Resumo em Português:

Este trabalho descreve um método espectrofotométrico simples, rápido e sensível para a determinação de metildopa em formulações farmacêuticas. O método é baseado na reação entre tetracloro-p-benzoquinona (p-cloranil) e metildopa, a qual é acelerada por peróxido de hidrogênio (H2O2), produzindo um composto vermelho-violeta (λmax = 535 nm) à temperatura ambiente (25,0 ± 0,2 ºC). As melhores condições para a reação foram obtidas por planejamento experimental. A lei de Beer é obedecida em um intervalo de concentração de 2,10 x 10-4 to 2,48 x 10-3 mol L-1 (r = 0,9997). O limite de detecção determinado foi de 7,55 x 10-6 mol L-1 e o limite de quantificação foi de 2,52 x 10-5 mol L-1. A precisão intradia e interdia do método proposto foram determinadas pela análise em decuplicata (n=10) de uma solução de metildopa 1,59 x 10-3 mol L-1 e apresentaram coeficientes de variação de 0,7 e 1,1%, respectivamente. O método proposto foi aplicado com sucesso na determinação de metildopa em diferentes marcas de medicamentos. Os resultados obtidos pelo método proposto estiveram em boa concordância com aqueles obtidos pelo método da Farmacopéia Brasileira em um nível de confiança de 95%.

Resumo em Inglês:

A simple, rapid and sensitive spectrophotometric method has been developed for the determination of methyldopa in pharmaceutical formulations. The method is based on the reaction between tetrachloro-p-benzoquinone (p-chloranil) and methyldopa, accelerated by hydrogen peroxide (H2O2), producing a violet-red compound (λmax = 535 nm) at ambient temperature (25.0 ± 0.2 ºC). Experimental design methodologies were used to optimize the measurement conditions. Beer's law is obeyed in a concentration range from 2.10 x 10-4 to 2.48 x 10-3 mol L-1 (r = 0.9997). The limit of detection was 7.55 x 10-6 mol L-1 and the limit of quantification was 2.52 x 10-5 mol L-1. The intraday precision and interday precision were studied for 10 replicate analyses of 1.59 x 10-3 mol L-1 methyldopa solution and the respective coefficients of variation were 0.7 and 1.1 %. The proposed method was successfully applied to the determination of methyldopa in commercial brands of pharmaceuticals. No interferences were observed from the common excipients in the formulations. The results obtained by the proposed method were favorably compared with those given by the Brazilian Pharmacopoeia procedure at 95 % confidence level.

Resumo em Português:

Os amidos nativos são estruturalmente fracos e pouco resistentes para aplicações tecnológicas na indústria alimentícia. O processamento é necessário para conferir aos amidos maior aplicabilidade. Os amidos nativos podem ser modificados por vários processos como: físicos, químicos, enzimáticos ou até combinações dos mesmos, dependendo da finalidade industrial. Amostras de amido de milho nativo foram submetidas à hidrólise por solução de ácido clorídrico e investigadas através das técnicas termoanalíticas: termogravimetria (TG), análise térmica diferencial (DTA) e calorimetria exploratória diferencial (DSC), bem como microscopia óptica e difratometria de raios X pelo método do pó. Após tratamento com ácido clorídrico a 30 e a 50 ºC, foi verificado um decréscimo na entalpia de gelatinização (ΔHgel). A microscopia óptica e difratometria de raios X permitiram verificar os contornos de grão e rugosidade típica dos amidos de cereais.

Resumo em Inglês:

Unprocessed native starches are structurally too weak and functionally too restricted for application in today's advanced food technologies. Processing is necessary to engender a range of functionality. Naturals or natives starches can be modified by using several methods physical, chemical, enzymatic or combined, according industrial purposes. In this work, native corn starch was hydrolyzed by hydrochloric acid solution and investigated by using thermoanalytical techniques (thermogravimetry - TG, differential thermal analysis - DTA and differential scanning calorimetry - DSC), as well as optical microscopy and X-ray diffractometry. After acid treatment at 30 and 50°C, a decrease of gelatinization enthalpy (ΔHgel) was verified. Optical microscopy and X-ray diffractometry allowed us to verify the granules contorn and rugosity typical of cereal starches.

Resumo em Inglês:

The present investigation reports on the interaction of the C/O triplet atoms inside of the [60] fullerene (C60) species with small polar molecules (H²O, CH³OH, HF, NH³) using Density Functional Theory (DFT) calculations. The calculations show that in all the computed cases the encapuslated complexes with the molecules are more stable than without internal atoms.

Resumo em Português:

Um novo método, simples e sensível para a determinação de arsênio em solo é proposto neste trabalho. Este método é baseado na redução de prata (I) e ferro (III) pela arsina seguida da reação de complexação do ferro (II) com o reagente espectrofotométrico 2-(5-bromo-2-piridilazo)-5-di-etilaminofenol (Br-PADAP). A determinação de arsênio apresentou uma sensitividade de Sandell de 3.1x10-4 cm-2, foi linear na faixa de 0.1 µg ml-1 to 2.0 µg ml-1 (r560 = 0.9995), apresentou uma absortividade molar de 2.45x10(5) l mol-1 cm-1 e um limite de detecção de 1.4 ng ml-1 (3s) estes dados foram obtidos para 10 ml de amostra. A seletividade foi melhorada com o uso de EDTA com agente mascarante. O método proposto foi aplicado na determinação do arsênio na presença de outros íons e em amostras de solo. Os resultados revelaram que antimônio (III), mercúrio (II), germânio (IV), platina (IV) interferem na análise em todas as proporções analisadas. As interferências podem ser facilmente removidas pelo uso do EDTA. A precisão e a exatidão deram resultados satisfatórios, com desvio padrão relativo abaixo de 5%. As recuperações de arsênio em solo variaram de 95,55 a 102,70% com uma média de 99,63%. Estes resultados demonstraram que o método proposto é aplicável para a análise do arsênio em diferentes amostras de solo.

Resumo em Inglês:

In this paper, a new, simple and sensitive method for arsenic determination in soil is proposed. This is based on the reduction of silver (I) and iron (III) ions by arsine followed by a complexation reaction of iron (II) with the spectrophotometric reagent Br-PADAP 2-(5-bromo-2-pyridylazo)-5-di-ethylaminophenol. Arsenic determination with a Sandell's sensitivity of 3.1 10-4 cm-2, linear range from 0.1 µg ml-1 to 2.0 µg ml-1 (r560 = 0.9995), molar absorptivity of 2.45 10(5) l mol-1 cm-1 and a concentration detection limit of 1.4 ng ml-1 (3s) were obtained using a 10 ml sample volume. Selectivity was increased with the use of EDTA as a masking agent. The proposed method was applied for arsenic determination in the presence of several ions amounts in digested soil samples. The results revealed that antimony (III), mercury (II), germanium (IV), platinum (IV) interferes at all analyzed proportions. The interferences can be easily removed by the use of EDTA. Precision and accuracy obtained were satisfactory with a R.S.D. < 5 %. Recovery of arsenic in soil samples varied from 95.55 to 102.70 % with a mean of 99.63 %. These results demonstrated that the proposed method is applicable for arsenic analysis in different soil samples.

Resumo em Inglês:

The Co(II), Ni(II) and Cu(II) metal ions complexes of Bis(4-amino-5-mercapto-1,2,4-triazol-3-yl) alkanes (BATs) have been prepared and characterized by elemental analysis, conductivity measurements infrared, magnetic susceptibility, the electronic spectral data and thermal studies. Based on spectral and magnetic results, the ligands are tetradentate coordinating through the N and S-atoms of BATs; six-coordinated octahedral or distorted octahedral and some times four-coordinated square planar were proposed for these complexes. Activation energies computed for the thermal decomposition steps were compared. The ligands and their metal complexes were tested in vitro for their biological effects. Their activities against two gram-positive, two gram-negative bacteria and two fungal species were found to vary from moderate to very strong.

Resumo em Português:

Bis-(µ2-oxo)-tetrakis{[1-feniltriazeno-1,3-diil)-2-(feniltriazenil)benzeno cobre(II) é um complexo tetranuclear que apresenta quatro íons Cu(II) coordenados por quatro ligantes 1,2-bis(feniltriazeno)benzeno em ponte, com uma cadeia diazoamínica desprotonada, e dois ligantes O2-. O complexo apresenta um processo de redução por dois elétrons a E1/2 = -0,95 V vs Fc+/Fc. Voltametria cíclica e espectroeletroquímica demonstraram um processo reversível. Quando imobilizado em eletrodo de pasta de carbono, o complexo eletrocatalisa a redução de O2 dissolvido em solução aquosa a -0,3 V vs SCE. A corrente obtida apresenta linearidade com a concentração de O2.

Resumo em Inglês:

Bis-(µ2-oxo)-tetrakis{[1-feniltriazene-1,3-diil)-2-(phenyltriazenil)benzene copper(II) is a tetranuclear complex which shows four Cu(II) ions coordinated by four 1,2-bis(phenyltriazene)benzene bridged ligands, with one diazoaminic deprotonated chain, and two O2- ligands. The complex reduces at E1/2 = -0.95 V vs Fc+/Fc, a two electrons process. Cyclic voltammetric and spectroelectrochemical studies showed a reversible process. When immobilized on carbon paste electrode, the complex electrocatalyses the reduction of O2 dissolved on aqueous solution at -0.3 V vs SCE potential. The obtained current shows linearity with O2 concentration.

Resumo em Inglês:

Highly sensitive and selective spectrophotometric methods (A and B) were developed for the determination of micro amounts of olanzapine (OLZ). Method A (direct method) is based on the oxidation of olanzapine with a known excess of iodine monochloride (ICl) in an acidic medium. Under the same condition, thymol blue was iodinated by unreacted ICl, and the absorbance of uniodinated thymol blue was measured at 536 nm. The decrease in ICl concentration is a measure of drug concentration. In method B (indirect method), oxidation of OLZ by a known excess of Ce(IV) in sulfuric acid medium followed by the reaction of unreacted Ce(IV) with leuco crystal violet (LCV) to crystal violet (CV), which is measured in an acetate buffer medium ( pH 4.9) at 580 nm. These methods obey the Beer's law in the concentration range of 0.2-1.6 µg mL-1 (method A) and 0.1-1.4 µg mL-1 (method B). The developed procedures have been successfully applied to the determination of OLZ in pure and in dosage forms. The results exhibit no interference from the presence of excipients. The reliability of the methods was established by parallel determination of OLZ against the reference method.

Resumo em Português:

A própolis é um produto resinoso que as abelhas recolhem de certas partes da planta e que apresenta excelentes propriedades medicinais. Este trabalho descreve a isolamento e identificação de triterpenóides e derivados de ácido anacárdico de própolies Brasileira e sua anti-atividade. Suas estruturas foram elucidadas por RMN ¹H e 13C, incluindo técnicas uni e bidimensionais, e comparação com dados da literatura. Os compostos foram caracterizados como: cardanóis (1a + 1b), cardóis (2a + 2b), ácido anacárdico monoeno (3), α-amirina (4), β-amirina (5), cicloartenol (6), 24-metileno-cicloartenol (7) e lupeol (8). A determinação da posição da ligação dupla após reação com dissulfeto de dimetila (DMDS) é descrita para os derivados fenólicos. O extrato etanólico foi testado in vitro para atividade anti-bacterina pelo método de difusão em disco e mostrou resultados significativos contra Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa e Shigella spp.

Resumo em Inglês:

Propolis is a sticky, gummy, resinous substance collected by honeybees (Apis mellifera L.) from various plant sources, which has excellent medicinal properties. This paper describes the isolation and identification of triterpenoids and anacardic acid derivatives from Brazilian propolis and their antibacterial activity. Their structures were elucidated by ¹H and 13C NMR, including uni- and bidimensional techniques; in addition, comparisons were made with data from academic literature. These compounds were identified as: cardanols (1a + 1b), cardols (2a + 2b), monoene anacardic acid (3), a-amirine (4), b-amirine (5), cycloartenol (6), 24-methylene-cycloartenol (7) and lupeol (8). The determination of the position of the double bond after a reaction with Dimethyl disulfide (DMDS) is described for the phenol derivatives. The ethanolic extract was tested in vitro for antimicrobial activity by using the disc diffusion method and it showed significant results against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Shigella spp.

Resumo em Inglês:

Electrode kinetics and complex formation of Zn(II) using doxycycline, chlortetracycline, oxytetracycline, tetracycline, minocycline, amoxicillin, chloramphenicol and cephaloglycin were reported at pH = 7.30 ± 0.01 in = 1.0 molL-1 NaClO4 used as supporting electrolyte at 25.0°C. Kinetic parameters viz. transfer coefficient (α), degree of irreversibility (λ) and rate constant (k) were determined. The study showed that 'Transition state' behaves between reactant (O) and product (R) response to applied potential. The stability constants varied from 2.14 to 10.31 showing that these drugs or their complexes could be used against Zn toxicity.

Resumo em Inglês:

Quantum Chemical calculations for group 14 elements of Periodic Table (C, Si, Ge, Sn, Pb) and their functional groups have been carried out using Density Functional Theory (DFT) based reactivity descriptors such as group electronegativities, hardness and softness. DFT calculations were performed for a large series of tetracoordinated Sn compounds of the CH3SnRR'X type, where X is a halogen and R and R' are alkyl, halogenated alkyl, alkoxy, or alkyl thio groups. The results were interpreted in terms of calculated electronegativity and hardness of the SnRR'X groups, applying a methodology previously developed by Geerlings and coworkers (J. Phys. Chem. 1993, 97, 1826). These calculations allowed to see the regularities concerning the influence of the nature of organic groups RR' and inorganic group X on electronegativities and hardness of the SnRR'X groups; in this case, it was found a very good correlation between the electronegativity of the fragment and experimental 119Sn chemical shifts, a property that sensitively reflects the change in the valence electronic structure of molecules. This work was complemented with the study of some compounds of the EX and ER types, where E= C, Si, Ge, Sn and R= CH3, H, which was performed to study the influence that the central atom has on the electronegativity and hardness of molecules, or whether these properties are mainly affected for the type of ligand bound to the central atom. All these calculations were performed using the B3PW91 functional together with the 6-311++G** basis set level for H, C, Si, Ge, F, Cl and Br atoms and the 3-21G for Sn and I atoms.