Anti-influenza virus activity of propolis in vitro and its efficacy against influenza infection in mice.

BACKGROUND Propolis has been used worldwide as a dietary supplement to maintain and improve human health. We examined whether ethanol extracts of Brazilian propolis exhibit antiviral activity against influenza virus in vitro and in vivo. METHODS Among 13 ethanol extracts screened in a plaque reduction assay, four showed anti-influenza virus activity. The anti-influenza efficacy of the four extracts was further examined in a murine influenza virus infection model. The mice were infected intranasally with influenza virus, and the four extracts were orally administered at 10 mg/kg three times daily for seven successive days after infection. RESULTS In this infection model, only one extract, AF-08, was significantly effective at 10 mg/kg in reducing the body weight loss of infected mice. The doses of 2 and 10 mg/kg were also effective in prolonging the survival times of infected mice significantly, but 0.4 mg/kg was not. The anti-influenza efficacy of AF-08 at 10 mg/kg was confirmed in a dose-dependent manner in mice. AF-08 at 10 mg/kg significantly reduced virus yields in the bronchoalveolar lavage fluids of lungs in infected mice as compared with the control. The reduction of virus yields by AF-08 at 10 mg/kg significantly corresponded to those induced by oseltamivir at 1 mg/kg twice daily from day 1 to day 4 after infection. CONCLUSION The Brazilian propolis AF-08 was indicated to possess anti-influenza virus activity and to ameliorate influenza symptoms in mice. AF-08 may be a possible candidate for an anti-influenza dietary supplement for humans.