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 eluci
dated by means of spectral analysis. In addition, (2S)-(-)-7,8-dimethoxypla
tydesmine (4), cis-(+)-7,8-dimethoxymyrtopsine (5), and (3R)-(-)-8,9-dimeth
oxygeibalansine (6) were isolated as new natural products. Several of these
isolates were determined as exhibiting significant antiplatelet aggregatio
n activities in vitro.