New amide alkaloids and carbazole alkaloid from the stems of Clausena lansium

Five unreported alkaloids including four amide alkaloids (1a, 2a, 3a, and 3b) and one carbazole alkaloid (4) with two known compounds (1b, 2b) were obtained from the stems of Clausena lansium. Their structures were demonstrated by spectroscopic experiments. And the absolute configurations of compounds 1a, 1b, 2b, and 3b were determined by single X-ray diffraction analysis. The neuroprotection assay showed that compound 4 had moderate inhibition effect on PC12 cells induced by serum withdrawal at the concentration of 10 μM. And compounds 1a and 4 had weak protective effects on primary neurons against oxygen glucose deprivation injury at the concentration of 10 μM. [Display omitted]