Abstract
One isomer (A) of tralomethrin [(S)-α-cyano-3-phenoxybenzyl (1′RS)-cis-(1R, 3R)-3-(1, 2, 2, 2-tetrabromoethyl)-2, 2-dimethylcyclopropanecarboxylate] and deltamethrin [(S)-α-cyano-3-phenoxybenzyl (1R, 3R)-3-(2, 2-dibromovinyl)-2, 2-dimethylcyclopropanecarboxylate] labeled with 14C in the benzylic carbon were applied on or injected into the larvae of tobacco cutworm, Spodoptera litura (F.). On topical application, tralomethrin A was rapidly converted to deltamethrin on the surface and in the body of the larvae. The conversion occurred in the insect body to a larger extent than on the surface. Injection of tralomethrin A led to more rapid formation of deltamethrin than topical application. Formed deltamethrin exceeded tralomethrin A in amount within several minutes after injection. In vitro studies revealed that the conversion was facilitated nonenzymatically by thiols such as glutathione, cysteine and dithiothreitol, but inhibited by N-ethylmaleimide and 1, 2-dibromotetrachloroethane. 1, 1, 2, 2-Tetrabromoethane, 1, 2-dibromoethane and 1, 2-dibromo-1, 2-diphenylethane, however, showed hardly any inhibitory effects on the conversion. There was no significant difference between tralomethrin A and another isomer, tralomethrin B, in the conversion rate to deltamethrin.
