Synthesis, thermal analyses, characterization and biological evaluation of new enrofloxacin vanadium(V) solvates(L) (L = An, DMF, Py, Et3N and o-Tol)

Vanadium complexes as potential metal-based antimicrobial drugs

Radical increase of antibiotic resistance among microbes has become a serious problem for clinics all over the world that has led to the need for search of novel types of antimicrobial drugs. Each year, researchers synthesize a multitude of compounds in pursuit of identifying potential chemotherapeutic agents through diverse methodological evaluations. Among the vast array of biologically significant compounds, coordination compounds exhibit a broad range of activities within biological systems. Chelation, in particular, induces significant alterations in the biological properties of ligands and the metal component, contributing to their efficacy. Chelation increases the lipophilicity of metal complexes as a result of which they are easily absorbed by the microorganisms, thus leading to their easy passage across cell membrane. The research and development in the field of metallodrugs can be advantageous to overcome the problem encountered in antibiotic resistance. The multifaceted involvement of vanadium relative to other biometals within biological systems, coupled with its comparatively lower toxicity, underscores its utility in the advancement of novel metal-based therapeutic agents. This review aims to delineate the biological significance of V(V/IV/III) complexes as antimicrobial agents. The amassed data indicate a correlation between the potency of vanadium complexes as antimicrobial agents and the oxidation state of the metal, with III being the least toxic and V representing the most toxic oxidation state of vanadium.

Copper(II) aromatic heterocyclic complexes of Gatifloxacin with multi-targeting capabilities for antibacterial therapy and combating antibiotic resistance

In recent years, the pace of novel antibiotic development has been relatively slow, intensifying the urgency of the antibiotic resistance issue. Consequently, scientists have turned their attention to enhancing antibiotic activity by coordinating antibiotics with metal elements. This study designs and synthesizes three novel antibacterial copper complexes based on Gatifloxacin. These complexes exhibit potent antibacterial activity, notably Cu-1, with a minimum inhibitory concentration (MIC) of only 0.063 μg/mL against Staphylococcus aureus (S.aureus), demonstrating potent bacteriostatic capabilities. Further investigations unveil the antibacterial mechanisms of complex Cu-1, revealing its ability not only to suppress the activities of DNA gyrase and topoisomerases IV, but also to effectively inhibit biofilm formation and disrupt the integrity of cell membrane. This multi-targeting action contributes to mitigating the risk of bacterial resistance emergence. Additionally, synergy between Cu-1 and conventional antibiotics is confirmed through checkerboard assays, offering novel strategies for antibacterial therapy. In vivo experiments using a murine model of S.aureus infection demonstrate the significant antibacterial efficacy of Cu-1, providing robust support for its potential in treating S.aureus infections. This study demonstrates that the coordination complexes formed by copper, Gatifloxacin and suitable aromatic heterocyclic ligands exhibit multi-targeting characteristics against bacteria, offering a new direction for combating antibiotic resistance in antibacterial therapy.

Enhancing the solubility and antibacterial activity of novel molecular salts of enrofloxacin drug with isomeric pyridinedicarboxylic acids

Enrofloxacin (EFX) is a third-generation synthetic fluoroquinolone with a broad spectrum of antibacterial activity but suffers from low water solubility, affecting its bioavailability. This study attempts to enhance the physicochemical and biological properties of enrofloxacin by converting it into multicomponent forms using crystal engineering concepts. Cocrystallization of enrofloxacin with isomeric pyridine-2,n-dicarboxylic acids (n = 3,4,5,6) resulted in four new crystalline salts (1:1): EFX·Py2,3DCA, EFX·Py2,4DCA, EFX·Py2,5DCA·H2O and EFX·Py2,6DCA·H2O; two of these are monohydrates. The protonation of the nitrogen atom of the piperazine moiety and the presence of crystallization water molecules were confirmed by single-crystal X-ray diffraction and Fourier transform infrared spectroscopy. Thermogravimetric analysis provided information on the thermal behaviour of multicomponent forms. The biological studies showed that the obtained salts are characterized by high antibacterial activity against Gram-positive and Gram-negative bacteria, and their haemolytic activity is low. The new salts demonstrate significantly greater solubility in water compared to the parent drug, along with enhanced antibacterial activity; hence, pyridinedicarboxylic acids appear to be efficient cocrystallizing agents for improving the efficacy of pharmaceutical ingredients.

Health Risk Assessment of Antibiotic Pollutants in Large Yellow Croakers from Zhejiang Aquaculture Sites

Intensive aquaculture combatting the decline of large yellow croaker populations can trigger bacterial outbreaks, resulting in extensive antibiotic use. In this study, we screened 5 aquaculture sites in the coastal areas of Zhejiang and identified 17 antibiotics in large yellow croakers using UPLC-MS/MS. The distribution and occurrence of antibiotic pollutants were different in the different tissues of large yellow croakers, being primarily dominated by quinolones. Relatively higher average residue levels of enrofloxacin and ciprofloxacin were detected in the inedible parts, specifically the gills (37.29 μg/kg). Meanwhile, relatively high average residue levels of enrofloxacin and ciprofloxacin were also found in the edible parts, particularly in the muscle (23.18 μg/kg). We observed that the residue levels detected in the swim bladder exceeded the prescribed limit for fish muscle, but there is currently no specific regulatory limit established for this particular tissue. Despite the HI values of enrofloxacin and ciprofloxacin being below 0.01, the health risks should not be disregarded. The findings of this research provide significant practical implications for assessing antibiotic contamination and enhancing the risk management of coastal regions.

Antitumor Properties of a New Macrocyclic Tetranuclear Oxidovanadium(V) Complex with 3-Methoxysalicylidenvaline Ligand

A wide variety of metal-based compounds have been obtained and studied for their antitumor activity since the intensely used cytostatic drugs (e.g., cisplatin) failed to accomplish their expected pharmacological properties. Thus, we aimed to develop a new vanadium-based drug and assess its antitumor properties using the human hepatocarcinoma (HepG2) cell line. The compound was synthesized from vanadyl sulfate, DL-valine, and o-vanillin and was spectrally and structurally characterized (UV-Vis, IR, CD, and single-crystal/powder-XRD). Compound stability in biological media, cell uptake, and the interaction with albumin were assessed. The mechanisms of its antitumor activity were determined compared to cisplatin by performing cytotoxicity, oxidative and mitochondrial status, DNA fragmentation, β-Tubulin synthesis investigation, and cell cycle studies. Herein, we developed a macrocyclic tetranuclear oxidovanadium(V) compound, [(V^VO)(L)(CH₃O)]₄, having coordinated four Schiff base (H₂L) ligands, 3-methoxysalicylidenvaline. We showed that [(V^VO)(L)(CH₃O)]₄: (i) has pH-dependent stability in biological media, (ii) binds to albumin in a dose-dependent manner, (iii) is taken up by cells in a time-dependent way, (iv) has a higher capacity to induce cell death compared to cisplatin (IC₅₀ = 6 μM vs. 10 μM), by altering the oxidative and mitochondrial status in HepG2 cells. Unlike cisplatin, which blocks the cell cycle in the S-phase, the new vanadium-based compound arrests it in S and G2/M-phase, whereas no differences in the induction of DNA fragmentation and reduction of β-Tubulin synthesis between the two were determined. Thus, the [(V^VO)(L)(CH₃O)]₄ antitumor mechanism involved corroboration between the generation of oxidative species, mitochondrial dysfunction, degradation of DNA, cell cycle arrest in the S and G2/M-phase, and β-Tubulin synthesis reduction. Our studies demonstrate the potent antitumor activity of [(V^VO)(L)(CH₃O)]₄ and propose it as an attractive candidate for anticancer therapy.

Nano-Azo Ligand and Its Superhydrophobic Complexes: Synthesis, Characterization, DFT, Contact Angle, Molecular Docking, and Antimicrobial Studies

Metal complexes of the 2,2'-(1,3-phenylenebis(diazene-2,1-diyl))bis(4-aminobenzoic acid) diazo ligand (H2L) derived from m-phenylenediamine and p-aminobenzoic acid were synthesized and characterized by different spectral, thermal, and analytical tools. The H2L ligand reacted with the metal ions Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) as 1 : 1 stoichiometry. All complexes displayed an octahedral geometry according to the electronic and magnetic moment measurements. The IR spectra revealed the binding of the azo ligand to the metal ions via two azo nitrogen atoms and protonated carboxylate O in a neutral tetradentate manner. Both IR and 1H NMR spectra documented the involvement of the carboxylate group without proton displacement. The thermal studies pointed out that the complexes had higher thermal stability comparable with that of the free ligand. SEM images revealed the presence of the diazo ligand and its Cd(II) complex in a nanostructure form. The contact angle measurements proved that the Cd(II) complex can be considered as a superhydrophobic material. The molecular and electronic structure of H2L and [Cd(H2L)Cl2].H2O were optimized theoretically, and the quantum chemical parameters were calculated. The biological activities of the ligand, as well as its metal complexes, have been tested in vitro against some bacteria and fungi species. The results showed that all the tested compounds have significant biological activities with different sensitivity levels. The binding between H2L and its Cd(II) complex with receptors of the crystal structure of S. aureus (PDB ID: 3Q8U), crystal structure of protein phosphatase (PPZ1) of Candida albicans (PDB ID: 5JPE), receptors of breast cancer mutant oxidoreductase (PDB ID: 3HB5), and crystal structure of Escherichia coli (PDB ID: 3T88) was predicted and given in detail using molecular docking.

Synthesis of Mono- and Dinuclear Vanadium Complexes and Their Reactivity toward Dehydroperoxidation of Alkyl Hydroperoxides

Several vanadium(V) complexes with either dipic-based or Schiff base ligands were synthesized. The complexes were fully characterized by elemental analysis, IR, ¹H, ¹³C, and ⁵¹V NMR spectroscopy, as well as mass spectrometry and X-ray diffraction. Furthermore, they were tested toward their catalytic deperoxidation behavior and a significant difference between 4-heptyl hydroperoxide and cyclohexyl hydroperoxide was observed. In the case of 4-heptyl hydroperoxide, the selectivity toward the corresponding ketone was higher than with cyclohexyl hydroperoxide. DFT calculations performed on the vanadium complex showed that selective decomposition of secondary hydroperoxides with vanadium(V) to yield the corresponding ketone and water is indeed energetically feasible. The computed catalytic path, involving cleavage of the O-O bond, hydrogen transfer, release of ketone/water, and finally addition of hydroperoxide, can proceed without the generation of radical species.