Synthesis and anti-mycobacterial activity of (E)-N′-(monosubstituted-benzylidene)isonicotinohydrazide derivatives

Article abstract of DOI:10.1016/j.ejmech.2007.08.003

A series of 22 (E)-N′-(monosubstituted-benzylidene)isonicotinohydrazide derivatives have been synthesized and evaluated for their in vitro antibacterial activity against Mycobacterium tuberculosis H₃₇Rv using Alamar Blue susceptibility test and

Full text of DOI:10.1016/j.ejmech.2007.08.003

Available online at www.sciencedirect.com
European Journal of Medicinal Chemistry 43 (2008) 1344e1347
http://www.elsevier.com/locate/ejmech
Preliminary communication
Synthesis and anti-mycobacterial activity of
(E )-N0-(monosubstituted-benzylidene)isonicotinohydrazide derivatives
Maria Cristina da Silva Lourenc¸o a, Marcelle de Lima Ferreira b,
b,
Marcus Vinıcius Nora de Souza , Monica Amado Peralta ,
b
*
´
ˆ
Thatyana Rocha Alves Vasconcelos c, Maria das Grac¸as M.O. Henriques b
a Fundac¸~ao Oswaldo Cruz, Instituto de Pesquisas Cl´ınicas Evandro Chagas, Departamento de Bacteriologia,
Av. Brasil, 4365, Manguinhos, Rio de Janeiro, Brazil
b Fundac¸~ao Oswaldo Cruz, Instituto de Tecnologia em Fa´rmacos, Rua Sizenando Nabuco, 100, Manguinhos, 21041-250 Rio de Janeiro, Brazil
c Universidade Federal Fluminense, Instituto de Qu´ımica, Departamento de Qu´ımica Orgaˆnica,
Outeiro de S~ao Jo~ao Batista, s/no, Centro, Nitero´i, CEP 24020-150 Rio de Janeiro, Brazil
Received 10 July 2007; received in revised form 22 August 2007; accepted 24 August 2007
Available online 2 September 2007
Abstract
A series of 22 (E )-N0-(monosubstituted-benzylidene)isonicotinohydrazide derivatives have been synthesized and evaluated for their in vitro
antibacterial activity against Mycobacterium tuberculosis H37Rv using Alamar Blue susceptibility test and the activity expressed as the minimum
inhibitory concentration (MIC) in mg/mL. Compounds 2f, 2g, 2j, 2k and 2q exhibited a significant activity (0.31e0.62 mg/mL) when compared
with first line drugs such as isoniazid (INH) and rifampicin (RIP) and could be a good starting point to develop new lead compounds in the fight
against multi-drug resistant tuberculosis.
Ó 2007 Elsevier Masson SAS. All rights reserved.
Keywords: Isoniazid; Derivatives; Anti-mycobacterial; Mycobacterium tuberculosis
1. Introduction
tuberculosis (MDR TB) that arise from inconsistent or partial
treatment [1e7]. At present, according to statistics, TB kills
four people every minute somewhere in the world and accounts
about two million deaths per year. It is estimated that one-third
of the world’s population is currently infected with the TB bacil-
lus and 30 million people will die in the next 10 years [8]. In this
context, there is an urgent need for new drugs to fight against this
disease. Considering that there are three basic objectives in-
volved in the development of new tuberculosis drugs; to reduce
the total duration of treatment, to improve the MDR TB and to
provide more effectivetreatment of latent tuberculosis infection.
In the search of new compounds, isoniazid derivatives
have been found to possess potential tuberculostatic activi-
ties [4,9e15]. Studies suggest that isoniazid, a prodrug
which is converted into its active form by mycobacterial
catalaseeperoxidase, acts on the mycobacterial cell wall
by preventing the FAS-II (fatty acid synthetase II) system
Tuberculosis (TB) is a chronic bacterial infection, spread
through the air, and caused by a bacterium called Mycobacte-
rium tuberculosis, first identified in 1882 by Robert Koch, which
can mainly attack the lungs, although can affect other organs as
well. Unfortunately, nowadays TB is becoming again a world-
wide problem, declared in 1993 by the World Health Organiza-
tion (WHO), a global health emergency. The resurgence of TB
became a serious world-wide problem during the period
1985e1992, particularly in people infected with the HIV virus.
However, there are also other problems that contribute to the in-
creasing incidence of TB nowadays, such as immigration, war,
famine, the lack of new drugs, and multi-drug-resistant
* Corresponding author. Tel.: þ552139772404; fax: þ552125602518.
E-mail address: marcos_souza@far.fiocruz.br (M.V.N. de Souza).
0223-5234/$ - see front matter Ó 2007 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2007.08.003

M.C. da S. Lourenc¸o et al. / European Journal of Medicinal Chemistry 43 (2008) 1344e1347
1345
from producing long chain fatty acid precursors for mycolic
acid synthesis [16,17].
at 140.6e140.0 ppm. The lipophilicities of the synthesized
compounds 2aev and the standard drugs (INH and RIP),
which were expressed as log P values, were determined
through CSlogP method, a commercially available program
(Table 1).
As part of a current work of synthesis, anti-mycobacterial
investigation and crystallographic studies of isoniazid deriva-
tives [18e20], the aim of this article is to present a series of
22 (E )-N0-(monosubstituted-benzylidene)isonicotinohydrazide
derivatives, which have been synthesized, see Scheme 1, and
evaluated for their in vitro antibacterial activity against
M. tuberculosis (Table 1).
2.2. Anti-mycobacterial activity
The anti-mycobacterial activities of compounds 2aev were
assessed against M. tuberculosis ATTC 27294 [21] using the
micro plate Alamar Blue assay (MABA) [22] (Table 1). This
methodology is nontoxic, uses a thermally-stable reagent
and shows good correlation with proportional and BACTEC
radiometric methods [23,24]. Briefly, 200 mL of sterile deion-
ized water was added to all outer-perimeter wells of sterile 96
well plates (falcon, 3072: Becton Dickinson, Lincoln Park,
NJ) to minimize evaporation of the medium in the test wells
during incubation. The 96 plates received 100 mL of the Mid-
dlebrook 7H9 broth (Difco laboratories, Detroit, MI, USA)
and a serial dilution of the compounds 2aev was made di-
rectly on the plate. The final drug concentrations tested were
0.01e20.0 mg/mL. Plates were covered and sealed with paraf-
ilm and incubated at 37 ꢁC for five days. After this time, 25 mL
of a freshly prepared 1:1 mixture of Alamar Blue (Accumed
International, Westlake Ohio) reagent and 10% tween 80
was added to the plate and incubated for 24 h. A blue color
in the well was interpreted as no bacterial growth, and
a pink color was scored as growth. The MIC (minimal inhibi-
tion concentration) was defined as the lowest drug concentra-
tion, which prevented a color change from blue to pink.
2. Results and discussion
2.1. Chemistry
The synthesis of (monosubstituted-benzylidene)isonicoti-
nohydrazide derivatives involved the reaction between
appropriate monossubstituted benzaldehydes (1aev) and
isoniazid, as described in the general procedure. Reaction
mixtures were maintained at room temperature, leading to
the desired compounds 2aev in 70e91% yields. All the
compounds were identified by spectral data. In general, IR
spectra showed the CaO peak at 1651e1703 and the NH
stretching vibrations at 3013e3213 cmꢀ1. In the nuclear
magnetic resonance spectra (1H NMR) the signals of the re-
spective protons of the synthesized compounds were verified
on the basis of their chemical shifts, multiplicities and cou-
pling constants. The spectra showed the hydrazide (NH)
proton as a singlet at 12.42e11.94 ppm and the imine pro-
ton (NaCeH) at 8.89e8.40 ppm. The 13C NMR spectrum
showed the CaO signals at 162.0e161.4 and CaN signals
R
O
O
CHO
N
NHNH2
NH
1a-v
R
N
EtOH/H2O
r.t., 1-3 h
N
2a-v (70-91%)
isoniazid
R = H
R = 3-CN
R3 = 4-CN
2a
2b
2c
2d
2e
2f
2l
R = 2-Br
R = 3-Br
R = 4-Br
R = 2-Cl
R = 3-Cl
2m
2n
2o
2p
2q
R = 2-NO2
R = 3-NO2
R = 4-NO2
R = 2-OCH3
R = 3-OCH3
R = 4-Cl
R = 2-F
R = 3-F
2g
2h
2i
2r
2s
2t
R = 4-OCH3
R = 2-OCH2CH3
R2 = 3-OCH2CH3
R = 3-OH
R = 4-F
2j
2u
2v
R = 2-CN
2k
Scheme 1. Synthetic route used for the preparation of isoniazid derivatives 2aev.

1346
M.C. da S. Lourenc¸o et al. / European Journal of Medicinal Chemistry 43 (2008) 1344e1347
Table 1
The in vitro activity of compounds 2aev against M. tuberculosis H37Rv strain
(ATCC 27294, susceptible both to rifampin and isoniazid)
Table 2
Data of cytotoxic effects of test compounds on murine macrophages cells 18 h
after the treatment
Number
Compound
MIC (mg/mL)
log Pa
Compound
% Cell viability/dose (mg/mL)
2a
2b
2c
2d
2e
2f
R ¼ H
3.12
5.0
2.34
3.00
3.11
3.12
2.91
3.05
2.86
2.15
2.48
2.34
2.22
2.26
2.28
2.01
1.95
2.00
2.38
2.44
2.49
2.88
2.96
2.54
ꢀ0.58
ꢀ2.38
0.1
1.0
10
100
R ¼ 2-Br
R ¼ 3-Br
R ¼ 4-Br
R ¼ 2-Cl
R ¼ 3-Cl
R ¼ 4-Cl
R ¼ 2-F
2f
100
100
100
100
100
100
97
100
97
100
96
2.5
5.0
2g
2j
100
100
100
97
96
95
1.25
0.31
0.31
3.12
3.12
0.31
0.62
1.25
5.0
2k
2q
100
100
98
2g
2h
2i
and 2k (o-cyanophenyl) (MIC ¼ 0.62 mg/mL) exhibited a sig-
nificant activity when compared with first line drugs such as
isoniazid (INH, MIC ¼ 0.2 mg/mL) and rifampicin (RIP,
MIC ¼ 1.0 mg/mL). These results suggest that they may be se-
lectively targeted to M. tuberculosis growth, also considering
that they were not cytotoxic to host cells at the same concen-
tration. Alluding to studies involved structure, metabolism and
anti-tuberculosis in vitro activity of isoniazid derivatives, these
compounds can be considered original isoniazid derivatives
prodrugs since hydrazides are cleaved into isonicotinic acid,
that is the bioactive form of isoniazid [5].
In the 1950s, several 20-monosubstituted isonicotinoylhy-
drazides were synthesized, however, few information about
elucidation, conformation and biological activity was reported
[26]. In the present work all the compounds have been also
characterized through precise analytical methods.
R ¼ 3-F
2j
R ¼ 4-F
2k
2l
R ¼ 2-CN
R ¼ 3-CN
R3 ¼ 4-CN
R ¼ 2-NO2
R ¼ 3-NO2
R ¼ 4-NO2
R ¼ 2-OCH3
R ¼ 3-OCH3
R ¼ 4-OCH3
R ¼ 2-OCH2CH3
R2 ¼ 3-OCH2CH3
R ¼ 3-OH
e
2m
2n
2o
2p
2q
2r
2s
5.0
5.0
1.25
0.31
5.0
5.0
2t
1.25
1.25
1.25
0.2
2u
2v
INH
RIP
a
e
1.0
Calculated using online www.logp.com site.
Information about structureeactivity relationship (QSAR),
and their in vivo antibacterial activity test are in progress in
our laboratory.
2.3. Cell viability assay
Cellular viability in the presence and absence of test
compounds was determined by Mosmans’s MTT(3-(4,5-
dimethylthylthiazol-2yl)-2,5-dimethyl tetrazolium bromide;
Merck) microcultured tetrazolium assay [25]. The cells were
plated in flat bottom 96 well plates (2.5 ꢂ 106 cells/mL) cul-
tured for 1 h in a controlled atmosphere (CO2 5% at 37 ꢁC),
and nonadherent cells were washed by gentle flushing with
RPMI 1640. Adherent cells were cultured in the presence of
medium alone, tween 20 (3%) (live and dead controls, respec-
tively) or different concentrations of compounds (0.1, 1.0, 10.0
and 100 mg/mL) in a triplicate assay. After 18 h, stock MTT
solution (5 mg/mL of saline; 20 mL/well) was added to the cul-
ture and 4 h later supernatant was discharged and DMSO
(100 mL/well) was added for formazan crystals’ solubilization
and the absorbance was read at 540 nm in a plate reader
(Biorad e 450).
4. Experimental
4.1. Materials and methods
Melting points were determined on a Buchi apparatus and are
uncorrected. Infrared spectra were recorded on a Thermo Nicolet
Nexus 670 spectrometer as potassium bromide pellets and fre-
quencies are expressed in cmꢀ1. Mass spectra (CG/MS) were
recorded on a Agilent Technologies 6890/5972A mass spectrom-
eter. NMR spectra were recorded on a Bruker Avance 500 spec-
trometer operating at 500.00 MHz (1H) and 125.0 MHz (13C),
in deuterated dimethylsulfoxide. Chemical shifts are reported in
ppm (d) relative to tetramethylsilane. Proton and carbon spectra
were typically obtained at room temperature. For TLC, plates
coated with silica gel were run in chloroform/methanol mixture
and spots were developed in ultraviolet.
The results were represented as percentage cell viability
(Table 2). This table shows that the compounds 2aev were
not cytotoxic to host cells at the same concentration.
4.2. General procedures for the synthesis of
(E )-N0-(monosubstituted-benzylidene)isonicotinohydrazide
(2aev)
3. Conclusion
The synthesis of the 22 isonicotinohydrazide derivatives (2ae
v), among them three are unpublished (2k, 2l and 2u), was per-
formed with good yields from commercially available materials.
In relation to the biological studies, it was found that the
compounds 2f (m-chlorophenyl), 2g ( p-chlorophenyl), 2j
( p-fluorophenyl)), 2q (o-methoxyphenyl) (MIC ¼ 0.31 mg/mL)
The isonicotinoyl hydrazide derivatives 2aev were pre-
pared by reaction between the appropriate benzaldehyde
1aev (1.0 equiv.) with isoniazid (1.0 equiv.) in ethanol/H2O
(10 mL), initially dissolving the isoniazid in H2O and adding
the respective solution over a solution of the respective

M.C. da S. Lourenc¸o et al. / European Journal of Medicinal Chemistry 43 (2008) 1344e1347
1347
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at room temperature, the resulting mixture was concentrated
under reduced pressure. The residue purified by washing
with cold ethyl alcohol and ethyl ether, afforded the pure
derivatives 2aev.
´
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4.3.1. (E )-N0-(2-Cyanobenzylidene)isonicotinohydrazide(2k)
Yield: 70%; m.p.: 160e162 ꢁC. CG/MS: m/z [M]þꢃ: 250.
1H NMR [500.00 MHz (FIDRES ꢄ 0.15 Hz), DMSO-d6] d:
12.43 (1H; s; NH ); 8.86 (1H; s; NaCeH); 8.82 (2H; d;
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`
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J ¼ 5.2 Hz; H2 and H6); 8.15 (1H; d; J ¼ 8.0 Hz; H3 ); 7.93
0
(1H; d; 7.6 Hz; H6 ); 7.88 (2H; d; J ¼ 5.2 Hz; H3 and H5);
`
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0
7.81 (1H; dd; J ¼ 7.2 and 8.0 Hz; H5 ); 7.64 (1H; dd; J ¼ 7.6
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0
161.7; 150.2; 144.3; 140.2; 136.6; 133.6; 133.4; 130.7;
125.8; 121.6; 116.9; 111.1 ppm. IR nmax (cmꢀ1; KBr pellets):
3198 (NH); 2225 (CN); 1703 (CO).
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`
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4.3.2. (E)-N0-(3-Cyanobenzylidene)isonicotinohydrazide (2l)
Yield: 79%; m.p.: 169e170 ꢁC. CG/MS: m/z [M]þꢃ: 250. 1H
NMR [500.00 MHz (FIDRES ꢄ 0.15 Hz), DMSO-d6] d: 12.19
(1H; s; NH ); 8.73 (2H; d; J ¼ 5.5 Hz; H2 and H6); 8.48 (1H; s;
`
2211.
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´
´
[17] H. Marrakchi, G. Laneelle, A. Quemard, Microbiology 146 (2000)
0
0
289e296.
NaCeH); 8.08 (1H; s; H2 ); 8.01 (1H; d; J ¼ 8.0 Hz; H4 );
´
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7.82 (2H; d; J ¼ 5.5 Hz; H3 and H5); 7.71 (1H; d; J ¼ 7.5 Hz;
H6 ); 7.56 (1H; dd; J ¼ 8.0 and 8.0 Hz; H5 ) ppm. 13C NMR
(125 MHz, DMSO-d6) d: 161.8; 150.4; 146.7; 140.2; 135.4;
133.6; 131.1; 131.0; 130.1; 121.5; 118.3; 112.1 ppm. IR nmax
(cmꢀ1; KBr pellets): 3213 (NH); 2230 (CN); 1673 (CO).
0
0
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NMR [500.00 MHz (FIDRES ꢄ 0.15 Hz), DMSO-d6] d: 12.08
(1H; s; NH ); 8.79 (2H; d; J ¼ 6.0 Hz; H2 and H6); 8.43 (1H; s;
NaCeH); 7.82 (2H; d; J ¼ 6.0 Hz; H3 and H5); 7.38 (1H; dd;
´
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0
0
0
J ¼ 7.5 and 8.0 Hz; H5 ); 7.30 (1H; d; J ¼ 7.5 Hz; H4 or H6 );
0
0
7.28 (1H; s; H2 ); 7.02 (1H; dd; J ¼ 2.0 and 8.0 Hz; H6 or
0
H4 ); 4.08 (2H; q; J ¼ 7.0 Hz; OCH2CH3); 1.35 (3H; t;
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J ¼ 7.0 Hz; OCH2CH3) ppm. 13C NMR (125 MHz, DMSO-
d6) d: 161.6; 158.8; 150.3; 148.9; 140.4; 135.4; 130.0; 121.5;
120.0; 116.9; 112.0; 63.2; 14.6 ppm. IR nmax (cmꢀ1; KBr pel-
lets): 3076 (NH); 1651 (CO).
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