Syntheses and antibacterial activity of soluble 9-bromo substituted indolizinoquinoline-5,12-dione derivatives

In our previous research, 9-bromo indolizinoquinoline-5,12-dione 1 has been found to be a good anti-MRSA agent. However, it had very low bioavailability in vivo possibly due to its low solubility in water. In order to obtain the derivatives with higher anti-MRSA activity and good water solubility, twenty eight bromo-substituted indolizinoquinoline-5,12-dione derivatives were synthesized in the present study. The antibacterial activity of the synthesized compounds was evaluated against one gram-negative and some gram-positive bacterial strains including 100 clinical MRSA strains. The UV assays were carried out to determine the solubility of six active compounds 16, 21, 23 and 27–29 . The most potent compound 28 exhibited strong activity against clinical MRSA strains with both MIC 50 and MIC 90 values lower than 7.8 ng/mL. Compound 27 had good water solubility of 1.98 mg/mL and strong activity against clinical MRSA strains with MIC 50 value of 63 ng/mL and MIC 90 value of 125 ng/mL, 16-fold higher than that of Vancomycin .