新烟碱类手性农药立体环境行为及对映体毒理差异分子机制

Neonicotinoid chiral pesticides were extensively used in the agricultural production in China, which posed a serious threat to our environment and biological safety because of its high toxic to honeybee. Previous studies proved that neonicotinoid chiral pesticides have significant enantioselective toxicity to honeybee. Then, it is helpful for the problem solving to conduct the studies of environmental fate and different toxicology mechanism in enantiomer level. In this study, two typical novel neonicotinoid chiral pesticides dinotefuran and sulfoxaflor were selected, and their single enantiomers were separated and prepared by chiral chromatography. The environmental fate of racemate and optical pure enantiomers were studied to disclose the main degradation products and metabolic pathways, and to find out the metabolic differences and influencing factors in vegetable-soil ecosystem. The mechanisms of analytes stereoselectivity and the major trending behavior of high-toxic enantiomer in the vegetables and soils were revealed, to make sure the critical control points of the safe use of neonicotinoid chiral pesticides. Meanwhile, the enantioselective toxicology on target and non-target organism (aphid, Aphis gossypii and honeybee, Apis mellifera) between the enantiomers was studied based on the molecular biology method. It is helpful to provide a data support and theoretical basis for environmental risk assessment, safe application, and development of efficient low-risk enantiomer of neonicotinoid chiral pesticides.

我国农业生产中新烟碱类手性农药环境投放量大，对媒介昆虫蜜蜂毒性高，给农业环境生物安全带来了严重威胁。前期研究表明新烟碱类手性农药对蜜蜂存在显著对映体毒性差异，开展对映体水平的残留环境行为和毒理差异机制研究有利于该问题的解决。本课题拟选取典型新烟碱类手性农药呋虫胺和氟啶虫胺腈为研究对象，通过手性色谱分离制备光学纯手性农药单体，研究手性农药对映体在蔬菜和土壤中的对映体选择性环境行为规律，明确其主要降解产物和代谢途径，分析其在不同环境中代谢差异及影响因素，探讨其立体选择性机制，揭示供试手性农药高毒体在土壤-蔬菜体系中主要行为归趋，明确手性农药安全使用的关键控制点。同时，通过分子生物学手段，研究和探讨手性农药对映体对靶标生物蚜虫和非靶标生物蜜蜂毒理差异的分子机制。为新烟碱类手性农药的环境风险评估、安全使用和高效低风险手性单体农药开发提供基础数据和理论依据。

本项目选取典型新烟碱类手性农药呋虫胺为研究对象，通过超高效合相色谱串联质谱对呋虫胺及其代谢物对映体实现了手性分离，并制备了高纯度呋虫胺单体。明确了呋虫胺对映体在设施蔬菜和土壤中选择性环境行为，发现番茄设施栽培过程中，R-(-)-呋虫胺优先降解，导致S-(+)-呋虫胺相对富集，且选择性代谢产生UF对映体，茎叶吸收途径下表现为(-)-UF优先降解；呋虫胺对映体在羽衣甘蓝中的分布、转化、代谢研究表明，S-(+)-呋虫胺在甘蓝体内的吸收速率、转化速率和转化量都明显快于R-(-)-呋虫胺。土壤中选择性降解结果显示，中性的砂质土壤中，R-(-)-呋虫胺优先降解导致S-(+)-呋虫胺相对富集，而在酸性和碱性粉质土壤中选择性降解出现反转，表现为S-(+)-呋虫胺优先降解。生物活性和生态毒性结果显示，S-(+)-呋虫胺与R-(-)-呋虫胺对棉蚜和绿盲蝽的生物活性差异不显著，而S-(+)-呋虫胺对赤子爱胜蚓的毒性为高毒，毒性为R-(-)-呋虫胺的71.5倍，S-(+)-呋虫胺为高毒体。最后利用分子对接从分子水平上阐明了呋虫胺对映体对意大利蜜蜂的致毒机制及其选择性差异机制，从蛋白水平上阐明了呋虫胺对映体对赤子爱胜蚓的致毒机制及其选择性差异机制。建议开发高比例或全比例的R-(-)-呋虫胺替代外消旋体，能够在降低蜜蜂风险的同时达到控制害虫的效果。本项目共培养博士生3名，发表文章7篇，SCI收录6篇。