A hemicellulose B fraction from grape skin (Vitis vinifera, Palomino variety)

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.