In‐vitro evidence for activative thiolysis and selfsynergism of sulfenyl dicarbamate derivatives of 3,4 methylenedioxyphenyl N‐methylcarbamate

Activative thiolytic cleavage of the N‐S bond and self‐synergism in sulfenyl dicarbamate (SD) derivatives of 3,4‐methylenedioxyphenyl N‐methylcarbamate has been investigated. The formation of precursor carbamates by the reaction of the propoxur derivative with glutathione and cysteine was demonstrated by HPLC. The slower rate of insectidal action of SD‐propoxur compared with propoxur and its lower ki for inhibition of housefly acetylcholinesterase measured after preincubation of housefly head homogenate with N‐ethylmaleimide were considered as indirect evidence of the N‐S breakdown as a delay factor in toxicity. The SD‐carbaryl derivative, 3,4‐methylenedioxyphenyl N‐methylcarbamate, and piperonyl butoxide similarly inhibited the oxidative metabolism of [14C]carbaryl in post‐mitochondrial homogenates of housefly abdomens. The results indicated that activative thiolysis and self‐synergism performed by the methylenedioxyphenyl group could be processes involved in the insecticidal action of the sulfenyl dicarbamates.