Abstract: In order to isolate and purify Arenaria kansuensis polysaccharide from natural Arenaria kansuensis,and study its molecular weight,monosaccharide component and immune activity,Arenaria kansuensis crude polysaccharide (AKCP) was extracted by water extraction and alcohol precipitation,and separated and purified into AKP-1-AKP-5 by DEAE cellulose 52 column.AKP-2 was further purified using Sephadex G-75 column and AKP-2a polysaccharide component was obtained.The total sugar content of AKCP,AKP-2 and AKP-2a was measured as 52%,70% and 79% respectively by phenol-sulfuric acid method.The GPC-MALS was applied to measure the molecular weight of AKP-2a.Results showed that the weight-average molecular weight (Mw) of AKP-2a was 2.07× 10⁵ Da,and the number-average molecular weight (Mn) was 9.838× 10⁴ Da.The 10 main monosaccharides in AKP-2a detected by HPLC are galacturonic acid,mannose,ribose,rhamnose,glucuronic acid,glucose,galactose,xylose,arabinose and fucose,the molar ratio of which was 1∶0.25∶0.01∶0.20∶0.11∶0.25∶0.61∶0.07∶0.21∶0.12 respectively.Compared with control group,the AKCP,AKP-2 and AKP-2a treatment groups with high,medium and low concentrations had a promoting effect on the proliferation of mice spleen lymphocytes by MTT in vitro (P<0.05).By NO release experiment and ELISA detection,AKP-2a showed a concentration dependent activation effect on mice peritoneal macrophages in vitro (P<0.01)． In conclusion,this study obtained AKP-2a polysaccharide through isolation and purification of Arenaria kansuensis,which has a high total sugar content.The multiple monosaccharides and the molecular weight of AKP-2a were identified,and the preliminary results showed that AKP-2a had the biological activities on lymphocyte proliferation andmacrophage function.

Key words: Arenaria kansuensis, polysaccharide, purification, immune activation