Design, synthesis, biological and computational screening of novel pyridine-based thiadiazole derivatives as prospective anti-inflammatory agents

In this study, a novel series of pyridine-based thiadiazole derivatives (NTD1-NTD5) were synthesized as prospective anti-inflammatory agents by combining substituted carboxylic acid derivatives of 5-substituted-2-amino-1,3,4-thiadiazole with nicotinoyl isothiocyanate in the presence of acetone. The newly synthesized compounds were characterized by FTIR, 1H NMR, 13C NMR, and mass spectrometry. First, the compounds underwent rigorous in vivo testing for acute toxicity and anti-inflammatory activity and the results revealed that three compounds-NTD1, NTD2, and NTD3, displayed no acute toxicity and significant anti-inflammatory activity, surpassing the efficacy of the standard drug, diclofenac. Notably, NTD3, which featured benzoic acid substitution, emerged as the most potent anti-inflammatory agent among the screened compounds. To further validate these findings, an in silico docking study was carried out against COX-2 bound to diclofenac (PDB ID: 1pxx). The computational analysis demonstrated that NTD2, and NTD3, exhibited substantial binding affinity, with the lowest binding energies (-8.5 and -8.4, kcal/mol) compared to diclofenac (-8.4 kcal/mol). This alignment between in vivo and in silico data supported the robust anti-inflammatory potential of these derivatives. Moreover, molecular dynamics simulations were conducted, extending over 100 ns, to examine the dynamic interactions between the ligands and the target protein. The results solidified NTD3's position as a leading candidate, showing potent inhibitory activity through strong and sustained interactions, including stable hydrogen bond formations. This was further confirmed by RMSD values of 2-2.5 Å and 2-3Ǻ, reinforcing NTD3's potential as a useful anti-inflammatory agent. The drug likeness analysis of NTD3 through SwissADME indicated that most of the predicted parameters including Lipinski rule were within acceptable limits. While these findings are promising, further research is necessary to elucidate the precise relationships between the chemical structures and their activity, as well as to understand the mechanisms underlying their pharmacological effects. This study lays the foundation for the development of novel anti-inflammatory therapeutics, potentially offering improved efficacy and safety profiles.

NAD+ Precursors Nicotinamide Mononucleotide (NMN) and Nicotinamide Riboside (NR): Potential Dietary Contribution to Health

PURPOSE OF REVIEW

NAD+ is a vital molecule that takes part as a redox cofactor in several metabolic reactions besides being used as a substrate in important cellular signaling in regulation pathways for energetic, genotoxic, and infectious stress. In stress conditions, NAD+ biosynthesis and levels decrease as well as the activity of consuming enzymes rises. Dietary precursors can promote NAD+ biosynthesis and increase intracellular levels, being a potential strategy for reversing physiological decline and preventing diseases. In this review, we will show the biochemistry and metabolism of NAD+ precursors NR (nicotinamide riboside) and NMN (nicotinamide mononucleotide), the latest findings on their beneficial physiological effects, their interplay with gut microbiota, and the future perspectives for research in nutrition and food science fields.

RECENT FINDINGS

NMN and NR demonstrated protect against diabetes, Alzheimer disease, endothelial dysfunction, and inflammation. They also reverse gut dysbiosis and promote beneficial effects at intestinal and extraintestinal levels. NR and NMN have been found in vegetables, meat, and milk, and microorganisms in fermented beverages can also produce them. NMN and NR can be obtained through the diet either in their free form or as metabolites derivate from the digestion of NAD+. The prospection of NR and NMN to find potential food sources and their dietary contribution in increasing NAD+ levels are still an unexplored field of research. Moreover, it could enable the development of new functional foods and processing strategies to maintain and enhance their physiological benefits, besides the studies of new raw materials for extraction and biotechnological development.

Intermolecular interactions in the crystalline structure of some polyhalogenated Di- And triamino Pyridines: Spectroscopical perspectives

Supramolecular synthon is identified as a unit and provides important structural and energetic information in the study of organic crystals. However, the direct estimation of the supramolecular interaction remains challenging. In the present work six polyhalogenated di- or triamino pyridines were synthesised, their crystalline structure was characterised, and corresponding supramolecular synthons were studied using a combination of quantum mechanical calculations and FT-IR and Raman spectroscopy. Some distinctive features were identified especially for three vibrational normal modes (RNMs) related to the pyridine ring (viz. RNM₁, RNM₃ and RNM₇) in the vibrational spectra (FT-IR and Raman) of the solid samples, which are due to the supramolecular interactions, hydrogen bond (hb) in particular, according to the quantum mechanical calculations. The comparison between the IR and Raman spectra of experimental and simulated results indicates that the adjacent intermolecular hydrogen bonds between two same molecules extensively exist in the solid samples. Moreover, some quantitative correlation was established among the dimerisation energies for hb dimers (hb1 dimers for compounds 1 and 2), the ring structure defined by the distribution of the substituents and quantitative characteristics of the vibrational spectra, for instance, the splitting magnitudes for RNM₃(2) in IR spectra and the peak gap between RNM₁ and RNM₂ in Raman spectra.

Structure-activity relationship around PI-2620 highlights the importance of the nitrogen atom position in the tricyclic core

Tau aggregates represent a critical pathology in Alzheimer's disease (AD) and other forms of dementia. The extent of Tau neurofibrillary tangles across defined brain regions corresponds well to the observed level of cognitive decline in AD. Compound 1 (PI-2620) was recently identified as a promising Tau positron emission tomography tracer for AD and non-AD tauopathies. To evaluate the impact of the N-atom position with respect to Tau- and off-target binding, tricyclic core analogs of PI-2620 with nitrogen atoms at different positions were prepared. Affinity to aggregated Tau was evaluated using human AD brain homogenates, and their off-target binding was evaluated in a monoamine oxidase A (MAO-A) competition assay. The novel tricyclic core derivatives all displayed inferior Tau binding or MAO-A off-target selectivity, indicating PI-2620 to be the optimal design for high affinity binding to Tau and high MAO-A selectivity.

Fluorescent sensing for some nitric oxide donors in dosage forms and biological matrices

New fluorescent sensing of some nitric oxide donors, nitroglycerin and isosorbide dinitrate was developed in our laboratories. Two fluorescent reagents, 2-(2-hydroxyethylamino)-4,6-dimethylpyridine-3-carbonitrile, 3a and 2-(3-chloro-phenylamino)-4,6-dimethylpyridine-3-carbonitrile, 3b were synthesized in our laboratories and a comparative study was performed between them from the point of fluorescence intensity. The fluorophore, 3a, was selected for the analytical study as it exhibit higher quantum yield value. The interaction between the selected drugs and the fluorophore was noticed to be quenching. The mechanism of quenching was studied and it was supposed to be collisional quenching through photo induced electron transfer process. The proposed sensing method was applied successfully for the analysis of nitroglycerin and isosorbide dinitrate in dosage forms within concentration range of (0.05-0.5 µg/mL) with percentage recoveries of 99.9 ± 0.5 and 99.9 ± 0.7 respectively. The studied drugs, nitroglycerin and isosorbide dinitrate, were also probed in spiked biological matrices such as plasma samples with percentage recoveries of 99.1 ± 1.97 and 100.7 ± 1.96 and urine samples with percentage recoveries of 100.4 ± 1.8 and 100.3 ± 1.7 respectively. In vivo analysis of both drugs in real plasma was also investigated. The sensing method exhibit well intra-day and inter day precision with %RSD < 2%.

Ionic liquid as an effective green media for the synthesis of (5Z, 8Z)-7H-pyrido[2,3-d]azepine derivatives and recycable Fe3O4/TiO2/multi-wall cabon nanotubes magnetic nanocomposites as high performance organometallic nanocatalyst

In this research we investigated the preparation of new (5Z, 8Z)-7H-pyrido[2,3-d]azepine derivatives in high yields via multicomponent reaction of isatins, alkyl bromides, activated acetylenic compounds and ammonium acetate using ionic liquid 1-octhyl-3-methyl imidazolium bromide ([OMIM]Br) as a stabilizer and soft template at room temperature in the presence of Fe₃O₄/TiO₂/Carbon nanotubes magnetic nanocomposites as a reusable and effective nanocatalyst that are synthesized using ionic liquid [OMIM]Br as a stabilizer, soft template, green media and moderate base. Because of having a NH group in the synthesized pyridine derivatives, we investigate antioxidant property of some synthesized compounds by diphenyl-picrylhydrazine (DPPH) radical trapping and power of ferric reduction experiment. Short time of reaction, high yields of product, easy separation of catalyst and products are some advantages of this procedure.

Synthesis of Novel Pyridine Bearing Biologically Active Imidiazolyl, Pyrazolyl, Oxa/thiadiazolyl and Urea Derivatives as Promising Anticancer Agents

BACKGROUND

A novel series of pyridine containing 1,3,4-oxa/thiadiazol derivatives 4a,b, pyrazole derivatives 5-7, thiazole derivatives 9a,b and 17a-c, urea derivatives 12a-c, imidiazole derivative 16, imidazo[1,2-a]pyridine derivatives 18a, b, tetrazole 19, pyrane 20 and pyridine derivatives 21 has been synthesized.

OBJECTIVE

This research aims to synthesize 6-(Trifluoromethyl)-2-{[3-(trifluoromethyl)phenyl] amino} nicotinohydrazide 2 and 6-(trifluoromethyl)-2-{[3-(trifluoromethyl)phenyl]amino} pyridin-3-carboaldhyde 15 as key intermediate for the synthesis of novel pyridine derivatives bearing different heterocyclic rings in order to study the additive effect of this ring toward tumor cell lines.

METHODS

6-(Trifluoromethyl)-2-{[3-(trifluoromethyl)phenyl]amino} nicotinohydrazide 2 was synthesized in a series of synthetic steps and was used as key intermediate for the synthesis of compounds 3-(1,3,4- oxa/thiadiazol-2-yl)-6-(trifluoromethyl)-N-(3- trifluoromethyl) phenyl) pyridin-2-amine 4a,b, (3,5-dimethyl- 1H-pyrazol-1-yl derivatives) [6-(trifluoromethyl)-2-{[3- trifluoromethyl) phenyl] amino} pyridin-3- yl]methanone 5a,b, 6-8, 9a,b and 12a-c. Also, 6-(trifluoromethyl)-2-{[3-(trifluoromethyl)phenyl]amino} pyridin-3-carboaldhyde (15) was used as a key intermediate for the synthesis of novel series of pyridine derivatives with different heterocyclic ring (16-21).

RESULTS

Structures of the newly synthesized compounds were established by elemental analysis and spectral data. All the synthesized compounds were screened for their in vitro anticancer activity against liver cancer (HepG2), human colon cancer (HT-29) and human breast adenocarcinoma cell lines (MCF-7).

CONCLUSION

All the synthesized compounds were investigated for their in vitro antitumor activity. Compounds 4b, 9a,b and 19 showed higher antitumor activity than the doxorubicin. Interestingly, pyridine with pfluorophenyl urea 12a demonstrated the most potent antitumor activity. The activity of these compounds is strongly dependent on the basic skeleton of the molecules and the nature of the heterocyclic ring attached to the pyridine moiety.

Effect of the functionalisation agent on the surface-enhanced Raman scattering (SERS) spectrum: Case study of pyridine derivatives

Nowadays, the use of functionalised surface-enhanced Raman scattering (SERS) substrates has become common. These surface modifying agents notably act as Raman reporters, as sensors of biological processes (pH, redox probes) or to increase the sensitivity and/or the specificity of SERS detections. However, the effects of the functionalisation agents are deeply examined in very few studies, even though they can affect the aggregation behaviour of the SERS substrate. Moreover, depending on their concentration and on the pH, their spectral signature can be modified and they can even degrade if stored inappropriately. In this context, this paper aims at emphasising the importance of the different aspects previously listed in the selection of a functionalisation agent. Pyridine derivatives were picked out to highlight these parameters, as some of these compounds are commonly used to be grafted onto SERS substrates. Two widespread syntheses of nanoparticles were selected as SERS substrates: citrate-reduced gold and silver nanoparticles. The surface of the nanoparticles was functionalised with several pyridine derivatives at different concentrations and in several solvents. It was observed that the molecules under study had a concentration-dependent effect on nanoparticle aggregation. A stability study was furthermore conducted in order to determine the best preservation conditions of the grafting solutions. In conclusion, this paper shines a light on the relevance of the investigation of the too-often neglected behaviour of the surface modifying agents. Before their application in SERS analyses, parameters such as the label concentration should therefore be included in an experimental design to optimise the sample preparation.

Potent colchicine-site ligands with improved intrinsic solubility by replacement of the 3,4,5-trimethoxyphenyl ring with a 2-methylsulfanyl-6-methoxypyridine ring

Colchicine site antimitotic agents typically suffer from low aqueous solubilities and are formulated as phosphate prodrugs of phenolic groups. These hydroxyl groups are the aim of metabolic transformations leading to resistance. There is an urgent need for more intrinsically soluble analogues lacking these hydroxyl groups. The 3,4,5-trimethoxyphenyl ring of combretastatin A-4 is a liability in terms of solubility but it is considered essential for high cytotoxic and tubulin polymerization inhibitory (TPI) activity. We have synthesized 36 new analogues of combretastatin A-4 replacing the trimethoxyphenyl moiety with more polar pyridine based moieties, measured their aqueous solubility, and studied their anti-proliferative effects against 3 human cancer cell lines. We show here that pyridine rings can be successful replacements for the trimethoxyphenyl ring, resulting in potent and more soluble analogues. The more straightforward replacement, a 2,6-dimethoxypyridine ring led to inactive analogues, but a 2-methoxy-6-methylsulfanylpyridine moiety led to active analogues when combined with different B rings. This replacement led to potent cytotoxic activity against sensitive human cancer cell lines due to tubulin inhibition, as shown by cell cycle analysis, confocal microscopy, and tubulin polymerization inhibitory activity studies. Cell cycle analysis also showed apoptotic responses following treatment. Docking studies suggested binding at the colchicine site of tubulin and provided a good agreement with the observed SAR. A 2-methoxy-6-methylsulfanylpyridine moiety is a good trimethoxyphenyl ring replacement for the development of new colchicine site ligands.

Design, synthesis, biological evaluation and molecular modeling of novel 2-amino-4-(1-phenylethoxy) pyridine derivatives as potential ROS1 inhibitors

With the aim of discovering potential and selective inhibitors targeting ROS1 kinase, we rationally designed, synthesized and evaluated two series of novel 2-amino-pyridine derivatives with 1-phenylethoxy at C-3 and C-4 position. The enzymic assays results indicated that six of the new compounds 13b-13d and 14a-14c showed remarkably higher inhibitory activities against ROS1 kinase. The most promising compounds, 13d and 14c displayed the most desired ROS1 inhibitory activity with IC₅₀ values of 440 nM and 370 nM respectively. Furthermore, 13d and 14c displayed ROS1 inhibitory selectivity of about 7-fold and 12-fold, relative to that of ALK sharing about 49% amino acid sequence homology in the kinase domains. They also showed good anti-proliferative effects against ROS1-addicted HCC78 cell lines with the IC₅₀ values of 8.1 μM and 65.3 μM, respectively. Moreover, molecular docking and molecular dynamics simulation studies disclosed that compound 14c and 13d shared similar binding poses with Crizotinib except the selective binding site of ROS1. It also gave a probable molecular explanation for their activity and selectivity, which the methoxyl group in benzene ring was the crucial to the selectivity to ROS1 versus ALK.

Desing and synthesis of potent anti-Trypanosoma cruzi agents new thiazoles derivatives which induce apoptotic parasite death

Chagas disease, caused by the kinetoplastid protozoan parasite Trypanosoma cruzi, remains a relevant cause of illness and premature death and it is estimated that 6 million to 7 million people are infected worldwide. Although chemotherapy options are limited presenting serious problems, such as low efficacy and high toxicity. T. cruzi is susceptible to thiazoles, making this class of compounds appealing for drug development. Previously, thiazoles resulted in an increase in anti-T. cruzi activity in comparison to thiosemicarbazones. Here, we report the structural planning, synthesis and anti-T. cruzi evaluation of new thiazoles derivatives (3a-m and 4a-m), designed from molecular hybridization associated with non-classical bioisosterism. By varying substituents attached to the phenyl and thiazole rings, substituents were observed to retain, enhance or greatly increase their anti-T. cruzi activity, in comparison to the corresponding thiosemicarbazones. In most cases, electron-withdrawing substituents, such as bromine, 3,4-dichloro and nitro groups, greatly increased antiparasitic activity. Specifically, new thiazoles were identified that inhibit the epimastigote proliferation and were toxic for trypomastigotes without affecting macrophages viability. These compounds were also evaluated against cruzain. However, inhibition of this enzyme was not observed, suggesting that the compounds work through another mechanism. In addition, examination of T. cruzi cell death showed that these molecules induce apoptosis. In conclusion, except for compounds 3h and 3k, all thiazoles derivatives evaluated exhibited higher cytotoxic activity against the trypomastigote forms than the reference medicament benznidazole, without affecting macrophages viability. Compounds 4d and 4k were highlights, CC50 = 1.2 e 1.6 μM, respectively. Mechanistically, these compounds do not inhibit the cruzain, but induce T. cruzi cell death by an apoptotic process, being considered a good starting point for the development of new anti-Chagas drug candidates.

Simulation and comparative analysis of binding modes of nucleoside and non-nucleoside agonists at the A2B adenosine receptor

PURPOSE

A2B receptor agonists are studied as possible therapeutic tools for a variety of pathological conditions. Unfortunately, medicinal chemistry efforts have led to the development of a limited number of potent agonists of this receptor, in most cases with a low or no selectivity versus the other adenosine receptor subtypes. Among the developed molecules, two structural families of compounds have been identified based on nucleoside and non-nucleoside (pyridine) scaffolds. The aim of this work is to analyse the binding mode of these molecules at 3D models of the human A2B receptor to identify possible common interaction features and the key receptor residues involved in ligand interaction.

METHODS

The A2B receptor models are built by using two recently published crystal structures of the human A2A receptor in complex with two different agonists. The developed models are used as targets for molecular docking studies of nucleoside and non-nucleoside agonists. The generated docking conformations are subjected to energy minimization and rescoring by using three different scoring functions. Further analysis of top-score conformations are performed with a tool evaluating the interaction energy between the ligand and the binding site residues.

RESULTS

Results suggest a set of common interaction points between the two structural families of agonists and the receptor binding site, as evidenced by the superimposition of docking conformations and by analysis of interaction energy with the receptor residues.

CONCLUSIONS

The obtained results show that there is a conserved pattern of interaction between the A2B receptor and its agonists. These information and can provide useful data to support the design and the development of A2B receptor agonists belonging to nucleoside or non-nucleoside structural families.