Structural characterization and in vitro hypolipidemic and hypoglycemic activities of a novel neutral polysaccharide from Siraitia grosvenorii (Luo Han Guo) flowers

Abstract Siraitia grosvenorii, commonly known as Luo Han Guo, is a medicinal and edible plant whose flowers contain bioactive polysaccharides with underexplored therapeutic potential. This study isolated a novel polysaccharide fraction (SGFP-2) from Siraitia grosvenorii flowers through DEAE-Crystarose Fast Flow chromatography. Structural analysis revealed SGFP-2 is a heteropolysaccharide with average molecular weight of 1.67 × 10 5 Da and composed of Rha, Glc, Gal, GlcA, GalA, Man, and Ara with a molar ratio of 8.17:1.54:60.06:3.41:5.37:3.54:15.44. Methylation analysis identified dominant glycosidic linkages of SGFP-2 as → 6)-Gal p -(1 → (30.42%), Gal p -(1 → (22.69%), Ara f -(1 → (18.29%), Rha p -(1 → (8.70%), → 3,6)-Gal p -(1 → (8.54%). Scanning electron microscopy and Congo red staining results showed that the network structure of SGFP-2 was lamellar without trihelix conformation. In vitro experiments have revealed that SGFP-2 possesses lipid-binding capacity, bile salt adsorption properties, and potent inhibitory activity against crucial enzymes involved in glucose-lipid metabolism, specifically pancreatic lipase, cholesterol esterase, α-amylase, and α-glucosidase. These findings suggest that SGFP-2 demonstrates potential hypolipidemic and hypoglycemic effects in vitro. This study provides preliminary evidence to support further development and utilization of Siraitia grosvenorii flower polysaccharides. Graphical Abstract