In Silico Studies on Binding of Vernonia Amygdalina Phytochemicals to Main Protease (Mpro) of SARS-CoV-2

Objectives: The corona virus SARS-CoV-2 emerged in late December 2019 and since then has created a global pandemic, which shows no signs of abating as of this date. As of July 9 2021, the virus has been responsible throughout the world for 186,357,958 infections and 4.026,907 deaths. Any drugs against this virus remains to be discovered. Several vaccines have been approved by the World Health Organization but administering the vaccines have been difficult because of production shortages and distribution anomalies between rich and poor nations. Towards finding a new and affordable antiviral drug against SARS-CoV-2, we evaluated the in silico binding capabilities of several phytochemicals of an African plant, Vernonia amygdalina Del. (Asteraceae) to the main protease (Mpro) of SARS-CoV-2, which plays an integral part in the replication of the virus. Methods: Binding of phytochemicals to Mpro were carried out through molecular docking (blind) with the help of AutoDockVina program. Results: We observed that of the ten phytochemicals studied, seven showed moderate to strong binding affinities to Mpro. Furthermore, the binding of these seven phytochemicals in each case was to at least one of the two amino acids forming the catalytic dyad of Mpro, indicating that the Mpro catalytic site was involved. The highest binding affinity was shown by luteolin7-O-glucuronide with a binding energy (ΔG) of -8.7 kcal/mol. Conclusion: Binding to the catalytic site can lead to Mpro inhibitory activity. Since the protease plays an essential part in viral replication, the phytochemicals from Vernonia amygdalina merit further antiviral activity studies for their potential as lead compounds or drugs.