Two new alkaloids from the twigs of Trigonostemon filipes.

A phytochemical investigation of the alkaloid constituents from Trigonostemon filipes Y. T. Chang et S. L. Mo led to the isolation of two new indole alkaloids, trigonostemine G (1) and trigonostemone J (2), together with two known ones, trigonostemine A (3) and trigonostemine B (4). Their structures were determined by extensive spectroscopic methods. Compounds 1-4 exhibited moderate AChE inhibitory activity with inhibition ratio of 31.6, 31.7, 41.7, and 42.4%, respectively. In addition, compounds 1-2 showed weak cytotoxicity against K562 and BEL-7402 human cancer cell lines.