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)-α-D-Gal p -(1→6)-α-D-Gal p -(1→5)-α-L-Ara f -(1→3,5)-α-L-Ara f -(1→, terminal sugar residue α-L-Ara f -(1→ linked to residue →3,5)-α-L-Ara f -(1→ on the main chain by an O-3 bond. The other two terminal sugar residues α-D-Gal p -(1→ and →6)-β-D-Gal p were linked to the end of the main chain. The main chain of SDH-0.2A was →2,4)-α-L-Rha p -(1→4)-α-D-Gal p A-(1→. Three branched chains α-D-Gal p -(1→6)-α-D-Gal p -(1→5)-α-L-Ara f -(1→3,5)-α-L-Ara f -(1→, →3,6)-β-D-Gal p -(1→5)-α-L-Ara f -(1→, and →4)-β-D-Gal p -(1→5)-α-L-Ara f -(1→ were linked to the main chain residue →2,4)-α-L-Rha p -(1→ by an O-2 bond. Three terminal sugar residues α-D-Gal p -(1→, α-L-Ara f -(1→, and →6)-β-D-Gal p 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-α and IL-6 by RAW264.7 cells, but attenuated the secretion of lysozymes, TNF-α, IL-6, IL-1β, and nitric oxide by lipopolysaccharide-induced RAW264.7 cells. The present studies suggest that PRR polysaccharide is a valuable source with immunomodulating. • Two polysaccharides (SDH-WA, SDH-0.2A) were purified from Rehmanniae Radix Praeparata. • Structures of SDH-WA and SDH-0.2A were characterized. • Immunomodulating activities of SDH-WA and SDH-0.2A in RAW264.7 cells were studied. [ABSTRACT FROM AUTHOR]