Institute of Nuclear Agricultural Sciences, Key Laboratory of Nuclear Agricultural Sciences of Ministry of Agriculture of PRC, Zhejiang University, Hangzhou 310029, China.
Shanghai Institute of Organic Chemistry, Chinese Academy of Science, Shanghai 200032, China.
Sci Total Environ. 2014 Feb 15;472:582-9. doi: 10.1016/j.scitotenv.2013.11.068. Epub 2013 Dec 6.
Pyribambenz propyl (ZJ0273) is a polycyclic herbicide with increasing use, although studies show that it tends to be persistent in soil and pose phytotoxicity to rotational crops. This study employed an improved ring-specific (14)C labeling method to characterize its anoxic metabolism, with (14)C positioned on the benzoate, pyrimidyl or benzyl rings. Separation and identification of the metabolites were achieved by liquid chromatography (LC), ultralow-level liquid scintillation spectrometry, and LC-mass spectrometry (MS). Results show that the anoxic degradation follows first-order kinetics and the half-lives are approximately 38.7, 50.2 and 70.7d for loamy, saline and clayey soils, respectively. A total of five radioactive intermediates (M1-M5) were detected, and due to the loss of radiolabels, different radiochromatograms were obtained from different labels, i.e., radioactive M5 was only detected for pyrimidinyl-(14)C; M3 and M4 were only detected for pyrimidinyl-(14)C and benzyl-(14)C, while M1 and M2 were detected for all labels. Based on their appearance pattern and fragmentations from LC-MS, the structures of M1-M5 were identified, and they were proposed to form by reactions such as de-estering, hydrolysis, acylation, CN cleavage, and demethylation. All metabolites have been previously detected in aerobic soils except M4, which is a demethylation product from M3, and identified as 2-(4-hydroxy-6-methoxypyrimidin-2-yloxy)benzoic acid. The results show that ZJ0273 is more persistent in anoxic soils, and its degradation pathways and intermediates are different from aerobic metabolism and differ with the soil types, suggesting that soil-specific and farming practices may be important considerations in the use of this herbicide. The ring-specific labeling provides full molecular information about the referred compound and guarantees the reliability of the results, and can be used as an effective tool for metabolite profiling of polycyclic compounds.
吡唑草酰胺丙基（ZJ0273）是一种多环除草剂，使用量不断增加，尽管研究表明它在土壤中往往具有持久性，并对轮作作物具有植物毒性。本研究采用改进的环特异性（14）C 标记方法来表征其缺氧代谢，（14）C 标记在苯甲酸酯、嘧啶基或苄基环上。通过液相色谱（LC）、超低水平液体闪烁谱仪和 LC-质谱（MS）实现代谢物的分离和鉴定。结果表明，缺氧降解遵循一级动力学，半衰期分别约为壤土、盐土和粘土中的 38.7、50.2 和 70.7d。共检测到五种放射性中间产物（M1-M5），由于放射性标记物的丢失，不同标记物获得了不同的放射性色谱图，即放射性 M5 仅在嘧啶基-（14）C 中检测到；M3 和 M4 仅在嘧啶基-（14）C 和苄基-（14）C 中检测到，而 M1 和 M2 则在所有标记物中均检测到。根据 LC-MS 的出现模式和碎片，鉴定了 M1-M5 的结构，它们被认为是通过去酯化、水解、酰化、CN 裂解和脱甲基化等反应形成的。除 M4 外，所有代谢物均在前好氧土壤中检测到，M4 是 M3 的脱甲基产物，被鉴定为 2-（4-羟基-6-甲氧基嘧啶-2-基氧基）苯甲酸。结果表明，ZJ0273 在缺氧土壤中更持久，其降解途径和中间产物与好氧代谢不同，且随土壤类型而不同，这表明土壤特异性和耕作方式可能是使用该除草剂的重要考虑因素。环特异性标记提供了关于参考化合物的完整分子信息，并保证了结果的可靠性，可作为多环化合物代谢产物分析的有效工具。
