Preparation, structural elucidation and immunomodulatory activity of a polysaccharide from Millettia Speciosa Champ

Millettia Speciosa Champ (M. speciose) is an important medicinal plant applied for multiple disease treatments, however, the polysaccharide composition in M. speciose is rarely investigated. In this study, the structural features and immunomodulatory activities of a polysaccharide (MSCP1) from M. speciose were studied. Results suggested that MSCP1, with a molecular weight of 9.36 × 103 g/mol, consisted of glucose and xylose at a molar ratio of 1.31: 0.01. The glycosidic bond types and linkage manners were successfully elucidated by methylation and multi-dimensional nuclear magnetic resonance spectroscopy. The backbones of MSCP1 were composed of 1,4-linked-α-D-Glcp, 1,4-linked-α-D-Xylp and 1,4,6-linked-β-D-Glcp. The branch chain T-linked-α-D-Glcp was confirmed to be attached at C-6 of 1,4,6-linked-β-D-Glcp. An in vitro cell assay demonstrated that MSCP1 could prominently enhance the pinocytic activity and up-regulate the release of nitric oxide (NO) and cytokines in RAW 264.7 macrophages, implying a potent immunomodulatory activity. Overall, MSCP1 exhibits characteristics that qualify it as a promising candidate for immunologic adjuvant.