Synthesis and antibacterial activity of some metal complexes of beta-lactamic antibiotics

An overview of the results of the interaction of beta -lactamic antibiotics with some transition metal ions is given. Several complexes have been synthesized and characterized by physicochemical and spectroscopic methods. Some exhibit very promising antibacterial activity. Clavulanic acid (L-1), penicillin (L-2), ampicillin (L-3), cephalexin (L-4), cefazolin (L-5) and cephalothin (L-6) were allowed to react with metal ions in methanol under nitrogen. IR spectra of clavulanic acid, penicillin and ampicillin complexes showed strong modifications of the carbonyl group located on the lactamic ring, indicating that this oxygen participates in the coordination to the metal ions along with the carboxylate group. Thus L-1 and L-2 behave as monoanionic bidentate ligands while L-3 behaves as a monoanionic tridentate ligand. The IR spectra of cephalexin, cefazolin and cephalotin chelates show that the beta lactamic carbonyl group does not participate in coordination to the metal ions. A relationship between the structure of the complexes and their antibacterial activity can be observed. In vitro antibacterial activity of the antibiotics and the complexes were tested using the filter paper diffusion method and the chosen strains include Escherichia coli ATCC 10536, Pseudomonas aeruginosa ATCC 9027, Salmonella typhimorium ATCC 14028, Staphylococcus aureus ATCC 6538, Bacillus cereus ATCC 9634, Proteus mirabilis 35659, Proteus vulgaris ATCC 9920, Klebsiella pneumoniae ATCC 10031, Salmonella sp, Shigella sp ATCC 11126, Streptococcus viridans and Salmonella enteritidis ATCC 497.