Neuroprotective carbazole alkaloids from the stems and leaves of Clausena lenis.

The investigation on the stems and leaves of Clausena lenis led to the isolation of a previously undescribed carbazole alkaloid, clausenalenine A (1), along with seven known analogues (2-8). The structure of 1 was elucidated based on comprehensive spectroscopic analyses and the known compounds were identified by comparisons with data reported in the literatures. All known compounds (2-8) were isolated from C. lenis for the first time. All isolated compounds were evaluated for their neuroprotective activities against 6-hydroxydopamine induced cell death in human neuroblastoma SH-SY5Y cells in vitro. Compounds 1-8 showed significant neuroprotective effects with EC50 values ranging from 0.68 to 18.76 μM.