Flavonols Explained

Flavonols should not be confused with Flavanols.

Flavonols are a class of flavonoids that have the 3-hydroxyflavone backbone (IUPAC name: 3-hydroxy-2-phenylchromen-4-one). Their diversity stems from the different positions of the phenolic –OH groups. They are distinct from flavanols (with "a") such as catechin, another class of flavonoids, and an unrelated group of metabolically important molecules, the flavins (with "i"), derived from the yellow B vitamin riboflavin.

Flavonols are present in a wide variety of fruits and vegetables. In Western populations, estimated daily intake is in the range of 20–50 mg per day for flavonols. Individual intake varies depending on the type of diet consumed.[1]

The phenomenon of dual fluorescence (due to excited state intramolecular proton transfer or ESIPT) is induced by tautomerism of flavonols (and glucosides) and could contribute to plant UV protection and flower colour.[2]

Besides being a subclass of flavonoids, flavonols are suggested by a study of cranberry juice to play a role along with proanthocyanidins, in the juice's ability to block bacterial adhesion, demonstrated by the compressing the fimbria of E. coli bacteria in the urinary tract so as to greatly reduce the ability of those bacteria to stay put and initiate an infection.[3] Flavonol aglycones in plants are potent antioxidants that serve to protect the plant from reactive oxygen species (ROS).[4]

Flavonols

Flavonols! Name!!IUPAC name!!5!!6!!7!!8!!2′!!3′!!4′!!5′!!6′
3-hydroxy-2-phenylchromen-4-one H H H H H H H H H
2-(3,4-dihydroxyphenyl)-3,7-dihydroxy-5-methoxychromen-4-one OCH3 H OH H H H OH OH H
3,3′,4′,7-tetrahydroxy-2-phenylchromen-4-one H H OH H H OH OH H H
3,5,7-trihydroxy-2-phenylchromen-4-one OH H OH H H H H H H
2-(3,4-dihydroxyphenyl)-3,5,7,8-tetrahydroxychromen-4-one OH H OH OH H OH OH H H
3,5,7-trihydroxy-2-(4-methoxyphenyl)chromen-4-one OH H OH H H H OCH3 H H
3,4′,5,7-tetrahydroxy-2-phenylchromen-4-one OH H OH H H H OH H H
3,5,7-trihydroxy-2-(4-hydroxy-3-methoxyphenyl)chromen-4-one OH H OH H H OCH3 OH H H
2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one OH H OH H OH H OH H H
3,3′,4′,5′,5,7-hexahydroxy-2-phenylchromen-4-one OH H OH H H OH OH OH H
2-(3,4-dimethoxyphenyl)-3-hydroxy-5,6,7,8-tetramethoxychromen-4-one OCH3 OCH3 OCH3 OCH3 H H OCH3 OCH3 H
5-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3,7-dimethoxychromen-4-one OH H OCH3 H H OCH3 OH H H
3,3′,4′,5,7-pentahydroxy-2-phenylchromen-4-one OH H OH H H OH OH H H
3,5-dihydroxy-2-(4-hydroxy-3-methoxyphenyl)-7-methoxychromen-4-one OH H OCH3 H H OCH3 OH H H
2-(3,4-dihydroxyphenyl)-3,5-dihydroxy-7-methoxychromen-4-one OH H OCH3 H H OH OH H H

Flavonol glycosides

Flavonols glycosides and acetylated glycosides! Name!!Aglycone!!3!!5!!6!!7!!8!!2′!!3′!!4′!!5′!!6′
Glc
Rha
Gal
Glc
Rha Rha
Rha
Rha
Robinose Rha
Rutinose
Glc
trisaccharide
Glc tert-amyl
Rha Glc tert-amyl
Rutinose hydroxyethyl hydroxyethyl hydroxyethyl

Drug interactions

Flavonoids have effects on CYP (P450) activity. Flavonols are inhibitor of CYP2C9[5] and CYP3A4,[1] which are enzymes that metabolize most drugs in the body.

Technological uses

A 2013 study showed that it is possible by optical methods to quantify the flavonol accumulation in some fruit and thus to sort fruit according to fruit quality and storage durability.[6]

Effects on health

A 2022 study indicated an association between consumption of flavonols (found in food) and a lower rate of decline of cognitive ability, including memory.[7]

See also

Notes and References

  1. Cermak R, Wolffram S . The potential of flavonoids to influence drug metabolism and pharmacokinetics by local gastrointestinal mechanisms . Curr. Drug Metab. . 7 . 7 . 729–44 . October 2006 . 17073577 . 10.2174/138920006778520570 . https://archive.today/20120720144359/http://www.bentham-direct.org/pages/content.php?CDM/2006/00000007/00000007/0004F.SGM . dead . 2012-07-20 .
  2. Smith . Gerald J. . Markham . Kenneth R. . 1998 . Tautomerism of flavonol glucosides: relevance to plant UV protection and flower colour . Journal of Photochemistry and Photobiology A: Chemistry . 118 . 2. 99–105 . 10.1016/s1010-6030(98)00354-2.
  3. Web site: Juicy news about cranberries. medicalxpress.com. 13 April 2018.
  4. Enhancement of oxidative and drought tolerance in Arabidopsis by overaccumulation of antioxidant flavonoids.. Nakabayashi R, Yonekura-Sakakibara K, Urano K, Suzuki M, Yamada Y, Nishizawa T, Matsuda F, Kojima M, Sakakibara H, Shinozaki K, Michael AJ, Tohge T, Yamazaki M, Saito K. . 24274116 . 10.1111/tpj.12388. 77. 3. 4282528. Plant J. 2014 . 367–79.
  5. Si D, Wang Y, Zhou YH . Mechanism of CYP2C9 inhibition by flavones and flavonols . Drug Metab. Dispos. . 37 . 3 . 629–34 . March 2009 . 19074529 . 10.1124/dmd.108.023416 . 285706 . etal.
  6. 10.1002/pca.2443. Characterisation of the Polyphenol Content in the Kiwifruit (Actinidia deliciosa) Exocarp for the Calibration of a Fruit-sorting Optical Sensor. 2013. Pinelli. Patrizia. Romani. Annalisa. Fierini. Elisa. Remorini. Damiano. Agati. Giovanni. Phytochemical Analysis. 24. 5. 460–466. 23716352. 2158/1013486. 33903704 . free.
  7. Holland . Thomas Monroe . Agarwal . Puja . Wang . Yamin . Dhana . Klodian . Leurgans . Sue E. . Shea . Kyla . Booth . Sarah L . Rajan . Kumar . Schneider . Julie A. . Barnes . Lisa L. . Association of Dietary Intake of Flavonols With Changes in Global Cognition and Several Cognitive Abilities . Neurology . 22 November 2022 . 100 . 7 . e694–e702 . 10.1212/WNL.0000000000201541. 253800625 . 9969915 .

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