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Skeletal formula of quercetin
Ball-and-stick model of the quercetin molecule
IUPAC name
Other names
Flavin meletin
117-39-5 YesY
6151-25-3 (Quercetin dihydrate)[1] N
ChemSpider 4444051 YesY
DrugBank DB04216 N
Jmol interactive 3D Image
KEGG C00389 YesY
PubChem 5280343
Molar mass 302.236 g/mol
Appearance yellow crystalline powder[1]
Density 1.799 g/cm3
Melting point 316 °C (601 °F; 589 K)
Practically insoluble in water; soluble in aqueous alkaline solutions[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references
UV visible spectrum of quercetin, with lambda max at 369 nm.

Quercetin /ˈkwɜrsɨtɨn/ is a flavonol found in many fruits, vegetables, leaves and grains. It can be used as an ingredient in supplements, beverages, or foods.

Health effects[edit]

While quercetin supplements have been promoted for prevention and treatment of cancer, "there is no reliable clinical evidence that quercetin can prevent or treat cancer in humans".[2] Also, there is no evidence that consuming foods rich in quercetin reduces the risk of cancer or any other disease.[3]

The European Food Safety Authority evaluated possible health claims associated with consumption of quercetin, finding that no cause-and-effect relationship has been established for any physiological effect in human health or diseases.[4]

Drug interactions[edit]

Quercetin is contraindicated with some antibiotics; it may interact with fluoroquinolones (an antibiotic), as quercetin competitively binds to bacterial DNA gyrase. Whether this inhibits or enhances the effect of fluoroquinolones is not certain.[5]

AHFS Drug Information (2010)[citation needed] identifies quercetin as an inhibitor of CYP2C8, and specifically names it as a drug with potential to have harmful interactions with taxol/paclitaxel. As paclitaxel is metabolized primarily by CYP2C8, its bioavailability may be increased unpredictably, potentially leading to harmful side-effects.[6][7]


Quercetin is a flavonoid widely distributed in nature. The name has been used since 1857, and is derived from quercetum (oak forest), after Quercus.[8][9] It is a naturally occurring polar auxin transport inhibitor.[10]

Foods containing quercetin Quercetin (mg/100g of edible portion)
capers, raw 234[11]
capers, canned 173[11]
lovage 170[11]
dock like sorrel 86[11]
radish leaves 70[11]
carob fiber 58[11]
dill 55[12] (48-110)[13]
cilantro 53[11]
Hungarian wax pepper 51[11]
fennel leaves 48.8[11]
onion, red 32[14]
radicchio 31.5[11]
watercress 30[14]
buckwheat 23[15]
kale 23[14]
chokeberry 19[14]
cranberry 15[14]
lingonberry 13[14]
plums, black 12[14]
cow peas 11[14]
sweet potato 10[14]
blueberry, cultivated 8[14]
sea buckthorn berry 8[14]
rowanberry 7[14]
crowberry 5[14]
prickly pear cactus fruits 5[14]
apples, Red Delicious 4[14]
broccoli 3[14]
bilberry 3[14]
tea, black or green Camellia sinensis 2[14]

In red onions, higher concentrations of quercetin occur in the outermost rings and in the part closest to the root, the latter being the part of the plant with the highest concentration.[16] One study found that organically grown tomatoes had 79% more quercetin than chemically grown fruit.[17] Quercetin is present in various kinds of honey from different plant sources.[18]



Phenylalanine is converted to 4-coumaroyl-CoA in a series of steps known as the general phenylpropanoid pathway using phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, and 4-coumaroyl-CoA-ligase.[19] 4-Coumaroyl-CoA is added to three molecules of malonyl-CoA to form tetrahydroxychalcone using 7,2’-dihydroxy-4’-methoxyisoflavanol synthase. Tetrahydroxychalcone is then converted into naringenin using chalcone isomerase.

Naringenin is converted into eriodictyol using flavanoid 3’-hydroxylase. Eriodictyol is then converted into dihydroquercetin with flavanone 3-hydroxylase, which is then converted into quercetin using flavonol synthase.[19]

Rutin degradation pathway[edit]

The enzyme quercitrinase can be found in Aspergillus flavus.[20] Its substrates are quercitrin and H2O and releases quercetin and L-rhamnose. It is an enzyme in the rutin catabolic pathway[21]


Quercetin 3-O-sulfate is a human plasma quercetin metabolite.


Quercetin is the aglycone form of a number of other flavonoid glycosides, such as rutin and quercitrin, found in citrus fruit, buckwheat and onions. Quercetin forms the glycosides quercitrin and rutin together with rhamnose and rutinose, respectively. Likewise guaijaverin is the 3-O-arabinoside, hyperoside is the 3-O-galactoside, isoquercitin is the 3-O-glucoside and spiraeoside is the 4'-O-glucoside. CTN-986 is a quercetin derivative found in cottonseeds and cottonseed oil. Miquelianin is the quercetin 3-o-β-d-glucuronopyranoside.[22]

Fate in vivo[edit]

Following dietary ingestion, quercetin undergoes rapid and extensive metabolism that makes the biological effects presumed from in vitro studies unlikely to apply in vivo.[23][24]


Although quercetin is under basic and early-stage clinical research for a variety of disease conditions, there exists no sufficient evidence that it has any beneficial effect in the human body.[25][4] The US FDA has issued warning letters,[26] e.g. to emphasize that quercetin is not a defined nutrient, cannot be assigned a dietary content level and is not regulated as a drug to treat any human disease.

See also[edit]


  1. ^ a b c Quercetin dihydrate safety sheet on http://www.pvp.com.br (English)
  2. ^ Ades TB, ed. (2009). Quercetin. American Cancer Society Complete Guide to Complementary and Alternative Cancer Therapies (2nd ed.) (American Cancer Society). ISBN 9780944235713. 
  3. ^ "Flavonoids". Linus Pauling Institute, Micronutrient Information Center, Oregon State University, Corvallis. 2015. Retrieved 19 October 2015. 
  4. ^ a b "Scientific Opinion on the substantiation of health claims related to quercetin and protection of DNA, proteins and lipids from oxidative damage (ID 1647), “cardiovascular system” (ID 1844), “mental state and performance” (ID 1845), and “liver, kidneys” (ID 1846) pursuant to Article 13(1) of Regulation (EC) No 1924/2006". EFSA Journal. 8 April 2011. Retrieved 24 September 2014. 
  5. ^ Hilliard JJ, Krause HM, Bernstein JI, Fernandez JA, Nguyen V, Ohemeng KA, Barrett JF (1995). "A comparison of active site binding of 4-quinolones and novel flavone gyrase inhibitors to DNA gyrase". Adv. Exp. Med. Biol. 390: 59–69. doi:10.1007/978-1-4757-9203-4_5. PMID 8718602. 
  6. ^ Bun SS, Ciccolini J, Bun H, Aubert C, Catalin J (June 2003). "Drug interactions of paclitaxel metabolism in human liver microsomes". J Chemother 15 (3): 266–74. doi:10.1179/joc.2003.15.3.266. PMID 12868554. 
  7. ^ Bun SS, Giacometti S, Fanciullino R, Ciccolini J, Bun H, Aubert C (July 2005). "Effect of several compounds on biliary excretion of paclitaxel and its metabolites in guinea-pigs". Anticancer Drugs 16 (6): 675–82. doi:10.1097/00001813-200507000-00013. PMID 15930897. 
  8. ^ "Quercetin". Merriam-Webster. 
  9. ^ "Quercitin (biochemistry)". Encyclopædia Britannica. 
  10. ^ Fischer C, Speth V, Fleig-Eberenz S, Neuhaus G (October 1997). "Induction of Zygotic Polyembryos in Wheat: Influence of Auxin Polar Transport". Plant Cell 9 (10): 1767–80. doi:10.1105/tpc.9.10.1767. PMC 157020. PMID 12237347. 
  11. ^ a b c d e f g h i j "USDA Database for the Flavonoid Content of Selected Foods, Release 3.1" (PDF). U.S. Department of Agriculture. 2013. 
  12. ^ "Dill weed, fresh". Merschat family website. 
  13. ^ Justesen U, Knuthsen P (May 2001). "Composition of flavonoids in fresh herbs and calculation of flavonoid intake by use of herbs in traditional Danish dishes". Food Chemistry 73 (2): 245–50. doi:10.1016/S0308-8146(01)00114-5. 
  14. ^ a b c d e f g h i j k l m n o p q r "USDA Database for the Flavonoid Content of Selected Foods, Release 3" (PDF). U.S. Department of Agriculture. 2011. 
  15. ^ "Food Nutrition Facts: Buckwheat". Merschat family website. 
  16. ^ Smith C, Lombard KA, Peffley EB, Liu W (2003). "Genetic Analysis of Quercetin in Onion (Allium cepa L.) Lady Raider" (PDF). The Texas Journal of Agriculture and Natural Resource (Agriculture Consortium of Texas) 16: 24–8. Archived from the original (PDF) on February 25, 2007. 
  17. ^ Mitchell AE, Hong YJ, Koh E, Barrett DM, Bryant DE, Denison RF, Kaffka S (July 2007). "Ten-year comparison of the influence of organic and conventional crop management practices on the content of flavonoids in tomatoes". J. Agric. Food Chem. 55 (15): 6154–9. doi:10.1021/jf070344. PMID 17590007. 
  18. ^ Petrus K, Schwartz H, Sontag G (June 2011). "Analysis of flavonoids in honey by HPLC coupled with coulometric electrode array detection and electrospray ionization mass spectrometry". Anal Bioanal Chem 400 (8): 2555–63. doi:10.1007/s00216-010-4614-7. PMID 21229237. 
  19. ^ a b Winkel-Shirley B (June 2001). "Flavonoid biosynthesis. A colorful model for genetics, biochemistry, cell biology, and biotechnology". Plant Physiol. 126 (2): 485–93. doi:10.1104/pp.126.2.485. PMC 1540115. PMID 11402179. 
  20. ^ "Information on EC - quercitrinase". BRENDA (BRaunschweig ENzyme DAtabase). Helmholtz Centre for Infection Research. 
  21. ^ Tranchimand S, Brouant P, Iacazio G (November 2010). "The rutin catabolic pathway with special emphasis on quercetinase". Biodegradation 21 (6): 833–59. doi:10.1007/s10532-010-9359-7. PMID 20419500. 
  22. ^ Juergenliemk G, Boje K, Huewel S, Lohmann C, Galla HJ, Nahrstedt A (November 2003). "In vitro studies indicate that miquelianin (quercetin 3-o-β-d-glucuronopyranoside) is able to reach the CNS from the small intestine". Planta Med. 69 (11): 1013–7. doi:10.1055/s-2003-45148. PMID 14735439. 
  23. ^ Williams RJ, Spencer JP, Rice-Evans C (April 2004). "Flavonoids: antioxidants or signalling molecules?". Free Radical Biology & Medicine 36 (7): 838–49. doi:10.1016/j.freeradbiomed.2004.01.001. PMID 15019969. 
  24. ^ Barnes, Stephen; Prasain, Jeevan; D'Alessandro, Tracy; Arabshahi, Ali; Botting, Nigel; Lila, Mary Ann; Jackson, George; Janle, Elsa M.; Weaver, Connie M. (2011). "The metabolism and analysis of isoflavones and other dietary polyphenols in foods and biological systems". Food & Function 2 (5): 235. doi:10.1039/c1fo10025d. 
  25. ^ Gross P (March 1, 2009), New Roles for Polyphenols. A 3-Part report on Current Regulations & the State of Science, Nutraceuticals World 
  26. ^ "River Hills Harvest dba Elderberrylife". Adams, AM, Inspections, Compliance, Enforcement, and Criminal Investigations, US FDA. 22 April 2014. Retrieved 5 November 2014. 

External links[edit]