Multiple Roles of Cu(II) in Catalyzing Hydrolysis and Oxidation of β-Lactam Antibiotics

Abstract

The widely used β-lactam antibiotics such as penicillins and cephalosporins are known to be susceptible to Cu-catalyzed hydrolysis at their four-membered β-lactam ring. However, this study elucidates that Cu can in fact play multiple roles in promoting the hydrolysis and/or oxidation of β-lactam antibiotics under environmental aquatic conditions (pH 5.0-9.0 and 22 °C), depending on β-lactams' structural characteristics and solution pH. Most significantly, the β-lactam antibiotics that contain a phenylglycine primary amine group on the side chain can undergo direct oxidation by Cu via this functional group. On the other hand, the β-lactam ring of penicillins is susceptible to Cu-catalyzed hydrolysis, followed by oxidation of the hydrolysis product by Cu. In contrast, the β-lactam ring of cephalosporins is susceptible to Cu-catalyzed hydrolysis only. Solution pH influences the Cu-promoted transformation by affecting the β-lactam and Cu complexation through protonation/deprotonation of critical organic functional groups. When Cu acts as an oxidant to promote the transformation of β-lactam antibiotics to yield Cu, the overall role of Cu appears catalytic if the reaction occurs under ambient atmospheric condition, due to quick oxidation of Cu by oxygen to regenerate Cu. Compared to earlier literature that largely assumed only the hydrolytic catalyst role of Cu in promoting degradation of β-lactam antibiotics, the oxidative roles of Cu identified by this study mark important contributions to a more accurate mechanistic understanding.

N-doped graphene aerogels as efficient heterogeneous catalytic activators for peroxymonosulfate to remove 2-sec-butyl-4,6-dinitrphenol (DNBP) in aqueous solution

“…The catalytic degradation efficiencies of DNBP in the presence of PMS were obviously enhanced from 63.62% to 86.85% within 180 min as the concentration of PMS increased from 3 to 6 mmol l −1 . The higher PMS concentration is propitious to generating more active SO 4 •− radicals which could contribute to higher degradation rate of DNBP. Nevertheless, a further increase in PMS concentration had no obvious influence on DNBP degradation efficiency, which could be due to the fact that the generated SO 4 •− radicals could be selfconsumed and captured by excess PMS [48].…”

“…The dramatical development of industrialization and rapid depletion of resource lead to environmental detrimental aspects to the eco-environment and human beings [1,2]. The widespread and potential risky refractory pollutants, especially water pollution, have triggered worldwide concern for environmentalists and researchers [3,4]. A variety of physical, chemical and biological the-state-of-the-art technologies have been leveraged to address the issues [5], among which adsorption and catalytic oxidation treatment of organic pollutants have intensively investigated and proven to be efficient on wastewater treatment [6,7].…”

“…On the other hand, advanced oxidation processes (AOPs) have aroused wide concern because of their ability to thoroughly decompose refractory organic pollutants into harmless substances without secondary pollution, mild reaction conditions and high efficiency. AOPs mainly depend on highly reactive radicals with high redox potentials such as hydroxyl radicals ( • OH) and sulfate radicals (SO 4 •− ) to oxide organic pollutants. Compared with hydroxyl radicals, sulfate radicals generated from peroxydisulfate (PDS) or peroxymonosulfate (PMS) activation have a higher redox potential (2.5∼3.1 V), broader pH applicability, and longer survival time [8][9][10].…”

Detection of the iron complexes with hydrolysis products of cephalexin and cefradine upon high‐performance liquid chromatography/electrospray ionization mass spectrometry analysis

“…There are a number of enzymes (β‐lactamases) which effectively deactivate the antibiotics . Hydrolysis of the β‐lactam ring may be also promoted by metal cations . Because of the importance of the process of hydrolysis of the β‐lactam ring this process has been also theoretically studied in detail …”

“…In general, there is no ESI‐MS data reported concerning the products of hydrolysis of cephalosporins (to the best of our knowledge). Only in a paper by Chen et al was it mentioned that the product of cephalexin hydrolysis was identified by LC/MS . A number of cephalosporins have been subjected to hydrolysis and the products have been analyzed by ESI‐MS .…”