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.     

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.     

Trypanosoma cruzi: activities of lapachol and alpha- and beta-lapachone derivatives against epimastigote and trypomastigote forms

Derivatives of natural quinones with biological activities, such as lapachol, alpha- and beta-lapachones, have been synthesized and their trypanocidal activity evaluated in vitro in Trypanosoma cruzi cells. All tested compounds inhibited epimastigote growth and trypomastigote viability. Several compounds showed similar or higher activity as compared with current trypanocidal drugs, nifurtimox and benznidazole. The results presented here show that the anti-T. cruzi activity of the alpha-lapachone derivatives can be increased by the replacement of the benzene ring by a pyridine moiety. Free radical production and consequently oxidative stress through redox cycling or production of electrophilic metabolites are the potential biological mechanism of action for these synthetic quinones.     

Novel 3-nitro-1H-1,2,4-triazole-based piperazines and 2-amino-1,3-benzothiazoles as antichagasic agents

We have previously shown that 3-nitro-1H-1,2,4-triazole-based amines demonstrate significant trypanocidal activity, in particular against Trypanosoma cruzi, the causative parasite of Chagas disease. In the present work we further expanded our research by evaluating in vitro the trypanocidal activity of nitrotriazole-based piperazines and nitrotriazole-based 2-amino-1,3-benzothiazoles to establish additional SARs. All nitrotriazole-based derivatives were active or moderately active against T. cruzi; however two of them did not fulfill the selectivity criteria. Five derivatives were active or moderately active against Trypanosoma brucei rhodesiense while one derivative was moderately active against Leishmania donovani. Active compounds against T. cruzi demonstrated selectivity indexes (toxicity to host cells/toxicity to T. cruzi amastigotes) from 117 to 1725 and 12 of 13 compounds were up to 39-fold more potent than the reference compound benznidazole. Detailed SARs are discussed.     

Novel N-benzylpyridinium moiety linked to arylisoxazole derivatives as selective butyrylcholinesterase inhibitors: Synthesis,biological evaluation,and docking study

A novel series of N-benzylpyridinium moiety linked to arylisoxazole ring were designed, synthesized, and evaluated for their in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities. Synthesized compounds were classified into two series of 5a-i and 5j-q considering the position of positively charged nitrogen of pyridinium moiety (3- or 4- position, respectively) connected to isoxazole carboxamide group. Among the synthesized compounds, compound 5n from the second series of compounds possessing 2,4-dichloroaryl group connected to isoxazole ring was found to be the most potent AChE inhibitor (IC₅₀ = 5.96 µM) and compound 5j also from the same series of compounds containing phenyl group connected to isoxazole ring demonstrated the most promising inhibitory activity against BChE (IC₅₀ = 0.32 µM). Also, kinetic study demonstrated competitive inhibition mode for both AChE and BChE inhibitory activity. Docking study was also performed for those compounds and desired interactions with those active site amino acid residues were confirmed through hydrogen bonding as well as π-π and π-anion interactions. In addition, the most potent compounds were tested against BACE1 and their neuroprotectivity on Aβ-treated neurotoxicity in PC12 cells which depicted negligible activity. It should be noted that most of the synthesized compounds from both categories 5a-i and 5j-q showed a significant selectivity toward BChE. However, series 5j-q were more active toward AChE than series 5a-i.     

Synthesis,structural elucidation and in vitro antiparasitic activity against Trypanosoma cruzi and Leishmania chagasi parasites of novel tetrahydro-1-benzazepine derivatives

Forty six new 1,4-epoxy-2-exo-aryl- and cis-2-aryl-4-hydroxytetrahydro-1-benzazepine derivatives were synthesized and fully characterized. All compounds were tested in vitro against both Trypanosoma cruzi and Leishmania chagasi parasites and also for cytotoxicity using Vero and THP-1 mammalian cell lines. Many of the evaluated compounds showed remarkable activity against the epimastigote and intracellular amastigote forms of T. cruzi, with IC₅₀ values comparable with that of control drug nifurtimox, a nitrofuran derivative currently used in the treatment of Chagas’ disease. Other derivatives were found to have good activity against L. chagasi promastigotes, with low toxicity against the mammalian cells, but neither of them was active on intracellular amastigotes of L. chagasi infecting THP-1 macrophages.     

Synthesis,antioxidant and antiproliferative activities of 1,3,4-thiadiazoles derived from phenolic acids

Two 2-amino-1,3,4-thiadiazoles containing phenolic hydroxyl groups were combined with different carboxylic acid chlorides giving sixteen amide derivatives with good antioxidant and antiproliferative potential. The compound 3′c with an adamantane ring displayed excellent DPPH radical scavenging activity and good cytotoxic activity against human acute promyelocytic leukemia HL-60 cells, while 1,3,4-thiadiazole 3′h with 4-chlorophenyl moiety was found to be the most effective in inhibition of survival of lung carcinoma A549 cells. All examined thiadiazoles except 3a and 3′a exerted higher cytotoxic activities on A549 and HL-60 cancer cells when compared with normal fibroblasts MRC-5, pointing to selectivity in their antiproliferative action. Some of the most active novel compounds 3c, 3′c, 3′g and 3′h induced significant increase in the percentage of HL-60 cells in the subG1 cell cycle phase in comparison with the control cells. The induction of cell death in HL-60 cells by these compounds was at least partially dependent on activation of caspase-3 and caspase-8. The compounds 3c and 3′c exerted strong antiangiogenic activity. Furthermore, compounds 3c, 3′c, 3′g and 3′h showed the ability to down-regulate the MMP2 and VEGFA expression levels in the treated HL-60 cells when compared with the control cell samples.     

Design,synthesis, molecular docking and biological evaluation of thiophen-2-iminothiazolidine derivatives for use against Trypanosoma cruzi

In this study, we designed and synthesized a series of thiophen-2-iminothiazolidine derivatives from thiophen-2-thioureic with good anti-Trypanosoma cruzi activity. Several of the final compounds displayed remarkable trypanocidal activity. The ability of the new compounds to inhibit the activity of the enzyme cruzain, the major cysteine protease of T. cruzi, was also explored. The compounds 3b, 4b, 8b and 8c were the most active derivatives against amastigote form, with significant IC₅₀ values between 9.7 and 6.03 μM. The 8c derivative showed the highest potency against cruzain (IC₅₀ = 2.4 μM). Molecular docking study showed that this compound can interact with subsites S1 and S2 simultaneously, and the negative values for the theoretical energy binding (E_b = −7.39 kcal·mol⁻¹) indicates interaction (via dipole–dipole) between the hybridized sulfur sp³ atom at the thiazolidine ring and Gly66. Finally, the results suggest that the thiophen-2-iminothiazolidines synthesized are important lead compounds for the continuing battle against Chagas disease.     

Trypanocidal,leishmanicidal and cytotoxic effects of anthecotulide-type linear sesquiterpene lactones from Anthemis auriculata

Trypanosomiasis and leishmaniasis pose major public health threats for many countries, particularly those in sub-Saharan Africa and South America. In the present study, we evaluated the in vitro antiprotozoal activity of three irregular, linear sesquiterpene lactones recently isolated from Greek Anthemis auriculata, namely anthecotulide (1), 4-hydroxyanthecotulide (2) and 4-acetoxyanthecotulide (3). Trypomastigote forms of Trypanosoma brucei rhodesiense and T. cruzi as well as axenic amastigotes of Leishmania donovani were used for testing. The cytotoxic potential of the compounds was also assessed against mammalian (rat) skeletal myoblasts (L6 cells). All compounds showed potent trypanocidal and leishmanicidal activity. 4-Hydroxyanthecotulide (2) appeared to be the most active compound against all parasites, particularly towards T. b. rhodesiense (IC₅₀ 0.56 μg/ml), whereas 4-acetoxyanthecotulide (3) was the least active. All three metabolites possessed toxicity on mammalian cells, which might limit their use as antiprotozoal agents.     

New potent 5-nitroindazole derivatives as inhibitors of Trypanosoma cruzi growth: Synthesis,biological evaluation,and mechanism of action studies

New 5-nitroindazole derivatives were developed and their antichagasic properties studied. Eight compounds (14–18, 20, 26 and 28) displayed remarkable in vitro activities against Trypanosoma cruzi (T. cruzi). Its unspecific cytotoxicity against macrophages was evaluated being not toxic at a concentration at least twice that of T. cruzi IC₅₀, for some derivatives. The electrochemical studies, parasite respiration studies and ESR experiment showed that 5-nitroindazole derivatives not be able to yield a redox cycling with molecular oxygen such as occurs with nifurtimox (Nfx). The study on the mechanism of action proves to be related to the production of reduced species of the nitro moiety similar to that observed with benznidazole.     

Carbonic anhydrase inhibitors: Synthesis,molecular docking,cytotoxic and inhibition of the human carbonic anhydrase isoforms I,II, IX,XII with novel benzenesulfonamides incorporating pyrrole,pyrrolopyrimidine and fused pyrrolopyrimidine moieties

A series of novel pyrroles, pyrrolopyrimidines, pyrazolopyrrolopyrimidine, triazolopyrrolopyrimidines, tetrazolopyrrolopyrimidine, triazinopyrrolopyrimidines and pyrrolopyrimidotriazepines bearing the biologically active benzenesulfonamide moiety were synthesized by using pyrrole-o-amino-carbonitrile as key intermediate. All the synthesized compounds were evaluated for their in vitro carbonic anhydrase (CA, EC 4.2.1.1) inhibitory effects against the human (h) isoforms hCA I, II, IX and XII. Among the tested derivatives, compounds 16, 18 and 20–24 showed potent activity as inhibitors for the tumor associated transmembrane isoforms (hCA IX and XII) in the nanomolar and subnanomolar range, with high selectivity. All compounds underwent cytotoxic activity assays on human breast cancer cell line (MCF-7) showing effective activity, comparable to that of the clinically used drug doxorubicin.     

Aryl- or heteroaryl-based hydrazinylphthalazine derivatives as new potential antitrypanosomal agents

A series of twenty phthalazinyl-hydrazones were synthesized and tested as potential anti-Trypanosoma cruzi agents. The phthalazines containing 5-nitroheteroaryl moiety 3l and 3m displayed an excellent in vitro antitrypanosomal profile, exhibiting low micromolar EC₅₀ values against proliferative epimastigote of T. cruzi and minimal toxicity toward Vero cells. These derivatives were more potent than the reference drug benznidazole against the epimastigote stage of the parasite. Structure-property analysis indicates that the highly conjugated 5-nitroheteroaryl moiety connected to the phthalazin scaffold play an important role in the antichagasic activity of these phthalazines. The decrease on the mitochondrial dehydrogenase activity and significant ROS production found for the parasites treated with 3l and 3m suggest that both nitro-derivatives can act through an oxidative stress mechanism.     

Synthesis and anti-Trypanosoma cruzi activity of naphthoquinone-containing triazoles: Electrochemical studies on the effects of the quinoidal moiety

In our continued search for novel trypanocidal compounds, twenty-six derivatives of para- and ortho-naphthoquinones coupled to 1,2,3-triazoles were synthesized. These compounds were evaluated against the infective bloodstream form of Trypanosoma cruzi, the etiological agent of Chagas disease. Compounds 17–24, 28–30 and 36–38 are described herein for the first time. Three of these novel compounds (28–30) were found to be more potent than the standard drug benznidazole, with IC₅₀/24 h values between 6.8 and 80.8 μM. Analysis of the toxicity to heart muscle cells led to LC₅₀/24 h of <125, 63.1 and 281.6 μM for 28, 29 and 30, respectively. Displaying a selectivity index of 34.3, compound 30 will be further evaluated in vivo. The electrochemical properties of selected compounds were evaluated in an attempt to find correlations with trypanocidal activity, and it was observed that more electrophilic quinones were generally more potent.     

Synthesis and biological evaluation of 5-aryloxypyrazole derivatives bearing a rhodanine-3-aromatic acid as potential antimicrobial agents

Three novel series of 5-aryloxypyrazole derivatives have been synthesized and tested for their antibacterial activity. The majority of the synthesized compounds showed potent inhibitory activity against Gram-positive bacteria Staphylococcus aureus 4220, especially against the strains of multidrug-resistant clinical isolates (MRSA3167/3506 and QRSA3505/3519). Among which compounds IIIb, IIIg and IIIm showed the most potent levels of activity (MIC = 1 μg/mL) against the multidrug-resistant strains. And cytotoxic activity assay showed that the compounds tested did not affect cell viability on the Human cervical (HeLa) cells at their MICs. The current study therefore suggests that 5-aryloxypyrazoles bearing a rhodanine-3-aromatic acid moiety are promising scaffolds for the development of novel Gram-positive antibacterial agents.     

Synthesis,cytotoxic activity,and tubulin polymerization inhibitory activity of new pyrrol-2(3H)-ones and pyridazin-3(2H)-ones

A series of new pyrrol-2(3H)-ones 4a-f and pyridazin-3(2H)-ones 7a-f were synthesized and characterized using different spectroscopic tools. Some of the tested compounds revealed moderate activity against 60 cell lines. The E form of the pyrrolones 4 showed good cytotoxic activity than both the Z form and the corresponding open amide form. Furthermore, the in vitro cytotoxic activity against HepG2 and MCF-7 cell lines revealed that compounds (E)4b, 6f and 7f showed good cytotoxic activity against HepG2 with IC₅₀ values of 11.47, 7.11 and 14.80 μM, respectively. Compounds (E)4b, 6f, 7d and 7f showed a pronounced inhibitory effect against cellular localization of tubulin. Flow cytometric analysis indicated that HepG2 cells treated with (E)4b showed a predominated growth arrest at the S-phase compared to that of G2/M-phase. Molecular modeling study using MOE® program indicated that most of the target compounds showed good binding of β-subunit of tubulin with the binding free energy (dG) values about −10 kcal/mole.     

Platinum-based complexes of bioactive 3-(5-nitrofuryl)acroleine thiosemicarbazones showing anti-Trypanosoma cruzi activity

Eight new platinum(II) complexes with 3-(5-nitrofuryl)acroleine thiosemicarbazones showing anti-trypanosomal activity were synthesized, characterized and in vitro evaluated. Most of the complexes showed IC₅₀ values in the micromolar range against two different strains of Trypanosoma cruzi, causative agent of Chagas disease (American Trypanosomiasis). In addition, most of the newly developed complexes, together with the analogous platinum 5-nitrofuraldehyde containing thiosemicarbazones previously reported, resulted more active than the reference trypanocidal drug nifurtimox on the infective trypomastigote form of the parasite. Their capacity to produce free radicals that could lead to parasite death was evaluated by ESR experiments in the parasite and by respiration measurements. Compounds were tested for their DNA interaction ability. Results showed that some of the compounds could act as dual inhibitors in the parasite, through production of toxic free radicals and interaction with DNA. All the results were compared with those previously reported for the free ligands, the analogous palladium(II) compounds and the previously reported series of platinum(II) compounds.     

Novel Pyrazoloquinolin-2-ones: Design,synthesis, docking studies,and biological evaluation as antiproliferative EGFR-TK inhibitors

Two new series of diethyl 2-[2-(substituted-2-oxo-1,2-dihydroquinolin-4-yl)hydrazono]-succinates 6a-g and 1-(2-oxo-1,2-dihydroquinolin-4-yl)-1H-pyrazoles 7a-f have been designed and synthesized. The structures of the synthesized compounds were proved by IR, mass, NMR (2D) spectra and elemental analyses. The target compounds were evaluated for their in vitro cytotoxic activity against 60 cancer cell lines according to NCI protocol. Consequently, seven compounds were further examined against the most sensitive cell lines, leukemia CCRF-CEM, and MOLT-4. 5-Amino-1-(6-bromo-2-oxo-1,2-dihydroquinolin-4-yl)-1H-pyrazole-3,4-dicarbonitrile (7f) was the most active product, with IC₅₀ = 1.35 uM and 2.42 uM against MOLT-4 and CCRF-CEM, respectively. Also, it showed a remarkable inhibitory activity compared to erlotinib on the EGFR TK with IC₅₀ = 247.14 nM and 208.42 nM, respectively. Cell cycle analysis of MOLT-4 cells treated with 7f showed cell cycle arrest at G2/M phase (supported by Caspases, BAX and Bcl-2 studies) with a significant pro-apoptotic activity as indicated by annexin V-FITC staining. Moreover, the docking study indicated that both the pyrazole moiety and the quinolin-2-one ring showed good fitting into EGFR (PDB code: 1M17). In order to interpret SAR of the designed compounds, and provide a basis for further optimization, molecular docking of the synthesized compounds to known EGFR inhibitors was performed. The study illustrated the effect of several factors on the compounds’ activity.     

Synthesis and biological evaluation of benzo[b]furo[3,4-e][1,4]diazepin-1-one derivatives as anti-cancer agents

A new series of novel Podophyllotoxin-like benzo[b]furo[3,4-e][1,4]diazepin-1-ones possessing structural elements of 4-aza-2,3-didehydropodophyllotoxins with central diazepine ring was designed and synthesized as anti-cancer agents. In initial assessment, the cytotoxic activity of the synthesized compounds was evaluated against three cancer cell lines including MCF-7, PC3 and B16-F10 employing the MTT assay. Some of compounds (12h, 13a, 13c and 14b) showed significant cytotoxic activity. So, we investigated the cytotoxicity of compounds 12h, 13a, 13c and 14b, along with podophyllotoxin as the reference drug in different cancer cell lines including A549, A2780, DU145, HeLa, and normal Huvec cell line. Among these four compounds, 13c showed promising antiproliferative activity against all cancer cells stronger than the other compounds and comparable to reference drug podophyllotoxin in some cancer cells. All these four compounds did not show significant cytotoxicity on normal Huvec cell line. The flow cytometry analysis of the MCF-7, PC3 and A2780 human cancer cell lines treated with 13c showed that 13c, induced apoptosis in the MCF-7, PC3 and A2780 human cancer cell lines, which is in good agreement to its cytotoxic activity as well. Compound 13c did not show significant influence on tubulin assembly and exert its cytotoxic effects via induction of apoptosis and has potent and selective cytotoxic effects in cancer cells.     

Trypanocidal activity of N-isopropyl oxamate on cultured epimastigotes and murine trypanosomiasis using different Trypanosoma cruzi strains

The trypanocidal activity of N-isopropyl oxamate (NIPOx) and the ethyl ester of N-isopropyl oxamate (Et-NIPOx) were tested on cultured epimastigotes (in vitro) and on murine trypanosomiasis (in vivo) using five different T. cruzi strains. When benznidazole and nifurtimox, used for comparison, were tested we found that only three of these T. cruzi strains were affected, whereas the other two strains, Miguz and Compostela, were resistant to the in vitro and the in vivo trypanocidal activity of these substances. In addition, when NIPOx was tested on cultured epimastigotes and on mice parasitaemia, trypanocidal activity was not obtained on either of these T. cruzi strains. Our experiments strongly suggest that NIPOx does not penetrate intact epimastigotes due to the polarity of its carboxylate whereas Et-NIPOx, acting as a prodrug, exhibited in vitro and in vivo trypanocidal activity in the five tested T. cruzi strains.     

Synthesis and anti-proliferative activity of allogibberic acid derivatives containing 1,2,3-triazole pharmacophore

Sixty novel allogibberic acid derivatives containing 1,2,3-triazole pharmacophore were designed and synthesized. The key chemical processes include aromatization of the A ring in gibberellins, formation of allogibberic azides and its copper mediated Huisgen 1,3-dipolar cycloaddition with alkynes. A number of hybrids containing α,β-unsaturated ketone moiety exhibited excellent in vitro cytotoxic activities. Some of the hybrids were more selective to MCF-7 and SW480 cell lines with IC₅₀ values at least 8-fold more cytotoxic than cisplatin (DDP). The most potent compounds C43 and C45 are more cytotoxic than cisplatin (DDP) against all tested five tumor cell lines, with IC₅₀ values of 0.25–1.72?µM. Mechanism of action studies indicated that allogibberic-triazole derivative C45 could induce the S phase cell cycle arrest and apoptosis in SMMC-7721 cell lines.