Water-soluble polysaccharides of the red alga Laurencia pinnatifida. Part II. Methylation analysis of the galactan sulphate

Abstract

Methylation of the galactan sulphate from Laurencia pinnatifida and hydrolysis of the methylated polysaccharide furnished 2,4,6-tri-, 4,6-di-, and 2,6-di-O-methyl-D-galactose, 2,3-di- and 2-O-methyl-L-galactose, and 2,4-di-O-methyl-D-galacturonic acid as the main products. These products, together with evidence previously cited for the location of the sulphate groups, suggest that in the galactan sulphate both D-galactose and 6-O-methyl-D-galactose units are linked through position 3, while L-galactose and 2-O-methyl-L-galactose units are linked through position 4. In addition, there may be some branching in the molecule. The D-galacturonic acid is present as 1,3-linked units, either in the galactan sulphate, or in an associated polysaccharide.