Structure characterization, chemical and enzymatic degradation, and chain conformation of an acidic polysaccharide from Lycium barbarum L.

• A purified acidic polysaccharide was obtained from fruits of Lycium barbarum L.
• The structural characteristics were investigated by a combination of chemical and instrumental analysis approaches along with a degradation pattern study.
• The fine primary structure and chain conformation of this polysaccharide was elucidated.

An acidic polysaccharide, named as p-LBP, was isolated from Lycium barbarum L. by water extraction and purified by decoloration, ion exchange chromatography, dialysis and gel chromatography, successively. The primary structure analysis was determined by HPAEC-PAD, HPSEC, FT-IR, GC–MS, and NMR. The results showed p-LBP was a homogeneous heteropolysaccharide as a pectin molecule with an average molecular weight of 64 kDa p-LBP was an approximately 87 nm hollow sphere in 0.05 mol/L sodium sulfate solution determined by HPSEC-MALLS, DLS and TEM. A discussion of degradation patterns gave the detailed structural information of p-LBP. Therefore, the results from degraded fragments elucidated that the backbone of p-LBP was formed by → 4-α-GalpA-(1 →, repeatedly. Partial region was connected by → 4-α-GalpA-(1 → and → 2-α-Rhap-(1 →, alternatively. On the C-4 of partial → 2-α-Rhap-(1 → residues existed branches forming by → 4-β-Galp-(1 →, → 3-β-Galp-(1 → or → 5-α-Araf-(1 →, while on the C-6 of partial → 3-β-Galp-(1 → residues existed secondary branches forming by terminal-α-Araf, terminal-β-Galp or → 3-α-Araf-(1 →.