title: Benzoxazinone-Mediated Triazine Degradation: A Proposed Reaction Mechanism.
abstract: The role of benzoxazinones (Bx, 2-hydroxy-2H-1,4-benzoxazin-3(4H)-one) in triazine resistance in plants has been studied for over half a century. In this research, fundamental parameters of the reaction between DIBOA-Glc (2-β-d-glucopyranosyloxy-4-hydroxy-1,4-benzoxazin-3-one) and atrazine (ATR, 6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine) were examined. Through a series of experiments employing a variety of chromatographic and spectroscopic techniques, the DIBOA-Glc/ATR reaction was characterized in terms of reactant and product kinetics, stoichiometry, identification of a reaction intermediate, and reaction products formed. Results of these experiments demonstrated that the reaction mechanism proceeds via nucleophilic attack of the hydroxamic acid moiety of DIBOA-Glc at the C-2 position of the triazine ring to form hydroxyatrazine (HA, 2-hydroxy-4-ethylamino-6-isopropylamino-s-triazine), with associated degradation of DIBOA-Glc. Degradation of reactants followed first-order kinetics with a noncatalytic role of DIBOA-Glc. A reaction intermediate was identified as a DIBOA-Glc-HA conjugate, indicating a 1:1 DIBOA-Glc:ATR stoichiometry. Reaction products included HA and Cl(-), but definitive identification of DIBOA-Glc reaction product(s) was not attained. With these reaction parameters elucidated, DIBOA-Glc can be evaluated in terms of its potential for a myriad of applications, including its use to address the problem of widespread ATR contamination of soil and water resources.
authors.affiliation: Department of Crop, Soil and Environmental Sciences, University of Arkansas , 1366 West Altheimer Drive, Fayetteville, Arkansas 72704, United States.
authors.forename: C D
authors.initials: CD
authors.lastname: Willett
authors.affiliation: USDA-Agricultural Research Service , Cropping Systems and Water Quality Research Unit, 269 Ag. Eng. Bldg, Columbia, Missouri 65211, United States.
authors.forename: R N
authors.initials: RN
authors.lastname: Lerch
authors.affiliation: Department of Forestry, Center for Agroforestry, University of Missouri , 203 ABNR Bldg., Columbia, Missouri 65211, United States.
authors.forename: C-H
authors.initials: CH
authors.lastname: Lin
authors.affiliation: Department of Crop, Soil and Environmental Sciences, University of Arkansas , 1366 West Altheimer Drive, Fayetteville, Arkansas 72704, United States.
authors.forename: K W
authors.initials: KW
authors.lastname: Goyne
authors.affiliation: Department of Chemistry, Missouri University of Science and Technology , 142 Schrenk Hall, 400 West 11th Street, Rolla, Missouri 65409, United States.
authors.forename: N D
authors.initials: ND
authors.lastname: Leigh
authors.affiliation: Division of Plant Sciences, University of Missouri , 214D Waters Hall, Columbia, Missouri 65211, United States.
authors.forename: C A
authors.initials: CA
authors.lastname: Roberts
mesh_terms: D048588:Benzoxazines / Q000737:chemistry*; D006540:Herbicides / Q000737:chemistry*; D015394:Molecular Structure; D014227:Triazines / Q000737:chemistry*
chemical_list: D048588:Benzoxazines; D006540:Herbicides; D014227:Triazines
keywords: DIBOA-Glc; atrazine; benzoxazinones; hydroxyatrazine; nonenzymatic atrazine degradation; phytochemistry