Composição centesimal e de minerais de casca e polpa de manga (Mangifera indica L.) cv. Tommy Atkins

O Brasil produz cerca de 140 milhões de toneladas de alimento por ano; entretanto, a fome ainda é um dos maiores problemas enfrentados por grande parte da sua população. O aproveitamento integral de alimentos é uma alternativa para suprir as necessidades nutricionais e contribuir para reduzir o lixo orgânico. Nesse sentido, cascas, talos, sementes e outras partes, tradicionalmente não utilizadas como alimentos, podem ser incorporadas na dieta alimentar. Estudos revelam que cascas de muitas hortifrutícolas possuem mais nutrientes que determinadas polpas, a parte tradicionalmente consumida. No entanto, o conhecimento sobre a concentração de metais pesados nessas frações também é importante, uma vez que podem provocar intoxicações alimentares, se consumidos, mesmo em concentrações reduzidas. O Brasil é o sétimo produtor mundial de manga e dentre as cultivares de importância comercial, a cv. Tommy Atkins é a mais plantada e exportada pelo Brasil. A pesquisa teve como objetivo determinar a composição centesimal e o perfil de macro e microminerais, inclusive, os elementos-traço, da casca e da polpa de manga cv. Tommy Atkins. A maior fração da composição centesimal da casca estudada foi a umidade, seguida dos carboidratos totais, com destaque para o teor de fibra alimentar total (FAT), que representou cerca 11% dessa quantidade. Já os teores de proteína e de cinzas apresentaram cerca de 2,5%, enquanto a fração lipídica foi inferior aos demais componentes. O perfil de minerais da casca revelou que as concentrações desses elementos foram superiores aos encontrados na polpa, exceto para zinco e ferro. As concentrações de metais pesados presentes na casca, em função das concentrações menores que 0,1 mg/100g, possibilitam a sua utilização na alimentação humana. A composição centesimal e perfil mineral da casca da manga demonstraram a sua importância nutricional e a possibilidade da utilização dessa parte, até então considerada não comestível na dieta brasileira, visando a contribuir para a melhora do estado nutricional da população e a reduzir os resíduos do processo industrial.

Crescimento e conteúdo de nutrientes minerais em mudas de mirtileiro em sistema convencional e semi-hidropônico

O mirtileiro possui alto potencial econômico, no entanto, sua expansão de cultivo é limitada pela dificuldade de propagação. O cultivo hidropônico possibilita melhor crescimento devido à eficiência no fornecimento de nutrientes. O objetivo deste estudo foi avaliar o crescimento e o conteúdo de nutrientes minerais de mudas micropropagadas de mirtileiro em sistema convencional e semi-hidropônico. Mudas das cultivares Bluebelle e Woodard, com 3 meses de aclimatização, foram submetidas a dois sistemas de cultivo: sistema convencional,em que foram mantidas em sacos de polietileno contendo Plantmax® + vermiculita (1:1) e irrigadas com solução nutritiva a cada 15 dias; e sistema semi-hidropônico, na qual permaneceram em floreiras plásticas contendo areia, sendo irrigadas com solução nutritiva diariamente. O delineamento experimental foi em blocos casualizados com quatro tratamentos, com quatro repetições compostas por doze plantas. Foram avaliados mensalmente a altura da parte aérea, número de brotações e comprimento médio das brotações, e aos 90 dias a massa fresca da parte aérea, massa fresca e seca radicular e análise nutricional das folhas. O sistema semi-hidropônico proporcionou melhores resultados para todas as variáveis avaliadas, em ambas as cultivares. As mudas cultivadas no sistema semi-hidropônico apresentaram teores de nutrientes mais elevados e adequados para esta cultura.

Ácido L-ascórbico: reações de complexação e de óxido-redução com alguns íons metálicos de transição

The strong reducing action of L-ascorbic acid (Vitamin C) are of fundamental interest in biochemical and related process. The oxidation of ascorbic acid by molecular oxygen and others oxidants are of fundamental importance, involving the intervention of transition metal ions as catalysts and the formation transition metal complexes of ascorbic acid as intermediates. The present article is intended to cover some aspects of the reactions of ascorbic acid and related compounds involving some transition metal ions.

Cinética e mecanismo da reação de auto-oxidação de S(IV) catalisada por íons metálicos de transição

The oxidation process of sulfur (IV) species (SO2, HSO3- e SO32-) by oxygen, catalysed by trace metal ion and complexes, can play an important role in atmospheric, analytical and bioinorganic chemistry. An overview of the most important reactions in these fields is presented. A fascinating redox cycling of the metal ions and complexes during such autoxidation process was revealed by the combination of kinetics and coordination chemistry studies.

Substâncias húmicas aquáticas: fracionamento molecular e caracterização de rearranjos internos após complexação com íons metálicos

The aquatic humic substances (AHS) investigated in this study were conventionally isolated from Rio Negro waters - Amazonas State/Brazil by means of the collector XAD 8. A special five-stage tangential-flow ultrafiltration device was used for analytical fractionation of AHS. The fractionation patterns (6 fractions each) showed that metal traces remaining in AHS after their XAD 8 isolation have different size distributions. For instance, the major percentage of traces of Ni, Cu, Zn, Cd and Pb (determined using ICP-AES) was preferably complexed by molecules with relatively high molecular size (30-100 kDa) and the following complexation order was characterized: F2 >> F1 = F4 = F5 > F3 > F6. Moreover, the species formed between AHS and metals prepared by spiking, showed distribution patterns changing as a function of the complexation time (ageing process), indicating a slow transformation process and an inner rearrangements in the binding sites within the AHS molecules.

Química de sistemas supramoleculares constituídos por porfirinas e complexos metálicos

Supramolecular chemistry is expected to keep a high developing pace in the next years, giving support to the advancement of molecular devices and nanotechnology. In this sense, porphyrins and their analogues should play a significant role as a consequence of their catalytic, electrocatalytic, photochemical and photoelectrochemical properties. In this review we focused on our own strategy based on coordination chemistry for the design and build-up of supermolecules and supramolecular structures constituted by polynuclear porphyrins and metalloporphyrins. Included are also their properties and potential applications.

O uso de pseudopotenciais e modelos HF/MP2/DFT na previsão de freqüências vibracionais em complexos metálicos

Four different pseudopotentials and three methodologies were employed in the calculation of the geometry and the frequencies of metal complexes like [M(NH3)2X2] [X=halogen, M=Zn, Cd], and [Hg(NH3)2]Cl2. The vibrational assignments were carefully checked and compared to the theoretically calculated ones. Graphical procedures were employed to estimate family errors and their average behavior. The calculated results show the SBK-X basis set with the best results for the geometries and calculated frequencies, for individual species and statistical results. Its use is recommend, mainly if the neighborhood atoms are described with similar pseudopotentials. Excellent results were also obtained with the Hay and Wadt pseudopotential.

Interações hiperfinas em catalisadores metálicos

Heterogeneous catalysts are of fundamental importance in several modern chemical processes. The characterization of catalysts is an issue of very present interest as it can provide a better understanding of the fundamental aspects of the catalytic phenomena, thus helping in the development of more efficient catalysts. In order to extend and improve the characterization of catalysts, new and less conventional methods are being applied, such as nuclear spectroscopies. In this paper we focus on the application of angular correlation, with can be used to resolve different local environments of probe atoms in solids and can be applied, as shown here, in the characterization of heterogeneous catalysts. A brief theoretical introduction is given and experimental results related to catalytic systems of alumina and niobia-supported Pt-In and Pd-In catalysts are presented.

Los electrodos de pasta de carbono en el estudio electroquímico de minerales metálicos

This paper shows the applicability of the carbon paste electrode-mineral (CPE-mineral) to study the dissolution mechanisms of minerals in powder form and in flotation concentrates. A potentiodynamic strategy to find the dissolution mechanism of galena (PbS) is presented. In this way, minerals less studied such as orpiment (As2S3) and realgar (As2S2) are investigated. The electrochemical activity of a more complicated mineral such as sphalerite (ZnS), containing 12.3 and 0.43% of iron in solid solution, is discussed. The mechanism of a complex zinc concentrate (containing 63.4% ZnS, 20.1% FeS2, 5% CuFeS2, 0.33% PbS, 0.45% Cu12Sb4S13 and 0.4% FeAsS) is described. Finally, an electrochemical method for the detection of the different leachable and refractory silver phases (contained in two mineral concentrates) is presented. This paper reviews the power of the use of CPE-mineral coupled to electrochemical techniques in hydrometallurgy.

Complexos metálicos com o herbicida glifosato: revisão

We present studies involving metallic ions and the herbicide glyphosate. The metallic complexes of Cu(II), Zn(II), Mn(II), Ni(II), Cd(II), Pb(II), Cr(III), Fe(III), Co(III), ammonium, sodium, Ag(I), alkaline earth metals and of some lanthanides ions are described. The complexes are discussed in terms of their synthesis, identification, stability and structural properties, based on data from the current literature.

Classificação de água de coco processada e natural por meio de HCA, PCA e teores de íons metálicos determinados por ICP OES

Inductively Coupled Plasma Optical Emission Spectrometry was used to determine Ca, Mg, Mn, Fe, Zn and Cu in samples of processed and natural coconut water. The sample preparation consisted in a filtration step followed by a dilution. The analysis was made employing optimized instrumental parameters and the results were evaluated using methods of Pattern Recognition. The data showed common concentration values for the analytes present in processed and natural samples. Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) indicated that the samples of different kinds were statistically different when the concentrations of all the analytes were considered simultaneously.

Adsorção de aminoácidos sobre minerais e a origem da vida

Minerals adsorb more readily amino acids with charged R groups than those with uncharged R groups, so that the incorporation of amino acids with charged R groups into peptides would be more frequent than that of amino acids with uncharged R groups. However, 74% of the amino acids in the proteins of modern organisms contain uncharged R groups. Thus, what could have been the mechanism that produced peptides/proteins with more amino acids with uncharged R groups than precursors with charged R groups? The lipid world offers an alternative view of the origin of life. In the present paper, several other mechanisms are also discussed.

Adsorção de glifosato sobre solos e minerais

Glyphosate, an enzyme inhibitor herbicide, has been widely used around the world in agriculture. Dr. John Franz from Monsanto Corporation (USA) discovered glyphosate in 1970. It has been showed that glyphosate is strongly adsorbed by inorganic soil components especially aluminium and iron oxides, and the phosphate group is involved in this interaction. The inactivation of glyphosate in soils can last for days or even months depending on soil characteristics. The addition of phosphate from fertilizers can displace glyphosate from the soils and this could be the cause of decreased productivity of some crops.

Lesões em DNA induzidas pela autoxidação de S(IV) na presença de íons metálicos de transição

The oxidation of sulfite catalyzed by transition metal ions produces reactive oxysulfur species that can damage plasmid and isolated DNA in vitro. Among the four DNA bases, guanine is the most sensitive to one-electron oxidation promoted by the species formed in the autoxidation of sulfite (HSO5-, HO•, SO3•-, SO4•- and SO5•-) due to its low reduction potential and ability to bind transition metal ions capable to catalyze oxidative processes. Some oxidative DNA lesions are promutagenic and oxidative DNA damage is proposed to play a crucial role in certain human pathologies, including cancer.

Avaliação da concentração de alguns íons metálicos em diferentes espécies de líquens do cerrado Sul-Mato-Grossense

Concentrations of Fe, Mn, Co, Cr, Zn and Cu were determinated using flame atomic absorption spectrometry in nine lichen species of the Sul-Mato-Grossense cerrado. The average metal ion concentrations varied in the following ranges: Fe, 248.41-1568.01; Mn, 98.50-397.33; Co, 10.08-24.81; Cr, 18.24-44.26; Zn, 14.62-34.79 and Cu, 3.23-7.57 mg kg-1. Statistical analysis (Pearson and Cluster) applied to the metal ion concentrations indicated that the accumulation of these ions can be due to several anthropogenic sources including agricultural activities, mineral exploration, biomass burning, soil mineral composition and leather tanning processes by chromium.