Mononuclear dioxomolybdenum(VI) complexes with the quinolones enrofloxacin and sparfloxacin: Synthesis, structure, antibacterial activity and interaction with DNA

Spectroscopic Analyses and Antimicrobial Activity of Novel Ciprofloxacin and 7-Hydroxy-4-methylcoumarin, the Plant-Based Natural Benzopyrone Derivative

Coumarin is highly distributed in nature, notably in higher plants. The biological features of coumarin include antibacterial, anticancer and antioxidant effects. It is well known that metal ions present in complexes accelerate the drug action and the efficacy of organic therapeutic agents. The main aim of the current study is the synthesis of different complexes of the interaction between ciprofloxacin hydrochloride (CIP) and coumarin derivative 7-hydroxy-4-methylcoumarin (HMC) with Zr(IV). The chelates of CIP with Zr(IV) were prepared and characterized by elemental analysis, melting point, conductance measurements, spectroscopic techniques involving IR, UV-Vis, ¹H NMR, and thermal behavior (TG-DTG) in the presence of HMC, dimethylformamide (DMF), pyridine (Py), and triethylamine (Et₃N). Results of molar conductivity tests showed that the new synthesized complexes are electrolytes with a 1:1 or 1:2 electrolyte ratio, with the chloride ions functioning as counter ions. According to IR spectra, CIP acts as a neutral bidentate ligand with Zr(IV) through one carboxylato oxygen and the carbonyl group, HMC as a monodentate through the carbonyl group, and DMF through the oxygen atom of the carbonyl group and the N atom of Py and Et₃N. The thermal behavior of the complexes was carefully investigated using TG and DTG techniques. TG findings signal that water molecules are found as hydrated and coordinated. The thermal decomposition mechanisms proposed for CIP, HMC, and Zr(IV) complexes are discussed and the activation energies (E_a), Gibbs free energies (∆G*), entropies (∆S*), and enthalpies (∆H*) of thermal decomposition reactions have been calculated using Coats–Redfern (CR) and Horowitz–Metzeger (HM) methods. The studied complexes were tested against some human pathogens and phytopathogens, including three Gram-positive bacteria (Bacillus subtilis, B. cereus, Brevibacterium otitidis) and three Gram-negative bacteria (Escherichiacoli, Pseudomonas aeruginosa and Klebsiella pneumoniae), and compared to the free CIP and HMC parent compounds.

Ceftriaxone-based Schiff base transition metal(II) complexes. Synthesis, characterization, bacterial toxicity, and DFT calculations. Enhanced antibacterial activity of a novel Zn(II) complex against S. aureus and E. coli

From the reaction of ceftriaxone 1 antibiotic with 2,6-diaminopyridine 2 a ceftriaxone-based Schiff base (H₂L,3) was obtained and its transition metal complexes were synthesized. Spectroscopic and physicochemical techniques, namely, UV-visible, FT-IR, ¹H NMR, EPR, mass spectrometry, molar conductance, magnetic susceptibility and density functional theory (DFT) calculations, together with elemental and thermal analyses, were used to find out the binding mode and composition of these complexes. The ceftriaxone-based Schiff base 3 behaves as a monoanionic tridentate N,N,O ligand. Spectral and magnetic data suggest an octahedral geometry for all complexes and the general formulae [M(HL)(OAc)(H₂O)₂] (M(II) = Mn²⁺4, Co²⁺5, Ni²⁺6, Cu²⁺7, Zn²⁺8), are proposed for them. All compounds were screened for antibacterial activity using both the agar disc diffusion method and the minimal inhibitory concentration (MIC). It was found that complex 8 exhibited the most promising bactericidal activity against S. aureus (MIC = 0.0048 μmol/ml) and E. coli (MIC = 0.0024 μmol/ml). It is more active than the free ligand 1 (MIC = 0.0560 μmol/ml for S. aureus and 0.0140 μmol/ml for E. coli). These MIC results were compared with those obtained using similar zinc(II) Schiff base complexes, and with the values obtained using ceftriaxone conjugated with silver and gold nanoparticles (NPs), using earlier published data. Synthesized metal complexes exhibited LC₅₀ values >1000 ppm indicating their nontoxicity against brine shrimp nauplii (Artemia Salina).

A new calcium(II) complex of marbofloxacin showing much lower acute toxicity with retained antibacterial activity

Marbofloxacin (MB) is a newly developed veterinary drug with broad-spectrum antibacterial activity. In this study, a new calcium(II)-based complex of marbofloxacin, MB-Ca, was synthesized and structurally characterized by IR, ESI-MS, UV-Vis and single crystal X-ray diffraction analysis. The characterization of this complex in solution state indicated that the coordinated MB-Ca was partly retained, along with the monomeric and dimeric forms of MB. It also showed satisfactory water solubility (1.89 mg/mL), comparing with MB (2.82 mg/mL) at 35 °C. The in vitro antibacterial activity of MB-Ca was also screened towards a series of typical pathogenic bacteria, and determined by the methods of turbidimetry and disc diffusion. The results indicated it showed comparable antibacterial activity to MB. However, it exhibited higher inhibitive ability in vitro on DNA gyrase than MB alone. Furthermore, MB-Ca showed significantly lower acute toxicity (LD₅₀, 3186 mg/kg) than MB (LD₅₀, 1294 mg/kg) in mice, based on the in vivo acute toxicity test. The histopathological examination on the major organs of the mice by the oral administration of MB-Ca did not show obvious organic lesions, which is similar to those treated by MB. The research results suggest that MB-Ca could be further developed into a new promising metal-based veterinary drug and a better substitute of MB, showing unabated antibacterial activity along with lower toxicity.

Relationship between copper(ii) complexes with FomA adhesin fragments ofF. nucleatumand colorectal cancer. Coordination pattern and ability to promote ROS production

The copper(ii) binding of the fragments of FomA was studied. Complexes stimulate the CT26 cell line to produce ROS which lead to oxidative stress.

Copper(i) complexes with phosphine derived from sparfloxacin. Part I - structures, spectroscopic properties and cytotoxicity

In this paper we present new copper(i) iodide or copper(i) thiocyanate complexes with hydroxymethyldiphenylphosphine (PPh2(CH2OH)) or phosphine derivatives of sparfloxacin, a 3(rd) generation fluoroquinolone antibiotic agent (PPh2(CH2-Sf)) and 2,9-dimethyl-1,10-phenanthroline (dmp) or 2,2'-biquinoline (bq) auxiliary ligands. The synthesised complexes were fully characterised by NMR and UV-Vis spectroscopy as well as by mass spectrometry. Selected structures were additionally analysed using X-ray and DFT methods. All complexes proved to be stable in solution in the presence of water and atmospheric oxygen for several days. The cytotoxic activity of the complexes was tested against two cancer cell lines (CT26 - mouse colon carcinoma and A549 - human lung adenocarcinoma). Applying two different incubation times, the studies enabled a preliminary estimation of the dependence of the selectivity and the mechanism of action on the type of diimine and phosphine ligands. The results obtained showed that complexes with PPh2(CH2-Sf) are significantly more active than those with PPh2(CH2OH). On the other hand, the relative impact of diimine on cytotoxicity is less pronounced. However, the dmp complexes are characterised by strong inhibitory properties, while the bq ones are rather not. This confirms the interesting and promising biological properties of the investigated group of copper(i) complexes, which undoubtedly are worthy of further biological studies.

Metal complex of the first-generation quinolone antimicrobial drug nalidixic acid: structure and its biological evaluation

A novel binuclear squire planar complex of nalidixic acid with Ag(I) metal ion with the formula [Ag(Nal)2] has been synthesized. The synthesized metal complex was characterized using CHN analysis, Fourier-transformed infra-red (FT-IR), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), ultra violet-visible (Uv-vis) and single-crystal X-ray diffraction (XRD). The newly synthesized complex shows more advanced antifungal activity compared to the parent quinolone against four fungi, namely Pythium aphanidermatum, Sclerotinia rolfsii, Rhizoctonia solani and Rhizoctonia bataticola.

Metal complexes of quinolone antibiotics and their applications: an update

Quinolones are synthetic broad-spectrum antibiotics with good oral absorption and excellent bioavailability. Due to the chemical functions found on their nucleus (a carboxylic acid function at the 3-position, and in most cases a basic piperazinyl ring (or another N-heterocycle) at the 7-position, and a carbonyl oxygen atom at the 4-position) quinolones bind metal ions forming complexes in which they can act as bidentate, as unidentate and as bridging ligand, respectively. In the polymeric complexes in solid state, multiple modes of coordination are simultaneously possible. In strongly acidic conditions, quinolone molecules possessing a basic side nucleus are protonated and appear as cations in the ionic complexes. Interaction with metal ions has some important consequences for the solubility, pharmacokinetics and bioavailability of quinolones, and is also involved in the mechanism of action of these bactericidal agents. Many metal complexes with equal or enhanced antimicrobial activity compared to the parent quinolones were obtained. New strategies in the design of metal complexes of quinolones have led to compounds with anticancer activity. Analytical applications of complexation with metal ions were oriented toward two main directions: determination of quinolones based on complexation with metal ions or, reversely, determination of metal ions based on complexation with quinolones.

Sparfloxacin‐Metal Complexes as Urease Inhibitors: Their Synthesis, Characterization, Antimicrobial, and Antienzymatic Evaluation

Four new metal complexes (S12–S15) of SPFX (third‐generation quinolones) via heavy metals have been synthesized in good yield and characterized by physicochemical and spectroscopic methods including TLC, IR, NMR, and elemental analyses. Sparfloxacinato ligand binds with metals through pyridone and oxygen atom of carboxylic group. The biological actives of complexes have been tested against four Gram‐positive and seven Gram‐negative bacteria and six different fungi. Statistical analysis of antimicrobial data was done by one‐way ANOVA, Dunnett’s test; it was observed that S13, S14, and S15 were found to be most active complexes. Antifungal data confirm that all four synthesized complexes are most active and show significant activity against F. solani with respect to parent drug and none of complexes show activity against A. parasiticus, A. effuris, and S. cervicis. To study inhibitory effects of newly formed complexes, enzyme inhibition studies have been conducted against urease, α‐chymotrypsin, and carbonic anhydrase. Enzymatic activity results of these complexes indicated them to be good inhibitors of urease enzyme while all complexes show mild activities against carbonic anhydrase enzyme. Further research may prove the promising role of these synthesized complexes as urease inhibitors.

Spectroscopic, structure and antimicrobial activity of new Y(III) and Zr(IV) ciprofloxacin

The preparation and characterization of the new solid complexes [Y(CIP)2(H2O)2]Cl(3)·10H2O and [ZrO(CIP)2Cl]Cl·15H2O formed in the reaction of ciprofloxacin (CIP) with YCl3 and ZrOCl(2)·8H2O in ethanol and methanol, respectively, at room temperature were reported. The isolated complexes have been characterized with elemental analysis, IR spectroscopy, conductance measurements, UV-vis and 1H NMR spectroscopic methods and thermal analyses. The results support the formation of the complexes and indicate that ciprofloxacin reacts as a bidentate ligand bound to the metal ion through the pyridone oxygen and one carboxylato oxygen. The activation energies, E*; entropies, ΔS*; enthalpies, ΔH*; Gibbs free energies, ΔG*, of the thermal decomposition reactions have been derived from thermogravimetric (TGA) and differential thermogravimetric (DTG) curves, using Coats-Redfern and Horowitz-Metzeger methods. The proposed structure of the two complexes was detected by using the density functional theory (DFT) at the B3LYP/CEP-31G level of theory. The ligand as well as their metal complexes was also evaluated for their antibacterial activity against several bacterial species, such as Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) and antifungal screening was studied against two species (Penicillium (P. rotatum) and Trichoderma (T. sp.)). This study showed that the metal complexes are more antibacterial as compared to free ligand and no antifungal activity observed for ligand and their complexes.

High‐Performance Liquid Chromatography Assay for Moxifloxacin in Bulk, Pharmaceutical Formulations and Serum: Application to In‐Vitro Metal Interactions

A simple reversed phase HPLC method have been successfully developed and validated for the quantitative determination of moxifloxacin (MOX) in bulk material, pharmaceutical formulation and serum. Purospher STAR C18 (25 cm × 4.6 mm, 5 μm) and Discovery C18 (25 cm × 4.6 mm, 5 μm) columns were used. The mobile phase, methanol: acetonitrile: water (85:5:10, v/v/v), pH 2.75 adjusted by phosphoric acid was delivered at a flow rate of 1 mL min−1. The eluents was monitored using UV detector at 290 nm. The proposed method is specific, accurate (99.39‐102.67%), precise (intra‐day variation 0.04‐0.86% and inter‐day variation 0.12‐0.94%) and linearity (R2 > 0.999) within the desired range 0.39‐25 μg mL−1 concentration. The detection and quantification limit was 0.002‐0.51 μg mL−1 and 0.01‐0.555 μg mL−1, respectively. The analysis of variance (ANOVA) and student's t‐test were applied to verify the results. The anticipated method is applicable to routine analysis of MOX in pharmaceutical formulations and human serum samples. It is also applied on interaction of MOX with several essential and trace metals as well as interaction with antacids.

Copper(II) complexes with sparfloxacin and nitrogen-donor heterocyclic ligands: Structure-activity relationship

Three novel neutral mononuclear copper(II) complexes of the third-generation quinolone antibacterial drug sparfloxacin in the presence of a nitrogen donor heterocyclic ligand 2,2'-bipyridine, 1,10-phenanthroline or 2,2'-dipyridylamine have been prepared and characterized physicochemically and spectroscopically. The resultant complexes are of the type Cu(sparfloxacinato)(N-donor)Cl. Copper(II) is pentacoordinate having a distorted square pyramidal geometry. Molecular modeling calculations have been performed in order to propose the lowest energy model structure of the complexes. The interaction of the complexes with calf-thymus DNA has been investigated with diverse spectroscopic techniques and has shown that the complexes can bind to calf-thymus DNA by the intercalative mode. The antimicrobial activity of the complexes has been tested on three different microorganisms. The Cu(sparfloxacinato)(N-donor)Cl complexes are among the most active ones against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, when compared to the other corresponding copper-quinolone complexes studied by our group and their antimicrobial activity is increased in the order bipyam<bipy=phen. We have also shown that two of the Cu(sparfloxacinato)(N-donor)Cl complexes have decreased the viability of human leukemia cells HL-60 in a time-dependent manner.