Glycyrrhizin effectively neutralizes SARS-CoV-2 in vitro by inhibiting the viral main protease

The newly emerged coronavirus, which was designated as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the COVID-19 disease. High effective and well-tolerated medication for hospitalized and non-hospitalized patients is urgently needed. Traditional herbal medicine substances were discussed as promising candidates for the complementary treatment of viral diseases and recently suggested for the treatment of COVID-19. In the present study, we investigated aqueous licorice root extract for its neutralizing activity against SARS-CoV-2 in vitro, identified the active compound glycyrrhizin and uncovered the respective mechanism of viral neutralization. We demonstrated that glycyrrhizin, the primary active ingredient of the licorice root, potently neutralizes SARS-CoV-2 by inhibiting the viral main protease. Our experiments highlight glycyrrhizin as a potential antiviral compound that should be further investigated for the treatment of COVID-19.