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)GalAp(α1 → and →2)Rhap(α1 → 4)GalAp(α1→, repeatedly. The residue of →4)Galp(β1 → and →5)Araf(α1 → alternately exists on the O-4 of partial →2)Rhap(α1 → residues as side chains. On the O-3 of sectional →5)Araf(α1 → residues is a secondary branch assembled by →3)Araf(α1→. Moreover, on the non-reducing terminus of →4)Galp(β1 → occasionally have an →5)Araf(α1 → chain. Surprisingly, a sub-branch constructed by →6)Hexp(β1 → with a galacturonate or methyl galacturonate exists on the O-3 of certain →4)Galp(β1 → residues in the non-reducing terminus. In addition, a terminal Xyl is located on the O-3 of fractional →4)GalAp(β1 → residue. The highly branched polysaccharide CP-III with high water solubility can be used as food supplement and medicinal carrier in the future.
Keywords: Cyclocarya paliurus; Highly-branched polysaccharide; Mass spectrometry; Oligosaccharide sequence; Structural characterization.
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