Abstract: In this study, the composition and content of polyphenols in Flos Sophorae Immaturus (FSI) were analyzed by high performance liquid chromatography (HPLC), and their antibacterial activity against the non-pathogenic standard type strain Escherichia coli ATCC 25922 was explored. Additionally, the antibacterial mechanism was elucidated from multiple aspects, including cell wall and membrane alterations, morphological characteristics, metabolic pathways, and oxidative stress responses in E. coli, and it was verified by molecular docking analysis. The results showed that the polyphenol extract contained 10 polyphenolic compounds and exhibited significant antibacterial activity against E. coli. Its minimum inhibitory concentration (MIC) and minimum bactericidal concentration were 12.5 and 100 mg/mL, respectively, and this effect was concentration-dependent. The mechanistic study demonstrated that at MIC, FSI polyphenols mainly damaged the cell membrane and cell wall integrity and reduced their resistance. Simultaneously, these compounds inhibited the biosynthesis of RNA, lipid and protein, ultimately resulting in bacterial cell death. Moreover, FSI polyphenols potentially targeted the 3-hydroxyacyl-[acyl-carrier-protein] dehydratase (fabZ) and acriflavine resistance regulator (acrR) proteins in E. coli. At 2 MIC and 4 MIC, FSI polyphenols mainly triggered excessive accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA), disrupted membrane structure and function, inhibited the synthesis of RNA, protein and peptidoglycan, reduced bacterial resistance, and ultimately caused bacterial death. Furthermore, FSI polyphenols may target the 2,5-diketo-D-gluconic acid reductase A (dkgA) protein in E. coli. This study lays the basis for the application of FSI polyphenols as an antibacterial agent against foodborne pathogenic E. coli, and provides theoretical support the development of polyphenol-based natural antibacterial agents.

Key words: polyphenol extract from Flos Sophorae Immaturus; Escherichia coli; bacteriostasis mechanism; resistance