Evaluation Of In Vitro Methods Of Antioxidant Activity Determination Using Caffeic Acid

Abstract The differences in chemical composition of natural antioxidants provides challenges at separating, detecting, and quantifying individual non-enzymatic antioxidants in complex food/biological systems. Consequently, the antioxidant capacity is a better approach at assaying beneficial health effects that can result from the combined actions of individual antioxidant species. Antioxidant assay methods are based either on electron transfer (ET) or hydrogen atom transfer (HAT) mechanisms. The results obtained are different because of the mechanisms, redox potentials, pH and solvent requirements of the various assay methods. Antioxidant activities of caffeic acid were evaluated and compared with that of Ascorbic acid using different in vitro methods of 1, 1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, hydrogen peroxide scavenging and Phosphomolybdenum antioxidative power methods. At tested concentrations of 1mM and 2mM, caffeic acid showed an inhibition of 84.63% and 84.93% on the DPPH radical respectively, while Ascorbic acid gave 83.43% and 85.43% inhibition respectively. Both substances showed significant antioxidant activities in the tested analytical methods. The study showed that the two substances are good scavengers of the DPPH radical. However caffeic acid demonstrated a better H2O2 radical scavenging ability with ascorbic acid ranking better in the scavenging assay of the Phosphomolybdenum radical.