Diterpenoids with diverse scaffolds from Vitex trifolia as potential topoisomerase I inhibitor

Abstract Eleven new compounds, including six labdane ( 1 – 6 ), three halimane ( 7 – 9 ), and two clerodane ( 10 – 11 ) diterpenoids and 16 known analogues ( 12 – 27 ), were isolated from the leaves of Vitex trifolia . The structures of 1 – 11 were established by extensive 1D- and 2D-NMR and HRMS spectroscopic data. The absolute configurations of compounds 3 , 7 , and 10 were assigned using X-ray diffraction. Compounds 1 – 27 were evaluated for DNA topoisomerases I (Top1) inhibitory activity and cytotoxicity against HCT 116 cells. Compounds 8 and 11 exhibited equipotent Top1 inhibitory activity to the positive control, camptothecin (CPT), at 100 μM. Compounds 8 , 9 , 16 , and 27 showed moderate cytotoxicity at low micromolar concentrations.