Characterization of arabinogalactans from Larix principis-rupprechtii and their effects on NO production by macrophages

Abstract

Arabinogalactans are a source of dietary fiber with health benefits. In this work, two arabinogalactans assigned as AGW and AGS were isolated from Larix principis-rupprechtii, and characterized by gel permeation chromatography (GPC), monosaccharide analysis, methylation analysis and NMR spectroscopy analysis. The average molecular weights of AGW and AGS were 1.53 × 10⁴ and 1.84 × 10⁴ Da, respectively. Methylation analysis and NMR spectra suggested that AGW and AGS have a 1,3-linked Galp backbone, branched at C-6 with 1,6-linked Galp side residues. The Ara residues were substituted at C-6 of 1,6-linked Galp consisting of α-L-Araf-(1→3)-α-L-Araf-(1→6)-β-D-Galp-(1→ and β-L-Arap-(1→6)-β-D-Galp-(1→. Significantly, AGS (0.74%) was shown to contain 25 times more uronic acid than AGW (0.03%), which demonstrated a polyelectrolyte effect. Application of these two polysaccharides to macrophage RAW 264.7 cells was shown to increase nitric oxide (NO) production. These results provide a basis for studying the relationship between the structure and biological activity of arabinogalactans.

Keywords: Arabinogalactan; Larix principis-rupprechtii; NMR; Nitric oxide; Polyelectrolyte effect.