Cryptotanshinone but not tanshinone IIA inhibits angiogenesis in vitro

In the course of screening of angiogenesis inhibitor from natural products, cryptotanshinone from Salvia miltiorrhiza was isolated as a potent small molecule inhibitor of angiogenesis. Cryptotanshinone inhibits bFGF-induced angiogenesis of BAECs at ten micromolar ranges in vitro without cytotoxicity. Tanshinone IIA, another tanshinone isolated from S. miltiorrhiza, which is structurally very similar to cryptotanshinone except C-15 position of dihydrofuran ring does not inhibit angiogenesis induced by bFGF. These results demonstrate that cryptotanshinone is a new anti-angiogenic agent and double bond at C-15 position of the dihydrofuran ring plays a crucial role in the activity.