Abstract: Ten alkaloids were isolated from the roots of Melodinus henryi by a combination of various chromatographic techniques,including column chromatography over silica gel,pH-zone-refining high-speed counter-current chromatography,and reversed-phase HPLC,etc.The structures of these alkaloids were determined on the basis of spectroscopic analysis including MS and NMR data,which were divided into three types,including quinine-type alkaloids:melodinhenine D（1）,melaxilline A（2）,11-methoxytabersonine（3）,meloscandonine（4）,melodinine T（5）;aspidospermidine-type alkaloids:venalstonidine（6）,vandrikidine（7）;vincadine-type alkaloids:14,15-dehydrovincine（8）,14,15-dehydro-16-epi-vincamine（9）,△¹⁴-vincanol（10）.All the compounds except 1,5 and 8 were isolated from Melodinus henryi for the first time.All the compounds were tested for their cytotoxicities against human breast cancer MCF-7 cells using the MTT method,and compound 3 exhibited significant cytotoxic effect with IC₅₀  value of 23.4 μM.

Key words: Apocynaceae, Melodinus henryi, 11-methoxytabersonine, cytotoxicity, MCF-7