Structural, molecular docking computational studies and in-vitro evidence for antibacterial activity of mixed ligand complexes

Eugenol's electrochemical behavior, complexation interaction with copper chloride, antioxidant activity, and potential drug molecular docking application for Covid-19

Electrochemical studies were conducted to analyze the behavior of eugenol, CuCl2, and their complex using cyclic voltammetry. The oxidation mechanisms of eugenol and the redox behavior of copper ions were elucidated, showing differences in reversibility and charge transfer coefficients. Various kinetic and solvation parameters were determined. The redox behavior of CuCl2 was found to be more reversible compared to the copper-eugenol complex. The copper-eugenol complex exhibited enhanced antioxidant activity compared to eugenol and standard ascorbic acid. The eugenol was oxidized to form eugenol quinone methide through two postulated irreversible mechanisms. Molecular docking studies suggested higher potential bioactivity of the copper-eugenol complex towards the target protein of COVID-19 than the eugenol ligand.

Synthesis, Spectral Characterization, Antimicrobial Activity, DFT Calculations, Molecular Docking and ADME Studies of Novel Schiff Base Co(II), Ni(II), Cu(II) and Zn(II) Complexes Derived from 4-nitro-ortho-phenylenediamine

A condensation reaction was carried out between 4-nitro-ortho-phenylenediamine and 5-bromosalicyaldehyde to synthesize a novel Schiff base ligand 2,2'-[(1E,1'E)-(4-nitro-1,2-phenylene) bis (azaneylylidene) bis (methaneylylidene)] bis (4-bromophenol) [NB] in the current investigation. This was followed by the synthesis of metallic complexes comprising the Co(II), Ni(II), Cu(II) and Zn(II) transition metal ions. A hexadentate environment encircling metal complexes was corroborated by the results of varied spectroscopic methods that were employed to unravel the structure of the ligand and metal complexes. The Tauc's plot and Urbach energy were utilized for quantifying the optical energy band gap to provide insight into optical characteristics. The Coats-Redfern method of thermal analysis was implemented to do the kinetic and thermodynamic calculations. Furthermore, DFT studies were performed to predict geometrical structures and the stability of the compounds. Thorough investigation to evaluate their biological efficacies, docking studies was executed against COVID-19 main protease (PDB-7VAH), Dengue virus NS2B/NS3 protease (PDB-2FOM) and Mycobacterium Tuberculosis (PDB-5AF3). Apart from this, in silico ADMET studies were also accomplished for elucidation of drug likeness characteristics and the results attained disclose the significant proficiency of synthesized compounds. Besides this, antimicrobial studies were assessed with different microbial strains and result validates cobalt and zinc complexes as most potent against the selected bacterial and fungal strains.

Theoretical and experimental investigation of mixed-ligand metal(II) Schiff base complexes using maleic acid as the auxiliary ligand

This work is focused on the synthesis of several transition metal complexes [ML(MA)], where M = Copper (II), Zinc (II), Cobalt (II) and Nickel (II), MA = maleic acid and L = Schiff base generated from benzene-1,2-diamine [o-phenylenediamine] and 4-chlorobenzaldehyde. The characterization using Fourier-Transform Infrared, Nuclear Magnetic Resonance spectroscopy, Ultraviolet-Visible spectra, Mass, Electro Paramagnetic Resonance and elemental analysis confirm the square planar geometry of the complexes. The in vitro antimicrobial potential of the complexes has been tested by the broth dilution method and the antioxidant method has been done by free radical scavenging analysis. The in vitro methods reveal the outstanding biological characteristics of the copper complexes. The molecular structure of the ligand and its metal (II) complexes has been optimized using Density Functional Theory studies performed by the Gaussian-09 software and their parameters have been discussed. Natural Bond Orbital and Frontier Molecular Orbital analyses have assessed the presence of a metal-ligand bond in complexes. In addition, molecular docking studies have also been performed on antiviral activity of all the complexes using a viral protein and their interacting amino acids.

Synthesis, Structural Characterization, and Computational Studies of Novel Co(II) and Zn(II) Fluoroquinoline Complexes for Antibacterial and Antioxidant Activities

Research into heterocyclic ligands has increased in popularity due to their versatile applications in the biomedical field. Quinoline derivatives with their transition metal complexes are popular scaffolding molecules in the ongoing pursuit of newer and more effective bioactive molecules. Subsequently, this work reports on the synthesis and possible biological application of new Zn(II) and Co(II) complexes with a bidentate quinoline derivative ligand (H2 L), [(H2 L):(E)-2-(((6-fluoro-2-((2-hydroxyethyl)amino)quinolin-3-yl)methylene)amino)ethanol]. The ligand and its metal complexes were structurally characterized by spectroscopic methods (1H NMR, 13C NMR, Fourier transform infrared (FTIR), UV-vis, fluorescence, and mass spectroscopy), as well as by thermogravimetric and elemental analysis methods. The spectroscopic findings were further supported by density functional theory (DFT) and time-dependent (TD)-DFT calculations. The biological application was examined by investigating the inhibitory action of the complexes against bacterial strains using diffusion and agar dilution methods, and their profiles against two Gram-positive and Gram-negative bacterial strains were supported by molecular docking analysis. To rationalize the in vitro activity and establish the possible mechanism of action, the interactions and binding affinity of the ligand and complexes were investigated against three different bacterial enzymes (Escherichia coli DNA gyrase (PDB ID 6f86), E. coli dihydrofolate reductase B (PDB ID: 7r6g), and Staphylococcus aureus tyrosyl-tRNA synthetase (PDB ID: 1JIJ)) using AutoDock with the standard protocol. The MIC value of 0.20 μg/mL for zinc complex against E. coli and associated binding affinities -7.2 and -9.9 kcal/mol with DNA gyrase (PDB ID 6f86) and dihydrofolate reductase B (PDB ID: 7r6g), as well as the MIC value of 2.4 μg/mL for cobalt(II) complex against Staphylococcus aureus and the associated binding affinity of -10.5 kcal/mol with tyrosyl-tRNA synthetase (PDB ID: 1JIJ), revealed that the complexes' inhibitory actions were strong and comparable with those of the standard drug in the experiments. In addition, the ability of the new quinoline-based complexes to scavenge 1,1-diphenyl-picrylhydrazyl radicals was investigated; the findings suggested that the complexes exhibit potent antioxidant activities, which may be of therapeutic significance.

Remediation of multifarious metal ions and molecular docking assessment for pathogenic microbe disinfection in aqueous solution by waste-derived Ca-MOF

The present study demonstrates an eco-friendly and cost-effective synthesis of calcium terephthalate metal-organic frameworks (Ca-MOF). The Ca-MOF were composed of metal ions (Ca2+) and organic ligands (terephthalic acid; TPA); the former was obtained from egg shells, and the latter was obtained from processing waste plastic bottles. Detailed characterization using standard techniques confirmed the synthesis of Ca-MOF with an average particle size of 461.9 ± 15 nm. The synthesized Ca-MOF was screened for its ability to remove multiple metal ions from an aqueous solution. Based on the maximum sorption capacity, Pb2+, Cd2+, and Cu2+ ions were selected for individual parametric batch studies. The obtained results were interpreted using standard isotherms and kinetic models. The maximum sorption capacity (qm) obtained from the Langmuir model was found to be 644.07 ± 47, 391.4 ± 26, and 260.5 ± 14 mg g-1 for Pb2+, Cd2+, and Cu2+, respectively. Moreover, Ca-MOF also showed an excellent ability to remove all three metal ions simultaneously from a mixed solution. The metal nodes and bonded TPA from Ca-MOF were dissociated by the acid dissolution method, which protonated and isolated TPA for reuse. Further, the crystal structure of Ca-MOF was prepared and docked with protein targets of selected pathogenic water-borne microbes, which showed its disinfection potential. Overall, multiple metal sorption capability, regeneration studies, and broad-spectrum antimicrobial activity confirmed the versatility of synthesized Ca-MOF for industrial wastewater treatment.

Novel N-acylsulfonamides: Synthesis, in silico prediction, molecular docking dynamic simulation, antimicrobial and anti-inflammatory activities

Microbial resistance to drugs currently traded in the market is a serious problem in modern medicine. In this field of research, we synthesized a novel N-acylsulfonamides (NAS) derivatives starting from commercially available compounds; morpholine, isocyanate of chlorosulfonyl and alcohols. The in vitro antimicrobial potential of synthesized compounds was screened against 04 Gram-negative bacteria; Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Acinetobacter baumannii, 02 Gram-positive bacteria: Streptococcus sp, Staphylococcus aureus and 07 yeasts and fungi: Candida albicans, Candida spp, Penicillum spp, Aspegillus sp, Aspergillus flavus, Fusarium sp, and Cladosporium spp. The results of inhibition growth were compared with standard antimicrobial drugs with the goal of exploring their potential antimicrobial activity. In addition, the anti-inflammatory activity of the synthesized compounds was determined in-vitro by protein denaturation method. The obtained bioactivity results were further validated by in silico DFT (Density Functional Theory), ADME (Absorption-Distribution-Métabolisation-Excrétion), molecular docking studies and molecular dynamics simulations.Communicated by Ramaswamy H. Sarma.

Spectroscopy and molecular dynamic study of the interaction of calf thymus DNA by anticancer Pt complex with butyl glycine ligand

Despite the past few decades since the discovery of anticancer drugs, there is still no definitive treatment for its treatment. Cisplatin is a chemotherapy medication used to treat some cancers. In this research, the DNA binding affinity of Pt complex with butyl glycine ligand was studied by various spectroscopy methods and simulation studies. Fluorescence and UV-Vis spectroscopic data showed groove binding in ct-DNA-[Pt(NH₃)₂(butylgly)]NO₃ complex formation by the spontaneous process. The results were also confirmed by small changes in CD spectra and thermal study (T_m), as well as the quenching emission of [Pt(NH₃)₂(butylgly)]NO₃ complex on DNA. Finally, thermodynamic and binding parameters displayed that hydrophobic forces are the main forces. Based on docking simulation, [Pt(NH₃)₂(butylgly)]NO₃ could bind to DNA and via minor groove binding on C-G center on DNA, formed a stable DNA complex.

Cytotoxicity and Antibacterial Potentials of Mixed Ligand Cu(II) and Zn(II) Complexes: A Combined Experimental and Computational Study

[Cu(C₁₅H₉O₄)(C₁₂H₈N₂)O₂C₂H₃]·3H₂O (1) and [Zn(C₁₅H₉O₄)(C₁₂H₈N₂)]O₂C₂H₃ (2) have been synthesized and characterized by ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, mass spectrometry, thermogravimetric analysis/differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX), and molar conductance, and supported by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. Square pyramidal and tetrahedral geometries are proposed for Cu(II) and Zn(II) complexes, respectively, and the XRD patterns showed the polycrystalline nature of the complexes. Furthermore, in vitro cytotoxic activity of the complexes was evaluated against the human breast cancer cell line (MCF-7). A Cu(II) centered complex with an IC₅₀ value of 4.09 μM was more effective than the Zn(II) centered complex and positive control, cisplatin, which displayed IC₅₀ values of 75.78 and 18.62 μM, respectively. In addition, the newly synthesized complexes experienced the innate antioxidant nature of the metal centers for scavenging the DPPH free radical (up to 81% at 400 ppm). The biological significance of the metal complexes was inferred from the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy band gap, which was found to be 2.784 and 3.333 eV, respectively for 1 and 2, compared to the ligands, 1,10-phenathroline (4.755 eV) and chrysin (4.403 eV). Moreover, the molecular docking simulations against estrogen receptor alpha (ERα; PDB: 5GS4) were strongly associated with the in vitro biological activity results (E _B and K _i are -8.35 kcal/mol and 0.76 μM for 1, -7.52 kcal/mol and 3.07 μM for 2, and -6.32 kcal/mol and 23.42 μM for cisplatin). However, more research on in vivo cytotoxicity is suggested to confirm the promising cytotoxicity results.

Organic-inorganic hybrid salt and mixed ligand Cr(III) complexes containing the natural flavonoid chrysin: Synthesis, characterization, computational, and biological studies

Organic-inorganic hybrid salt and mixed ligand Cr(III) complexes (Cr1 and Cr2) containing the natural flavonoid chrysin were synthesized. The metal complexes were characterized using UV-Vis, Fourier-transform infrared, MS, SEM-EDX, XRD, and molar conductance measurements. Based on experimental and DFT/TD-DFT calculations, octahedral geometries for the synthesized complexes were suggested. The powder XRD analysis confirms that the synthesized complexes were polycrystalline, with orthorhombic and monoclinic crystal systems having average crystallite sizes of 21.453 and 19.600 nm, percent crystallinities of 51% and 31.37%, and dislocation densities of 2.324 × 10^-3 and 2.603 × 10^-3 nm^-2 for Cr1 and Cr2, respectively. The complexes were subjected to cytotoxicity, antibacterial, and antioxidant studies. The in vitro biological studies were supported with quantum chemical and molecular docking computational studies. Cr1 showed significant cytotoxicity to the MCF-7 cell line, with an IC₅₀ value of 8.08 μM compared to 30.85 μM for Cr2 and 18.62 μM for cisplatin. Cr2 showed better antibacterial activity than Cr1. The higher E _HOMO (-5.959 eV) and dipole moment (10.838 Debye) values of Cr2 obtained from the quantum chemical calculations support the observed in vitro antibacterial activities. The overall results indicated that Cr1 is a promising cytotoxic drug candidate.

Density functional theory studies on molecular geometry, spectroscopy, HOMO-LUMO and reactivity descriptors of titanium(IV) and oxidozirconium(IV) complexes of phenylacetohydroxamic acid

The molecular geometry of new titanium(IV) and oxidozirconium(IV) phenylacetohydroxamate complexes [TiCl₂ (L1)₂ ] (I) and [ZrO(L1)₂ ] (II) (where L1 = Potassium phenylacetohydroxamate = C₆ H₅ CH₂ CONHOK) computed by B3LYP/6-311++G(d,p) method has shown these to be distorted octahedral and square pyramidal, respectively. A comparison of computed characteristic bond lengths (CO, CN, and NO) of complexes with that of free ligand has shown chelation through carbonyl and hydroxamic oxygen atoms (O, O coordination). The TiO/ZrO bond lengths in complexes are suggestive of weak coordination through (carbonyl CO) and strong covalent (hydroxamic NO) bonding of the ligand. The magnitude of ClTiCl bond angle involving two chloride atoms is suggestive of cis-conformation at titanium metal in (I). The thermodynamic parameters Gibbs free energy, enthalpy, entropy, nuclear internal energy, constant volume heat capacity, and internal energy of ligand and complexes have been computed. From the energies of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), the global reactivity descriptors such as ionization potential (IP), electron affinity (EA), chemical potential (μ), hardness (η), softness (S), electronegativity (χ), electrophilicity index (ω), and dipole moment have been calculated. The computed vibrational frequencies, ¹ H and ¹³ C NMR spectra have substantiated the molecular structure of complexes. The thermal behavior of complexes has been studied by thermogravimetric techniques (TGA, DTG, and DTA) in N₂ atmosphere has shown complexes are thermally stable.

Functionalized Cu-based metal oxide nanoparticles with enhanced Cd+2 adsorption capacity and their ecotoxicity assessment by molecular docking

In the present study, synthesis of eco-friendly Cu-based metal oxides nanoparticles [CuO, Cu₂O, and CuO&Cu₂O nanoparticles (NPs)] without and with functionalization with Diethylene glycol (DEG) has been demonstrated. The synthesized NPs were screened for their ability to adsorb multiple heavy metal ions from an aqueous solution. Based on the maximum Cadmium (Cd⁺²) ion adsorption capacity, functionalized Cu₂O (fCu₂O) NPs were selected for the detailed characterization and batch studies. The average size of fCu₂O NPs was found to be 57.4 ± 6.14 nm in comparison to NPs without capping (72.6 ± 5.19 nm). The experimental parameters viz. contact time, initial pH, and initial concentration were optimized, and the obtained results were interpreted using standard isotherms and kinetic models. The maximum Cd⁺² adsorption on fCu₂O NPs was observed at initial solution pH 7. The adsorption of Cd⁺² was found to be decreased at acidic pH due to the protonation of functional groups present on the NPs surface. A maximum Cd⁺² adsorption capacity of 204 ± 6.2 mg g^-1 was obtained from the Langmuir adsorption isotherm. The crystal structure of NPs was prepared and docked with the protein targets of selected soil microbes in order to determine their ecotoxicity. The obtained results showed that NPs exhibited low affinity towards protein targets in comparison to the standard used. It suggests that NPs have less impact on the functionality of soil microbes and are thus safe for their disposal into the soil micro-environment.