Antiviral Effect of Amentoflavone Against Influenza Viruses.

Amentoflavone (AF) is a biflavonoid compound found in many plants. In this study, we first demonstrate that AF has a potent antiviral effect against the influenza virus via the inhibition of viral attachment and virucidal effects. The anti-influenza-viral effect of AF was evaluated using green fluorescent protein-tagged Influenza A virus (IAV) with fluorescent microscopy and flow cytometry analysis. AF decreased the GFP expression by viral infection, dose-dependently. Fifty micromoles of AF suppressed the GFP expression by virus infection of up to 70% of untreated infected control cells. Consistently, immunofluorescence results showed the inhibitory effect of AF on viral protein expression. Time-of-addition and hemagglutination assays revealed that AF inhibits viral binding to cells by interfering with the hemagglutinin (HA) of IAV. Furthermore, AF has a virucidal effect and blocks cytopathic effects caused by the Influenza B virus and H3N2 IAV. Additionally, AF represses the neuraminidase (NA) activity of IAV. In silico analysis confirmed the potential interaction of AF with both HA and NA. Our findings indicate that AF has antiviral effects by modulating HA and NA during the attachment and release stages of influenza viral infection.