Structural characterization and osteoprotective effects of a polysaccharide purified from Achyranthes bidentata

Achyranthes bidentata has been traditionally used in China as a nature remedy for osteoporosis; however, little is known about the osteoprotective effects of its polysaccharides. The crude A. bidentata polysaccharide (AB70) was prepared by hot water extraction- ethanol precipitation method and a homogeneous fructan (ABW70-1) was purified from AB70 by ion-exchange and gel filtration column chromatography. Structural analysis indicated that ABW70-1 was composed of (2 → 1)-linked-β-d-fructofuranosyl (Fruf), (2 → 6)-linked-β-d-Fruf and (2 → 1,6)-linked-β-d-Fruf residues, and terminated with fructose and glucose residue. AB70 treatment for 13 weeks has shown a therapeutic effect on ovariectomized rats by restoring bone mineral content and biomechanical properties of the femur. Moreover, such osteoprotective effects of AB70 on bone mass were accompanied by improving trabecular bone microarchitecture and decreasing serum levels of bone turnover biomarkers. Furthermore, ABW70-1 stimulated the osteogenic differentiation of MC3T3-E1 cells by promoting cell proliferation, ALP activity, mineral nodules formation and the gene expression of Osx, Ocn and Bsp. These results suggest that A. bidentata polysaccharides have a great potential in the prevention and treatment of osteoporosis.