Structural characteristics and bioactivities of an exopolysaccharide from mycelial fermentation of a medicinal fungus Cs-HK1.

Cs-HK1 fungus is originated from the Chinese caterpillar fungus, Cordyceps (=Ophiocordyceps) sinensis, a valuable in Chinese Tibetan medicine. The exopolysaccharides (EPS) produced by Cs-HK1 mycelial fermentation have shown multiple bioactivities that are dependent on their structural characteristics. In this study, a neutral polysaccharide, EPS-LM-n was isolated from the lower molecular weight (MW) Cs-HK1 EPS and further purified through anion-exchange and gel permeation chromatography. EPS-LM-n had a weight-average MW of 417 kDa, a monosaccharide composition of Man:Glc:Gal 1:0.49:0.21 molar ratio, and a backbone structure of →2)-α-Manp-(1 → with branches →4)-α-Glcp-(1→, →3)-α-Galp-(1→. EPS-LM-n showed potential hypoglycemic activities by inhibiting α-amylase and α-glucosidase (IC50 values of 0.64 and 0.74 mg/mL, respectively) and significant antioxidant, and radical scavenging activities by several chemical assays. Furthermore, EPS-LM-n suppressed the ROS level and H2O2-induced cell damage and apoptosis in human vascular endothelial cell EA.hy926 culture. The results and findings collectively indicate that EPS-LM-n isolated from the Cs-HK1 EPS may serve as a potential candidate for dietary and therapeutic treatment of hyperglycemia and oxidative stress-induced metabolic and cardiovascular diseases.