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	{{chembox		{{chembox
			| Verifiedfields = changed
	| verifiedrevid = 408975110
			| Watchedfields = changed
	| Name = Quercetin
			| verifiedrevid = 415155335
	| ImageFile = Quercetin.svg
			| Name = Quercetin
	| ImageSize = 250px
			| pronounce = {{IPAc-en|ˈ|k|w|ɜːr|s|ᵻ|t|ᵻ|n}}
	| ImageName = Quercetin
			| ImageFile = Quercetin.svg
	| IUPACName = 2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-4''H''-chromen-4-one
			| ImageSize = 250px
	| OtherNames = Sophoretin<br />Meletin<br />Quercetine<br />Xanthaurine<br />Quercetol<br />Quercitin<br />Quertine<br />Flavin meletin
			| ImageAlt = Skeletal formula of quercetin
	| Section1 = {{Chembox Identifiers
			| ImageFile1 = Quercetin-3D-balls.png
	| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
			| ImageAlt1 = Ball-and-stick model of the quercetin molecule
			| IUPACName = 3,3′,4′,5,7-Pentahydroxyflavone
			| SystematicName = 2-(3,4-Dihydroxyphenyl)-3,5,7-trihydroxy-4''H''-1-benzopyran-4-one
			| OtherNames = 5,7,3′,4′-], Sophoretin, Meletin, Quercetine, Xanthaurine, Quercetol, Quercitin, Quertine, Flavin meletin
			|Section1={{Chembox Identifiers
			| CASNo_Ref = {{cascite|correct|CAS}}
			| CASNo = 117-39-5
			| CASNo2_Ref = {{cascite|correct|CAS}}
			| CASNo2 = 6151-25-3
			| CASNo2_Comment = (dihydrate)<ref name=PVP>{{Cite web|url=http://www.pvp.com.br/EN_quercetin_dihydrate_safety_data.htm|archive-url=https://web.archive.org/web/20110916172444/http://www.pvp.com.br/EN_quercetin_dihydrate_safety_data.htm|url-status= dead|title=Quercetin dihydrate safety sheet|archive-date=September 16, 2011}}</ref>
			| ChEBI_Ref = {{ebicite|correct|EBI}}
			| ChEBI = 16243
			| Beilstein = 317313
			| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
			| ChEMBL_Ref = {{ebicite|correct|EBI}}
			| ChEMBL = 50
	| ChemSpiderID = 4444051		| ChemSpiderID = 4444051
			| DrugBank_Ref = {{drugbankcite|correct|drugbank}}
			| DrugBank = DB04216
			| EINECS = 204-187-1
			| Gmelin = 579210
			| IUPHAR_ligand = 5346
			| KEGG_Ref = {{keggcite|correct|kegg}}
			| KEGG = C00389
			| PubChem = 5280343
	| UNII_Ref = {{fdacite|correct|FDA}}		| UNII_Ref = {{fdacite|correct|FDA}}
	| UNII = 9IKM0I5T1E		| UNII = 9IKM0I5T1E
	| KEGG_Ref = {{keggcite|correct|kegg}}		| UNII1_Ref = {{fdacite|correct|FDA}}
	| KEGG = C00389		| UNII1 = 53B03V78A6
			| UNII1_Comment = (dihydrate)
			| UNNumber = 2811
	| InChI = 1/C15H10O7/c16-7-4-10(19)12-11(5-7)22-15(14(21)13(12)20)6-1-2-8(17)9(18)3-6/h1-5,16-19,21H		| InChI = 1/C15H10O7/c16-7-4-10(19)12-11(5-7)22-15(14(21)13(12)20)6-1-2-8(17)9(18)3-6/h1-5,16-19,21H
	| InChIKey = REFJWTPEDVJJIY-UHFFFAOYAW		| InChIKey = REFJWTPEDVJJIY-UHFFFAOYAW
	| ChEMBL_Ref = {{ebicite|correct|EBI}}
	| ChEMBL = 50
	| StdInChI_Ref = {{stdinchicite|correct|chemspider}}		| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
	| StdInChI = 1S/C15H10O7/c16-7-4-10(19)12-11(5-7)22-15(14(21)13(12)20)6-1-2-8(17)9(18)3-6/h1-5,16-19,21H		| StdInChI = 1S/C15H10O7/c16-7-4-10(19)12-11(5-7)22-15(14(21)13(12)20)6-1-2-8(17)9(18)3-6/h1-5,16-19,21H
	| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}		| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
	| StdInChIKey = REFJWTPEDVJJIY-UHFFFAOYSA-N		| StdInChIKey = REFJWTPEDVJJIY-UHFFFAOYSA-N
			| SMILES = O=C1c3c(O/C(=C1/O)c2ccc(O)c(O)c2)cc(O)cc3O
	| CASNo_Ref = {{cascite|correct|CAS}}
	| CASNo = 117-39-5
	| PubChem = 5280343
	| SMILES = O=C1c3c(O/C(=C1/O)c2ccc(O)c(O)c2)cc(O)cc3O
	}}		}}
	| Section2 = {{Chembox Properties		|Section2={{Chembox Properties
	| Formula = C<sub>15</sub>H<sub>10</sub>O<sub>7</sub>		| Formula = C<sub>15</sub>H<sub>10</sub>O<sub>7</sub>
	| MolarMass = 302.236&nbsp;g/mol		| MolarMass = 302.236&nbsp;g/mol
			| Density = 1.799&nbsp;g/cm<sup>3</sup>
	| ExactMass = 302.042653
			| MeltingPtC = 316
	| Density = 1.799&nbsp;g/cm<sup>3</sup>
			| BoilingPt =
	| MeltingPt = 316&nbsp;°C
			| Appearance = yellow crystalline powder<ref name=PVP/>
	| BoilingPt =
			| Solubility = Practically insoluble in water; soluble in aqueous alkaline solutions<ref name=PVP/>
	}}		}}
	}}		}}
			]
			'''Quercetin''' is a plant ] from the ] group of ]s. It is found in many fruits, vegetables, leaves, seeds, and grains; capers, red onions, and ] are common foods containing appreciable amounts of it.<ref name="lpi">{{cite web|url=http://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/flavonoids|title=Flavonoids |publisher=Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR|date=November 2015|access-date=1 April 2018}}</ref><ref name=usda/> It has a ] and is used as an ingredient in ]s, beverages, and foods.
			== Occurrence ==
	'''Quercetin''' {{IPA-en|ˈkwɜrsɨtɨn|}}, a ], is a plant-derived ] found in fruits, vegetables, leaves and grains. It also may be used as an ingredient in supplements, beverages or foods.
			Quercetin is a ] widely distributed in nature.<ref name=lpi/> The name has been used since 1857, and is derived from ''quercetum'' (oak forest), after the oak genus '']''.<ref>{{cite web|url=http://www.merriam-webster.com/dictionary/quercetin|title=Quercetin|date=29 November 2023 |publisher=Merriam-Webster}}</ref><ref>{{cite web|url=http://www.britannica.com/EBchecked/topic/487030/quercitin|title=Quercetin (biochemistry)|publisher=Encyclopædia Britannica}}</ref> It is a naturally occurring ] inhibitor.<ref name="pmid12237347">{{cite journal | vauthors = Fischer C, Speth V, Fleig-Eberenz S, Neuhaus G | title = Induction of Zygotic Polyembryos in Wheat: Influence of Auxin Polar Transport | journal = The Plant Cell | volume = 9 | issue = 10 | pages = 1767–1780 | date = Oct 1997 | pmid = 12237347 | pmc = 157020 | doi = 10.1105/tpc.9.10.1767 }}</ref>
			Quercetin is one of the most abundant dietary flavonoids,<ref name=lpi/><ref name=usda>{{cite web |url=http://www.ars.usda.gov/SP2UserFiles/Place/12354500/Data/Flav/Flav_R03.pdf |title=USDA Database for the Flavonoid Content of Selected Foods, Release 3 |year=2011 |publisher=U.S. Department of Agriculture}}</ref> with an average daily consumption of 25–50 ].<ref name="pmid8847003">{{cite journal | vauthors = Formica JV, Regelson W | title = Review of the biology of quercetin and related bioflavonoids | journal = Food and Chemical Toxicology | volume = 33 | issue = 12 | pages = 1061–80 | year = 1995 | pmid = 8847003 | doi = 10.1016/0278-6915(95)00077-1 }}</ref>
	==Research==
	Several laboratory studies show quercetin may have ] and ] properties,<ref name="stewart08">
	{{cite journal
	| title = Quercetin transiently increases energy expenditure but persistently decreases circulating markers of inflammation in C57BL/6J mice fed a high-fat diet
	| author = Laura K. Stewart, Jeff L. Soileau, David Ribnicky, Zhong Q. Wang, Ilya Raskin, Alexander Poulev, Martin Majewski, William T. Cefalu, and Thomas W. Gettys
	| journal = Metabolism
	| year = 2008
	| volume = 57
	}}</ref><ref name="davis09"/> and it is being investigated for a wide range of potential health benefits.<ref name="davis09">{{ cite
	| title = Quercetin increases brain and muscle ] and exercise tolerance
	| author = J. Mark Davis, E. Angela Murphy, Martin D. Carmichael, and Ben Davis
	| journal = Am J Physiol Regul Integr Comp Physiol
	| volume = 296
	| year = 2009
	}}</ref><ref>
	By Gretchen Reynolds. ], October 7, 2009. Review of the research.</ref>
			{| class="wikitable sortable"
	Quercetin has been shown to increase energy expenditure in ], but only for short periods (fewer than 8 weeks).<ref name="stewart08"/> Effects of quercetin on ] tolerance in mice have been associated with increased ].<ref name="davis09"/>
			|-
			! Foods !! data-sort-type="number" | Quercetin,<br />mg / 100 g
			|-
			| ], raw || 234<ref name=usda/>
			|-
			| ], canned || 173<ref name=usda/>
			|-
			| ] leaves, raw || 170<ref name=usda/>
			|-
			| ] like ] || 86<ref name=usda/>
			|-
			| ] leaves || 70<ref name=usda/>
			|-
			| ] fiber || 58<ref name=usda/>
			|-
			| ] weed, fresh || 55<ref name=usda/>
			|-
			| ] || 53<ref name=usda/>
			|-
			| ], raw || 51<ref name=usda/>
			|-
			| ] leaves || 49<ref name=usda/>
			|-
			| ] || 32<ref name=usda/>
			|-
			| ] || 32<ref name=usda/>
			|-
			| ] || 30<ref name=usda/>
			|-
			| ] || 23<ref name=usda/>
			|-
			| ] || 19<ref name=usda/>
			|-
			| ] || 18<ref name=usda/>
			|-
			| ] seeds || 15<ref name=usda/>
			|-
			| ] || 15<ref name=usda/>
			|-
			| ] || 13<ref name=usda/>
			|-
			| ] || 12<ref name=usda/>
			|-
			|}
			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.<ref>{{cite journal | vauthors = Slimestad R, Fossen T, Vågen IM | title = Onions: a source of unique dietary flavonoids | journal = Journal of Agricultural and Food Chemistry | volume = 55 | issue = 25 | pages = 10067–80 | date = December 2007 | pmid = 17997520 | doi = 10.1021/jf0712503 }}</ref> One study found that ] ]es had 79% more quercetin than non-organically grown fruit.<ref name="pmid17590007">{{cite journal | vauthors = Mitchell AE, Hong YJ, Koh E, Barrett DM, Bryant DE, Denison RF, Kaffka S | title = Ten-year comparison of the influence of organic and conventional crop management practices on the content of flavonoids in tomatoes | journal = Journal of Agricultural and Food Chemistry | volume = 55 | issue = 15 | pages = 6154–9 | date = Jul 2007 | pmid = 17590007 | doi = 10.1021/jf070344+ }}</ref> Quercetin is present in various kinds of ] from different plant sources.<ref name="pmid21229237">{{cite journal | vauthors = Petrus K, Schwartz H, Sontag G | title = Analysis of flavonoids in honey by HPLC coupled with coulometric electrode array detection and electrospray ionization mass spectrometry | journal = Analytical and Bioanalytical Chemistry | volume = 400 | issue = 8 | pages = 2555–63 | date = Jun 2011 | pmid = 21229237 | doi = 10.1007/s00216-010-4614-7 | s2cid = 24796542 }}</ref>
			== Biosynthesis ==
	The American Cancer Society says while quercetin "has been promoted as being effective against a wide variety of diseases, including cancer," and "some early lab results appear promising, as of yet there is no reliable clinical evidence that quercetin can prevent or treat cancer in humans." In the amounts consumed in a healthy diet, quercetin "is unlikely to cause any major problems or benefits."<ref>American Cancer Society, </ref>
			In plants, ] is converted to ] in a series of steps known as the general ] pathway using ], ], and ].<ref name="pmid11402179">{{cite journal | vauthors = Winkel-Shirley B | title = Flavonoid biosynthesis. A colorful model for genetics, biochemistry, cell biology, and biotechnology | journal = Plant Physiology | volume = 126 | issue = 2 | pages = 485–93 | date = Jun 2001 | pmid = 11402179 | pmc = 1540115 | doi = 10.1104/pp.126.2.485 }}</ref> One molecule of 4-coumaroyl-CoA is added to three molecules of ] to form tetrahydroxychalcone using 7,2′-dihydroxy-4′-methoxyisoflavanol synthase. Tetrahydroxychalcone is then converted into ] using ].
	Adequate dietary intake of fruits and vegetables may ''reduce the risk'' of cancer.<ref>{{cite web | title = Guidance for Industry: A Food Labeling Guide XI. Appendix C: Health Claims, 21 CFR 101.76 and 21 CFR 101.78, April 2008 | publisher = US Department of Health and Human Services, Food and Drug Administration| url = http://www.fda.gov/Food/GuidanceComplianceRegulatoryInformation/GuidanceDocuments/FoodLabelingNutrition/FoodLabelingGuide/ucm064919.htm}}</ref> Research shows quercetin influences cellular mechanisms ''in vitro''{{specify|date=March 2010}} and, in animal studies, there is evidence from human population studies that quercetin may, in a very limited fashion, reduce the risk of certain cancers.<ref>{{cite journal |author=Neuhouser ML |title=Dietary flavonoids and cancer risk: evidence from human population studies |journal=Nutr Cancer |volume=50 |issue=1 |pages=1–7 |year=2004 |pmid=15572291 |doi=10.1207/s15327914nc5001_1 }}</ref><ref>{{cite journal |author=Murakami A, Ashida H, Terao J |title=Multitargeted cancer prevention by quercetin |journal=Cancer Lett. |volume=269 |issue=2 |pages=315–25 |year=2008 |month=October |pmid=18467024 |doi=10.1016/j.canlet.2008.03.046 }}</ref>
			Naringenin is converted into ] using flavanoid 3′-hydroxylase. Eriodictyol is then converted into ] with flavanone 3-hydroxylase, which is then converted into quercetin using ].<ref name="pmid11402179"/>
	In laboratory studies of cells ], quercetin produces changes that are also produced by compounds that cause cancer (]), but these studies do not report increased cancer in animals or humans.<ref>{{cite journal |author=Verschoyle RD, Steward WP, Gescher AJ |title=Putative cancer chemopreventive agents of dietary origin-how safe are they? |journal=Nutr Cancer |volume=59 |issue=2 |pages=152–62 |year=2007 |pmid=18001209 |doi=10.1080/01635580701458186 |doi_brokendate=2009-06-26 }}</ref><ref>{{cite journal |author=Rietjens IM, Boersma MG, van der Woude H, Jeurissen SM, Schutte ME, Alink GM |title=Flavonoids and alkenylbenzenes: mechanisms of mutagenic action and carcinogenic risk |journal=Mutat. Res. |volume=574 |issue=1-2 |pages=124–38 |year=2005 |month=July |pmid=15914212 |doi=10.1016/j.mrfmmm.2005.01.028 }}</ref><ref>{{cite journal |author=van der Woude H, Alink GM, van Rossum BE, ''et al.'' |title=Formation of transient covalent protein and DNA adducts by quercetin in cells with and without oxidative enzyme activity |journal=Chem. Res. Toxicol. |volume=18 |issue=12 |pages=1907–16 |year=2005 |month=December |pmid=16359181 |doi=10.1021/tx050201m }}</ref> The U.S. Food and Drug Administration has not approved any health claims for quercetin.<ref>US FDA, Center for Food Safety and Nutrition, Qualified Health Claims Subject to Enforcement Discretion, April 2007 {{dead link|date=November 2010}}</ref> There is current early-stage clinical research on quercetin addressing safety and efficacy against ], ] and ] absorption in ] and ] (February 2009).<ref></ref>
			=== Glycosides ===
	Quercetin is the ] form of a number of other flavonoid ]s, such as ] and ], found in ] fruit, ] and onions. Quercetin forms the ]s ] and ] together with ] and ], respectively. Quercetin is classified as ] (no evidence of ]icity in humans).
			]
			Quercetin is the ] form of a number of other flavonoid ]s, such as ] (also known as quercetin-3-O-rutinoside) and ], found in ] fruit, ], and onions.<ref name=lpi/> Quercetin forms the ]s ] and ] together with ] and ], respectively. Likewise ] is the 3-''O''-], ] is the 3-''O''-], ] is the 3-''O''-] and ] is the 4′-''O''-glucoside. ] is a quercetin derivative found in cottonseeds and cottonseed oil. ] is the quercetin 3-''O''-β-<small>D</small>-glucuronopyranoside.<ref name="pmid14735439">{{cite journal | vauthors = Juergenliemk G, Boje K, Huewel S, Lohmann C, Galla HJ, Nahrstedt A | title = In vitro studies indicate that miquelianin (quercetin 3-''O''-beta-D-glucuronopyranoside) is able to reach the CNS from the small intestine | journal = Planta Medica | volume = 69 | issue = 11 | pages = 1013–7 | date = Nov 2003 | pmid = 14735439 | doi = 10.1055/s-2003-45148 | s2cid = 260253046 }}</ref>
			Several ] (also known as dihydroquercetin) glycosides also exist. ] is the 3-''O''-glucoside of quercetin.
	==Occurrence==
	Quercetin is a naturally-occurring ] inhibitor.{{Citation needed|date=May 2008}}
			=== Rutin degradation pathway ===
	Foods rich in quercetin include black and green ] ('']''; 2000–2500&nbsp;mg/kg), ]s (1800&nbsp;mg/kg),<ref></ref> ] (1700&nbsp;mg/kg), ]s (44&nbsp;mg/kg), ], especially ] (1910&nbsp;mg/kg) (higher concentrations of quercetin occur in the outermost rings<ref>{{cite journal | author=Crystal Smith, Kevin A. Lombard, Ellen B. Peffley, Weixin Liu | title =Genetic Analysis of Quercetin in Onion (''Allium cepa L.'') ''Lady Raider'' | journal =The Texas Journal of Agriculture and Natural Resource | volume = 16 | pages = 24–8 | publisher = Agriculture Consortium of Texas | year= 2003 | url = http://www.tarleton.edu/~txjanr/2003issue/article3.pdf| format =|archiveurl = http://web.archive.org/web/20070225125621/http%3A//www.tarleton.edu/%7Etxjanr/2003issue/article3.pdf |archivedate = February 25, 2007|deadurl=yes}}</ref>), ], ], ], ] and other ], and a number of berries, including ], ] (158&nbsp;mg/kg, fresh weight), ] (cultivated 74&nbsp;mg/kg, wild 146&nbsp;mg/kg), ] (cultivated 83&nbsp;mg/kg, wild 121&nbsp;mg/kg), ] (89&nbsp;mg/kg), ] (85&nbsp;mg/kg), ]berry (63&nbsp;mg/kg), ] berry (62&nbsp;mg/kg), ] (cultivated 53&nbsp;mg/kg, wild 56&nbsp;mg/kg),<ref>{{cite journal | author = Sari H. Häkkinen ''et al.'' | title = Content of the Flavonols Quercetin, Myricetin, and Kaempferol in 25 Edible Berries | journal = ] | volume = 47 | issue = 6 | pages = 2274–9 | year= 1999 | doi = 10.1021/jf9811065 | pmid = 10794622 | accessdate = }}</ref> and the fruit of the ] cactus. A recent study found that ] tomatoes had 79% more quercetin than ].<ref>{{cite journal | author = A. E. Mitchell, Y. J. Hong, E. Koh, D. M. Barrett, D. E. Bryant, R. F. Denison and S. Kaffka | title = Ten-Year Comparison of the Influence of Organic and Conventional Crop Management Practices on the Content of Flavonoids in Tomatoes | year = 2007 | journal = ] | volume = 55 | pmid = 17590007 | issue = 15 | pages = 6154–9 | doi=10.1021/jf070344 }}</ref>
			The enzyme ] can be found in '']''.<ref name="urlInformation on EC 3.2.1.66 - quercitrinase">{{cite web | url = http://www.brenda-enzymes.org/php/result_flat.php4?ecno=3.2.1.66 | title = Information on EC 3.2.1.66 - quercitrinase | publisher = Helmholtz Centre for Infection Research | work = ] (BRaunschweig ENzyme DAtabase) }}</ref> This enzyme ] the glycoside ] to release quercetin and <small>L</small>-]. It is an enzyme in the ] catabolic pathway.<ref name="pmid20419500">{{cite journal | vauthors = Tranchimand S, Brouant P, Iacazio G | title = The rutin catabolic pathway with special emphasis on quercetinase | journal = Biodegradation | volume = 21 | issue = 6 | pages = 833–59 | date = Nov 2010 | pmid = 20419500 | doi = 10.1007/s10532-010-9359-7 | s2cid = 30101803 }}</ref>
	A study<ref></ref> by the ], ], has also indicated the presence of quercetin in varieties of ], including honey derived from ] and ] ]s.<ref></ref>
	==Biosynthesis==		== Pharmacology ==
	] The biosynthesis of quercetin is summarized in the above figure.<ref>]</ref> Phenylalanine(1) is converted to 4-coumaroyl-CoA(2) in a series of steps known as the general phenylpropanoid pathway using phenyl ammonia-lyase, cinnamate-4-hydroxylase, and 4-coumaroylCoA-ligase. 4-coumaroyl-CoA(2) is added to three molecules of malonyl-CoA(3) to form tetrahydroxychalcone(4) using 7,2’-dihydroxy, 4’-methoxyisoflavanol synthase. Tetrahydroxychalcone(4) is then converted into naringenin(5) using chalcone isomerase. Naringenin(5) is then converted into eriodictyol(6) using flavanoid 3’ hydroxylase. Eriodictyol(6) is then converted into dihydroquercetin(7) with flavanone 3-hydroxylase, which is then converted into quercetin using flavanol synthase.<ref>{{Cite journal
	|journal = Plant Physiol
	|last = Winkel-Shirley
	|first = Brenda
	|url = http://www.plantphysiol.org/cgi/content/full/126/2/485
	|title = Flavonoid Biosynthesis. A Colorful Model for Genetics, Biochemistry, Cell Biology, and Biotechnology
	|date = June 2001
	|volume = 126
	|pages = 485–493
	|doi = 10.1104/pp.126.2.485
	|pmid = 11402179
	|issue = 2
	|pmc = 1540115}}</ref>
			=== Pharmacokinetics ===
	==Possible medicinal properties==
			The ] of quercetin in humans after oral intake is very low, with one study concluding it must be less than 1%.<ref name="pharmokinetics">{{cite journal |last1=Gugler |first1=R. |last2=Leschik |first2=M. |last3=Dengler |first3=H. J. |title=Disposition of quercetin in man after single oral and intravenous doses |journal=European Journal of Clinical Pharmacology |date=1 March 1975 |volume=9 |issue=2 |pages=229–234 |doi=10.1007/BF00614022|pmid=1233267 |s2cid=23812714 }}</ref> Intravenous injection of quercetin shows a rapid decay in concentration described by a two-compartment model (initial ] of 8.8 minutes, terminal half-life of 2.4 hours).<ref name="pharmokinetics"/> Because it undergoes rapid and extensive metabolism, the biological effects presumed from ''in vitro'' studies are unlikely to apply ''in vivo''.<ref name=lpi/><ref name=Williams>{{cite journal | vauthors = Williams RJ, Spencer JP, Rice-Evans C | title = Flavonoids: antioxidants or signalling molecules? | journal = Free Radical Biology & Medicine | volume = 36 | issue = 7 | pages = 838–49 | date = Apr 2004 | pmid = 15019969 | doi = 10.1016/j.freeradbiomed.2004.01.001 | department = (review) }}</ref><ref>{{cite journal | vauthors = Barnes S, Prasain J, D'Alessandro T, Arabshahi A, Botting N, Lila MA, Jackson G, Janle EM, Weaver CM | title = The metabolism and analysis of isoflavones and other dietary polyphenols in foods and biological systems | journal = Food & Function | volume = 2 | issue = 5 | pages = 235–44 | date = May 2011 | pmid = 21779561 | doi = 10.1039/c1fo10025d | department = (review) | pmc=4122511}}</ref><ref name="pmid30614249">{{cite journal | vauthors=Luca SV, Macovei I, Bujor A, Trifan A | title=Bioactivity of dietary polyphenols: The role of metabolites | journal=] | volume=60 | issue=4 | pages=626–659 | year=2020 | doi = 10.1080/10408398.2018.1546669 | pmid=30614249| s2cid=58651581 }}</ref> Quercetin supplements in the ] form are less ] than the quercetin ] often found in foods, especially red onions.<ref name=lpi/><ref name="pmid31557798">{{cite journal | vauthors = Dabeek WM, Marra MV | title = Dietary Quercetin and Kaempferol: Bioavailability and Potential Cardiovascular-Related Bioactivity in Humans | journal = Nutrients | volume = 11 | issue=10 | pages = 2288 | date=2019 | doi = 10.3390/nu11102288 | pmc=6835347 | pmid = 31557798| doi-access = free }}</ref> Ingestion with high-fat foods may increase bioavailability compared to ingestion with low-fat foods,<ref name="pmid31557798" /> and carbohydrate-rich foods may increase absorption of quercetin by stimulating ] and ] ].<ref name=lpi/> Whereas quercetin has been shown to be a potent anti-inflammatory compound in a variety of in vitro and in vivo bioassay models, oral quercetin in human subjects has not exhibited the desired effects.<ref name="pmid34248976">{{cite journal |vauthors=Shen P, Lin W, Deng X, Ba X, Han L, Chen Z, Qin K, Huang Y, Tu S |title=Potential Implications of Quercetin in Autoimmune Diseases |journal=Front Immunol |volume=12 |issue= |pages=689044 |date=2021 |pmid=34248976 |pmc=8260830 |doi=10.3389/fimmu.2021.689044 |doi-access=free |url=}}</ref> Because of low solubility and poor bioavailability of quercetin, derivatives have been synthesized to overcome these challenges and enhance its biological activity, leading to compounds with improved properties for possible therapeutic applications.<ref name="pmid34971873">{{cite journal |vauthors=Alizadeh SR, Ebrahimzadeh MA |title=Quercetin derivatives: Drug design, development, and biological activities, a review |journal=Eur J Med Chem |volume=229 |issue= |pages=114068 |date=February 2022 |pmid=34971873 |doi=10.1016/j.ejmech.2021.114068 |s2cid=245485982 |url=}}</ref>
	{{Refimprove|section|date=February 2010}}
	{{Misleading|section|date=February 2010}}
	From in vitro studies, quercetin has demonstrated significant ] activity by inhibiting both synthesis and release of ] and other ]/inflammatory ]s.{{Citation needed|date=February 2011}} In addition, it may have ] activity and ]-sparing action.{{Citation needed|date=February 2011}}
			=== Metabolism ===
	In vitro, cultured skin and prostate cancer cells were suppressed (compared to nonmalignant cells) when treated with a combination of quercetin and ].<ref>{{cite journal
			Quercetin is rapidly metabolized (via ]) after the ingestion of quercetin foods or supplements.<ref name="pmid10363620">{{cite journal | vauthors = Graefe EU, Derendorf H, Veit M | title = Pharmacokinetics and bioavailability of the flavonol quercetin in humans | journal = International Journal of Clinical Pharmacology and Therapeutics | volume = 37 | issue = 5 | pages = 219–33 | year = 1999 | pmid = 10363620 | url = http://ucce.ucdavis.edu/files/datastore/608-67.pdf | department = (review) | access-date = 2016-01-01 | archive-date = 2017-05-17 | archive-url = https://web.archive.org/web/20170517030352/http://ucce.ucdavis.edu/files/datastore/608-67.pdf | url-status = dead }}</ref> Five metabolites (quercetin glucuronides) have been found in human plasma after quercetin ingestion.<ref>{{cite journal |last1=Wittig |first1=Jörg |last2=Herderich |first2=Markus |last3=Graefe |first3=Eva Ulrike |last4=Veit |first4=Markus |title=Identification of quercetin glucuronides in human plasma by high-performance liquid chromatography–tandem mass spectrometry |journal=Journal of Chromatography B: Biomedical Sciences and Applications |date=April 2001 |volume=753 |issue=2 |pages=237–243 |doi=10.1016/s0378-4347(00)00549-1|pmid=11334336 }}</ref><ref name="pmid10363620"/> Taken together, the quercetin glucuronides have a half-life around 11–12 hours.<ref name="pmid10363620"/>
	| title = Induction of cancer-specific cytotoxicity towards human prostate and skin cells using quercetin and ultrasound
	| journal = British Journal of Cancer
	| volume = 92
	| issue = 3
	| pages = 499–502
	| publisher =
	| year= 2005
	| url = http://www.nature.com/bjc/journal/v92/n3/abs/6602364a.html
	| doi = 10.1038/sj.bjc.6602364
	| author =Paliwal S
	| pmid = 15685239
	| last2 = Sundaram
	| first2 = J
	| last3 = Mitragotri
	| first3 = S
	| pmc = 2362095 }}</ref>
			In rats, quercetin did not undergo any significant ].<ref name = "Day_2004"/> In contrast, quercetin did undergo extensive ] (conjugation) to produce ]s that are more ] than the parent substance, hence are more rapidly excreted from the body. ''In vitro'', the meta-] of ] is methylated by ]. Four of the five hydroxyl groups of quercetin are ] by ]. The exception is the 5-hydroxyl group of the flavonoid ring, which generally does not undergo glucuronidation. The major metabolites of orally absorbed quercetin are ], ], and ].<ref name = "Day_2004">{{cite book | veditors = Bao Y, Fenwick R | title = Phytochemicals in health and disease | chapter = Characterization of polyphenol metabolites | vauthors = Day AJ, Rothwell JA, Morgan RA | date = 2004 | publisher = Dekker | location = New York, NY | isbn = 0-8247-4023-8 | pages = 50–67 | chapter-url = https://books.google.com/books?id=ruD5AWlELmgC&q=Quercetin%20%E2%80%8E%20estrogen%20receptor&pg=PA58}}</ref> A methyl metabolite of quercetin has been shown ''in vitro ''to be more effective than quercetin at inhibiting ]-activated ]s.<ref name="pmid30614249" />
	It has also been claimed that quercetin reduces blood pressure in hypertensive<ref>{{cite journal |author=Edwards RL, Lyon T, Litwin SE, Rabovsky A, Symons JD, Jalili T |title=Quercetin reduces blood pressure in hypertensive subjects |journal=J. Nutr. |volume=137 |issue=11 |pages=2405–11 |date=1 November 2007|pmid=17951477 |url=http://jn.nutrition.org/cgi/pmidlookup?view=long&pmid=17951477 }}</ref> and obese subjects in whom ] levels were also reduced.<ref>{{cite journal | author=Egert S et al. |title= Quercetin reduces systolic blood pressure and plasma oxidised low-density lipoprotein concentrations in overweight subjects with a high-cardiovascular disease risk phenotype: A double-blinded, placebo-controlled cross-over study |journal= Br J Nutr |volume=102 | issue=7 | pages= 1065-1074 | year=2009 | pmid= 19402938}}</ref>
	An 8-year study found the presence of three ]s — ], quercetin, and ] — in a normal diet was associated with 23% reduced risk of ], a rare but frequently fatal disease, in tobacco smokers.<ref>{{cite journal | journal = ] | title = Flavonols and pancreatic cancer risk | author = Nöthlings U et al. | volume = 166 | issue = 8 | pages = 924–931 | year = 2007 | doi = 10.1093/aje/kwm172 | pmid = 17690219}}</ref> There was no benefit in subjects who had never smoked or had previously quit smoking.		Compared to other ]s, quercetin is one of the most effective inducers of the phase II detoxification enzymes.<ref name="pmid21277359">{{cite journal | vauthors=Procházková D, Boušová I, Wilhelmová N | title=Antioxidant and prooxidant properties of flavonoids | journal=] | volume=82 | issue=4 | pages=513–523 | year=2011 | doi = 10.1016/j.fitote.2011.01.018 | pmid=21277359| doi-access=free }}</ref>
			''In vitro'' studies show that quercetin is a strong inhibitor of the ] enzymes ] and ] and a moderate inhibitor of ].<ref>{{cite journal | vauthors = Elbarbry F, Ung A, Abdelkawy K | title = Studying the Inhibitory Effect of Quercetin and Thymoquinone on Human Cytochrome P450 Enzyme Activities | journal = Pharmacognosy Magazine | volume = 13 | issue = Suppl 4 | pages = S895–S899 | date = January 2018 | pmid = 29491651 | pmc = 5822518 |doi = 10.4103/0973-1296.224342 |doi-broken-date = 1 November 2024 |doi-access=free}}</ref><ref>{{cite journal |last1=Rastogi |first1=Himanshu |last2=Jana |first2=Snehasis |title= Evaluation of Inhibitory Effects of Caffeic acid and Quercetin on Human Liver Cytochrome P450 Activities|journal=Phytotherapy Research |date=December 2014 |volume=28 |issue=12 |pages=1873–1878 |doi=10.1002/ptr.5220|pmid=25196644 |s2cid=41563915 |doi-access=free }}</ref> Drugs that are metabolized by these pathways may have increased effect. An ''in vivo'' study found that quercetin supplementation slows the metabolism of ] to a statistically significant extent in a particular genetic subpopulation, but in absolute terms the effect was almost negligible.<ref>{{cite journal |title= Quercetin Significantly Inhibits the Metabolism of Caffeine, a Substrate of Cytochrome P450 1A2 Unrelated to ''CYP''1''A''2*1''C'' (−2964G>A) and 1''F''* (734C>A) Gene Polymorphisms|journal= BioMed Research International|year= 2014|doi=10.1155/2014/405071|doi-access= free|last1= Xiao|first1= Jian|last2= Huang|first2= Wei-Hua|last3= Peng|first3= Jing-Bo|last4= Tan|first4= Zhi-Rong|last5= Ou-Yang|first5= Dong-Sheng|last6= Hu|first6= Dong-Li|last7= Zhang|first7= Wei|last8= Chen|first8= Yao|volume= 2014|pages= 1–6|pmid= 25025048|pmc= 4082882}}</ref>
	In mice, an oral quercetin dose of 12.5 to 25&nbsp;mg/kg increased ] of ]l ] and improved exercise endurance.<ref>{{cite journal | journal = Am J Physiol Regul Integr Comp Physiol. | year=2009 | pmid = 19211721 | author = Davis JM, Murphy EA, Carmichael MD, Davis B. | title = Quercetin increases brain and muscle mitochondrial biogenesis and exercise tolerance. | volume = 296 | issue = 4 | pages = R1071–7 | doi = 10.1152/ajpregu.90925.2008 | pmid=19211721 }}</ref>
			==Food safety==
	An in vitro study showed quercetin and ] combined inhibited production of fat cells.<ref>{{cite journal
			In 2010, the U. S. ] <!-- (FDA) --> acknowledged high-purity quercetin as ] <!-- (GRAS) --> for use as an ingredient in various specified food categories at levels up to 500 mg per serving.<ref name=GRN341>{{cite web|title=GRN No. 341 (Quercetin)|url=https://www.accessdata.fda.gov/scripts/fdcc/index.cfm?set=GRASNotices&id=341|publisher=US Food and Drug Administration|date=22 November 2010|access-date=27 October 2021}}</ref>
	| journal = Life Sci.
	| title = Enhanced inhibition of adipogenesis and induction of apoptosis in 3T3-L1 adipocytes with combinations of resveratrol and quercetin
	| year = 2008
	| volume = 82
	| issue = 19-20
	| pages = 1032–9
	| pmid = 18433793
	| author = Yang JY, Della-Fera MA, Rayalam S, Ambati S, Hartzell DL, Park HJ, Baile CA
	| doi = 10.1016/j.lfs.2008.03.003
	}}</ref>
			== Health claims ==
	A possible antagonistic interaction occurred in rats between quercetin and niacin (vitamin B<sub>3</sub>) which, in sustained, high doses, produces a cutaneous reddening or flush.<ref>{{cite journal | doi = 10.1038/sj.bjp.0707668 | journal = Brit J Pharmacol | year = 2008 | pmid = 18223672 | author = Papaliodis D, Boucher W, Kempuraj D, Theoharides TC | title = The flavonoid luteolin inhibits niacin-induced flush | volume = 153 | issue = 7 | pages = 1382–87 | pmc = 2437911}}</ref>
			Quercetin has been studied in ] and small ].<ref name=lpi/><ref>{{cite journal |vauthors=Yang F, Song L, Wang H, Wang J, Xu Z, Xing N |title=Quercetin in prostate cancer: Chemotherapeutic and chemopreventive effects, mechanisms and clinical application potential (Review) |journal=Oncol. Rep. |volume=33 |issue=6 |pages=2659–68 |date=June 2015 |pmid=25845380 |doi=10.3892/or.2015.3886 |doi-access=free }}</ref><ref name="roles">{{citation | title = New Roles for Polyphenols. A 3-Part Report on Current Regulations & the State of Science | vauthors = Gross P| date = March 1, 2009 | publisher = Nutraceuticals World | url = http://www.nutraceuticalsworld.com/issues/2009-03/view_features/new-roles-for-polyphenols/ }}</ref><ref name="pmid25323953">{{cite journal | vauthors = Miles SL, McFarland M, Niles RM | title = Molecular and physiological actions of quercetin: need for clinical trials to assess its benefits in human disease | journal = Nutrition Reviews | volume = 72 | issue = 11 | pages = 720–34 | year = 2014 | pmid = 25323953 | doi = 10.1111/nure.12152 | doi-access = free }}</ref> While supplements have been promoted for the treatment of cancer and various other diseases,<ref name=lpi/><ref name="pmid26393898">{{cite journal | vauthors = D'Andrea G | title = Quercetin: A flavonol with multifaceted therapeutic applications? | journal = Fitoterapia | volume = 106 | pages = 256–71 | year = 2015 | pmid = 26393898 | doi = 10.1016/j.fitote.2015.09.018 }}</ref> there is no high-quality evidence that quercetin (via supplements or in food) is useful to treat cancer<ref name=acs>{{cite book |publisher=] |title=American Cancer Society Complete Guide to Complementary and Alternative Cancer Therapies |edition=2nd |year=2009 |isbn=9780944235713 |veditors=Ades TB |chapter=Quercetin |url-access=registration |url=https://archive.org/details/americancancerso0000unse }}</ref> or any other disease.<ref name=lpi/><ref name="efsa">{{cite journal | author = European Food Safety Agency (EFSA) NDA Panel (Dietetic Products, Nutrition and Allergies) | title = 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 | journal = EFSA Journal | date = 8 April 2011 | volume = 9 | issue = 4 | pages = 2067–82 | doi = 10.2903/j.efsa.2011.2067 | url = http://www.efsa.europa.eu/en/efsajournal/pub/2067 | access-date = 24 September 2014 | doi-access = free }}</ref>
			The US ] has issued ] to several manufacturers advertising on their product labels and websites that quercetin product(s) can be used to treat diseases.<ref name="fda">{{cite web | url = https://www.fda.gov/ICECI/EnforcementActions/WarningLetters/2017/ucm545773.htm | title = Warning Letter to Cape Fear Naturals | date = 2 March 2017 | vauthors = King JL | publisher = Inspections, Compliance, Enforcement, and Criminal Investigations, US Food and Drug Administration | access-date = 29 November 2018 }}</ref><ref name="fda2">{{cite web|url=https://www.fda.gov/ICECI/EnforcementActions/WarningLetters/2017/ucm554022.htm|title=Warning Letter to DoctorVicks.com|publisher=Inspections, Compliance, Enforcement, and Criminal Investigations, US Food and Drug Administration|date=17 April 2017| vauthors = Pace R |access-date=29 November 2018}}</ref> The FDA regards such quercetin advertising and products as unapproved&nbsp;&ndash; with unauthorized ]s concerning the anti-disease products&nbsp;&ndash; as defined by "sections 201(g)(1)(B) and/or 201 (g)(1)(C) of the Act because they are intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease",<ref name=fda/><ref name=fda2/> conditions not met by the manufacturers.
	Despite these preliminary indications of possible medicinal effects, quercetin has neither been confirmed as a specific therapeutic for any condition, nor has it been approved by any regulatory agency. A bioavailability study done on rats showed ingested quercetin is extensively metabolized into inactive phenolic acids, with more than 96% of the ingested amount excreted within 72 hours, indicating actual physiological roles, if they exist, involve quercetin in only minute amounts.<ref>{{cite journal | title = Bioavailability of quercetin-4'-glucoside in rats. | journal = J Agric Food Chem. | year = 2008 | month= December| volume=2456 | issue=24 | pages = 12127–37 | pmid = 19053221 | author = Mullen W et al. | doi = 10.1021/jf802754s}}</ref>
			===Safety===
	==Drug interactions==
			Little research has been conducted into the safety of quercetin supplementation in humans, and the results are insufficient to give confidence that the practice is safe. In particular, a lack of safety information exists on the effect of quercetin supplementation for pregnant women, breastfeeding women, children, and adolescents. The hormonal effects of quercetin found in animal studies raise the suspicion of a parallel effect in humans, particularly in respect of ]-dependent tumors.<ref name=andres/>
	Quercetin is contraindicated with some antibiotics; it may interact with ]s (an ]), as quercetin competitively binds to bacterial DNA ]. Whether this inhibits or enhances the effect of fluoroquinolones is not certain.<ref>{{cite journal |author=Hilliard JJ, Krause HM, Bernstein JI, ''et al.'' |title=A comparison of active site binding of 4-quinolones and novel flavone gyrase inhibitors to DNA gyrase |journal=Adv. Exp. Med. Biol. |volume=390 |issue= |pages=59–69 |year=1995 |pmid=8718602 }}</ref>
			Quercetin supplementation can interfere with the effects of medications. The precise nature of this interaction is known for some common medicines, but for many, it is not.<ref name=andres>{{cite journal |vauthors=Andres S, Pevny S, Ziegenhagen R, Bakhiya N, Schäfer B, Hirsch-Ernst KI, Lampen A |title=Safety Aspects of the Use of Quercetin as a Dietary Supplement |journal=Mol Nutr Food Res |volume=62 |issue=1 |pages= |date=January 2018 |pmid=29127724 |doi=10.1002/mnfr.201700447 |s2cid=24772872 |type=Review|doi-access=free }}</ref>
	Quercetin is described as an ] of ].<ref name="Si_2009">{{cite journal | author = Si Dayong, Wang Y, Zhou Y-H, Guo Y, Wang J, Zhou H, Li Z-S, Fawcett JP | title = Mechanism of CYP2C9 inhibition by flavones and flavonols | journal = Drug Metabolism and Disposition | volume =37 | issue = 3| pages =629–634. | year = 2009 | month =March| doi = 10.1124/dmd.108.023416 | url = http://p4502c.googlepages.com/dmd2.pdf | pmid = 19074529 }}</ref> Sources are inconsistent as to whether quercetin is an inhibitor<ref>{{cite journal | author = Su-Lan Hsiu; Yu-Chi Hou; Yao-Horng Wang; Chih-Wan Tsao; Sheng-Fang Sue; and Pei-Dawn L. Chao | journal = ] | volume = 72 | issue = 3 | date = 6 December 2002 | pages = 227–235 | title = Quercetin significantly decreased cyclosporin oral bioavailability in pigs and rats | doi = 10.1016/S0024-3205(02)02235-X}}</ref> or ]<ref>{{cite journal | author = Judy L. Raucy | journal = Drug Metabolism and Disposition | volume = 31 | issue = 3 | date = 1 May 2003 | pages = 533–539 | title = Regulation of CYP3A4 Expression in Human Hepatocytes by Pharmaceuticals and Natural Products | doi = 10.1124/dmd.31.5.533 }}</ref> of ]. CYP2C9 and CPY3A4 are members of the ] mixed-function oxidase system, and as such are ]s involved in the metabolism of ] in the body. In either case, quercetin may alter serum levels, and potentially, effects of drugs metabolized by these enzymes.
			== See also ==
	In cattle, there is a synergystic interaction between bovine papillomavirus-2 infection and exposure to quercetin, promoting bladder neoplasia, clinically presenting as enzootic haematuria. A similar effect is seen on exposure to the bracken fern '']'', and the chemical ] found within it.
			{{div col|colwidth=28em}}
			* ]
	==Glycosides==
	* ] is the 3-O-] of quercetin.
	* ] is the 3-O-] of quercetin.
	* ] is the 3-O-] of quercetin.
	* ] is the 4'-O-glucoside of quercetin.
	==See also==
	{{Col-begin}}
	{{Col-3}}
	* ]		* ]
	* ]		* ]
	{{Col-3}}
	* ]		* ]
	* ]		* ]
	* ]		* ]
	{{Col-3}}
	* ]		* ]
	* ]		* ]
	* ]		* ]
	{{col-end}}		{{div col end}}
	==References==		== References ==
	{{Reflist|2}}		{{Reflist}}
	==External links==		==External links==
			*{{Commons category-inline}}
	* (] Website)
			{{Flavonols}}
	{{Antioxidants}}		{{Antioxidants}}
	{{Flavonol}}		{{Phytoestrogens}}
			{{Estrogen receptor modulators}}
			{{Purine receptor modulators}}
			{{Authority control}}
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