Bioactive flavonoids from Flos Sophorae

Three new flavonoid glycosides—soyaflavonosides A (1), B (2), and C (3)—together with 23 known ones were obtained from the 70% EtOH extract of Flos Sophorae (Sophora japonica, Leguminosae). Their structures were elucidated by chemical and spectroscopic methods. Among the known isolates, 14, 18, 20, 22, and 26 were isolated from the Sophora genus for the first time; 12, 19, 24, and 25 were obtained from the species firstly. Moreover, NMR data for compounds 18 and 26 are reported for the first time here. Meanwhile, compounds 4, 8–13, 15, 16, 19, 21, and 22 presented obvious inhibitory effects on TG accumulation in HepG2 cells. Analysis of the structure–activity relationship indicated that all of the quercetin glycosides examined in this study possess significant activity that is not significantly influenced by the amount of glycosyl present, whereas increasing the amount of glycosyl reduced the activities of isorhamnetin glycosides and orobol. In addition, a high dose (30 μmol/l) of kaempferol was found to inhibit HepG2 cell growth, while a low dose (10 μmol/l) was observed to decrease TG accumulation.