Raquel M.F. Sousa

Batch-injection analysis with amperometric detection of the DPPH radical for evaluation of antioxidant capacity.

This work proposes the application of batch-injection analysis with amperometric detection to determine the antioxidant capacity of real samples based on the measurement of DPPH radical consumption. The efficient concentration or EC50 value corresponds to the concentration of sample or standard required to scavenge 50% DPPH radicals. For the accurate determination of EC50, samples were incubated with DPPH radical for 1h because many polyphenolic compounds typically found in plants and responsible for the antioxidant activity exhibit slow kinetics. The BIA system with amperometric detection using a glassy-carbon electrode presented high precision (RSD = 0.7%, n = 12), low detection limit (1 μmol L(-1)) and selective detection of DPPH (free of interferences from antioxidants). These contributed to low detection limits for the antioxidant (0.015 and 0.19 μmol L(-1) for gallic acid and butylated hydroxytoluene, respectively). Moreover, BIA methods show great promise for portable analysis because battery-powered instrumentation (electronic micropipette and potentiostats) is commercially available.

Peel of araticum fruit (Annona crassiflora Mart.) as a source of antioxidant compounds with α-amylase, α-glucosidase and glycation inhibitory activities

Annona crassiflora Mart., whose fruit is popularly known as araticum, is a member of the Annonaceae family found in the Brazilian Cerrado. Although this plant has several medicinal uses, its bioactive molecules are not fully understood. A bioguided assay was performed to identify the main bioactive compounds of A. crassiflora fruit peel from the ethanol extract fractions with antioxidant capacity and α-amylase, α-glucosidase and glycation inhibitory activities. Ethyl acetate and n-butanol fractions showed, respectively, higher antioxidant capacity (DPPH IC50 1.5±0.1 and 0.8±0.1μgmL-1, ORAC 3355±164 and 2714±79μmoltroloxeq/g, and FRAP 888±16 and 921±9μmoltroloxeq/g) and inhibitory activities against α-amylase (IC50 4.5±0.8 and 1.7±0.3μgmL-1), α-glucosidase (IC50 554.5±158.6 and 787.8±140.6μgmL-1) and glycation (IC50 14.3±3.3 and 16.0±4.2μgmL-1), and lower cytotoxicity, compared to the other fractions and crude ethanol extract. The HPLC-ESI-MS/MS analysis identified various biomolecules known as potent antioxidants, such as chlorogenic acid, (epi)catechin, procyanidins, caffeoyl-hexosides, quercetin-glucosides and kaempferol. The fruit peel of A. crassiflora, a specie from Cerrado, the Brazilian Savanna, provided a source of antioxidant compounds with properties to block carbohydrate digestive enzymes and formation of glycation products. Thus, there is potential to use the by-products of araticum in order to identify and isolate phytochemicals for application in nutraceutical supplements, food additives and pharmaceuticals products.

Antiparasitic Activity of Natural and Semi-Synthetic Tirucallane Triterpenoids from Schinus terebinthifolius (Anacardiaceae): Structure/Activity Relationships

Leishmaniasis and Chagas are diseases caused by parasitic protozoans that affect the poorest population in the World, causing a high mortality and morbidity. As a result of highly toxic and long-term treatments, the discovery of novel, safe and more efficacious drugs is essential. In this work, the in vitro antiparasitic activity and mammalian cytotoxicity of three natural tirucallane triterpenoids, isolated from leaves of Schinus terebinthifolius (Anacardiaceae), and nine semi-synthetic derivatives were investigated against Leishmania (L.) infantum and Trypanosoma cruzi. Trypomastigotes of T. cruzi were the most susceptible parasites and seven compounds demonstrated a trypanocidal activity with IC50 values in the range between 15 and 58 µg/mL. Four compounds demonstrated selectivity towards the intracellular amastigotes of Leishmania, with IC50 values in the range between 28 and 97 µg/mL. The complete characterization of triterpenoids was afforded after thorough analysis of nuclear magnetic resonance (NMR) data as well as electrospray ionization mass spectrometry (ESI-MS). Additionally, structure-activity relationships were performed using Decision Trees.

Biodiesel: Production, Characterization, Metallic Corrosion and Analytical Methods for Contaminants

In face of recent changes in the edaphoclimatic conditions (climate and soil) occurring worldwide, it has been necessary reflections on the need to exploit natural resources in a sustainable manner. Sustainability is a systemic concept, relating to the continuity of eco‐ nomic, social, cultural and environmental aspects of human society. It proposes to be a means of configuring the civilization and human activity so that the society, its members and its economies can fulfill its needs and express its greatest potential at present, while pre‐ serving biodiversity and natural ecosystems, planning and acting to achieve pro-efficiency in maintaining undefined these ideals [1].

Caracterização de membranas assimétricas de acetato de celulose produzidas a partir do aproveitamento do resíduo da palha de milho para uso em ultrafiltração

Cellulose acetates (CA) with different degrees of acetylation were synthesized from cellulose extracted from corn stover. Membranes were prepared for the ultrafiltration process with pure polymers and blend form of CA utilizing a dioxane/acetone system. The membranes were characterized according to their transport properties. The blend form materials presented the best results for application in ultrafiltration experiments. M-TAC/DAC (corn stover triacetate and diacetate) and M-TAC/DAC-Rho (corn stover triacetate and Rhodia diacetate) presented rejection to egg albumin protein of 87.39% and 80.50%, respectively. Thus, MWCO of 45 kDa was determined for these materials.

Phytochemical characterization of the Vochysia rufa (Vochysiaceae) extract and its effects on oxidative stress in the pancreata of streptozotocin-induced diabetic rats

Aqueous extract of macerated Vochysia rufa stem bark has been commonly used in the treatment of diabetes. Therefore, we evaluated the antihyperglycemic and antioxidant effects of an extract of V. rufa on the pancreata of streptozotocin (STZ)-induced diabetic rats. Animals received one of the following treatments daily by oral gavage: water (diabetic-control), V. rufa extract (diabetic-V. rufa), or glibenclamide (diabetic-GBD). Total antioxidant capacity; levels of thiobarbituric acid reactive substances, reduced glutathione, and sulfhydryls; and superoxide dismutase, catalase, and glutathione peroxidase (GPx) activities were measured in the pancreas. Biochemical analysis of serum total cholesterol and fractions, triglycerides, creatinine, urea, acid uric, ALP, γ-GT, AST, and ALT was performed, and pancreatic β-cells positive for insulin were evaluated by immunohistochemistry. Rats treated with extract exhibited a decrease in fasting blood glucose compared with levels in diabetic control rats. GPx activity and sulfhydryl levels were significantly lower in diabetic-V. rufa rats compared with those of diabetic-control rats. V. rufa extract acted to normalize the biochemical alterations found in diabetic rats (diabetic-controls), as demonstrated by increases in urea, HDL, ALP, AST, and ALT. Reduction in blood glucose was independent of an increase in insulin. The V. rufa extract was found to be composed of free sugars (inositol, galactose, glucose, mannose, sucrose, arabinose, and ribose) as the main metabolites. Thus, aqueous extract of the stem bark of V. rufa is capable of reducing blood glucose, resulting in an antioxidant effect on the pancreatic tissue of STZ-diabetic rats.

Polymeric blends of hydrocolloid from chia seeds/apple pectin with potential antioxidant for food packaging applications

The aim of this study was to investigate the antioxidant, mechanical and physical properties of a new film-based polymeric blend of hydrocolloids obtained from the aqueous extraction of chia seeds (source antioxidants) and apple pectin. The individual matrices films were brittle and rigid with poor mechanical properties. The blends formulations contributed to improved mechanical properties regarding workability and resistance. The antioxidant results showed the potential hydrocolloid from chia seeds as natural source of antioxidant in these polymeric films. The formulation 3 (14(hydrocolloid):41(pectin):25(glycerol):20(glutaraldehyde) displayed well thermal, mechanical, morphological and antioxidant properties, suggesting their great potential for food packaging.

Electrochemical sensing of NBOMes and other new psychoactive substances in blotting paper by square-wave voltammetry on a boron-doped diamond electrode

The electrochemical quantification of new psychoactive substances 2,5-dimethoxy-N-(2-methoxybenzyl)phenethylamines, commonly described as NBOMes and their correlates, 2,5-dimethoxy phenethylamine structures, also known as 2C family compounds, in seized blotting paper is presented using square-wave voltammetry (SWV) on a boron-doped diamond (BDD) electrode. Under optimized experimental conditions, linear analytical curves were obtained in the range from 1 to 555 μmol L−1 for three NBOMes and 2C–B with detection limit values between 0.1 and 0.3 μmol L−1 (corresponding to 0.03 and 0.10 μg mL−1) and a repeatability of around 1% (n = 10) for the detection of all analytes. The accuracy of the proposed method was evaluated using seized samples, which were also analyzed by quadrupole time of flight liquid chromatography-mass spectrometry (QTOF LC-MS), with perfect agreement, and free from interference of the sample matrix (recovery values between 98 and 110%).

Utilização de hemiceluloses catiônicas, obtidas a partir do aproveitamento da palha de milho, associadas com tanino para o tratamento de efluentes de lavanderia industrial

Elaine Angélica Mundim Ribeiroa, Fúlvio Rafael Bento de Souzaa, Fábio Augusto do Amarala, Guimes Rodrigues Filhoa,*,#, Raquel Maria Ferreira de Sousaa, Júlia Graciele Vieiraa, Talita Ferreira de Rezende Costaa, José Pedro Thompson Juniora, Rosana Maria Nascimento de Assunçãob e Sheila Cristina Canobrea Instituto de Química, Universidade Federal de Uberlândia, Campus Santa Mônica, 38.400-902, Uberlândia – MG, Brasil Faculdade de Ciências Integradas do Pontal, Universidade Federal de Uberlândia, Campus do Pontal, 38302-000, Ituiutaba – MG, Brasil

Tântalo: Breve histórico, propriedades e aplicações

ABSTRACT (Tantalum: Brief history, properties and applications) Tantalum, a malleable metal, ductile, of high melting point, is mainly used to obtain special alloys, capacitors, and plates for skull fractures repairing, among other applications . Consid-ering the importance of this element, in this article we describe its history, properties and ap-plications. KEYWORDS: tantalum, discovery of tantalum, Anders Gustaf Ekeberg elemental *Instituto de Quimica, Universidade Federal de Uberlândia , Campus Santa monica, Bloco 1D, 38400-902, Uberlândia – minas Gerais, Brasil. correo electronico: Wendell Guerra Fecha de recepcion: 21 de julio de 2012. Fecha de aceptacion: 6 de diciembre de 2012. Resumen Tantalo, un metal maleable, ductil, de alto punto de fusion, es utilizado primordialmente en la obtencion de aleaciones especiales, capacitores, placas para reparar fracturas de craneo, entre otras cuestiones. Al considerar la importancia de este elemento describimos aqui su historia, propiedades y aplicaciones.