Antibacterial, Trichomonacidal, and Cytotoxic Activities of Pleopeltis crassinervata Extracts.

Pleopeltis crassinervata is a fern documented in ethnobotanical records for its use in Mexican traditional medicine to treat gastric disorders and mouth ulcers. Consequently, conducting biological and pharmacological assays is crucial to validate the therapeutic efficacy of this plant within the context of traditional medicine. In the present study, we investigated the biological activity of extracts and fractions obtained from P. crassinervata organs against bacteria (Salmonella typhimurium, Salmonella typhi, Staphylococcus aureus, Proteus mirabilis, Shigella flexneri, Bacillus subtilis, Escherichia coli) and Trichomonas vaginalis using in vitro models. The precipitate fraction obtained from the frond methanolic extract showed significant antibacterial activity (minimal inhibitory concentration [MIC] 120 µg/mL) against the Staphylococcus aureus strain and was effective against both Gram-positive and Gram-negative bacteria. The hexane fraction also obtained from frond methanolic extract, showed a trichomonacidal effect with an IC50 of 82.8 µg/mL and a low cytotoxic effect. Hsf6 exhibited the highest activity against T. vaginalis, and the GC-MS analysis revealed that the predominant compound was 16-pregnenolone. The remaining identified compounds were primarily terpene-type compounds.

Synthesis and Biophysical and Biological Studies of N-Phenylbenzamide Derivatives Targeting Kinetoplastid Parasites.

The AT-rich mitochondrial DNA (kDNA) of trypanosomatid parasites is a target of DNA minor groove binders. We report the synthesis, antiprotozoal screening, and SAR studies of three series of analogues of the known antiprotozoal kDNA binder 2-((4-(4-((4,5-dihydro-1H-imidazol-3-ium-2-yl)amino)benzamido)phenyl)amino)-4,5-dihydro-1H-imidazol-3-ium (1a). Bis(2-aminoimidazolines) (1) and bis(2-aminobenzimidazoles) (2) showed micromolar range activity against Trypanosoma brucei, whereas bisarylimidamides (3) were submicromolar inhibitors of T. brucei, Trypanosoma cruzi, and Leishmania donovani. None of the compounds showed relevant activity against the urogenital, nonkinetoplastid parasite Trichomonas vaginalis. We show that series 1 and 3 bind strongly and selectively to the minor groove of AT DNA, whereas series 2 also binds by intercalation. The measured pKa indicated different ionization states at pH 7.4, which correlated with the DNA binding affinities (ΔTm) for series 2 and 3. Compound 3a, which was active and selective against the three parasites and displayed adequate metabolic stability, is a fine candidate for in vivo studies.

5-Nitroindazole-based compounds: further studies for activity optimization as anti-Trypanosoma cruzi agents.

In this study, a new series of eleven 5-nitroindazole derivatives (10-20) and a related 6-nitroquinazoline (21) was synthesized and tested in vitro against different forms of the kinetoplastid parasite Trypanosoma cruzi, etiological agent of Chagas disease. Among these compounds, derivatives 11-14 and 17 showed trypanocidal profiles on epimastigotes (IC50 = 1.00-8.75 µM) considerably better than that of the reference drug benznidazole, BZ (IC50 = 25.22 µM). Furthermore, the lack of cytotoxicity observed for compounds 11, 12, 14, 17 and 18 over L929 fibroblasts, led to a notable selectivity (SI) on the extracellular replicative form of the parasite: SIEPI > 12.41 to > 256 µM. Since these five derivatives overpassed the cut-off value established by BZ (SIEPI ≥ 10), they were moved to a more specific assay against the intracellular and replicative form of T. cruzi, i.e, amastigotes. These molecules were not as active as BZ (IC50 = 0.57 µM) against this parasite form; however, all of them showed remarkable IC50 values lower than 7 µM. Special mention deserve compounds 12 and 17, whose SIAMA were > 246.15 and > 188.23, respectively. The results compiled in the present work, point to a positive impact over the trypanocidal activity of the electron withdrawing substituents introduced at position 2 of the N-2 benzyl moiety of these compounds, especially fluorine, i.e., derivatives 12 and 17. These outcomes, supported by the in silico prediction of good oral bioavailability and suitable risk profile, reinforce the 5-nitroindazole scaffold as an adequate template for preparing potential antichagasic agents.

Thio- and selenosemicarbazones as antiprotozoal agents against Trypanosoma cruzi and Trichomonas vaginalis.

Herein, we report the preparation of a panel of Schiff bases analogues as antiprotozoal agents by modification of the stereoelectronic effects of the substituents on N-1 and N-4 and the nature of the chalcogen atom (S, Se). These compounds were evaluated towards Trypanosoma cruzi and Trichomonas vaginalis. Thiosemicarbazide 31 showed the best trypanocidal profile (epimastigotes), similar to benznidazole (BZ): IC50 (31)=28.72 µM (CL-B5 strain) and 33.65 µM (Y strain), IC50 (BZ)=25.31 µM (CL-B5) and 22.73 µM (Y); it lacked toxicity over mammalian cells (CC50 > 256 µM). Thiosemicarbazones 49, 51 and 63 showed remarkable trichomonacidal effects (IC50 =16.39, 14.84 and 14.89 µM) and no unspecific cytotoxicity towards Vero cells (CC50 ≥ 275 µM). Selenoisosters 74 and 75 presented a slightly enhanced activity (IC50=11.10 and 11.02 µM, respectively). Hydrogenosome membrane potential and structural changes were analysed to get more insight into the trichomonacidal mechanism.

Promising hit compounds against resistant trichomoniasis: Synthesis and antiparasitic activity of 3-(ω-aminoalkoxy)-1-benzyl-5-nitroindazoles.

A series of 11 3-(ω-aminoalkoxy)-1-benzyl-5-nitroindazoles (2-12) has been prepared starting from 1-benzyl-5-nitroindazol-3-ol 13, and evaluated against sensitive and resistant isolates of the sexually transmitted protozoan Trichomonas vaginalis. Compounds 2, 3, 6, 9, 10 and 11 showed trichomonacidal profiles with IC50 < 20 µM against the metronidazole-sensitive isolate. Moreover, all these compounds submitted to cytotoxicity assays against mammalian cells exhibited low non-specific cytotoxic effects, except compounds 3 and 9 which displayed moderate cytotoxicity (CC50 = 74.7 and 59.1 µM, respectively). Those compounds with trichomonacidal effect were also evaluated against a metronidazole-resistant culture. Special mention deserve compounds 6 and 10, which displayed better IC50 values (1.3 and 0.5 µM respectively) than that of the reference drug (IC50 MTZ = 3.0 µM). The high activity of these compounds against the resistant isolate reinforces the absence of cross-resistance with the reference drug. The remarkable trichomonacidal results against resistant T. vaginalis isolates suggest the interest of 3-(ω-aminoalkoxy)-1-benzyl-5-nitroindazoles to be considered as good prototypes to continue in the development of new drugs with enhanced trichomonacidal activity, aiming to increase the non-existent drugs to face clinical resistance efficiently for those patients in whom therapy with 5-nitroimidazoles is contraindicated.

Activity profile of two 5-nitroindazole derivatives over the moderately drug-resistant Trypanosoma cruzi Y strain (DTU TcII): in vitro and in vivo studies.

In previous studies, we have identified several families of 5-nitroindazole derivatives as promising antichagasic prototypes. Among them, 1-(2-aminoethyl)-2-benzyl-5-nitro-1,2-dihydro-3H-indazol-3-one, (hydrochloride) and 1-(2-acetoxyethyl)-2-benzyl-5-nitro-1,2-dihydro-3H-indazol-3-one (compounds 16 and 24, respectively) have recently shown outstanding activity in vitro over the drug-sensitive Trypanosoma cruzi CL strain (DTU TcVI). Here, we explored the activity of these derivatives against the moderately drug-resistant Y strain (DTU TcII), in vitro and in vivo. The outcomes confirmed their activity over replicative forms, showing IC50 values of 0.49 (16) and 5.75 µm (24) towards epimastigotes, 0.41 (16) and 1.17 µm (24) against intracellular amastigotes. These results, supported by the lack of toxicity on cardiac cells, led to better selectivities than benznidazole (BZ). Otherwise, they were not as active as BZ in vitro against the non-replicative form of the parasite, i.e. bloodstream trypomastigotes. In vivo, acute toxicity assays revealed the absence of toxic events when administered to mice. Moreover, different therapeutic schemes pointed to their capability for decreasing the parasitaemia of T. cruzi Y acute infected mice, reaching up to 60% of reduction at the peak day as monotherapy (16), 79.24 and 91.11% when 16 and 24 were co-administered with BZ. These combined therapies had also a positive impact over the mortality, yielding survivals of 83.33 and 66.67%, respectively, while untreated animals reached a cumulative mortality of 100%. These findings confirm the 5-nitroindazole scaffold as a putative prototype for developing novel drugs potentially applicable to the treatment of Chagas disease and introduce their suitability to act in combination with the reference drug.

The natural matching of harmonic responses in the pulmonary circulation.

KEY POINTS: The right ventricle of the mammal heart is highly sensitive to the afterload imposed by a combination of the pulmonary circulation and the retrograde contribution of the left heart. Right ventricular afterload can be analysed in terms of pulmonary artery input impedance, which we were able to decompose as the result of the harmonic frequency responses of the pulmonary vessels and the left heart attached in series. Using spectral methods, we found a natural matching between the pulmonary vasculature and the left chambers of the heart. This coupling implies that the upstream transmission of the left heart frequency-response has favourable effects on the pulmonary tree. This physiological mechanism protects the right ventricle against acute changes in preload, and its impairment may be a relevant contribution to right ventricle dysfunction in pulmonary hypertension. ABSTRACT: The right ventricle (RV) of the mammal heart is highly sensitive to the afterload imposed by the pulmonary circulation, and the left heart (LH) retrogradely contributes significantly to this vascular load. Transmission-line theory anticipates that the degree of matching between the frequency responses of the pulmonary vasculature and the LH should modulate the global right haemodynamic burden. We measured simultaneous high-fidelity flow (pulmonary artery) and pressure (pulmonary artery and left atrium) in 18 healthy minipigs under acute haemodynamic interventions. From these data, we decomposed the impedance spectra of the total right-circulation system into the impedance of the pulmonary vessels and the harmonic response of the LH. For frequencies above the first harmonic, total impedance was below the pulmonary impedance during all phases (P < 0.001; pooled phases), demonstrating a favourable effect of the LH harmonic response on RV pulsatile load: the LH harmonic response was responsible for a 20% reduction of pulse pulmonary artery pressure (P < 0.001 vs. a theoretical purely-resistive response) and a 15% increase of pulmonary compliance (P = 0.009). This effect on compliance was highest during acute volume overload. In the normal right circulation, the longitudinal impedance of the pulmonary vasculature is matched to the harmonic response of the LH in a way that efficiently reduces the pulmonary pulsatile vascular load. This source of interaction between the right and left circulations of mammals protects the RV against excessive afterload during acute volume transients and its disruption may be an important contributor to pulmonary hypertension.

Experimental models in Chagas disease: a review of the methodologies applied for screening compounds against Trypanosoma cruzi.

One of the main problems of Chagas disease (CD), the parasitic infection caused by Trypanosoma cruzi, is the lack of a completely satisfactory treatment, which is currently based on two old nitroheterocyclic drugs (i.e., nifurtimox and benznidazole) that show important limitations for treating patients. In this context, many laboratories look for alternative therapies potentially applicable to the treatment, and therefore, research in CD chemotherapy works in the design of experimental protocols for detecting molecules with activity against T. cruzi. Phenotypic assays are considered the most valuable strategy for screening these antiparasitic compounds. Among them, in vitro experiments are the first step to test potential anti-T. cruzi drugs directly on the different parasite forms (i.e., epimastigotes, trypomastigotes, and amastigotes) and to detect cytotoxicity. Once the putative trypanocidal drug has been identified in vitro, it must be moved to in vivo models of T. cruzi infection, to explore (i) acute toxicity, (ii) efficacy during the acute infection, and (iii) efficacy in the chronic disease. Moreover, in silico approaches for predicting activity have emerged as a supporting tool for drug screening procedures. Accordingly, this work reviews those in vitro, in vivo, and in silico methods that have been routinely applied during the last decades, aiming to discover trypanocidal compounds that contribute to developing more effective CD treatments.

Antichagasic, Leishmanicidal, and Trichomonacidal Activity of 2-Benzyl-5-nitroindazole-Derived Amines.

Three different series of new 5-nitroindazole derivatives-1-(ω-aminoalkyl)-2-benzylindazolin-3-ones (series A; ten compounds), 3-(ω-aminoalkoxy)-2-benzylindazoles (series B; four compounds) and 3-alkylamino-2-benzylindazoles (series C; five compounds)-have been synthesized and evaluated against the protozoan parasites Trypanosoma cruzi, Leishmania amazonensis, and Trichomonas vaginalis: etiological agents of Chagas disease, cutaneous leishmaniasis, and trichomoniasis, respectively. Many indazoles of series A, B, and C were efficient against T. cruzi. Some compounds in series A, after successfully passing the preliminary screening for epimastigotes, exhibited activity values against amastigotes of several T. cruzi strains that were better than or similar to those shown by the reference drug benznidazole and displayed low nonspecific toxicity against mammalian cells. On the other hand, preliminary studies against promastigotes of L. amazonensis showed high leishmanicidal activity for some derivatives of series A and C. With regard to activity against T. vaginalis, some indazoles of series B and C were rather efficient against trophozoites of a metronidazole-sensitive isolate and showed low nonspecific toxicities toward Vero cell cultures. Additionally, some of these compounds displayed similar activity against metronidazole-sensitive and resistant isolates, showing the absence of cross-resistance between these derivatives and the reference drug.

Drug repositioning for novel antitrichomonas from known antiprotozoan drugs using hierarchical screening.

AIM: Metronidazole is the most widely used drug in trichomoniasis therapy. However, the emergence of metronidazole-resistant Trichomonas vaginalis isolates calls for the search for new drugs to counter the pathogenicity of these parasites. RESULTS: Classification models for predicting the antitrichomonas activity of molecules were built. These models were employed to screen antiprotozoal drugs, from which 20 were classified as active. The in vitro experiments showed moderate to high activity for 19 of the molecules at 10 µg/ml, while 3 compounds yielded higher activity than the reference at 1 µg/ml. The 11 most active chemicals were evaluated in vivo using Naval Medical Research Institute (NMRI) mice. CONCLUSION: Benznidazole showed similar results as metronidazole, and can thus be considered as a potential candidate in antitrichomonas therapy.

Novel Imidazo[4,5-c][1,2,6]thiadiazine 2,2-dioxides as antiproliferative trypanosoma cruzi drugs: Computational screening from neural network, synthesis and in vivo biological properties.

A new family of imidazo[4,5-c][1,2,6]thiadiazine 2,2-dioxide with antiproliferative Trypanosoma cruzi properties was identified from a neural network model published by our group. The synthesis and evaluation of this new class of trypanocidal agents are described. These compounds inhibit the growth of Trypanosoma cruzi, comparable with benznidazole or nifurtimox. In vitro assays were performed to study their effects on the growth of the epimastigote form of the Tulahuen 2 strain, as well as the epimastigote and amastigote forms of CL clone B5 of Trypanosoma cruzi. To verify selectivity towards parasite cells, the non-specific cytotoxicity of the most relevant compounds was studied in mammalian cells, i.e. J774 murine macrophages and NCTC clone 929 fibroblasts. Furthermore, these compounds were assayed regarding the inhibition of cruzipain. In vivo studies revealed that one of the compounds, 19, showed interesting trypanocidal activity, and could be a very promising candidate for the treatment of Chagas disease.

Trichomonas vaginalis: la versatilidad de un parásito tenaz / The versatility of a tenacious parasite

La tricomonosis urogenital humana, causada por el parásito Trichomonas vaginalis, es una de las infecciones de transmisión sexual (I.T.S.) de mayor prevalencia en el mundo, con un total de 276 millones de casos cada año, según la OMS. Algunos autores la han calificado como una enfermedad desatendida u olvidada ligada a la pobreza, a pesar de que más del 50% de las I.T.S. curables se deben a este agente etiológico. La tricomonosis cursa con un rango amplio de manifestaciones clínicas, que van desde casos asintomáticos hasta cuadros más graves e invasivos de los conductos genitourinarios. Se ha relacionado la infección con el riesgo de adquisición y transmisión del VIH y de lesiones preneoplásicas de cérvix y próstata. Este protozoo parásito presenta una gran variabilidad intraespecífica en su comportamiento patogénico, probablemente por el tamaño y complejidad de su genoma, con más de 60.000 genes codificantes. Es capaz de sobrevivir y colonizar un nicho complejo sometido a constantes fluctuaciones, el aparato genitourinario, pasando desapercibido en muchos casos. El tamaño y complejidad de su genoma convierten a T. vaginalis en un parásito de gran interés científico para el estudio de los mecanismos de patogenia y evasión de la respuesta inmune (AU)

Trichomonosis is one of the most prevalent nonviral sexually transmitted infection (S.T.I.) worldwide, with an estimated 276 million cases per year according to WHO overview. Little attention is paid to this disease, although more than 50% of S.T.I. curable are caused by this protozoon. Clinically, Trichomonas vaginalis infection can produce a wide range of pathological manifestations, from asymptomatic presentation to severe inflammatory and invasive lesions in the genitourinary tract of both men and women. The possible role displayed by T. vaginalis as a viral vector might also explain its role as a risk factor in the development of cervical and prostate neoplasia. In addition, trichomonosis is strongly associated with transmission and acquisition of other bacterial and viral pathogens like HIV. T. vaginalis is a very complex organism and has developed diverse mechanisms for the colonization of the genitourinary tract probably due to its extensive genome. This parasite must survive in a hostile environment exposed to continue fluctuations. Surprisingly, T. vaginalis possesses one of the largest and most repetitive genomes, with a core set of 60,000 protein-coding genes. According to all these features, T. vaginalis could be considered an excellent model of parasite to be studied in order to better understand the dynamics and immune evasion mechanisms of such versatile parasite (AU)

New Imidazole-Based Compounds Active Against Trypanosoma cruzi.

BACKGROUND: Current drugs available for the treatment of Chagas disease are fraught with several challenges including severe toxicity and limited efficacy. These factors coupled with the absence of effective drugs for treating the chronic stage of the disease have rendered the development of new drugs against Chagas disease a priority. OBJECTIVE: This study screened several imidazole-based compounds for anti-Trypanosoma potential. METHOD: Using an in vitro experimental infection model, several imidazole-based compounds were screened for anti-proliferative effect on Trypanosoma cruzi epimastigotes. Additionally, all test compounds were evaluated for unspecific cytotoxicity on L929 murine fibroblasts. Benznidazole (BZN) served as reference drug. RESULTS: All test compounds demonstrated interesting trypanocidal potential with IC50 values in the µM range (1< 1C50 <8 µM). The activities of the test compounds compared favorably with BZN, which had an IC50 value ca. 30 µM. Conversely, most of the test compounds were highly cytotoxic, resulting in selectivity lower than that of BZN (SI > 9.42). CONCLUSION: We provide evidence which implicate the imidazole-based compounds as potential prototypes for the development of anti-parasitic agents. Findings have far-reaching relevance to drug discovery efforts for trypanosomiasis.

Clinical assessment of intraventricular blood transport in patients undergoing cardiac resynchronization therapy.

In the healthy heart, left ventricular (LV) filling generates different flow patterns which have been proposed to optimize blood transport by coupling diastole and systole. This work presents a novel image-based method to assess how different flow patterns influence LV blood transport in patients undergoing cardiac resynchronization therapy (CRT). Our approach is based on solving the advection equation for a passive scalar field from time-resolved blood velocity fields. Imposing time-varying inflow boundary conditions for the scalar field provides a straightforward method to distinctly track the transport of blood entering the LV in the different filling waves of a given cardiac cycle, as well as the transport barriers which couple filling and ejection. We applied this method to analyze flow transport in a group of patients with implanted CRT devices and a group of healthy volunteers. Velocity fields were obtained using echocardiographic color Doppler velocimetry, which provides two-dimensional time-resolved flow maps in the apical long axis three-chamber view of the LV. In the patients under CRT, the device programming was varied to analyze flow transport under different values of the atrioventricular conduction delay, and to model tachycardia (100 bpm). Using this method, we show how CRT influences the transit of blood inside the left ventricle, contributes to conserving kinetic energy, and favors the generation of hemodynamic forces that accelerate blood in the direction of the LV outflow tract. These novel aspects of ventricular function are clinically accessible by quantitative analysis of color-Doppler echocardiograms.

The Functional Significance of Paradoxical Low-Gradient Aortic Valve Stenosis: Hemodynamic Findings During Cardiopulmonary Exercise Testing.

OBJECTIVES: The goal of this study was to determine the functional impact of paradoxical low-gradient aortic stenosis (PLGAS) and clarify whether the relevance of the valvular obstruction is related to baseline flow. BACKGROUND: Establishing the significance of PLGAS is particularly challenging. METHODS: Twenty symptomatic patients (77 ± 6 years of age; 17 female subjects) with PLGAS (mean gradient 28 ± 6 mm Hg; aortic valve area 0.8 ± 0.1 cm2; ejection fraction 66 ± 7%) underwent cardiopulmonary exercise testing combined with right-heart catheterization and Doppler echocardiographic measurements. RESULTS: Aortic valve area increased by 84 ± 23% (p < 0.001) and, in 70% of subjects, it reached values >1.0 cm2 at peak exercise. Stroke volume index and blood pressure increased by 83 ± 56% and 26 ± 16%, respectively (both p < 0.0001). Peak oxygen consumption inversely correlated with the rate of increase in pulmonary capillary wedge pressure (PCWP) (PCWP slope: R = -0.61; p = 0.004). In turn, the PCWP slope was determined by changes in the valvular and vascular load but not by the rest of the indices of aortic stenosis. The functional impact of PLGAS was also not related to baseline flow. Agreement between Doppler echocardiography and the Fick technique was good up to intermediate workload. CONCLUSIONS: In symptomatic patients with PLGAS, the capacity to dynamically reduce vascular and valvular loads determines the effect of exercise on PCWP, which, in turn, conditions the functional status. A critically fixed valvular obstruction may not be the main mechanism of functional impairment in a large proportion of patients with PLGAS. Exercise echocardiography is suitable to study the dynamics of PLGAS.

Biological approaches to characterize the mode of action of two 5-nitroindazolinone prototypes on Trypanosoma cruzi bloodstream trypomastigotes.

The phenotypic activity of two 5-nitroindazolinones, i.e. 2-benzyl-1-propyl (22) and 2-benzyl-1-butyl (24) derivatives, previously proposed as anti-Trypanosoma cruzi prototypes, was presently assayed on bloodstream trypomastigotes (BT) of the moderately drug-resistant Y strain. Further exploration of putative targets and cellular mechanisms involved in their activity was also carried out. Therefore, transmission electron microscopy, high-resolution respirometry and flow cytometry procedures were performed on BT treated for up to 24 h with the respective EC50 value of each derivative. Results demonstrated that although 22 and 24 were not as active as benznidazole in this in vitro assay on BT, both compounds triggered important damages in T. cruzi that lead to the parasite death. Ultrastructural alterations included shedding events, detachment of plasma membrane and nuclear envelope, loss of mitochondrial integrity, besides the occurrence of a large number of intracellular vesicles and profiles of endoplasmic reticulum surrounding cytoplasmic organelles such as mitochondrion. Moreover, both derivatives affected mitochondrion leading to this organelle dysfunction, as reflected by the inhibition in oxygen consumption and the loss of mitochondrial membrane potential. Altogether, the findings exposed in the present study propose autophagic processes and mitochondrial machinery as part of the mode of action of both 5-nitroindazolinones 22 and 24 on T. cruzi trypomastigotes.

Antichagasic and trichomonacidal activity of 1-substituted 2-benzyl-5-nitroindazolin-3-ones and 3-alkoxy-2-benzyl-5-nitro-2H-indazoles.

Two series of new 5-nitroindazole derivatives, 1-substituted 2-benzylindazolin-3-ones (6-29, series A) and 3-alkoxy-2-benzyl-2H-indazoles (30-37, series B), containing differently functionalized chains at position 1 and 3, respectively, have been synthesized starting from 2-benzyl-5-nitroindazolin-3-one 5, and evaluated against the protozoan parasites Trypanosoma cruzi and Trichomonas vaginalis, etiological agents of Chagas disease and trichomonosis, respectively. Many indazolinones of series A were efficient against different morphological forms of T. cruzi CL Brener strain (compounds 6, 7, 9, 10 and 19-21: IC50 = 1.58-4.19 µM for epimastigotes; compounds 6, 19-21 and 24: IC50 = 0.22-0.54 µM for amastigotes) being as potent as the reference drug benznidazole. SAR analysis suggests that electron-donating groups at position 1 of indazolinone ring are associated with an improved antichagasic activity. Moreover, compounds of series A displayed low unspecific toxicities against an in vitro model of mammalian cells (fibroblasts), which were reflected in high values of the selectivity indexes (SI). Compound 20 was also very efficient against amastigotes from Tulahuen and Y strains of T. cruzi (IC50 = 0.81 and 0.60 µM, respectively), showing low toxicity towards cardiac cells (LC50 > 100 µM). In what concerns compounds of series B, some of them displayed moderate activity against trophozoites of a metronidazole-sensitive isolate of T. vaginalis (35 and 36: IC50 = 9.82 and 7.25 µM, respectively), with low unspecific toxicity towards Vero cells. Compound 36 was also active against a metronidazole-resistant isolate (IC50 = 9.11 µM) and can thus be considered a good prototype for the development of drugs directed to T. vaginalis resistant to 5-nitroimidazoles.

In vitro trichomonacidal activity and preliminary in silico chemometric studies of 5-nitroindazolin-3-one and 3-alkoxy-5-nitroindazole derivatives.

A selection of 1,2-disubstituted 5-nitroindazolin-3-ones (1-19) and 3-alkoxy-5-nitroindazoles substituted at positions 1 (20-24) or 2 (25-39) from our in-house compound library were screened in vitro against the most common curable sexually transmitted pathogen, Trichomonas vaginalis. A total of 41% of the studied molecules (16/39) achieved a significant activity of more than 85% growth inhibition at the highest concentration assayed (100 µg mL(-1)). Among these compounds, 3-alkoxy-5-nitroindazole derivatives 23, 24, 25 and 27 inhibited parasite growth by more than 50% at 10 µg mL(-1). In addition, the first two compounds (23, 24) still showed remarkable activity at the lowest dose tested (1 µg mL(-1)), inhibiting parasite growth by nearly 40%. Their specific activity towards the parasite was corroborated by the determination of their non-specific cytotoxicity against mammalian cells. The four mentioned compounds exhibited non-cytotoxic profiles at all of the concentrations assayed, showing a fair antiparasitic selectivity index (SI > 7·5). In silico studies were performed to predict pharmacokinetic properties, toxicity and drug-score using Molinspiration and OSIRIS computational tools. The current in vitro results supported by the virtual screening suggest 2-substituted and, especially, 1-substituted 3-alkoxy-5-nitroindazoles as promising starting scaffolds for further development of novel chemical compounds with the main aim of promoting highly selective trichomonacidal lead-like drugs with adequate pharmacokinetic and toxicological profiles.