Abstract: Proanthocyanidins (PAs), as a predominant group of both flavonoids and polyphenols, are less studied than other simpler compounds due to their large molecular size, complicated structure and polymeric nature, though they play major roles in both human diet and animal forages and have noticeable health effects. In this review, the absorption and bioavailability of PAs are compared among catechin (CC) monomers, PA dimers/trimers and larger PA oligomers. The metabolic fate of PAs is summarized, and one possible mechanism of PA degradation in vivo is discussed, based on some evidence of a preliminary depolymerization. Regarding to various physi-ological potential of PAs, plasma circulation and cellular uptake of these compounds and their metabolites are also briefly referred. These help to figure out to what extent the monomers, dimers/trimers, larger PA polymers, or their metabolites directly contribute to the multiple biological effects in vivo, so as to demonstrate the health effects of PAs, and elucidate the relevant mechanisms.

Key words: proanthocyanidins, procyanidins, metabolism, bioavailability