Cyanobacteria a potential source of antiviral substances against influenza virus.

Aqueous and methanolic extracts of cultured cyanobacteria of several genera, Microcystis, Nodularia, Oscillatoria, Scytonema, Lyngbya and Calothrix were evaluated for their in vitro antiviral activity against influenza A virus in Madin Darby canine kidney cells. None of the methanolic extracts showed cytotoxic effects. The inhibitory concentration (IC(50)) of antiviral activity ranged between 20.0 micro g to 79.0 micro g extract/ml. The most active extract in this screening derived from genus Microcystis. The further analysis of methanolic extracts of cultured strains of genus Microcystis revealed a remarkable antiviral activity against influenza A virus for M. aeruginosa, M. ichthyoblabe and M. wesenbergii. The observed antiviral activity was associated with protease inhibitory activity of approximately 90% and suggest that protease inhibitory activity may be responsible for reducing virus replication. These results show that cyanobacteria are able to produce compounds with biological activity that may be of potential clinical interest.