Imidazole and Imidazolium Antibacterial Drugs Derived from Amino Acids

Antibacterial Agents and Adjuvants against Pseudomonas Aeruginosa Infections

The development of narrow-spectrum antimicrobial agents is paramount for swiftly eradicating pathogenic bacteria, mitigating the onset of drug resistance, and preserving the homeostasis of bacterial microbiota in tissues. Owing to the limited affinity between the hydrophobic lipid bilayer interior of bacterial cells and most hydrophilic, polar peptides, the construction of a distinctive class of four-armed host-defense peptides/peptidomimetics (HDPs) is proposed with enhanced specificity and membrane perturbation capability against Pseudomonas aeruginosa by incorporating imidazole groups. These groups demonstrate substantial affinity for unsaturated phospholipids, which are predominantly expressed in the cell membrane of P. aeruginosa, thereby enabling HDPs to exhibit narrow-spectrum activity against this bacterium. Computational simulations and experimental investigations have corroborated that the imidazole-rich, four-armed peptidomimetics exhibit notable selectivity toward bacteria over mammalian cells. Among them, 4H10, characterized by its abundant and densely distributed imidazole groups, exhibits impressive activity against various clinically isolated P. aeruginosa strains. Moreover, 4H10 has demonstrated potential as an antibiotic adjuvant, enhancing doxycycline accumulation and exerting effects on intracellular targets by efficiently disrupting bacterial cell membranes. Consequently, the hydrogel composed of 4H10 and doxycycline emerged as a promising topical agent, significantly diminishing the skin P. aeruginosa burden by 97.1% within 2 days while inducing minimal local and systemic toxicity.

Various synthesis and biological evaluation of some tri -tetra-substituted imidazoles derivatives: A review

The imidazole nucleus represents a significant group of heterocyclic molecules with diverse significance in the modern world due to its exploration potential and various pharmacological applications. The relevance of imidazole and its derivatives has gained popularity in recent years, especially in the production of commercial drugs and the treatment of various conditions. The imidazole nucleus is present in many natural compounds and widely distributed in essential amino acids, such as l-histidine, whose derivatives exhibit powerful pharmacological properties. In this review, we delve into the historical timeline and development of synthetic pathways for tri- and tetra-substituted imidazoles used in the renowned Radziszewski reaction. Furthermore, we explore various bacteriological applications documented in the literature, as well as current advances in preclinical approaches to imidazole-based drug discovery. Tri- or tetra-substituted imidazole derivatives show strong potential for new synthesis methods, such as reflux or microwave, as well as various biological activities.

Discovery of Novel Inhibitors of Cruzain Cysteine Protease of Trypanosoma cruzi

Chagas disease (CD) is a parasitic disease endemic in several developing countries. According to the World Health Organization, approximately 6-8 million people worldwide are inflicted by CD. The scarcity of new drugs, mainly for the chronic phase, is the main reason for treatment limitation in CD. Therefore, there is an urgent need to discover new targets for which new therapeutical agents could be developed. Cruzain cysteine protease (CCP) is a promising alternative because this enzyme exhibits pleiotropic effects by acting as a virulence factor, modulating host immune cells, and interacting with host cells. This systematic review was conducted to discover new compounds that act as cruzain inhibitors, and their effects in vitro were studied through enzymatic assays and molecular docking. Additionally, the advances and perspectives of these inhibitors are discussed. These findings are expected to contribute to medicinal chemistry in view of the design of new, safe, and efficacious inhibitors against Trypanosoma cruzi CCP detected in the last decade (2013-2022) to provide scaffolds for further optimization, aiming toward the discovery of new drugs.

Efficacy of Novel Quaternary Ammonium and Phosphonium Salts Differing in Cation Type and Alkyl Chain Length against Antibiotic-Resistant Staphylococcus aureus

Antibacterial resistance poses a critical public health threat, challenging the prevention and treatment of bacterial infections. The search for innovative antibacterial agents has spurred significant interest in quaternary heteronium salts (QHSs), such as quaternary ammonium and phosphonium compounds as potential candidates. In this study, a library of 49 structurally related QHSs was synthesized, varying the cation type and alkyl chain length. Their antibacterial activities against Staphylococcus aureus, including antibiotic-resistant strains, were evaluated by determining minimum inhibitory/bactericidal concentrations (MIC/MBC) ≤ 64 µg/mL. Structure-activity relationship analyses highlighted alkyl-triphenylphosphonium and alkyl-methylimidazolium salts as the most effective against S. aureus CECT 976. The length of the alkyl side chain significantly influenced the antibacterial activity, with optimal chain lengths observed between C10 and C14. Dose-response relationships were assessed for selected QHSs, showing dose-dependent antibacterial activity following a non-linear pattern. Survival curves indicated effective eradication of S. aureus CECT 976 by QHSs at low concentrations, particularly compounds 1e, 3e, and 5e. Moreover, in vitro human cellular data indicated that compounds 2e, 4e, and 5e showed favourable safety profiles at concentrations ≤ 2 µg/mL. These findings highlight the potential of these QHSs as effective agents against susceptible and resistant bacterial strains, providing valuable insights for the rational design of bioactive QHSs.

Recent Advances in Antibiofouling Materials for Seawater-Uranium Extraction: A Review

Nuclear power has experienced rapid development as a green energy source due to the increasing global demand for energy. Uranium, as the primary fuel for nuclear reactions, plays a crucial role in nuclear energy production, and seawater-uranium extraction has gained significant attention. However, the extraction of uranium is usually susceptible to contamination by microorganisms, such as bacteria, which can negatively affect the adsorption performance of uranium adsorption materials. Therefore, an important challenge lies in the development of new antibacterial and antiadhesion materials to inhibit the attachment of marine microorganisms. These advancements aim to reduce the impact on the adsorption capability of the adsorbent materials. This paper reviews the antibiofouling materials used for extracting seawater uranium, and corresponding mechanisms are discussed.

Polyimidazolium Protects against an Invasive Clinical Isolate of Salmonella Typhimurium

Frequent outbreaks of Salmonella Typhimurium infection, in both animal and human populations and with the potential for zoonotic transmission, pose a significant threat to the public health sector. The rapid emergence and spread of more invasive multidrug-resistant clinical isolates of Salmonella further highlight the need for the development of new drugs with effective broad-spectrum bactericidal activities. The synthesis and evaluation of main-chain cationic polyimidazolium 1 (PIM1) against several Gram-positive and Gram-negative bacteria have previously demonstrated the efficacy profile of PIM1. The present study focuses on the antibacterial and anti-biofilm activities of PIM1 against Salmonella in both in vitro and in ovo settings. In vitro, PIM1 exhibited bactericidal activity against three strains of Salmonella at a low dosage of 8 μg/mL. The anti-biofilm activity of PIM1 was evident by its elimination of planktonic cells within preformed biofilms in a dose-dependent manner. During the host cell infection process, PIM1 reduces the extracellular bacterial load, which reduces adhesion and invasion to limit the establishment of infection. Once intracellular, Salmonella strains were tolerant and protected from PIM1 treatment. In a chicken egg infection model, PIM1 exhibited therapeutic activity for both Salmonella strains, using stationary-phase and exponential-phase inocula. Moreover, PIM1 showed a remarkable efficacy against the stationary-phase inocula of drug-resistant Salmonella by eliminating the bacterial burden in >50% of the infected chicken egg embryos. Collectively, our results highlight the potential for PIM1 as a replacement therapy for existing antibiotic applications on the poultry farm, given the efficiency and low toxicity profile demonstrated in our agriculturally relevant chicken embryo model.

Cationic, Steroid-Based Imidazolium Amphiphiles Show Tunable Backbone-Dependent Membrane Selectivity in Fungi

Cationic amphiphiles have been reported to show broad antimicrobial activity. The potential for antimicrobial resistance to these molecules is low owing to their general cell membrane permeabilizing mode of action. However, their applications are often limited by toxicity resulting from their low selectivity for microbial cell membranes. Herein, we report a library of cationic, steroid-based imidazolium amphiphiles that show tunable antifungal activity in a variety of fungal pathogens of the genus Candida. We show that adoption of an ergosterol-derived backbone increases antifungal activity while modestly affecting hemolytic activity, thereby increasing overall selectivity by more than 8-fold in comparison to cholesterol-derived imidazolium salts. We hypothesize that this effect is caused by a privileged integration of the ergosterol-derived salts into fungal membranes leading to increased membrane disorder. We propose that these findings offer a useful platform for the development of improved amphiphilic fungicides.

Anticancer effects of imidazole nucleus in hepatocellular carcinoma cell lines via the inhibition of AKT and ERK1/2 signaling pathways

BACKGROUND

Imidazole nucleus has been used efficiently in the development of many drug molecules due to its therapeutic effects. Many derivatives of it have been produced particularly for use in cancer treatment. However, the anti-cancer effects of imidazole nucleus in liver cancer cells are as yet unclear. In this study, we aimed to investigate the anti-cancer effects of imidazole nucleus in hepatocellular carcinoma (HCC) cell lines.

METHODS AND RESULTS

Anti-cancer effect of imidazole nucleus was investigated using cell viability assay, apoptosis analysis, cell migration analysis, cell morphology analysis, colony formation assay and 3D cell culture techniques in HuH-7 and Mahlavu cell lines. Also, effect of imidazole on AKT and ERK1/2 pathways were determined using by western blot analysis. Imidazole decreased cell viability in both HCC cell lines in a dose and time-dependent manner and also suppressed the colony forming ability of the cells (p < 0.05). Imidazole increased the cleaved caspase 3 protein levels and thus induced apoptosis (p < 0.05). Imidazole induced morphological alterations and autophagy by increasing intracellular vacuolization. Also, imidazole decreased the viability and dimensions of HCC cell tumor spheroids produced in 3D cell cultures (p < 0.05). Moreover, it was observed that all of these effects, are defined above, appeared in parallel with suppression of AKT and ERK1/2 signaling pathways by imidazole nucleus.

CONCLUSIONS

The findings of this present study established the anti-cancer effects of imidazole nucleus in HCC cell lines and showed that it could be a potential molecule in the treatment of HCC via inhibition of AKT and ERK1/2 signaling pathways.

Exploration of Nitroaromatic Antibiotics via Sanger's Reagent: Synthesis, In Silico, and Antimicrobial Evaluation

Facile synthesis of molecular hybrids containing a 2,4-dinitrophenyl moiety was achieved via nucleophilic aromatic substitution of the fluoride anion of Sanger's reagent (2,4-dinitrofluorobenzene) with various N, S, and O nucleophiles, considered as bioactive moieties. Antimicrobial evaluation of the new hybrids was carried out using amoxicillin and nystatin as antibacterial and antifungal reference standards, respectively. MIC test results identified the compounds 3, 4, and 7 as the most active hybrids against standard strains and multidrug-resistant strains (MDR) of Staphylococcus aureus, Escherichia coli, and Pseudomonas aurginosa. Most of the hybrids displayed two times the antibacterial activity of AMOX against MDR Pseudomonas aeruginosa, E. coli, and a standard strain of P. aeruginosa (ATCC 29853), while demonstrating a weak antifungal profile against Candida albicans. Selectivity profiles of the promising compounds 3, 4, 6, 7, 8, and 11 on WI-38 human cells were characterized, which indicated that compound 3 is the safest one (CC₅₀ 343.72 μM). The preferential anti-Gram-negative activity of our compounds led us to do docking studies on DNA gyrase B. Docking revealed that the potential antimicrobial compounds fit well into the active site of DNA gyrase B. Furthermore, in silico absorption, distribution, metabolism, and excretion (ADME) predictions revealed that most of the new compounds have high gastrointestinal absorption and a good oral bioavailability with no BBB permeability.

Structure-antitumor activity relationships of tripodal imidazolium-amino acid based salts. Effect of the nature of the amino acid, amide substitution and anion

The antitumor activity of imidazolium salts is highly dependent upon their lipophilicity that can be tuned by the introduction of different hydrophobic substituents on the nitrogen atoms of the imidazolium ring of the molecule. Taking this into consideration, we have synthesized and characterized a series of tripodal imidazolium salts derived from L-valine and L-phenylalanine containing different hydrophobic groups and tested them against four cancer cell lines at physiological and acidic pH. At acidic pH (6.2) the anticancer activity of some of the tripodal compounds changes dramatically, and this parameter is crucial to control their cytotoxicity and selectivity. Moreover, several of these compounds displayed selectivity against the control healthy cell line higher than four. The transmembrane anion transport studies revealed moderate transport abilities suggesting that the observed biological activity is likely not the result of just their transport activity. The observed trends in biological activity at acidic pH agree well with the results for the CF leakage assay. These results strongly suggest that this class of compounds can serve as potential chemotherapeutic agents.

Decoupling manufacturing from application in additive manufactured antimicrobial materials

3D printable materials based on polymeric ionic liquids (PILs) capable of controlling the synthesis and stabilisation of silver nanoparticles (AgNPs) and their synergistic antimicrobial activity are reported. The interaction of the ionic liquid moieties with the silver precursor enabled the controlled in situ formation and stabilisation of AgNPs via extended UV photoreduction after the printing process, thus demonstrating an effective decoupling of the device manufacturing from the on-demand generation of nanomaterials, which avoids the potential aging of the nanomaterials through oxidation. The printed devices showed a multi-functional and tuneable microbicidal activity against Gram positive (B. subtilis) and Gram negative (E. coli) bacteria and against the mould Aspergillus niger. While the polymeric material alone was found to be bacteriostatic, the AgNPs conferred bactericidal properties to the material. Combining PIL-based materials with functionalities, such as in situ and photoactivated on-demand fabricated antimicrobial AgNPs, provides a synergistic functionality that could be harnessed for a variety of applications, especially when coupled to the freedom of design inherent to additive manufacturing techniques.

Hypochlorite-Activated Fluorescence Emission and Antibacterial Activities of Imidazole Derivatives for Biological Applications

The ability to detect hypochlorite (HOCl/ClO-) in vivo is of great importance to identify and visualize infection. Here, we report the use of imidazoline-2-thione (R 1 SR 2 ) probes, which act to both sense ClO- and kill bacteria. The N2C=S moieties can recognize ClO- among various typical reactive oxygen species (ROS) and turn into imidazolium moieties (R 1 IR 2 ) via desulfurization. This was observed through UV-vis absorption and fluorescence emission spectroscopy, with a high fluorescence emission quantum yield (ՓF = 43-99%) and large Stokes shift (∆v∼115 nm). Furthermore, the DIM probe, which was prepared by treating the DSM probe with ClO-, also displayed antibacterial efficacy toward not only Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) but also methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum ß-lactamase-producing Escherichia coli (ESBL-EC), that is, antibiotic-resistant bacteria. These results suggest that the DSM probe has great potential to carry out the dual roles of a fluorogenic probe and killer of bacteria.

Special Issue "Novel Antibacterial Agents"

This Special Issue of Pharmaceuticals is devoted to significant advances achieved in the field of antibacterial agents [...].