A new modified pterocarpan glycoside from Sophora flavescens

Sophora flavescens is a widely used traditional Chinese herbal medicine. In this work, a new pterocarpan glycoside, kurarinol C (1) together with six known compounds, sophoracarpan A (2), trifohrhizin-6'-monoacetate (3), trifohrhizin (4), maackiain (5), (6S,6aS,11aR）-6α-methoxy-pterocarpin (6), L-maackiain (7) were isolated from the roots of S. flavescens. Among them, compounds 2 and 6 were discovered from S. flavescens for the first time. Their chemical structures were elucidated on the basis of extensive NMR and MS analyses. Furthermore, the antioxidant activities of these compounds were evaluated by the ABTS and DPPH free radical scavenging assay. Three compounds (5, 6, 7) exhibited stronger antioxidant capacity against the ABTS enzyme at 20 µg/mL (scavenging rates > 55%).