Jing Xu, Yao Guojun, Wang Peng, Liu Donghui, Qi Yanli, Zhou Zhiqiang
Beijing Advanced Innovation Center for Food Nutrition and Human Health, Department of Applied Chemistry, China Agricultural University, Beijing, P.R. China.
Chirality. 2016 May;28(5):382-6. doi: 10.1002/chir.22585. Epub 2016 Mar 23.
Metalaxyl is an important chiral acetanilide fungicide, and the activity almost entirely originates from the R-enantiomer. Racemic metalaxyl has been gradually replaced by the enantiopure R-enantiomer (metalaxyl-M). In this study a chiral residue analysis method for metalaxyl and the metabolite metalaxyl acid was set up based on high-performance liquid chromatography tandem mass spectroscopy (HPLC-MS/MS). The enantioselective degradation and chiral stability of metalaxyl-M in tomato fruits in two geographically distinct regions of China (Heilongjiang and Hunan Province) were evaluated and the enantioselectivity of metalaxyl acid was also investigated. Tomato plants grew under field conditions with a one-time spray application of metalaxyl-M wettable powder. It was found that R-metalaxyl was not chirally stable and the inactive S-metalaxyl was detected in tomato fruits. At day 40, S-metalaxyl derived from R-metalaxyl accounted for 32% and 26% of the total amount of metalaxyl, respectively. The metabolites R-metalaxyl acid and S-metalaxyl acid were both observed in tomato, and the ratio of S-metalaxyl acid to the sum of S- and R-metalaxyl acid was 36% and 28% at day 40, respectively. For both metalaxyl and metalaxyl acid, the half-life of the S-enantiomer was longer than the R-enantiomer. The results indicated that the enantiomeric conversion should be considered in the bioactivity evaluation and environmental pollution assessment. Chirality 28:382-386, 2016. © 2016 Wiley Periodicals, Inc.
甲霜灵是一种重要的手性乙酰苯胺类杀菌剂，其活性几乎完全源自R-对映体。外消旋甲霜灵已逐渐被纯对映体R-对映体（甲霜灵-M）所取代。本研究基于高效液相色谱串联质谱法（HPLC-MS/MS）建立了甲霜灵及其代谢产物甲霜灵酸的手性残留分析方法。评估了甲霜灵-M在中国两个地理区域（黑龙江省和湖南省）番茄果实中的对映体选择性降解和手性稳定性，并研究了甲霜灵酸的对映选择性。番茄植株在田间条件下生长，一次性喷施甲霜灵-M可湿性粉剂。结果发现，R-甲霜灵在手性方面不稳定，在番茄果实中检测到了无活性的S-甲霜灵。在第40天，由R-甲霜灵衍生而来的S-甲霜灵分别占甲霜灵总量的32%和26%。在番茄中均观察到了代谢产物R-甲霜灵酸和S-甲霜灵酸，在第40天，S-甲霜灵酸与S-和R-甲霜灵酸总量的比值分别为36%和28%。对于甲霜灵和甲霜灵酸，S-对映体的半衰期均长于R-对映体。结果表明，在生物活性评价和环境污染评估中应考虑对映体转化。《手性》2016年第28卷：382 - 386页。© 2016威利期刊公司。
