Methylation and 2D NMR analysis of arabinoxylan from the seeds of Plantago asiatica L.

PLP-3 (Plantago asiatica L. polysaccharide 3) was isolated and purified from the seeds of Plantago asiatica L. Its structure characters were elucidated by monosaccharide composition analysis, partial acid hydrolysis and methylation analysis, combined with FT-IR, GC/MS, 1D and 2D NMR spectroscopy. PLP-3 was found to be arabinoxylan, containing glucuronic acid. It was consisted of β-1,4-linked Xylp backbone with short side chains attached to its O-2 (1,2,4-linked Xylp, 17.87%) or O-3 (1,3,4-linked Xylp, 24.24%) positions. The main terminal residues were T-linked Araf (8.13%), T-linked Xylp (15.58%) and T-linked GlcAp (13.22%). Small amounts of other residues were also found in PLP-3, such as 1,2,5-linked Araf, 1,2-linked Rhap, T-linked Glcp and T-linked Galp. A possible molecular structure was proposed.