Free Radical Scavenging Activity of 4-(3,4-Dihydroxybenzoyloxymethyl)phenyl-O-β-D-glucopyranoside from Origanum vulgare and Its Protection against Oxidative Damage

4-(3,4-Dihydroxybenzoyloxymethyl)phenyl-O-beta-D-glucopyranoside (DBPG), a polyphenolic glycoside, isolated from Origanum vulgare has shown 1,1-diphenyl-2-picrylhydrazyl (DPPH center dot)-scavenging capacity in previous work. This study demonstrated that DBPG exhibits antioxidant activity by a series of DPPH center dot, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS(center dot+)), and superoxide anion radical (O-2(center dot-)) radical-scavenging assays. The inhibition of lipid peroxidation (LP) by DBPG exceeded that by L-ascorbic acid (AA) in a liposome model system. Adding DBPG to mouse liver and brain tissue inhibited the formation of thiobarbituric acid reactive substances (TBARS) to a greater extent than did trolox. In the oxygen stress test, BNLCL2 and HaCaT cells pretreated with DBPG showed increased activities of glutathione peroxidase (GPx), perhaps as a result of reduction of the production of reactive oxygen species (ROS). These findings proved that DBPG had antioxidant activities and a cytoprotective effect in hepatocytes and keratinocytes, suggesting that DBPG may be a useful food and cosmetic additive.