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Five novel bisindole alkaloids,cyclovinblastine A~C (1~3),4-desacetoxyvinblastine Nb-oxide (4),and 4-deoxyvinblastine Nb-oxide (5),together with nine known alkaloids leurosine,cycloleurosine,vinblastine,leurosidine,vinblastine Nb-oxide,isoleurosine,4-deoxyleurosidine,4-deoxyleurosidine Nb-oxide and 4-desacetoxyvinblastine were isolated from the leaves of Catharanthus roseus.The structures of 1~5 were established by analysis of their NMR and HR-ESI-MS spectroscopic data.All alkaloids were evaluated for their cytotoxic activities against the human hepatocellular carcinoma (HepG2) cell line,human colorectal carcinoma (Lovo) cell line,and human breast carcinoma (MCF-7) cell line by the MTT method in vitro,respectively.The results indicated that cytotoxic activities of alkaloids isoleurosine,4-deoxyleurosidine and 4-desacetoxyvinblastine were much more potent than those of the positive control vinblastine.In addition,the structure-activity relationships (SAR) were conducted on the basis of the cytotoxicity of these isolated alkaloids.