Structural Characteristics, Antioxidant and Hypoglycemic Activities of Polysaccharide from Siraitia grosvenorii

The structural characterization, the in vitro antioxidant activity, and the hypoglycemic activity of a polysaccharide (SGP-1-1) isolated from Siraitia grosvenorii (SG) were studied in this paper. SGP-1-1, whose molecular weight is 19.037 kDa, consisted of Gal:Man:Glc in the molar ratio of 1:2.56:4.90. According to the results of methylation analysis, GC-MS, and NMR, HSQC was interpreted as a glucomannan with a backbone composed of 4)-beta-D-Glcp-(1 -> 4)-, alpha-D-Glcp-(1 -> 4)-, and 4)-Manp-(1 residues. alpha-1,6 linked an alpha-D-Galp branch, and alpha-1,6 linked an alpha-D-Glcp branch. The study indirectly showed that SGP-1-1 has good in vitro hypoglycemic and antioxidant activities and that these activities may be related to the fact that the SGP-1-1's monosaccharide composition (a higher proportion of Gal and Man) is the glycosidic-bond type (alpha- and beta-glycosidic bonds). SGP-1-1 could be used as a potential antioxidant and hypoglycemic candidate for functional and nutritional food applications.