Structural features of alkali-soluble acidic xylans isolated from the bark of Ceiba pentandra var. indica

The insoluble residue of C. pentandra var. indica, obtained by delignification of the bark, gave an alkali-soluble polysaccharide fraction containing l-fucose, d-xylose, l-arabinose, d-glucose, d-galactose, d-glucuronic acid, and 4-O-methyl-d-glucuronic acid. Fractional precipitation with Cetavlon and barium hydroxide afforded three hemicellulose-type acidic xylans that differed in the contents of uronic acid and mol. wts., and a fucose-containing acidic polysaccharide. Methylation analysis of the carboxyl-reduced acidic xylans suggested a (1→2)- or (1→4)-linked backbone and different patterns of substitution. Partial hydrolysis of one acidic xylan gave 4-O-β-d-xylopyranosyl-d-xylose and 2-O-(α-d-glucopyranosyluronic acid)-d-xylose. The oxidation of this polysaccharide with chromium trioxide and periodate was studied.