flavan3ol

Flavan-3-ols, also known as flavanols, are a subclass of flavonoids characterized by a saturated carbon skeleton with a hydroxyl group at the 3-position. They are typically monomeric units such as catechin and epicatechin, and include their gallocatechin and epigallocatechin derivatives. The term flavan-3-ol distinguishes them from other flavonoids by the absence of a double bond between C2 and C3.

These compounds occur widely in the plant kingdom and are especially abundant in tea leaves from Camellia sinensis, cocoa beans, grapes, apples, and berries. In foods, they exist as monomers and as components of larger polymers called proanthocyanidins or condensed tannins, formed by linking multiple flavan-3-ol units.

Flavan-3-ols are produced in plants through the flavonoid biosynthesis pathway, a branch of phenylpropanoid metabolism. They serve as precursors to proanthocyanidins and contribute to the pigmentation and defense of plants. The most common monomers are catechin and epicatechin, with their gallate derivatives such as gallocatechin and epigallocatechin found in some sources like tea.

Biological effects of flavan-3-ols include antioxidant activity and the ability to interact with proteins and metal ions. In foods, their presence contributes to astringency and mouthfeel. They are also studied for potential health effects, including cardiovascular, anti-inflammatory, and antimicrobial activities, though human evidence is variable and often inconclusive.

Metabolism after consumption involves limited intestinal absorption of monomeric forms, with extensive metabolism by the liver and gut microbiota, yielding various metabolites. Because of their complex metabolism, effects observed in vitro do not always translate to clinical outcomes. Flavan-3-ols remain an area of active nutraceutical and food science research.