Polysaccharide of "junsai (Brasenia schreberi J.F. Gmel)" mucilage: constitution and linkage analysis.

Abstract

An acidic polysaccharide which coats young leaves and stems of Junsai (Brasenia schreberi J. F. Gmel) was extracted with hot water and purified with cetylpyridinium chloride. The polysaccharide ([α]25D+9°) comprises n-galactose (32_??_40%), D-mannose (10_??_14%), e-fucose (13_??_16%), L-rhamnose (6_??_9%), D-xylose (2_??_7%), L-arabinose (2_??_3%), D-glucuro-nic acid (19_??_29%) and a trace of n-glucose. These proportions are different, depending on the habitats. Methylated polysaccharide yielded, on acid hydrolysis, more than 17 methyl sugar fragments, which included 2, 4, 6-tri- and 3, 4, 6-tri-O-methyl-D-galactose, 2, 3-di-O-methyl-D-glucuronic acid, 2, 4-di-O-methyl-L-fucose, 2, 4-di-O-methyl-L-rhamnose, di- and mono-O-methyl-D-galactoses and -D-mannoses, in addition to tri-O-methyl-L-arabinose, -D-xylose, -L-fucose, -L-rhamnose and tetra-O-methyl-D-galactose. These results indicate that the polysaccharide has an extremely highly branched structure, consisting mainly of (1→3)-linked D-galactose, L-rhamnose and L-fucose, (1→2)-linked D-galactose and (1→4)-linked D-glucuronic acid residues. The mild Smith degradation gave a degraded polysaccharide which contains (1→3)-linked L-fucose, D-galactose and D-mannose residues. Methylation analysis revealed that branches occur at C-2 of the (1→3)-linked mannan chain.