Characterization of Pectins Isolated from Mongolian Plants

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Abstract
Pectic polysaccharides (HP, RP) were extracted from Mongolia hawthorn berries and from rhubarb stalks by hot aqueous oxalic acid treatment. Both polysaccharides contained approximately 78% of galacturonate. HP displayed a low degree of esterification (DE) and arabinose/galactose molar ratio 1.7:1. RP was higher in DE and contained these sugars in a molar ratio 0.5:1. Rhamnose, fucose, xylose, glucose, mannose, 2-O-methylxylose, and 2-O-methylfucose were found in lower amounts. Results from 13C NMR spectroscopy and methylation analysis indicated the presence of branched arabinans, (1−>4)-and (1−>3,6)-linked galactans and hemicelluloses of the xylan and glucan types. The pectins differed in theirmolecular properties. HP exhibited a low molecular weight (M W = 45,000), whereas RP had a broad M W-distribution with M W= 360,000. Independently of these differences, the binding capacity of both pectins towards divalent cations was influenced by the DE only and increased in the order: Ca2+ < Cd2+ < Pb2+ < Cu2+.