Cereal arabinoxylans: advances in structure and physicochemical properties

Novel food and non-food uses for sorghum and millets.

Publisher Summary This chapter focuses on the hemicelluloses of the Gramineae (grasses and cereals). The term “hemicelluloses” is also often extended to include certain carbohydrates in cereal endosperms—namely, non-starch polysaccharides. Hemicellulose refers to all of the types of polysaccharide in the Gramineae, other than celluloses, starches, and fructans. Hemicellulose chemistry has a vocabulary lacking invariant definitions, and insight into the nature of hemicelluloses has been gained by the work not only of chemists and biochemists but of applied scientists having research interests in animal nutrition, brewing, cereals, paper manufacture, and starch production. The chapter also discusses species and various tribes of Gramineae, isolation of hemicellulosimca materials and of pure hemicelluloses, and structural feature in hemicelluloses. The importance of knowledge about the hemicelluloses may be gauged by looking at the abundance of photosynthetically renewable grasses and bearing in mind that, apart from the materials in the seed, one third of their composition is hemicellulose.

The Hemicelluloses of Grasses and Cereals

The partial purification and characterization of cell wall polysaccharides isolated from suspension-cultured Douglas fir (Pseudotsuga menziesii) cells are described. Extraction of isolated cell walls with 1.0 m LiCl solubilized pectic polysaccharides with glycosyl-linkage compositions similar to those of rhamnogalacturonans I and II, pectic polysaccharides isolated from walls of suspension-cultured sycamore cells. Treatment of LiCl-extracted Douglas fir walls with an endo-alpha-1,4-polygalacturonase released only small, additional amounts of pectic polysaccharide, which had a glycosyl-linkage composition similar to that of rhamnogalacturonan I. Xyloglucan oligosaccharides were released from the endo-alpha-1,4-polygalacturonase-treated walls by treatment with an endo-beta-1,4-glucanase. These oligosaccharides included hepta- and nonasaccharides similar or identical to those released from sycamore cell walls by the same enzyme, and structurally related octa- and decasaccharides similar to those isolated from various angiosperms. Finally, additional xyloglucan and small amounts of xylan were extracted from the endo-beta-1,4-glucanase-treated walls by 0.5 n NaOH. The xylan resembled that extracted by NaOH from dicot cell walls in that it contained 2,4- but not 3,4-linked xylosyl residues. In this study, a total of 15% of the cell wall was isolated as pectic material, 10% as xyloglucan, and less than 1% as xylan. The noncellulosic polysaccharides accounted for 26% of the cell walls, cellulose for 23%, protein for 34%, and ash for 5%, for a total of 88% of the cell wall. The cell walls of Douglas fir were more similar to dicot (sycamore) cell walls than to those of graminaceous monocots, because they had a predominance of xyloglucan over xylan as the principle hemicellulose and because they possessed relatively large amounts of rhamnogalacturonan-like pectic polysaccharides.

Structure of Plant Cell Walls: XIX. Isolation and Characterization of Wall Polysaccharides from Suspension-Cultured Douglas Fir Cells

3 – The Primary Cell Walls of Flowering Plants

Structural studies on a glucuronoarabinoxylan from the husk of sorghum grain

A hemicellulosic β-D-glucan from the endosperm of sorghum grain

Structural studies on the water-soluble gums from the endosperm of sorghum grain☆

Conformational analysis of 1,2:3,4-di-O-isopropylidene-α-d-galacto-octopyranose derivatives: a 1H- and 13C-N.M.R.-spectral and x-ray comparative study

Synthesis and crystal structure of 7-acetamido-6,7,8-trideoxy-1,2:3,4-Di-O-isopropylidene-α-d-glycero-d-galacto-octo-pyranose

Elner B. Rathbone

Papers

Structural studies on a glucuronoarabinoxylan from the husk of sorghum grain

A hemicellulosic β-D-glucan from the endosperm of sorghum grain

Structural studies on the water-soluble gums from the endosperm of sorghum grain☆

Conformational analysis of 1,2:3,4-di-O-isopropylidene-α-d-galacto-octopyranose derivatives: a 1H- and 13C-N.M.R.-spectral and x-ray comparative study

Synthesis and crystal structure of 7-acetamido-6,7,8-trideoxy-1,2:3,4-Di-O-isopropylidene-α-d-glycero-d-galacto-octo-pyranose