Study of benznidazole–cyclodextrin inclusion complexes, cytotoxicity and trypanocidal activity

The current chemotherapy for Chagas disease is still based on benznidazole, which has low solubility, but complexation with cyclodextrins provides a way of increasing the solubility. The objective of this work was to characterize the inclusion complexes formed between benznidazole (BNZ) and randomly 2-methyled-β-cyclodextrin (RM-β-CD) in aqueous solution and study cytotoxicity and trypanocidal. BNZ:RM-β-CD solution complex systems were prepared and characterized using the phase solubility diagram, nuclear magnetic resonance and a photostability assays, also to investigate the in vitro trypanocidal activity with epimastigote forms of Trypanossoma cruzi and the study of cytotoxicity against mammal cells. The phase-solubility diagram displayed an A _L-type feature, providing evidence of the formation of soluble inclusion complexes. The continuous variation method showed the existence of a complex with 1:1 stoichiometry. Toxicity assays demonstrated that inclusion complexes were able to reduce the toxic effects caused by benznidazole alone and that this did not interfere with the trypanocidal activity of the benznidazole. The use of inclusion complexes benznidazole:cyclodextrin is thus a promising alternative for the development of a safe and stable liquid formulation and a new option for the treatment of Chagas disease.     

On concentration of solution to a Schrödinger logarithmic equation with deepening potential well

In this work, we prove the existence of positive solution for the following class of problems where λ>0 and is a potential satisfying some conditions. Using the variational method developed by Szulkin for functionals, which are the sum of a C¹ functional with a convex lower semicontinuous functional, we prove that for each large enough λ>0, there exists a positive solution for the problem, and that, as λ→+∞, such solutions converge to a positive solution of the limit problem defined on the domain Ω=int(V^?1({0})).     

Trace elements status in the terrain of an impounded vehicle scrapyard

Journal of Radioanalytical and Nuclear Chemistry - The impact of a scrapyard of impounded vehicles in São Paulo state on topsoil was evaluated for As, Ba, Co, Cr, Cu, Mo, Ni, Pb, V, Zn and...     

Temperature dependence of the director reorientation of dye-doped nematic liquid crystals subjected to an optical field and its relation with the non-linear absorption coefficient

The temperature behaviour of the torque amplification factor η in the E48-D4 dye-host/liquid crystal-guest dyed system illuminated by a laser beam has been investigated using a single beam Z-Scan experimental technique. A plot of η versus temperature showed a monotonic aspect, different from other anthraquinone dyed liquid crystals. This behaviour, in our case, is consistent with the monotonic dependence on temperature of the linear α_o and non-linear β optical absorption coefficients. In particular, the non-linear optical absorption coefficient related to the reorienting process is negative and of the order of-0.25 mm W^-1. The temperature dependence of η seems to be directly correlated to β and not to α_o. Since drastic conformational modifications on dye molecules are not expected on passing from the ground to the excited state, the role of the electronic structure seems to be dominant in the reorienting process in dyed nematics.     

Synthesis of α-Metoylene-γ-Lactones in Furanosidic Systems

Abstract

Synthesis of stereoisomeric α-methylene-γ-lactones in furanose-and furanuronoamide derivatives was easily accomplished by Reformatsky Reaction with ethyl bromcmethylacrylic ester and zinc. Pyridinium chlorochromate/3Å molecular sieve powder showed to be an excellent reagent for the oxidation of secondary hydroxyl groups of a furanose system and of α-hydroxy amides.     

Implementation of the k 0-standardization method for analysis of geological samples at the Neutron Activation Analysis Laboratory, São Paulo, Brazil

The Neutron Activation Analysis Laboratory (LAN-IPEN) has been analysing geological samples for many years with the INAA comparative method, for geochemical and environmental research. This study presents the results obtained in the implementation of the k ₀-standardization method at LAN-IPEN, for geological samples analysis, by using the program k ₀-IAEA, provided by the International Atomic Energy Agency (IAEA). The thermal to epithermal flux ratio f and the shape factor α of the epithermal flux distribution of the IEA-R1 nuclear reactor of IPEN were determined for the pneumatic irradiation facility and one selected irradiation position, for short and long irradiations, respectively. To obtain these factors, the “bare triple-monitor” method with ¹⁹⁷Au–⁹⁶Zr–⁹⁴Zr was used. In order to validate the methodology, the geological reference materials basalts JB-1 (GSJ) and BE-N (IWG-GIT), andesite AGV-1 (USGS), granite GS-N (ANRT), SOIL-7 (IAEA) and sediment Buffalo River Sediment (NIST–BRS-8704), which represent different geological matrices, were analysed. The concentration results obtained agreed with assigned, with bias <10 % except for Zn in AGV-1. The U-score test showed that all results, except Mg in JB-1, are within 95 % confidence interval. These results indicate excellent possibilities of using this parametric method at the LAN-IPEN for geochemical and environmental studies.     

Laguncularia racemosa Phenolics Profiling by Three-Phase Solvent System Step-Gradient Using High-Performance Countercurrent Chromatography with Off-Line Electrospray Mass-Spectrometry Detection

The detailed metabolite profiling of Laguncularia racemosa was accomplished by high-performance countercurrent chromatography (HPCCC) using the three-phase system n-hexane–tert-butyl methyl ether–acetonitrile–water 2:3:3:2 (v/v/v/v) in step-gradient elution mode. The gradient elution was adjusted to the chemical complexity of the L. racemosa ethyl acetate partition and strongly improved the polarity range of chromatography. The three-phase solvent system was chosen for the gradient to avoid equilibrium problems when changing mobile phase compositions encountered between the gradient steps. The tentative recognition of metabolites including the identification of novel ones was possible due to the off-line injection of fractions to electrospray ionization mass spectrometry (ESI-MS/MS) in the sequence of recovery. The off-line hyphenation profiling experiment of HPCCC and ESI-MS projected the preparative elution by selected single ion traces in the negative ionization mode. Co-elution effects were monitored and MS/MS fragmentation data of more than 100 substances were used for structural characterization and identification. The metabolite profile in the L. racemosa extract comprised flavonoids, hydrolysable tannins, condensed tannins and low molecular weight polyphenols.     

Drying Effects on Chemical Composition and Antioxidant Activity of Lippia thymoides Essential Oil,a Natural Source of Thymol

Leaves of Lippia thymoides (Verbenaceae) were dried in an oven at 40, 50 and 60 °C and the kinetic of drying and the influence of the drying process on the chemical composition, yield, and DPPH radical scavenging activity of the obtained essential oils were evaluated. The composition of the essential oils was determined with gas chromatography-mass spectrometry and gas chromatography-flame ionization detection analyses. The influence of drying on the chemical composition of the essential oils of L. thymoides was evaluated by multivariate analysis, and their antioxidant activity was investigated via the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The Midilli model was the most appropriate to describe the behavior of drying kinetic data of L. thymoides leaves. Thymol was the major compound for all analyzed conditions; the maximum content was obtained from fresh leaves (62.78 ± 0.63%). The essential oils showed DPPH radical scavenging activity with an average of 73.10 ± 12.08%, and the fresh leaves showed higher inhibition (89.97 ± 0.31%). This is the first study to evaluate the influence of drying on the chemical composition and antioxidant activity of L. thymoides essential oils rich in thymol.