IDENTIFICATION OF METABOLITES OF THE HERBICIDE SAFENER BENOXACOR ISOLATED FROM SUSPENSION-CULTURED ZEA-MAYS CELLS 3 AND 24 H AFTER TREATMENT

The metabolic fate of the herbicide safener benoxacor was studied in s uspension cultures of Zea mays (cv. Black Mexican Sweet) 3 and 24 h af ter treatment (HAT) with [C-14]benoxacor. Following purification by re versed phase HPLC, metabolites were subjected to H-1-NMR or mass spect rometry for structural analysis. A catabolic alpha-hydroxyacetamide de rivative was detected as well as several amino acid conjugates either containing GSH or presumably derived from GSH. A relatively abundant d i(GSH) conjugate, which consisted of two GSH molecules linked to benox acor, was biosynthesized following the apparent addition of a suitable activating group to the benzoxazine-ring C2 atom of the previously de scribed mono(GSH) conjugate. The remaining metabolites identified were all presumably derived from either the mono(GSH) or di(GSH) conjugate s of benoxacor. A disaccharide conjugate was identified as S-O-(diglyc oside)GSH and was apparently formed by one or more glycosyl transferas es which used the mono(GSH) conjugate as a substrate. Two additional m etabolites identified were the mono- and di(gamma-GluCys) conjugates o f benoxacor, the formation of which was most likely the result of pept idase activity on the mono- and di(GSH) conjugates of benoxacor, respe ctively. An S-(S'-Cys)GSH conjugate was also identified and was likely formed by both peptidase and dipeptidase activities on the di(GSH) co njugate. Metabolite structures and postulated pathways of their biosyn thesis in vivo are presented.