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Four new carbazole alkaloids, claurailas A-D (1-4), as well as 12 known carbazoles and three known coumarins were isolated from the roots of Clausena harmandiana. Heptaphylline (6) and 7-methoxyheptaphylline (7) showed strong cytotoxicity against NCI-H187 and KB cell lines with IC(50) values ranging from 1.3 to 2.7 μM. Compound 7 showed no cytotoxicity against Vero cells.

Activity guided fractionation of extracts from Clausena harmandiana have led to the identification of four known compounds, heptaphylline (1), clausine K (2), dentatin (5), and clausarin (6). All these compounds, except clausine K (2), exhibited antiplasmodial activity against Plasmodium falciparum. While the new dimethylated derivative 4, derived from 2, showed no antiplasmodial activity, the monomethylated product 3 (clausine H) exhibited activity comparable to that observed for compounds 1 and 5.