Encontrados 11 documentos, a visualizar página 1 de 2
A conformational study of hydroxylated isoflavones by vibrational spectroscopy ...
Machado, N. F. L.; Carvalho, L. A. E. Batista de; Otero, J. C.; Marques, M. P. M.The conformational preferences of a series of hydroxylated isoflavones were studied by optical vibrational spectroscopy (FTIR and Raman) coupled with density functional theory (DFT) calculations. Special attention was paid to the effect of the hydroxyl substitution, due to the importance of this group in the biological activity of these systems. The isoflavones investigated – daidzein, genistein and formononeti...
Conformational stability of ibuprofen: Assessed by DFT calculations and optical...
Vueba, M. L.; Pina, M. E.; Carvalho, L. A. E. Batista deA thorough conformational analysis of ibuprofen [2-(4-isobutylphenyl) propionic acid] was carried by out, using density functional theory (DFT) calculations coupled to optical vibrational spectroscopy (both Raman and FTIR). Eight different geometries were found to be energy minima. The relative orientations of the substituent groups in the ibuprofen molecule, which can be considered as a para-substituted phenyl...
Drug-excipient interactions in ketoprofen: A vibrational spectroscopy study
Carvalho, L. A. E. Batista de; Marques, M. Paula M.; Tomkinson, JohnKetoprofen (3-benzoyl-alpha-methylbenzeneacetic acid) is a widely used nonsteroidal anti-inflammatory drug (NSAID), always administered in the form of drug-excipient physical mixtures (PMs). The occurrence of possible interactions between ketoprofen and two commonly used excipients - lactose (LAC) and polyvinylpyrrolidone (PVP) - was evaluated, through vibrational spectroscopy techniques [both Raman and Inelast...
Conformational study of ketoprofen by combined DFT calculations and Raman spect...
Vueba, M. L.; Pina, M. E.; Veiga, F.; Sousa, J. J.; Carvalho, L. A. E. Batista deA conformational study of ketoprofen was carried out by both density functional theory (DFT) calculations and Raman spectroscopy. Nine different geometries were found to correspond to energy minimum conformations but only one of them was experimentally detected in the condensed phase spectra. ; http://www.sciencedirect.com/science/article/B6T7W-4HGM796-2/1/6cedf602b0e0b1233ab158acd2f80f23
Influence of Cellulose Ether Mixtures on Ibuprofen Release: MC25, HPC and HPMC ...
Vueba, M. L.; Carvalho, L. A. E. Batista de; Veiga, F.; Sousa, J. J.; Pina, M. E.The influence of cellulose ether derivatives on ibuprofen release from matrix tablets was investigated. Raman spectroscopy and differential scanning calorimetry (DSC) experiments were used, in order to examine the compatibility between the matrix components: both excipients and ibuprofen. While both the DSC and Raman results did not detect any incompatibilities, DSC revealed the existence of some drug:excipient...
Influence of cellulose ether polymers on ketoprofen release from hydrophilic ma...
Vueba, M. L.; Carvalho, L. A. E. Batista de; Veiga, F.; Sousa, J. J.; Pina, M. E.The present work reports the study of different ketoprofen:excipient formulations, in order to determine the effect of the polymer substitution and type of diluent on the drug-release mechanism. Substituted cellulose--methylcellulose, hydroxypropylcellulose and hydroxypropylmethylcellulose were used as polymers, while lactose monohydrate and [beta]-cyclodextrin were tested as diluents. Distinct test formulation...
Raman spectra of putrescine, spermidine and spermine polyamines and their N-deu...
Costa, A. M. Amorim da; Marques, M. P. M.; Carvalho, L. A. E. Batista deThe experimental and calculated Raman spectra of the N-hydrogenated and N-deuterated biogenic polyamines putrescine, spermidine and spermine and of their N-hydrogenated and N-deuterated hydrochloride salts in the 2000-3400 cm-1 spectral region (at distinct temperatures) are reported and analysed. A complete assignment of the N-H, C-H and N-D stretching modes is carried out, in the light of both steric and hydro...
The carbon---hydrogen stretching region of the Raman spectra of 1,6-hexanediami...
Costa, A. M. Amorim da; Marques, M. P. M.; Carvalho, L. A. E. Batista deThe Fermi resonance interaction between the methylene symmetric C---H stretching mode and appropriate binary combinations involving the methylene bending mode in the Raman spectra of polyamines, namely in 1,6-hexanediamine derivatives, under different conditions of deuteration and ionisation of the head amino groups and varying temperature has been analysed. The tentative assignment of the observed bands in the...
Study of carvedilol by combined Raman spectroscopy and ab initio MO calculations
Marques, M. P. M.; Oliveira, P. J.; Moreno, A. J. M.; Carvalho, L. A. E. Batista deThe novel cardioprotective drug carvedilol was studied by both Raman spectroscopy and ab initio molecular orbital methods (using the density functional theory approach). The spectra, acquired both for the solid samples and DMSO solutions as a function of pH, were assigned in view of the calculated wavenumbers and intensities, and also based on the experimental data obtained for individual compounds which compri...
A molecular mechanics force field for conformational analysis of aliphatic acyc...
Carvalho, L A. E. Batista de; Teixeira-Dias, J. J. C.; Fausto, R.An improved molecular mechanics force field for conformational and vibrational studies of aliphatic acyclic amines is developed. The resulting force field reproduces molecular structures adequately and provides a good fit for energy differences between conformers and barriers to internal rotation for a large number of amines. In addition, vibrational frequencies are calculated in good agreement with available e...
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