Abstract: The molecular properties and immunomodulatory activities of the polysaccharide were investigated in this study,which was extracted from Folium isatidis by the distilled water with the assistance of ultrasound-microwave.Firstly,the chemical compositions of the polysaccharide were analyzed,and its monosaccharide composition and glycosidic linkage were investigated by GC-MS after derivatization.The molecular weight assay was conducted using HPSEC-MALLS-RI system.Finally,the immunomodulatory activities of the polysaccharide were carried out using RAW264.7 cells.In conclusion,the optimal extraction parameters studied by the orthogonal experiment,were as follows,ratio of liquid to solid 25∶1 (V/m),temperature 90 ℃,distilled water extraction 70 min,ultrasound-microwave extraction time 50 min,microwave power 500 W,ultrasound power 50 W,with the yield of polysaccharide 10.49%.The polysaccharide contained 63.8% neutral sugar,13.1% protein,14.2% sulfate and 12.6% uronic acid.Its major monosaccharide units were galactose,arabinose,rhamnose and glucose.The M_w and Rg of the polysaccharide were 7.85×10⁵ u and 183.3 nm,respectively.The glycosidic linkage of polysaccharide was also investigated.According to the results of immunomodulatory activities,the polysaccharide can enhance the proliferation of RAW264.7 to produce NO.

Key words: Folium isatidis, polysaccharide, ultrasound-microwave, molecular properties, immunomodulatory activities