School of Environmental Science and Engineering, Suzhou University of Science and Technology , Suzhou 215009, P. R. China.
School of Civil and Environmental Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
Environ Sci Technol. 2018 Feb 6;52(3):1461-1470. doi: 10.1021/acs.est.7b05543. Epub 2018 Jan 18.
While the β-lactam antibiotics are known to be susceptible to oxidative degradation by sulfate radical (SO), here we report that peroxymonosulfate (PMS) exhibits specific high reactivity toward β-lactam antibiotics without SO generation for the first time. Apparent second-order reaction constants (k) were determined for the reaction of PMS with three penicillins, five cephalosporins, two carbapenems, and several structurally related chemicals. The pH-dependency of k 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 of a phenylglycine side chain significantly enhanced cephalosporins' reactivity toward PMS. Product analysis indicated oxidation of β-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., SO). Thus, the PMS-induced oxidation of β-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 β-lactam antibiotic contamination, because PMS exhibits specific high reactivity and suffers less interference from the water matrix than the radical process.
虽然众所周知β-内酰胺抗生素容易被硫酸根自由基（SO）氧化降解，但我们首次报道过过一硫酸盐（PMS）在没有生成 SO 的情况下，对β-内酰胺抗生素表现出特定的高反应性。确定了 PMS 与三种青霉素、五种头孢菌素、两种碳青霉烯类抗生素以及几种结构相关的化学物质的反应的表观二级反应常数（k）。k 的 pH 值依赖性可以根据特定物种的反应很好地建模。基于反应动力学、化学计量和结构活性评估，六元或五元环上的硫醚硫（青霉素和头孢菌素）和侧链（碳青霉烯类）是 PMS 氧化的主要反应部位。头孢菌素比青霉素和碳青霉烯类抗生素对 PMS 的反应性更高，而苯甘氨酸侧链的存在显著提高了头孢菌素对 PMS 的反应性。产物分析表明β-内酰胺抗生素被氧化为两种立体异构的亚砜。自由基清除研究和电子顺磁共振（EPR）技术证实了没有自由基物种（例如 SO）的参与。因此，提出了 PMS 诱导的β-内酰胺抗生素氧化通过涉及沿 PMS 过氧键的直接两电子转移以及异裂裂解的非自由基机制进行。这项研究的新发现对于消除β-内酰胺抗生素的污染很重要，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小。
