CHLORIMURON ETHYL METABOLISM IN CORN

[14C]Chlorimuron ethyl was readily absorbed by the roots of young intact corn seedlings and through the cut ends of excised leaves, but it was not readily absorbed by intact leaves. Under the conditions employed, [14C]chlorimuron ethyl was metabolized at a moderate rate in both intact roots and excised leaves (ca. 2.4 nmol/g fresh wt tissue/hr). Based upon high-performance liquid chromatography (HPLC) analysis, [14C]chlorimuron ethyl appeared to be metabolized by similar routes in both the roots and leaves. [14C]Chlorimuron ethyl and 10 radioactive metabolites were detected in the roots of corn 7 hr following herbicide treatment. [14C]Chlorimuron ethyl and seven metabolites, listed in approximate order of their abundance, were isolated and characterized: chlorimuron ethyl (N-[4-chloro-6-methoxypyrimidine-2-yl]-N′-[2-ethoxycarbonylbenzenesul-fonyl]urea; (I) N-(4-chloro-5-hydroxy-6-methoxypyrimidine-2-yl)-N′-(2-ethoxycarbonylbenzene-sulfonyl)urea; (II) 2-ethoxycarbonylbenzene sulfonamide, (IV) N-(4-[S-glutathionyl]-6-methoxypyrimidine-2-yl)-N′(2-ethoxycarbonylbenzenesulfonyl)urea, (VI) N-(4-[S-glutathionyl]-5-hydroxy-6-methoxypyrimidine-2-yl)-N′-(2-ethoxycarbonylbenzenesulfonyl)urea, (III) N-(4-chloro-5-[O-β-d-glucosyl]-6-methoxypyrimidine-2-yl)-N′-(2-ethoxycarbonylbenzenesulfonyl)urea, (VII) N-(4-chloro-6-methoxypyrimidine-2-yl)-N′-(2-ethoxy-?-[O-β-d-glucosyl]benzenesulfonyl)urea, and (V) N-(4-[S-cysteinyl]-6-methoxypyrimidine-2-yl)-N′-(2-ethoxycarbonylbenzenesulfonyl)urea. Chlorimuron ethyl and these metabolites were purified by HPLC and were characterized by fast atom bombardment mass spectrometry (FAB MS). In addition to FAB MS, the following methods were used in the characterization of some metabolites: synthesis, hydrolysis with β-glucosidase, analysis of hydrolysis products, electron impact mass spectrometry, and proton nuclear magnetic resonance (400 MH). © 1991.