The flexible docking was performed using the refined spike protein of SARS-CoV (6CRV) and RBD domain of SARS-CoV-2 (6M0J). The grid maps of the interaction energies of various atom types were pre-calculated using AutoGrid 4.2. In each docking for spike surface glycoprotein and spike RBD, a grid box was created using a grid map of 45 × 45 × 45 points, 60 × 60 × 60 points with grid spacing of 0.375 Å and 0.420 Å respectively. The grid maps were centred on the corresponding ligand binding site within the protein structure.