flavonole

Flavonol, or flavonole, is a class of flavonoids, polyphenolic compounds produced by plants. They are defined by the flavonol core: a 4H-chromen-4-one (chromone) skeleton with a hydroxyl group at position 3, a C2=C3 double bond, and various hydroxyl or methoxy substitutions. The core structure is C6-C3-C6.

Flavonols occur widely in fruits, vegetables, tea, and wine. Common representatives include quercetin, kaempferol, and myricetin. They frequently exist as glycosides, such as quercetin-3-O-glucoside (isoquercitrin) or rutin (quercetin-3-O-rutinoside). The concentration and profile vary by plant species, tissue, and ripening stage.

In plants, flavonols participate in pigmentation, UV protection, and defense against pathogens. In humans, dietary flavonols are studied for antioxidant activity, free radical scavenging, anti-inflammatory effects, and potential cardioprotective or anticancer properties, though effects depend on bioavailability and metabolism. They are typically poorly absorbed in the free form and are metabolized to conjugates by intestinal and hepatic enzymes, with substantial bacterial metabolism.

Flavonols are used as nutritional markers in food science and are measured by analytical methods such as HPLC and mass spectrometry after extraction. They are also of interest for plant breeding to enhance polyphenol content.

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