An acidic galactoarabinoxylan from the stem of Avena sativa

Abstract

An l-arabino- d( l?)-galacto- d-glucurono-(4- O-methyl)- d-glucurono- d-xylan has been isolated from the stem tissues of the oat plant. The hemicellulose has D.P. 80 and the percentages of arabinose, galactose, xylose and uronic acid residues are 22, 6·7, 63 and 8·5 respectively. It has ca. 1 in every 1·8 residues on the main xylan chain carrying substitutents, namely, d-glucuronic acid and 4- O-methyl- d-glucuronic acid on C2 positions, d-glucopyranuronosyl-(1 → 4)- d-xylopyranosyl-(1 → 4)- d-galactopyranose on C2 or C3 positions, and, on C3 positions, α- l-arabinofuranosyl, 5- O-β?- d-galactopyranosyl- l-arabinofuranosyl, 4?- O-β?- l?-galactopyranosyl-2- O-β?- d-xylopyranosyl- l-arabinofuranosyl, and β?- d-xylopyranosyl-(1 → 2)- l-arabinofuranosyl residues or side-chains.