ISOLATION AND SOME STRUCTURAL FEATURES OF A POLYSACCHARIDE FROM BIRCH SAP

Abstract

A polysaccharide, precipitated by cetyltrimethylammonium hydroxide from the non-dialyzable portion of birch xylem sap, contained D-galactose, D-mannose, and D-glucose in a molar ratio of 2:1.4:1 and small amounts of D-glucuronic acid. Periodate oxidation studies indicated that the polysaccharide was branched and contained a high proportion of periodate-resistant monosaccharides. This was confirmed by methylation and hydrolysis which yielded 2,3,4,6-tetra-O-methyl-D-glucose (2.0 moles); 2,4,6-tri-O-methyl-D-mannose (0.9 mole); 2,4,6-tri-O-methyl-D-galactose (3.8 moles); unidentified tri-O-methyl hexose (1.2 moles); and 3,5-di-O-methyl-D-mannose (1.8 moles). The latter, a new di-O-methyl-D-mannose, snowed the presence of D-mannofuranose units in the polysaccharide. This, together with the 1 → 3 linked α-D-mannopyranose units, makes this polysaccharide unique among plant products. Immunochemical tests with antipneumococcal and antiparatyphoid B horse sera confirmed the presence of D-glucuronic acid and D-glucopyranose non-reducing end groups and supported the other structural conclusions by showing that there were few, if any, 1 → 4 and 1 → 6 linked D-mannopyranose units or D-galactopyranose non-reducing end groups.