Monoterpenoid indole alkaloids from Alstonia rostrata

Four new monoterpenoid indole alkaloids, alstrostines C-F together with thirteen known alkaloids were isolated from the leaves and twigs of Alstonia rostrata. All structures of new compounds were elucidated based on NMR, FTIR, UV, and MS spectroscopic data. Alstrostines C-E might originate from keto-enol tautomerism of preakummicine during biogenetic pathway of akummicine.