Identification and preliminary structure-activity relationship studies of novel pyridyl sulfonamides as potential Chagas disease therapeutic agents

Chagas disease is a neglected pathology responsible for about 12,000 deaths every year across Latin America. Although six million people are infected by the Trypanosoma cruzi, current therapeutic options are limited, highlighting the need for new drugs. Here we report the preliminary structure activity relationships of a small library of 17 novel pyridyl sulfonamide derivatives. Analogues 4 and 15 displayed significant potency against intracellular amastigotes with EC₅₀ of 5.4?µM and 8.6?µM. In cytotoxicity assays using mice fibroblast L929 cell lines, both compounds indicated low toxicity with decent selectivity indices (SI) >36 and?>23 respectively. Hence these compounds represent good starting points for further lead optimization.     

Synthesis,in-vitro antiprotozoal activity and molecular docking study of isothiocyanate derivatives

Novel isothiocyanate derivatives were synthesized starting from noscapine, bile acids, amino acids, and some aromatic compounds. Antiparasitic activities of the synthesized derivatives were tested against four unicellular protozoa, i.e., Trypanosoma brucei rhodesiense, T. cruzi, Leishmania donovani, and Plasmodium falciparum. Interestingly, seven isothiocyanate analogues displayed promising antiparasitic activity against Leishmania donovani with IC₅₀ values between 0.4 and 1.0 µM and selectivity index (SI) ranged from 7.8 to 18.4, comparable to the standard drug miltefosine (IC₅₀ = 0.7 μM). Compound 7h demonstrated the best antileishmanial activity with an IC₅₀ value of 0.4 µM. Seven products exhibited inhibition activity against T. brucei rhodesiense with IC₅₀s below 2.0 μM and SI between 2.7 and 29.3. Four primary amine derivatives of noscapine and five isothiocyanate derivatives exhibited antiplasmodial activity with IC₅₀s in the range of 1.1–2.7 µM and SI values between 1.1 and 14.5. The isothiocyanate derivative 7c showed against T. cruzi with an IC₅₀ value of 1.9 µM and SI 4. Molecular docking and ADMET studies were performed to investigate the interaction between active ligands and T. brucei trypanothione reductase active site. The docking studies showed significant binding affinity of noscapine derivatives to enzyme active site and good compatibility with experimental data.     

Synthesis and biological evaluation of isoxazolyl-sulfonamides: A non-cytotoxic scaffold active against Trypanosoma cruzi, Leishmania amazonensis and Herpes Simplex Virus

In this study we report the synthesis, characterization, biological evaluation, and druglikeness assessment of a series of 20 novel isoxazolyl-sulfonamides, obtained by a four-step synthetic route. The compounds had their activity against Trypanosoma cruzi, Leishmania amazonensis, Herpes Simplex Virus type 1 and cytotoxicity evaluated in phenotypic assays. All compounds have drug-like properties, showed low cytotoxicity and were promising regarding all other biological activities reported herein, especially the inhibitory activity against T. cruzi. The compounds 8 and 16 showed significant potency and selectivity against T. cruzi (GI₅₀?=?14.3?µM, SI?>?34.8 and GI₅₀?=?11.6?µM, SI?=?29.1, respectively). These values, close to the values of the reference drug benznidazole (GI₅₀?=?10.2?µM), suggest that compounds 8 and 16 represent promising candidates for further pre-clinical development targeting Chagas disease.     

Synthesis and biological evaluation of 2-methyl-1H-benzimidazole-5-carbohydrazides derivatives as modifiers of redox homeostasis of Trypanosoma cruzi

Twelve novel benzimidazole derivatives were synthesized and their in vitro activities against epimastigotes of Trypanosoma cruzi were evaluated. Two derivatives (6 and 7), which have 4-hydroxy-3-methoxyphenyl moiety in their structures, proved to be the most active in inhibiting the parasite growth. Compound 6 showed a trypanocidal activity higher than benznidazole (IC₅₀ = 5 µM and 7.5 µM, respectively) and less than nifurtimox (IC₅₀ = 3.6 µM). In addition, the ability of 6 and 7 to modify the redox homeostasis in T cruzi epimastigote was studied; cysteine and glutathione increased in parasites exposed to both compounds, whereas trypanothione only increased with 7 treatment. These results suggest that the decrease in viability of T. cruzi may be attributed to the change in cellular redox balance caused by compound 6 or 7. Furthermore, compounds 6 and 7 showed CC₅₀ values of 160.64 and 160.66 µM when tested in mouse macrophage cell line J774 and selectivity indexes (macrophage/parasite) of 32 and 20.1, respectively.     

Rational design,molecular docking and synthesis of novel homopiperazine linked imidazo[1,2-a]pyrimidine derivatives as potent cytotoxic and antimicrobial agents

Designed and synthesized novel homopiperazine linked imidazo[1,2-a]pyrimidine derivatives (10a–i, 11a–g, 12), and evaluated them for their in vitro cytotoxicity against HeLa cells (cervical cancer), A549 cells (lung cancer) cells, by MTT assay. Compound 12 (IC₅₀ = 4.14 µM) and compound 10c (IC₅₀ = 5.98 µM) were found to be 2.5 fold, and 1.74 fold more potent when compared with standard Etoposide (IC₅₀ = 10.44 µM), against A549 (lung cancer cells). Compound 12 also found to be 1.57 and 1.13 fold potent against DU145 (IC₅₀ = 6.24 µM) and HeLa (IC₅₀ = 6.54 µM), respectively when compared with Etoposide (DU145, IC₅₀ = 9.8 µM; HeLa, IC₅₀ = 7.43 µM). Compound 10f (IC₅₀ = 6.12 µM) was found to be 1.31 fold more potent than Etoposide (IC₅₀ = 7.43 µM) against HeLa cell lines.Moreover compounds 10a and 11a showed cytotoxicity at low micro-molar concentrations against A549 cells. Synthesized compounds were also evaluated for their antimicrobial activity by Cup plate diffusion method. Compounds 10c, 11b, 11d and 11f displayed remarkable antimicrobial activity relating to their standard drugs Gentamycin, Amphotericin B and Ampicillin. Significantly, compound 10c showed broad spectrum activity against tested microbial strains. All the designed compounds were well occupied the binding site of the colchicine and interacted with both α- and β-tubuline interface (PDB ID: 3E22), which demonstrates that synthesized compounds are promising tubulin inhibitors. Also, the synthesized compounds occupied the catalytic triad and adenine-binding site, in the active site of β-ketoacyl-acyl carrier protein synthase III enzyme (PDB ID: 1MZS). The molecular docking results provided the useful information for the future design of more potent inhibitors. These preliminary results convinced further investigation and modifications on synthesized compounds aiming towards the development of potential cytotoxic as well as antimicrobial agents.     

Antiprotozoal activities of marine polyether triterpenoids

Chagas disease and leishmaniasis are tropical neglected diseases caused by kinetoplastids protozoan parasites of Trypanosoma and Leishmania genera, and a public health burden with high morbidity and mortality rates in developing countries. Among difficulties with their epidemiological control, a major problem is their limited and toxic treatments to attend the affected populations; therefore, new therapies are needed in order to find new active molecules. In this work, sixteen Laurencia oxasqualenoid metabolites, natural compounds 1–11 and semisynthetic derivatives 12–16, were tested against Leishmania amazonensis, Leishmania donovani and Trypanosoma cruzi. The results obtained point out that eight substances possess potent activities, with IC₅₀ values in the range of 5.40–46.45 µM. The antikinetoplastid action mode of the main metabolite dehydrothyrsiferol (1) was developed, also supported by AFM images.The semi-synthetic active compound 28-iodosaiyacenol B (15) showed an IC₅₀ 5.40 µM against Leishmania amazonensis, turned to be non-toxic against the murine macrophage cell line J774A.1 (CC₅₀ > 100). These values are comparable with the reference compound miltefosine IC₅₀ 6.48 ± 0.24 and CC₅₀ 72.19 ± 3.06 μM, suggesting that this substance could be scaffold for development of new antikinetoplastid drugs.     

Semisynthesis,cytotoxicity, antimalarial evaluation and structure-activity relationship of two series of triterpene derivatives

In this report, we describe the semisynthesis of two series of ursolic and betulinic acid derivatives through designed by modifications at the C-3 and C-28 positions and demonstrate their antimalarial activity against chloroquine-resistant P. falciparum (W2 strain). Structural modifications at C-3 were more advantageous to antimalarial activity than simultaneous modifications at C-3 and C-28 positions. The ester derivative, 3β-butanoyl betulinic acid (7b), was the most active compound (IC₅₀?=?3.4?µM) and it did not exhibit cytotoxicity against VERO nor HepG2 cells (CC₅₀?>?400?µM), showing selectivity towards parasites (selectivity index?>?117.47). In combination with artemisinin, compound 7b showed an additive effect (CI?=?1.14). While docking analysis showed a possible interaction of 7b with the Plasmodium protease PfSUB1, with an optimum binding affinity of ?7.02?kcal/mol, the rather low inhibition displayed on a Bacillus licheniformis subtilisin A protease activity assay (IC₅₀?=?93?µM) and the observed accumulation of ring forms together with a delay of appearance of trophozoites in vitro suggests that the main target of 3β-butanoyl betulinic acid on Plasmodium may be related to other molecules and processes pertaining to the ring stage. Therefore, compound 7b is the most promising compound for further studies on antimalarial chemotherapy. The results obtained in this study provide suitable information about scaffolds to develop novel antimalarials from natural sources.     

In vitro and in silico evaluation of new thiazole compounds as monoamine oxidase inhibitors

New twenty compounds bearing thiazole ring (3a-3t) were designed and synthesized as monoamine oxidase (MAO) inhibitors. The fluorometric enzyme inhibition assay was used to determine the biological effects of synthesized compounds. Most of them showed remarkable inhibitory activity against both MAO-A and MAO-B. By comparing their IC₅₀ values, it can be seen that active derivatives displayed generally selectivity on MAO-B enzyme. Compounds 3j and 3t, which bear dihydroxy moiety at the 3rd and 4th position of phenyl ring, were the most active derivatives in the series against both isoenzymes. Compounds 3j and 3t showed significant inhibition profile on MAO-A with the IC₅₀ values of 0.134 ± 0.004 µM and 0.123 ± 0.005 µM, respectively, while they performed selectivity against MAO-B with the IC₅₀ values of 0.027 ± 0.001 µM and 0.025 ± 0.001 µM, respectively. Also, docking studies about these compounds were carried out to evaluate their binding modes on the active regions of MAO-A and MAO-B.     

Design,synthesis, in silico and in vitro evaluation of thiophene derivatives: A potent tyrosine phosphatase 1B inhibitor and anticancer activity

A series of novel methyl 4-(4-amidoaryl)-3-methoxythiophene-2-carboxylate derivatives were designed against the active site of protein tyrosine phosphatise 1B (PTP1B) enzyme using MOE.2008.10. These molecules are also subjected for in silico toxicity prediction studies and considering their corresponding drug scores, it implied that, the molecules are promising as anticancer agents. The designed compounds were synthesized by using suitable methods and characterized. They were subjected to inhibitory activity against PTP1B and in vitro anticancer activity by MTT assay. Most of the tested compounds showed potent inhibitory activity against PTP1B, among the compounds tested, compound 5b exhibited the highest activity (IC₅₀ = 5.25 µM) and remarkable cytotoxic activity at 0.09 µM of IC₅₀ against the MCF-7 cell line. In addition to this, compound 5c also showed potential anticancer activity at 2.22 µM of IC₅₀ against MCF-7 and 0.72 µM against HepG2 cell lines as well as PTP1B inhibitory activity at IC₅₀ of 6.37 µM.     

VEGFR-2 inhibiting effect and molecular modeling of newly synthesized coumarin derivatives as anti-breast cancer agents

Twenty five newly synthesized coumarin scaffold based derivatives were assayed for their in vitro anticancer activity against MCF-7 breast and PC-3 prostate cancer cell lines and were further assessed for their in vitro VEGFR-2 kinase inhibitory activity. The in vitro cytotoxic studies revealed that most of the synthesized compounds possessed very promising cytotoxicity against MCF-7, particularly; compounds 4a (IC₅₀ = 1.24 µM) and 3d (IC₅₀ = 1.65 µM) exhibited exceptional activities superior to the positive control staurosporine (IC₅₀ = 8.81 µM). Similarly, the majority of the compounds exhibited higher antiproliferative activities compared to the reference standard with IC₅₀ values ranging from 2.07 to 8.68 µM. The two cytotoxic derivatives 4a and 3d were selected to evaluate their inhibitory potencies against VEGFR-2 kinase. Remarkably, compound 4a, exhibited significant IC₅₀ of 0.36 µM comparable to staurosporine (IC₅₀; 0.33 µM). Moreover, it was capable of inducing preG1 apoptosis, cell growth arrest at G2/M phase and activating caspase-9. On the other hand, insignificant cytotoxic activity was observed for all compounds towards PC-3 cell line. Molecular docking study was carried out for the most active anti-VEGFR-2 derivative 4a, which demonstrated the ability of the tested compound to interact with the key amino acids in the target VEGFR-2 kinase binding site. Additionally, the ADME parameters and physicochemical properties of compound 4a were examined in silico.     

Rational drug design based synthesis of novel arylquinolines as anti-tuberculosis agents

A series of novel arylquinoline derivatives was designed retaining significant pharmacophoric features and three dimensional geometry of bedaquiline. In silico ADME study was performed to assess drug likeness and toxicity profiles of the designed molecules. The compounds were evaluated for activity against Mycobacterium tuberculosis H₃₇Rv using Resazurin Microtitre Assay (REMA) plate method and cytotoxicity in VERO C1008 cell line. Several of the synthesized compounds exhibited good antituberculosis activity and selectivity, especially compounds, 12i (MIC: 5.18 μM and MIC/CC₅₀: 152.86) and 12l (MIC: 5.59 μM and MIC/CC₅₀: 160.57). The study opens up a new platform for the development of arylquinoline based drugs for treating tuberculosis.     

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.     

Lead selection of antiparasitic compounds from a focused library of benzenesulfonyl derivatives of heterocycles

A library of 89 synthetic benzenesulfonyl derivatives of heterocycles with drug-like properties was assayed for in vitro antiparasitic activity and the results were added to our previously reported derivatives for a comprehensive SAR evaluation. Four compounds showed an IC₅₀ between 0.25 and 3 μM against Leishmania donovani and low cytotoxicity. Compound G{16} (1-(2,3,5,6-tetramethylphenylsulfonyl)-2-methylindoline), was particularly interesting with an IC₅₀ similar to the reference drug miltefosine. Seven compounds showed an IC₅₀ below 6 µM against Trypanosoma cruzi, and three of them (E{3}, E{9} and G{3}) were identified as lead scaffolds for further optimization based on their activity-toxicity profile. Two promising structures (B{15} and G{15}) showed moderate inhibitory activity against Plasmodium falciparum. In general, the presence of a benzenesulfonyl moiety improves the antiparasitic activity of the heterocycles included in this study (with the exception of Trypanosoma brucei rhodesiense), validating the criteria used in the selection of the privileged structures and diversification used to generate this library. SAR analysis showed that the presence of lipophilic and electron withdrawing groups were favorable for the antiparasitic activity.     

Design,molecular docking and synthesis of novel 5,6-dichloro-2-methyl-1H-benzimidazole derivatives as potential urease enzyme inhibitors

A novel series of 5,6-dichloro-2-methyl-1H-benzimidazole derivatives was synthesized and then screened for their urease inhibitory activity. All compounds showed more potent inhibitory activity in the range of IC₅₀ = 0.0294 ± 0.0015–0.1494 ± 0.0041 µM than thiourea (IC₅₀ = 0.5117 ± 0.0159 µM), as a reference inhibitor. Among all the tested compounds, the compound 15 (IC₅₀ = 0.0294 ± 0.0015 µM) having strong electron-withdrawing nitro group on the phenyl ring was recorded as the most potent inhibitor of urease. All compounds were docked at the active sites of the Jack bean urease enzyme to investigate the reason of the inhibitory activity and the possible binding interactions of enzyme-ligand complexes.     

Design,synthesis, in vitro evaluation,molecular docking and ADME properties studies of hybrid bis-coumarin with thiadiazole as a new inhibitor of Urease

Hybrid bis-coumarin derivatives 1–18 were synthesized and evaluated for their in vitro urease inhibitory potential. All compounds showed outstanding urease inhibitory potential with IC₅₀ value (The half maximal inhibitory concentration) ranging in between 0.12 SD 0.01 and 38.04 SD 0.63 µM (SD standard deviation). When compared with the standard thiourea (IC₅₀ = 21.40 ± 0.21 µM). Among these derivatives, compounds 7 (IC₅₀ = 0.29 ± 0.01), 9 (IC₅₀ = 2.4 ± 0.05), 10 (IC₅₀ = 2.25 ± 0.05) and 16 (IC₅₀ = 0.12 ± 0.01) are better inhibitors of the urease compared with thiourea (IC₅₀ = 21.40 ± 0.21 µM). To find structure–activity relationship molecular docking as well as absorption, distribution, metabolism, and excretion (ADME) studies were also performed. Various spectroscopic techniques like ¹H NMR, ¹³C NMR, and EI-MS were used for characterization of all synthesized analogs. All compounds were tested for cytotoxicity and found non-toxic.     

Anti-inflammatory drug approach: Synthesis and biological evaluation of novel pyrazolo[3,4-d]pyrimidine compounds

In this study, the acid chlorides of pyrazolo[3,4-d]pyrimidine compounds were prepared and reacted with a number of nucleophiles. The novel compounds were experimentally tested via enzyme assay and they showed cyclooxygenase-2 inhibition activity in the middle micro molar range (4b had a COX-1 IC₅₀ of 26 µM and a COX-2 IC₅₀ of 34 µM, 3b had a COX-1 IC₅₀ of 19 µM and a COX-2 IC₅₀ of 31 µM, 3a had a COX-2 IC₅₀ of 42 µM). These compounds were analyzed via docking and were predicted to interact with some of the COX-2 key residues. Our best hit, 4d (COX-1 IC₅₀ of 28 µM, COX-2 IC₅₀ of 23 µM), appears to adopt similar binding modes to the standard COX-2 inhibitor, celecoxib, proposing room for possible selectivity. Additionally, the resultant novel compounds were tested in several in vivo assays. Four compounds 3a (COX-2 IC₅₀ of 42 µM), 3d, 4d and 4f were notable for their anti-inflammatory activity that was comparable to that of the clinically available COX-2 inhibitor celecoxib. Interestingly, they showed greater potency than the famous non-steroidal anti-inflammatory drug, Diclofenac sodium. In summary, these novel pyrazolo[3,4-d]pyrimidine analogues showed interesting anti-inflammatory activity and could act as a starting point for future drugs.     

Amino acid prodrugs of NVR3-778: Design,synthesis and anti-HBV activity

A series of amino acid prodrugs of NVR3-778, a potent anti-HBV candidate currently under phase II clinical trial, were designed and synthesized as new anti-HBV agents. Except for 1e, all of them displayed roughly comparable anti-HBV activity (IC₅₀, 0.28–0.56 µM) to NVR3-778 (IC₅₀, 0.26 µM). Compound 1a, a l-valine ester prodrug of NVR3-778, was found to show significantly improved water solubility (0.7 mg/mL, pH 2) as we expected, and lower cytotoxicity (CC₅₀ > 10 µM) than NVR3-778 (CC₅₀, 4.81 µM). Moreover, 1a also exhibited acceptable PK properties and comparable in vivo efficacy in HBV DNA hydrodynamic mouse model to that of NVR3-778, suggesting it may serve as a promising lead compound for further anti-HBV drug discovery.     

Synthesis and biological evaluation of new pyrazolone Schiff bases as monoamine oxidase and cholinesterase inhibitors

In the current work, Schiff base derivatives of antipyrine were synthesized. The chemical characterization of the compounds was confirmed using IR, ¹H NMR, ¹³C NMR and mass spectroscopies. The inhibitory potency of synthesized compounds was investigated towards acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), and monoamine oxidases A and B (MAO-A and MAO-B) enzymes. Some of the compounds displayed significant inhibitory activity against AChE and MAO-B enzymes, respectively. According to AChE enzyme inhibition assay, compounds 3e and 3g were found as the most potent derivatives with IC₅₀ values of 0.285 µM and 0.057 µM, respectively. Also, compounds 3a (IC₅₀ = 0.114 µM), 3h (IC₅₀ = 0.049 µM), and 3i (IC₅₀ = 0.054 µM) were the most active derivatives against MAO-B enzyme activity. So as to understand inhibition type, enzyme kinetics studies were carried out. Furthermore, molecular docking studies were performed to define and evaluate the interaction mechanism between compounds 3g and 3h and related enzymes. ADME (Absorption, Distribution, Metabolism, and Excretion) and BBB (Blood, Brain, Barier) permeability predictions were applied to estimate pharmacokinetic profiles of synthesized compounds.     

Aromatic glycosyl disulfide derivatives: Evaluation of their inhibitory activities against Trypanosoma cruzi

Aromatic oligovalent glycosyl disulfides and some diglycosyl disulfides were tested against three different Trypanosoma cruzi strains. Di-(β-d-galactopyranosyl-dithiomethylene) benzenes 2b and 4b proved to be the most active derivatives against all three strains of cell culture-derived trypomastigotes with IC₅₀ values ranging from 4 to 11 μM at 37 °C. The inhibitory activities were maintained, although somewhat lowered, at a temperature of 4 °C as well. Three further derivatives displayed similar activities against at least one of the three strains. Low cytotoxicities of the active compounds, tested on confluent HeLa, Vero and peritoneal macrophage cell cultures, resulted in significantly higher selectivity indices (SI) than that of the reference drug benznidazole. Remarkably, several molecules of the tested panel strongly inhibited the parasite release from T. cruzi infected HeLa cell cultures suggesting an effect against the intracellular development of T. cruzi amastigotes as well.     

Discovery of 1,3-diphenyl-1H-pyrazole derivatives containing rhodanine-3-alkanoic acid groups as potential PTP1B inhibitors

Two series of 1,3-diphenyl-1H-pyrazole derivatives containing rhodanine-3-alkanoic acid groups were identified as competitive protein tyrosine phosphatase 1B (PTP1B) inhibitors. Among the compounds studied, IIIv was found to have the best in vitro inhibition activity against PTP1B (IC₅₀?=?0.67?±?0.09?µM) and the best selectivity (9-fold) between PTP1B and T-cell protein tyrosine phosphatase (TCPTP). Molecular docking studies demonstrated that compounds IIIm, IIIv and IVg could occupy simultaneously at both the catalytic site and the adjacent pTyr binding site. These results provide novel lead compounds for the design of inhibitors of PTP1B as well as other PTPs.