Synthesis and in vitro antimycobacterial activity of N1-nicotinoyl-3-(4′-hydroxy-3′-methyl phenyl)-5-[(sub)phenyl]-2-pyrazolines

Article abstract of DOI:10.1016/j.bmcl.2006.05.024

A series of N¹-nicotinoyl-3- (4′-hydroxy-3′-methyl phenyl)-5-(substituted phenyl)-2-pyrazolines were synthesized by the reaction between isoniazid (INH) and chalcones and were tested for their antimycobacterial activity in vitro against Mycobac

Full text of DOI:10.1016/j.bmcl.2006.05.024

Bioorganic & Medicinal Chemistry Letters 16 (2006) 3947–3949
Synthesis and in vitro antimycobacterial activity of N1-nicotinoyl-3-
(40-hydroxy-30-methyl phenyl)-5-[(sub)phenyl]-2-pyrazolines
Mohammad Shaharyar,a Anees Ahamed Siddiqui,a Mohamed Ashraf Ali,a
Dharmarajan Sriramb,* and Perumal Yogeeswarib
aFaculty of Pharmacy, Jamia Hamdard University, Department of Pharmaceutical Chemistry,
Hamdard Nagar, New Delhi-110062, India
bMedicinal Chemistry Research Laboratory, Pharmacy group, Birla Institute of Technology and Science, Pilani-333031, India
Received 2 March 2006; revised 24 April 2006; accepted 8 May 2006
Available online 24 May 2006
Abstract—A series of N1-nicotinoyl-3- (40-hydroxy-30-methyl phenyl)-5-(substituted phenyl)-2-pyrazolines were synthesized by the
reaction between isoniazid (INH) and chalcones and were tested for their antimycobacterial activity in vitro against Mycobacterium
tuberculosis H37Rv (MTB) and INH-resistant M. tuberculosis (INHR-MTB) using the agar dilution method. Among the synthe-
sized compounds, compound (i) N1-nicotinyl-3-(40-hydroxy-30-methyl phenyl)-5-(100-chlorophenyl)-2-pyrazoline was found to be
the most active agent against MTB and INHR-MTB, with minimum inhibitory concentration of 0.26 lm. When compared to
INH-compound i was found to be 2.8- and 43.7-fold more active against MTB and INHR-MTB, respectively.
Ó 2006 Elsevier Ltd. All rights reserved.
Tuberculosis (TB) is considered by the WHO to be the
most important chronic communicable disease in the
world.1 The emergence of AIDS, decline of socioeco-
nomic standards and a reduced emphasis on tuberculosis
control programs contribute to the disease’s resurgence
in industrialized countries.2 In most parts of the world,
we are limited to combinations of five drugs to treat
TB effectively, namely rifampicin, isoniazid (INH),
ethambutol, streptomycin and pyrazinamide. Problems
in the chemotherapy of tuberculosis arise when patients
develop bacterial resistance to any of these first-line
drugs and because second-line drugs, such as ethiona-
mide, aminosalicylic acid, cycloserine, amikacin, kana-
mycin and capreomycin are too toxic and cannot be
employed simultaneously.3 Resistance of Mycobacterium
tuberculosis (MTB) strains to antimycobacterial agents is
an increasing problem worldwide.4–6 The key tasks for
an antituberculosis regimens are (a) the development of
long-acting drugs with large dosage intervals in order
to facilitate Directly Observed Treatment Short Course
(DOTS) and enhance patient compliance; (b) the preven-
tion of multidrug-resistant MTB (MDR-TB) strains
using drugs that exhibit potent early microbicidal
activity; and (c) the eradication of slowly metabolizing
and, if possible, dormant populations of MTB organisms
that cause relapse, using new classes of antituberculous
drugs. Despite the current use of rifampicin and pyrazin-
amide, therapy for TB requires at least 6 months. To
decrease the risk of bacteriological reactivation of TB,
long-term therapies for more than 6 months are generally
needed. This frequently leads to patient non-adherence,
thereby causing the emergence/increase of MDR-MTB
strains. Notably, the cost of treating MDR-TB patients
is much greater than that for patients carrying drug-
susceptible MTB strains. In addition, there are thought
to be two billion people latently infected with TB, more
are exposed. Because dormant types of MTB organisms
may survive in vivo for as long as several decades, new
drugs effective against dormant MTB organisms would
be highly useful in preventing bacteriological reactiva-
tion of MTB in such populations. Thus, the development
of new anti-TB drugs that are effective against a persis-
tent MTB infection is urgently desired. Among the stan-
dard antimycobacterial agents, in spite of toxicity on
repeated dosing isoniazid (INH) is still considered to
be a first-line drug for chemotherapy of tuberculosis.7
On the other hand, pyrazoline derivatives were active
against many mycobacterias.8,9 The current work
describes the incorporation of INH in a pyrazoline
Keywords: Antimycobacterial activity; Pyrazolines.
*
Corresponding author. Tel.: +91 1596 244684; fax: +91 1596
244183; e-mail: dsriram@bits-pilani.ac.in
0960-894X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2006.05.024

3948
M. Shaharyar et al. / Bioorg. Med. Chem. Lett. 16 (2006) 3947–3949
moiety and screen its antimycobacterial activity against
M. tuberculosis H37Rv and INH-resistant M. tuberculosis
(INHR-MTB).
The purity of the compounds was checked by TLC
and elemental analyses. Both analytical and spectral
data (1H NMR, IR) of all the synthesized compounds
were in full agreement with the proposed structures. In
general, Infrared spectra (IR) revealed OH, C@O,
C@N and CAN peak at 3307, 1640, 1590 and
1320 cmꢀ1, respectively. In the nuclear magnetic reso-
nance spectra (1H NMR) the signals of the respective
protons of the prepared titled compounds were verified
on the basis of their chemical shifts, multiplicities and
coupling constants. The spectra showed a singlet at d
2.2 ppm corresponding to methyl group; singlet at d
2.57 ppm corresponding to C4-methylene group; singlet
at d 5.78 ppm corresponding to C5 proton; and multi-
plet at d 8.22–8.5 ppm for pyridyl proton. The elemental
N1-Nicotinoyl-3-(40-hydroxy-30-methyl phenyl)-5-[(sub-)
phenyl]-2-pyrazolines a–k described in this study are
shown in Table 1, and a reaction sequence for the prep-
aration is outlined in Scheme 1. The required chalcones
were prepared by reacting 3-methyl-4-hydroxy acetoph-
enone with appropriate aldehyde in presence of base by
conventional Claisen-Schmidt condensation. Reaction
between chalcone with isonicotinyl hydrazide in ethano-
lic solution in the presence of glacial acetic acid (reaction
time varies from 8 to 14 h) afforded titled thiazolines a–k
in 65–94% yield after recrystallization with methanol.
Table 1. Physical constants and antimycobacterial activity of the synthesized compounds
N
CH3
N
OH
O
N
R
a-k
Compound
R
Yield (%)
MP (°C)
Molecular formula
Molecular weight
MIC (lM)
MTBa
MTBb
a
4-Methoxy phenyl-
4-Chloro phenyl-
4-Dimethylamino phenyl-
Phenyl-
72
78
66
80
82
86
94
86
80
78
65
—
119
166
110
140
138
186
152
146
194
212
112
—
C23H21N3O3
C22H18ClN3O2
387.4
391.8
400.47
357.4
417.4
447.4
347.3
375.3
391.8
426.2
402.4
—
16.13
1.99
1.95
8.73
1.87
3.93
0.58
0.27
0.26
0.47
15.53
0.73
8.05
3.98
1.95
4.36
0.93
0.87
0.58
0.54
0.26
0.23
7.75
11.37
b
c
C24H24N4O2
C22H19N3O2
C24H23N3O4
d
e
3,4-Dimethoxy phenyl-
2,3,4-Trimethoxy phenyl-
Furyl-
f
C
C
25H25N3O5
20H17N3O3
g
h
4-Fluoro phenyl-
2-Chloro phenyl-
2,6-Dichloro phenyl-
3-Nitro Phenyl-
—
C22H18FN3O2
C22H18ClN3O2
i
j
C22H17Cl2N3O2
C22H18N4O4
—
k
INH
a Mycobacterium tuberculosis H37Rv.
b INH-resistant Mycobacterium tuberculosis.
CH3
CH3
R
OH
INH
OH
NaOH
+
R-CHO
N
CH3COOH
C2H5OH
H3C
O
O
CH3
OH
N
O
N
R
a-k
Scheme 1. Protocol for the synthesis of N1-nicotinoyl-3-(40-hydroxy-30-methyl phenyl)-5-[(sub)phenyl]-2-pyrazolines.

M. Shaharyar et al. / Bioorg. Med. Chem. Lett. 16 (2006) 3947–3949
3949
analysis results were within 0.4% of the theoretical
values.
a formazan product using the Promega Cell Titer 96
non-radioactive cell proliferation assay.11 These com-
pounds were found to be non-toxic till 62.5 lg/mL.
The synthesized compounds a–k were tested for their
antimycobacterial activity in vitro against MTB and
INHR-MTB by agar dilution method in Middlebrook
7H11 supplemented with OADC media (Hi-Media)
using double dilution technique (drug concentrations of
12.5, 6.25, 3.125, etc.) similar to that recommended by
the National Committee for Clinical Laboratory Stan-
dards10 for the determination of minimum inhibitory
concentration (MIC). The INHR-MTB clinical isolate
was obtained from Tuberculosis Research Center, Chen-
nai, India. The MIC was defined as the minimum concen-
tration of compound required to inhibit 99% of bacterial
growth and MIC’s of the compounds are reported in
Table 1 with standard drug INH for comparison.
Among the newer derivatives, compound i showed a
promising activity in vitro. It is conceivable that these
derivatives showing antimycobacterial activity can be
further modified to exhibit better potency than the stan-
dard drugs. Further studies to acquire more information
about structure–activity relationships are in progress in
our laboratory.
References and notes
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