Extraction, isolation and structural characterization of a novel polysaccharide from Cyclocarya paliurus

A water soluble polysaccharide CP-III was extracted and purified from Cyclocarya paliurus. CP-III is identified as a novel pectin-like polysaccharide with molecular weight (Mw) of 72.7 kDa. The structural features of CP-III were characterized by methylation and nuclear magnetic resonance (NMR) spectroscopy. Its depolymerized fragments were analyzed by hydrophilic interaction chromatography-Fourier transform mass spectrometry (HILIC-FTMS). The main chain of CP-III is composed of →4)GalA_p(α1 → and →2)Rha_p(α1 → 4)GalA_p(α1→, repeatedly. The residue of →4)Gal_p(β1 → and →5)Ara_f(α1 → alternately exists on the O-4 of partial →2)Rha_p(α1 → residues as side chains. On the O-3 of sectional →5)Ara_f(α1 → residues is a secondary branch assembled by →3)Ara_f(α1→. Moreover, on the non-reducing terminus of →4)Gal_p(β1 → occasionally have an →5)Ara_f(α1 → chain. Surprisingly, a sub-branch constructed by →6)Hex_p(β1 → with a galacturonate or methyl galacturonate exists on the O-3 of certain →4)Gal_p(β1 → residues in the non-reducing terminus. In addition, a terminal Xyl is located on the O-3 of fractional →4)GalA_p(β1 → residue. The highly branched polysaccharide CP-III with high water solubility can be used as food supplement and medicinal carrier in the future.