Characterization of a novel polysaccharide from the leaves of Moringa oleifera and its immunostimulatory activity

Abstract

A novel polysaccharide (MOP-2) was extracted and purified from the leaves of Moringa oleifera by hot water extraction and chromatographic purification. Structural characterization revealed that MOP-2 had an average molecular weight of 155.35 kDa and consisted of arabinose, glucose and galactose with molar percentages of 35.8, 6.67, and 57.53%, respectively. The backbone chain of MOP-2 was proven to be →3,6)-β-D-Galp(1→ and →6)-β-D-Galp-(1→, and the side chains contained →5)-α-L-Araf-(1→, α-L-Araf-(1→, and α-D-Glcp-(1→. In vitro immunomodulatory assay revealed that MOP-2 could significantly enhance the proliferation and pinocytic capacity of the RAW264.7 macrophage cells. Furthermore, MOP-2 promoted the secretion of reactive oxygen species (ROS), nitric oxide (NO), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) by activating mRNA expressions of iNOS, IL-6 and TNF-α. These findings suggest that MOP-2 can be developed as a novel natural immunoregulatory agent in functional foods.