Metabolism of Flumetsulam (DE-498) in Wheat, Corn, and Barley

• Published in: Pesticide biochemistry and physiology Vol. 45; no. 3; pp. 178 - 192
• Main Authors: Frear, D.S., Swanson, H.R., Tanaka, F.S.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.03.1993; Elsevier
• Subjects: ABSORCION; ABSORPTION; ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; Agronomy. Soil science and plant productions; Biological and medical sciences; Chemical control; COENZIMAS; COENZYME; DESINTOXICACION; DETOXIFICATION; ENZIMAS; ENZYME; FEUILLE; Fundamental and applied biological sciences. Psychology; HERBICIDAS; HERBICIDE; HOJAS; HORDEUM VULGARE; INHIBIDORES DE ENZIMAS; INHIBITEUR D'ENZYME; LUMIERE; LUZ; METABOLISME; METABOLISMO; METABOLITE; METABOLITOS; METALLOPROTEINE; METALPROTEINAS; MONOXIDO DE CARBONO; NUCLEOTIDE; NUCLEOTIDOS; OXIGENO; OXYDE DE CARBONE; OXYGENE; Parasitic plants. Weeds; Phytopathology. Animal pests. Plant and forest protection; TALLO; TIGE; TRITICUM AESTIVUM; VIA BIOQUIMICA DEL METABOLISMO; VOIE BIOCHIMIQUE DU METABOLISME; Weeds; ZEA MAYS; Biological properties; Monocotyledones; Sulfonamide; Zea mays; Hordeum vulgare; Enzyme; Metabolite; Primary reaction; Hydroxylase; Tolerance; Detoxication; Selectivity; Microsome; Metabolism; Herbicide; Cereal crop; In vivo; Enzymatic activity; Gramineae; Angiospermae; Spermatophyta; Labelled compound; Triticum aestivum
• ISSN: 0048-3575; 1095-9939
• DOI: 10.1006/pest.1993.1020

Flumetsulam ( N-[2,6-difluorophenyl]-5-methyl(1,2,4)-triazolo[1,5- a]pyrimidine-2-sulfonamide) was metabolized by similar hydroxylation and glucose conjugation pathways in tolerant corn, wheat, and barley seedlings. Two primary monohydroxylated metabolites, N-[2,6-difluoro-4-hydroxyphenyl]-5-methyl(1,2,4)-triazolo[1,5- a]pyrimidine-2-sulfonamide (M 1) and N-[2,6-difluorophenyl]-5-hydroxymethyl(1,2,4)-triazolo[1,5- a]pyrimidine-2-sulfonamide (M 2) and a dihydroxylated metabolite N-[2,6-difluoro-4-hydroxyphenyl]-5-hydroxymethyl(1,2,4)-triazolo[1,5- a]pyrimidine-2-sulfonamide (M 3) were isolated and identified by negative FAB/MS and proton NMR spectroscopy. Isolated secondary O-glucosides of metabolites M 1, M 2 and M 3 were tentatively identified by negative FAB/MS and/or β-glucosidase hydrolysis. Microsomal cytochrome P450-dependent monooxygenases responsible for flumetsulam hydroxylation were isolated from naphthalic anhydride- and ethanol-induced shoot tissues of etiolated corn, wheat, and barley seedlings. Enzyme activity required NADPH and molecular oxygen and was inhibited by carbon monoxide in the dark and by other cytochrome P450 inhibitors. Inhibition by carbon monoxide was reversed by light. Enzyme kinetic and inhibition studies suggested that different cytochrome P450 forms may be involved in flumetsulam hydroxylation at the 4-position on the 2,6-difluorophenyl ring (M 1) and the methyl group on the substituted pyrimidine moiety (M 2).