The effect of procyanidin solutions on superoxide anion radicals was studied with an enzymatic method and their EC(50) values were determined. A comparative study of the results suggested that the free radical scavenger potential of these phenolic compounds closely depends on their chemical and stereochemical structures. Oligomeric procyanidins were isolated in different fractions from grapes and wines by low- and high-pressure liquid chromatography. These compounds were found to be efficient free radical scavengers even for the weak concentrations in wines. Their activity in grapes or wines was much stronger than that of other commercially available natural antioxidants (such as ascorbic acid and gallic acid). The effect of tannins isolated from grapes on different radicals was analyzed according to three distinct methods: an enzymatic method for superoxide anion radicals (O(2)(*)(-)), a chemical method for the stable 1,1-diphenyl-2-picrylhydrazyl radical (DPPH(*)), and an immunochemical method to study the scavenging activity of seed procyanidins on DNA lesions induced by the radical HO(*).

Neither ethanol nor red wine polyphenols reduced mature atherosclerosis or changed the content of collagen in plaques in apolipoprotein E-deficient mice.

The effect of pure monomeric and dimeric procyanidins on superoxide anion radicals (O2°−) was studied with an enzymatic method and their IC50 was determined. A comparative study of the results suggested that the antiradical potential of these phenolic compounds closely depends on their stereochemical structure. Modification of the chiral carbon, C3 involved in the oxidation mechanism induces differences in the scavenging action of (+)‐catechin (2R : 3S) or (−)‐epicatechin (2R : 3R). The stereochemical conformation of the interflavan linkage (axial or pseudo) according to the chemical nature of dimeric procyanidin units also influences the radical oxidation mechanism. The nature of the interflavan linkage between the two units in dimeric procyanidins (C4–C8 or C4–C6 linkage) is an important factor responsible for effectiveness of the behaviour polyphenols towards O2°−. The extraction of oligomeric procyanidins in grape seeds enabled us to study the effect of polymerisation and galloylation on their scavenging activities. The results clearly showed that the molecular scavenging mechanism of these molecules is closely connected with their spatial conformation. © 1999 Society of Chemical Industry

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Seed extracts of one clone of Merlot Noir were studied during maturation using low-pressure and high-performance liquid chromatography to observe changes in composition and to follow the evolution of the main procyanidins. These observations have prompted our laboratory to investigate the polymerisation of procyanidins associated with their extraction with an alcoholic solvent. We report the observed correlations for procyanidin dimers, which are relatively high between procyanidins B 2 /C 1 /A 2 themselves (linked by C 4 -C 8 bond), but which are non-existent between procyanidins linked by C 4 -C 8 and by C 4 -C 6 bonds. These observations have enabled us to propose a hypothesis regarding procyanidin oligomer biosynthesis.

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