Synthesis, characterization and demonstration of superoxide dismutase-like activity of copper(II) chloride, bromide, nitrate, thiocyanate, sulphate, and perchlorate complexes with 2-methyl-amino pyridine

Investigation of singlet oxygen and superoxide radical produced from vortex-based hydrodynamic cavitation: Mechanism and its relation to cavitation intensity

Presently, the hydroxyl radical oxidation mechanism is widely acknowledged for the degradation of organic pollutants based on hydrodynamic cavitation technology. The presence and production mechanism of other potential reactive oxygen species (ROS) in the cavitation systems are still unclear. In this paper, singlet oxygen (1O2) and superoxide radical (·O2-) were selected as the target ROS, and their generation rules and mechanism in vortex-based hydrodynamic cavitation (VBHC) were analyzed. Computational fluid dynamics (CFD) were used to simulate and analyze the intensity characteristics of VBHC, and the relationship between the generation of ROS and cavitation intensity was thoroughly revealed. The results show that the operating conditions of the device have a significant and complicated influence on the generation of 1O2 and ·O2-. When the inlet pressure reaches to 4.5 bar, it is more favorable for the generation of 1O2 and ·O2- comparing with those lower pressure. However, higher temperature (45 °C) and aeration rate (15 (L/min)/L) do not always have positive effect on the 1O2 and ·O2- productions, and their optimal parameters need to be analyzed in combination with the inlet pressure. Through quenching experiments, it is found that 1O2 is completely transformed from ·O2-, and ·O2- comes from the transformation of hydroxyl radicals and dissolved oxygen. Higher cavitation intensity is captured and shown more disperse in the vortex cavitation region, which is consistent with the larger production and stronger diffusion of 1O2 and ·O2-. This paper shed light to the generation mechanism of 1O2 and ·O2- in VBHC reactors and the relationship with cavitation intensity. The conclusion provides new ideas for the research of effective ROS in hydrodynamic cavitation process.

Roles of Natural Phenolic Compounds in Polycyclic Aromatic Hydrocarbons Abiotic Attenuation at Soil-Air Interfaces through Oxidative Coupling Reactions

Little information is available on the roles of natural phenolic compounds in polycyclic aromatic hydrocarbons (PAHs) attenuation at dry soil-air interfaces. The purpose of this study was to determine the roles of model phenolic constituents of soil organic matter (SOM) on the abiotic attenuation of PAHs. The phenolic compounds can significantly change the attenuation rates of PAHs, among which hydroquinone was the most effective in promoting anthracene and benzo[a]anthracene attenuation. Product identification and sequential extraction experiments revealed hydroquinone enhanced the formation of oxidative coupling products and promoted the incorporation of PAHs into humic analogues, thereby reducing potential risks to humans and ecosystems. Electron paramagnetic resonance spectroscopy analyses showed both PAHs and phenolic compounds could donate electrons to Lewis acid sites of soil minerals, resulting in the generation of persistent free radicals (PFRs). PFRs could promote the generation of ·OH to enhance PAH oxidation and could cross-couple with PAHs, resulting in high-molecular-weight oxidative coupling products. This study revealed for the first time the reaction mechanism between PAHs and phenolic components of SOM under relatively dry conditions and provided new insights into promoting PAHs detoxification in soils but also a potential strategy to increase the organic carbon sequestration.

Colloidal activated carbon as a highly efficient bifunctional catalyst for phenol degradation

A preparation of colloidal activated carbon (CAC) for phenol remediation from groundwater was introduced. The CAC prepared by a simple pulverization technique was an excellent metal-free catalyst for persulfate (PS) activation due to high contact surface area. The removal efficiency of phenol in the PS/CAC system (~100%) was higher than that in the PS/activated carbon (AC) system (90.1%) and was superior to the conventional PS/Fe²⁺ system (27.9%) within 30 min. The phenol removal reaction occurred both in bulk solution and at the surface of the CAC, as confirmed by Langmuir-Hinshelwood (L-H) kinetic model fitting, FT-IR, and electron spin resonance (ESR) analyses. The downsizing of particle size from AC to CAC played a critical role in the radical oxidation mechanism by leading to the formation of predominant superoxide radical (O₂^•-) species in the PS/CAC system. Anions NO₃^-, SO₄^2-, and Cl^- slightly inhibited the phenol removal efficiency, whereas CO₃^2-, HCO₃^- and PO₄3^- did not. Ferulic acid (C₁₀H₁₀O₄) was detected as an organic byproduct of phenol oxidation. The use of CAC as a metal-free bifunctional catalyst has an important implication in the PS activation for phenol degradation in groundwater.

Two New Mononuclear Copper(II)-Dipeptide Complexes of 2-(2'-Pyridyl)Benzoxazole: DNA Interaction, Antioxidation and in Vitro Cytotoxicity Studies

Two new mononuclear mixed ligand copper(II) complexes [Cu(PBO)(Gly-gly)(H₂O)]·ClO₄·1.5H₂O (1) and [Cu(PBO)(Gly-L-leu)(H₂O)]·ClO₄ (2) (PBO is 2-(2'-pyridyl)benzoxazole, Gly-gly and Gly-L-leu are Glycyl-glycine anion and Glycyl-L-leucine anion, respectively), have been prepared and characterized by various analytical and spectral techniques. The interactions of the complexes with DNA were investigated using multi-spectroscopic methods (absorption, emission, circular dichroism), viscometry and electrochemical titration as well as molecular docking technique. The results indicated that 1 and 2 are bound to calf thymus DNA (CT-DNA) through an intercalative mode. The thermodynamic analyses revealed that the reactions between the Cu(II) complexes with DNA are spontaneous with negative Gibbs free energy (ΔG). The positive changes of enthalpy (ΔH) and entropy (ΔS) suggested that the binding processes are dominated by hydrophobic interaction accompanying with endothermic. Also, the complexes exhibited efficient oxidative cleavage of pBR322 plasmid DNA in the presence of ascorbic acid, probably induced by •OH as reactive oxygen species. In addition, 1 and 2 displayed excellent antioxidant activities with the IC₅₀ values of 0.112 and 0.191 μM, respectively, using the mean of nitroblue tetrazolium (NBT) photochemical reduction under a nonenzymatic condition. Moreover, the complexes were screened for their in vitro cytotoxicity against three human carcinoma cell lines (HeLa, PC-3 and A549), in which 2 owns higher cytotoxicity, which was consistent with DNA binding and cleavage ability order of the complexes. This results showed the in vitro biochemical potentials of the Cu(II)-dipeptide complexes with aromatic heterocyclic, viz. effective metallopeptide-nucleases, SOD mimics and non-platinum chemotherapeutic metallopharmaceuticals and their structure-activity relationship, which may contribute to the rational molecular design of new metallopeptide based chemotherapeutic agents.

Two new mixed copper(ii)–dipeptide complexes of N,N-donor heterocycle ligands: studies on their non-covalent DNA binding, chemical nuclease, antioxidant and anticancer activities

Two novel mononuclear mixed ligand copper(ii)-dipeptide complexes have been synthesized. The DNA interactions of the complexes were investigated. In addition, the antioxidant and antitumor activities of the complexes were evaluated.

Enhanced analgesic properties and reduced ulcerogenic effect of a mononuclear copper(II) complex with fenoprofen in comparison to the parent drug: promising insights in the treatment of chronic inflammatory diseases

Analgesic and ulcerogenic properties have been studied for the copper(II) coordination complex of the nonsteroidal anti-inflammatory drug Fenoprofen and imidazole [Cu(fen)2(im)2] (Cu: copper(II) ion; fen: fenoprofenate anion from Fenoprofen, im: imidazole). A therapeutic dose of 28 mg/kg was tested for [Cu(fen)2(im)2] and 21 mg/kg was employed for Fenoprofen calcium, administered by oral gavage in female mice to compare the therapeutic properties of the new entity. The acetic acid induced writhing test was employed to study visceral pain. The percentage of inhibition in writhing and stretching was 78.9% and 46.2% for the [Cu(fen)2(im)2] and Fenoprofen calcium, respectively. This result indicates that the complex could be more effective in diminishing visceral pain. The formalin test was evaluated to study the impact of the drugs over nociceptive and inflammatory pain. The complex is a more potent analgesic on inflammatory pain than the parent drug. Ulcerogenic effects were evaluated using a model of gastric lesions induced by hypothermic-restraint stress. Fenoprofen calcium salt caused an ulcer index of about 79 mm(2) while the one caused by [Cu(fen)2(im)2] was 22 mm(2). The complex diminished the development of gastric mucosal ulcers in comparison to the uncomplexed drug. Possible mechanisms of action related to both therapeutic properties have been discussed.

Crystallographic, experimental (FT-IR and FT-RS) and theoretical (DFT) investigation, UV-Vis, MEP, HOMO-LUMO and NBO/NLMO of (E)-1-[1-(4-Chlorophenyl)ethylidene]thiosemicarbazide

Crystallographic, experimental (FT-IR and FT-RS) and theoretical density function theory (DFT) and UV-Vis spectra of (E)-1-[1-(4-Chlorophenyl)ethylidene]thiosemicarbazide) (ECET) are investigated. The optimized geometry of the compound was calculated from the DFT-B3LYP gradient calculations employing 6-31G (d,p) basis set and calculated vibrational frequencies are evaluated via comparison with experimental values. Molecular stability has been analyzed using Natural Bond Orbital (NBO) and Natural Localized Molecular Orbital (NLMO) analysis and the limits of the molecular electrostatic potential observed. The calculated HOMO and LUMO energies show the charge transfer occurs within the molecule.

Synthesis and structural investigation of mono- and polynuclear copper complexes of 4-ethyl-1-(pyridin-2-yl) thiosemicarbazide

The reaction between 2-hydrazinopyridine and ethylisothiocyanate produced 4-ethyl-1-(pyridin-2-yl) thiosemicarbazide (HEPTS). Its reaction with copper fluoride, chloride, bromide, acetate, nitrate, perchlorate, sulfate, carbonate, hydroxide and copper metal produced 15 Cu(II) complexes. The copper metal is easily oxidized in aqueous-ethanol solution of HEPTS giving [Cu2(EPTS)(H2O)3(OH)3]EtOH. Different complexes for the same anion were synthesized by controlling the heating time. Characterization by elemental, thermal, magnetic and spectral (electronic, IR, mass and ESR) studies showed the formation of mono-, di-, tri- and tetra nuclear complexes. The room temperature solid state ESR spectra of the complexes show an axial spectrum with dx2-y2 ground state, suggesting distorted tetragonal geometry around Cu(II) center. The kinetic and thermodynamic parameters for the different decomposition steps in the complexes were calculated. HEPTS and its Cu(II) complexes showed high activity against gram negative bacteria; [Cu3(EPTS)2(EtOH)2Br4] has more activity.

A study on the mimics of Cu-Zn superoxide dismutase with high activity and stability: two copper(II) complexes of 1,4,7-triazacyclononane with benzimidazole groups

Two copper(II) complexes [CuL(1)Cl]ClO(4) and [CuL(2)MeCN](ClO(4))(2)xH(2)O were synthesized (L(1)= 1-(benzimidazole-2-ylmethyl)-1,4,7-triazacyclononane, L(2)= 1,4-bis(benzimidazole-2-ylmethyl)-1,4,7-triazacyclonone). The benzimidazole groups were N-substituents of tacn, and the complexes are more stable than their parents. They are able to catalyse the dismutation of superoxide anion in aqueous solutions at physiological pH and in bovine serum albumin solution (0.5 mg ml(-1)). X-ray structure analysis and EPR and electronic spectra show that the structure of complex is more similar to the Cu(II) centre of Cu(2)Zn(2)SOD than that. Comparing with other Cu(II) complexes, the complex possesses both high SOD activity and highly thermodynamic stability.

The membrane-associated methane monooxygenase (pMMO) and pMMO-NADH:quinone oxidoreductase complex from Methylococcus capsulatus Bath

Improvements in purification of membrane-associated methane monooxygenase (pMMO) have resulted in preparations of pMMO with activities more representative of physiological rates: i.e., >130 nmol.min(-1).mg of protein(-1). Altered culture and assay conditions, optimization of the detergent/protein ratio, and simplification of the purification procedure were responsible for the higher-activity preparations. Changes in the culture conditions focused on the rate of copper addition. To document the physiological events that occur during copper addition, cultures were initiated in medium with cells expressing soluble methane monooxygenase (sMMO) and then monitored for morphological changes, copper acquisition, fatty acid concentration, and pMMO and sMMO expression as the amended copper concentration was increased from 0 (approximately 0.3 microM) to 95 microM. The results demonstrate that copper not only regulates the metabolic switch between the two methane monooxygenases but also regulates the level of expression of the pMMO and the development of internal membranes. With respect to stabilization of cell-free pMMO activity, the highest cell-free pMMO activity was observed when copper addition exceeded maximal pMMO expression. Optimization of detergent/protein ratios and simplification of the purification procedure also contributed to the higher activity levels in purified pMMO preparations. Finally, the addition of the type 2 NADH:quinone oxidoreductase complex (NADH dehydrogenase [NDH]) from M. capsulatus Bath, along with NADH and duroquinol, to enzyme assays increased the activity of purified preparations. The NDH and NADH were added to maintain a high duroquinol/duroquinone ratio.

Cu(III)-polypeptide complexes exhibiting SOD-like activity

The SOD-like activity of Cu(III)-complexes with polypeptides poly-L-lysine and poly-L-glutamic acid respectively was investigated. The Cu(II)-polypeptide complexes were first oxidized by K2IrCl6 to give the corresponding Cu(III)-compounds. The oxidation of Cu(II) and the corresponding Cu(II)/Cu(III) potential was evaluated by cyclic voltammetry (c.v.), UV-Vis and EPR spectroscopic (r.t.) experiments. Spin trapping EPR spectra were also conducted to confirm the formation of the superoxide radical. The SOD-like activity of each Cu(III)-complex was proved using the nitro blue tetrazolium (NBT) method slightly modified.

Models for superoxide dismutases: characterization of mononuclear Cu(II), Fe(III), and Mn(II) complexes with 4',5'-bis(salicylideneimino)benzo-15-crown-5

Mononuclear Cu(II), Fe(III), and Mn(II) complexes with 4',5'-bis (salicylideneimino)benzo-15-crown-5, (SALH2), were characterized by elemental analysis, IR and UV-Vis spectroscopy and tested spectrometrically as catalysts for superoxide disproportionation by utilizing xanthine-xanthine oxidase (XXO) assays. The results indicate that the examined mononuclear complexes are speculative potent superoxide dismutase mimics.

Antitumor activities of vanadium(IV), manganese(IV), iron(III), cobalt(II) and copper(II) complexes of 2-methylaminopyridine

The effect of Cu(II), Mn(IV), Fe(III), V(IV) and Co(II) complexes of 2-methylaminopyridine (L) having superoxide dismutase (SOD)-like activities on Ehrlich ascites carcinoma (EAC) cells was studied. Each of these complexes was intraperitoneally administered (10 mg/kg body weight for 9 days) to Swiss albino mice implanted intraperitoneally with 1 x 10(6) EAC cells. Six days after the last treatment the EAC cells were harvested using a heparinized syringe. The volume of EAC cells and EAC cell viability as well as changes in the levels of tumor cell enzyme activities of SOD, catalase, glutathione peroxidase (GSH-Px), glutathione reductase (GSH-R) and glucose-6-phosphate dehydrogenase (G6PD) were tested to examine the antitumor effects of these complexes. Both tumor volume and tumor cell viability were significantly lowered in complex-treated mice. After tumor transplantation and treatment with the complexes, the activities of GSH-Px and GSH-R were significantly lowered while SOD and G6PD activities were increased in EAC cells compared to their levels in EAC cells harvested from saline-treated mice.

Vanadium-mediated oxidation of NADH is enhanced by aluminium and inhibited by vitamin E and some copper (II) complexes

The effect of aluminium on vanadium-mediated oxidation of NADH was examined. The oxidation of NADH was enhanced in the presence of aluminium. The effect was concentration dependent. Vitamin E and copper (II) complexes with superoxide dismutase (SOD)-like activities containing isobutyric acid hydrazine were tested for their effect on the vanadium-mediated oxidation of NADH. The stimulatory effect of aluminium was decreased upon addition of different concentrations of vitamin E and copper (II) complexes. These results indicate that the biological toxicity of aluminium may be attributed to its enhancement of the production of superoxide radicals (O2.-) in association with the accumulation of other trace elements such as vanadium.

Structural and biological aspects of copper (II) complexes with 2-methyl-3-amino-(3H)-quinazolin-4-one

A series of new copper (II) complexes with 2-methyl-3-amino(3H)-quinazolin-4-one (MAQ) and various anions (Cl-, Br-, ClO(-)4, NO(-)3, SCN-, and SO(2-)4 was prepared. Their structures and properties were characterized by elemental analysis, IR, UV-Vis and ESR spectroscopy, molar conductivity, and magnetic moment measurements. The square-planar complex was only obtained in the presence of perchlorate anion, whereas the five coordinate species, which have a square-pyramidal structure, were obtained for chloro and bromo complexes. In the case of hexa coordinate complexes, in which nitrate, sulphate, or thiocyanate is attached to a copper(II) ion in a 1:2 (metal:ligand) ratio, a distorted octahedral geometry around copper(II) is proposed. The antimicrobial activity of the free ligand and its copper(II) complexes clearly illustrates that the compounds have both an antibacterial and antifungal potency against the organisms tested. In most cases, the complexes were found to be more active than the free ligand, but in some cases, an equal activity was displayed. To further elucidate the biological activity of the complexes, their activities towards active oxygen species, such as H2O2 and O(-)2, were investigated. A probable mechanism for the cytotoxic reaction with the different organisms is proposed.