Fractionation and chemical properties of immunomodulating polysaccharides from roots of Dipsacus asperoides.

Abstract

A crude polysaccharide fraction (DAP-1) was prepared from roots of Dipsacus asperoides by hot water extraction and EtOH precipitation, and tested for anti-complementary activity, mitogenic activity of lymphocytes, and effects on acid phosphatase and phagocytic activities of macrophages. DAP-1 showed not only anti-complementary activity but also a stimulating effect on the mitogenic activity of lymphocytes. DAP-1 also significantly suppressed the phagocytic activity of macrophages. Although DAP-1 directly stimulated the mitogenecity of lymphocytes, it had no effect on lipopolysaccharide- or concanavalin A-induced mitogenic activity of lymphocytes. Periodate oxidation and pronase digestion suggested that the polysaccharide moiety in DAP-1 contributed to the expression of its anti-complementary and mitogenic activities and that the protein moiety in DAP-1 was responsible for its effect on phagocytosis. DAP-1 gave three polysaccharide fractions (DAP-2, 3, and 4) by fractionation using cetyltrimethylammonium bromide. All the fractions had potent anti-complementary activity, but showed different stimulating or suppressive effects on the proliferation of lymphocytes, phagocytosis, or acid phosphatase activity. Three potent anti-complementary polysaccharides (DAP-4I-1a, DAP-4I-1b, and DAP-4IIa-1) were purified from DAP-4 by anion-exchange chromatography, gel filtration, and HPLC. DAP-4I-1a, I-1b, and IIa-1 consisted of Ara, Rha, Xyl, Gal, Glc and GlcA in a molar ratio of 1.0:0.7:1.0:18.6:22.2:nil; 1.0:0.1:0.3:19.3:26.8:nil; and 3.7:trace:0.6:26.3:5.5:1.0; respectively. Among the polysaccharides, only DAP-4IIa-1 reacted with beta-glucosyl-Yariv antigen. Methylation analysis indicated that DAP-4I-1a mainly comprised 4-linked Gal and 3-, 4-, and 6-linked Glc, whereas DAP-4IIa-1 consisted mainly of terminal Araf, 3-linked Glc, and 3,6-branched Gal.