Structural characteristics of water-soluble polysaccharides from Heracleum sosnowskyi Manden

Fractions containing arabinogalactan proteins (AGPs) and pectic polysaccharides were isolated from above-ground parts of Heracleum sosnowskyi. Major units of their structure were elucidated using ion-exchange chromatography, gel chromatography, and NMR spectroscopy. The carbohydrate backbone of the polysaccharides consisted of 1,3-β-D-galactopyranosyl residues, whereas side chains of the branched region consisted of the residues of 1,6-β-galactopyranose, 1,5-α-L-arabinofuranose, 1,4-β-D-glucuronic acid, and 1,6-β-D-glucopyranose. The branching points were identified as 1,3,6-β-D-galactopyranose residues. Side chains were terminated with β-D-galactopyranose, α-L-arabinofuranose and α-L-rhamnopyranose. A significant part of the side-chain β-1,6-galactan was substituted at C6 by 4-OMe-β-D-glucuronic acid. A minor part of glucuronic acid was included in the α-Rhap-(1 → 4)-β-GlcA-(→ fragment. All the studied fractions contained 1,4-β-D-galacturonic acid as well.