Investigation of the polysaccharides synthesised by three genera of the phaeophyceae

Abstract

1. The three brown seaweeds (Himanthalia lorea, Bifurcaria bifurcata and Padina pavonia) of widely different morphology are each shown to synthesise D-mannitol. 2. Aqueous or dilute acid extraction after 80% ethanol extraction led to the isolation of complex mixtures of laminaran "fucans" and alginic acid. The separation of these polysaccharides proved impossible. 3. It was found that a 2% aqueous calcium chloride extraction before acid extraction renders the alginic acid completely insoluble and a very small proportion of the "fucans" contaminated the laminaran extracted into the aqueous solution. Subsequent extraction of the weed with dilute acid gave "fucans" virtually free from alginic acid. Further extraction of the residual material with dilute alkali gave a mixture of alginic acid and glucuronoxylofucans. Sequential extractions of the residual material with ammonium oxalate-oxalic acid and acid chlorite gave additional quantities of crude glucuronoxylofucans and the final residual algal material. The same polysaccharides in different proportions were isolated from eachof the weeds. 4. Pure laminaran was obtained from each of the three weeds after fractionation of the aqueous calcium chloride extract. This was characterised as a brown algal-type glucan comprising essentially 1,3- and 1,6-linked glucose residues, but devoid of mannitol terminated chains.