Ccxcvi. Cress Seed Mucilage

THE dispersed cellulose component which is found in white mustard seed mucilage [Bailey and Norris, 1932] and in quince seed mucilage [Schmidt, 1844; Kirchner and Tollens, 1874; Renfrew and Cretcher, 1932] has now been obtained from the mucilage of cress seed, Lepidium sativum. The present communication, which deals mainly with the chemistry of this seed mucilage, falls into three sections: (1) the products obtained by acid hydrolysis of cress seed mucilage are characterised; (2) the mucilage is shown to be a heterogeneous polysaccharide system, and its behaviour towards fractionating agents is contrasted and compared with those of the closely related mucilage of white mustard seed and the non-cellulosic mucilage of linseed; (3) the factors responsible for the hvdration and dispersion of the cellulose component in seed mucilages and in other cellulose polyuronide systems are discussed. Since the earlier review of Bailey and Norris [1932] several contributions to the chemistry of the mucilages have been made, chiefly by American workers in this field. d-Galactose, l-rhamnose and galacturonic acid have been found in the hydrolytic products of the mucilage of slippery elm bark [Anderson, 1934]. The uronic acid is combined in part as a rhamnosegalacturonide, an aldobionic acid found previously by Anderson and Crowder [1930] in the hydrolysis products of linseed mucilage. The latter mucilage has now been shown to contain the i-form of galactose [Anderson, 1933] and the d-form of galacturonic acid [Niemann and Link, 1934]. The frequent occurrence of structurally related carbohydrates, i.e. of d-galactose, d-galacturonic acid with l-arabinose, and of d-glucose, d-glycuronic acid with d-xylose, has given considerable support to the classical hypothesis of de Chalmot [1894, 1, 2], who first suggested that pentosan may arise from hexosan by a two-stage process; oxidation of the hexose to the uronic acid followed by decarboxylation to the pentose. The occurrence of l-galactose with d-galacturonic acid in linseed mucilage is therefore an interesting anomaly. The mucilage of Psyllium seed, investigated by Anderson and Fireman [1935] consisted of a mixture of polyuronides, which were hydrolysed to dgalacturonic acid, 1-arabinose and d-xylose. This latter sugar has also been isolated from Psyllium seed mucilage by the present author. Quince seed mucilage on hydrolysis yields d-xylose, 1-arabinose and a mixture of monomethylated and unmethylated pentoseuronide [Renfrew and Cretcher, 1932]. The ultimate constituents of white mustard seed mucilage are arabinose, rhamnose, galactose, galacturonic and glycuronic acids [Bailey and Norris, 1932].