Synthesis, characterization, crystal structure and DNA, HSA-binding studies of four Schiff base complexes derived from salicylaldehyde and isopropylamine

Structural investigations and antibacterial, antifungal and anticancer studies on zinc salicylaldimine complexes

Aim: Zinc salicylaldimines may act as multidrug agents.Results: Three zinc salicylaldimines C1-C3 and respective ligands HL1-HL3 were examined for antimicrobial/anticancer drug action and C3 was structurally analyzed (tetrahedral, triclinic). Against two fungi, C1 inhibited Candida albicans with 12 mm (21 mm for amphotericin B). Among four bacteria, two ligands inhibited Staphylococcus aureus and Escherichia coli (9-10 mm), but the complexes inhibited all bacteria with 10-14 mm (21-26 mm for ampicillin). The half-maximal inhibitory concentrations for the ligands, complexes and doxorubicin were 195.5-310.7, 22.18-70.05 and 9.66 μM against cancerous MCF-7 cells and 186.4-199.9, 14.95-18.87 and 36.42 μM against normal BHK cells.Conclusion: The complexation produced pronounced enhancement in the ligand antimicrobial/anticancer activities, despite these activities are moderate comparing with standards.

In vitro biological activity of cobalt(II) complexes with salicylaldimine ligands in microbial and cancer cells

Background: More studies using cobalt complexes as drugs are needed. Results: The drug action of two cobalt salicylaldimines was determined. The complexes and amphotericin B (20 mg/ml) inhibited Candida albicans at 9-15 and 21 mm. This concentration of both ligands inhibited Staphylococcus aureus at 10 mm and one ligand inhibited Escherichia coli at 9 mm, but the complexes and ampicillin inhibited four bacteria at 9-20 and 21-26 mm. The ligands were inactive against cancer and normal cells, but the complexes and doxorubicin provided IC50 values of 28.18-54.19 and 9.66 μM against MCF-7 cells and 15.76-20.49 and 36.42 μM against BHK cells. Conclusion: The ligands' activity was much improved by complexation, although they remained substandard.

Biological activity of mixed chelate copper(II) complexes, with substituted diimine and tridentate Schiff bases (NNO) and their hydrogenated derivatives as secondary ligands: Casiopeína's fourth generation

We synthesize and characterize nine copper(II) compounds. Four with general formula [Cu(NNO)(NO₃)] and five mixed chelates [Cu(NNO)(N-N)]⁺, where NNO corresponds to asymmetric salen ligands (E)-2-((2-(methylamino)ethylimino)methyl)phenolate (L1) and (E)-3-((2-(methylamino)ethylimino)methyl)naphthalenolate (LN1); and their hydrogenated derivatives 2-((2-(methylamino)ethylamino)methyl)phenolate (LH1) and 3-((2-(methylamino)ethylamino)methyl)naphthalenolate (LNH1); and N-N correspond to 4,4'-dimethyl-2,2'-bipiridyne(dmbpy) or 1,10-phenanthroline (phen). Using EPR, the geometries of the compounds in solution in DMSO were assigned, [Cu(LN1)(NO₃)] and [Cu(LNH1)(NO₃)] a square-planar, [Cu(L1)(NO₃)], [Cu(LH1)(NO₃)], [Cu(L1)(dmby)]⁺ and [Cu(LH1)(dmby)]⁺ a square-based pyramid; and [Cu(LN1)(dmby)]⁺, [Cu(LNH1)(dmby)]⁺ and [Cu(L1)(phen)]⁺ and elongated octahedral. By X-ray it was observed that [Cu(L1)(dmby)]⁺ and. [Cu(LN1)(dmby)]⁺ presented a square-based pyramidal, and [Cu(LN1)(NO₃)]⁺ a square-planar geometry. The electrochemical study showed that copper reduction process is a quasi-reversible system, where the complexes with hydrogenated ligands were less oxidizing. The cytotoxicity of the complexes was tested by MTT assay, all the compounds showed biological activity in HeLa cell line, the mixed compounds were the more active ones. Naphthalene moiety, imine hydrogenation and aromatic diimine coordination, increased biological activity. A structure-activity relationships were found: Log(IC₅₀) =  - 1.01(E_pc) - 0.35(Conjugated Rings) + 0.87, for Schiff base complexes and Log(IC₅₀) = 0.078(E_pc) - 0.32(Conjugated Rings) + 1.94, for hydrogenated complexes; the less oxidizing species with a great number of conjugated rings presented the best biological activity. Complexes-DNA binding constants were obtained by uv-vis studies using CT-DNA, the results suggested that the complexes can interact through the grooves, except the phenanthroline mixed complex that intercalate with DNA. Gel electrophoresis study with pBR 322 showed that compounds can produce changes in the form of DNA and some complexes can cleave DNA in the presence of H₂O₂.

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, Spectroscopic, Structural and Molecular Docking Studies of Some New Nano-Sized Ferrocene-Based Imine Chelates as Antimicrobial and Anticancer Agents

The newly synthesized organometallic acetyl ferrocene imine ligand (HL) was obtained by the direct combination of 2-acetyl ferrocene with 2-aminothiophenol. The electronic and molecular structure of acetyl ferrocene imine ligand (HL) was refined theoretically and the chemical quantum factors were computed. Complexes of the acetyl ferrocene imine ligand with metal(II)/(III) ions (Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)) were fabricated. They were inspected by thermal (DTG/TG), spectroscopic techniques (FT-IR, 1H NMR, mass, UV-Vis), molar conductivity, and CHNClM to explicate their structures. Studies using scanning electron microscope (SEM) were conducted on the free acetyl ferrocene imine ligand and its Cd(II) chelate to confirm their nano-structure. To collect an idea about the effect of metal ions on anti-pathogenic properties upon chelation, the newly synthesized acetyl ferrocene imine ligand and some of its metal chelates were tested against a variety of microorganisms, including Bacillus subtilis, Staphylococcus aureus, Salmonella typhimurium, Escherichia coli, Aspergillus fumigatus, and Candida albicans. The ligand and its metal chelate were tested for cytotoxic activity in human cancer (MCF-7 cell viability) and human melanocyte cell line HBF4. It was discovered that the Cd(II) chelate had the lowest IC50 of the three and thus had the prior activity. Molecular docking was utilized to investigate the interaction of acetyl ferrocene imine ligand (HL) with the receptors of the vascular endothelial growth factor receptor VEGFR (PDB ID: 1Y6a), human Topo IIA-bound G-segment DNA crystal structure (PDB ID: 2RGR), and Escherichia coli crystal structure (PDB ID: 3T88).

Synthesis, structural studies, interaction with DNA/HSA and antitumor evaluation of new Cu(ii) complexes containing 2-(1H-imidazol-2-yl)pyridine and amino acids

New Cu(ii) complexes with promising anticancer activity induce apoptosis in HepG2 cells through DNA damage and cytotoxic ROS-mediated mitochondrial dysfunction pathways.

Copper(ii) complexes with tridentate halogen-substituted Schiff base ligands: synthesis, crystal structures and investigating the effect of halogenation, leaving groups and ligand flexibility on antiproliferative activities

To investigate the effect of different halogen substituents and leaving groups and the flexibility of ligands on the anticancer activity of copper complexes, sixteen copper(ii) complexes with eight different tridentate Schiff-base ligands containing pyridine and 3,5-halogen-substituted phenol moieties were synthesized and characterized by spectroscopic methods. Four of these complexes were also characterized by X-ray crystallography. The cytotoxicity of the complexes was determined in three different tumor cell lines (i.e. the A2780 ovarian, HCT116 colorectal and MCF7 breast cancer cell line) and in a normal primary fibroblast cell line. Complexes were demonstrated to induce a higher loss of cell viability in the ovarian carcinoma cell line (A2780) with respect to the other two tumor cell lines, and therefore the biological mechanisms underlying this loss of viability were further investigated. Complexes with ligand L₁ (containing a 2-pycolylamine-type motif) were more cytotoxic than complexes with L₂ (containing a 2-(2-pyridyl)ethylamine-type motif). The loss of cell viability in A2780 tumor cells was observed in the order Cu(Cl₂-L₁)NO₃ > Cu(Cl₂-L₁)Cl > Cu(Br₂-L₁)Cl > Cu(BrCl-L₁)Cl. All complexes were able to induce reactive oxygen species (ROS) that could be related to the loss of cell viability. Complexes Cu(BrCl-L₁)Cl and Cu(Cl₂-L₁)NO₃ were able to promote A2780 cell apoptosis and autophagy and for complex Cu(BrCl-L₁)Cl the increase in apoptosis was due to the intrinsic pathway. Cu(Cl₂-L₁)Cl and Cu(Br₂-L₁)Cl complexes lead to cellular detachment allowing to correlate with the results of loss of cell viability. Despite the ability of the Cu(BrCl-L₁)Cl complex to induce programmed cell death in A2780 cells, its therapeutic window turned out to be low making the Cu(Cl₂-L₁)NO₃ complex the most promising candidate for additional biological applications.

Developing novel zinc(ii) and copper(ii) Schiff base complexes: combined experimental and theoretical investigation on their DNA/protein binding efficacy and anticancer activity

Zn(ii) and Cu(ii) Schiff base complexes having DNA and HSA binding efficacy have been exploited as cancer therapeutic agents.

Highly functionalized piperidines: Free radical scavenging, anticancer activity, DNA interaction and correlation with biological activity

Twenty-five piperidines were studied as potential radical scavengers and antitumor agents. Quantitative interaction of compounds with ctDNA using spectroscopic techniques was also evaluated. Our results demonstrate that the evaluated piperidines possesses different abilities to scavenge the radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) and the anion radical superoxide (^•O₂⁻). The piperidine 19 was the most potent radical DPPH scavenger, while the most effective to ^•O₂⁻ scavenger was piperidine 10. In general, U251, MCF7, NCI/ADR-RES, NCI-H460 and HT29 cells were least sensitive to the tested compounds and all compounds were considerably more toxic to the studied cancer cell lines than to the normal cell line HaCaT. The binding mode of the compounds and ctDNA was preferably via intercalation. In addition, these results were confirmed based on theoretical studies. Finally, a linear and exponential correlation between interaction constant (K_b) and GI₅₀ for several human cancer cell was observed.