Optimization of anti-Trypanosoma cruzi oxadiazoles leads to identification of compounds with efficacy in infected mice

We recently showed that oxadiazoles have anti-Trypanosoma cruzi activity at micromolar concentrations. These compounds are easy to synthesize and show a number of clear and interpretable structure–activity relationships (SAR), features that make them attractive to pursue potency enhancement. We present here the structural design, synthesis, and anti-T. cruzi evaluation of new oxadiazoles denoted 5a–h and 6a–h. The design of these compounds was based on a previous model of computational docking of oxadiazoles on the T. cruzi protease cruzain. We tested the ability of these compounds to inhibit catalytic activity of cruzain, but we found no correlation between the enzyme inhibition and the antiparasitic activity of the compounds. However, we found reliable SAR data when we tested these compounds against the whole parasite. While none of these oxadiazoles showed toxicity for mammalian cells, oxadiazoles 6c (fluorine), 6d (chlorine), and 6e (bromine) reduced epimastigote proliferation and were cidal for trypomastigotes of T. cruzi Y strain. Oxadiazoles 6c and 6d have IC₅₀ of 9.5 ± 2.8 and 3.5 ± 1.8 μM for trypomastigotes, while Benznidazole, which is the currently used drug for Chagas disease treatment, showed an IC₅₀ of 11.3 ± 2.8 μM. Compounds 6c and 6d impair trypomastigote development and invasion in macrophages, and also induce ultrastructural alterations in trypomastigotes. Finally, compound 6d given orally at 50 mg/kg substantially reduces the parasitemia in T. cruzi-infected BALB/c mice. Our drug design resulted in potency enhancement of oxadiazoles as anti-Chagas disease agents, and culminated with the identification of oxadiazole 6d, a trypanosomicidal compound in an animal model of infection.     

Bis-phosphonium salts of pyridoxine: The relationship between structure and antibacterial activity

A series of 23 novel bis-phosphonium salts based on pyridoxine were synthesized and their antibacterial activities were evaluated in vitro. All compounds were inactive against gram-negative bacteria and exhibited the structure-dependent activity against gram-positive bacteria. The antibacterial activity enhanced with the increase in chain length at acetal carbon atom in the order n-Pr > Et > Me. Further increasing of length and branching of alkyl chain leads to the reduction of antibacterial activity. Replacement of the phenyl substituents at the phosphorus atoms in 5,6-bis(triphenylphosphonio(methyl))-2,2,8-trimethyl-4H-[1,3]-dioxino[4,5-c]pyridine dichloride (compound 1) with n-butyl, m-tolyl or p-tolyl as well as chloride anions in the compound 1 with bromides (compound 14a) increased the activity against Staphylococcus aureus and Staphylococcus epidermidis up to 5 times (MICs = 1–1.25 μg/ml). But in practically all cases chemical modifications of compound 1 led to the increase of its toxicity for HEK-293 cells. The only exception is compound 5,6-bis[tributylphosphonio(methyl)]-2,2,8-trimethyl-4H-[1,3]dioxino[4,5-c]pyridine dichloride (10a) which demonstrated lower MIC values against S. aureus and S. epidermidis (1 μg/ml) and lower cytotoxicity on HEK-293 cells (CC₅₀ = 200 μg/ml). Compound 10a had no significant mutagenic and genotoxic effects and was selected for further evaluation. It should be noted that all bis-phosphonium salt based on pyridoxine were much more toxic than vancomycin.     

Synthesis and biological evaluation of simple methoxylated chalcones as anticancer,anti-inflammatory and antioxidant agents

Chalcones have been identified as interesting compounds with cytotoxicity, anti-inflammatory and antioxidant properties. In the present study, simple methoxychalcones were synthesized by Claisen–Schmidt condensation reaction and evaluated for above biological activities. The structures of the compounds were established by IR, ¹H NMR and mass spectral analysis. The data revealed that compound 3s (99–100% at 10 μM concentration) completely inhibit the selected five human cancer cell lines as compared to standard flavopiridol and gemcitabine (70–90% at 700 nM and 500 nM concentrations, respectively), followed by 3a, 3n, 3o, 3p, 3q, 3r. Among the tested compounds 3l, 3m, 3r, and 3s exhibited promising anti-inflammatory activity against TNF-α and IL-6 with 90–100% inhibition at 10 μM concentration. DPPH free radical scavenging activity was given by the compounds 3o, 3n, 3l, 3r, 3m, 3a, 3p, 3c and 3s at 1 mM concentration. Overall, 3s was obtained as lead compound with promising anticancer, anti-inflammatory and antioxidant activities. Bioavailability of compounds were checked by in vitro cytotoxicity study and confirmed to be nontoxic. The structure activity relationship (SAR) and in silico drug relevant properties (HBDs, HBAs, PSA, c Log P, ionization potential, molecular weight, E_HOMO and E_LUMO) further confirmed that the compounds were potential candidates for future drug discovery study.     

Synthesis and biological evaluation of compounds which contain pyrazole,thiazole and naphthalene ring as antitumor agents

A series of compounds which contain pyrazole, thiazole and naphthalene ring (1a–7a, 1b–7b, 1c–7c, 1d–7d) were firstly synthesized and their anti-proliferative activity, EGFR inhibitory activity, cytotoxicity and inhibition to Hela cell migration were evaluated. Compound 2-(3-(3,4-dimethylphenyl)-5-(naphthalen-2-yl)-4,5-dihydro-1H-pyrazol-1-yl)thiazol-4(5H)-one (7d) displayed the most potent inhibitory activity (IC₅₀ = 0.86 μM for Hela and IC₅₀ = 0.12 μM for EGFR). Structure–activity relationship (SAR) analysis showed that the anti-proliferative activity was affected by A-ring-substituent (–OCH₃ > –CH₃ > –H > –Br > –Cl > –F). Docking simulation of compound 7d into EGFR active site showed that naphthalene ring of 7d with LYS721 formed two p–π bonds, which enhanced antitumor activity. Therefore, compound 7d may be developed as a potential antitumor agent.     

Synthesis and biological evaluation of a novel series of pyrazole chalcones as anti-inflammatory,antioxidant and antimicrobial agents

A novel series of 1-(2,4-dimethoxy-phenyl)-3-(1,3-diphenyl-1H-pyrazol-4-yl)-propenone (3) have been prepared by the Claisen–Schmidt condensation of 1-(2,4-dimethoxy-phenyl)-ethanone (1) and substituted 1,3-diphenyl-1H-pyrazole-4-carbaldehydes (2). Substituted 1,3-diphenyl-1H-pyrazole-4-carbaldehydes (2) were prepared by Vilsmeir–Haack reaction on acetophenonephenylhydrazones to offer the target compounds. The structures of the compounds were established by IR, ¹H NMR and mass spectral analysis. All the compounds were evaluated for their anti-inflammatory (TNF-α and IL-6 inhibitory assays), antioxidant (DPPH free radical scavenging assay) and antimicrobial activities (agar diffusion method) against some pathogenic bacteria and fungi. Of 10 compounds screened, compounds 3a, 3c and 3g exhibited promising IL-6 inhibitory (35–70% inhibition, 10 μM), free radical scavenging (25–35% DPPH activity) and antimicrobial activities (MIC 100 μg/mL and 250 μg/mL) at varied concentrations. The structure–activity relationship (SAR) and in silico drug relevant properties (HBD, HBA, PSA, c Log P, molecular weight, E_HOMO and E_LUMO) further confirmed that the compounds are potential lead compounds for future drug discovery study. Toxicity of the compounds was evaluated theoretically and experimentally and revealed to be nontoxic except 3d and 3j.     

Synthesis and antinociceptive properties of N-phenyl-N-(1-(2-(thiophen-2-yl)ethyl)azepane-4-yl)propionamide in the mouse tail-flick and hot-plate tests

The goals of this study, were to synthesize N-phenyl-N-(1-(2-(thiophen-2-yl)ethyl)azepane-4-yl)propionamide (1c) and determine its antinociceptive properties. The effect of clonidine on 1c antinociception and the involvement of opioid, α₂-adrenergic, and I₂ imidazoline receptors in 1c antinociception were studied. Also examined was the effect of an endothelin ET_A receptor antagonist on 1c antinociception. Synthesis of 1c was accomplished in two steps using modifications of previously reported methods. Antinociceptive (tail-flick and hot-plate) latencies were measured in male Swiss Webster mice treated with 1c; antagonists + 1c; clonidine + 1c; or antagonists + clonidine + 1c. Mice were pretreated with naloxone (opioid antagonist), yohimbine (α₂-adrenoceptor antagonist), idazoxan (α₂-adrenoceptor/I₂-imidazoline antagonist), BU224 (I₂-imidazoline antagonist) or BQ123 (endothelin ET_A receptor antagonist) to study the involvement of these receptors. Compound 1c produced a dose-dependent increase in antinociceptive latencies; ED₅₀ values were 0.15 mg/kg and 0.16 mg/kg, respectively, in the tail flick and hot plate tests. Naloxone, but not yohimbine, idazoxan or BU224, blocked 1c antinociception. Neither clonidine nor BQ123 potentiated 1c antinociception. Results demonstrate that 1c is 15-times more potent than morphine. The antinociceptive effect of 1c is mediated through opioid receptors. The α₂-adrenergic, I₂-imidazoline and endothelin ET_A receptors are not involved in 1c antinociception.     

In vitro cytotoxic activity of isolated acridones alkaloids from Zanthoxylum leprieurii Guill. et Perr

Chemical investigation of the roots and fruits of Zanthoxylum leprieurii Guill. et Perr. led to the isolation of three new alkaloids including two acridone derivatives, 3-hydroxy-1,4-dimethoxy-10-methyl-9-acridone (2) and 3-hydroxy-1,2-dimethoxy-10-methyl-9-acridone (3) named helebelicine A and B, respectively, and one secobenzo[c]phenantridine, 10-O-demethyl-12-O-methylarnottianamide (10), together with thirteen other compounds. The structures of compounds 2, 3 and 10 as well as those of the known compounds were elucidated by using spectroscopic methods and by comparison with reported data. The brine-shrimp (artemia salina) lethality bioassay of the chloroform extract of the fruits showed modest cytotoxicity with LD₅₀ at 13.1 μg/mL. Isolated compounds 1, 4–6 were found to be moderately active against lung carcinoma cells (A549), colorectal adenocarcinoma cells (DLD-1) and normal cells (WS1) with IC₅₀ values ranging from 27 to 77 μM. In contrast to the positive control etoposide used, the cytotoxicity of the most active compound 4 was found to be selective against cancer cells in comparison to normal cells WS1 with IC₅₀ of 51 ± 8 μM and 4.3 ± 0.4 μM, respectively.     

Synthesis and pharmacological evaluation of new arylpiperazines N-{4-[4-(aryl) piperazine-1-yl]-phenyl}-amine derivatives: Putative role of 5-HT1A receptors

In an attempt to design novel 5-HT_1A agonists/partial agonists, based on an arylpiperazine nucleus, a series of N-{4-[4-(aryl)piperazine-1-yl]-phenyl}-amine derivatives were synthesized and biologically tested. The anxiolytic effect of the compounds was investigated employing the Elevated plus Maze (EPM) task. On the basis of in vivo functional test, compound 1c (3 mg/kg) and 4c (3 mg/kg) induced significant increments in open arm entries and time on EPM as compared to Buspirone. The anxiolytic effects of compounds 1c and 4c were effectively antagonized by WAY-100635, a 5-HT_1A receptor antagonist (0.5 mg/kg). Furthermore, we have also evaluated the concentration of 5-HT in the brain tissue using HPLC with fluorescent detection. Our result showed that serotonin levels were significantly decreased by ～38% (p < 0.001) and ～32% (p < 0.001) after acute administration of compounds 1c and 4c, respectively. These findings suggest that the anxiolytic like activity of these new arylpiperazines is mediated via 5-HT_1A receptors in the brain.     

Design,synthesis and biological evaluation of benzyl 2-(1H-imidazole-1-yl) pyrimidine analogues as selective and potent Raf inhibitors

The synthesis of a novel series of (4-aminobenzyl/benzoyl)-1H-imidazol-1-yl pyrimidin-2-yl derivatives 9, 10, 18, 19 and their in vitro antiproliferative activities against the A375P human melanoma cell line and the U937 human leukemic monocyte lymphoma cell line are described. Potent antiproliferative effects were found from 9l, 9s and 10c; 10c was found to be a highly potent and selective BRAF V600E and CRAF inhibitor (IC₅₀ = 38.3 nM and 8.79 nM).     

Iodine catalyzed three component synthesis of 1-((2-hydroxy naphthalen-1-yl)(phenyl)(methyl))pyrrolidin-2-one derivatives: Rationale as potent PI3K inhibitors and anticancer agents

A series of 1-((2-hydroxynaphthalen-1-yl)(phenyl)(methyl))pyrrolidin-2-one derivatives by an efficient iodine catalyzed domino reaction involving various aromatic aldehydes, 2-pyrrolidinone and β-naphthol was achieved and the structures were elucidated by FTIR ¹H NMR, ¹³C NMR, and HRMS. Subsequently they were evaluated for cytotoxicity against breast cancer (MCF-7), colon cancer (HCT116) cell lines. In the cytotoxicity, the relative inhibition activity was remarkably found to be high in MCF-7 cell lines as 79% (4c), 83% (4f) and the IC₅₀values were 1.03 µM (4c), 0.98 µM (4f). Compounds 4a, 4e, 4k–m, and 4q were found to be inactive and rest showed a moderate activity. In order to get more insight into the binding mode and inhibitor binding affinity, compounds (4a–q) were docked into the active site phosphoinositide 3-kinase (PI3K) (PDB ID: 4JPS) which is a crucial regulator of apoptosis or programmed cell death. Results suggested that the hydrophobic interactions in the binding pockets of PI3K exploited affinity of the most favourable binding ligands (4c and 4f: inhibitory constant (ki) = 66.22 nM and 107.39 nM). The SAR studies demonstrated that the most potent compounds are 4c and 4f and can be developed into precise PI3K inhibitors with the capability to treat various cancers.     

Novel 1,2,3-thiadiazole derivatives as HIV-1 NNRTIs with improved potency: Synthesis and preliminary SAR studies

A novel synthetic route and anti-HIV activity evaluation of a new series of 2-(4-(2,4-dibromophenyl)-1,2,3-thiadiazol-5-ylthio)acetamide (TTA) derivatives are described. Bioactivity assay indicated that most of the title compounds showed good activities against HIV-1. In particular, compound 7c displayed the most potent anti-HIV-1 activity (EC₅₀ = 36.4 nM), inhibiting HIV-1 replication in MT-4 cells more effectively than NVP (by sevenfold) and DLV (by eightfold). The preliminary structure–activity relationships (SAR) of the newly synthesized congeners are discussed, and molecular modeling of compound 7c in complex with HIV-1 RT is described, allowing rationalization of some SAR conclusions.     

Discovery of novel 3-benzylquinazolin-4(3H)-ones as potent vasodilative agents

In the present study, a series of 3-benzylquinazolin-4(3H)-ones were synthesized and characterized. Their vasodilative effects were evaluated by wire myograph on isolated rat mesenteric arterial ring induced contraction with 60 mM KCl. The SAR of target compounds was discussed preliminarily. Among these compounds, 2a and 2c displayed potent vasodilatation action and could compete significantly the rat mesenteric arterial rings induced contraction with phenylephrine. Compounds 2a and 2c were further tested for their antihypertensive effects in SHR by oral administration. The results indicated that 2a and 2c could reduce significantly both diastolic and systolic blood pressure. Moreover, 2c displayed antihypertensive effect in a dose dependent manner, and could maintain the effects for 6 h at a dosage of 4.0 mg/kg. These findings suggest that the title compounds are novel vasodilative agents, representing a novel series of promising antihypertensive agents.     

Synthesis and anti-proliferative activity of aromatic substituted 5-((1-benzyl-1H-indol-3-yl)methylene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione analogs against human tumor cell lines

Based on previous SAR studies on N-benzylindole and barbituric acid hybrid molecules, we have synthesized a series of aromatic substituted 5-((1-benzyl-1H-indol-3-yl)methylene)-1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione analogs (3a–i) and evaluated them for their in vitro growth inhibition and cytotoxicity against a panel of 60 human tumor cell lines. Compounds 3c, 3d, 3f and 3g were identified as highly potent anti-proliferative compounds against ovarian, renal and breast cancer cell lines with GI₅₀ values in low the nanomolar range. The 4-methoxy-N-benzyl analog (3d) was the most active compound with GI₅₀ values of 20 nM and 40 nM against OVCAR-5 ovarian cancer cells and MDA-MB-468 breast cancer cells, respectively. Two other analogs, 3c (the 4-methyl-N-benzyl analog) and 3g (the 4-fluoro-N-benzyl analog) exhibited equimolar potency against MDA-MB-468 cells GI₅₀ = 30 nM). Analog 3f (the 4-chloro-N-benzyl analog) exhibited a GI₅₀ value of 40 nM against renal cancer cell line A498. These results suggest that aromatic substituted N-benzylindole dimethylbarbituric acid hybrids may have potential for development as clinical candidates to treat a variety of solid tumors.     

Discovery of new low-molecular-weight p53–Mdmx disruptors and their anti-cancer activities

Although several p53–Mdm2-binding disruptors have been identified to date, few studies have been published on p53–Mdmx-interaction inhibitors. In the present study, we demonstrated that o-aminothiophenol derivatives with molecular weights of 200–300 selectively inhibited the p53–Mdmx interaction. S-2-Isobutyramidophenyl 2-methylpropanethioate (K-178) (1c) activated p53, up-regulated the expression of its downstream genes such as p21 and Mdm2, and preferentially inhibited the growth of cancer cells with wild-type p53 over those with mutant p53. Furthermore, we found that the S-isobutyryl-deprotected forms 1b and 3b of 1c and S-2-benzamidophenyl 2-methylpropanethioate (K-181) (3c) preferentially inhibited the p53–Mdmx interaction over the p53–Mdm2 interaction, respectively, by using a Flag-p53 and glutathione S-transferase (GST)-fused protein complex (Mdm2, Mdmx, DAPK1, or PPID). In addition, the interaction of p53 with Mdmx was lost by replacing a sulfur atom with an oxygen atom in 1b and 1c. These results suggest that sulfides such as 1b, 3b, 4b, and 5b interfere with the binding of p53–Mdmx, resulting in the dissociation of the two proteins. Furthermore, the results of oral administration experiments using xenografts in nude mice indicated that 1c reduced the volume of tumor masses to 49.0% and 36.6% that of the control at 100 mg/kg and 150 mg/kg, respectively, in 40 days.     

Synthesis of novel fenfuram-diarylether hybrids as potent succinate dehydrogenase inhibitors

Twelve novel fenfuram-diarylether hybrids were designed, synthesized and characterized by ¹H NMR and MS. Their in vitro antifungal activities were evaluated against five phytopathogenic fungi by mycelial growth inhibition method. Most compounds showed significant antifungal effect on Rhizoctonia solani and Sclerotinia sclerotiorum. Compound 1c exhibited the most potent antifungal effect on R. solani with an EC₅₀ value of 0.242 mg/L, superior to the commercial fungicide boscalid (EC₅₀ = 1.758 mg/L) and the lead fungicide fenfuram (EC₅₀ = 7.691 mg/L). Molecular docking revealed that compound 1c featured a higher affinity for succinate dehydrogenase (SDH) than fenfuram. Furthermore, it was shown that the 2-chlorophenyl group of compound 1c formed a π-π stacking with D/Tyr-128 and a Cl-π interaction with B/His-249, which made compound 1c more active than fenfuram against SDH.     

Azabenzthiazole inhibitors of leukotriene A4 hydrolase

Previously, benzthiazole containing LTA₄H inhibitors were discovered that were potent (1–3), but were associated with the potential for a hERG liability. Utilizing medicinal chemistry first principles (e.g., introducing rigidity, lowering c Log D) a new benzthiazole series was designed, congeners of 1–3, which led to compounds 7a, 7c, 12a–d which exhibited LTA₄H IC₅₀ = 3–6 nM and hERG Dofetilide Binding IC₅₀ = 8.9–> >10 μM.     

Design,synthesis and dopamine D4 receptor binding activities of new N-heteroaromatic 5/6-ring Mannich bases

A series of phenylpiperazine-methyl-substituted 1H-pyrrolo[2,3-c]pyridine, imidazo[1,2-c]-, pyrrolo[2,3-d]- and pyrrolo[3,2-d]pyrimidines were prepared as selective dopamine D4-ligands. The pyrrolo[2,3-d]pyrimidine derivatives 12d (K_i = 1,9 nM) and 34d (K_i = 2,4 nM) as well as the pyrrolo[3,2-d]pyrimidine Mannich base 49f (K_i = 2,8 nM) showed high dopamine D4 receptor activity superior to the atypical antipsychotic agent clozapine.     

Design and synthesis of γ-butyrolactone derivatives as potential spermicidal agents

A series of γ-butyrolactone derivatives has been designed and synthesized from commercially available 2-acetyl butyrolactone (3-acetyldihydrofuran-2(3H)-one, 1) by aminoalkylating its active methylene followed by condensation with different aldehydes. Compounds having amino group were further converted to their respective tartrate salts and were evaluated for spermicidal activity against human sperm in vitro. Compounds showing appreciable spermicidal activity at ⩽0.5% [3c, 4d (0.5%); 2c, 3d (0.1%); 2d, 4c (0.05%)] were tested for safety studies against human cervical (HeLa) cell line. These compounds were found safer than, Nonoxynol-9. One of the two most active compounds was also found to be the safest (IC₅₀ = 961 μg/ml; 4c), while the second compound exhibited lower safety against HeLa (IC₅₀ = 269 μg/ml; 2d). The compound 4c significantly reduced the number of free thiols on human sperm. All the compounds were inactive against Trichomonas vaginalis.     

Design and synthesis of triarylacrylonitrile analogues of tamoxifen with improved binding selectivity to protein kinase C

The clinical selective estrogen receptor modulator tamoxifen is also a modest inhibitor of protein kinase C, a target implicated in several untreatable brain diseases such as amphetamine abuse. This inhibition and tamoxifen’s ability to cross the blood brain barrier make it an attractive scaffold to conduct further SAR studies toward uncovering effective therapies for such diseases. Utilizing the known compound 6a as a starting template and guided by computational tools to derive physicochemical properties known to be important for CNS permeable drugs, the design and synthesis of a small series of novel triarylacrylonitrile analogues have been carried out providing compounds with enhanced potency and selectivity for PKC over the estrogen receptor relative to tamoxifen. Shortened synthetic routes compared to classical procedures have been developed for analogues incorporating a β-phenyl ring, which involve installing dialkylaminoalkoxy side chains first off the α and/or α′ rings of a precursor benzophenone and then condensing the resultant ketones with phenylacetonitrile anion. A second novel, efficient and versatile route utilizing Suzuki chemistry has also been developed, which will allow for the introduction of a wide range of β-aryl or β-heteroaryl moieties and side-chain substituents onto the acrylonitrile core. For analogues possessing a single side chain off the α- or α′-ring, novel 2D NMR experiments have been carried out that allow for unambiguous assignment of E- and Z-stereochemistry. From the SAR analysis, one compound, 6c, shows markedly increased potency and selectivity for inhibiting PKC with an IC₅₀ of 80 nM for inhibition of PKC protein substrate and >10 μM for binding to the estrogen receptor α (tamoxifen IC₅₀ = 20 μM and 222 nM, respectively). The data on 6c provide support for further exploration of PKC as a druggable target for the treatment of amphetamine abuse.