Structural analysis and bioactivity of a polysaccharide from the roots of Astragalus membranaceus (Fisch) Bge. var. mongolicus (Bge.) Hsiao

The Astragalus polysaccharide (APS) was extracted and purified from the roots of Astragalus membranaceus, and characterised for its chemical structure and potential health properties. The APS was composed of α-d-glc residues with the estimated equivalent dextran molecular weight of 2.07 × 104 Da. Periodate oxidation analysis, 1D and 2D NMR spectroscopy demonstrated that APS has repeating (1 → 4)-linked backbone with a (1 → 6)-linked branch every 10 residues. The APS possessed scavenging activities against hydroxyl radicals and hydrogen peroxide, and showed chelating effect on ferrous ions. The APS was also able to bind cholic and chenodeoxycholic acids in vitro. In addition, APS was able to stimulate activity of purified mouse B cells without promoting T cell proliferation. These data provided information for future development of APS as a nutraceutical.