Phenolic and flavonoid contents in Malva sylvestris and exploration of active drugs as antioxidant and anti-COVID19 by quantum chemical and molecular docking studies

The exploration of natural sources of antioxidant phytochemicals for human use with little toxicity gained worldwide attention. The preliminary screening of Malva sylvestris extracts revealed that its phytochemicals such as polyphenols, flavonoids and tannins, have high therapeutic potential. The total phenolic/flavonoids compounds of Malva sylvestris were extracted and isolated using bioassay guidelines, as well as in-silico studies. The extracts radical scavenging activity was further investigated using 1-diphenyl-2-picrylhydrazyl (DPPH) and nitric oxide (NO) radical bioassays. The antioxidant potentials of various fractions were compared to standard antioxidants such as ascorbic acid and quercetin. The dichloromethane extracts of Malva sylvestris exhibited the antiradical activity against DPPH and NO with radical scavenging activities (RSA) of 88.52 and 91.05% with IC50 values 22.11 and 19.01 µg/mL respectively. Bio guided isolation form the dichloromethane sub fractions that afforded twelve phytochemicals. Furthermore, the frontier molecular orbitals (FMO), several molecular descriptors, electron affinity, ionization potential and molecular electrostatic potential (MEP) have been discussed to probe the active sites of various phytochemicals. A systematic study of isolated drugs was conducted, as well as docking, frontier molecular orbitals energies, active sites and molecular descriptors were compared with drugs currently used against COVID19 namely, dexamethasone, hydroxychloroquine, favipiravir and remdesivir. For the first time, through molecular docking approach, the inhibitions of these plant phytochemicals with NADPH were recorded to show antioxidant behavior and to explore anti-SARS-CoV-2 using core protease (6LU7) protein.