Time Stability Studies of Quinazoline Derivative Designed to Fight Drug Resistance Acquired by Bacteria

The 3-[2-(dimethylamino)ethyl]-6-nitroquinazolin-4(3H)-one (BG1188) may modify the antibiotic susceptibility of human Gram-negative bacteria which present multidrug resistant phenotype. This application requires to know the time stability of BG1188 solutions. This paper reports for the first time about the time stability of the BG1188 solutions measured by optical absorption; the solvents were ultrapure de-ionized water and dimethyl sulfoxide (DMSO). In ultrapure water, BG1188 concentration varied between 2×10-3M (stock solution) and 10-6M, at pH = 6.7. In DMSO, the concentration was 10-3M (recommended by higher activity on bacteria). Solutions in ultrapure water were kept in dark at 4°C and measured at room temperature (22°C). The ultraviolet-visible (UV-Vis) absorption spectra have shown that only monomer forms were present in solutions. One of the obtained results is that the time evolution of the absorption spectra at 10-3M in ultrapure water shows a reproducibility within the measuring errors (±1.045%) for time intervals up to 1032 hours (more than 40 days) after preparation, showing a high stability of BG1188 solutions; generally, samples are stable within the experimental errors at concentrations higher than 10-5M, but the stability time interval may be variable: from 119 days at 10-4M to 34 days at 10-5M. As for solutions in the DMSO, the absorption spectra show that the samples exhibit modifications immediately after preparation, in terms of peak intensities and shapes, so that the BG1188 solutions in DMSO may be considered as unstable.