Antibacterial Activity and DNA Binding Studies of Co3+, Cu2+, Zn2+ and Pd2+ Complexes: Investigating Antibacterial Combination Therapy on These Complexes

Therapy with antimicrobial combinations has been used since antimicrobials have been accessible[1], although clinical data from prospective randomized trials, fulfilling the criteria ofevidence- based medicine, are rare [2]. In this study, four Co(III)-, Cu(II)-, Zn(II)- and Pd(II)-based potent antibacterial complexes of formula K3[Co(ox)3].3H2O (I), [Cu(phen)(bpy)Cl]Cl(II), ([Zn(bpy)2(phen)]Cl2.6H2O (III) and [Pd(bpy)(phen)](NO3)2 (IV) (where ox is oxalate,phen is 1,10-phenanthroline and bpy is 2,2-bipyridine) were synthesized. They were characterizedanalytically and spectroscopically by elemental analyses, molar conductance measurements,UV–Vis, FT-IR and 1HNMR spectra. These metal complexes were ordered in threecombination series of I+II, I+II+III and I+II+III+IV. Antibacterial activity was tested foreach of these four metal complexes and their combinations against gram positive (Staphylococcusaureus and Enterococcus faecalis) and gram negative (Escherichia coli and Pseudomonasaeruginosa) bacteria. All compounds were more potent antibacterial agents against thegram negative than those of the gram positive bacteria. The four metal complexes showed antibacterialactivity in the order I  II  III  IV and the activity of their combinations followedthe order of I+II+III+IV  I+II+III  I+II.