4. DISCUSSION:
Mushrooms are found to possess antiviral activity also they are reviewed to have therapeutic effect against inflammation and pneumonic superinfection against recent global pandemic of COVID-1929. We focused on the edible mushrooms which are commonly available in the markets rather than deep search in the forest and examined the main compounds which has broad activity against upper respiratory viruses via literature review and found out four compounds fall into the above categories mentioned. And targets Main Protease (Mpro) and Spike Protein were chosen to see the inhibitory effect of the ligands on the pre-entry stage and protein cleavage stage in the life cycle of the SARS-CoV-2 virus leading to disruption and decrease of the viral load in vivo . And also due to recent outbreak of different variants, whose mutation took place in the spike protein of the SARS-CoV-2 virus, thankfully they carry similar inhibition sites and the most mutation took place in the furin loops and so the spike protein was chosen as the target of interest 30.
The ligands were successfully docked against inhibition site of Main Protease with following docking scores -1.068 Kcal/ mol for Eritadenine, -3.617 Kcal/ mol for Gallic Acid, -0.420 Kcal/ mol for Ergosterol Peroxide and -5.035 Kcal/ mol for Pleuran respectively. Similarly, the ligands also docked successfully against Spike Protein with docking scores such as -0.783 Kcal/ mol for Eritadenine, -2.140 Kcal/ mol for Gallic Acid, 1.027 Kcal/ mol for Ergosterol Peroxide and -5.241 Kcal/ mol for Pleuran respectively. And the docked complexes exhibited convergence within 10 ns of molecular dynamics whose RMSD values ranged from 1Å to 2.5Å for all ligands which has been bound to Main protease and RMSF values ranged from 5Å to 6.5Å. Similarly, RMSD values ranged from 1Å to 2Å and also the RMSF values ranged from 0.5Å to 3.5Å respectively in the Spike Protein target, therefore all protein ligand complexes are stable in both targets according to results in RMSD analysis as well as in RMSF analysis. All complexes expressed strong hydrogen bonding throughout the time of molecular dynamics simulation through which it gives an inference that the protein ligand complexes are stable 31. All other compounds except pleuran did express good druggability properties during in silico ADME analysis. Similarly, during target analysis the compounds except pleuran showed good targeting against protease enzymes. But in literature pleuran has been found to express good activity against protease enzymes and also effective in progressivity towards being a drug and also has immunomodulatory effect 32. Based on toxicity all ligands expressed minimum toxicity levels except eritadenine but are mostly non-toxic to the important organs such as liver, heart and kidneys based on the simulation projected in the results.
When comparing these compounds with already repurposed drugs such as Lopinavir , Famciclovir, Drunavir, Amprenavir and N3 whose docking scores are -9.918 Kcal/ mol, -7.546 Kcal/ mol, -7.505 Kcal/ mol, -8.655 Kcal/ mol, -7.5 Kcal/ mol respectively. And the repurposed drugs which are mentioned above exhibit higher docking score than the compounds of interest 33, 34. The ligand of interest has lesser docking score and has more significance. Therefore the compounds which were studied can be used for therapeutic purposes against COVID-19. We the authors also propose as the inhibition site of all spike proteins in variants of concern are similar, one particular drug or a compound which has been studied to have inhibitory effect can be used to treat SARS-CoV-2.