Cytotoxic neoclerodane diterpenoids from scutellaria barbata D. Don.

A new neoclerodane 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 HRMS 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 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 neoclerodane 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. Compound 14 showed significant cytotoxic activities against four tested tumor cells among those compounds with IC50 values of 4.57, 7.68, 5.31 and 6.23 μM, respectively, which indicated it might be a potential chemotherapeutic agents.