Abstract: Twenty compounds were isolated from Melodinus tenuicaudatus.Their structures were identified as tabersonine (1),11-methoxytabersonine (2),11-hydroxytabersonine (3),19R-acetoxy-tabersonine (4),11,19R-hydroxytabersonine (5),11-methoxy-19R-hydroxytabersonine (6),19R-acetoxy-11-hydroxytabersonine (7),11-hydroxy-19R-hydroxytabersonine (8),△¹⁴-vincamine (9),△¹⁴-vincanol (10),scandine (11),10-hydroxyscandine (12),melodinine T (13),meloscandonine (14),venalstonine (15),19-hydroxyvenalstonine(16),vindolinine (17),melodinine M (18),voaphyline (19),and melofusine I (20).By analysis of NMR,MASS,spectrum and data.Alkaloids 4-6,8,9,13,16 and 18-20 were obtained from the plants of Melodinus tenuicaudatus for the first time.The isolates were evaluated for the cytotoxic activities by MTT assay.Among them,compounds 1,2,4,6,10 and 17 showed growth inhibitory activityagainst the five human tumor cell lines.

Key words: Melodinus tenuicaudatus, alkaloids, chemical constituents, tumor cell proliferation