A Novel Polysaccharide Purified from Tricholoma matsutake: Structural Characterization and In Vitro Immunological Activity

<i>Tricholoma matsutake</i>, as a rare wild edible mushroom, is popular due to its unique flavor and taste, as well as high nutritional and economic value. Investigating the relationship between the complex structure and in vitro immunological activity of TMP-2a, a novel polysaccharide isolated from <i>T. matsutake</i>, was the aim of this study. The results showed that TMP-2a consisted of six monosaccharides, fucose, glucosamine hydrochloride, galactose, glucose, mannose, and glucuronic acid, with molar ratios of 8.8:0.6:23.4:48.1:15.1:4.0 and a molecular weight of 27,749 Da. Furthermore, TMP-2a was mainly composed of →6)-β-Glc<i>p</i>-(1→ with →3)-β-D-Glc<i>p</i>-(1→ forming the main chain, with a small amount of →2,6)-α-D-Man<i>p</i>-(1→ and →6)-α-D-Gal<i>p</i>-(1→ structural units attached, and the branched chain was mainly composed of β-Glc<i>p</i>-(1→ or a small amount of α-L-Fuc<i>p</i>-(1→ as a telosaccharide attached at the O-6 position of →3,6)-β-D-Glc<i>p</i>-(1→. TMP-2a enhanced the proliferation and phagocytic activity of mouse macrophage RAW264.7, as well as the secretion of NO and cytokines (TNF-α, IL-6, IL-1β) to a considerable degree, maybe attributable to its glucan structure and the elevated presence of (1→3)-β-D-Glc<i>p</i> glycosidic bonds. This study establishes a basis for the structural identification and comprehensive investigation of the functional activities of <i>T. matsutake</i> polysaccharides while also offering a theoretical framework for the creation of <i>T. matsutake</i>-related food products.