Abstract: The polysaccharide was extracted and purified from Gynura procumbens stem,further analysed its monosaccharide composition and tested its antioxidant and immunomodulatory activities,this research would provide comprehensive utilization basis for this natural resource.The crude polysaccharide from Gynura procumbens stem(GPSCP) was obtained by water extraction and alcohol precipitation method.The extraction yield,uronic acid content,sulfate content,and protein content were investigated of GPSCP.The polysaccharide from Gynura procumbens stem(GPSP) by the sevage reagent and dialysis method.The monosaccharide compositions was analyzed by Gas Chromatography Spectrometer (GC) method.And IR spectra of taxus polysaccharide were determined,too.The in vitro antioxidant capacity of GPSP was evaluated by the total antioxidant activity,DPPH and OH free radicals scavenging assay,and its immunomodulatory activities on Macrophage RAW264.7.of GPSP were investigated.The results have showed that the contend of GPSCP was 52.32±1.56 g/100 g with the yield of 15.56%,and the contend of GPSP was 78.54±2.13 g/100 g with the yield of 8.67%.The GPSP mainly composed of rhamnose,arabinose,xylose,mannose,glucose,galactose with an average molar ratio of 1.69∶4.64∶9.17∶1.00∶1.92∶4.85,respectively.The result of antioxidant tests in vitro showed that the scavenging effects on total antioxidant capacity,DPPH and OH free radicals were obvious.The results indicated that GPSP significantly promoted the production of intracellular nitric oxide (NO).When the dosage of GPSP was 500 μg/mL,the secretion of NO could reach to the maximum values of 39.28±3.25 μM,indicating that GPLP can improve immunity,and could be explored as a potential immunomodulatory agent in functional food.

Key words: Gynura procumbens stem, polysaccharides, gas chromatography(GC), monosaccharide compositions, free radical scavenging activity, immunomodulatory activity