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.

Derivado cinamoílico com atividade no reparo de DNA e outras substâncias de Cinnamomum australe (Lauraceae)

The bioactive compound trans-3'-methylsulphonylallyl trans-cinnamate (1) along with the inactives iryelliptin (2) and (7R,8S,1'S)-delta8'-3',5'-dimethoxy-1',4'-dihydro-4'-oxo-7.0.2',8.1'-neolignan (3) were isolated from the leaves of Cinnamomum australe. The structures of these compounds were assigned by analysis of 1D and 2D NMR data and comparison with data registered in the literature for these compounds. The DNA-damaging activity of 1 is being described for the first time.

Síntese e atividade antiedematogênica de derivados N-triptofil-5-benzilideno-2,4-tiazolidinadiona e N-triptofil-5-benzilideno-rodanina

Derivatives of N-tryptophyl-5-benzylidene-2,4-thiazolidinedione (7a-c) and N-tryptophyl-5-benzylidene-rhodanine (7d-f) were prepared by condensation of the intermediates 5 and 6 with different benzaldehydes, respectively. Their structural elucidation was carried through by IR, ¹H NMR and MS. The acute toxicity and antiedematogenic activity of the compounds 7b,c and 7e,f were evaluated. The data did not reveal any sign of toxicity, and no mortality was registered. As indomethacin (10 mg/kg; v.o.), the antiedematogenic activity of the compounds 7b (50 mg/kg; v.o.) and 7e, 7f (50 or 100 mg/kg; v.o.) against carrageenan-induced paw edema was verified at time intervals of 180 min.

Estudo fitoquímico e avaliação da atividade moluscicida do Calophyllum brasiliense Camb (Clusiaceae)

The bioassay-guided fractionation against Biomphalaria glabrata of hydroalcoholic extracts of Calophyllum brasiliense aerial parts led to the isolation of the coumarin, named (-) mammea A/BB. The compound had its structure determined by both spectroscopic techniques (NMR ¹H, NMR 13C, gHSQC, gHMBC and MS) and some literature comparison data. The probit analysis of (-) mammea A/BB showed LD50 = 0.67 ppm and LD90 = 1.47 ppm. In addition, the dichloromethane extract obtained from C. brasiliense leaves with significant molluscicidal activity against Biomphalaria glabrata was analyzed by HPLC-UV.

Catalisador Pd/gama-Al2O3: efeito do tamanho de partícula na atividade catalítica para combustão do CH4

Methane, the main constituent of natural gas (> 85%), is employed in large scale as an energy source (thermoelectric power plants, automobiles, etc). However, significant quantities of this gas contribute to the greenhouse effect. The catalytic combustion of methane can minimize these emissions. Palladium is one of the metals that shows the highest activity, depending on the different active forms of the metal. In this article, we focus on the influence of particle size and pretreatment on the catalytic performance of palladium in the methane combustion reaction.

Estratégias utilizadas no combate a resistência bacteriana

This article provides an overview on the recent achievements to combat Gram-positive bacteria and the mechanisms related to antimicrobial activity and bacterial resistance. Selected synthetic methodologies to access structurally diverse bioactive compounds are presented in order to emphasize the most important substances currently developed to overcome multiresistant strains. The main properties of vancomycin and related glycopeptide antibiotics are also discussed as a background to understanding the design of new chemotherapeutic agents.

Atividade antioxidante de óleos essenciais de espécies de Croton do nordeste do Brasil

Three Croton species, C. zenhtneri, C. nepetaefolius and C. argyrophylloides, were collected at two different times, 6:00 and 13:00 h, their essential oils were extracted by steam distillation and analyzed by gas Chromatography / Mass Spectrometry. The percentage yield of oil constituents changes along the day. The oils were submitted to the antioxidant test thiobarbituric acid reactive species, using BHT and a-tocoferol as the reference compounds. All oils exhibited good antioxidant activities. In general, C. zenhtneri and C. argyrophylloides essential oils showed higher antioxidant activity than C. nepetaefolius.

Constituintes químicos e atividade antioxidante de Sida galheirensiS Ulbr. (Malvaceae)

The phytochemical investigation of Sida galheirensis led to the isolation of 5,4'-dihydroxy-3,7,3´-trimethoxyflavone, 17³-ethoxyphaeoforbide, a rare natural product, 6,7-dimethoxycoumarin, ortho-hydroxybenzoic acid, sitosterol-3-O-beta-D-glucopyranoside, stigmasterol-3-O-beta-D-glucopyranoside, 5,7,4'-trihydroxyflavone, 5,7,3',4'-tetrahydroxyflavone, kaempferol-3-O-beta-D-(6"-E-p-coumaroyl) glucopyranoside and luteolin 7-O-beta-D-glucopyranoside. Their structures were assigned based on spectroscopic analyses, including two-dimensional NMR techniques. Antioxidant activities of hexane, CHCl3, EtOAc, BuOH and EtOH extracts of Sida galheirensis were measured using the 1,2-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging assay. This is also the first work reporting the chemical investigation of Sida galheirensis.

Fenóis totais e atividade antioxidante de cinco plantas medicinais

This paper describes total phenolics content and antioxidant activity in the ethanolic extract of leaves, bark and roots of five medicinal plants: Terminalia brasiliensis Camb., Terminalia fagifolia Mart. & Zucc., Copernicia cerifera (Miller) H.E. Moore, Cenostigma macrophyllum Tul. var. acuminata Teles Freire and Qualea grandiflora Mart. The total phenolics content of the plant extracts, determined by the Folin-Ciocalteu method, varied from 250.0 ±8,2 to 763,63 ± 13.03 mg of gallic acid equivalent/g dry EtOH extract. The antioxidant activity of extracts was evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay system. Extract of bark from T. brasiliensis, the most active, with an EC50 value of 27.59 ± 0.82 µg/mL, was comparable to rutin (EC50 = 27.80 ± 1.38) and gallic acid (EC50 = 24.27 ± 0.31), used as positive controls. The relationship between total phenolic content and antioxidant activity was positive and significant for T. brasiliensis, C. macrophyllum and C. cerifera.