Rosmarinus officinalis L. (Rosemary) Extracts Containing Carnosic Acid and Carnosol are Potent Quorum Sensing Inhibitors of Staphylococcus aureus Virulence

The study found that carnosic acid and carnosol, compounds in rosemary, are effective at inhibiting the quorum sensing system of Staphylococcus aureus, which is crucial for the bacterium's virulence. These compounds were able to suppress the expression of the agr operon, a key virulence factor, at low concentrations (5 µM for pure compounds and 5 µg/mL for rosemary extracts), without inhibiting bacterial growth. This suggests a potential for using rosemary extracts to reduce S. aureus virulence, particularly in atopic dermatitis, without contributing to antibiotic resistance. Rosmarinic acid, another compound in rosemary, did not show the same effects. The study highlights the possibility of developing topical rosemary extract formulations as an alternative to traditional antibiotics for treating infections related to S. aureus.