We previously analyzed the PCET reaction between electrogenerated O2 •-and phenolic antioxidants, 1,2-and 1,4-benzendiols, 24,25 1,2-and 1,4-dihydroxynaphthalenes, and monophenols including tocopherols and aminophenols, polyphenols, and trans-resveratrol, in N,N-dimethylformamide (DMF). Here, O2 •-cannot accept electrons from phenolic substrates because O2 •-is not so electrophilic; however, HO2 • (a protonated form of O2 •-) is a strong oxidant. Thus, ET and PT from antioxidants/deprotonated anion to O2 •-/HO2 • are closely related, potentially embodying the actual scavenging mechanism. Among them, concerted two-protoncoupled electron transfer (2PCET)-a type of PCET mechanism characterized by quinonehydroquinone π-conjugation via the catechol moiety-is necessary for the efficient scavenging of O2 •-. Conversely, trans-resveratrol scavenges O2 •-through a PT forming HO2 • followed by a concerted PCET via 4′OH, where the stilbene moiety is essential for the PCET. Notably, piceatannol possesses catechol and stilbene moieties, although it remains unclear how they contribute to O2 •-scavenging via PCET. Herein, we investigated the reaction mechanism between piceatannol and electrogenerated O2 in DMF by focusing on the role of the catechol and stilbene moieties of piceatannol. Next, we clarified which moiety primarily plays a functional role in the O2 •-scavenging, showing the differences between piceatannol and trans-resveratrol. Accordingly, we reveal the O2 •- scavenging mechanism of piceatannol, which is important for understanding its health benefits to use. (Tokyo, Japan) were used as received. We purchased tetrapropylammonium perchlorate (TPAP, >98.0%) from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan) and prepared for a supporting electrolyte as described previously. Dinitrogen (N2, 99.0%) and O2 (99.0%) gasses were purchased from Medical Sakai Co., Ltd. (Gifu, Japan). Ferrocene (Fc)-used as a reference for the electrochemical potential-was purchased from Nacalai Tesque Inc. (Kyoto, Japan) and used as received.