Glycyrrhizin in Licorice Root Neutralizes SARS-CoV-2

A pre-print paper revealed that glycyrrhizin in licorice root neutralizes SARS-CoV-2 in vitro by inhibiting the main protease Mpro. An in-silico simulation study suggested the antiviral activity of glycyrrhizin against SARS-CoV-2. Researchers from Germany analyzed aqueous licorice root extract. Cytotoxicity was determined at 4-time points using Orangu cell counting solution.

The licorice root extract exhibited neutralizing effects even at a subtoxic concentration of 2 mg/ml, which is lower than the typical consuming dilution. For example, in tea, it is 12.5 mg/ml. Complete neutralization of the virus was achieved at 0.5 mg/ml under pre- and  1 mg/ml under post-entry conditions. Researchers found only a tiny difference in the antiviral activity of glycyrrhizin between pre-and post-entry conditions. So they concluded that glycyrrhizin neutralizes the virus by a mechanism that is different from inhibition of TMPRSS2.

In further experiments, the researchers found that glycyrrhizin fully inhibited Mpro activity at a concentration of 2000 µM (1.6 mg/ml) and reduced Mpro activity by 70.3% at a concentration of 30 µM (0.024 mg/ml). Mpro is responsible for the processing of viral polyproteins translated from the viral RNA and hence essential for virus replication. Thus, they concluded that glycyrrhizin effectively neutralizes SARS-CoV-2 by inhibiting the viral main protease Mpro. This study highlights that glycyrrhizin is a promising antiviral compound and further investigations could lead to it being a treatment in COVID-19.

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