Journal of the Brazilian Chemical Society via MedWorm.com

Biomimetic hydrogen generation catalyzed by triironnonacarbonyl disulfide cluster

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

Triironnonacarbonyl disulfide cluster, a stable and synthetic precursor for active site models of [Fe-Fe] hydrogenase enzyme, has been evaluated as catalyst for the electrochemical generation of hydrogen by cyclic voltammetry. In the presence of acetic acid, Fe3S2(CO)9 catalyzes the reduction of proton to hydrogen at -2.24 V (vs. Fc/Fc+) with an overpotential of -0.78 V (acetonitrile as solvent). The overpotential is comparable to those reported for diironcarbonyl models of [Fe-Fe] hydrogenase.O "cluster" dissulfeto de triferrononacarbonila, um precursor sintético e estável para modelos do sítio ativo da enzima hidrogenase [Fe-Fe], foi avaliado como catalisador para a geração eletroquímica de hidrogênio por voltametria cíclica. Na presença de ácido acético, Fe3S2(CO)9 catalisa a...

Effects of the essential oil from fruits of Schinus terebinthifolius Raddi (Anacardiaceae) on reproductive functions in male rats

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

The essential oil of Schinus terebinthifolius (Anacardiaceae) was analyzed by GC and GC-MS. α-Fenchene, limonene, β-pinene, α-phellandrene, and β-isosylvestrene represent about 80% of the oil composition. The reproductive toxicity of the essential oil in Wistar male rats was evaluated. No changes were observed in the mass of the reproductive organs, number and morphology of spermatozoa, reproductive rates, and the body mass of offspring of male rats after treatment with the essential oil of S. terebinthifolius.O óleo essencial de Schinus terebinthifolius foi analisado por CG e CG-EM. α-Fencheno, limoneno, β-pineno, α-felandreno e β-isosilvestreno representam aproximadamente 80% da composição do óleo. A toxicidade na reprodução de ratos Wistar machos foi avaliada. Não foram o...

Metal chloride hydrates as Lewis acid catalysts in multicomponent synthesis of 2,4,5-triarylimidazoles or 2,4,5-triaryloxazoles

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

A series of nine metal chloride hydrates (ZnCl2.2H2O, SnCl2.2H2O, CdCl2.2H2O, MnCl2.4H2O, CoCl2.6H2O, SrCl2.6H2O, NiCl2.6H2O, CrCl3.6H2O and CeCl3.7H2O) was investigated as mild and inexpensive Lewis acid catalysts to promote the multicomponent synthesis of triarylimidazoles. Reactions starting from benzil showed the best results when SnCl2.2H2O was used, while for benzoin as the starting material, CeCl3.7H2O was more efficient. All reactions were performed in EtOH as solvent. These catalysts were also successfully employed in the synthesis of triaryloxazoles.Uma série de nove hidratos de cloretos metálicos (ZnCl2.2H2O, SnCl2.2H2O, CdCl2.2H2O, MnCl2.4H2O, CoCl2.6H2O, SrCl2.6H2O, NiCl2.6H2O, CrCl3.6H2O e CeCl3.7H2O) foi investigada como catalisadores ácidos de Lewis brandos e baratos na ...

Molecular docking and molecular dynamic studies of semi-synthetic piperidine alkaloids as acetylcholinesterase inhibitors

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

The mixture of semi-synthetic derivatives (-)-3-O-acetyl-cassine hydrochloride and (-)-3-O-acetyl-spectaline hydrochloride, prepared from the mixture of natural alkaloids (-)-cassine and (-)-spectaline (4:1) isolated from Senna spectabilis, has been shown to be a potent acetylcholinesterase (AChE) inhibitor, thereby prompting further molecular studies. In this sense, docking and dynamic molecular studies were carried out in this work, aiming to acquire a deeper understanding about all the structural aspects of molecules (-)-3-O-acetyl-cassine and (-)-3-O-acetyl-spectaline hydrochlorides, which differ with respect to their AChE inhibitory potentials. Both molecules establish important interactions with the peripheral anionic site within the catalytic gorge of Torpedo californica AChE. Howev...

Cooking effects on iron and proteins content of beans (Phaseolus Vulgaris L.) by GF AAS and MALDI-TOF MS

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

The effects of domestic cooking on proteins, organic compounds and Fe distribution in beans (Phaseolus vulgaris L.) were investigated. Sequential extraction with different extractant solutions (mixture of methanol and chloroform 1:2 v/v, water, 0.5 mol L-1 NaCl, 70% v/v ethanol and 0.5 mol L-1 NaOH) were used for extracting lipids, albumins, globulins, prolamins and glutelins, respectively. Iron determination by graphite furnace atomic absorption spectrometry (GF AAS), proteins by Bradford method and organic compounds by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) were carried out in this work. High concentration of albumins, globulins and glutelins were found in raw beans, while in the cooked beans, albumins and glutelins are main proteins t...

Ultra-performance liquid chromatographic method for measurement of voriconazole in human plasma and oral fluid

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

A simple, sensitive and selective ultra-performance liquid chromatography method for the determination of voriconazole in plasma and oral fluid was developed and validated. After a liquid-liquid extraction with methyl-tert-butyl ether, the analyte and internal standard were separated on a Hypersil Gold C18 column (2.1 × 100 mm, p.d. 1.9 µm), eluted with a mobile phase composed of thietylammonium phosphate buffer and acetonitrile (70:30, v/v). Total run time was 4 min, total mobile phase consumption of 2.2 mL. Detection was performed with a photodiode array detector with quantitation at 256 nm. Voriconazole concentrations in oral fluid were on average 57.5% (±5.3) of those measured in paired plasma samples.Um método simples, sensível e seletivo para determinação de voriconazol em pla...

A method for determination of ammonia in air using oxalic acid-impregnated cellulose filters and fluorimetric detection

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

A fluorimetric method was developed for the determination of ammonia in ambient air. Samples were collected using cellulose filters impregnated with oxalic acid, followed by solubilization of the ammonium ion, addition of reagents and fluorimetric detection. Important analytical parameters that were evaluated included sampling time and flow rate. Formaldehyde, diethylamine and hydrogen sulfide did not interfere in the method. The analytical curve was linear up to at least 34 ppbv of ammonia, using a sample flow rate of 0.3 L min-1 and a sampling time of 20 min. The limit of detection achieved under these conditions was 3 ppbv. The proposed method offers advantages compared to the indophenol colorimetric method, especially the ability to use a shorter sampling time. The method proved to be ...

Determination of polychlorinated biphenyls in seawater using headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry with the aid of experimental design

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

A simple and reliable pretreatment approach in gas chromatography-mass spectrometry (GC-MS) was developed for concurrent clean-up of seawater and the concentration of lipophilic polychlorinated biphenyls (PCBs) with 1-8 chlorine atoms based on the combination of KMnO4 oxidation with headspace sampling and solid-phase microextraction (SPME). Factors affecting the extraction process were studied using a multivariable approach. Under optimum conditions such as PDMS 7 µm of fiber, 78 ºC of extraction temperature, 33 min of extraction time, 8 mL of volume, the limits of detection ranged from 0.3 to 7.5 ng L-1 and precisions were between 3.9 and 9.9% at spiked 0.05 µg L-1 PCBs. Humic acids in seawater exhibited remarkably negative effects; recoveries of PCBs were significantly improved, espec...

Total synthesis and allelopathic activity of cytosporones A-C

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

The search for efficient, environmentally friendly herbicides has been the focus of numerous studies on the organic synthesis of compounds isolated from natural sources. Cytosporones, which are phenolic lipids isolated from fungi, exhibit noteworthy biological properties. This paper reports the preparation of cytosporones A-C from the same starting material through a short synthetic route, with good yields. All compounds were tested for allelopathic activity on lettuce (Lactuca sativa L) seeds. Cytosporone A and its methylated precursor showed remarkable allelopathic activity, inhibiting seed germination and plantule growth.A busca por herbicidas eficientes e ambientalmente corretos tem sido foco de numerosos estudos sobre a síntese de compostos isolados de fontes naturais. Citosporonas, ...

Morphology, microstructure and electrocatalytic properties of activated copper surfaces

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

Morphologic changes on copper surfaces upon applying an established potential protocol were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results showed a good correlation between the time employed in the electrode activation and the resulting microstructure and electrochemical activity.Alterações morfológicas em superfícies de cobre resultantes da aplicação de um protocolo definido de potencial foram examinadas por microscopia eletrônica de varredura (MEV) e microscopia de força atômica (AFM). Os resultados mostraram uma boa correlação entre o tempo empregado na ativação do eletrodo, microestrutura resultante e a atividade eletroquímica. (Source: Journal of the Brazilian Chemical Society)

Direct electrochemical analysis of dexamethasone endocrine disruptor in raw natural waters

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

This paper describes an electroanalytical methodology using square-wave adsorptive voltammetry, which has been successfully applied for the direct determination of dexamethasone residues in raw natural waters used for the public supply of the Ceará State, Brazil. The obtained detection limits ranged from 7.47 × 10-9 to 1.80 × 10-8 mol L-1 for the three matrices of raw natural waters evaluated. High percentages of average recovery (98.86% ± 0.72), repeatability (0.32% ± 0.05) and reproducibility (0.91% ± 0.20) were obtained in these samples, reaffirming the sensitivity of the procedure. Energy of the LUMO orbitals and Müllikens atomic charges were calculated using the functional BLYP/DNP. The theoretical results allied to the diagnostic criteria of the square-wave voltammetry indic...

Simultaneous extraction and detection of ochratoxin A and citrinin in rice

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

This study compared four extraction procedures for the simultaneous determination of mycotoxins ochratoxin A and citrinin in samples of rice. Soares and Rodriguez-Amaya and Tanaka procedures and the extraction methods QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) and by ultrasound were compared in terms of residue generation, limit of detection, limit of quantification and simultaneous recovery of mycotoxins. Soares and Rodriguez-Amaya and the method by ultrasound presented the lowest recoveries, 83 and 55% for ochratoxin A (OTA) and 48 and 55% for citrinin (CIT), respectively. Tanaka procedure and QuEChERS method presented the highest recoveries, 98 and 105% for OTA and 64 and 78% for CIT, respectively. The latter enabled the simultaneous extraction of the two mycotoxins, with...

HPCL determination of histamine, tyramine and amino acids in shrimp by-products

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

Biogenic amines in high concentration can affect the quality of foods and cause several diseases since they are present in products like seafood, wines, and other fermented products. Shrimp by-products are a rich source of protein hydrolysate that can be used as dietary supplements. Samples (from shrimp by-products) of dry protein powder, liquid protein hydrolysate and flour of shrimp head were analyzed to evaluate the histamine and tyramine contents. Amines were extracted with trichloroacetic acid 5% and derivatized with o-phthaldialdehyde. The chromatographic separation was performed in an analytical column, Chrom SEP SS C18 5 µm (4.6 mm × 150 mm) and a fluorescence detector was used with wavelengths at λex = 335 nm and λem = 440 nm. The mobile phase was a mixture of tetrahydrofuran,...

Advanced QSAR studies on PPARδ ligands related to metabolic diseases

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

PPARδ is a nuclear receptor that, when activated, regulates the metabolism of carbohydrates and lipids and is related to metabolic syndrome and type 2 diabetes. To understand the main interactions between ligands and PPARδ, we have constructed 2D and 3D QSAR models and compared them with HOMO, LUMO and electrostatic potential maps of the compounds studied, as well as docking results. All QSAR models showed good statistical parameters and prediction outcomes. The QSAR models were used to predict the biological activity of an external test set, and the predicted values are in good agreement with the experimental results. Furthermore, we employed all maps to evaluate the possible interactions between the ligands and PPARδ. These predictive QSAR models, along with the HOMO, LUMO and MEP map...

In situ solvent formation microextraction based on ionic liquids and 1-(2-hydroxynaphtalene-1-yl)ethane oxime for determination of zinc

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

A simple in situ solvent formation microextraction (ISFME) method based on use of ionic liquid (IL) as extractant solvent and sodium hexafluorophosphate (NaPF6) as ion-pairing agent was proposed for the concentration of trace levels of zinc. In this method, zinc ion was complexed with 1-(2-hydroxynaphtalene-1-yl)ethane oxime (HNEO) and extracted into an ionic liquid phase. After phase separation, the enriched analyte in the final solution was determined by flame atomic absorption spectrometry (FAAS). ISFME is a fast, simple and suitable method for extraction and concentration of inorganic such as metal ions from sample solutions containing a high concentration of salts. The influences of the analytical parameters on the microextraction efficiency were investigated and optimized. Under the ...

Migration of phthalate-based plasticizers from PVC and non-PVC containers and medical devices

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

The presence of five plasticizer phthalates in bags and sets for intravenous administration and hemodialyzers (HD), which are made of polyvinyl chloride (PVC) and of other polymeric materials, was investigated. Di-(2-ethylhexyl) phthalate (DEHP) in PVC is the only authorized phthalate by regulatory agencies. Phthalate determination was carried out by high resolution liquid chromatograph (HPLC) with UV detection. The results showed that the infusion bags that are made of both PVC and ethylene vinyl acetate (EVA) contained only DEHP. In contrast, the tubing of infusion sets and of HD (as well as the cellulose capillaries of HD) contained not only DEHP but also dibutyl phthalate (DBP). Moreover, all five investigated phthalates were found in HD polysulfone capillaries. Migration of DEHP into ...

Electrospray ionization tandem mass spectrometry of the two main antimalarial drugs: artemether and lumefantrine

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

Electrospray ionization in the positive ion mode and high resolution and high accuracy tandem mass spectrometry performed in a hybrid quadrupole time-of-flight mass spectrometer were used to investigate the dissociation chemistry of the intact molecules of two most widely used antimalarial drugs: artemether and lumefantrine. The dissociation pathways of their cationized and protonated forms were rationalized based on high accuracy mass measurements and isotopic distributions. The obtained results should benefit LC-MS/MS monitoring and quantitation by mass spectrometry of the artemether and lumefantrine molecules, as well as of new derivatives or other structurally related antimalarial drugs.Ionização por electrospray no modo de íons positivos, e espectrometria de massas de alta resoluç...

Evaluation of solid-phase microextraction using a polythiophene film and liquid chromatography with spectrophotometric detection for the determination of antidepressants in plasma samples

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

Polythiophene (PTh) phase electropolymerized on the stainless steel wire was evaluated as solid-phase microextraction (SPME), and analysis by liquid chromatography with spectrophotometric detection (LC-UV) for determination of new-generation antidepressants, selective serotonin reuptake inhibitors (SSRIs) (citalopram, paroxetine, fluoxetine and sertraline), in plasma samples. The influence of electropolymerization variables (scan rate, potential range and scan cycles) was evaluated on SPME performance. The SPME variables (extraction time, temperature, matrix pH, ionic strength and desorption procedure), as well as the influence of plasma proteins on sorption mechanisms were also evaluated. The SPME/LC-UV method developed for determination of antidepressants in plasma sample presented a lin...

Layered metal laurates as active catalysts in the methyl/ethyl esterification reactions of lauric acid

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

In this work we report the synthesis, characterization and investigation of the catalytic activity of layered copper(II), manganese(II), lanthanum(III) and nickel(II) laurates in the methyl and ethyl esterification reactions of lauric acid. In the methyl esterification, conversions between 80 and 90% were observed for all catalysts, while for the ethyl esterification only manganese laurate showed reasonable catalytic activity, with conversions close to 75%. Reuse of copper and lanthanum laurates in three cycles of reaction was also investigated and both catalysts preserved the structure and retained catalytic activity close to that observed for the first reaction cycle.No presente trabalho são reportadas as sínteses, caracterizações e investigações das atividades catalíticas de laur...

Tributyltin in crustacean tissues: analytical performance and validation of method

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

The hermit crab Clibanarius vittatus is a typical organism from intertidal regions being considered as a good bioindicator of tributyltin presence at these environments. Thus this study presents the analytical performance and validation method for TBT quantification in tissues of C. vittatus by gas chromatography with pulsed flame photometric detector (GC-PFPD) after extraction with an apolar solvent (toluene) and Grignard derivatization. The limits of detection of the method (LOD) were 2.0 and 2.8 ng g-1 for TBT and DBT (dibutyltin), respectively, and its limits of quantification (LOQ) were 6.6 and 8.9 ng g-1 for TBT and DBT, respectively. The method was applied to samples from Santos Estuary, São Paulo State, Brazil. TBT and DBT concentrations ranged from 26.7 to 175.0 ng g-1 and from 4...

Pt L2,3 - Edge X-ray absorption spectroscopy investigation of zerovalent [Pt(PPh3)2(η2-L)] {L = C2H4, C60 and C2(CN)4} compounds

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

X-ray absorption spectra at the Pt L2,3-edges have been measured for three [Pt(PPh3)2(η2-L)] {L = C2H4, C60 and C2(CN)4} compounds. The spectral features are effective for measuring the π*-acid strength of ligands (L) coordinated to the Pt(PPh3)2 fragment. The energies of the dπ-orbitals are quantitatively determined using the difference between the edge jumping and the edge maximum shifts of the L2,3-white lines in the second derivatives of the spectra. The dπ-orbital energies follow the order [Pt(PPh3)2(η2-C2H4)] < [Pt(PPh3)2(η2-C60)] < [Pt(PPh3)2{η2-C2(CN)4}]. These dπ-orbital energies are in good agreement with the changes in the bound olefinic carbon bond lengths and the 31P NMR chemical shifts of the coordinated phosphines. Furthermore, the experimental values are in good agr...

Synthesis, characterization and photophysical properties of ESIPT reactive triazine derivatives

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

Four new reactive fluorescent triazine derivatives were obtained from nucleophilic aromatic substitution of cyanuric chloride. The compounds were characterized by infrared spectroscopy (IR), nuclear magnetic resonance (13C and ¹H NMR) and high resolution mass spectrometry (HRMS MALDI). UV-Vis and steady-state fluorescence (in solution and in solid state) spectroscopies were also applied to characterize the photophysical behavior. The dyes are fluorescent by an intramolecular proton transfer mechanism (ESIPT) in the blue-orange region, with a large Stokes shift between 6365-10290 cm-1. The fluorescent cyanuric derivatives could successfully react with cellulose fibers to give new fluorescent cellulosic materials.Uma série de quatro compostos fotoativos derivados da triazina foi obtida a p...

Biomedical applications of nanobiosensors: the state-of-the-art

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

Development of nanobiosensor is one of the most recent advancement in the field of Nanotechnology. Research on optical nanobiosensors with submicron-sized dimensions has opened new horizons for intracellular measurements. Taking advantage of the unique properties of the nanomaterials, faster and sensitive nanobiosensors can be developed. Apart from being sensitive and fast, the studies related to nanobiosensors have geared their efforts towards the development of nanomaterial-based sensors that are affordable, robust and reproducible. The nanobiosensors are equipped with immobilized bioreceptor probes, e.g., antibodies, enzyme substrate. Laser excitation is transmitted to photometric system in the form of optical signal (fluorescence). Nanobiosensors will revolutionize the future of diseas...

A polyether glycol derived from cashew nutshell as a kinetic inhibitor for methane hydrate formation

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

The polyether glycol derived from cashew nutshell liquid (CNSL) inhibited the formation of methane hydrate. The polymer proved to be more efficient than the polyvinyl pyrrolidone-poly(N-vinyl) caprolactam (PVP-PVCap) co-polymer under tested conditions (CH4, 1470 psi and 4 ºC), being the latter one of the best commercially available hydrate inhibitors.O polieterglicol derivado do líquido da casca da castanha do caju (CNSL) inibiu a formação de hidrato de metano. O polímero mostrou-se mais eficiente que o copolímero poli(vinilpirrolidona)-poli-(N-vinilcaprolactama)(PVP-PVCap) nas condições testadas (CH4, 1470 psi e 4 ºC), sendo esse último um dos melhores inibidores de hidratos comercialmente disponíveis. (Source: Journal of the Brazilian Chemical Society)

Asymmetric organocatalytic synthesis of β-Hydroxyynones with a quaternary carbon center under aqueous conditions

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

The chiral tertiary amine thiourea catalyzed direct aldol reaction of unmodified methyl ynones under aqueous conditions is described. This procedure avoided the retro-aldol reaction of the β-hydroxyynone products, and tolerated both the isatin (1H-indole-2,3-dione) and the less active acyclic α-keto esters as acceptors, affording a structurally diverse array of β-hydroxyynones bearing a quaternary carbon center with moderate to good yields and enantioselectivities.A reação aldólica direta de metil inonas não-modificadas sob condições aquosas catalisada pela amina terciária quiral de tiouréia é descrita. Este procedimento evitou a reação retroaldólica dos produtos β-hidroxinonas, e admite as isatinas (1H-indol-2,3-diona) e os menos ativos ésteres α-ceto acíclicos como ace...

New year, new challenges!

Journal of the Brazilian Chemical Society — Thu, 09 Feb 2012 17:45:36 +0100

(Source: Journal of the Brazilian Chemical Society)

Microwave-assisted synthesis under solvent-free conditions of (E)-2-(Benzo[d]thiazol-2-yl)-3-arylacrylonitriles

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

A series of (E)-2-(benzo[d]thiazol-2-yl)-3-arylacrylonitriles was synthesized by microwave assisted Knoevenagel condensation under solvent-free conditions from the corresponding 2-(benzo[d]thiazol-2-yl)acetonitrile and aromatic aldehydes with electrondonating/electron-withdrawing groups. The reaction times were considerably short and the products obtained in moderate yields (50 to 75%) and good purity. The configuration of the acrylonitrile double bond could not be established by regular NMR methods. However, theoretical studies suggest that the E isomer is more stable than Z, which is in good agreement with some experimental evidences.Uma série de (E)-2-(benzo[d]tiazol-2-il)-3-arilacrilonitrilas foi sintetizada pela condensação de Knoevenagel assistida por microondas, na ausência de s...

Topical anti-inflammatory activity of Calea prunifolia HBK (Asteraceae) in the TPA model of mouse ear inflammation

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

Phytochemical study of Calea prunifolia HBK identified two compounds derived from p-hydroxyacetophenone, the 1-(2-hydroxy-5-(1-methoxyethyl)phenyl)-3-methylbut-2 -en-1-one showed a satisfactory anti-inflammatory activity (58.33%), when considering that this is a natural product. Although the two derived compounds are structurally similar, the anti-inflammatory activity of 1-(2-hydroxy-5-methoxyphenyl)-3-methylbut-2-en-1-one was not significant (2.08%). The test was conducted in a model of inflammation induced by topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA) in the ear of mice. The positive control was tested with indomethacin and the negative control was done only with vehicle. These results allow the identification of a pharmacophore group that through molecular modeli...

Integrated utilization of guava (Psidium guajava L.): antioxidant activity of phenolic extracts obtained from guava seeds with supercritical CO2-ethanol

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

In this work, it was explored the possibility of obtaining phenolic extracts with antioxidant activity (AA) from Colombian guava seeds (Psidium guajava L.) using supercritical carbon dioxide adding ethanol as cosolvent (SC CO2/EtOH). The crude extracts were obtained by block extraction designs step to step (four steps) as function of pressure (10, 15 and 20 MPa) and temperature (313, 323 and 333 K) (with four different extraction step designs). In each one of the extracts, the total phenolic content (TPC) and AA were determined (β-carotene bleaching and scavenging DPPH (2,2-diphenyl-1-picrylhydrazyl) methods). This work allowed to obtain a most effective phenolic extract, that presented a most potent antioxidant activity compared toward previous works. The most active extract was subjecte...

Chemometric analysis of ESIMS and NMR data from Piper species

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

The metabolomic profiling based on the application of multivariate analysis (principal component analysis, PCA) of positive mode electrospray ionization mass spectrometric (ESIMS) and ¹H nuclear magnetic resonance (NMR) data of crude extracts highlighted some species characterized by lignans (P. solmsianum, P. truncatum and P. cernuum), neolignans (P. regnellii) and chromenes (P. gaudichaudianum). A specific analysis focusing on species having pendant and globular inflorescences (P. caldense, P. carniconnectivum, P. bowiei and P. permucronatum) or amides-producing species indicated higher potential of the methodology in determining similarities and establishing priorities for further phytochemical investigation. Such intraspecific analysis applied to analyzed seedling leaves of the P. sol...

Electrochemical detection of arsenite with silver electrodes in inorganic electrolyte and natural system mixtures

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

The electrochemical detection of arsenite with silver wire (SWE) or silver disc (SDE) electrodes was carried out in inorganic aqueous solutions, which are similar to those found under natural conditions. Cyclic voltammetry (CV), linear sweep voltammetry (LSV) and anodic stripping voltammetry (ASV) were applied. The investigated factors were pH, nature and concentration of supporting electrolyte and deposition time and voltage for ASV. The changes in the As(III) anodic peak current and potential in standard solutions (e.g., 0.1 mol L-1 Na2SO4, NaNO3, HNO3 and H2SO4) were evaluated. The neutral and basic media of inorganic salts were found to enhance the silver electrode sensitivity more than the acidic media. Thus, it was possible to work in alkaline medium with increased sensitivity for As...

Production of indole-3-acetic acid in the culture medium of microalga Scenedesmus obliquus (UTEX 393)

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

The indoleacetic acid (IAA) is a natural auxin and one of the main growth regulators in higher plants. The extracellular indoleacetic acid (IAA) amount produced by the green microalga Scenedesmus obliquus culture was detected by high performance liquid chromatography (HPLC). It was evaluated the effect of three process variables in the extracellular IAA production in these cultures using 2³ factorial design for screening methodology. The experimental design variables were agitation, illuminance (intensity of luminous flux) and carbon source (CO2/air v/v (%) mixture) at three different levels. The IAA concentration and the specific growth rate were used as response variables. The HPLC analyses showed that under experimental conditions, the IAA amount that is released to the medium by S. ob...

Determination of acidic herbicides in water samples by in situ derivatization, single drop microextraction and gas chromatography-mass spectrometry

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

A method for the determination of trace amounts of acidic herbicides in water samples was developed. The analytical procedure involves in situ derivatization of analytes to their methyl esters with dimethyl sulfate, sampling using single drop microextraction (SDME) and gas chromatography-mass spectrometry (GC-MS). The effects of pH, ionic strength, extraction time, solvent of extraction as well as derivatization conditions were studied. Methyl esters were extracted using 2 µL of n-heptane. The response was linearly dependent on the concentration in the range 0.05-10.0 ng mL-1. Limits of detection were achieved at the level of 1.8-3.0 ng L-1. Derivatization-SDME/GC-MS analysis yielded good precision (RSD between 7.0 and 15.2%). The method was validated by analysis of spiked matrix samples....

Chemistry and bioactivity of Haplopappus remyanus ("bailahuen"), a chilean medicinal plant

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

Chromatography on the resinous extract of aerial parts of Haplopappus remyanus led to the isolation of 18-acetoxy-labda-7,13E-dien-15-oic acid along with the monoterpene derivatives 9-hydroxy-α-terpineol, 9-benzoyloxy-α-terpineol,7-hydroxy-9-benzoyloxy-α-terpineoland 9-benzoyloxy-(1-formyl)-α-terpineol. Structures for the new compounds are proposed on spectroscopic evidence. The presence of quercetin and five other known flavonoids identified in this study could account for the reported high antioxidant activity and the moderate topic anti-inflammatory effect on induced ear oedema. MTT assay with CCRF-CEM tumor cells showed 50% of the cytotoxic activity displayed by doxorubicin under the same conditions. Quantitative differences in chemical composition were detected in comparison with ...

Enzymatic hydrolysis of cassava starch for production of bioethanol with a colombian wild yeast strain

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

Enzymatic hydrolysis of cassava starch for producing glucose syrups was evaluated using alpha-amylase from Bacillus licheniformis and glucoamylase from Aspergillus niger. Moreover, an enzyme mixture of α-amylase from Aspergillus kawachi and glucoamylase from Aspergillus niger was tested. Enzyme conditions for starch hydrolysis were optimized by a factorial experimental design (3³×2) using as variables substrate concentration, enzyme/substrate ratio and time reaction. Optimal enzyme reactions with 100 g of starch per L were: α-amylase at pH 5.0, 80 °C and enzyme dosage of 130.5 U g-1 of starch; and glucoamylase, pH 4.5, 70 °C and enzyme dosage of 81.5 U g-1 of starch. Additionally, optimal conditions for the enzymatic mixture were pH 4.5, 46 °C, and enzyme dosage of 16.4 U g-1 of sta...

Optimization of the HS-SPME technique by using response surface methodology for evaluating chlorine disinfection by-products by GC in drinking water

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

In this work the results of the optimization of headspace solid phase microextraction technique and determination by gas chromatography with micro electron capture detector (HS-SPME/GC-µECD) are described. The best condition of extraction for the four trihalomethanes in drinking water was reached through a response surface methodology's study using a composite 2(5) factorial design. Five experimental conditions of influence such as the type of fiber, extraction and desorption temperatures and extraction and desorption times were evaluated. The most influential factors in the technique of HS-SPME were the extraction temperature and extraction and desorption times. The type of fiber and the desorption temperature had little influence on extraction's efficiency. The best conditions were obta...

Palladium nanoparticles supported on layered hydroxide salts and their use in carbon-carbon coupling organic reactions

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

Palladium nanoparticles supported on zinc hydroxide salts were prepared by intercalation of [PdCl6]2- and its further reduction with ethanol under reflux. All the materials were completely characterized by atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), thermogravimetric/derivative thermogravimetric (TG/DTG) analyses, scanning electron microscopy (SEM), UV-Visible spectrometry and transmission electron microscopy (TEM). TEM analysis confirmed that the palladium nanoparticles were properly supported. The material containing supported palladium nanoparticles was used to promote Heck and Suzuki coupling reactions starting from aryl halides, with isolated yields of 98, 75 and 62% of biphenyl, cinnamic acid and 3-nitrobiphenyl, respectively.Nanopartículas de paládio suportadas ...

Contribution to the study of the formation mechanism of ordered porous carbons from a soft-template method using the copolymer triblock (PEO140PPO39PEO140) and a phenolic resin

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

Different porous carbons were synthesized using direct self-assembly of a nonionic surfactant (PEO140PPO39PEO140, PEO poly(ethylene oxide) and PPO poly(propylene oxide)) and a phenolic resin. According to dynamic light scattering (DLS) experiments realized before the flocculation, the formation of covered hybrid micelles (precursors of ordered mesoporous materials) competes with the formation of resol particles depending on the surfactant concentration. High synthesis temperature increases the formation of mesoporosity. When monomers (instead of oligomers) are used as resin precursors, the mesoporosity is also enhanced. However in this case, the formation of resol particles is also favored. The obtained materials are mainly microporous, indicating that the formed polymer/surfactant hybrid ...

Effect of the molecular weight on the physicochemical properties of poly(lactic acid) nanoparticles and on the amount of ovalbumin adsorption

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

Poly(lactic acid) (PLA) nanoparticles were prepared to be used as potential platform for vaccine systems. Commercial high molecular weight PLA (PLA HMW) with Mw 1.5 × 10(5) and low molecular weight poly(lactic acid) (PLA LMW) with Mw 9.3 × 10³ were obtained by direct polycondensation from D,L lactic acid and used to prepare nanoparticles by solvent displacement method. The effect of the molecular weight on the physicochemical properties of the polymers, on the nanoparticles dispersions and the amount of ovalbumin (OVA) adsorption was studied. The PLA HMW and PLA LMW were characterized by Fourier transformed infrared spectroscopy (FTIR), thermogravimetrical analysis (TGA), modulated temperature differential scanning calorimetry (MTDSC) and gel permeation chromatography (GPC). The particl...

Chemical and spectroscopic characterization of a vegetable oil used as dielectric coolant in distribution transformers

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

In this work, a complete UV-Vis, IR and (¹H, 13C and DEPT) NMR spectroscopic analysis was performed for a FR3® vegetable oil sample used as dielectric coolant in an experimental distribution transformer. The same spectroscopic analysis was performed for three used FR3® oil samples (i.e., 4 months in use, 8 months in use and 7 years in use), removed from several operating distribution transformers. Comparison of the data indicated that no significant spectroscopic changes, and hence, no structural changes occurred to the oils by the use. Chemical transformations like catalytic hydrogenation (hardening) and hydrolysis were performed to the FR3® oil sample and the obtained products were analyzed by spectroscopic methods in order to collect further structural information about the FR3® oi...

Study of growth, optical and morphological properties of Zn(O;OH)S thin films synthesized by CBD method

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

In this work, we investigated thin films of Zn(O;OH)S as substitute of thin films of CdS, which are conventionally used as buffer layer in chalcopyrite based solar cells. Thin films of Zn(O;OH)S were deposited by chemical bath deposition (CBD) method using a chemical bath containing thiourea, zinc acetate, sodium citrate and ammonium. Soda-lime glass and soda-lime glass covered with thin films of CuGaSe2 (CGS) were used as substrates in the deposition of thin films of Zn(O;OH)S. The Avrami equation was used to study the growth rate of thin film of Zn(O,OH)S on both substrates. The influence of the substrate kind and time of synthesis on the growth rate, optical and morphological properties of the as-grown thin films of Zn(O,OH)S have been carried out through spectrophotometry and atomic fo...

Polar compounds isolated from the leaves of Calea prunifolia H.B.K. and their anti-adrenergic related vasodilator activity

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

The leaves of Calea prunifolia H.B.K., medicinal specie used in Colombian folk medicine for hypertension have been analysed for their chemical constituents, resulting in the isolation of one flavonoid glycoside, one quinic acid derivative and one kaurane diterpenoid glycoside. Their chemical structures were elucidated on the basis of spectral analysis, including HRMS, 1D- and 2D-NMR data. The vasodilator effect related to anti adrenergic activity of the three compounds was evaluated in isolated aortic rings from Wistar rats contracted cumulatively with phenylephrine (from 1× 10-9 to 5 × 10-5 mol L-1). Although these compounds were devoid of significant vasodilator activity when they were tested alone (1 µg mL-1), mixtures of them (1:1:1) and the own EtOH extract exerted preventive anti-...

Principal component analysis of changes due to water stress for some osmolytes, pigments and antioxidant enzymes in Gmelina arborea Robx: leaves from trees planted in northern Colombia

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

This study was thus aimed at measuring catalase, peroxidase and ascorbate peroxidase activities as well as total sugar, reducing sugar, proline, carotenoids, chlorophyll A, B and total chlorophyll content in G. arborea leaves sampled during three seasons of the year. Principal component analysis showed that the measured variables had patterns depending on age and season, in addition to an inverse correlation between chlorophyll A, B and total chlorophyll and the other measured variables.Gmelina arborea é uma espécie de alto impacto econômico devido a vantagens como árvore madeireira de rápido crescimento. A G. arborea é plantada na costa norte da Colômbia, especialmente nas planícies secas do Caribe. No entanto, condições de déficit hídrico a que estão periodicamente submetido...

DFT-GIAO calculation of properties of 19F NMR and stability study of environmentally relevant perfluoroalkylsulfonamides (PFASAmide)

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

In this study we have determined the shielding constant (Σ) for different fluorine nucleus of the 18 molecules under study, using density functional theory (DFT) and GIAO method with the B3PW91/6-31+G(d,p) level of calculation. The Σ calculations were made at vacuum and in presence of a solvent. The values of chemical shifts (d), were also calculated in a different level of theory. The best results were obtained with the level of calculation DFT-GIAO/B3PW91/6-31+G(d,p) by considering the solvent such as dimethylsulfoxide (DMSO), chloroform (CHCl3), acetone (CH3COCH3) and methanol (CH3OH). The results were interpreted in terms of calculated hardness at DFT/B3PW91/6-31+G(d, p) level. The behaviour of the hardness was higher in the molecules of four carbons PFASA than eight carbons. This ex...

Alkaline reactivity of arsenical natrojarosite

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

Jarosites are compounds that can undergo substitutions with several elements of environmental importance (such as As5+) during precipitation. Arsenic integrated in the structure could influence the solubility of the jarosite, potentially stabilizing the structure under a wide range of conditions that are tolerated by pure jarosite. Alkaline reactivity is characterized by the removal of sulfate and sodium ions from the lattice and by the formation of a gel consisting of iron hydroxides with adsorbed arsenate. The decomposition curves show an induction period, followed by a conversion period. The induction period is independent from the particle size and decreases exponentially as the temperature increases. The conversion period is characterized by the formation of a hydroxide halo around an...

Searching of protein targets for alpha lipoic acid

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

Alpha lipoic acid (ALA) is one of the most powerful antioxidants and a cofactor in enzyme complexes, although its mechanisms are still unknown. The search for protein targets of ALA is fundamental to understand its signaling pathways. A bioinformatics approach was used to find hypothetical targets for ALA using the Target Fishing Dock Server (TarFisDock). Affinity scores for the best hits were calculated by AutoDock Vina. Relevant targets included leukotriene A4 hydrolase, voltage gated potassium channel, alpha hydroxysteroid dehydrogenase and epoxide hydrolase, proteins involved in cancer, diabetes, and neurological and cardiovascular disorders. The counterpoise-corrected interaction energies calculated for proteins that bind R-ALA showed favorable interactions R-ALA-residues. Superpositi...

Molecular interactions of mefenamic acid with lipid bilayers and red blood cells

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

This report presents evidence that mefenamic acid interacts with red cell membranes as follows: (i) in scanning electron microscopy (SEM) studies on human erythrocytes it has been observed that the drug induced shape changes, forming stomatocytes; (ii) X-ray diffraction showed that the drug interacted with DMPC bilayers; somewhat lower perturbing effects on DMPE were detected; (iii) FT-IR measurements showed that NSAID induced fluidization of both DMPC and DMPE acyl chains; (iv) Förster resonance energy transfer spectroscopy (FRET) indicated a rapid intercalation of the mefenamic acid into DMPC liposome hydrophobic chains.O ácido mefenâmico é um anti-inflamatório não esteroidal (NSAID), também prescrito no tratamento da dor. No presente trabalho, os efeitos estruturais na membrana d...

XXIX Latin American Congress of Chemistry

Journal of the Brazilian Chemical Society — Sun, 15 Jan 2012 07:04:39 +0100

(Source: Journal of the Brazilian Chemical Society)

A new megastigmane diglycoside from Litsea glutinosa (Lour.) C. B. Rob.