Synthesis, characterization and in vitro DNA binding studies of a new copper(II) complex containing antioxidant ferulic acid

Antioxidant activity of an Mg(II) compound containing ferulic acid as a chelator: potential application for active packaging and riboflavin stabilisation

Foods rich in riboflavin (Rf) are susceptible to degradation due to oxidative processes with the formation of radicals. Herein, we describe the features and stability of an Mg(II) complex containing ferulic acid (fer) and 1,10-phenanthroline (phen) as chelators: henceforth called Mg(phen)(fer). The electrochemical behavior of Mg(phen)(fer) is pH dependent and results from the stabilisation of the corresponding phenoxyl radical via complexation with Mg(II). This stabilisation enhances the antioxidant activity of Mg(phen)(fer) with respect to free fer and commercial antioxidants. Mg(phen)(fer) scavenges and neutralizes DPPH˙ (IC50 = 15.6 μmol L-1), ABTS˙+ (IC50 = 5.65 μmol L-1), peroxyl radical (IC50 = 5.64 μg L-1) and 1O2 (IC50 = 0.7 μg m-1). Mg(phen)(fer) effectively protects riboflavin (Rf) against photodegradation by quenching the singlet excited states of Rf regardless of the conditions. Also, the complex Mg(phen)(fer) was effectively incorporated into starch films, broadening its applications, as shown by microbiological studies. Thus, Mg(phen)(fer) has high potential for use in Rf-rich foods and to become a new alternative to the synthetic antioxidants currently used.

Interaction studies of water-soluble Zn(II) complex with calf thymus DNA using biophysical and molecular docking methods"

The binding between a fluorescent water-soluble Zn(II) complex of {2-[N-(2-hydroxyethylammonioethyl) imino methyl] phenol} and calf thymus DNA (ct-DNA) was investigated using spectroscopic techniques. The complex was prepared and identified by FT-IR, and 1H NMR spectroscopies. The significant changes in the absorption and the circular dichroism spectra of ct-DNA in the presence of the Zn(II) complex implied the interaction between the Zn(II) complex and ct-DNA. Upon addition of ct-DNA, the fluorescence emission intensity of the Zn(II) complex was increased and indicated the interaction between the Zn(II) complex and ct-DNA was occurred. The binding constant values (Kb) resulted from fluorescence spectra clearly showed the Zn(II) complex affinity to ct-DNA. The fluorescence studies also approved the static enhancement mechanism in the Zn(II) complex-DNA complexation process. The thermodynamic profile exhibited the exothermic and spontaneous formation of ct-DNA-Zn(II) complex system via hydrogen bonds and van der Waals forces. The competitive fluorescence investigation by methylene blue (MB), and Hoechst 33258 demonstrated that the Zn(II) complex could replace the DNA-bound Hoechst and bind to the minor groove binding site in ct-DNA. The viscosity changes were negligible, representing the Zn(II) complex binding to DNA via the groove binding mode. Molecular docking simulation affirmed that the Zn(II) complex is located in the minor groove of ct-DNA near the DG12, DA17, DA18, and DG16 nucleobases.

Experimental and Molecular Docking Studies on the Interaction of a Water-Soluble Pd(II) Complex Containing β-Amino Alcohol with Calf Thymus DNA

The interaction of water-soluble and fluorescent [Pd (HEAC) Cl₂] complex, in which HEAC is 2-((2-((2-hydroxyethyl)amino)ethyl)amino) cyclohexanol, with calf thymus DNA (ct-DNA) has been studied. This study was performed using electronic absorption and fluorescence emission spectroscopies, cyclic voltammetry and circular dichroism analyses, dynamic viscosity measurements, and molecular docking theory. From hypochromic effect observed in ct-DNA absorption spectra, it was found that the Pd(II) complex could form a conjugate with ct-DNA strands through the groove binding mode. The K_b values obtained from fluorescence measurements clearly assert the Pd(II) complex affinity to ct-DNA. The fluorescence quenching of the DNA-Hoechst compound following the successive additions of the Pd(II) complex to the solution revealed that the Pd(II) complex is located in the ct-DNA grooves, and Hoechst molecules have been released into solution; moreover, the resulting measurements from relative viscosity authenticate the Pd(II) complex binding to the grooves. Negative quantities of thermodynamic parameters imply that the Pd(II) complex binds to ct-DNA mainly by the hydrogen bonds and van der Waals forces; also, the Gibbs-free energy changes show the exothermic and spontaneous formation of the Pd(II) complex-DNA system. The electrochemical behavior of the Pd(II) complex in the attendance of ct-DNA was investigated using the cyclic voltammetry method (CV). Several quasi-reversible redox waves were observed along with increasing the anodic/cathodic peak currents, as well as a shift in anodic/cathodic peak potentials. Circular dichroism (CD) observations suggested that the Pd(II)-DNA interaction could alter ct-DNA conformation. The results of molecular modeling confirmed that groove mechanism is followed by the Pd(II) complex to interact with ct-DNA.

Synthesis, spectroscopic and biological activity evaluation of Ni(II), Cu(II) and Zn(II) complexes of schiff base derived from pyridoxal and 4-fluorobenzohydrazide

A novel Schiff base ligand, 4-fluoro-N-((3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl)methylene)benzohydrazide (PLFBH) was synthesized by condensationof pyridoxal and 4-fluorobenzohydrazide. Its complexes with Ni(II), Cu(II), and Zn(II) metal ionswere prepared and characterized by spectroscopic IR, ¹H-NMR, UV, LC-MS, ESR, and powder XRD studies and by elemental analysis and thermal analysis, molar conductance, and magnetic susceptibility measurements. The results indicate the geometry of the complexes to be hexa coordinate distorted octahedral. Based on the electronic absorption and fluorescence emission spectra and viscosity studies, an intercalative mode of binding of the complexes with CT-DNA was suggested, which was also supported by DNA docking studies. The docking studies of metal complexes with DNA were carried out using Autodock 4.2. The in vitro anticancer assay for the Cu(II)-PLFBH complex was performed to assess the ability of the complex to inhibit human cell proliferation on HeLa human cervical carcinoma cells, MCF-7 human breast carcinoma cells, and A549 human lung carcinoma cells. The Cu(II)-PLFBH complex exhibited moderate to good inhibitory effect on the cancer cell lines studied. The complexes showed good cleavageability toward plasmid pBR322 DNA. The metal complexes were found to show good antibacterial activity against gram positive bacteria, Staphylococcus aureus and Bacillus cereus and gram negative bacteria Escherichia coli and Pseudomonas aeruginosa cultures,while the ligand showed marginal activity.Supplemental data for this article is available online at https://doi.org/10.1080/15257770.2021.1961271 .