Arabinose‐Containing Oligosaccharides from Tamarind Xyloglucan

Abstract

AbstractOligosaccharide mixtures were obtained by enzymatic degradation of tamarind xyloglucan from the seeds of Tamarindus indica by commercial Aspergillus niger endo‐(1→4)‐β‐D‐glucanase, and their composition analyzed by HPAE‐PAD liquid chromatography revealing two major groups of oligosaccharides. The first group contained oligomers of DP 7, 8 and 9, while the second group consisted of a large variety of oligomers of DP 12 to 18. After purification by SEC and HPLC in semi‐preparative scale, single oligomers were characterized by glycosyl‐residue composition, glycosyl‐linkage analysis and plasma desorption mass spectrometry. Beside β‐D‐Glucosyl, β‐D‐galactosyl and α‐D‐xylosyl units, some higher oligomers contained β‐D‐galactosyl‐(1→5)‐α‐L‐arabinosyl units, linked to O‐6 in the glucosyl units of the (1→4)‐β‐D‐glucan backbone. Other L‐arabinosyl residues were located in terminal positions of α‐D‐xylosyl side chains. The variety of isolated oligomers reflected a complicated random distribution of side chains in tamarind xyloglucan. Based on the characteristics of the oligomers, four structure forming units for the polysaccharide are proposed.