A dihydropylidone alkaloid, cenocladamide, and a derivative of piplartine, 4'-desmethylpiplartine were isolated along with piplartine from the leaves of Piper cenocladum. The structures of the new compounds were determined by spectroscopic methods and by comparison to piplartine. Concentrations of these amides in plants with and without ant mutualists. are compared. (C) 2000 Elsevier Science Ltd. All rights reserved.