Galactans from cystocarpic plants of the red seaweed Callophyllis variegata (Kallymeniaceae, Gigartinales)

The polysaccharide extracted from cystocarpic Callophyllis variegata was fractionated with potassium chloride yielding three small fractions that precipitated in the ranges of 0-0.05 M KCl, 1.20-1.25 M KCl, and 1.80-2.00 M KCl, and a main product soluble in 2.00 M KCl. These fractions were analyzed, and as the first one contained very high amounts of protein, it was not studied further. Structural analysis of the rest of the fractions (F1-F3) was carried out by methylation, desulfation-methylation, IR, and 13C NMR spectroscopy. The results are consistent for F1 with a carrageenan-type backbone mainly constituted by β-d-galactose 2-sulfate linked to α-d-galactose 2,3,6-trisulfate and β-d-galactose 2,4-disulfate linked to 3,6-anhydro-d-galactose 2-sulfate as dominant diads. In F2 these diads are present together with low amounts of β-d-galactose 2-sulfate linked to 3,6-anhydro-d-galactose 2-sulfate, whose contribution becomes higher in F3. In addition, minor but significant amounts of l-galactose were detected. F1-F3 showed potent antiviral activity against herpes simplex types 1 and 2 and dengue type 2.