AN ACIDIC GALACTOARABINOXYLAN AND OTHER PURE HEMICELLULOSES IN OAT LEAF

The total hemicellulose (with galactose:glucose:arabinose:xylose ratio 2·8:11·4:10:23·5) was extracted from the holocellulose of the leaves of young oat plants, Avena sativa (var. Blenda), by treatments with 5 and 24% KOH. The water-soluble part of the hemicellulosic material extracted by the 5% KOH was fractionated on a column of DEAE-cellulose irrigated by water and aqueous KOAc. The hemicellulosic material eluted by 0·5 M KOAc was subjected to further fractionation, to ultracentrifugal examination, to zone electrophoresis and to preliminary structural studies. A number of hydrolysis products from the methylated hemicellulosic material have been identified. The material is a pure acidic galactoarbinoxylan (galactose:arabinose:xylose, 2·8:10:18·5; uronic acids not less than 3-4 per cent). It is similar to the land-plant xylans but is unusual in having terminal and non-terminal residues of galactose. © 1970.