Influence of oligomer chain length on the antioxidant activity of procyanidins

The antioxidant activity of catechin monomers and procyanidin (dimers to he xamers) fractions purified from cocoa was studied in two in vitro systems: liposomes and human LDL. Liposome oxidation (evaluated as formation of a-th iobarbituric acid reactive substances) was initiated with 2,2'-azobis (2-am idinopropane) hydrochloride (AAPH), 2,2'-azobis (2,4-dimethylvaleronitrile) (AMVN), iron/ascorbate, or W-C; LDL oxidation (evaluated as formation of c onjugated dienes) was initiated with Cu2+ or AAPH. Catechin monomers and pr ocyanidin fractions inhibited both liposome and LDL oxidation. Monomers, di mers, and trimers fractions were the most effective antioxidants when lipos ome oxidation was initiated in the aqueous phase. When oxidation was initia ted in the lipid domains, higher molecular weight procyanidins were the mos t effective. All fractions significantly inhibited Cu-mediated LDL oxidatio n; no significant effect of procyanidin molecular weight was observed. The hexamer fraction was the least effective with respect to preventing AAPH in itiated LDL oxidation. Results reported herein give further evidence on the influence of the oligomer chain length on the antioxidant protection by pr ocyanidins. (C) 2000 Academic Press.