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Review
J. Braz. Chem. Soc., Vol. 25, No. 10, 1780-1798, 2014.
Printed in Brazil - ©2014 Sociedade Brasileira de Química
0103 - 5053 $6.00+0.00
http://dx.doi.org/10.5935/0103-5053.20140180
*e-mail: solange@ioc.fiocruz.br
Anti-Trypanosoma cruzi Compounds: Our Contribution for the Evaluation and
Insights on the Mode of Action of Naphthoquinones and Derivatives
Eufrânio N. da Silva Júnior,a Guilherme A. M. Jardim,a Rubem F. S. Menna-Barretob
and Solange L. de Castro*,b
aLaboratório de Química Sintética e Heterocíclica, Departamento de Química, Instituto de Ciências
Exatas, Universidade Federal de Minas Gerais (UFMG), 31270-901 Belo Horizonte-MG, Brazil
bLaboratório de Biologia Celular, Instituto Oswaldo Cruz, Fiocruz,
Av. Brasil, 4365, Manguinhos, 21045-900 Rio de Janeiro-RJ, Brazil
A doença de Chagas causada pelo Trypanosoma cruzi afeta cerca de oito milhões de pessoas
em países em desenvolvimento, sendo classificada como uma doença tropical negligenciada pela
Organização Mundial da Saúde. A quimioterapia disponível para esta doença é baseada em dois
nitro-heterocíclicos, nifurtimox e benznidazol, ambos com graves efeitos colaterais e eficácia
variável, e assim novos medicamentos visando um tratamento mais eficiente são necessários
com urgência. Nos últimos 20 anos, temos desenvolvido em colaboração com grupos focados em
química medicinal, um programa de quimioterapia experimental da doença de Chagas, investigando
a eficácia, seletividade, toxicidade, alvos celulares e mecanismos de ação de diferentes classes de
compostos sobre T. cruzi. Neste artigo, apresentamos uma visão geral desses estudos, enfocando
protótipos naftoquinoidais e derivados, examinando a sua síntese, a atividade e mecanismo de
ação, o que foi realizado e o que precisa ser abordado, avaliando e discutindo possíveis melhorias.
Esta mini-revisão discute nosso esforço continuado visando a caracterização biológica e a síntese
de compostos naftoquinoidais, auxiliando no desenvolvimento de um novo arsenal de drogas
candidatas com eficácia contra o T. cruzi.
Chagas disease is caused by the parasite Trypanosoma cruzi and affects approximately
eight million individuals in the developing world; it is also classified as a neglected tropical
disease by the World Health Organization. The available therapy for this disease is based on two
nitroheterocycles, nifurtimox and benznidazole, both of which exhibit severe side effects and
variable efficacy; therefore, new drugs and better treatment schedules are urgently needed. For
the past 20 years, we have been collaborating with groups focused on medicinal chemistry to
produce experimental therapies for Chagas disease by investigating the efficacy, selectivity, toxicity,
cellular targets and mechanisms of action of different classes of compounds against T. cruzi. In
this report, we present an overview of these studies, focusing on naphthoquinonoid prototypes
and discuss their synthesis, activity and mechanisms of action. Furthermore, we summarise the
research that has been performed to date and suggest future research directions while assessing
and discussing potential improvements. This mini-review discusses our continued efforts toward
the biological characterisation and synthesis of naphthoquinoidal compounds, aiming to contribute
to the development of a new arsenal of candidate drugs that exhibit effective anti-T. cruzi activity
Keywords: naphthoquinones, β-lapachone, Trypanosoma cruzi, Chagas disease, chemotherapy
1. Introduction
Chagas disease (CD) is caused by the intracellular
obligatory parasite Trypanosoma cruzi and was first described
more than one hundred years ago, in 1909, by Carlos
Chagas.1 This disease has high morbidity and mortality
rates, affects approximately eight million individuals in the
developing world and displays a limited response to therapy;
it has also been classified as a neglected tropical disease by
the World Health Organization (WHO).2,3 Chagas disease
can be transmitted through the faeces of sucking Triatominae
insects, blood transfusions, organ transplantation, oral
Silva Júnior et al. 1781Vol. 25, No. 10, 2014
contamination, through laboratory accidents and congenital
routes. T. cruzi is a hemoflagellate protozoan (family
Trypanosomatidae, order Kinetoplastida)4 that exhibits a
complex life cycle involving distinct morphological stages
during its passage through vertebrate and invertebrate hosts.
Briefly, after ingestion of bloodstream trypomastigotes by
insect vectors, the parasites are converted to epimastigote
forms, which proliferate and subsequently differentiate
into metacyclic forms within the posterior intestine of the
triatomine. These infective parasite forms are released in the
faeces of the triatomine and can invade new vertebrate cells.
The parasites then undergo another round of differentiation
into intracellular amastigote forms, which proliferate and
subsequently transform back into trypomastigotes, the form
that disseminates the infection.
Although vector and transfusion transmissions have
sharply declined over the past 20 years due to the Southern
Cone countries policy, several challenges still need to be
overcome including those related to sustainable disease
control through the adoption of public policies in the
endemic areas.5,6 In addition, despite effective efforts to
control vector and blood transmission, Chagas disease still
presents many challenges including the following: (i) its
peculiar epidemiology is characterised by a variety of risk
factors (many potential vectors and reservoirs, different
forms of transmission and diverse parasite isolates present
in domiciliar, peridomiciliar and sylvatic environments);
and importantly, (ii) the lack of prophylactic therapies
and effective therapeutic treatments.7,8 Current major
concerns include disease transmission by the ingestion of
contaminated food or liquids and the disease’s emergence
in nonendemic areas such as North America and Europe,
a phenomenon which is likely due to the immigration of
infected individuals.9,10 This disease is also recognised as
an opportunistic infection in HIV-infected individuals.11
Outbreaks of acute Chagas disease associated with the
ingestion of contaminated food and drink have been
reported in South America,12,13 and are associated with a
high mortality rate mainly due to myocarditis.
Chagas disease is characterised by two clinical phases.
The acute phase appears shortly after infection, and in some
cases the individual may not even realise he/she is infected.
Symptoms range from flu-like symptoms to intense
myocarditis (in approximately 10% of infected people).
If left untreated, symptomatic chronic disease develops in
about one third of the individuals after a long latent period
(10-30 years) that is known as the indeterminate form. The
main clinical manifestations of Chagas disease include
digestive and/or cardiac alterations, although disorders
of the central and peripheral nervous system may also
occur.14,15 In the chronic digestive form of the disease, the
clinical manifestations are caused by dysperistalsis of the
oesophagus and colon, which are due to the destruction of
the myenteric plexus and leads to mega syndromes.16 The
chronic cardiac form of the disease is the most significant
clinical manifestation, and consequences include dilated
cardiomyopathy, congestive heart failure, arrhythmias,
cardioembolism and stroke.17 The pathogenesis of Chagas
disease is the result of a sustained inflammatory process
due to an anti-parasitic and/or anti-self-immune response,
which is associated with low-grade persistent parasite
presence.18-22 Growing evidence shows that parasite
persistence within the target organs associated with an
unregulated host immune response are involved in disease
progression and clinical outcomes.19,23 Control of T. cruzi
infection depends on both the innate and acquired immune
responses which are triggered during early infection and
are critical for host survival. These responses involve
macrophages, natural killer cells, T and B lymphocytes and
the production of pro-inflammatory cytokines.24
The available therapy for Chagas disease is based on
two nitroheterocyclic agents that were developed over five
decades ago (Figure 1).
Nifurtimox (Nif, 3-methyl-4-(5’-nitrofurfurylidene-
amine)tetrahydro-4H-1,4-tiazine-1,1-dioxide) is a
nitrofuran that was developed by Bayer in 1967 and
marketed as Lampit®. It acts by reducing the nitro group
to generate nitro-anions that subsequently react with
molecular oxygen to produce toxic superoxide and peroxide
radicals. Today, Nif is produced by Bayer HealthCare at
the Corporacion Bonima in El Salvador. Benznidazole (Bz,
N-benzyl-2-nitroimidazole acetamide) is a nitroimidazole
that was developed by Roche in 1972 and was formerly
marketed as Rochagan® or Radanil®; it is currently
produced by the Laboratório Farmacêutico do Estado
de Pernambuco, Brazil (www.pe.gov.br/orgaos/lafepe-
laboratorio-farmaceutico-de-pernambuco/). This drug
appears to act differently, as it produces metabolites that
react with macromolecules such as DNA, RNA, proteins,
and possibly lipids. In both cases, the antiparasitic activity
of the drug is intimately linked with their inherent toxicity.
Both drugs are effective against acute infections, but they
show poor activity during the late chronic phase.16 Due
to their severe side effects and limited efficacy against
Figure 1. Chemical structures of nifurtimox and benznidazole.
Anti-Trypanosoma cruzi Compounds J. Braz. Chem. Soc.
1782
different parasitic isolates,25 these drugs are hardly the
best treatment options to offer patients. One of the major
drawbacks of Nif is its high incidence of side effects,
which is observed in up to 40% of patients and includes
nausea, vomiting, abdominal pain, weight loss and severe
anorexia. Furthermore, adverse neurological effects such as
restlessness, paresthesia, twitching, insomnia and seizures
have also been observed.21 In comparison to Nif, Bz has the
advantage of a lower incidence of side effects; however, its
side effects include hypersensitivity (dermatitis, generalised
oedema, ganglionic infarction and joint and muscle pains),
bone marrow depletion and peripheral polyneuropathy.26
Because of the challenges regarding the efficacy vs. the
toxicity of both nitro-heterocyclic compounds, the current
recommendations for using either drug to treat Chagas
disease suggest that all acute cases, including reactivations
due to immunosuppression, recent chronic cases (including
children up to 12 years of age), and indeterminate or benign
chronic forms should be treated. In addition, cases should be
treated at the discretion of the attending physician. In contrast,
the contra-indications for specific treatment are pregnancy,
liver and kidney failure, neurological diseases unrelated
to CD, advanced CD with grade III or IV cardiopathy
(Pan American Health Organization, PAHO)/(WHO), or
other pathologies that may be worsened by treatment.26
Between 12 and 18% of patients who undergo treatment
have to suspend their therapy prematurely because of side
effects.27 Overall, the 2010 Latin American Guidelines for
Chagas cardiomyopathy indicate that unrestricted treatment
for patients with chronic Chagas disease should not be
regarded as standard therapy.28
Several new compounds are currently under preclinical
development, and different approaches have been used
to identify new drug leads including in vitro parasite
phenotype screens and target-based drug discovery.29
Although many attempts have been made to treat the
disease since its identification in 1912, only allopurinol
and some antifungals have been used in clinical trials
since the introduction of Nif and Bz.25,30 In 2009, the
Drugs for Neglected Diseases initiative (DNDi) and its
partners launched the Chagas disease Clinical Research
Platform (http://www.dndi.org/strenghtening-capacity/
chagas-platform/publications.html), which aims to promote
technical discussions, develop a critical mass of expertise,
strengthen institutional research capacities, and link
investigators through a collaborative network. As a result,
three phase II clinical trials began in 2011 to investigate
the potential uses of posaconazole (a structural analogue
of itraconazole) (SCH 56592; Schering-Plough Research
Institute, SPRI) and of a prodrug of ravuconazole (E1224;
Eisai) (Figure 2).
Both drugs are triazole derivatives that inhibit fungal
and protozoan cytochrome P-450-dependent enzyme
CYP51 (C14α-lanosterol demethylase) (TcCYP51).31-33
Two clinical studies were performed with posaconazole:
STOP-CHAGAS (in Argentina, Colombia, Mexico and
Venezuela, funded by Merck) with results expected by
2014 and CHAGASAZOL (in Spain at University Hospital
Vall d’Hebron Research Institute in Barcelona), which
was completed in March 2013 (results were posted at
http://clinicaltrials.gov/show/NCT01162967, accessed in
July, 2014). Another study investigated the use of E1224
(DNDi/Eisai Pharmaceuticals) and was developed in
Bolivia. It involved a total of 231 patients, and the drug
exhibited a good safety profile and was effective at clearing
the parasite; however, it had little to no sustained efficacy
one year after treatment. The key disadvantages of novel
azole derivatives (i.e., posaconazole) are their complexity
and manufacturing costs.31
Among the drugs identified in preclinical studies,
several of them have yielded valuable results. For example,
CYP51 inhibitors such as tipifarnib (an anti-cancer drug
that inhibits the human protein farnesyltransferase)32
and the fenarimol series show promise.33 In addition,
fexinidazole (a substituted 5-nitroimidazole that was
rediscovered by the DNDi and is currently in phase II/III
clinical study for the treatment of human African
trypanosomiasis),34 diamidine analogues35 and a series of
oxaboroles (prototype AN4169) are promising new drugs
for the treatment of T. cruzi infections.36 Other drug targets
under investigation include cysteine proteases because
T. cruzi contains a cathepsin L-like enzyme (cruzipain)
that is responsible for the majority of the proteolytic
activity that occurs in all developmental forms. The vinyl
Figure 2. Chemical structures of posaconazole and ravuconazole.
Silva Júnior et al. 1783Vol. 25, No. 10, 2014
sulfone K777 is an irreversible cruzipain inhibitor that has
shown efficacy in chronic rodent models and is also under
preclinical development.29 Some of the most promising
targets identified in T. cruzi include protein prenylation,
hypoxanthine-guanine phosphoribosyltransferase,
cysteine proteases,29,37 and topoisomerases.38 The utility
of 14-demethylase inhibitors,39,40 squalene synthase
inhibitors,41 farnesyl pyrophosphate synthase inhibitors,42
farnesyl transferase inhibitors,43,44 dihydrofolate reductase
inhibitors45 and natural products such as canthinones,
quinolines, lignans, and naphthoquinones are also being
explored.46-48 New and established pharmacophores based
on synthetic and natural product chemistry have been
identified through improved screening technologies and
have generated hits from libraries provided largely by the
pharmaceutical industry and other entities.
Another approach aimed at the treatment of Chagas
disease is the achievement of greater efficacy through the
use of combinations of existing drugs that display different
mechanisms of action. Combination therapy has been
proven to be more effective than monotherapies for several
infectious diseases and also minimises the risk of drug
resistance. Several studies in animal models have examined
the use of combinations of Bz and CYP51 inhibitors,49-52
the arylimidamide DB766,53 and allopurinol,54,55 and the
results were encouraging. Coura26 proposed the use of
combinations of [Nif + Bz], [Nif or Bz + allopurinol] and
[Nif or Bz + ketoconazole, fluconazole or itraconazole] in
specified treatment schemes that were adapted according
to the side effects observed.
Based on current knowledge of parasite and host
biological characteristics, a desired drug candidate for
Chagas disease would include the following attributes:
(i) high activity against the evolving forms of the parasite
present in the mammalian hosts and different reservoirs
of the parasite, (ii) efficacy against both acute and chronic
infections, (iii) oral administration of only a few doses,
(iv) low toxicity and an improved safety profile (including
children and women of reproductive age), (v) low cost
and high stability suitable for a long shelf life in tropical
temperatures, and (vi) high levels of tissue accumulation
and long terminal half-lives.55
Over the past 20 years, our group has been working
on experimental chemotherapy for Chagas disease in
collaboration with research groups focused on medicinal
chemistry. We have been investigating the efficacy,
selectivity, toxicity, cellular targets and mechanisms of
action of different classes of compounds on T. cruzi. In this
report, we present an overview of these studies, focusing
on the development of novel naphthoquinonoid prototypes
for the clinical treatment of Chagas disease. We also
describe their synthesis, activity and mechanisms of action.
Furthermore, we summarise the current state of research
in the field and suggest future directions while assessing
and discussing potential improvements. This mini-review
discusses our continued efforts toward the biological
characterisation and synthesis of naphthoquinoidal
compounds, aiming to contribute in the development of
a new arsenal of candidate drugs that exhibit effective
anti-T. cruzi activity.
2. Quinoidal Compounds and Derivatives
Quinoidal compounds can be found in various plant
families or as synthetic substances.56-59 The structural
components of these compounds are the focus of many
studies attempting to determine their activity against several
parasites such as Leishmania,60 T. cruzi61 and Plasmodium
falciparum.62 Quinones participate in multiple biological
oxidative processes due to their structural properties and
their capacity to generate reactive oxygen species.63,64
The first report published in collaboration with Antonio
V. Pinto’s group from the Federal University of Rio de
Janeiro in 1994 described a series of natural and synthetic
drugs that exhibited activity against T. cruzi.65 In this
work, we evaluated 45 compounds for activity against
bloodstream forms of T. cruzi. From there, a fruitful
partnership began, and several molecules were synthesised
and screened for activity against this parasite.
Following this initial study, we dedicated our efforts to
the identification of new quinoidal molecules. Lapachol (1)
is an important natural naphthoquinone; we used it and its
derivatives to explore the chemical reactivity of the drug
class, and several heterocycles were obtained with good
yields (Schemes 1-3). Their effects on the bloodstream
forms of T. cruzi were evaluated, and the results are shown
in Table 1. Some compounds that exhibited initial activity
were identified as potential candidates for further studies
due to comparable activity with crystal violet, a substance
indicated for the sterilisation of chagasic blood.66 Unless
otherwise stated, all of the screening assays presented in this
review were performed using bloodstream trypomastigotes
of the Y strain obtained from infected albino mice at
the peak of parasitaemia. These trypomastigotes were
isolated by differential centrifugation and resuspended
(107 cells mL-1) in Dulbecco’s modified Eagle medium
containing 10% mouse blood. This parasite suspension
(100 µL) was added to the same volume of each previously
prepared compound at twice the desired final concentrations
in 96-well microplates and was incubated for 24 h at
4 °C. For experiments using epimastigotes (Y strain),
the parasites were maintained axenically at 28 °C with
Anti-Trypanosoma cruzi Compounds J. Braz. Chem. Soc.
1784
weekly transfers of liver infusion tryptose (LIT) medium
and harvested during the exponential phase of growth
(5-day-old culture forms). The assays were performed in
24-well microplates and were incubated up to 4 days at
28 °C in LIT medium. Cell counts were performed in a
Neubauer chamber, and trypanocidal activity was expressed
as an IC50 value corresponding to the concentration that
lyses 50% of the parasites.
Meanwhile, we reported the synthesis and evaluation
of naphthoxazoles containing both electron donating and
withdrawing groups (Figure 3).67,68 Heterocycles, as for
instance, indole and 1,3-benzodioxole, as substituent groups
were also evaluated. The compounds were easily obtained
from the reaction of β-lapachone or nor-β-lapachone and
aromatic aldehydes in the presence of an ammonium salt.
In general, these structures exhibited efficient anti-T. cruzi
activity and represented an excellent starting point for the
synthesis of new prototypes.
Another class of structures prepared from the
same reaction were the naphthoimidazole derivatives
27-39 (Figure 4). The trypanocidal activities of the
naphthoxazoles 19-26 and naphthoimidazoles 27-39 are
displayed in Table 2. From these substances, compounds
18 (IC50 = 37.0 ± 0.7 µM), 27 (IC50 = 15.4 ± 0.2 µM) and
39 (IC50 = 15.5 ± 2.9 µM) were selected for further studies
of the trypanocidal mechanism of action.69
The naphthoimidazoles 18, 27 and 39 were also
effective against the proliferative forms of T. cruzi
(intracellular amastigotes and epimastigotes), and the main
ultrastructural targets identified were the mitochondrion
and nuclear DNA.70 Electron microscopy analyses
revealed mitochondrial swelling, abnormal chromatin
condensation, endoplasmic reticulum profiles surrounding
organelles and autophagosome-like structures in treated
parasites. We also observed reservosome disorganisation
and trans-Golgi network cisternae disruption specifically
in the epimastigote forms.70,71 Interestingly, the pre-
incubation of the parasites with the cysteine protease
inhibitor E64 or calpain inhibitor I partially attenuated the
trypanocidal effect of the naphthoimidazoles suggesting
that the deactivation of cysteine proteases is involved
in their mode of action.70 Because the reservosome is a
target in epimastigotes and is rich in cysteine proteases,
disruption of this organelle could release proteases into
the cytosol and initiate a proteolytic pathway, ultimately
leading to parasite death. Alterations of mitochondrion,
chromatin, and reservosomes and the detection of an
autophagy process encouraged further studies regarding
death pathways. The investigation of the apoptotic features
demonstrated discrete phosphatidylserine exposure and
strong DNA fragmentation by both electrophoresis and
terminal deoxynucleotidyl transferase dUTP nick end
labeling (TUNEL) techniques.70-72 Naphthoimidazoles
are planar in structure and could possibly interact with
the parasite’s DNA to induce fragmentation, which is a
decisive event during trypanocidal activity. In contrast,
Scheme 2. Lawsone 7 and its derivatives 8 and 9.66
Scheme 1. Synthetic route for the preparation of lapachol derivatives 1-6.66
Silva Júnior et al. 1785Vol. 25, No. 10, 2014
the morphological evidence of autophagy induction after
treatment with compounds 18, 27 and 39 stimulated a more
detailed evaluation of this pathway. Strong labelling of
monodansylcadaverine (an autophagosome probe) together
with ATG (autophagic-related genes) overexpression and
total abolition of the compounds’ effects by the well-known
autophagic inhibitors wortmannin or 3-methyladenine in
both treated epimastigotes and trypomastigotes supported
the hypothesis that autophagy was involved in the
naphthoimidazoles’ mode of action.72 However, further
proteomic analysis is needed to identify T. cruzi molecules
involved in the mechanism of action of compounds 18,
27 and 39. In 2010, the first assessment of the proteomic
profile of naphthoimidazole-treated epimastigotes was
performed. Multiple biochemical pathways were involved
in their trypanocidal activity including redox metabolism,
energy production, ergosterol biosynthesis, cytoskeleton
assembly, protein metabolism and chaperone modulation.
An imbalance among these fundamental pathways could
lead to the loss of homeostasis and culminate in T. cruzi
death.73 Among the proteins modulated by the treatment, 26
proteins were downregulated, and only three proteins were
overexpressed. Surprisingly, most of the modulated proteins
were exclusive to each particular compound, indicating
that differences in their modes of action existed (Figure 5).
Mitochondrial proteins were the most commonly
modulated proteins, thus confirming the previous biochemical
and ultrastructural evidence that described this organelle as
the primary target of these compounds.70,71,73 Tubulin was
downregulated in parasites treated with compounds 18,
27 and 39. In trypanosomatids, different tubulin isoforms
are present because each one is linked to the kinetics of
microtubule assembly. Enzyme-linked immunosorbent
assay (ELISA) data showed that the tyrosinated tubulin
Scheme 3. Synthetic route for the attainment of compounds 9-18.66
Anti-Trypanosoma cruzi Compounds J. Braz. Chem. Soc.
1786
pool decreased after treatment. This protein isoform was
associated with labile microtubules, suggesting that these
compounds interfered with intracellular vesicle traffic and/or
mitotic spindle formation. This hypothesis was also
supported by the absence of ultra-structural damage in
subpellicular and flagellar microtubules and the blockage
of mitosis in treated epimastigotes.70,71,73 Due to the results
obtained about the activity and mechanism of action of
18, 27 and 39 higher amounts of the compounds were
synthesised and experiments are underway in our laboratory
aiming the evaluation of nitroimidazoles in the treatment
of experimentally T. cruzi-infected mice.74
To synthesise new heterocycles, Pinto and co-workers67
developed a methodology to produce pyran derivatives
of β-lapachone (3) through a reaction using active
methylene reagents under basic conditions. The resulting
cyclopentenones and chromenes were evaluated for
anti-T. cruzi activity in addition to the other heterocyclic
compounds shown in Figure 6. The results of the trypanocidal
activity studies are shown in Table 3. Unfortunately, this
class of compounds did not exhibit trypanocidal activity
comparable to that of the naphthoimidazole derivatives,
with the exception of compound 45. Thus, these substances
have not been the subject of subsequent studies.
In the same manner, we continued the search for
trypanocidal heterocyclic compounds and obtained a
phenazine derivative 50 (Figure 7) from β-lapachone (3),
which was subsequently well characterised by
crystallographic methods. This compound was almost
twice as active as Bz, with an IC50 (24 h) of 61.3 ± 9.6 µM.75
Despite its promising activity level, the yield for obtaining
compound 50 from lapachone (3) was low (25% yield),
which discouraged further studies. However, phenazines
obtained from lapachones generally exhibited low levels of
cytotoxicity,76 and this phenazine represents an important
prototype for the design of novel trypanocidal drugs.
Over the last few years, our group has focused on
synthesising and measuring the trypanocidal activity of
nor-β-lapachones substituted with heterocyclic rings.
In general, a molecular hybridisation strategy was used
to design the new compounds,77 and the subject of our
study was the combination of a quinoidal moiety with a
1,2,3-triazole group. The first synthetic route we developed
followed the principles of medicinal chemistry and
Table 1. Effects of the original quinones and their naphthoxazole and
naphthoimidazole derivatives on T. cruzi
Compound IC50, 24 h / µMa
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Crystal violet
410.8 ± 53.5
> 4800
391.5 ± 16.5
1280.6 ± 167.2
> 400
164.8 ± 30.5
> 2500
420.7 ± 71.2
330.7 ± 62.4
> 2500
49.5 ± 1.4
283.5 ± 25.0
171.9 ± 51.2
197.3 ± 25.8
> 2500
325.2 ± 21.3
> 4800
37.0 ± 0.7
536.0 ± 3.0
aMean ± standard deviation from three experiments performed in triplicate.
Figure 3. Naphthoxazoles 19-26 obtained from β-lapachone (3) and nor-β-lapachone (5).67,68
Silva Júnior et al. 1787Vol. 25, No. 10, 2014
Figure 4. Naphthoimidazoles 27-39 obtained from β-lapachone (3).67,68
Table 2. Effects of naphthoxazoles and naphthoimidazoles on T. cruzi
Compound IC50, 24 h / µMa
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
Benznidazole
283.5 ± 25.0
> 9600
3502.5 ± 305.3
1641.3 ± 147.0
269.5 ± 46.5
351.4 ± 12.4
> 4800
> 2500
15.4 ± 0.2
6444.6 ± 483.7
3057.8 ± 836.7
259.3 ± 40.4
1858.1 ± 366.7
579.3 ± 52.5
303.6 ± 12.2
243.3
372.0
1064.2
1850.5
4455.5 ± 465.8
15.5 + 2.9
103.6 ± 0.6
aMean ± standard deviation from three experiments performed in triplicate.
produced lapachone-based 1,2,3-triazoles with global yields
higher than 50%. Using the Hooker oxidation method,78
nor-lapachol (4) was prepared and used to obtain the key
intermediate 3-azido nor-β-lapachone (51). Compound 51
was used to prepare the respective 1,2,3-triazole derivatives
52-61 by employing a 1,3-dipolar reaction catalysed by
Cu(I), a type of reaction also known as “click chemistry”
(Scheme 4).79 The results of the trypanocidal activity studies
are shown in Table 4.80,81
Overall, all compounds exhibited good trypanocidal
activity, and several compounds were even more active
than Bz. It was recently suggested in the Perspectives
Section of the Journal of Medicinal Chemistry82 that a
triazolic naphthofuranquinone compound (56) represents
an important trypanocidal prototype. Compound 56 was
the most active with an IC50 (24 h) value of 17.3 ± 2.0 µM,
and this substance was chosen for further studies of its
mechanism of action.83 This compound was also effective
against the epimastigote and intracellular amastigote
forms of T. cruzi, with IC50 (24 h) values below 25 µM.
Scanning electron microscopy analyses revealed bizarre
multiflagellar parasites in the treated group that also
exhibited abnormal morphology during parasite division.
Anti-Trypanosoma cruzi Compounds J. Braz. Chem. Soc.
1788
Figure 5. Similarities and differences among the mechanisms of action of each naphthoimidazole in T. cruzi epimastigotes. Most of the modulated proteins
are mitochondrial proteins, indicating that this organelle is the main target of compounds 18, 27 and 39. These three compounds regulate the trypanothione
pathway, cytoskeleton assembly, protein metabolism/synthesis and chaperone diversity. These alterations compromise different biological processes and
lead to parasite death. Other proteins and/or pathways were also affected by the naphthoimidazoles including the polyamine pathway and peptidase T
activity (18), ergosterol biosynthesis, energetic metabolism, histamine-releasing factor activity (27 and 39), and protein kinase C signalling (39).
Figure 6. Heterocyclic compounds 40-49 obtained from lapachol (1), β-lapachone (3) and nor-β-lapachone (5).67
Silva Júnior et al. 1789Vol. 25, No. 10, 2014
Cell cycle evaluations revealed a reduction in the number
of parasites with duplicated genetic material, suggesting
that the compound blocked cytokinesis. Transmission
electron microscopy analyses of epimastigotes revealed
the formation of well-developed endoplasmic reticulum
profiles surrounding the reservosomes; these results suggest
that there is close contact between both membranes. The
appearance of cytosolic concentric membrane structures
was another morphological feature, suggesting that
autophagy is a partial mode of action for compound 56.
Fluorescence microscopy analyses reinforced these data
and indicated that a high percentage of MDC-labelled
epimastigotes was present after treatment. Morphological
damage in Golgi cisternae and blebbing of the flagellar
membrane were also frequent alterations induced by this
triazolic quinone. Interestingly, ultra-structural and flow
cytometry studies showed that the mitochondrion was not
affected by the treatment, suggesting that this organelle
is not a target of compound 56. The mechanism of action
of this triazolic naphthofuranquinone differs from that
of the other naphthoquinones studied because it involves
autophagy (especially of the reservosomes) and cytokinesis
impairment (Figure 8).83
Compound 56 was considered an important prototype
for anti-T. cruzi activity, but its high level of cytotoxicity
Table 3. Effects of the heterocyclic compounds 40-49 on T. cruzi
Compound IC50, 24 h / µMa
40 > 4000
41 1216.7 ± 349.1
42 ndb
43 > 4000
44 > 4000
45 56.1 ± 15.5
46 > 4000
47 786.9 ± 80.0
48 ndb
49 > 4000
Benznidazole 103.6 ± 0.6
aMean ± standard deviation from three experiments performed in triplicate;
bnot determined.
Figure 7. Phenazine derivative 50 obtained from β-lapachone (3).75
Scheme 4. Nor-β-lapachone-based 1,2,3-triazoles 52-61.80,81
Table 4. Effects of nor-β-lapachone-based 1,2,3-triazoles on T. cruzi
Compound IC50 / µMa
51 50.2 ± 3.8
52 151.9 ± 8.0
53 256.7 ± 38.7
54 57.8 ± 5.6
55 348.1 ± 44.2
56 17.3 ± 2.0
57 20.8 ± 1.9
58 101.5 ± 5.7
59 39.6 ± 4.0
60 21.8 ± 3.1
61 359.2 ± 11.1
Crystal violet 536.0 ± 3.0
Benznidazole 103.6 ± 0.6
aMean ± standard deviation from three experiments performed in triplicate.
Anti-Trypanosoma cruzi Compounds J. Braz. Chem. Soc.
1790
in mammalian cells was an impediment for further studies.
We believed that it was necessary to structurally modify this
compound to obtain a substance with a higher selectivity
index (SI) that corresponds to the ratio LC50 (concentration
that leads to damage of 50% of the mammalian cells)/IC50.
Another possibility would be to develop the compound
within a controlled delivery system, which has been the
focus of several studies aimed at solving drug toxicity
issues. This important strategy can be used to optimise
the therapeutic efficacy of the drug and reduce toxic side
effects.84 In Scheme 5, the naphthoquinoidal compounds
designed to couple ortho-quinone to para-quinoidal
structures are displayed. Our strategy was based on the
combination of ortho- and para-quinoidal moieties that
are able to generate high concentrations of reactive oxygen
species, a property that is generally associated with the
activity of this class of compounds. Based on the structural
skeleton of compound 56, compounds 62-64 were designed
to preserve the main group, the quinoidal pharmacophore.
Our approach proved to be effective, and compounds 62, 63,
and 64 exhibited IC50 (24 h) values of 80.8, 6.8 and 8.2 µM,
respectively (Table 5).85 We were pleasantly surprised when
heart muscle cell toxicity analyses produced LC50 (24 h)
values of 63.1 and 281.6 µM for compounds 63 and 64,
respectively, which corresponded to SI of 9.3 and 34.3.85
Aiming the establishment of a panel of minimum
standardised procedures to advance leading compounds
to clinical trials, the workshop Experimental Models in
Drug Screening and Development for Chagas Disease was
held in Rio de Janeiro (Brazil) organised by the Fiocruz
Program for Research and Technological Development on
Chagas Disease (PIDC) and DNDi. During the meeting,
the minimum steps, requirements and decision gates for
the determination of the efficacy of lead compounds were
evaluated by interdisciplinary experts and an in vitro
and in vivo flowchart was designed to serve as a general
and standardised protocol for drug screening.86 Based
on this flowchart and due to the high SI value attained,
compound 64 will be assayed further for its effectiveness
in T. cruzi-infected mice.
To obtain additional trypanocidal molecules with
low toxicity in mammalian cells, new triazolic α- and
nor-α-lapachones were synthesised and assayed for
anti-T. cruzi activity based on a strategy we recently
described involving C-ring modification.87
α-Lapachone-based 1,2,3-triazoles were synthesised as
previously described (Scheme 6).88 4-Bromo-α-lapachone
was prepared from α-lapachone (2) by obtaining a key
Figure 8. Ultra-structural analysis of T. cruzi epimastigotes treated with
compound 56. (a) Transmission electron microscopy revealed reservosome
disorganisation (R) and endoplasmic reticulum (ER) profiles in close
contact with this organelle’s membrane (black arrows). The nucleus
and mitochondrion (M) exhibited typical morphologies. (b) Scanning
electron microscopy examination revealed parasite body retraction
(white thick arrows) and the impairment of mitosis (white arrowhead).
Bar in (a): 0.2 µm. Bar in (b): 1 µm.
Scheme 5. Nor-β-lapachone 1,2,3-triazole coupled 1,4-naphthoquinones 62-64.85
Table 5. Effects of compounds 62-64 on T. cruzi
Compound IC50 / µMa
62 80.8 ± 6.5
63 6.8 ± 0.7
64 8.2 ± 0.7
Benznidazole 103.6 ± 0.6
Crystal violet 536.0 ± 3.0
aMean ± standard deviation from at least three experiments.
Silva Júnior et al. 1791Vol. 25, No. 10, 2014
intermediate, 4-azido-α-lapachone (65). Using the click
chemistry method,89 several 1,2,3-triazoles 66-68 were
synthesised. Unfortunately, this class of compounds was
not active against trypomastigotes of T. cruzi and revealed
IC50 (24 h) values greater than 500 µM for all derivatives.
Using the same methodology with one minor difference
(in this case, the initial compound used was nor-α-
lapachone (69)), we prepared compounds 71-74 with high
yields (Scheme 7). These substances were evaluated under
the same conditions for anti-T. cruzi activity and were also
found to be inactive.85
To structurally modify β-lapachone (3), C-ring
modification87 was used to synthesise compounds
that were more active and selective towards T. cruzi.
Thus, we described the insertion of 1,2,3-triazoles into
compound 3. The preparation of these derivatives was
easily accomplished using the 3,4-dibromo-β-lapachone
(75) obtained from compound 3. After two steps, the
key intermediate 77 was isolated and used to prepare
β-lapachone-based 1,2,3-triazoles with moderate yields
(Scheme 8).90 These triazoles were evaluated against the
trypomastigote form of T. cruzi, and all of the substances
were more effective than crystal violet. When compared
to Bz, compound 77 was 4 times more active than the
standard drug and compound 81 exhibited similar activity
(Table 6).90
Scheme 6. Nor-α-lapachone 1,2,3-triazoles 66-68.88
Scheme 7. Nor-α-lapachone-based 1,2,3-triazole 71-74.88
Scheme 8. β-Lapachone-based 1,2,3-triazoles 78-81.90
Table 6. Activity of β-lapachone-based 1,2,3-triazoles 78-81 on T. cruzi
Compound IC50, 24 h / µMa
76 248.3 ± 29.1
77 23.4 ± 3.8
78 313.0 ± 26.4
79 439.6 ± 31.6
80 219.8 ± 27.2
81 106.1 ± 19.0
Benznidazole 103.6 ± 0.6
Crystal violet 536.0 ± 3.0
aMean ± standard deviation from at least three experiments.
Anti-Trypanosoma cruzi Compounds J. Braz. Chem. Soc.
1792
1,4-Naphthoquinone coupled to 1,2,3-triazole
N-phthalimides (82-91) were recently prepared from
brominated, chlorinated or unsubstituted quinones
(Scheme 9).85 Compounds 82-91 were inactive against
T. cruzi and more studies regarding the mechanism of
insertion of the 1,2,3-triazole ring into 1,4-naphthoquinone
are necessary.
Meanwhile, 1,4-naphthoquinones with a direct insertion
of a heterocyclic ring 1,2,3-triazole into the quinoidal
structure were prepared, as shown in Scheme 10. Synthesis
of the naphthoquinones coupled to 1,2,3-triazoles was
initially reported by Nascimento et al. (Scheme 10).91 In
assays with trypomastigote forms of T. cruzi, the most
active substances displayed IC50 values in the range of 10.9
to 80.2 µM (Table 7).85 Compounds 93 and 98 exhibited
IC50 values of 10.9 and 17.7 µM, respectively, and are thus
very promising structures. Further studies regarding their
mechanism of action, cytotoxicity levels and in vivo activity
are therefore necessary. It is important to note that the
para-naphthoquinone 1,2,3-triazoles are easily obtained in
only two steps from the starting material 1,4-naphthoquinone
and both reactions have good to excellent yields.
Using the methodology described by the Pinto group,92
we prepared substituted nor-β-lapachones arylamino
from nor-lapachol (4) at high yields (Figure 9), and these
compounds were evaluated for anti-T. cruzi activity
(Table 8).93,94 The trypanocidal activity of compounds 103,
108, 110, and 112-114 was higher than that of Bz, a drug
commonly used to combat T. cruzi infections. Compound
112, which contained the bromine atoms, was the most
active compound and exhibited an IC50 value of 24.9 µM.
Scheme 9. 1,4-Naphthoquinone-derived 1,2,3-triazoles 82-91.85
Scheme 10. Naphthoquinone-based 1,2,3-triazoles 93-100.91
Table 7. Effects of naphthoquinone-based 1,2,3-triazoles 93-100 on
T. cruzi
Compound IC50 / µMa
93 10.9 ± 1.8
94 45.8 ± 5.1
95 492.2 ± 17.5
96 2005.7 ± 9.9
97 113.1 ± 5.7
98 17.7 ± 3.1
99 80.2 ± 5.4
100 67.6 ± 7.7
Benznidazole 103.6 ± 0.6
Crystal violet 536.0 ± 3.0
aMean ± standard deviation from three experiments performed in triplicate. Figure 9. Nor-β-lapachone arylamino substituted compounds 101-116.93,94
Silva Júnior et al. 1793Vol. 25, No. 10, 2014
Table 10. Effects of the naphthoquinones 117-119 on epimastigote forms
of T. cruzi (in µM)
Compounds IC50, 1 day IC50, 2 day IC50, 3 day IC50, 4 day
117 13.2 ± 2.2 12.4 ± 1.4 11.7 ± 1.5 12.7 ± 2.0
118 24.9 ± 1.8 21.8 ± 2.4 19.5 ± 2.4 18.3 ± 4.9
119 7.9 ± 1.3a3.7 ± 0.3 3.0 ± 0.7 2.6 ± 0.3
aMean ± standard deviation from three independent experiments.
Table 9. Effects of the naphthoquinones 117-119 on T. cruzi
Compounds IC50 / µMa
117 641 ± 38
118 398 ± 56
119 158 ± 9
Benznidazole 103.6 ± 0.6
aMean ± standard deviation from three experiments performed in triplicate.
Table 8. Activity of nor-β-lapachone arylamino substituted compounds
101-116 on T. cruzi
Compounds IC50 / µMa
101 332.8 ± 23.3
102 140.8 ± 11.9
103 86.3 ± 4.6
104 > 4000
105 384.4 ± 52.5
106 952.5 ± 71.1
107 857.3 ± 96.4
108 88.2 ± 6.7
109 2517.9 ± 169.8
110 55.6 ± 4.6
111 1756.1 ± 91.8
112 24.9 ± 7.4
113 43.8 ± 7.4
114 59.6 ± 13.2
115 526.2 ± 80.5
116 156.2 ± 9.1
Benznidazole 103.6 ± 0.6
aMean ± standard deviation from three experiments performed in triplicate.
These structures represent an important starting point for
the attainment of new trypanocidal compounds.
In a previous work,92 Silva et al. described the synthesis
of derivatives obtained from C-allyl lawsone, as shown
in Scheme 11. These compounds exhibited activity
against T. cruzi in both the bloodstream trypomastigote
and epimastigote forms (Tables 9 and 10). The effects of
compounds 117-119 on epimastigote proliferation were
monitored for up to 4 days.
Compounds 117-119 derived from C-allyl lawsone
were effective against the three forms of the parasite,
and the intracellular amastigote was the most susceptible
form.95 Transmission electron microscopy examination of
treated epimastigotes and bloodstream trypomastigotes
revealed a drastic mitochondrial swelling with a
washed-out matrix profile. Potent dose-dependent collapse
of the mitochondrial membrane potential revealed by
rhodamine 123 staining together with an inhibition of
mitochondrial complex I-III activities and a reduction
in succinate-induced oxygen consumption strongly
corroborated the central role of the mitochondrion in
these compounds’ mechanisms of action. Moreover, an
Scheme 11. Synthetic route for the attainment of methylated and iodinated naphthoquinones 117-119.92
increase in the production of hydrogen peroxide by this
organelle in treated epimastigotes was also observed.
However, some differences in the mode of action of
naphthofuranquinones were apparent in epimastigotes
and trypomastigotes. In the insect form, the trypanocidal
effects of the compounds were a consequence of the
parasite redox balance modulation, whereas in the
bloodstream form, mitochondrial dysfunction affected
energy transduction reactions, which compromised
the protozoa’s bioenergy efficiency. Naphthoquinones
interfere with electron flow at the inner mitochondrial
membrane by diverting electrons away from ubiquinone.
The oxidation of semiquinones back to quinones leads to
the generation of reactive oxygen species that compromise
the activity of complex I-III and oxygen consumption
capability, which culminates in parasite death.95
In another set of experiments, the trypanocidal activity
of sixteen 1,4-naphthoquinones was assessed on both
T. cruzi trypomastigotes and epimastigotes (Figure 10 and
Table 11).96 In the case of the naphthoquinones 120-134,
different assay conditions were used to analyse the effects
on trypomastigotes. While all of the previous experiments
were performed in the presence of 5% mouse blood and at
4 °C (Bz IC50 = 103.6 ± 0.6 µM) as previously mentioned,
the present compounds were assayed at 37 °C in absence
of blood (Bz IC50= 26.0 ± 4.0 µM).
Anti-Trypanosoma cruzi Compounds J. Braz. Chem. Soc.
1794
Table 11. Effects of the naphthoquinones 120-134 on T. cruzi at 37 °C
Compound IC50 / µMa
120 0.79 ± 0.02
121 6.04 ± 0.35
122 63.02 ± 5.8
123 1.37 ± 0.03
124 2.17 ± 0.29
125 6.51 ± 0.48
126 0.16 ± 0.01
127 1.02 ± 0.29
128 2.15 ± 0.22
129 2.43 ± 0.50
130 1.25 ± 0.26
131 2.52 ± 0.37
132 0.85 ± 0.08
133 1.41 ± 0.15
134 1.38 ± 0.26
7563.18 ± 83.28
Benznidazole 26.0 ± 4.0
aMean ± standard deviation from three experiments performed in triplicate.
Figure 10. Naphthoquinones 120-134 and lawsone (7).96
Four compounds were selected from this series for mode
of action studies: the prototype naphthoquinone 120 and
three juglone derivatives (126, 127 and 130).96 These four
compounds were effective against parasite proliferative
forms (epimastigotes and intracellular amastigotes) and
reduced the infection of peritoneal macrophages and heart
muscle cells. Ultra-structural studies of treated epimastigotes
suggested that the mitochondrion are a primary target, due
to the apparent swelling of the organelle and the appearance
of membranous structures in its matrix (Figure 11).
Mitochondrial membrane potential was evaluated by
tetramethylrhodamine ethyl ester (TMRE) labelling, and
all four quinones induced a depolarisation of this organelle,
which reduced the intensity of TMRE fluorescence by up to
50%. Since an uncoupled mitochondrion generates reactive
oxygen species (ROS), ROS production can be examined by
DHE labelling; only compound 126 led to a discrete increase
in the percentage of DHE+ epimastigotes. Mechanistically,
it was reasonable to postulate that the collapse of the
mitochondrial potential was mediated by ROS generation in
the treated parasites. The absence of oxidative stress induced
by compounds 120, 127 and 130 could be attributable to
the involvement of more than one mode of action in the
trypanocidal activity of these compounds, leaving ROS
generation suppressed by the detoxification system of the
parasite. The intense redox activity of compound 126 could
be attributed to the acetyl group present in its structure
that facilitates quinone reduction. Furthermore, other
morphological alterations were described, such as atypical
cytosolic membranous structures and the appearance of
Silva Júnior et al. 1795Vol. 25, No. 10, 2014
endoplasmic reticulum surrounding reservosomes, which
is indicative of autophagy. In addition, intense cytosolic
vacuolisation, the formation of blebs in the flagellar
membrane and the loss of cytosolic electron-density were
also observed. The ultra-structural autophagic evidence
suggests that the endoplasmic reticulum participates in the
observed pre-autophagosomal formation.96
3. Conclusions
This review describes our efforts to develop an effective
trypanocidal drug. Synthesis procedures and biological data
regarding anti-T. cruzi activity were described and studies of
the mechanism of action of these compounds were detailed
to provide an overview of the progress made by our research
group in collaboration with several researchers around the
world. Among the quinones and derivatives investigated,
naphthoimidazoles derived from β-lapachone presented
promising biological activity together with low toxicity
to the host cells, opening interesting perspectives for their
investigation in vivo. On the other hand, naphthoquinones
presenting different moieties in their structures showed
distinct modes of action. It is well-known that quinones
induce ROS production also in T. cruzi. Our previous data
pointed to ROS generation as part of the naphtoquinones’
mechanism of action and the central role of the parasite
mitochondrion, depending on the moiety linked to the
quinoidal ring. In this scenario, as an example, a triazolic
naphthoquinone led to discrete increase in ROS levels and
Figure 11. Transmission electron microscopy analysis of a T. cruzi
epimastigote treated with compound 130. The treatment induced the
appearance of membranous structures inside the mitochondrion (black
thick arrows). N: nucleus; G: Golgi; FP: flagellar pocket; F: flagellum;
K: kinetoplast. Bar: 0.5 µm.
did not compromise the mitochondrial functionality as
well. The naphthofuranquinone and juglone derivatives
strongly affected this organelle physiology interfering
with the oxygen uptake and mitochondrial membrane
potential. High amounts of ROS were produced by the
mitochondrion of treated parasites culminating in T. cruzi
death. Notwithstanding, many questions still remain
unanswered about the molecular mechanisms involved
in the trypanocidal effect of these compounds and their
selectivity for different cellular structures in the protozoa,
we hope that this review contributes to the development of
new candidates for Chagas disease.
Acknowledgments
We wish to thank Conselho Nacional de Pesquisa
(CNPq), Coordenadoria de Aperfeiçoamento de Pessoal de
Nível Superior (CAPES), FAPEMIG and FAPERJ. Dr. E. N.
da Silva Júnior thanks Programa Institucional de Auxílio à
Pesquisa de Doutores Recém-Contratados and Universidade
Federal de Minas Gerais. This paper is dedicated to the
memory of our beloved Professor Antonio Ventura Pinto
because of his intense commitment to the development of
novel trypanocidal drugs. Prof. Ventura always believed in
the potential of the quinoidal compounds, especially the
structures obtained from lapachol. His passion for the study
of the chemical reactivity of naphthoquinonoid compounds
and discovering new reactions was a key point in our lives.
Eufrânio N. da Silva Júnior received
his degree in chemistry from the Catholic
University of Brasília (UCB). In 2007,
he completed his MSc at the Fluminense
Federal University (UFF) and in 2009
he concluded his PhD at the University
of Brasilia (UnB). In 2010, he became
Professor of Chemistry at the Federal University of Minas
Gerais (UFMG). His research interests are focused on click
chemistry reactions, asymmetric organocatalysis and on the
synthesis of heterocyclic and naphthoquinoidal bioactive
compounds. Currently, he is also interested in obtaining
fluorescent substances for the study of pharmacological
and DNA-binding properties.
Guilherme A. M. Jardim received his
degree in Chemistry from the Federal
University of Minas Gerais (UFMG).
He is currently pursuing his MSc at the
same university under the supervision
of Prof Eufrânio N. da Silva Júnior. His
dissertation work is focused largely
Anti-Trypanosoma cruzi Compounds J. Braz. Chem. Soc.
1796
on the synthesis and biological study of heterocyclic
compounds besides the preparation of biosensors with
application in molecular biology.
Rubem F. S. Menna-Barreto received
his degree in Biology in Santa Ursula
University (2003). In 2008, he completed
his PhD in Cell and Molecular Biology at
the Oswaldo Cruz Institute (FIOCRUZ)
and after a postdoctoral period at the
Federal University of Rio de Janeiro
in Biochemistry at the Medical Biochemistry Institute,
he became an associate researcher at the Oswaldo
Cruz Foundation. His research interests are focused on
parasitology, specially animal protozoology, Trypanosoma
cruzi, chemotherapy, electron microscopy, mitochondrion,
cell death, autophagy and naphthoquinones.
Solange L. de Castro received
her degree in Industrial Chemistry
from the Federal University of Rio
de Janeiro (UFRJ). In 1991, she
completed her PhD at the Oswaldo Cruz
Institute (FIOCRUZ) in experimental
chemotherapy of Chagas disease. She
is a senior researcher at FIOCRUZ. Her research interests
are focused on chemotherapy, with special interest in the
studies about the trypanocidal activity and mechanism of
action of naphthoquinones and derivatives.
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Submitted: March 5, 2014
Published online: August 1, 2014
