ent ‐Abietane Diterpenoids From Phlogacanthus curviflorus

ABSTRACT Eight previously undescribed ent ‐abietanes, comprising four nor‐diterpenoids ( 1 – 4 ), two intact ones ( 5 and 6 ), and two pairs of equilibrium isomers ( 7 and 8 ), as well as six known analogues ( 9 – 14 ), have been separated from the twigs and leaves of an ethnological herb, Phlogacanthus curviflorus . Their structures were characterized by spectroscopic methods, including HR‐ESIMS, NMR, ECD, and X‐ray crystallography. Their inhibitory activity against the diabetic target α ‐glucosidase and cytotoxicity toward three human tumor cell lines (MDA‐MB‐231, HeLa and A549) were evaluated. Compound 1 displayed significant inhibition against α ‐glucosidase with an IC 50 value of 19.06 ± 1.47 µM, while none of them exhibited obvious cytotoxicity.