Development of Receptor for Advanced Glycation End Products (RAGE) ligands through target directed dynamic combinatorial chemistry: a novel class of possible antagonists.

RAGE is a transmembrane receptor of immunoglobulin family that can bind various endogenous and exogenous ligands, initiating the inflammatory downstream signaling pathways, including inflammaging. Therefore, RAGE represents an attractive drug target for age-related diseases. For the development of small-molecule RAGE antagonists, we employed protein-templated dynamic combinatorial chemistry (ptDCC) using RAGE's VC1 domain as a template, the first application of this approach in the context of RAGE. The affinities of DCC hits were validated using microscale thermophoresis. Subsequent screening against AGE2 (glyceraldehyde-modified AGE)-sRAGE (solubleRAGE) (AGE2-BSA/sRAGE) interaction using ELISA tests led to the identification of antagonists with micromolar potency. Our findings not only demonstrate the successful application of ptDCC on RAGE but also highlight its potential to address the pressing need for alternative strategies for the development of small-molecule RAGE antagonists, an area of research that has experienced a slowdown in recent years.

Synthesis, biochemical and computational evaluations of novel bis-acylhydrazones of 2,2'-(1,1'-biphenyl)-4,4'-diylbis(oxy))di(acetohydrazide) as dual cholinesterase inhibitors.

A series of twenty-seven bis(acylhydrazones) were successfully synthesized with high yields through a multistep process, which entailed the esterification of hydroxyl groups, hydrazination with an excess of hydrazine hydrate, and subsequent reactions with various carbonyl moieties (aldehydes). In the final stage of synthesis, different chemical species including aromatic, heterocyclic, and aliphatic compounds were integrated into the framework. The resulting compounds were characterized using several spectroscopic techniques (1H NMR, 13C NMR, and mass spectrometry). Their anticholinesterase activities were assessed in vitro by examining their interactions with two cholinesterase enzymes: acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Among the synthesized hits, compounds 3, 5, 6, 9-12, and 14 exhibited good to moderate inhibition of AChE. Specifically, 10 (IC50 = 26.3 ± 0.4 µM) and 11 (IC50 = 28.4 ± 0.5 µM) showed good inhibitory activity against AChE, while 9, 12, 3, and 6 exhibited significant inhibition potential against AChE with IC50 values ranging from 35.2 ± 1.1 µM to 64.4 ± 0.3 µM. On the other hand, 5 (IC50 = 22.0 ± 1.1 µM) and 27 (IC50 = 31.3 ± 1.3 µM) displayed significant, and 19 (IC50 = 92.6 ± 0.4 µM) showed moderate inhibitory potential for BChE. Notably, 5 and 27 exhibited dual inhibition of AChE and BChE, with greater potency than the standard drug galantamine. The binding patterns of these molecules within the binding cavities of AChE and BChE were anticipated by molecular docking which showed good correlation with our in vitro findings. Further structural optimization of these molecules may yield more potent AChE and BChE inhibitors.

Synthesis and application of hypochlorite mediated acylhydrazone fluorescence probes.

Hypochlorous acid (HClO/ClO- ) is one of the important reactive oxygen species (ROS). It acts as a second signaling molecule within and between cells and is an indispensable active molecule in living organisms to regulate physiological and pathological processes. In this article, two fluorescent probes (PTF and PTA) for highly selective fluorescent recognition of ClO- were successfully synthesized based on the ICT mechanism by condensing phenothiazines with two hydrazides via the hydrazide structure (). PTF can identify different concentrations of ClO- in two steps. Due to its ClO- two site recognition, the probe exhibited good selectivity (specific recognition of ClO- over a wide concentration range), a fast time response (rapid recognition in seconds), a sufficiently low detection limit (3.6 and 11.0 nM), and large Stokes shifts (180 and 145 nm). Furthermore, the recognition of ClO- by contrasting probes with different substituents exhibited different fluorescence changes of ratiometric type and turn-off. PTF successfully achieves the detection of exogenous and endogenous ClO- in aqueous solution and living cells.

Cardiotoxicity and ROS Protection Assessment of three Structure-Related N-Acylhydrazones with Potential for the Treatment of Neurodegenerative Diseases.

The senescence process is associated with accumulated oxidative damage and increased metal concentration in the heart and brain. Besides, abnormal metal-protein interactions have also been linked with the development of several conditions, including Alzheimer's and Parkinson's diseases. Over the years we have described a series of structure-related compounds with different activities towards models of such diseases. In this work, we evaluated the potential of three N-acylhydrazones (INHHQ: 8-hydroxyquinoline-2-carboxaldehyde isonicotinoyl hydrazone, HPCIH: pyridine-2-carboxaldehyde isonicotinoyl hydrazone and X1INH: 1-methyl-1H-imidazole-2-carboxaldehyde isonicotinoyl hydrazone) to prevent oxidative stress in cellular models, with the dual intent of being active on this pathway and also to confirm their lack of cardiotoxicity as an important step in the drug development process, especially considering that the target population often presents cardiovascular comorbidity. The 8-hydroxyquinoline-contaning compound, INHHQ, exhibits a significant cardioprotective effect against hydrogen peroxide and a robust antioxidant activity. However, this compound is the most toxic to the studied cell models and seems to induce oxidative damage on its own. Interestingly, although not possessing a phenol group in its structure, the new-generation 1-methylimidazole derivative X1INH showed a cardioprotective tendency towards H9c2 cells, demonstrating the importance of attaining a compromise between activity and intrinsic cytotoxicity when developing a drug candidate.

Synthesis, Structural Properties and Biological Activities of Novel Hydrazones of 2-, 3-, 4-Iodobenzoic Acid.

Nowadays, searching for novel antimicrobial agents is crucial due to the increasing number of resistant bacterial strains. Moreover, cancer therapy is a major challenge for modern medicine. Currently used cytostatics have a large number of side effects and insufficient therapeutic effects. Due to the above-mentioned facts, we undertook research to synthesize novel compounds from the acylhydrazone group aimed at obtaining potential antimicrobial and anticancer agents. As a starting material, we employed hydrazides of 2-, 3- or 4-iodobenzoic acid, which gave three series of acylhydrazones in the condensation reaction with various aldehydes. The chemical structure of all obtained compounds was confirmed by IR, 1H NMR, and 13C NMR. The structure of selected compounds was determined by single-crystal X-ray diffraction analysis. Additionally, all samples were characterized using powder X-ray diffraction. The other issue in this research was to examine the possibility of the solvent-free synthesis of compounds using mechanochemical methods. The biological screening results revealed that some of the newly synthesized compounds indicated a beneficial antimicrobial effect even against MRSA-the methicillin-resistant Staphylococcus aureus ATCC 43300 strain. In many cases, the antibacterial activity of synthesized acylhydrazones was equal to or better than that of commercially available antibacterial agents that were used as reference substances in this research. Significantly, the tested compounds do not show toxicity to normal cell lines either.

Behavior of a Dynamic Covalent Library Driven by Combined Pd(II) and Biphasic Effectors for Metal Transport between Phases.

This work reports the effect of Pd(II) as chemical effector on an acylhydrazone-based dynamic covalent library (DCL) in biphasic systems (water/chloroform). The constituents of the DCL are self-built and distributed in the two phases, two of them are lipophilic enough to play the role of a carrier agent that may transfer Pd(II) from the aqueous phase to the organic phase. Upon addition of Pd(II), the DCL of components exhibits a strong amplification of the constituent that is the most adapted to stabilize Pd(II) in chloroform as well as its agonist in water. This evolution is driven by the combination of the interaction of the DCL with Pd(II) and the presence of the two phases. This study paves the way to a novel approach for liquid/liquid extraction and metal recovery by means of adaptive extractant species generated in situ by a DCL.

Optimization of G-Quadruplex Ligands through a SAR Study Combining Parallel Synthesis and Screening of Cationic Bis(acylhydrazones).

G-quadruplexes (G4s), secondary structures adopted by guanine-rich DNA and RNA sequences, are implicated in numerous biological processes and have been suggested as potential drug targets. Accordingly, there is an increasing interest in developing high-throughput methods that allow the generation of congeneric series of G4-targeting molecules ("ligands") and investigating their interactions with the targets. We have developed an operationally simple method of parallel synthesis to generate "ready-to-screen" libraries of cationic acylhydrazones, a motif that we have previously identified as a promising scaffold for potent, biologically active G4 ligands. Combined with well-established screening techniques, such as fluorescence melting, this method enables the rapid synthesis and screening of combinatorial libraries of potential G4 ligands. Following this protocol, we synthesized a combinatorial library of 90 bis(acylhydrazones) and screened it against five different nucleic acid structures. This way, we were able to analyze the structure-activity relationships within this series of G4 ligands, and identified three novel promising ligands whose interactions with G4-DNAs of different topologies were studied in detail by a combination of several biophysical techniques, including native mass spectrometry, and molecular modeling.

New Insights into Acylhydrazones E/Z Isomerization: An Experimental and Theoretical Approach.

A family of acylhydrazones have been prepared and characterized with the aim of investigating their potential as information storage systems. Their well-established synthetic methodologies allowed for the preparation of seven chemically stable acylhydrazones in excellent yields that have been photophysically and photochemically characterized. In addition, DFT and TD-DFT calculations have been performed to gain more insights into the structural, energetic and photophysical properties of the E/Z isomers. Our results reveal that E/Z configurational isomerization upon irradiation is highly dependent on the stabilization of the E or Z isomers due to the formation of intramolecular H bonds and the electronic/steric effects intrinsically related to their structures. In addition, Raman spectroscopy is also used to confirm the molecular structural changes after the formation of hydrogen bonds in the isomers.

Trifluoromethylated hydrazones and acylhydrazones as potent nitrogen-containing fluorinated building blocks.

Nitrogen-containing organofluorine derivatives, which are prepared using fluorinated building blocks, are among the most important active fragments in various pharmaceutical and agrochemical products. This review focuses on the reactivity, synthesis, and applications of fluoromethylated hydrazones and acylhydrazones. It summarizes recent methodologies that have been used for the synthesis of various nitrogen-containing organofluorine compounds.

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.

Chloramine Trihydrate-Mediated Tandem Synthesis of New Pyrrole and/or Arene-Linked Mono- and Bis(1,3,4-Oxadiazole) Hybrids as Potential Bacterial Biofilm and MRSA Inhibitors.

A two-step tandem protocol was used to prepare new pyrrole and/or arene-linked bis(1,3,4-oxadiazoles) as well as their mono-analogs. The appropriate aldehydes and benzohydrazides were first condensed in ethanol at 80 °C to yield the corresponding N-benzoylhydrazones. Without isolation, the previous intermediates were subjected to a chloramine trihydrate-mediated oxidative cyclization in DMSO at 180 °C to yield the target molecules. The antibacterial potency of the (pyrrole-arene)-linked hybrids exceeded the arene-linked hybrids, and the bis(1,3,4-oxadiazoles) exceeded their mono-analogs against six different ATCC strains. Furthermore, the antibacterial efficacy of bis(1,3,4-oxadiazoles) 11c, and 11f, which are linked to pyrrole, and (p-tolylthio)methyl units, was highest against S. aureus, E. coli, and P. aeruginosa strains. Their MIC ranged between 3.8 and 3.9 µM, while their MBC values ranged between 7.7 and 15.8 µM. Additionally, they showed promising bacterial biofilm inhibitory activity against the same strains tested, with IC50 values ranging from 4.7 to 5.3 µM. They were also effective against MRSA ATCC : 33591, and ATCC : 43300 strains, with MIC, and MBC values ranging from 3.8-7.9 and 7.7-15.8 µM, respectively. When tested against the MCF-10A cell lines, hybrids 11c, and 11f are cytotoxic at concEntrations that are more than 6 and 13-fold higher than their MIC values against the S. aureus, E. coli, and P. aeruginosa strains, respectively. This lends support to both hybrids' potential as safe antibacterial agents.

Synthesis, Biological Activity and Molecular Docking Studies of Novel Nicotinic Acid Derivatives.

In our research, we used nicotinic acid as a starting compound, which was subjected to a series of condensation reactions with appropriate aldehydes. As a result of these reactions, we were able to obtain a series of twelve acylhydrazones, two of which showed promising activity against Gram-positive bacteria (MIC = 1.95-15.62 µg/mL), especially against Staphylococcus epidermidis ATCC 12228 (MIC = 1.95 µg/mL). Moreover, the activity of compound 13 against the Staphylococcus aureus ATCC 43300 strain, i.e., the MRSA strain, was MIC = 7.81 µg/mL. Then, we subjected the entire series of acylhydrazones to a cyclization reaction in the acetic anhydride, thanks to which we were able to obtain twelve new 3-acetyl-2,5-disubstituted-1,3,4-oxadiazoline derivatives. Obtained 1,3,4-oxadiazolines were also tested for antimicrobial activity. The results showed high activity of compound 25 with a 5-nitrofuran substituent, which was active against all tested strains. The most promising activity of this compound was found against Gram-positive bacteria, in particular against Bacillus subtilis ATCC 6633 and Staphylococcus aureus ATCC 6538 (MIC = 7.81 µg/mL) and ATCC 43300 MRSA strains (MIC = 15.62 µg/mL). Importantly, the best performing compounds did not show cytotoxicity against normal cell lines. It seems practical to use some of these compounds or their derivatives in the future in the prevention and treatment of infections caused by some pathogenic or opportunistic microorganisms.

The Future of Antifungal Drug Therapy: Novel Compounds and Targets.

Fungal infections are a universal problem and are routinely associated with high morbidity and mortality rates in immunocompromised patients. Existing therapies comprise five different classes of antifungal agents, four of which target the synthesis of ergosterol and cell wall glucans. However, the currently available antifungals have many limitations, including poor oral bioavailability, narrow therapeutic indices, and emerging drug resistance resulting from their use, thus making it essential to investigate the development of novel drugs which can overcome these limitations and add to the antifungal armamentarium. Advances have been made in antifungal drug discovery research and development over the past few years as evidenced by the presence of several new compounds currently in various stages of development. In the following minireview, we provide a comprehensive summary of compounds aimed at one or more novel molecular targets. We also briefly describe potential pathways relevant for fungal pathogenesis that can be considered for drug development in the near future.

Acylhydrazone Subunits as a Proton Cargo Delivery System in 7-Hydroxyquinoline.

The reimagined concept of long-range tautomeric proton transfer using crane subunits is shown by designing and synthesising two new acylhydrazones containing a 7-hydroxyquinoline (7-OHQ) platform. The acylhydrazone subunits attached to the 7-OHQ at the 8th position act as crane arms for delivering proton cargo to the quinoline nitrogen. Light-induced tautomerization to their keto forms leads to Z/E isomerization of the C=C axle bond, followed by proton delivery to the quinoline nitrogen by the formation of covalent or hydrogen bonds. The axle's being either an imine or ketimine bond is the structural difference between the studied compounds. The -CH3 group in the latter provides steric strain, resulting in different proton transport pathways. Both compounds show long thermal stability in the switched state, which creates a tuneable action of bidirectional proton cargo transport by using different wavelengths of irradiation. Upon the addition of acid, the quinoline nitrogen is protonated; this results in E/Z configuration switching of the acylhydrazone subunits. This was proven by single-crystal X-ray structure analysis and NMR spectroscopy.

Novel arylcarbamate-N-acylhydrazones derivatives as promising BuChE inhibitors: Design, synthesis, molecular modeling and biological evaluation.

A novel series of arylcarbamate-N-acylhydrazones derivatives have been designed and synthesized as potential anti-cholinesterase agents. In vitro studies revealed that these compounds demonstrated selective for butyrylcholinesterase (BuChE) with potent inhibitory activity. The compounds 10a-d, 12b and 12d were the most potent BuChE inhibitors with IC50 values of 0.07-2.07 µM, highlighting the compound 10c (IC50 = 0.07 µM) which showed inhibitory activity 50 times greater than the reference drug donepezil (IC50 = 3.54 µM). The activity data indicates that the position of the carbamate group in the aromatic ring has a greater influence on the inhibitory activity of the derivatives. The enzyme kinetics studies indicate that the compound 10c has a non-competitive inhibition against BuChE with Ki value of 0.097 mM. Molecular modeling studies corroborated the in vitro inhibitory mode of interaction and show that compound 10c is stabilized into hBuChE by strong hydrogen bond interaction with Tyr128, π-π stacking interaction with Trp82 and CH⋯O interactions with His438, Gly121 and Glu197. Based on these data, compound10cwas identified as low-cost promising candidate for a drug prototype for AD treatment.

Synthesis and antifungal activity of new hybrids pyrimido[4,5-d]pyridazinone-N-acylhydrazones.

Paracoccidioidomycosis is an endemic mycosis in Latin America for which there is a high mortality rate and limited treatment options. There are no specific drugs to treat the systemic disease. Thus, there is a need for further studies focused on the development of specific drugs. In this work we synthesized new hybrids pyrimido[4,5-d]pyridazinone-N-acylhydrazone (5a-p) by simple methodologies with good yields. The antifungal activity of compounds was evaluated against P. brasiliensis (Pb18) and Candida spp. Compounds 5a, 5f, 5i, 5 k, 5m and 5n showed significant inhibition against Pb18 with MIC of 0.125 to 64 µg mL-1. Compound 5a is the most promising, showing potent fungicidal profile with MFC of 0.5 µg mL-1, synergic effect with amphotericin B, besides showing no toxicity against HeLa and Vero cells.

Quinolone-N-acylhydrazone hybrids as potent Zika and Chikungunya virus inhibitors.

This work reports the synthesis of quinolone-N-acylhydrazone hybrids, namely 6-R-N'-(2-hydxoxybenzylidene)-4-oxo-1,4-dihydroquinoline-3-carbohydrazide (R = H: 5a, F: 5b, Cl: 5c and Br: 5d), which exhibited excellent activity against arbovirus Zika (ZIKV) and Chikungunya (CHIKV). In vitro screening towards ZIKV and CHIKV inhibition revealed that all substances have significant antiviral activity, most of them being more potent than standard Ribavirin (5a-d: EC50 = 0.75-0.81 µM, Ribavirin: EC50 = 3.95 µM for ZIKV and 5a-d: 1.16-2.85 µM, Ribavirin: EC50 = 2.42 µM for CHIKV). The quinolone-N-acylhydrazone hybrids were non-toxic against Vero cells, in which compounds 5c and 5d showed the best selectivities (SI = 1410 and 630 against ZIKV and CHIKV, respectively). Antiviral activity was identified by inhibition of viral RNA production in a dose-dependent manner. In the evaluation of the time of addition of the compounds, we observed that 5b and 5c remain with strong effect even in the addition for 12 h after infection. The above results indicate that quinolone-N-acylhydrazones represent a new and promising class to be further investigated as anti-ZIKV and anti-CHIKV agents.

Self-Assembly in Water with N-Substituted Imines.

Imine synthesis has enjoyed a long history as the dynamic covalent reaction of choice for the construction of purely covalent molecular architectures. In organic solvents, the formation of imine bonds is reversible but leads to thermodynamically stable products. In the presence of water, however, imine bonds are labile, a fact which limits their utility as mediators of self-assembly in aqueous and biological media. In this Review, we discuss water-compatible dynamic covalent bonds based on N-substituted imine derivatives, namely hydrazones and oximes, for the self-assembly of metal-free organic architectures with well-defined structures. The reasons why hydrazones and oximes are more robust in water than their parent imines are explained. Recent progress in the self-assembly, characterization, and design principles of a variety of complex molecules including macrocycles, cages, catenanes, and knots in aqueous media is highlighted. Emerging applications for these molecules, including guest recognition and separations, are also discussed.

New sulfonamides containing organometallic-acylhydrazones: synthesis, characterisation and biological evaluation as inhibitors of human carbonic anhydrases.

A series of organometallic acylhydrazones was prepared, incorporating Re(CO)3, Mn(CO)3 and ferrocenyl moieties, which were subsequently reacted with amino-sulfonamides in order to obtain carbonic anhydrase (CA, EC 4.2.1.1) inhibitors possessing organometallic moieties in their molecules. The new derivatives were investigated as inhibitors of four human (h) CA isoforms with pharmaceutical applications, such as the cytosolic hCA I, II and VII and the mitochondrial hCA VA. An interesting inhibitory profile against these isoforms was obtained, with some of these metal complexes acting as subnanomolar or low nanomolar inhibitors. They were also thoroughly characterised from the chemical point of view, making them of interest for further developments in the field of metal complexes of sulfonamides with CA inhibitory action.

Acylhydrazones as Antifungal Agents Targeting the Synthesis of Fungal Sphingolipids.

The incidence of invasive fungal infections has risen dramatically in recent decades. Current antifungal drugs are either toxic, likely to interact with other drugs, have a narrow spectrum of activity, or induce fungal resistance. Hence, there is a great need for new antifungals, possibly with novel mechanisms of action. Previously our group reported an acylhydrazone called BHBM that targeted the sphingolipid pathway and showed strong antifungal activity against several fungi. In this study, we screened 19 derivatives of BHBM. Three out of 19 derivatives were highly active against Cryptococcus neoformansin vitro and had low toxicity in mammalian cells. In particular, one of them, called D13, had a high selectivity index and showed better activity in an animal model of cryptococcosis, candidiasis, and pulmonary aspergillosis. D13 also displayed suitable pharmacokinetic properties and was able to pass through the blood-brain barrier. These results suggest that acylhydrazones are promising molecules for the research and development of new antifungal agents.