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.