The Comparative Metabolism of Some Substituted Phenyl-N-Methylcarbamate Insecticides

Abstract

1. The metabolism of the N-methylcarbamates of 3-tertbutylphenol; 3,5-ditertbutylphenol; and 2-isopropoxyphenol was investigated in insects and mammals. 2. The major degradative pathway in enzyme systems from insects and mice was oxidative. The major metabolites from tertbutyl substituted phenyl-N-methylcarbamates were N-hydroxymethyl derivatives and tertbutanol derivatives. Baygon yielded N-hydroxymethyl, ring hydroxyl and O-dealkyl derivatives as major metabolites. 3. The rates of oxidation of the three insecticides in each enzyme system were similar. 4. Oxidation was inhibited by piperonyl butoxide and Metopirone, apparent I50 for singly oxidised metabolites was 10-4 M, and for metabolites with two oxidations 10-5M. 5. Enzymic hydrolysis of carbamate insecticides required reduced cofactor in insect and mouse systems. Mouse blood did not effect hydrolysis. 6. A wide variation of oxidising ability was found in live insects. Musca domestica was most active, Tenebrio molitor and Costelytra zealandica were least active. 7. Insecticide synergists reduce insects' ability to oxidise Baygon to acetone. 8. Musca domestica and Lucilia sericata larvae oxidised carbamate insecticides slower than the adult forms. 9. Mice excrete 3-tertbutylphenyl-N-methylcarbamate as phenolic metabolites, with only minor oxidative products. 10. Different rates of metabolism among insects could account for the selective toxicity of aryl-N-methylcarbamates.