Neuroprotective schinortriterpenoids from Schisandra neglecta collected in Medog County, Tibet, China

Schisdilactones K–U (1–11), a series of previously unreported 16,17-secopreschisanartane-type schinortriterpenoids (SNTs), were isolated from the leaves and stems of Schisandra neglecta A. C. Smith. Their structures were mainly established through analysis of their spectroscopic data. Besides, schisdilactones K (1), O (5) and R (8) were confirmed by single-crystal X-ray crystallographic analysis, and the configurations of schisdilactones T and U (10 and 11) were elucidated via quantum chemical calculation of their NMR chemical shifts and electronic circular dichroism (ECD) spectra. Schisdilactones L–S (2–8) and U (11) were found to exhibit moderate protective activities against corticosterone-induced apoptosis of PC12 cells at 20 μM, with cell viability in the range of 62.95–66.97%.