ent-Pimarane diterpenoids from the aerial parts of Sigesbeckia pubescens and their myocardial protective activity.

Eight new ent-pimarane diterpenoids (1-8), along with three known compounds (9-11), were isolated from the aerial parts of Sigesbeckia pubescens. The structures of the new ent-pimarane diterpenoids were established by extensive spectroscopic techniques, X-ray diffraction crystallography, ECD calculations and Mo2(OAc)4-induced ECD. The isolated compounds were evaluated for their myocardial protective activities in an H9c2 cell hypoxia/reoxygenation (H/R) induced myocardial ischemia-reperfusion injury model. Bioassay results showed that pubescens B (2), pubescens H (8) and darutigenol (9) enhanced the cell viability at concentrations of 1, 10, and 50 µM and molecular docking explored their binding mode with H/R connected protein Ubiquitin C-terminal hydrolase L5 (UCHL5).