Seven new indole alkaloids (aspidofractinine type 1e3, kopsine type 5, strychnos type 6, and vincamine type 7, 8) were isolated from Kopsia jasminiflora (Apocynaceae) collected in Thailand. 5-Oxokopsinic acid (4) was isolated from nature for the first time. The structures of the new alkaloids were determined by spectroscopic analyses and chemical transformation of a known alkaloid. 5,6-Secokopsinine (1) possesses a dialdehyde function that is formed by oxidative cleavage of the C-5eC-6 bond of kopsinine (9). New vincamine-type alkaloid 8 showed potent inhibitory activity toward human cancer cell lines (A549, HT29, HCT116).