The ESR spectrum of product radical was obtained only in the presence of α-tocopherol. With reference to RsvH3 and PtsH, the CVs demonstrated the type A showing the scavenging of O2 •-/HO2 • , although ESR spectra were not observed, where their product radicals (RsvH2 • and Pts • ) formed through the PCET were undetectable. These CV results demonstrate that the 4'OH (para-OH) is essential for the successful scavenging of O2 •-/HO2 • , although the other structural features also play an important role in its reaction mechanism.