Bhupesh S. Bhatt

Synthesis, characterization, antibacterial activity, SOD mimic and interaction with DNA of drug based copper(II) complexes.

Novel metal complexes of the second-generation quinolone antibacterial agent enrofloxacin with copper(II) and neutral bidentate ligands have been prepared and characterized with elemental analysis reflectance, IR and mass spectroscopy. Complexes have been screened for their in-vitro antibacterial activity against two Gram(+ve) Staphylococcus aureus, Bacillus subtilis, and three Gram((-ve)) Serratia marcescens, Escherichia coli and Pseudomonas aeruginosa organisms using the double dilution technique. The binding of this complex with CT-DNA has been investigated by absorption titration, salt effect and viscosity measurements. Binding constant is ranging from 1.3×10(4)-3.7×10(4). The cleavage ability of complexes has been assessed by gel electrophoresis using pUC19 DNA. The catalytic activity of the copper(II) complexes towards the superoxide anion (O2.-) dismutation was assayed by their ability to inhibit the reduction of nitroblue tetrazolium (NBT).

Square planar palladium(II) complexes of bipyridines: synthesis, characterization, and biological studies

A series of square planar mononuclear palladium(II) complexes, [Pd(L n )(OMe)2] (where L n  = 4-(4-chlorophenyl)-6-phenyl-2,2′-bipyridine, 4,6-bis(4-chlorophenyl)-2,2′-bipyridine, 4-(4-bromophenyl)-6-(4-chlorophenyl)-2,2′-bipyridine, and 6-(4-chlorophenyl)-4-p-tolyl-2,2′-bipyridine), have been synthesized and characterized. Interaction of palladium complexes with DNA has been investigated by electronic absorption spectra, viscosity measurements and DNA melting temperature techniques. The metal complex-DNA interaction produced hypochromism and bathochromism, suggesting intercalative binding. Viscosity data support the intercalation mode of binding. Palladium(II) complexes promote cleavage of plasmid pUC19 DNA from the supercoiled form to the open circular form. Antibacterial activities of the complexes have also been evaluated against five pathogenic bacteria. The antimicrobial test results reveal that all compounds have good antibacterial activity against both Gram(−ve) and Gram(+ve) bacterial species compared to the ligands and metal salt.

Nucleic acid interaction and antibacterial behaviours of a ternary palladium(II) complexes

The bidentate ligands and Pd(II) complexes have been synthesized and characterized using elemental analysis (C, H, N), (1)H NMR, (13)C NMR, electronic spectra, FT-IR and FAB mass spectroscopy. The binding of palladium complexes with calf thymus DNA (CT DNA) has been explored using absorption titration, DNA melting temperature and viscosity measurements. The cleavage reaction on pUC19 DNA has been monitored by agarose gel electrophoresis. The results suggest that complexes can bind to DNA by intercalative modes and exhibit nuclease activities in which supercoil form is converted to open circular form. The antibacterial activity of ligands and complexes has been performed against three Gram(-ve) and two Gram(+ve) microorganisms and the study indicates that all the complexes show better microbial inhibition activity than ligands and palladium salt.

Topoisomerase inhibition, nucleolytic and electrolytic contribution on DNA binding activity exerted by biological active analogue of coordination compounds.

The neutral mononuclear copper complexes with the quinolone antibacterial drug ciprofloxacin and bipyridine derivatives have been synthesized and characterized. Complexes were screened for their antibacterial activity against three Gram(−) and two Gram(+) bacteria, and study suggests inhibition of gyrase activity by metal complexes as the possible mechanism. The nucleolytic activity of adducts was carried out on double stranded pUC19 DNA using gel electrophoresis in the presence of radical scavenging agents that suggest hydrolytic cleavage mechanism for plasmid DNA.

In vitro bacteriostatic and DNA interaction studies of drug-based mixed-ligand complexes of cobalt(II)

The dinuclear cobalt(II) complexes with ciprofloxacin and bidentate ligands were synthesized and characterized using infrared spectra, electronic spectra, magnetic measurements, elemental analyses, thermal investigation, and mass spectroscopy. Here in we tried to increase an antibacterial activity of ciprofloxacin drug due to formation of mixed-ligand complexes. Synthesized compounds were found to be more potent compared to drugs, ligands, and metal salt against selective gram(+ve) and gram(−ve) organisms. Interaction of the complexes with nucleic acid (DNA) was investigated using spectroscopic technique, viscosity measurement, and gel electrophoresis and it was found that the complexes bind to DNA via intercalative mode.

Synthesis and evaluation of gold(III) complexes as efficient DNA binders and cytotoxic agents

In recent years, great interest has been focused on gold(III) complexes as cytotoxic and antitumor drugs. Recent studies demonstrated that simple bidentate or polydentate ligands containing nitrogen donor atoms may offer sufficient redox stabilization to produce viable Au(III) anticancer drug targets under physiologic conditions. So, we have synthesized square planer Au(III) complexes of type [Au(A(n))Clx]·Cly and characterized them using UV-Vis absorption, C, H, N elemental analysis, FT-IR, LC-MS, (1)H and (13)C NMR spectroscopy. These compounds manifested significant cytotoxic properties in vitro for brine shrimp lethality bioassay. The metal complexes were screened for series of DNA binding activity using UV-Vis absorption titration, hydrodynamic measurement and thermal DNA denaturation study. The nucleolytic activity was performed on plasmid pUC19 DNA. The Michaelis-Menten kinetic studies were performed to evaluate rate of enhancement in metal complexes mediated DNA cleavage over the non-catalyzed DNA cleavage.

Synthesis, characterization, antibacterial activity and DNA interaction studies of drug-based mixed ligand copper(II) complexes with terpyridines

A series of ternary copper(II) complexes have been derived using ciprofloxacin and four terpyridine derivatives. Complexes were characterized using metal estimation, IR spectroscopy, FAB-mass spectrometry and reflectance spectra. Compounds were screened for their in vitro antimicrobial activity against gram(+ve) and gram(−ve) bacterial species. Binding behaviour of the complexes towards DNA were determined using UV–Vis absorption titration, viscometric and DNA thermal denaturation experiment, where as the cleavage efficacy of the complexes towards pUC19 DNA was determined by gel electrophoresis in the presence of ethidium bromide. The catalytic activity of the copper(II) complexes towards the superoxide anion (O2•−) dismutation was assayed by their ability to inhibit the reduction of nitroblue tetrazolium.

Thermal, spectral, and thermodynamic studies for evaluation of calf thymus DNA interaction activity of some copper(II) complexes

The square-pyramidal copper(II) complexes with ciprofloxacin in the presence of bipyridine derivatives have been synthesized and characterized using elemental analysis, magnetic moment measurement, thermal analysis (TG), IR, mass and reflectance spectra. The thermal denaturation study has been used for evaluating calf thymus DNA interaction activity. Spectral and hydrodynamic measurements have been used for validating the DNA interaction study. The thermodynamic profile was established for proper understanding of DNA binding Gibbs free energy.

Spectrophotometric determination of ciprofloxacin by ion pair formation

Various aspects of application of derivative spectrophotometry to chemical analysis and investigations of equilibria and kinetics of reactions are scrutinised. In this work the viability of a spectrophotometric technique for the determination of ciprofloxacin has been deliberated. The method is based on the formation of ion-association complexes of ciprofloxacin with nickel(II) tetra thiocyanate, which are extracted into organic solvent (40% n-butanol in methylene chloride) having absorption maxima at 623 nm. The precision and accuracy of the method was checked by UV reference methods. The validation study indicated the parameters, which are in good agreement with the data obtained from standard methods. The proposed method was fruitfully applied to determine ciprofloxacin in their tablet formulations.

Study of SOD Mimic and Nucleic Acid Interaction Activity Exerted by Enrofloxacin‐Based Copper(II) Complexes

Five new copper(II) complexes of type [Cu(erx)(L)Cl] (erx, enrofloxacin; thiophene‐2‐carbaldehyde (L1); pyridine‐2‐carbaldehyde (L2); 2,2′‐dipyridylamine (L3); 4,5‐diazafluoren‐9‐one (L4); bis(3,5‐dimethyl‐1‐pyrazolyl)methane (L5)) have been synthesized and characterized by elemental analysis, reflectance, IR, and FAB‐MS. Complexes have been investigated for their interaction with calf thymus (CT) DNA utilizing the absorption‐titration method, viscometric and DNA thermal denaturation studies. The cleavage reaction on pUC19 DNA has been monitored by agarose gel electrophoresis. The results indicated that the CuII complexes can more effectively promote the cleavage of plasmid DNA at physiological pH and superoxide dismutase. The (SOD) activity of the complexes has been evaluated by the nitroblue tetrazolium assay, and the complexes catalyzed the dismutation of superoxide at pH 7.8 with IC50 values of 0.35–1.25 μM. The complexes have also been screened for their antibacterial activity against five pathogenic bacteria.