Electrochemical determination of antioxidant activity and HPLC profiling of some dry fruits

Abstract

This study explored the antioxidant activities of eight dry fruits (almond, apricot, cashew, figs, peanut, pistachio, raisins, and walnut) against electrochemically generated superoxide anion radical (O2·−) in a cyclic voltammetric cell. The HPLC profiling of phenolic aglycones was carried out to determine the antioxidant compounds present in these extracts. Most of the dry fruits showed strong O2·− scavenging activity quantitated in terms of IC50 (concentration for 50% inhibition) and antioxidant activity coefficient (Kao). The antiradical activity followed the descending order: apricot > raisins > walnuts > figs > pistachio > peanut > almond > cashew. Based on experimental observations, the interaction mechanism of O2·− with the –OH-bearing compounds, present in the dry fruit extracts, has been proposed. This mechanism showed the relative proton transfer (H+) ability of all the dry fruit extracts. Electrochemically, it is reversible charge transfer followed by irreversible chemical step (ErCi). HPLC profiling showed seven phenolic aglycones (pyrocatechol, gallic acid, catechin, vanillic acid, caffeic acid, coumaric acid, and sinapic acid) in all the dry fruits. Among these, walnut was the only fruit that contained all identified compounds, while the rest contained gallic acid, catechin, caffeic acid, and coumaric acid as major compounds.