Significance of Antioxidants and Methods to Evaluate Their Potency

Antioxidants are vital bioactive components which garnered attention of various researchers in the area of in pharmacy, medicine and food engineering. Here we have endeavored our effort to highlight the significance of antioxidants and critical assay methods to analyze the inhibitory activity of the antioxidants. Various in vitro and in vivo assay methods are available to estimate the inhibitory activity of which, hydroxyl radical antioxidant capacity (HORAC) test, the oxygen radical absorption capacity (ORAC) test, the total oxyradical scavenging capacity (TOSC) test and the total peroxyl radical trapping antioxidant parameter (TRAP) test are based on the transfer of hydrogen atom. The ferric reducing antioxidant power (FRAP) test, cupric reducing antioxidant power (CUPRAC) test, and the folin–ciocalteu test are based on transfer of an electron. Whereas, the [2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl] (DPPH) test and, 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) tests are based on transfer of both hydrogen and electron. All these assays preliminarily assess the chemical kinetics to reach the chemical equilibrium state and develop chromogenic color or discoloration or develop fluorescence or quenches the fluorescence which can be analyzed in colorimeter or spectrophotometer respectively. In the present review, we have summarized the synthesis of antioxidant materials and their significance and the assay methods which were employed to estimate the inhibitory activity of the antioxidants.