## 2 Materials and Methods
### Experimental
#### 2.2.15 Docking Studies  
Molecular docking is the _in-silico_ modeling of two or more molecules to create a stable product. Docking depicts the three-dimensional structure of any complex based on the properties of target molecules, such as protein or DNA and ligand [27]. The program's score function rates and classifies various possible adduct structures made via molecular docking. The best-docked conformers are suggested via docking simulations based on the system's total energy. The ultimate objective is to predict bound conformations and binding affinity [28]. The Receptors  
The SARS-CoV-2 spike glycoprotein was chosen to test the antiviral properties of myrrh, and the catalase and superoxide dismutase (SOD) enzymes were chosen for molecular docking research to predict the interaction of metabolites of the myrrh resin extract with two major enzymes of the cellular anti-oxidant mechanism. The three-dimensional structures of human erythrocyte catalase 3-amino-1,2,4-triazole complex (PDB id: 1 DGH) [29] and human SOD1 complexed with iso-proteranol (PDB id: 5 YTU) [30] and the SARS-CoV-2 spike glycoprotein (closed state) (PDB id: 6 VXX) [31] were downloaded from Protein Databank ([[https://www.rcsb.org/](https://www.rcsb.org/)]([https://www.rcsb.org/](https://www.rcsb.org/)), accessed on 23 January 2022). The structures were chosen based on resolution, source organism, and availability of the bound ligand for active site reference. Receptor crystal structures were discovered using X-ray diffraction at wavelengths of 2, 1.9, and 2.8 nm, respectively. The active constituents of myrrh resin are 2,3-furandione, Curzerene, delta-Elemene, and Furanoeudesma-1,3-Diene [32]. All of the ligands' three-dimensional structures were retrieved in structure-data file (SDF) format from the NCBI PubChem compounds database ([[https://pubchem.ncbi.nlm.nih.gov](https://pubchem.ncbi.nlm.nih.gov)]([https://pubchem.ncbi.nlm.nih.gov](https://pubchem.ncbi.nlm.nih.gov)), accessed on 23 January 2022) [33]. Then, using the Open Babel program ([[https://sourceforge.net/projects/openbabel/](https://sourceforge.net/projects/openbabel/)]([https://sourceforge.net/projects/openbabel/](https://sourceforge.net/projects/openbabel/)), accessed on 23 January 2022), these files were translated into the Protein Databank (PDB) file format. Tables 2 and 3 provide comprehensive details on the ligands and their properties. Molecular Docking  
A sophisticated computational modeling method for figuring out how a ligand (photochemicals or other substances) interacts with the active site of an enzyme or receptor is called molecular docking. Through the use of molecular docking, the interaction between the substrate and enzyme was identified. The proteins were processed appropriately in Biovia Discovery Studio Visualizer ([https://discover.3 ds.com/discovery-studio-visualizer-download/](https://discover.3 ds.com/discovery-studio-visualizer-download/), accessed on 23 January 2022) and docked using AutoDock vina ([[https://vina.scripps.edu/](https://vina.scripps.edu/)]([https://vina.scripps.edu/](https://vina.scripps.edu/)), accessed on 23 January 2022). Before docking, the hydrogen atoms were added, charges were applied, all crystallographic water molecules were eliminated, and default values for other parameters were selected. For 1 DGH along the size 20 for the X-, Y-, and Z-axis, the docking grid dimensions were center x = 25.0, center y = 40.0, center z = 60.0, and for 5 YTU along the size 20 for X-, Y-, and Z-axis, the docking grid dimensions were center x = \(-\)67.09, center y = 32.2, center z = 20.5. While the X-, Y-, and Z-axis along the size 20 of the grid for 6 VXX of the docking were center x = 181.11, center y = 233.11, and center z = 243.26. Before the docking experiment, polar hydrogens were given to each protein receptor, and [PERSON]'s partial atomic charges were employed to lower the energy.