Clerochinoids A‒H, aromatic abietane diterpenoids with cytotoxic activity from the roots and stems of Clerodendrum chinense

Abstract

Eight previously undescribed aromatic abietane diterpenoids, clerochinoids A−H (1–8), including seven 17(15 → 16)-abeo-abietanes (1–7) and one 17(15 → 16),18(4 → 3)-diabeo-abietane (8), along with 12 known analogues (9–20) were isolated from the roots and stems of Clerodendrum chinense. Their structures were elucidated by extensive spectroscopic data analysis, X-ray crystallography, and ECD calculations. All the compounds were screened for their cytotoxic activity against two human non-small cell lung cancer cell lines, H1975 and HCC827. Compounds 3, 9, 10, 12−14, 16, 17, 18, and 20 exhibited enhanced activity compared to the positive control, gefitinib. The succinct structure−activity relationship of these abietane diterpenoids was also discussed.