Abstract

The polysaccharide extracts from Lophurella hookeriana and Lophurella caespitosa together with some derivatives have been examined by ¹³C nuclear magnetic resonance spectroscopy and the spectra analysed with the techniques of set theory. The polysaccharides are agaroids that consist of 3-linked D-galactose and 4-linked L-galactose or anhydro-L-galactose. The polysaccharides from both algae were partially sulfated at the 2- and 6-positions of both the 3- and 4-linked units. The polysaccharide from Lophurella hookeriana comprised at least 90% anhydrogalactosyl precursor diads, and was otherwise between 65–75% unsubstituted, with approximately 22% of the 4-linked units being 2-sulfated, 12% of the 3-linked units being 2-sulfated, and 15% of the 3-linked units being 6-sulfated. The polysaccharide from Lophurella caespitosa contained approximately 15% anhydrogalactosyl precursors, 40% L-galactose that was not convertible to anhydrogalactose, and no more than 25% unsubstituted agarose diads following alkali treatment. Approximately 55% of the 4-linked units were 2-sulfated, 28% of the 3-linked units were 2-sulfated, and 25% of the 3-linked units were 6-sulfated.