Structural characterisation and immunomodulatory activity of a polysaccharide isolated from lotus (Nelumbo nucifera Gaertn.) root residues

摘要

An active water-soluble lotus root polysaccharide (LRP) with average molecular weight of 1.24 x 10(4) Da was purified from lotus (Nelumbo nucifera Gaertn.) root residues. The structure of LRP was determined to be alpha-D-(1 -> 4)-linked glucopyranosyl moieties with non-reducing terminal alpha-D-Glcp at O-6 as branches approximately every six residues. An immunological activity assay indicated that LRP significantly promoted the production of nitric oxide, interleukin-6, and tumour necrosis factor-alpha (TNF-alpha). LRP induced nuclear translocation of activator protein-1 and nuclear factor-kappa B. Intriguingly, LRP remarkably increased phosphorylation of upstream signalling molecules, including extracellular signal-regulated kinase, c-Jun N-terminal protein kinase, I kappa B alpha, Akt, and p85. Moreover, LRP promoted the secretion of TNF-alpha and interleukin-2 in cyclophosphamide-induced immunosuppressive mice. Collectively, these results suggest that LRP can improve immunity by enhancing immune function both in vitro and in vivo and this substance might be explored as an immunomodulatory agent for use in dietary supplements.