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Recebido em 27/2/12; aceito em 23/10/12; publicado na web em 20/2/13 SYNTHESIS, CHARACTERIZATION AND STUDY OF THE PROPERTIES OF A NEW MONONUCLEAR QUERCETIN COMPLEX CONTAINING Ga(III) IONS. Flavonoids are one of the most important compound groups applied as medicine given their antioxidant properties, but several intrinsic properties can be improved through structural modifications to their molecules. Here, the synthesis and characterization of a new gallium (III) complex with quercetin is described. Electrochemical properties, as well as antioxidant and cytotoxic activities, were investigated and compared to the free flavonoid molecule. The mononuclear complex obtained, [Ga(C 15 INTRODUÇÃOOs flavonoides são compostos de baixa massa molar com uma estrutura base constituída por dois anéis aromáticos (A e B) ligados através de um anel pirano (C), como pode ser visualizado na Figura 1. Eles representam um dos grupos fenólicos mais importantes e diversificados entre os produtos de origem natural, sendo amplamente distribuídos no reino vegetal.1 Nos últimos anos essas moléculas têm atraído a atenção de muitos pesquisadores, pois exibem notável variedade de atividades biológicas, físicas e farmacológicas.2,3 Elas podem atuar como sequestradores de radicais livres, neutralizando espécies reativas de oxigênio, e como ligantes quelatos para íons metálicos, sendo que se atribui a essas características a responsabilidade por suas propriedades benéficas. 4,5 A quercetina (Figura 1) é um dos flavonoides mais presentes na dieta humana, pois é encontrada em grande quantidade nas frutas, verduras e chás. Possui propriedades de grande interesse, entre elas estão seus efeitos anticarcinogênicos, protetores do sistema renal, cardiovascular e hepático.6 A interação dos flavonoides com íons metálicos pode mudar as propriedades antioxidantes e alguns outros efeitos biológicos, sendo a maioria de suas propriedades muitas vezes superiores às dos compostos originais.3 Pesquisas têm mostrado que alguns complexos metálicos com a quercetina possuem resistência à atividade neoplasmática e apresentam atividades antisséptica, anti--inflamatória e/ou antioxidante. 7O gálio atua em nosso organismo em focos de inflamação e infecção particularmente nos neutrófilos granulosos e leucócitos polimorfonucleares.8 O principal interesse clínico do gálio deriva da observação de que suas propriedades metabólicas são similares às do ferro.9-11 Desde os anos 70, o gálio mostrou-se eficaz na diminuição da reabsorção óssea acelerada, redução associada aos níveis plasmáticos elevados de cálcio ou inibidores da proliferação neoplásica, tornando-se o segundo íon metálico depois da platina, a ser utilizado no tratamento de câncer.10 Entretanto, seus sais trivalentes (Ga 3+ ) são fracamente absorvidos pelo intestino e alguns derivados são susceptíveis à hidrólise, diminuindo, assim, sua eficiência biológica.11 Por isso o grande interesse na síntese de compostos de coordenação com o íon metálico, visando uma possível correção dessas deficiências. Estudos demonstr...

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The ester content of all the blends was higher than 96.5%, which is the minimum value required by the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (Agência Nacional do Petróleo, Gás Natural e Biocombustíveis, ANP). The thermal properties of the babassu, soybean and binary mixtures of esters were investigated by thermogravimetry-differential thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC). The thermal stability of the blended biodiesels decreased as the total contents of the babassu esters increased. From the experiments it was found that babassu methanol biodiesel is stable up to 49.6 °C and the ethanol biodiesel is stable up to 53.7 °C in air. The methyl esters blends were thermally stable up to 83.2 and 56.8 °C, for 90:10 and 50:50 blends (soybean:babassu), respectively. The ethyl ester blends presented values of temperature ranges somewhat higher than the methyl esters, such as 85.2 and 64.5 °C for 90:10 and 50:50 blends, respectively. The esters from babassu oil have satisfactory performance at low temperatures with respect to the point of crystallization, which were below-9.8 °C for ethylic esters and-8.5 °C for methylic esters. A good correlation between the crystallization onset temperature and the increase in the concentration of the babassu oil esters was obtained in the mixtures analyses. In the 50:50 combination (babassu:soybean), the crystallization onset temperature were-6.73 and-9.12 °C for methyl and ethyl esters, respectively.

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The titanium dioxide phase formation is dependent on the synthesis method, temperature of calcination and modifiers insertion. By using chemical methods, such as Polymeric Precursor Method, the organic impurities or extrinsic defects caused by doping play an important rule on the formation of precursor structure before the phase crystallization above 500 oC. Some dopants can change the decomposition mechanism of the precursor, which affects the anatase-rutile phase transition. In this work, the Polymeric Precursor Method was used to synthesize titanium dioxide powder samples in order to investigate the effects of iron (III) and vanadium (V) dopants on the phase formation. Through thermal analysis of polymeric precursors and X-ray diffractometry for calcined powder samples it was possible to show the existence of antagonistic effects for both investigated dopants. While the iron doping reduces the anatase phase tetragonality and delays the rutile phase conversion, the vanadium one changes the mechanism of decomposition of polymeric precursor and leads to more amount of rutile phase.

Carbon-supported platinum nanoparticles Pt/C (NPs) are used in many fields of science. These kinds of materials have been extensively studied in electrochemistry due to the fact that they are applied in fuel cell technology. Although there are a myriad of methods for Pt NP synthesis, the need for obtaining Pt/C NPs with a good dispersion (covering over the entire support), a narrow size distribution, and clean surface (among other parameters) is far to be overcome. On this sense herein we describe a very easy and quick method of synthesis of highly dispersed Pt NPs followed by a simple electrochemical cleaning step. The catalysts were electrochemically characterized by studying their behavior in 0.5 M H 2 SO 4 and also by using CO as a probe during the CO electro-oxidation reaction (COEOR). This paper shows how to obtain highly dispersed and clean Pt/C NPs that produce very reproducible results. Besides, we demonstrate how the presence of impurities negatively affects the electrochemical reproducibility of Pt NPs with a clear impact on their catalytic activity.