An investigation of the carbohydrate obtainable from the green alga uliva

Abstract

The carbohydrate obtainable from a member of the chlorophyceae has been investigated for the first time. This polysaccharide is of an acidic nature and its extraction from the alga has been effected with hot dilute sodium carbonate solution. Uronic acid residues do not appear to be present and the acidity of the material has been shown to be dependent on the presence of organically bound sulphur. It is suggested that such sulphur exists as a sulphuric acid ester group of the type R.O.SO2.OH, but complete quantitative confirmation of this view is difficult to obtain. The polysaccharide has been shown to consist in part of methyl pentose units, which are apparently removed preferentially during dilute acid hydrolysis, since the simple sugar fractions from such hydrolyses are richer in methyl pentose than the original material. Methylation of simple hydrolysis products has led to the isolation of a fully methylated methyl pentose and the identification of the sugar as (1) rhamnose, the presence of which in algal carbohydrates has not previously been reported. Little evidence has been obtained as to the constitution of the remaining part of the carbohydrate complex but it apparently contains a certain amount of highly unstable material. An arbitrary separation of the polysaccharide extract into two fractions according to their solubility in 50% alcohol has been effected. The fractions differ appreciably in their equivalent weights but in view of their very similar sulphate figures it appears that the higher equivalent weight of the more soluble fraction is due to the presence in it of a certain amount of sodium salt. There is a well-defined difference in the rhamnose contents of the two fractions, suggesting that a more profitable separation into a rhamnosan and a rhamnose-free polysaccharide might be possible.