Exploration of 5‐(5‐nitrothiophen‐2‐yl)‐4,5‐dihydro‐1H‐pyrazoles as selective, multitargeted antimycobacterial agents

Abstract

We report the biological evaluation of 5‐(5‐nitrothiophen‐2‐yl)‐4,5‐dihydro‐1H‐pyrazole derivatives against bacteria, eukaryotic cell lines and the assessment of their mechanisms of action to determine their prospects of being developed into potent antituberculosis agents. The compounds were evaluated for their antibacterial property against Mycobacterium tuberculosis H37Rv, multidrug‐resistant M. tuberculosis, Mycobacterium bovis BCG, Mycobacterium aurum, Escherichia coli, and Staphylococcus aureus using high‐throughput spot‐culture growth inhibition assay. They were found to be selective toward slow‐growing mycobacteria and Gram‐positive bacteria. In M. bovis BCG, they exhibited a bactericidal mode of action. Cytotoxicity was assessed in human THP‐1 and murine RAW 264.7 cell lines, and the compounds showed a lower cytotoxicity potential when compared with their antibacterial activity. They were found to be excellent whole‐cell efflux pump inhibitors of the mycobacterial surrogate M. aurum, performing better than known efflux pump inhibitor verapamil. The 5‐nitrothiophene moiety was identified for the first time as a prospective inhibitor scaffold of mycobacterial arylamine N‐acetyltransferase enzyme, which is the key enzyme in metabolizing isoniazid, a first‐line antituberculosis drug. The two aforementioned findings make the compounds potential hits in the development of adjunctive tuberculosis therapy.

Multitargeting Compounds: A Promising Strategy to Overcome Multi-Drug Resistant Tuberculosis

“…Through this analysis they selected seven scaffolds, three of them showing significant activity against both enzymes (Figure 4). Moreover, the three compounds displayed interesting antimycobacterial activity against M. smegmatis, both planktonic and in biofilm, demonstrating the validity of this approach to achieve novel drug candidates [28].…”

“…For instance, the recently described 5-(5-nitrothiophen-2-yl)-4,5-dihydro-1H-pyrazoles, have been selected as potential inhibitors of the arylamine N-acetyltransferase enzyme, and were found to be also potent efflux pump inhibitors [27,28]. Another example is the case of the tetrahydroisoquinoline compounds, that have been selected as inhibitors of the ATP-dependent MurE ligase, but were found to have pleiotropic mechanisms of action, not fully clarified yet [29].…”

Mycobactin Analogues with Excellent Pharmacokinetic Profile Demonstrate Potent Antitubercular Specific Activity and Exceptional Efflux Pump Inhibition

“…Compounds 44 and 49 were then subjected to cytotoxicity evaluation using RAW 264.7 and THP-1 cell lines following the REMA assay protocol. 44,48 The concentration (μg/mL) required for 90% growth inhibition (GIC 90 ) was determined and was used to calculate the selectivity index (SI). Both compounds exhibited selective toxicity toward M. smegmatis, M. aurum, M. bovis BCG, and M. tuberculosis (Table 6).…”

3-(5-Nitrofuran-2-yl)prop-2-en-1-one Derivatives, with Potent Antituberculosis Activity, Inhibit A Novel Therapeutic Target, Arylamine N-acetyltransferase, in Mycobacteria

“…The compounds were analyzed using HT-SPOTi, as described previously [ 18 ]. Briefly, the compounds were dissolved in dimethyl sulfoxide, DMSO (Sigma Aldrich, London, UK) to achieve a concentration of 50 mg/mL.…”