A novel polysaccharide from Pholiota nameko (T. Itô) S. Ito & S. Imai residue: chemical structure and hypoglycaemic activity in vitro

A novel polysaccharide (APNP) with a molecular weight of 3.56 × 10³ KDa and a total sugar content of 92.35 ± 0.07% was isolated from Pholiota nameko (T. Itô) S. Ito & S. Imai residue using alkaline extraction. Monosaccharide composition analysis revealed that APNP consisted of galactose, glucose, and mannose. FT-IR and NMR analysis results indicate that APNP form linkages between (1→3), (1→6), and (1→3,6)-β-D-glucose, (1→)-α-D-glucose, (1→)-α-D-galactose, and (1→3,6)-β-D-mannose. Thermogravimetric analysis revealed three distinct pyrolysis phases in APNP. Congo Red assay results indicated the absence of triple-helical conformation in APNP under weakly alkaline conditions. In vitro assays demonstrated α-glucosidase inhibitory activity of APNP, with an IC₅₀ value of 0.165 mg/mL. HepG2-IR insulin resistance model and Western blot analyses demonstrated APNP's ability to ameliorate insulin resistance and enhance glucose metabolism.