Polysaccharides from the roots of the marsh mallow (Althaea officinalis L., var. Rhobusta): structural features of an acidic polysaccharide

Abstract

An acidic heteropolysaccharide isolated from the mucilage of the roots of the marsh mallow ( Althaea officinalis L., var. Rhobusta) via its insoluble barium salt contained d-galactose, l-rhamnose, d-glucuronic acid, and d-galacturonic acid in the molar ratios 1.2:1.0:1.0:1.0. It was homogenous on free-boundary electrophoresis and in the anlytical ultracentrifuge, and it had M w = 26,700, M n = 23,900. Partial acid hydrolysis and analyses of the methylated and the methylated, carboxyl-reduced polysaccharide indicated that the polymer backbone is composed of (1→4)-linked d-galactopyranuronic acid and (1→2)-linked l-rhamnopyranose units in the ratio of 1:1. Each d-galacturonic unit carries a single β- d-glucopyranuronic residue linked to C-3, and each l-rhamnopyranose unit carries d-galactopyranose residues, mainly as non-reducing terminals linked to C-4. A smal number of presumably short chains of (1→4)-linked d-galactopyranose units are also involved in branching.