SAR Studies and Biological Characterization of a Chromen-4-one Derivative as an Anti- Trypanosoma brucei Agent

Article abstract of DOI:10.1021/acsmedchemlett.8b00565

Chemical modulation of the flavonol 2-(benzo[d][1,3]dioxol-5-yl)-chromen-4-one (1), a promising anti-Trypanosomatid agent previously identified, was evaluated through a phenotypic screening approach. Herein, we have performed structure-activity relationsh

Full text of DOI:10.1021/acsmedchemlett.8b00565

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Letter
SAR Studies and Biological Characterization of a chromen-4-
one derivative as an Anti-Trypanosoma brucei Agent
Chiara Borsari, Nuno Santarém, Sara Macedo, María Dolores Jiménez-Antón, Juan Jose Torrado,
Ana Isabel Olías-Molero, Maria Jesùs Corral, Stefania Ferrari, Annalisa Tait, Luca Costantino,
Rosaria Luciani, Glauco Ponterini, Sheraz Gul, Maria Kuzikov, Bernhard Ellinger, Birte Behrens,
Jeanette Reinshagen, José Maria Alunda, Anabela Cordeiro-da-Silva, and Maria Paola Costi
ACS Med. Chem. Lett., Just Accepted Manuscript • Publication Date (Web): 29 Jan 2019
Downloaded from http://pubs.acs.org on January 29, 2019
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SAR Studies and Biological Characterization of a chromen-4-one
derivative as an Anti-Trypanosoma brucei Agent
Chiara Borsari,‡,† Nuno Santarem,§ Sara Macedo,§ María Dolores Jiménez-Antón,∥ Juan J. Torrado,∥ Ana
Isabel Olías-Molero,∥ María J. Corral,∥ Annalisa Tait,‡ Stefania Ferrari,‡ Luca Costantino,‡ Rosaria
Luciani‡ Glauco Ponterini,‡ Sheraz Gul,⊥ Maria Kuzikov,⊥ Bernhard Ellinger,⊥ Birte Behrens,⊥ Jeanette
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⊥
∥
§,
‡*
#
Reinshagen, José María Alunda, Anabela Cordeiro-da-Silva, Maria Paola Costi.
‡University of Modena and Reggio Emilia, Via Campi 103, 41125 Modena, Italy
§
IBMC and Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4150-180 Porto, Portugal
∥
Complutense University of Madrid, 28040 Madrid, Spain
⊥
Fraunhofer Institute for Molecular Biology and Applied Ecology Screening Port, Hamburg, Germany
# Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, 4050-313 Porto
KEYWORDS: Trypanosoma brucei, flavonol-like compounds, SAR studies, ADME-tox properties, neglected tropical
diseases.
ABSTRACT: chemical modulation of the flavonol 2-(benzo[d][1,3]dioxol-5-yl)-chromen-4-one (1), a promising anti-
Trypanosomatid agent previously identified, was evaluated through a phenotypic screening approach. Herein, we have performed
structure-activity relationship studies around hit compound 1. The pivaloyl derivative (13) showed significant anti-T. brucei activity
(EC50= 1.1 μM) together with a selectivity index higher than 92. The early in vitro ADME-tox properties (cytotoxicity,
mitochondrial toxicity, cytochrome P450 and hERG inhibition) were determined for compound 1 and its derivatives and these led
to the identification of some liabilities. The 1,3-benzodioxole moiety in the presented compounds confers better in vivo
pharmacokinetic properties than those of classical flavonols. Further studies using different delivery systems could lead to an
increase of compound blood levels.
Neglected tropical diseases (NTDs) are a group of infections
that affect more than 1.4 billion people worldwide and mainly
thrive among the poorest populations in tropical and
subtropical areas.1 Kinetoplastid parasites are responsible for
the potentially fatal insect-borne diseases, namely Chagas
disease, Human African Trypanosomiasis (HAT) and
Leishmaniasis.2 HAT, also known as sleeping sickness, is
caused by infection with the gambiense and rhodesiense
subspecies of the extracellular protozoan parasite
Trypanosoma brucei (T. brucei).3 The tsetse fly, Glossina spp.,
is the vector of the sleeping sickness disease.4 According to the
World Health Organization (WHO), HAT continues to be a
public health issue with an estimated number of new cases per
year around 20000 and an estimated population at risk of 65
million people.5 Despite the serious health, economic and
social consequences of T. brucei infections, effective vaccines
are lacking and the limited existing drug therapy presents
drawbacks including toxicity, poor efficacy and serious side
effects. Most of the available drugs have been used for over
half a century, thus problems of drug resistance are emerging.
Therefore, there is an urgent need for new, safe and effective
drugs.6 A phenotypic approach is a useful tool for drug
discovery with the advantage of identifying compounds which
are active against the whole cell. Membrane permeability, cell
uptake and cell efflux are taken into account in the selection of
new hits through phenotypic screening.7 Phenotypic
approaches to drug discovery have been successfully used in
the field of neglected diseases, particularly for the treatment of
HAT.8-9 Two compounds discovered through phenotypic
screening have recently been progressed into clinical trials by
DNDi (Drugs for Neglected Diseases initiative): fexinidazole,
a nitroimidazole and SCYX-7158, an oxaborole.10 A wide
range of chemical structures, including flavonols (3-hydroxy-
2-phenylchromen-4-one), have been investigated in drug
discovery programs with the aim of identifying novel
antileishmanial and anti-trypanosomatid agents.11-15 Very
recently, we had replaced the phenyl ring of classical flavonols
with heteroaromatic rings and biphenyl rings and we had
synthesized
a series of flavonol-like compounds with
improved antiparasitic activity with respect to classical
flavonols (Figure 1). Compound 1 bearing a 1,3-benzodioxole
was identified as the most active and selective molecule
towards T. brucei (EC50 = 0.4 μM, Selectivity Index (SI) =
250) (Figure 1).16 According to the biological activity profile,
compound 1 was suitable for progression in the drug discovery
path. Moreover, the 1,3-benzodioxole represents a crucial
pharmacophore with diverse biological activities and has been
exploited in bioactive compounds with a wide range of
medical applications, including cancer17,18, tuberculosis19,
hepatitis B20, fungal infections21 and parasitic diseases22,23
.
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The aims of our study were to validate compound 1 through
two fluorine atoms instead of two hydrogens linked to the
dioxolane ring, was less active than the starting compound 1.
The anti-T. brucei activity decreased replacing the dioxolane
ring of 1 with a dioxane (compound 20), while it was
maintained in compound 21, bearing a tetrahydrofurane.
Compound 21 presented an EC50 towards T. brucei equal to
3.1 µM, but SI = 8. Overall, six compounds (8, 11-15) showed
a low micromolar EC50 and SI >20. Compound 13, the 3-
pivaloyl derivative of 1, was the most selective among the
novel synthesized molecules.
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Structure Activity Relationship (SAR) studies, discover
follow-up hits and characterize their biological profile for
potential liabilities identifications. The synthetic procedure
followed for the synthesis of the compounds (1-21) is shown
in Scheme 1 and the chemical structures are depicted in Table
1-3. The chalcones (22-34) were synthesized by Claisen-
Schmidt condensation using substituted acetophenones and
benzaldehydes in presence of NaOH as base. The reaction was
carried out in ethanol as previously reported.15 The chalcones
were converted into the corresponding flavonol-like
compounds (1-10, 19-21) using the Flynn-Algar-Oyamada
method for epoxidation and subsequent intramolecular
cyclization of the open-chain structure (Scheme 1A). For the
synthesis of esters (11-15) and carbamate 16, compound 1 was
treated with an excess of acyl chloride in dry DCM and in
presence of triethylamine. The reaction was carried out at
room temperature overnight. For the synthesis of ethers 17 and
18, alkyl halide was added to a solution of compound 1 in dry
DMF and in presence of K2CO3. The reaction was carried out
under microwave irradiation (Scheme 1B).
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The synthesized library was assessed at 10 μM in a panel of
early in vitro ADME-tox assays including cytotoxicity (A549
cell line), mitochondrial toxicity, cytochrome P450 (CYP1A2,
CYP2C9, CYP2C19, CYP2D6 and CYP3A4 isoforms) and
hERG inhibition. The data are reported in Figure 2 using a
traffic light system. Compound 1 and all of its derivatives
exhibited no liability towards hERG and mitochondrial
toxicity. Some compounds were shown to be cytostatic, with
two compounds (9 and 12) being cytotoxic (<0% A549 cell
growth). Most of the compounds displayed varying degrees of
CYP450 liability. The IC50 towards hERG and CYP isoforms
were measured for compound 1. The hERG IC50 (>100 μM)
was over 250-fold higher than the EC50 towards the parasite,
thus in accord with the Target Product Profile (TPP) for hit
prioritization. Compound 1 IC50 towards CYP1A2 and
CYP2D6 were 0.4 and 0.05 μM, respectively, whereas for
CYP2C9, CYP2C19 and CYP3A4 the IC50 were equal to 1.6,
1.5 and 6.0 μM, respectively. Compound 1 was the most
optimal for its anti-trypanosomatid activity and ADME-tox
profile and progressed to in vivo pharmacokinetic studies.
The novel library of flavonol-like compounds (2-21) was
evaluated towards T. brucei bloodstream form. The series was
assessed for cytotoxicity on THP1 macrophage-like cells to
estimate the CC50. For compounds showing a percentage of
parasite growth inhibition higher than 70%, the dose-response
curve (DRC) was performed. The percentages of parasite
growth inhibition at 10 µM are reported in Table S1 of the
Supporting Information.
We started the SAR investigation of this scaffold by
modifying the substituents on ring A (Table 1). Nine
compounds (2-10) were synthesized introducing different
substituents in position 6 and 7 of ring A. Five compounds (2,
4, 8-10) showed a significant activity towards T. brucei with
EC50 lower than 5 µM. When the OCH3 in position 7 of
compound 1 was replaced with a methyl group and a chlorine
or fluorine (8, 9 and 10, respectively), the compounds
maintained a meaningful anti-T. brucei activity. Moving the
methoxy group from position 7 to 6 (compound 3), we
observed a huge drop of the antiparasitic activity. Compound
2, bearing unsubstituted ring A, and compound 4, with a
methyl group in position 6 showed activity towards T. brucei,
while compounds bearing halogen in position 6 (5-bromide; 6-
chlorine; 7-fluorine) did not significantly inhibit T. brucei
cells growth. Compound 8 (EC50 = 0.4 µM) displayed a
potency comparable to that of the starting hit 1, however it
presented a reduced selectivity index (SI = 31).
Following this, our SAR was focused on modifications of the
hydroxyl group in position 3 of the chromen-4-one scaffold
(Table 2). The presence of an ester instead of a hydroxyl group
in position 3 (11-15) led to significant activity on T. brucei
(EC50 <1.1 µM) together with a SI >20. Among the esters, the
3-pivaloyl derivative of compound 1 (13) showed the most
interesting profile with an EC50 towards T. brucei of 1.1 µM
and SI >92. On the contrary, the presence of a carbamate (16)
or an ether (17 and 18) led to inactivity towards T. brucei.
These data suggested that the hydroxyl group in position 3
should be free in order to have a meaningful anti-T. brucei
activity. The activity of esters can be related to an easier
hydrolysis with respect to ethers and carbamates. We enlarged
the SAR study modifying the 1,3-benzodioxole ring of
compound 1 (compounds 19-21, Table 3). Compound 19, with
In vivo bioavailability and half-life were evaluated in BALB/c
mice treated IV with 1 mg/kg and orally 20 mg/kg. Compound
1 displayed a half-life of 19 hrs after iv administration and of
45 hrs after oral (os) administration (Table 4). Both AUC and
Cmax values were similar despite the much higher dose
administered per os. Tmax for IV administration was reached
after 1h this suggesting the possible intravascular aggregation
of compound 1 given its low solubility.
The aggregation behavior of compound 1 in aqueous solution
was investigated spectroscopically and the albumin
sequestration assay performed. As compound 1 concentration
is increased, both the absorption and the emission spectra
show an increase of bands due to aggregates relative to the
monomer bands (Figure 3). The absorption data were well
fitted in terms of a monomer/dimer equilibrium, with a 1.8
(±0.3) x 105 M-1 equilibrium constant at 20 °C (see the
Supporting Information). The fact that the aggregate
absorption band is found at shorter wavelengths and its
emission band at longer wavelengths than the corresponding
bands of the monomeric form indicates the aggregates to be of
H-type (as opposed to a J-type), i.e., with the monomers
stacked on top of each other with a small slip angle.24-25
Subsequent additions of human serum albumin (HSA) caused
a progressive recovery of the monomer absorption band and
the replacement of both aggregate and free monomer emission
bands by a single new band that we assign to a compound
1/HSA complex. Therefore, the latter represents a stable state
with respect to the monomeric and dimeric states. Emission
data analysis provided in the Supporting Information allowed
us to estimate the 1/HSA binding equilibrium constant, 2.5
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(±1) x 105 M-1. These results indicate that compound 1 has a
tendency to aggregate in aqueous solution that can be reverted
by albumin binding. We expect this behavior to occur in blood
where albumin binding should help compound solubilization.
Chemical changes enhancing solubility are expected to avoid
aggregate formation and increase the blood levels of
compound 1, thus producing
†Department of Biomedicine, University of Basel, Mattenstrasse
28, 4058 Basel, Switzerland.
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Author Contributions
The manuscript was written through contributions of all authors.
All authors have given approval to the final version of the
manuscript.
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testing.
Funding Sources
Although removal of systemic infection may be beneficial to
host survival, in the second stage HAT (which represents 90%
of the total cases), the parasites colonize the central nervous
system. To understand the suitability of compound 1 to pass
the BBB we evaluated molecular descriptors, such as
lipophilicity (cLogP), molecular weight (MW) and polar
surface area (PSA) that provide insight into the factors that
govern BBB penetration. Compound 1 fulfils the requirements
for BBB penetration, i.e., cLogP in the range 1.5-2.7 (2.19 for
compound 1), MW < 400 (312.3 for compound 1) and PSA <
90 Å2 (74.22 Å2 for compound 1). Additionally, the 105 order
of magnitude of the 1/HSA binding equilibrium constant is
consistent with that of CNS drugs that do cross the BBB (6
x104 M-1).Therefore, we expect compound 1 to be sufficiently
lipophilic to be transported by HSA and pass the CNS
barrier.26
This project has received funding from the European Union’s
Seventh Framework Programme for research, technological
development and demonstration under grant agreement n° 603240
(NMTrypI - New Medicine for Trypanosomatidic Infections).
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ACKNOWLEDGMENT
The authors acknowledge the COST Action CM1307,
http://www.cost.eu/COST_Actions/cmst/CM1307
contribution to the discussion of the research results.
for
the
ABBREVIATIONS
ADME-tox, Absorption, Distribution, Metabolism, and Excretion-
tox; A549, human lung adenocarcinoma epithelial cell line; CC50,
half maximal cytotoxicity concentration; DCM, dichloromethane;
DMF, dimethylformamide; DRC, dose-response curve; EC50, half
maximal effective concentration; EtOH, Ethanol; HAT, Human
African trypanosomiasis; hERG, human ether-a-go-go-related
gene; HAS, human serum albumin; NaOH, sodium hydroxide; SI,
Selectivity Index; T. brucei, Trypanosoma brucei; THP1, human
monocytic cell line.
In summary, we have validated compound 1 bearing a 1,3-
benzodioxole moiety as a potent anti-Trypanosomatid agent in
vitro.16 SAR studies around compound 1 have confirmed its
profile as a valuable hit to progress to animal studies. We have
synthesized twenty derivatives (2-21), compounds 10-21 are
novel structure and have not been previously reported. The
pivaloyl derivative (13) was the best compound of the hit-to-
lead optimization process. Compound 13 has significant anti-
T. brucei activity (EC50 = 1.1 μM) together with SI >92 and a
reduced toxicity, thus showing a biological profile similar to 1.
The pharmacokinetic (PK) studies on 1 have demonstrated the
ability of the 1,3-benzodioxole flavonol derivative to reach
plasma concentrations >EC50 for T. brucei with oral
administration, thus increasing classical flavonols half-life.15
Compound 1 blood exposure was probably limited due to its
low solubility and sequestration by albumin, as shown in
aqueous solution experiments. Compound 1 is an interesting
scaffold for anti-Trypanosomatid drug development that can
be further exploited using drug delivery systems such as β-
cyclodextrins which have a proven capacity to improve
solubility of flavonoids.27
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ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website.
Antiparasitic activity towards Trypanosoma brucei (Table S1);
Early ADME-tox data (Table S2); General information and
Experimental data of synthesized compounds (pp. S6-S16).
Molecular formula strings (CSV).
AUTHOR INFORMATION
Corresponding Author
*M.P.C.: phone, 0039-059-205-8579; E-mail, mariapaola.
(10) Eperon, G.; Balasegaram, M.; Potet, J.; Mowbray, C.; Valverde,
O.; Chappuis, F. Treatment options for second-stage gambiense
costi@unimore.it.
Present Addresses
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Ekins, S.; Clark, J.; Connelly, M.C.; Sigal, M.; Hodges, D.;
Guiguemde, A.; Guy, R.K.; Tropsha, A. Discovery of novel
antimalarial compounds enabled by QSAR-based virtual screening. J
Chem Inf Model. 2013, 53 (2), 475-492.
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(14) Arioka, S.; Sakagami, M.; Uematsu, R.; Yamaguchi, H.;
Togame, H.; Takemoto, H.; Hinou, H.; Nishimura, S. Potent inhibitor
scaffold against Trypanosoma cruzi trans-sialidase. Bioorg. Med.
Chem. 2010, 18 (4), 1633-1640.
(15) Borsari, C.; Luciani, R.; Pozzi, C.; Pöhner, I.; Henrich, S.;
Trande, M.; Cordeiro-da-Silva, A.; Santarém, N.; Baptista, C.; Tait,
A.; Di Pisa, F.; DelloIacono, L.; Landi, G.; Gul, S.; Wolf, M.;
Kuzikov, M.; Ellinger, B.; Reinshagen, J.; Witt, G.; Gribbon, P.;
Kohler, M.; Keminer, O.; Behrens, B.; Costantino, L.; Tejera Nevado,
P.; Bifeld, E.; Eick, J.; Clos, J.; Torrado, J.; Jiménez-Antón, M. D.;
Corral, M. J.; Alunda, J. M.; Pellati, F.; Wade, R. C.; Ferrari, S.;
Mangani, S.; Costi, M. P. Profiling of flavonol derivatives for the
development of anti-trypanosomatidic drugs. J. Med. Chem. 2016, 59
(16), 7598-7616.
(16) PhD thesis Chiara Borsari: Drug discovery and delivery
approaches for the identification and optimization of novel agents for
neglected tropical diseases and tuberculosis.
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C. H.; Huang, C. S.; Chang, H. W.; Chang, C. H.; Tseng, H.; Ho, Y.
S.J- The in vivo antitumor effects on human COLO 205 cancer cells
of the 4,7-dimethoxy-5-(2-propen-1-yl)-1,3-benzodioxole (apiole)
derivative of 5-substituted 4,7-dimethoxy-5-methyl-l,3-benzodioxole
(SY-1) isolated from the fruiting body of Antrodia camphorate.
Cancer Res Ther. 2012, 8 (4), 532-536.
(18) Goodarzi, S.; Hadjiakhoondi, A.; Yassa, N.; Khanavi, M.;
Tofighi, Z. New Benzodioxole Compounds from the Root Extract of
Astrodaucuspersicus. Iran J Pharm Res. 2016, 15 (4), 901-906.
(19) Deshpande, S. R.; Nagrale, S. N.; Patil, M. V.; Chavan, P. S.
Novel 3,4-Methylenedioxybenzene Scaffold Incorporated 1,3,5-
Trisubstituted-2-pyrazolines: Synthesis, Characterization and
Evaluation for Chemotherapeutic Activity. Indian J Pharm Sci. 2015,
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(20) Huber, R.; Hockenjos, B.; Blum, H. E. DDB treatment of
patients with chronic hepatitis. Hepatology. 2004, 39 (6), 1732-1733.
(21) Moon, Y. S.; Choi, W. S.; Park, E. S.; Bae, I. K.; Choi, S. D.;
Paek, O.; Kim, S. H.; Chun, H. S.; Lee, S. Antifungal and
Antiaflatoxigenic Methylenedioxy-Containing Compounds and
O
O
O
OH
OH
1
R1
A
C
O
EC50 T. brucei = 0.4 M
O
O
SI = 250
O
B
R
Figure 1. SAR studies on flavonol-like compounds and identification of compound 1.
Entry
1
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
% in. hERG
% in. CYP1A2
% in. CYP2C9
% in. CYP2C19
% in. CYP2D6
% in. CYP3A4
% cell growth A549
% tox. Mitochondria
Figure 2. Early in vitro ADME-tox properties of compounds 1-21. All the assays were performed at 10 μM. The data are reported
as a traffic light system. An ideal compound would be expected to be associated with a green color (yielding <30% effect). For
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CYP450, hERG and mitochondrial toxicity, the cell is colored green when the value is 0-30%, yellow for values 31- 60% and red
for values ≥61%. Compounds are non-cytotoxic (green) when A549 cell growth value is 60-100%, cytostatic (yellow) for values 0-
59% and cytotoxic (red) for values <0%.
1
2
3
4
5
6
A)
O
O
O
O
OH
Ar
i)
ii)
Ar
+
H
Ar
R
R
R
O
OH
OH
7
8
9
FLAVONOL-LIKE
CHALCONES
1-10
19-21
and
O
22-34
B)
R
O
iii)
O
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
O
O
O
O
O
Cl
R
11-15
O
O
N
O
OH
O
iv)
O
O
O
O
O
O
O
O
1
16
Cl
N
O
R
O
O
v)
O
I
R
O
O
17-18
O
Scheme 1. A) Synthesis of the compounds 1-10 and 19-21. Reaction conditions: (i) NaOH (3 M), EtOH, r.t.; (ii) H2O2, NaOH (1
M), EtOH, r.t. B) Synthesis of the compounds 11-18. Reaction conditions: (iii) acyl chloride, dry DCM, N2, r.t.; (iv) carbamoyl
chloride, dry DCM, r.t.; (v) alkyl halide, dry DMF, MW 80°C, 0.5 h.
Figure 3. Absorption (left) and fluorescence emission spectra of compound 1 in
phosphate buffer at pH 8 in the absence (top) and in the presence of human serum
albumin (HSA). Top: effect of increasing concentration of compound 1: 1.25, 2.5,
3.75, 5, 6.25, 7.5, 8.75, 10, 11.25 M. Bottom: the arrows indicate the effect of the
subsequent additions of HSA (1.68, 2.72, 4.11, 6.65, 9.65, 13.86 M) to the 11.25
M solution of compound 1. Absorption maxima: free and HSA-complexed
monomer,  360 nm; aggregate, 325 nm. Emission maxima: free monomer, 475 nm;
aggregate, 560 nm, HSA-complexed monomer, 540 nm. exc = 320 nm. The
emission spectra were normalized to their maximum values for ease of presentation.
Table 1. SAR study on ring A of the cromen-4-one scaffold.
O
R6
R7
OH
A
O
O
O
EC50
SD
(µM)
±
CC50
(μM)
Comp.
R3
R6
R7
SI
1
2
3
4
5
6
7
8
9
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
H
H
OCH3 0.4± 0.1
>100
12.5<CC50<25
<12.5
<12.5
12.5<CC50<25
<12.5
12.5<CC50<25
12.5<CC50<25
<12.5
250
4
H
H
H
H
H
2.9 ± 0.4
OCH3
CH3
Br
-
-
4.1 ± 2.1
3*
-
-
-
-
Cl
F
H
H
-
-
H
CH3
Cl
F
0.4 ± 0.1
3.8 ± 4.0
2.4 ± 0.3
31
3*
8*
10
H
<12.5
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ACS Medicinal Chemistry Letters
* Only estimations as the lower threshold of toxicity was not determined, EC50 >10M. The reference compound for T. brucei
was pentamidine (IC50 = 1.55 ± 0.24 nM). The synthesis of compounds 128, 229, 330, 431, 530, 630, 730, 832 and 933 has been already
published in literature. Compound 10 is a novel structure and has not been previously reported in literature.
1
2
3
4
5
6
Table 2. SAR study on the hydroxyl group in position 3 of the cromen-4-one scaffold.
O
R3
O
7
O
O
8
O
9
EC50 ± SD
(µM)
CC50
(μM)
Comp.
11
R3
SI
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
O
0.3 ± 0.3
<12.5
46*
*
O
O
12
13
14
0.5 ± 0.1
<12.5
24*
>92
22*
*
*
O
O
O
O
1.1 ± 0.2
0.6 ± 0.2
>100
O
*
<12.5
O
15
16
0.5 ± 0.1
-
12.5<CC50<25 25
*
O
O
N
>100
-
*
*
O
O
17
18
-
-
50<CC50<100
12.5<CC50<25
-
-
*
O
*Only estimations as the lower threshold of toxicity was not determined, EC50 >10M. The reference compound for T. brucei
was pentamidine (IC50 = 1.55 ± 0.24 nM). Compounds 11-18 are novel structures and have not been previously reported in
literature.
Table 3. SAR study modifying the 1,3-benzodioxole ring of compound 1.
O
OH
O
O
R2
EC50 ± SD
(µM)
CC50
(μM)
Comp.
19
R2
SI
-
O
O
F
F
*
-
>100
O
*
*
20
-
50<CC50<100
25<CC50<50
-
O
21
3.1 ± 0.5
8
O
- EC50 >10M. The reference compound for T. brucei was pentamidine (IC50 = 1.55 ± 0.24 nM). Compounds 19-21 are novel
structures and have not been previously reported in literature.
Table 4. Pharmacokinetic parameters of compound 1.
Dose (mg)
Cmax
Cmax Tmax
AUCtot
AUCtot
Half life
(h)
19.8
Comp.
and route (ng/mL) (μM)
(h)
1.00
0.50
(ng/mL h) (nmol/mL h)
1
1
1 (IV)
340
290
1.08
0.91
3120
2700
9.99
8.65
20 (per os)
45.4
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