The recently emerged COVID-19 has been declared a pandemic by the World Health Organization as to date; no therapeutic drug/vaccine is available for the treatment. Due to the lack of time and the urgency to contain the pandemic, computational screening appears to be the best tool to find a therapeutic solution. Accumulated evidence suggests that many phyto-compounds possess anti-viral activity. Therefore, we identified possible phyto-compounds that could be developed and used for COVID-19 treatment. In particular, molecular docking was used to prioritize the possible active phyto-compounds against two key targets namely RNA dependent RNA polymerase (RdRp) and main protease (M^pro) of SARS-CoV-2. In this study, an antiviral drug- Remdesivir (RdRp inhibitor) and Darunavir (M^pro inhibitor) are used as reference drugs. This study revealed that phyto-molecules- Mulberroside-A/C/E/F, Emblicanin A, Nimbolide, and Punigluconin showed high binding affinity against RdRp while Andrographolides, Mulberrosides, Anolignans, Chebulic acid, Mimusopic acid, and Punigluconin showed better binding affinity against M^pro as compared with the reference drug. Furthermore, ADME profiles validated the drug-likeness properties of prioritized phyto-compounds. Besides, to assess the stability, MD simulations studies were performed along with reference inhibitors for M^pro (Darunavir) and RdRp (Remdesivir). Binding free energy calculations (MM-PBSA) revealed the estimated value (ΔG) of M^pro_Darunavir; M^pro_Mulberroside E; RdRp_Remdesivir and RdRp_Emblicanin A were −111.62 ± 6.788, −141.443 ± 9.313, 30.782 ± 5.85 and −89.424 ± 3.130 kJmol⁻¹, respectively. Taken together, the study revealed the potential of these phyto-compounds as inhibitors of RdRp and M^pro inhibitor that could be further validated against SARS-CoV-2 for clinical benefits. Communicated by Ramaswamy H. Sarma

Novel coronavirus SARS-CoV-2 has infected millions of people with thousands of mortalities globally. The main protease (Mpro) is vital in processing replicase polyproteins. Both the CoV’s Mpro shares 97% identity, with 12 mutations, but none are present in the active site. Although many therapeutics and vaccines are available to combat SARS-CoV-2, these treatments may not be practical due to their high mutational rate. On the other hand, Mpro has a high degree of conservation throughout variants, making Mpro a stout drug target. Here, we report a detailed comparison of both the monomeric Mpro and the biologically active dimeric Mpro using MD simulation to understand the impact of the 12 divergent residues (T35V, A46S, S65N, L86V, R88K, S94A, H134F, K180N, L202V, A267S, T285A and I286L) on the molecular microenvironment and the interaction between crucial residues. The present study concluded that the change in the microenvironment of residues at the entrance (T25, T26, M49 and Q189), near the catalytic site (F140, H163, H164, M165 and H172) and in the substrate-binding site (V35, N65, K88 and N180) is due to 12 mutations in the SARS-CoV-2 Mpro. Furthermore, the involvement of F140, E166 and H172 residues in dimerization stabilizes the Mpro dimer, which should be considered. We anticipate that networks and microenvironment changes identified here might guide repurposing attempts and optimization of new Mpro inhibitors.