Initial metabolism of dimethenamid in safened and unsafened wheat shoots
1996
Riechers, D.E. | Fuerst, E.P. | Miller, K.D.
The metabolic fate of the chloroacetamide herbicide dimethenamid was examined in excised shoots of unsafened and safened wheat seedlings. Compared to unsafened controls, fluxofenim treatment increased the rate of metabolism of dimethenamid to water-soluble compounds. Thin layer chromatography revealed that similar dimethenamid metabolites were present in extracts from both safened and unsafened wheat shoots. However, three metabolites were more abundant in extracts from fluxofenim-treated wheat relative to unsafened wheat. Reversed-phase high-performance liquid chromatography and mass spectrometry were used to isolate and confirm the identity of dimethenamid metabolites extracted from safened wheat shoots 1 h after treatment with dimethenamid. In addition to the presence of the glutathione conjugate of dimethenamid, gamma-glutamylcysteine and cysteinylglycine dipeptide conjugates, as well as a cysteine conjugate and an oxygenated glutathione conjugate of dimethenamid, were detected. On the basis of time course analysis of dimethenamid metabolites by thin layer chromatography and structural identification by mass spectrometry, it appears that from 5 to 100 min after treatment with dimethenamid metabolism occurs exclusively via the glutathione conjugation pathway in wheat. Thus, the protection conferred to wheat by fluxofenim treatment is most likely due to increased glutathione-mediated detoxification of dimethenamid.
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