Anti-influenza virus activity of tricin, 4',5,7-trihydroxy-3',5'-dimethoxyflavone.

BACKGROUND We examined the anti-influenza virus activity of tricin, 4',5,7-trihydroxy-3',5'-dimethoxyflavone, against five viruses: A/Solomon islands/3/2006 (H1N1), A/Hiroshima/52/2005 (H3N2), A/California/07/2009 (H1N1pdm), A/Narita/1/2009 (H1N1pdm) and B/Malaysia/2506/2004 strains in vitro and against A/PR/8/34 virus in vivo. METHODS The effect of tricin was studied by an infectious virus yield reduction assay. The anti-influenza virus mechanism of the tricin was examined by western blot analysis, real-time reverse transcriptase PCR analysis, haemagglutination inhibition (HI) assay and neuraminidase (NA) inhibition assay. The anti-influenza virus efficacy of tricin was further examined in a murine influenza virus infection model. RESULTS Tricin of 3.3 to 30 μM significantly reduced seasonal A (H1N1), (H3N2) viruses, novel A (H1N1pdm) virus, as well as B virus in a dose-dependent manner. The 50% effective concentrations of tricin were 3.4 μM for seasonal A (H3N2) virus, 4.9 μM for B virus and 8.2 μM for A/Narita (H1N1pdm) virus. Tricin decreased the expression of haemagglutinin (HA) protein and matrix (M) protein, and messenger RNA expression of HA and M of influenza virus in the infected cells. Tricin exhibited little or no effects on influenza virus HI and NA activities. In the mouse infection model, tricin was significantly effective in reducing body weight loss, and also effective in prolonging survival times of infected mice. CONCLUSIONS Tricin was indicated to possess anti-influenza virus activity and to ameliorate body weight loss and survival rate of influenza-A-virus-infected mice. Tricin is a novel compound with potential anti-influenza virus activity in vitro and in vivo.