The antioxidant activities of crude extract and its derived soluble fractions from the flower of Sophora viciifolia were evaluated in five different test systems (DPPH, ABTS, FRAP, reducing power and inhibition of lipid peroxidant models) for the first time. The ethylacetate soluble fraction exhibited the highest antioxidant effect. Correlation analysis suggested that the flavonoids might be the major contributors for the high antioxidant activity of this flower. In addition, 11 compounds were isolated from this flower, and the antioxidant capacities of 5 flavonoids were evaluated by DPPH assay. Compound 3 (luteolin) had a significant DPPH radical-scavenging activity, and was also present at the highest concentration (5.56 mg/g dry sample), implying an important role of 3 for the antioxidant activity of this flower. The study suggests that the flower of S. viciifolia can provide valuable functional ingredients and can be used for the prevention of diseases related to various oxidant by-products of human metabolism. (C) 2010 Elsevier Ltd. All rights reserved.