Purification, structural characterization, and immunoregulatory activity of a polysaccharide from mulberry branch

In view of the fact that mulberry branch has not been effectively utilized and polysaccharide is one of the main active components in mulberry branch, this study aims to reveal the structure and immunomodulatory activity of its polysaccharide. A type of neutral polysaccharides, named mulberry branch polysaccharide-2 (MBP-2), was separated from mulberry branch using DEAE-52 and Sephadex G-100. As analyzed, they were mainly composed of glucose with a molecular weight of approximately 21.7 kDa. Methylation analysis demonstrated that MBP-2 primary contained a → 4)-α-d-Glcp-(1 → , α-d-Glcp-(1 → and → 4, 6)-α-d-Glcp-(1 → structure, which was validated by nuclear magnetic resonance (NMR). In addition, cellular experiments indicated that MBP-2 significantly enhanced the production of NO, TNF-α and IL-6 in RAW264.7 cells, unraveling the potential immunoregulatory activity of MBP-2. Further analysis showed that MBP-2 exerted their immunoregulatory activity mainly via binding with TLR4 to activate the downstream TRIF-dependent signaling pathways.