Prenylated flavonoids and derivatives isolated from the root barks of Sophora flavescens as potent antibacterial agents against Staphylococcus aureus

Sophora flavescens Alt. is widely used in traditional medicine as a functional food ingredient for the treatment of diseases, used as antipyretics, pesticide, and antibacterial agents to treat pruritus and other skin infections. In this study, ten new prenylated flavonoids and analogs (1–10) including nine flavanones (1–6 and 8–9), one flavanol (7), and one chromone (10), along with thirteen known flavonoids (11–23), have been obtained from the root barks of Sophora flavescens. Their structures were elucidated through comprehensive spectroscopic analysis. Bioactive assay discovered that 2R-sophoflavonoid A (2) possessed an excellent ability to suppress the growth of Staphylococcus aureus (MIC = 2 µg/mL) and low cytotoxicity toward the LO2 cells. Furthermore, the time-kill curves showed compound 2 had the ability to kill S. aureus rapidly. The bactericidal rate of compound 2 was faster than that of ampicillin at the concentration of 10 times MIC, and the bactericidal time of compound 2 was 3 min while ampicillin for 90. Crystal violet assay showed that compound 2 not only inhibited the formation of biofilms but also eradicated mature biofilms in a concentration-dependent mode. Preliminary mechanistic studies revealed that 2 possessed grateful antibacterial effects through damaging the membrane integrity, stimulating ROS generation, and reducing bacterial metabolism. In summary, these results suggested that compound 2 was a potential lead compound against S. aureus and can also be a candidate for a disinfectant.