Identification of Main Protease of Coronavirus SARS-CoV-2 (M^pro) Inhibitors from Melissa officinalis

Background: The recent outbreak of Coronavirus SARS-CoV-2 (Covid-19), which has rapidly spread around the world in about three months with tens of thousands of deaths recorded so far is a global concern. An urgent need for potential therapeutic intervention is of necessity. M^pro is an attractive druggable target for the development of anti-COVID-19 drug development. Methods: Compounds previously characterized by Melissa officinalis were queried against the main protease of coronavirus SARS-CoV-2 using a computational approach. Results: Melitric acid A and salvanolic acid A had higher affinity than lopinavir and ivermectin using both AutodockVina and XP docking algorithms. The computational approach was employed in the generation of the QSAR model using automated QSAR, and in the docking of ligands from Melissa officinalis with SARS-CoV-2 Mpro inhibitors. The best model obtained was KPLS_Radial_ 28 (R² = 0.8548 and Q²=0.6474, which was used in predicting the bioactivity of the lead compounds. Molecular mechanics based MM-GBSA confirmed salvanolic acid A as the compound with the highest free energy and predicted bioactivity of 4.777; it interacted with His-41 of the catalytic dyad (Cys145-His41) of SARS-CoV-2 main protease (M^pro), as this may hinder the cutting of inactive viral protein into active ones capable of replication. Conclusion: Salvanolic acid A can be further evaluated as a potential M^pro inhibitor.