RESUMEN
Directly compressed theophylline tablets, containing commercial xanthan (X) (Keltrol) and a highly hydrophilic galactomannan (G) from the seeds of Mimosa scabrella (a brazilian leguminous tree called bracatinga) as release-controlling agents, were obtained. Gums were used at 4, 8, 12.5 and 25% (w/w), either alone or in mixture (X:G 1:1). During galactomannan extraction process, the biopolymer was dried in a scale up, by vacuum oven (VO) or spray dryer (SD). The in vitro drug release was evaluated at different time intervals during 8 h using apparatus 1 (USP 26) at 100 rpm. The pH of the dissolution medium (1.4) was changed to 4.0 and 6.8 after 2 and 3 h, respectively. Tablets containing G(SD) resulted in more uniform drug release than G(VO) ones, due to their smaller particle size. The drug release decreased with the increase of polymer concentration and all formulations at 25% w/w of gums showed excessive sustained release effect. The matrices made with alone X showed higher drug retention for all concentrations, compared with G matrices that released the drug too fast. The XG matrices were able to produce near zero-order drug release. The XG(SD) 8% tablets provided the required release rate (about 90% at the end of 8 h), with zero-order release kinetics. Tablets containing G(VO) in low concentration showed a complete erosion, while the others demonstrated fast hydration and swelling in contact with the dissolution medium. The release mechanism was a combination of diffusion and relaxation. The relative importance of these two processes varied with matrix composition. The XG(SD) 8% matrix showed higher contribution of polymer relaxation.
Asunto(s)
Sistemas de Liberación de Medicamentos/métodos , Mananos/farmacocinética , Mimosa , Polisacáridos Bacterianos/metabolismo , Teofilina/farmacocinética , Administración Oral , Galactosa/análogos & derivados , Mananos/administración & dosificación , Polisacáridos Bacterianos/administración & dosificación , Comprimidos , Teofilina/administración & dosificaciónRESUMEN
A highly substituted galactomannan (G) from Mimosa scabrella Bentham (Man:Gal 1.1:1), isolated from the seeds of a Brazilian leguminous tree and xanthan (X), an exopolysaccharide secreted by Xanthomonas campestris (Keltrol), were evaluated as a hydrophilic matrix system (XG) for controlled release (CR) of diclofenac sodium (DS) in tablets and capsules. The performance of XG (2:1) matrices containing 50 mg (A) or 100 mg (B) of DS was compared with a commercial CR product of DS. The drug release studies were carried out using a dissolution apparatus (paddle method) with gradual increase of pH values, from pH 1.4, to pH 4.0 (after 1 h) and to pH 6.8 (after 2 h). The results suggested the potential of XG systems as release retarding materials, which released 78.6 and 35.1% of drug after 24 h for capsules (A) and tablets (A), respectively. Drug release decreased with the increase of amount of drug and it is dependent of dosage form. Analysis of release data indicate a rather zero-order drug release with the erosion mechanism playing a dominant role.
Asunto(s)
Preparaciones de Acción Retardada/química , Mananos/química , Mimosa , Polisacáridos Bacterianos/química , Diclofenaco/administración & dosificación , Diclofenaco/química , Galactosa/análogos & derivados , Concentración de Iones de Hidrógeno , Semillas , SolubilidadRESUMEN
The structure and rheological properties of water-soluble polysaccharides from industrialized mango pulp were investigated. Soluble fraction (SF) 2 was heterogeneous on high performance size exclusion chromatography, giving two peaks as determined by multi-angle laser light scattering and refractive index detectors. The presence of starch in SF2 was demonstrated by a positive iodine reaction and by 13C nuclear magnetic resonance (NMR) spectroscopy. The presence of pectic polysaccharides was shown by a calorimetric method, 13C-NMR spectroscopy and carboxyl reduction. The main pectic polysaccharide was polygalacturonic acid; type I rhamnogalacturonan was also detected. Analysis of the rheological properties of SF2 showed a pseudoplastic behavior up to 3 g x l(-1). 'Creep and recovery' tests and analysis performed under a dynamic state revealed a weak gel character for solutions at concentrations of 15, 20 and 30 g x l(-1).
Asunto(s)
Polisacáridos/química , Yodo/química , Espectroscopía de Resonancia Magnética , Mangifera , Pectinas/química , Factores de TiempoRESUMEN
Mature fruit of Chorisia speciosa yield an exudate (E-I) following mechanical injury. The polysaccharide contains rhamnose, arabinose, xylose, mannose, glucose, galactose and glucuronic acid in molar ratios of 20:11:1:3:2:40:23. The main chain of the structure is composed by beta-galactopyranosyl units linked (1 --> 3) and (1 --> 6) as indicated by NMR spectra and methylation data. Arabinosef and rhamnose are terminal residues. In order to compare E-I with the polysaccharides from the fruit mesocarp, the latter was submitted to different extractions. The water fraction contains rhamnose, arabinose, xylose, mannose, glucose, galactose and uronic acid in molar ratios of 18:4:1:2:3:44:28. It was treated with CTAB yielding a precipitate which was decomplexed with NaCl, giving four fractions. The fraction obtained using 0.15 M NaCl had a quantitative composition similar that of E-I.
Asunto(s)
Frutas/química , Extractos Vegetales/química , Polisacáridos/química , Árboles , Arabinosa/análisis , Fraccionamiento Celular , Cromatografía , Frutas/citología , Frutas/metabolismo , Hidrólisis , Espectroscopía de Resonancia Magnética , Metilación , Polisacáridos/aislamiento & purificaciónRESUMEN
In view of the wide industrial applications of galactomannans as a thickening agent, those of Mimosa scabrella (bracatinga), a leguminous tree abundant in Southern Brazil, are under investigation. Seeds of bracatinga were processed on a pilot plant scale in order to obtain its galactomannan. The process consisted of successive milling, enzyme inactivation, aqueous extraction, precipitation of polysaccharide, and drying and milling. The product was obtained in 20% yield, with characteristics similar to those obtained on the laboratory scale, namely mannose:galactose ratio (M:G) 1.1:1.0 and intrinsic viscosity. Considering the seed availability in the metropolitan regions of Curitiba, it should be possible to obtain 3000 ton/year of this polysaccharide.
Asunto(s)
Biotecnología/métodos , Fabaceae/química , Mananos/aislamiento & purificación , Plantas Medicinales , Semillas/química , Animales , Brasil , Activación Enzimática , Galactosa/análogos & derivados , Mananos/toxicidad , Ratones , ViscosidadRESUMEN
The seeds of Senna multijuga were extracted with water or 1% acetic acid and treated with ethanol, resulting in two insoluble fractions. After purification, the major one (FIA, 23%) was shown to be a galactomannan (Man:Gal 2.3:1; [alpha] = +54.6; [eta] = 1340 ml g-1). It consists of a main chain of (1-->4)-linked beta-D-mannopyranosyl residues substituted at O6 by single-unit alpha-D-galactopyranosyl side chains. The second fraction (FIB, 2.5%) was an O-acetyl-glucuronoarabinoxylan from the seed coats (O-acetyl 8.3 mol%; glucuronic acid 11.7%, Xyl:Ara ratio 20:1), which showed a predominance of 4-O-substituted Xylp units (84.4%), branched at O3 with non-reducing end units of Xylp, Araf and glucuronic acid. The O-acetyl positions in D-xylosyl units are at O2 (4.8%), O3 (4.4%) and O2,3 (0.9%). The ratio between O3 and O2 determined by 13C-nuclear magnetic resonance spectroscopy is 1.5:1.
Asunto(s)
Polisacáridos/aislamiento & purificación , Extracto de Senna/química , Xilanos/aislamiento & purificación , Acetatos , Ácido Acético , Cromatografía en Gel , Etanol , Galactosa/análogos & derivados , Cromatografía de Gases y Espectrometría de Masas , Espectroscopía de Resonancia Magnética , Mananos/aislamiento & purificación , Extractos Vegetales/química , Semillas/química , Solubilidad , Agua , Xilosa/aislamiento & purificaciónRESUMEN
On aqueous extraction, Hymenaea courbaril var. stilbocarpa, known in Brazil as jatobá, furnishes a high yield of viscous xyloglucan (45%) from its seeds. The crude polysaccharide (B1) was hydrolysed and the products, analysed as alditol acetates, were glucose, xylose, galactose and arabinose in the ratio 50:35:13:2. After further fractionation on DEAE-cellulose column (chloride form), the main fraction (70% yield, B2) was obtained. The basic structure of the xyloglucan was determined as a cellulose-type (1-->4)-linked beta-D-glucan backbone partially substituted with side chains at O6 of alpha-D-xylopyranose, some of which were themselves substituted at O2 by the units of beta-D-galactopyranose. Treatment of the xyloglucan (B2) with commercial cellulase from Trichoderma sp. yielded six oligosaccharides. These oligosaccharides were isolated by preparative paper chromatography, and their structures were determined by gas-liquid chromatography-mass spectroscopy of the derived partially O-methylated alditol acetates. These results confirm the structure proposed for jatobá seed xyloglucan.
Asunto(s)
Fabaceae/química , Glucanos , Oligosacáridos/aislamiento & purificación , Plantas Medicinales , Polisacáridos/química , Xilanos , Brasil , Conformación de Carbohidratos , Secuencia de Carbohidratos , Celulasa/metabolismo , Cromatografía en Papel , Cromatografía de Gases y Espectrometría de Masas , Hidrólisis , Espectroscopía de Resonancia Magnética , Datos de Secuencia Molecular , Semillas/química , Solubilidad , AguaRESUMEN
Galactomannans with Man:Gal ratios ranging from 1.1:1 to 3:1, obtained from the seeds of Mimosa scabrella, Stryphnodendron barbatiman, Schizolobium parahybum and Schizolobium amazonicum, were submitted to mild acid hydrolysis. The products were fractionated by gel permeation chromatography on BioGel P2 yielding fractions with degrees of polymerization (DP) of 1 to 6. Those with DP 2 to 6 from each species were analysed by ion-exchange high-performance liquid chromatography and characterized by 13C- and 1H-nuclear magnetic resonance (NMR) spectroscopy. The distribution of the oligosaccharides of each degree of polymerization was very similar for the products from S. parahybum and S. amazonicum, indicating the same D-galactosyl distribution on the D-mannan backbone, in agreement with the 13C-NMR splitting in the C4 region of the D-mannosyl units in the original polymers. The hydrolytic conditions adopted allowed characterization of compounds that are not generally produced by enzymatic treatments. The results show that the structures of the oligosaccharides, even if there is a preferential hydrolysis of Gal-Man linkages, reflect the composition of the parent polymer.