The widely used β-lactam antibiotics are susceptible to oxidative and/or hydrolytic degradation promoted by some metal ions (e.g., Cu(II)). Ferric (Fe(III)) and manganese ions (Mn(II)) are among the most common metal ions, but their role in the environmental transformation of β-lactam antibiotics are still unknown. New research results indicate that Fe(III) and Mn(II) can promote degradation of β-lactam antibiotics under environmental aquatic conditions, and their role is hydrolysis catalyst. Fe(III) (or Mn(II))-promoted degradation of ampicillin followed first-order kinetics, and the degradation rate constants linearly increased with increasing metal ion concentration. Fe(III)-induced degradation of ampicillin was most favorable at neutral pH; while Mn(II)-promoted degradation was only observed at neutral and slight alkaline pHs, but not at acidic pH. Among the various β-lactam antibiotics, metal ion-promoted degradation of penicillins was faster than that of cephalosporins. Product analysis indicated that only isomers of hydrolysis products were observed without detection of oxidation products. The metal ion-promoted degradation likely occurred via complexation of β-lactam antibiotics with carboxyl group and tertiary nitrogen, and then enhancing the hydrolytic cleavage of β-lactam ring. This study elucidates the role of Fe(III) and Mn(II) in the environmental transformation of β-lactam antibiotics which has not been recognized before. The new findings indicate iron or manganese species are among the factors affecting the environmental fate of β-lactam antibiotics.<br/>

Transformation of β-lactam antibiotics induced by Fe(III) and Mn(II) ions: The overlooked hydrolysis

254th National Meeting (2017)

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