Activity of ring-substituted 8-hydroxyquinoline-2-carboxanilides against intestinal sulfate-reducing bacteria Desulfovibrio piger

Desulfovibrio genus is dominant among sulfate-reducing bacteria (SRB) in the large intestine of healthy people and animals. It is mostly isolated from patients with inflammatory bowel disease (IBD) and can be involved in the disease initiation. Primary in vitro screening of 8-hydroxyquinoline-2-carboxanilides was performed against Desulfovibrio piger Vib-7 representing SRB. The most effective compounds with MIC90/MBC values in the range of 17-23 mu M/20-23 mu M, respectively, were substituted in C'((3)) by CF3, OCH3, CH3 and in C'((4)) by CF3. Their activity was twofold higher than that of ciprofloxacin. These compounds did not express any significant cytotoxic effect on THP-1 cells up to the tested concentration of 30 mu M. The antibacterial efficacy of the most active C'((3))-substituted compounds practically did not change with increasing compound lipophilicity, indicating that this position of substitution is favorable for significant antimicrobial effect, while the antibacterial activity of most of C'((2)) and C'((4))-substituted derivatives decreased linearly with increasing compound lipophilicity. In addition, the dependence of activity on electronic Hammett's sigma parameter of the substituent R was quasi-parabolic for the most effective C'((3))-substituted compounds.