Ethnopharmacological relevance: Cochlospermum regium, known as "algodãozinho", is an important plant belonging to Brazilian biodiversity used in traditional medicine to treat infections, wounds and skin conditions.

Aim of the study: To assess the effects of aqueous and ethanolic extracts from C. regium leaves on methicillin-resistant Staphylococcus aureus planktonic cells and biofilm formation.

Material and methods: The phytochemical characterization of the extracts was carried out by quantification of flavonoids, phenols and tannins and HPLC-DAD. Minimum inhibitory concentrations, cell viability, and enzyme activity inhibition were determined in planktonic cells exposed to C. regium extracts. The effect of the extracts on biofilms was assessed by quantifying colony-forming units (CFUs) and the extracellular matrix, and by visualizing the biofilm structure using scanning electron microscopy.

Results: Leaf extract contents showed high concentration of phenols and the gallic and ellagic acids were identified. The extracts showed potent antimicrobial activities at concentrations ranging from 62.5-250 μg/mL, and decreased coagulase activity. In addition, the extracts prevented biofilm formation, and the aqueous extract completely inhibited its formation.

Conclusions: C. regium extracts stand out as promising alternative treatments for the prevention and treatment of methicillin-resistant Staphylococcus aureus infections.

Keywords: CA-MRSA; HA-MRSA; antibacterial; antibiofilm; medicinal plant.