THE STRUCTURE OF LINSEED MUCILAGE: PART II

Abstract

Linseed mucilage has been separated into an acidic and a neutral fraction. The acidic fraction was further separated, by the use of cupric acetate solution, into two fractions, CuI and CuII. Fraction CuI contained L-rhamnose, L-galactose, and D-galacturonic acid. The methylated reduced polysaccharide gave on hydrolysis 2,3,4-tri-O-methyl-L-rhamnose, 3,4-di-O-methyl-L-rhamnose, 4-O-methyl-L-rhamnose, 2,3,4,6-tetra-O-methyl-D-galactose, 2,3,6-tri-O-methyl-D-galactose, and 2,3-di-O-methyl-D-galactose (?); L-galactose was lost during the methylation process. Periodate oxidation studies on the material indicated that the polymer was composed of a main chain of L-rhamnose units with most of the L-galactose units attached as non-reducing end groups. Fraction CuII contained L-rhamnose, L-fucose, L-galactose, and D-galacturonic acid. The methylated reduced polysaccharide gave on hydrolysis 2,3,4-tri-O-methyl-L-fucose, 2,3,4,6-tetra-O-methyl-L-galactose, 2,3,6-tri-O-methyl-D-galactose, 4-O-methyl-L-rhamnose, L-rhamnose, and possibly 2,3-di-O-methyl-D-galactose and 3-O-methyl-D-galactose. Periodate oxidation studies and a degradation by the Smith procedure indicated the presence of a L-rhamnose backbone with L-fucose and L-galactose units attached as non-reducing end groups.The neutral fraction yielded a periodate-oxidizable material after one Smith-type degradation. Periodate oxidation studies indicated that the degraded material was branched. Methylation of the degraded polysaccharide followed by hydrolysis yielded 2,3,4-tri-O-methyl-D-xylose, 2,3-di-O-methyl-D-xylose, 2,4-di-O-methyl-D-xylose, 4-O-methyl-D-xylose, D-xylose, and traces of 2,3,4-trt-O-methyl- or 2,5-di-O-methyl-L-arabinose, 2,4-di-O-methyl-D-xylose, and 3-O-methyl-D-xylose. The main backbone of the degraded polysaccharide appeared to consist of (1 → 4)-linked D-xylose units. Linkages of the (1 → 3) type were also present. The smaller fragments from the Smith-type degradation, L-arabinose, 2-O-α-L-arabinosyl glycerol, and glycerol were characterized. A partial acid hydrolysis of the neutral fraction yielded a number of oligosaccharides.