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 IC50 value of 19.06 ± 1.47 µM, while none of them exhibited obvious cytotoxicity.
Ren-fen et al. (Sun,) studied this question.