A comparative study of bacteriostatic activity of synthetic hydroxylated flavonoids

Among other properties, flavonoids present a notable bacteriostatic activity. In this paper, minimal inhibitory concentrations (MICs) of 5,7,4'-trihydroxyflavanone (naringenin), 5,7-dihydroxyflavone and 2',4',4-trihydroxychalcone (isoliquitirigenin) against Staphylococcus aureus ATCC 25 923 were determined and compared to values obtained for other chalcones and flavanones previously investigated. Specific growth rates and MICs were determined by a turbidimetric kinetic method. The observed sequence MICflavone (inactive) > MIC7-hidroxyflavanone (197.6 mugml(-1)) > MIC5,7,4'trihydroxyflavanone (120 mugml(-1)) showed that the introduction of an electron donating group (-OH) causes an increase in bioactivity. On the other hand, the comparisons MIC5,7,4'-trihydroxyflavanone ( 120 mugml(-1)) >>> MIC2',4',4-trihydroxychalcone (29 mugml(-1)) and MIC5,7-dihydroxyflavone (105 mugml(-1)) >>> MIC2',4'-dihydroxychalcone (28.8 mugml(-1)) indicated that the chalcone structure is the most favourable for bacteriostatic activity within the flavonoid family.