Carbohydrates of the brown seaweed lessonia nigrescens

Stipes plus haptera and fronds were extracted separately. Crystalline mannitol and two oligouronic acids were separated from the ethanolic extracts of both parts of the weed. ‘Fucans’ were present in all the sequential aqueous, acidic and alkaline extracts. Each of the '‘fucans’ contained varying proportions of fucose (major), galactose, mannose, xylose, glucuronic acid, half ester sulphate and small proportions of protein. Fractionation of the aqueous extract failed to reveal any laminaran. Alginates were present in the sequential and direct alkaline extracts. The only significant differences between stipes and fronds were the higher proportion of glucuronic acid in the ‘fucans’ from the stipes and of the alginic acid in the stipes.