Inhibitory effects of baicalein on the influenza virus in vivo is determined by baicalin in the serum.

Baicalein, an extract from Scutellaria baicalensis, was evaluated for its ability to inhibit the influenza virus in vivo. Oral administration of baicalein to BALB/c mice infected with the influenza A/FM1/1/47(H1N1) virus showed significant effects in preventing death, increasing the mean time to death, inhibiting lung consolidation, and reducing the lung virus titer in a dose-dependent manner. These effects are believed to be due to baicalin, the metabolite of baicalein in the serum. At a concentration of baicalin 2 microg/ml in overlay medium, it showed significant inhibition in the plaque assay, and the mean IC(50) value of baicalin was calculated as 1.2 microg/ml in the cytopathic effect assay. Our results showed that baicalein warrants further research as a potential antiinfluenza viral agent.