NMR spectroscopy and chemical studies of an arabinan-rich system from the endosperm of the seed of Gleditsia triacanthos Original Research Article

Exhaustive extraction of the endosperm from the seed of Gleditsia triacanthos using water at room temperature and 50 °C left a residue, which was further extracted at 95 °C. Precipitation of this extract with 2-propanol yielded major amounts of galactomannan components, while the supernatant was mainly composed of arabinose-rich constituents. Two fractions were obtained by anion-exchange chromatography. The fraction that eluted with water is an arabinan with (1→5) α-l linkages and branching mainly on C-2, accompanied with equal amounts of a low-galactose galactomannan oligosaccharide, and a small proportion of a β-(1→4)-galactan. The fraction eluted with an increased ionic strength consists mainly of a similar arabinan, and lower proportions of a high-galactose galactomannan, galactan, and protein. The arabinan moiety in both fractions was characterized by chemical analysis and 1D and 2D NMR spectroscopic techniques.