Characterization and hypoglycemic effect of a neutral polysaccharide extracted from the residue of Codonopsis Pilosula

A neutral polysaccharide coded as CERP1 was extracted and purified from the residue of Codonopsis pilosula by ethanol precipitation and column chromatography. The structure of CERP1 was determined by HPAEC-PAD, HPLC, HPSEC-MALLS, FT-IR, NMR, and TEM. The results showed that CERP1 was a heteropolysaccharide composed of Arabinose, Glucose, and Galactose in the ratio of 1.00:19.83:6.94. HPSEC-MALLS showed that CERP1 was homogeneous with an absolute molecular weight of 4.840 × 10 3  Da. The NMR results and the GC–MS result of methylation indicated that 1-linked β- d -glucose, 1,3-linked β- d -glucose, 1,6-linked β- d -glucose and 1,3,6-linked β- d -galactose were the main linkages in CERP1. TEM results indicated that CERP1 had a homogeneous particle size and good dispersibility both in purified water and 0.05 M sodium sulfate. Pre-treatment with CERP1 could result in a significant improvement of the insulin secretion of the INS-1 cells. While in vivo assays, CERP1 exhibited a potent hypoglycemic effect on T2DM mice for its ability to relieve oxidative stress, ameliorate lipid metabolism, increase glycolytic enzyme activity as well as decrease liver transaminase activity. This study gives a chance for exploring the residue of Codonopsis pilosula.