Structural Characterization, and Antioxidant, Hypoglycemic and Immunomodulatory Activity of Exopolysaccharide from Sanghuangporus sanghuang JM-1

Sanghuang as a medicinal fungus in China has a history of more than 2000 years, and is known as the “forest gold”. Most notably, the polysaccharides of Sanghuangporus sp. have attracted widespread attention due to their significant bioactivity in recent years. At present, extensive studies are being carried out on the extraction methods, structural characterization, and activity evaluation of polysaccharides. Here, we aimed to evaluate the structure and bioactivity of LEPS-1, an exopolysaccharide derived from the S. sanghuang JM-1 strain. The structure was elucidated by chromatography/spectral methods and hydrolyzation, and the solubility, the antioxidant activity, hypoglycemic activity and immunomodulatory activity were investigated. Results showed that LEPS-1 contained a →2)-α-Manp(1→6)-α-Galp(1→[2)-α-Manp(1→]n→2,6)-α-Manp(1→6,2)-α-Manp(1→3)-α-Manp(1→ backbone substituted at the O-6 and O-2 positions with side chains. These two branching fragments were β-Manp(1→. The molecular weight of LEPS-1 is 36.131 kDa. The results of biological activity analysis suggested that LEPS-1 was easily soluble in water, with reducing capability and DPPH radical scavenging capability. Furthermore, the IC50 values of LEPS-1 against α-amylase and α-glucosidase were 0.96 mg/mL and 1.92 mg/mL. LEPS-1 stimulated RAW264.7 cells to release NO, TNF-α and IL-6 with no cytotoxicity, showing potent potential for immunomodulatory activity. These findings describe a potential natural exopolysaccharide with medicinal value and a basis for the development of S. sanghuang exopolysaccharides.