| 题名 | 酰苯胺类手性农药在黄粉虫体内的手性转化和选择性富集代谢 |
| 作者 | 高永鑫 |
| 学位类别 | 博士 |
| 答辩日期 | 2014-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 李建中 |
| 关键词 | 手性农药 手性合成 黄粉虫 手性转化 选择性富集 chiral pesticide chiral synthesis enantioselectivity Tenebrio molitor larvae enantiomerization bioaccumulation |
| 其他题名 | Enantiomerization and Enantioselective Bioaccumulation of anilide chiral fungicide in Tenebrio molitor Larvae from Wheat Bran |
| 学位专业 | 环境科学 |
| 中文摘要 | 目前使用的农药大约有 30%是手性的，研究表明，手性农药对映体在手性环境中会表现出不同的活性、毒性、转移及代谢等，并且使用具有高生物活性的单一对映体的手性农药可以减少农药的使用量和环境污染。在未来，可能有越来越多的具有高活性的单一对映体的手性农药取代外消旋体。但是在一些条件下(微生物、酶和化学条件)，具有光学活性的手性农药对映体可能不稳定，发生手性转化，即外消旋化，从而使得手性农药的环境行为和生态效应变得更为复杂。因此，研究手性农药在环境中的稳定性和手性转化作用机制对于准确的评价手性农药的安全性具有十分重要的意义。 昆虫是生物圈里数量最为庞大的种类，处于食物链的底部，也是沟通生物与生态环境的重要桥梁，目前关于手性农药在昆虫体内的手性行为研究甚少。黄粉虫是一种重要的鞘翅目类昆虫，是很多动物的食物源，本论文以黄粉虫幼虫为研究对象，研究了 3种酰苯胺类手性杀菌剂在黄粉虫幼虫体内的手性转化和选择性生物富集和代谢，并对手性转化机理进行了初步的研究。 本论文研究了酰苯胺类手性杀菌剂苯霜灵、甲霜灵和呋霜灵对映体的手性合成方法。用光学纯的化合物为起始原料，设计了一条合成酰苯胺类手性杀菌剂单一对映体的方法，该合成方法十分便捷。具体过程是，首先用前手性化合物 L-乳酸和 D-乳酸作为起始原料，进行甲酯化和三氟甲磺酰化，再与 2,6-二甲基苯胺进行胺烷基化，最后进行酰化得到与起始立体构型相反的光学对映体。产物经 HPLC结合手性柱检测，光学纯度均达 98%以上。 利用高效液相色谱串联质谱 (HPLC-MS/MS)与手性柱(Chiralcel OD-3R和ChiralPAK IC)结合，在反相条件下对酰苯胺类手性杀菌剂的对映体进行手性分离，并且先后建立了苯霜灵、甲霜灵和呋霜灵在麦麸和黄粉虫幼虫中的对映体残留分析方法。方法的准确度、精密度及灵敏度均符合农药残留分析的要求。该方法的优点是很好的解决了传统分析方法灵敏度低、基质干扰大等分离难题。 研究了苯霜灵、甲霜灵和呋霜灵对映体在黄粉虫幼虫体内的手性转化情况，结果显示，三个手性农药的对映体在黄粉虫幼虫体内均发生了明显的手性转化,而在麦麸中没有发生转化。初步分析认为是黄粉虫体内的某种消旋酶的作用导致了对映体之间的快速转化。根据苯霜灵、甲霜灵和呋霜灵对映体在黄粉虫体内的吸收，对映体转化和降解过程，建立了动力学模型。借助 SPSS16.0的非线性拟合功能，将苯霜灵、甲霜灵和呋霜灵对映体在黄粉虫幼虫体内的平均浓度(n=3)和时间进行拟合。分别求得了各个对映体近似的吸收速率、转化速率和降解速率。根据手性转化的结果，探讨了酰苯胺类手性杀菌剂对映体的手性转化机理。从分子结构的角度假设了一种机理，酰苯胺类手性农药的手性碳上连有一个羰基和一个与之共轭的酰胺基团，羰基和氨基的吸电子诱导效应使得与手性中心碳原子相连的氢质子显酸性，氢质子在生物碱或酶的作用下容易离去产生一个碳负离子中间态。如果在新的质子化环境中，另外的氢质子会从碳负离子的上面，或者下面进攻，从而导致对映体之间的手性转化。从分子结构上比较了苯霜灵、甲霜灵和呋霜灵这三个手性农药手性转化趋势的差异性，其中苯霜灵的手性转化趋势最明显。认为是不同酰基的吸电子诱导效应导致了苯霜灵、甲霜灵和呋霜灵对映体在手性转化过程中的差异。 研究了苯霜灵、甲霜灵和呋霜灵在黄粉虫幼虫体内的选择性富集及代谢行为。经过 21 d的暴露，结果显示，三种手性农药均在黄粉虫幼虫体内具有比较低的富集能力，富集能力的大小顺序为：苯霜灵>呋霜灵>甲霜灵。另外，三种手性农药对映体在黄粉虫体内的富集均具有明显的立体选择性。结果为： S-苯霜灵＞R-苯霜灵，S-甲霜灵＞R-甲霜灵，S-呋霜灵＞R-呋霜灵。在代谢行为实验中发现，这三种手性农药在黄粉虫体内消除较快，半衰期均小于 1.5 d，在代谢过程中，对映体没有明显的立体选择性。 |
| 英文摘要 | It has been estimated that approximately 30% of pesticides are chiral molecules,most of which are commercialized as racemic mixtures due to the limitation of chiral separation and synthesis. Enantiomers usually exhibit different properties in chiral environment, which may lead to variations in bioactivity, toxicity, biological uptake,metabolic pathways, degradation, and so on. Some chiral pesticides were configurationally instable under certain conditions and might undergo enantiomerization, which could make the environmental behavior and ecological effects of chiral pesticides complicated. Therefore, it is quite important to obtain the information on the stability of individual enantiomers of a chiral pesticide when assessing the possibility of developing a single enantiomer as a commercial pesticide. Insects are among the most diverse group of animals on the planet, including more than a million described species and representing more than half of known living organisms. They are at the bottom of the food chain and an important bridge communicating with biological and ecological environment. In this work, the enantiomerization and enatioselecive bioaccumulation of benalaxyl, metalaxyl and furalaxyl by a single dose of exposure to Tenebrio molitor larvae under laboratory conditions were studied by HPLC-MS/MS based on two types of chiral columns and the mechanism of enantiomerization was also explored. In this study, the synthetic method of the anilides chiral fungicides benalaxyl,metalaxyl and furalaxyl enantiomers was explored. A simple synthesis method was designed by using an optically active starting material. The specific process is subjecting L-lactic acid and D-lactic acid as starting raw materials to methyl esterification, acylation with trifluoromethanesulfonic anhydride, alkylation of amines and acylation with acyl chloride. The optical purity of the products was about 98% by HPLC with chiral column. A series of novel and sensitive single or multi-residue methods for enantiomeric analysis of anilides chiral fungicides in wheat bran and Tenebrio molitor larvae by HPLC-MS/MS based on two types of chiral columns were established. Validation of the methods included precisions, linearity and limit of detection which were in accordance with pesticide residue analysis. The developed methods were effective for detecting the residual enantiomers in the matrix and could be used for exploring the enantioselective environmental behaviors. Exposure of enantiopure R enantiomers and S enantiomers of benalaxyl,metalaxyl and furalaxyl in Tenebrio molitor larvae exhibited significant enantiomerization with formation of the R antiomers from the S enantiomers, and vice-versa, which might be attributed to the chiral pesticide catalyzed by a certain enzyme in Tenebrio molitor larvae. Enantiomerization was not observed in wheat bran during the period of 21 days. Mathematical models for a process of uptake,degradation and enantiomerization were developed and the rates of uptake,degradation and enantiomerization of R enantiomers and S enantiomers were estimated, respectively. One hypothetical pathway of enatiomerization was mentioned via deprotonation of an active proton at the chiral center in the view of a molecular structure. The chiral carbon in anilides chiral fungicides holds an electron-withdrawing carbonyl group and a conjugated acetanilide functional group. Therefore, the proton on the chiral center is relatively acidic and is thus easily lost to create an intermediate carbanion. Under protic environment, reprotonation regenerates the parent compound from either the top or the bottom face of the anion,thus interconverting enantiomers. The enatioselecive bioaccumulation of benalaxyl, metalaxyl and furalaxyl by dietary exposure to Tenebrio molitor larvae under laboratory conditions were studied. After 21 days of exposure, the results showed that the enantiomers of chiral pesticides in three all have relatively low bioaccumulation capacity in Tenebrio molitor larvae. Overall, the order of accumulation ability in Tenebrio molitor larvae is benalaxyl > furalaxyl > metalaxyl. The bioaccumulation of benalaxyl, metalaxyl and furalaxyl was enantioselective in Tenebrio molitor larvae. The result is S-benalaxyl > R-benalaxyl, S-metalaxyl > R-metalaxyl, S-furalaxyl > R-furalaxyl. In degradation experiments, it was found that three chiral pesticides in Tenebrio molitor larvae were degradated rapidly and the half-lives of three all were less than 1.5 days. |
| 公开日期 | 2015-06-16 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/13470]  |
| 专题 | 生态环境研究中心_中国科学院环境生物技术重点实验室 |
| 推荐引用方式 GB/T 7714 | 高永鑫. 酰苯胺类手性农药在黄粉虫体内的手性转化和选择性富集代谢[D]. 北京. 中国科学院研究生院. 2014. |
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