The Effect of BAS 145138 Safener on Chlorimuron Ethyl Metabolism and Toxicity in Corn

Abstract

Abstract BAS 145138 was moderately effective in protecting corn from injury due to chlorimuron ethyl. BAS 145138 increased the I50 of chlorimuron ethyl to corn, determined by root-growth in a sandy loam soil, from 6 g chlorimuron ethyl/ha to 25 g/ha. BAS 145138 caused an increase in the rate of chlorimuron ethyl metabolism , but it did not effect the rate of chlorimuron ethyl uptake or the nature of the metabolites produced. Major metabolites included chlorimuron ethyl hydroxylated in the pyrimidine ring (hydroxychlorimuron ethyl), the glucoside of hydroxychlorimuron ethyl, the glutathione conjugate formed by displacement of chlorine, a metabolite characterized as the glutathione conjugate sulfoxide or a hydroxylated glutathione conjugate, four unidentified polar metabolites, and 2-sulfonylamino benzoic acid ethyl ester. Metabolites were characterized by mass spectrometry and hydrolysis. It was concluded that BAS 145138 partially protects corn from chlorimuron ethyl by causing an increase in the rate of herbicide metabolism by hydroxylation, glucoside conjugation and by glutathione conjugation.