Partial Structural Characterization of Complex Polysaccharide Isolated from Sugar Maple (Acer saccharum Marsh) Bark and its Anti-Inflammatory Activity

Abstract

The rationale of the present novel research was to report the properties of a major complex polysaccharide from an aqueous extract of sugar maple bark obtained after catalytic organosolv pulping of the maple bark, which impacted the chemical composition of residual liquor. By using such an aqueous extract of bark, a complex polysaccharide was obtained through ultrafiltration, followed by gel filtration on Sephadex G-50, which was named WSF-3, as the third eluted polysaccharide sub-fraction. Partial polymer and structural characterization revealed that WSF-3 had an average molecular weight of 21.5 kDa and consisted of a backbone of glucose residues (87.2%) linked together by α-(1 → 6) glycosidic bonds. The presence of galactose (9.8%) and rhamnose (3.1%) units may represent polysaccharide impurities as their structures have not been confirmed belonging to the glucan structure. If this was the case, WSF-3 could be similar to dextran, polysaccharide previously reported in sugar maple sap. An anti-inflammatory assay indicated that WSF-3 along with WE and its polysaccharide-rich fraction, all at 100 μg/mL, inhibited TNF-α production in LPS-stimulated RAW 264.7 cells. These results indicate that the concentrated WSF-3 was responsible, at least in part, for the anti-inflammatory effect of WE, suggest that WSF-3 could have therapeutic implications in the treatment of inflammation and inflammatory-related diseases.