Buxaustroines A–N, a Series of 17(13→18)abeo-Cycloartenol Triterpenoidal Alkaloids from Buxus austro-yunnanensis and Their Cardioprotective Activities

Buxaustroines A–N (1–14), a series of triterpenoidal alkaloids featuring a novel 17(13→18)abeo motif, were obtained from the extract of Buxus austro-yunnanensis. Their structures were assigned based on NMR data analysis and X-ray diffraction crystallography. A putative biosynthetic pathway for one of the alkaloids from a co-isolate 15 is proposed. In the assessment of their bioactivities, some of the compounds displayed protective effects against doxorubicin-induced injury of myocardial cells. Preliminary structure–activity relationship studies of 1–14, which are based on the same skeleton, were conducted.