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.