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clarify half life stuff!! also claim about highly variable bioavailability (0-50%) needs a reference!
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=== Pharmacokinetics ===
=== Pharmacokinetics ===


The [[bioavailability]] of quercetin in humans is low and highly variable (0–50%), and it is rapidly [[clearance (medicine)|cleared]] with an [[elimination half-life]] of 1–2 hours after ingesting 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> Following dietary ingestion, quercetin undergoes rapid and extensive metabolism that makes the biological effects presumed from ''in vitro'' studies unlikely to apply ''in vivo''.<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>
The [[bioavailability]] of quercetin in humans is 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}}</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"/> 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> Because of such rapid and extensive metabolism, the biological effects presumed from ''in vitro'' studies unlikely to apply ''in vivo''.<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> The half life of the quercetin glucuronides, taken all together, is about 11-12 hours.<ref name="pmid10363620"/>


Quercetin supplements in the [[aglycone]] form are far 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/>
Quercetin supplements in the [[aglycone]] form are far 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/>


=== Metabolism ===
=== Metabolism ===

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 and 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" />
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 and 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}}</ref>
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}}</ref>


Quercetin is a strong inhibitor of the cytochrome P450 enzymes CYP3A4 and 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 = 31 July 2022 }}</ref> Drugs that are metabolized by these pathways may have increased effect.
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 = 31 July 2022 }}</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: INHIBITORY EFFECTS OF CAFFEIC ACID AND QUERCETIN ON HLMS |journal=Phytotherapy Research |date=December 2014 |volume=28 |issue=12 |pages=1873–1878 |doi=10.1002/ptr.5220}}</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 sub-population, 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 (−2964G>A) and (734C>A) Gene Polymorphisms |journal=www.hindawi.com |doi=10.1155/2014/405071}}</ref>


=== Pharmacological research ===
=== Pharmacological research ===

Revision as of 14:30, 24 September 2022

Quercetin
Skeletal formula of quercetin
Ball-and-stick model of the quercetin molecule
Names
Pronunciation /ˈkwɜːrsɪtɪn/
IUPAC name
3,3′,4′,5,7-Pentahydroxyflavone
Preferred IUPAC name
2-(3,4-Dihydroxyphenyl)-5,7-dihydroxy-4H-1-benzopyran-4-one
Other names
5,7,3′,4′-flavon-3-ol, Sophoretin, Meletin, Quercetine, Xanthaurine, Quercetol, Quercitin, Quertine, Flavin meletin
Identifiers
3D model (JSmol)
317313
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.003.807 Edit this at Wikidata
EC Number
  • 204-187-1
579210
KEGG
UNII
UN number 2811
  • InChI=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 checkY
    Key: REFJWTPEDVJJIY-UHFFFAOYSA-N checkY
  • 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
    Key: REFJWTPEDVJJIY-UHFFFAOYAW
  • O=C1c3c(O/C(=C1/O)c2ccc(O)c(O)c2)cc(O)cc3O
Properties
C15H10O7
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 checkY☒N ?)
UV visible spectrum of quercetin, with lambda max at 369 nm

Quercetin is a plant flavonol from the flavonoid group of polyphenols. It is found in many fruits, vegetables, leaves, seeds, and grains; capers, red onions, and kale are common foods containing appreciable amounts of it.[2][3] It has a bitter flavor and is used as an ingredient in dietary supplements, beverages, and foods.

Occurrence

Quercetin is a flavonoid widely distributed in nature.[2] The name has been used since 1857, and is derived from quercetum (oak forest), after the oak genus Quercus.[4][5] It is a naturally occurring polar auxin transport inhibitor.[6]

Quercetin is one of the most abundant dietary flavonoids,[2][3] with an average daily consumption of 25–50 milligrams.[7]

Foods Quercetin
(mg/100g)
capers, raw 234[3]
capers, canned 173[3]
lovage leaves, raw 170[3]
buckwheat seeds 90
dock like sorrel 86[3]
radish leaves 70[3]
carob fiber 58[3]
dill 55[8]
cilantro 53[3]
Hungarian wax pepper 51[3]
fennel leaves 49[3]
onion, red 32[3]
radicchio 32[3]
watercress 30[3]
kale 23[3]
chokeberry 19[3]
bog blueberry 18[3]
cranberry 15[3]
lingonberry 13[3]
plums, black 12[3]

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.[9] One study found that organically grown tomatoes had 79% more quercetin than non-organically grown fruit.[10] Quercetin is present in various kinds of honey from different plant sources.[11]

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.[12] 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.[12]

Glycosides

3-O-Glycosides of quercetin

Quercetin is the aglycone form of a number of other flavonoid glycosides, such as rutin (also known as quercetin-3-O-rutinoside) and quercitrin, found in citrus fruit, buckwheat and onions.[2] 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.[13]

A number of taxifolin (also known as dihydroquercetin) glycosides also exists.

Isoquercetin is the 3-O-glucoside of quercetin.

Rutin degradation pathway

The enzyme quercitrinase can be found in Aspergillus flavus.[14] This enzyme hydrolyzes the glycoside quercitrin to release quercetin and L-rhamnose. It is an enzyme in the rutin catabolic pathway.[15]

Pharmacology

Pharmacokinetics

The bioavailability of quercetin in humans is after oral intake is very low, with one study concluding it must be less than 1%.[16] 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).[16] Quercetin is rapidly metabolized (via glucuronidation) after the ingestion of quercetin foods or supplements.[17] Because of such rapid and extensive metabolism, the biological effects presumed from in vitro studies unlikely to apply in vivo.[18][19][20] The half life of the quercetin glucuronides, taken all together, is about 11-12 hours.[17]

Quercetin supplements in the aglycone form are far less bioavailable than the quercetin glycoside often found in foods, especially red onions.[2][21] Ingestion with high-fat foods may increase bioavailability compared to ingestion with low-fat foods,[21] and carbohydrate-rich foods may increase absorption of quercetin by stimulating gastrointestinal motility and colonic fermentation.[2]

Metabolism

In rats, quercetin did not undergo any significant phase I metabolism.[22] In contrast, quercetin did undergo extensive phase II (conjugation) to produce metabolites that are more polar than the parent substance and 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.[22] A methyl metabolite of quercetin has been shown in vitro to be more effective than quercetin at inhibiting lipopolysaccharide-activated macrophages.[20]

Compared to other flavonoids quercetin is one of the most effective inducers of the phase II detoxification enzymes.[23]

In-vitro studies show that quercetin is a strong inhibitor of the cytochrome P450 enzymes CYP3A4 and CYP2C19 and a moderate inhibitor of CYP2D6.[24][25] 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 sub-population, but in absolute terms the effect was almost negligible.[26]

Pharmacological research

Quercetin has been reported to inhibit the oxidation of other molecules and hence is classified as an antioxidant in vitro.[18] It contains a polyphenolic chemical substructure that stops oxidation in vitro by acting as a scavenger of free radicals. Quercetin has been shown to inhibit the PI3K/AKT pathway leading to downregulation of the anti-apoptotic protein Bcl-w.[27][28] Quercetin activates or inhibits the activities of a number of proteins in vitro. For example, it is a nonspecific protein kinase enzyme inhibitor.[18]

Food safety

In 2010, the FDA acknowledged high-purity quercetin as GRAS for use as an ingredient in various specified food categories at levels up to 500 milligrams per serving.[29]

Health claims

Quercetin has been studied in basic research and small clinical trials.[2][30][31][32] While supplements have been promoted for the treatment of cancer and various other diseases,[2][33] there is no high-quality evidence that quercetin (via supplements or in food) is useful to treat cancer[34] or any other disease.[2][35]

The US Food and Drug Administration has issued warning letters to several manufacturers advertising on their product labels and websites that quercetin product(s) can be used to treat diseases.[36][37] The FDA regards such quercetin advertising and products as unapproved – with unauthorized health claims concerning the anti-disease products – 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",[36][37] conditions not met by the manufacturers.

Safety

There has been little research into the safety of quercetin supplementation in humans, and the results are insufficient to give confidence that the practice is safe. In particular, there is a lack of safety information 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.[38]

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.[38]

See also

References

  1. ^ a b c "Quercetin dihydrate safety sheet". Archived from the original on September 16, 2011.
  2. ^ a b c d e f g h i "Flavonoids". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR. November 2015. Retrieved 1 April 2018.
  3. ^ a b c d e f g h i j k l m n o p q r s t "USDA Database for the Flavonoid Content of Selected Foods, Release 3" (PDF). U.S. Department of Agriculture. 2011.
  4. ^ "Quercetin". Merriam-Webster.
  5. ^ "Quercetin (biochemistry)". Encyclopædia Britannica.
  6. ^ Fischer C, Speth V, Fleig-Eberenz S, Neuhaus G (Oct 1997). "Induction of Zygotic Polyembryos in Wheat: Influence of Auxin Polar Transport". The Plant Cell. 9 (10): 1767–1780. doi:10.1105/tpc.9.10.1767. PMC 157020. PMID 12237347.
  7. ^ Formica JV, Regelson W (1995). "Review of the biology of quercetin and related bioflavonoids". Food and Chemical Toxicology. 33 (12): 1061–80. doi:10.1016/0278-6915(95)00077-1. PMID 8847003.
  8. ^ 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.
  9. ^ Slimestad R, Fossen T, Vågen IM (December 2007). "Onions: a source of unique dietary flavonoids". Journal of Agricultural and Food Chemistry. 55 (25): 10067–80. doi:10.1021/jf0712503. PMID 17997520.
  10. ^ Mitchell AE, Hong YJ, Koh E, Barrett DM, Bryant DE, Denison RF, Kaffka S (Jul 2007). "Ten-year comparison of the influence of organic and conventional crop management practices on the content of flavonoids in tomatoes". Journal of Agricultural and Food Chemistry. 55 (15): 6154–9. doi:10.1021/jf070344+. PMID 17590007.
  11. ^ Petrus K, Schwartz H, Sontag G (Jun 2011). "Analysis of flavonoids in honey by HPLC coupled with coulometric electrode array detection and electrospray ionization mass spectrometry". Analytical and Bioanalytical Chemistry. 400 (8): 2555–63. doi:10.1007/s00216-010-4614-7. PMID 21229237. S2CID 24796542.
  12. ^ a b Winkel-Shirley B (Jun 2001). "Flavonoid biosynthesis. A colorful model for genetics, biochemistry, cell biology, and biotechnology". Plant Physiology. 126 (2): 485–93. doi:10.1104/pp.126.2.485. PMC 1540115. PMID 11402179.
  13. ^ Juergenliemk G, Boje K, Huewel S, Lohmann C, Galla HJ, Nahrstedt A (Nov 2003). "In vitro studies indicate that miquelianin (quercetin 3-O-beta-D-glucuronopyranoside) is able to reach the CNS from the small intestine". Planta Medica. 69 (11): 1013–7. doi:10.1055/s-2003-45148. PMID 14735439.
  14. ^ "Information on EC 3.2.1.66 - quercitrinase". BRENDA (BRaunschweig ENzyme DAtabase). Helmholtz Centre for Infection Research.
  15. ^ Tranchimand S, Brouant P, Iacazio G (Nov 2010). "The rutin catabolic pathway with special emphasis on quercetinase". Biodegradation. 21 (6): 833–59. doi:10.1007/s10532-010-9359-7. PMID 20419500. S2CID 30101803.
  16. ^ a b Gugler, R.; Leschik, M.; Dengler, H. J. (1 March 1975). "Disposition of quercetin in man after single oral and intravenous doses". European Journal of Clinical Pharmacology. 9 (2): 229–234. doi:10.1007/BF00614022.
  17. ^ a b Graefe EU, Derendorf H, Veit M (1999). "Pharmacokinetics and bioavailability of the flavonol quercetin in humans" (PDF). (review). International Journal of Clinical Pharmacology and Therapeutics. 37 (5): 219–33. PMID 10363620. Archived from the original (PDF) on 2017-05-17. Retrieved 2016-01-01.
  18. ^ a b c Williams RJ, Spencer JP, Rice-Evans C (Apr 2004). "Flavonoids: antioxidants or signalling molecules?". (review). Free Radical Biology & Medicine. 36 (7): 838–49. doi:10.1016/j.freeradbiomed.2004.01.001. PMID 15019969.
  19. ^ Barnes S, Prasain J, D'Alessandro T, Arabshahi A, Botting N, Lila MA, Jackson G, Janle EM, Weaver CM (May 2011). "The metabolism and analysis of isoflavones and other dietary polyphenols in foods and biological systems". (review). Food & Function. 2 (5): 235–44. doi:10.1039/c1fo10025d. PMC 4122511. PMID 21779561.
  20. ^ a b Luca SV, Macovei I, Bujor A, Trifan A (2020). "Bioactivity of dietary polyphenols: The role of metabolites". Critical Reviews in Food Science and Nutrition. 60 (4): 626–659. doi:10.1080/10408398.2018.1546669. PMID 30614249. S2CID 58651581.
  21. ^ a b Dabeek WM, Marra MV (2019). "Dietary Quercetin and Kaempferol: Bioavailability and Potential Cardiovascular-Related Bioactivity in Humans". Nutrients. 11 (10): 2288. doi:10.3390/nu11102288. PMC 6835347. PMID 31557798.
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External links

  • Media related to Quercetin at Wikimedia Commons
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