Electrochemical redox behavior of 2,2-diphenyl-1-picrylhydrazyl radical solubilized by β-cyclodextrin in water

2,2-Diphenyl-1-picrylhydrazyl radical (DPPH center dot) is a water-insoluble stable radical that has been used to evaluate the activity of antioxidants as a reactivity model of reactive oxygen species. In this work, the cyclic voltammetry of DPPH center dot solubilized in water by complexation with beta-cyclodextrin was studied in phosphate buffer solutions (0.1 M, pH 6.0, 7.0, and 8.0). DPPH center dot undergoes a reversible proton-coupled reduction, where the half-wave potential linearly shifts in the negative direction as the solution pH increases. On the other hand, the cyclic voltammogram of the oxidation of DPPH center dot is quasi-reversible, indicating that the oxidized product of DPPH center dot undergoes a chemical reaction.