Structural characterization of arabinogalactan extracted from Ixeris chinensis (Thunb.) Nakai and its immunomodulatory effect on RAW264.7 macrophages

An arabinogalactan (ICPA) was isolated from the water extract of Ixeris chinensis (Thunb.) Nakai. ICPA was mainly composed of galactose and arabinose with minor amount of glucose. The molecular weight of ICPA was 58.1 kDa. Structural analysis by methylation and NMR spectroscopy indicated that ICPA contained alpha-D-Glcp(1 ->, -> 5)-alpha-L-Araf(1 ->, beta-D-Galf(1 ->, -> 3)-beta-D-Galf(1 ->, beta-D-Galp(1 ->, -> 6)-beta-D-Galp(1 ->, and -> 3,6)-beta-D-Galp(1 ->, and that the molar ratio of the sugar residues was about 0.1:1.0:0.1:0.2:1.1:1.0:1.3, respectively. The immunomodulatory activity on RAW264.7 cells was measured in vitro. ICPA stimulated RAW 264.7 cell proliferation at 25400 mu g/mL in a dose-dependent manner. ICPA also enhanced phagocytosis, and the secretion of NO, TNF-alpha, and IL-6 by the cells. The results suggested the potential utilization of ICPA as an immunomodulatory agent. (C) 2019 Elsevier B.V. All rights reserved.