Structural analysis of carrageenans from the tetrasporic stages of the red algae, Gigartina lanceata and Gigartina chapmanii (Gigartinaceae, Rhodophyta)

The use of modern analytical techniques has facilitated the identification of the polysaccharides from tetrasporophytic Gigartina lanceata and Gigartina chapmanii. The G. lanceata polysaccharide corresponds, very closely, to the idealised structure of λ-carrageenan ([G2S-D2S,6S]n). That from G. chapmanii contains predominantly ξ-carrageenan ([G2S-D2S]n), but with about one in seven of the 3-linked units also has a pyruvate acetal group at the 4- and 6-positions, one in four of the 4-linked units is also sulfated at the 6-position, and a small but significant number of 4-linked 3,6-anhydrogalactosyl 2-sulfate units are present.