Chiral quizalofop-ethyl and its metabolite quizalofop-acid in soils: Enantioselective degradation, enzymes interaction and toxicity to Eisenia foetida

• Published in: Chemosphere (Oxford) 2016-06, Vol.152, p.173-180
• Main Authors: Ma, Lin, Liu, Hui, Qu, Han, Xu, Yangguang, Wang, Peng, Sun, Mingjing, Zhou, Zhiqiang, Liu, Donghui
• Format: Article
• Language: English
• Subjects: Animals; Biodegradation, Environmental; Catalase - analysis; Chromatography, High Pressure Liquid; Earthworm; Eisenia foetida; Enantioselective; Environmental behavior; Kinetics; Oligochaeta - drug effects; Propionates - chemistry; Propionates - toxicity; Quinoxalines - chemistry; Quinoxalines - toxicity; Quizalofop; Soil; Soil - chemistry; Soil Pollutants - analysis; Soil Pollutants - chemistry; Soil Pollutants - toxicity; Stereoisomerism; Urease - analysis
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2016.02.084

An enantioselective chromatographic method to analyze enantiomers of quizalofop-ethyl and its metabolite quizalofop-acid was established using a high-performance liquid chromatography (HPLC) on (R, R) Whelk-O 1 column. The enantioselective degradation kinetics of quizalofop-ethyl and quizalofop-acid in three soils were investigated. Moreover, the interaction with urease and catalase in the soils and the acute toxicity to Eisenia foetida of quizalofop-ethyl were also determined in order to assess their metabolism mechanism and environmental risk. From the results, quizalofop-ethyl was configurationally stable and was hydrolyzed rapidly to quizalofop-acid, which also degraded enantioselectively but slowly, and the inversion of the S-(−)-quizalofop-acid into the R-(+)-quizalofop-acid was observed in Xinxiang soil. In addition, quizalofop-ethyl and quizalofop-acid enantioselectively affected urease activity but not catalase. The acute toxicity assays to earthworm indicated that the racemic quizalofop-ethyl and quizalofop-acid were more toxic than quizalofop-p-ethyl and quizalofop-p-acid respectively, dramatically, the toxicity of the metabolite was much higher than the parent compound. These results revealed the enantioselective degradation of quizalofop-ethyl and quizalofop-acid, and the differences of toxicity among the enantiomers of the parent compound and the metabolite, which should be considered in future environmental risk evaluation. [Display omitted] •The degradation of quizalofop-ethyl and quizalofop-acid in the soils was enantioselective.•Quizalofop-ethyl and quizalofop-acid enantioselectively affected urease activity but not catalase.•Racemic quizalofop-ethyl and quizalofop-acid were more toxic than (R)-enantiomers.•The toxicity of the metabolite to earthworm was much higher than the parent compound.