A novel dicationic ionic liquids encompassing pyridinium hydrazone-phenoxy conjugates as antimicrobial agents targeting diverse high resistant microbial strains

Use of ionic liquids in amidation reactions for proteolysis targeting chimera synthesis

Selective degradation of disease-causing proteins using proteolysis targeting chimeras (PROTACs) has gained great attention, thanks to its several advantages over traditional therapeutic modalities. Despite the advances made so far, the structural chemical complexity of PROTACs poses challenges in their synthetic approaches. PROTACs are typically prepared through a convergent approach, first synthesizing two fragments separately (target protein and E3 ligase ligands) and then coupling them to produce a fully assembled PROTAC. The amidation reaction represents the most common coupling exploited in PROTACs synthesis. Unfortunately, the overall isolated yields of such synthetic procedures are usually low due to one or more purification steps to obtain the final PROTAC with acceptable purity. In this work, we focused our attention on the optimization of the final amidation step for the synthesis of an anti-SARS-CoV-2 PROTAC by investigating different amidation coupling reagents and a range of alternative solvents, including ionic liquids (ILs). Among the ILs screened, [OMIM][ClO4] emerged as a successful replacement for the commonly used DMF within the HATU-mediated amidation reaction, thus allowing the synthesis of the target PROTAC under mild and sustainable conditions in very high isolated yields. With the optimised conditions in hand, we explored the scalability of the synthetic approach and the substrate scope of the reaction by employing different E3 ligase ligand (VHL and CRBN)-based intermediates containing linkers of different lengths and compositions or by using different target protein ligands. Interestingly, in all cases, we obtained high isolated yields and complete conversion in short reaction times.

Ionic Liquids in Pharmaceutical and Biomedical Applications: A Review

The unique properties of ionic liquids (ILs), such as structural tunability, good solubility, chemical/thermal stability, favorable biocompatibility, and simplicity of preparation, have led to a wide range of applications in the pharmaceutical and biomedical fields. ILs can not only speed up the chemical reaction process, improve the yield, and reduce environmental pollution but also improve many problems in the field of medicine, such as the poor drug solubility, product crystal instability, poor biological activity, and low drug delivery efficiency. This paper presents a systematic and concise analysis of the recent advancements and further applications of ILs in the pharmaceutical field from the aspects of drug synthesis, drug analysis, drug solubilization, and drug crystal engineering. Additionally, it explores the biomedical field, covering aspects such as drug carriers, stabilization of proteins, antimicrobials, and bioactive ionic liquids.

Effects of the aldehyde-derived ring substituent on the properties of two new bioinspired trimethoxybenzoylhydrazones: methyl vs nitro groups

N-Acylhydrazones are a versatile class of organic compounds with a diversity of potential applications. In this study, two new structure-related 3,4,5-trimethoxybenzoyl-containing N-acylhydrazones were synthesized and fully characterized, both in solution and in the solid state. The compounds differ with respect to the carbonyl precursors, i.e., 3-substituted salicylaldehydes with either a methyl or a nitro group. Single crystals of both compounds were isolated from the respective mother liquors and, in both cases, XRD confirmed the obtention of the (E)-isomer, in an anti-conformation. Computational calculations (gas and water phases) were performed in order to confirm some of the structural and vibrational aspects of the compounds. An important intramolecular H bond involving the phenolic hydroxy group and the azomethine nitrogen was identified in the solid state and seems to be maintained in solution. Moreover, the presence of the electron-withdrawing nitro substituent makes this interaction stronger. However, the contact should probably not subsist for the nitro compound under physiological conditions since the presence of this substituent significantly affects the pKa of the phenol: an apparent value of 5.68 ± 0.02 was obtained. This also impacts the basicity of the azomethine nitrogen and, as a consequence, increases the hydrazone's susceptibility to hydrolysis. Nevertheless, both compounds are stable at physiological-like conditions, especially the methyl-derived one, which qualifies them for further toxicological and activity studies, such as those involving trivalent metal ions sequestering in the context of neurodegenerative diseases.

Introducing of novel class of pyrano[2,3-c]pyrazole-5-carbonitrile analogs with potent antimicrobial activity, DNA gyrase inhibition, and prominent pharmacokinetic and CNS toxicity profiles supported by molecular dynamic simulation

Microbiological DNA gyrase is recognized as an exceptional microbial target for the innovative development of low-resistant and more effective antimicrobial drugs. Hence, we introduced a one-pot facile synthesis of a novel pyranopyrazole scaffold bearing different functionalities; substituted aryl ring, nitrile, and hydroxyl groups. All new analogs were characterized with full spectroscopic data. The antimicrobial screening for all analogs was assessed against standard strains of Gm + ve and Gm-ve through in vitro considers. The screened compounds displayed very promising MIC/MBC values against some of the bacterial strains with broad or selective antibacterial effects. Of these, 4j biphenyl analog showed 0.5-2/2-8 µg/mL MIC/MBC for suppression and killing of Gm + ve and Gm-ve strains. Moreover, the antimicrobial screening was assessed for the most potent analogs against certain highly resistant microbial strains. Consequently, DNA gyrase supercoiling assay was done for all analogs using ciprofloxacin as reference positive control. Obviously, the results showed a different activity profile with potent analog 4j with IC50 value 6.29 µg/mL better than reference drug 10.2 µg/mL. Additionally, CNS toxicity testing was done using the HiB5 cell line for attenuation of GABA/NMDA expression to both 4j and ciprofloxacin compounds that revealed better neurotransmitter modulation by novel scaffold. Importantly, docking and dynamic simulations were performed for the most active 4j analog to investigate its interaction with DNA binding sites, which supported the in vitro observations and compound stability with binding pocket. Finally, a novel scaffold pyranopyrazole was introduced as a DNA gyrase inhibitor with prominent antibacterial efficacy and low CNS side effect toxicity better than quinolones.Communicated by Ramaswamy H. Sarma.

Recent advances in the application of ionic liquids in antimicrobial material for air disinfection and sterilization

Airborne transmission is one of the most unpredictable routes of infection. Nowadays, airborne diseases increase ever than before because of the complex living air environment. Apart from the inorganic particles, active microorganisms including bacteria, viruses, and fungi are incorporated in the pathogens acting as threaten to public health, which can hardly be treated by the traditional air purification methods based on adsorption. Therefore, effective filtration material with antimicrobial activity is demanded to solve the problem. Ionic liquids (ILs) are a category of salts that remain liquid at room temperature. The stable physico-chemical properties and extremely low vapor pressure make them suitable for a wide range of applications. Thanks to the numerous combinations of cations and anions, as well as the ability of inheriting properties from the parent ions, Ils are believed to be a promising industrial material. In recent decades, several Ils, such as imidazolium, pyridinium, pyrrolidinium, phosphonium, and choline, have been found to have antimicrobial activity in their monomeric or polymeric forms. This work focuses on the antimicrobial activity and safety of the latest types of ionic liquids, discussing the synthesis or manufacturing methods of Ils for air purification and filtration. Furthermore, possible applications of Ils antimicrobial materials in medical instruments and indoor environments are mentioned to encourage the scientific community to further explore the potential applications of Ils.

Design and synthesis of novel bis-pyridinium based-ionic liquids as potent antiparasitic agents

Focused bis-pyridinium based-ionic liquids were successfully synthesized through the quaternization of the selected 1,2-di(pyridin-4-yl)ethane followed by metathetical anion exchange. The synthesized pyridinium derivatives were fully characterized using various NMR-spectroscopic techniques including ¹H, ¹³C, ¹¹B, ³¹P and ¹⁹F NMR. The synthesized compounds were tested for their potential effect against Toxoplasma gondii. It was revealed that compound 5 had higher antiparasitic activity compared to other compounds. Parasitic reduction percentage reached 38, 50, 77 and 79 for groups III, IV, V and VI respectively in the liver with noticed distortion and deformation in tachyzoites' shape. Surprisingly there was no statistically significant difference between the synthesized compound 5 and the known anti-toxoplasmosis drug pyrimethamine. Histopathological study proved the effectiveness of the synthesized compound 5 on liver, spleen and brain tissues with observed better histological features compared to pyrimethamine treated group. The present investigation may pave the way to the possible use of compound 5 to replace the known drug pyrimethamine with better antiparasitic profile and fewer side effects.

Fungal Secondary Metabolites/Dicationic Pyridinium Iodide Combinations in Combat against Multi-Drug Resistant Microorganisms

The spread of antibiotic-resistant opportunistic microbes is a huge socioeconomic burden and a growing concern for global public health. In the current study, two endophytic fungal strains were isolated from Mangifera Indica roots and identified as Aspergillus niger MT597434.1 and Trichoderma lixii KU324798.1. Secondary metabolites produced by A. niger and T. lixii were extracted and tested for their antimicrobial activity. The highest activity was noticed against Staphylococcus aureus and E. coli treated with A. niger and T. lixii secondary metabolites, respectively. A. niger crude extract was mainly composed of Pentadecanoic acid, 14-methyl-, methyl ester and 9-Octadecenoic acid (Z)-, methyl ester (26.66 and 18.01%, respectively), while T. lixii crude extract's major components were 2,4-Decadienal, (E,E) and 9-Octadecenoic acid (Z)-, and methyl ester (10.69 and 10.32%, respectively). Moreover, a comparative study between the fungal extracts and dicationic pyridinium iodide showed that the combination of A. niger and T. lixii secondary metabolites with dicationic pyridinium iodide compound showed a synergistic effect against Klebsiella pneumoniae. The combined formulae inhibited the bacterial growth after 4 to 6 h through cell wall breakage and cells deformation, with intracellular components leakage and increased ROS production.

Acylhydrazones and Their Biological Activity: A Review

Due to the structure of acylhydrazones both by the pharmacophore -CO-NH-N= group and by the different substituents present in the molecules of compounds of this class, various pharmacological activities were reported, including antitumor, antimicrobial, antiviral, antiparasitic, anti-inflammatory, immunomodulatory, antiedematous, antiglaucomatous, antidiabetic, antioxidant, and actions on the central nervous system and on the cardiovascular system. This fragment is found in the structure of several drugs used in the therapy of some diseases that are at the top of public health problems, like microbial infections and cardiovascular diseases. Moreover, the acylhydrazone moiety is present in the structure of some compounds with possible applications in the treatment of other different pathologies, such as schizophrenia, Parkinson's disease, Alzheimer's disease, and Huntington's disease. Considering these aspects, we consider that a study of the literature data regarding the structural and biological properties of these compounds is useful.

Efficient Antibacterial Dimeric Nitro Imidazolium Type of Ionic Liquids from a Simple Synthetic Approach

Synthesis of dimeric nitro-substituted imidazolium salts under the conventional/solvent-free method is reported. The solvent-free method is more important than the conventional one because of its shorter reaction time, higher yield from easily available starting material, environmental safety, and so forth. Counter anion exchange is carried out using inorganic salt, which is dissolved in deionized water at room temperature. In antibacterial studies, dimeric nitro-substituted imidazolium cations with bromide counter anions showed excellent inhibition against E. coli and P. aeruginosa bacteria. These experimental results were further supported by molecular docking studies. All the compounds (3-6) (a-d) showed excellent antibacterial activity than the standard drugs (gentamycin, nalidixic acid, oflaxacin, ciproflaxacin, and amikacin). Molecular docking studies showed strong hydrogen bonding, polar and hydrophobic interactions between the dimeric imidazolium salts, and Escherichia coli/Pseudomonas aeruginosa/Proteus vulgaris/Staphylococcus aureus receptors.

Dicationic Bis-Pyridinium Hydrazone-Based Amphiphiles Encompassing Fluorinated Counteranions: Synthesis, Characterization, TGA-DSC, and DFT Investigations

Quaternization and metathesis approaches were used to successfully design and synthesize the targeted dicationic bis-dipyridinium hydrazones carrying long alkyl side chain extending from C8 to C18 as countercation, and attracted to halide (I^-) or fluorinated ion (PF₆^-, BF₄^-, CF₃COO^-) as counteranion. Spectroscopic characterization using NMR and mass spectroscopy was used to establish the structures of the formed compounds. In addition, their thermal properties were investigated utilizing thermogravimetric analyses (TGA), and differential scanning calorimetry (DSC). The thermal study illustrated that regardless of the alkyl group length (Cn) or the attracted anions, the thermograms of the tested derivatives are composed of three stages. The mode of thermal decomposition demonstrates the important roles of both anion and alkyl chain length. Longer chain length results in greater van der Waals forces; meanwhile, with anions of low nucleophilicity, it could also decrease the intramolecular electrostatic interaction, which leads to an overall interaction decrease and lower thermal stability. The DFT theoretical calculations have been carried out to investigate the thermal stability in terms of the T_onset. The results revealed that the type of the counteranion and chain length had a substantial impact on thermal stability, which was presumably related to the degree of intermolecular interactions. However, the DFT results illustrated that there is no dominant parameter affecting the thermal stability, but rather a cumulative effect of many factors of different extents.

Quaternary Ammonium Compounds (QACs) and Ionic Liquids (ILs) as Biocides: From Simple Antiseptics to Tunable Antimicrobials

Quaternary ammonium compounds (QACs) belong to a well-known class of cationic biocides with a broad spectrum of antimicrobial activity. They are used as essential components in surfactants, personal hygiene products, cosmetics, softeners, dyes, biological dyes, antiseptics, and disinfectants. Simple but varied in their structure, QACs are divided into several subclasses: Mono-, bis-, multi-, and poly-derivatives. Since the beginning of the 20th century, a significant amount of work has been dedicated to the advancement of this class of biocides. Thus, more than 700 articles on QACs were published only in 2020, according to the modern literature. The structural variability and diverse biological activity of ionic liquids (ILs) make them highly prospective for developing new types of biocides. QACs and ILs bear a common key element in the molecular structure-quaternary positively charged nitrogen atoms within a cyclic or acyclic structural framework. The state-of-the-art research level and paramount demand in modern society recall the rapid development of a new generation of tunable antimicrobials. This review focuses on the main QACs exhibiting antimicrobial and antifungal properties, commercial products based on QACs, and the latest discoveries in QACs and ILs connected with biocide development.

Third-generation ionic liquids with N-alkylated 1,4-diazabicyclo[2.2.2]octane cations and pelargonate anions

Ionic liquids that belong to the third-generation designs due to their intended biological activity are compounds with high potential applications as plant-protection products. The present study describes the synthesis and characterization of novel ionic liquids with cations based on the alkyl derivatives of 1,4-diazabicyclo[2.2.2]octane (DABCO) and an anion derived from naturally occurring pelargonic acid. The developed synthesis method allowed obtaining products with a high yield (≥96%), and the liquids were characterized as high-viscosity liquids at room temperature. This allowed classifying the products as ionic liquids (ILs). The structures of the obtained ILs were confirmed on the basis of their NMR and IR spectra as well as by elemental analysis. All the products exhibited surface activity and were capable of partially wetting a hydrophobic surface. The tested ionic liquids exhibited higher herbicidal activity against winter oilseed rape (Brassica napus L.) and common lambsquarters (Chenopodium album L.) at a lower dose compared to a commercial preparation in greenhouse studies. The studied ionic liquids also exhibited different effects as antifeedants on various insect species. The best results were obtained against beetles belonging to the granary weevil species (Sitophilus granarius L.). The relation between the surface-tension-reduction efficiency pC₂₀ and biological activity was investigated. The herbicidal activity was also correlated with the value of the contact angles for the studied pelargonates. All the obtained results indicate that the designed and synthesized ionic liquids possess double biological functions: herbicidal activity and deterrent activity.