Structural Characterization of Blueberry Fruit Polysaccharides and Assessment of its Hypolipidemic and Immunological Activity

In this study, polysaccharides were extracted from blueberry fruit (BFP) and isolated to three components (BFP-1, BFP-2 and BFP-3). The molecular weight, monosaccharide composition, characteristic groups, microscopic morphology, and triple helical conformation of the polysaccharides were characterized using HPGPC, HPLC, GC-MS, FT-IR, SEM and Congo red staining. Moreover, the hypolipidemic and immunological activities of the polysaccharides were also assessed. Results showed that the molecular weights of polysaccharides BFP-1, BFP-2, and BFP-3 were 5.547 ´ 10⁴, 5.671 ´ 10⁴, and 3.951 ´ 10⁴Da, respectively, the main monosaccharides were Glc, Gal and Ara,but BFP-3 was mainly composed of GalA, Glc, Gal, and Ara. The backbone of BFP-1 was →4)-Glcp-(1→, which branches to Ara and Xyl residues, while the backbone of BFP-2 was →5)-Araf-(1→, which branches to Xyl, Glu, Rha and Gal residues, in particularly, BFP-3 has a more complex branching with a →3,6)-Galp-(1→) backbone, The side chain is dominated by Araf-(1→). Blueberry polysaccharides are pyran-type polysaccharides with α-glycosidic bonds, and BFP-1 has a typical triple-helical structure. The activity assay revealed that the binding of BFP-3 to sodium glycylcholate hydrate and sodium taurocholate was 79.95% and 78.5%, respectively, indicating that it had better hypolipidemic activity than the others. Immunoactivity assay showed that BFP promoted NO secretion through activating the NF-κB signalling pathway in RAW264.7 cells, which played a role in enhancing the immune function of the organism. These findings may provide a reference for the development and application of blueberry polysaccharides in functional food and medicine.