Nortriterpenoids from Schisandra chinensis and their absolute configurational assignments by electronic circular dichroism study

Twelve new nortriterpenoids, namely wuweizidilactones J-P (1-7), schindilactones I-K (8-10), preschisanartanin N (11), and schisdilactone J (12), as well as 23 known analogues, were isolated from the leaves and stems of Schisandra chinensis. The absolute configurations of 1 and 11 were established by calculated electronic circular dichroism (ECD) spectra and that of 7 was confirmed by single-crystal X-ray diffraction. The absolute configurations of 2-6, 8, and 9 were determined by an empirical comparison of their experimental ECD spectra with that of 1. It is the first time that the ECD spectra of 18(13→14)-abeo-schiartane-, 18-norschiartane-, and schisanartane-type nortriterpenoids possessing an α,β-unsaturated-γ-lactone moiety are presented, this method providing an alternative means of obtaining absolute configurational assignments for these types of nortriterpenoids. All isolates were evaluated for their anti-acetylcholinesterase and anti- butyrylcholinesterase activities, and compounds 8, 13, 23, and 31 show anti-acetylcholinesterase activity at concentrations of 50 μM, with 12.7, 10.7, 16.6, and 32.1% inhibition, respectively.