Abstract:In this study the polysaccharides from salt-processed Morinda officinalis SMP was extracted by water extraction and ethanol precipitation, and then purified sequentially by DEAE-52 cellulose and Sephadex-G100 columns, to yield a purified polysaccharide (named SMP-4). Fourier transform infrared spectroscopy, high performance gel permeation chromatography, gas chromatography and nuclear magnetic resonance were employed to characterize the structural properties of SMP-4, and its immunomodulatory activities were examined in Macrophage RAW264.7 through determining its cell proliferation activity and levels of secreted cytokines. The polysaccharide structure analysis showed that SMP-4 consisted of arabinose, galactose, rhamnose, ribose, xylose, glucose and mannose in the molar ratio of 0.55:0.23:0.16:0.03:0.02:0.01:0.01, and had a molecular weight of 1.32×105 u. SMP-4 had six kinds of glycosidic bonds, with →3)-D-linked-Araf-(1→ accounting for the highest proportion (58.35%). The immunological activity analyses showed that the proliferation of RAW264.7 cells was not affected in the concentration range of 15.625~500.000 μg/mL as compared with the control group, whilst the secretions of tumour necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) were significantly promoted. At a SMP-4 concentration of 500 μg/mL, the amount of TNF-α secreted by RAW264.7 cells reached the highest level (2 100.00 pg/mL) (P<0.001); At a SMP-4 concentration of 31.25 μg/mL, RAW264.7 cells secreted the highest amount of IL-1β (14.50 pg/mL) (P<0.05). In conclusion, SMP-4 exhibited a good immune activity and has the potential to be a natural immunomodulator.
