Exploiting the biological efficacy of benzimidazole based Schiff base complexes with l-Histidine as a co-ligand: Combined molecular docking, DNA interaction, antimicrobial and cytotoxic studies

Synthesis of quercetin-iron (Fe) complex and its in silico and in vitro confirmation towards antibacterial activity

Aim: In this study quercetin-iron complex (QFC) was synthesized, and the structural characterizations such as x-ray diffraction, field emission-scanning electron microscopy, energy-dispersive x-ray and Brunner-Emmitt-Teller adsorption-desorption isotherm analysis revealed the crystallinity state, surface morphology and nature of the adsorbing surface with surface area value. Methodology: Functional characterizations such as UV-visible spectrometric and Fourier transform infrared analysis collectively indicated the chemical changes that appeared after complex formation in terms of characteristic change in the spectrum and band position, respectively. Results: The in vitro antibacterial activity against Escherichia coli and Staphylococcus aureus has shown a dose-dependent decrease in colony count and achieved significant removal at 15 mg/ml concentration of QFC. Conclusion: The molecular docking study supports the therapeutic application of QFC.

Synthesis, spectral characterization, computational studies, antifungal, DNA interaction, antioxidant and fluorescence property of novel Schiff base ligand and its metal chelates

Cobalt, Copper, Nickel and Zinc coordinated metal complexes were synthesized by novel thiazole Schiff base ligand 2-ethoxy-4-((5-methylthiazol-2-ylimino)methyl) phenol derived from 3-ethoxy-4-hydroxybenzaldehyde and 2-amino- 5-methylthiazol. The synthesized compounds were spectrochemically characterized by elemental analysis, molar conductance, FT-IR, UV-Vis, Mass spectral analysis, Powdered-XRD and cyclic voltammetry. The thermal stability of synthesized complexes were investigated by using thermogravimetric analysis (TGA). Theoretical computational study were performed for all the synthesized compounds utilizing the DFT/B3LYP method at the 6-31G basic set for Schiff base ligand whereas LANL2DZ basis set for metal complexes. Molecular Electrostatic Potential (MEP), HOMO-LUMO, Mulliken charges and global reactivity descriptors, including chemical potential (μ), global softness (S), chemical hardness (η), and electrophilicity index (ω) were measured and correlated with antimicrobial activity. The synthesized thiazole Schiff base ligand and its coordinated metal complexes shows good antifungal agreement against Fusarium Oxysporum and Aspergillus Niger species. These compounds also exhibit DNA binding, DNA cleaving and antioxidant activity. All the synthesized molecules indicate potential fluorescence property.

Novel Biologically Active N-Substituted Benzimidazole Derived Schiff Bases: Design, Synthesis, and Biological Evaluation

Herein, we present the design and synthesis of novel N-substituted benzimidazole-derived Schiff bases, and the evaluation of their antiviral, antibacterial, and antiproliferative activity. The impact on the biological activity of substituents placed at the N atom of the benzimidazole nuclei and the type of substituents attached at the phenyl ring were examined. All of the synthesized Schiff bases were evaluated in vitro for their antiviral activity against different viruses, antibacterial activity against a panel of bacterial strains, and antiproliferative activity on several human cancer cell lines, thus enabling the study of the structure-activity relationships. Some mild antiviral effects were noted, although at higher concentrations in comparison with the included reference drugs. Additionally, some derivatives showed a moderate antibacterial activity, with precursor 23 being broadly active against most of the tested bacterial strains. Lastly, Schiff base 40, a 4-N,N-diethylamino-2-hydroxy-substituted derivative bearing a phenyl ring at the N atom on the benzimidazole nuclei, displayed a strong antiproliferative activity against several cancer cell lines (IC₅₀ 1.1-4.4 μM). The strongest antitumoral effect was observed towards acute myeloid leukemia (HL-60).

Precision syntheses of molecular necklaces based on coordination interactions

Molecular necklaces (MNs) are mechanically interlocked molecules that have attracted considerable attention due to their delicate structures and potential applications, such as in the syntheses of polymeric materials and DNA cleavage. However, complex and lengthy synthetic routes have limited development of further applications. Owing to their dynamic reversibility, strong bond energy and high orientation, coordination interactions were employed to synthesize MNs. In this review, progress in the coordination-based MNs has been summarized, with emphasis on design strategies and potential applications based on coordination interactions.

Novel Benzimidazole Derived Imine Ligand and Its Co(III) and Cu(II) Complexes as Anticancer Agents: Chemical Synthesis, DFT Studies, In Vitro and In Vivo Biological Investigations

The emerging interest in the field of coordination chemistry and their biological applications has created a novel impact in the field of chemical biology. With this motivation, in this work we have synthesized a novel benzimidazole derived imine ligand, 2-((E)-((1H-benzo[d]-2-yl)methylimino)methyl)-4-fluorophenol (HBMF) and its Co(III) and Cu(II) complexes. The metal complexes (C1-C4) were synthesized in 2:1 (HBMF: metal ion) and 1:1:1 (HBMF: metal ion: 1,10-phen) ratios. Structural elucidations of all the synthesized compounds were performed using FT-IR, UV-Visible, NMR, Mass spectroscopy and elemental analysis techniques. A combination of first principles calculations and molecular dynamics simulations was applied to computationally investigate the structural, reactive, and spectroscopic properties of the newly synthesized HBMF ligand and its complexes with copper and cobalt metal ions. Quantum-mechanical calculations in this study were based on the density functional theory (DFT), while molecular dynamics (MD) simulations were based on the OPLS4 force field. The DFT calculations were used to obtain the reactive and spectroscopic properties of the ligand and its complexes, while molecular dynamics (MD) simulations were used to address the ligand's reactivity with water. Further, the in vitro anti-proliferative activity of the compounds was tested against the A549, Ehrlich-Lettre ascites carcinoma (EAC), SIHA and NIH3T3 cell lines. The biological results depicted that the compound C4, with molecular formula C₂₇H₂₃Cl₂CoFN₅O₃ exhibited profound anti-proliferative activity against the EAC cell line with a significant IC₅₀ value of 10 µm when compared to its parent ligand and other remaining metal complexes under study. Various assays of hematological parameters (alkaline phosphate, creatinine, urea, RBC and WBC) were performed, and significant results were obtained from the experiments. Furthermore, the effect of C4 on neovascularization was evaluated by stimulating the angiogenesis with rVEGF₁₆₅, which was compared with non-tumor models. The EAC cells were cultured in vivo and administrated with 50 and 75 mg/kg of two doses and tumor parameters were evaluated.

An Integrated Analysis of Mechanistic Insights into Biomolecular Interactions and Molecular Dynamics of Bio-Inspired Cu(II) and Zn(II) Complexes towards DNA/BSA/SARS-CoV-2 3CLpro by Molecular Docking-Based Virtual Screening and FRET Detection

Novel constructed bioactive mixed-ligand complexes (1b) [Cu^II(L)₂(phen)] and (2b) [Zn^II(L)₂(phen)] {where, L = 2-(4-morpholinobenzylideneamino)phenol), phen = 1,10-phenanthroline} have been structurally analysed by various analytical and spectroscopic techniques, including, magnetic moments, thermogravimetric analysis, and X-ray crystallography. Various analytical and spectral measurements assigned showed that all complexes appear to have an octahedral geometry. Agar gel electrophoresis's output demonstrated that the Cu(II) complex (1b) had efficient deoxyribonucleic cleavage and complex (2b) demonstrated the partial cleavage accomplished with an oxidation agent, which generates spreadable OH^● through the Fenton type mechanism. The DNA binding constants observed from viscosity, UV-Vis spectral, fluorometric, and electrochemical titrations were in the following sequence: (1b) > (2b) > (HL), which suggests that the complexes (1b-2b) might intercalate DNA, a possibility that is supported by the biothermodynamic measurements. In addition, the observed binding constant results of BSA by electronic absorption and fluorometric titrations indicate that complex (1b) revealed the best binding efficacy as compared to complex (2b) and free ligand. Interestingly, all compounds are found to interact with BSA through a static approach, as further attested by FRET detection. The DFT and molecular docking calculations were also performed to realize the electronic structure, reactivity, and binding capability of all test samples with CT-DNA, BSA, and the SARS-CoV-2 3CL^Pro, which revealed the binding energies were in a range of -8.1 to -8.9, -7.5 to -10.5 and -6.7--8.8 kcal/mol, respectively. The higher reactivity of the complexes than the free ligand is supported by the FMO theory. Among all the observed data for antioxidant properties against DPPH^᛫, ^᛫OH, O₂^-• and NO^᛫ free radicals, complex (1a) had the best biological efficacy. The antimicrobial and cytotoxic characteristics of all test compounds have been studied by screening against certain selected microorganisms as well as against A549, HepG2, MCF-7, and NHDF cell lines, respectively. The observed findings revealed that the activity enhances coordination as compared to free ligand via Overtone's and Tweedy's chelation mechanisms. This is especially encouraging given that in every case, the experimental findings and theoretical detections were in perfect accord.

Spectro-electrochemical, fluorometric and biothermodynamic evaluation of pharmacologically active morpholine scaffold single crystal ligand and its metal(II) complexes: A comparative study on in-vitro and in-silico screening towards DNA/BSA/SARS-CoV-19

A novel series of metal(II) complexes (1-5) [M^II(L)₂]{Where M = Cu (1), Co (2), Mn (3), Ni (4) and Zn (5)} constructed from 2-(4-morpholinobenzylideneamino)phenol Schiff base ligand (HL) in a 1:2 M ratio and the spectral and analytical results put forward square planar geometry. Spectro-electrochemical, hydrodynamic, gel electrophoresis, and DNA binding/cleavage results for all the compounds demonstrate that complex (1) had excellent DNA binding/cleavage properties compared to other compounds. The observation also suggests that test compounds could intercalate with DNA, and the biothermodynamic property more strongly supports the stabilizing of the double helix DNA with the complexes. BSA binding constant results show that complex (1) exposes the best binding property via a static mode, which is further confirmed by FRET calculations. The DFT calculations and docking results for all compounds towards DNA, BSA and SARS-CoV-19 main protease (3CLPro), reveal the binding energies were in the range of -7.8 to -9.4, -6.6 to -10.2 and - 6.1 - -8.2 kcal/mol for all test compounds respectively. In this case, complexes showed favorable binding energies compared to free ligand, which stimulates further studies aimed at validating the predicted activity as well as contributing to tackling the current and future viral pandemics. The in-vitro antioxidant, antimicrobial, and anticancer results for all compounds revealed that copper complex (1) has better activity compared to others. This might result in an effective anticancer drug for future research, which is especially promising since the observed experimental results for all cases were in close agreement with the theoretical calculations.

Schiff-base ligands containing phenanthroline terminals: Synthesis, characterization, biological activities and molecular docking study

Three new phenanthroline-derived ligands were synthesized by the Schiff base condensation method. The first ligand was the result of 1,10-phenanthroline-2-carboxyaldehyde reaction with 1,4-diaminobutane (L1). The other ligands were obtained 1,6-diaminohexane (L2) and 1,8-diaminooctane (L3) with the phenanthroline aldehyde in separate reactions. The structures of all ligands were elucidated using spectral techniques such as FT-IR, ¹³C NMR, ¹H NMR and LC ESI/MS. The geometric properties of ligands such as bond lengths, bond angles, dihedral angles, electronic properties, HOMO and LUMO energies were calculated by using the Gaussian 09w programme. Ligands were optimized with B3LYP and 6-311++G(2d,p) basis set and NMR and FT-IR spectra were calculated. Experimental and theoretical spectrum data were compared. All of the ligands showed antibacterial activity against Staphylococcus aureus ATCC 25923 and Bacillus cereus ATCC 11778. The anticancer activities of the ligands were also determined against human breast cancer (MCF7) and prostate cancer (DU145) cell lines. In addition, which conformation of the ligands was determined by the theoretical calculations. Docking studies of ligands with bovine serum albumin (BSA) were performed using Autock Tools 1.5.6 programme.

Water-soluble nickel (II) Schiff base complexes: Synthesis, structural characterization, DNA binding affinity, DNA cleavage, cytotoxicity, and computational studies

Two water-soluble nickel (II) Schiff base complexes were prepared and their interaction with fish sperm DNA (FS-DNA) was investigated by various methods including UV-vis spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and viscometric measurements. Complex 1: [N,N'-bis{5-[(triphenyl phosphonium chloride)-methyl] salicylidine}-3,4-diaminobenzophenone]nickel(II) perchloride dihydrate: [Ni(5-CH₂PPh₃-3,4-salophen)] (ClO₄)₂.2 H₂O was synthesized as a new complex and characterized by elemental analysis, IR, ¹H NMR, thermal gravimetric analysis (TGA) and UV-vis spectroscopy. Complex 2: sodium [(N,N'-bis(5-sulfosalicyliden)-3, 4-diaminobenzophenone)aqua] nickel(II) hydrate: Na₂[Ni (5-SO₃-3,4-salbenz)(H₂O)]. H₂O was already synthesized by our research team, but in this study, its function as a DNA-binding compound was tested, and compared with the results of complex 1-DNA binding. The calculation of different constants using absorption and emission data, all confirmed the stronger binding ability of complex 1 than complex 2 with DNA. Different thermodynamic parameters showed the interactions between DNA and complexes were the type of hydrophobic interaction for complex 1 and electrostatic interaction for complex 2. Also, the negative values of free energy changes proved a spontaneous DNA binding process. Based on cell toxicity assay against two different cell lines including Jurkat and MCF-7, the effect of complex 1 was comparable to cisplatin, and the toxicity mechanism was further justified by bright field microscopy, flow cytometry, and cleavage of DNA in the presence of H₂O₂. Besides, the docking calculations suggested intercalation after measuring the lowest-energy between the complexes and DNA. For both complexes, all analytical, spectroscopic, and molecular modeling methods supported partial intercalation as the main binding mode between the complexes and DNA.

Synthesis, Identification and Antibacterial Activities of Amino Acid Schiff Base Cu(II) Complexes with Chlorinated Aromatic Moieties

Amino acid Schiff base Cu(II) complexes were synthesized under microwave irradiation using methanol as a solvent, to maximize the best conditions to obtain the attained compounds, containing aromatics possessing no, one or two chlorine atoms. The compounds’ antibacterial activities were tested against Gram-positive and Gram-negative bacteria, and the most active were tested for their antioxidant activities, and as E. coli, in particular, was found to be sensitive to these compounds, their interaction with this bacterium was investigated. It was found that, depending on the amino acid used for the formation of the Schiff base ligand, its LogPo/w mono-chlorinated or bis-chlorinated compounds are the most efficient against the tested bacteria.

Synthesis, Characterization and Biological Activities of New Schiff Base Compound and Its Lanthanide Complexes

The thermal condensation of 3-(2-Furyl)acrolein with 2-Amino-6-ethoxybenzothiazole generated a new Schiff base, (1E,2E)-N-(6-ethoxybenzo[d]thiazol-2-yl)-3-(furan-2-yl)prop-2-en-1-imine (L), with general formula of C16H14N2O2S. Also, a series of lanthanide complexes of gadolinium, samarium, and neodymium (La–Lc) were synthesized utilizing acetonitrile as the solvent and triethylamine as a buffer and catalyst. Based on elemental analysis, mass spectroscopy, and FTIR analysis, all of the Bis-(1E,2E)-N-(6-ethoxybenzo[d]thiazol-2-yl)-3-(furan-2-yl)prop-2-en-1-iminetri-nitratolanthanide(III) complexes with the general formula [LnL2(NO3)3]·H2O are solids with a 2:1 molar ratio (ligand: metal). Based on conductivity estimates, they are nonelectrolytes and monoatomic paramagnetic according to the magnetic moment measurements, and one mole of lattice water was found after thermal gravimetric measurements and FTIR analysis. Therefore, the lanthanide complexes show a ten-coordination structure with a deformed bicapped square antiprismatic. The Schiff base and its complexes were screened for their antimicrobial, antifungal, antioxidant, and antitumor properties. Their antimicrobial and antifungal activities were strong, and they also produced good antioxidant and antitumor effects.

Metal Complexes as DNA Synthesis and/or Repair Inhibitors: Anticancer and Antimicrobial Agents

Medicinal inorganic chemistry involving the utilization of metal-based compounds as therapeutics has become a field showing distinct promise. DNA and RNA are ideal drug targets for therapeutic intervention in the case of various diseases, such as cancer and microbial infection. Metals play a vital role in medicine, with at least 10 metals known to be essential for human life and a further 46 nonessential metals having been involved in drug therapies and diagnosis. These metal-based complexes interact with DNA in various ways, and are often delivered as prodrugs which undergo activation in vivo. Metal complexes cause DNA crosslinking, leading to the inhibition of DNA synthesis and repair. In this review, the various interactions of metal complexes with DNA nucleic acids, as well as the underlying mechanism of action, were highlighted. Furthermore, we also discussed various tools used to investigate the interaction between metal complexes and the DNA. The tools included in vitro techniques such as spectroscopy and electrophoresis, and in silico studies such as protein docking and density-functional theory that are highlighted for preclinical development.

Design, DFT studies, antimicrobial and antioxidant potential of Binuclear N-heterocyclic Carbene (NHCs) complexes, Probing the aspect of DNA interaction through In-vitro and In-silico approach

N-heterocyclic carbene (NHC) adducts have shown remarkable biological potential for numerous medical applications. With an aim to improve biological potential of benzimidazolium salts, newer analogues of benzimidazole and their silver complexes were synthesized and characterized. Synthesized salts (L₁-L₂) and silver complexes (C₁-C₂) were confirmed through elemental analysis, UV-visible spectroscopy, FTIR, ¹H NMR & ¹³C NMR spectroscopy. The compounds C1 & C2 were found stable in solution form for studied time period when examined spectroscopically and showed optimum lipophilicity when measured for their partition coefficient through flask shake method. Synthesized compounds showed good antimicrobial potential against gram positive bacterial strain S. Aureus with IC₅₀ 2.02±0.12 and 2.11±0.13 µM respectively while 2.11±0.1 and 2.28±0.17 µM against gram negative bacterial strain E. Coli for C1 and C2 respectively. The interaction study of the related compounds with DNA was predicted by molecular docking study, which confirmed that the studied compound C1 (-8.04 kcal/mol) has a higher binding energy than compound C2 (-4.23 kcal/mol); Also, the compound C1 exhibits a better affinity against to DNA than Ethidium bromide (-7.68 kcal/mol) and cisplatin (-6.21 kcal/mol).The claim was practically assured through spectroscopic and viscometeric method which confirmed that compounds have good affinity for DNA with binding constant kb, 5.78×10⁴ M^-1 and 6.84×10⁴ M^-1 for C1 and C2 respectively.

Efficient self-assembly of heterometallic triangular necklace with strong antibacterial activity

Sophisticated mechanically interlocked molecules (MIMs) with interesting structures, properties and applications have attracted great interest in the field of supramolecular chemistry. We herein report a highly efficient self-assembly of heterometallic triangular necklace 1 containing Cu and Pt metals with strong antibacterial activity. Single-crystal X-ray analysis shows that the finely arranged triangular necklace 1 has two racemic enantiomers in its solid state with intriguing packing motif. The superior antibacterial activity of necklace 1 against both standard and clinically drug-resistant pathogens implies that the presence of Cu(I) center and platinum(II) significantly enhance the bacterium-binding/damaging activity, which is mainly attributed to the highly positively charged nature, the possible synergistic effect of heterometals in the necklace, and the improved stability in culture media. This work clearly discloses the structure-property relationships that the existence of two different metal centers not only facilitates successful construction of heterometallic triangular necklace but also endows it with superior nuclease properties and antibacterial activities.

Precise assembly of heterometallic complexes is a challenge. Here, the authors design a heterometallic triangular necklace through a highly efficient threading-and-ring-closing approach driven by metal-ligand coordination, which shows strong bacterium-binding and cell wall/plasma membrane-disrupting capacity for killing bacterial cells.

Investi̇gati̇on of pyrazoly derivatives schi̇ff base li̇gands and thei̇r metal complexes used as anti-cancer drug

In this study, six pyrazole derivatives containing hetero atoms have been analyzed using theoretical calculation method. The ligands were tested by HF, B3LYP and M06-2X methods using 3-21G, 6-31G, 6-31G(d, p), and sdd basis sets. The results showed that Ligand 5 has a HOMO value of -7.470 at HF / 6-31g (d.p) level. These ligands were investigated in IR, NMR, and UV-VIS spectrum, then experimental values were compared with IR and NMR spectrum data. The solvents, whose effects were investigated in UV-VIS spectrum, were gas phase (ε = 1), toluene (ε = 2.3741), chloroform (ε = 4.7113), methanol (ε = 32.613), water (ε = 78.3553), and n-methylformamide-mixture (ε = 181.56). Metal complexes of tested ligands were produced with copper, nickel, and zinc. Lastly, the interactions between these six pyrazole derivatives and three proteins, namely 3dju, 2IJN, and 1JNX, were also examined. Biological and anti-cancer properties of six pyrazole derivatives were analyzed by DockingServer. In docking calculations, Estimated Free Energy of Binding value of Ligand 5 was found to be -4.87, -4.82, -1.73 respectively, which indicated the highest biological activity.

Co(ii) and Zn(ii) pyrazolyl-benzimidazole complexes with remarkable antibacterial activity

Three pseudopolymorphs based on a coordination complex of a pyrazolyl-benzimidazole ligand have been synthesized and characterized by single crystal X-diffraction, and showed remarkable antibacterial properties.

Electrochemical behavior, structural, morphological, Calf Thymus-DNA interaction and in-vitro antimicrobial studies of synthesized Schiff base transition metal complexes

New tetradentate Schiff base transition metal complexes have been derived from salicylidene-4-imino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one and histidine were characterized by CHN analysis, magnetic susceptibility measurements, molar conductance, FAB-MS, IR, ¹H-NMR, UV, CV, EPR, Fluorescence emission, AFM and Powder XRD techniques. AFM images and Powder XRD data endure that the complexes are nano-size grains with polycrystalline structure. The spectral evidences showed that all the metal chelates are square planar geometry except [VOL] complex which exist square-pyramidal geometry. Electrochemical data (CV) for [CuL] and [VOL] complexes in acetonitrile solution indicates that the redox potential of metal ions is affected by the coordinated ligand. Electron Spin Resonance (ESR) spectra of [CuL] and [VOL] complexes were well coinciding with proposed geometries and other reported complexes. CT-DNA interaction studies of [CuL] complex reveals that an intercalation binding mode occurs between complex and DNA base pairs. The in vitro antimicrobial activity of complexes has been tested against the growth of some fungal and bacterial species persist that chelates have better control than ligand.