Structure-activity relationship study on the antibacterial properties of B-ring brominated 1,3-dithiolium flavonoids.

The synthesis of twelve new tricyclic flavonoids, with a bromine substituent at the ortho, meta or para position of the B ring, from the corresponding flavanones is described. Four structures were unambiguously proven by X-ray analysis. An SAR study of the antibacterial properties against Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, and Klebsiella pneumoniae was performed and revealed compound- and strain-dependent activity, with 5h showing the most promising broad-spectrum antibacterial profile, while 5f, 5i and 5j also exhibited strong activity against selected strains. Cytotoxicity assays showed high cell viability (>90%) at 0.001 mg mL-1 for all compounds, indicating dose-dependent cytotoxicity. These findings highlight 5h as a promising candidate for further investigation.