Chemical constituents, antibacterial activity and mechanism of <i>Paeonia suffruticosa</i> Andr. buds extract against <i>Staphylococcus aureus</i> and <i>Escherichia coli</i> O157:H7

Abstract

Sixteen chemical constituents of <i>Paeonia suffruticosa</i> Andr. buds extract (PSABE) were identified by UHPLC-PDA-Q/TOF-MS, belonging to phenolic acids, flavonoids, monoterpene glycosides and gallotannins. PSABE exhibited significant antibacterial activity against six tested microorganisms. Particularly, it showed the most efficient antibacterial effect against <i>Staphylococcus aureus</i> and <i>Escherichia coli</i> O157:H7, which the minimum inhibition concentration (MIC) and minimum bactericide concentration (MBC) both were 1.56 mg/mL and 6.25 mg/mL, respectively. The results showed that PSABE induced obvious alterations in membrane fatty acid composition of <i>S. aureus</i> and <i>E. coli</i> O157:H7, such as the decrease of unsaturated fatty acids, leading to the reduce of membrane fluidity. Membrane integrity was destroyed and cell morphology was obviously changed with PSABE. Furthermore, the transcription level of virulence factors was inhibited in the presence of PSABE. These results indicated that PSABE mainly exerted antibacterial effect by damaging cell membrane and inhibiting transcription level of virulence factors.[Figure: see text].