Synthesis and pharmacological evaluation of a novel series of 5-(substituted)aryl-3-(3-coumarinyl)-1-phenyl-2-pyrazolines as novel anti-inflammatory and analgesic agents

Article abstract of DOI:10.1016/j.ejmech.2008.09.020

A novel series of 5-(substituted)aryl-3-(3-coumarinyl)-1-phenyl-2-pyrazolines (3a-l) were synthesized by reacting various substituted 3-aryl-1-(3-coumarinyl)propan-1-ones (2a-l) with phenylhydrazine in the presence of hot pyridine. Structures of all new s

Full text of DOI:10.1016/j.ejmech.2008.09.020

European Journal of Medicinal Chemistry 44 (2009) 1682–1688
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and pharmacological evaluation of a novel series of 5-(substituted)
aryl-3-(3-coumarinyl)-1-phenyl-2-pyrazolines as novel anti-inflammatory and
analgesic agents
,
a
a
a
Suresh Khode a, Veeresh Maddi a , Prashant Aragade , Mahesh Palkar , Pradeep Kumar Ronad ,
*
Shivalingarao Mamledesai a, A.H.M. Thippeswamy b, D. Satyanarayana c
a Department of Pharmaceutical Chemistry, KLES College of Pharmacy, Vidyanagar, Hubli 580 031, Karnataka, India
b Department of Pharmacology, KLES College of Pharmacy, Vidyanagar, Hubli 580 031, Karnataka, India
c Department of Pharmaceutical Chemistry, NGSM Institute of Pharmaceutical Sciences, Paneer, Deralakatte, Mangalore, Karnataka, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 June 2008
Received in revised form 5 September 2008
Accepted 11 September 2008
Available online 30 September 2008
A novel series of 5-(substituted)aryl-3-(3-coumarinyl)-1-phenyl-2-pyrazolines (3a–l) were synthesized
by reacting various substituted 3-aryl-1-(3-coumarinyl)propan-1-ones (2a–l) with phenylhydrazine in
the presence of hot pyridine. Structures of all new synthesized compounds were characterized on the
basis of elemental analysis and spectral data (IR, 1H NMR and 13C NMR). The title compounds were
screened for in vivo anti-inflammatory and analgesic activities at a dose of 200 mg/kg b.w. Among the 12
prepared compounds, Compounds 3d, e, i and j exhibited significant anti-inflammatory activity in model
of acute inflammation such as carrageenan-induced rat edema paw while compounds 3d and e showed
considerable activity in model of chronic inflammation such as adjuvant-induced arthritis and were
compared with diclofenac (13.5 mg/kg b.w.) as a standard drug. These compounds were also found to
have significant analgesic activity in the acetic acid induced writhing model and antipyretic activity in
yeast-induced pyrexia model along with minimum ulcerogenic index.
Keywords:
Anti-inflammatory
Analgesic
Coumarin
NSAIDs
Pyrazoline
Ó 2008 Elsevier Masson SAS. All rights reserved.
1. Introduction
isoforms by classical NSAIDs with preferential binding affinity for
enzyme COX-1 causes serious side effects.
Cyclooxygenase (COX), the rate limiting enzyme of the prosta-
noid biosynthetic pathway catalyzes the conversion of arachidonic
acid to important inflammatory mediators such as prostaglandins
(PGs), prostacyclins and thromboxanes [1]. The existence of
enzyme cyclooxygenase in its two distinct isoforms and thus non-
selective action of classical non-steroidal anti-inflammatory drugs
(NSAIDs) results in certain mechanism based side effects including
dyspepsia, gastrointestinal ulcerations, bleeding and nephrotoxi-
city [2]. Both the isoforms differ in their regulation and expression.
The constitutive COX-1 is responsible for the biosynthesis of PGs,
which involves the cytoprotection of gastrointestinal tract and
platelet aggregation [3]. COX-2 is induced by pro-inflammatory
molecules such as interleukin-1 (IL-1), tumor necrosis factor-
The association of COX-2 with induced inflammation has led to
the hypothesis that selective inhibition of COX-2 over COX-1 might
provide good anti-inflammatory agents with reduced side effects
than classical NSAIDs. Therefore, selective COX-2 inhibitors (coxibs)
with better safety profile have been marketed as a new generation
NSAIDs [5,6]. But careful prospective examination of coxibs has
revealed unexpected cardiovascular adverse effect [7]. Therefore,
development of novel compounds having anti-inflammatory and
analgesic activities with an improved safety profile is still a neces-
sity. In addition, inflammation is known not only as a symptom of
great deal of common diseases but also as an early phase of some
life-threatening diseases such as cancer, heart vascular diseases and
Alzheimer’s dementia. Thus the discovery of novel anti-inflam-
matory agents has been attracting a lot of interests.
a
(TNF-a), lipopolysaccharide (LPS), carrageenan, etc. that leads to
inflammation [4]. COX-2 levels are undetectable in most tissues
under normal physiological conditions, but are significantly
elevated in acute and chronic inflammations. Inhibition of both
The synthesis of coumarins and their derivatives has engrossed
substantial attention from organic and medicinal chemists for
many years as they belong to a class of compounds with proven
utility in medicinal chemistry. Coumarin is an important scaffold
since several coumarin derivatives are known to be associated
with multiple biological activities [8–12] and especially anti-
inflammatory/antioxidant activities. Recently the synthesis and in
* Corresponding author. Tel./fax: þ91 836 2371694.
E-mail address: veeresh_m@rediffmail.com (V. Maddi).
0223-5234/$ – see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.09.020

S. Khode et al. / European Journal of Medicinal Chemistry 44 (2009) 1682–1688
1683
O
CHO
OH
O
O
(a)
+
CH3
CH3
O
CH3
Ethylacetoacetate
O
(1)
O
Salicyladehyde
(b)
O
O
1
2
Substituted
Aryl / Phenyl
N
N
(c)
Substituted
Aryl / Phenyl
5
4
3
O
H
H
H
(2a-l)
O
O
(3a-l)
Scheme 1. Synthesis of 5-(substituted)aryl-3-(3-coumarinyl)-1-phenyl-2-pyrazolines (3a–l). Reagents and conditions: (a) Piperidine, stir, rt, 20 min; (b) Ar-CHO, Piperidine/n-
butanol, reflux, 4 h; (c) Phenyl hydrazine, Pyridine, reflux, 6 h.
vivo/in vitro anti-inflammatory/antioxidant activities of several
new coumarin derivatives with a 7-azomethine linkage have been
reported [13].
phenyl hydrazines seemed to be a convenient route to fulfil this aim.
Numerous synthetic routes to 3-substituted coumarins from 2-
hydroxyarylaldehydes or 2-hydroxyarylketones have been reported
including syntheses requiring the use of noxious phosphorylating
agents such as POCl3, bases such as piperidine or solvents such as
DMF [26,27]. Synthesis of 3-acetyl coumarin (1) was carried out by
reacting salicylaldehyde with ethylacetoacetate in the presence of
catalytic amount of piperidine at room temperature. The reaction is
an example of the Knoevenagel reaction [28], in which the active
methylene compound reacts with 2-hydroxybenzaldehyde, has
Pyrazoline is an important nitrogenous five-membered
heterocyclic component of the drugs. Literature survey revealed
that numerous pyrazoline derivatives have found their clinical
application as NSAIDs. Antipyrine, 2,3-dimethyl-1-phenyl-3-pyr-
azolin-5-one, was the first pyrazolone derivative used in the
management of pain and inflammation. Several analogues of pyr-
azolidin-3,5-diones, pyrazolin-3-ones and pyrazolin-5-ones are
also available as NSAIDs; examples are felcobuzone, mefobutazone,
morazone, famprofazone, and ramifenazone [14]. Besides these,
many pyrazoline derivatives are also reported in literature as
having potent anti-inflammatory activity [15–18].
Table 1
Physicochemical data of 5-(substituted)aryl-3-(3-coumarinyl)-1-phenyl-2-pyrazo-
Therefore, both the coumarins and the pyrazolines possess
worthy and imperative bioactivities, which render them useful
substances in drug research. On this basis, Levai et al. [19] have
recently described only the synthesis of 1-substituted-5-aryl-3-(3-
coumarinyl)-2-pyrazolines by the reaction of (3-coumarinyl)-
chalcones and hydrazines. In view of these observations and in
continuation of our research programme on the synthesis of
heterocyclic compounds [20–23], we report herein the synthesis of
some new 2-pyrazoline derivatives, which have been found to
possess an interesting profile of anti-inflammatory, analgesic and
antipyretic activities along with significantly less ulcerogenic
potential.
lines (3a–l)
1
2
N
N
5
Substituted
3
Aryl / Phenyl
4
H
H
H
O
O
(3a-l)
Compound Aryl/phenyl
% Yield Solventa Melting pointb Rfc Molecular
formula
2. Chemistry
3a
3b
3c
3d
3e
3f
3g
3h
3i
C6H5
4-OMe-C6H4
–CH]CH–C6H5 46
4-Cl-C6H4 69
2,4-(Cl)2-C6H3 65
4-NMe2-C6H4 55
3-NO2-C6H4
4-Me-C6H4
3-OMe-C6H4
4-F-C6H4
68
65
Ethanol 180–182
Ethanol 166–168
Ethanol 186–188
Methanol 150–152
Ethanol 178–180
Ethanol 134–136
Methanol 182–184
Ethanol 193–194
Ethanol 174–176
Methanol 108–110
Methanol 160–162
Methanol 150–152
0.48 C24H18N2O2
0.53 C25H20N2O3
0.64 C26H20N2O2
0.48 C24H17ClN2O2
0.90 C24H16Cl2N2O2
0.56 C26H23N3O2
0.50 C24H17N3O4
0.81 C25H20N2O2
0.63 C25H20N2O3
0.76 C24H17FN2O2
0.62 C24H17N3O4
0.72 C24H18N2O3
2-Pyrazolines are the most frequently studied compounds
and various methods have been worked out for their synthesis
[24]. Since the milestone work of Fischer and Knovenagel pub-
lished in late 19th century, the reaction of
a,b-unsaturated
71
70
68
56
61
59
aldehydes and ketones with hydrazines became a generally used,
simple and convenient procedure for the synthesis of 2-pyr-
azolines [25].
Synthetic methods for the preparation of 5-(substituted)aryl-
3-(3-coumarinyl)-1-phenyl-2-pyrazoline derivatives (3a–l) are
summarized in Scheme 1. It is apparent from the scheme that the
new heterocyclic compounds possess both a coumarinyl moiety and
a 2-pyrazoline unit. Reaction of (3-coumarinyl)-chalcones with
3j
3k
3l
2-NO2-C6H4
4-OH-C6H4
a
b
c
Recrystallisation solvent.
Melting point in ꢀC.
Benzene:petroleum ether:methanol 9:1:0.1 as
a
mobile phase and iodine
vapours as visualizing agent.

1684
S. Khode et al. / European Journal of Medicinal Chemistry 44 (2009) 1682–1688
been extensively used as the first step in the synthesis of 3-ace-
tylcoumarins. 3-Aryl-1-(3-coumarinyl)propan-1-ones (2a–l) were
synthesized by the reaction of 3-acetyl coumarin and various
substituted aromatic aldehydes in the presence of mixture of
piperidine and glacial acetic acid. 5-(Substituted)aryl-3-(3-cou-
marinyl)-1-phenyl-2-pyrazoline compounds (3a–l) were obtained
in good yields by reacting 3-aryl-1-(3-coumarinyl)propan-1-ones
(2a–l) with phenylhydrazine in hot pyridine [19].
evaluated for their ability to inhibit edema formation in chronic
anti-inflammatory model using adjuvant-induced arthritis method
by following the method of Newbould [31]. Further, analgesic
activity, antipyretic activity and ulcerogenic studies were carried
out for compounds 3d, e, i and j by following the method of Koster
et al. [32], Loux et al. [33] and Vogel [34], respectively.
4. Results and discussion
3. Pharmacological evaluation
4.1. Synthetic and spectral studies
The acute toxicity test was carried out according to the Orga-
nization for Economic Co-operation and Development (OECD)
guidelines [29] to establish the effective dose of all the synthesized
compounds. The in vivo acute anti-inflammatory activity for all test
compounds was evaluated on male albino rats using carrageenan-
induced rat paw edema model by adopting the earlier reported
method of Winter et al. [30]. The compounds 3d, e, i and j were
We have synthesized a series of 5-(substituted)aryl-3-(3-cou-
marinyl)-1-phenyl-2-pyrazolinederivativesbyreactingappropriately
substituted 3-aryl-1-(3-coumarinyl)propan-1-ones with phenyl-
hydrazine in hot pyridine as illustrated in Scheme 1. Structure of the
synthesized compounds (3a–l) was established on the basis of phys-
icochemical, elemental analysis and spectral data (IR,1H NMR and 13
NMR), which are summarized in Tables 1 and 2, respectively.
C
Table 2
Spectral and elemental analyses data of 5-(substituted)aryl-3-(3-coumarinyl)-1-phenyl-2-pyrazolines (3a–l)
Compound UV (CH3OH) IR (KBr, cmꢁ1 1H NMR (CDCl3/DMSO) 13C NMR (CDCl3/DMSO)
3.42 (dd, 1H, J ¼ 7.1, 17.9 Hz, 4-Htrans), 45.5, 65.1, 113.4, 116.1, 117.8,
)
Elemental (CHN) analysis
3a
3b
lmax 294
26 554)
1729.84 (lactone of
coumarin), 1599.06
d
d
Anal. Calcd for C24H18N2O2C,
78.67; H, 4.95; N, 7.65.
Found: C, 78.75; H, 4.90;
N, 7.68
Anal. Calcd for C25H20N2O3C,
75.75; H, 5.08; N, 7.07.
Found: C, 75.78; H, 5.12;
N, 7.11
(
3
4.05 (dd, 1H, J ¼ 12.5, 18.5 Hz, 4-Hcis), 5.34
120.1, 124.6, 125.3, 127.7, 128.4,
129.1, 131.1, 131.8, 132.5, 137.2,
141.8, 144.1, 154.1, 160.3
(C]N), 1533.98 (C]C) (dd, 1H, 5-H of pyrazoline), 6.85–7.70 (m,
14H, Ar-H), 8.44 (s, 1H, 4-H of coumarin)
lmax 297
24 500)
1728.01 (lactone of
coumarin), 1599.13
(C]N), 1536.14 (C]C)
d
3.37 (dd, 1H, J ¼ 7.2, 18.3 Hz, 4-Htrans),
d
45.2, 55.6, 64.1, 113.2, 115.0,
(
3
3.82 (s, 3H, OCH3), 4.09 (dd, 1H, J ¼ 12.4,
18.4 Hz, 4-Hcis), 5.33 (dd, 1H, 5-H of
pyrazoline), 6.9–7.6 (m, 13H, Ar-H), 8.39
(s, 1H, 4-H of coumarin)
116.7, 119.8, 124.5, 126.6, 127.9,
128.8, 131.3, 134.5, 137.6, 142.9,
144.3, 152.7, 160.6
3c
3d
3e
3f
lmax 257
31544)
1723.46 (lactone of
coumarin), 1599.89
(C]N), 1495.01 (C]C) (dd, 1H, 5-H of pyrazoline), 6.63–7.86 (m,
d
3.34 (dd, 1H, J ¼ 7.0, 17.8 Hz, 4-Htrans),
d
40.2, 62.7, 111.9, 113.2, 114.2,
Anal. Calcd for C26H20N2O2C,
79.56; H, 5.14; N, 7.15.
Found: C, 79.67; H, 5.11;
N, 7.19
Anal. Calcd for C24H17ClN2O2
C, 71.92; H, 4.25; N, 6.99.
Found: C, 71.69; H, 4.22;
N, 7.08
(
3
4.15 (dd, 1H, J ¼ 12.8, 18.2 Hz, 4-Hcis), 5.40
117.0, 120.5, 124.5, 126.6, 127.9,
128.8, 131.3, 133.1, 133.9, 138.6,
142.9, 143.6, 151.5, 155.3, 159.6
16H, Ar-H), 8.48 (s, 1H, 4-H of coumarin)
d
lmax 294
31416)
1727.09 (lactone of
coumarin), 1596.14
(C]N), 1566.07 (C]C) (dd, 1H, 5-H of pyrazoline), 6.82–7.60 (m,
3.32 (dd, 1H, J ¼ 7.4, 18.3 Hz, 4-Htrans),
d
44.9, 64.6, 113.6, 116.2, 120.0,
(
3
4.06 (dd, 1H, J ¼ 12.2, 18.2 Hz, 4-Hcis), 5.28
120.6, 121.3, 125.4, 127.5, 128.2,
129.1, 129.5, 131.7, 133.3, 138.0,
140.9, 144.4, 152.9, 160.2
13H, Ar-H), 8.42 (s, 1H, 4-H of coumarin)
d
lmax 292
28 327)
1725.13 (lactone of
coumarin), 1595.47
(C]N), 1534.59 (C]C) 1H, 5-H of pyrazoline), 6.88–7.61 (m, 12H,
3.29 (dd, 1H, J ¼ 7.2, 18.6 Hz, 4-Htrans),
d
44.8, 63.9, 113.5, 116.9, 120.7,
Anal. Calcd for C24H16Cl2N2O2C,
(
3
4.19 (dd, J ¼ 12.8, 18.6 Hz, 4-Hcis), 5.65 (dd,
121.3, 122.3, 123.8, 125.4, 126.5, 66.22; H, 3.71; N, 6.44.
128.2, 129.4, 129.8, 131.7, 133.3,
141.8, 143.4, 151.3, 158.5
Found: C, 66.29; H, 3.82;
N, 6.38
Anal. Calcd for C26H23N3O2C,
76.26; H, 5.66; N, 10.26.
Found: C, 76.19; H, 5.78;
N, 10.33
Ar-H), 8.40 (s, 1H, 4-H of coumarin)
d
lmax 340
30188)
1721.24 (lactone of
coumarin), 1601.51
(C]N), 1493.18 (C]C)
2.73 (s, 6H, N(CH3)2), 3.43 (dd, 1H, J ¼ 7.3,
d
38.5, 43.7, 64.4, 113.7, 114.6,
(
3
18.5 Hz, 4-Htrans), 4.08 (dd, J ¼ 12.1, 18.7 Hz,
4-Hcis), 5.55 (dd, 1H, 5-H of pyrazoline),
6.94–7.58 (m, 13H, Ar-H), 8.47 (s, 1H, 4-H
of coumarin)
117.2, 121.3, 122.3, 123.8, 125.4,
126.5, 128.2, 129.1, 129.7, 132.8,
133.4, 142.8, 146.4, 150.9, 160.8
3g
3h
3i
lmax 268
33 496)
1723.16 (lactone of
coumarin), 1600.04
(C]N), 1532.62 (C]C) 1H, 5-H of pyrazoline), 6.84–7.63 (m, 13H,
d
3.37 (dd, 1H, J ¼ 7.4, 18.2 Hz, 4-Htrans), 4.03
d
45.1, 61.9, 113.4, 117.0, 118.9,
Anal. Calcd for C24H17N3O4C,
70.08; H, 4.15; N, 10.22.
Found: C, 70.13; H, 4.25;
N, 10.28.
Anal. Calcd for C25H20N2O2
C, 78.93; H, 5.28; N, 7.37.
Found: C, 78.99; H, 5.25;
N, 7.38
(
3
(dd, 1H, J ¼ 12.3, 18.1 Hz, 4-Hcis), 5.41 (dd,
121.2, 124.3, 126.8, 127.6, 128.3,
132.3, 133.5, 134.7, 139.6, 143.9,
145.6, 151.8, 155.6, 162.3
Ar-H), 8.48 (s, 1H, 4-H of coumarin)
d
lmax 296
23 499)
1725.71 (lactone of
coumarin), 1601.31
(C]N), 1496.34 (C]C) (dd, 1H, 5-H of pyrazoline), 6.76–7.38 (m, 13H,
2.25 (s, 3H, CH3), 3.33 (dd, 1H, J ¼ 7.0, 18.3 Hz,
d
22.4, 46.1, 64.8, 110.2, 113.2,
(
3
4-Htrans), 4.15 (dd, J ¼ 12.4, 18.8 Hz, 4-Hcis), 5.48
116.7, 120.1, 124.6, 125.4, 126.5,
127.7, 128.5, 128.9, 129.7, 132.3,
137.1, 138.0, 140.3, 160.1
Ar-H), 8.36 (s, 1H, 4-H of coumarin).
d
lmax 294
20 968)
1726.54 (lactone of
coumarin), 1599.02
(C]N), 1536.03 (C]C) 4-Hcis), 5.35 (dd, 1H, 5-H of pyrazoline),
6.85–7.51 (m, 13H, Ar-H), 8.42 (s, 1H, 4-H
of coumarin)
3.41 (dd, 1H, J ¼ 7.6, 18.2 Hz, 4-Htrans), 3.81
d
45.0, 55.3, 64.7, 110.9, 112.6,
Anal. Calcd for C25H20N2O3C,
75.75; H, 5.08; N, 7.08.
(
3
(s, 3H, OCH3), 4.13 (dd, 1H, J ¼ 12.8, 18.4 Hz,
114.1, 116.4, 118.2, 119.8, 120.6,
123.5, 124.5, 125.4, 127.9, 128.9, Found: C, 75.83; H, 5.14;
130.3, 131.5, 137.6, 142.9, 143.3,
145.1, 154.2, 161.1
N, 7.11
3j
lmax 305
32 474)
1727.93 (lactone of
coumarin), 1599.02
(C]N), 1533.99 (C]C) (dd, 1H, 5-H of pyrazoline), 6.72–7.65 (m,
d
3.36 (dd, 1H, J ¼ 7.4, 18.6 Hz, 4-Htrans),
d
45.4, 64.1, 113.9, 115.6, 116.1,
Anal. Calcd for C24H17FN2O2C,
74.99; H, 4.47; N, 7.29.
Found: C, 75.05; H, 4.44;
N, 7.32
(
3
4.08 (dd, 1H, J ¼ 12.6, 18.6 Hz, 4-Hcis), 5.36
117.4, 119.8, 120.3, 121.0, 121.9,
124.5, 127.7, 128.3, 129.3, 131.5,
137.8, 138.9, 143.5, 154.0, 159.3
13H, Ar-H), 8.5 (s, 1H, 4-H of coumarin)
3k
3l
lmax 343
27426)
1723.10 (lactone of
coumarin), 1599.28
(C]N), 1531.95 (C]C)
d
3.44 (dd, 1H, J ¼ 7.1, 17.9 Hz, 4-Htrans), 4.13
d
45.1, 62.3, 113.7, 117.2, 119.1,
Anal. Calcd for C24H17N3O4C,
(
3
(dd, 1H, J ¼ 12.6, 18.6 Hz, 4-Hcis), 5.47 (dd,
1H, 5-H of pyrazoline), 6.74–7.53 (m, 13H,
Ar-H), 8.39 (s, 1H, 4-H of coumarin)
120.8, 123.7, 126.3, 127.3, 128.8, 70.07; H, 4.16; N, 10.21.
132.5, 133.9, 135.1, 142.6, 144.0,
146.1, 151.8, 154.5, 161.8
Found: C, 70.13; H, 4.24;
N, 10.15
Anal. Calcd for C24H18N2O3C,
lmax 278
27148)
1727.06 (lactone of
coumarin), 1611.54
(C]N), 1501.60 (C]C)
d
3.35 (dd, 1H, J ¼ 7.8, 18.8 Hz, 4-Htrans),
d
45.6, 62.5, 113.5, 117.1, 120.1,
(
3
4.09 (dd, 1H, J ¼ 12.7, 18.7 Hz, 4-Hcis), 5.15
(s, 1H, –OH), 5.33 (dd, 1H, 5-H of pyrazoline),
6.66–7.93 (m, 13H, Ar-H), 8.4 (s, 1H, 4-H
of coumarin)
120.9, 123.7, 126.3, 127.8, 128.5, 75.38; H, 4.74; N, 7.33.
131.9, 133.7, 135.4, 142.1, 144.8,
145.9, 153.2, 156.2, 159.5, 160.4
Found: C, 75.43; H, 4.74;
N, 7.35

S. Khode et al. / European Journal of Medicinal Chemistry 44 (2009) 1682–1688
1685
Table 4
4.2. Acute toxicity study
In vivo chronic anti-inflammatory activity of selected compounds in adjuvant-
induced arthritis model
From the preliminary toxicity studies, it was observed that, all
the test compounds have revealed good safety profile till the
uppermost dose (2000 mg/kg). No mortality of animals observed
even after 24 h but there were few changes in the behavioral
response like alertness, touch response and restlessness. Therefore,
1/10th of the maximum tolerated dose i.e. 200 mg/kg b.w. was
chosen for the various pharmacological evaluations.
Compound
Anti-inflammatory activitya
Paw edema volume (mean ꢂ SEM)
% Inhibition after
treatment (on day 19)
Day 15b
Day 19c
Control
3d
3e
3i
0.92 ꢂ 0.08
0.87 ꢂ 0.12
0.86 ꢂ 0.07
0.81 ꢂ 0.05
0.89 ꢂ 0.04
0.83 ꢂ 0.09
0.87 ꢂ 0.02
0.53 ꢂ 0.07
0.47 ꢂ 0.06
0.64 ꢂ 0.09
0.53 ꢂ 0.03
0.39 ꢂ 0.05
05.5 ꢂ 0.24
39.1 ꢂ 0.81*
45.4 ꢂ 1.63*
20.9 ꢂ 1.25
40.5 ꢂ 1.80*
53.0 ꢂ 1.92**
3j
Diclofenac
4.3. Acute anti-inflammatory activity
The results are expressed as mean ꢂ SEM (n ¼ 6). Significance was calculated by
using one-way ANOVA with Dunnet’s t- test. The difference in results was consid-
ered significant when p < 0.05. *p < 0.05 vs control at 200 mg/kg b.w.; **p < 0.01 vs
control at 13.5 mg/kg b.w.
Table 3 reveals the in vivo acute anti-inflammatory activity of
a novel series of 5-(substituted)aryl-3-(3-coumarinyl)-1-phenyl-2-
pyrazolines (3a–l) at a dose of 200 mg/kg in carrageenan-induced
paw edema method. Carrageenan-induced edema is a non-specific
inflammation resulting from a complex of diverse mediators. Since
edema of this type is highly sensitive to NSAIDs, carrageenan has
been accepted as a useful agent for studying new anti-inflamma-
tory agents. This model reliably predicts the anti-inflammatory
efficacy of the NSAIDs, and during the second phase it detects
compounds that are anti-inflammatory agents as a result of inhi-
bition of prostaglandin amplification [35]. As shown in Table 3, the
entire investigated compounds exhibited moderate to good anti-
inflammatory activity with the percentage inhibition of edema
formation ranged from 26.6 to 67.5, while the reference drug
diclofenac (13.5 mg/kg) showed 78.7% inhibition at fourth hour.
Compound 3d (39.2 and 64.7%) and 3i (38.3 and 61.2%) showed
good inhibitory activity at second and fourth hour, respectively,
while the most active compounds 3e (56.7 and 67.5%) and 3j (45.0
a
Inhibitory activity in Freund’s adjuvant-induced rat paw edema.
Paw edema volume before treatment.
Paw edema volume after treatment.
b
c
and 66.7%) among the series, exhibited the excellent inhibitory
activity at second and fourth hour, respectively. The anti-inflam-
matory activity of these compounds was comparable with that of
the standard drug diclofenac, although not equal. Compounds that
showed significant anti-inflammatory activity profile were further
tested for chronic anti-inflammatory, analgesic, antipyretic and
ulcerogenic activities.
4.4. Chronic anti-inflammatory activity
Table 4 explains the in vivo chronic anti-inflammatory activity of
compounds 3d, e, i and j in adjuvant-induced arthritis in rats.
Injection of Freund’s complete adjuvant to the hind footpad in rats
produced arthritis and rats with developed arthritis were chosen
for the study. On day 15, there were not many variations in the
edema volumes of different groups. Administration of 3d, e, i and j
at a dose of 200 mg/kg and diclofenac (13.5 mg/kg) for four days
(from day 16 to day 19) in rats has produced significant reduction in
paw volume (by day 19) when compared to the arthritic control
group. Compounds 3d (39.1 ꢂ0.81), 3e (45.4 ꢂ1.63) and 3j
(40.5 ꢂ1.80) were found to possess a substantial inhibition of
edema formation when compared to 3i (20.9 ꢂ 1.25) while diclo-
fenac (53.0 ꢂ 1.92) exhibited significant anti-inflammatory activity.
Table 3
In vivo acute anti-inflammatory activity of 5-(substituted)aryl-3-(3-coumarinyl)-1-
phenyl-2-pyrazolines (3a–l) in carrageenan-induced paw edema
1
2
N
N
5
Substituted
Aryl / Phenyl
3
4
H
H
H
4.5. Analgesic activity
O
O
(3a-l)
Abdominal constriction response induced by acetic acid is
a sensitive procedure to establish efficacy of peripherally acting
analgesics. The compounds 3d, e, i and j were tested for analgesic
activity at 200 mg/kg b.w. in mice. The results of analgesic activity
indicated that all test compounds exhibited moderate to good
Compound
Aryl/phenyl
Anti-inflammatory activitya
% Inhibition after
% Inhibition after
2 h (ꢂSEM)
4 h (ꢂSEM)
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
C6H5
27.2 (ꢂ0.02)
32.7 (ꢂ0.01)
4-OMe-C6H4
–CH]CH–C6H5
4-Cl-C6H4
2,4-(Cl)2-C6H3
4-NMe2-C6H4
3-NO2-C6H4
4-Me-C6H4
3-OMe-C6H4
4-F-C6H4
24.8 (ꢂ0.005)
26.7 (ꢂ0.006)
39.2 (ꢂ0.026)*
56.7 (ꢂ0.030)**
28.4 (ꢂ0.040)
26.1 (ꢂ0.13)
36.2 (ꢂ0.006)
42.5 (ꢂ0.003)*
64.7 (ꢂ0.021)*
67.5 (ꢂ0.024)**
40.1 (ꢂ0.044)*
31.2 (ꢂ0.006)
38.0 (ꢂ0.013)
61.5 (ꢂ0.013)**
66.7 (ꢂ0.011)**
26.6 (ꢂ0.037)
34.6 (ꢂ0.013)
78.7 (ꢂ0.013)***
Table 5
Analgesic activity of compounds 3d, e, i and j by acetic acid induced writhing
method
Compound
No. of wriths in 15 min (mean ꢂ SEM)
% Protection
30.1 (ꢂ0.017)
38.3 (ꢂ0.030)*
44.9 (ꢂ0.023)**
24.7 (ꢂ0.046)
28.8 (ꢂ0.035)
63.7 (ꢂ0.017)***
Control
3d
3e
3i
66.9 ꢂ 0.21
–
38.2 ꢂ 0.29*
27.1 ꢂ 0.36**
43.3 ꢂ 0.45*
30.5 ꢂ 0.46**
22.4 ꢂ 0.57***
41.0
59.0
35.0
55.0
67.0
2-NO2-C6H4
4-OH-C6H4
Diclofenac
3j
Acetylsalicylic acid
The results are expressed as mean ꢂ SEM (n ¼ 6). Significance was calculated by
using one-way ANOVA with Dunnet’s t- test. The difference in results was consid-
ered significant when p < 0.05. *p < 0.05 vs control at 200 mg/kg b.w; **p < 0.01 vs
control at 200 mg/kg b.w; ***p < 0.001 vs control at 13.5 mg/kg b.w.
The results are expressed as mean ꢂ SEM (n ¼ 6). Significance was calculated by
using one-way ANOVA with Dunnet’s t- test. The difference in results was consid-
ered significant when p < 0.05. *p < 0.05 vs control at 200 mg/kg b.w.; **p < 0.01 vs
control at 200 mg/kg b.w.; ***p < 0.001 vs control at 135 mg/kg b.w.
a
Inhibitory activity in carrageenan-induced rat paw edema.

1686
S. Khode et al. / European Journal of Medicinal Chemistry 44 (2009) 1682–1688
Table 6
ring systems were prepared by the condensation process between
3-aryl-1-(3-coumarinyl)propan-1-ones (2a–l) and phenylhydra
zine in hot pyridine. The examined compounds did not show
toxic effects at doses upto 2000 mg/kg b.w. in acute toxicity
experiments.
Antipyretic activity of compounds 3d, e, i and j by yeast-induced pyrexia
Serial no. Compound
Mean temperature in ꢀC at intervalsb
TIc
0a
1
2
3
4
5
1
2
3
4
5
6
Control
3d
3e
3i
3j
39.5 39.4
39.3 39.1
39.2
38.9
38.9
38.5
38.7
38.1*
38.2 ꢁ3.1
38.0 ꢁ3.9
The preliminary in vivo biological activities of these novel
compounds evidenced that the presence of chlorine, fluorine and
methoxy groups in the aromatic ring of 5-position of the pyrazoline
nucleus gave rise to an increased anti-inflammatory and analgesic
activities. Among the 12 prepared compounds, compounds 3d, e, i
and j exhibited significant anti-inflammatory activity in model of
acute inflammation such as carrageenan-induced rat edema paw
while compounds 3d and e showed considerable activity in model
of chronic inflammation such as adjuvant-induced arthritis. These
compounds were also found to have significant analgesic activity in
the acetic acid induced writhing model and antipyretic activity in
yeast-induced pyrexia model. In addition, the tested compounds
were also found to possess less degree of ulcerogenic potential as
compared to aspirin. Thus these compounds constitute an inter-
esting template for the evaluation of new inflammatory inhibitors
and may be helpful for the design of new therapeutic tools against
inflammation.
39.2 38.9* 38.6*
38.1** 37.8** 37.2** ꢁ5.4
39.6 39.4
39.4 39.2
38.8
38.6
38.2* 37.9
ꢁ5.1
38.3** 37.9*** 37.7*** 37.1** ꢁ6.6
p-Acetaminophenol 39.0 38.4** 38.0*** 37.6*** 37.3*** 37.0** ꢁ6.7
The results are expressed as mean values (n ¼ 6). Significance was calculated by
using one-way ANOVA with Dunnet’s t- test. The difference in results was consid-
ered significant when p < 0.05. *p < 0.05 vs control; **p < 0.01 vs control;
***p < 0.001 vs control.
a
Eighteenth hour after yeast injection was considered as 0 h.
Temperature was recorded hourly from 0 to 5 h after dosing.
Temperature index (TI) is the sum of mean temperature changes from the 0 h.
b
c
analgesic activity (Table 5). Compounds 3e (59%) and 3j (55%) have
shown nearly the comparable activity to that of reference drug
acetylsalicylic acid (67%) in peripheral analgesic activity model.
4.6. Antipyretic activity
6. Experimental
Furthermore, the encouraging results from analgesic activity
prompted us to carry out the antipyretic activity in yeast-induced
pyrexia for compounds 3d, e, i and j at a dose of 200 mg/kg b.w. in
rats. Results of antipyretic activity are given in Table 6, perusal of
data suggests that compounds 3e, i and j possess reasonable to
good antipyretic activity as compared to standard drug p-acet-
aminophenol. However, compound 3d was found to be less active
as antipyretic among the tested compounds.
6.1. Chemistry protocols
All research chemicals were purchased from Sigma–Aldrich (St.
Louis, Missouri, USA) or Lancaster Co. (Ward Hill, MA, USA) and
used as such for the reactions. Solvents except laboratory reagent
grade were dried and purified according to the literature when
necessary. Reactions were monitored by thin-layer chromatog-
raphy (TLC) on pre-coated silica gel plates from E. Merck and Co.
(Darmstadt, Germany).
4.7. Ulcerogenic activity
Melting points of synthesized compounds were determined in
Thermonik (Mumbai, India) melting point apparatus and are
uncorrected. UV spectra were recorded on Thermospectronic
(Rochester, NY, USA) and IR spectra were recorded on Thermo
Nicolet IR200 FT-IR Spectrometer (Madison, WI, USA) by using KBr
pellets. The 1H NMR and 13C NMR were recorded on Bruker AVANCE
300 (Bruker, Rheinstetten/Karlsruhe, Germany) using CDCl3/
The major drawback of NSAIDs is their gastric ulcer formation
due to gastric irritation. The extent of ulcerogenic effect was eval-
uated for compounds 3d, e, i and j in rat stress model at the ther-
apeutic dose (i.e. 200 mg/kg b.w.). The gastric ulcerogenic potential
was evaluated by calculating the ulcer index in treated and control
animals. Results are given in Table 7 that indicates these four
compounds (ulcer index ranges from 1.6 to 2.7) cause less gastric
ulceration and disruption of gastric epithelial cells at the above-
mentioned oral dose as compared to acetylsalicylic acid (ulcer
index 4.3). Hence gastric tolerance to these compounds was better
than that of standard drug.
DMSO-d6 as solvent. Chemical shifts are reported in
d ppm units
with respect to TMS as internal standard. The elemental analysis
(C, H, N) of the compounds was performed on Heraus CHN rapid
analyzer. Results of elemental analysis were within ꢂ0.4% of the
theoretical values. Purity of the compounds was checked on TLC
plates using silica gel G as stationary phase and iodine vapors as
visualizing agent. The anti-inflammatory activity was carried out
using digital plethysmometer (Ugo-Basile, Italy) and antipyretic
activity was carried out using Elico telethermometer (Hyderabad,
India).
5. Conclusion
In the present paper, we report the synthesis, spectral studies,
and pharmacological evaluation of a novel series of 5-(substituted)
aryl-3-(3-coumarinyl)-1-phenyl-2-pyrazolines (3a–l). These bihe-
terocyclic compounds containing both coumarin and pyrazoline
6.2. Synthesis
6.2.1. General procedure for the synthesis of 3-acetyl coumarin (1)
Table 7
To
a cold mixture of salicylaldehyde (0.2 M) and ethyl-
Ulcerogenic activity of selected compounds in comparison with acetylsalicylic acid
acetoacetate (0.2 M), 2 ml of piperidine was added by rapid stir-
ring. After 20 min the yellowish solid separated was filtered off
subsequently washed with ethanol and was recrystallised from
water:ethanol (3:7), M.P. 120 ꢀC and yield was 83.6%.
Compound
Ulcer index (ꢂSEM)
Control
3d
3e
3i
1.33 (ꢂ0.28)
2.33 (ꢂ0.25)
2.67 (ꢂ0.28)*
2.12 (ꢂ0.11)
1.66 (ꢂ0.14)
4.33 (ꢂ0.63)**
6.2.2. General procedure of preparation of 3-aryl-1-(3-
coumarinyl)propan-1-ones (2a–l)
A mixture of 3-acetyl coumarin (1, 0.01 M) and the various
substituted aromatic aldehydes (0.012 M) were dissolved in 10 ml of
n-butanol under heating; then 0.3 ml of glacial acetic acid and the
3j
Acetylsalicylic acid
The results are expressed as mean ꢂ SEM (n ¼ 6). Data analyzed by one-way ANOVA
followed by Dunnett’s t-test. *p < 0.05 significant from control; **p < 0.01 significant
from control.

S. Khode et al. / European Journal of Medicinal Chemistry 44 (2009) 1682–1688
1687
same quantity of piperidine were added. The reaction mixture was
refluxed for 4 h and then the solvent was removed in vacuum. The
residue was triturated with 10 ml of ethanol until a precipitate
formed. The precipitate was filtered off and crystallized from
appropriate solvent.
utilizing the earlier reported method of Newbould [31]. Normally
fed male albino rats weighing between 150 and 230 g were used for
the experiment. On day 1, 0.1 ml of heat-killed Mycobacterium
tuberculosis (Freund’s adjuvant complete) was injected into the left
hind footpad of each rat. The rats were kept in cages for 15 days. On
day 15, all animals with ‘developed’ arthritis were used for the
study and were divided into six groups of six rats each for various
treatments as shown in Table 4. Control group received 1 ml of 0.5%
sodium CMC, standard group received 13.5 mg/kg b.w. of diclofe-
nac. Test groups received 200 mg/kg b.w. of selected compounds
3d, e, i and j. All compounds were administered orally from day 16
to 19. The hind paw volumes, body weight and degree of secondary
lesions were recorded daily from day 16 to 19. The decrease or
increase, in mean paw volume per group per day was calculated as
a percent inhibition from day 15 onwards.
6.2.3. General procedure for the synthesis 5-(substituted)aryl-3-(3-
coumarinyl)-1-phenyl-2-pyrazoline (3a–l)
3-Aryl-1-(3-coumarinyl)propan-1-ones (2a–l, 0.05 M) and
phenylhydrazine (0.2 M) were dissolved in pyridine (30 ml) and
refluxed for 6 h. Reaction mixture was poured onto the crushed ice
and neutralized with 2 N hydrochloric acid. The precipitated solid
was filtered, dried and recrystallised from appropriated solvent to
afford the title compounds (3a–l). The physicochemical, spectral
and elemental analysis data of the synthesized compounds are
depicted in Tables 1 and 2, respectively.
6.3.5. Analgesic activity
6.3. Pharmacological evaluation
Twenty-four hours prior to actual testing a large number of mice
(20–25 g) received intraperitoneally 10 ml/kg 0.6% glacial acetic
acid. Animals were observed for writhing movements. Only those
showing one or other type of writhing movements (positive
responders) were chosen for the test on the next day. On the test
day the responders received compounds half an hour prior to
glacial acetic acid challenge. Compounds 3d, e, i and j were orally
administered at a dose of 200 mg/kg as a suspension in 0.5% sodium
CMC. Standard drug used was acetylsalicyclic acid at a dose of
30 mg/kg as a suspension in 0.5% sodium CMC. Each mouse was
then observed for the total number of stretching episodes or
writhings for 15 min following glacial acetic acid injection. The
mean value for each group was calculated.
6.3.1. Animals
Albino mice of either sex weighing 20–25 g were used for acute
toxicity studies and analgesic activity. Healthy male albino adult rats
weighing 150–230 g were used for various pharmacological screen-
ings. Animals were procured from Venkateshwara Enterprises, Ban-
galore, India,(245/CPCSEA)andhousedindividuallyinpolypropylene
cages, maintained under standard conditions of alternating 12 h light
and dark cycles at a constant temperature (25 ꢂ 2 ꢀC and 35–60%
relative humidity). Animals were fed with standard rat pellet diet,
(Hindustan Lever Ltd., Mumbai, India) and water ad libitum.
6.3.2. Acute toxicity
The acute toxicity test was carried out according to the Orga-
nization for Economic Co-operation and Development (OECD)
guidelines to establish the effective dose of test compounds after
obtaining ethical clearance from Animal Ethics Committee of KLES
College of Pharmacy, Hubli (India). Albino mice of either sex
weighing between 20 and 25 g were grouped into 12 groups of six
animals each, starved for 24 h with water ad libitum prior to test.
On the day of the experiment animals were administered with
different compounds to different groups in an increasing dose of 10,
20, 100, 200, 1000 and 2000 mg/kg body weight orally. The animals
were then observed continuously for 3 h for general behavioral,
neurological, autonomic profiles and then every 30 min for next 3 h
and finally for next 24 h or till death.
6.3.6. Antipyretic activity
Male albino rats weighing between 170 and 230 g were injected
subcutaneously with 2.5 ml of 20% aqueous suspension of baker’s
yeast. Rectal temperature was recorded using telethermometer
prior to and at 18 h after yeast injection. Rats developing satisfac-
tory pyrexia (raise in body temperature 1.8–2.0 ꢀC) were divided
into six groups of six animals each. Thirty minutes after the eigh-
teenth hour reading, animals of control group received orally 1 ml
of 0.5% sodium CMC, standard group received 135 mg/kg of
p-acetaminophenol and test groups received compounds 3d, e, i
and j at a dose of 200 mg/kg. Temperatures were recorded hourly
up to fifth hour after dosing. The mean temperatures after the
treatment were compared with those of eighteenth hour and
expressed as a temperature index, which was the sum of mean
temperature changes.
6.3.3. Acute anti-inflammatory activity
In vivo acute anti-inflammatory activity was evaluated using
carrageenan-induced rat paw edema assay model of inflammation
by adopting the method of Winter et al. [30] for the compounds
listed in Table 3. Male albino rats (170–220 g) were fasted with free
access to water at least 12 h prior to experiments and were divided
randomly into 14 groups of six each. Control group received 1 ml of
0.5% sodium carboxymethyl cellulose (sodium CMC), standard
group received 13.5 mg/kg of diclofenac and test groups received
200 mg/kg of synthesized compounds (3a–l). The rats were dosed
orally, 1 h later; a subplantar injection of 0.05 ml of 1% solution of
carrageenan in sterile distilled water was administered to the left
hind footpad of each animal. The paw edema volume was measured
with a digital plethysmometer at 0, 2, 4 h after carrageenan injec-
tion. Paw edema volume was compared with vehicle control group
and percent reduction was calculated as 1ꢁ(edema volume in the
drug treated group/edema volume in the control group) ꢃ 100.
6.3.7. Ulcerogenic activity
Albino rats of either sex were divided into control, standard and
different test groups of six animals each group (170–250 g). They
were starved for 48 h (water ad libitum) prior to drug administration.
Control group received only 0.5% sodium CMC solution, standard
group was orally administered with acetylsalicylic acid in sodium
CMC solution and test compounds 3d, e, i and j were administered
orally at the dose of 200 mg/kg b.w. All animals were sacrificed after
7 h of drug administration. Stomach was removed and placed on
saline-soaked filter paper until inspection. A longitudinal incision
along the greater curvature was made with fine scissors. The stomach
was everted over the index finger and the presence or absence of
gastric irritation was determined. The ulcer index for each group was
determined according to a previously reported method [36] by
counting the number of lesions (x) in each of five size classes (y). The
classes were defined as y ¼ 1 (pinpoint lesion), y ¼ 2 (lesions <1 mm
diameter), y ¼ 3 (lesions 1–2 mm diameter), y ¼ 4 (lesions 2–4 mm
diameter) and y ¼ 5 (lesions > 4 mm diameter). The ulcer index was
6.3.4. Chronic anti-inflammatory activity
In vivo chronic anti-inflammatory activity was assessed using
adjuvant-induced arthritis assay model of inflammation by
calculated using
S5i¼1 xiyi.

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