B. Sonawane, C. O. Knowles
Dec 1, 1971
Citations
0
Influential Citations
12
Citations
Journal
Pesticide Biochemistry and Physiology
Abstract
Abstract The metabolic fate of EP-475 or ethyl m-hydroxycarbanilate carbanilate and phenmedipham or methyl m-hydroxycarbanilate m-methylcarbanilate, two relatively new postemergence herbicides for control of weed pests of sugar beets, was studied in vivo in white rats and in vitro by rat hepatic subcellular fractions and plasma from various organisms. Both EP-475 and phenmedipham were rapidly metabolized and eliminated when administered orally to whete rats. The recovery of the administered dose in the urine and feces by 72-hr posttreatment was 95.4% for EP-475 and 99.1% for phenmedipham. Hydrolysis and conjugation were the most important reactions for the herbicides and their metabolites in vivo. EP-475 and phenmedipham were hydrolyzed to ethyl-N-(3-hydroxyphenyl)-carbamate (EHPC) and methyl-N-(3-hydroxyphenyl)-carbamate (MHPC), respectively. Both hydroxyphenylcarbamates were subsequently cleaved to m-aminophenol. The m-aminophenol was then N-acetylated forming 3′-hydroxyacetanilide. EHPC, MHPC, m-aminophenol, and 3′-hydroxyacetanilide underwent the glucuronide and ethereal sulfate synthetic reactions. All of these compounds were tentatively identified from rat urine. Other unidentified radioactive materials were also present; however, they were all more polar than the parent compounds. Microsomal and soluble fractions prepared from rat liver homogenates contained enzymes that catalyzed the degradation of EP-475 and phenmedipham. Human, chicken, cow, and rat blood plasma also catalyzed the degradation of both herbicides. The major in vitro metabolites were the hydroxyphenylcarbamates (EHPC, MHPC), and their formation by liver fractions and blood plasma was inhibited by diisopropyl phosphorofluoridate (DFP) and 1-naphthyl methylcarbamate (carbaryl).