The antioxidant activity of a triterpenoid glycoside [3-O-(beta-D-glucopyranosyl)-hederagenin; OGH] isolated from the berries of Hedera colchica, an ivy species endemic in Georgia, was investigated. The antioxidant properties of OGH were evaluated using different antioxidant assays: 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH-) scavenging, total antioxidant activity, reducing power, superoxide anion radical (O-2(-)) scavenging, hydrogen peroxide (H2O2) scavenging and metal chelating activities. The total antioxidant activity was measured according to the ferric thiocyanate method. alpha-Tocopherol and trolox, a water-soluble analogue of tocopherol, were used as reference antioxidant compounds. At a 30 mu g/mL concentration, the inhibitory effects of OGH on the peroxidation of linoleic acid emulsion was found to be 95.3%, whereas a-tocopherol and trolox exhibited 88.8% and 86.2% inhibition of peroxidation in the system, respectively. In addition, OGH had effective DPPH center dot scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, total reducing power and metal chelation of ferrous ions activities. These various antioxidant activities were compared with (c)-tocopherol and trolox. Copyright (c) 2006 John Wiley & Sons, Ltd.