Abietane diterpenoids from Clerodendrum trichotomum and correction of NMR data of Villosin C and B.

Nine abietane diterpenoids (1-9) were isolated from the stems of Clerodendrum trichotomum Thunb. and identified by spectroscopic methods. Furthermore, corrected NMR data is provided for Villosin C (1) and B (2) whose absolute configurations were elucidated from circular dichroism (CD) data. All isolates were tested for cytotoxicity against four cancer cell lines (A549, HepG-2, MCF-7 and 4T1). Compounds 1, 2, 3, 4 and 8 were found to have remarkable cytotoxic effects with IC50 values ranging from 8.79 to 35.46 microM.