Common Name: Quercetin
Synonyms: Meletin, sophretin, 3, 3’, 4’, 5, 7-pentahydroxy flavone

Overview:

Quercetin belongs to the flavonoid family of phytonutrients and is one of the most abundant. As with other flavonoids, quercetin is responsible for the colors found in many fruits and vegetables. Quercetin is almost insoluble in water and only a small portion of it is absorbed into the body during digestion. It has been found, however, that the addition of the digestive enzymes bromelain increases the absorption of this nutrient. Quercetin is a powerful antioxidant neutralizing free radicals (naturally occurring but harmful substances) and reduce or prevent the cellular damage that they cause.

Benefits

Much research has been done on what an increase in quercetin uptake can do to help improve and maintain optimum health. Quercetin has shown promise in the treatment of such conditions as allergies, conditions characterized by capillary fragility, chronic prostatitis ( infection and enlargement of the prostate gland), complications of diabetes such as cataracts, diabetic retinopathy (damage to the retina of the eye), neuropathy (nerve damage) and nephropathy (kidney damage) Studies have confirmed that:

1. The anti oxidant activity of quercetin may help to prevent damage to the eye. Quercetin and other flavonoids neutralize free radicals and play a role in the prevention and or treatment of cataracts, macular degeneration. In a study of 3,072 adults with symptoms of macular degeneration, moderate red wine consumption (which is high in quercetin) offered protection against the development and progression of these diseases. Preliminary studies have also shown that quercetin inhibit aldose rectucase ( an enzyme linked to the long term complications of diabetes) therefore helping to reduce development of cataracts, neuropathy, nephropathy and retinopathy so prevelent in long term diabetics.
2. Quercetin is one of many flavonoids that effect mast cells and basophiles (white blood cells that are active in allergic reactions). By preventing the release of histamines (a substance that contributes to the runny noses, watery eyes and other allergic reaction symptoms), quercetin is showing great promise in the treatment of allergic reactions such as hay fever. It is believed that quercetin does this by stabilizing cell membranes so that they are less reactive to these substances, Quercetin also shows anti inflammatory properties by inhibiting the formation of prostaglandins and leukotrienes that contribute to some of the inflammatory symptoms in an allergic reaction.
3. This anti-inflammatory property of quecertin is also showing promise in the treatment of atheritis and fibromyalgia.
4. In an open-labeled study, quercetin showed promise in the treatment of chronic prostatitis (a nonbacterial inflammation of the prostate gland) and prostatodynia (pain in the prostate gland). This ability to quercetin to relieve pain and inflammation of the prostate gland has been confirmed in randomized, double- blind study in which 30 men who suffered from these disorders were given either 500mg of quercetin or a placebo twice a day for a month. The group that received the quercetin showed significant improvement compared to the group who received the placebo. Sixty seven percent of the group supplemented with quercetin showed a 25% improvement in symptoms while only those in the placebo group received only 20%. In a follow up study combining quercetin with bromelain and papin (both improve the absorption of quercetin), 82% of the group showed at least a 25% improvement. Those conducting the research concluded that quercetin supplementation was effective, well tolerated, safe and inexpensive combined with a durable effectiveness that was seen in few other therapies for prostatitis. In vitro (in the test tube studies) testing with quercetin shows that it may inhibit the growth of prostate cancer cells. This preliminary finding needs to be confirmed by animal and human testing.
5. A preliminary study of 11 people with various forms of cancer showed that quercetin reduced the actual size of tumors in 2 people and in the other nine showed that it inhibited the activity of a protein that plays a major role in tumor growth. More studies in this area of tumor growth are needed to confirm this preliminary finding.

Dietary Sources

	Red wine		Apples
	Citrus Fruits		Onions contain the highest amounts of quercetin.
	Tea contain the highest amounts of quercetin.		Dark Cherries
	Dark Berries		Olive Oil
Red grapes are also high in quercetin and other flavonoids.

Recommended Dosage:

Quercetin is supplied as:
Capsules 250mg, 300mg or 500mg
Tablets 50mg, 250mg, 500mg

Pediatric dosage for allergies

Pediatric dosages are calculated by a child’s body weight. Since adult dosages are calculated using a body weight of 150 lbs, to calculate a pediatric dose simply take the child’s weight and divide by 150 lbs. For example, if a child weights 50 lbs and the adult dose for a supplement is 150mg:
50lbs/150lbs=.33 or 1/3 of adult dose. Adult supplementation for allergies is 100-200mg 3 times a day. So 100 to 200mg/3= 33 to 66mg 3 times a day for a child of 50lbs.

Adult

Nutritional supplementation: 100-250mg/3 times per day
Allergy symptoms: 250-600mg/3 times per day
Chronic hives: 200-400mg/3 times per day
Chronic prostatitis: 500mg/2 times per day fro 30 days
If bromelain is used to increase the absorption of quercetin, the bromelain should equal the amount of quercetin.

Contra-indications

None known

Women who are pregnant or breastfeeding or those with liver or kidney disease should consult a health care provider before using quercetin.

Drug interactions

Quinolones (a family of antibiotics) In studies conducted in vitro, quercetin and the antibiotic attached to the same cell membrane sites. Because of this quercetin could cause a quinolone antibiotic to be less effective

Cisplatin & doxorubicin Again in vitro studies indicate that quercetin may enhance the effects of doxorubicin and cisplatin, two chemotherapeutic agents used in the treatment of cancers. It is recommended that quercetin not be taken with either of these medications.

Web References

1. http://www.umm.edu/altmed/ConsSupplements/Quercetincs.html
2. http://www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/que_0219.shtml
3. http://healthlibrary.epnet.com/GetContent.aspx?token=e0498803-7f62-4563-8d47-5fe33da65dd4&chunkiid=33802#B

Printed Reference Material

1. Alarcon de la Lastra C. Martin MJ, Motilve V. Antiulcer and gastroprotective effects of quercetin: a gross and histologic study. Pharmacol. 1994; 48:56-62.
2. Alliangana DM. Effects of beta-carotene, flavonoid quercetin and quinacrine on cell proliferation and lipid peroxidation breakdown products in BHK-21 cells. East Afr MedJ. 1996;73:752–757.
3. Balasubramanian S, Govindasamy S. Inhibitory effect of dietary flavonol quercetin on 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch carcinogenesis. Carcinogenesis. 1996;17:877–879.
4. Boulton DW, Walle UK, Walle T. Extensive binding of the bioflavonoid quercetin to human plasma proteins. J Pharm Pharmacol. 1998; 50:243-249.
5. 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; 128:593-597.
6. Constant J. Alcohol, ischemic heart disease, and the French paradox. Coron Artery Dis. 1997;8:645–649.
7. Costantino L, Rastelli G, Gamberini MC, et al. 1-Benzopyran-4-one antioxidants as aldose reductase inhibitors. J Med Chem. 1999; 42:1881-1893.
8. Cross HJ, Tilby M, Chipman JK, et al. Effect of quercetin on the genotoxic potential of cisplatin. Int J Cancer. 1996;66:404–408.
9. de Vries JH, Jenssen PL, Hollman PC, et al. Consumption of quercetin and kaempferol in free-living subjects eating a variety of diets. Cancer Lett. 1997. 114:141-144.
10. ElAttar TM, Virji AS. Modulating effect of resveratrol and quercetin on oral cancer cell growth and proliferation. Anticancer Drugs. 1999;10:187–193.
11. Ferry DR, Smith A, Malkhandi J, et al. Phase I clinical trial of the flavonoid quercetine: phonmacokinetics and evidence for tyrosine kinase inhibition. Clin Cancer Res. 1996; 2:659-668.
12. Frankel EN, Waterhouse AL, Kinsella JE. Inhibition of human LDL oxidation by resveratrol. Lancet. 1993;341:1103–1104.
13. Friedman M, Smith GA. Factors which facilitate inactivation of quercetin mutagenicity. Adv Exp Med Biol. 1984;177:527–544.
14. Hayek T, Fuhrman B, Vaya J. 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;17:2744–2752.
15. Hilliard JJ, Krause HM, Bernstein JI, et al. A comparison of active site binding of 4-quinolones and novel flavone gyrase inhibitors to DNA gyrase. Adv Exp Med Biol. 1995; 390:59-69.
16. Hoffman R, Graham L, Newlands ES. Enhanced anti-proliferative action of busulphan by quercetin on the human leukaemia cell line K562. Br J Cancer. 1989;59:347–348.
17. Hollman PC, Bijsman MN, van Gameren Y, et al. The sugar moiety is a major determinant of the absorption of dietary flavonoid glycosides in man. Free Rad Res. 1999; 31:569-573.
18. Hollman PC, de Vries JH, van Leeuwen SD, et al. Absorption of dietary quercetin glycosides and quercetin in healthy ileostomy volunteers. Am J Clin Nutr. 1995; 62:1276-1282.
19. Hollman PCH, Gaag MVD, Mengelers MJB, et al. Absorpotion and disposition kinetics of the dietary antioxidant quercetin in man. Free Red Biol Med. 1996; 21:703-707.
20. Hollman PCH, van Trijp JMP, Mengelers MJB, et al. Bioavailability of the dietary antioxidant flavonol quercetin in man. Cancer Lett. 1997; 114:139-140.
21. Ito N, Hagiwara A, Tamano S, et al. Lack of carcinogencity of quercetin in F344/DuCrj rats. Jpn J Cancer Res. 1989; 80:317-325.
22. Kaul TN, Middleton E Jr, Ogra PL. Antiviral effect of flavonoids on human viruses. J Med Virol. 1985;15:71–79.
23. Keli SO, Hertog MG, Feskens EJ, et al. Dietary flavonoids, antioxidant vitamins, and incidence of stroke: the Zupthen study. Arch Intern Med. 1996;156:637–642.
24. Martin MJ, La-Casa C, Alarcon-de-la-Lastra C, et al. Anti-oxidant mechanisms involved in gastroprotective effects of quercetin. Z Naturforsch[C]. 1998; 53:82-88.
25. Middleton E Jr. Effect of flavonoids on basophil histamine release and other secretory systems. Prog Clin Biol Res. 1986;213:493–506.
26. Middleton Jr E, Anne S. Quercetin inhibits lipopolysaccharide-induced expression of endothelial cell intracellular adhesion molecule-1. Int Arch Allergy Immunol. 1995; 107:435-436.
27. Musci I, Pragai BM. Inhibition of virus multiplication and alteration of cyclic AMP level in cell cultures by flavonoids. Experientia. 1985;41:930–931.
28. Ogasawara H, Middleton E Jr. Effect of selected flavonoids on histamine release (HR) and hydrogen peroxide (H2O2) generation by human leukocytes [abstract]. J Allergy Clin Immunol. 1985;75(suppl):184.
29. Rodriguez LV, Janzen N, Raz S, et al. Treatment of interstitial cystitis with a quercetin containing compound: a preliminary, double-blind placebo control trial. Presented at: American Urological Association 2001 Annual Meeting; June 2–7, 2001; Anaheim, Calif.
30. Sato M, Miyazaki T, Kambe F, et al. Quercetin, a bioflavonoid, inhibits the induction of interleukin 8 and monocyte chemoattractant protein-1 expression by tumor necrosis factor-alpha in cultured human synovial cells. J Rheumatol. 1997; 24:1680-1684.
31. Shoskes DA, Zeitlin SI, Shahed A, et al. Quercetin in men with category III chronic prostatitis: a preliminary prospective, double-blind, placebo-controlled trial. Urology. 1999;54:960–963.
32. Shoskes DA, Zeitlin SI, Shahed A, Rajfer J. Quercetin in men with category III chronic prostatitis: a preliminary prospective double-blind, placebo-controlled trial. Urology. 1999; 54:960-963.
33. Shoskes DA. Effect of the bioflavonoids quercetin and curcumin on ischemic renal injury: a new class of renoprotective agents. Transplantation. 1998; 66:147-152.
34. Stavric B. Quercetin in our diet: from potent mutagen to probable anticarcinogen. Clin Biochem. 1994; 27:245-248.
35. Stavric B. Quercetin in our diet: from potent mutagen to probable anticarcinogen. Clin Biochem. 1994;27:245–248.
36. Strick R, Strissel PL, Borgers S, et al. Dietary bioflavonoids induce cleavage in the MLL gene and may contribute to infant leukemia. Proc Natl Acad Sci. 2000;97:4790–4795.
37. Varma SD, Kinoshita JH. Inhibition of lens aldose reductase by flavonoids. Their possible role in the prevention of diabetic cataracts. Biochem Pharmacol. 1976; 25:2505-2513.
38. Varma SD, Mizuno A, Kinoshita JH. Diabetic cataracts and flavonoids. Science. 1977;195:205–206.
39. Weldin J, Jack R, Dugaw K et al. Quercetin, an over-the-counter supplement, causes neuroblastoma-like elevation of plasma homovanillic acid. Pediatr Dev Pathol. 2004;6:547-51.
40. Yoshida M, Yamamoto M, Nikaido T. Quercetin arrests human leukemic T-cells in late G1 phase of the cell cycle. Cancer Res. 1992;52:6676–6681.
41. Yoshimoto T, Furukawa M, Yamamoto S, et al. Flavonoids: potent inhibitors of arachidonate 5-lipoxygenase. Biochem Biophys Res Commun. 1983;116:612–618.

Permalink