CHARACTERIZATION OF PECTINS ISOLATED FROM MONGOLIAN PLANTS

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 C-13 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 their molecular properties. HP exhibited a low molecular weight (M(W)BAR = 45,000), whereas RP had a broad M(W)-distribution with M(W)BAR = 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+.