In vitro sortase a inhibitory and antimicrobial activity of flavonoids isolated from the roots of Sophora flavescens

A series of flavonoids ( 1 – 14 ) was isolated from the roots of Sophora flavescens . We evaluated their ability to inhibit both microbial growth and sortase A, an enzyme that plays a key role in cell wall protein anchoring and virulence in Staphylococcus aureus . Most prenylated flavonoids ( 7 – 13 ) displayed potent inhibitory activity against gram-positive and gram-negative bacteria except E. coli , with minimum inhibitory concentrations values ranging from 4.40 to 27.7 μM, and weak or no activity against fungal strains tested. Kurarinol ( 6 ) was a potent inhibitor of sortase A, with an IC 50 value of 107.7 ± 6.6 μM. A preliminary structure-activity relationship, including essential structural requirements, is described.