Metabolism of neolignans from P. regnellii (Piperaceae) in the beetle Naupactus bipes (Coleoptera: Curculionidae)

Piper regnellii (Piperaceae) contains high levels neolignans with diverse biological activities, including insecticidal. Despite the insecticidal activity of these neolignans, Naupactus bipes (Coleoptera: Curculionidae) larvae and adults were found feeding on the leaves (adults) and roots (larvae) of P. regnellii. The present study investigated the metabolic pathway of neolignans from P. regnellii leaves in the beetle N. bipes, focusing on possible biotransformation or sequestration of these compounds by the beetle. Two of the four plant neolignans could be recovered in the feces of adults feeding on P. regnellii leaves. In addition, four degradation products were detected, including the neolignan 3-(2R,3R)-2,3-dihydro-3-(methyl)-2-(4-hydroxyphenyl)-5-benzofuranyl]-(2E)-propenal (7), an oxidation product of conocarpan, the major plant neolignan. The adult beetle sequesters the neolignan conocarpan selectively from leaves as well as accumulates neolignan 7. Neolignan 7 was also detected in the larvae of lab-reared beetles.