Cytotoxic Neo-Clerodane Diterpenoids from Scutellaria barbata D.Don

A new neo-clerodane diterpenoid, barbatin H (1), together with fifteen known analogues (2-16) were isolated from Scutellaria barbata D.Don. Their structures were determined on the basis of NMR and HR-MS spectral analysis and comparison with the reported data. All of those compounds were comparatively predicted for their cytotoxic activities against four human tumor cell lines, i. e. LoVo (colon cancer), MCF-7 (breast cancer), SMMC-7721 (hepatoma cancer), and HCT-116 (colon cancer) cells by MTT method in vitro. The results turned out that the series of neo-clerodane diterpenoids exhibited varying degrees of cytotoxic activities against the growth of the tested tumor cell lines, and most of them exhibited selective cytotoxicity against LoVo cell lines. Scutebata A (14) showed significant cytotoxic activities against four tested tumor cells with IC₅₀ values of 4.57, 7.68, 5.31, and 6.23 μm, respectively, which indicated that it might be a potential chemotherapeutic agent.