Structural characterization of three polysaccharides from the roots of Codonopsis pilosula and their immunomodulatory effects on RAW264.7 macrophages

摘要

Three polysaccharides were isolated from the roots of Codonopsis pilosula by ion-exchange and gel-filtration chromatography. They were named RCNP, RCAP-1, and RCAP-2, and had apparent molecular weights of 1.14X10(4), 5.09X10(4), and 2.58X10(5), respectively. Their structures were characterized by HPGPC, chemical derivative analysis, GC-MS and NMR analyses. Results showed that RCNP contained arabinan and arabinogalactan regions. The arabinan region had a main chain comprising (1 -> 5)-linked Araf residues, and the side chains branched at the O-3 position by the single Araf residues. The arabinogalactan region comprised alternating (1 -> 4)-, (1 -> 6)- or (1 -> 3)-linked Galp along with small amounts of branches mainly at the O-3 position of the (1 -> 6)-linked Galp or O-6 position of the (1 -> 3)-linked Galp residues by terminally linked Araf residues. RCAP-1 and RCAP-2 were highly methyl-esterified pectin-type polysaccharides with long homogalacturonan regions interrupted by a short rhamnogalacturonan I (RG-I) region. The side chains of the RG-I region consisted of (1 -> 2)-linked Rha residues attached to the position O-4 of rhamnose. Their degrees of methyl-esterification were approximately 60.6% and 68.1%, respectively. Bioactivity tests showed that RCAP-1 and RCAP-2 exerted a significant immunostimulatory effect based on NO production from RAW264.7 macrophages. These results suggested that these two pectin-type polysaccharides were potential immunostimulation agents. Copyright (C) 2019 Elsevier B.V. All rights reserved.