Synthesis, characterization and comparative biological activity of a novel set of Cu(II) complexes containing azole-based ligand frames

The synthesis and spectroscopic characterization of three complexes containing a substituted 2-(2-pyridyl)benzothiazole (PyBTh) group in the ligand frame are reported along with the comparative biological activity. The ligands have been substituted at the 6-position with either a methoxy (Py(OMe)BTh) or a methyl group (Py(Me)BTh). Reaction of Py(OMe)BTh with either CuCl2 or Cu(NO3)2·2.5 H2O yielded the monomeric [Cu(Py(OMe)BTh))2(NO3)]NO3·1.5 MeOH, (1·1.5 MeOH) complex or the dimeric [Cu(Py(OMe)BTh)Cl2]2 (2), respectively, with the nuclearity of the complex dependent on the starting Cu(II) salt. Reaction between the methyl substituted ligand and Cu(NO3)2·2.5 H2O resulted in the isolation of Cu(Py(Me)BTh)(NO3)2·0.5 THF (3·0.5 THF). Complexes 1-3 were fully characterized. Cyclic voltammetry measurements were performed on all three complexes as well as on [Cu(PyBTh)2(H2O)](BF4)2 (4), a compound previously reported by us which contains the unsubstituted 2-(2-pyridyl)benzothiazole ligand. The biological activity was studied and included concentration dependent DNA binding and cleavage, antibacterial activity, and cancer cell toxicity. All complexes exhibited DNA cleavage activity, however 2 and 4 were found to be the most potent. Mechanistic studies revealed that the nuclease activity is dependent on an oxidative mechanism reliant principally on O2-. Antibacterial studies revealed complex 4 was more potent compared to 1-3. Cancer cell toxicity studies were carried out on HeLa, PC-3, and MCF7 cells with 1-4, Cu(QBTh)(NO3)2(H2O) and Cu(PyBIm)3(BF4)2. The differences in the observed toxicities suggests the importance of the ligand and its substituents in modulating cell death.

Azaneylylidene-based tetradentate Schiff base as a new "ON-OFF" fluorescent probe for the detection of Cu(II) ion: Synthesis, characterization and real sample analysis

Herein we describe the synthesis of Cu²⁺ sensor, 2,2'-((1E,1'E)-((4-chloro-1,2-phenylene)bis(azaneylylidene))bis(methane-ylylidene))bis(4-bromophenol) (CPMB) and characterization using various spectral and analytical techniques. CPMB exhibited high selectivity towards Cu²⁺ ions via fluorescence quenching mechanism, which combined the character of high selectivity towards Cu²⁺ assay even in the presence of other common metal ions such as Cu²⁺, Al³⁺, Co²⁺, Ni²⁺, Mn²⁺, Zn²⁺ Pb²⁺ Cd²⁺, Fe²⁺, Hg²⁺, Mg²⁺ and Fe³⁺ (30 μM) ethanol-water (1:9 v/v) system. Upon the addition of the solution of Cu²⁺ ions to CPMB, the complexation of Cu²⁺ with CPMB leads to the immediate formation of light green color, indicating that CPMB can act as simple colorimetric sensor, particularly for Cu²⁺ in the presence of most interfering metal ions in ethanol-water medium. More interestingly, the ability of sensing behavior of CPMB for Cu²⁺ ion in the real water samples (tap water and lake water samples) was also investigated. Further, Job's plot confirmed that the complexation occurred in 1:1 ratio (ligand:metal). Furthermore, the fluorescence inhibiting factor showed a good linear relationship with the concentration of Cu²⁺ with detection limit of 0.302 μM. The electronic transitions of the complex in ethanol were studied using DFT calculations.

R. B, M. M, Iqbal M, Shivamallu C, Amachawadi RG, Kollur SP. Highly selective and sensitive fluorescent “TURN-ON” furan-based Schiff base for zinc(ii) ion probing: chemical synthesis, DFT studies, and X-ray crystal structure

A simple and efficient fluorescent probe (E)-4-bromo-2-((((5-methylfuran-2-yl)methyl)imino)methyl)phenol (BFMP) for the detection of Zn2+ ions was synthesized by the condensation of 5-methyl-furfurylamine and 5-bromosalicylaldehyde.

Green synthesis of silver nanoparticles using pollen extract: Characterization, assessment of their electrochemical and antioxidant activities

In the present study, a simple, cheaply and environmental friendly method was evaluated for the synthesis of silver nanoparticle via Cupressus sempervirens L. (CSPE) pollen extract as reducing and stabilizing agent. Various parameters such as volume of CSPE, temperature and reaction time on AgNPs formation were investigated spectrophotometrically to optimize reaction conditions. The electrochemical behavior of the biosynthesized AgNPs were investigated by cyclic voltammetry and square wave voltammetry techniques. An electrosensor based on AgNPs modified glassy carbon electrode were constructed and tested on electro reduction of hydrogen peroxide in phosphate buffer medium. The prepared electrosensor could detect the H₂O₂ in the range of 5.0 μM - 2.5 mM with a detection limit of 0.23 μM. In addition, the antioxidant activity of biosynthesized AgNPs were evaluated against DPPH free radical. Results obtained from the antioxidant study suggested that CSPE mediated AgNPs exhibit a good antioxidant effect.

DNA binding, antibacterial, hemolytic and anticancer studies of some fluorescent emissive surfactant-ruthenium(II) complexes

Designing the effective metallodrugs with amphiphilic nature is an active approach for the biomedical applications such as chemotheraphy, bioimaging, drug carrier, etc. To elaborate this, some fluorescent emissive surfactant-ruthenium(II) complexes and its precursor ruthenium(II) complexes have been interacted with calf thymus DNA (CT-DNA) for understanding the biophysical impacts of head and tail parts of the metallosurfactants. Here, DNA binding studies were examined by UV-visible absorption, fluorescence, circular dichroism and viscosity measurements. The obtained results showed that surfactant-ruthenium(II) complexes effectively bind with CT-DNA through hydrophobic interactions dominated moderate intercalation, whereas precursor ruthenium(II) complexes interact CT-DNA through electrostatic interactions dominated moderate intercalation. Also, increase of hydrophobic alkyl amine chain length as well as size of the head group in surfactant-ruthenium(II) complexes increased the binding affinity with CT-DNA, in which tail group played a dominant role. Further investigations of antibacterial, hemolytic and anticancer activities showed that desired biological activities could be obtained by tuning the head and tail groups of the metallodrugs in near future.Communicated by Ramaswamy H. Sarma.

Synthesis and Characterization of Oxidovanadium(IV) Complexes of 2-((E)-(6-Fluorobenzo[d]thiazol-2-ylimino)methyl)-6-methoxyphenol and Their Antimicrobial, Antioxidant, and DNA-Binding Studies

Two novel oxidovanadium(IV) complexes with a new bidentate (O- and N-) imine-based ligand 2-((E)-(6-fluorobenzo[d]thiazol-2-ylimino)methyl)-6-methoxyphenol (HL) were synthesized under in situ experimental condition where VOSO₄ acts as a kinetic template in the ratio 2 : 1 (L : M) and mixed ligand complex using 1,10-phenanthroline (phen) in 1 : 1 : 1 (L : M : phen) ratio. The synthesized compounds were structurally characterized by microanalysis, magnetic susceptibility, FTIR, electronic spectra, TG/DTA, ESR, and molar conductance studies. Based on the spectral studies, the complexes have the general composition [VO(L)₂] (C ₁ ) and [VO(L)phen] (C ₂ ) in a square pyramid geometrical fashion. The synthesized compounds were primarily screened for their in vitro growth inhibiting activity against different strains of bacteria, namely, E. coli, B. subtilis, S. aureus, and P. aeruginosa by the disc diffusion method. Also, the antifungal activity was determined against C. albicans and A. niger by the Bateman poisoned technique. The in vitro antioxidant activity of all the compounds was determined by DPPH free radical-scavenging assay. Intercalative mode of DNA-binding properties of the oxidovanadium(IV) complexes with calf-thymus DNA (CT-DNA) was investigated using UV, fluorescence spectra, and viscosity measurements.

Magnesium Oxide Nanoparticles: Effective Agricultural Antibacterial Agent Against Ralstonia solanacearum

Magnesium (Mg) is an essential mineral element for plants and is nontoxic to organisms. In this study, we took advantage of nanotechnologies to systematically investigate the antibacterial mechanisms of magnesium oxide nanoparticles (MgONPs) against the phytopathogen Ralstonia solanacearum (R. solanacearum) in vitro and in vivo for the first time. R. solanacearum has contributed to catastrophic bacterial wilt, which has resulted in the world-wide reduction of tobacco production. The results demonstrated that MgONPs possessed statistically significant concentration-dependent antibacterial activity, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were measured as 200 and 250 μg/mL, respectively. Additional studies, aimed at understanding the toxicity mechanism of MgONPs, indicated that physical injury occurred to the cell membranes, along with decreased motility and biofilm formation ability of R. solanacearum, due to the direct attachment of MgONPs to the surfaces of the bacterial cells, which was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Reactive oxygen species (ROS) accumulation could also be an important reason for the antibacterial action, inducing DNA damage. The toxicity assessment assay under greenhouse conditions demonstrated that the MgONPs had exerted a large effect on tobacco bacterial wilt, reducing the bacterial wilt index. Altogether, the results suggest that the development of MgONPs as alternative antibacterial agents will become a new research subject.

Synthesis and Characterization of Cobalt(III) and Copper(II) Complexes of 2-((E)-(6-Fluorobenzo[d]thiazol-2-ylimino) methyl)-4-chlorophenol: DNA Binding and Nuclease Studies—SOD and Antimicrobial Activities

A bidentate (N- and O-) imine-based ligand (L1) and its metal complexes of types [CuII(L1)2] (C1), [CuII(L1)(Phen)] (C2), [CoIII(L1)2] (C3), and [CoIII(L1)(Phen)] (C4) (L1 = 2-((E)-(6-fluorobenzo[d]thiazol-2-ylimino)methyl)-4-chlorophenol and phen = 1,10-phenanthroline) were synthesized as potential chemotherapeutic drug candidates. The prepared complexes were structurally characterized by spectral techniques (NMR, FT-IR, LC-MS, EPR, and electronic absorption), thermogravimetric analysis (TGA/DTA), magnetic moment, and CHNO elemental analysis. Spectroscopic studies suggested the distorted octahedral structure for all complexes. In vitro bioassay studies include binding and nuclease activities of the ligand and its complexes with target calf thymus- (CT-) DNA were carried out by employing UV-Vis, fluorescence spectroscopy, viscosity, and gel electrophoresis techniques. The extent of binding propensity was determined quantitatively by Kb and Ksv values which revealed a higher binding affinity for C2 and C4 as compared to C1 and C3. In addition, the scavenging superoxide anion free radical (O∙-2) activity of metal complexes was determined by nitroblue tetrazolium (NBT) light reduction assay. Molecular docking studies with DNA and SOD enzyme were also carried out on these compounds. The antimicrobial study has shown that all the compounds are potential antibacterial agents against Gram-negative bacterial strains and better antifungal agents with respect to standard drugs used.

Synthesis, characterization, X-ray crystal structure, DFT calculation, DNA binding, and antimicrobial assays of two new mixed-ligand copper(II) complexes

Two new Cu(II) complexes, [Cu(L)(phen)] (1), [Cu(L)(bipy)] (2), where L(2-)=(3-methoxy-2oxidobenzylidene)benzohydrazidato, phen=1,10 phenanthroline, and bipy=2,2' bipyridine, were prepared and fully characterized using elemental analyses, FT-IR, molar conductivity, and electronic spectra. The structures of both complexes were also determined by X-ray diffraction. It was found that, both complexes possessed square pyramidal coordination environment in which, Cu(II) ions were coordinated by donor atoms of HL and two nitrogens of heterocyclic bases. Computational studies were performed using DFT calculations at B3LYP/6-311+G(d,p) level of theory. DNA binding activities of these complexes were also investigated using electronic absorption, competitive fluorescence titration and cyclic voltammetry studies. The obtained results indicated that binding of the complexes to DNA was of intercalative mode. Furthermore, antimicrobial activities of these compounds were screened against microorganisms.

Mononuclear Cu(ii) and Zn(ii) complexes with a simple diamine ligand: synthesis, structure, phosphodiester binding and DNA cleavage studies

Mononuclear Cu(ii) and Zn(ii) complexes with simple 1,2-diaminocylohexane were synthesized. They interact with phosphodiesters and CT-DNA. Cu(ii) complex with ascorbate efficiently cleaves supercoiled DNA up to Form III at 25 µM under oxidative pathway.

Interaction of drug based copper(II) complexes with Herring Sperm DNA and their biological activities

Square pyramidal Cu(II) complexes with NS donor ligand and ciprofloxacin have been synthesized and characterized using analytical and spectral techniques. The synthesized complexes have been tested for their antimicrobial activity using double dilution technique in terms of minimum inhibitory concentration (MIC) and colony forming unit (CFU). The DNA binding ability of the complexes with Sperm Herring DNA has been performed using absorption titration and viscosity measurement. The nuclease activity of complexes with plasmid DNA (pUC19) has been carried out using agarose gel electrophoresis technique. Synthesized complexes have been tested for their SOD mimic activity using NBT/NADH/PMS system. The cytotoxic properties of metal complexes have been evaluated using brine shrimp lethality bioassay.