Trichotomone, a new cytotoxic dimeric abietane-derived diterpene from Clerodendrum trichotomum

A novel dimeric diterpene (named trichotomone, 1 ) was isolated from the roots of the medicinal ornamental plant Clerodendrum trichotomum . Compound 1 is a rare phenolic ketal of a regular abietane derivative cyrtophyllone B and a rearranged abietane derivative containing a 17(15→16),18(4→3)- diabeo -abietane framework related to uncinatone. The structure was elucidated by extensive spectroscopic methods. The absolute configuration was defined by comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Trichotomone ( 1 ) exhibited in vitro cytotoxicities against several human cancer cell lines (A549, Jurkat, BGC-823 and 293T WT) with IC 50 values ranged from 7.51 to 19.38 μM.