Synthesis, characterization and interaction with DNA of mononuclear metal complexes with oxolinic acid

Quinoline Derivatives in Discovery and Development of Pesticides

Finding highly active molecular scaffold structures is always the key research content of new pesticide discovery. In the research and development of new pesticides, the discovery of new agricultural molecular scaffold structures and new targets still faces great challenges. In recent years, quinoline derivatives have developed rapidly in the discovery of new agriculturally active molecules, especially in the discovery of fungicides. The unique quinoline scaffold has many advantages in the discovery of new pesticides and can provide innovative and feasible solutions for the discovery of new pesticides. Therefore, we reviewed the use of quinoline derivatives and their analogues as molecular scaffolds in the discovery of new pesticides since 2000. We systematically summarized the agricultural biological activity of quinoline compounds and discussed the structure-activity relationship (SAR), physiological and biochemical properties, and mechanism of action of the active compounds, hoping to provide ideas and inspiration for the discovery of new pesticides.

Synthesis, Spectral Characterization and Potential Fluorescent Properties of Three Lanthanide(III) Ions Complexes with Nalidixic Acid

Three new solid lanthanide complexes with nalidixic acid (HNal) with the stoichiometry [Ln(Nal)₃]·5·.5H₂O (Ln = Tb, Dy and Ho) were synthesized applying the green synthesis method from the aqueous solutions without the organic solvent addition and fully characterized by the elemental analysis, XRF, complexometric titration, gravimetric analysis, molar conductivity and solubility measurements, powder X-Ray diffraction, UV-Vis and infrared (FT-IR) spectroscopies. Moreover, the luminescent properties of the Tb(III), Dy(III), and Ho(III) complexes in the solid state and in the solutions were investigated. On the basis of the detailed spectral analysis, it was concluded that the nalidixate ligands bind to the lanthanide ions by the bidentate carboxylate and carbonyl groups while water molecules belong to the outer coordination sphere. At the excitation of UV light, the complexes exhibited characteristic emission of central lanthanide ions, the intensity of which depends significantly on the excitation wavelength and/or the solvent. Thus, the application of nalidixic acid (apart from biological activity) for the synthesis of luminescent lanthanide complexes was confirmed which can find potential applications in the field of photonic devices and/or bioimaging agents.

Mixed Ni(II) and Co(II) complexes of nalidixic acid drug: Synthesis, characterization, DNA/BSA binding profile and in vitro cytotoxic evaluation against MDA-MB-231 and HepG2 cancer cell lines

In this work, herein we report the synthesis, structural characterization and in vitro cytotoxic evaluation of two mixed Co(II)/Ni(II)-nalidixic acid-bipyridyl complexes (1 and 2). The structural analysis of metal complexes 1 and 2 was carried out by analytical and multispectroscopic techniques (FT-IR, UV-vis, EPR, sXRD). The crystallographic details of complexes 1 and 2 revealed a monoclinic crystal system with P21/c space group. DFT studies of complexes were performed to get electronic structure and localization of HOMO and LUMO electron densities. Hirshfeld surface analysis of metal complexes 1 and 2 was employed to understand the various intermolecular interactions (C-H···O, N-H···H and O-H···O) that define the stability of crystal lattice structures. The comparative interaction studies of complex 1 and complex 2 with DNA/BSA were performed by diverse multispectroscopic and analytical techniques to evaluate their chemotherapeutic potential. The magnitude of the DNA binding propensity and binding mode was verified by calculating K_b, K and K_sv values. Higher binding affinity was observed in case of complex 2via intercalative mode. Furthermore, the cytotoxic assessment of complexes 1 and 2 was examined against MDA-MB-231 (triple negative human breast cancer cell line) and HepG2 (liver carcinoma cell line) employing MTT assay which revealed remarkably effecient and specific cytotoxic activity of complex 2.

Rare-Earth Metal Complexes of the Antibacterial Drug Oxolinic Acid: Synthesis, Characterization, DNA/Protein Binding and Cytotoxicity Studies

"Drug repositioning" is a current trend which proved useful in the search for new applications for existing, failed, no longer in use or abandoned drugs, particularly when addressing issues such as bacterial or cancer cells resistance to current therapeutic approaches. In this context, six new complexes of the first-generation quinolone oxolinic acid with rare-earth metal cations (Y³⁺, La³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺) have been synthesized and characterized. The experimental data suggest that the quinolone acts as a bidentate ligand, binding to the metal ion via the keto and carboxylate oxygen atoms; these findings are supported by DFT (density functional theory) calculations for the Sm³⁺ complex. The cytotoxic activity of the complexes, as well as the ligand, has been studied on MDA-MB 231 (human breast adenocarcinoma), LoVo (human colon adenocarcinoma) and HUVEC (normal human umbilical vein endothelial cells) cell lines. UV-Vis spectroscopy and competitive binding studies show that the complexes display binding affinities (K_b) towards double stranded DNA in the range of 9.33 × 10⁴ - 10.72 × 10⁵. Major and minor groove-binding most likely play a significant role in the interactions of the complexes with DNA. Moreover, the complexes bind human serum albumin more avidly than apo-transferrin.

Design of nalidixic acid‑vanadium complex loaded into chitosan hybrid nanoparticles as smart strategy to inhibit bacterial growth and quorum sensing

The discovery of new alternatives for the treatment of infectious diseases has become the focus of burgeoning global interest. The complexation of the wide-spectrum antibiotic nalidixic acid (NA) with oxidovanadium(IV) ion and its incorporation into hybrid nanoparticulate systems were explored. The V-NA complex proved to be a stronger antimicrobial agent against E. coli, B. cereus, S. aureus and P. aeruginosa than NA, based on inhibition experiments. Myristyl myristate nanostructured lipid carriers (NLCs) and polymeric nanoparticles of Eudragit NE30D (EuNPs) were hybridized with chitosan (chi) to increase their stability and mucoadhesivity. They showed V-NA encapsulation of 97.8 ± 0.5% and 96.1 ± 0.1% respectively. TEM and DLS characterization ascertained the presence of spherical positive charged NPs ranging from 170 to 330 nm. Controlled release of V-NA from NPs was observed with 30-40% release in 3 days. A considerable potentiation of V-NA antimicrobial activity from 5 to 10 times was elucidated against P. aeruginosa with MIC values of 59.3 and 129.9 μM for NLC/chi and EuNPs/chi respectively, in comparison with 625 μM of the free complex. Hybrid NPs were able to interfere with the quorum sensing of the reporter Chromobacterium violaceum. Cytotoxicity on mouse fibroblast L929 cells was evaluated in the range of 29.7-519 μM by MTT assay showing that, NLC/chi particles supported cell growth in the range of at 29.7-60 μM while Eu/chi do not exert cytotoxicity between 29.7 and 120 μM. These results suggest that nanoparticles are suitable systems for drug delivery applications.

Structure, DNA/proteins binding, docking and cytotoxicity studies of copper(II) complexes with the first quinolone drug nalidixic acid and 2,2'‑dipyridylamine

This work presents the synthesis, structural characterization and biological affinity of the newly synthesized copper(II) complexes with the first antibacterial quinolone drug nalidixic acid (nal) or N-donor ligand 2,2'‑dipyridylamine (bipyam). [Cu(II)(nal)(bipyam)Cl], (2) reveals a distorted square pyramidal based geometry in Cu(II) atom confirmed by X-ray crystallography technique. The theoretical stabilities and optimized structures of the complex were obtained from DFT calculations. The ability of the complexes to bind with calf thymus DNA (CT DNA) were investigated by electronic absorption, fluorescence, circular dichroism, and viscosity measurements techniques. The experimental results reveal that the complexes strongly interact with CT DNA via intercalative mode but complex 2 exhibits the highest affinity giving K_b=3.91±0.13×10⁶, M^-1. The fluorescence spectroscopy measurements show that both complexes have the superior ability to the replacement of EtBr from DNA-bound EtBr solution and bind to DNA through intercalative mode. Both complex also shows the superior affinity towards proteins with comparatively high binding constant values which have been further revealed by fluorescence spectroscopy measurements. Molecular docking analysis indicates that the interaction of the complexes and proteins are stabilized by hydrogen bonding and hydrophobic interaction. Furthermore, the results of in vitro cytotoxicity reveal that the complex 2 has excellent cytotoxicity than 1 against human breast cancer cell lines (MCF-7).

VIVO complexes with antibacterial quinolone ligands and their interaction with serum proteins

Quinolone derivatives are among the most commonly prescribed antibacterials in the world and could also attract interest as organic ligands in the design of metal complexes with potential pharmacological activity. In this study, five compounds, belonging to the first (nalidixic acid or Hnal), second (ciprofloxacin or Hcip, and norfloxacin or Hnor) and third generation (levofloxacin or Hlev, and sparfloxacin or Hspar) of quinolones, were used as ligands to bind the V^IVO²⁺ ion. In aqueous solution, mono- and bis-chelated species were formed as a function of pH, with cis-[VOH_xL₂(H₂O)]^x+ and [VOH_xL₂]^x+, x = 0-2, being the major complexes at pH 7.4. DFT calculations indicate that the most stable isomers are the octahedral OC-6-32 and the square pyramidal SPY-5-12, in equilibrium with each other. To the best of our knowledge, this is the first case that an equilibrium between a penta-coordinated square pyramidal complex and a hexa-coordinated octahedral complex is observed in solution for ligands forming six-membered chelated rings. Nalidixic acid forms the solid compound [VO(nal)₂(H₂O)], to which a cis-octahedral geometry was assigned. The interaction with 1-methylimidazole (MeIm) causes a shift of the equilibrium SPY-5 + H₂O ⇄ OC-6 toward the right after the formation of cis-[VOH_xL₂(MeIm)]^x+, where MeIm replaces an equatorial water ligand. The study of the systems containing [VO(nal)₂(H₂O)] and the serum proteins - albumin (HSA), apo-transferrin (apo-hTf) and holo-transferrin (holo-hTf) - indicates that HSA and holo-hTf form the mixed species {VO(nal)₂}_y(HSA) and {VO(nal)₂}_y(holo-hTf), where y = 1-3 denotes the number of VO(nal)₂ moieties bound to accessible histidines (His105, His367, His510 for HSA, and His25, His349, His606 for holo-hTf), whereas apo-hTf yields VO(nal)₂(apo-hTf) with the coordination of the His289 residue only. Docking calculations suggest that the specific conformation of apo-hTf and the steric hindrance of the cis-VO(nal)₂ moiety interfere with its interaction with all the surface His residues and the formation of a hydrogen bond network which could stabilize the binding sites.

Spectroscopic and molecular docking studies on the interaction of antiviral drug nevirapine with calf thymus DNA

The interaction of calf thymus DNA with nevirapine at physiological pH was studied by using absorption, circular dichroism, viscosity, differential pulse voltammetry, fluorescence techniques, salt effect studies and computational methods. The drug binds to ct-DNA in a groove binding mode, as shown by slight variation in the viscosity of ct-DNA. Furthermore, competitive fluorimetric studies with Hoechst 33258 indicate that nevirapine binds to DNA via groove binding. Moreover, the structure of nevirapine was optimized by DFT calculations and was used for the molecular docking calculations. The molecular docking results suggested that nevirapine prefers to bind on the minor groove of ct-DNA.

Oxolinic Acid Binding at Goethite and Akaganéite Surfaces: Experimental Study and Modeling

Oxolinic acid (OA) is a widely used quinolone antibiotic in aquaculture. In this study, its interactions with synthetic goethite (α-FeOOH) and akaganéite (β-FeOOH) particle surfaces were monitored to understand the potential fate of OA in marine sediments where these phases occur. Batch sorption experiments, liquid chromatography (LC) analyses of supernatants, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and multisite complexation (MUSIC) modeling were used to monitor OA binding at these particle surfaces. Both LC and ATR-FTIR showed that adsorption did not degrade OA, and that OA adsorption was largely unaffected by NaCl concentrations (10-1000 mM). This was explained further by ATR-FTIR suggesting the formation of metal-bonded complexes at circumneutral to low pHc = -log [H(+)] and with a strongly hydrogen-bonded complex at high pHc. The stronger OA binding to akaganéite can be explained both by the higher isoelectric point/point-of-zero charge (9.6-10) of this mineral than of goethite (9.1-9.4), and an additional OA surface complexation mechanism at the (010) plane. Geminal sites (≡Fe(OH2)2(+)) at this plane could be especially reactive for metal-bonded complexes, as they facilitate a mononuclear six-membered chelate complex via the displacement of two hydroxo/aquo groups at the equatorial plane of a single Fe octahedron. Collectively, these findings revealed that Fe-oxyhydroxides may strongly contribute to the fate and transport of OA-type antibacterial agents in marine sediments and waters.

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.

Anticancer and DNA binding activities of platinum (IV) complexes; importance of leaving group departure rate

The two six-coordinate Pt(IV) complexes, containing bidentate nitrogen donor/methyl ligands with general formula [Pt(X)2Me2((t)bu2bpy)], where (t)bu2bpy = 4,4'-ditert-butyl-2,2'-bipyridine and X = Cl (C1) or Br (C2), serving as the leaving groups were synthesized for evaluation of their anticancer activities and DNA binding properties. To examine anticancer activities of the synthetic complexes, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and ethidium bromide/acridine orange (EB/AO) staining method were performed. The binding properties of these complexes to DNA and purine nucleotides were examined, using different spectroscopic techniques. These complexes demonstrated significant anticancer activities against three cancer cell lines Jurkat, K562, and MCF-7. On the basis of the results of EB/AO staining, C1 and C2 were also capable to induce apoptosis in cancer cells. These complexes comprise halide leaving groups, displaying different departure rates; accordingly, they demonstrated slightly dissimilar anticancer activity and significantly different DNA/purine nucleotide binding properties. The results of DNA interaction studies of these complexes suggest a mixed-binding mode, comprising partial intercalation and groove binding. Overall, the results presented herein indicate that the newly synthesized Pt(IV) complexes are promising class of the potential anticancer agents which can be considered as molecular templates in designing novel platinum anticancer drugs. This study also highlights the importance of leaving group in anticancer activity and DNA binding properties of Pt(IV) complexes.

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.

Nickel-quinolones interaction. Part 1 - Nickel(II) complexes with the antibacterial drug sparfloxacin: structure and biological properties

The mononuclear nickel(II) complexes with the third-generation quinolone antibacterial agent sparfloxacin in the absence or presence of nitrogen donor heterocyclic ligands (1,10-phenanthroline or 2,2'-bipyridine) have been synthesized and characterized. The experimental data suggest that sparfloxacin acts as deprotonated bidentate ligand coordinated to Ni(II) ion through the ketone and carboxylato oxygens. The crystal structure of (1,10-phenanthroline)bis(sparfloxacinato) nickel(II), 2 has been determined by X-ray crystallography. The cyclic voltammograms of the complexes recorded in dmso solution and in 1/2 dmso/buffer (containing 150 mM NaCl and 15 mM trisodium citrate at pH 7.0) solution have shown that in the presence of CT DNA they can bind to CT DNA by the intercalative binding mode. UV study of the interaction of the complexes with calf-thymus DNA (CT DNA) has shown that the complexes can bind to CT DNA and 2 exhibits the highest binding constant to CT DNA. Competitive study with ethidium bromide (EB) has shown that the complexes can displace the DNA-bound EB indicating that they bind to DNA in strong competition with EB for the intercalative binding site. The antimicrobial activity of the complexes has been tested on three different microorganisms and has revealed that the inhibition provided by the complexes is slightly decreased in comparison to free sparfloxacin. The complexes exhibit good binding propensity to human and bovine serum albumin proteins having relatively high binding constant values.

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.