Quinoline alkaloids and other constituents of Melicope semecarpifolia with antiplatelet aggregation activity.

Three new quinoline alkaloids, 2-acetylevolitrine (1), 2-acetylpteleine (2), and semecarpifoline (3), along with 26 known compounds were isolated from the root bark of Melicope semecarpifolia. The structures of 1-3 were elucidated by means of spectral analysis. In addition, (2S)-(--)-7,8-dimethoxyplatydesmine (4), cis-(+)-7,8-dimethoxymyrtopsine (5), and (3R)-(--)-8,9-dimethoxygeibalansine (6) were isolated as new natural products. Several of these isolates were determined as exhibiting significant antiplatelet aggregation activities in vitro.