The aim of this study was to isolate the chemical constituents of the aerial parts of Polygala tenuifolia Willd. and to determine their antioxidant activities. Ten flavonoids were isolated and purified by silica gel, Sephadex LH-20, and ODS column chromatography, and semi-preparative HPLC. Their structures were elucidated by spectroscopic analysis and identified as isorhamnetin-3-O-13-D-glucopyranoside （1）, isorhamnetin-3-O-13-D-galactopyranoside （2）, quercetin-3-O-13-o-glucopyranosyl （1--＊2）-I^-D-galactopyranoside （3）, quercetin-3-O-13-O-glucopyranosyl （1---~2）-13-D-glucopyranoside （4）, linarin （5）, quercetin-3-O- 13-D-glucopyranoside （6）, 5,7-dihydroxy-8-methxoyflavone-7-O-13-o-glucuronoside （7）, isorhamnetin （8）, kaempferol （9） and quercetin （10）. All these compounds were isolated from this plant for the first time, and compounds 1-5 and 7 were isolated from the genus of Polygala for the first time. The antioxidant activities of the isolated compounds were evaluated by DPPH free radical scavenging assay, and compounds 3, 4, 6, 8, 9 and 10 showed potent antioxidant activities.
