Chain conformation and immunomodulatory activity of a hyperbranched polysaccharide from Cordyceps sinensis

•A hyperbranched heteropolysaccharide was isolated from natural Cordyceps sinensis.•Methylation analysis of polysaccharide was performed under microwave irradiation.•SEC-MALLS and SEC-TDA were applied for determination of hydrodynamic characterization of polysaccharide.•The chain conformation of polysaccharide from natural C. sinensis was firstly provided.

A polysaccharide, named as cordysinan, extracted from natural Cordyceps sinensis, was identified as a hyperbranched heteropolysaccharide from the results of FT-IR, GC–MS, and carbohydrate analysis by carbohydrate gel electrophoresis analysis, as well as the degree of branching of cordysinan was 43.3%. The solution properties of cordysinan were investigated by using size exclusion chromatography coupled with multi-angle laser light scattering and triple detector array, respectively. The molecular weights, the radius of gyration and the intrinsic viscosity of cordysinan were determined as 22.45 ± 0.26 kDa and 22.37 kDa, 15.4 ± 2.4 nm and 1.41 mL/g, respectively. By applying the polymer solution theory, the exponent (ν and α  ) values of S2z1/2=kMwν and [η]=kMwα were calculated as 0.28 and 0.42, respectively, which firstly revealed that cordysinan existed as a globular shape in 0.9% NaCl aqueous solution. Moreover, the results showed that cordysinan could obviously stimulate macrophages functions.