Complete assignment of 1H and 13C NMR spectra of Gigartina skottsbergii λ-carrageenan using carrabiose oligosaccharides prepared by enzymatic hydrolysis

λ-Carrageenan extracted from Gigartina skottsbergii tetrasporophyte was completely digested by a purified Pseudoalteromonas carrageenovora λ-carrageenase. The main digestion products were fractionated and analysed by 1H and 13C NMR spectroscopy. All the oligosaccharides observed belong to the neo-carrabiose oligosaccharide series indicating that the λ-carrageenase cleaves the β-(1→4) glycosidic bonds. 1H and 13C NMR spectra recorded on oligomers from DP 2 to DP 8 were fully interpreted allowing unambiguous assignment of the λ-carrageenan spectra. Besides the typical oligo-λ-carrageenans, we have also characterised a heptasulfated tetrasaccharide which demonstrates the random over-sulfation along the chain of G. skottsbergii λ-carrageenan.

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