Limonoids with diverse frameworks from the stem bark of Entandrophragma angolense and their bioactivitiesElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ra19532f

Entangolensins A-P ( 1-16 ), sixteen new limonoids with diverse frameworks, were isolated from the stem bark of Entandrophragma angolense . Their planar structures were elucidated on the basis of spectroscopic data (HRMS, 1D/2D NMR), and the absolute configurations of most isolates were determined by the electronic circular dichroism (ECD) exciton chirality method and time-dependent density functional theory (TDDFT)/ECD calculations. Entangolensin A ( 1 ) was the first example of C-9/10- seco mexicanolide reported as a natural product. These diverse carbon skeletons, associated in a clear plausible biosynthetic pathway, indicated that the biosynthetic reactions in the title plant were varied and active. Bioactivity screening indicated that compounds 6 , 12 , 15 and 17 showed moderate cytotoxicities against HepG2 and MCF-7 cell lines, with IC 50 values from 13.19 to 36.93 μM; meanwhile, 6 , 11 and 17 exhibited significant NO inhibitory activities in LPS-activated RAW 264.7 macrophages, with IC 50 values of 1.75, 7.94 and 4.63 μM. Entangolensins A-P ( 1-16 ), sixteen new limonoids with diverse frameworks, were obtained from the stem bark of Entandrophragma angolense .