Pedro P. Corbi

Pt(II) and Ag(I) complexes with acesulfame: Crystal structure and a study of their antitumoral, antimicrobial and antiviral activities

Two new complexes of platinum(II) and silver(I) with acesulfame were synthesized. Acesulfame is in the anionic form acesulfamate (ace). The structures of both complexes were determined by X-ray crystallography. For K(2)[PtCl(2)(ace)(2)] the platinum atom is coordinated to two Cl(-) and two N-acesulfamate atoms forming a trans-square planar geometry. Each K(+) ion interacts with two oxygen atoms of the S(O)(2) group of each acesulfamate. For the polymeric complex [Ag(ace)](n) the water molecule bridges between two crystallographic equivalent Ag1 atoms which are related each other by a twofold symmetry axis. Two Ag1 atoms, related to each other by a symmetry centre, make bond contact with two equivalent oxygen atoms. These bonds give rise to infinite chains along the unit cell diagonal in the ac plane. The in vitro cytotoxic analyses for the platinum complex using HeLa (human cervix cancer) cells show its low activity when compared to the vehicle-treated cells. The Ag(I) complex submitted to in vitro antimycobacterial tests, using the Microplate Alamar Blue (MABA) method, showed a good activity against Mycobacterium tuberculosis, responsible for tuberculosis, with a minimal inhibitory concentration (MIC) value of 11.6microM. The Ag(I) complex also presented a promising activity against Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive (Enterococcus faecalis) microorganisms. The complex K(2)[PtCl(2)(ace)(2)] was also evaluated for antiviral properties against dengue virus type 2 (New Guinea C strain) in Vero cells and showed a good inhibition of dengue virus type 2 (New Guinea C strain) replication at 200microM, when compared to vehicle-treated cells.

Chemical, spectroscopic characterization, and in vitro antibacterial studies of a new gold(I) complex with N-acetyl-L-cysteine

A new gold(I) complex with N-acetyl-L-cysteine was synthesized and characterized by chemical and spectroscopic techniques. The elemental and thermal analyses of the solid compound fit to the composition AuC5H8NO3S · 0.75H2O. Solid-state 13C-nuclear magnetic resonance (SSNMR) and infrared (IR) analyses indicate the coordination of the ligand to Au(I) through sulfur. The insolubility of the complex in both polar and non-polar solvents supports a polymeric structure. The antibacterial activity of the complex was evaluated by antibiogram assays using the disc diffusion method. The compound showed effective antibacterial activity against Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative) bacterial cells.

Synthesis, spectroscopic characterization, DFT studies, and initial antibacterial assays in vitro of a new palladium(II) complex with tryptophan

A new palladium(II) complex with the amino acid L-tryptophan (Pd-TRP) was synthesized in aqueous solution and characterized by chemical and spectroscopic methods. Elemental, ESI-QTOF mass spectrometric, and thermal analyses of the solid compound permitted proposing the [Pd(C11H11N2O2)2] · 2H2O composition. Infrared, Raman, and UV-Vis spectroscopic data indicate the coordination of the ligand to Pd(II) through monodentate oxygen of carboxylate and through nitrogen of the amino group. The 1H and 13C NMR spectroscopic data confirm coordination through the carboxylate, while 15N NMR data confirm coordination of nitrogen of NH2. Density functional theory studies confirmed nitrogen and oxygen coordination to palladium(II) as a minimum of the potential energy surface with calculations of the hessians showing no imaginary frequencies. Biological studies were performed to provide information concerning the antibacterial activities of the compound. The Pd-TRP complex was shown to be active against Gram-positive and Gram-negative pathogenic bacterial strains.

Palladium(II) complex with S-allyl-L-cysteine: new solid-state NMR spectroscopic measurements, molecular modeling and antibacterial assays.

Nuclear magnetic resonance studies, molecular modeling and antibacterial assays of the palladium(II) complex with S-allyl-L-cysteine (deoxyalliin) are presented. Studies based on solid and solution 13C and 15N nuclear magnetic resonance (NMR) spectroscopy confirmed that the palladium(II) complex preserved the same structural arrangement in both states, with no modifications on coordination sphere when dissolved in water. Density functional theory (DFT) studies stated that the trans isomer is the most stable one. Antibacterial activities of S-allyl-L-cysteine and its palladium(II) complex were evaluated by antibiogram assays using the disc diffusion method. The palladium(II) complex showed an effective antibacterial activity against Staphylococcus aureus (Gram-positive), Escherichia coli and Pseudomonas aeruginosa (Gram-negative) bacterial cells.

Characterization and biological studies of a new platinum(II) complex with the amino acid L-alliin

Synthesis and characterization of a new Pt(II) complex with the amino acid L-alliin (S-allyl-L-cysteine sulfoxide, C6H11NO3S) are described. Elemental and mass spectrometric analyses of the solid complex are consistent with [PtCl2(alliin)], or [PtCl2(C6H11NO3S)]. 13C nuclear magnetic resonance (NMR), [1H–15N] two dimensional (2D) NMR and infrared spectroscopy indicate coordination of the ligand to Pt(II) through the N and S atoms. The complex is very soluble in dimethyl sulfoxide. Biological analysis for evaluation of a potential cytotoxic effect of the complex was performed using HeLa cells derived from human cervical adenocarcinoma. The complex presented moderate cytotoxic activity, inducing about 40% cell death at a concentration of 400 μmol  · L−1.

Four new metal complexes with the amino acid deoxyalliin

The solid complexes [Co(C6H10NO2S)2], [Ni(C6H10NO2S)2], [Cu(C6H10NO2S)2] and [Fe(C6H10NO2S)2] were obtained from the reaction of cobalt(II), nickel(II), copper(II) and iron(II) salts with the potassium salt of the amino acid deoxyalliin (S-allyl-L-cysteine). Electronic absorption spectra of the complexes are typical of octahedral structures. Infrared spectroscopy confirms the ligand coordination to the metal ions through (COO-) and (NH2) groups. EPR spectrum of the Cu(II) complex indicates a slight distortion of its octahedral symmetry. Mossbauer parameters permitted to identify the presence of iron(II) and iron(III) species in the same sample, both of octahedral geometry. Thermal decomposition of the complexes lead to the formation of CoO, NiO, CuO and Fe2O3 as final products. The compounds show poor solubility in water and in the common organic solvents.

Synthesis and spectroscopic characterization of new metal(II) complexes with methionine sulfoxide

Methionine sulfoxide complexes of iron(II) and copper(II) were synthesized and characterized by chemical and spectroscopic techniques. Elemental and atomic absorption analyses fit the compositions K2[Fe(metSO)2]SO4·H2O and [Cu(metSO)2]·H2O. Electronic absorption spectra of the complexes are typical of octahedral geometries. Infrared spectroscopy suggests coordination of the ligand to the metal through the carboxylate and sulfoxide groups. An EPR spectrum of the Cu(II) complex indicates tetragonal distortion of its octahedral symmetry. 57Fe Mössbauer parameters are also consistent with octahedral stereochemistry for the iron(II) complex. The complexes are very soluble in water.

Characterization of bilayer bacterial cellulose membranes with different fiber densities: a promising system for controlled release of the antibiotic ceftriaxone

This work describes the synthesis of bilayer bacterial cellulose membranes (BCs) produced by Gluconacetobacter hansenii ATCC 23769 in culture media with different carbon sources (sugarcane molasses, syrup and fructose) as well as their retention capacity and sustained release of the antibacterial agent ceftriaxone. Scanning electronic microscopy analysis showed that BCs produced in all culture media exhibit a double layer and three-dimensional fiber network obtained in only one step. Elemental and thermogravimetric analyses, Fourier transform infrared spectroscopy and X-ray diffraction show that the BC membranes are composed of pure cellulose. In particular, the BC produced in sugarcane molasses medium presented a three-dimensional network structure of the bilayer with high-density fiber entangling, which was responsible for the largest holding capacity and sustained release of the antibiotic ceftriaxone in relation to Staphylococcus aureus bacterial strains. This behavior shows the potential of applying such BC membranes in wound dressings as a sustained support to release different antibiotics to treat skin infections.

Synthesis and characterization of a platinum(II) complex with N-acetyl-L-cysteine

Synthesis and spectroscopic studies in the solid-state of a platinum(II) complex with N-acetyl-L-cysteine are described. Elemental analyses are consistent with composition Pt2(C5H8NO3S)4 · 3H2O. Solid-state 13C NMR, infrared, and U-Vis spectroscopic results are consistent with coordination of the ligand to platinum(II) through sulfur. Thermal analyses confirmed water in the complex composition. Final residue of the thermal treatment was identified by powder X-ray diffractometry as metallic platinum.

Synthesis, spectroscopic studies, and preliminary antibacterial assays of a palladium(II) complex with 2-mercaptothiazoline

In this article, synthesis of a palladium(II) complex with 2-mercaptothiazoline in aqueous solution is presented. Composition of the complex was defined as 1 : 2 (metal : ligand). Infrared and solid-state nuclear magnetic resonance indicate ligand coordination to Pd(II) through nitrogen of thiazole ring and sulfur of thiol. ESI–QTOF–mass spectrometric analysis shows primarily the dimeric form in solution. An antibiogram assay of the complex was performed by the disc diffusion method. The compound did not show antibacterial activity against the considered bacterial cells in the tested concentrations.