Structural characterization and immune enhancement activity of a novel polysaccharide from Moringa oleifera leaves

A novel polysaccharide, designated as MOP-3, was extracted and isolated from the leaves of Moringa oleifera. Structural characterization showed that MOP-3 had a molecular weight (MW) of 4.033 × 106 Da and was composed of arabinose, glucose and galactose with a molar ratio of 47.73:1.00:57.65. Methylation and nuclear magnetic resonance (NMR) analysis revealed that the main glycosidic linkage types of MOP-3 were (1→3,6)-β-D-Galp, (1→6)-β-D-Galp, (1→5)-α-L-Araf, and T-α-L-Araf. MOP-3 containing no lipopolysaccharides showed no direct cytotoxicity to the macrophage RAW 264.7 cells within the tested concentrations. The immunomodulatory assay suggested that MOP-3 could significantly enhance pinocytic capacity and increase the secretion of reactive oxygen species (ROS), nitric oxide (NO), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) by up-regulating the corresponding mRNA expression levels in RAW 264.7 cells. Our findings demonstrated that MOP-3 could potentially be used as a functional food for the hypoimmunity therapies.