Aroylpropionic acid based 2,5-disubstituted-1,3,4-oxadiazoles: Synthesis and their anti-inflammatory and analgesic activities

Article abstract of DOI:10.1016/j.ejmech.2008.09.005

Synthesis and biological evaluation of various aroylpropionic acid derivatives containing 1,3,4-Oxadiazole nucleus is reported here. The compounds (3a-w) were synthesized by cyclization of 3-aroylpropionic acids into 1,3,4-oxadiazole nucleus by treating with various aryl acid hydrazides in the presence of POCl₃. The structures of new compounds are supported by IR, ¹H NMR and MS data. These compounds were tested in vivo for their anti-inflammatory activity. All the compounds tested showed anti-inflammatory activity. The compounds which showed activity comparable to the standard drug ibuprofen were screened for their analgesic, ulcerogenic and lipid peroxidation activities. Seven (3c, g, i, j, m, o, p) out of 23 new compounds showed very good anti-inflammatory activity in the carrageenan-induced rat paw edema test with very less ulcerogenic action. The compounds, which showed less ulcerogenic action, also showed reduced malondialdehyde production (MDA), which is one of the byproducts of lipid peroxidation. Compound 3i and o showed 89.50 and 88.88% of inhibition in paw edema, 69.80 and 66.25% protection against acetic acid induced writhings and 0.7 and 0.65 of severity index respectively, compared to 90.12, 72.50 and 1.95 values of ibuprofen. The study showed that the cyclization of carboxylic group of aroylpropionic acids into an oxadiazole nucleus resulted in compounds having good anti-inflammatory and analgesic effects with reduced gastric irritation.

Full text of DOI:10.1016/j.ejmech.2008.09.005

European Journal of Medicinal Chemistry 44 (2009) 2372–2378
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Aroylpropionic acid based 2,5-disubstituted-1,3,4-oxadiazoles: Synthesis and
their anti-inflammatory and analgesic activities
*
Mymoona Akhter , Asif Husain, Bismillah Azad, Mohd. Ajmal
Faculty of Pharmacy, Jamia Hamdard University, Department of Pharmaceutical Chemistry, Hamdard Nagar, New Delhi 110062, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 24 April 2008
Received in revised form 25 July 2008
Accepted 1 September 2008
Available online 16 September 2008
Synthesis and biological evaluation of various aroylpropionic acid derivatives containing 1,3,4-Oxadiazole
nucleus is reported here. The compounds (3a–w) were synthesized by cyclization of 3-aroylpropionic acids
into 1,3,4-oxadiazole nucleus by treating with various aryl acid hydrazides in the presence of POCl3. The
structures of new compounds are supported by IR, 1H NMR and MS data. These compounds were tested in
vivo for their anti-inflammatory activity. All the compounds tested showed anti-inflammatory activity. The
compounds which showed activity comparable to the standard drug ibuprofen were screened for their
analgesic, ulcerogenic and lipid peroxidation activities. Seven (3c, g, i, j, m, o, p) out of 23 new compounds
showed very good anti-inflammatory activity in the carrageenan-induced rat paw edema test with very less
ulcerogenic action. The compounds, which showed less ulcerogenic action, also showed reduced malon-
dialdehyde production (MDA), which is one of the byproducts of lipid peroxidation. Compound 3i and o
showed 89.50 and 88.88% of inhibition in paw edema, 69.80 and 66.25% protection against acetic acid induced
writhingsand 0.7 and 0.65 ofseverityindexrespectively, comparedto90.12, 72.50 and 1.95 valuesofibuprofen.
The study showed that the cyclization of carboxylic group of aroylpropionic acids into an oxadiazole nucleus
resulted in compounds having good anti-inflammatory and analgesic effects with reduced gastric irritation.
Ó 2008 Elsevier Masson SAS. All rights reserved.
Keywords:
1,3,4-Oxadiazoles
Aroylpropionic acid
Anti-inflammatory agents
1. Introduction
Studies have shown that derivatization of the carboxylate
function of these agents resulted in reduced ulcerogenic effect
Aryl/aroyl acetic/propionic acid derivatives are widely used as
anti-inflammatory and analgesic agents. But almost all the deriva-
tives of this category like ibuprofen (1), fenbuprofen (2), diclofenac
(3), fenbufen (4) under current clinical usage suffer from a common
drawback of gastrointestinal toxicity due to direct contact of free
carboxylic group with gastrointestinal mucosa and inhibition of
cyclooxygenase enzyme non-selectively [1–3].
while sparing the anti-inflammatory and analgesic activities [4–8].
Furthermore substituted 1,3,4-oxadiazole derivatives also have
been reported to show broad spectrum of biological activities
including anticancer [9], antibacterial [10], anti-inflammatory and
analgesic activities [11–17]. It was of interest to convert the free
carboxylic function of these aroylpropionic acid derivatives into
1,3,4-oxadiazole nucleus and screen the synthesized compounds
for their biological activity. In this paper we report 1,3,4-oxadiazole
derivatives of three different 3-aroylpropionic acids as safer agents
for treatment of inflammatory conditions (Table 1). The synthe-
sized compounds were found to possess an interesting profile of
anti-inflammatory and analgesic activities with significant reduc-
tion in the ulcerogenic effect (Table 2).
HO
O
COOH
O
Ibuprofen (1)
Fenbuprofen (2)
2. Chemistry
COOH
O
Cl
H
N
The synthesis of the title compounds (3a–w) is outlined in
Scheme 1. The required 3-aroylpropionic acids (1a–c) were
prepared by condensing appropriate aromatic compound with
succinic anhydride in presence of anhydrous aluminium chloride
following Friedel-Craft’s acylation reaction conditions [18]. The acid
hydrazides (2a–j) were prepared by esterification of different aryl
acids followed by treatment with hydrazine hydrate in absolute
ethanol [19]. Treatment of 3-aroylpropionic acids (1a–c) with aryl
OH
O
Cl
Diclofenac (3)
Fenbufen (4)
* Corresponding author. Tel.: þ91 11 26059688x5645; fax: þ91 11 26059663.
E-mail address: myzoon@rediffmail.com (M. Akhter).
0223-5234/$ – see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.09.005

M. Akhter et al. / European Journal of Medicinal Chemistry 44 (2009) 2372–2378
2373
Table 1
Physical constants of the newly synthesized 2,5-substituted-1,3,4-oxadiazole derivatives (3a–w)
R
N
N
H
C2
R'
C
O
H2
O
3a-w
Compound
R
R0
MP (ꢄC)
Yield (%)
Compound
R
R0
MP (ꢄC)
Yield (%)
3a
3b
3c
3d
3e
3f
3g
3h
3i
H
H
H
H
C6H5
167–169
158–160
197–199
164–166
176–177
164–166
152–154
148–150
140–142
136–138
132–134
126–128
48
65
56
41
62
58
60
46
56
66
61
52
3m
3n
3o
3p
3q
3r
3s
3t
3u
3v
3w
2,4-(CH3)2
2,4-(CH3)2
2,4-(CH3)2
2,4-(CH3)2
4-CH3
4-Cl C6H5
118–120
108–110
134–136
122–124
166–168
152–154
126–128
130–132
145–148
160–162
144–146
56
38
52
56
54
62
61
39
41
46
56
2-Cl C6H5
4-Cl C6H5
4-NO2 C6H5
C6H5
2-Cl C6H5
4-Cl C6H5
4-NO2 C6H5
4-OCH3 C6H5
3,4-(OCH3)2 C6H5
C6H5
4-NO2 C6H5
4-OCH3 C6H5
3,4-(OCH3)2 C6H5
CH2C6H5
CH2O C6H5
CH2C6H5
4-CH3
4-CH3
4-CH3
4-CH3
4-CH3
4-CH3
2,4-(CH3)2
2,4-(CH3)2
4-CH3
2,4-(CH3)2
2,4-(CH3)2
H
4-CH3
4-CH3
CH2O C6H5
CH2 O 2-C10H7
CH2O 2-C10H7
CH2O 1-C10H7
3j
3k
3l
2-Cl C6H5
acid hydrazides (2a–j) in phosphorus oxychloride resulted in
cyclization of the carboxylic function of 3-aroylpropionic acid into
title compounds (3a–w) in 38–66% yield after crystallization with
methanol. The purity of compounds was checked by TLC in ben-
zene:acetone (8:2). The structure of all the synthesized compounds
was established by 1H NMR, IR, Mass spectral analysis. The result of
elemental analysis of the synthesized compounds were in all cases
within ꢀ0.4% of the theoretical values.
the drugs is shown in Table 2. The percentages of swelling of the
drugs were calculated using Eq. (1).
Inhibition ð%Þ ¼ f½ðVt ꢁ VOÞ control ꢁ ðVt ꢁ VOÞ treatedꢂ=
ꢃ ðVt ꢁ VOÞ controlg ꢃ 100
ð1Þ
(Vt and VO relates to the average volume in the hind paw of the rats
(n ¼ 6) before any treatment and after anti-inflammatory agent
treatment, respectively).
All the synthesized compounds tested for anti-inflammatory
activity showed inhibition of edema ranging from 24 to 90%.
Compounds (3c, g, i, j, m, o, p) showed very good anti-inflamma-
tory activity. 2-[3-(4-Methylphenyl)-propane-3-one]-5-(4-metho
xyphenyl)-1,3,4-oxadiazoles (3i) (89.50%) and 2-[3-(2,4-dimethyl-
phenyl)-propane-3-one]-5-(4-methoxyphenyl)-1,3,4-oxadiazoles
(3o) (88.88%) were equipotent to ibuprofen (90.12%) in inhibiting
the paw edema in rats. Compound 2-(3-phenyl propane-3-one)-5-
(4-chlorophenyl)-1,3,4-oxadiazole (3c), 2-[3-(4-methyl phenyl)-
propane-3-one]-5-(4-chlorophenyl)-1,3,4-oxadiazole (3g) showed
anti-inflammatory activity 81.46 and 81.48%, respectively,
compared to the standard drug. Compounds 3j, m, n and p showed
inhibition in edema equivalent to 80% of inhibition by ibuprofen.
Oxadiazoles having substituted phenyl ring at 5th position were in
general more active than unsubstituted ones, indicating that the
presence of functional groups may be helpful in properly orienting
the molecule in active site. The presence of 4-methoxyphenyl or
3,4-dimethoxyphenyl substitution at 5th position of oxadiazole
3. Results and discussion
Protocol of animal experiments has been approved by the
Institutional Animal Ethics Committee (IAEC). The anti-inflamma-
tory activity of newly synthesized compounds (3a–w) was carried
out on Wistar rats by Winter et al. [20] method using ibuprofen as
reference compound. Analgesic activity was carried out on albino
mice by Seigmund et al. [21] method and ulcerogenic activity was
carried out by Cioli et al. [22] method. Lipid peroxidation studies
were carried by Ohkawa et al. [23] method.
3.1. Anti-inflammatory activity
The anti-inflammatory activity of compounds was carried out at
an equimolar oral dose relative to 20 mg kgꢁ1 of ibuprofen. The
percent edema inhibition relative to control was measured after 2
and 3 h of the treatment. The inhibition of swelling in carrageenan-
induced edema in rat paw brought about by oral administration of
Table 2
Percentage of inhibition caused by synthesized compounds in carrageenan-induced edema in rats after 2 and 3 h of test drug administration
Compound
Anti-inflammatory activity
Compound
Anti-inflammatory activity
(% inhibition ꢀ S.E.M.)
(% inhibition ꢀ S.E.M.)
2h
3h
2h
3h
3a
3b
3c
3d
3e
3f
3g
3h
3i
18.66 ꢀ 4.34
26.89 ꢀ 3.20
41.97 ꢀ 3.76
40.88 ꢀ 3.29
33.33 ꢀ 3.20
36.21 ꢀ 2.30
62.667 ꢀ 1.52
52.0 ꢀ 2.98
29.42 ꢀ 3.22
35.80 ꢀ 2.67
81.46 ꢀ 1.52*
62.66 ꢀ 3.29*
49.3 ꢀ 2.72
3n
3o
3p
3q
3r
3s
3t
3u
3v
3w
Ibuprofen
Control
40.0 ꢀ 3.18
62.66 ꢀ 3.29
58.66 ꢀ 3.49
24.66 ꢀ 1.94
25.33 ꢀ 2.70
25.33 ꢀ 4041
27.55 ꢀ 3.11
29.78 ꢀ 3.39
24.66 ꢀ 2.48
24.00 ꢀ 3.87
80.89 ꢀ 3.11
–
69.13 ꢀ 1.68*
88.88 ꢀ 2.09*
75.31 ꢀ 2.04*
51.85 ꢀ 2.40
41.97 ꢀ 1.71
49.98 ꢀ 3.4
45.67 ꢀ 2.76
51.03 ꢀ 4.16
49.38 ꢀ 3.40
37.03 ꢀ 2.24
90.12 ꢀ 1.79*
–
57.33 ꢀ 2.39
81.48 ꢀ 0.64*
60.49 ꢀ 2.14
89.50 ꢀ 2.60*
72.63 ꢀ 2.25*
58.02 ꢀ 2.16
60.49 ꢀ 2.35
72.63 ꢀ 2.25*
69.33 ꢀ 1.94
53.31 ꢀ 2.39
36.0 ꢀ 3.89
3j
3k
3l
33.54 ꢀ 2.93
53.33 ꢀ 2.39
3m
n ¼ 6, *p < 0.01 compared to control.

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M. Akhter et al. / European Journal of Medicinal Chemistry 44 (2009) 2372–2378
R'
N
N
R'
H2
H2NHN
O
O
C
O
C
H2
(2a-f)
(3a-p)
R
R
R'
R
R'
R
R'
3a H
H
4- CH3
4- CH3
4- CH3
4- CH3
2,4-(CH3),
2,4-(CH3),
3m 2,4-(CH3),
3n 2,4-(CH3),
3o 2,4-(CH3),
3p 2,4-(CH3),
4-Cl
3g
3h
3i
4-Cl
3b H
2-Cl
4-Cl
4-No2
4-NO2
4-OCH3
3, 4-(OCH3)2
H
3c H
4-OCH3
3, 4-(OCH3)2
3d H
4-NO2
H
2-Cl
3j
3e 4- CH3
3k
3l
3f
4- CH3
2-Cl
R
O
X
N
N
H2
C
(i )
H2 NHN
O
X
C
H2
O
(2g, 2h)
H2
(3q-t)
C
COOH
O
R
C
R
X
(ii)
H2
R
3q 4-CH3
3r 4-CH3
3s 2,4-(CH3), CH2
3t 2,4-(CH3), CH2O
CH2
CH2O
R
N
CH2-O
N
H2NHN
1a = H
1b = 4-CH3
1c= 2,4-(CH3)2
H2
C
O
O
C
H2
CH2O
(3u, v)
3u: R = H; 3v:R = 4-CH3
O
(2i)
R
O
N
N
H2
C
NHNH2
(2j)
O
C
H2
O
C
H2
(3w)
CH3
Scheme 1. Reagent and conditions: (i) succinic anhydride, anhydrous AlCl3, reflux; (ii) POCl3, reflux.
ring seems important for good anti-inflammatory activity. Presence
of other electronegative group at para position of phenyl ring at 5th
position of oxadiazole nucleus also resulted in increased activity.
However, replacement of substituted phenyl with benzoyl group
resulted in decrease in activity. Loss of activity was also observed
when phenyl group at 5th position oxadiazole nucleus was
replaced by bulky group like naphthoyl. Statistical significance
testing using one-way analysis of variance showed that the anti-
inflammatory activity of ibuprofen and all the newly synthesized
compounds were effective in comparison with the control group
(p < 0.01). Since compounds (3i and o) showed anti-inflammatory
activity at par to ibuprofen; therefore, it was of interest to study the
anti-inflammatory of these compounds for longer duration (12 h).
It was observed that the compounds were practically effective in
inhibiting the edema for longer duration (8 h) compared to
ibuprofen (Table 3). Compounds, which showed more than 60%
inhibition in edema, were further screened for their analgesic effect
and ulcerogenic profile.
3.2. Analgesic activity
Compounds (3c, d, g–j, l–p) showing more than 60% of inhibi-
tion in swelling induced by carrageenan were further tested for
analgesic activity at the same dose as used for anti-inflammatory
activity. The percent protection in mice brought about by admin-
istration of the drugs is shown in Table 4. The compounds tested
showed analgesic activity in the range of 47–70%. The percent
protection was calculated using Eq. (2).
Protection ð%Þ ¼ 100 ꢁ ½number of writhings in test=number of writhing in control ꢃ 100ꢂ
(2)

M. Akhter et al. / European Journal of Medicinal Chemistry 44 (2009) 2372–2378
2375
Table 3
irritant to gastric mucosa. To correlate the ulcerogenic profile of
compounds the lipid peroxidation values were also determined.
Compounds which were screened for ulcerogenic activity were
therefore analyzed for lipid peroxidation. The lipid peroxidation
was measured as nmoles of MDA per 100 mg of tissue. Animals
treated with ibuprofen exhibited 7.51 whereas control group
showed 2.59 and the groups treated with synthesized compounds
showed lipid peroxidation in the range of (3–5.5) (Table 4). These
findings further confirm that the synthesized compounds are less
irritant to gastric mucosa.
Percentage of inhibition caused by ibuprofen, 3j and t in carrageenan-induced
edema in rats
Time (h)
2
3
4
8
12
Ibuprofen 80.89 ꢀ 2.05* 90.12 ꢀ 1.79* 65.45 ꢀ 1.68* 46.72 ꢀ 1.12* 39.06 ꢀ 1.22*
3i
3o
69.33 ꢀ 1.94* 89.50 ꢀ 2.60* 77.14 ꢀ 2.23* 63.39 ꢀ 1.68* 42.71 ꢀ 1.54*
62.66 ꢀ 3.29* 88.88 ꢀ 2.09* 75.70 ꢀ 1.98* 57.14 ꢀ 1.59* 44.82 ꢀ 1.86*
Data are represented as mean ꢀ SEM, n ¼ 6, *p < 0.01 compared to control.
All the above observations suggest that cyclization of carboxylic
group of aroylpropionic acids into oxadiazole nucleus results in safe
anti-inflammatory agents which is supported by the fact that the
synthesized compounds were less corrosive to GIT as indicated by
severity index and lipid peroxidation values. Further studies to
acquire more information about structure–activity relationship are
in progress in our laboratory.
Compound 3i and o showed 69.80 and 66.25% of protection
respectively, against acetic acid induced writhings compared to
72.50%protectionwithibuprofen.Similarpatterninanalgesiceffectof
compounds was observed as was seen in anti-inflammatory activity.
Compound bearing electronegative group at 4th position of phenyl
ring were good in analgesic effect compared to other substitutions.
3.3. Acute ulcerogenesis
4. Conclusions
The compounds which were screened for analgesic activity were
studied for their gastric irritation activity. The ulcerogenic effect of
ibuprofen and newly synthesized compounds were studied at
60 mg kgꢁ1 in rats. It was observed that the ulcerogenic effect of
test compounds (3c, d, g–j, l–p) was appreciably less than
ibuprofen. Less number of ulcers were seen in animals treated with
test compounds compared with the animals treated with
ibuprofen. The tested compounds showed severity index ranging
from 0.65 to 1.15, whereas the standard drug ibuprofen showed
high severity index of 1.95 comparatively (Table 4). Compounds 3i,
m and o showed severity index of 0.7, 0.71 and 0.65 respectively,
which is less than half the value of ibuprofen (1.95). These findings
support the statement that the derivatization of carboxylic function
of aroylpropionic acids results in decreased gastric irritation and
that these newly synthesized compounds may be considered as
safer drugs for treating inflammation conditions.
Various derivatives of aroylpropanoic acid containing oxadia-
zole nucleus were successfully synthesized and screened for anti-
inflammatory, analgesic, ulcerogenic activities and lipid perox-
idation studies. Some of the synthesized compounds (3c, g, i, j, m, o,
p) were very safe with anti-inflammatory and analgesic activities
comparable to ibuprofen. All the synthesized compounds showed
anti-inflammatory activity but only compounds 3c, d, g, h–j, l–p
were tested for analgesic and ulcerogenic activities and lipid per-
oxidation studies. The tested compounds were found good in anal-
gesic effects and less irritant to gastric mucosa as indicated by
severity index. The lipid peroxidation values of the compounds
tested were also less than the standard drug. The results obtained
support the statement that the synthesized compounds may be used
as safer anti-inflammatory agents.
5. Experimental
3.4. Lipid peroxidation
All the reagents and solvents used were procured from E Merck
(India) Ltd., ibuprofen was obtained as gift sample from Sun Phar-
maceuticals Pvt. Ltd. All the solvents used were dried and distilled
before use. Animals were procured from Institutional animal house.
Melting points were determined in open-end capillary tubes using
Kjeldhal flask containing liquid paraffin and are uncorrected. IR
spectra were recorded in KBr on Bio-Rad FTIR spectrometer FTS 135
and proton nuclear magnetic resonance (1H NMR) spectra were
recorded on Brucker Avance (300 MHz) in DMSO-d6. Chemical
shifts are reported in parts per million (ppm) using tetramethyl
silane (TMS) as an internal standard. Mass spectra were recorded
on JEOL 5x102/DA-6000 Mass Spectrometer/Data system using
Argon/Xenon (6 kV, 10 mA) as the FAB gas. The purity of the
compounds was monitored by ascending thin layer chromatog-
raphy (TLC) on silica gel G (Merck), visualized by iodine vapour or
UV. Developing solvents were benzene:acetone (8:2).
Compounds, which are less irritant to gastric mucosa, are also
reported to show reduced malondialdehyde (MDA) content,
a byproduct of lipid peroxidation [23]. Therefore by determining
the MDA levels it can be ascertained that the compounds are less
Table 4
Percentage protection in acetic acid induced writhings by test compounds and
corrosive effects observed on gastric mucosa of rats treated with single oral dose of
test compounds
Compound
number
Analgesic activity
No. of
Ulcerogenic
activity (S.I.)
nmols of MDA
content ꢀ S.E.M.
per
%
writhings ꢀ SEM Protection
100 mg tissue
3c
3d
3g
3h
3i
3j
3l
3m
3n
3o
3p
Ibuprofen
Control
8.99 ꢀ 1.12
10.17 ꢀ 0.79
10.00 ꢀ 0.82
11.33 ꢀ 0.89
7.33 ꢀ 0.66
9.15 ꢀ 0.76
10.49 ꢀ 0.95
9.63 ꢀ 0.86
12.83 ꢀ 0.95
8.21 ꢀ 1.32
10.66 ꢀ 1.21
6.67 ꢀ 0.68
24.33 ꢀ 0.24
63.00*
58.20*
58.89*
53.43*
69.80*,
62.39*
56.80*
60.42*
47.20*
66.25*,
56.10*
72.50*,
–
1.12 ꢀ 0.12**
0.98 ꢀ 0.18**
5.32 ꢀ 0.65Y
4.95 ꢀ 0.56Y
0.98 ꢀ 0.25** 4.25 ꢀ 0.35Y
0.95 ꢀ 0.32** 3.95 ꢀ 0.85Y
Y
0.70 ꢀ 0.21**
0.87 ꢀ 0.14**
0.89 ꢀ 0.36**
3.15 ꢀ 0.46Y
3.85 ꢀ 0.35Y
4.15 ꢀ 0.74Y
5.1. Synthesis of 3-aroylpropionic acid derivatives (1a–c)
Synthesis of 3-aroylpropionic acid derivatives (1a–c) was
carried out by reported procedure given in Organic Synthesis
Collective Vol III [18].
0.71 ꢀ 0.51** 3.26 ꢀ 0.23Y
0.87 ꢀ 0.18**
4.42 ꢀ 0.52Y
0.65 ꢀ 0.21** 3.79 ꢀ 0.52Y
Y
Y
1.12 ꢀ 0.13**
1.95 ꢀ 0.10**
–
5.12 ꢀ 0.36Y
7.51 ꢀ 0.65
2.59 ꢀ 0.20
5.2. General procedure for 2-[3-(substituted phenyl)propan-3-
one]-5-(aryl)-1,3,4-oxadiazole (3a–w)
Severity index (S.I.): mean score of each treated group minus the mean score of the
control group.
Appropriate aryl acid hydrazide (2) (1 mmol) was dissolved in
phosphorus oxychloride (5 mL) and to it was added appropriate
propanoic acid (1) (1 mmol). The reaction mixture, after refluxing for
*p < 0.01 compared to control, **p < 0.001 compared to control, *Yp < 0.001
compared to control.
Yp < 0.001 compared to control.

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M. Akhter et al. / European Journal of Medicinal Chemistry 44 (2009) 2372–2378
5 h, wascooledtoroom temperatureandpouredontocrushedice. The
contents were neutralized with sodium bicarbonate solution (20%),
a solid mass separated out which was filtered, washed with water and
dried. It was crystallized from methanol/ethanol.
2.68 and 3.31 (t, each, 2 ꢃ CH2), 6.99 (d, 1H, H-5, dimethoxyphenyl),
7.15 (d, 1H, H-2, dimethoxyphenyl), 7.39 (dd, 1H, H-6, dimethox-
yphenyl), 7.24 and 7.86 (d, each, A2B2, p-methyl phenyl); Mass (m/z)
352 (Mþ).
5.2.1. 2-(3-Phenyl propane-3-one)-5-phenyl-1,3,4-oxadiazole (3a)
IR (cmꢁ1, KBr): 2963, 1670, 1445, 1056, 783. 1H NMR (DMSO-d6)
5.2.11. 2-[3-(2,4-Dimethylphenyl)-propane-3-one]-5-phenyl-1,3,4-
oxadiazole (3k)
d
2.62 and 3.28 (t, each, 2 ꢃ CH2), 7.49–7.52 (m, 3H, H-3,4,5,phenyl),
IR (cmꢁ1, KBr): 2940, 1655, 1458, 1059, 755; 1H NMR (DMSO-d6)
7.73–7.77 (m, 2H, H-2,6,phenyl), 7.87–7.92 (m, 5H, phenyl); Mass
d
2.34 and 2.51 (s, each, 2 ꢃ CH3), 2.76 and 3.27 (t, each, 2 ꢃ CH2),
(m/z) 278 (Mþ).
7.07–7.21, 7.38–7.40, 7.62–7.66, 7.75–7.78 (m, each, 8H, 2 ꢃ phenyl);
Mass (m/z) 306 (Mþ).
5.2.2. 2-(3-Phenyl propane-3-one)-5-(2-chlorophenyl)-1,3,4-
oxadiazole (3b)
5.2.12. 2-[3-(2,4-Dimethylphenyl)-propane-3-one]-5-(2-
chlorophenyl)-1,3,4-oxadiazole (3l)
IR (cmꢁ1, KBr): 2982, 1665, 1475, 1070, 812. 1H NMR (DMSO-d6)
d
2.64 and 3.32 (t, each, 2 ꢃ CH2), 7.52–7.56 (m, 4H, H-3,4,5,6,o-
IR (cmꢁ1, KBr): 2955, 1650, 1465, 1070, 807; 1H NMR (DMSO-d6)
chloro phenyl), 7.76–7.91 (m, 5H, phenyl); Mass (m/z) 312 (Mþ).
d
2.35 and 2.49 (s, each, 2 ꢃ CH3), 2.78 and 3.27 (t, each, 2 ꢃ CH2),
7.11–7.16 (m, 2H, H-3,5,xylene), 7.32–7.37 (m, 4H, H-3,4,5,6,o-chloro
phenyl), 7.65 (d, 1H, H-6, xylene); Mass (m/z) 341 (Mþ).
5.2.3. 2-(3-Phenyl propane-3-one)-5-(4-chlorophenyl)-1,3,4-
oxadiazole (3c)
IR (cmꢁ1, KBr): 3005, 1650, 1456, 1071, 805; 1H NMR (DMSO-d6)
5.2.13. 2-[3-(2,4-Dimethylphenyl)-propane-3-one]-5-(4-
chlorophenyl)-1,3,4-oxadiazole (3m)
d
2.65 and 3.36 (t, each, 2 ꢃ CH2), 7.31–7.33 and 7.47–7.51 (m, 4H, p-
chlorophenyl), 7.66–7.69 (m, 5H, phenyl); Mass (m/z) 312 (Mþ).
IR (cmꢁ1, KBr): 2955, 1666, 1510, 1072, 821; 1H NMR (DMSO-d6)
d
2.39 and 2.52 (s, each, 2 ꢃ CH3), 2.81 and 3.29 (t, each, 2 ꢃ CH2),
5.2.4. 2-(3-Phenyl propane-3-one)-5-(4-nitrophenyl)-1,3,4-
oxadiazole (3d)
7.15–7.20 (m, 2H, H-3,5,phenyl), 7.66 (d, 1H, H-6, phenyl), 7.71 and
7.78 (d, each, A2B2, p-chlorophenyl); Mass (m/z) 341 (Mþ).
IR (cmꢁ1, KBr): 2991, 1671, 1485, 1078, 812; 1H NMR (DMSO-d6)
d
2.61 and 3.31 (t, each, 2 ꢃ CH2), 7.26–7.98 (complex m, 8H,
5.2.14. 2-[3-(2,4-Dimethylphenyl)-propane-3-one]-5-(4-
nitrophenyl)-1,3,4-oxadiazole (3n)
2 ꢃ phenyl); Mass (m/z) 323 (Mþ).
IR (cmꢁ1, KBr): 2956, 1665, 1504, 1073, 825; 1H NMR (DMSO-d6)
5.2.5. 2-[3-(4-Methylphenyl)-propane-3-one]-5-phenyl-1,3,4-
oxadiazole (3e)
d
2.38 and 2.53 (s, each, 2 ꢃ CH3), 2.79 and 3.28 (t, each, 2 ꢃ CH2),
7.13–7.17 (m, 2H, H-3,5,phenyl), 7.67 (d, 1H, H-6, phenyl), 7.75 and
IR (cmꢁ1, KBr): 2970, 1650, 1455, 1058, 793; 1H NMR (DMSO-d6)
7.83 (d, each, A2B2, p-nitrophenyl); Mass (m/z) 365 (Mþ).
d
2.39 (s, 3H, CH3), 2.68 and 3.32 (t, each, 2 ꢃ CH2), 7.29–7.32 (m, 3H,
H-3,4,5,phenyl), 7.73–7.75 (m, 2H, H-2,6,phenyl), 7.28 and 7.87 (d,
5.2.15. 2-[3-(2,4-Dimethylphenyl)-propane-3-one]-5-(4-
methoxyphenyl)-1,3,4-oxadiazole (3o)
each, A2B2, p-methyl phenyl); Mass (m/z) 292 (Mþ).
IR (cmꢁ1, KBr): 2945, 1655, 1461, 1057, 783; 1H NMR (DMSO-d6)
5.2.6. 2-[3-(4-Methylphenyl)-propane-3-one]-5-(2-chlorophenyl)-
1,3,4-oxadiazole (3f)
d
2.33 and 2.48 (s, each, 2 ꢃ CH3), 2.77 and 3.27 (t, each, 2 ꢃ CH2),
7.05–7.13 (m, 2H, H-3,5,phenyl), 7.63 (d, 1H, H-6, phenyl), 6.97 and
IR (cmꢁ1, KBr): 2990, 1656, 1470, 1069, 810; 1H NMR (DMSO-d6)
7.68 (d, each, A2B2, p-methoxyphenyl); Mass (m/z) 336 (Mþ).
d
2.41 (s, 3H, CH3), 2.68 and 3.33 (t, each, 2 ꢃ CH2), 7.32–7.36 (m, 4H,
H-3,4,5,6,o-chloro phenyl), 7.34 and 7.86 (d, each, A2B2, p-methyl
phenyl); Mass (m/z) 326 (Mþ).
5.2.16. 2-[3-(2,4-Dimethylphenyl)-propane-3-one]-5-(3,4-
dimethoxyphenyl)-1,3,4-oxadiazole (3p)
IR (cmꢁ1, KBr): 2962, 1655, 1471, 1071, 806; 1H NMR (DMSO-d6)
5.2.7. 2-[3-(4-Methylphenyl)-propane-3-one]-5-(4-chlorophenyl)-
1,3,4-oxadiazole (3g)
d
2.35 and 2.49 (s, each, 2 ꢃ CH3), 2.78 and 3.27 (t, each, 2 ꢃ CH2),
3.93 and 3.98 (s, each, 6H, 2 ꢃ OCH3), 7.03–7.56 (m, 6H, 2 ꢃ phenyl);
IR (cmꢁ1, KBr): 3005, 1660, 1462, 1071, 809; 1H NMR (DMSO-d6)
Mass (m/z) 366 (Mþ).
d
2.36 (s, 3H, CH3), 2.67 and 3.35 (t, each, 2 ꢃ CH2), 7.31, 7.47, 7.66,
7.89 (d, each, 2 ꢃ A2B2, 2 ꢃ phenyl); Mass (m/z) 326 (Mþ).
5.2.17. 2-[3-(4-Methylphenyl)-propane-3-one]-5-benzyl-1,3,4-
oxadiazole (3q)
IR (cmꢁ1, KBr): 2969, 1650, 1480, 1056, 805; 1H NMR (DMSO-d6)
5.2.8. 2-[3-(4-Methylphenyl)-propane-3-one]-5-(4-nitrophenyl)-
1,3,4-oxadiazole (3h)
d
2.37 (s, 3H, CH3), 2.66 and 3.31 (t, each, 2 ꢃ CH2), 4.12 (s, 2H, CH2),
IR (cmꢁ1, KBr): 2996, 1650, 1490, 1075, 818; 1H NMR (DMSO-d6)
7.42–7.46 (m, 3H, H-3,4,5,phenyl), 7.61–7.65 (m, 2H, H-2,6,phenyl),
7.33 and 7.81 (d, each, A2B2, p-methyl phenyl); Mass (m/z) 306 (Mþ).
d
2.37 (s, 3H, CH3), 2.62 and 3.23 (t, each, 2 ꢃ CH2), 7.26–7.98
(complex m, 8H, 2 ꢃ phenyl); Mass (m/z) 337 (Mþ).
5.2.18. 2-[3-(4-Methylphenyl)-propane-3-one]-5-phenoxymethyl-
1,3,4-oxadiazole (3r)
5.2.9. 2-[3-(4-Methylphenyl)-propane-3-one]-5-(4-
methoxyphenyl)-1,3,4-oxadiazoles (3i)
IR (cmꢁ1, KBr): 2990, 1655, 1485, 1055, 790; 1H NMR (DMSO-d6)
IR (cmꢁ1, KBr): 3010, 1665, 1490, 1062, 795; 1H NMR (DMSO-d6)
d
2.38 (s, 3H, CH3), 2.68 and 3.29 (t, each, 2 ꢃ CH2), 4.56 (s, 2H,
d
2.36 (s, 3H, CH3), 3.84 (s, 3H, OCH3), 2.64 and 3.23 (t, each,
OCH2), 7.48–7.51 (m, 3H, H-3,4,5,phenyl), 7.64–7.67 (m, 2H, H-
2,6,phenyl), 7.28 and 7.79 (d, each, A2B2, p-methyl phenyl); Mass
(m/z) 322 (Mþ).
2 ꢃ CH2), 7.09 and 7.78 (d, each, A2B2, p-methyl phenyl), 7.46 and
7.96 (d, each, A2B2, p-methoxyl phenyl); Mass (m/z) 322 (Mþ).
5.2.10. 2-[3-(4-Methylphenyl)-propane-3-one]-5-(3,4-
dimethoxyphenyl)-1,3,4-oxadiazole (3j)
5.2.19. 2-[3-(2,4-Dimethylphenyl)-propane-3-one]-5-benzyl-1,3,4-
oxadiazole (3s)
IR (cmꢁ1, KBr): 3010, 1655, 1484, 1060, 822; 1H NMR (DMSO-d6)
IR (cmꢁ1, KBr): 2908, 1654, 1451, 1061, 780; 1H NMR (DMSO-d6)
d
2.41 (s, 3H, CH3), 3.97 (two closely spaced singlets, 6H, 2 ꢃ OCH3),
d
2.33 and 2.50 (s, each, 2 ꢃ CH3), 2.75 and 3.28 (t, each, 2 ꢃ CH2),

M. Akhter et al. / European Journal of Medicinal Chemistry 44 (2009) 2372–2378
2377
4.11 (s, 2H, CH2), 7.05–7.75 (complex m, 8H, 2 ꢃ phenyl); Mass (m/z)
1 mL per 100 g body weight of the animal. Number of writhings
were counted for 10 min in control, standard and test compounds
and compared. Analgesic activity was measured as percent
decrease in writhings in comparison to control. All the results are
expressed as mean ꢀ S.E.M. Statistical evaluation was performed
using analysis of variance followed by t-test for sub-group
comparison.
320 (Mþ).
5.2.20. 2-[3-(2,4-Dimethylphenyl)-propane-3-one]-5-
phenoxymethyl-1,3,4-oxadiazole (3t)
IR (cmꢁ1, KBr): 2916, 1650, 1463, 1060, 762; 1H NMR (DMSO-d6)
d
2.36 and 2.53 (s, each, 2 ꢃ CH3), 2.77 and 3.31 (t, each, 2 ꢃ CH2),
4.59 (s, 2H, OCH2), 7.09–7.93 (complex m, 8H, 2 ꢃ phenyl); Mass (m/
z) 336 (Mþ).
5.5. Acute ulcerogenesis
5.2.21. 2-(3-Phenyl propane-3-one)-5-(1-naphthoxymethyl)-1,3,4-
oxadiazole (3u)
The studies were carried out on healthy Wistar rats (150–200 g)
at a dose three times the anti-inflammatory dose viz. 60 mg kgꢁ1
.
IR (cmꢁ1, KBr): 3015, 1655, 1470, 1056, 790; 1H NMR (DMSO-d6)
The animals were divided into different groups of six each, group I
served as control and received vehicle only and groups II received
pure ibuprofen 60 mg kgꢁ1. Other groups were administered test
compounds in dose molecularly equivalent to 60 mg kgꢁ1 of
ibuprofen. The animals were fasted 8 h prior to a single dose of each
of the vehicle, standard and test compounds, respectively, and
sacrificed 17 h later during which period food and water were
available. The gastric mucosa of the rats was examined by means of
a 4ꢃ binocular magnifier. For each stomach the severity of mucosal
damage was assessed according to the following scoring system:
0 – no lesions of upto five punctiform lesions; 1 – more than five
punctiform lesions; 2 – one to five small ulcers; 3 – more than five
small ulcers of one large ulcer; 4 – more than one large ulcer [22].
The mean score of each treated group minus the mean score of the
control group was considered as the ‘severity index’ of gastric
damage (level of significance p < 0.001).
d
2.63 and 3.29 (t, each, 2 ꢃ CH2), 2.75 (s, 2H, CH2), 7.36–7.39 and
7.79–7.81 (m, each, 7H, naphthyl), 7.29–7.33 (m, 5H phenyl); Mass
(m/z) 358 (Mþ).
5.2.22. 2-[3-(4-Methylphenyl)-propane-3-one]-5-(2-
naphthoxymethyl)-1,3,4-oxadiazole (3v)
IR (cmꢁ1, KBr): 2985, 1655, 1460, 1062, 823; 1H NMR (DMSO-d6)
2.41 (s, 3H, CH3), 2.69 and 3.31 (t, each, 2 ꢃ CH2), 2.92 (s, 2H, CH2),
d
7.28–7.31 and 7.83–7.88 (m, each, 7H, naphthyl), 7.34 and 7.86 (d,
each, A2B2, p-methyl phenyl); Mass (m/z) 372 (Mþ).
5.2.23. 2-[3-(4-Methylphenyl)-propane-3-one]-5-(1-
naphthoxymethyl)-1,3,4-oxadiazole (3w)
IR (cmꢁ1, KBr): 3005, 1650, 1460, 1060, 810; 1H NMR (DMSO-d6)
2.39 (s, 3H, CH3), 2.65 and 3.25 (t, each, 2 ꢃ CH2), 2.85 (s, 2H, CH2),
d
7.36–7.39 and 7.79–7.82 (m, each, 7H, naphthyl), 7.29 and 7.88 (d,
each, A2B2, p-methyl phenyl); Mass (m/z) 372 (Mþ).
5.6. Lipid peroxidation
5.3. Anti-inflammatory activity
Lipid peroxidation in the gastric mucosa was determined
according to the method of Ohkawa et al. [23]. After screening the
animals for ulcerogenic effect of synthesized drugs the gastric
mucosa of animals was scraped with two glass slides, weighed
(100 mg) and homogenized in 1.8 mL of 1.15% ice-cold KCl solution.
The homogenate was supplemented with 0.2 mL of 8.1% sodium
dodecyl sulphate (SDS), 1.5 mL of acetate buffer (pH 3.5) and 1.5 mL
of 0.8% thiobarbituric acid (TBA). The mixture was heated at 95 ꢄC
for 60 min. The cooled reactants were shaken vigorously for 1 min
and centrifuged for 10 min at 4000 rpm after supplementing with
5 mL of a mixture of n-butanol and pyridine (15:1 v/v). The
supernatant organic layer was collected and absorbance was
measured at 532 nm on UV spectrophotometer. The results are
expressed as nmols of MDA per 100 mg tissue, using extinction
The anti-inflammatory activity was evaluated using carra-
geenan-induced paw odema on rat [20] method. Wistar rats (150–
200 g) were divided into groups of six animals each. Group I served
as the control group without using the drug, group II received
ibuprofen 20 mg kgꢁ1, other groups received test drugs in dose
molecularly equivalent to the ibuprofen. Drug solutions were
prepared as a homogeneous suspension in aqueous solution of
sodium CMC (0.5% w/v) and were administered orally to the
animals. Thirty minutes after administration of drugs, each rat
received a sub-planter injection of 0.1 mL of 1% carrageenan solu-
tion in its left hind paw. The measurement of the hind paw volume
was carried out using a Ugo Basile Plethysmometer before any
treatment (Vo) and in any interval (Vt) after the administration of
the drugs. All the results are expressed as mean ꢀ S.E.M. Statistical
evaluation was performed using analysis of variance followed by
t-test for sub-group comparison.
coefficient 1.56 ꢃ 105 cmꢁ1 Mꢁ1
.
Acknowledgement
5.4. Analgesic activity
The authors are thankful to Hakeem Abdul Hameed Saheb
(founder Chancellor and builder of Jamia Hamdard) and Mr. A.
Mueed (President, Hamdard National foundation) for providing the
necessary facilities to carry out this research work. Authors are also
thankful to CDRI for spectral analysis of the compounds and Mrs.
Shaukat Shah, in-charge Animal House Jamia Hamdard for
providing animals.
Compounds 3c, d, g–j, l–p were tested for analgesic activity.
Analgesic activity was carried out by using acetic acid induced
writhing method [21] in Swiss albino mice (25–30 g) of either sex.
A 1% v/v solution of acetic acid was used as writhing inducing agent.
Since the maximum anti-inflammatory effect was observed at 3 h
post-treatment the analgesic effect was also studied after 3 h of
drug administration. Test compounds were administered orally 3 h
prior to acetic acid injection. Mice were divided into groups of six
animals each. Group I served as a control group without using the
drug, while group II received ibuprofen 20 mg kgꢁ1, other groups
received test drugs in dose molecularly equivalent to 20 mg kgꢁ1 of
ibuprofen. All drugs were prepared as a homogeneous suspension
in aqueous solution of sodium CMC (0.5% w/v) and administered
orally to animals. Acetic acid was administered intraperitoneally
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