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

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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.
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