Antibacterial effects of trisubstituted quinazoline derivatives

Five trisubstituted quinazolones and eight trisubstituted quinazoline-4-thi ones have been tested for antibacterial effects by a microdilution method. Four derivatives exerted a significant effect on E. coli, P, aeruginosa, S, aureus and B. subtilis (IC50 < 100 mg/L). In the bacterium P. aeruginosa s ix quinazolines showed a higher antibacterial effect than ampicillin. The m ost sensitive to the effects of the quinazolines was S. aureus; a concentra tion of 100 mg/L of six derivatives induced a bacteriostatic effect on S. a ureus. The quinazoline-4-thiones were generally more active than the quinaz olones. All the tested concentrations of the four most effective quinazolin es influenced the specific growth rate.