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 mu M, and weak or no activity against fungal strains tested. Kurarinol (6) was a potent inhibitor of sortase A, with an IC50 value of 107.7 +/- 6.6 mu M. A preliminary structure-activity relationship, including essential structural requirements, is described.