Theoretical insight into the degradation reaction of cefradine in aqueous medium: Mechanism, kinetics, and ecotoxicity

Abstract

The extensive use of antibiotics has raised growing environmental concerns about their potential threat to aquatic ecosystems. Cefradine (CFD) is one of the first-generation beta-lactam cephalosporin antibiotics. In this study, the mechanism and kinetics of the OH radical degradation reaction of cefradine and its protonated form were investigated. Quantum chemical modeling of all reaction paths was performed with Density Functional Theory (DFT) at the B3LYP/6-31g(d,p)//6-311+g(d,p) level. The main reaction path with the highest calculated branching ratio among the reaction paths was the OH addition path to the carbonyl group of beta-lactam. The temperature effect for the reactions was also calculated. The calculated second-order rate constant, 4.82x109 M- 1s- 1, is consistent with the literature data. The possible subsequent mechanism and the potential for direct photolysis of the reaction intermediates were also investigated. Furthermore, the toxicities of the CFD and reaction products were calculated and some of the reaction products are developmental toxicants.