Two new neoclerodane diterpenoids from Scutellaria barbata D. Don growing in Vietnam

Various chromatographic separations of the aerial parts of Scutellaria barbata afforded two new neoclerodane diterpenoids, scutebatas S and T (1 and 2), along with scutebata D (3). Their structures were elucidated by spectroscopic methods including high-resolution electrospray ionization mass spectrometry, 1D and 2D NMR and comparison with the literature values. Compounds 1 and 3 exhibited moderate cytotoxic activities against HL-60 (promyeloblast) human cancer cells. Weak cytotoxic effects toward four tested human cancer cell lines including KB (epidermoid carcinoma), LU-1 (lung adenocarcinoma), MCF7 (breast cancer), and Hep-G2 (hepatoma cancer) were observed for 1 and 3; whereas 2 was inactive on all five tested cell lines.