Synthesis and antibacterial activity of cephradine metal complexes : part II complexes with cobalt, copper, zinc and cadmium.

Cephradine, the first generation cephalosporin, is active against a wide range of Gram-positive and Gram-negative bacteria including penicillinase-producing Staphylococci. Since the presence of complexing ligand may affect the bioavailability of a metal in the blood or tissues, therefore, in order to study the probable interaction of cephradine with essential and trace elements present in human body, cephradine has been reacted with cobalt, copper, zinc and cadmium metal halides in L:M ratio of 2:1 in methanol and the products recrystallized from suitable solvents to pure crystals of consistent melting points. Infrared and ultraviolet studies of these complexes were carried out and compared with ligand. Magnetic susceptibility studies of these complexes were also carried out showing their paramagnetic behavior. From the infra red studies and elemental analysis of the complexes, it has been shown that the drug molecule serves as a bidentate ligand coordinating through both its carboxylate at C-3 and beta-lactam nitrogen and the metal having a square planar or octahedral geometry. To evaluate the changes in microbiological activity of cephradine after complexation, antibacterial studies were carried out by observing the changes in MIC (minimum inhibitory concentration) of the complexes and compared with the parent drug by measuring the zone of inhibition of complexes and compared with the parent cephalosporin against both Gram-positive and Gram-negative organisms. For MIC observation, serial dilution method was employed and zone series were determined by disk diffusion method. Our investigations reveal that formation of complexes results in decrease in antibacterial activity of cephradine and MIC values are increased.