title: Enantioselective separation and transformation of metalaxyl and its major metabolite metalaxyl acid in tomato and cucumber.
abstract: Many studies have shown the enantioselective transformation of metalaxyl in soil and animals, but little is known about the enantioselective biotransformation of metalaxyl in plants. In this study, a sensitive and convenient chiral liquid chromatography-tandem mass spectrometry method was developed for simultaneous measurement of the enantiomers of metalaxyl and its major metabolite, metalaxyl acid, in tomato and cucumber. Separation was by reversed-phase chromatography on a Chiralcel OD-RH column under isocratic conditions using acetonitrile-water (60/40, v/v) as mobile phase. The proposed method was successfully applied to investigate the possible enantioselective transformation of metalaxyl as well as the formation of metalaxyl acid in tomato and cucumber. In both vegetables, the (-)-R-enantiomer was preferentially degraded, resulting in relative enrichment of the (+)-S-enantiomer. Furthermore, formation of the metalaxyl acid enantiomers was also shown to be enantioselective, with the R-metalaxyl acid formed at a faster rate. This is the first evidence of enantioselective transformation of metalaxyl in vegetables, and the results should be considered in future environmental risk and food safety evaluations.
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
authors.forename: Yuanbo
authors.initials: Y
authors.lastname: Li
authors.forename: Fengshou
authors.initials: F
authors.lastname: Dong
authors.forename: Xingang
authors.initials: X
authors.lastname: Liu
authors.forename: Jun
authors.initials: J
authors.lastname: Xu
authors.forename: Xiu
authors.initials: X
authors.lastname: Chen
authors.forename: Yongtao
authors.initials: Y
authors.lastname: Han
authors.forename: Youpu
authors.initials: Y
authors.lastname: Cheng
authors.forename: Qiu
authors.initials: Q
authors.lastname: Jian
authors.forename: Yongquan
authors.initials: Y
authors.lastname: Zheng
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D001711:Biotransformation; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D028462:Cucumis / Q000737:chemistry / Q000378:metabolism*; D005659:Fungicides, Industrial / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D018551:Solanum lycopersicum / Q000737:chemistry / Q000378:metabolism*; D013237:Stereoisomerism; D053719:Tandem Mass Spectrometry / Q000379:methods
chemical_list: D005659:Fungicides, Industrial; C028175:metalaxyl; D000409:Alanine