Mannose‐rich exopolysaccharide from Agaricus sinodeliciosus var. Chaidam: Purification, chemical characterization, and neuroprotective activity

Abstract

Amyloid β (Aβ) aggregation is a hallmark of Alzheimer's disease (AD). Searching for compounds that attenuate Aβ aggregation could uncover novel prevention for AD. Herein, an exopolysaccharide (EPS)‐2 was purified from the fermentation broth of Agaricus sinodeliciosus var. Chaidam. Morphology characterization, circular dichroism spectroscopy, and molecular docking demonstrated that EPS‐2 inhibited oligomer formation and remodeled the conformational conversion of Aβ1‐42, thus reducing the cytotoxicity and oxidative stress induced by Aβ1‐42 oligomers in vitro. Structural characterization revealed that the neuroprotective EPS‐2 with an average molecular weight of 18 kDa consisted of mannose, galactose, and a small proportion of rhamnose, glucose, fucose, ribose, glucuronic acid, and galactosamine. Glycosidic linkage and nuclear magnetic resonance analysis suggested that EPS‐2 has a backbone of →1)‐D‐Galp‐(6→, →1)‐D‐Manp‐(2, 6→, →1)‐D‐Galp‐(2→ and →1)‐t‐Manp with branched chains. Therefore, EPS‐2 was able to block Aβ1‐42 aggregation and reduced its neurotoxicity, and thus can be developed into a potential functional food ingredient for AD patients.