RESUMO
The structure of a hemicellulose B fraction (B-1) isolated from grape skins (Vitis vinifera) of the Palomino variety has been studied by methylation analysis, (1)H NMR and (13)C NMR spectroscopy, and partial acid hydrolysis. Hemicellulose B-1 appeared to be homogeneous by gel filtration with a weight-average molecular weight of 22 600. This polysaccharide is a linear xyloglucan chain composed of xylopyranosyl and glucopyranosyl residues linked by beta-(1-->4) glycosidic bonds. Attached to this backbone, 4-O-methyl-D-glucuronopyranosyl acid, D-glucopyranosyl, and L-fucopyranosyl residues occur at position 2 in a ratio of one residue for every five units of xylose in the main chain, with D-xylopyranosyl residues attached at position 6 of glucose units in a ratio of one residue for every two glucose-derived moieties in the main chain.
Assuntos
Celulose/isolamento & purificação , Fibras na Dieta/análise , Polissacarídeos/química , Vitis/química , Sequência de Carboidratos , Celulose/química , Cromatografia Gasosa , Cromatografia Líquida de Alta Pressão , Cromatografia em Papel , Cromatografia Gasosa-Espectrometria de Massas , Hidrólise , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Metilação , Dados de Sequência Molecular , Estrutura Molecular , Polissacarídeos/isolamento & purificação , Sementes/química , Espanha , Espectrofotometria InfravermelhoRESUMO
The structure of one of the hemicellulose A fractions (HA-1) extracted from the seeds of the grape variety Palomino (Vitis vinifera cv. Palomino) has been studied by means of methylation, 1H NMR, 13C NMR, and partial hydrolysis. This hemicellulose seems to be a homogeneous polysaccharide with an apparent molecular weight of 68 500. Its structure is that of an acidic xylan, a linear chain of beta-D-xylopyranosyl units, bonded together by (1-->4) glycosidic links, containing single alpha-D-xylopyranosyl and 4-O-methyl-alpha-D-glucopyranuronosyl residues joined by glycosidic links to position 2 of the xylose units of the main chain, in proportions of one residue to every 25 units of xylose.
Assuntos
Fibras na Dieta/análise , Polissacarídeos/química , Rosales/química , Sequência de Carboidratos , Cromatografia em Gel , Cromatografia Líquida de Alta Pressão , Cromatografia Gasosa-Espectrometria de Massas , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Metilação , Dados de Sequência Molecular , Sementes/químicaRESUMO
The structure of one of the hemicellulose B fractions (HB-1) extracted from the seeds of the grape variety Palomino (Vitis vinifera cv. Palomino) has been studied by means of methylation analysis, 1H NMR, 13C NMR, and partial acid hydrolysis. This hemicellulose seems to be a homogeneous polysaccharide with an apparent molecular weight of 35 000. Its structure is that of an acidic arabinoxylan, a linear chain of beta-D-xylopyranosyl units, bonded together by (1-->4) glycosidic links, containing a single L-arabinofuranosyl, alpha-D-xylopyranosyl and 4-O-methyl-alpha-D-glucopyranuronosyl residues joined by glycosidic links to position 2 of the xylose units of the main chain, in proportions of one branch to every seven units of xylose.
