ACE2 and viral infectious disease: Notably, candidate silymarin compounds, such as silybin A/B and silymonin, display triplicate functions against SARS-CoV-2 infection, including directly binding with the host receptor ACE2 to inhibit SARS-CoV-2 entry to the host cells, directly binding with viral proteins RdRp and helicase to inhibit virus replication and proliferation, and regulating host immune response to indirectly inhibit viral infection.