The Fine Structure of Alginic Acid Components

Sodium alginate, a brown seaweed polysaccharide, is capable of preventing intestinal absorption of radioactive strontium and its radiotoxicological importance is now well established. Alginic acid was found to be composed of 1,4-linked poly-L-guluronic acid and poly-D-mannuronic acid chains with some glycosidic linkages between these uronic acids. Polyguluronic and polymannuronic acid were prepared by acid hydrolysis of alginic acid from Laminaria hyperborea followed by fractionation of the partially degraded sodium alginate at pH 2.8. These components consist almost exclusively of a single uronic acid (polyguluronic acid: man/gul = 0.27; polymannuronic acid: man/gul = 10.7). Sodium polyguluronate inhibits absorption of radiostrontium more effectively than sodium polymannuronate.