Quinone Hydroquinone π-Conjugated Redox Reaction Involving Proton-coupled Electron Transfer Plays an Important Role in Scavenging Superoxide by Polyphenolic Antioxidants

The proton-coupled electron transfer (PCET) from p-, o-, and m-dihydroxybenzenes (PQH(2), OQH(2), and MQH(2), respectively) to the hydroperoxy radical (HO2 center dot) derived from superoxide (O-2(center dot-)) is investigated. It is demonstrated that quinone-hydroquinone pi-conjugated redox systems characterized by electron transfer in PQH(2) and OQH(2) moieties play an important role in scavenging O-2(center dot-) by polyphenolic antioxidants.