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A complex pectic polysaccharide, GL-5IIdl-B has been purified with interleukin-6 production enhancing activity from the leaves of Panax ginseng C.A. Meyer. By selective degradation using partial acid hydrolysis of GL-5IIdl-B, an intermediate size oligosaccharide fraction (dp=7 to 9), AH-2 was isolated and its structure was characterized. AH-2 consisted mainly of 2-methylfucose, rhamnose, arabinose, apiose, aceric acid and galactose. Negative-ion fast-atom bombardment mass spectrometry (FAB-MS), FAB-B/E linked scan MS and methylation analyses suggested that AH-2 fraction comprised branched oligosaccharide chains possessing a nonasaccharide unit, in which terminal rhamnose was additionally attached to position 3 of a 2-linked arabinopyranoside of octasaccharide chain observed in sycamore RG-Ⅱ. Also, the results of FAB-B/E scan provided evidence that the site of acetylation in this nonasaccharide was on 2-methylfucose residue.
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