Insecticidal activity of <i>Piper tuberculatum</i> Jacq. extracts: synergistic interaction of piperamides

Abstract The insecticidal activity of the neotropical pepper Piper tuberculatum Jacq. and its isolated piperamides was studied. Bioassays with the mosquito Aedes atropalpus L. assessed the relative toxicity of the whole extract of Piper tuberculatum and four of the piperamides, which were isolated and identified, then prepared synthetically. The results confirm that P. tuberculatum leaf extracts are as effective as black pepper seed extract and provide an alternative pepper insecticide from a more convenient source, the leaves. Experiments with piperamides showed that the tertiary and quaternary mixtures have greater‐than‐additive toxicity compared to single compounds or binary mixtures. One of the four amide compounds, 4,5‐dihydropiperlonguminine, was the most acutely toxic in mosquito larvae bioassays. A study of piperamide levels from different P. tuberculatum populations in Costa Rica determined that they were relatively homogeneous . Piper tuberculatum from only one of the five sites had higher levels of one piperamide, 4,5‐dihydropiperine, in both leaf and stem parts. One explanation for differences in the amide concentrations between populations is that one site is ecologically unique compared to the other four.