Trypanocidal structure-activity relationship for cis- and trans-methylpluviatolide

The trypanocidal activity of racemic mixtures of cis- and trans-methylpluviatolides was evaluated in vitro against trypomastigote forms of two strains of Trypanosoma cruzi, and in the enzymatic assay of T. cruzi gGAPDH. The cytotoxicity of the compounds was assessed by the MTT method using LLC-MK2 cells. The effect of the compounds on peroxide and NO production were also investigated. The mixture of the trans stereoisomers displayed trypanocidal activity (IC50 approximately 89.3 microM). Therefore, it was separated by chiral HPLC, furnishing the (+) and (-)-enantiomers. Only the (-)-enantiomer was active against the parasite (IC50 approximately 18.7 microM). Despite being inactive, the (+)-enantiomer acted as an antagonistic competitor. Trans-methylpluviatolide displayed low toxicity for LLC-MK2 cells, with an IC50 of 6.53 mM. Furthermore, methylpluviatolide neither inhibited gGAPDH activity nor hindered peroxide and NO production at the evaluated concentrations.     

In vitro and in vivo trypanocidal activity of the ethyl esters of N-allyl and N-propyl oxamates using different Trypanosoma cruzi strains

The trypanocidal activity of N-allyl (NAOx) and N-propyl (NPOx) oxamates and that of the ethyl esters ofN-allyl (Et-NAOx) and N-propyl (Et-NPOx) oxamates were tested on cultured epimastigotes (in vitro) and murine trypanosomiasis (in vivo) using five different T. cruzi strains. NAOx and NPOx did not penetrate intact epimastigotes and therefore we were not able to detect any trypanocidal effect with these oxamates. Whereas the ethyl esters (Et-NAOx and Et-NPOx), acting as prodrugs, exhibited in vitro and in vivo trypanocidal activity on the five tested T. cruzi strains. On the contrary, when Nifurtimox and Benznidazole used as reference drugs were tested, we found that only three of the five tested T cruzi strains were affected, whereas the other two strains, Miguz and Compostela, were resistant to the in vitro and in vivo trypanocidal activity of these compounds.     

Trypanocidal agents with low cytotoxicity to mammalian cell line: a comparison of the theoretical and biological features of lapachone derivatives

Starting from alpha- and beta-lapachones, in this work we compared the biological and theoretical profile of several oxyran derivatives of lapachone as potential trypanocidal agents. Our biological results showed that the oxyrans tested act as trypanocidal agents against Trypanosoma cruzi with minimal cytotoxicity in the VERO cell line compared to naphthoquinones. The oxyran derivative of alpha-lapachone (7a) showed to be one of the most potent compounds. In our molecular modeling study, we analyzed the C-ring moiety and the redox center of beta-lapachone molecule as the moieties responsible for the trypanocidal and cytotoxic effects on mammalian cell line. The computational methods used to delineate the structural requirements for the trypanocidal profile pointed out that the transposition of the C-ring moiety of beta-lapachone, combined with its oxyran ring, introduced important molecular requirements for trypanocidal activity in the HOMO energy, HOMO orbital coefficient, LUMO density, electrostatic potential map, dipole moment vector, and calculated logP (clogP) parameter. This study could lead to the development of new antichagasic medicines based on alpha-lapachone analogs.     

2-Phenylaminonaphthoquinones and related compounds: Synthesis,trypanocidal and cytotoxic activities

A series of new 2-aminonaphthoquinones and related compounds were synthesized and evaluated in vitro as trypanocidal and cytotoxic agents. Some tested compounds inhibited epimastigote growth and trypomastigote viability. Several compounds showed similar or higher activity and selectivity as compared with current trypanocidal drug, nifurtimox. Compound 4l exhibit higher selectivity than nifurtimox against Trypanosoma cruzi in comparison with Vero cells. Some of the synthesized quinones were tested against cancer cells and normal fibroblasts, showing that certain chemical modifications on the naphthoquinone moiety induce and excellent increase the selectivity index of the cytotoxicity (4g and 10). The results presented here show that the anti-T. cruzi activity of 2-aminonaphthoquinones derivatives can be improved by the replacement of the benzene ring by a pyridine moiety. Interestingly, the presence of a chlorine atom at C-3 and a highly lipophilic alkyl group or aromatic ring are newly observed elements that should lead to the discovery of more selective cytotoxic and trypanocidal compounds.     

New trypanocidal hybrid compounds from the association of hydrazone moieties and benzofuroxan heterocycle

Hybrid compounds containing hydrazones and benzofuroxan pharmacophores were designed as potential Trypanosoma cruzi-enzyme inhibitors. The majority of the designed compounds was successfully synthesized and biologically evaluated displaying remarkable in vitro activity against different strains of T. cruzi. Unspecific cytotoxicity was evaluated using mouse macrophages, displaying isothiosemicarbazone 10 and thiosemicarbazone 12 selectivity indexes (macrophage/parasite) of 21 and 27, respectively. In addition, the mode of anti-trypanosomal action of the derivatives was investigated. Some of these derivatives were moderate inhibitors of cysteinyl active site enzymes of T. cruzi, cruzipain and trypanothione reductase. ESR experiments using T. cruzi microsomal fraction suggest that the main mechanism of action of the trypanocidal effects is the production of oxidative stress into the parasite.     

Synthesis of dihydronaphthofurandiones and dihydrofuroquinolinediones with trypanocidal activity and analysis of their stereoelectronic properties

The synthesis of dihydronaphthofurandione and dihydrofuroquinolinedione derivatives 4-11 was performed through Diels-Alder reactions of dihydrobenzofurandione 1 with several carbodienes and acrolein N,N-dimethylhydrazone. Then, the use of 5-bromobenzofurandione 2 toward 1,3-pentadiene and the 1-azadiene afforded quinones 6 and 11 with a total regioselectivity. All the prepared quinones were tested for trypanocidal activity in vitro against Trypanosoma epimastigotes, Tulahuen strain. Among the tested compounds, the furoquinolinediones 10 and 11 have shown potent trypanocidal activities but, only the 1,5-regioisomer (11) was found active as a redox cycling agent. Calculation of their stereoelectronic properties by the density-functional theory method provided a new insight for the trypanocidal activity of these heterocyclic quinones.     

Inhibition of Trypanosoma cruzi alpha-hydroxyacid dehydrogenase-isozyme II by N-isopropyl oxamate and its effect on intact epimastigotes

The effect of N-isopropyl oxamate on the activity of alpha-hydroxyacid dehydrogenase-isozyme II (HADH-isozyme II) from Trypanosoma cruzi was investigated. The kinetic studies showed that this substance was a competitive inhibitor of this isozyme. The attachment of the nonpolar isopropylic branched chain to the nitrogen of oxamate increased 12-fold the affinity of N-isopropyl oxamate for the active site of T. cruzi HADH-isozyme II. N-isopropyl oxamate was a selective inhibitor of HADH-isozyme II, since other T. cruzi dehydrogenases were not inhibited by this substance. Since HADH-isozyme II participates in the energy metabolism of T. cruzi, a trypanocidal effect can be expected with inhibitors of this isozyme. However, although it was not possible to detect any trypanocidal activity with N-isopropyl oxamate when the ethyl ester was tested as a possible trypanocidal prodrug, the expected trypanocidal effect was obtained, comparable to that obtained with nifurtimox and benznidazole.     

New oxirane derivatives of 1,4-naphthoquinones and their evaluation against T. cruzi epimastigote forms

New oxirane derivatives were synthesized using six naphthoquinones as the starting materials. Our biological results showed that these oxiranes acted as trypanocidal agents against Trypanosoma cruzi with minimal cytotoxicity in the VERO cell line compared to naphthoquinones. In particular, oxirane derivative 14 showed low cytotoxicity in a mammalian cell line and exhibited better activity against epimastigote forms of T.cruzi than the current drug used to treat Chagas disease, benznidazole.     

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.     

Trypanosoma cruzi: inhibition of alpha-hydroxyacid dehydrogenase isozyme II by N-allyl and N-propyl oxamates and their effects on intact epimastigotes

N-allyl (NAOx) and N-propyl (NPOx) oxamates were designed as inhibitors of alpha-hydroxyacid dehydrogenase (HADH) isozyme II from Trypanosoma cruzi. The kinetic studies showed that NAOx and NPOx were competitive inhibitors of HADH-isozyme II (Ki = 72 microM, IC50 = 0.33 mM and 70 microM, IC50 = 0.32 mM, respectively). The attachment of the allylic and propylic chains to nitrogen of the competitive inhibitor oxamate (Ki = 0.91 mM, IC50 = 4.25 mM), increased 12.6 and 13-folds respectively, the affinity for T. cruzi HADH-isozyme II. NAOx and NPOx were selective inhibitors of HADH-isozyme II, because other T. cruzi dehydrogenases were not inhibited by these substances. Since HADH-isozyme II participates in the energy metabolism of T. cruzi, a trypanocidal effect can be expected with these inhibitors. However, we were not able to detect any trypanocidal activity with these oxamates. When the corresponding ethyl esters of N-allyl (Et-NAOx) and N-propyl (Et-NPOx) oxamates were tested as a possible trypanocidal prodrugs, in comparison with nifurtimox and benznidazole, the expected trypanocidal effects were obtained.     

Taiwaniaquinoid and abietane quinone derivatives with trypanocidal activity against T. cruzi and Leishmania spp

The in vitro leishmanicidal (Leishmania infantum and Leishmania braziliensis) and trypanocidal (Trypanosoma cruzi) activities of different compounds were evaluated. These compounds, of vegetal origin but synthesised in our laboratory, included five taiwaniaquinoid derivatives (S-567; S-569; S-589; S-602 and A-246) and one abietane quinone (P-1). The in vitro activity of the compounds on extracellular and intracellular forms of the two Leishmania species and T. cruzi was assayed. Infectivity and cytotoxicity tests for the Leishmania species were conducted on J774.2 macrophage cells using Glucantime as the reference drug. From all the compounds assayed, the derivatives P-1>S-567 were more active and less toxic than Glucantime. Infection rates and amastigote means indicated that these two compounds were the most active in both Leishmania species. In the case of T. cruzi, the best derivatives were P-1 and S-567, at the same levels as for the Leishmania species. These compounds exhibited the most potent anti-proliferative activity against the extracellular vector form (the epimastigote), the extracellular host form (the trypomastigote), and the intracellular host form (the amastigote), with lower toxicity than that of the reference drug Benznidazole. Metabolite excretion studies showed that alterations mainly at the level of the mitochondria may explain observed metabolic changes in succinate and acetate production, perhaps due to the disturbance of enzymes involved in sugar metabolism within the mitochondrion. The in vivo studies for T. cruzi provided results consistent with those found in vitro. No signs of toxicity were detected in mice treated with the compounds tested, and the parasitic charge was slightly lower than in the control. The effects of these two compounds were also demonstrated with the change in the anti-T. cruzi antibody levels during the chronic stage.     

Trypanocidal action of eupomatenoid-5 is related to mitochondrion dysfunction and oxidative damage in Trypanosoma cruzi

Because of its severe side effects and variable efficacy, the current treatment for Chagas disease is unsatisfactory. Natural compounds are good alternative chemotherapeutic agents for the treatment of this infection. Recently, our group reported the antiproliferative activity and morphological alterations in epimastigotes and intracellular amastigotes of Trypanosoma cruzi treated with eupomatenoid-5, a neolignan isolated from leaves of Piper regnellii var. pallescens. Here, we demonstrate that eupomatenoid-5 exhibited activity against trypomastigotes, the infective form of T. cruzi (EC?? 40.5 μM), leading to ultrastructural alteration and lipoperoxidation in the cell membrane. Additionally, eupomatenoid-5 induced depolarization of the mitochondrial membrane, lipoperoxidation and increased G6PD activity in epimastigotes of T. cruzi. These findings support the possibility that different mechanisms may be targeted, according to the form of the parasite, and that the plasma membrane and mitochondria are the structures that are most affected in trypomastigotes and epimastigotes, respectively. Thus, the trypanocidal action of eupomatenoid-5 may be associated with mitochondrial dysfunction and oxidative damage, which can trigger destructive effects on biological molecules of T. cruzi, leading to parasite death.     

Diterpenoids from Azorella compacta (Umbelliferae) active on Trypanosoma cruzi

The anti-Trypanosoma cruzi activity of natural products isolated from Azorella compacta was evaluated, with particular emphasis on their effect against intracellular amastigotes. Five diterpenoids from A. compacta derived from mulinane and azorellane were isolated and identified. Only two products, named azorellanol (Y-2) and mulin-11,3-dien-20-oic acid (Y-5), showed trypanocidal activity against all stages of T. cruzi including intracellular amastigotes. At 10 M, these compounds displayed a strong lytic activity. It ranged from 88.4 0.6 to 99.0 1 % for all strains and stages evaluate, with an IC50 /18 h values of 20-84 M and 41-87 M, respectively. The development of intracellular amastigotes was also inhibited by nearly 60% at 25 M. The trypanocidal molecules Y-2 and Y-5 did show different degrees of cytotoxicity depending on the cell line tested, with an IC50 /24 h ranging from 33.2 to 161.2 M. We evaluated the effect of diterpenoids against intracellular T. cruzi forms by immunofluorescent identification of a specific membrane molecular marker (Ssp-4 antigen) of the T. cruzi amastigote forms. The accuracy and reproducibility of the measurements were found to be outstanding when examined by confocal microscopy.     

Synthesis and trypanocidal activity of 1,4-bis-(3,4,5-trimethoxy-phenyl)-1,4-butanediol and 1,4-bis-(3,4-dimethoxyphenyl)-1,4-butanediol

Chagas' disease is endemic in Central and South American countries. Specific chemotherapy with nifurtimox or benznidazole has been recommended for treatment of recent infection but they have limited efficacy. The natural products veraguensin (1) and grandisin (2) have shown potent in vitro activity against trypomastigote parasite (Y strain) with IC(50) 2.3 microM (1) and 3.7 microM (2). We report herein the synthesis and in vitro trypanocidal evaluation of symmetrical and unsymmetrical 1,4-diaryl-1,4-diol derivatives as potential trypanocidal analogs of natural compounds 1 and 2. Among the synthesized products, compounds 1,4-bis-(3,4,5-trimethoxyphenyl)-1,4-butanediol (6a) and 1,4-bis-(3,4-dimethoxyphenyl)-1,4-butanediol (6b) showed better activity against Trypanosoma cruzi trypomastigotes with IC(50) 100 and 105 microM (Y strain), respectively, and 110 microM (Bolivia strain) for both compounds. However, the most active compound of this series was 1,4-bis-(3,4-dimethoxyphenyl)butane-1,4-dione (7b) with IC(50) 10 and 200 microM against Y and Bolivia strains, respectively.     

Trypanocidal activity of Lychnophora staavioides Mart. (Vernonieae, Asteraceae)

In the continuing search for new compounds with trypanocidal activity for use in blood banks to prevent the transmission of Chagas' disease, a trypanocidal extract of Lychnophora staavioides Mart. (Vernonieae, Asteraceae) was fractionated using several chromatographic techniques and afforded the following flavonoids: tectochrysin, pinostrobin, pinobanksin, pinobanksin 3-acetate, pinocembrin, chrysin, galangin 3-methyl ether, quercetin 3-methyl ether, chrysoeriol and vicenin-2. The most active compound was quercetin 3-methyl ether, which showed no blood lysis activity and which represents a promising compound for use against T. cruzi in blood banks.     

Toxic effects of natural piperine and its derivatives on epimastigotes and amastigotes of Trypanosoma cruzi

We describe herein an evaluation of trypanocidal effects of the natural alkaloid piperine and twelve synthetic derivatives against epimastigote and amastigote forms of the protozoan parasite Trypanosoma cruzi, the causative agent of the incurable human disease, Chagas' disease. The results obtained point to piperine as a suitable template for the development of new drugs with trypanocidal activity.     

Potent inhibitor scaffold against Trypanosoma cruzi trans-sialidase

The protozoan Trypanosoma cruzi, the causative agent of Chagas’ disease, can infect the heart, causing cardiac arrest frequently followed by death. To treat this disease, a potential molecular drug target is T. cruzi trans-sialidase (TcTS). However, inhibitors found to date are not strong enough to serve as a lead scaffold; most inhibitors reported thus far are derivatives of the substrate sialic acid or a transition state analogue known as 2,3-dehydro-3-deoxy-N-acetylneuraminic acid (DANA) with an IC₅₀ value of more than hundreds of micromolar. Since natural products are highly stereodiversified and often provide highly specific biological activity, we screened a natural product library for inhibitors of TcTS and identified promising flavonoid and anthraquinone derivatives. A structure–activity relationship (SAR) analysis of the flavonoids revealed that apigenin had the minimal and sufficient structure for inhibition. Intriguingly, the compound has been reported to possess trypanocidal activity. An SAR analysis of anthraquinones showed that 6-chloro-9,10-dihydro-4,5,7-trihydroxy-9,10-dioxo-2-anthracenecarboxylic acid had the strongest inhibitory activity ever found against TcTS. Moreover, its inhibitory activity appeared to be specific to TcTS. These compounds may serve as potent lead chemotherapeutic scaffolds against Chagas’ disease.     

Antitrypanosomal and antioxidant properties of 4-hydroxycoumarins derivatives

In the present communication we prepared a series of six 4-hydroxycoumarin derivatives, isosters of quercetin, recognized as an antioxidant natural compound, with the aim of evaluating the antitrypanosomal activity against Trypanosoma cruzi, the parasite responsible for Chagas disease, and the antioxidant properties. We have used the 4-hydroxycoumarin moiety (compound 1) as the molecular template for the synthesis of compounds 2-7. These derivates have shown moderate trypanocidal activity. However they have been proved to be good antioxidants. In particular compound 7 is the most active antioxidant and it is, therefore, a potential candidate for a successful employment in conditions characterized by free radicals overproduction.     

Enzymatic inhibitory activity and trypanocidal effects of extracts and compounds from Siphoneugena densiflora O. Berg and Vitex polygama Cham

Hexanic, methanolic, and hydroalcoholic extracts, and 34 isolated compounds from Vitex polygama Cham. (Lamiaceae, formely Verbenaceae) and Siphoneugena densiflora O. Berg (Myrtaceae) were screened for their trypanocidal effects on bloodstream forms of Trypanosoma cruzi and T brucei, as well as for their enzymatic inhibitory activities on glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH) and trypanothione reductase (TR) enzymes from T cruzi and adeninephosphoribosyl transferase (APRT) enzyme from Leishmania tarentolae. In general, polar extracts displayed strong effects and some of the tested compounds have shown good results in comparison to positive controls of the bioassays.