Synthesis of a novel series of thiazole-based histone acetyltransferase inhibitors.

Acetylation, which targets a broad range of histone and non-histone proteins, is a reversible mechanism and plays a critical role in eukaryotic genes activation/deactivation. Acetyltransferases are very well conserved through evolution. This allows the use of a simple model organism, such as budding yeast, for the study of their related processes and to discover specific inhibitors. Following a simple yeast-based chemogenetic approach, we have identified a novel HAT (histone acetyltransferase) inhibitor active both in vitro and in vivo. This new synthetic compound, 1-(4-(4-chlorophenyl)thiazol-2-yl)-2-(propan-2-ylidene)hydrazine, named BF1, showed substrate selectivity for histone H3 acetylation and inhibitory activity in vitro on recombinant HAT Gcn5 and p300. Finally, we tested BF1 on human cells, HeLa as control and two aggressive cancer cell lines: a neuroblastoma from neuronal tissue and glioblastoma from brain tumour. Both global acetylation of histone H3 and specific acetylation at lysine 18 (H3AcK18) were lowered by BF1 treatment. Collectively, our results show the efficacy of this novel HAT inhibitor and propose the utilization of BF1 as a new, promising tool for future pharmacological studies.

Selective MAO-B inhibitors: a lesson from natural products.

Monoamine oxidases (MAOs) are mitochondrial bound enzymes, which catalyze the oxidative deamination of monoamine neurotransmitters. Inside the brain, MAOs are present in two isoforms: MAO-A and MAO-B. The activity of MAO-B is generally higher in patients affected by neurodegenerative diseases like Alzheimer's and Parkinson's. Therefore, the search for potent and selective MAO-B inhibitors is still a challenge for medicinal chemists. Nature has always been a source of inspiration for the discovery of new lead compounds. Moreover, natural medicine is a major component in all traditional medicine systems. In this review, we present the latest discoveries in the search for selective MAO-B inhibitors from natural sources. For clarity, compounds have been classified on the basis of structural analogy or source: flavonoids, xanthones, tannins, proanthocyanidins, iridoid glucosides, curcumin, alkaloids, cannabinoids, and natural sources extracts. MAO inhibition values reported in the text are not always consistent due to the high variability of MAO sources (bovine, pig, rat brain or liver, and human) and to the heterogeneity of the experimental protocols used.

Computer-aided molecular design of asymmetric pyrazole derivatives with exceptional enantioselective recognition toward the Chiralcel OJ-H stationary phase.

A computer-aided design of novel asymmetric pyrazoles with improved enantioselective properties was performed by docking experiments starting from a model of Chiralcel OJ chiral in the stationary phase. Synthesis and HPLC experiments confirmed the theoretical prediction and led to a detailed investigation of the enantioselective recognition process. For the first time, looking at the time spent by each enantiomer in contact with the CSP during long molecular dynamic simulations, the experimental analytical trend has been reproduced.

Synthesis and selective inhibitory activity against human COX-1 of novel 1-(4-substituted-thiazol-2-yl)-3,5-di(hetero)aryl-pyrazoline derivatives.

Novel 1-(4-ethyl carboxylate-thiazol-2-yl)-3,5-di(hetero)aryl-2-pyrazoline derivatives were obtained by reacting 3,5-di(hetero)aryl-1-thiocarbamoyl-2-pyrazolines with the ethyl ester of α-bromo-pyruvic acid. The synthesized compounds were confirmed by spectroscopic data and assayed to evaluate their in vitro ability to inhibit both isoforms of human cyclooxygenase (hCOX). Some derivatives (compounds 5, 6, 13, 16, and 17) displayed promising selectivity against hCOX-1 in the micromolar range and were shown to have a selectivity index similar or better than the reference drugs (indometacin, diclofenac). The introduction of a phenyl or a 4-F-phenyl ring on the C5 associated with a 4-substituted phenyl or a heteroaryl group on the C3 of (4-substituted-thiazol-2-yl)pyrazoline derivatives improved the activity against hCOX-1. Thanks to these preliminary results it could be possible to extend our knowledge of the pharmacophoric requirements for the discovery of new pyrazoline-based hCOX-1 inhibitors.

Synthesis and molecular modelling studies of prenylated pyrazolines as MAO-B inhibitors.

A series of N-substituted-3-[(2'-hydroxy-4'-prenyloxy)-phenyl]-5-phenyl-4,5-dihydro-(1H)-pyrazolines were synthesized and tested on human monoamine oxidase-A and -B isoforms. Structure-activity relationships and molecular modelling showed that some substitutions, such as benzyloxy or chlorine atom, improve the best interaction with active site of hMAO-B.

Synthesis, selective anti-Helicobacter pylori activity, and cytotoxicity of novel N-substituted-2-oxo-2H-1-benzopyran-3-carboxamides.

N-substituted-3-carboxamido-coumarin derivatives were prepared and evaluated for selective antibacterial activity against 20 isolates of Helicobacter pylori clinical strains, including five metronidazole resistant ones. Some of them possessed the best activity against H. pylori metronidazole resistant strains with MIC values lower than the drug reference (metronidazole). Furthermore, anti-inflammatory activity through the inhibition of the IL-8 production was investigated.

Investigations on the 2-thiazolylhydrazyne scaffold: synthesis and molecular modeling of selective human monoamine oxidase inhibitors.

A new series of [4-(3-methoxyphenyl)-thiazol-2-yl]hydrazyne derivatives were synthesized in good yield (71-99%) and characterized by elemental analysis and (1)H NMR studies. The compounds were assayed for their in vitro human monoamine oxidase (hMAO) inhibitory activity and selectivity and most of them showed IC(50) values in the nanomolar range, thus demonstrating our interest in this privileged scaffold. The most active and selective derivative (20), bearing a pyridine moiety on the CN, displayed IC(50)=3.81+/-0.12 nM and selectivity ratio=119 toward hMAO-B. Molecular modeling studies were carried out on recent and high resolution hMAO-A and hMAO-B crystallographic structures to better justify the enzyme-inhibitor interaction toward hMAO isoforms and to explain the structure-activity relationship of this kind of inhibitors.

A new series of flavones, thioflavones, and flavanones as selective monoamine oxidase-B inhibitors.

A new series of synthetic flavones, thioflavones, and flavanones has been synthesized and evaluated as potential inhibitors of monoamine oxidase isoforms (MAO-A and -B). The most active series is the flavanone one with higher selective inhibitory activity against MAO-B. Some of these flavanones (mainly the most effective) have been separated and tested as single enantiomers. In order to investigate the MAOs recognition of the most active and selective compounds, a molecular modeling study has been performed using available Protein Data Bank (PDB) structures as receptor models for docking experiments.

Synthesis, semipreparative HPLC separation, biological evaluation, and 3D-QSAR of hydrazothiazole derivatives as human monoamine oxidase B inhibitors.

The present study reports on synthesis in high yields (70-99%), HPLC enantioseparation, inhibitory activity against human monoamino oxidases, and molecular modeling including 3D-QSAR studies, of a large series of (4-aryl-thiazol-2-yl)hydrazones (1-45). Most of the synthesized compounds proved to be potent and selective inhibitors of hMAO-B isoform in the micromolar or nanomolar range, thus demonstrating that hydrazothiazole could be considered a good pharmacophore to design new hMAO-B inhibitors. Due to the presence in some derivatives of a chiral center, we also performed a semipreparative chromatographic enantioseparation of these compounds obtained by a stereoconservative pattern. The separated enantiomers were submitted to in vitro biological evaluation to point out the stereorecognition of the active site of the enzyme towards these structures. Finally, a 3D-QSAR study was carried out using Comparative Molecular Field Analysis (CoMFA), aiming to deduce rational guidelines for the further structural modification of these lead compounds.

Use of cyclodextrins in biotransformation reactions with cell cultures of Morus nigra: biosynthesis of prenylated chalcone isocordoin.

In vivo biotransformation experiments were performed by using a cell suspension culture of Morus nigra expressing a high PT (prenyltransferase) activity, fed with the target substrate 2',4'-dihydroxychalcone. In order to improve the reaction yields by enhancing the chalcone solubility, three different cyclodextrins have been used to host the substrate. The respective complexes have been studied by means of both spectroscopic and calorimetric techniques (Fourier-transform infrared, 1H-NMR and differential scanning calorimetry) and the solution behaviours have been characterized by solubility phase studies. The hydroxypropyl-beta-cyclodextrin complex was found to be the most suitable for biotransformation, and the reaction of prenylation resulted in a 6-fold higher yield of the final product when compared with the use of the free substrate. The reaction provided as the sole product the 3'-dimethylallyl derivative isocordoin, a biologically active plant compound. The results obtained allow the development of systems based on the use of biofermentors or the use of immobilized cells in order to enhance the biotransformation yields.

Synthesis, molecular modeling studies and selective inhibitory activity against MAO of N1-propanoyl-3,5-diphenyl-4,5-dihydro-(1H)-pyrazole derivatives.

A series of N1-propanoyl-3,5-diphenyl-4,5-dihydro-(1H)-pyrazole derivatives were synthesized and assayed as inhibitors of MAO-A and MAO-B isoforms. Most of the tested compounds showed inhibitory activity with micromolar values and MAO-A selectivity. In addition a computational work was carried out on the most selective compound 3b to highlight the most relevant interactions in the mechanism of recognition within both the MAO-A and the MAO-B enzyme active sites.

Monoamine oxidase isoform-dependent tautomeric influence in the recognition of 3,5-diaryl pyrazole inhibitors.

A series of 3,5-diaryl pyrazoles were prepared and assayed for their ability to inhibit reversibly monoamine oxidase-A (MAO-A) and monoamine oxidase B (MAO-B). Several compounds show inhibitory activity with concentration values in the nanomolar range. A computational work was carried out on the two most selective inhibitors that have tautomeric pyrazole forms. The binding free energies of these compounds for each MAO isoform were influenced by the tautomeric equilibria.

Selective inhibitory activity against MAO and molecular modeling studies of 2-thiazolylhydrazone derivatives.

A series of 2-thiazolylhydrazone derivatives have been investigated for the ability to inhibit the activity of the A and B isoforms of monoamine oxidase (MAO) selectively. All of the compounds showed high activity against both the MAO-A and the MAO-B isoforms with pKi values ranging between 5.92 and 8.14 for the MAO-A and between 4.69 and 9.09 for the MAO-B isoforms. Both the MAO-A and the MAO-B isoforms, deposited in the Protein Data Bank as model 2BXR and 1GOS, respectively, were considered in a computational study performed with docking techniques on the most active and MAO-B-selective inhibitor, 18.

Synthesis, biological evaluation and 3D-QSAR of 1,3,5-trisubstituted-4,5-dihydro-(1H)-pyrazole derivatives as potent and highly selective monoamine oxidase A inhibitors.

The present report provides a extended study of the chemistry, the inhibitory activity against monoamino oxidases (MAO), and molecular modeling including the 3D-QSAR hypothesis of 1,3,5-trisubstituted-4,5-dihydro-(1H)-pyrazole derivatives. Four series of about eighty novel pyrazoline derivatives were prepared and investigated for their ability to inhibit the activity of the A and B isoforms of MAO selectively. Most of the new synthesized compounds proved more reversible, potent, and selective inhibitors of MAO-A than of MAO-B, and could be taken into account to develop the search further in this field, knowing that reversible and selective MAO-A inhibitors are used as antidepressant and antianxiety drug. The 30 most active compounds show inhibitory activity on MAO-A in the 8.6 x 10(-8) - 9.0 x 10(-9)M range. Moreover, it should be pointed out that for most of them a high IC(50) > or = 10(-9)M value is associated with a high A-selectivity (Selectivity Index MAO-B/MAO-A in the 10,000-16,250 range). Furthermore, due to the presence of a chiral centre at the C5 position of the pyrazole moiety, we performed the semi-preparative chromatographic enantioseparation of the most potent, selective, and chiral compounds. The separated enantiomers were then submitted to in vitro biological evaluation, and from the results of these experiments it has been possible to point out a difference in inhibiting the two isoforms selectively between the racemic mixture and the single enantiomers. The molecular modeling work was carried out combining the Glide docking approach with CoMFA with the aim to rationalize the structure-activity relationships of each pyrazoline inhibitor toward MAO-A and MAO-B isoforms and to derive a suitable selectivity model.

Synthesis and in vitro selective anti-Helicobacter pylori activity of N-substituted-2-oxo-2H-1-benzopyran-3-carboxamides.

In order to develop new anti-Helicobacter pylori agents, five new and three already known N-substituted-2-oxo-2H-1-benzopyran-3-carboxamides (coumarin-3-carboxamides) were prepared and evaluated for their antibacterial activity. All synthesized compounds showed little or no activity against different species of Gram-positive and Gram-negative bacteria of clinical relevance and against various strains of pathogenic fungi. Among the prepared compounds those with a 4-acyl-phenyl group showed the best activity against H. pylori metronidazole resistant strains in the 0.25-1 microg/ml MIC range, indicating the presence of an acyl function as an important feature for activity.

Anti-Candida activity and cytotoxicity of a large library of new N-substituted-1,3-thiazolidin-4-one derivatives.

On the basis of the recent findings about the biological properties of thiazolidinones and taking into account the encouraging results about the antifungal activity of some (thiazol-2-yl)hydrazines, new N-substituted heterocyclic derivatives were designed combining the thiazolidinone nucleus with the hydrazonic portion. In details, 1,3-thiazolidin-4-ones bearing (cyclo)aliphatic or (hetero)aromatic moieties linked to the N1-hydrazine at C2 were synthesized and classified into three series according to the aromatic or bicyclic rings connected to the lactam nitrogen of the thiazolidinone. These molecules were assayed for their anti-Candida effects in reference to the biological activity of the conventional topic (clotrimazole, miconazole, tioconazole) and systemic drugs (fluconazole, ketoconazole, amphotericin B). Finally, we investigated the selectivity against fungal cells by testing the compounds endowed with the best MICs on Hep2 cells in order to assess their cell toxicity (CC50) and we noticed that two derivatives were less cytotoxic than the reference drug clotrimazole. Moreover, a preliminary molecular modelling approach has been performed against lanosterol 14-α demethylase (CYP51A1) to rationalize the activity of the tested compounds and to specify the target protein or enzyme.

Synthesis, molecular modeling studies, and selective inhibitory activity against monoamine oxidase of 1-thiocarbamoyl-3,5-diaryl-4,5-dihydro-(1H)- pyrazole derivatives.

A novel series of 1-thiocarbamoyl-3,5-diaryl-4,5-dihydro-(1H)-pyrazole derivatives have been synthesized and investigated for the ability to inhibit selectively the activity of the A and B isoforms of monoamine oxidase (MAO). All the synthesized compounds show high activity against both the MAO-A and the MAO-B isoforms with Ki values between 27 and 4 nM and between 50 and 1.5 nM, respectively, except for a few derivatives whose inhibitory activity against MAO-B was in the micromolar range. Knowing that stereochemistry may be an important modulator of biological activity, we performed the semipreparative chromatographic enantioseparation of the most potent, selective, and chiral compounds. The separated enantiomers were then submitted to in vitro biological evaluation. The selectivity of the (-)-(S)-1 enantiomer against MAO-B increases twice and a half, while the selectivity of the (-)-(S)-4 enantiomer against MAO-A triples. Both the MAO-A and MAO-B isoforms respectively of the 1O5W and 1GOS models deposited in the Protein Data Bank were considered in the computational study. The docking study was carried out using several computational approaches with the aim of proposing possible binding modes of the MAO enantioselective compounds 1 and 4.

Synthesis and selective inhibitory activity of 1-acetyl-3,5-diphenyl-4,5-dihydro-(1H)-pyrazole derivatives against monoamine oxidase.

A novel series of 1-acetyl-3-(4-hydroxy- and 2,4-dihydroxyphenyl)-5-phenyl-4,5-dihydro-(1H)-pyrazole derivatives 1-12 have been synthesized and investigated for the ability to selectively inhibit the activity of the A and B isoforms of monoamine oxidase (MAO). The new synthesized compounds 1-12 proved to be more reversible, potent, and selective inhibitors of MAO-A than of MAO-B. Knowing that stereochemistry may be an important modulator of biological activity, we performed the semipreparative chromatographic enantioseparation of the most potent, selective, and chiral compounds, 6 and 11. The separated enantiomers were then submitted to in vitro biological evaluation while increasing their inhibitory activity and A selectivity. The (-)-6 enantiomer shows K(i(MAO-A)) = 2 nM and SI = 165 000, (+)-6 shows K(i(MAO-A)) = 6 nM and SI = 166 666, (-)-11 shows K(i(MAO-A)) = 4 nM and SI = 80 000, and (+)-11 shows K(i(MAO-A)) = 7 nM and SI = 38 571.

Design, synthesis and biological characterization of thiazolidin-4-one derivatives as promising inhibitors of Toxoplasma gondii.

We designed and synthesized a large number of novel thiazolidin-4-one derivatives for the evaluation of their anti-Toxoplasma gondii activity. This scaffold was functionalized at the N1-hydrazine portion with aliphatic, cycloaliphatic and (hetero)aromatic moieties. Then, a benzyl pendant was introduced at the lactamic NH of the core nucleus to evaluate the influence of this chemical modification on biological activity. The compounds were subjected to several in vitro assays to assess their anti-parasitic efficacy, cytotoxicity on fibroblasts, inhibition of tachyzoite invasion/attachment and replication after treatment. Results showed that fourteen of these thiazole-based compounds compare favorably to control compound trimethoprim in terms of parasite growth inhibition.

Synthesis and cytotoxicity of novel (thiazol-2-yl)hydrazine derivatives as promising anti-Candida agents.

Thirty-eight new (4-(4-substituted-phenyl/2,4-disubstituted-phenyl)-thiazol-2-yl)hydrazine derivatives were synthesized in good yield and assayed for their in vitro anti-Candida activity, compared to topical and systemic antifungal drugs, against twenty-two clinical isolates of Candida spp. The concurrent presence of aliphatic chains or cycloaliphatic rings at N1-hydrazine and a 4-methyl/4-methoxyphenyl at C4 position of the thiazole nucleus exhibited an interesting anti-Candida inhibitory activity. Moreover, some of the most active compounds showed synergistic antifungal effects and lower cell toxicity when combined with clotrimazole.