Effect of salithion enantiomers on larval growth, carbohydrases, acetylcholinesterase, adenylate cyclase activities and cyclic adenosine 3',5'-monophosphate level of Musca domestica and Tribolium castaneum.

Abstract

Dietary (R)(+)-salithion was a more potent insecticide (LC50 = 9.3 ppm) than the (S)(−)-enantiomer (LC50 = 63 ppm), correlating acetylcholinesterase (AChE) inhibition in vivo (I50 = 7.7 and 63 ppm) against Tribolium castaneum larvae. (S)(−)-Salioxon derived from (R)(+)-salithion had a stronger inhibitory activity (I50 = 8.8µm) than the (R)(+)-enantiomer (I50 = 22µm) in vitro against larval AChE. However, against Musca domestica female adults, a reversed tendency was observed: (S)(−)-salithion and (R)(+)-salioxon were more potent than (R)(+)-salithion and (S)(−)-salioxon in topical insecticidal and anticholinesterase activities in vivo and in vitro, respectively. Hence, the reversed stereospecificity between the T. castaneum larvicidal and M. domestica insecticidal activities of salithion enantiomers is due to a stereospecific difference in the intrincic potency of salioxon enantiomers as an AChE inhibitor with the two insects. A suppression of M. domestica larval growth, gut amylase and invertase activiti...