Structural characterisation and immunomodulatory activity of a neutral polysaccharide from Sambucus adnata Wall

A neutral polysaccharide, SPW-2, was purified from the leaves of Sambucus adnata Wall. using water extraction and alcohol precipitation, Sevage deproteination, ion exchange chromatography and gel filtration chromatography. This molecule had an average molecular weight of 7040 Da and was composed of arabinose, xylose, mannose, glucose and galactose at a molar ratio of 1.5:0.5:1.2:5.0:1.8. The repetitive structural units of SPW-2 were deduced using methylation analysis and nuclear magnetic resonance (one- and two-dimensional) spectroscopy. In vitro immunological activity test showed that SPW-2 could induce the secretion of nitric oxide, interleukin-1β (IL-1β), IL-6 and tumour necrosis factor-alpha (TNF-α), and increase the mRNA expression level of inducible nitric oxide synthase (iNOS), IL-1β, IL-6 and TNF-α in macrophages. The data supported the notion that SPW-2 exerts an immunomodulatory effect by activating macrophages and enhancing the host immune system function, which enabled it to be used as a novel immunomodulator for application in the treatment of immunological diseases.