Caracterização de catalisadores Cu/CeO2/Al2O3 por redução a temperatura programada e atividade para oxidação de CO

The kinetic parameters for the CO oxidation reaction using copper/alumina-modified ceria as catalysts were determined. The catalysts with different concentrations of the metals were prepared using impregnation methods. In addition, the reduction-oxidation behaviour of the catalysts were investigated by temperature-programmed reduction. The activity results show that the mechanism for CO oxidation is bifunctional : oxygen is activated on the anionic vacancies of ceria surface, while carbon monoxide is adsorbed preferentially on the higher oxidation copper site. Therefore, the reaction occurs on the interfacial active centers. Temperatures-programmed Reduction patterns show a higher disperdion when cerium oxide is present.

A combustão catalítica do metano: estudo estatístico do efeito das variáveis de preparação e pré-tratamento de catalisadores de paládio suportado sobre a atividade catalítica

The catalytic combustion of methane on alumina supported palladium catalysts was studied. It has been reported that the activity of the catalyst increases with its time on line, despite of an increase of the palladium particle size. However, different preparation, pretreatment and testing conditions can be the reason for the observed different results. An experimental design, which allows to verify the influence of several parameters at the same time with a good statistical quality, was used. A Plackett-Burman design was selected for the screening of the variables which have an effect on the increase of the catalyst activity.

Proposição, validação e análise dos modelos que correlacionam estrutura química e atividade biológica

The present paper aims to bring under discussion some theoretical and practical aspects about the proposition, validation and analysis of QSAR models based on multiple linear regression. A comprehensive approach for the derivation of extrathermodynamic equations is reviewed. Some examples of QSAR models published in the literature are analyzed and criticized.

Síntese e avaliação da atividade fitotóxica de lactonas derivadas do 2,4-dimetil-8-oxabiciclo[3.2.1]-oct-6-en-3-ona

The alkene 2,4-dimethyl-8-oxabicyclo[3.2.1]-oct-6-en-3-one (3) was converted to 1,3,10-trimethyl-8-oxabicyclo[5.3.0]-dec-3-ene-2,9-dione (7) and 1,3-dimethyl-8-oxabicyclo[5.3.0]-dec-3-ene-2,9-dione (8) with a 55% overall yield in both cases. Lactones (7) and (8) were converted in two steps to 1,3,4-trimethyl-13-methylene-6-oxatricyclo[8.3.0.0(3,7)]-trideca-2,5,12-trione (12) (63%) and 1,3-dimethyl-13-methylene-6-oxatricycle[8.3.0.0(3,7)]-trideca-2,5,12-trione (13) (45% from 8). The effect of lactones (7), (8), (12), (13) and the intermediates (5) and (6), at the concentration of 250 mug mL-1, on the growth of Cucumis sativus L. and Sorghum bicolor L. was evaluated. The best results were observed for lactone (13) that caused 100% inhibition on the root growth of C. sativus and lactone (12) that inhibited 90% of the root growth for S. bicolor.

Validação lateral em relações quantitativas entre estrutura e atividade farmacológica, QSAR

The comparative QSAR is a tool for validating any statistical model that seems to be reasonable in describing an interaction between a bioactive new chemical entity, BIONCE, and the biological system. In order to deeper the understanding of the relationships and the meaning of parameters within the model it is necessary some kind of lateral validation. This validation can be accomplished by chemical procedures using physicochemical organic reactions and by means of biological systems. In this paper we review some of such comparisons and also present a lateral validation between the same set of antimicrobial hydrazides acting against Saccharomyces cerevisiae yeast and Escherichia coli bacterium cells. QSARs are presented to shed light in this important way of stating that the QSAR model is not the endpoint, but the beginning.

Espectroscopia vibracional: sistemática para o cálculo dos estiramentos CO de complexos carbonílicos e determinação da sua atividade IV e Raman

IR bands related to M-C stretchings are not diagnostically significant for the identification of carbonyl groups in the spectra of carbonyl complexes. Otherwise, the frequency, intensity and number of bands for the CO stretchings provide very useful informations about the number of CO ligands and many others structural proprieties, like the presence of bridged CO groups. We report about a relatively simple and useful method for the determination of the CO stretchings of carbonyl complexes, which considers only the bond stretching internal coordinates of the CO groups.

Compostos organolantanídeos contendo o ligante pirazinamida: síntese, caracterização e atividade catalítica na polimerização do etileno

In this work we report the synthesis of some organolanthanide compounds which were identified as LnCl2Cp(PzA)2, Ln = Nd, Sm, Eu and Tb, Cp = cyclopentadienyl and PzA = pirazinamide, by elemental analyses, complexometric titration with EDTA, thermal analyses and IR spectra. Thermal analysis and infrared spectra indicated that the coordination of the pyrazinamide to the lanthanide ions was made by the O atom of the carbonyl group and by one or both N atoms of the pyrazinamide ring. This class of compound showed catalytic activity of ca. 4.0 to 6.4 kgPE molLn-1 h-1 bar-1, in ethylene polymerization, using methylaluminoxane as cocatalyst. The resulting polyethylene presented low crystallinity (20%).

Estudo fitoquímico e avaliação da atividade moluscicida da Kielmeyera variabilis Mart (Clusiaceae)

Methanol extract obtained from Kielmeyera variabilis stems showed significant molluscicidal activity against Biomphalaria glabrata. The phytochemical studies of the plants stem to the isolation of three xanthones (assiguxanthone-B, kielcorin and 1,3,5,6-tetrahtydroxy-2-prenylxanthone) and a organic acid (2,5-dihydroxy benzoic acid). The structures of these compounds were identified by IR, MS, ¹H and 13C NMR spectral analysis and comparison with literature data.

Sistema de alimentação gás-líquido para medidas de atividade catalítica

This note has as objective to present the advantages of the use of syringe-type pumps for the feeding of liquid reactants, together with mass flow controllers for gases, instead of the saturators, as it is generally accomplished. Among the advantages, the system with syringe pumps presents a greater flexibility in flow control as well as in composition compared with the system that uses saturator. In addition, the flow of the liquid reactants is known with precision in the syringe pump system.

Seleção de plantas com atividade anticolinasterase para tratamento da doença de Alzheimer

Alzheimer's disease (AD) is a neurodegenerative disease characterized by cognite impairment and personality changes. The development of drugs for the treatment of the cognitive deficits of AD has focused on agents which counteract loss in cholinergic activities. These symptons of AD have been successfully treated with acetylcholinesterase (AchE) inhibitors (eg. galanthamine). There still is great interest in finding better AchE inhibitors. We use Ellmann's microplate assay and silica gel thin-layer chromatography (TLC) to screen natural products from plants as new sources of AchE inhibitors.

Isolamento e avaliação da atividade nematicida de constituintes químicos de Mucuna cinerea contra Meloidogyne incognita e Heterodera glycines

Phytochemical investigation of the aerial parts and roots of Mucuna cinerea led to the isolation of a mixture of fatty acids, triacylglicerols, beta-sitosterol, stigmasterol, stigmasterol glucoside, daucosterol, asperglaucide (4) and the isoflavonoids prunetin (1), genistein (2), medicarpin (3), daidzein (5), 7-O-alpha-glycopiranosyl daidzein (6). An in vitro bioassay was carried out with compounds 1-4, at the concentration of 50 and 5 mug mL-1 against the phytonematodes M. incognita and H. glycines. Although the four compounds showed some nematocidal property, the most active was (1), causing 70% mortality of M. incognita at the concentration of 50 mug mL-1.

Terpenos com atividade inseticida: uma alternativa para o controle químico de insetos

Many substances from different sources have been used by men for decades to control insects. After the 2nd World War, the use of inorganic compounds have declined drastically and natural products, as well as synthetic derivatives, have been widely used instead. The search for natural alternatives have improved the development of bench top bioassays and an array of synthetic approaches for known and novel natural products that shows relevant activities as feeding supressors and deterrents. The studies concerning mode of action and environmental impact of these substances, that may be biodegradable and selective for undesired insects, had led to the evaluation and discovery of a number of molecules, mostly terpenoids and alkaloids, that are well reported as candidates for inseticidal compounds that could be an effective alternative for insects control with a lower impact on human health, household animals and the environment.

Síntese e avaliação da atividade fitotóxica de novos análogos oxigenados do ácido helmintospórico

Several compounds related to helminthosporic acid (3) were synthesized via the [3+4] cycloaddition. The reaction of 3-hydroxymethyl-2-methylfuran (12) with 1,1,3,3-tetrabromo-4-methylpentan-2-one (13) resulted in 7-hydroxymethyl-4alpha-isopropyl-1alpha-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (8) (37%) and 7-hydroxymethyl-2alpha-isopropyl-1alpha-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (14) (12%), which were converted into 7-formyl-4alpha-isopropyl-1alpha-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (16) (32% from 8) and 7-formyl-2alpha-isopropyl-1alpha-methyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (18) (40% from 14), respectively. Reduction of (8) resulted in 7-hydroxymethyl-4alpha-isopropyl-1alpha-methyl-8-oxabicyclo[3.2.1]oct-6 -en-3alpha-ol (11) (63% from 8) and 7-hydroxymethyl-4alpha-isopropyl-1alpha-methyl-8-oxabicyclo[3.2.1]oct-6-en-3 beta-ol (15) (30% from 8). The 4alpha-isopropyl-1alpha-methyl-3-oxo-8-oxabicyclo[3.2.1]oct-6-en-7-oic acid (19) was obtained by oxidation of (16) (78%). The results of biological tests are described in details. The best result was observed for compound (15) that caused 76% inhibition on the root growth of D. tortuosum.

Métodos de preparação e atividade biológica do ácido quinolínico e derivados

In 1981 2,3-pyridine dicarboxylic acid (quinolinic acid) was discovery to be a selective agonist for the N-methyl -D-aspartic acid (NMDA) receptor. As a consequence it possesses neurotoxic activity resulting from overstimulation of the receptor. Quinolinic acid is implicated as an etiological factor in a range of neurodegenerative disease including AIDS related dementia, Huntington´s disease and Lyme disease. In the design of novel therapies to treat these diseases, some molecules have been identified as an important target. In this paper we described different methods to prepare quinolinic acid and derivatives.

Produtos naturais para o controle da transmissão da dengue: atividade larvicida de Myroxylon balsamum (óleo vermelho) e de terpenóides e fenilpropanóides

The bioassay-guided fractionation of the hexane extract obtained from the medicinal plant Myroxylon balsamum (red oil) was conducted in preparative thin layer chromatography on silica gel. The obtained fractions and some terpenoids and phenylpropanoids were assayed as larvicidal on third instar Aedes aegypti larvae, NPPN colony. The results indicate that the sesquiterpene nerolidol was the active constituent in the extract and that the sesquiterpenes were more active than the monoterpenes and phenylpropanoids utilized in this study. Lipophilicity seems to be an important property for the activity since the compounds with hydroxyl, carbonyl and methoxyl groups were less active. The results confirm also that essential oils can be a good tool for the control of dengue.