Synthesis and pharmacological evaluation of novel isoquinoline N-sulphonylhydrazones designed as ROCK inhibitors

In this study, we synthesized a new congener series of N-sulphonylhydrazones designed as candidate ROCK inhibitors using the molecular hybridization of the clinically approved drug fasudil (1) and the IKK-β inhibitor LASSBio-1524 (2). Among the synthesized compounds, the N-methylated derivative 11 (LASSBio-2065) showed the best inhibitory profile for both ROCK isoforms, with IC₅₀ values of 3.1 and 3.8?µM for ROCK1 and ROCK2, respectively. Moreover, these compounds were also active in the scratch assay performed in human breast cancer MDA-MB 231 cells and did not display toxicity in MTT and LDH assays. Molecular modelling studies provided insights into the possible binding modes of these N-sulphonylhydrazones, which present a new molecular architecture capable of being optimized and developed as therapeutically useful ROCK inhibitors.     

Peptides based on CcdB protein as novel inhibitors of bacterial topoisomerases

The ccd toxin-antitoxin system of the F plasmid encodes CcdB, a protein that poisons the essential Escherichia coli DNA gyrase, unique type IIA topoisomerase able to introduce negative supercoils into DNA. Based on CcdB structure, a series of linear peptide analogues were obtained by the solid-phase methodology. One of these peptides (CcdBET2) displayed inhibition of the supercoiling activity of bacterial DNA gyrase with a concentration required for complete inhibition (IC(100)=10 microM) lower than the wild type CcdB. For Topo IV, a second type IIA bacterial topoisomerase, CcdBET2 was better inhibited the relaxation activity with an IC(100) of 5 microM (wt CcdB>10 microM). The replacement of Gly, present in the three C-terminal amino acid residues, by Glu, abolished the capacity to inhibit the gyrase but not the Topo IV activities. These findings demonstrate that the mechanism by which CcdBET2 inhibits DNA gyrase is different of the mechanism by which inhibits Topo IV. Therefore, CcdBET2 is a new type II topoisomerase inhibitor with specificity for Topo IV.     

Discovery of pyrazolthiazoles as novel and potent inhibitors of bacterial gyrase

Bacterial DNA gyrase is an attractive target for the investigation of new antibacterial agents. Inhibitors of the GyrB subunit, which contains the ATP-binding site, are described in this communication. Novel, substituted 5-(1H-pyrazol-3-yl)thiazole compounds were identified as inhibitors of bacterial gyrase. Structure-guided optimization led to greater enzymatic potency and moderate antibacterial potency. Data are presented for the demonstration of selective enzyme inhibition of Escherichia coli GyrB over Staphlococcus aureus GyrB.     

Synthesis and evaluation of novel 17-indazole androstene derivatives designed as CYP17 inhibitors

A series of novel 1H- and 2H-indazole derivatives of the commercially available dehydroepiandrosterone acetate have been synthesized and tested for inhibition of human cytochrome 17alpha-hydroxylase-C(17,20)-lyase (CYP17), androgen receptor (AR) binding affinity, and cytotoxic potential against three prostate cancer (PC) cell lines.     

Synthesis,trypanocidal activity and docking studies of novel quinoxaline-N-acylhydrazones,designed as cruzain inhibitors candidates

In this paper, we report the structural design, synthesis, trypanocidal activity and docking studies of novel quinoxaline-N-acylhydrazone (NAH) derivatives, planned as cruzain inhibitors candidates, a cysteine protease essential for the survival of Trypanosoma cruzi within the host cell. The salicylaldehyde N-acylhydrazones 7a and 8a presented IC₅₀ values of the same magnitude order than the standard drug nifurtimox (Nfx), when tested in vitro against epimastigote forms of Trypanosoma cruzi (Tulahuen 2 strain) and were non-toxic at the highest assayed doses rendering selectivity indexes (IC₅₀ (macrophages)/IC₅₀ (Trypanosoma cruzi)) of >25 for 7a and >20 for 8a, with IC₅₀ values in macrophages >400 μM.     

Antibiotics LL-Z1272 identified as novel inhibitors discriminating bacterial and mitochondrial quinol oxidases

To counter antibiotic-resistant bacteria, we screened the Kitasato Institute for Life Sciences Chemical Library with bacterial quinol oxidase, which does not exist in the mitochondrial respiratory chain. We identified five prenylphenols, LL-Z1272β, γ, δ, ? and ζ, as new inhibitors for the Escherichia coli cytochrome bd. We found that these compounds also inhibited the E. coli bo-type ubiquinol oxidase and trypanosome alternative oxidase, although these three oxidases are structurally unrelated. LL-Z1272β and ? (dechlorinated derivatives) were more active against cytochrome bd while LL-Z1272γ, δ, and ζ (chlorinated derivatives) were potent inhibitors of cytochrome bo and trypanosome alternative oxidase. Thus prenylphenols are useful for the selective inhibition of quinol oxidases and for understanding the molecular mechanisms of respiratory quinol oxidases as a probe for the quinol oxidation site. Since quinol oxidases are absent from mammalian mitochondria, LL-Z1272β and δ, which are less toxic to human cells, could be used as lead compounds for development of novel chemotherapeutic agents against pathogenic bacteria and African trypanosomiasis.     

Syntheses of novel myxopyronin B analogs as potential inhibitors of bacterial RNA polymerase

Based upon observations from our initial findings, additional myxopyronin B analogs have been prepared and tested for in vitro inhibitory activity against DNA-dependent RNA polymerase and antibacterial activity against Escherichia coli and Staphylococcus aureus.     

Dihydropyrrolones as bacterial quorum sensing inhibitors

Bacteria regulate their pathogenicity and biofilm formation through quorum sensing (QS), which is an intercellular communication system mediated by the binding of signaling molecules to QS receptors such as LasR. In this study, a range of dihydropyrrolone (DHP) analogues were synthesized via the lactone-lactam conversion of lactone intermediates. The synthesized compounds were tested for their ability to inhibit QS, biofilm formation and bacterial growth of Pseudomonas aeruginosa. The compounds were also docked into a LasR crystal structure to rationalize the observed structure-activity relationships. The most active compound identified in this study was compound 9i, which showed 63.1% QS inhibition of at 31.25?µM and 60% biofilm reduction at 250?µM with only moderate toxicity towards bacterial cell growth.     

Prenylated pterocarpans as bacterial neuraminidase inhibitors

During the course of a neuraminidase inhibitor screening program on natural products, four new (6, 8, 11, and 12) and eleven known (1–5, 7, 9–10, and 13–15) pterocarpan derivatives were isolated as active principles from the EtOAc extract of the stem bark of Erythrina abyssinica. Their structures were identified by spectroscopic data analyses. All isolates exhibited significant inhibitory effects on the neuraminidases from Clostridium perfringens and Vibrio cholerae with IC₅₀ values ranging from 1.32 to 77.10 μM and 0.35 to 77.73 μM, respectively. The isolates (1–3, 5–8, 10, and 13–15), which possessed noncompetitive inhibition modes in kinetic studies, showed stronger activity against C. perfringens neuraminidase (IC₅₀ 1.32–19.82 μM) than quercetin (IC₅₀ 25.34 μM), which was used as the positive control. In contrast, compounds 4 and 9 behaved as competitive inhibitors and were displayed less effective (IC₅₀ 26.39–33.55 μM). Furthermore, calopocarpine, as a neuraminidase inhibitor, produced a decrease of V. cholerae adhesion to the host cell. Overall, these results suggest that neuraminidase inhibitors can be used in the development of new treatments to combat infectious diseases.     

Synthetic molecules designed as potential inhibitors in ecdysone biosynthesis

For fundamental studies as well as applied research, we have set up a programme for the synthesis of irreversible and selective inhibitors of ecdysone biosynthesis. Suicide substrate type inhibitors have been synthesized in order to react in the last steps of ecdysone biosynthesis on C-22 and C-25 hydroxylases which are cytochrome P-450-dependent monooxygenases. The most active inhibitors are formed of a steroid nucleus on which a short side chain, with an acetylenic or an allenic function closely linked to an hydroxyl group, has been grafted. The exact form of the steroid nucleus (as in cholesterol, 7-dehydrocholesterol, 3-dehydrocholesterol or a molecule with a saturated B cycle) did not appear essential for the activity of the chemicals. These molecules injectedin vivo in larvae ofLocusta migratoria induced some morphological modifications of the adults and a very slight delay in metamorphosis.

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Résumé Dans le but d'inhiber la biosynthèse de l'ecdysone au cours du développement chez l'Insecte, plus de 50 molécules ont été synthétisées selon la conception des substrats-suicides. Deux enzymes des dernières étapes de la biosynthèse de l'ecdysone, parfaitement connues, les C-22 et C-25 hydroxylases, qui sont des monooxygénases à cytochrome P-450, ont été choisies pour cibles. A partir d'une molécule de base présentant à la fois un bon pouvoir inhibiteur et des caractéristiques d'activité de type substrat-suicide, c'està-dire irréversibilité de l'action, spécificité de l'inhibition et sélectivité sur l'enzyme visé, de nombreuses modifications ont été introduites. Elles ont concernés notamment la longueur de la cha?ne latérale, la nature et la position du groupement inhibiteur, la position du ou des groupements hydroxyles et la nature du noyau stéro?de. Des divers résultats obtenus, il est possible de conclure que les meilleurs inhibiteurs, qui diminuent significativement la production d'ecdysone des glandes prothoraciques incubéesin vitro, sont composés d'une cha?ne latérale courte à groupement inhibiteur alcyne ou allénique dans le voisinage d'un groupement hydroxyle et d'un noyau stéro?de qui peut-être, indifféremment, de type cholestérol, 7-déshydrocholestérol, 3-déshydrocholestérol ou porter un cycle B saturé. On peut noter que les noyaux qui se rapprochent le plus de celui des ecdystéro?des diminuent ou empêchentl' activité. Malheureusement, jusqu'à présent, ces molécules injectéesin vivo chez des larves deLocusta migratoria n'ont qu'une action réduite: elles ne produisent, dans les meilleurs cas, que de rares retards de métamorphose et quelques modifications morphologiques chez les adultes.

     

Serendipitous discovery of novel bacterial methionine aminopeptidase inhibitors

In this article we describe the application of structural biology methods to the discovery of novel potent inhibitors of methionine aminopeptidases. These enzymes are employed by the cells to cleave the N-terminal methionine from nascent peptides and proteins. As this is one of the critical steps in protein maturation, it is very likely that inhibitors of these enzymes may prove useful as novel antibacterial agents. Involvement of crystallography at the very early stages of the inhibitor design process resulted in serendipitous discovery of a new inhibitor class, the pyrazole-diamines. Atomic-resolution structures of several inhibitors bound to the enzyme illuminate a new mode of inhibitor binding.     

Quinazolin-2-ylamino-quinazolin-4-ols as novel non-nucleoside inhibitors of bacterial DNA polymerase III

High throughput screening led to the discovery of a novel series of quinazolin-2-ylamino-quinazolin-4-ols as a new class of DNA polymerase III inhibitors. The inhibition of chromosomal DNA replication results in bacterial cell death. The synthesis, structure–activity relationships and functional activity are described.     

Dihydroquinolines as novel n-NOS inhibitors

Dihydroquinolines have been synthesized and have been shown to be potent n-NOS inhibitors. Selectivity versus e-NOS was increased to approximately 100-fold through appropriate substitution at the benzene ring.     

N-caffeoylphenalkylamide derivatives as bacterial efflux pump inhibitors

As part of an ongoing project to identify plant natural products as efflux pump inhibitors (EPIs), bioassay-guided fractionation of the methanolic extract of Mirabilis jalapa Linn. (Nyctaginaceae) led to the isolation of an active polyphenolic amide: N-trans-feruloyl 4'-O-methyldopamine. This compound showed moderate activity as an EPI against multidrug-resistant (MDR) Staphylococcus aureus overexpressing the multidrug efflux transporter NorA, causing an 8-fold reduction of norfloxacin MIC at 292 microM (100 microg/mL). This prompted us to synthesize derivatives in order to provide structure-activity relationships and to access more potent inhibitors. Among the synthetic compounds, some were more active than the natural compound and N-trans-3,4-O-dimethylcaffeoyl tryptamine showed potentiation of norfloxacin in MDR S. aureus comparable to that of the standard reserpine.     

Phosphorylated hydroxyethylamines as novel inhibitors of the bacterial cell wall biosynthesis enzymes MurC to MurF

Enzymes involved in the biosynthesis of bacterial peptidoglycan represent important targets for development of new antibacterial drugs. Among them, Mur ligases (MurC to MurF) catalyze the formation of the final cytoplasmic precursor UDP-N-acetylmuramyl-pentapeptide from UDP-N-acetylmuramic acid. We present the design, synthesis and biological evaluation of a series of phosphorylated hydroxyethylamines as new type of small-molecule inhibitors of Mur ligases. We show that the phosphate group attached to the hydroxyl moiety of the hydroxyethylamine core is essential for good inhibitory activity. The IC₅₀ values of these inhibitors were in the micromolar range, which makes them a promising starting point for the development of multiple inhibitors of Mur ligases as potential antibacterial agents. In addition, 1-(4-methoxyphenylsulfonamido)-3-morpholinopropan-2-yl dihydrogen phosphate 7a was discovered as one of the best inhibitors of MurE described so far.     

Pulvinones as bacterial cell wall biosynthesis inhibitors

Pulvinones were synthesized (>180) in arrays and evaluated as inhibitors of early stage cell wall biosynthesis enzymes MurA-MurD. Several pulvinones inhibited Mur enzymes with IC(50)'s in the 1-10 microg/mL range and demonstrated antibacterial activity against Gram-positive bacteria including methicillin-resistant Staphyloccus aureus, vancomycin-resistant Enterococcus faecalis, and penicillin-resistant Streptococcus pneumoniae.     

Structurally diverse 5-substituted pyrimidine nucleosides as inhibitors of Leishmania donovani promastigotes in vitro

The following structurally diverse 5-substituted-2'-deoxyuridine nucleosides displayed potent in vitro antileishmanial activity: 5-formyl, 5-(2,2,-dicyanovinyl)-, 5-(2-cyano-2-ethoxycarbonylvinyl), 5-(2-cyano-2-methoxycarbonylvinyl)-, 5-(2-amino-3-cyano-5-oxo-5,6,7,8-tetrahydro-4H-chromen-4-yl)- and related congeners, and the 5-(3-methyl-5-oxo-1-phenyl-4,5-dihydro-4H-pyrazol-4-ylidene) group.