The structure and characteristics of LEOPs, β-oligosaccharides from the fruiting body of Lentinus edodes obtained via acid degradation and gel permeation chromatography, were investigated. We performed high-performance liquid chromatography, infrared spectroscopy, methylation analysis, nuclear magnetic resonance, and correlated activity experiments, including antioxidant, immunomodulatory, and liver injury protection to gain insights. LEOPs comprised an oligosaccharide (Mw 2445 Da) based on six β-1, 3-D-glucose residues as the main chain and six β-1, 6-D-glucose residues as the side chain. Surface plasmon resonance analysis indicated that LEOPs directly bound to dectin-1, which facilitated their immunoenhancing activity via downstream NF-κB activation. The results implied that LEOPs may be the active unit of the shiitake β-glucan. The determination of LEOPs structure was performed to reveal the anti-tumor effect and immune-regulatory function of shiitake β-glucan on a molecular level to provide a basis.
