Carbazole alkaloids from the peels of Clausena lansium

A new carbazole alkaloid, claulansine K (1), together with six known carbazole alkaloids (2–7), was isolated from the peels of Clausena lansium (Lour.) Skeels. The new compound was elucidated using a combination of 1D and 2D NMR (HMQC, HMBC, COSY, and ROESY) techniques, and HR-EI-MS analyses. Compound 1 showed in vitro α-glucosidase inhibitory activity with the IC50 value of 0.11 mM. Compound 2 exhibited moderate antibacterial activity against Staphylococcus aureus with the diameter of inhibition zone of 14.2 mm.