A new cytotoxic carbazole alkaloid and two new other alkaloids from Clausena excavata.

One new carbazole alkaloid, excavatine A (1), and two additional new alkaloids, excavatine B (2) and excavatine C (3), were isolated from the stems and leaves of Clausena excavata Burm.f. (Rutaceae). Their structures were determined on the basis of detailed spectroscopic analyses, especially 2D-NMR and HR-EI-MS data. Compounds 1-3 were tested for their cytotoxic activities against A549, HeLa, and BGC-823 cancer cell lines, and for their antimicrobial activities against Candida albicans and Staphylococcus aureus. Only 1 exhibited cytotoxicity against A549 and HeLa cell lines with the IC50 values of 5.25 and 1.91 μg/ml, respectively.