Structural characterization and in vitro osteogenic activity of ABPB-4, a heteropolysaccharide from the rhizome of Achyranthes bidentata

Achyranthes bidentata is a species of flowering plant that is mainly distributed in China. The A. bidentata rhizome is a famous traditional Chinese medicine that has been widely used to treat lumbago, arthritis, and bone hyperplasia. In this work, A. bidentata rhizome was isolated and purified to obtain a pectic polysaccharide (ABPB-4). Chemical and spectral analyses showed that ABPB-4 had a main chain of -> 4)-alpha-D-GalpA-(1 -> and -> 2,4)-alpha-L-Rhap-(1 ->, and the branch chains included -> 4)-beta-D-Galp-(1 ->, -> 6)-beta-D-Galp-(1 ->, -> 3,6)-beta-D-Galp-(1 ->, -> 5)-alpha-L-Araf-(1 -> and -> 3,5)-alpha-L-Araf-(1 ->, and it was terminated with alpha-L-Araf-(1 -> and beta-D-Galp-(1 ->. At concentrations of 0.01, 0.02, and 0.04 mu mol/L, ABPB-4 significantly promotes the proliferation, differentiation, and mineralization of MC3T3-E1 cells in vitro, and it appreciably enhances the mRNA expression levels of osteogenic-related genes in these cells. Overall, the results reported herein indicate that ABPB-4 has outstanding osteogenic activity, and that it may be used as an anti-osteoporosis agent in the future.