Depolymerization of cranberry procyanidins using (+)-catechin, (−)-epicatechin, and (−)-epigallocatechin gallate as chain breakers

Procyanidin dimers, trimers, and tetramers are absorbable, whereas larger oligomers are not. Procyanidins in cranberries are bioactive components that help prevent chronic diseases; however, 85% of cranberry procyanidins are large oligomers or polymers with a degree of polymerization above four. The objective of this study was to depolymerize cranberry procyanidins, particularly the polymers, into absorbable oligomers. Partially purified cranberry procyanidins (PCP) were obtained using chromatographic methods. The resultant extract contained predominant polymers with a degree of polymerization above ten (77.2% w/w). The extract was depolymerized, using 0.1 or 1 M methanolic HCl, with (+)-catechin, (−)-epicatechin, or (−)-epigallocatechin gallate (EGCG) added as chain breakers. Depolymerization converted polymers into A-type and B-type dimers, trimers and tetramers. Use of EGCG as a chain breaker resulted in A- and B-type oligomers with EGCG as a terminal unit, indicating that the added flavan-3-ol attached to the C4 carbocations from procyanidins during depolymerization. The yield of B-type oligomers was higher than that of A-type oligomers. The yield increased when higher amounts of flavan-3-ols were used for depolymerization. EGCG, as a chain breaker, produced fewer procyanidin oligomers than did catechin or epicatechin. This research provided a practical approach that may enhance the bioavailability and bioactivity of procyanidins in cranberries.