Cell wall polysaccharides from Australian red algae of the family Solieriaceae (Gigartinales, Rhodophyta): Iota/kappa/beta-carrageenans from Melanema dumosum

The cell wall galactan from Melanema abumosurn (Harvey) Min-Thein et Womersley collected from south-eastern Australia was extracted (46% w/w yield) and analysed by chemical and physical methods. The preparation has a high sulphate ester content (26.9% w/w as SO3Na) and the dominant constituent sugars of the sample are galactose and 3,6-anhydrogalactose in approximately equimolar proportions. Small amounts of xylose and glucose are also present. No mono-O-methylgalactose or pyruvate was detected. Evidence from infrared and C-13-nuclear magnetic resonance spectroscopy indicates that the polysaccharide is a hybrid or mixture of iota (iota)-, kappa (kappa)- and beta (beta)-carrageenans. The chemistry of the polysaccharide from M. dumosum is compared with that of polysaccharides from species of the Solieriaceae and the Caulacanthaceae. We conclude from the polysaccharide data that, although Melanema dumosum may not be closely allied to the genera Areschougia, Rhabdonia and Erythroclonium, it can be retained provisionally in the family Solieriaceae, although its possible inclusion in the Caulacanthaceae cannot be dismissed.