Nitroimidazole-containing compounds and their antibacterial and antitubercular activities

ε-Poly-l-lysine: A Naturally Occurring Biodegradable Polypeptide for Selective Detection of 5-Nitroimidazole Antibiotics in Animal Products and Living Cells via Fluorescence

The 5-nitroimidazole (5-NI) class of antibiotics, such as metronidazole, ornidazole, secnidazole, and tinidazole, are widely used to prevent bacterial infection in humans and livestock industries. However, their overuse contaminates the farmed animal products and water bodies. Hence, a selective, sensitive, and cost-effective method to detect 5-NI antibiotics is the need of the hour. Herein, we report a rapid, inexpensive, and efficient sensing system to detect 5-NI drugs using an as-prepared solution of ε-poly-l-lysine (ε-PL), a naturally occurring and biodegradable homopolypeptide that has an intrinsic fluorescence via clustering-triggered emission. The low nanomolar detection limit (3.25-3.97 nM) for the aforementioned representative 5-NI drugs highlights the sensitivity of the system, outperforming most of the reported sensors alike. The resulting fluorescence quenching was found to be static in nature. Importantly, excellent recovery (100.26-104.41%) was obtained for all real samples and animal products tested. Visual detection was demonstrated by using paper strips and silica gel for practical applications. Furthermore, ε-PL could detect 5-NI antibiotics in living 3T3-L1 mouse fibroblast cells via cellular imaging. Taken together, the present work demonstrates the detection of 5-NI antibiotics using a biocompatible natural polypeptide, ε-PL, and represents a simple and inexpensive analytical tool for practical application.

Non-tuberculous mycobacterial disease: progress and advances in the development of novel candidate and repurposed drugs

Non-tuberculous mycobacteria (NTM) are opportunistic pathogens that can infect all body tissues and organs. In particular, the lungs are the most commonly involved organ, with NTM pulmonary diseases causing serious health issues in patients with underlying lung disease. Moreover, NTM infections have been steadily increasing worldwide in recent years. NTM are also naturally resistant to many antibiotics, specifically anti-tuberculosis (anti-TB) drugs. The lack of drugs targeting NTM infections and the increasing drug resistance of NTM have further made treating these mycobacterial diseases extremely difficult. The currently recommended NTM treatments rely on the extended indications of existing drugs, which underlines the difficulties of new antibiotic discovery against NTM. Another challenge is determining which drug combinations are most effective against NTM infection. To a certain extent, anti-NTM drug development depends on using already available antibiotics and compounds. Here, we aimed to review new antibiotics or compounds with good antibacterial activity against NTM, focusing on their mechanisms of action, in vitro and in vivo antibacterial activities.

Evaluation of 2,3-dihydroimidazo[2,1-b]oxazole and imidazo[2,1-b]oxazole derivatives as chemotherapeutic agents

Imidazo[2,1-b]oxazole and 2,3-dihydroimidazo[2,1-b]oxazole ring systems are commonly employed in therapeutically active molecules. In this article, the authors review the utilization of these core scaffolds as chemotherapeutic agents from 2018 to 2022. These scaffolds possess many important biological activities including antimicrobial and anticancer, among others. This review covers their biological activities and structure-activity relationships. One of the most important drugs in this class of compounds is the antitubercular agent delamanid. In this paper, the compounds structure-activity relationship and preclinical and clinical trial data are thoroughly presented.

Magnetic solid-phase extraction based on GO/Fe3O4 coupled with UPLC-MS/MS for determining nitroimidazoles and their metabolites in honey

A magnetic graphene oxide (GO/Fe₃O₄) nanocomposite was synthesized in one step by a chemical coprecipitation method, which was further used for magnetic solid-phase extraction (MSPE). This study aimed to combine GO/Fe₃O₄ with ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to detect the nitroimidazoles (NDZs) and their three major metabolites in honey samples. GO/Fe₃O₄ was characterized by transmission electron microscopy (TEM), Fourier transform-infrared (FT-IR) spectroscopy, and magnetic property measurement system (MPMS), and the influencing parameters such as adsorbent amount, pH of the dissolved sample solution, sample volume, type and volume of the eluent, shaking speed, and adsorption and desorption time were optimized. Under the optimized conditions, the limits of detection (LOD) and quantitation (LOQ) of the method were 0.003-0.08 μg kg^-1 and 0.009-0.3 μg kg^-1, respectively, with good linearity reported in the range of 0.5-20 μg kg^-1 (R² ≥ 0.9991). The average recoveries of 10 analytes were in the range of 66.0%-90.8% with relative standard deviations (RSD) lower than 6.9% (n = 6). The preparation of GO/Fe₃O₄ and the extraction process were convenient and rapid, and consumed small amounts of organic solvents. The optimized method was successfully applied for extracting NDZs and their three major metabolites from honey samples with good accuracy.

Targeting mycobacterial membranes and membrane proteins: Progress and limitations

Among the various bacterial infections, tuberculosis continues to hold center stage. Its causative agent, Mycobacterium tuberculosis, possesses robust defense mechanisms against most front-line antibiotic drugs and host responses due to their complex cell membranes with unique lipid molecules. It is now well-established that bacteria change their membrane composition to optimize their environment to survive and elude drug action. Thus targeting membrane or membrane components is a promising avenue for exploiting the chemical space focussed on developing novel membrane-centric anti-bacterial small molecules. These approaches are more effective, non-toxic, and can attenuate resistance phenotype. We present the relevance of targeting the mycobacterial membrane as a practical therapeutic approach. The review highlights the direct and indirect targeting of membrane structure and function. Direct membrane targeting agents cause perturbation in the membrane potential and can cause leakage of the cytoplasmic contents. In contrast, indirect membrane targeting agents disrupt the function of membrane-associated proteins involved in cell wall biosynthesis or energy production. We discuss the chronological chemical improvements in various scaffolds targeting specific membrane-associated protein targets, their clinical evaluation, and up-to-date account of their ''mechanisms of action, potency, selectivity'' and limitations. The sources of anti-TB drugs/inhibitors discussed in this work have emerged from target-based identification, cell-based phenotypic screening, drug repurposing, and natural products. We believe this review will inspire the exploration of uncharted chemical space for informing the development of new scaffolds that can inhibit novel mycobacterial membrane targets.

Pretomanid development and its clinical roles in treating tuberculosis

Tuberculosis (TB) is the leading infectious cause of mortality worldwide. Despite the development of different antituberculosis drugs, managing resistant mycobacteria is still challenging. The discovery of novel drugs and new methods of targeted drug delivery have the potential to improve treatment outcomes, lower the duration of treatment, and reduce adverse events. Following bedaquiline and delamanid, pretomanid is the third medicine approved as part of a novel drug regimen for treating drug-resistant TB. It is a promising drug that has the capacity to shape TB treatment and achieve the End TB strategy set by the World Health Organization. The effectiveness of pretomanid has been reported in different observational and clinical studies. However, long-term safety data in humans are not yet available and the pretomanid-based regimen is recommended under an operational research framework that prohibits its wider and programmatic use. Further research is needed before pretomanid can be celebrated as a promising candidate for the treatment of different categories of TB and specific patients. This review covers the update on pretomanid development and its clinical roles in treating Mycobacterium tuberculosis.

Discovery of 1,5-diaryl-1,2,4-triazole derivatives as myoferlin inhibitors and their antitumor effects in pancreatic cancer

Aim: The first inhibitor targeting myoferlin (MYOF), WJ460, bears poor metabolic stability and water solubility. Therefore, this study aimed to improve the druglike properties of WJ460. Materials & methods: The authors synthesized an array of 1,5-diaryl-1,2,4-triazole analogs and appraised the binding activities with MYOF and their antiproliferative and antimigratory activities against pancreatic cancer cells. Results: Molecular docking and surface plasmon resonance results showed that E4 was directly bound to the MYOF-C2D domain. E4 effectively inhibited the proliferation and migration of pancreatic cancer cells in vitro. In silico study suggested that the water solubility of E4 was improved by about 22-times than that of WJ460. Conclusion: The findings suggested that the druglike ability of E4 was significantly improved.

Drug re-engineering and repurposing: A significant and rapid approach to tuberculosis drug discovery

The prevalence of tuberculosis (TB) remains the leading cause of death from a single infectious agent, ranking it above all other contagious diseases. The problem to tackle this disease seems to become even worse due to the outbreak of SARS-CoV-2. Further, the complications related to drug-resistant TB, prolonged treatment regimens, and synergy between TB and HIV are significant drawbacks. There are several drugs to treat TB, but there is still no rapid and accurate treatment available. Intensive research is, therefore, necessary to discover newer molecular analogs that can probably eliminate this disease within a short span. An increase in efficacy can be achieved through re-engineering old TB-drug families and repurposing known drugs. These two approaches have led to the production of newer classes of compounds with novel mechanisms to treat multidrug-resistant strains. With respect to this context, we discuss structural aspects of developing new anti-TB drugs as well as examine advances in TB drug discovery. It was found that the fluoroquinolone, oxazolidinone, and nitroimidazole classes of compounds have greater potential to be further explored for TB drug development. Most of the TB drug candidates in the clinical phase are modified versions of these classes of compounds. Therefore, here we anticipate that modification or repurposing of these classes of compounds has a higher probability to reach the clinical phase of drug development. The information provided will pave the way for researchers to design and identify newer molecular analogs for TB drug development and also broaden the scope of exploring future-generation potent, yet safer anti-TB drugs.

Fluidized ZnO@BCFPs Particle Electrodes for Efficient Degradation and Detoxification of Metronidazole in 3D Electro-Peroxone Process

A novel material of self-shaped ZnO-embedded biomass carbon foam pellets (ZnO@BCFPs) was successfully synthesized and used as fluidized particle electrodes in three-dimensional (3D) electro-peroxone systems for metronidazole degradation. Compared with 3D and 2D + O₃ systems, the energy consumption was greatly reduced and the removal efficiencies of metronidazole were improved in the 3D + O₃ system. The degradation rate constants increased from 0.0369 min^-1 and 0.0337 min^-1 to 0.0553 min^-1, respectively. The removal efficiencies of metronidazole and total organic carbon reached 100% and 50.5% within 60 min under optimal conditions. It indicated that adding ZnO@BCFPs particle electrodes was beneficial to simultaneous adsorption and degradation of metronidazole due to improving mass transfer of metronidazole and forming numerous tiny electrolytic cells. In addition, the process of metronidazole degradation in 3D electro-peroxone systems involved hydroxyethyl cleavage, hydroxylation, nitro-reduction, N-denitrification and ring-opening. The active species of ·OH and ·O₂^- played an important role. Furthermore, the acute toxicity LD₅₀ and the bioconcentration factor of intermediate products decreased with the increasing reaction time.

WITHDRAWN: Pretomanid for the treatment of Mycobacterium tuberculosis: Evidence on the development and clinical roles

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Profiling Pretomanid as a Therapeutic Option for TB Infection: Evidence to Date

Tuberculosis (TB) is the most deadly infectious disease globally. Although most individuals achieve a cure, a substantial portion develop multi-drug resistant TB which is exceedingly difficult to treat, and the number of effective agents is dwindling. Development of new anti-tubercular medications is imperative to combat existing drug resistance and accelerate global eradication of TB. Pretomanid (PA-824) represents one of the newest drug classes (ie, nitroimidazooxazines) approved in 2019 by the United States Food and Drug Administration as part of a multi-drug regimen (with bedaquiline and linezolid, BPaL) and recommended by the World Health Organization (WHO) to treat extensively-resistant (XR-TB) and multi-drug resistant tuberculosis (MDR-TB). Approval was granted through the FDA's Limited Population Pathway for Antibacterial and Antifungal Drugs, which accelerates approval for antimicrobial drugs used to treat life-threatening or serious infections in a limited population with unmet need. This review details the pharmacology, efficacy, and safety of this new agent and describes evidence to date for its role in the treatment of drug resistant TB including published, ongoing, and planned studies.

Design, synthesis and antibacterial evaluation of ocotillol derivatives with polycyclic nitrogen-containing groups

Aim: With the increasing abuse of antibacterial drugs, multidrug-resistant bacteria have become a burden on human health and the healthcare system. To find alternative compounds effective against hospital-acquired methicillin-resistant Staphylococcus aureus (HA-MRSA), novel derivatives of ocotillol were synthesized. Methods & Results: Ocotillol derivatives with polycyclic nitrogen-containing groups were synthesized and evaluated for in vitro antibacterial activity. Compounds 36-39 exhibited potent antibacterial activity against HA-MRSA, with MIC = 8-64 μg/ml. Additionally, a combination of compound 37 and the commercially available antibiotic kanamycin showed synergistic inhibitory effects, with a fractional inhibitory concentration index of ≤0.375. Conclusion: Compound 37 has a strong inhibitory effect, and this derivative has potential for use as a pharmacological tool to explore antibacterial mechanisms.

Screening of FDA-Approved Drugs Using a 384-Well Plate-Based Biofilm Platform: The Case of Fingolimod

In an effort to find new repurposed antibacterial compounds, we performed the screening of an FDA-approved compounds library against Staphylococcus aureus American Type Culture Collection (ATCC) 25923. Compounds were evaluated for their capacity to prevent both planktonic growth and biofilm formation as well as to disrupt pre-formed biofilms. One of the identified initial hits was fingolimod (FTY720), an immunomodulator approved for the treatment of multiple sclerosis, which was then selected for follow-up studies. Fingolimod displayed a potent activity against S. aureus and S. epidermidis with a minimum inhibitory concentration (MIC) within the range of 12–15 µM at which concentration killing of all the bacteria was confirmed. A time–kill kinetic study revealed that fingolimod started to drastically reduce the viable bacterial count within two hours and we showed that no resistance developed against this compound for up to 20 days. Fingolimod also displayed a high activity against Acinetobacter baumannii (MIC 25 µM) as well as a modest activity against Escherichia coli and Pseudomonas aeruginosa. In addition, fingolimod inhibited quorum sensing in Chromobacterium violaceum and might therefore target this signaling pathway in certain Gram-negative bacteria. In conclusion, we present the identification of fingolimod from a compound library and its evaluation as a potential repurposed antibacterial compound.

Capsaicin derivatives with nitrothiophene substituents: Design, synthesis and antibacterial activity against multidrug-resistant S. aureus

To address the emergency caused by multi-drug resistant Staphylococcus aureus, a series of novel capsaicin derivatives with nitrothiophene substituents have been designed and evaluated for the antibacterial activities against S. aureus Newman and multidrug-resistant strains (NRS-1, NRS-70, NRS-100, NRS-108, and NRS-271). The structure-activity relationship was further revealed. Compound 13c, 13f, and 13g were highly active against staphylococcal growth, with minimal inhibition concentration (MIC) values of 0.39-1.56 μg/mL. The oxadiazole-derived compound 21, a bioisostere of ester 13f, is the most potent candidate for anti-growth of five multidrug-resistant S. aureus strains with MICs of 0.20-0.78 μg/mL, which is more active compared with vancomycin in vitro. Notably, these anti-staphylococcal compounds are much less cytotoxic to the normal kidney epithelial cell line (HK293T).