Analysis of carrageenans by enzymic degradation, gel filtration and 1H NMR spectroscopy

Abstract

Carrageenans from Furcellaria lumbricalis and Eucheuma gelatinae were degraded by κ-carrageenase from Pseudomonas carrageenovora. Higher and lower molecular weight fractions were separated by ethanol precipitation and further fractionated by GPC on serially connected Sephacryl S-100 and S-200, and BioGel P4, respectively, and investigated by 500 MHz 1H NMR spectroscopy. Except for the lowest molecular weight oligosaccharide fractions from E. gelatinae, which contained di- and tetrasaccharides of κ-carrageenan, the lower molecular weight fractions of the carrageenans contained mixtures of neocarrabiose oligosaccharides with different content of d-galactose-4-sulphate. Both neocarrabiose and neocarrabiose-4-sulphate were detected on the non-reducing end. Varying with the source, the higher molecular weight fractions contained methyl, sulphate and other substitutions masking the general repeating backbone of neocarrabiose and neocarrabiose-4-sulphate.