Fig. 3.

Glycyrrhetinic acid (GA) and licorice-saponin A3 inhibit the infection of SARS-CoV-2 in vitro. (A) Antiviral activities of GA, GA-g, GA-gg, and A3 against SARS-CoV-2 in Vero E6 cells at 3 μM, n ≥ 3. Remdesivir (3 μM) was the positive control. (B) and (C) Dose-dependent inhibition of GA and A3 on SARS-COV-2 infection, n ≥ 3. Vero E6 cells and Caco-2 cells incubated with SARS-CoV-2 at an MOI = 0.01 were treated with increasing concentrations of GA and A3 for 24 h, respectively. qRT-PCR was applied to quantify the copy number of viral ORF1ab RNA in the culture medium. (D) IFA analysis of the inhibition of GA and A3 on SARS-CoV-2 replication. Infected cells were fixed at 24 h post-infection after treatment with 3 µM and 10 µM of GA and 0.11 µM and 0.33 µM of A3, respectively, and were subjected to IFA using the primary antibody against viral spike protein.