Anti-herpes simplex virus target of an acidic polysaccharide, nostoflan, from the edible blue-green alga Nostoc flagelliforme

The acidic polysaccharide nostoflan was previously isolated as an antiviral component from the terrestrial alga Nostoc flagelliforme. In the present study, we examined the target for its anti-herpes simplex virus type I action. In time-of-addition experiments, the most sensitive stage of viral replication to nostoflan was found to be early events, including the virus binding and/or penetration processes. In order to determine what extent nostoftan may be involved in these processes, virus binding and penetration assays were separately performed. The results indicated that the inhibition of virus binding to but not penetration into host cells was responsible for the antiherpetic effect induced by nostoflan. Our study suggests that nostoflan may be a potential antiherpes agent.