【作者】 程有普；

【导师】 郑永权；

【作者基本信息】 沈阳农业大学 ， 农药学， 2014， 博士

【摘要】 手性农药不同立体异构体之间对靶标生物的生物活性、对非靶标生物的毒性以及在植物体和环境中的降解行为往往存在很大差异,传统意义上的农药风险评估通常将手性农药视作一种化合物,得到的数据缺乏准确性,给环境安全带来隐患。丙环唑是稻田中广泛使用的一种三唑类广谱内吸手性杀菌剂,然而在对映体水平上系统研究丙环唑的活性、毒性以及在稻田立体环境行为尚属空白。首先探讨了丙环唑四种立体异构体的分离方法。正相HPLC条件下,利用OD-H或AD-H手性色谱柱,通过优化分离条件,丙环唑四种异构体得到了完美分离；在UPC2-MS/MS检测体系下,利用Chiralpak(?) IA-3,3μm手性色谱柱,通过优化质谱、合相等条件,实现了丙环唑四种异构体短时间内的基线分离。并成功建立了水稻植株、水稻土及稻田水等五种基质中同时检测丙环唑四种异构体的手性UPC2-MS/MS方法,方法的准确度、灵敏度、精密度等均符合实验要求。其次,利用建立的分析方法研究了丙环唑异构体田间条件下在稻田体系中的立体选择性降解行为。结果表明,在水稻嫩株中丙环唑异构体降解速率最快,稻粒中降解最慢。在水稻嫩株中,立体选择性降解最为明显,老熟茎秆次之,而稻粒、稻壳中较弱。在水稻植株中,均表现为(+)-丙环唑-B和(-)-丙环唑-A优先降解。在稻田水和稻田土中丙环唑的降解均未出现明显的对映体选择性。研究了实验室条件下3种水稻土中丙环唑异构体的立体选择性降解行为。有氧条件下,丙环唑(-)A和(-)B优先降解,海南水稻土最明显；无氧条件下,没有显现或仅显现出微弱的对映体选择性,丙环唑(+)A和(+)B优先降解;灭菌条件下无对映体选择性。三种培养条件下,丙环唑立体异构体构型稳定,无相互转化。第三,研究了丙环唑异构体在7种溶剂的光化学降解,结果表明,丙环唑4个异构体无相互转化现象发生,其光解符合一级反应动力学方程。在六种有机溶剂中,以甲醇中的光解速率最快,乙醇次之,异丙醇中光解最慢。排除光解产物的干扰,四种异构体光解速率差异不显著。最后,测定了丙环唑立体异构体对水稻5种致病菌(稻瘟病菌、稻恶苗病菌、稻纹枯病菌、稻立枯病菌、稻曲病菌)的生物活性及对斜生栅藻和大型溞的急性毒性。结果表明,丙环唑异构体的生物活性对稻恶苗病菌的差异最大,活性EC50值相差最高达23.47倍；稻曲病的差异最小,活性EC50值相差2.43倍；四种单体的活性次序因病菌而异。丙环唑四种异构体的急性毒性差异不大,对斜生栅藻毒性最低的ECso值是最高的2.25倍(72h)和2.13倍(96h),对大型溞毒性最低的48h-EC50值仅为最高的1.48倍。基于研究结果,不建议开发使用丙环唑单一光学纯异构体。更多还原

【Abstract】 The pure stereoisomers of the same chiral pesticide may differ dramatically in bioactivity to pathogens, toxicity to non-target organisms, and degradation in plants and environment. In conventional risk evaluations, the chiral pesticides were often treated as one compound, and the data obtained were incomplete and nonspecific, bringing potential risks posed by these pesticides to environment and public health. Propiconazole, a broad spectrum systemic chiral triazole fungicide, was extensively used in paddy field. However, little work was made to date about bioactivity, toxicity, and stereoselectivity degradation of propiconazole isomers in paddy environments.Firstly, enantioseparation of four propiconazole isomers was studied. Baseline separation of four propiconazole stereoisomers was successfully obtained using OD-H or AD-H chiral column with optimal conditions by HPLC; Under UPC2-MS/MS determination system, baseline separation of the four isomers was also achieved within short time using Chiralpak(?) IA-3,3μm chiral column with optimization of MS/MS and ultra performance convergence chromatography(UPC2) conditions.Next, stereoselective analysis method for propiconazole in five matrices (i.e., rice grain, rice husk, rice straw, paddy soil and paddy water) by UPC2-MS/MS was successfully developed for the first report, and the validated method with high accuracy, precision, sensitivity was found to meet the test requirements.Based on above method, enantioselective degradation of propiconazole stereoisomers in rice plants, paddy soils and paddy water was studied. The results indicated that the dissipation rates of the four isomers in rice plants followed the order of in tender rice plants> in old rice straw>in rice grains, as the same order as degradation enantioselectivity in rice stems and leaves. The preferential dissipation of (+)-propiconazole-B and (-)-propiconazole-A in rice plants was also determined. No obvious enantioselective degradation was observed in paddy soil and water under field condition.Secondly, enantioselective degradation of propiconazole stereoisomers in three paddy soils under laboratory-controlled conditions were investigated. Under aerobic conditions,(-)-propiconazole-B and (-)-propiconazole-A were degraded preferentially, that could be observed obviously in Hainan paddy soil. But in anaerobic incubation, not obvious or only weak enantioselective degradation was observed with preferential dissipation of (+)-propiconazole-B and (+)-propiconazole-A. No enantioselective degradation was found in three paddy soils under sterile conditions. Results also showed that the four stereoisomers of propiconazole were configurationally stable in three incubation mode, and no interconversion occurred among them.Thirdly, photolysis of propiconazole four isomers in seven solvents was studied. Results indicated that there were no interconversion among propiconazole stereoisomers under photolysis condition. The photo-degradation of the four isomers complied with the first-order kinetics. Among six organic solvents, the photolysis rates were the fastest in methanol, followed by which in ethanol, and the slowest in2-propanol. Eliminating the interference of photolysis products, the photolysis rates of them had little differences.Finally, stereoselective bioactivity towards five rice pathogens (including Pyricularia oryzae Cav., Fusarium moniliforme Sheld., Thanatephorus cucumeris (Frank) Donk., Rhizoctonia solani kuhn, Ustilaginoidea oryzae (Patou.) Bref) and acute toxicity towards S. obliquus and D. magna of propiconazole stereoisomers were determined. The results showed that bioactivities of the stereoisomers against Fusarium moniliforme Sheld had the maximum difference, EC50value of the isomer with the lowest activity was about23.47times of that with the highest activity; while the difference of bioactivities towards Ustilaginoidea oryzae (Patou.) Bref was minimum, with only2.43fold differences in bioactivity. The biological activities orders of the four stereoisomers varied with pathogens. Small differences of acute toxicity among the four stereoisomers towards S. obliquus and D. magna were observed. As for S. obliquus, EC50value of (+)-propiconazole-B was2.25times (72h) and2.13times (96h) of that of (-)-propiconazole-B; for D. magna, ratio of the highest48h-EC50to the lowest48h-EC50was only1.48.Thus, development and use of individual stereoisomers of triazole fungicide propiconazole were not recommended.更多还原