Antiviral activity of Undaria pinnatifida against herpes simplex virus

The major component of an aqueous extract of the seaweed Undaria pinnati fi da has been identified previously as a galactofucan (GFS), a sulfated polysaccharide. The galactofucan was partially purified and the material tested in this study is 75% pure galactofucan sulfate. GFS was evaluated for antiviral activity against 32 clinical strains of herpes simplex virus (HSV): 14 strains of HSV-1 and 18 strains of HSV-2. Twelve strains (four HSV-1 and eight HSV-2) were resistant to acyclovir (ACV-R) and 20 strains (10 HSV-1 and 10 HSV-2) were susceptible to ACV (ACV-S). The median IC(50) of GFS for the 14 strains of HSV-1 was 32 micro g/mL. The median IC(50) of GFS for the 18 strains of HSV-2 was 0.5 micro g/mL. GFS is significantly more active against clinical strains of HSV-2 than HSV-1, p < 0.001. The mode of action of the GFS was shown to be the inhibition of viral binding and entry into the host cell. The cytotoxicity of GFS was >4.0 mg/mL in the neutral red dye uptake assay indicating that GFS is non-toxic in this assay.