One new alkaloid amide, piperlongumide (1) [N-isobutyl-19-(3',4'-methylenedioxyphenyl)-2E,4E nonadecadienamide], and six known compounds with leishmanicidal activity against promastigotes and axenic amastigotes of Leishmania donovani were isolated from the n-hexane fraction of the fruits of Piper longum. The structure of 1 was elucidated by spectroscopic evidences.