Synthesis and antimycobacterial activity of novel 4-[5-(substituted phenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methylphenol derivatives

Article abstract of DOI:10.1007/s00044-007-9000-4

In the present investigation, 4-hydroxy-3-methylacetophenone, on condensation with appropriate aldehydes in methanolic potassium hydroxide solution, yielded the corresponding chalcones (C_I-XI). These corresponding chalcones were reacted with ph

Full text of DOI:10.1007/s00044-007-9000-4

Med Chem Res (2007) 15:463–470
DOI 10.1007/s00044-007-9000-4
Synthesis and antimycobacterial activity of novel
4-[5-(substituted phenyl)-1-phenyl-4,5-dihydro-1H-3-
pyrazolyl]-2-methylphenol derivatives
Mohamed Ashraf Ali Æ Mohammad Shahar Yar
Received: 10 October 2006 / Accepted: 9 January 2007 / Published online: 30 June 2007
¨
Ó Birkhauser Boston 2007
Abstract In the present investigation, 4-hydroxy-3-methylacetophenone, on con-
densation with appropriate aldehydes in methanolic potassium hydroxide solution,
yielded the corresponding chalcones (CI-XI). These corresponding chalcones were
reacted with phenyl hydrazide in glacial acetic acid, which led to the formation of
novel 4-[5-(substituted phenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methyl-
phenol derivatives. All newly synthesized compounds were evaluated for their
antimycobacterial activities against isoniazid-resistant Mycobacterium tuberculosis
using agar dilution. 4-[5-(4-Fluoro phenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-
2-methylphenol showed good antimycobacterial activity, with a minimum inhibi-
tory concentration of 0.62 mg/ml.
Introduction
Tuberculosis (TB) is by far the most frequently encountered mycobacterial disease
in the world. Among infectious diseases, TB is the number one killer, with more
than 2 million casualties annually worldwide. Mycobacteria are ubiquitous
organisms that are becoming increasingly important intracellular pathogens that
establish an infection in oxygen-rich macrophages of the lung (O’Brien and Nunn,
2001). The emergence of acquired immunodeficiency syndrome (AIDS), decline of
socioeconomic standards, and a reduced emphasis on tuberculosis control programs
contribute to the resurgence of the disease in industrialized countries (Barnes et al.,
1991). Resistance of Mycobacterium tuberculosis strains to antimycobacterial
M. A. Ali ꢀ M. S. Yar (&)
Faculty of Pharmacy, Jamia Hamdard University, Department of Pharmaceutical Chemistry,
Hamdard Nagar, New Delhi 110062, India
e-mail: yarmsy@rediffmail.com

464
Med Chem Res (2007) 15:463–470
agents is an increasing problem worldwide (Schaberg et al., 1996; Fujiwara et al.,
1997; Sbarbaro, 1997). However, powerful new anti-TB drugs with new mecha-
nisms of action have not been developed in the last 40 years. In spite of severe
toxicity on repeated dosing, isoniazid (INH) is still considered a first-line drug for
chemotherapy of tuberculosis (Blair et al., 1985). A literature survey revealed
pyrazoline derivatives are active against many mycobacteria (Nauduri and Reddy,
1998; Kucukguzel et al., 2000; Shenoy et al., 2001; Kucukguzel and Rolla, 2002).
The current work describes the synthesis of novel pyrazoline moiety with
encouraging antimycobacterial activity against INH-resistant M. tuberculosis.
Results and Discussion
Chemistry
The synthesis of chalcone and new 4-[5-(substituted phenyl)-1-phenyl-4,5-dihydro-
1H-3-pyrazolyl]-2-methylphenol derivatives was carried via the steps shown in
Scheme 1. In the initial step, chalcones were synthesized by condensing 4-hydroxy-
3-methylacetophenone with appropriate aromatic aldehydes in dilute methanolic
potassium hydroxide solution at room temperature. The 4-[5-(substituted phenyl)-1-
phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methylphenol(PI-XI) compounds were syn-
thesized via cyclocondensation with phenyl hydrazine in glacial acetic acid. The
purity of the compounds was checked via thin-layer chromatography (TLC) using
various mobile bases and elemental analyses. Both analytical and spectral data (1H
nuclear magnetic resonance [NMR], infrared [IR] spectroscopy) of all the
synthesized compounds were in full agreement with the proposed structures.
NHNH2
CH3
CH3
R
OH
OH
KOH
+
R-CHO
CH3COOH
CH3OH
H3C
CI-CXI
O
O
CH3
N
N
OH
R
PI-PXI
Scheme 1 Protocol for the synthesis novel 4-[2-(substituted phenyl)-3-phenyl-2,3-dihydro-1H-5-
pyrazolyl]-2-methylphenol derivatives

Med Chem Res (2007) 15:463–470
465
Antimycobacterial activity
The synthesized compounds (PI-XI) were tested for their antimycobacterial activity
in vitro against INH-resistant Mycobacterium tuberculosis (INHR-MTB) using the
agar dilution method for the determination of minimum inhibitory concentration
(MIC). The MIC was defined as the minimum concentration of compound required
to inhibit 90% of bacterial growth, and MICs of the compounds are reported in
Table 1 with the standard drug INH for reference.
Among the 11 newly synthesized compounds, 4 compounds were found to be
most active, having an MIC of less than 1 mg/ml. Compound PVII, bearing a 4-
fluorophenyl radical at p-5 of the pyrazoline nucleus, was found to be the most
active one against INHR-MTB at a concentration of 0.62 mg/ml. PXI, PIII, and PIX
showed moderate inhibitory activity, with 0.81 mg/ml, 0.84 mg/ml, 0.92 mg/ml,
respectively. The 4-flurophenyl group substitution (PVII) derivatives displayed
relatively higher inhibitory activity in general. However, electron-rich groups such
as 4-cholrophenyl, 2-chlorophenyl, and 3-nitrophenyl substituted analog compounds
produced moderate in inhibitory activity against INH-resistant Mycobacterium
Table 1 Physical constants and antimycobacterial activity of the synthesized compounds
PI-XI
H3C
R1
HO
N
N
PI-XI
Compound R1
Yield (%) m.p. (8C) Mol. formula Mol. Wt. (MIC) mg/ml
PI
4-Methoxy-phenyl-
4-Chloro-phenyl-
85
82
104
125
102
130
111
118
151
166
174
173
136
–
C22H19ON2
358.43
1.45
1.24
0.84
1.60
1.16
1.86
0.62
1.00
0.92
1.96
0.81
0.63
PII
C22H19ON2Cl 362.85
PIII
PIV
PV
4-Dimethyl-amino phenyl- 76
C24H25ON3
C22H20ON2
C24H24O3N2
C25H27O4N2
371.48
328.41
388.46
418.49
318.37
Phenyl-
65
75
3,4-Dimethoxy-phenyl-
PVI
PVII
PVIII
PIX
PX
3,4,5-Trimethoxy-phenyl- 65
4-Fluoro-phenyl-
2-Chloro-phenyl-
2,6-Dichloro-phenyl-
3-Nitro-phenyl-
2-Furfuryl-
80
86
78
72
80
–
C22H19ON2 F
C22H19ON2Cl 362.85
C22H18ON2Cl2 397.30
C22H19O2N3
C20H18O2N2
–
373.41
346.40
–
PXI
INH
a
–
Recrystallization from ethanol
b
INH-resistant Mycobacterium tuberculosis

466
Med Chem Res (2007) 15:463–470
tuberculosis. On the other hand, the analogue (OCH3) group substituted 4-methoxy
phenyl (PI), 3,4-dimethoxy phenyl (PV), and 30,4,5-trimethoxy phenyl (PVI) showed
relatively moderate to low antitubercular activity.
All compounds were tested for cytotoxicity (IC50) in VERO cells at concentra-
tions of 62.5 mg/ml, or 10-fold. After 72 h of exposure, viability was assessed on the
basis of cellular conversion of MTT (3-(4,5-dimethylthiozole-2yl)-2,5-diphenyl
tetrazolium bromide) assay into a formazan product using the Promega Cell Titer 96
nonradioactive cell proliferation method. Most of the active compounds were found
to be nontoxic until 62.5 mg/ml.
Conclusion
Among the new synthesized 4-[5-(substituted phenyl)-1-phenyl-4,5-dihydro-1H-3-
pyrazolyl]-2-methylphenol derivatives, 4-[5-(4-flurophenyl)-1-phenyl-4,5-dihydro-
1H-3-pyrazolyl]-2-methylphenol (PVII) has the highest antimycobacterial activity
in vitro. It is conceivable that these derivatives showing antimycobacterial activity
can be further modified to exhibit better potency than the standard drugs. Further
studies to acquire more information about structure–activity relationships are in
progress in our laboratory.
Experimental
All chemicals were supplied by E. Merck (Germany) and S.D. Fine Chemicals
(India). Melting points were determined via the open tube capillary method and are
uncorrected. Purity of the compounds was checked on TLC plates (silica gel G) in
the solvent system toluene–ethyl formate–formic acid (5:4:1) and benzene–
methanol (8:2). The spots were located under iodine vapors or UV light. IR
spectrums were obtained on a Perkin Elmer 1720 FT-IR spectrometer (KBr Pellets).
1H NMR spectra were recorded or a Bruker AC 300 MHz spectrometer using
trimethyl silane (TMS) as internal standard in dimethyl sulfoxide (DMSO)–CDCl3,
Mass spectra were recorded on a Bruker Esquire LCMS using ESI, and elemental
analyses were performed on a Carlo Erba 1106 elemental analyzer.
General procedure
Synthesis of 1-(4-hydroxy-3-methylphenyl)-3-(substituted phenyl)-2-propen-1-one
(CI-XI). 4-Hydroxy-3-methylacetophenone (0.01 mol) was dissolved in ethanol.
Next, a solution of potassium hydroxide (30%, 5 ml) and suitable substituted
aldehydes (0.01 mol) in 10 ml of pet. ether was added to the resulting solution with
continuous stirring. The resulting solution was allowed to stand overnight. After 4 h
of stirring, the solution was poured into ice-cold water and neutralized with
hydrochloric acid. The solid product was filtered, dried, and purified from ethanol.
1-(4-Hydroxy-3-methyl-phenyl-3-(4-methoxyphenyl)-2-propen-1-one.
IR: (KBr) cmꢁ1: 3210(OH), 1682 (C=O), 3030 (CH); 1H NMR (DMSO-d6) ppm:
2.2 (3H, s, CH3), 3.9 (3H, s, OCH3), 6.8–7.5 (1Hx2, dd J = 7.5 Hz, 8.5 Hz CH=CH),
7.7–8.2 (7H, s, aromatic), 9.2 (1H, s, OH).

Med Chem Res (2007) 15:463–470
467
1-(4-Hydroxy-3-methylphenyl-3-(4-cholorophenyl)-2-propen-1-one.
1
IR: (KBr) cmꢁ1: 3210 (OH), 782 (C-Cl), 1680 (C=O), 3042 (CH); H NMR
(DMSO-d6) ppm: 2.2 (3H, s, CH3), 6.7–7.2 (1Hx2, dd J = 8.34 Hz, 6.79 Hz
CH=CH), 7.7–8.0 (7H, m, aromatic), 9.2 (1H, s, OH).
1-(4-Hydroxy-3-methylphenyl-3-(4-dimethylaminophenyl)-2-propen-1-one. IR:
1
(KBr) cmꢁ1: 3200 (OH), 1684 (C=O), 3040 (CH); H NMR (DMSO-d6) ppm:
2.2 (3H, s, CH3), 3.9 (6H, s, N (CH3x2), 6.8–7.5 (1Hx2, dd J = 7.61 Hz, 7.63 Hz
CH=CH), 7.6–8.1 (7H, m, aromatic), 9.2 (1H, s, OH).
1-(4-Hydroxy-3-methylphenyl-3-phenyl-2-propen-1-one. IR: (KBr) cmꢁ1
:
3210(OH), 1670 (C=O), 3040 (CH); 1H NMR (DMSO-d6) ppm: 2.2 (3H, s,
CH3), 6.8–7.4 (1Hx2, dd J = 8.28 Hz, 6.70 Hz CH=CH), 7.7–8.2 (8H, m, aromatic),
9.2 (1H, s, OH).
1-(4-Hydroxy-3-methylphenyl-3-(3,4-dimethoxyphenyl)-2-propen-1-one.
1
IR:(KBr) cmꢁ1: 3210 (OH), 1686 (C=O), 3030 (CH); H NMR (DMSO-d6) ppm:
2.2 (3H, s, CH3), 3.9 (6H, s, OCH3 x2), 6.9–7.3 (1Hx2, dd J = 7.45 Hz, 7.29 Hz
CH=CH), 7.6–8.2 (6H, m, aromatic), 9.2 (1H, s, OH).
1-(4-Hydroxy-3-methylphenyl-3-(3, 4, 5 trimethoxyphenyl)-2-propen-1-one. IR:
1
(KBr) cmꢁ1: 3200 (OH), 1680 (C=O), 3040 (CH); H NMR (DMSO-d6 ppm): 9.2
(1H, s, OH), 2.2(3H, s, CH3), 7.7–8.2 (5H, m, aromatic), 3.9 (9H, s, OCH3x3), 6.9–
7.5(1Hx2, dd J = 7.55 Hz, 7.27 Hz CH=CH).
1-(4-Hydroxy-3-methylphenyl-3-(4-fluorophenyl)-2-propen-1-one.
IR: (KBr) cmꢁ1: 3200 (OH), 1680 (C=O), 3040 (CH), 670(C-F); 1H NMR
(DMSO-d6 ppm): 9.2 (1H, s, OH), 2.2 (3H, s, CH3), 7.7–8.2 (7H, m, aromatic), 6.9–
7.5 (1Hx2, dd J = 7.24 Hz, 7.29 Hz -CH=CH).
1-(4-Hydroxy-3-methylphenyl-3-(2-chlorophenyl)-2-propen-1-one.
1
IR: (KBr) cmꢁ1: 3200 (OH), 1680 (C=O), 3040 (CH), 770(C-Cl); H NMR
(DMSO-d6 ppm): 9.2 (1H, s, OH), 2.2 (3H, s, CH3), 7.6–8.0 (7H, m, aromatic), 6.9–
7.5 (1Hx2, dd J = 8.35 Hz, 3.63 Hz -CH=CH).
1-(4-Hydroxy-3-methylphenyl-3-(2, 6 dichlorophenyl)-2-propen-1-one. IR: (KBr)
cmꢁ1: 3200 (OH), 1680 (C=O), 3040 (CH), 770 (C-Cl); 1H NMR (DMSO-d6 ppm):
9.2 (1H, s, OH), 2.2 (3H, s, CH3), 7.7–8.2 (6H, m, aromatic), 6.9–7.5 (1Hx2, dd J =
5.41 Hz, 15.68 Hz CH=CH).
1-(4-Hydroxy-3-methyl-phenyl-3-(3-nitrophenyl)-2-propen-1-one.
IR: (KBr) cmꢁ1: 3200 (OH), 1680 (C=O), 3040 (CH); 1H NMR (DMSO-d6 ppm):
9.2 (1H, s, OH), 2.2 (3H, s, CH3), 7.7–8.2 (7H, m, aromatic), 6.9–7.5 1Hx2, dd J =
5.46 Hz, 16.3 Hz CH=CH).
1-(4-Hydroxy-3-methyl-phenyl-3-furfuryl-2-propen-1-one.
IR:(KBr) cmꢁ1: 3200 (OH), 1680 (C=O), 3040 (CH); 1H NMR (DMSO-d6 ppm):
9.2 (1H, s, OH), 2.2 (3H, s, CH3), 7.7–8.2 (6H, m, aromatic), 7.43–7.48 (3H, m,
furan), 6.9–7.5 (1Hx2, dd J = 3.0 Hz, 8.36 Hz, CH=CH).
General method
Synthesis of novel 4-[5-(substituted phenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-
2-methylphenol (PI-XI). To the solution of (0.002) mol of the appropriate (PI-XI)
derivatives in 15 ml of glacial acetic acid, 0.002 mol phenyl hydrazine was added

468
Med Chem Res (2007) 15:463–470
and the reaction mixture was refluxed for 12 h and cooled. Excess solvent was
removed under reduced pressure, and the reaction mixture was poured on crushed
ice (20 g) to cool. The product obtained was filtered, washed with water, and
recrystallized from methanol.
4-[5-(4-Methoxyphenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methylphenol
1
(PI). IR: (KBr) cmꢁ1: 3307 (OH), 1590 (C=N), 1320 (C-N). H NMR(DMSO-d6)
ppm: 1.8 (3H, s, CH3), 2.5(2H,s,CH2), 3.8 (3H,s,OCH3), 5.2(1H,t,CH), 6.9–
7.9(12H, s, aromatic), 9.6 (1H, s, OH); EI-MS: m/z: 359 (M+); calcd./analyz.: C
(77.07) 77.15, H (6.19) 6.10, N (7.82) 7.80.
4-[5-(4-Chlorophenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methylphenol
1
(PII). IR: (KBr) cmꢁ1: 3307 (OH), 1590 (C=N), 1320 (C-N); H NMR (DMSO-d6)
ppm 1.8 (3H, s, CH3), 2.5(2H, s, CH2), 5.2 (1H, t, CH), 6.9–7.9 (12H, s, aromatic),
9.6 (1H, s, OH); EI-MS: m/z: 362 (M+); calcd./analyz. C (72.82) 72.40, H (5.28)
5.42, N (7.72) 7.74.
4-[5-(4-Dimethylaminophenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methyl-
1
phenol (PIII). IR: (KBr) cmꢁ1: 3307 (OH), 1590 (C=N), 1320 (C-N); H NMR
(DMSO-d6) ppm: 1.8 (3H, s, CH3), 2.3 (6H, s, N-(CH3)2), 2.5 (2H, s, CH2), 5.2 (1H,
t, CH), 6.9–7.9 (12H, s, aromatic), 9.6 (1H, s, OH); EI-MS: m/z: 372 (M+1); calcd./
analyz.: C (77.60) 77.64, H (6.78) 6.76, N (11.31) 11.34.
4-(1,5-Diphenyl-4,5-dihydro-1H-3-pyrazolyl)-2-methylphenol (PIV).
1
IR: (KBr) cmꢁ1: 3307 (OH), 1590 (C=N), 1320 (C-N). H NMR (DMSO-d6)
ppm: 1.8 (3H, s, CH3), 2.5 (2H, s, CH2), 5.2 (1H, t, CH), 6.9–7.9 (13H, s, aromatic),
9.6 (1H, s, OH); EI-MS: m/z: 328 (M+); calcd./analyz. C (80.46) 80.35, H (6.14)
6.12, N (8.53) 8.70.
4-[5-(3,4-Dimethoxyphenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methylphe-
1
nol (PV). IR: (KBr) cmꢁ1: 3307(OH), 1590 (C=N), 1320 (C-N). H NMR (DMSO-
d6) ppm: 2.1 (3H, s, CH3), 2.5 (2H, s, CH2), 3.8 (3H, s, OCH3x2), 5.2 (1H, t, CH),
6.9–7.9 (11H, s, aromatic), 10.3 (1H, s, OH); EI-MS: m/z: 389(M+1); calcd./analyz.:
C (74.21) 74.18, H (6.23) 6.18, N (7.21) 7.28.
4-[5-(3,4,5-Trimethoxyphenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methyl-
phenol(PVI). IR: (KBr) cmꢁ1: 3307 (OH), 1590 (C=N), 1320 (C-N). 1H NMR
(DMSO-d6) ppm: 2.1 (3H, s, CH3), 2.5 (2H, s, CH2), 3.8 (3H, s, OCH3x3), 5.2 (1H,
t, CH), 6.9–7.9 (10H, s, aromatic), 10.1 (1H, s, OH); EI-MS: m/z: 417 (M-1); calcd./
analyz.: C (71.75) 71.97, H (6.26) 6.19, N (6.69) 6.62.
4-[5-(4-Fluorophenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methylphenol
(PVII). IR: (KBr) cmꢁ1: 3307 (OH), 1590 (C=N), 1320 (C-N); 1H NMR (DMSO-d6)
ppm: 1.8 (3H, s, CH3), 2.5 (2H, s, CH2), 5.2 (1H,t,CH), 6.6–7.6 (12H, s, aromatic),
9.6 (1H, s, OH); EI-MS: m/z: 319 (M+1); calcd./analyz.: C (76.28) 76.24,H (5.53)
5.53, N (8.09) 8.03.
4-[5-(2-Chlorophenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methylphenol
(PVIII). IR:(KBr) cmꢁ1: 3307 (OH), 1590 (C=N), 1320 (C-N); 1H NMR (DMSO-d6)
ppm: 2.1 (3H, s, CH3), 2.5 (2H, s, CH2), 5.2 (1H, t, CH), 6.8–7.5 (12H, s,
aromatic),10.3 (1H, s, OH); EI-MS: m/z: 361 (M-1); calcd./analyz.: C (72.82) 72.60,
H (5.28) 5.22, N (7.72) 7.12.
4-[5-(2,6-Dichlorophenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methylphe-
nol (PIX). IR: (KBr) cmꢁ1: 3307 (OH), 1590 (C=N), 1320 (C-N); 1H NMR (DMSO-

Med Chem Res (2007) 15:463–470
469
d6) ppm: 1.8 (3H, s, CH3), 2.5 (2H, s, CH2), 5.2 (1H, t, CH), 6.6–7.6 (11H, s,
aromatic),10.3 (1H, s, OH); EI-MS: m/z: 397 (M+1); calcd./analyz.: C (66.51) 66.50,
H (4.57) 4.52, N (7.05) 7.0.
4-[5-(3-Nitro phenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methylphenol
1
(PX). IR: (KBr) cmꢁ1: 3307 (OH), 1590 (C=N), 1320 (C-N); H NMR (DMSO-
d6) ppm: 1.8 (3H, s, CH3), 2.5 (2H, s, CH2), 5.2 (1H, t, CH), 6.6–8.4 (12H, s,
aromatic), 9.6 (1H, s, OH); EI-MS: m/z: 372 (Mꢁ1); calcd./analyz. C (70.76) 70.70,
H (5.13) 5.10, N (11.25) 11.20.
4-[5-(2-Furyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methylphenol (PXI). IR:
(KBr) cmꢁ1: 3307 (OH), 1590 (C=N), 1320 (C-N); 1H NMR (DMSO-d6) ppm: 1.8
(3H, s, CH3), 2.5 (2H, s, CH2), 5.2 (1H, t, CH), 6.6–7.9 (11H, s, aromatic),10.4 (1H,
s, OH); EI-MS: m/z: 317 (Mꢁ1); calcd./analyz.: C (75.45) 75.35, H (5.70) 5.72, N
(8.80) 8.82.
Biology
The primary screening was conducted at a concentration of 6.25 mg/ml (or molar
equivalent of the highest molecular weight compound in a series of congeners)
against Mycobacterium tuberculosis H37Rv (ATCC27294) in BACTEC 12B
medium using the BACTEC 460 radiometric system (Interleid, 1991; Colins and
Franzblau, 1997). Compounds demonstrating at least 90% inhibition in the primary
screen were reexamined at a lower concentration (MIC) in broth microdilution assay
with almar blue. The MIC was defined as the lowest concentration inhibiting 99% of
the inoculum. Concurrent with the determination of MICs, compounds were tested
for cytotoxicity (IC50) in VERO at concentrations equal to and greater than the MIC
for Mycobacterium tuberculosis H37Rv after 72 h of exposure. Viability was
assessed on the basis of cellular conversion of MTT in to a formazan product using
the Promega cell Titer 96 nonradioactive cell proliferation assay (Heifets et al.,
1989).
Acknowledgments M. Shahar Yar thanks the University Grant Commission-New Delhi, India for a
research award. We thank the Tuberculosis Antimicrobial Acquisition and Coordinating Facility
(TAACF), National Institute of Allergy and Infections Diseases Southern Research Institute/GW Long
Hansen’s Disease Center, Colorado State University Birmingham, AL, for in vitro antimycobacterial
screening and Dr. Kiran Smith, National Cancer Institute, Bethesda, MD, for valuable suggestions.
References
Barnes P, Blotch AB, Davidson BT, Snyder Jr DE (1991) Tuberculosis in patients with immuno-
deficiency virus infection. N Engl J Med 324:1644–1650
Blair IA, Mansilla Tinoco R, Brodie MJ, Clare RA, Dollery CT, Timbrell JA, Beever IA (1985) Plasma
hydrazine concentrations in man after isoniazid and hydralazine administration. Hum Toxicol 4:195
Collins L, Franzblau SG (1997) Microplate alamar blue assay versus BACTEC 460 system for high-
throughput screening of compounds against Mycobacterium tuberculosis and Mycobacterium avium.
Antimicrob Agents Chemother 41:1004–1009
Fujiwara PI, Cook SV, Rutherford CM, Crawford JT, Glickman SE, Kreiswirth BN, Sachdev PS, Osahan
SS, Ebrahimzadeh A, Frieden TR (1997) A continuing survey of drug-resistant tuberculosis, New
York City, April 1994. Arch Intern Med 157:531–536

470
Med Chem Res (2007) 15:463–470
Heifets LB, Flory MA, Lindholm-Levy PJ (1989) Does pyrazinoic acid as an active moiety of
pyrazinamide have specific activity against Mycobacterium tuberculosis? Antimicrob Agents
Chemother 33:1252–1254
Inderlied C (1991) Antimycobacterial agents: in vitro susceptibility testing, spectrums of activity,
mechanisms of action and resistance, and assays for activity in biological fluids. In: Lorian V (ed.)
Antibiotics in laboratory medicine, 3rd ed. The Williams & Wilkins Co., Baltimore p. 134–197
Gu¨niz Ku¨c¸u¨kgu¨zel S, Rollas S (2002) Synthesis, characterization of novel coupling products and 4-
arylhydrazono-2-pyrazoline-5-ones as potential antimycobacterial agents. Farmaco 57:583–587
Kucukguzel SG, Rollas S, Erdeniz H, Kiraz M, Ekinci AC, Vidin A (2000) Synthesis, characterization
and pharmacological properties of some 4-arylhydrazono-2-pyrazoline-5-one derivatives obtained
from heterocyclic amines. Eur J Med Chem 35:761–771
Nauduri D, Reddy GB (1998) Part-1: Antibactirials & antimycotics: Synthesis and structure activity
relationship of 2-pyrazolines derivatives. Chem Pharm Bull 46(8):1254–1260
O’Brien RJ, Nunn PP (2001) The need for new drugs against tuberculosis. Am J Respir Crit Care Med
163:1055–1058
Sbarbaro JA (1997) Multidrug’-resistant tuberculosis. It is time to focus on the private sector of medicine.
Chest 111:1149–1151
Schaberg T, Glocer G, Reichert B, Mauch H, Lode H (1996) Resistant lung tuberculosis in Berlin 1987–
1993. Pneumologie 50:21–27
Shenoy GG, Bhat AR, Bhat GV, Kotian M (2001) Synthesis and antimicrobial activities of 1,3,5
trisubstituted 2-pyrazolines. Ind J Het Chem 10:197–200