Structural characterization of a bioactive water-soluble heteropolysaccharide from Nostoc sphaeroids kütz.

A water soluble Nostoc sphaeroids kütz polysaccharide (NSKP) was extracted and purified by precipitating hot-water extract from Nostoc sphaeroids kütz with 40% (v/v) ethanol. The yield was 40.10% (w/w), and weight average molecular weight (Mw) was determined as 1.31 × 105 g/mol. Cell culture study showed that NSKP could stimulate the NO release from RAW264.7 macrophages. The ρ value (Rg/Rh) of NSKP was calculated as 1.50, indicating flexible random coils conformation of NSKP in aqueous solution. According to methylation analysis, and 1D & 2D NMR spectra, the molecular structure of polysaccharide NSKP was deduced as below.