Structure of a polysaccharide from Urtica fissa determined by NMR spectra.

A polysaccharide, isolated and purified from the aqueous extract of nettle plant Urtica fissa, was found to consist of D-glucose and D-arabinose. Molecular weight was determined to be Mn 4140. The NMR experiments (¹H, ¹³C, ¹H--¹H COSY, TOCSY, HSQC, NOESY, and HMBC) revealed the structure as the following repeating unit: -->6)-α-D-Glcp-(1-->6)-α-D-Glcp-(1-->6)-ß-D-Glcp--(1-->5)-ß-D-Araf-(1-->3)-ß-D-Glcp-(1-->

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 x 10(3) contained a linear chain of 1-linked beta-D-glucopyranosyl, 1,6-linked beta-D-glucopyranosyl, 1,6-linked alpha-galactopyranosyl, and 1,5-linked beta-arabinofuranosyl moieties. Polysaccharide B of MW 7.7 x 10(4) possessed a chain consisting of 1,5-linked alpha-D-arabinofuranosyl, 1,3-linked beta-D-mannopyranosyl, 1,6-linked beta-D-glucopyranosyl, and 1,6-linked alpha-D-galactopyranosyl residues, but 4-O of alpha-D-galactopyranosyl residues were branched by terminal beta-D-glucopyranosyl residues. Polysaccharide C of MW 5.3 x 10(4) composed of a chain of 1,5-linked alpha-D-arabinofuranosyl, 1,4-linked beta-D-galactopyranosyl, 1,5-linked beta-D-xylopyranosyl, 1,4-linked beta-D-mannopyranosyl, 1-linked beta-D-glucopyranosyl residues, and the terminal beta-D-glucopyranosyl residues are attached to 3-O positions of 1,6-linked alpha-D-glucopyranosyl residues.