Synergistic, Additive and Antagonistic Interactions of Some Phenolic Compounds and Organic Acids Found in Grapes

The antioxidant interactions between several natural phenolic and non-phenolic compounds (catechin, quercetin, rutin, resveratrol, gallic acid and ascorbic acid) and organic acids (tartaric, citric and dihydroxyfumaric acids) were studied using the DPPH method. Main additive and antagonistic interactions have been found for the combinations of catechin, quercetin, resveratrol and gallic acid with tartaric and citric acids; such behavoir can be due to the enhanced stability of the phenolic compounds in acidic media. Rutin and ascorbic acid showed good synergistic effects with tartaric and citric organic acids, which could be due to the polymerization processes in the case of rutin and the change in the mechanism of action in the case of ascorbic acid. In combination with dihydroxyfumaric acid, the mixtures showed dose-dependent synergistic, additive, or antagonistic antioxidant interactions. Good synergistic effects were observed for the binary mixtures of dihydroxyfumaric acid with ascorbic acid, catechin, and rutin.