Since the ESR spectrum was undetectable using the in situ electrolytic system, it was suggested that RsvH2 • has decomposed by further subsequent reaction. Compared to the irreversible CVs of O2/O2 •-in the presence of PtsH (dimethoxylated RsvH3 at 3OH and 5OH) and α-tocopherol (Figure )) showing the type A, a notable CV behavior in the presence of RsvH3 was observed (Figure ), in which its cathodic peak-potential (Epc) has shifted to the negative-potential side (from -1.355 to -1.474 V vs Fc + /Fc) with a concentrationdependency of added RsvH3 (0 to 5.0). The shift of Epc is inferred to be caused by HBs formed between the 3OH/5OH (not 4'OH) of RsvH3 and O2/O2 •-. The kinetics of the electrode process has not changed along the formation of the HB complex because the shift-width of Epc was the same even at the faster (1.0 V s -1 ) scan rate (Supporting Information, Figure ). Therefore, the shift of Epc is caused by a change in the redox potential (EOx,Red) due to the HB effect or by a change in the diffusion coefficient of the HB complex, not a peak-separation caused by the slow kinetics of the electrode process. The Nernst equation is used for the thermodynamic analysis with EOx,Red of O2/O2 •-and the equilibrium scheme shown in Scheme 1,