Monthly changes in the content of fucans, their constituent sugars and sulphate in cultured Laminaria japonica

Abstract

Crude fucan was extracted monthly from makonbu, Laminaria japonica Areschoug, cultured from April to October at a southern site of the Hokkaido bay. The crude fucan yield tended to gradually increase from April to September, and rose markedly in October when spore formation was over. The fucans were fractionated on DEAE-Sephadex A-25 into three acidic components, A, B and C. In all the monthly extracts, fraction C was the largest. It was entirely free of laminaran and alginate, as was fraction B. Several sugars such as mannose and glucuronic acid, were identified in fraction C beside a large amount of fucose and sulphate. Only the proportion of the latter two constituents continued to increase as the alga matured to reach twice or even more than three times as much as all the other sugars in the September extract.