State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China; Shandong Engineering Research Center for Environment-Friendly Agricultural Pest Management, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao 266109, China.
Shandong Engineering Research Center for Environment-Friendly Agricultural Pest Management, College of Plant Health and Medicine, Qingdao Agricultural University, Qingdao 266109, China.
Sci Total Environ. 2022 Nov 25;849:157725. doi: 10.1016/j.scitotenv.2022.157725. Epub 2022 Jul 29.
Enestroburin is the first strobilurin fungicide developed by China and has been widely used to control fungal disease for 15 years. Investigation of its photolytic behaviour is essential for the comprehensive evaluation of its ecological risk. The effects of solution pH, humic acid (HA) and Fe(III) ions on photolysis were studied. The direct photolysis rates of enestroburin in the acidic solution (pH = 4) was faster than that in the basic (pH = 7) or neutral condition (pH = 9). HA and Fe ions inhibited photolysis by the light screening effect. The photolysis of enestroburin was very fast due to the generation of photo-isomers. Seven isomeric products of enestroburin were observed using SFC-MS/MS, and the reaction mechanism for photo-induced isomers was proposed. The reaction occurred on three double bonds, including tautomerism of enol ether and oxonium and the triplet energy transfer of the CC and CN double bond. 12 transformation products (TPs) were identified by screening suspect compounds and non-target compounds, and one product (M-381) was synthesized for confirmation and quantification. A probable transformation mechanism was suggested based on the identified TPs and DFT calculations. The main transformation reactions included hydration, hydrolysis, oxidation, reduction and decarboxylation. Finally, the toxicities of the identified TPs and parent compound to aquatic organisms were predicted using ECOSAR software, and the toxicities of enestroburin and M-381 to daphnia magna were tested in the laboratory. The toxicity classification proposed by ECOSAR is reliable to a certain extent. Enestroburin and 2 TPs (M-313 and M-327) were classified as "very toxic", which may pose a potential threat to aquatic ecosystems.
烯肟菌酯是中国自主研发的第一个甲氧基丙烯酸酯类杀菌剂，已广泛应用 15 年用于防治真菌病害。研究其光解行为对全面评估其生态风险至关重要。考察了溶液 pH 值、腐殖酸（HA）和三价铁离子对烯肟菌酯光解的影响。结果表明，在酸性溶液（pH=4）中烯肟菌酯的直接光解速率大于碱性（pH=7）或中性（pH=9）条件。腐殖酸和三价铁离子通过光屏蔽效应抑制了光解。由于光异构体的生成，烯肟菌酯的光解非常迅速。利用 SFC-MS/MS 观察到烯肟菌酯的 7 种光异构体产物，并提出了光诱导异构体的反应机制。该反应发生在三个双键上，包括烯醇醚和氧鎓的互变异构以及 CC 和 CN 双键的三重态能量转移。通过筛选疑似化合物和非靶向化合物共鉴定了 12 种转化产物（TPs），并合成了一个产物（M-381）进行确证和定量分析。基于鉴定的 TPs 和 DFT 计算提出了可能的转化机制。主要的转化反应包括水合、水解、氧化、还原和脱羧。最后，利用 ECOSAR 软件预测了鉴定的 TPs 和母体化合物对水生生物的毒性，并在实验室中测试了烯肟菌酯和 M-381 对大型蚤的毒性。ECOSAR 提出的毒性分类在一定程度上是可靠的。烯肟菌酯和 2 种 TPs（M-313 和 M-327）被归类为“极毒”，这可能对水生生态系统构成潜在威胁。
