Structural characterization of three aldobiuronic acids derived from the capsular polysaccharide produced by the thermophilic cyanobacterium Mastigocladus laminosus.

This study deals with the chemical characterization of a capsular polysaccharide (CPS) produced by a thermal biomass formed by the cyanobacterium Mastigocladus laminosus. Acid hydrolysis performed on the purified polysaccharide has led to the isolation of several acid-resistant oligosaccharides. Two of them have already been reported and assigned as: alpha - GlcA - (1 --> 2) - alpha - GalA - (1 --> 2) - Man. and alpha - GlcA - (1 --> 2) - alpha - GalA - (1 --> 2) - beta - Man - (1 --> 4) - beta - Gal(1 --> 2) - Rha. In this report, results on the isolation and partial purification of three supplementary oligosaccharidic units are presented. Gas chromatography-mass spectrometry (GC-MS) and H-nuclear magnetic resonance (NMR) spectroscopy investigations allowed them to be assigned as three aldobiuronic acids with the following structures: alpha - GlcA - (1 --> 3) - Gal alpha - GlcA - (1 --> 3) - Fuc alpha - GalA - (1 --> 3) - Fuc.