Structural characterization and antiviral activity of two fucoidans from the brown algae Sargassum henslowianum

Purified fucoidans SHAP-1 and SHAP-2 with apparent molecular weights of 6.55 x 10(5) and 5.89 x 10(5), respectively, were isolated from Sargassum henslowianum by ion-exchange and gel-filtration column chromatography. They are both composed of fucose and galactose at a ratio of around 3:1 and 31.9% sulfate. The backbone of two fucoidans consists of alpha-(1 -> 3)-linked L-Fucp residues which are mainly sulfated on the C-2 and C-4 positions. Side chains composed of terminally linked alpha-L-Fucp and alpha-D-Galp residues, and (1 -> 2)-, (1 -> 6)-, and (1 -> 2,6)-linked beta--Galp residues attach mainly at O-4 position of backbone residues. Antiviral test showed that the IC50 values of SHAP-1 and SHAP-2 against HSV-1 were estimated to be 0.89 and 0.82 mu g/mL by plaque reduction assay, respectively, whereas both as low as 0.48 mu g/mL against HSV-2. The antiviral mechanism of the fucoidans might be at least through blocking HSV-2 virion adsorption to host cells. These results suggest that the fucoidans have potential clinical applications.