Redox Behavior of 2,2-Diphenyl-1-picrylhydrazyl Radical (DPPH•) Solubilized in Water by β-Cyclodextrin

2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical is a relatively stable radical and frequently used as a reactivity model of reactive oxygen species. However, its insolubility in water precludes the investigation of the redox behavior of the DPPH radical in aqueous media, especially in concentrated buffer solutions. We have recently reported that the DPPH radical can be successfully solubilized in water by β-cyclodextrin (β-CD). The as-obtained β-CD-solubilized DPPH radical was demonstrated to be a powerful tool for evaluating the antioxidative activity of water-soluble antioxidants, such as ascorbic acid, Trolox, and caffeic, in concentrated buffer solutions. In this study, the redox behavior of the β-CD-solubilized DPPH radical was investigated by cyclic voltammeter. A well-defined reversible wave was observed for one-electron reduction of the β-CD-solubilized DPPH radical in phosphate buffer (0.1 M, pH 7.4). On the other hand, one-electron oxidation of the β-CD-solubilized DPPH radical showed a quasi-reversible redox wave, which suggests that DPPH cation generated by the electrochemical one-electron oxidation may undergo a follow-up chemical reaction, such as an addition of a water molecule.23rd Annual Meeting of the Society for Redox Biology and Medicine (SFRBM 2016)/SFRR International 18th Biennial Congres