Isolation, purification, structural characterization and immunostimulatory activity of water-soluble polysaccharides from Lepidium meyenii.

A water-soluble polysaccharide LMP-1 was isolated and purified by ion-exchange chromatography from maca (Lepidium meyenii Walp.). LMP-1 has a molecular weight of 1.01 × 104  Da, and is composed of glucose and arabinose with a molar ratio of 7.03:1.08. Methylation and the 1D and 2D NMR spectroscopy of LMP-1 revealed that it is mainly composed of →4)-α-D-Glcp-(1→, →6)-α-D-Glcp-(1→, →3)-α-D-Glcp-(1→, and β-D-Araf-(1→, with branching at O-6 of →4,6)-α-D-Glcp-(1 → . LMP-1 showed up-regulation of Toll-like receptor 4 (TLR4) and Toll-like receptor 2 (TLR2). The upstream proteins of Toll-like receptors (TLRs) (CD14 and MD2) and mRNA level of IL-1β also increased. Increased transcription factor nuclear factor-kappa B (NF-κB) p65 was found in the nuclei and cytoplasm in LMP-1-treated RAW264.7 macrophages. These results indicated that LMP-1 activated RAW264.7 macrophages and elicited immunostimulatory activities via the TLRs/NF-κB signalling pathway.