S. Nacak et al. / Il Farmaco 54 (1999) 768–772
771
3.1.3. (3-Benzyl-2(3H)-benzimidazolon-3-yl-)acetyl
chloride
(3 - Benzyl - 2(3H)-benzimidazolon - 3 - yl)acetic acid
(0.01 mol) was dispersed in 30 ml toluene, and 0.01 mol
of thionyl chloride was added. The final solution was
refluxed for 3 h, and then evaporated to dryness.
peated characteristic stretching movements [17]. This
method was modified later by S¸afak et al. [4] using
acetic acid at a dose level of 300 mg/kg (3% solution).
Acetylsalicylic acid (ASA) was used as reference [18].
Each compound was suspended in 0.5% car-
boxymethyl cellulose to form a solution at the concen-
tration 10 mg/ml and given orally to mice in groups of
six at a dose of 100 mg/kg. One hour after this admin-
istration; pain was induced by intraperitoneal injection
of 3% solution of acetic acid at 300 mg/kg. The control
group animals received carboxymethyl cellulose 1 h
prior to injection of acetic acid. Animals were placed in
private cages 5 min after acetic acid injection and the
number of ‘stretching’ per animal was recorded during
the following 10 min period; percent analgesic activity
was calculated by using the formula:
3.1.4. (3-Benzyl-2(3H)-benzimidazolon-3-yl)acetamide
deri6ati6es (6a–6f)
(3-benzyl-2(3H)-benzimidazolon-3-yl-)acetyl chloride
(0.01 mol), 0.011 mol of Na2CO3 and 0.01 mol of an
appropriate secondary amine were mixed in 30 ml
tetrahydrofurane, refluxed for 8 h and stirred for 12 h
at room temperature. Then the eventual mixture was
filtered. The filtrate was evaporated to dryness and 100
ml of water was added. This mixture was extracted
three times with 30 ml of chloroform. The chloroform
extracts were pooled, dried with sodium sulfate, filtered
and evaporated to dryness. The residue was crystallized
from appropriate crystallization solvents. Compound 6f
was characterized as its hydrochloride salt, that was
prepared by treatment of reaction product in alcohol
with alcoholic HCl.
n−n%
n
Percent anti-nociceptive activity=
×100
where n is the average number of ‘stretching’ of the
control group, and n% is the average number of ‘stretch-
ing’ of the test group.
According to this calculation maximum antinocicep-
tive activity could be 100%, whereas it equals 0% in the
control. The reference drug was administered according
to the test protocol.
3.1.5. Spectral data of the compounds
The IR spectra of the benzimidazolone derivatives
exhibited the following characteristic bands (cm−1):
heterocyclic carbonyl: 1660–1650, amide carbonyl:
3.2.2.2. Statistical analysis. Data were expressed as
means9S.E.M. Statistical comparisons were made by
one way analysis of variance (ANOVA) following by a
post hoc Dunnett Multiple Comparisons test. A P
value of B0.05 was considered indicative of statistical
significance.
1
1710–1690. The H NMR spectra did not exhibit any
peculiar features, thus only the spectrum of compound
6a is indicated as an example: l 7–8 (m, 9H, aromatic
H); 5.1 (s, 2H, NꢀCH2ꢀCOꢀ); 4.82 (s, 2H, NꢀCH2ꢀ¥);
3.65 (m, 4H, CH2ꢀOꢀCH2); 2.51 (m, 4H, CH2ꢀNꢀCH2).
3.2. Biology
4. Results and discussion
3.2.1. Materials
Swiss albino mice of both sexes (2595.0 g), which
are a local breed, were employed. The animals were
housed in groups of eight with food and tap water ad
libitum and were received to the laboratory at least 2
days before the experiments to allow them to get accus-
tomed to the environment. The food was withdrawn
one day before the experiment, but they were allowed
free access to tap water. The experiments were per-
formed in full awareness of the test animals. Acetic acid
(Merck A.G), carboxymethyl cellulose sodium salt
(CMC Na) (Aldrich), aspirin (Bayer), gauge callipers
(Peacock, Ozaki Co., Tokyo) were used.
The antinociceptive activities of the compounds are
shown in Table 2. All the compounds except compound
6c were shown to be equally potent in comparison with
aspirin. Compounds 3, 6a and 6b are the more promis-
ing ones and slightly more potent than the others.
Antinociceptive activities of compounds 3, 4, 6a, 6b,
6d and 6e were significantly different from the control
group. However, for these compounds there was no
statistical difference from aspirin.
In the literature, 2(3H)-benzothiazolone acetic acids,
which have morpholine, pyrrolidine and phenylpiper-
azine rings on the side chain were reported to exhibit
high antinociceptive activity. In our study, 4-[(1-benzyl-
2(3H)benzimidazolon-3-yl)acetyl]morpholine and 4-[(1-
benzyl - 2(3H)benzimidazolon - 3 - yl)acetyl]pyrrolidine
also showed higher activity than the others. Therefore,
one can be inclined to say that morpholine and pyrro-
lidine rings on the side chain may be critical for anti-
nociceptive activity in this kind of compounds.
3.2.2. Methods
3.2.2.1. Antinocicepti6e acti6ity test.
A
modified
Koster’s test was employed [4]. Koster test was first
used by Koster et al. in mice at 60 mg/kg acetic acid
(0.6% solution) given by i.p. injection to produce re-
Nacak, Sultan
