Recently, a number of studies on health benefits associated with natural compounds have been demonstrated. Phenolics in fruits, vegetables, herbs and spices possess potent antioxidant, anti-inflammatory, antimutagenic and anticarcinogenic activities. The fringe tree (Chionanthus virginicus) is used as a raw material by pharmaceutical industries for the preparation of homeopathy tinctures. The potential antioxidant activities of two secoiridoids from root bark of fringe tree (Chionanthus virginicus L.) were investigated to evaluate their potential value as the natural products for foods or cosmetic applications. In this study, antioxidant activities were measured by 2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH center dot) scavenging, superoxide anion (O (2) (center dot-) ) radical scavenging, total antioxidant activity, reducing activity, hydrogen peroxide (H(2)O(2)) scavenging and ferrous metal chelating activity assays. These secoiridoids, as antioxidants neutralized the activities of radicals and inhibited the peroxidation reactions of linoleic acid emulsion. Total antioxidant activity was measured according to ferric thiocyanate method. Butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), alpha-tocopherol and trolox, a water-soluble analog of tocopherol, were used as the reference antioxidant compounds. Ligustroside (3.70 x 10(-3) M) and oleuropein (3.80 x 10(-3) M) showed 71.9, 82.4, 80.7 and 90.4% inhibition on lipid peroxidation of linoleic acid emulsion, at the concentrations of 10 and 20 mu g/mL. On the other hand, 20 mu g/mL of standard antioxidant such as alpha-tocopherol (4.64 x 10(-3) M), trolox (7.98 x 10(-3) M), BHA (10.08 x 10(-3) M) and BHT (9.06 x 10(-3) M) exhibited 61.5, 29.8, 74.4 and 71.2% inhibition on peroxidation of linoleic acid emulsion, respectively. In addition, ligustroside and oleuropein had effective DPPH center dot, ABTS(center dot+) and superoxide anion radicals scavenging, hydrogen peroxide scavenging, total reducing power and metal chelating on ferrous ions activities. Also, those various antioxidant activities were compared to BHA and BHT, alpha-tocopherol and trolox that are references antioxidants.