Limonoids with neuroprotective activity from the stems of Clausena emarginata

Two new limonoids, clauemargines M-N (1–2), together with five known compounds (3–7), were isolated from the stems of Clausena emarginata, and compounds 6 and 7 were gained from this plant for the first time. Their structures were established and elucidated on the basis of comprehensive spectroscopic analysis. The absolute configurations of 1–2 were further determined by the octant rule of saturated cyclic ketone. Compounds 1, 2, 4, and 5 showed moderate neuroprotective effects against L-glutamic acid-induced cellular damage in human neuroblastoma SK-N-SH cells at 10 μM.