Autohydrolysis of a partially cyclized mu/nu-carrageenan and structural elucidation of the oligosaccharides by chemical analysis, NMR spectroscopy and UV-MALDI mass spectrometry

Abstract

A partially cyclized mu/nu-carrageenan from Gigartina skottsbergii was submitted to autohydrolysis and the resulting mixture of oligosaccharides was fractionated using sequential dialysis through tubings of molecular weight cutoff 12000, 3500 and 1000. In this way four fractions were separated and characterized. Structural analysis of the major fraction, obtained from the solution inside the dialysis tubing of molecular weight cutoff 12000 (D120), was carried out. A significant difference was found by 13C NMR spectroscopy and UV-MALDI-TOF mass spectrometry: in the 13C NMR spectrum the reducing end-chain unit was the hydrated aldehyde of 3,6-anhydrogalactose while the UV-MALDI-TOF mass spectrum showed an unimodal distribution of even and odd peaks, suggesting fragmentation of glycosidic linkages. © ARKAT.