Abstract
Thirteen undescribed diterpenoids, including an ent-isopimarane (1), ten ent-atisanes (2-8 and 15-17), and two ingenanes (20 and 21) and ten known compounds, were separated from the whole plant of E. wallichii. The structures and absolute stereochemistry of these compounds were delineated by 1D and 2D NMR, mass spectrometry, pyridine-induced solvent shifts, and X-ray diffraction analyses. Euphwanoid A (1) is elucidated as an ent-16‑norisopimarane type diterpenoid featuring a C-8-O-C-15 lactone fragment. And euphwanoid B (2) represents a rare ent-atisane type tetranorditerpene possessing a tetrahydrofuran moiety. In addition, all these isolated compounds were assayed for their protective effects on H2O2-induced BV-2 microglial cells damage. And representative compound 1 could protect BV-2 cells against oxidative damage via the NRF2/HO-1 signaling pathway.