Flavonoids as Auxiliary Means in the Therapy and Prevention of COVID-19: Part II. Potential Targets

The second part of this review is concerned with analysis of the possible effect of flavonoids on the SARS-CoV-2 enzymes directly involved in the infectious cycle of the virus, taking into account the peculiarities of host cell functioning. The results of virtual screening of flavonoids in conditions of molecular docking and molecular modeling are considered in this review. In the experiments in silico, binding of flavonoids to three SARS-CoV-2 enzymes was analyzed: 3-chymotrypsin-like protease (3CL^pro), papain-like protease (PL^pro), and RNA-dependent RNA polymerase (RdRp). A high affinity of binding of flavonoids to these viral proteins (most pronounced for flavonols, flavones, and flavan-3-ols and often superior to the control antiviral drugs) was demonstrated. The process of penetration of SARS-CoV-2 into the cell and host cell components involved in the infectious cycle of the virus, as well as the possible effect of flavonoids on them, are considered separately.