Xyloglucans from flaxseed kernel cell wall: Structural and conformational characterisation

•Xyloglucans from flaxseed kernel cell wall was studied for the first time.•Flaxseed kernel xyloglucans have highly substituted short-branched structure.•Flexible linear-chain conformation of flaxseed kernel xyloglucans was deduced.

The structure of ethanol precipitated fraction from 1 M KOH extracted flaxseed kernel polysaccharides (KPI-EPF) was studied for better understanding the molecular structures of flaxseed kernel cell wall polysaccharides. Based on methylation/GC–MS, NMR spectroscopy, and MALDI-TOF-MS analysis, the dominate sugar residues of KPI-EPF fraction comprised of (1,4,6)-linked-β-d-glucopyranose (24.1 mol%), terminal α-d-xylopyranose (16.2 mol%), (1,2)-α-d-linked-xylopyranose (10.7 mol%), (1,4)-β-d-linked-glucopyranose (10.7 mol%), and terminal β-d-galactopyranose (8.5 mol%). KPI-EPF was proposed as xyloglucans:Figure optionsDownload full-size imageDownload as PowerPoint slideThe substitution rate of the backbone is 69.3%; R1 could be T-α-d-Xylp-(1→, or none; R2 could be T-α-d-Xylp-(1→, T-β-d-Galp-(1 → 2)-α-d-Xylp-(1→, or T-α-l-Araf-(1 → 2)-α-d-Xylp-(1→; R3 could be T-α-d-Xylp-(1→, T-β-d-Galp-(1 → 2)-α-d-Xylp-(1→, T-α-l-Fucp-(1 → 2)-β-d-Galp-(1 → 2)-α-d-Xylp-(1→, or none. The Mw of KPI-EPF was calculated to be 1506 kDa by static light scattering (SLS). The structure-sensitive parameter (ρ) of KPI-EPF was calculated as 1.44, which confirmed the highly branched structure of extracted xyloglucans. This new findings on flaxseed kernel xyloglucans will be helpful for understanding its fermentation properties and potential applications.