Effect of lipophilicity at N-1 on activity of fluoroquinolones against mycobacteria
Related Experiment Videos
T E Renau1, J P Sanchez, M A Shapiro
1Parke-Davis Pharmaceutical Research Division, Warner Lambert Company, Ann Arbor, Michigan 48105, USA.
Abstract:
The dramatic increase in drug resistant Mycobacterium tuberculosis has caused a resurgence in research targeted toward these organisms. As part of a systematic study to optimize the quinolone antibacterials against mycobacteria, we have prepared a series of N-1-phenyl-substituted derivatives to explore the effect of increasing lipophilicity on potency at this position. The compounds, synthesized by the modification of a literature procedure, were evaluated for activity against Gram-negative and Gram-positive bacteria, Mycobacterium fortuitum and Mycobacterium smegmatis, and the results correlated with log P, pKa, and other attributes. The activity of the compounds against the rapidly growing, less hazardous organism M. fortuitum was used as a measure of M. tuberculosis activity. The results demonstrate that increasing lipophilic character by itself does not correlate with increased potency against mycobacteria. Rather, intrinsic activity against Gram-negative and/or Gram-positive bacteria is the governing factor for corresponding activity against mycobacteria.
Insights
Researchers explored how lipophilicity affects quinolone potency against drug-resistant Mycobacterium tuberculosis. Increased lipophilicity alone did not enhance antibacterial activity; intrinsic activity against other bacteria was the key factor.
Area of Science:
- Medicinal Chemistry
- Microbiology
- Drug Discovery
Background:
- Rising incidence of drug-resistant Mycobacterium tuberculosis necessitates novel antibacterial strategies.
- Quinolone antibacterials are a focus for optimizing efficacy against mycobacteria.
- N-1-phenyl substitution was investigated to modulate lipophilicity and potency.
Purpose of the Study:
- To systematically synthesize and evaluate N-1-phenyl-substituted quinolone derivatives.
- To determine the impact of increasing lipophilicity on antibacterial potency against mycobacteria.
- To correlate compound activity with physicochemical properties like log P and pKa.
Main Methods:
- Synthesis of N-1-phenyl-substituted quinolone derivatives via modified literature procedures.
- Antimicrobial susceptibility testing against Gram-negative bacteria, Gram-positive bacteria, Mycobacterium fortuitum, and Mycobacterium smegmatis.
- Correlation analysis of biological activity with physicochemical parameters (log P, pKa).
Main Results:
- Increasing lipophilicity of N-1-phenyl substituents did not inherently increase potency against mycobacteria.
- Antibacterial activity against Mycobacterium fortuitum (as a surrogate for M. tuberculosis) was not solely dependent on lipophilicity.
- Intrinsic activity against Gram-negative and/or Gram-positive bacteria was identified as the primary determinant of antimycobacterial efficacy.
Conclusions:
- Lipophilicity alone is not sufficient to enhance quinolone potency against Mycobacterium tuberculosis.
- The antibacterial spectrum against common bacteria influences efficacy against mycobacteria.
- Optimizing quinolones for mycobacterial infections requires consideration of broader antibacterial activity profiles.