In vitro cytotoxicity of Tanshinones isolated from Salvia miltiorrhiza Bunge against P388 lymphocytic leukemia cells

The cytotoxic effect of four tanshinones isolated from the dried root of Salvia miltiorrhiza Bunge (Lamiaceae) were studied in vitro using P388 lymphocytic leukemia cells. Tanshinone I and tanshinone IIA were shown to be quite strongly cytotoxic against the cells (86.76% and 56.05% cell inhibition at 25 mug/ml). Dihydrotanshinone I and cryptotanshinone, which lack of saturation at C-15, showed little cytotoxicity (13.71% and 39.21% cell inhibition at 25 mug/ml). The results also revealed a structure activity relationship. We suggest that the unsaturation at C-15 and saturation on ring A may be critical structural components for cytotoxicity in these diterpenes.