%0 Journal Article
%T Mixed-Ligand Nickel(II) Complexes Containing Sulfathiazole and Cephalosporin Antibiotics: Synthesis, Characterization, and Antibacterial Activity
%A J. R. Anacona
%A Maried Lopez
%J International Journal of Inorganic Chemistry
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/106187
%X Nickel(II) reacts with cephalosporins plus sulfathiazole (Hstz) to form the following mixed-ligand complexes of general formulae [Ni(L)(stz) ( , ; , ; L = monoanion of cefazolin , cephalothin , cefotaxime , ceftriaxone ) and [Ni( )(stz)]Cl (cefepime ), which were characterized by physicochemical and spectroscopic methods. Their spectra indicated that cephalosporins are acting as multidentate chelating agents, via the lactam carbonyl and carboxylate and N-azomoieties. The complexes are insoluble in water and common organic solvents but soluble in DMSO, where the [Ni( )(stz)]Cl complex is 1£¿:£¿1 electrolyte. They probably have polymeric structures. They have been screened for antibacterial activity, and the results are compared with the activity of commercial cephalosporins. 1. Introduction Cephalosporins are classed as ¦Â-lactam antibiotics, and they are widely used in clinical therapy for the treatment of severe infections, because of their antibacterial activity [1, 2]. Most common among several mechanisms by which bacteria develop resistance to ¦Â-lactam antibiotics is by elaboration of the enzyme ¦Â-lactamase, which hydrolyzes the ¦Â-lactam ring. A second mechanism is through alteration of penicillin-binding proteins (PBPs), which are found as both membrane-bound and cytoplasmic enzymes that catalyze cross-linking reactions in bacterial cell wall synthesis [3, 4]. PBPs are targets of ¦Â-lactam antibiotics, which interfere with cell wall synthesis by binding covalently to the catalytic site. Most bacterial species produce several PBPs, differing in molecular weight, affinity for binding ¦Â-lactam antibiotics, and enzymatic function (e.g., transpeptidase, carboxypeptidase, or endopeptidase). The PBPs are usually broadly classified into high-molecular-weight and low-molecular-weight categories [3, 4]. Prior to the availability and application of antibiotics for the control of diseases, sulfonamides were employed as effective chemotherapeutic agents for the prevention and cure of bacterial infections in humans [5, 6]. Certain microbes require p-aminobenzoic acid (PABA) in order to synthesize dihydrofolic acid, which is required to produce purines and ultimately nucleic acids. Sulfonamides, chemical analogs of PABA, are competitive inhibitors of dihydropteroate synthetase. The complex formation between metal ions and sulfa drugs has also been extensively studied with a view to establish the relationship and importance of metal-drug interactions [7¨C10]. The interaction of antibiotics with main and transition metal ions has attracted our attention and compelled us
%U http://www.hindawi.com/journals/ijic/2012/106187/