Baicalein and baicalin are potent inhibitors of angiogenesis: Inhibition of endothelial cell proliferation, migration and differentiation

In recent studies, we have shown that baicalein and baicalin, 2 major flavonoids of Scutellaria baicatensis Georgi, exhibit anticancer activity against several cancers in vitro. In our present study, we assessed their potential as anti-angiogenic agents in vivo employing chicken chorioallantoic membrane (CAM) assay and in vitro human umbilical vein endothelial cells (HUVECs) culture. When CAMs were treated with either baicalein or baicalin for 48 hr, the angiogenic response induced by basic fibroblast growth factor (bFGF) was markedly reduced in a dose-dependent manner. Further characterization showed that both flavonoids exhibited dual antiproliferative (at low dose) and apoptogenic (at high dose) effects on HUVECs. In biochemical analysis, treatment of HUVECs with baicalein and baicalin for 24 hr resulted in a dose-dependent decrease in the matrix metalloproteinase (MMP)-2 activity. Moreover, the migration of endothelial cells and the differentiation of endothelial cells into branching networks of tubular structures in vitro were also inhibited by these 2 flavonoids in a dose-dependent manner. Baicalein is more potent than baicalin in anti-angiogenesis in vivo as well as in vitro. Taken together, the results of our study provide evidence that baicalein and baicalin possess an antiangiogenesis potential that is a previously unrecognized biologic activity.