Structural features of (1→3),(1→4)-β-D-glucan and arabinoxylan fractions isolated from rye bran

A water unextractable fraction from rye bran was isolated by means of a sequential extraction. Gel filtration revealed a homogeneous beta-glucan and at least two different arabinoxylans. H-1 and C-13 NMR spectroscopy were used to identify the structural units in both polysaccharides. The isolated arabinoxylan contained a relatively high amount of unsubstituted xylose residues (56.7%). The molar ratio of cellotriosyl to cellotetraosyl units and the ratio of (1 --> 4) to (1 --> 3)-linkages in beta-glucan were determined using high performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) and H-1 NMR, respectively. The molar ratio of cellotriosyl to cellotetraosyl was found to be 1.94. From this, the ratio of (1 --> 4) to (1 --> 3)-linkages was calculated to be 2.34, as compared to 2.31 obtained by H-1 NMR, showing that the results from both methods are in close agreement. (C) 2000 Elsevier Science Ltd. All rights reserved.