Flavonols

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Not to be confused with Flavanols.
Backbone of a flavonol, substituent numbers are indicated.

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 the phenolic -OH groups. They are distinct from flavanols (with "a") such as catechin, another class of flavonoids.

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 (health effects), 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[edit]

Flavonols
Name IUPAC name 5 6 7 8 2' 3' 4' 5' 6'
3-Hydroxyflavone 3-hydroxy-2-phenylchromen-4-one H H H H H H H H H
Azaleatin 2-(3,4-dihydroxyphenyl)-3,7-dihydroxy-5-methoxychromen-4-one OCH3 H OH H H H OH OH H
Fisetin 3,3',4',7-tetrahydroxy-2-phenylchromen-4-one H H OH H H H OH OH H
Galangin 3,5,7-trihydroxy-2-phenylchromen-4-one OH H OH H H H H H H
Gossypetin 2-(3,4-dihydroxyphenyl)-3,5,7,8-tetrahydroxychromen-4-one OH H OH OH H OH OH H H
Kaempferide 3,5,7-trihydroxy-2-(4-methoxyphenyl)chromen-4-one OH H OH H H H OCH3 H H
Kaempferol 3,4',5,7-tetrahydroxy-2-phenylchromen-4-one OH H OH H H H OH H H
Isorhamnetin 3,5,7-trihydroxy-2-(4-hydroxy-3-methoxyphenyl)chromen-4-one OH H OH H H OCH3 OH H H
Morin 2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one OH H OH H OH H OH H H
Myricetin 3,3',4',5',5,7-hexahydroxy-2-phenylchromen-4-one OH H OH H H OH OH OH H
Natsudaidain 2-(3,4-dimethoxyphenyl)-3-hydroxy-5,6,7,8-tetramethoxychromen-4-one OCH3 OCH3 OCH3 OCH3 H H OCH3 OCH3 H
Pachypodol 5-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3,7-dimethoxychromen-4-one OH H OCH3 H H OCH3 OH H H
Quercetin 3,3',4',5,7-pentahydroxy-2-phenylchromen-4-one OH H OH H H OH OH H H

n

I

Rhamnazin 3,5-dihydroxy-2-(4-hydroxy-3-methoxyphenyl)-7-methoxychromen-4-one OH H OCH3 H H OCH3 OH H H
Rhamnetin 2-(3,4-dihydroxyphenyl)-3,5-dihydroxy-7-methoxychromen-4-one OH H OCH3 H H OH OH H H

Flavonol glycosides[edit]

Flavonols glycosides and acetylated glycosides
Name Aglycone 3 5 6 7 8 2' 3' 4' 5' 6'
Astragalin Kaempferol Glc
Azalein Azaleatin Rha
Hyperoside Quercetin Gal
Isoquercitin Quercetin Glc
Kaempferitrin Kaempferol Rha Rha
Myricitrin Myricetin Rha
Quercitrin Quercetin Rha
Robinin Kaempferol Robinose Rha
Rutin Quercetin Rutinose
Spiraeoside Quercetin Glc
Xanthorhamnin Rhamnetin trisaccharide
Amurensin Kaempferol Glc tert-amyl
Icariin Kaempferide Rha Glc tert-amyl
Troxerutin Quercetin Rutinose hydroxyethyl hydroxyethyl hydroxyethyl

Drug interactions[edit]

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.

See also[edit]

References[edit]

  1. ^ a b Cermak R, Wolffram S (October 2006). "The potential of flavonoids to influence drug metabolism and pharmacokinetics by local gastrointestinal mechanisms". Curr. Drug Metab. 7 (7): 729–44. doi:10.2174/138920006778520570. PMID 17073577. 
  2. ^ Tautomerism of flavonol glucosides: relevance to plant UV protection and flower colour, Gerald J. Smith and Kenneth R. Markham. Journal of Photochemistry and Photobiology A: Chemistry, Volume 118, Issue 2, 30 October 1998, Pages 99-105
  3. ^ http://medicalxpress.com/news/2016-07-juicy-news-cranberries.html
  4. ^ Nakabayashi R1, 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. "Enhancement of oxidative and drought tolerance in Arabidopsis by overaccumulation of antioxidant flavonoids.". 
  5. ^ Si D, Wang Y, Zhou YH, et al. (March 2009). "Mechanism of CYP2C9 inhibition by flavones and flavonols". Drug Metab. Dispos. 37 (3): 629–34. doi:10.1124/dmd.108.023416. PMID 19074529. 
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