A.C. polarographic study of the interaction between thiol compounds and cephradoxil

The interaction of glutathione and cysteine with the Cephalosporin Cephradoxil was investigated by a.c. polarography. From measurements of the peak potential at different antibiotic concentrations, the following interaction constants at physiological conditions were calculated : GSH-Cephradoxil = 5.71 x 104 M-1; Cys-Cephradoxil = 1.92 x 103 M-1. The interaction processes were spontaneous for both thiol compounds with an important entropic contribution to the free energy. Linear correlations for the in vivo first order elimination constants and the in vitro affinity constant of three cephalosporins are also reported