Diterpenoid and C20 diterpenoid alkaloid as a potent inhibitor of SARS-CoV-2 main protease (M pro ): from Piper barberi Gamble, an endemic and endangered species of Southern Western Ghats.

The present study investigated the phytochemicals and in silico anti-nCoV properties of Piper barberi , an endangered and endemic species of Southern Western Ghats. Using conventional soxhlet extraction method, the leaf and stem were extracted separately with methanol (PBLM and PBSM). The bioactive compounds from the extracts were identified using HR-LCMS/MS-qTOF analysis. These compounds were subjected to various in silico analyses to identify potential drug candidates against nCoV. The HR LCMS/MS analysis of PBLM and PBSM revealed the presence of phenols, flavonoids, alkaloids, and terpenoids in it and this is the first report of the phytoconstituents present in the species P. barberi . All the identified bioactive compounds were subjected to predict ADMET. Out of 49 identified compounds, only 31 passed drug-likeness properties and toxicity tests. Molecular interaction studies were conducted using the AutoDockTools 4.2.6., which showed that only 13 compounds exhibited acceptable binding affinity with the nCoV target M ^pro . Structural stability and binding free energy analyses of the five compounds with the higher binding affinity indicated that the bioactive compounds Hetisine and Ajaconine are stable with both hydrogen bonds and hydrophobic interactions. Hetisine shows stable binding among these two compounds with two hydrogen bond interactions with the crucial catalytic dyad residue (His41). Thus, this study concludes that these compounds might potentially be used as an alternative drug candidate for managing nCoV. However, further experimental validation, including in vitro and in vivo assays, is required to substantiate the results.Communicated by Ramaswamy H. Sarma.