In vivo conversion of 6-O-sulfo-l-galactopyranosyl residues into 3,6-anhydro-l-galactopyranosyl residues in Gracilaria chilensis Bird, McLachlan et Oliveira

The agar polysaccharides of the red seaweed Gracilaria chilensis Bird, McLachlan et Oliveira were labelled with the stable isotope 13C by pulse feeding NaH13CO3 to samples of this alga acclimatised to indoor culture. 13C NMR spectroscopy of the labelled polysaccharides extracted from these samples has been used to demonstrate conversion in vivo of 6-O-sulfo-l-galactopyranosyl residues into 3,6-anhydro-l-galactopyranosyl residues. The 6-O-sulfo-l-galactopyranosyl residues can be linked to either 6-O-methyl-d-galactopyranosyl residues or d-galactopyranosyl residues.