Potential of Terminalia Arjuna as a Promising PhytoremedyAgainst COVID-19: DPPH Scavenging, Catalase Inhibition and Molecular Docking Studies

Stem and bark of the tree Terminalia arjuna Wight &Arn. (Combretaceae) has been documented to exhibit therapeutic properties like cardiotonic, anticancer, antiviral, antibacterial, antifungal, hypocholsteremic, hypolipidemic and anti-coagulant. In previous studies, ethanolic extract of T.arjunabark effectively inhibited catalase activity along with demonstration of DPPH radical scavenging activity. Further,four known oleananetriterpenoids type compounds viz., oleanolic acid, arjunolic acid, arjunolitin, arjunetin were isolated from ethaolic bark extract and the structures of which were elucidated using 1 H, 13C NMR, HR-ESIMS, IR and compared with literature data. Of the various compounds, Arjunetin showed significant inhibition of catalase activity as compared to the other compounds and most probably conferring antibacterial and antiviral property of the extract. In the present study, considering the currently on going viral pandemic of SARS-CoV-2 and the need for an effective antiviral agent, T.arjuna with its cardioprotective ability and inhibitory action against catalase presents to be a promising candidate against the virus. Molecular docking studies showed that arjunetin binds to protease of SARS-CoV-2 (3CL, PL andRdRP) and had higher binder energy values (3CL, -8.4 kcal/mol; PL, -7.6 kcal/mol and RdRP, -8.1 kcal/mol as compared with FDA approved protease inhibitor drugs lopinavir (3CL, -7.2 kcal/mole and PL -7.7 kcal/mole) and Remdesivir (RdRP -7.6 kcal/ mole). We conclude that there is profound evidence of arjunetin as a potential protease inhibitor of SARS-CoV-2 which is comparable to FDA approved antivirals Lopinavir and Remdesivir and can serve as a candidate for drug development against SARS-CoV-2.