Physicochemical Characterization and Bioactivities of Polysaccharides From Siraitia grosvenorii : Effects of Different Extraction Methods

ABSTRACT Five Siraitia grosvenorii polysaccharides (SGPs), namely, SGP‐H, SGP‐A, SGP‐B, SGP‐E, and SGP‐U, were extracted from hot air‐dried fruits using hot water extraction (HWE), acid‐assisted extraction (ACAE), alkaline‐assisted extraction (ALAE), enzyme‐assisted extraction (EAE), and ultrasonic‐assisted extraction (UAE), respectively. The extraction yields of ACAE and ALAE were 1.65‐ and 1.59‐fold higher than that of traditional HWE, respectively. Monosaccharide composition analysis showed that SGP‐H, SGP‐A, SGP‐E, and SGP‐U were acidic heteropolysaccharides composed of mannose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, and arabinose with a notable discrepancy in the molar ratio, whereas SGP‐B exhibited the lowest uronic acid content and a unique monosaccharide profile dominated by glucose (76.62%). Comprehensive characterization confirmed significant differences in molecular weight, glycosidic linkage, and surface morphology among the five SGPs. Antioxidant assays indicated that SGP‐B exhibited the stronger ABTS and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) scavenging activity than the other SGPs, with EC 50 values of 416 ± 5.4 and 338 ± 14.8 µg/mL, respectively. Meanwhile, immunomodulatory studies on RAW264.7 macrophages revealed that SGP‐B significantly enhanced phagocytosis by 29% and stimulated the secretion of immune factors. Therefore, SGP‐B, obtained via ALAE, shows great application potential in the development of antioxidants and immunomodulators, and further research deserves attention.