Antibacterial activity and proposed action mechanism of a new class of synthetic tricyclic flavonoids

AIMS: This study reports on the inhibitory and bactericidal properties of a new synthetized flavonoid. METHODS AND RESULTS: Tricyclic flavonoid 1 has been synthesized through a two‐step reaction sequence. The antimicrobial effects were tested using the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. Also DNA fragmentation assay, fluorescence microscopy and SEM were used to study the mechanism of action. Our tested flavonoid displayed a strong antimicrobial activity with MIC and MBC values as low as 0·24 μg ml⁻¹ against Staphylococcus aureus and 3·9 μg ml⁻¹ against Escherichia coli. Flavonoid 1 displayed antimicrobial properties, causing not only the inhibition of bacterial growth, but also killing bacterial cells. The mechanism of action is related to the impairment of the cell membrane integrity and to cell agglutination. CONCLUSIONS: Tricyclic flavonoid 1 was found to have a stronger antibacterial effect at lower concentrations than those described in the earlier reports. SIGNIFICANCE AND IMPACT OF THE STUDY: Based on the strong antimicrobial activity observed, this new tricyclic flavonoid has a good potential for the design of new antimicrobial agents.