Alismanoid A, an unprecedented 1,2-seco bisabolene from Alisma orientale, and its protective activity against H2O2-induced damage in SH-SY5Y cells.

A pair of novel sesquiterpenoids, (8R)-alismanoid A (1a) and (8S)-alismanoid A (1b), possessing an unprecedented 1,2-seco bisabolene carbon skeleton, were isolated from rhizomes of Alisma orientale together with two new sesquiterpenoids: a 15-nor guaiane alismanoid B (2) and alismanoid C (3). Their structures were elucidated by 1D and 2D NMR, HRESIMS, electronic circular dichroism (ECD), and theoretical calculations, and a plausible biosynthetic pathway for compound 1 is discussed. Meanwhile, compounds 1–3 were investigated for their protective effects on H2O2-induced damage in human dopaminergic neuroblastoma cells (SH-SY5Y), and compounds 1b, 2, and 3 showed significantly protective activities at a certain concentration. Further, the action mechanism of compound 3 was proved to be through inhibition of H2O2-induced apoptosis in SH-SY5Y cells. Herein, these results suggest that sesquiterpenoids are potential candidate drugs for treating Parkinson's disease induced by reactive oxygen species. [ABSTRACT FROM AUTHOR]