Preparation of a new arabinoxylooligosaccharide from wheat bran hemicellulose and its structure

A novel arabinoxylooligosaccharide was prepared from wheat bran and its structure was analyzed. Wheat bran hemicellulose was digested with a commercial Aspergillus japonicus hemicellulase preparation and an oligosaccharide was purified by carbon column and gel filtration chromatographies to be a single component. The oligosaccharide has D.P. of 6 and contains arabinose and xylose with a molar ratio of 2:1. Xylotetraose was formed as an intermediate hydrolyzate on acid hydrolysis of this oligosaccharide. Methylation analysis indicated that both reducing and non-reducing end xylose residues were free from arabinose residues and that there is only one xylose residue attached by two arabinose residues. The structure of this saccharide was finally identified by 13C NMR as beta-D-Xylp-(1-->4)[alpha-L-Araf-(1-->2)][alpha-L-Araf -(1-->3)]-beta-D- Xylp-(1-->4)-beta-D-Xylp-(1-->4)-D-Xylp.