Synthesis and electronic structure of novel Schiff bases Ni/Cu (II) complexes: Evaluation of DNA/serum protein binding by spectroscopic studies

Building Porous Ni(Salen)-Based Catalysts from Waste Styrofoam via Autocatalytic Coupling Chemistry for Heterogeneous Oxidation with Molecular Oxygen

The development of robust and industrially viable catalysts from plastic waste is of great significance, and the facile construction of high performance heterogeneous catalyst systems for phenol-quinone conversions remains a grand challenge. Herein, a feasible strategy is demonstrated to reclaim Styrofoam into hierarchically porous nickel-salen-loaded hypercrosslinked polystyrene (PS@Ni-salen) catalysts with high activities through an unusual autocatalytic coupling route. The salen is immobilized onto PS chain by Friedel-Crafts alkylation of benzyl chloride derivatives, and the generated hydrogen chloride coordinately promotes the simultaneous crosslinking and bridge formation between aromatic rings via a Scholl coupling route, leading to hierarchically porous networks. After the metallization with Ni, the resultant networks exhibit high catalytic activity for the oxidation of 2,3,6-trimethylphenol to 2,3,5-trimethyl-1,4-benzoquinone under mild conditions (303 K, 1 bar of O2 ). This catalyst also demonstrates attractive recycling performance without an obvious loss of catalytic efficiency over five consecutive cycles. This methodology might provide a potential sustainable alternative to construct environmentally benign and cost-effective catalysts for specific organic transformation.

Synthesis, DNA/BSA binding studies and in vitro biological assay of nickel(II) complexes incorporating tridentate aroylhydrazone and triphenylphosphine ligands

Two new nickel (II) triphenylphosphine complexes derived from tridentate aroylhydrazone ligands [H2L1 = 2-hydroxy-3-methoxybenzylidene)benzohydrazone and H2L2 = N'-(2-hydroxy-3-methoxybenzylidene)-2-hydroxybenzoylhydrazone] and triphenylphosphine were prepared and their molecular structures were determined by single crystal X-ray diffraction analysis. Both nickel(II) complexes showed slightly distorted square planar geometry with one tridentate aroylhydrazone ligand coordinated through ONO donor atoms and one triphenylphosphine ligand coordinated to the nickel center through the phosphorus atom. DNA interaction studies indicated that both complexes possessed higher affinity to herring sperm DNA (HS-DNA) than the corresponding free aroylhydrazone ligand. Molecular docking investigations showed that both complexes could bind to DNA through intercalation of the phenyl rings between adjacent base pairs in the double helix. Meanwhile, bovine serum albumin (BSA) binding studies revealed the complexes could effectively interact with BSA and change the secondary structure of BSA. Further pharmacological evaluations of the synthesized complexes by in vitro antioxidant assays demonstrated high antioxidant activity against NO· and O2˙- radicals. The anticancer activity of each complex was assessed through in vitro cytotoxicity assays (CCK-8 kit) toward A549 and MCF-7 cancer cell and normal L-02 cell lines. Significantly, the Ni(II) complex derived from H2L1 ligand was found to be more effective cytotoxic toward MCF-7cancerous cell with the IC50 value equaled 9.7 μM, which showed potent cytotoxic activity over standard drug cisplatin. AbbreviationsA549human lung carcinoma cellBSAbovine serum albuminCCK-8Cell Counting Kit-8DFTdensity functional theoryDNAdeoxyribonucleic acidDPPH˙2,2-diphenyl-1-picrylhydrazylH2L12-hydroxy-3-methoxybenzylidene)benzohydrazone N'-(2-hydroxy-3-methoxybenzylidene)-2-hydroxybenzoylhydrazoneH2L2N'-(2-hydroxy-3-methoxybenzylidene)-2-hydroxybenzoylhydrazoneHOMOhighest occupied molecular orbitalIC50the 50% activityL-02human normal liver cellLOMOlowest unoccupied molecular orbital (LUMO)MCF-7human breast carcinoma cellNO˙nitric oxideO2˙-superoxide anionSODsuperoxide dismutaseCommunicated by Ramaswamy H. Sarma.

Molecular docking, QSAR properties and DNA/BSA binding, anti-proliferative studies of 6-methoxy benzothiozole imine base and its metal complexes

The molecular and QSAR (Quantitative Structure-Activity Relationship) properties of title compound 2-((6-Methoxybenzo[d]thiazol-2-ylimino)methyl)-6-ethoxyphenol (HL) were evaluated employing HyperChem 7.5 tools. The interaction of the 1a-1e complexes of HL with calf thymus DNA (CT-DNA) was investigated by absorption titrations, Fluorescence quenching and viscosity measurements. The experimental data suggest that these complexes bind to CT-DNA through an intercalative mode, wherein DNA-binding affinity of 1e is found to be greater compared to other complexes. The tryptophan emission-quenching with bovine serum albumin (BSA) experiment revealed stronger binding of 1e than other complexes in the hydrophobic region of protein. The photocleavage of plasmid pBR322 DNA investigated in the presence of the title complexes inferred conversion of supercoiled form of DNA plasmid to circular nicked form. Free-radical scavenging activity studies of HL and its metal complexes determined by their interaction with the stable free-radical DPPH have shown promising antioxidant property. Further cytotoxicity studies with HeLa and MCF-7 cell lines indicated that the compounds can efficiently inhibit the cell proliferation in a dose dependent manner. The DAPI staining assay studies revealed the higher potency of 1e to induce apoptosis. AbbreviationsBSABovine serum albumin proteinCT-DNACalf thymus DNADMSODimethyl sulfoxideDAPI4',-6-Diamidino-2-phenylindole dihydrochlorideESI-MSElectrospray ionization mass spectrometryIC₅₀Half-maximal inhibitory concentrationMBTYE2-((6-methoxybenzo[d]thiazol-2-ylimino) methyl)-6-ethoxyphenolMTT3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromidePBSPhosphate-buffered salineTrisTris(hydroxymethyl)aminomethaneCommunicated by Ramaswamy H. Sarma.

Bioactive Heterometallic CuII-ZnII Complexes with Potential Biomedical Applications

A series of multinuclear heterometallic Cu-Zn complexes of molecular formula [(CuL)₂Zn(dca)₂] (1), [(CuL)₂Zn(NO₃)₂] (2), [(CuL)₂Zn₂(Cl)₄] (3), and [(CuL)₂Zn₂(NO₂)₄] (4) have been synthesized by reacting [CuL] as a "metalloligand (ML)" (where HL = N,N'-bis(5-chloro-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine) and by varying the anions or coligands using the same molar ratios of the reactants. All of the four products including the ML have been characterized by infrared and UV-vis spectroscopies and elemental and single-crystal X-ray diffraction analyses. By varying the anions, different structures and topologies are obtained which we have tried to rationalize by means of thorough density functional theory calculations. All of the complexes (1-4) have now been applied for several biological investigations to verify their therapeutic worth. First, their cytotoxicity properties were assessed against HeLa human cervical carcinoma along with the determination of IC₅₀ values. The study was extended with extensive DNA and protein binding experiments followed by detailed fluorescence quenching study with suitable reagents to comprehend the mechanistic pathway. From all of these biological studies, it has been found that all of these heterometallic complexes show more than a few fold improvement of their therapeutic values as compared to the similar homometallic ones probably because of the simultaneous synergic effect of copper and zinc. Among all of the four heterometallic complexes, complex 3 exhibits highest binding constants and IC₅₀ values suggest for their better interaction toward the biological targets and hence have better clinical importance.

Evaluation of anthocyanins in Aronia melanocarpa/BSA binding by spectroscopic studies

The interaction between Anthocyanins in Aronia melanocarpa (AMA) and bovine serum albumin (BSA) were studied in this paper by multispectral technology, such as fluorescence quenching titration, circular dichroism (CD) spectroscopy and Fourier transform infrared spectroscopy (FTIR). The results of the fluorescence titration revealed that AMA could strongly quench the intrinsic fluorescence of BSA by static quenching. The apparent binding constants K_SV and number of binding sites n of AMA with BSA were obtained by fluorescence quenching method. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS), were calculated to be 18.45 kJ mol⁻¹ > 0 and 149.72 J mol⁻¹ K⁻¹ > 0, respectively, which indicated that the interaction of AMA with BSA was driven mainly by hydrophobic forces. The binding process was a spontaneous process of Gibbs free energy change. Based on Förster’s non-radiative energy transfer theory, the distance r between the donor (BSA) and the receptor (AMA) was calculated to be 3.88 nm. Their conformations were analyzed using infrared spectroscopy and CD. The results of multispectral technology showed that the binding of AMA to BSA induced the conformational change of BSA.