Luciano Dornelles

New organochalcogen multitarget drug: synthesis and antioxidant and antitumoral activities of chalcogenozidovudine derivatives.

In this article we present the synthesis, characterization, and in vitro biological and biochemical activities of new chalcogenozidovudine derivatives as antioxidant (inhibition of TBARS in brain membranes and thiol peroxidase-like activity) as well as antitumoral agents in bladder carcinoma 5637. A prominent response was obtained for the selected chalcogenonucleosides, showing effective antioxidant and antitumoral activities.

Evaluation of in vitro antioxidant effect of new mono and diselenides

This study was designed to examine the antioxidant activity in vitro of novel mono- and diselenide compounds. We compared whether the formation of p-methyl-selenol from compounds 1-phenyl-3-(p-tolylselanyl)propan-2-amine (C1) and 1,2-dip-tolyldiselenide (C4) and o-methoxy-selenol from compounds 1-(2-methoxyphenylselanyl)-3-phenylpropan-2-amine (C2) and 1,2-bis(2-methoxyphenyl)diselenide (C3) may be involved in their antioxidant effects. The compounds were tested against Fe(II) and sodium nitroprusside (SNP)-induced lipid peroxidation in rat brain and liver homogenates. Likewise, the antioxidant capacity of the compounds was assessed by their ability to decolorize the DPPH radical as well as the Fe(II) chelating assay through the reduction of molybdenum(VI) (Mo6+) to molybdenum(V) (Mo5+). This colorimetric assay was also used to quantify thiol peroxidase (GPx) and oxidase activity and thioredoxin reductase (TrxR) activity. The results showed that the novel selenide compounds inhibit the thiobarbituric acid reactive species (TBARS) induced by different pro-oxidants, but the monoselenides effects were significant only at concentrations higher than the concentrations of the diselenides. Similarly, the total antioxidant activity was higher in the diselenides. Moreover, GPx and TrxR activity was only observed for the diselenides, which indicates that these compounds are more stable selenol molecules than monoselenides.

Addition of tellurium tetrabromides and alkyl and aryl tellurium tribromides to terminal acetylenes

Abstract The addition of tellurium tetrabromides and alkyl and aryl tellurium tribromides to terminal acetylenes gives rise to thecorresponding bis(b-bromovinyl)tellurium dibromides and (b-bromovinyl)organyl tellurium dibromides which, by treatment withNaBH 4 , leads to formation of the reduced tellurides.

Dichloro-bis(2-chloro-2-phenyl-vinyl)Te(IV) and dibromo-bis(2-bromo-2-phenyl-vinyl)Te(IV): supramolecular self-assembly through different π-aryl interactions

Abstract C16H12Cl4Te, (1), Mr = 473.66, P21/c, a = 8.3919(9), b = 14.474(1), c = 14.585(1) Å, β = 94.057(9)°, Z = 4, R1 = 0.0378. C16H12Br4Te, (2), Mr = 651.50, Pnma, a = 19.159(2), b = 16.787(1), c = 5.781(1) Å, Z = 4, R1 = 0.0437. In both compounds the primary geometry about the TeIV atom is a pseudo-trigonal-bipyramidal arrangement, with two halide atoms in apical positions, and the lone pair of electrons and C atoms in the equatorial plane. The TeIV atoms are involved in secondary interactions resulting in the self-assembly of a chain-like supramolecular array in (1) and into a three dimensional supramolecular array in (2). Compound (1) has a Z configuration with the chlorine atom and the tellurium moiety bonded at the same side in adjacent atoms. In (2) the bromine atom and the dibromotellurium moiety are bonded at adjacent carbons in a cis fashion.

CuO nano particles and [bmim]BF4: an application towards the synthesis of chiral β-seleno amino derivatives via ring opening reaction of aziridines with diorganyl diselenides

A series of chiral β-seleno amino derivatives were synthesized via a ring opening reaction of different aziridines with diorganyl diselenides mediated by recyclable CuO nanopowder and an ionic liquid affording the corresponding products in good to excellent yields. The [bmim]BF4 ionic liquid acts as both promoter and reaction medium. Compared to the usual organic solvents the ionic liquid exhibited better performance with the advantage of its recyclability.

Transition metal oxide nanopowder and ionic liquid: an efficient system for the synthesis of diorganyl selenides, selenocysteine and derivatives

We have developed an efficient method for the synthesis of diorganyl selenides and β-seleno amines using Zn, catalytic amounts of ZnO nanopowder, as a catalyst and ionic liquid as a recyclable solvent. This ZnO/ionic liquid system shows high efficiency in catalyzing these transformations with the formation of the desired products in high yields.

Effect of diselenide administration in thioacetamide-induced acute neurological and hepatic failure in mice

Hepatic encephalopathy is a common complication of severe acute hepatic failure and has been associated with high short-term mortality rates. Therefore, the aim of this study was to investigate the effect of diphenyl diselenide (DPDS) and its analogues in protecting against thioacetamide (TAA)-induced acute neurological and hepatic failure in mice. The animals received a TAA dose of 200 mg kg−1 intraperitoneally, and then, 1 hour later, they received 15.6 mg kg−1 of diselenides intraperitoneally. Twenty three hours after diselenide administration, the animals were sacrificed, and blood, brain and liver samples were collected for analysis. The results showed that mice exposed to TAA presented oxidative stress characteristics, such as an increase in lipid peroxidation (LPO), enhanced glutathione peroxidase activity and a decrease in the GSH/GSSH ratio in the brain and liver. In addition, the TAA group showed a decrease in cellular viability in both tissues. TAA treatments also generate reactive oxygen species and cause inhibition of glutathione-S-transferase in liver, which were associated with TAA exacerbated half-life in this tissue. In the histopathological analyses, we observed that TAA induced a large inflammation process that was confirmed according to the elevation of liver myeloperoxidase activity. Moreover, the treatment with diselenides reduced the oxidative stress significantly. Additionally, after the establishment of acute hepatic failure (AHF), DPDS was able to inhibit the inflammatory processes with a more significant decrease in major hepatic damage effects than was presented after treatment with its analogues. Thus, our results showed that DPDS is a promising therapeutic option for the treatment of AHF and hepatic encephalopathy as mice returned to normal conditions after the damage.

CATALYST-DEPENDENT SELECTIVE SYNTHESIS OF O/S- AND S/S-ACETALS FROM ENOL ETHERS

Abstract Enol ethers are reacted with mercaptanes to give the corresponding O/S- or S/S-acetals in medium to high yield. Either product can be formed selectively depending on the acid catalyst and the reaction time applied.

Synthesis and electrochemical and antioxidant properties of chalcogenocyanate oxadiazole and 5-heteroarylchalcogenomethyl-1H-tetrazole derivatives

This article presents the chalcogenocyanate oxadiazoles 7 and 8 and their derivatives 5-heteroarylchalcogenomethyl-1H-tetrazoles 9 and 10, which were synthesized in high yields. The 5-substituted-1H-tetrazoles were obtained via [3+2] cycloaddition reactions of chalcogenocyanates 7 and 8 with sodium azide (NaN3) using a simple methodology. All the obtained compounds were characterized by NMR and high resolution mass spectrometry analysis. Their in vitro antioxidant activity was evaluated by measuring their ability to eliminate free radicals in the form of 2,2-diphenyl-2-picrylhydrazyl (DPPH) and through the reduction of molybdenum(VI) to molybdenum(V). The results for the phosphomolybdenum method indicated that some compounds have antioxidant properties, as evidenced by electrochemical oxidation tests to which they were subjected, which correlate their oxidation potentials (Epa) with their activity values (EC50).

Antibacterial effect of chalcogenoesters on planktonic cells and biofilms of Streptococcus mutans and Streptococcus parasanguinis

The purpose of this work was to evaluate the antibacterial and antibiofilm activity of five chalcogenoesters synthetics on oral bacteria, Streptococcus mutans, and Streptococcus parasanguinis. Five chalcogenoesters were synthesized, purified by chromatography in silica gel and its chemical structure determined by nuclear magnetic resonance. Antibacterial assays were performed using the microdilution methodology. The antibiofilm activity of chalcogenoesters was determined on biofilm formation and preformed biofilms by biofilm mass quantification (by crystal violet staining) and colony forming unit enumeration. Moreover, biofilms were also analyzed by scanning electron microscopy. In general, it was observed that the chalcogenolesters showed antibacterial activity against Streptococcus mutans and Streptococcus parasanguinis. Regarding biofilm formation and preformed biofilm, all compounds reduced efficiently the biofilm mass and of viable cells of Streptococcus parasanguinis and Streptococcus mutans biofilms. However, Streptococcus mutans biofilms showed greater resistance to action of chalcogenolesters. Scanning electron microscopy examination confirmed the results, showing a reduction of the extracellular polymeric substance and number of cells in biofilm. Our result indicated that the chalcogenoesters tested here can be considered as promising molecules for prevention and control of oral biofilms formed by Streptococcus mutans and Streptococcus parasanguinis.