Xanthohumol (XN) is a natural compound with multifunctional potentials, including antiviral activity. In this study, the antiviral activity of addition of XN to interferon (IFN)-alpha was examined and compared with each compound alone using bovine viral diarrhea virus (BVDV), a surrogate model of hepatitis C virus (HCV). BVDV E2 protein and the viral RNA level were determined by immunofluorescence and quantitative real-time RT-PCR, respectively. The addition of XN to IFN-alpha significantly improved CPEs induced by the virus and inhibited BVDV E2 protein and viral RNA levels. The interaction between XN and IFN-alpha was significant (P<0.001). XN at 3.13 microg/ml in combination with IFN-alpha at 50 IU/ml showed greater inhibitory effect on the viral RNA level than each compound used alone at 6.25 microg/ml and 100 IU/ml, respectively, indicating synergistic effect on BVDV replication in this combination. The inhibitory activity in all the tested combinations of XN and IFN-alpha was stronger than that of each compound used alone at the corresponding concentration. These results suggest that XN in combination with IFN-alpha exhibited a greater in vitro antiviral effect compared with each compound used alone. Further studies are deserved to investigate the anti-HCV activity of XN and the potential of XN in formulating novel anti-HCV regimen.
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