The Structure of Arabinoxylan and Arabinoglucuronoxylan Isolated from Rice Endosperm Cell Wall

Abstract
A neutral and an acidic arabinoxylan fraction (H-l and H-2) were obtained from rice endosperm cell wall. The results of methylation analysis and partial hydrolysis of these fractions showed that both of them have highly branched structures in which approximately 6 out of 7 (H-l) and 5 out of 6 (H-2) of the (1→4)-linked d-xylose residues are branched. Most of the side chains in H-l consists of single α-l-arabinofuranose residues, whereas some of them in H-2 were substituted with α-d-glucuronic acid or 4-O-methyl-α-d-glucuronic acid residues, both attached to the O-2 position of d-xylose residues. These highly branched arabinoxylans are not readily hydrolyzed by an endoxylanase of Streptomyces sp.