A nearly idealized 6′-O-methylated η-carrageenan from the Australian red alga Claviclonium ovatum (Acrotylaceae, Gigartinales) Original Research Article

The polysaccharides extracted from Claviclonium ovatum were studied by a combination of compositional assays, reductive partial hydrolysis, linkage analysis, Fourier Transform infrared (FTIR) spectroscopy, and 13C, 1H, and 13C/1H heteronuclear multiple quantum correlation (HMQC) two-dimensional nuclear magnetic resonance (NMR) spectroscopy. The chemical and spectroscopic data showed that the alkali-modified C. ovatum polysaccharides are composed of a nearly idealized repeating unit of 6′-O-methylcarrabiose 2,4′-disulfate (the repeating unit of 6′-O-methylated η-carrageenan), although some minor components were also present. The C. ovatum galactans are the most highly methylated carrageenans reported.