A novel l-fuco-4-O-methyl-d-glucurono-d-xylan from Hyptis suaveolens

The acidic polysaccharide from the seed-coat mucilage of Hyptis suaveolens is a highly branched l-fuco-4-O-methyl-d-glucurono-d-xylan for which a structure is proposed having a 4-linked β-d-xylan backbone carrying side chains of single 4-O-methyl-α-d-glucuronic acid residues at O-2 and 2-O-l-fucopyranosyl-d-xylopyranose units at O-3. The structural analysis involves base-catalyzed β-elimination of uronic acid residues from the methylated glycan followed by degradation using a modified Svensson oxidation-elimination sequence.