N-acylhydrazones containing thiophene nucleus: a new anticancer class

Article abstract of DOI:10.1007/s00044-017-1832-y

In this study, we present a series of N-acylhydrazones containing thiophene nuclei as a new anticancer class. Fifty-seven compounds in this series were evaluated for their activity against four human cancer cell lines. Cytotoxicity (IC₅₀) ranged from 0.82 to 12.90 μM. The compound (E)-N′-(2-hydroxy-3-methoxybenzylidene)thiophene-2-carbohydrazide displayed good cytotoxic activity in all cell lines (IC₅₀ = 0.82–5.36 μM) and yielded the best result in this series; therefore, it is an important lead compound in this new class.

Full text of DOI:10.1007/s00044-017-1832-y

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-017-1832-y
ORIGINAL RESEARCH
N-acylhydrazones containing thiophene nucleus: a new anticancer
class
Laura N. F. Cardoso1,2 Thais C. M. Nogueira1 Felipe A. R. Rodrigues3
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Augusto Cesar Aragão Oliveira3 Maria Claudia dos Santos Luciano3
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Claudia Pessoa3,4 Marcus V. N. de Souza1
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Received: 27 April 2016 / Accepted: 1 March 2017
© Springer Science+Business Media New York 2017
Abstract In this study, we present a series of N-acylhy-
drazones containing thiophene nuclei as a new anticancer
class. Fifty-seven compounds in this series were evaluated
for their activity against four human cancer cell lines.
Cytotoxicity (IC50) ranged from 0.82 to 12.90 μM. The
compound (E)-N′-(2-hydroxy-3-methoxybenzylidene)thio-
phene-2-carbohydrazide displayed good cytotoxic activity
in all cell lines (IC50 = 0.82–5.36 μM) and yielded the best
result in this series; therefore, it is an important lead com-
pound in this new class.
Introduction
Sulfur is an important chemical element present in various
synthetic and natural products, which plays a critical role in
earth processes. In the field of drug discovery, there are
several classes that incorporate sulfur into their structure,
resulting in a wide range of biological applications, such as
cancer. Note that cancer is the leading cause of death
worldwide; it accounted for 8.2 million deaths in 2012
(Ferlay et al. 2013).
Because of the importance of a thiophene nucleus to drug
discovery and the continuous search for effective and safe
anticancer agents (Fig. 1) (Palkowitz et al. 1997; Romagnoli
et al. 2014), this study presents a series of N-acylhydrazones
containing a thiophene nucleus designed by molecular
hybridization (Schemes 1 and 2).
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Keywords Thienyl derivatives N-acylhydrazones
Cancer Antitumor
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The series was tested against three human cancer cell
lines with good results (Table 1). The choice of thiophene
N-acylhydrazones derivatives was based on the importance
of these as functional groups and their involvement in
various pharmacological activities such as anticancer agents
(Montenegro et al. 2012).
Electronic supplementary material The online version of this article
(doi:10.1007/s00044-017-1832-y) contains supplementary material,
which is available to authorized users.
* Marcus V. N. de Souza
marcos_souza@far.fiocruz.br
Results and discussion
Chemistry
1
FioCruz - Fundação Oswaldo Cruz, Instituto de Tecnologia em
Fármacos-Far-Manguinhos, Rua Sizenando Nabuco, 100,
Manguinhos, Rio de Janeiro, RJ 21041-250, Brazil
All series I (1a–u), II (2a–i), and III (3a–j) were previously
synthesized in three steps by our research group (Scheme 1)
and evaluated as antituberculosis class (Cardoso et al.
2014). The series IV (4a–k) were synthesized by the same
strategy (Scheme 1) and the series V (5a–e) were synthe-
sized using the derivatives from series II and IV (Scheme 2)
(Cardoso et al. 2016).
2
Instituto de Química, Cidade Universitária, Universidade Federal
do Rio de Janeiro, Avenida Athos da Silveira Ramos, 149 Bloco A
- 7° Andar, Rio de Janeiro, RJ 21941-909, Brazil
3
Laboratório de Oncologia Experimental, Universidade Federal do
Ceará, Fortaleza, CE, Brazil
4
FioCruz - Fundação Oswaldo Cruz/ Ceará, Av. Santos Dumont,
5753 - Papicu, Fortaleza, CE 60176-032, Brazil

Med Chem Res
Fig. 1 Synthesized thiophene
derivatives identified with
anticancer activity
Scheme 1 Reagents and
conditions: a (6); MeOH, r.t, 4 h,
100%; (7); SOCl2, MeOH, 0 °C-
r.t., 3 h, 96%; b N2H4·H2O
(55%), EtOH, 80 °C, 2 h, 75%
(8), 18 h, 80% (9); c EtOH,
appropriate aldehyde, r.t, 1–72
h, 52–87%
Scheme 2 Reagents and
conditions: a K2CO3, CH3I,
acetone, 40 °C, 2–24 h, 65–89%
that induced 50% cell GI (IC50) in vitro anticancer activity
against four human cancer cell lines: OVCAR-8 (human
ovary), SF-295 (glioblastoma), HCT-116 (colon) and HL-
60 (leukemia), using the MTT assay. The concentrations
(μM) that induced 50% cell GI (IC50) are in Table 1.
Initially, we synthesized series I and II; based on their
large cytotoxicity to human cells, found in our previous
study (Cardoso et al. 2014), we now suggest an evaluation
of their potential activity against cancer cell lines. Because
of poor results from the first synthesized series (I and II),
we propose a new series (III) by maintaining important
substituents and their positions, although we include other
substituents at different positions in benzene.
Cytotoxicity against cancer cell lines
All compounds in series I, II, III, IV, and V were tested
in vitro against three cancer cell lines: SF-295 (glio-
blastoma), OVCAR-8 (human ovary), and HCT-116 (colon)
(National Cancer Institute, Bethesda, MD) at 5 μg/mL using
an MTT assay. The compounds were then classified by the
percentage of growth inhibition (GI) displayed, i.e., at least
one active cell line (100% GI), moderately active (75% <
GI < 100%), or inactive (GI < 50%).
Compounds which presented more than 96% GI in
5 μg/mL were selected to determine the concentrations (µM)

Med Chem Res
Table 1 Cytotoxic activity of
compounds with GI > 96%
[IC50 (µM)] on tumor cell lines
Compounds
IC50
HCT-116
OVCAR-8
HL-60
SF-295
2a (5-NO2-furan-2-yl)
5.43
6.02
5.36
10.73
6.71
3.30
1.46
3.57
3.11
4.00
6.86
5.99
9.44
9.70
0.23
3.39
1.13
5.26
7.32
5.80
2.56
0.83
2.28
2.97
2.17
4.15
1.67
3.81
10.55
0.49
6.86
6.57
1.24
5.43
12.21
1.29
0.51
1.04
0.82
0.92
1.38
1.93
1.76
8.44
0.04
12.90
10.37
5.71
6.82
10.00
4.32
1.34
1.43
5.36
1.49
5.49
6.66
5.80
11.24
0.42
2b (5-NO2-thien-2-yl)
3a (R = 2,3-diOH)
3e (R = 2-OH, 4-Me)
3j (R = 2-OH, 5-NO2)
4a (n = 0; R = H; Ar; R1 = OH)
4b (n = 0; R = H; Ar; R1 = 2,3-diOH)
4c (n = 0; R = H; Ar; R1 = 2,4-diOH)
4d (n = 0; R = H; Ar; R1 = 2-OH, 3-OMe)
4e (n = 0; R = H; Ar; R1 = 2-OH, 4-OMe)
4f (n = 0; R = H; Ar; R1 = 2-OH, 4-Me)
4g (n = 0; R = H; Ar; R1 = 2-OH, 5-Me)
4h (n = 0; R = H; Ar; R1 = 2-OH, 5-NO2)
5a (n = 0; R = CH3; Het; 5-NO2-furan-2-yl)
Doxorubicin
Fig. 2 Structure–activity
relationship (SAR) for the N-
acylhydrazones containing the
thiophene ring (series I, II, III,
IV, and V)
From this results (series III), we can confirm the
importance of the hydroxyl group at the ortho position of
benzene (Ma et al. 2014). This result suggests that the
mechanism of action of this class is based on the formation
of complexes; hydroxyl groups located in the ortho position
in N-acylhydrazone systems are good metal ligands for iron,
zinc, and copper, which are essential for cell replication (Li
et al. 2014; Gup et al. 2015; Rodríguez-Argüelles et al.
2009).
According to the results from the firsts series (I, II, and
III), we applied strategies from medicinal chemistry, such
as conformational retention, to synthesized series IV and V.
Furthermore, these series (series IV and V) were helpful to
identify the presence of conformers, syn/anti, as discussed
previously (Cardoso et al. 2014).
acylhydrazone, generally increased the activity (Cardoso
et al. 2014). However, the undefined conformation com-
plicated the molecule-enzyme interaction, the results from
series V show the opposite.
The structure–activity relationship (SAR) analysis indi-
cated that the number, position, and type of substituents
attached to the aromatic ring are critical for biological
activity. Considering that, the disubstituted derivatives were
more active than the respective mono. Moreover, the deri-
vatives without the methylene group between N-acylhy-
drazone and the thiophene ring were more active than their
counterparts in the methylene group. Another important
observation was the retention of conformation, syn/anti,
where the derivatives without retention were more active
than the ones with retention (Fig. 2).
When the methylene group between N-acylhydrazones
and the thiophene ring (4a–k) was removed, more deriva-
tives displayed good activity. Furthermore, when the
hydrogen from NH in N-acylhydrazone was substituted
with a methyl group (5a–e) the number of active derivatives
decreased (Table 1).
Conclusion
A series of 57 N-acylhydrazones containing a thiophene
ring were evaluated as a new anticancer class. Compound
4d showed good cytotoxic activity compared with the
reference drug doxorubicin and is an important lead
The retention of conformation, syn/anti, through sub-
stitution of hydrogen for methyl groups in the nitrogen of N-

Med Chem Res
worldwide: IARC CancerBase No. 11 [Internet]. International
Agency for Research on Cancer, Lyon, http://www.who.int/
mediacentre/factsheets/fs297/en/ Accessed 13 January 2016
Gup R, Gökçe C, Aktürk S (2015) Copper(II) complexes with 4-
hydroxyacetophenone-derived acylhydrazones: synthesis, char-
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Li Z, Wu L, Zhang T, Huang Z, Qiu G et al. (2014) N-2-Hydro-
xybenzaldehyde acylhydrazone-Fe(III) complex: synthesis, crys-
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compound in this class. The SAR analysis of this class gave
us important information for further studies. For example,
hydroxyl groups located at the ortho position in N-acylhy-
drazone systems are good ligands for metals this may
indicate that the action mechanism of this class is based on
the formation of complexes, which could inactivate
enzymes involved in abnormal cell division. Furthermore,
the retention of conformation generally decreases the
activity.
Ma J, Zhang G, Han X, Bao G, Wang L et al. (2014) Synthesis and
biological evaluation of benzothiazole derivatives bearing theo-
rtho-hydroxy-N-acylhydrazone moiety as potent antitumor
agents. Arch Pharm Chem 347:936–949
Acknowledgement The authors would like to acknowledge CNPq
and Fiocruz for financial and infrastructure assistance.
Montenegro RC, Lotufo LVC, Moraes MO, Pessoa C, Rodrigues FAR
et al. (2012) Synthesis and antitumoral evaluation of benzyl
(1S)-2-[2-(monosubstituted-benzylidene)hydrazino]-1-(hydroxy
methyl)-2-oxo-ethylcarbamate. Lett Drug Des Discov
9:257–262
Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of
interest.
Palkowitz AD, Glasebrook AL, Thrasher KJ, Hauser KL, Short LL
et al. (1997) Discovery and synthesis of [6-Hydroxy-3-[4-[2-(1-
piperidinyl)ethoxy]phenoxy]-
thiophene: a novel, highly potent, selective estrogen receptor
modulator 8. J Med Chem 40:1407–1416
2-(4-hydroxyphenyl)]benzo[b]
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