Arabinoxylan from finger millet (Eleusine coracana, v. Indaf 15) bran: Purification and characterization

Water unextractable portion from finger millet bran was sequentially extracted with saturated barium hydroxide (BE) and 1 M potassium hydroxide (KE) solutions. They consisted preponderantly of arabinose and xylose in different ratios. Ferulic, caffeic, coumaric and vanillic acids were identified as major bound phenolic acids. BE and KE were purified on DEAE-cellulose column by eluting successively with different eluants. The major fractions (0.1 M ammonium carbonate) were resolved into one (BE) and two subfractions (KE1 and KE2) respectively on Sephacryl S-400 gel filtration chromatography and their homogeneity was ascertained by gel filtration, cellulose acetate membrane electrophoresis and capillary electrophoresis. The average molecular weight of BE, KE1 and KE2 were found to be 430, 1028 and 40 kDa respectively. The structural elucidation of the purified polysaccharides by 1H and 13C NMR analysis indicated the backbone to be 1,4-β-d-linked xylan with substitution mainly at O-2 or O-3 and/or both by α-l-arabinose residues.