Inhibition of juvenile hormone biosynthesis in the tobacco hornworm, Manduca sexta, by a bisthiolcarbamate juvenoid and related compounds

Biosynthesis of juvenile hormone in the tobacco hornworm, Manduca sexta, is inhibited by the bisthiolcarbamate juvenoid N-ethyl-1,2-bis(isobutylthiolcarbamoyl)ethane both in vitro and in vivo. In vitro an extremely steep dose-response curve was obtained with an ID₅₀ value of 6 × 10^?6M. However, in vivo topical treatment with the compound resulted in mild JH antagonistic symptoms, suggesting rapid metabolism of the compound. In agreement with results from metabolic studies performed on plants and in mammals, sulfoxidation of the thiocarbamate S-(4-chlorobenzyl)N,N-diethylthiocarbamate resulted in an enhanced inhibitory effect on JH biosynthesis in vitro. This suggests that the corresponding thiocarbamate sulfoxides may act as intermediates in carbomylating critical thiol sites important in the terpenoid biosynthesis pathway. Furthermore, this study shows that these prototype compounds are interesting tools for further investigation of chemical inhibition of JH biosynthesis in insects.