Bridelia ferruginea phytocompounds interact with SARS-COV-2 drug targets: Experimental validation of corilagin contribution

Abstract

The high mutation rate of SARS-CoV-2 genomic RNA has made COVID-19 more difficult to eradicate using currently available interventions. Hence, newer pharmaceutical strategies must be developed, especially those generally complementary and alternative medicines. In the current study, stem bark of Bridelia ferruginea Benth is presented as plausible source of ethno-pharmaceuticals actionable against key SARS-CoV-2 life cycle-dependent enzymes based on in vitro inhibition studies, LC-ESI-MS characterization and molecular docking studies. Bridelia ferruginea stem bark extracted with 1 % HCL-acidified water, water, butanol, chloroform, ethyl-acetate, and petroleum ether and assayed for in vitro inhibition of SARS-COV-2-gp/human ACE2 interaction. The lowest and the highest IC50 value were recorded for ethyl-acetate (3.550 mg/L) and chloroform (413.4 mg/L) extracts respectively. When the ethyl-acetate extract was tested for SARS-COV-2 protease inhibition in vitro, papain-like protease (PL-pro, IC50=1.981 mg/L) presented as the better target in comparison to the main protease (3CL-pro, IC50=10.13 mg/L). LC/MS analysis identified corilagin and Gallocatechin-[4-O-7]-epigallocatechin as the active principles whilst molecular docking revealed the plausible poses of the compounds within the binding pockets of SARS-COV-2-glycoprotien receptor binding pocket, 3CL-pro and PL-pro. Taken together, these findings identified Bridelia ferruginea stem bark as a plausible source of anti-SARS-COV-2 phytochemicals and propose that corilagin may play important role in this activity.