Structure and hypoglycemic activity of a novel exopolysaccharide of Cordyceps militaris.

A novel neutral exopolysaccharide (EPS-III) was isolated from culture broth of Cordyceps militaris (C. militaris). The EPS-III was a homogeneous polysaccharide with M w of 1.56 × 103 kDa. The yield of EPS-III from culture broth was 123.2 ± 3.1 mg/L and the sugar content was 93.32 ± 0.87%. The backbone of EPS-III was mainly consisted of →4)-α-D-Gal p -(1→, while →3, 6)-α-D-Man p -(1→, →4)-α-D-Man p -(1→, →3)-β-D-Gal p -(1→ and →3)-α-D-Glc p -(1→ were distributed in the backbone or in the branch chains. The EPS-III had helix structure when dissolved in weak alkaline solution. It also had branched and intertwined form on the surface. The inhibition of α-glucosidase significantly increased as the increase of purity of exopolysaccharides. The EPS-III had effective inhibition on the α-glucosidase with dose-effect relationship. Besides, the results of hypoglycemic activity analysis in vivo indicated that EPS-III can alleviate weight loss, reduce plasma glucose concentration, improve glucose tolerance, protect immune organs and repair dyslipidemia to relieve diabetes in STZ-induced diabetic mice. The manuscript first studied the hypoglycemic activity of exopolysaccharide of by C. militaris , proving and promoting the application value of culture broth. The structure characterization of EPS-III laid experimental foundations on the exploration of structure-activity relationship. • A novel exopolysaccharide (EPS-III) of Cordyceps militaris was isolated. • The yield of EPS-III from culture broth was 123.2 ± 3.1 mg/L. • The chemical structure of EPS-III was accurately characterized. • The EPS-III has effective inhibition on α-glucosidase. • The EPS-III can relieve diabetes in STZ-induced diabetic mice. [ABSTRACT FROM AUTHOR]