Characterisation of an anti-ulcer pectic polysaccharide from leaves of Panax ginseng C.A. Meyer

Structural characterisation of an anti-ulcer polysaccharide (GL-BIII), purified from leaves of Panax ginseng C.A. Meyer, was studied. Methylation analysis indicated that GL-BIII consisted mainly of terminal Arap, 4- or 5-substituted Ara, 2,4-disubstituted Rha, 4- and 6-substituted Gal, and 3,6-disubstituted Gal. Single radial gel diffusion using β-glucosyl-Yariv antigen indicated that GL-BIII contained a small proportion of a β-(1 → 3,6)-galactan moiety. GL-BIII also contained terminal, 4-substituted, and 3,4-disubstituted GalA, and terminal and 4-substituted GlcA. Base-catalysed β-elimination suggested that some 2-substituted Rha in GL-BIII was attached to position 4 of a 4-substituted uronic acid. Both mild acid hydrolysis and endo-α-(1 → 4)-polygalacturonase digestion of GL-BIII did not give fragments consisting mainly of GalA. Methylation analysis and GC-MS analysis of acidic oligosaccharides liberated by partial acid hydrolysis indicated that GL-BIII contained a GalA-(1 → 4)-Rha unit in addition to longer acidic units consisting of 2-substituted Rha and 4-substituted GalA. Lithium-mediated degradation of GL-BIII followed by borohydride reduction gave small amounts of fractions containing long and intermediate neutral oligosaccharide-alditols and a large amount of a fraction containing short oligosaccharide-alditols. The long neutral oligosaccharide-alditol fraction mainly comprised 4- or 5-substituted Ara, terminal Galf, 6-substituted Glc, and 2-substituted Man, whereas the intermediate oligosaccharide-alditol fraction consisted mainly of terminal and 6-substituted Galp, 6-substituted Glc, and 2-substituted Man. Methylation analysis and GC-MS analysis of the short oligosaccharide-alditol fraction suggested that it contained at least ???