The leaves of the plant Mitragyna parvifolia have afforded two alkaloids, 16,17-dihydro-17beta-hydroxy isomitraphylline (1) and 16, 17-dihydro-17beta-hydroxy mitraphylline (2), together with two known alkaloids, isomitraphylline (3) and mitraphylline (4). The structures of 1 and 2 were elucidated