Quercetinのソースを表示

{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 415155335
| Name = Quercetin
| pronounce = {{IPAc-en|ˈ|k|w|ɜːr|s|ᵻ|t|ᵻ|n}}
| ImageFile = Quercetin.svg
| ImageSize = 250px
| ImageAlt = Skeletal formula of quercetin
| ImageFile1 = Quercetin-3D-balls.png
| 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′-[[flavonol|flavon-3-ol]], 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
| 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 = 9IKM0I5T1E
| UNII1_Ref = {{fdacite|correct|FDA}}
| 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
| InChIKey = REFJWTPEDVJJIY-UHFFFAOYAW
| 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
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = REFJWTPEDVJJIY-UHFFFAOYSA-N
| SMILES = O=C1c3c(O/C(=C1/O)c2ccc(O)c(O)c2)cc(O)cc3O
}}
|Section2={{Chembox Properties
| Formula = C<sub>15</sub>H<sub>10</sub>O<sub>7</sub>
| MolarMass = 302.236&nbsp;g/mol
| Density = 1.799&nbsp;g/cm<sup>3</sup>
| MeltingPtC = 316
| BoilingPt =
| Appearance = yellow crystalline powder<ref name=PVP/>
| Solubility = Practically insoluble in water; soluble in aqueous alkaline solutions<ref name=PVP/>
}}
}}
[[File:Spectre UV vis Quercétine.PNG|thumb|right|UV visible spectrum of quercetin, with lambda max at 369&nbsp;nm]]
'''Quercetin''' is a plant [[flavonol]] from the [[flavonoid]] group of [[polyphenol]]s. It is found in many fruits, vegetables, leaves, seeds, and grains; capers, red onions, and [[kale]] 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 [[bitter flavor]] and is used as an ingredient in [[dietary supplement]]s, beverages, and foods.

== Occurrence ==
Quercetin is a [[flavonoid]] 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 ''[[Quercus]]''.<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 [[polar auxin transport]] 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 [[milligram|mg]].<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>

{| class="wikitable sortable"
|-
! Foods !! data-sort-type="number" | Quercetin,<br />mg / 100 g
|-
| [[capers]], raw || 234<ref name=usda/>
|-
| [[capers]], canned || 173<ref name=usda/>
|-
| [[lovage]] leaves, raw || 170<ref name=usda/>
|-
| [[rumex|dock]] like [[sorrel]] || 86<ref name=usda/>
|-
| [[radish]] leaves || 70<ref name=usda/>
|-
| [[carob]] fiber || 58<ref name=usda/>
|-
| [[dill]] weed, fresh || 55<ref name=usda/>
|- 
| [[coriander]] || 53<ref name=usda/>
|- 
| [[Hungarian wax pepper|yellow wax pepper]], raw || 51<ref name=usda/>
|- 
| [[fennel]] leaves || 49<ref name=usda/>
|- 
| [[red onion|onion, red]] || 32<ref name=usda/>
|- 
| [[radicchio]] || 32<ref name=usda/>
|- 
| [[watercress]] || 30<ref name=usda/>
|-
| [[kale]] || 23<ref name=usda/>
|-
| [[chokeberry]] || 19<ref name=usda/>
|-
| [[Vaccinium uliginosum|bog blueberry]] || 18<ref name=usda/>
|- 
| [[buckwheat]] seeds || 15<ref name=usda/>
|-
| [[cranberry]] || 15<ref name=usda/>
|-  
| [[lingonberry]] || 13<ref name=usda/>
|-
| [[black plum|plums, black]] || 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 [[organic farming|organically grown]] [[tomato]]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 [[honey]] 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 ==

In plants, [[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]].<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 [[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]].<ref name="pmid11402179"/>

=== Glycosides ===
[[File:3-O-Glycosides of quercetin-en.svg|thumb|3-O-Glycosides of quercetin]]
Quercetin is the [[aglycone]] form of a number of other flavonoid [[glycoside]]s, such as [[rutin]] (also known as quercetin-3-O-rutinoside) and [[quercitrin]], found in [[citrus]] fruit, [[buckwheat]], and onions.<ref name=lpi/> Quercetin forms the [[glycoside]]s [[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-<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 [[Taxifolin#Glycosides|taxifolin]] (also known as dihydroquercetin) glycosides also exist. [[Isoquercetin]] is the 3-''O''-glucoside of quercetin.

=== Rutin degradation pathway ===

The enzyme [[quercitrinase]] can be found in ''[[Aspergillus flavus]]''.<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 = [[BRENDA]] (BRaunschweig ENzyme DAtabase)  }}</ref> This enzyme [[hydrolyzes]] the glycoside [[quercitrin]] to release quercetin and <small>L</small>-[[rhamnose]]. It is an enzyme in the [[rutin]] 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>

== Pharmacology ==

=== Pharmacokinetics ===
The [[bioavailability]] 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 [[half-life]] 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=[[Critical Reviews in Food Science and Nutrition]] | volume=60 | issue=4 | pages=626–659 | year=2020 | doi = 10.1080/10408398.2018.1546669 | pmid=30614249| s2cid=58651581 }}</ref> Quercetin supplements in the [[aglycone]] form are less [[Bioavailability|bioavailable]] than the quercetin [[glycoside]] 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 [[gastrointestinal motility]] and [[colon (anatomy)|colonic]] [[fermentation]].<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>

=== Metabolism ===
Quercetin is rapidly metabolized (via [[glucuronidation]]) 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"/>

In rats, quercetin did not undergo any significant [[Drug metabolism#Phase I .E2.80.93 modification|phase I metabolism]].<ref name = "Day_2004"/> In contrast, quercetin did undergo extensive [[Drug metabolism#Phase II .E2.80.93 conjugation|phase II]] (conjugation) to produce [[metabolite]]s that are more [[chemical polarity|polar]] than the parent substance, hence are more rapidly excreted from the body. ''In vitro'', the meta-[[hydroxyl group]] of [[catechol]] is methylated by [[catechol-O-methyltransferase]]. Four of the five hydroxyl groups of quercetin are [[glucuronidated]] by [[UDP-glucuronosyltransferase]]. 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 [[quercetin-3-glucuronide]], [[3'-methylquercetin-3-glucuronide]], and [[quercetin-3'-sulfate]].<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 [[lipopolysaccharide]]-activated [[macrophage]]s.<ref name="pmid30614249" />

Compared to other [[flavonoid]]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=[[Fitoterapia]] | 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 [[cytochrome P450]] enzymes [[CYP3A4]] and [[CYP2C19]] and a moderate inhibitor of [[CYP2D6]].<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 [[caffeine]] 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>

==Food safety==
In 2010, the U. S. [[Food and Drug Administration]] <!-- (FDA) --> acknowledged high-purity quercetin as [[generally recognized as safe]] <!-- (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>

== Health claims ==
Quercetin has been studied in [[basic research]] and small [[clinical trials]].<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=[[American Cancer Society]] |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 [[Food and Drug Administration]] has issued [[FDA warning letter|warning letters]] 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 [[health claim]]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 [21 U.S.C. § 321(g)(1)(B) and/or 21 U.S.C. § 321(g)(1)(C)] 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.

===Safety===
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 [[estrogen]]-dependent tumors.<ref name=andres/>

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>

== See also ==
{{div col|colwidth=28em}}
* [[List of ineffective cancer treatments]]
* [[Flavonol 3-sulfotransferase]]
* [[Phenolic compounds in wine]]
* [[Phytochemical]]
* [[Quercetin 2,3-dioxygenase]]
* [[Quercetin 3-O-methyltransferase]]
* [[Quercetin-3-sulfate 3'-sulfotransferase]]
* [[Quercetin-3-sulfate 4'-sulfotransferase]]
* [[Quercetin-3,3'-bissulfate 7-sulfotransferase]]
{{div col end}}

== References ==
{{Reflist}}

==External links==
*{{Commons category-inline}}

{{Flavonols}}
{{Antioxidants}}
{{Phytoestrogens}}
{{Estrogen receptor modulators}}
{{Purine receptor modulators}}
{{Authority control}}

[[Category:Quercetin| ]]
[[Category:Aromatase inhibitors]]
[[Category:CYP2C8 inhibitors]]
[[Category:CYP3A4 inhibitors]]
[[Category:Flavonoid antioxidants]]
[[Category:GPER agonists]]
[[Category:Xanthine oxidase inhibitors]]
[[Category:Experimental medical treatments]]
[[Category:Phytoestrogens]]
[[Category:Selective ERβ agonists]]
[[Category:Pentols]]