Structure characterization and immunomodulatory activity of a new neutral polysaccharide SMP-0b from Solanum muricatum

Abstract In the present study, a novel neutral polysaccharide SMP-0b was extracted and purified from the pulp of Solanum muricatum. Monosaccharide composition analysis revealed that SMP-0b was mainly composed of l -arabinose, d -mannose, d -glucose and d -galactose with the molar ratio of 5.31:2.92:42.23:25.38. The weight-average molecular weight and number-average molecular weight of SMP-0b was calculated to be 13.51 kDa and 9.91 kDa respectively through high performance gel permeation chromatography. The structure of SMP-0b was characterized by methylation and NMR analysis. It showed that the backbone chain of SMP-0b was consisted of →4)-β- d -Galp-(1→, →3,6)-β- d -Manp-(1→ and →6)-α- d -Glcp-(1→, and the side chain was composed of α- l -Araf-(1→ and →4)-α- d -Glcp-(1→. In immunomodulation assays in vitro, SMP-0b exhibited good immunomodulatory activity and could significantly stimulate proliferation and NO production of RAW 264.7 macrophage cells. The results suggested that the neutral polysaccharide from Solanum muricatum might have potential as an immunomodulator or supplement in functional food to enhance immunity.