Metabolism of Furametpyr. 1. Identification of Metabolites and in Vitro Biotransformation in Rats and Humans

Urinary and fecal metabolites in male rats treated with a (14)C-labeled fungicide, furametpyr [N-(1,3-dihydro-1,1, 3-trimethylisobenzofuran-4-yl)-5-chloro-1, 3-dimethylpyrazole-4-carboxamide, Limber], were purified by a combination of chromatographic techniques, and chemical structures of 14 metabolites were identified by spectroanalyses (NMR and MS). The major biotransformation reactions of furametpyr in rats were found to be (1) N-demethylation, (2) oxidation of the methyl group at C3 of the pyrazole ring, (3) oxidation of the methyl group at C1 of the 1,3-dihydroisobenzofuran ring, (4) hydroxylation at C3 of the 1,3-dihydroisobenzofuran ring, and (5) hydroxylation at C7 of the 1, 3-dihydroisobenzofuran ring. In vitro metabolism by recombinant human cytochrome P450 revealed that a major biotransformation in humans is N-demethylation, catalyzed by CYP1A1, 1A2, 2C19, and 3A4.