Kurarinone is a prenylated flavonone isolated from the roots of Sophora flavescens. Among its known functions,
kurarinone has both anti-apoptotic and anti-inflammatory properties. Coronaviruses (CoVs), including HCoV-OC43, SARS-CoV, MERS-CoV, and SARS-CoV-2, are the causative agents of respiratory
virus infections that range in severity from the
common cold to severe
pneumonia. There are currently no effective treatments for coronavirus-associated diseases. In this report, we examined the anti-viral impact of
kurarinone against
infection with the human coronavirus, HCoV-OC43. We found that
kurarinone inhibited HCoV-OC43
infection in human lung fibroblast MRC-5 cells in a dose-dependent manner with an IC50 of 3.458 ± 0.101 μM.
Kurarinone inhibited the virus-induced cytopathic effect, as well as extracellular and intracellular
viral RNA and
viral protein expression. Time-of-addition experiments suggested that
kurarinone acted at an early stage of
virus infection. Finally, we found that HCoV-OC43
infection increased the autophagic flux in MRC-5 cells;
kurarinone inhibited viral replication via its capacity to impair the virus-induced autophagic flux. As such, we suggest that
kurarinone may be a useful therapeutic for the treatment of diseases associated with
coronavirus infection.