Artigos Científicos - FAQUI/ICEN

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2437

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Ab Initio correlated all electron Dirac-Fock calculations for eka-francium fluoride (E119F)
(2012-06) MIRANDA, Patrícia S.; MENDES, Anna Paula S.; GOMES, José da Silva; ALVES, Claudio Nahum; SOUZA, Aguinaldo R. de; SAMBRANO, Julio Ricardo; GARGANO, Ricardo; MACEDO, Luiz Guilherme Machado de
Results obtained with correlated 4-component Dirac-Fock calculations for element E119 (eka-francium) fluoride with stable and accurate basis set (prolapse-free) are reported in this work. At CCSD(T) level, the equilibrium distance Re, harmonic frequency ωe and dissociation energy De are 2.432 Å, 354.97 cm-1 and 116.92 kcal mol-1, respectively. A 4-component prolapse free basis set for E119, an accurate analytical potential energy curve and vibrational spectra from CCSD(T) data are also reported. Our results suggest that E119F should be less ionic than lighter alkaline fluoride homologues, in contrast to the common chemical belief based on periodic trends - it would be expected in this molecule the most ionic bond possible. We also found that the charge model correction to neglect SS integrals leads to negligible errors and speed up calculations close to three times at CCSD(T) level and close to 4 times at DFT/B3LYP level.
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Ácidos fenólicos, flavonoides e atividade antioxidante em méis de Melipona fasciculata, M. flavolineata (Apidae, Meliponini) e Apis mellifera (Apidae, Apini) da Amazônia
(2012) OLIVEIRA, Patricia Sertão; MÜLLER, Regina Celi Sarkis; DANTAS, Kelly das Graças Fernandes; ALVES, Claudio Nahum; VASCONCELOS, Marcus Arthur Marçal de; VENTURIERI, Giorgio Cristino
Honey produced by three stingless bee species (Melipona flavolineata, M. fasciculata and Apis mellifera) from different regions of the Amazon was analyzed by separating phenolic acids and flavonoids using the HPLC technique. Data were subjected to multivariate statistical analysis (PCA, HCA and DA). Results showed the three species of honey samples could be distinguished by phenolic composition. Antioxidant activity of the honeys was determined by studying the capacity of inhibiting radicals using DPPH assay. Honeys with higher phenolic compound contents had greater antioxidant capacity and darker color.
Acesso aberto (Open Access)
Avaliação de minerais em plantas medicinais amazônicas
(2009-06) MARTINS, Alexsandro Sozar; ALVES, Claudio Nahum; LAMEIRA, Osmar Alves; SANTOS, Alberdan Silva; MÜLLER, Regina Celi Sarkis
The Amazonian Brazilian offers an appreciable potential of plants with therapeutic properties, although most are little known. In this way, with the objective of verifying the potentiality nutritional of medicinal herbs, a work was developed to determine the concentration of Ca, Mg, Fe, Cu and Zn in the leaves and in the teas of these species: Piper callosum Ruiz & Pav., Piperaceae, Mikania lindleyana DC., Asteraceae e Arrabidaea chica (Humb. & Bonpl.) B. Verl., Bignoniaceae. After the plants samples have been processed, they were submitted to digestion and soon afterwards the metals were analyzed in an spectrophotometer of Atomic Absorption. The results showed the follow yields: for the tea of Arrabidaea chica Ca were detected (6955 to 20058 mg/L), Mg (2390 to 3094 mg/L) and Fe (40 to 61 mg/L). For the tea of Mikania lindleyana besides the presence of high values of Ca (17722 to 22336 mg/L), Mg (4531 to 9370 mg/L) and Fe (20 to 87 mg/L) they were found from 7 to 16 mg/L of Cu and 9 to 41 mg/L of Zn. The tea of the Piper callosum presented 2036 to 4344 mg/L of Ca, 618 to 4023 mg/L of Mg and 39 to 60 mg/L of Fe. Being compared the results of the minerals with the values recommended by the Health World Organization, is possible that the present metals in the teas of the plants could contribute in the complementation of the people's alimentary diets that use these medicinal plants.
Acesso aberto (Open Access)
Biotransformation of chalcones by the endophytic fungus Aspergillus flavus isolated from Paspalum maritimum trin
(2011-07) CORRÊA, Marivaldo José Costa; NUNES, Fátima Miranda; BITENCOURT, Heriberto Rodrigues; BORGES, Fábio Cardoso; GUILHON, Giselle Maria Skelding Pinheiro; ARRUDA, Mara Silvia Pinheiro; MARINHO, Andrey Moacir do Rosário; SANTOS, Alberdan Silva; ALVES, Claudio Nahum; BRASIL, Davi do Socorro Barros; SANTOS, Lourivaldo da Silva
The fungus Aspergillus flavus isolated as endophytic of the plant Paspalum maritimum Trin. was evaluated for its potential application in biotransformation reactions. The compounds chalcone (1), 3,4,5-trimethoxychalcone (2) and 2,3,4,4'-tetramethoxychalcone (3) were biotransformed, respectively, in dihydrochalcone (4), 3,4,5-trimethoxydihydrochalcone (5) and 2,3,4,4'-tetramethoxydihydrochalcone (6). The structures were elucidated by spectroscopic methods including 1D and 2D NMR techniques, and MS analysis. The dihydrochalcones 5 and 6 are new compounds.
Acesso aberto (Open Access)
Classification of honeys from Pará State (Amazon region, Brazil) produced by three different species of bees
(2013-07) SILVA, Antonio dos Santos; ALVES, Claudio Nahum; DANTAS, Kelly das Graças Fernandes; MÜLLER, Regina Celi Sarkis
Twenty seven samples of honey produced in ten cities of Pará State (Amazon region, North of Brazil) by three different species of bee (Apis mellifera, Melipona fasciculata and Melipona flavoneata) were characterized based on mineral composition (Al, As, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, Sr and Zn), and some physicochemical parameters, namely color, moisture, density, pH, total soluble solids, insoluble solids, ash, electrical conductivity, formol index, free acidity, hydroxymethylfurfural, reducing sugars, total sugars and sucrose. The mineral content was determined using inductively coupled plasma-optical emission spectrometry (ICP OES), and the physicochemical parameters were determined according to officially approved methods. The results of the physicochemical analysis were in agreement with national and international regulations, and with the results of similar studies from around the world. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied in the study of the results of the mineral contents and physicochemical parameters, and it was possible to distinguish the honey samples produced by each of the three different species of bee.
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Dados espectroscópicos de diterpenos labdânicos: uma análise teórica via RMN e DFT
(2015-06) SOUZA, Fabrine Silva de; SILVA, Silvana de Oliveira; FARIA, Lênio José Guerreiro de; ALVES, Claudio Nahum; MÜLLER, Adolfo Henrique; GUILHON, Giselle Maria Skelding Pinheiro; BRASIL, Davi do Socorro Barros
Labdane diterpenes exhibit important bioactivities such as cardiovascular effects in rats as well as effects in the treatment of autoimmune diseases and Alzheimer syndrome. Recently, the labdane diterpenes ent-13-epi-manoil oxide, ribenone and ribenol were isolated from Croton palanostigma. The computational method DFT/B3LYP/cc-pVDZ was used to optimize the structures of these diterpenes and to calculate infrared data. Chemical shifts (δH and δC) of the minimum energy structures (local minimum) were calculated and compared with the experimental data. Comparison of the NMR data by simple linear regression (SLR) showed satisfactory statistical results with a correlation coefficient (R2) and predictive ability (Q2) of over 98%. The predicted NMR data were used to confirm the δH values that have not been published.
Acesso aberto (Open Access)
Levels of As, Cd, Pb and Hg found in the hair from people living in Altamira, Pará, Brazil: environmental implications in the Belo Monte area
(2009) CARVALHO, Antonio Sergio Costa; SANTOS, Alberdan Silva; PEREIRA, Simone de Fátima Pinheiro; ALVES, Claudio Nahum
Human hair was used as a bioindicator to evaluate the levels of As, Cd, Pb and Hg in the resident population of the "Volta Grande" area of the Xingu river, in the North of Brazil. The concentrations of As and Cd are in agreement with the values found in the literature, however, the Pb and Hg concentration is very different, which can suggest an inter-regional variation. Moreover, the high values found for these elements in the residents of the Canteiro Island can be attributed to environmental exposure of this population in an area with environmental impact from activities of gold mining. The application of these methods showed that the concentrations of the metals studied in this work can correctly classify two different localities in the Altamira district. The results reflect the impact of these elements on the health of the inhabitants of this auriferous area.
Acesso aberto (Open Access)
A structure-activity relationship (SAR) study of neolignan compounds with anti-schistosomiasis activity
(2002-06) ALVES, Claudio Nahum; MACEDO, Luiz Guilherme Machado de; HONORIO, Kathia Maria; CAMARGO, Ademir João; SANTOS, Lourivaldo da Silva; JARDIM, Iselino Nogueira; BARATA, Lauro Euclides Soares; SILVA, Alberico Borges Ferreira da
A set of eighteen neolignan derivative compounds with anti-schistosomiasis activity was studied by using the quantum mechanical semi-empirical method PM3 and other theoretical methods in order to calculate selected molecular properties (variables or descriptors) to be correlated to their biological activities. Exploratory data analysis (principal component analysis, PCA, and hierarchical cluster analysis, HCA), discriminant analysis (DA) and the Kth nearest neighbor (KNN) method were employed for obtaining possible relationships between the calculated descriptors and the biological activities studied and predicting the anti-schistosomiasis activity of new compounds from a test set. The molecular descriptors responsible for the separation between active and inactive compounds were: hydration energy (HE), molecular refractivity (MR) and charge on the C19 carbon atom (Q19). These descriptors give information on the kind of interaction that can occur between the compounds and their respective biological receptor. The prediction study was done with a new set of ten derivative compounds by using the PCA, HCA, DA and KNN methods and only five of them were predicted as active against schistosomiasis.
Acesso aberto (Open Access)
Structure-activity relationship of compounds which are anti-schistosomiasis active
(1998-12) ALVES, Claudio Nahum; BARROSO, Lucia Pereira; SANTOS, Lourivaldo da Silva; JARDIM, Iselino Nogueira
The molecular orbital method AM1 was employed to calculate a set of molecular descriptors for twenty synthetic neolignan derivatives with anti-schistosomiasis activity. The pattern recognition method (principal component analysis PCA and cluster analysis CA and discriminant analysis methods) have been employed to obtain the relationship between the molecular descriptors and biological activity. The set of molecules was classified into two groups according to their degree of biological activity. These results allow us to rationally project new compounds, potential candidates for synthesis and biological evaluation.
Acesso aberto (Open Access)
A study of neolignan compounds with biological activity against Paracoccidioides brasiliensis by using quantum chemical and chemometric methods
(2003-10) CAMARGO, Ademir João; HONORIO, Kathia Maria; MERCADANTE, Ricardo; MOLFETTA, Fábio Alberto de; ALVES, Claudio Nahum; SILVA, Alberico Borges Ferreira da
Chemometric (statistical) methods are employed to classify a set of neolignan compounds with activity against Paracoccidioides brasiliensis. The AM1 (Austin Model 1) method was used to calculate a set of molecular descriptors (properties) of the neolignan compounds under study. The descriptors were further analyzed using Principal Components Analysis (PCA), Hierarchical Cluster Analysis (HCA) and K-Nearest Neighbor (KNN) chemometric methods. The PCA and HCA methods were quite efficient to classify the compounds into two groups (active and inactive) and three descriptors were found to be important in the classification: the highest occupied molecular orbital energy (EHOMO), the bond order between C1'-R7 atoms (L14) and the bond order between C5' -R6 atoms (L22). The three variables responsible for the separation between active and inactive compounds are all electronic descriptors, therefore we can conclude that electronic effects should have an important role when one is trying to understand the activity of neolignan compounds against Paracoccidioides brasiliensis.

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