Structural and biological properties of polysaccharides from lotus root.

To investigate the structure, in vitro digestibility and activity of polysaccharides from lotus root, their main fractions named LRPs were isolated and purified by gel filtration chromatography. Structural analyses indicated that: LRPs were α­(1 → 6)­d­heteroglucans mainly composed of Glc-(1→, →6)-Glc-(1→, →6)-Gal-(1→, →4,6)-Gal-(1→ and →3,6)-Glc-(1→ at a molar ratio of 1.00: 4.33: 0.83: 0.13: 1.14; the total molar percentage of other monosaccharides in LRPs, including Man, Rha, GalA and Ara, was 8.10%; the molecular weights of LRPs was in the range of 1.33 kDa to 5.30 kDa. According to the change of molecular weight and the productions of reducing sugar and free monosaccharide, the simulated experiments of salivary, gastric and intestinal digestion confirmed that LRPs were almost undigestible. Moreover, LRPs showed the scavenging ability against DPPH and hydroxyl radicals, the growth inhibition ability against SGC7901 and HepG2 cancer cells in vitro, and the immunostimulating effect on the NO and TNF-α productions of macrophages in vitro. LRPs nearly remain their initial structure and activities in upper gastrointestinal tract and have health-improving potentials.