Carbazole alkaloids with bioactivities from the stems of Clausena lansium

Abstract Four unreported carbazole alkaloids named as claulansines U – W (1, 2, 4), (–) -(2′R)-claulamine A (3b) and one known analogue, claulamine A (3a) were obtained from the stems of Clausena lansium. Their structures were demonstrated by spectroscopic experiments. The absolute configuration of claulansine U (1) was determined by single-crystal X-ray diffraction analysis. Compounds 1 and 2 protected PC12 cells against serum deprivation injury at 10μM — an increase of cell survival rates from 47.4 ± 4.3 % (model) to 67.8 ± 6.6 % and 63.3 ± 8.2 %, respectively. And compound 4 showed significant cytotoxicities to four human cancer cell lines, with IC50 values ranging from 2.16 to 4.94 μM.