Antimicrobial activity and synergism of some substituted flavonoids.

Natural and synthetic substituted chalcones, flavones and flavanones were tested for antibacterial activity. In order to determine synergism, new combinations of substituted flavonoids against Staphylococcus aureus, Escherichia coli and Enterobacter aerogenes were assayed. The results allow us to establish relationships between antimicrobial effect of the compounds and membrane structures of these microorganisms. When flavonoid combinations were employed a stronger effect was found against E. coli than against S. aureus. This fact is due to the existence of porins in the outer membrane of G(-)-bacteria. The compound that acts as enhancer acts by blocking the charges of amino acids in the porins and thus facilitates the passage of the other compound by diffusion into the bacterial cell.