Oridonin Inhibits SARS-CoV-2 Replication by Targeting Viral Proteinase and Polymerase

COVID-19 has become a global public health crisis since its outbreak in China in December 2019.Currently there are few clinically effective drugs to combat SARS-CoV-2 infection.The main protein(Mpro),papain-like protease(PLpro)and RNA-dependent RNA polymerase(RdRp)of SARS-CoV-2 are involved in the viral replication,and might be prospective targets for anti-coronavirus drug development.Here,we investigated the antiviral activity of oridonin,a natural small-molecule compound,against SARS-CoV-2 infection in vitro.The time-of-addition analysis showed that oridonin efficiently inhibited SARS-CoV-2 infection by interfering with the genome replication at the post-entry stage.Mechanistically,the inhibition of viral replication by oridonin depends on the oxidation activity of α,β-unsaturated carbonyl.Further experiments showed that oridonin not only effectively inhibited SARS-CoV-2 Mpro activity,but also had some inhibitory effects on PLpro-mediated deubiquitinating and viral polymerase-catalyzed RNA elongation activities at high concentrations.In particular,oridonin could inhibit the bat SARS-like CoV and the newly emerged SARS-CoV-2 omicron variants(BA.1 and BA.2),which highlights its potential as a pan-coronavirus antiviral agent.Overall,our data provide strong evidence that oridonin is an efficient antiviral agent against SARS-CoV-2 infection.