The analgesic activity of 8-(Trifluoromethyl)-1,2,3,4,5-benzopentathiepine- 6-amine and its hydrochloride

Article abstract of DOI:10.2174/157018012800389296

8-(Trifluoromethyl)-1,2,3,4,5-benzopentathiepine-6-amine 1a and its hydrochloride revealed significant analgesic activity in the acetic acid-induced writhing test, and ED₅₀ of the compound 1a was 0.66 mg/kg. In the hot plate pain test, the reli

Full text of DOI:10.2174/157018012800389296

Letters in Drug Design & Discovery, 2012, 9, 513-516
513
The Analgesic Activity of 8-(Trifluoromethyl)-1,2,3,4,5-benzopentathie-
pine-6-amine and Its Hydrochloride
Tatyana G. Tolstikova, Alla V. Pavlova, Ekaterina A. Morozova, Tatyana M. Khomenko,
Konstantin P. Volcho* and Nariman F. Salakhutdinov
N.N.Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, Lavrentiev
av., 9, 630090 Novosibirsk, Russian Federation
Received December 09, 2011: Revised January 05, 2012: Accepted February 01, 2012
Abstract: 8-(Trifluoromethyl)-1,2,3,4,5-benzopentathiepine-6-amine 1a and its hydrochloride revealed significant
analgesic activity in the acetic acid-induced writhing test, and ED50 of the compound 1a was 0.66 mg/kg. In the hot plate
pain test, the reliable analgesic activity was found in hydrochloride 1a*HCl, whereas the free base 1a proved to be
inactive. Based on the results of the naloxone test, the analgesic effect of the compound 1a*HCl in both tests is mediated
with the opioidergic system. Both the free base 1a and its hydrochloride did not show the anti-inflammatory activity.
Replacement of the CF
induced writhing test.
3
group for the fluorine atom resulted in complete loss of analgesic activity in the acetic acid-
Keywords: Analgesic activity, Benzopentathiepine, Acetic acid-induced writhing test, Hot plate test, Opioidergic system.
INTRODUCTION
(trifluoromethyl)-1,2,3,4,5-benzopentathiepine-6-amine hy-
drochloride 1a*HCl were synthesized in accordance with
previously published methodic [7-9].
Pain is a common symptom, which non-steroidal anti-
inflammatory drugs are usually used to remove [1].
However, chronic use of these medications produces
significant adverse effects such as gastro- and
nephrotoxicity, renal impairment, etc. In recent years
medications have started to be used for pain control, which
were originally developed for other purposes, including
antidepressants and anti-seizure drugs [2]. According to data
on total value and market share by sales in the seven major
pharmaceutical markets of major pain drug classes in 2009,
shares of sales of antidepressants and anticonvulsant
medications for pain relief were 11% and 13%, respectively
Pharmacology
Animals
All studies were carried out on non-breeding albino mice
(
male) weighting 20-25 g, 8 animals in each group (SPF-
vivarium of the Institute of Cytology and Genetics of the
Siberian Branch of the Russian Academy of Sciences). Mice
o
were maintained at 22-25 C on a 12 h light-dark cycle with
food and water available ad libitum. All work with animals
was performed in strict accordance with the legislation of the
Russian Federation, the regulations of the European
Convention for the Protection of Vertebrate Animals Used
for Experimental and Other Scientific Purposes, and the
requirements and recommendations of the Guide for the Care
and Use of Laboratory Animals.
[
3]. Usually antidepressants are applied to control chronic
pain [4] and fibromyalgia [5], but research in the hot plate
model demonstrated [6] that the antidepressant Paroxetin
might be efficient for acute pain relief and its mechanism
probably involves the opioid and serotoninergic systems.
It was recently found that 8-(trifluoromethyl)-1,2,3,4,5-
benzopentathiepine-6-amine 1a showed a high anticon-
vulsant and anxiolytic activity [7]. The available data
indicate the involvement of the 5-HT brain system in the
mechanism of action of this compound [8]. The study of
acute toxicity of the compound 1a revealed that at oral
administration in rats, LD50 of this agent is more than 1000
mg/kg. In the present paper, we first studied the analgesic
activity of the compound 1a using the acute pain models.
Analgesic Tests
Agents were dissolved in saline containing 0.5% Tween
8
0 just before use and were administered p.o. 1 h before
testing. Naloxone (Sigma) was administered (dose of 1
mg/kg s.c.) 50 min after administration of the test agents (10
min before testing). Analgesic activity of test agents was
assessed using acetic acid-induced writhing test and hot plate
test.
MATERIALS AND METHODS
Chemistry
In the acetic acid-induced writhing test, the pain reaction
was determined by the number of abdominal convulsions,
recorded from the 5th to the 8th min following the acetic
acid injection (0.75%, 0.1 mL/mouse) [10]. The percentage
of pain reaction inhibition was calculated according to the
following equation: % inhibition = 100 x (A – B)/A, where
A is the mean number of writhes in the control group, and B
is the mean number of writhes in the test group.
8
-(Trifluoromethyl)-1,2,3,4,5-benzopentathiepine-6-amine
1
a, 8-(fluoro)-1,2,3,4,5-pentathiepin-6-amine 1b and 8-
*
Address correspondence to this author at the N.N.Vorozhtsov Novosibirsk
Institute of Organic Chemistry, Lavrentiev av., 9, 630090 Novosibirsk,
Russian Federation; Tel: +7 383 3308870; Fax: +7 383 3309752;
E-mail: volcho@nioch.nsc.ru
1
875-628X/12 $58.00+.00
© 2012 Bentham Science Publishers

5
14 Letters in Drug Design & Discovery, 2012, Vol. 9, No. 5
Tolstikova et al.
Cl
NO2
NH2
O N
NO2
NaSC(S)NMe2
NH Cl
3
2
S
S
S
S
S
S
S
S
S
S
S
NaHS
HCl
C
O
S
EtOH
DMSO
R
R
R
R
2
a,b
1
a,b
1
a*HCl
1a, 2a: R = CF3
1b, 2b: R = F
Scheme 1. Synthesis of compounds 1a,b.
In the hot plate test, animals were placed individually on
a metallic plate warmed to 54±0.5 C and the time until
Table 1. Percent Analgesic Activity (Acetic Acid-Induced
Writhing Test)
o
either licking of the hind paw or jumping occurred was
recorded by a stopwatch [11].
Compound
Dose (mg/kg)
Pain inhibition (%)
#
Anti-Inflammatory Activity
1a
1a
10
5
29
Anti-inflammatory activity of the compounds was
studied in inflammation model induced by injection of 0.1%
histamine (0.05 mL) into the aponeurosis of the hind limb
6
#
1
1
a
a
1
54
§
0.5
10
5
50
[
11]. Test compounds were administered 1 h before injection
of the inflammatory agent. The total dose used for agent was
0.0 mg/kg, and the total dose for sodium diclofenac was 20
#
1a*HCl
a*HCl
1a*HCl
a*HCl
45
1
@
1
41
mg/kg. Mice were killed 5 h after the inflammatory episode;
the hind limbs were severed and then weighed. The
inflammation percentage was calculated by the equation: %
inflammation = 100 x (Mil-Mnil)/Mnil; where Mil is inflamed
limb mass, and Mnil is non-inflamed limb mass.
#
1
27
§
1
0.5
10
10
28
1
b
18
#
Diclofenac sodium
90
@
§
#
RESULTS AND DISCUSSION
P < 0.05; P < 0.01; P < 0.001 in comparison with control.
The compound 1a was synthesized from commercially
available 4-chloro-3,5-dinitrobenzotrifluoride 2a in a two-
stage process, in accordance with the procedure proposed
earlier (Scheme 1) [7, 9]. Hydrochloride 1a*HCl was
obtained by the interaction of 1a with HCl in absolute
ED50 in the test of acetic acid-induced writhing test
constituted 0.66 mg/kg for the agent 1a. To compare, ED50
of acetylsalicylic acid is 155 mg/kg, of metamizole sodium,
5 mg/kg, and diclofenac sodium, 5 mg/kg [12].
5
In the hot plate test, the compounds 1a and 1b appeared
ethanol [8]. To find the effect of the CF
3
replacement in the
to be inefficient. At the same time, hydrochloride 1a*HCl in
doses of 1 and 0.5 mg/kg significantly (by 50 and 47%,
respectively) increased the latent time of the pain response
aromatic ring on biological activity, we also tested the
compound 1b, where the CF
fluorine atom (Scheme 1) [9].
3
group is replaced for the
(
Table 2). It is interesting that in the dose of 10 mg/kg, this
Analgesic activity of the agents was studied using
standard models of experimental pain, including the acetic
acid-induced writhing test (intraperitoneal administration of
agent did not show reliable analgesic activity.
The studies conducted demonstrated that the compound
1
a*HCl has the broad spectrum of antinociceptive effect,
0
.75% acetic acid, 0.1 ml per one animal) and the hot plate
o
pain test (T= 54±0.5 C) in doses of 0.5, 1.0, 5.0 and 10.0
mg/kg orally [10, 11].
expressing high analgesic activity both in the visceral pain
test and thermal pain test. To define the recruitment of the
opioid system in the mechanism of analgesic activity of that
compound, its activity was studies using models of pain
stimuli against the background of administering naloxone,
the opioid receptor antagonist.
In the acetic acid-induced writhing test, which represents
the model of acute visceral pain, the compound 1a in the 10
mg/kg showed reliable analgesic activity (Table 1) as it
significantly reduced the number of convulsions provoked
by intraperitoneal administration of acetic acid. In the dose
of 5 mg/kg, the compound 1a only insignificantly, and with a
low degree of reliability, decreased the number of the
convulsions. However, further decreasing the dose (to 1 and
Treatment of animals with naloxone 10 min prior to
testing completely blocked analgesic activity of the
compound 1a*HCl in the acetic acid-induced writhing and
hot plate tests (Table 3). Thus, the obtained results suggest
that analgesic effect of the compound 1a*HCl is mediated
by the opioidergic system.
0
.5 mg/kg) led to a pronounced increase of the analgesic
effect. Interestingly, for hydrochloride 1a*HCl, another
dynamics of the dose-effect dependence was observed:
raising the dose increased its analgesic activity. At the
It appeared that the compound 1a*HCl did not possess
anti-inflammatory activity in histamine inflammation model
3
replacement of the CF group for the fluorine atom, the
compound 1b in the dose of 10 mg/kg, no reliable analgesic
(
Table 4) enabling the supposition that its ability to inhibit
effect was found.

Analgesic Activity of Benzopentathiepine Amine
Letters in Drug Design & Discovery, 2012, Vol. 9, No. 5 515
Table 2. Percent Analgesic Activity (Hot Plate Test)
Compound
Dose (mg/kg)
Mean ± SD
Control
Protection, (%)
1
1
1
a
a
a
10
1
19.0 ± 1.0
13.6 ± 1.1
13.2 ± 1.5
23.9 ± 2.0
17.9 ± 2.8
17.5 ± 2.5
20.5 ± 1.4
33.4 ± 2.3
19.5 ± 2.2
10.8 ± 1.1
13.2 ± 0.9
22.8 ± 3.1
11.9 ± 1.6
11.9 ± 1.6
19.9 ± 1.8
20.4 ± 2.2
0
21
0
0.5
10
1
1
1
1
a*HCl
a*HCl
a*HCl
5
@
50
@
0.5
10
10
47
1
b
3
§
Diclofenac sodium
64
@
§
P < 0.05; P < 0.01.
Table 3. Interaction of 1a*HCl (1 mg/kg) with Naloxone (1 mg/kg)
Acetic acid-induced writing test
Compound
Hot plate test
Mean ± SD
Control
Mean ± SD
Control
Naloxone
13.9 ± 0.8
13.3 ± 1
13.4 ± 1
13.4 ± 1
13.4 ± 1
11.3 ± 0.7
11.6 ± 0.8
10.6 ± 1
10.6 ± 1
10.6 ± 1
Naloxone +1a*HCl
§
§
1
a*HCl
10.6 ± 0.5
14.5 ± 1.2
§
P < 0.01.
Table 4. Inflammation Percentage
Compound
Dose (mg/kg)
Inflammation percentage ± SD
Control
21.1 ± 2.1
@
Diclofenac sodium
20
10
12.5 ± 1.8
1
a*HCl
21.0 ± 2.4
@
P < 0.05.
the pain reaction caused by chemical disturbance of the
peritoneum is preconditioned only by its analgesic activity.
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The compound 1a both in the form of free base and
hydrochloride showed significant analgesic activity in the
acetic acid-induced writhing test. In the hot plate test, sole
hydrochloride demonstrated the reliable analgesic activity
and only at low dose (0.5 and 1 mg/kg). It seems that the
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[
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[
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3
the CF group for the fluorine atom resulted in complete loss
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CONFLICT OF INTEREST
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anticonvulsant and anxiolytic activities. Lett. Drug Design &
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Declared none.
ACKNOWLEDGEMENTS
The study has been supported by the Interdisciplinary
Integration Project No. 18 of Siberian Branch of Russian
Academy of Sciences.
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