Extraction, structural characterization, and immunobiological activity of ABP Ia polysaccharide from Agaricus bisporus

The extraction, purification, immunobiological activities, and structure of Agaricus bisporus polysaccharides (ABP) were investigated. Especially we purified and identified the polysaccharides with the highest in vitro immunobiological activity. The extraction conditions of ABP were optimized using single factor and orthogonal experiment. ABP Ia was screened after double purification with DEAE-52 and Sephadex G-200 and showed the best immunoregulatory activity. UV spectra analysis and high-performance gel permeation chromatography results indicated that the ABP Ia fraction did not contain any proteins or nucleotides and was a homogeneous polysaccharide with a relative molecular weight of 784 kDa. Gas chromatography mass spectroscopy results showed that ABP Ia was a heteropolysaccharide consisting of ribose, rhamnose, arabinose, xylose, mannose, glucose, and galactose at a molar ratio of 2.08:4.61:2.45:22.25:36.45:89.22:1.55. FT-IR and periodic acid oxidation analysis indicated that ABP Ia was an α-pyran polysaccharide composed of 1 → 2 and 1 → 4 glycosidic bonds, as well as a possible 1 → 3 glycosidic bond. Furthermore, atomic force microscopy revealed that ABP Ia polysaccharide chains twisted to form a rod-like architecture and, at a 5% concentration, aggregated into a tight structure similar to the shape of a stone forest. These findings identify ABP Ia as a potential functional food ingredient or pharmaceutical for immunoregulation.