Concerted Two-Proton-Coupled Electron Transfer from Piceatannol to Electrogenerated Superoxide in N , N -Dimethylformamide.

The reactivity of 4-[( E )-2-(3,5-dihydroxyphenyl)ethenyl]benzene-1,2-diol (piceatannol) toward electrochemically generated superoxide radical anion (O 2 •- ) was investigated using electrochemistry and in situ controlled-potential electrolytic electron spin resonance (ESR) measurements in N , N -dimethylformamide with density functional theory (DFT) calculations. The quasireversible cyclic voltammogram of dioxygen/O 2 •- , modified in the presence of piceatannol, indicated that the electrogenerated O 2 •- was scavenged by piceatannol via proton-coupled electron transfer. Differences in the reactivities of piceatannol and 5-[( E )-2-(4-hydroxyphenyl)ethen-1-yl]benzene-1,3-diol ( trans -resveratrol) toward O 2 •- , originating from the presence of the benzene-1,2-diol (catechol) moiety, were observed in the voltammograms and ESR measurements. The electrochemical and computational results show that the reaction mechanism is a concerted two-proton-coupled electron transfer (2PCET) via the catechol moiety of piceatannol. The stilbene moiety of piceatannol kinetically promotes 2PCET via its catechol moiety. These findings indicate that piceatannol is a better O 2 •- scavenger than catechol and trans -resveratrol.