Effect of solute-solvent interactions on DPPH radical scavenging efficiency of some flavonoid antioxidants in various binary water-methanol mixtures

Scavenging ability of three kinds of natural flavonoid antioxidants including chrysin, naringenin, and quercetin against the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical was evaluated by the UV-vis spectrophotometric technique in different aqueous mixtures of methanol (50%-90% v/v) at physiological pH. The studied flavonoids showed their activity to be comparable with ascorbic acid (vitamin C), which is used as a standard reference material in most testing methods. Our findings indicated that an increase in the organic solvent percentage (v/v) has different effects on the radical scavenging efficiency of flavonoids presumably due to solute-solvent interactions. These variations were analyzed in light of various simple and multiple regression equations using the normalized polarity parameter (E-T(N)) and Kamlet, Abboud, and Taft solvatochromic parameters. Moreover, The IC50 values of the samples were then obtained by the Yasuda-Shedlovsky extrapolation procedure in pure water.