Liang Chuanzhou, Huang Junxing, Zhang Xu
School of Resources and Environmental Science, Wuhan University , Wuhan 430079, P.R. China.
J Agric Food Chem. 2016 Oct 19;64(41):7688-7695. doi: 10.1021/acs.jafc.6b02961. Epub 2016 Oct 11.
The adsorption coefficient of racemic metalaxyl onto an agriculture soil was small and nonenantioselective. Biotransformation was the predominant pathway for the elimination of R-metalaxyl, while abiotic and biotransformation made a comparable contribution to the degradation of S-metalaxyl. Metalaxyl acid was the main transformation intermediate. The enantiomer fraction of metalaxyl decreased with an increase in its initial spike concentration or the presence of the co-constituents in metalaxyl commercial products. Under simulated solar irradiation, the presence of TiO promoted the overall transformation kinetics through enhanced biotransformation and extra photoinduced chemical reactions. The promotion was enantioselective and thereafter changed the enantiomer fraction. The results obtained in this study showed that some achiral parameters, although they have no direct impact on enantioselective reactions with enantiomers, can significantly affect the enantioselective transformation of racemic metalaxyl. Thus, our results indicate that the contribution of chemical interactions on the enantioselective transformation of chiral pesticides may be underestimated.
消旋甲霜灵在农业土壤上的吸附系数较小且无对映体选择性。生物转化是R-甲霜灵消除的主要途径，而非生物转化和生物转化对S-甲霜灵的降解贡献相当。甲霜灵酸是主要的转化中间体。甲霜灵的对映体分数随其初始添加浓度的增加或甲霜灵商业产品中共存成分的存在而降低。在模拟太阳辐射下，TiO的存在通过增强生物转化和额外的光诱导化学反应促进了整体转化动力学。这种促进是对映体选择性的，进而改变了对映体分数。本研究获得的结果表明，一些非手性参数虽然对与对映体的对映体选择性反应没有直接影响，但可以显著影响消旋甲霜灵的对映体选择性转化。因此，我们的结果表明，化学相互作用对手性农药对映体选择性转化的贡献可能被低估了。
