Comparison of Structure and Immune Activity of Dioscorea opposita Thunb. Polysaccharides Before and After Starch Removal
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Abstract:
The effect of starch removal treatment on molecular weight, monosaccharide composition, functional groups, and in vitro immune activity of Dioscorea opposita Thunb. polysaccharides (DOP) were investigated. The polysaccharides were extracted by aqueous alcoholic precipitation. Specifically, the aqueous extract was directly precipitated with alcohol to obtain Dioscorea opposita Thunb. starch-containing polysaccharides (WDRP), and alcohol precipitated after α-amylase treatment to obtain Dioscorea opposita Thunb. non-starch polysaccharides (CDRP). This experiment combined chromatography and spectroscopy to compare the structural information of the polysaccharides before and after starch removal. The molecular of WDRP has one more 1590 kDa weight peak for starch than CDRP. WDRP and CDRP have the same monosaccharides, yet there are notable differences in the molar percentage of specific monosaccharides. The relative amount of glucose in WDRP was about 20.93% lower than in CDRP, while the percentage of other monosaccharides was greater than in CDRP. In the cell assay, the cell viability of WDRP was found to be up to 188.50% compared to 166.69% in the CDRP group, and the phagocytosis rate was significantly higher in the WDRP group than CDRP group. Further studies revealed that WDRP and CDRP play an immunomodulatory role by activating the p38 MAPK/NF-κB pathway to regulate the secretion of NO, TNF-α, IL-6 and IL-1β. In addition, the p38 MAPK and NF-κB protein expression levels were higher in WDRP than in CDRP, suggesting that WDRP was better than CDRP in vitro immune activity. The results of this paper indicate that yam except starch leads to differences in the structure of polysaccharides, which in turn leads to somewhat different activities. It suggested that amylase may disrupt the deconstruction of non-starch polysaccharides leading to reduced activity. The result provided a reference for the subsequent studies on the isolation and purification of DOP.
