Abstract: The main antibacterial active ingredients and mechanism of Isatis indigotica were predicted based on network pharmacology. The active ingredients and targets of Isatis indigotica were screened by using TCMSP database; The related targets were searched by OMIM and GeneCards databases with the keyword of "antibacterial"; The intersection target of Isatis indigotica and bacteriostasis were collected through the Venny platform; STRING database combined with Cytoscape software were used to construct the PPI network and screen the key targets; GO function enrichment analysis and KEGG pathway enrichment analysis were carried out by using DAVID database; The key pharmacodynamic ingredients with the antibacterial targets were connected through Autodock Tools 1.5.7 software; The bacteriostatic effects against Escherichia coli(CVCC1515) and targets of the key ingredients were verified by colony counting and SDS-PAGE. A total of 33 active components of Isatis indigotica, 61 potential drug targets, 2 192 bacteriostatic targets, and 32 intersection targets of Isatis indigotica and bacteriostatic action were screened. Protein interaction network analysis revealed that 30 proteins, including TNF, TP53, CASP3, JUN, ESR1 and PTGS2 and so on, might be the key targets of antibacterial activity of Isatis indigotica. The GO functional enrichment analysis yielded 126 entries, including 86 biological process items (e.g. response to estradiol apoptotic signaling pathway, positive regulation of neuron apoptotic process), 11 cell composition items (e.g. cytoplasm, nucleus), and 29 molecular function items (e.g protein homodimerization activity, enzyme binding). KEGG pathway enrichment analysis yielded 20 related signal pathways. Molecular docking result showed that the binding energies of the key active components (beta-sitosterol, stigmasterol and acacetin) with the coding proteins of key antibacterial targets were all less than 0 kJ·mol^-1. Antibacterial experiments showed that stigmasterol was the key active component of Isatis indigotica which might down-regulated the expression of intracellular CASP3 and PTGS2 proteins. Stigmasterol of the active components of Isatis indigotica exerts antibacterial effect through the targets of CASP3 and PTGS2 which involved in TNF signaling pathway and pathways in cancer.

Key words: Isatis indigotica, network pharmacology, antibacterial activity, mechanism