Five compounds formed by peroxydisulfate oxidation of primaquine were isolated using chromatographic methods and evaluated for antimalarial activity in vitro. One compound 6-methoxy-5,8 bis(4'-amino-1'-methylbutylamino)quinoline [P(1)] was found to have good gametocytocidal activity against Plasmodium yoelli infected mice at 10mg kg(-1) dose in vivo.