Antiviral activity of the red marine alga Ceramium rubrum.

An extract from the red marine alga Ceramium rubrum (Huds.) Ag. from the Bulgarian Black Sea seacoast considerably inhibited the reproduction of influenza viruses type A and B in vitro and in ovo. The virus-induced cytopathogenic effect (CPE), infectious virus yields and the production of hemagglutinin were all reduced at non-toxic concentrations of the extract. The virus-inhibitory effect was selective, dose-related and strain-specific; selectivity indices ranged 9.5-68.3. The inhibition affected adsorption as well as the intracellular stages of viral replication. The extract inhibited also the reproduction of herpes simplex virus (HSV) type 1 and type 2 in cell cultures. The preparation exhibited a strong HSV-inactivating activity.