To investigate the material basis and mechanism of Liupao tea on preventing COVID-19 by network pharmacology and molecular docking.The active ingredients and targets of Liupao tea were searched through the literature and the TCMSP databases and the network between the two was built by Cytoscape 3.7.1.Then using GenCards platform to predict the disease targets,mapping the common targets between Liupao tea and disease.The common targets were imported into the STRING database for exploring the protein-protein interaction.Core targets were enriched by gene ontology (GO) enrichment analysis and KEGG (kyoto encyclopedia of genes and genomes) pathway enrichment analysis using DAVID database etc..Finally,the screened active components were docked with the receptor protein SARS-CoV-2 3CL hydrolase (Mpro).Six active ingredients of Liupao tea were screened,such as (-)-epigallocatechin gallate (EGCG),(+)-catechin,(-)-catechin gallate,α-spinasterol,pelargonidin chloride and squalene,and 156 targets were identified.Among them,there were 112 common targets and 38 core targets with COVID-19.GO enrichment analysis (P<0.01) involved lipopolysaccharide,cell response to hypoxia,etc..And the KEGG pathway enrichment analysis (P<0.01)was conducted to obtain the HIF-1,IL-17,T cell receptor and other signaling pathways associated with COVID-19.The results of molecular docking showed that the active ingredients of Liupao tea were well bound to the receptor protein Mpro.The active ingredients of Liupao tea may control HIF-1,IL-17,T cell receptors signaling pathways by binding Mpro hydrolase and acting on inflammation and immune related targets such as MAPK1,TNF to prevent COVID-19.The EGCG of Mpro activity was determined ,and the IC50 was 3.4 μmol/L,which confirmed that EGCG was a certain inhibition effect on Mpro.

The outbreak of coronavirus disease (COVID-19) caused by SARS-CoV-2 virus continually lead to worldwide human infections and deaths. Currently, there is no specific viral protein-targeted therapeutics. Viral nucleocapsid protein is a potential antiviral drug target, serving multiple critical functions during the viral life cycle. However, the structural information of SARS-CoV-2 nucleocapsid protein remains unclear. Herein, we have determined the 2.7 Å crystal structure of the N-terminal RNA binding domain of SARS-CoV-2 nucleocapsid protein. Although the overall structure is similar as other reported coronavirus nucleocapsid protein N-terminal domain, the surface electrostatic potential characteristics between them are distinct. Further comparison with mild virus type HCoV-OC43 equivalent domain demonstrates a unique potential RNA binding pocket alongside the -sheet core. Complemented by binding studies, our data provide several atomic resolution features of SARS-CoV-2 nucleocapsid protein N-terminal domain, guiding the design of novel antiviral agents specific targeting to SARS-CoV-2.