Abstract
Pathogenic coronavirus, including COVID-19, threatens human health, and there have been strong demands for efficient therapeutics. Cordyceps militaris is a medicinal mushroom that has long been used for immune enhancement, anticancer, and antiviral effects. Therefore, the inhibitory potentials of constituents of C. militaris against COVID-19 were analyzed using various virtual screening analyses. Among ten constituents of C. militaris, cordycepin, the major component, and 3'-deoxyuridine and 2'-O-methyl-adenosine showed strong binding affinity to M(pro), a potential target for COVID-19 therapeutics. Considering the structure-activity relationship, nucleosides having deoxyribose and methoxyribose moiety are important for the affinity to M(pro). Cordycepin is also bound to M(pro) mutants, and the binding mechanisms between cordycepin and M(pro) were investigated further by MD simulation and MM/PBSA analysis. Principal component analysis also confirmed the conformational change of M(pro) by cordycepin, which inhibits the function of M(pro). In vitro, the efficacy of cordycepin was measured using Vero cells infected with SARS-CoV-2, which showed excellent inhibition with an IC(50) value of 29 μM. Conclusively, the constituents of C. militaris are expected to inhibit SARS-CoV-2 replication through binding to M(pro). Therefore, C. militaris can be an essential therapeutic for coronavirus through the synergistic effect of its constituents.