Design, synthesis and antitrypanosomatid activity of 2-nitroimidazole-3,5-disubstituted isoxazole compounds based on benznidazole

Exploring chloro-isoxazole compounds inspired on tetrahydrofuran neolignans as promising antileishmanial agents

The present work aims to synthesize and to identify a potential antileishmanial agent from chloro-diphenyl isoxazole methoxylated compounds. We have synthesized ten new chloro-isoxazole analogs inspired by the scaffold of tetrahydrofuran neolignans veraguensin 1a, grandisin 1b, and machilin G 1c. To obtain analogs 4a-4j, we used a cycloaddition reaction with yields ranging from 45 % to 89 %. All compounds were characterized using Nuclear Magnetic Resonance of 1H and 13C and analyzed by using High-Resolution Mass Spectrometry. The HPLC analysis confirmed that all compounds were more than 95 % pure. Finally, we tested the antileishmanial activity of these analogs against promastigote and intracellular amastigote forms of L. amazonensis in vitro. We conducted tests on murine peritoneal macrophages to determine the cytotoxicity of the analogs. Our findings revealed that 4e (R1-R3 = -OCH3, X1 = -Cl, R4 and R5 = -OCH2O-), a hybrid compound of grandisin and machilin G, showed moderate activity on promastigotes (IC50 = 38.1 ± 1.5 μM). 4e was also effective against intracellular amastigotes with similar IC50 values to AmB-treated control (IC50 = 2.2 ± 0.4 μM and IC50 = 2.0 ± 0.1, respectively). Moreover, it exhibited a selectivity index (SI) for amastigote forms equal to 22.7, higher than the reference drugs we tested. Analog 4e displayed non-mutagenic potential at all tested concentrations in the Ames test. We also evaluated the therapeutic effect of 4e on the experimental cutaneous leishmaniasis model with BALB/c mice infected with promastigote forms of L. amazonensis and treated with intralesional (IL) injections. Our study found that mice treated with 4e had a significant reduction (99.5 % drop) in the footpad tissue parasite load compared to the control group treated with the vehicle. The effect of 4e was similar, controlling the infection, to that of N-methylglucamine antimonate (Sb, Glucantime, 99.8 % drop), which is a reference treatment. Based on our results, we suggest that chloro-isoxazole analog 4e shows potential as an antileishmanial agent for treating cutaneous leishmaniasis (CL).

Design, Synthesis, and Structure-Activity Relationship of 2-(Piperazin-1-yl)quinazolin-4(3H)-one Derivatives as Active Agents against Toxoplasma gondii

A novel series of quinazolin-4(3H)-one derivatives were synthesized using a hybridization strategy that combined the quinazolin-4(3H)-one scaffold, the diarylether fragment, and the piperazine ring. The in vitro activity evaluation of these compounds against Toxoplasma gondii demonstrated that most of this series of compounds showed moderate to good effectiveness, with IC50 values ranging from 5.94 to 102.2 μM. Among the synthesized derivatives, compounds 11 and 18 emerged as the most potent inhibitors, significantly reducing the replication rate of T. gondii with IC50 values of 6.33 and 5.94 μM, as well as demonstrated low cytotoxicity with CC50 values of 285 and 59.2 μM, respectively. The structure-activity relationship investigation indicates that the substituent at the N-3 position of the quinazolin-4(3H)-one is important for anti-T. gondii activity while the replacements at the phenyl moiety of the quinazolin-4(3H)-one and at the diarylether fragment cannot improve activity. The invasion and proliferation assay demonstrated that compound 11 could inhibit both parasite invasion and replication ability. Further investigation of the in vitro efficacy revealed irreversible action of compound 11 against T. gondii. In vivo investigations conducted within a murine model of acute infection revealed that compounds 11 and 18 exhibited a remarkable capacity to significantly diminish the parasitic load in comparison to the control group while also extending the survival duration of the subjects. These results underscore the potential of compound 11 as a candidate for further exploration in the development of antitoxoplasmosis therapies.

Design and Synthesis of 2-Nitroimidazole-1,2,3-triazole Sulfonamide Hybrids as Potent and Selective Anti-Trypanosomatid Agents

A series of 2-nitroimidazole-1,2,3-triazole sulfonamide hybrid analogs were designed using medicinal chemistry approaches, such as bioisosterism, molecular hybridization, Topliss tree decision, and Craig plot. A total of 24 compounds were synthesized via click chemistry in satisfactory yields. Overall, analogs 15 a-x exhibited relevant in vitro anti-trypanosomatid activity against amastigote forms of T. cruzi and without cytotoxic effect on LLC-MK2 cells. Analogs 15 b (R1=4-Cl-Ph; IC50=1.63 μM, SI=>30.65), 15 m (R1=3,4-di-Cl-Ph; IC50=0.63 μM, SI=>78.96), and 15 s (R1=Ph-4-O-Ph; IC50=0.63 μM, SI=>79.90) demonstrated pronounced antitrypanosomal activity, more active than the reference drug, benznidazole and with good selectivity indexes. Furthermore, analog 15 b (R1=4-Cl-Ph; IC50=0.5 μM, SI=>100) exhibited an outstanding antileishmanial activity against amastigote forms of Leishmania (L.) amazonensis and impressive selectivity index, comparable to the reference compound amphotericin B. The mutagenicity of compounds 15 b and 15 m were evaluated against Salmonella typhimurium strains (TA98, TA100 and TA102). Compound 15 b exhibited mutageniticy only at a concentration of 500  μg/plate for the TA100 strain, whereas compound 15 m was considered non-mutagenic. These findings suggest that 2-nitroimidazoles-1,2,3-triazole sulfonamide hybrid analogs are promising anti-trypanosomatid candidates for future in vivo studies.

Discovery of a new eugenol-benznidazole hybrid active against different evolutive stages of Trypanosoma cruzi

Chagas disease (CD) is a life-threatening illness caused by the protozoan Trypanosoma cruzi and there are only two drugs currently available for pharmacotherapy of this neglected infection (benznidazole and nifurtimox). Their limited efficacy in chronic phase of the disease, problems of toxicity and the growing resistance by the protozoan are directly associated to high rates of drug discontinuation by the patients. In the context of the search for new trypanocidal drug candidates, our group has been working with the chemical manipulation of eugenol to obtain new agents active against T. cruzi and promising results have been achieved. In this work we designed molecular hybrids between eugenol and benznidazole (BZN) by performing a bioisosteric replacement between the nitroimidazole ring of BZN by the eugenol or analogues nucleus in nitrated or non-nitrated forms. The obtained compounds were initially evaluated against epimastigote stages of T. cruzi for selecting the most active ones. Three hybrids (8, 10 and 15) showed activity against this evolutive stage and the most promising was eugenol nitro derivative 8 (IC50: 24.7 µM) that showed a similar potential than BZN (IC50: 29.9 µM). Compounds 8, 10 and 15 were then evaluated against infective trypomastigote and intracellular amastigote forms of T. cruzi and the cytotoxicity of them was investigated against healthy Vero and H9c2 cells. The nitro derivative 8 was once again the most promising compound against trypomastigote (IC50: 1.8 µM) and amastigote (IC50: 1.6 µM) forms, with selectivity indices greater than 63 considering both health cells evaluated. This compound was more active than BZN, that showed IC50 values of 6.1 µM (trypomastigotes) and 3.1 µM (amastigotes) and showed the most significant effect in reducing the infection rate and accumulation of parasites in infected cells. Calculated logP values suggest that the higher lipophilicity of derivative 8 (clogP: 3.25) in relation to BZN (clogP: 0.77) may be correlated to a greater ability of this eugenol derivative to cross the membranes of infected cells. Finally, to try understand the possible mode of action for compound 8, we have evaluated three important targets of the parasite (T. cruzi nitroreductase type I - TcNRT, trypanothione reductase - TR and mitochondrial membrane depolarization), but none of these metabolic pathways seem to be related to the mechanism of action of this compound. All in vitro assays employed the T. cruzi Y strain which exhibits partial resistance to benznidazole and these results indicate compound 8 as a new promising hit for the development of drug candidates to treat CD.

New drug discovery strategies for the treatment of benznidazole-resistance in Trypanosoma cruzi, the causative agent of Chagas disease

INTRODUCTION

Benznidazole, the drug of choice for treating Chagas Disease (CD), has significant limitations, such as poor cure efficacy, mainly in the chronic phase of CD, association with side effects, and parasite resistance. Understanding parasite resistance to benznidazole is crucial for developing new drugs to treat CD.

AREAS COVERED

Here, the authors review the current understanding of the molecular basis of benznidazole resistance. Furthermore, they discuss the state-of-the-art methods and critical outcomes employed to evaluate the efficacy of potential drugs against T. cruzi, aiming to select better compounds likely to succeed in the clinic. Finally, the authors describe the different strategies employed to overcome resistance to benznidazole and find effective new treatments for CD.

EXPERT OPINION

Resistance to benznidazole is a complex phenomenon that occurs naturally among T. cruzi strains. The combination of compounds that inhibit different metabolic pathways of the parasite is an important strategy for developing a new chemotherapeutic protocol.

Exploring novel pyrazole-nitroimidazole hybrids: Synthesis and antiprotozoal activity against the human pathogen trichomonas vaginalis

Trichomoniasis, a prevalent sexually transmitted infection (STI) caused by the protozoan Trichomonas vaginalis, has gained increased significance globally. Its relevance has grown in recent years due to its association with a heightened risk of acquiring and transmitting the human immunodeficiency virus (HIV) and other STIs. In addition, many publications have revealed a potential link between trichomoniasis and certain cancers. Metronidazole (MTZ), a nitroimidazole compound developed over 50 years ago, remains the first-choice drug for treatment. However, reports of genotoxicity and side effects underscore the necessity for new compounds to address this pressing global health concern. In this study, we synthesized ten pyrazole-nitroimidazoles 1(a-j) and 4-nitro-1-(hydroxyethyl)-1H-imidazole 2, an analog of metronidazole (MTZ), and assessed their trichomonacidal and cytotoxic effects. All compounds 1(a-j) and 2 exhibited IC50 values ≤ 20 μM and ≤ 41 μM, after 24 h and 48 h, respectively. Compounds 1d (IC50 5.3 μM), 1e (IC50 4.8 μM), and 1i (IC50 5.2 μM) exhibited potencies equivalent to MTZ (IC50 4.9 μM), the reference drug, after 24 h. Notably, compound 1i showed high anti-trichomonas activity after 24 h (IC50 5.2 μM) and 48 h (IC50 2.1 μM). Additionally, all compounds demonstrated either non-cytotoxic to HeLa cells (CC50 > 100 μM) or low cytotoxicity (CC50 between 69 and 100 μM). These findings suggest that pyrazole-nitroimidazole derivatives represent a promising heterocyclic system, serving as a potential lead for further optimization in trichomoniasis chemotherapy.

Neuroprotective Profile of Triazole Grandisin Analogue against Amyloid-Beta Oligomer-Induced Cognitive Impairment

Alzheimer's disease (AD) is a neurodegenerative disorder caused by accumulation of amyloid-β oligomers (AβO) in the brain, neuroinflammation, oxidative stress, and cognitive decline. Grandisin, a tetrahydrofuran neolignan, exhibits relevant anti-inflammatory and antioxidant properties. Interestingly, grandisin-based compounds were shown to prevent AβO-induced neuronal death in vitro. However, no study has assessed the effect of these compounds on the AD animal model. This study focuses on a triazole grandisin analogue (TGA) synthesized using simplification and bioisosteric drug design, which resulted in improved potency and solubility compared with the parent compound. This study aimed to investigate the possible in vivo effects of TGA against AβO-induced AD. Male C57/Bl6 mice underwent stereotaxic intracerebroventricular AβO (90 μM) or vehicle injections. 24 h after surgery, animals received intraperitoneal treatment with TGA (1 mg/kg) or vehicle, administered on a 14 day schedule. One day after treatment completion, a novel object recognition task (NORT) was performed. Memantine (10 mg/kg) was administered as a positive control. NORT retention sessions were performed on days 8 and 16 after AβO injection. Immediately after retention sessions, animals were euthanized for cortex and hippocampus collection. Specimens were subjected to oxidative stress and cytokine analyses. TGA reduced the level of cortex/hippocampus lipoperoxidation and prevented cognitive impairment in AβO-injected mice. Additionally, TGA reduced tumor necrosis factor (TNF) and interferon-γ (IFN-γ) levels in the hippocampus. By contrast, memantine failed to prevent cortex/hippocampus lipid peroxidation, recognition memory decline, and AβO-induced increases in TNF and IFN-γ levels in the hippocampus. Thus, memantine was unable to avoid the AβO-induced persistent cognitive impairment. The results showed that TGA may prevent memory impairment by exerting antioxidant and anti-inflammatory effects in AβO-injected mice. Moreover, TGA exhibited a persistent neuroprotective effect compared to memantine, reflecting an innovative profile of this promising agent against neurodegenerative diseases, such as AD.