New approach for evaluation of the antioxidant capacity based on scavenging DPPH free radical in micelle systems

A simple and sensitive method was developed to evaluate the antioxidant capacity using a 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) incorporated in surfactants. Parameters possibly affected the DPPH scavenging activity were investigated including the type of surfactant, concentration of surfactant, solution pH and concentration of buffer. The optimum micelle system for determining the antioxidant capacity was 2 mM CTAB in 0.1 M acetate buffer (pH 4.6). The IC₅₀ values of various antioxidants were calculated and compared to those prepared in methanol. Furthermore, the rate of the reaction between DPPH and antioxidants was investigated. The rate constants observed in the micelle system were significantly faster than those in methanol, and this allowed shorter analysis time. This method was validated through linearity, limit of detection and precision by comparing with conventional methanolic assay. The purposed method was applied to evaluate the antioxidant capacity from aqueous extracted plant samples with satisfactory results.