Atividades biológicas de xilana de sabugo de milho

The corn cob is an agricultural by-product still little used, this in part due to the low knowledge of the biotechnological potential of their molecules. Xylan from corn cobs (XSM) is a polysaccharide present in greater quantity in the structure of plant and its biotechnology potential is little known. This study aimed to the extraction, chemical characterization and evaluation of biological activities of xylan from corn cobs. To this end, corncobs were cleaned, cut, dried and crushed, resulting in flour. This was subjected to a methodology that combines the use of alkaline conditions with waves of ultrasound. After methanol precipitation, centrifugation and drying was obtained a yield of 40% (g/g flour). Chemical analysis indicated a high percentage of polysaccharides in the sample (60%) and low contamination by protein (0.4%) and phenolic compounds (> 0.01%). Analysis of monosaccharide composition indicated the presence of xylose:glucose:arabinose:galactose:mannose:glucuronic acid in a molar ratio 50:20:15:10:2.5:2.5. The presence of xylan in the sample was confirmed by nuclear magnetic resonance (¹H and ¹³C) and infrared spectroscopy (IR). Tests were conducted to evaluate the antioxidant potential of XSM. This showed a total antioxidant capacity of 48.45 EAA/g sample. However, did not show scavenging activity of superoxide and hydroxyl radical and also reducing power. But, showing a high capacity chelating iron ions with 70% with about 2 mg/mL. The ability to XSM to influence cell proliferation in culture was also evaluated. This polymer did not influence the proliferation of normal fibroblast cells (3T3), however, decreased the rate of proliferation of tumor cells (HeLa) in a dose-dependent, reaching an inhibition of about 50% with a concentration around 2 mg/mL. Analyzing proteins related to cell death, by immunoblotting, XSM increases the amount of Bax, Bcl-2 decrease, increase cytochrome c and AIF, and reduce pro-caspase-3, indicating the induction of cell death induced apoptosis dependent and independent of caspase. XSM did not show anticoagulant activity in the PT test. However, the test of activated partial thromboplastin time (aPTT), XSM increased clotting time at about 5 times with 600 μg of sample compared with the negative control. The presence of sulfate on the XSM was discarded by agarose gel electrophoresis and IR. After carboxyl-reduction of XSM the anticoagulant activity decreased dramatically. The data of this study demonstrate that XSM has potential as antioxidant, antiproliferative and anticoagulant compound. Future studies to characterize these activities of XSM will help to increase knowledge about this molecule extracted from corn and allow their use in functional foods, pharmaceuticals and chemical industries.

Estudo da adsorção de íons metálicos em caulinita para água de reuso

Dissertação (Mestrado em Tecnologia Nuclear)

Desenvolvimento e validação de metodologias para quantificação de 3,4 metilenodioximetanfetamina (MDMA) em comprimidos de ecstasy por cromatografia gasosa e ressonância magnética nuclear

Dissertação (mestrado)—Universidade de Brasília, Instituto de Química, 2016.

Poli-líquidos iônicos e complexos solúveis de Eu3+ e Tb3+ : bioimageamento celular seletivo

Dissertação (mestrado)—Universidade de Brasília, Instituto de Química, Programa de Pós-Graduação em Química, 2015.

Desenvolvimento de metodologias analíticas alternativas por cromatografia gasosa para análise de biodiesel

Since the beginning of the National Program for Production and Use of Biodiesel in Brazil, in 2004, different raw materials were evaluated for biodiesel production, trying to combine the agricultural diversity of the country to the desire to reduce production coasts. To determine the chemical composition of biodiesel produced from common vegetables oils, international methods have been used widely in Brazil. However, for analyzing biodiesel samples produced from some alternative raw materials analytical problems have been detected. That was the case of biodiesel from castor oil. Due the need to overcome these problems, new methodologies were developed using different chromatographic columns, standards and quantitative methods. The priority was simplifying the equipment configuration, realizing faster analyses, reducing the costs and facilitating the routine of biodiesel research and production laboratories. For quantifying free glycerin, the ethylene glycol was used in instead of 1,2,4-butanetriol, without loss of quality results. The ethylene glycol is a cheaper and easier standard. For methanol analyses the headspace was not used and the cost of the equipment used was lower. A detailed determination of the esters helped the deeper knowledge of the biodiesel composition. The report of the experiments and conclusions of the research that resulted in the development of alternative methods for quality control of the composition of the biodiesel produced in Brazil, a country with considerable variability of species in agriculture, are the goals of this thesis and are reported in the following pages

Determinação de paclobutrazol em manga por cromatografia líquida de alta eficiência.

Este trabalho descreve um método para determinação de paclobutrazol em amostras de manga. A extração foi feita em metanol e as análises por cromatografia líquida de alta eficiência (CLAE), usando coluna de fase-reversa, C-18, fase móvel metanol/água 60:40, v/v, detecção e quantificação a 220 nm. Os seguintes parâmetros de validação foram obtidos: limite de detecção do método de 0,025 mg kg-1, limite de quantificação do método de 0,050 mg kg-1, linearidade de 0,100?5,00 mg L-1 (r2? 0,9994); recuperação de 82 a 92%, precisão intermediária (%RSD) < 12%, para paclobutrazol. O método mostrou ser simples, eficiente e confiável para a determinação de resíduos de paclobutrazol em amostras de manga.

Aplicação do método QuEChERS na análise de agrotóxicos em uva in natura por cromatografia líquida acoplada à espectrometraia de massas em tandem (LC-MS-MS).

2008

Degradação de picloram em águas utilizando o reagente de fenton e monitoramento por cromatografia líquida.

2008

Degradação de glifosato por fotocatálise heterogênea utilizando filmes finos de TiO2 suportados em anéis de quartzo seguida de análise por cromatografia líquida com detecção por fluorescência.

2006

Calibração da Reflectometria no Domínio do Tempo (TDR) para a estimativa da concentração da solução no solo

Time Domain Reflectometry (TDR) is a reliable method for in-situ measurements of the humidity and the solution concentration at the same soil volume. Accurate interpretation of electrical conductivity (and soil humidity) measurements may require a specific calibration curve. The primary goal of this work was to establish a calibration procedure for using TDR to estimate potassium nitrate concentrations (KNO3) in soil solution. An equation relating the electrical conductivity measured by TDR and KNO3 concentration was established enabling the use of TDR technique to estimate soil water content and nitrate concentration for efficient fertigation management.

Efeito cariostático de restaurações adesivas em superfícies radiculares: estudo in vitro

Dental materials that release fluoride have been shown to be effective in caries inhibition around restorations. Adhesive materials would also be effective in caries inhibition by sealing and protecting cavity margins from acidic demineralization. This in vitro study tested the hypothesis that composite restorations with a dentin adhesive system have a caries preventive effect similar to that of an adhesive material with fluoride - glass-ionomer cement - on root surfaces. Twenty roots from extracted sound third molars were embedded in polystyrene resin and ground flat. Standardized cavities were prepared in leveled root surfaces and randomly restored with (a) Chelon-Fil (Espe) or (b) Z100/SingleBond (3M). Baseline indentations were measured at 100, 200 and 300 mum from the occlusal margins of each restoration and the surface microhardness values were obtained using a Knoop diamond indenter. A 2.0 mm wide margin around the restorations was submitted to a pH-cycling model, at 37ºC. After that, surface microhardness was measured again, as it was before. The differences between baseline and final surface microhardness were considered for statistical analysis. The median values of differences were (a): -3.8; -0.3; -1.0; and (b): 3.3; 2.5; 1.7, for the distances of 100, 200 and 300 mum, respectively. The Kruskal-Wallis test did not show statistically significant difference between 100, 200 and 300 mum distances in each tested group. There was no difference between the studied materials at the distances of 200 and 300 mum. Chelon-Fil was statistically different from Z100/SingleBond, at 100 mum (p<0.05). Under the studied conditions, the glass-ionomer cement had a higher caries preventive effect than the composite/dentin adhesive restorations.

ESTUDO DA PREPARAÇÃO DOS EXTRATOS DE PRÓPOLIS E SUAS APLICAÇÕES

Ethanolic extracts from propolis were performed by using lhe water and vaflous coneentrations of etanol as solvent. The extracts were investigated by measurement of absorption spectruin with Uv-spectrophotometer (UV-scanning), reversed phase-high performance thin-layer chromatography, Reversed phase-HPLC. Maximum absorption of ali extracts was 290 nm, resembling flavonoid compounds and 80% ethanolic extract showed highest absorption at 290 nm. The most isosakuranetin, quercefin, and kaempferol were extracted from mixtures of propolis and 60% etanol, whereas 70% etanol extracted te most pinocembrin and sakuranetin, but 80% etanol extracted more kaempferide, acacetin, and isorhamnetin from propolis. The 60 to 80% ethanolic extracts ofpropolis inhibited highly to microbial growth and 70 and 80% ethanolic extracts showed lhe greatest antioxidant activity and 80% ethanolic extract inhibited highly to hyaluronidase activity.

TEOR DE CAFEÍNA EM CAFÉS BRASILEIROS

Different brands and batches of brazilian regular and instant coffee were purchased in supermarkets of Campinas? city and analysed for caffeine content. The method used involved extraction with boiling water, clarification with saturated basic acetate and determination by high performance liquid cromatography. Analysis was carried out using a Model 6000 A solvent delivery system (Waters associates), and a Model 7125 sample injector system (Reodyne, Inc.) with a 5µl sample loop. The system was also equipped with a Waters Model M440 absorbance detector set at 254 nm. A Merck ODS 5µm column (15 cm x 4.6 mm i.d.) was used to separate the caffeine. The mobile phase was methanol:water (25:75, v/v). The caffeine content varied for different brands and types of coffee and according to the beverage preparation technique. Values in the range of 0.43 to 0.85 mg/ml and 0.61 to 0.82 mg/ml were determined in regular and instant coffee, respectively.