The starch and related polysaccharides of certain hardwoods

Abstract

The starch in the parenchymatous cells of English oak (Quercus sp.) sapwood are spherical or ovoid, with a max. diam. of 6-10[mu]. Under crossed nicols a distinct black interference cross is discernible at approximately 600 diam. The presence of a hilum could not be detected. To isolate wood starch in a high degree of purity, the parent wood substance must first be dried to a moisture content not greater than 12%. 50-60 mesh material is then exhaustively extracted with water at 60 [degree]C to remove tannin, coloring matter, soluble sugars, etc., during which treatment the greater proportion of the starch grains in the parenchymatous cells remain intact. Subsequent extraction with water at 100[degree] C removes the starch in colloidal soln. from which after concn. in vacuo the polysaccharide is precipitated by alcohol. After suitable purification and dehydration the product is isolated in the form of a pale pinkish buff impalpable powder. The av. yield from oak sapwood was 1.38% and from the outer sapwood of walnut (Juglans regia) 0.43% by wt. of oven-dry original wood. By the Tollens method, oak sapwood starch yielded furfural phloro-glucide (4.26%). It also contained a trace of methoxyl. Ca. 90% of the substance was hydrolyzed to sugars by takadiastase at pH 4.5 and 38-40[degree]. It is suggested that wood starch is an acid polysaccharide approximately 90% of which is composed of anhydro-glucose residues. The remainder appears to consist of an aldobionic anhydride (probably glueose-glucuronic anhydride) which jiiay or may not be partly methylated. It is indicated that the cell walls of oak sapwood contain a related polysaccharide. It is claimed that the wood starch now isolated for the first time is the substance to which Wilson has referred as the food of the larvae of Lyctus powder post beetles.