Objective: Melodinus (Apocynaceae) plants have been used in folks in China for a long time. Alkaloids from Melodinus genus have showed significant antitumor

antibacterial and antifertility activities. This study focuses on the chemical constituents of alkaloids from M. khasianus. Method: The compounds were isolated and purified by silica gel column chromatography

reversed-phase C18column chromatography and preparative liquid chromatography. The compounds were screened out for prostate cancer cells (PC-3)

lung cancer cells (A549)

gastric cancer cells (HGC-27) and human leukemia cells (HL-60) by MTT method. Result: Their chemical structures were established by their physicochemical properties and spectral data. Twelve compounds were isolated and characterized from the chloroform fraction of ethanol extract in M. khasianus. Their structures were identified as (+)epi-16α-hydro-14

15vincamine (1)

16β

21β-epoxy-vincadine (2)

melodinines G (3)

melodinines P (4)

melodinines N (5)

16β-hydroxy-19S-vindolinine (6)

16β-hydroxy-19R-vindolinine (7)

15α-hydroxy-14

15-dihydrovindolinine (8)

melodinines T (9)

19-epimeloscandonine (10)

meloscandonine (11) and scandine (12). Conclusion: Compounds 1-10 were isolated from M. khasianus for the first time. The cytotoxicity of these compounds was evaluated by MTT method in vitro. Compounds 4 and 5 displayed an inhibitory effect on the proliferation of prostate cancer cells (PC-3)

lung cancer cells (A549)

gastric cancer cells (HGC-27) and human leukemia cells (HL-60).