Heterogeneity and characterisation of mitogenic and anti-complementary pectic polysaccharides from the roots of Glycyrrhiza uralensis Fisch et D.C

Two anti-complementary polysaccharide fractions (GR-2IIa and GR-2IIb), isolated from the roots of Glycyrrhiza uralensis Fisch et D.C., each gave five anti-complementary polysaccharides (GR-2IIa-1–5 and GR-2IIb-1–5) on h.p.l.c; likewise, GR-2IIc gave two anti-complementary and mitogenic polysaccharides (GR-2IIc-1–2A and -2IIc-2) by gel filtration and h.p.l.c. GR-2IIc-1–2A showed the most potent anti-complementary activity. GR-2IIa-1–5 and GR-2IIb-1–5 contained 40–85% and 50–90% of GalA, respectively, in addition to Rha, Ara, and Gal. GR-2IIc-1–2A and -2IIc-2 mainly comprised Glc, Gal, GalA, and GlcA in addition to Rha, Fuc, Xyl, Ara, and Man. Methylation analysis and digestion with endo-α-(1→4)-polygalacturonase indicated that all of the polysaccharides contained polygalacturonan regions which were frequently methyl-esterified. GR-2II-a, -2IIb, and -2IIc gave enzyme-resistant fractions of large and intermediate sizes, in addition to oligogalacturonides. Each large fraction from GR-2IIa and -2IIb consistent mainly of Ara, Gal, and GalA, whereas the intermediate fractions were composed of small proportions of 2-Me-Fuc, 2-Me-Xyl, and apiose (Api), in addition to Rha, Ara, Gal, and GalA. The large fraction from GR-2IIc mainly contained Rha, Man, Gal, and GalA in addition to Fuc, Ara, Xyl, and Glc, whereas the intermediate fraction consisted of 2-Me-Fuc, 2-Me-Xyl, and Api, in addition to Rha, Ara, GalA, Fuc, Xyl, Man, Gal, and Glc. Base-catalysed β-elimination followed by ethylation indicated that all the polysaccharides except GR-2IIc-2 contained a 4-linked uronic acid attached to position 2 of 2,4-linked Rha. Single radical gel diffusion, using the β- d-glucosyl-Yariv antigen, indicated that GR-2IIa-1 and GR-2IIc-2 contained relatively large proportions of (1→3,6)-β- d-galactan moieties. The anti-complementary activities of GR-2IIa-3, GR-2IIa-4, and GR-2IIb-4 decreased after de-esterification followed by digestion with endo-α-(1→4)-polygalacturonase. The large fractions from GR-2IIa-2IIc showed more potent anti-complementary activities than the original polysaccharide fractions, whereas the intermediate fractions and oligogalacturonides were inactive. The large fraction from GR-2IIc had more potent mitogenic activity than GR-2IIc, whereas the intermediate fraction and oligogalacturonides from GR-2IIc were inactive.