Immunoenhancing glucuronoxylomannan from Tremella aurantialba Bandoni et Zang and its low-molecular-weight fractions by radical depolymerization: Properties, structures and effects on macrophages

In this study, a glucuronoxylomannan named TAP-3 was obtained from high-value Tremella aurantialba Bandoni et Zang. Physicochemical analysis revealed that TAP-3, which had a molecular weight of ∼624 kDa, mainly consisted of d -mannose (Man), d -xylose (Xyl), and d -glucuronic acid (GlcA) in a molar ratio of 3.0:1.0: 1.0. Structural analyses of its depolymerized fragments clarified that TAP-3 contained a (1 → 3) and (1 → 2)-linked α-Man p backbone, side chains formed by β-Xyl p and β-Glc p A linked to the C -2 position of α-Man p , and acetyl groups connected to the sixth hydroxyl positions of Man p . TAP-3 showed marked immune enhancement activity, promoting NO, IL-1β and TNF-α secretion from macrophages. The critical membrane receptor of TAP-3 was identified to be TLR4 , and the chain length was essential for its immunoregulatory activity. These findings expand knowledge of the structural types of glucuronoxylomannan and illustrate its biological activity as an immunopotentiator.