Structural characterization and preliminary functional evaluation of a novel Polysaccharide NS0-1 from Nostoc sphaeroides Kütz

Nostoc sphaeroides polysaccharides exhibit diverse bioactivities, but the link between their structural features and functional properties remains underexplored. In this study, a novel heteropolysaccharide, NS0-1, was extracted and purified from Nostoc sphaeroides Kütz., and characterized using FT-IR, AFM, GC-MS, HPLC, and NMR. The backbone consists of (1 → 4)-β-D-Glcp, (1 → 4)-α-D-Manp, and (1 → 4)-β-D-Xylp, with branches containing α-D-GlcUA, α-D-Galp, and (1 → 3,5)-β-D-Galf. Rare structural features such as O-2 acetylated mannose and galactofuranose were identified. NS0-1 showed moderate α-amylase inhibitory activity (36.11 % at 1 mg/mL), along with shear-thickening and weak gel-like rheological behavior. Molecular docking and 50 ns molecular dynamics simulations revealed stable binding with α-amylase through multiple hydrogen bonds, suggesting a structure-based inhibitory mechanism. These results highlight the importance of acetylation and branching in determining bioactivity and physicochemical properties. NS0-1 holds promise as a multifunctional ingredient in functional foods, particularly for glycemic control and texture modification. Further kinetic and in vivo studies are needed to confirm its therapeutic relevance.