Ordering a selected Zn(II), Cu(II), Pd(II) and Co(III) complex compounds. Their separately and combinedly antibacterial therapy and DNA-binding studies.

In this study, four Co(III)-, Cu(II)-, Zn(II)- and Pd(II)- based potent antibacterial complexes of formula K[Co(ox)]·3HO (I), [Cu(phen)Cl]Cl·6.5HO (II), [Zn(phen)]Cl (III) and [Pd(phen)](NO) (IV) (where ox is oxalato and phen is 1,10-phenanthroline) were synthesized. They were characterized by elemental analysis, molar conductivity measurements, UV-Vis, FT-IR and H-NMR techniques. These metal complexes were ordered in three combination series of I+II, I+II+III and I+II+III+IV. Antibacterial screening for each metal complex and their combinations against Gram positive and Gram negative bacteria revealed that all compounds were more potent antibacterial agents against the Gram negative than those of the Gram positive bacteria. The four metal complexes showed antibacterial activity in the order I > II > III > IV and the activity of their combinations followed the order of I+II+III+IV > I+II+III > I+II. The DNA-binding properties of complex (I) and its three combinations were studied using electronic absorption and fluorescence (ethidium bromide displacement assay) spectroscopy. The results obtained indicated that all series interact effectively with CT-DNA. The binding constant (K), the number of binding sites (n) and the Stern-Volmer constant (K) were obtained based on the results of fluorescence measurements. The calculated thermodynamic parameters supported that hydrogen bonding and van der Waals forces play a major role in the association of each series of metal complexes with CT-DNA and follow the above-binding affinity order for the series. Abbreviations ΔG° standard Gibbs free energy change ΔH° standard enthalpy change ΔS° standard entropy change AMK Amikacin CT-DNA calf thymus deoxyribonucleic acid EB ethidium bromide GEN Gentamycin IZ inhibition zone K binding constant k bimolecular quenching rate constant K Stern-Volmer constant MIC minimum inhibitory concentration n number of binding sites on DNA/HSA ox oxalato phen 1,10-phenanthroline.