Binary combinations of natural phenolic compounds with gallic acid or with its alkyl esters: an approach to understand the antioxidant interactions

The antioxidant activity of equimolar binary combinations of ten natural phenolic compounds (vanillic acid, vanillin, hydroquinone, caffeic acid, ellagic acid, resveratrol, genistein, kaempferol, quercetin and catechin) with gallic acid or its alkyl esters (propyl-, octyl- and dodecyl gallates) was determined measuring the scavenging 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical cation activity. Statistical significant antagonism was found for all combinations with gallic acid and for most combinations with alkyl esters. Statistical significant synergism was observed only for three combinations of dodecyl gallate with resveratrol, genistein or catechin. The antagonistic and synergistic effects were analysed from regeneration mechanisms, and most of them can be explained according to the one-electron reduction potentials of the phenolics selected. These results may facilitate the use of combinations of antioxidants, as part of the hurdle technology, which can be applied to different aspects of food preservation, in order to increase shelf life and retain nutritional quality.