RESUMO
Paramylon, a high molecular weight polysaccharide, is a linear and unbranched (1â¯ââ¯3)-ß-d-glucan. Despite its numerous biological benefits, the poor aqueous solubility of crystalline paramylon is a drawback that has hampered some of its applications. In an effort to make this biomaterial amenable to practical uses, cationic and anionic paramylon derivatives were obtained. The degrees of substitution of both products were determined. The products were characterized by FT-IR spectrocopy, ESI mass spectrometry, 1H, 13C and 1H-13C NMR and SEM microscopy. These techniques confirmed the success of the substitution reactions. 1H NMR analysis was used to develop alternative methods for an approximate estimation of the degree of substitution. 1H-13C HSQC NMR spectra were assigned for both derivatives. New applications of native, cationic and anionic paramylon were found. Native paramylon showed similar performance as pharmaceutical tablet disintegrant than sodium croscarmellose. Cationic paramylon behavior as colloid flocculant was comparable with commercial cationic polyacrylamides. The anionic derivative could eventually be used in the formulation of matrix controlled release systems or as a suspending agent.
Assuntos
Euglena gracilis/genética , Glucanos/síntese química , Ânions , Cátions , Coloides , Euglena gracilis/química , Floculação , Glucanos/química , Espectroscopia de Ressonância Magnética , Mutação , Solubilidade , ComprimidosRESUMO
Homopolymannuronic and homopolyguluronic fractions were obtained by partial hydrolysis of the alkaline extracts from the brown seaweeds Ascoseira mirabilis, Desmarestia menziessi, Desmarestia ligulata and Durvillaea sp. collected in southern Chile. Full characterization of the fractions was achieved by FT-IR and NMR spectroscopy. Total hydrolysis with 90% formic acid of the homopolymeric fractions allowed the preparation of mannuronic and guluronic acids. Both monomers and homopolymeric fractions as neutral salts were studied by CD and ORD. Chiroptical spectra were similar in shape and sign to those previously published in the literature, and permitted to assign D configuration to mannuronic acid and L configuration to guluronic acid in alginic acids. Specific optical rotation values at the sodium D light for the homopolymannuronic (â¼-100°) and homopolyguluronic (â¼-110°) acid fractions were obtained. These high negative values are proposed for the assignment of the absolute configuration of monomers in homopolymeric fractions.
Assuntos
Alginatos/química , Polímeros/química , Espectroscopia de Ressonância Magnética , Phaeophyceae/química , Espectroscopia de Infravermelho com Transformada de FourierRESUMO
The galactan system biosynthesized by the red seaweed Gymnogongrus tenuis (Phyllophoraceae) is constituted by major amounts of κ/ι-carrageenans, with predominance of ι-structures, which were isolated by extraction with hot water in high yield (â¼ 45%). A small amount of non-cyclized carrageenans mostly of the ν-type was also obtained. Besides, 12% of these galactans are agaran structures, which were present in major quantities in the room temperature water extracts, but they were also found in the hot water extract. They are constituted by 3-linked ß-D-galactose units partially substituted on C-6 with sulfate or single stubs of ß-D-xylose and 4-linked residues that comprise α-L-galactose units partially sulfated or methoxylated on C-3 or sulfated on C-3 and C-6 and 3,6-anhydro-α-L-galactose. Related structural patterns were previously found for agarans synthesized by other carrageenophytes. Results presented here show that these agarans are low molecular weight molecules independent of the carrageenan structures, with strong interactions between them.
Assuntos
Carragenina/química , Galactanos/química , Rodófitas/química , Alga Marinha/química , Carragenina/isolamento & purificação , Galactanos/isolamento & purificação , Temperatura Alta , Água/químicaRESUMO
Commercial kappa- and iota carrageenans were cationized with 3-chloro-2-hydroxypropyltrimethylammonium chloride in aqueous sodium hydroxide solution. For kappa-carrageenan three derivatives with different degrees of substitution were obtained. Native and amphoteric kappa-carrageenans were characterized by NMR and infrared spectroscopy, scanning electron and atomic force microscopy; methanolysis products were studied by electrospray ionization mass spectrometry. Young moduli and the strain at break of films, differential scanning calorimetry, rheological and flocculation behavior were also evaluated; the native and the amphoteric derivatives showed different and interesting properties. Cationization of iota-carrageenan was more difficult, indicating as it was previously observed for agarose, that substitution starts preferentially on the 2-position of 3,6-anhydrogalactose residues; in iota-carrageenan this latter unit is sulfated.
Assuntos
Carragenina/química , Polissacarídeos/química , Propanóis/química , Compostos de Amônio Quaternário/química , Cátions/química , Módulo de Elasticidade , Galactose/análogos & derivados , Galactose/química , Espectroscopia de Ressonância Magnética , Microscopia de Força Atômica , Reologia , Sefarose/química , Espectrometria de Massas por Ionização por ElectrosprayRESUMO
The water extracts from red seaweeds Laurencia obtusa and Laurencia filiformis comprise complex sulfated agarans. Those from L. obtusa have 3-linked ß-d-galactose units in part sulfated on 2-position or methylated on 6-position, while the 4-linked units are mostly 3,6-anhydro-α-l-galactose and α-l-galactose 6-sulfate, some of the latter units are substituted with ß-d-xylose on 3-position, precluding alkaline cyclization. The 3-linked ß-d-galactose units of the agarans from L. filiformis are mostly sulfated on 2-position, but approximately half of these residues also carry the 4,6-O-(1-carboxyethylidene) group. The 4-linked 3,6-anhydro-α-l-galactose units are methylated or substituted in part with single stubs of ß-d-xylose on 2-position. This is the first time that substitution with xylose of 3,6-anhydro-α-l-galactose is reported. Besides, α-l-galactose 2-sulfate carrying single stubs of ß-d-xylose on 3-position was also detected. These galactans have some common structural characteristics with those of other species of this genus, but also others that are specific for these species.
Assuntos
Galactanos/química , Laurencia/química , Isomerismo , Especificidade da Espécie , Sulfatos/químicaRESUMO
Novel interpolyelectrolyte complexes (IPECs) between naturally sulfated polysaccharides of the seaweed Polysiphonia nigrescens (PN) and cationized agaroses (CAG) and Eudragit E (EE) were prepared using an organic solvent free process, characterized, and explored for controlled drug release. Tablets containing model drug ibuprofen and IPECs were prepared by direct compression. Drug release in acid medium was low owing to the low solubility of ibuprofen in that condition and to the matrix action. Zero order drug release was determined in the buffer stage (pH=6.8), with Fickian diffusion predominating over relaxation during the initial phases. Relaxation appears to increase along the release process and even overcomes diffusion for some systems. Drug release profiles could be controlled by varying the content of IPECs in the tablets. Also, the change in molecular weight and the degree of substitution of the components allowed altering the release profiles.
Assuntos
Excipientes/química , Ibuprofeno/química , Polímeros/química , Alga Marinha/química , Preparações de Ação Retardada , Difusão , Composição de Medicamentos/métodos , Eletrólitos/química , Ibuprofeno/administração & dosagem , Peso Molecular , Ácidos Polimetacrílicos/química , Polissacarídeos/química , Sefarose/química , Solubilidade , ComprimidosRESUMO
The structures of two sulfated xylomannans extracted from the red alga Nemalion helminthoides were determined. These two fractions plus a sulfated mannan, isolated from the same alga and whose structure was previously reported, were subjected to chemical modification. The mannan was oversulfated with SO(3)-pyridine in dimethyl sulfoxide at 60 °C during two and three hours and the xylomannans were subjected to Smith degradation in order to eliminate xylose side-chains. Structural analysis of all derivatives was carried out by methylation analysis and (13)C NMR spectroscopy. Antiviral activity against herpes simplex virus type 1 and 2, and dengue virus type 2 of native and modified mannans and xylomannans was estimated. Anticoagulant effect of the active fractions was also determined.
Assuntos
Anticoagulantes/isolamento & purificação , Anticoagulantes/farmacologia , Antivirais/isolamento & purificação , Antivirais/farmacologia , Mananas/isolamento & purificação , Mananas/farmacologia , Rodófitas/química , Ésteres do Ácido Sulfúrico/isolamento & purificação , Ésteres do Ácido Sulfúrico/farmacologia , Anticoagulantes/química , Antivirais/química , Vírus da Dengue/efeitos dos fármacos , Herpesvirus Humano 1/efeitos dos fármacos , Herpesvirus Humano 2/efeitos dos fármacos , Mananas/química , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Ésteres do Ácido Sulfúrico/química , Xilose/química , Xilose/farmacologiaRESUMO
Xylans from five seaweeds belonging to the order Nemaliales (Galaxaura marginata, Galaxaura obtusata, Tricleocarpacylindrica, Tricleocarpa fragilis, and Scinaia halliae) and one of the order Palmariales (Palmaria palmata) collected on the Brazilian coasts were extracted with hot water and purified from acid xylomannans and/or xylogalactans through Cetavlon precipitation of the acid polysaccharides. The ß-D-(1â4), ß-D-(1â3) 'mixed linkage' structures were determined using methylation analysis and 1D and 2D NMR spectroscopy. The presence of large sequences of ß-(1â4)-linked units suggests transient aggregates of ribbon- or helical-ordered structures that would explain the low optical rotations.
Assuntos
Rodófitas/química , Xilanos/química , Configuração de Carboidratos , Espectroscopia de Ressonância Magnética , Metilação , Fenômenos Ópticos , Estereoisomerismo , Xilanos/isolamento & purificaçãoRESUMO
Cationized agaroses with different degrees of substitution (0.04-0.77) were synthesized, employing 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC). The influence of different reaction parameters on the substitution degree and molecular weight was evaluated. The investigated parameters were concentration of reagents, temperature, time, and addition of NaBH(4). The products were characterized by means of scanning electronic microscopy, infrared spectroscopy, viscosimetry, and NMR spectroscopy. Methanolysis products were studied by electrospray ionization mass spectrometry. The higher the concentration of CHPTAC employed, a higher degree of substitution was obtained, if the optimum concentration of NaOH in each case was employed. Insufficient quantities of NaOH reduced epoxide formation and the reacting alkoxides of the polysaccharide, whereas an excess of NaOH favored degradation of the epoxide and decrease in the molecular weight of the product. A reaction time of 2h was sufficient to obtain products with the maximum degree of substitution for each case. The addition of NaBH(4) gave products with a slightly higher molecular weight, but the extra cost involved should not justify its use for large-scale application.
Assuntos
Propanóis/química , Compostos de Amônio Quaternário/química , Sefarose/síntese química , Sefarose/ultraestrutura , Boroidretos/química , Cátions/química , Raios Infravermelhos , Espectroscopia de Ressonância Magnética , Microscopia Eletrônica de Varredura , Sefarose/química , Espectrometria de Massas por Ionização por Electrospray , Espectrofotometria Infravermelho , ViscosidadeRESUMO
Nemalion helminthoides, collected in the Argentine South Atlantic coast, was extracted with hot water and the crude product fractionated using cetrimide. The complexed material was subjected to fractional solubilization in solutions of increasing sodium chloride concentration and seven fractions were separated and analyzed. Structural analysis of the main fractions, those soluble in 3.0 and 4.0 M NaCl (yields 21.0% and 13.8%, respectively) and those insoluble in 4.0 M NaCl (yield 20.0%), indicated that this seaweed biosynthesizes (1-->3)-linked alpha-D-mannans that are sulfated at positions 4 and 6. Three mannan fractions comprising considerable amounts of xylose were also isolated in very low total yield (2.0%). The fractions that were soluble in 3.0 and 4.0 M NaCl showed low antiherpetic activity whereas this activity was considerable for the fraction solubilized in 2.0 M NaCl (yield 0.5%) which contained single stubs of beta-D-xylose. A xylan, soluble in cetrimide solution, containing (1-->3, 1-->4)-linked beta-D-xylose residues, was also isolated in minor amount.