Synthesis and pharmacological evaluation of novel 5-substituted-1-(phenylsulfonyl)-2-methylbenzimidazole derivatives as anti-inflammatory and analgesic agents

Article abstract of DOI:10.1016/j.ejmech.2010.01.067

A series of novel 5-substituted-1-(phenylsulfonyl)-2-methylbenzimidazole derivatives have been synthesized. The structures of these compounds were established by IR, ¹H NMR, ¹³C NMR, Mass spectral data and elemental analyses. Compounds were evaluated for their anti-inflammatory and analgesic activity as well as gastric ulcerogenic effects. Derivatives 4a, 4b and 4c exhibited moderate to good anti-inflammatory and analgesic activity in carrageenan-induced rat paw edema and acetic acid-induced writhing in mice, respectively, with low ulcerogenicity compared with the standard drug indomethacin.

Full text of DOI:10.1016/j.ejmech.2010.01.067

European Journal of Medicinal Chemistry 45 (2010) 2245–2249
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 novel
5-substituted-1-(phenylsulfonyl)-2-methylbenzimidazole
derivatives as anti-inflammatory and analgesic agents
,
b
,
b
b,
Monika Gaba a , Dhandeep Singh , Sarbjot Singh c, Vikas Sharma b, Punam Gaba a
*
a Department of Pharmaceutical Sciences, ASBASJSM College of Pharmacy, Bela, Ropar, Punjab, India
b Department of Pharmaceutical Sciences and Drug Research, Punjabi University, Patiala, Punjab, India
c Biology Research, Drug Discovery Research, Panacea Biotech Pvt. Ltd., Mohali, Punjab, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A
series of novel 5-substituted-1-(phenylsulfonyl)-2-methylbenzimidazole derivatives have been
synthesized. The structures of these compounds were established by IR, 1H NMR, 13C NMR, Mass spectral
data and elemental analyses. Compounds were evaluated for their anti-inflammatory and analgesic
activity as well as gastric ulcerogenic effects. Derivatives 4a, 4b and 4c exhibited moderate to good anti-
inflammatory and analgesic activity in carrageenan-induced rat paw edema and acetic acid-induced
writhing in mice, respectively, with low ulcerogenicity compared with the standard drug indomethacin.
Ó 2010 Elsevier Masson SAS. All rights reserved.
Received 24 June 2009
Received in revised form
25 January 2010
Accepted 28 January 2010
Available online 2 February 2010
Keywords:
2-Methylbenzimidazole
Analgesic activity
Anti-inflammatory activity
Carrageenan-induced paw edema model
1. Introduction
derivatives possess diverse pharmacological activities, including
antimicrobial, antiviral, antineoplastic, antihypertensive, and vas-
Non-steroidal anti-inflammatory drugs (NSAID) are one of the
most widely used drug category against inflammation, mild to
moderate pain, and fever. Specific uses also include the treatment
of headaches, arthritis, sports injuries, and menstrual cramps. Their
use is mainly restricted by their well known and serious adverse
gastrointestinal side effects such as gastroduodenal erosions and
ulcerations [1–5]. NSAID-induced gastropathy are estimated to
affect up to half of chronic NSAID users, with major world health
implications [6]. Therefore, search for better and safer anti-
inflammatory agents is always going on at a rapid pace. The ring
system in which a benzene ring is fused to the 4,5-positions of
imidazole is designated as Benzimidazole [7]. Benzimidazole is one
of the most promising heteroaryl moiety that yielded many
successful drugs [8]. Wide variety of pharmacological activities
have been reported by benzimidazole moiety itself [9] and its
derivatives [8]. The current literature indicates that benzimidazole
odilating activities [10]. Furthermore, it had been reported that
many compounds containing benzimidazole moiety possess
significant analgesic as well as anti-inflammatory activity [11].
Benzimidazole moiety fulfills the minimum structural require-
ments that are common for anti-inflammatory compounds [12–14].
In the past, many benzimidazole derivatives showed potential for
anti-inflammatory and analgesic activity in animal models of
inflammation and pain [15–23]. However, 5-substituted-1-(phe-
nylsulfonyl)-2-methylbenzimidazole derivatives were not been
studied towards anti-inflammatory activity. Therefore, it was
thought worthwhile to explore anti-inflammatory as well as anal-
gesic potential of some 5-substituted-1-(phenylsulfonyl)-2-meth-
ylbenzimidazole derivatives. Accordingly the present work is
concerned with the synthesis of different 5-substituted-1-(phe-
nylsulfonyl)-2-methylbenzimidazole derivatives with the objective
of discovering novel and potent anti-inflammatory agents that
might be devoid of gastrointestinal side effects. The compounds
were evaluated for their acute anti-inflammatory and analgesic
activity using carrageenan-induced rat paw edema model and
acetic acid-induced writhing model in mice. Moreover, the test
compounds showing potent anti-inflammatory and analgesic
activity were further evaluated for their ulcerogenic potential.
* Corresponding author. Department of Pharmaceutical Chemistry, ASBASJSM
College of Pharmacy, BELA, Ropar 140 111, India. Tel./fax: þ91 1881 263108,
þ919872390321.
E-mail address: gaba_monika12@yahoo.co.in (M. Gaba).
0223-5234/$ – see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.01.067

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M. Gaba et al. / European Journal of Medicinal Chemistry 45 (2010) 2245–2249
Table 1
Anti-inflammatory
2. Chemistry
activity
of
5-substituted-1-(phenylsulfonyl)-2-methyl-
benzimidazole derivatives.
The sequence of the reactions employed for the construction
of novel benzimidazole derivatives is outlined in Scheme 1.
Compound 1 2-methyl-5-nitro-1-(phenylsulfonyl) benzimidazole
was prepared according to reported literature [24–26]. Reduction of
compound 1 was done in the presence of Zn/NaOH to give 5-amino
derivative 2 [27]. The novel derivatives of title compound were
prepared by reacting different substituted alkyl and aryl halides to
obtain 3a–i, further reduction of nitro aryl derivatives was carried
out to obtain amino derivatives 4a–c. The purity of the compounds
was achieved by column chromatographic separation using silica
gel and chloroform:methanol (9:1).
Compound
%Edema
%Reduction in edema
Control
3a
3b
3c
3d
3e
3f
3g
100 ꢀ 1.52
93.3 ꢀ 1.6
92.8 ꢀ 1.2
92.3 ꢀ 1.12
92.1 ꢀ 1.34
89.4 ꢀ 1.34
89.8 ꢀ 4.55
89.2 ꢀ 1.74
90.8 ꢀ 1.63
91.4 ꢀ 0.98
60.3 ꢀ 1.6
63.0 ꢀ 1.2
66.3 ꢀ 1.2
56.6 ꢀ 1.15
0
6.7
7.2
7.7
7.9
10.6
10.2
10.8
9.2
3h
3i
8.6
4aa
39.7a
37.0a
33.7a
43.4a
4ba
4ca
3. Pharmacological results
Indomethacina
Values are mean ꢀ SEM of six animals in each group.
All the newly synthesized 5-substituted-1-(phenylsulfonyl)-2-
methylbenzimidazole derivatives were tested in vivo in order to
evaluate their pharmacological activity. Carrageenan-induced rat
paw edema model was used as initial screen. These derivatives
exhibited anti-inflammatory activity of varying degree from 6.7 to
39.7%. The results are summarized in Table 1 (Fig. 1). It was
observed that compounds 4a–c when administered at 200 mg/kg/
p.o. exhibits significant reduction in edema 1 h post-dosing of test
compounds, that is, 39.7, 37.0 and 33.7%, respectively, comparable
to standard drug indomethacin which was administered at 50 mg/
kg/p.o. These highly active compounds were further evaluated for
their analgesic as well as ulcerogenic activity which showed good
analgesic activity and lower ulcerogenic potential. The results of
analgesic activity are depicted in Table 2 (Fig. 2) and for ulcerogenic
activity results are shown in Table 3 (Fig. 3).
a
Statistically significant vs. control (p ꢁ 0.05).
or -chloro substitution in place of –NO2 group (compounds 3h & 3i)
did not influence the activity. However, the reduction of derivatives
3e, 3f, and 3g to 4a, 4b and 4c respectively resulted in highest anti-
inflammatory as well as analgesic activity. However, oral adminis-
tration of equipotent dose of compounds 4a, 4b and 4c exhibited
lower gastric ulceration and better gastrointestinal tolerability when
compared with indomethacin. Amide derivatization of four well-
known NSAID, i.e., diclofenac acid, tolfenamic acid, ibuprofen and
indomethacin, at –COOH has been reported in literature with signif-
icant reduction of ulcerogenicity [28] but with retention of the anti-
inflammatory activity of parent NSAID [29–31]. Thus, chemical
derivatizationofmoleculesthatwillleadtoneutraloramoleculewith
greatly reduced acidic character may be a useful approach to find safe
and potent NSAID, provided that the molecular modifications do not
abolish the anti-inflammatory activity. As oxidative stress is another
important component involved in pathophysiology of NSAID-
induced GI ulceration. The latter is further supported by the finding
that indomethacin administration results in increased reactive
oxygen species production in the gastric mucosa, followed by gastric
ulceration [32]. These results may be attributed to the devoid of acidic
characterand/orreductionof–NO2 groupofcompounds3e, 3f, and3g
to –NH2 group in compounds 4a, 4b and 4c that may lead to decrease
in oxidative stress.
4. Discussion
In this study we have synthesized novel series of 5-substituted-1-
(phenylsulfonyl)-2-methylbenzimidazole derivatives which exhibi-
ted good anti-inflammatory and analgesic activity. Modulation of the
basic structure through ring substituents and/or additional functio-
nation warrants further improvement in the biological activity.
Introductionto–CH2 betweenaminoandaryl moiety(compound 3g),
O2N
N
CH3
N
S
5. Conclusion
O
O
In summary, we have identified novel series of 5-substituted-1-
(phenylsulfonyl)-2-methylbenzimidazole derivatives, which may
develop into the potential class of anti-inflammatory, analgesic
1
(A)
H
H
N
N
H2N
N
N
N
R
CH3
R
CH3
CH3
N
S
N
S
N
S
(B)
(C)
O
O
O
O
O
O
3a-i
R = a, -CH3,
c, -C3H7
2
4a-c
b, -C2H5
d,-C4H9
R = a, p-NH2C6H4
b, o-NH2C6H4
e, p-NO2C6H4 f, o-NO2C6H4,
g, p-NO2C7H6 h, p-ClC7H6,
i, o-ClC7H6
c, p-NH2C7H6
Scheme 1. Reagents: (A) (i) Zn/NaOH and (ii) EtOH, (B) (i) R–X (R-alkyl/aryl; X–Cl/Br)
Fig. 1. Anti-inflammatory activity of 5-substituted-1-(phenylsulfonyl)-2-methyl-
and (ii) K2CO3, DMF, and (C) Zn/NaOH.
benzimidazole derivatives.

M. Gaba et al. / European Journal of Medicinal Chemistry 45 (2010) 2245–2249
2247
Table 2
Analgesic activity of 4a, 4b, 4c and acetyl salicylic acid.
Table 3
Ulcerogenic activity of 4a, 4b, 4c and indomethacin.
Compound
No. of wriths in 15 min
% Protection
Compound
Lesion score (mm)
Control
68.7 ꢀ 7
0
Controla
2 ꢀ 1a
16 ꢀ 2a
14 ꢀ 1a
15 ꢀ 1a
26 ꢀ 1
4aa
29.6 ꢀ 2.7
30.7 ꢀ 4.5
33.5 ꢀ 3.9
29 ꢀ 5.6
56.9a
55.3a
51.2a
57.8a
4aa
4ba
4ba
4a
4ca
Acetyl salicylic acida
Indomethacin
Values are mean ꢀ SEM (n ¼ 6).
Values are mean ꢀ SEM (n ¼ 6).
a
a
Statistically significant vs. control (p ꢁ 0.05).
Statistically significant vs. indomethacin (p ꢁ 0.05).
refluxing was continued until the solution became transparent. Hot
mixture was filtered; zinc residue returned to the flask and
extracted with three portions of hot rectified spirit. The extracts
were combined, sodium dithionite (Na2S2O4) was added and
solvent removed under reduced pressure using rotary evaporator.
The dried solid was washed with diethyl ether. The product was
recrystallized from chloroform giving 2 as yellowish crystals, which
gain moisture and turn into sticky mass. Molecular formula:
C14H13N3O2S, Rf: 0.63 [Chloroform:Methanol (88:12)], Melting
point: 205 ꢂC, %Yield: 89.2. IR (KBr) Vmax: 3543, 3433, 3106, 3060,
2970, 2848, 1622, 1517, 1473, 1445, 1320, 1150, 737, 825, 689, 576,
agents with lower ulcerogenic activity. Since GI problems due to
NSAID continue to be the major impediment to their use in ther-
apeutics, the novel properties (reduced acidic character: reduced
oxidative stress: GI protection) of the new anti-inflammatory
derivatives prove them useful lead molecules for the develop-
ment of better NSAID with greatly improved therapeutic index.
Further studies are required to confirm this suggestion.
6. Experimental
530 cmꢃ1
.
1H NMR (CDCl3, 400 MHz,
d
ppm): 8.10 (1H, d, J ¼ 7.9),
6.1. Chemistry
7.85 (2H, d, J ¼ 7.15), 7.65 (4H, m), 7.30 (1H, d, J ¼ 1.7), 3.55 (2H, s),
2.50 (3H, s). EIMS m/z (relative intensity) 287 (Mþ 36.67%), 235
(12.2%), 205 (37.7%), 177 (100%), 147 (79.41%), 105 (4.41%), 77 (8.5%).
Anal. Calcd. for C14H13N3O2S: C, 58.52; H, 4.54; N, 14.62; O, 11.12; S,
11.15%. Found: C, 58.50; H, 4.52; N, 14.60; O, 11.13; S, 11.14%.
All research chemicals were purchased from Sigma–Aldrich or
Lancaster Co. and used as such for the reactions. Solvents except LR
grade were dried and purified according to the literature when
necessary. Reactions were monitored by thin layer chromatography
(TLC) on silica gel G plates and compounds were visualized by
exposure to iodine vapours. Melting points were determined using
open capillary tube method and were uncorrected. Elemental
analysis was performed on a Perkin–Elmer 2400 analyser and
values were within ꢀ0.4% of the calculated. Spectra were obtained
as follows: infrared (IR) spectra were recorded on Hitachi 270-30
Infrared Spectrophotometer (Punjab University Chandigarh, India)
using KBr pellets. 1H NMR and 13C NMR spectra were recorded on
a Bruker Avance DPX-200 (400 MHz) (Punjab University Chandi-
garh, India) using TMS as an internal standard and the values are
expressed in ppm. The mass spectra were recorded using Bruker
Ion Trap Esquire 3000 from Regional Research Laboratory, (Jammu)
India. All the animal experiments were approved by Institutional
Animal Ethical Committee (IAEC).
6.1.2. General procedure for synthesis of 5-substituted
benzimidazole derivatives: 3a–i, and 4a–c
For benzimidazole derivatives compound 2 was refluxed for
24 h with different substituted aryl and alkyl halides in the pres-
ence of dimethylformamide and K2CO3. The mixture was poured in
ice-cold water after refluxing. The precipitates formed were filtered
at pump and recrystallized by using appropriate solvents. The
purity of the compounds was obtained by column chromatography
using silica gel as stationary phase, and chloroform:methanol (9:1)
as mobile phase.
6.1.3. N-2-dimethyl-1-(phenylsulfonyl)-1H-benzimidazol-5-amine 3a
Molecular formula: C15H15N3O2S, Rf: 0.47 [Chloroform:Methanol
(9:1)], Melting point: 260 ꢂC, %Yield: 66.9, IR (KBr) Vmax: 3409.6,
3050, 3005, 1444.8, 1538.9, 2920, 2853, 1389.0, 1128.1, 1196, 694.7,
6.1.1. 2-Methyl-1-(phenylsulfonyl)-benzimidazol-5-amine 2
1477.3 cmꢃ1 1H NMR (DMSO-d6, 400 MHz,
. d ppm): 2.97 (3H, s),
Compound 1 (10.46 g, 0.033 mol) was dissolved in rectified
spirit containing sodium hydroxide. The mixture was heated to
boiling in a two-necked round bottom flask fitted with condenser.
The source of heating was removed and zinc dust was added in
portions of to keep the solution boiling. After complete addition,
3.16 (3H, s), 4.23 (1NH, s), 8.11 (3H, m), 7.98 (2H, m), 7.93 (1H, m),
7.79 (1H, m), 7.48 (1H, dd, J ¼ 6.41, 3.16); 13C NMR (DMSO-d6)
d
141.5, 139.7, 137.9, 133.8, 129.8, 128.3, 119.5, 116.1, 115.6, 101.3, 29.7,
11.2 ppm: EIMS m/z (relative intensity) 301.09 (Mþ 20.54%), 285
(32.87%), 234 (15%), 232 (89.58%), 229 (1.36%), 192 (8.21%), 177
(78.08%), 161 (100%), 145 (12.32%). Anal. Calcd. for C15H15N3O2S: C,
80
70
60
50
30
25
b
b
40
30
20
10
0
b
b
20
b
b
b
15
10
b
5
0
Control
4a
4 b
4 c
Acetyl
salicylic acid
Control
4a
4 b
4 c
Indomethacin
Fig. 2. Analgesic activity of 4a, 4b, 4c and acetyl salicylic acid.
Fig. 3. Ulcerogenic activity of 4a, 4b, 4c and indomethacin.

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M. Gaba et al. / European Journal of Medicinal Chemistry 45 (2010) 2245–2249
59.81; H, 5.00; N,13.91; O,10.62; S, 10.64%. Found: C, 59.80; H, 5.02;
N, 13.94; O, 10.62; S, 10.62%.
C20H16N4O4S: C, 58.81; H, 3.95; N,13.72; O,15.67; S, 7.85%. Found: C,
58.78; H, 3.94; N, 13.70; O, 15.65; S, 7.84%.
6.1.4. N-ethyl-2-methyl-1-(phenylsulfonyl)-1H-benzimidazol-5-amine
3b
6.1.9. 2-Methyl-N-4-(nitrobenzyl)-1-(phenylsulfonyl)-1H-benzimi-
dazol-5-amine 3g
Molecular formula: C16H17N3O2S, Rf: 0.44 [Chloroform:Methanol
(9:1)], Melting point: 240 ꢂC, %Yield: 54.7, IR (KBr) Vmax: 3378.3,
3060, 3011, 1525.2 2920, 2810, 1345.8, 1165.2, 1108.7, 669.2,
Molecular formula: C20H18N4O4S, Rf: 0.52 [Chloroform:Methanol
(92:8)], Melting point: 179 ꢂC, %Yield: 73.2, IR (KBr) Vmax 3348, 3105,
3016, 2983, 2933, 1590, 1480, 1442, 1518, 1388, 1339, 1179, 830, 742,
1399.1 cmꢃ1. 1H NMR (DMSO-d6, 400 MHz,
d
ppm) 2.97 (3H, s), 4.3
664, 610, 533 cmꢃ1. 1H NMR (CDCl3, 400 MHz,
d
ppm): 8.52 (2H, d,
J ¼ 8.1), 8.32 (3H, d, J ¼ 7.5), 8.18 (5H, m), 7.68 (3H, m), 2.72 (2H, s),
1.56 (3H, s); 13C NMR (CDCl3)
141.5, 139.7, 137.9, 133.8, 129.8, 129,
(1NH, s),1.38 (3H, t), 2.73 (2H, q) 8.28 (2H, dd, J ¼ 2.12, 8.92), 7.98 (3H,
m), 7.86 (1H, m), 7.7 (IH, d, J ¼ 1.92), 7.49 (1H, m): 13C NMR (DMSO-
d
d6)
d
141.5, 139.7, 137.9, 133.8, 129.8, 128.3, 119.5, 116.1, 115.6, 101.3,
128.8,128.3,119.5,116.1,115.6,101.3, 37.9,15.2,11.2 ppm. Anal. Calcd.
for C20H18N4O4S: C, 58.52; H, 4.42; N,13.65; O,15.59; S, 7.81%. Found:
C, 58.49; H, 4.40; N, 13.62; O, 15.60; S, 7.80%.
37.9, 15.2, 11.2 ppm. EIMS m/z (relative intensity) 315 (Mþ 7.84%),
285 (4.90%), 268 (13.72%), 232 (8.82%), 205 (21.59%),175 (9.80%),174
(54.90%), 160 (100%), 134 (3.92%), 85 (1.96%). Anal. Calcd. for
C16H17N3O2S: C, 60.93; H, 5.43; N,13.32; O,10.15; S,10.17%. Found: C,
60.90; H, 5.42; N, 13.31; O, 10.13; S, 10.16%.
6.1.10. 2-Methyl-N-(4-chlorobenzyl)-1-(phenylsulfonyl)-1H-benzimi-
dazol-5-amine 3h
Molecular formula: C21H18N3O2SCl, Rf: 0.89 [Chloroform:Methanol
(92:8)], Melting point: 92 ꢂC, %Yield: 75.4, IR (KBr) Vmax 3419, 3115,
3067, 2933, 2877, 1598, 1444, 1413, 1330, 1164, 864, 753, 663, 678, 566,
6.1.5. 2-Methyl-1-(phenylsulfonyl)-N-propyl-1H-benzimidazol-5-
amine 3c
Molecular formula: C17H19N3O2S, Rf: 0.40 [Chloroform:Methanol
(9:1)], Melting point: 231 ꢂC, %Yield: 44.1, IR (KBr) Vmax 3454.0, 3102,
3059.3, 2965.1, 2826, 1516.7, 1464.6, 1340.9, 1128.1, 1020.1,
532 cmꢃ1.1H NMR (CDCl3, 400 MHz,
d
ppm): 8.05 (9H, m), 7.52 (1H, s),
7.34 (3H, m) 2.9 (2H, s), 2.1 (3H, s); 13C NMR (CDCl3)
d
141.5,139.7,137.9,
134.3, 133.8, 130.2, 129.8, 128.3, 128.9, 126.9, 119.5, 116.1, 115.6, 101.3,
37.9,11.2,15.2 ppm. Anal. Calcd. for C21H18N3O2SCl: C, 61.22; H, 4.40; Cl,
8.61; N, 10.20; O, 7.77; S, 7.78%. Found: C, 61.20; H, 4.39; Cl, 8.60; N,
10.19; O, 7.75; S, 7.75%.
615.1 cmꢃ1. 1H NMR (DMSO-d6 400 MHz,
d ppm): 2.97 (3H, s), 4.3
(1NH, s),1.81 (2H, m), 3.32 (2H, t),1.04 (3H, t), 8.16 (2H, m), 7.7(2H, dd,
J ¼ 4.3), 7.8 (1H, m), 7.39 (3H, m): 13C NMR (DMSO-d6)
d 141.5, 139.7,
137.9, 133.8, 129.8, 128.3, 119.5, 116.1, 115.6, 101.3, 47.3, 23.3, 11.5,
11.2 ppm; EIMS m/z (relative intensity) 329 (Mþ 32.14%), 268
(3.57%), 234 (32.14%), 220 (53.57%), 203 (17.85%), 186 (25%), 175
(100%), 160 (14.28%), 156 (92.85%), 130 (92.85%). Anal. Calcd. for
C17H19N3O2S: C, 61.95; H, 5.81; N, 12.74; O, 9.71; S, 9.72%. Found: C,
61.94; H, 5.80; N, 12.70; O, 9.71; S, 9.70%.
6.1.11. 2-Methyl-N-(2-chlorobenzyl)-1-(phenylsulfonyl)-1H-benzimi-
dazol-5-amine 3i
Molecular formula: C21H18N3O2SCl, Rf: 0.86 [Chloroform:Methanol
(92:8)], Melting point: 35 ꢂC, %Yield: 70.4, IR (KBr) Vmax 3367, 3069,
2971, 2960, 2854, 1521, 1445, 1397, 1340, 1152, 852, 753, 683, 668, 568
and 540 cmꢃ1.1H NMR (CDCl3, 400 MHz,
d
ppm): 8.59 (1H, s), 8.16 (2H,
d,J ¼ 7.56), 7.78 (1H, d,J ¼ 7.8), 7.49(2H, d,J ¼ 7.0), 7.15 (6H, m), 6.45(1H,
s), 2.75 (2H, s), 2.0 (3H, s); 13C NMR (CDCl3)
141.5, 139.7, 137.9, 133.8,
6.1.6. N-butyl-2-methyl-1-(phenylsulfonyl)-1H-benzimidazol-5-
amine 3d
d
Molecular formula: C18H21N3O2S, Rf: 0.39 [Chloroform:Methanol
(9:1)], Melting point: 220 ꢂC, %Yield: 54.3, IR (KBr) Vmax 3437.9, 3099,
3054.9, 2959.6, 2873.4, 1519.6, 1337.9, 1187.1, 1234.8, 689.5 cmꢃ1. 1H
134.3, 130.2, 129.8, 128.3, 119.5, 116.1, 115.6, 101.3, 37.9, 15.2, 11.2 ppm.
6.1.12. N-[2-methy-1-(phenylsulfonyl)-1H-benzimidazol-5-yl]-
benzene-1,4-diamine 4a
NMR (DMSO-d6 400 MHz,
t), 1.39 (2H, m), 1.73 (2H, m), 2.59 (2H, t), 8.2 (2H, m), 7.85 (2H, m), 7.69
(1H, m), 7.35 (3H, m); 13C NMR (DMSO-d6)
141.5, 139.7, 137.9, 133.8,
d ppm): 2.97 (3H, s), 4.28 (1NH, s), 0.99 (3H,
Molecular formula: C20H18N4O2S, Rf: 0.91 [Chloroform:Methanol
(92:8)], Melting point: 184 ꢂC, %Yield: 94.4, IR (KBr) Vmax 3443, 3364,
3090, 3050, 2970, 2848, 1518, 1479, 1402, 1338, 1148, 750, 669, 631,
d
129.8, 128.3, 119.5, 116.1, 115.6, 101.3, 44.8, 32.4, 20.2, 13.8, 11.2 ppm:
EIMS m/z (relative intensity) 343.14 (Mþ 20.6%), 281 (66.6%), 234
(22.2%), 229.8 (26.98%), 175.7 (100%), 157 (87.30%), 145 (25.39%), 102.3
(1.58%). Anal. Calcd. for C18H21N3O2S: C, 62.95; H, 6.16; N,12.23; O, 9.32;
S, 9.34%. Found: C, 62.91; H, 6.12; N, 12.20; O, 9.30; S, 9.30%.
518 cmꢃ1. 1H NMR (CDCl3, 400 MHz,
d ppm): 8.35 (6H, m), 7.82 (2H,
dd, J ¼ 7.6), 7.50 (4H, m), 7.25 (1H, d, J ¼ 1.7), 2.1 (2H, s), 1.5 (3H, s).
Anal. Calcd. for C20H18N4O2S: C, 63.47; H, 4.78; N, 14.80; O, 8.46; S,
8.47%. Found: C, 63.45; H, 4.75; N, 14.79; O, 8.45; S, 8.45%.
6.1.7. 2-Methyl-N-4-(Nitrophenyl)-1-(phenylsulfonyl)-1H-benzimi-
dazol-5-amine 3e
6.1.13. N-[2-methy-1-(phenylsulfonyl)-1H-benzimidazol-5-yl]-
benzene-1,2-diamine 4b
Molecular formula: C20H16N4O4S, Rf: 0.91 [Chloroform:Methanol
(92:8)], Melting point: 162 ꢂC, %Yield: 54.4, IR (KBr) Vmax 3442, 3102,
3060, 2963, 2908, 1598, 1492, 1445, 1515, 1341, 1330, 1164, 816, 742,
Molecular formula: C20H18N4O2S, Rf: 0.95 [Chloroform:Methanol
(92:8)], Melting point: 177 ꢂC, %Yield: 92.4, IR (KBr) Vmax 3460, 3338,
3103, 2880, 2972, 2853, 1600, 1480, 1442, 1340, 1128, 740, 688, 572,
678, 566, 529 cmꢃ1. 1H NMR (CDCl3, 400 MHz,
d
ppm): 8.25 (6H, d,
532 cmꢃ1. 1H NMR (CDCl3, 400 MHz,
d
ppm): 8.1 (1H, d, J ¼ 7.92), 7.8
(3H, m), 7.2 (4H, m), 6.9 (1H, d, J ¼ 7.3), 6.3 (1H, d, J ¼ 1.3), 2.1 (2H, s),1.7
(3H, s); 13C NMR (CDCl3)
141.5, 139.7, 139.3, 138.8, 137.9, 136.0, 133.8,
J ¼ 7.2), 7.55 (6 H, d, J ¼ 7.0), 7.23 (1H, s), 1.60 (3H, s). Anal. Calcd. for
C20H16N4O4S: C, 58.80; H, 3.93; N,13.71; O,15.66; S, 7.84%. Found: C,
58.78; H, 3.92; N, 13.70; O, 15.67; S, 7.82%.
d
129.8,128.3,121.2,120.6,119.9,119.7,119.1,117.2,116.2,106.9,11.2 ppm.
6.1.8. 2-Methyl-N-2-(nitrophenyl)-1-(phenylsulfonyl)-1H-benzimi-
dazol-5-amine 3f
6.1.14. N-4-(aminobenzyl)-2-methyl-1-(phenylsulfonyl)-1H-
benzimidazol-5-amine 4c
Molecular formula: C20H16N4O4S, Rf: 0.52 [Chloroform:Methanol
(92:8)], Melting point: 148 ꢂC, %Yield: 45.1, IR (KBr) Vmax 3351, 3096,
2963, 2920, 2853, 1592, 1530, 1467, 1530, 1372, 1348, 1168, 854, 738,
Molecular formula: C21H20N4O2S, Rf: 0.86 [Chloroform:Methanol
(92:8)], Melting point: 205 ꢂC, %Yield: 87.1, IR (KBr) Vmax 3433, 3342,
3105, 2992, 2972, 2853, 1594, 1460, 1432, 1353, 1139, 774, 674, 590,
678, 566, 532 cmꢃ1. 1H NMR (CDCl3, 400 MHz,
d
ppm): 8.63 (1H, d,
530 cmꢃ1. 1H NMR (CDCl3, 400 MHz,
d
ppm): 8.3 (3H, s), 7.9 (5H, s), 7.4
(5H, m), 2.1(2H, s), 1.7 (2H, s), 1.5 (3H, s); 13C NMR (CDCl3)
148.4,
141.5,139.7, 137.9, 133.8, 129.8, 129.6, 128.3, 119.5, 118.8, 116.3, 116.1,
J ¼ 7.5), 8.30 (1H, d, J ¼ 7.2), 8.15 (2H, d, J ¼ 7.42), 7.83 (3H, m), 7.52
d
(3H, m), 7.40 (2H, m), 7.22 (1H, s), 1.5 (3H, s). Anal. Calcd. for

M. Gaba et al. / European Journal of Medicinal Chemistry 45 (2010) 2245–2249
2249
115.6,101.3, 37.9,15.2,11.2 ppm. Anal. Calcd. for C21H20N4O2S: C, 64.27;
H, 5.14; N, 14.27; O, 8.15; S, 8.17%. Found: C, 64.26; H, 5.11; N, 14.26; O,
8.14; S, 8.15%.
are sacrificed by cervical dislocation and their stomachs were
removed. Formol saline (2% v/v) was then injected into the totally
ligated stomach for storage overnight. The next day, the stomachs are
opened along the greater curvature, then washed in warm water, and
examined under 3-fold magnifier. The lengths of the longest diame-
ters of the lesions are measured and summated to give a total lesion
score (in mm) for each animal, the mean count for each group being
calculated (Table 3) and plotted as Fig. 3.
6.2. Biological assays
Albino mice of either sex weighing 20–25 g were used for eval-
uation of analgesic activity. Male SD rats weighing 150–230 g were
used to study anti-inflammatory activity and ulcerogenic activity of
the test compounds. Animal ethical clearance was obtained from
Ethics Committee of Punjabi University, Patiala (Punjab), India.
Animals were procured from K. S. Hegde Medical Academy, Derala-
katte, Mangalore, India, and housed individually in polypropylene
cages, maintained under standard conditions of alternating 12-h
light-and-dark cycles at a constant temperature (25 ꢀ 2 ꢂC and
35–60%relative humidity). Animalswere fedwithstandard rat pellet
diet, (Hindustan Lever Ltd., Mumbai, India) and water ad libitum.
6.2.4. Statistical analysis
Data were presented as mean ꢀ SEM. Statistical analysis was
performed by one way variance (ANOVA) followed by Dunnett’s
test; a ‘‘p’’ value of less than 0.05 was considered as statistically
significant using PARAMETRIC STASTICS, IBM PC version 1.01 by
Londan software INC-1985.
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6.2.3. Gastric ulcerogenic activity
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