ABSTRACT
The NorA efflux pump is a potential drug target for reversal of resistance to selected antibacterial agents, and recently we described indole-based inhibitor candidates. Herein we report a second class of inhibitors derived from them but with significant differences in shape and size. In particular, compounds 13 and 14 are very potent inhibitors in that they demonstrated the lowest IC50 values (2 µM) ever observed among all indole-based compounds we have evaluated.
Subject(s)
Anti-Bacterial Agents/pharmacology , Drug Resistance, Bacterial/drug effects , Indoles/pharmacology , Drug Design , Indoles/chemistry , Microbial Sensitivity Tests , Staphylococcus aureus/drug effectsABSTRACT
Antibiotic resistance represents a worldwide concern, especially regarding the outbreak of methicillin-resistant Staphylococcus aureus, a common cause for serious skin and soft tissues infections. A major contributor to Staphylococcus aureus antibiotic resistance is the NorA efflux pump, which is able to extrude selected antibacterial drugs and biocides from the membrane, lowering their effective concentrations. Thus, the inhibition of NorA represents a promising and challenging strategy that would allow recycling of substrate antimicrobial agents. Among NorA inhibitors, the indole scaffold proved particularly effective and suitable for further optimization. In this study, some unexplored modifications on the indole scaffold are proposed. In particular, for the first time, substitutions at the C5 and N1 positions have been designed to give 48 compounds, which were synthesized and tested against norA-overexpressing S. aureus. Among them, 4 compounds have NorA IC50 values lower than 5.0 µM proving to be good efflux pump inhibitor (EPI) candidates. In addition, preliminary data on their ADME (absorption, distribution, metabolism, and excretion) profile is reported.
Subject(s)
Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Bacterial Proteins/antagonists & inhibitors , Drug Resistance, Microbial/drug effects , Indoles/chemistry , Indoles/pharmacology , Methicillin-Resistant Staphylococcus aureus/drug effects , Multidrug Resistance-Associated Proteins/antagonists & inhibitors , Dose-Response Relationship, Drug , Molecular Structure , Structure-Activity RelationshipABSTRACT
Long-range bonding interactions were evaluated using variable-temperature NMR spectroscopy and suitable 2'-CH2X-substituted phenylpyridines (X = Me, NMe2, OMe, F). It was found that the arylpyridyl rotational barriers were lower when electronegative atoms were bound to the α carbon of the 2' moiety. This effect was ascribed to a stabilizing interaction in the transition state due to the lone pair of the heterocyclic nitrogen with the α carbon. Computational support for this hypothesis came from CCSD(T)/6-31+G(d) calculations. Steric effects of the X moiety were ruled out by comparison of the rotational barriers of analogous biphenyls.
ABSTRACT
FMO enzymes (FMOs) play a key role in the processes of detoxification and/or bioactivation of specific pharmaceuticals and xenobiotics bearing nucleophilic centers. The N-oxide and S-oxide metabolites produced by FMOs are often active metabolites. The FMOs are more active than cytochromes in the brain and work in tandem with CYP3A4 in the liver. FMOs might reduce the risk of phospholipidosis of CAD-like drugs, although some FMOs metabolites seem to be neurotoxic and hepatotoxic. However, in silico methods for FMO metabolism prediction are not yet available. This paper reports, for the first time, a substrate-specificity and catalytic-activity model for FMO3, the most relevant isoform of the FMOs in humans. The application of this model to a series of compounds with unknown FMO metabolism is also reported. The model has also been very useful to design compounds with optimal clearance and in finding erroneous literature data, particularly cases in which substances have been reported to be FMO3 substrates when, in reality, the experimentally validated in silico model correctly predicts that they are not.
Subject(s)
Oxygenases/metabolism , Biocatalysis , Computer Simulation , Humans , Models, Molecular , Molecular Dynamics Simulation , Molecular Structure , Oxygenases/chemistry , Recombinant Proteins/chemistry , Recombinant Proteins/metabolism , Reproducibility of Results , Substrate SpecificityABSTRACT
An asymmetric synthetic strategy was designed for the preparation of the four possible diastereoisomers of 3,6-dimethyl-1-(2-methylphenyl)-4-(4-phenoxyphenyl)-4,8-dihydro-1H-pyrazolo[3,4-e][1,4]thiazepin-7-one, a non-steroidal FXR agonist, we recently discovered following a virtual screening approach. The results obtained from an AlphaScreen assay clearly demonstrated that only the isomer endowed with 4R,6S absolute configuration is responsible for the biological activity. A deep investigation of the different putative binding modes adopted by these enantiomerically pure ligands using computational modeling studies confirmed the enantioselectivity of FXR towards this class of molecules.
