Structural characterization and immunomodulatory activities of two polysaccharides from Rehmanniae Radix Praeparata

The structures and immunomodulatory activities of two polysaccharides (SDH-WA and SDH-0.2A) from Rehmanniae Radix Praeparata (RRP) were investigated. RRP crude polysaccharide was obtained by water extraction and purified. Ion chromatography, high-performance gel permeation chromatography, Fourier-transform infrared spectroscopy, methylation analysis, gas chromatography-mass spectrometry, and nuclear magnetic resonance were used to characterize the polysaccharides. The main chain of SDH-WA was -> 6)-alpha-D-Galp-(1 -> 6)-alpha-D-Galp-(1 -> 5)-alpha-L-Araf-(1 -> 3,5)-alpha-L-Araf-(1 ->, terminal sugar residue alpha-L-Araf-(1 -> linked to residue -> 3,5)-alpha-L-Araf-(1 -> on the main chain by an O-3 bond. The other two terminal sugar residues alpha-D-Galp-(1 -> and -> 6)-beta-D-Galp were linked to the end of the main chain. The main chain of SDH 0.2A was -> 2,4)alpha-L-Rhap-(1 -> 4)-alpha-D-GalpA-(1 ->. Three branched chains alpha-D-Galp-(1 -> 6)-alpha-D-Galp-(1-5)-alpha-L-Araf-(1 -> 3,5)-alpha-L-Araf-(1 -> 3,6)-beta-D-Galp-(1 ->, beta-D-Galp-(1-5)-alpha-L-Araf-(1 ->, and -> 4)-beta-D-Galp-(1 -> 5)-alpha-L-Araf (1 -> were linked to the main chain residue -> 2,4)-alpha-L-Rhap-(1 -> by an O-2 bond. Three terminal sugar residues alpha-D-Galp-(1 ->, alpha-L-Araf-(1 ->, and -> 6)-beta-D-Galp were linked to the end of the chain. Both polysaccharides showed no cytotoxic effects on and significantly promoted the phagocytic activity of RAW264.7 cells. They dose-dependently improved lysozyme activity and stimulated the production of TNF-alpha and IL-6 by RAW264.7 cells, but attenuated the secretion of lysozymes, TNF-alpha, IL-6, IL-1 beta, and nitric oxide by lipopolysaccharide-induced RAW264.7 cells. The present studies suggest that PRR polysaccharide is a valuable source with immunomodulating.

Automated summary

The structures and immunomodulatory activities of two polysaccharides from Rehmanniae Radix Praeparata were investigated. Both SDH-WA and SDH-0.2A showed no cytotoxic effects on RAW264.7 cells, but significantly promoted phagocytic activity and improved lysozyme activity. They also dose-dependently stimulated the production of TNF-alpha and IL-6, while attenuating the secretion of various immune factors by lipopolysaccharide-induced RAW264.7 cells.