Malouki Moulay Abderrahmane, Giry Géraldine, Besse Pascale, Combourieu Bruno, Sancelme Martine, Bonnemoy Frédérique, Richard Claire, Delort Anne-Marie
Laboratoire de Photochimie Moléculaire et Macromoléculaire, UMR 6505 du CNRS, Université Blaise Pascal, 63177 Aubière Cedex, France.
Environ Toxicol Chem. 2003 Sep;22(9):2013-9.
We investigated the transformation of methabenzthiazuron in water by microorganisms and solar light. This compound was very slowly phototransformed when irradiated at lambda > 290 nm, but it could be successfully oxidized into 6-hydroxymethabenzthiazuron by Aspergillus niger, as shown by nuclear magnetic resonance experiments. The toxicity of this metabolite, as determined by the standardized Microtox test, was sixfold lower than that of the parent molecule. The 6-hydroxymethabenzthiazuron was not further metabolized by A. niger but was photooxidized with ring cleavage of the aromatic ring and photodimerized on irradiation at lambda > 290 nm. In the presence of humic substances, the photodegradation was slower. We demonstrate that the transformations of methabenzthiazuron, observed either with the fungus A. niger or by the action of solar light, do not proceed via the urea chain N-dealkylation, as usually reported, but only via hydroxylation or cleavage of the benzene ring. This work shows the complementarity of both approaches, photo- and biodegradation, to study the fate of herbicides in the environment.
我们研究了微生物和太阳光作用下水环境中甲磺隆的转化情况。当在波长大于290nm的条件下照射时，该化合物的光转化非常缓慢，但通过核磁共振实验表明，黑曲霉能够成功地将其氧化为6-羟基甲磺隆。经标准化的Microtox测试测定，这种代谢物的毒性比母体分子低六倍。6-羟基甲磺隆不会被黑曲霉进一步代谢，但在波长大于290nm照射时会发生光氧化，伴随着芳香环的开环和光二聚化。在腐殖质存在的情况下，光降解速度较慢。我们证明，无论是在黑曲霉作用下还是在太阳光作用下观察到的甲磺隆转化，都不是像通常报道的那样通过脲链N-脱烷基化进行，而是仅通过羟基化或苯环裂解进行。这项工作展示了光降解和生物降解这两种方法在研究除草剂在环境中归宿方面的互补性。
