2.1.1.  Protein preparations
The crystal structure of SARS-CoV-2 RdRp (PDB ID: 6M71) (Yan et al., 2020) was retrieved from the protein databank (www.rcsb.org) (Berman et al., 2000). The crystal structure was prepared individually by adding hydrogen atoms and computing the Gasteiger charge using the AutoDock v4.2 program (Morris et al., 2009). Subsequently, the file was saved as .pdbqt format in preparation for molecular docking. Schematic representation of the work-flow for selecting potential natural polyphenolic inhibitors for the SARS-CoV-2 RdRp is shown in Figure 2.
Figure 2.  Flow chart of the methodology for shortlisting the best natural polyphenolic inhibitor of the SARS-CoV-2 RdRp.