A glucomannan from defatted Ganoderma lucidum spores: structural characterization and immunomodulatory activity via activating TLR4/ MyD88/NF-κB signaling pathway

Ganoderma lucidum spores are tiny mature germ cells ejected from the abaxial side of the pileus and were responsible for multiple pharmacological properties. The defatted G. lucidum spores are the byproducts after the extraction of G. lucidum spores oil by supercritical fluid extraction technology, which have not been given sufficient attention. In order to fully utilize the resources of G. lucidum spores, a glucomannan (SGL90-1, 6.4 kDa) was isolated from the defatted G. lucidum spores. SGL90-1 was composed of mannose, glucose, galactose, and fucose in a molar ratio of 23.9:28.7:9.0:1.0. The backbone of SGL90-1 was consisted of -> 2,4)-alpha-D-Man p-(1 ->, -> 6)-(3-D-Man p-(1 ->, -> 2,6)-alpha-D-Man p-(1 ->, -> 2)-alpha-D-Glc p-(1 ->, and -> 3,6)-(3-D-Glc p-(1 -> with seven side chains, and terminated with (3-D-Manp-(1 ->, (3-D-Glcp-(1 ->, alpha-L-Fucp-(1 ->, and (3-D-Galf-(1 ->. Moreover, SGL90-1 could significantly elevate the phagocytic capability of RAW264.7 macrophages and promote the levels of nitric oxide (NO), tumor necrosis factor-alpha (TNF-alpha), and interlrukin-6 (IL-6) through activating the TLR4/MyD88/NF-kappa B signaling pathway. Collectively, these findings demonstrated the potential of SGL90-1 as a natural functional food with strong immune-enhancing effect.