Substructure Reactivity Affecting the Manganese Dioxide Oxidation of Cephalosporins

Abstract

Cefotaxime (CTX), cephalexin (CFX), cephradine (CFD), cephapirin (CFP), and cefazolin (CFZ) were selected as target cephalosporin antibiotics to study their oxidative transformation by δ-MnO. Although they all have the same core structure (7-aminodesacetoxycephalosporanic acid), very different MnO oxidation rates were observed at pH 4 (the initial reaction rate constant k ranged from 0.014 to 2.6 h). An extensive investigation of the substructure compounds and byproduct analysis revealed that the oxidation mainly occurred at the following two sites on the core structure: (1) the sulfur atom in the cephem ring and (2) the carbon-carbon double bond (C═C) and its proximal carboxylic acid group. In the case of (2), when there is an acetyloxymethyl group at the C-3 position of the core structure, the formation of the keto-sulfone byproducts was inhibited. The overall results indicated that a substituent at the C-3 position could stabilize the core structure, which would result in a decrease in the oxidation rate; however, a substituent at the amine position of the core structure might affect the overall degradation rate of the cephalosporin, depending on its reactivity with MnO. Thus, the apparent reaction rates varied widely in the trend of CTX > CFP > CFD > core structure ≈ CFX > CFZ. The mechanistic elucidation can also help explain the degradation rates of cephalosporin antibiotics in other oxidation processes.

Rapid Hydrolysis of Penicillin Antibiotics Mediated by Adsorbed Zinc on Goethite Surfaces

“…The degradation of penicillin antibiotics via hydrolysis and oxidation reactions mediated by transition metals or minerals has been widely reported. ,,, To obtain insights into the mechanism of penicillin degradation in the Zn/goethite system, we conducted anoxic and radical quenching experiments with two typical penicillins (PG and AMX) and identified the reaction products arising from their degradation. As shown in Figure S10, neither oxygen nor isopropanol had a significant effect on the degradation, indicating that penicillin degradation did not involve oxygen or hydroxyl radicals.…”

“…Nonetheless, the intense veterinary usage of penicillins in livestock and the subsequent application of antibiotic-containing animal manure on agricultural fields as fertilizers have led to the release of considerable amounts of antibiotics into the soil. , According to the previous literatures, microbial-involved hydrolysis reaction in soil environment is deemed as the main degradation pathway for penicillins. − A recent study found that amoxicillin could still be quickly degraded in sterilized soil, suggesting that abiotic degradation of penicillins might also play an essential role in soil environment. Furthermore, the different physicochemical characteristics of penicillins, such as their solubility, speciation, and octanol–water partitioning coefficient ( K OW ), as well as the properties of the soil, including the pH, water content, and microbial activity, could also affect degradation. , The low K OW values of penicillins (0.87–1.83) would hinder their association with the organic components of soil, whereas soil minerals, for example, iron oxides, clays, and manganese oxides, may provide matrices to form surface complexes with penicillin functional groups. , …”

“…7,13 The low K OW values of penicillins (0.87− 1.83) 1 would hinder their association with the organic components of soil, whereas soil minerals, for example, iron oxides, clays, and manganese oxides, may provide matrices to form surface complexes with penicillin functional groups. 19,20 Goethite is a common mineral, which is ubiquitously distributed in soils and sediments. 21 Because of its unique surface structure, goethite is able to strongly adsorb several antibiotics in soil and subsequently catalyze their transformation.…”

Degradation of methylene blue by natural manganese oxides: kinetics and transformation products

“…It has been reported that manganese dioxide possesses high oxidation–reduction potential (1.29 V, 25°C) and that synthetic MnO 2 has been applied to degrade phenol and aromatic amines [26,27]. Studies have also found that it performs well in treating bisphenol A, bisphenol AF, bisphenol S and cephalosporins [28,29]. In addition, Fei et al [30] found that synthesized MnO 2 has a high removal efficiency for Congo red.…”

Comparative study of two cephalosporin antibiotics binding to calf thymus DNA by multispectroscopy, electrochemistry, and molecular docking

“…The second most commonly used antibiotic class is cephalosporin, and examples of this type of antibiotic include cefaclor and cefixime, which are the two cephalosporin classes of β‐lactam antibiotics that can act as penicillins to effectively interfere with survival of Gram‐positive and Gram‐negative microorganisms . Their inhibitory mechanism involves binding to and inactivating enzymes needed for synthesis of the bacterial cell wall . Within the research and development of cephalosporins, second‐generation cephalosporin exhibits different bioactivity from the other three generations.…”