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Structural characterization of rhamnogalacturonan domains from Panax ginseng C. A. Meyer

Sun, Lin, Ropartz, David, Cui, Liangnan, Shi, Huimin, Ralet, Marie-Christine, Zhou, Yifa
Carbohydrate polymers 2019 v.203 pp. 119-127
Panax ginseng, acid hydrolysis, anion exchange, antibody detection, arabinans, arabinogalactans, galacturonic acid, gel chromatography, glycosidic linkages, mass spectrometry, methyl ethers, moieties, monoclonal antibodies, oligosaccharides, pectins, polygalacturonase, saponification, structure-activity relationships
Rhamnogalacturonan I (RG-I) and rhamnogalacturonan II (RG-II) domains were isolated from ginseng pectin by alkali saponification and endo-polygalacturonase hydrolysis, then purified by anion-exchange and size-exclusion chromatography. Monoclonal antibody detection indicated that ginseng RG-I contained →4)-α-GalpA-(1→2)-α-Rhap-(1→ repeating units as backbone, with arabinan, galactan and type II arabinogalactan (AG-II) as side chains. The use of galactose- and arabinose-releasing enzymes, mass spectrometry analysis of the oligosaccharides generated by rhamnogalacturonan hydrolase, and glycosidic linkage analyses provided evidence that ginseng RG-I contains both single galactose-branched subunits and highly branched subunits with arabinan and AG-II side chains. RG-II was analyzed by sequential acid hydrolysis followed by mass spectrometry. Ginseng RG-II contains 9 galacturonic acid units as backbone. Side chain A is an octasaccharide with 0 ∼ 1 methyl ether group. Side chain B is a nonasaccharide with 0 ∼ 1 acetyl group. These results provide useful information for further investigation of structure-activity relationship of ginseng pectin.