Studies on interaction between quinolone derivatives (Antibiotics) and transition metals

Abstract

The redox behavior of few first row transition metal ions, Cr(III), Mn(II), Ni(II), Cu(II) and Zn(II) in presence and absence of the ligand ciprofloxacin were studied in the aqueous medium using Cyclic Voltammetry. Chronoamperomety and chronocoulometry were also performed to know some other electrochemical aspects. It was found that the redox systems involved in Cu(II), Mn(II) as well as Cu(II)-Ciprofloxacin and Mn(II)-Ciprofloxacin interactions in solutions are quasi-reversible. But the Zn(II) and Cr(III) systems are near to reversible and the Zn(II)-Ciprofloxacin and Cr(II)-Ciprofloxacin interactions are quasi-reversible and irreversible respectively. The findings from the Chronoamperometric study in solution is that after interaction the spike height is decreased, indicating towards a decrease in the rate of electrolysis. And from the Chronocoulometric study, it is observed that the charge at τ are decreased in all the cases. Both of these facts combinedly indicate occurance of interaction between the metal and ligand. The observations from the plots Q vs t1/2 and -Qr vs θ gives conclusion that adsorption of reactant or products occur on the electrode after compound formation. The solid product obtained from the interaction between metal ions and Ciprofloxacin were characterized by different physoci chemical methods. Cr(III), Mn(II) and Ni(II) form compounds with Ciprofloxacin in a ratio of 1:2 and on the other hand Cu(II) and Zn(II) form 1:1 compounds. All the compounds are stable in air and light. The compounds are insoluble in non-polar solvents but soluble in polar solvents. Almost all of the compounds have higher melting points which implies that the compounds have ionic character to some extent. The compounds were further characterized by IR spectra, electronic absorption spectra as well as NIR spectra. The observations of the spectral analysis do not show any significant changes with that of the ligand. Therefore it may be said that the products obtained after interaction are adduct type of compounds. DSC study signifies their endothermic and exothermic natures. The redox properties of the products obtained were studied at Glassy Carbon working electrode. But in case of Cr(III) compound Platinum working electrode was used. The findings from the cyclic voltammetric study of all metal-Ciprofloxacin compounds implies that the electrochemical process involved are quasi-reversible. It was also found that almost all the systems are diffusion controlled as well as adsorptive controlled. The concentration effects of all the compounds show a gradual increase of peak current with the increase in concentrations giving indication towards diffusion controlled situations. The findings from the Chronoamperometric study is that after compound formation the spike height is decreased, indicating towards a decrease in the rate of electrolysis. And from the Chronocoulometric study, it is observed that the charge at τ are decreased in all the cases. Both of these facts combinedly indicate that new compound formation occurs after interaction. And the observations from the plots Q vs t1/2 and -Qr vs θ gives conclusion that adsorption of reactant or products occur on the electrode also after compound formation. The concentration effect on Chronoamperometric as well as chronocoulometric study of of all the Metal-Ciprofloxacin compounds show a linear relationship of concentration and spike height. The findings from the antibacterial activity of the Metal-Ciprofloxacin compounds show that Mn(II)-Ciprofloxacin and Ni(II)-Ciprofloxacin compound are more active against Salmonella sp. compared to Ciprofloxacin. Similar is the case for E.coli. Mn(II)-Ciprofloxacin compound is more active than Ciprofloxacin in case of Bacillus sp. and S. aureus. As a result, it may be concluded that compared to Ciprofloxacin, Mn(II)-Ciprofloxacin compound shows the best activity against bacteria among the five Metal-Ciprofloxacin compounds used in the present study.