Chemical Heterogeneity of the Agar from Gracilaria verrucosa

Abstract

The agar from Gracilaria verrucosa was separated into five fractions in a good yield by a column chromatography. Chemical analysis showed that these fractions contained increasing proportions of galactose, uronic acid, and sulfate residues and decreasing proportions of 6-O-methylgalactose and 3, 6-anhydrogalactose residues in the order of elution from the column. The sums of molar contents of the anhydrogalactose and sulfate residues in all these agar fractions amounted to approximately half the molar content of total hexose residues. By a series of similar chromatography, at least two of the acidic fractions were found to be still remarkably heterogeneous with respect to the molar ratio of uronic acid and sulfate to the anhydrogalactose residue. These findings strongly suggest that the agar is a family of polydisperse polysaccharides consisting of various intermediate molecular forms between the two extreme types of macromolecules, that is, a non-sulfated, highly methylated galactan possibly made of repeating agarobiose residues and a non-methylated, highly sulfated galactan with lesser proportion of the anhydrogalactose residue.