Isolation and Purification of Water-Soluble Polysaccharide from Taro and Its Effect on Immune Activity of Macrophages

In order to explore the immune activity of water-soluble polysaccharide of taro,DEAE-52 cellulose anion exchange column chromatography was used to isolate and purify the water-soluble crude polysaccharide of taro,which extracted by water-extracted and alcohol-immersed method. Then,Sephadex G-200 gel column chromatography,SDS-polyacrylamide gel electrophoresis and Fourier infrared spectroscopy were used to analyze its composition. Next,CCK-8 reagent method,neutral red phagocytosis experiment,Griess method and enzyme-linked immunosorption method were used to determine its effect on the proliferation activity,phagocytosis ability and secretion of NO and cytokines in macrophages RAW264.7. Results showed that two kinds of taro water-soluble polysaccharides(TPS₁ and TPS₂)with purity of 87.4% and 81.5% were obtained. The main components of TPS₁ were neutral polysaccharide containing mannose and TPS₂ were β-pyranic acid polysaccharide containing sulfate group. Cell experiments showed that TPS₁ and TPS₂ had no toxic effect on RAW264.7 in the concentration range of 25~400 μg/mL.Among them,TPS₁ could significantly improve the phagocytosis of the cells(P<0.05),and the phagocytosis index was up to 2.07 times that of the blank control group. TPS₂,on the other hand,played a stronger role in promoting the secretion of NO and cytokines. The secretion of NO under the action of TPS₁ and TPS₂ was 3.07 and 4.57 times that of control group.The secretion of TNF-α was 3.04 and 3.76 times that of control group.The secretion of IL-1β was 1.37 and 1.54 times that of control group.The above results indicate that both TPS₁ and TPS₂ have immunomodulatory functions and are expected to be further developed and added to food as immunomodulators.