Modified procedures for extraction and analysis of carrageenan applied to the red alga Hypnea musciformis

Dried powder of Hypnea musciformis was extracted with water at pH 7 after an initial short pre-treatment with cold, diluted HCl. Carrageenans were isolated by alcohol precipitation after an amylase treatment and a filtration of the extracts. The yields at 25 and 90 degrees C were 25 and 75% (w/w) of the dry alga, with molecular weights (Mw) corresponding to 194 000 and 245 000, respectively. The chemical structure was dominated by G4S-DA-(kappa-carrageenan or carrageenose 4'-sulphate). A simple fractionation procedure for kappa-carrageenase hydrolysates, based on stirring in different enthanol/water mixtures, is introduced. NMR analysis showed that oligosaccharides with a repeating DA-G4S structure were the main constituents in the enzymic hydrolysates of the carrageenans from Hypnea musciformis. These oligosaccharides were solubilized in an ethanol concentration from 96 to 48% (v/v). In some enzyme resistant fractions D6S-G4S and DA2S-G4S sequences and D2S,6S unites were detected by C-13-NMR.