Structural characterization of polysaccharides from the roots of Urtica fissa

Three polysaccharides were isolated from the roots of Urtica fissa by extraction, ultrafiltration, anion-exchange, and gel-filtration chromatography. The structures were characterized using acetylation, methylation, and spectral methods (GCMS, NMR). All three polysaccharides are mainly composed of d-arabinofuranosyl, d-galactopyranosyl, d-glucopyranosyl residues with different structural characteristics. Polysaccharide A of MW 5.2 × 10³ contained a linear chain of 1-linked β-d-glucopyranosyl, 1,6-linked β-d-glucopyranosyl, 1,6-linked α-galactopyranosyl, and 1,5-linked β-arabinofuranosyl moieties. Polysaccharide B of MW 7.7 × 10⁴ possessed a chain consisting of 1,5-linked α-d-arabinofuranosyl, 1,3-linked β-d-mannopyranosyl, 1,6-linked β-d-glucopyranosyl, and 1,6-linked α-d-galactopyranosyl residues, but 4-O of α-d-galactopyranosyl residues were branched by terminal β-d-glucopyranosyl residues. Polysaccharide C of MW 5.3 × 10⁴ composed of a chain of 1,5-linked α-d-arabinofuranosyl, 1,4-linked β-d-galactopyranosyl, 1,5-linked β-d-xylopyranosyl, 1,4-linked β-d-mannopyranosyl, 1-linked β-d-glucopyranosyl residues, and the terminal β-d-glucopyranosyl residues are attached to 3-O positions of 1,6-linked α-d-glucopyranosyl residues.