X-ray structures of Mpro in complex with non-peptidic inhibitors. (a, c, e, g) The active site of Mpro (shown as an electrostatic surface) in complex with (a) 23R (PDB: 7KX5), (c) S-217622 (PDB: 7VU6), (e) masitinib (PDB: 7JU7) and (g) oxidized myricetin (PDB: 7DPP); (b, d, f, h) The Mpro-inhibitor interactions for (b) 23R, (d) S-217622, (f) masitinib and (h) oxidized myricetin. Hydrogen bonds are shown as yellow dashed lines.