin Nutr 2000;54(2):143-149. View abstract.

O'Reilly, J. D., Mallet, A. I., McAnlis, G. T., Young, I. S., Halliwell, B., Sanders, T. A., and Wiseman, H. Consumption of flavonoids in onions and black tea: lack of effect on F2-isoprostanes and autoantibodies to oxidized LDL in healthy humans. Am.J Clin.Nutr. 2001;73(6):1040-1044. View abstract.

O'Reilly, J. D., Sanders, T. A., and Wiseman, H. Flavonoids protect against oxidative damage to LDL in vitro: use in selection of a flavonoid rich diet and relevance to LDL oxidation resistance ex vivo? Free Radic.Res 2000;33(4):419-426. View abstract.

Olthof, M. R., Hollman, P. C., Vree, T. B., and Katan, M. B. Bioavailabilities of quercetin-3-glucoside and quercetin-4'-glucoside do not differ in humans. J.Nutr. 2000;130(5):1200-1203. View abstract.

Rachkauskas, GS. [The efficacy of enterosorption and a combination of antioxidants in schizophrenics]. Lik.Sprava. 1998;4:122-124.

Ranelletti, F. O., Ricci, R., Larocca, L. M., Maggiano, N., Capelli, A., Scambia, G., Benedetti-Panici, P., Mancuso, S., Rumi, C., and Piantelli, M. Growth-inhibitory effect of quercetin and presence of type-II estrogen-binding sites in human colon-cancer cell lines and primary colorectal tumors. Int.J.Cancer 2-1-1992;50(3):486-492. View abstract.

Rayalam, S., Della-Fera, M. A., and Baile, C. A. Phytochemicals and regulation of the adipocyte life cycle. J Nutr Biochem. 2008;19(11):717-726. View abstract.

Remberg, P., Bjork, L., Hedner, T., and Sterner, O. Characteristics, clinical effect profile and tolerability of a nasal spray preparation of Artemisia abrotanum L. for allergic rhinitis. Phytomedicine. 2004;11(1):36-42. View abstract.

Schaefer, E, Peil, H, Ambrosetti, L, and Petrini, O. Oedema protective properties of the red vine leaf extract AS 195 (Folia vitis viniferae) in the treatment of chronic venous insufficiency. A 6-weel observational trial. Arzineimittelforschung 2003;53(4):243-246.

Schulz, H. U., Schurer, M., Bassler, D., and Weiser, D. Investigation of the bioavailability of hypericin, pseudohypericin, hyperforin and the flavonoids quercetin and isorhamnetin following single and multiple oral dosing of a hypericum extract containing tablet. Arzneimittelforschung. 2005;55(1):15-22. View abstract.

Serafini, M., Bugianesi, R., Salucci, M., Azzini, E., Raguzzini, A., and Maiani, G. Effect of acute ingestion of fresh and stored lettuce (Lactuca sativa) on plasma total antioxidant capacity and antioxidant levels in human subjects. Br.J Nutr. 2002;88(6):615-623. View abstract.

Singhal, R. L., Yeh, Y. A., Praja, N., Olah, E., Sledge, G. W., Jr., and Weber, G. Quercetin down-regulates signal transduction in human breast carcinoma cells. Biochem.Biophys.Res.Commun. 3-8-1995;208(1):425-431. View abstract.

Sommer, H. and Harrer, G. Placebo-controlled double-blind study examining the effectiveness of an hypericum preparation in 105 mildly depressed patients. J Geriatr.Psychiatry Neurol. 1994;7 Suppl 1:S9-11. View abstract.

Stavric, B. Quercetin in our diet: from potent mutagen to probable anticarcinogen. Clin.Biochem. 1994;27(4):245-248. View abstract.

Terao, J., Kawai, Y., and Murota, K. Vegetable flavonoids and cardiovascular disease. Asia Pac.J Clin Nutr 2008;17 Suppl 1:291-293. View abstract.

Theoharides, T. C. and Sant, G. R. A pilot open label study of Cystoprotek in interstitial cystitis. Int J Immunopathol.Pharmacol 2005;18(1):183-188. View abstract.

Theoharides, T. C., Whitmore, K., Stanford, E., Moldwin, R., and O'Leary, M. P. Interstitial cystitis: bladder pain and beyond. Expert.Opin.Pharmacother. 2008;9(17):2979-2994. View abstract.

Vorbach, E. U., Hubner, W. D., and Arnoldt, K. H. Effectiveness and tolerance of the hypericum extract LI 160 in comparison with imipramine: randomized double-blind study with 135 outpatients. J Geriatr.Psychiatry Neurol. 1994;7 Suppl 1:S19-S23. View abstract.

Walle, T., Walle, U. K., and Halushka, P. V. Carbon dioxide is the major metabolite of quercetin in humans. J.Nutr. 2001;131(10):2648-2652. View abstract.

Wang, F. M., Yao, T. W., and Zeng, S. Determination of quercetin and kaempferol in human urine after orally administrated tablet of ginkgo biloba extract by HPLC. J Pharm Biomed.Anal. 9-19-2003;33(2):317-321. View abstract.

Wiczkowski, W., Romaszko, J., Bucinski, A., Szawara-Nowak, D., Honke, J., Zielinski, H., and Piskula, M. K. Quercetin from shallots (Allium cepa L. var. aggregatum) is more bioavailable than its glucosides. J Nutr 2008;138(5):885-888. View abstract.

Wilson, T., Singh, A. P., Vorsa, N., Goettl, C. D., Kittleson, K. M., Roe, C. M., Kastello, G. M., and Ragsdale, F. R. Human glycemic response and phenolic content of unsweetened cranberry juice. J Med Food 2008;11(1):46-54. View abstract.

Wojcicki, J., Gawronska-Szklarz, B., Bieganowski, W., Patalan, M., Smulski, H. K., Samochowiec, L., and Zakrzewski, J. Comparative pharmacokinetics and bioavailability of flavonoid glycosides of Ginkgo biloba after a single oral administration of three formulations to healthy volunteers. Mater.Med Pol. 1995;27(4):141-146. View abstract.

Yoshida, M., Sakai, T., Hosokawa, N., Marui, N., Matsumoto, K., Fujioka, A., Nishino, H., and Aoike, A. The effect of quercetin on cell cycle progression and growth of human gastric cancer cells. FEBS Lett. 1-15-1990;260(1):10-13. View abstract.

Young, J. F., Nielsen, S. E., Haraldsdottir, J., Daneshvar, B., Lauridsen, S. T., Knuthsen, P., Crozier, A., Sandstrom, B., and Dragsted, L. O. Effect of fruit juice intake on urinary quercetin excretion and biomarkers of antioxidative status. Am J Clin Nutr 1999;69(1):87-94. View abstract.

Anon. Quercetin. Alt Med Rev 1998;3:140-3.

Bobe G, Weinstein SJ, Albanes D, et al. Flavonoid intake and risk of pancreatic cancer in male smokers (Finland). Cancer Epidemiol Biomarkers Prev 2008;17:553-62. View abstract.

Choi JS, Choi BC, Choi KE. Effect of quercetin on the pharmacokinetics of oral cyclosporine. Am J Health Syst Pharm 2004;61:2406-9. View abstract.

Choi JS, Jo BW, Kim YC. Enhanced paclitaxel bioavailability after oral administration of paclitaxel or prodrug to rats pretreated with quercetin. Eur J Pharm Biopharm 2004;57:313-8. View abstract.

Conquer JA, Maiani G, Azzini E, et al. Supplementation with quercetin markedly increases plasma quercetin concentration without effect on selected risk factors for heart disease in healthy subjects. J Nutr 1998;128:593-7. View abstract.

de Pascual-Teresa S, Johnston KL, DuPont MS, et al. Quercetin metabolites downregulate cyclooxygenase-2 transcription in human lymphocytes ex vivo but not in vivo. J Nutr 2004;134:552-7. View abstract.

de Vries JH, Hollman PC, van Amersfoort I, et al. Red wine is a poor source of bioavailable flavonols in men. J Nutr 2001;131:745-8. View abstract.

Di Bari L, Ripoli S, Pradhan S, Salvadori P. Interactions between quercetin and warfarin for albumin binding: A new eye on food/drug interference. Chirality 2010;22:593-6. View abstract.

DiCenzo R, Frerichs V, Larppanichpoonphol P, et al. Effect of quercetin on the plasma and intracellular concentrations of saquinavir in healthy adults. Pharmacotherapy 2006;26:1255-61. View abstract.

Edwards RL, Lyon T, Litwin SE, et al. Quercetin reduces blood pressure in hypertensive subjects. J Nutr 2007;137:2405-11. View abstract.

El Attar TM, Virji AS. Modulating effect of resveratrol and quercetin on oral cancer cell growth and proliferation. Anticancer Drugs 1999;10:187-93. View abstract.

Erlund I, Freese R, Marniemi J, et al. Bioavailability of quercetin from berries and the diet. Nutr Cancer 2006;54:13-7. View abstract.

Erlund I, Kosonen T, Alfthan G, et al. Pharmacokinetics of quercetin from quercetin aglycone and rutin in healthy volunteers. Eur J Clin Pharmacol 2000;56:545-53.. View abstract.

Erlund I, Marniemi J, Hakala P, et al. Consumption of black currants, lingonberries and bilberries increases serum quercetin concentrations. Eur J Clin Nutr 2003;57:37-42. View abstract.

Ferry DR, Smith A, Malkhandi J, et al. Phase I clinical trial of the flavonoid quercetin: Pharmacokinetics and evidence for in vivo tyrosine kinase inhibition. Clin Cancer Res 1996;2:659-67.. View abstract.

Gates MA, Tworoger SS, Hecht JL, et al. A prospective study of dietary flavonoid intake and incidence of epithelial ovarian cancer. Int J Cancer 2007;121:2225-32. View abstract.

Goldberg DM, Yan J, Soleas GJ. Absorption of three wine-related polyphenols in three different matrices by healthy subjects. Clin Biochem 2003;36:79-87.. View abstract.

Grinder-Pedersen, L., Rasmussen, S. E., Bugel, S., Jorgensen, L. V., Dragsted, L. O., Gundersen, V., and Sandstrom, B. Effect of diets based on foods from conventional versus organic production on intake and excretion of flavonoids and markers of antioxidative defense in humans. J Agric Food Chem 2003;51(19):5671-5676. View abstract.

Harwood M, Danielewska-Nikiel B, Borzelleca JF, et al. A critical review of the data related to the safety of quercetin and lack of evidence of in vivo toxicity, including lack of genotoxic / carcinogenic properties. Food Chem Toxicol 2007;45:2179-205. View abstract.

Hertog MG, Feskens EJ, Hollman PC, et al. Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen Elderly Study. Lancet 1993;342:1007-1011. View abstract.

Huang Z, Fasco MJ, Kaminsky LS. Inhibition of estrone sulfatase in human liver microsomes by quercetin and other flavonoids. J Steroid Biochem Mol Biol 1997;63:9-15. View abstract.

Hubbard GP, Wolffram S, Lovegrove JA, Gibbins JM. Ingestion of quercetin inhibits platelet aggregation and essential components of the collagen-stimulated platelet activation pathway in humans. J Thromb Haemost 2004;2:2138-45. View abstract.

Janssen K, Mensink RP, Cox FJ, et al. Effects of the flavonoids quercetin and apigenin on hemostasis in healthy volunteers: results from an in vitro and a dietary supplement study. Am J Clin Nutr 1998;67:255-62. View abstract.

Kim KA, Park PW, Kim HK, et al. Effect of quercetin on the pharmacokinetics of rosiglitazone, a CYP2C8 substrate, in healthy subjects. J Clin Pharmacol 2005;45:941-6. View abstract.

Koga T, Meydani M. Effect of plasma metabolites of (+)-catechin and quercetin on monocyte adhesion to human aortic endothelial cells. Am J Clin Nutr 2001;73:941-8.. View abstract.

Kuo SM, Leavitt PS, Lin CP. Dietary flavonoids interact with trace metals and affect metallothionein level in human intestinal cells. Biol Trace Elem Res 1998;62:135-53. View abstract.

Laakmann G, Schule C, Baghai T, Kieser M. St. John's wort in mild to moderate depression: the relevance of hyperforin for the clinical efficacy. Pharmacopsych 1998;31:54-9. View abstract.

Lean ME, Noroozi M, Kelly I. Dietary flavonols protect diabetic human lymphocytes against oxidative damage to DNA. Diabetes 1999;48:176-81. View abstract.

McAnlis GT, McEneny J, Pearce J, Young IS. Absorption and antioxidant effects of quercetin from onions, in man. Eur J Clin Nutr 1999;53:92-6. View abstract.

Miodini P, Fioravanti L, Di Fronzo G, Cappelletti V. The two phyto-oestrogens genistein and quercetin exert different effects on oestrogen receptor function. Br J Cancer 1999;80:1150-5. View abstract.

Murota K, Terao J. Antioxidative flavonoid quercetin: implication of its intestinal absorption and metabolism. Arch Biochem Biophys 2003;417:12-7. View abstract.

Nemeth K, Piskula MK. Food content, processing, absorption and metabolism of onion flavonoids. Crit Rev Food Sci Nutr 2007;47:397-409. View abstract.

Nieman DC, Henson DA, Davis JM, et al. Quercetin ingestion does not alter cytokine changes in athletes competing in the Western States Endurance Run. J Interferon Cytokine Res 2007;27:1003-11. View abstract.

Nieman DC, Henson DA, Davis JM, et al. Quercetin's influence on exercise-induced changes in plasma cytokines and muscle and leukocyte cytokine mRNA. J Appl Physiol 2007;103:1728-35. View abstract.

Nieman DC, Henson DA, Gross SJ, et al. Quercetin reduces illness but not immune perturbations after intensive exercise. Med Sci Sports Exerc 2007;39:1561-9. View abstract.

Nöthlings U, Murphy SP, Wilkens LR, et al. Flavonols and pancreatic cancer risk: the multiethnic cohort study. Am J Epidemiol 2007;166:924-31. View abstract.

Obach RS. Inhibition of human cytochrome P450 enzymes by constituents of St. John's wort, an herbal preparation used in the treatment of depression. J Pharmacol Exp Ther 2000;294:88-95. View abstract.

Otsuka H, Inaba M, Fujikura T, Kunitomo M. Histochemical and functional characteristics of metachromatic cells in the nasal epithelium in allergic rhinitis: studies of nasal scrapings and their dispersed cells. J Allergy Clin Immunol 1995;96:528-36.. View abstract.

Perez-Vizcaino F, Duarte J, Andriantsitohaina R. Endothelial function and cardiovascular disease: effects of quercetin and wine polyphenols. Free Radic Res 2006;40:1054-65. View abstract.

Rachkauskas GS. The efficacy of enterosorption and a combination of antioxidants in schizophrenics. Lik Sprava 1998;4:122-4. View abstract.

Sesink AL, O'Leary KA, Hollman PC. Quercetin glucuronides but not glucosides are present in human plasma after consumption of quercetin-3-glucoside or quercetin-4'-glucoside. J Nutr 2001;131:1938-41.. View abstract.

Shoskes D, Lapierre C, Cruz-Corerra M, et al. Beneficial effects of the bioflavonoids curcumin and quercetin on early function in cadaveric renal transplantation: a randomized placebo controlled trial. Transplantation 2005;80:1556-9. View abstract.

Shoskes DA, Zeitlin SI, Shahed A, Rajfer J. Quercetin in men with category III chronic prostatitis: A preliminary prospective, double-blind, placebo-controlled trial. Urol 1999;54:960-3. View abstract.

Starvic B. Quercetin in our diet: from potent mutagen to probable anticarcinogen. Clin Biochem 1994;27:245-8.

Vaclavikova R, Horsky S, Simek P, Gut I. Paclitaxel metabolism in rat and human liver microsomes is inhibited by phenolic antioxidants. Naunyn Schmiedebergs Arch Pharmacol 2003;368:200-9. View abstract.

Vorbach EU, Arnoldt KH, Hubner WD. Efficacy and tolerability of St. John's wort extract LI 160 versus imipramine in patients with severe depressive episodes according to ICD- 10. Pharmacopsychiatry 1997;30:81-5. View abstract.

Walle T, Otake Y, Walle UK, Wilson FA. Quercetin glucosides are completely hydrolyzed in ileostomy patients before absorption. J Nutr 2000;130:2658-61.. View abstract.

Wiseman H. The bioavailability of non-nutrient plant factors: dietary flavonoids and phyto-oestrogens. Proc Nutr Soc 1999;58:139-46. View abstract.