Objective: To isolate and purify a polysaccharide fraction from Glycyrrhiza inflate

in order to analyze its basic chemical structure and immune activity. Method: Crude polysaccharide was extracted by the water extracting-alcohol precipitating method

and purified by DEAE cellulose-52 ion-exchange and Sepharose CL-6B gel column chromatography. Neutral homogeneous polysaccharide GiP-3 was purified from the water eluate fraction. HPGPC

IR

GC-MS and 1H-NMR were applied to analyze the basic chemical structure. 3-(4

5-dimethyl-2-thiazolyl)-2

5-diphenyl-2-H-tetrazolium bromide (MTT) assay was applied to evaluate the immune activity. Result: The molecular weight of GiP-3 was 2.1×104 Da. It was composed of arabinose

rhamnose and galactose

with the molar ratio of 1: 0.12: 18.The backbone of GiP-3 was mainly made up of 1

3-linked-α-Galp residues

and the side chains were composed of 1

5-linked-α-Araf residues and 1

2

4-linked-α-Rhap residues

and mainly linked at O-6 of α-Galp residue. The results of MTT assay showed that certain concentrations of GiP-3 could promote the proliferation of lymphocyte and RAW264.7 macrophage

with significant differences (P<0.05). Conclusion: GiP-3 is a homogeneous polysaccharide extracted from G. inflate

with an effect in enhancing immune responses.