Bioorganic & medicinal chemistry
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2-O-α-d-Glucopyranosyl-l-ascorbic acid (AA-2G) exhibits biological activities after enzymatic hydrolysis to ascorbic acid (AA) by α-glucosidase. We have found that AA-2G per se exerted radical-scavenging activity toward 1,1-diphenyl-2-picrylhydrazyl radical (DPPH radical). The radical-scavenging property of AA-2G was greatly different from that of AA; that is, the reaction rate with DPPH radical of AA-2G was far slower than that of AA, but the long-lasting radical-scavenging ability per one molecule of AA-2G was superior to that of AA. ⋯ The high reaction stoichiometry of AA-2G against DPPH radical was associated with adduct formation of AA-2G with DPPH radical. The radical-scavenging reaction mechanism of AA-2G consists of the following three steps: (1) At an early stage of the reaction, AA-2G scavenged DPPH radical to generate AA-2G radical, (2) AA-2G radical immediately reacted with an additional DPPH radical to give two types of AA-2G-DPPH adducts and (3) AA-2G-DPPH adducts slowly quenched the other DPPH radical to generate several reaction products. Our results suggest the practical value of AA-2G, even before being converted into AA, as a beneficial antioxidant in food and cosmetic applications.