Electrochemical modified electrodes based on metal-salen complexes

A general view of the electroanalytical applications of metal-salen complexes is discussed in this review. The family of Schiff bases derived from ethylenediamine and ortho-phenolic aldehydes (N,N'-ethylenebis(salicylideneiminato) - salen) and their complexes of various transition metals, such as Al, Ce, Co, Cu, Cr, Fe, Ga, Hg, Mn, Mo, Ni, and V have been used in many fields of chemical research for a wide range of applications such as catalysts for the oxygenation of organic molecules, epoxidation of alkenes, oxidation of hydrocarbons and many other catalyzed reactions; as electrocatalyst for novel sensors development; and mimicking the catalytic functions of enzymes. A brief history of the synthesis and reactivity of metal-salen complexes will be presented. The potentialities and possibilities of metal-Salen complexes modified electrodes in the development of electrochemical sensors as well as other types of sensors, their construction and methods of fabrication, and the potential application of these modified electrodes will be illustrated and discussed.

Biomimetic biosensor based on lipidic layers containing tyrosinase and lutetium bisphthalocyanine for the detection of antioxidants

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Polyphenol oxidase from yacon roots (Smallanthus sonchifolius)

Polyphenol oxidase (E.C. 1.14.18.1) (PPO) extracted from yacon roots (Smallanthus sonchifolius) was partially purified by ammonium sulfate fractionation and separation on Sephadex G-100. The enzyme had a molecular weight of 45 490 +/- 3500 da and K-m values of 0.23, 1.14, 1.34, and 5.0 mM for the substrates caffeic acid, chlorogenic acid, 4-methylcatechol, and catechol, respectively. When assayed with resorcinol, DL-DOPA, pyrogallol, protocatechuic, p-coumaric, ferulic, and cinnamic acids, catechin, and quercetin, the PPO showed no activity. The optimum pH varied from 5.0 to 6.6, depending on substrate. PPO activity was inhibited by various phenolic and nonphenolic compounds. p-Coumaric and cinnamic acids showed competitive inhibition, with K-i values of 0.017 and 0.011 mM, respectively, using chlorogenic acid as substrate. Heat inactivation from 60 to 90 degrees C showed the enzyme to be relatively stable at 60-70 degrees C, with progressive inactivation when incubated at 80 and 90 degrees C. The E-a (apparent activation energy) for inactivation was 93.69 kJ mol(-1). Sucrose, maltose, glucose, fructose, and trehalose at high concentrations appeared to protect yacon PPO against thermal inactivation at 75 and 80 degrees C.

POLYPHENOLOXIDASE FROM ATEMOYA FRUIT (ANNONA CHERIMOLA MILL. ANNONA SQUAMOSA L.)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Antioxidant Activity of Commercial Ready-to-Drink Orange Juice and Nectar

Total antioxidant activity (TAA), total phenolic compounds (TPC), and physicochemical characteristics of ready-to-drink orange juice and nectar from the most consumed brands available in Brazil were evaluated. TPC ranged from 18.7 to 54.2 mg of gallic acid/100 mL, and TAA varied from 57.88 to 349.32 mu mol TEAC/100 mL ready-to-drink orange juice and nectar. The ascorbic acid content was the only physicochemical parameter that showed strong variation among packages and brands. Correlation of TPC with TAA showed that the higher the level of TPC the higher the TAA. Correlation of ascorbic acid content with TAA is higher for ready-to-drink orange juice than nectar. The same was found for the correlation of ascorbic acid content with TPC. The results confirm the contribution of the TPC to TAA.

Radical scavenging activity of orange and tangerine varieties cultivated in Brazil

Four citrus fruit varieties cultivated in Brazil (two kinds of sweet orange and two kinds of tangerine) were analyzed for physicochemical characteristics contents of total phenolics, total carotenoids and ascorbic acid, and antioxidant activities. The antioxidant activities of aqueous, methanolic, and acetone extracts of the citrus fruit juices were assessed on the basis of their ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH(center dot)). The cravo tangerine has the highest content of citric acid, while the pera orange is richest in ascorbic acid. The lima orange has the highest total phenolic contents, and the ponkan the highest total carotenoids. The antioxidant activities, expressed as the concentration of antioxidant able to scavenge 50% of the initial DPPH(center dot) (EC(50)), ranged from 139.1+/-27.3 to 182.2+/-28.8 g extract/l for juice of orange varieties and 186.3+/-29.6 to 275.5+/-3.3g extract/l for juice of tangerine citrus varieties. In methanolic extracts the EC(50) ranged from 192.5+/-43.1 to 267.4+/-41.4 g extract/l for orange varieties and from 225.2+/-69.8 to 336.3+/-27.2 g extract/l for tangerine varieties. For EC(50) values of acetone fractions, there were no statistically significant differences between the different varieties. For every citrus fruit in the present study, the radical scavenging capacity was higher in the aqueous than in the methanolic or acetone fractions.

Antimycobacterial activity of lichen substances

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Chemical Profile and Biological Potential of Non-Polar Fractions from Centroceras clavulatum (C. Agardh) Montagne (Ceramiales, Rhodophyta)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structure-antimicrobial activity of some natural isocoumarins and their analogues

Three naturally occurring isocoumarins (paepalantine, paepalantine 9-O-beta-D-glucopyranoside and paepalantine 90-beta-D-allopyranosyl(1 -> 6) glucopyranoside) and two semi-synthetic analogues, 9,10-acylated compound and 9-OH-10-methylated compound,. structurally similar to paepalantine, were evaluated for antimicrobial activity using a spectrophotometric microdilution technique. The paepalantine was active against S. aureus, S. epidermidis, and E faecalis. while the other four compounds proved ineffective against all microorganisms tested at concentrations of 500 mu g/ml. Variations in phenolic substitution at OH-9 and/or OH-10 in the paepalantine molecule resulted in compounds without antimicrobial activity. A combination of structural features, two phenolic groups as cathecolic system, forms an oxygenated system arrangement that may reflect the potentially antimicrobial properties of paepalantine. (c) 2004 Elsevier GmbH. All rights reserved.

Análise fitoquímica e atividade antimicobacteriana de extratos metanólicos de Jacaranda cuspidifolia Mart. (Bignoniaceae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Antioxidant Activity and Total Phenols from the Methanolic Extract of Miconia albicans (Sw.) Triana Leaves

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Antimicrobial activity of Miconia species (melastomataceae)

This work evaluated the antimicrobial activity of the methanol and chloroform extracts of the leaves of Miconia cabucu, Miconia rubiginosa, and Miconia stenostachya using the disc-diffusion method. The results obtained showed that the methanol extracts of the leaves of M. rubiginosa and M. stenostachya and the chloroform extract of the leaves of M. cabucu presented antimicrobial activity against the tested microorganisms.

Nanoindentation mechanical properties characterization of glassy polymeric carbon treated with ion beam

Phenolic resins when heat treated in inert atmosphere up to 1000 degreesC become glassy polymeric carbon (GPC), a chemically inert and biocompatible material useful for medical applications, such as in the manufacture of heart valves and prosthetic devices. In earlier work we have shown that ion bombardment can modify the surface of GPC, increasing its roughness. The enhanced roughness, which depends on the species, energy and fluence of the ion beam, can improve the biocompatibility of GPC prosthetic artifacts. In this work, ion bombardment was used to make a layer of implanted ions under the surface to avoid the propagation of microcracks in regions where cardiac valves should have pins for fixation of the leaflets. GPC samples prepared at 700 and 1500 degreesC were bombarded with ions of silicon. carbon, oxygen and gold at energies of 5, 6, 8 and 10 MeV, respectively, and fluences between 1.0 x 10(13) and 1.0 x 10(16) ions/cm(2). Nanoindentation hardness characterization was used to compare bombarded with non-bombarded samples prepared at temperatures up to 2500 degreesC. The results with samples not bombarded showed that the hardness of GPC increases strongly with the heat treatment temperature. Comparison with ion bombarded samples shows that the hardness changes according to the ion used, the energy and fluence. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Mechanical behavior of natural fiber composites

The use of natural fibers as reinforcement in polymeric composites for technical applications has been a research subject of scientists during the last decade. There is a great interest in the application of sisal fiber as substitutes for glass fibers, motivated by potential advantages of weight saving, lower raw material price, and ecological advantages of using green resources which are renewable and biodegradable.Castor oil, a triglyceride vegetable that has hydroxyl groups, was reacted with 4,4' diphenylmethane diisocyanate (MDI) to produce the polyurethane matrix. Woven sisal fibers were used untreated and thermal treated at 60 C for 72h, and the composites were processed by compression molding.The present work study tensile behavior at four composites: dry sisal/polyurethane, humid sisal/polyurethane, dry sisal/phenolic and humid sisal/phenolic resin. The moisture content influences of sisal fibers on the mechanical behaviors were analyzed.Experimental results showed a higher tensile strength for the sisal/phenolic composites followed by sisal/polyurethane, respectively. In this research, sisal composites were also characterized by scanning electron microscopy. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of ICM11

Estudo da modificação de bentonita para a remoção de fenol em águas produzidas na indústria de petróleo

This study evaluates the inclusion of quaternary ammonium salt, bromide hexadecyl trimethyl ammonium (HDTMA-Br) on sodium bentonite to evaluate their performance on the adsorption of phenol present in produced water. It was observed an increase in d001 samples modified with HDTMA-Br by diffraction of X-rays, showing the intercalation of quaternary ammonium cations in the interlamellar layers of clay. Through the adsorption isotherms could be abserver adsorption behavior of sodium bentonite and organophilic bentonite produced in three different concentrations of HDTMA-Br for adsorption of phenol, which is the main phenolic compound found in the product water. Different concentrations of synthetic solutions of phenol were placed in contact with these adsorbents under the same conditions of agitation and temperature. The adsorbent showed adsorptive favorable, especially the clay modified with the highest concentration of HDTMA-Br, 150% CEC of clay, BEN30-14, with higher amounts of phenol adsorbed per gram of adsorbent (mg.g-1)