flavonolit

Flavonol is a class of flavonoids, a family of polyphenolic compounds produced by plants. Flavonols are defined by a 3-hydroxyflavone structure, a 2-phenylchromen-4-one skeleton with a hydroxyl group at the 3-position of the C ring. They commonly occur as glycosides, where sugars are attached to one or more hydroxyl groups, and are stored in various plant tissues. Notable aglycones include quercetin, kaempferol, and myricetin; common glycosides include rutin (quercetin-3-O-rutinoside) and isoquercitrin (quercetin-3-O-glucoside).

Occurrence and sources are widespread in the plant kingdom. Flavonols are found in fruits, vegetables, tea, wine, onions, apples, berries, grapes, and cacao products, often contributing to color, flavor, and plant defense. The concentration and composition of flavonols can vary with species, cultivar, stage of ripening, and environmental conditions.

Biosynthesis and metabolism occur through the plant flavonoid pathway. Phenylalanine is converted through a series of enzymes to form dihydroflavonols, which are then converted by flavonol synthase into flavonols. In plants, flavonols are frequently present as glycosides, which affect their solubility, storage, and bioavailability. In humans and other animals, flavonols are metabolized after ingestion by intestinal enzymes and gut microbiota, undergoing deglycosylation and phase II conjugation.

Biological activities and health aspects are widely studied. Flavonols exhibit antioxidant, anti-inflammatory, and potential cardioprotective and anticancer properties in various models. However, bioavailability is limited and highly variable, depending on the specific compound and its glycosylation form. Dietary intake from a variety of plant foods is the principal source of flavonols in humans.