Selective Transformation of β-Lactam Antibiotics by Peroxymonosulfate: Reaction Kinetics and Nonradical Mechanism
Selective Transformation of β-Lactam Antibiotics by Peroxymonosulfate: Reaction Kinetics and Nonradical Mechanism
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DOI：
10.1021/acs.est.7b05543
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发表时间：
2018-02-06
影响因子：
11.4
通讯作者：
Huang, Ching-Hua
中科院分区：
文献类型：
--
作者：
Chen, Jiabin;Fang, Cong;Huang, Ching-Hua
虽然已知β-内酰胺抗生素对硫酸根（SO 4中心点-）的氧化降解敏感，但在此我们首次报告过一硫酸盐（PMS）对β-内酰胺抗生素表现出特异性高反应性，而不会产生SO 4中心点-。表观二级反应常数（k（2，app））测定PMS与三种青霉素，五种头孢菌素，两种碳青霉烯类，和几种结构相关的化学品的反应。基于物种特异性反应，可以很好地模拟k（2，app）的pH依赖性。基于反应动力学、化学计量学和结构活性评估，六元或五元环（青霉素和头孢菌素）和侧链（碳青霉烯）上的硫醚硫是PMS氧化的主要反应位点。头孢菌素对PMS的反应性高于青霉素类和碳青霉烯类，苯甘氨酸侧链的存在显著增强了头孢菌素对PMS的反应性。产物分析表明β-内酰胺抗生素氧化为两种立体异构亚砜。自由基清除研究和电子顺磁共振（EPR）技术证实了缺乏自由基物质的参与（例如，SO 4中心点-）。因此，PMS诱导的β-内酰胺类抗生素的氧化被认为是通过非自由基机制进行的，该机制涉及直接的双电子转移沿着PMS过氧键的异裂。这项研究的新发现对于消除β-内酰胺抗生素污染非常重要，因为PMS表现出特定的高反应性，并且比自由基过程受到水基质的干扰更少。
While the beta-lactam antibiotics are known to be susceptible to oxidative degradation by sulfate radical (SO4 center dot-), here we report that peroxymonosulfate (PMS) exhibits specific high reactivity toward beta-lactam antibiotics without SO4 center dot- generation for the first time. Apparent second-order reaction constants (k(2,app)) were determined for the reaction of PMS with three penicillins, five cephalosporins, two carbapenems, and several structurally related chemicals. The pH-dependency of k(2,app) could be well modeled based on species-specific reactions. On the basis of reaction kinetics, stoichiometry, and structure-activity assessment, the thioether sulfur, on the six- or five-membered rings (penicillins and cephalosporins) and the side chain (carbapenems), was the main reaction site for PMS oxidation. Cephalosporins were more reactive toward PMS than penicillins and carbapenems, and the presence phenylglycine side chain significantly enhanced cephalosporins' reactivity toward PMS. Product analysis indicated oxidation of beta-lactam antibiotics to two stereoisomeric sulfoxides. A radical scavenging study and electron paramagnetic resonance (EPR) technique confirmed lack of involvement of radical species (e.g., SO4 center dot-). Thus, the PMS-induced oxidation of beta-lactam antibiotics was proposed to proceed through a nonradical mechanism involving direct two-electron transfer along with the heterolytic cleavage of the PMS peroxide bond. The new findings of this study are important for elimination of beta-lactam antibiotic contamination, because PMS exhibits specific high reactivity and suffers less interference from the water matrix than the radical process.