High-Content Screening of Thai Medicinal Plants Reveals Boesenbergia rotunda Extract and its Component Panduratin A as Anti-SARS-CoV-2 Agents

Abstract

Since December 2019, the emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has caused severe pneumonia, a disease named COVID-19, that became pandemic and created an acute threat to public health. The effective therapeutics are in urgent need. Here, we developed a high-content screening for the antiviral candidates using fluorescence-based SARS-CoV-2 nucleoprotein detection in Vero E6 cells coupled with plaque reduction assay. Among 122 Thai natural products, we found that Boesenbergia rotunda extract and its phytochemical compound, panduratin A, exhibited the potent anti-SARS-CoV-2 activity. Treatment with B. rotunda extract and panduratin A after viral infection drastically suppressed SARS-CoV-2 infectivity in Vero E6 cells with IC50 of 3.62 μg/mL (CC50 = 28.06 µg/mL) and 0.81 μΜ (CC50=14.71 µM), respectively. Also, the treatment of panduratin A at the pre-entry phase inhibited SARS-CoV-2 infection with IC50 of 5.30 µM (CC50=43.47 µM). Our study demonstrated, for the first time, that panduratin A exerts the inhibitory effect against SARS-CoV-2 infection at both pre-entry and post-infection phases. Since B. rotunda is a culinary herb generally grown in China and Southeast Asia, its extract and the purified panduratin A may serve as the promising candidates for therapeutic purposes with economic advantage during COVID-19 situation.

Anti-SARS-CoV-2 activity of Andrographis paniculata extract and its major component Andrographolide in human lung epithelial cells and cytotoxicity evaluation in major organ cell representatives

“…Hydroxychloroquine, a classical anti-malarial drug, had no inhibitory effect against SARS-CoV-2 infection in human lung epithelial cells (IC50>50 µM) ( Figure 2C and 2D), while niclosamide, a classical anti-helminthic drug, inhibited SARS-CoV-2 infection with the IC50 of 0.90 µM (Figure 2E and 2F). Of note, hydroxychloroquine can exhibit antiviral effect in Vero E6 cells 30 but not Calu-3 human lung epithelial cells. 31 These results were consistent to previous reports 31,32 and supported the validity of Calu-3-based anti-SARS-CoV-2 assay used in this study.…”

“…SARS-CoV-2 virus was isolated from nasopharyngeal swabs of a confirmed COVID-19 patient in Thailand (SARS-CoV-2/01/human/Jan2020/Thailand). The virus was propagated in Vero E6 cells as previous described 30 and stored at -80°C. Viral titration as TCID50 titer/mL was performed in the 96-well plate.…”

“…The fluorescent signal was detected and analyzed by the Operetta high-content imaging system (PerkinElmer, Waltham, MA, USA) as previously described. 30 Percentage of the infected cells in each well was automatically obtained from 13 fields per well using Harmony software (PerkinElmer, Waltham, MA, USA). Data was normalized to the infected control, and IC50 value was calculated by GraphPad Prism 7.…”

“…Therefore, a robust anti-SARS-CoV-2 screening platform established on the legitimate model is required to facilitate this process. For serving this proposes, we optimized our antiviral assay (which previously established upon Vero E6 cells) 30 to use Calu-3 human lung epithelial cells as the legitimate host cell for SARS-CoV-2 infection, 31 and then validated the assay applicability by hydroxychloroquine and niclosamide ( Figure 1B and 1C, respectively), two FDA-approved drugs with anti-SAR-CoV-2 activities in vitro. [31][32][33] (Figure 2A and 2B upper panel).…”

“…29 Furthermore, our group has utilized a phenotypic cell-based immunofluorescent assay (IFA) to reveal the anti-SARS-CoV-2 effect of A. paniculata extract and andrographolide in the African green monkey kidney cells (Vero E6). 30 Notably that the anti-SARS-CoV-2 activity of A. paniculata extract and andrographolide has never been elucidated in the infected human lung epithelial cells.…”