Triazole incorporated thiazoles as a new class of anticonvulsants: Design, synthesis and in vivo screening

Article abstract of DOI:10.1016/j.ejmech.2009.12.062

Various 3-[4-(substituted phenyl)-1,3-thiazol-2-ylamino]-4-(substituted phenyl)-4,5-dihydro-1H-1,2,4-triazole-5-thiones (7a-t) were designed keeping in view the structural requirements suggested in the pharmacophore model for anticonvulsant activity. Thiazole and triazole moieties being anticonvulsants were clubbed together to get the titled compounds and their in vivo anticonvulsant screening were performed by two most adopted seizure models, maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole (scPTZ). Two compounds 7d and 7f showed significant anticonvulsant activity in both the screens with ED₅₀ values 23.9?mg/kg and 13.4?mg/kg respectively in MES screen and 178.6?mg/kg and 81.6?mg/kg respectively in scPTZ test. They displayed a wide margin of safety with Protective index (PI), median hypnotic dose (HD₅₀) and median lethal dose (LD₅₀) much higher than the standard drugs.

Full text of DOI:10.1016/j.ejmech.2009.12.062

European Journal of Medicinal Chemistry 45 (2010) 1536–1543
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Triazole incorporated thiazoles as a new class of anticonvulsants: Design,
synthesis and in vivo screening
*
Nadeem Siddiqui , Waquar Ahsan
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Hamdard University, 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:
Various 3-[4-(substituted phenyl)-1,3-thiazol-2-ylamino]-4-(substituted phenyl)-4,5-dihydro-1H-1,2,4-
triazole-5-thiones (7a–t) were designed keeping in view the structural requirements suggested in the
pharmacophore model for anticonvulsant activity. Thiazole and triazole moieties being anticonvulsants
were clubbed together to get the titled compounds and their in vivo anticonvulsant screening were
performed by two most adopted seizure models, maximal electroshock seizure (MES) and subcutaneous
pentylenetetrazole (scPTZ). Two compounds 7d and 7f showed significant anticonvulsant activity in both
the screens with ED50 values 23.9 mg/kg and 13.4 mg/kg respectively in MES screen and 178.6 mg/kg and
81.6 mg/kg respectively in scPTZ test. They displayed a wide margin of safety with Protective index (PI),
median hypnotic dose (HD50) and median lethal dose (LD50) much higher than the standard drugs.
Ó 2010 Elsevier Masson SAS. All rights reserved.
Received 15 April 2009
Received in revised form
14 December 2009
Accepted 23 December 2009
Available online 13 January 2010
Keywords:
Thiazoles
Triazoles
Anticonvulsants
Neurotoxicity
Distance mapping
1. Introduction
designed by clubbing both the pharmacologically active moieties
viz. thiazole and triazole and the resulting compounds are expected
Epilepsy is a group of disorders of the central nervous system
characterized by paroxysmal cerebral dysrhythmia, manifesting as
brief episodes (seizures) of loss or disturbances of consciousness,
with or without characteristic body movements (convulsions),
sensory or psychiatric phenomenon [1]. Estimates suggest that
available medication controls the seizures in only 50% of patients or
decreases the incidence in only 75% of patients [2]. The search for
antiepileptic agents with more selectivity and lower toxicity
continues to be an area of investigation in medicinal chemistry.
In the effort to get those agents we have reported [3–6] several
five membered heterocyclic compounds, which have shown
considerable anticonvulsant activities. As part of our continuous
research in this area we have designed and synthesized several new
to have the synergistic effect in dealing with the epilepsy.
All the titled compounds comprised of the four pharmacophoric
elements (Fig. 1) that are necessary for good anticonvulsant activity
as suggested by Pandeya et al. [11]. These elements are present in
many currently used antiepileptic drugs. These are hydrophobic
domain A, Hydrogen bonding domain HBD, electron donor moiety
D, and distal hydrophobic domain R.
The attachment of a second aryl ring designated as the distal
ring to the proximal aryl ring to increase the Van der Waal’s
bonding at the binding site and to increase potency have also been
reported [12]. The present work further gives impetus to these
observations.
Our work also highlights the distance mapping and matching of
the synthesized compounds with the help of the given model.
3-[4-(substituted
phenyl)-1,3-thiazol-2-ylamino]-4-(substituted
phenyl)-4,5-dihydro-1H-1,2,4-triazole-5-thiones (7a–t) by incor-
porating triazole moiety into the thiazole ring.
2. Chemistry
Since the past few decades, the literature has been enriched
with progressive findings about the anticonvulsant activities of
various substituted thiazole derivatives [7,8]. In addition many
triazoles have attracted much attention due to their prominent
utilization as anticonvulsants [9,10]. The present series has been
The synthesis of the titled compounds (7a–t) was carried out
as presented in Scheme 1. Appropriate substituted acetophe-
nones were brominated and refluxed with thiourea in acetic acid
to get the substituted thiazoles (2a–d). These thiazole derivatives
on refluxing with ethylchloroformate and triethylamine afforded
the carbamate derivatives (3a–d). On the other hand, the
substituted phenylthioureas (4a–e) were obtained by treating the
substituted anilines with ammonium thiocyanates in presence of
* Corresponding author. Tel.: þ9111 26059688x5639; fax: þ9111 26059688x5307.
E-mail addresses: nadeems_03@yahoo.co.in, nadeems_03@rediffmail.com
(N. Siddiqui).
0223-5234/$ – see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2009.12.062

N. Siddiqui, W. Ahsan / European Journal of Medicinal Chemistry 45 (2010) 1536–1543
1537
D
D
HBD
R
N
O
A
N
R
HN
R
N
H
NH
S
N
S
NH
D
N
O
H
A
HBD
N
H
O
A
HBD
Compounds (7a-t)
Carbamazepine
Phenytoin
Fig. 1. Anticonvulsant agents showing the required pharmacophoric elements.
dilute hydrochloric acid. These phenylthioureas were then
refluxed with hydrazine hydrate to afford hydrazinecarbothioa-
mides (5a–e). The hydrazinecarbothioamides on condensation
with different substituted carbamates (3a–d) in presence of
ethanol gave substituted hydrazinecarboxamides (6a–t). Finally
the substituted hydrazinecarboxamides were cyclized in pres-
ence of aqueous sodium hydroxide to yield the titled compounds
(7a–t). The physicochemical parameters of the synthesized
compounds are presented in Table 1. The structures and purity of
the final compounds were confirmed in the basis of spectral and
elemental analyses and the data were within ꢀ0.4% of the
theoretical values.
3. Pharmacology
The pharmacological testing of all the final compounds were
performed according to the standard protocol given by epilepsy
branch of the National Institute of Neurological Disorders and
Stroke (NINDS) following the protocol adopted by the Antiepileptic
Drug Development (ADD) program [13].
The Phase I pharmacological screening comprised MES, scPTZ
and neurotoxicity. Compounds were administered intraperitone-
ally as a solution in polyethylene glycol (PEG). The most active
compounds were evaluated quantitatively in phase II screening in
which the ED50 and TD50 of the compounds were determined.
O
C
O
C
a
b
c
R
CH2Br
R
N
R
CH3
R
N
NH2
NHCOOEt
S
(1a-d)
S
(3a-d)
(2a-d)
S
C
S
C
H
H
N
d
e
NH2
N
NH2
NHNH2
R'
R'
R'
(4a-e)
(5a-e)
S
C
H
N
R
N
NHNH2
+
NHCOOEt
R'
S
(3a-d)
(5a-e)
f
R
N
O
NHC
S
C
H
N
H
N
H
N
S
R'
(6a-t)
g
R
N
NH
N
N
H
S
S
N
R'
(7a-t)
R = H, Cl, Br, NO2
R' = H, 2-CH3, 4-CH3, 2-OCH3, 4-OCH3
Reactions and conditions: a) Br2, Chloroform, r. t. b) Thiourea, glacial acetic acid, reflux
c) Ethylchloroformate, triethylamine, benzene, reflux d) NH4SCN, HCl e) NH2.NH2.H2O, ethanol, reflux
f) ethanol, reflux g) 2N NaOH, reflux
Scheme 1. Synthetic route to the synthesized compounds (7a–t).

1538
N. Siddiqui, W. Ahsan / European Journal of Medicinal Chemistry 45 (2010) 1536–1543
Table 1
Physicochemical parameters of the titled compounds (7a–t).
Compound
R
R0
Mol. formulaa
Log Pb found (calculated)
Rfc value
Elemental analyses % found (calculated)
C
H
N
7a
7b
7c
7d
7e
7f
7g
7h
7i
Cl
Cl
Cl
Cl
Cl
Br
Br
Br
2-CH3
4-CH3
2-OCH3
4-OCH3
H
2-CH3
4-CH3
2-OCH3
4-OCH3
H
2-CH3
4-CH3
2-OCH3
4-OCH3
H
2-CH3
4-CH3
2-OCH3
4-OCH3
H
C18H14ClN5S2
C18H14ClN5S2
C18H14ClN5OS2
C18H14ClN5OS2
C17H12ClN5S2
C18H14BrN5S2
C18H14BrN5S2
C18H14BrN5OS2
C18H14BrN5OS2
C17H12BrN5S2
C18H14N6O2S2
C18H14N6O2S2
C18H14N6O3S2
C18H14N6O3S2
C17H12N6O2S2
C18H15N5S2
4.39 (4.67)
4.43 (4.67)
4.32 (4.09)
4.39 (4.09)
4.46 (4.17)
5.08 (4.82)
4.98 (4.82)
4.48 (4.24)
4.41 (4.24)
4.49 (4.32)
3.52 (3.71)
3.59 (3.71)
3.44 (3.13)
3.40 (3.13)
3.09 (3.21)
4.21 (3.94)
4.11 (3.94)
3.24 (3.37)
3.19 (3.37)
3.59 (3.44)
0.69
0.78
0.54
0.61
0.68
0.74
0.79
0.72
0.64
0.71
0.50
0.66
0.70
0.77
0.63
0.49
0.52
0.57
0.64
0.53
54.10 (54.06)
54.12 (54.06)
51.93 (51.98)
51.91 (51.98)
52.96 (52.91)
48.59 (48.65)
48.71 (48.65)
46.91 (46.96)
46.92 (46.96)
47.51 (47.45)
52.61 (52.67)
52.64 (52.67)
50.71 (50.70)
50.74 (50.70)
51.48 (51.51)
59.19 (59.16)
59.09 (59.16)
56.69 (56.68)
56.71 (56.68)
58.07 (58.10)
3.50 (3.53)
3.55 (3.53)
3.32 (3.39)
3.35 (3.39)
3.16 (3.13)
3.23 (3.18)
3.19 (3.18)
3.01 (3.07)
3.12 (3.07)
2.78 (2.81)
3.49 (3.44)
3.39 (3.44)
3.29 (3.31)
3.29 (3.31)
3.12 (3.05)
4.09 (4.14)
4.16 (4.14)
3.91 (3.96)
3.89 (3.96)
3.71 (3.73)
17.47 (17.51)
17.49 (17.51)
16.81 (16.84)
16.87 (16.84)
18.21 (18.15)
15.71 (15.76)
15.70 (15.76)
15.26 (15.21)
15.29 (15.21)
16.35 (16.27)
20.49 (20.47)
20.41 (20.47)
19.74 (19.71)
19.77 (19.71)
21.19 (21.20)
19.22 (19.16)
19.11 (19.16)
18.41 (18.36)
18.34 (18.36)
19.96 (19.93)
Br
Br
7j
7k
7l
NO2
NO2
NO2
NO2
NO2
H
H
H
H
H
7m
7n
7o
7p
7q
7r
7s
7t
C18H15N5S2
C18H15N5OS2
C18H15N5OS2
C17H13N5S2
a
Solvent of crystallization–Ethanol.
Log P was determined by octanol:phosphate buffer method; CLog P was calculated using software ChemOffice 6.0.
Solvent system- Toluene: Ethyl acetate: Formic acid (5:4:1).
b
c
These compounds were also tested for their median hypnotic dose
(HD50) and median lethal dose (LD50) in phase III screening. The
promising nature of the compounds prompted us to undertake the
phase IV screening in which the ED50 and TD50 values were
determined after the oral administration (p.o.) of the compounds.
and 7s. Rest all the compounds showed some degree of neurotox-
icity but were less neurotoxic than the standard drug phenytoin.
The design of compounds was in such a way that the phenyl ring
attached to the thiazole moiety was substituted with electron
withdrawing groups and the phenyl ring attached to the triazole
moiety was substituted with different electron releasing groups at
different positions. The structure activity relationship was studied
4. Results and discussion
4.1. Anticonvulsant activity
Table 2
Anticonvulsant activity and minimal motor impairment of the synthesized
compounds (7a–t).
The anticonvulsant activity was assessed by two most adopted
animal models electroshock (MES) and chemoshock (scPTZ)
methods. All the synthesized compounds were administered
intraperitoneally into mice using doses of 30, 100 and 300 mg/kg
and the observations were taken at two different time intervals
(0.5 h and 4.0 h). Neurological impairment was evaluated by
rotorod method and the data are presented in Table 2.
Compound
Intraperitoneal injection in micea
MES screen scPTZ screen
Neurotoxicity
screen
0.5 h
4.0 h
0.5 h
4.0 h
0.5 h
4.0 h
b
7a
7b
100
300
100
30
–
30
–
–
–
300
–
–
–
–
300
300
–
–
–
300
–
–
300
–
–
300
–
300
–
–
–
–
100
–
300
300
–
–
–
300
100
100
300
30
300
300
300
300
100
300
100
300
300
–
In the phase I preliminary anticonvulsant screening, all the
compounds showed some degree of protection in MES screen
which was the indicative of the good ability of these compounds to
prevent the seizure spread. Among these compounds, 7d and 7f
showed protection from seizure at the lowest dose 30 mg/kg after
0.5 h. Interestingly, compound 7f continued the anticonvulsant
activity at 4.0 h also which indicated the promising nature of the
compound having quick onset and long duration of action.
Compound 7d was also active at 4.0 h but at a higher dose of
100 mg/kg. These compounds were also devoid of any sign of
neurotoxicity. Majority of the compounds were active at a dose of
100 mg/kg after 0.5 h. These include compounds 7a, 7c, 7g, 7k, 7l,
7m, 7n, 7p, 7r and 7s. Among these compounds, 7c, 7k, 7m and 7s
were also found to be active at the same dose after 4.0 h.
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
7m
7n
7o
7p
7q
7r
100
300
–
100
300
–
–
–
100
300
–
–
–
–
300
–
–
–
–
100
–
–
100
300
300
–
100
100
100
100
–
100
–
100
100
300
30
100
300
–
–
300
100
100
300
300
300
300
–
–
–
300
100
–
300
100
100
–
300
–
–
–
–
–
300
300
100
–
–
–
7s
300
300
–
300
–
In the scPTZ screen, compounds that were found to be active
include 7c, 7d, 7f, 7g, 7k, 7l and 7q. Among these compounds, 7c, 7f
and 7k were active at 100 mg/kg after 0.5 h. Compounds 7f and 7k
were also found to be active after 4.0 h but at a higher dose 300 mg/
kg. Compounds that were active at 300 mg/kg dose after 0.5 h were
7d, 7g, 7l and 7q. Compound 7g was also active at the same dose
after 4.0 h.
7t
Phenytoin
Ethosuximide
Phenobarbital
30
100
–
100
–
100
–
30
300
a
Number of animals used ¼ 6; Solvent used- Polyethylene glycol; Dose of 30, 100
and 300 mg/kg were administered i.p. The figures in the table indicate the minimum
dose whereby bioactivity was demonstrated in half or more of the mice. The animals
were examined at 0.5 h and 4 h after injections were administered.
b
In the neurotoxicity screening, compounds that were devoid of
minimal motor impairment at any dose were 7d, 7e, 7f, 7i, 7q, 7r
The dash (–) indicates an absence of activity at maximum dose administered
(300 mg/kg).

N. Siddiqui, W. Ahsan / European Journal of Medicinal Chemistry 45 (2010) 1536–1543
1539
Table 4
and found that the derivatives with nitro group attached to the
Phase III quantitative toxicity profile of selected compounds.
phenyl ring were most active of the series but were most neuro-
toxic too. The effect of electron releasing groups was found to be
uncertain on the anticonvulsant activity. Derivatives having methyl
group attached to the second position of the phenyl ring were
comparatively more effective than the derivatives having methyl
group at the fourth position. The unsubstituted derivatives were
found to be least neurotoxic.
In the phase II anticonvulsant screening, the two most active
compounds 7d and 7f were quantitatively evaluated for their
anticonvulsant activity (ED50) and neurotoxicity (TD50). The results
are presented in Table 3. Both the compounds showed comparable
anticonvulsant activity and higher protective index than the stan-
dard drugs. Compound 7f possessed strong anti-MES activity with
ED50 of 13.4 mg/kg, which was close to currently used antiepileptic
drugs phenytoin and carbamazepine and better than that of
phenobarbital and valproate. The motor impairment caused by it
was minimal and was markedly lower than all the drugs compared.
It showed a protective index of 51.0, which was many folds higher
than the current antiepileptic drugs having the PI values in the
range of 1.6–8.1. Compound 7d also displayed a better profile of
anticonvulsant activity with lesser neurotoxicity (PI ¼ 18.3). Since
the activity of both the compounds were very promising in both
phase I and phase II screening, therefore they were chosen to be
further evaluated in phase III and phase IV screening.
a
b
Compound
HD50
LD50
HD50/ED50
MES
scPTZ
7d
7f
Phenytoin
867 (645–1078)c
632 (578–702)
182 (136–229)
946 (773–1087)
834 (639–1092)
224 (202–251)
36.27
47.16
19.15
4.85
7.74
>0.60
a
Median hypnotic dose (HD50) in mg/kg; determined by loss of righting reflex.
Median lethal dose (LD50) in mg/kg; mortality was determined 24 h after i.p.
b
injection.
c
95% confidence interval in parentheses.
mice and the results are shown in Table 5. Both the compounds
showed the time to peak effect at 2 h, which was comparable to the
standard drug phenytoin. The ED50 values were higher than the
ED50 values found in phase II screening when the compounds were
administered intraperitoneally. It indicates the decrease in the
bioavailability of the compounds when given orally. But, never-
theless the ED50 values and the TD50 values were still comparable to
the standard drugs showing the adequate absorption of the
compounds in mice orally with lesser neurotoxic effects in both the
modes of administration.
4.2. Log P determination
The dependence of biological activity in the set of congeneric
agents or lipophilic character has been shown in many types of
drug action in particular, the reports by Lien and co-workers indi-
cate that the anticonvulsant activity of different types of
compounds were correlated with lipophilicity [14]. However it has
been observed that the maximum potency of the drugs that act on
the central nervous system (CNS) is obtained with congeners
having an optimum lipophilicity (log Po). In this study, we
attempted to correlate the anticonvulsant activity of synthesized
compounds with their log P value. The experimental log P values
were determined using octanol-phosphate buffer method and the
calculated log P values were taken from the software ChemOffice
6.0 and the results are shown in Table 1. Almost all the compounds
are found to be lipophilic and having potent anticonvulsant activity
in both MES as well as scPTZ test. Due to their higher lipophilicity
they are expected to have rapid onset and shorter duration of
action.
In phase III pharmacological testing the toxicity profile of
compounds 7d and 7f was determined and the results are shown in
Table 4. The test compounds were administered intraperitoneally
to mice at different doses in the multiple of TD50 (1TD50, 2TD50 and
4TD50) and the toxicity induced by them was characterized by
decreased motor activity, ataxia, sedation, muscular relaxation, loss
of righting reflex and decreased respiration. At higher doses,
animals were also seen to experience hypnosis, analgesia and
anesthesia.
The median hypnotic dose (HD50) of compound 7d was found to
be 867 mg/kg, which is nearly twice the TD50 of the compound. It
also showed the 24 h median lethal dose (LD50) of 946 mg/kg.
Compound 7f displayed the HD50 value 632 mg/kg with LD50
834 mg/kg. Both the compounds showed wide range of safety
profile as the HD50/ED50 values of 7d and 7f were found to be 36.27
and 47.16 against MES induced seizures. These values are much
higher than that showed by phenytoin. They showed a significant
safety profile in PTZ induced seizure also indicative of the effec-
tiveness of both the compounds as broad spectrum anticonvulsants.
In the phase IV pharmacological screening, the ED50 and TD50
values were determined after administering the test compounds
orally (p.o.). In order to increase the bioavailability of the
compounds they were converted to their respective hydrochloride
salts by treating them with dilute hydrochloric acid. The salts of the
compounds 7d and 7f were dissolved in water and given orally to
4.3. In silico studies
4.3.1. Distance mapping
Further the present work involves the comparison of the
structures for molecular modeling of well known and structurally
different compounds and the synthesized compounds. Comparison
of the structures of the synthesized compounds and other
Table 3
Phase II quantitative anticonvulsant evaluation in mice.
a
b
Compound
ED50
MES
TD50
PIc
scPTZ
MES
scPTZ
7d
7f
23.9 (19.2–28.4)d
13.4 (9.8–17.1)
9.5 (8.1–10.4)
8.8 (5.5–14.1)
21.8 (21.8–25.5)
272 (247–338)
178.6 (126.3–244.6)
81.6 (53.4–113.3)
>300
>100
13.2 (5.8–15.9)
149 (123–177)
439.3 (311.4–564.3)
684.1 (451.3–908.5)
65.5 (52.5–72.9)
71.6 (45.9–135)
69 (62.8–72.9)
18.3
51.0
6.9
8.1
3.2
2.4
8.3
<0.22
<0.22
5.2
Phenytoin
Carbamazepine
Phenobarbital
Valproate
426 (369–450)
1.6
2.9
Number of animals used ¼ 10; Solvent used: polyethylene glycol (0.1 mL, i.p.).
a
Dose in milligrams per kilogram body mass.
Minimal toxicity which was determined by rotorod test 30 min after the test drug was administered.
b
c
PI ¼ Protective index (TD50/ED50).
d
Data in parentheses are the 95% confidence limits.

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N. Siddiqui, W. Ahsan / European Journal of Medicinal Chemistry 45 (2010) 1536–1543
Table 5
Phase IV pharmacological evaluation of selected compounds given orally (p.o.) in
mice.
ED50 (MES)a
TD50
PIb
a
Compound
TPE (h)
7d
7f
Phenytoin
2
2
2
54.8 (43.9–67.1)
49.9 (40.1–60.4)
9.16 (7.9–11.4)
734.7 (683.1–793.9)
883.6 (739.1–998.3)
87.6 (78.3–98.4)
13.40
17.70
9.56
95% confidence interval in parentheses.
a
ED50 and TD50 values are in mg/kg units and determined at the indicated time.
b
PI (Protective index) was determined by TD50/ED50
.
molecules with anticonvulsant activity were performed to find out
the structural elements essential for action. The compounds
selected for this comparison have at least one aryl (R) hydrophobic
domain, one electron donor (D) and a hydrogen bond acceptor/
donor unit (HBD). In an initial study, calculations on the basis of
molecular mechanics, with the force field based on CHARMM
parameterization were performed to obtain an overview on their
minimum conformation for bioactivity. Table 6 shows the distances
between the various groups postulated as essential for anticon-
vulsant action. The synthesized compounds were examined to
check whether they reflect the conditions of the derived pharma-
cophore model. Analyses of the distance relationship showed that
synthesized compounds (7a–t) fulfil the essential demands of
pharmacophore when compared with other known anticonvulsant
drugs. In case of the titled compounds the distances R-D, R-HBD
and D-HBD were in conformity with the distances of active anti-
convulsant drugs.
Fig. 2. ORTEP diagram (50% probability) of 4-phenyl-3-(4-phenyl-1,3-thiazol-2-yla-
mino)-4,5-dihydro-1H-1,2,4-triazole-5-thione (7t) showing hydrogen bonding inter-
actions (N/H and S/H) as dotted line.
triazole-5-thiones has been identified. Two compounds showed
better anticonvulsant activity as compared to the standard drugs
when they were subjected to preliminary anticonvulsant screen-
ings. They also showed marked lower neurotoxicity and therefore
a higher protective index. These can be regarded as strong candi-
dates for future investigations.
4.3.2. Three dimensional structure analysis
The ORTEP diagram (50% probability) was drawn using the
software Ortep3v2 and the characteristics were studied. As noted in
Fig. 2 of the compound 7t, strong hydrogen bonding occurred
between the vinyl protons and the nitrogen atoms as well as with
the sulphur atoms. The N/H distance was calculated to be 1.89 Å
and that of S/H was found to be 2.49 Å. These hydrogen bondings
ensure the rings are planar. It was reported that the planarity of
molecules is an essential factor in determination of biological
activity [15].
6. Experimental protocols
6.1. Chemistry
The melting points were determined in open capillary tubes in
a Hicon melting point apparatus and are uncorrected. The homogen
elemental analyses (C, H, N) of all compounds were performed on
the CHNS Elimentar (Analysen systime, GmbH) Germany Vario EL
III. All the Fourier transform infra red (FTIR) spectra were recorded
in KBr pellets on a Jasco FT/IR 410 spectrometer. The 1H NMR
5. Conclusions
A new series of anticonvulsants 3-[4-(substituted phenyl)-1,3-
thiazol-2-ylamino]-4-(substituted phenyl)-4,5-dihydro-1H-1,2,4-
Table 6
Distance ranges between the essential structure elements R, D and HBD.
Compound
R-HBDa
R-Da
D-HBDa
7t
7.799
6.517
3.042
5.807
4.058
2.407
4.481
3.211
4.793
2.619
3.931
3.868
3.301
5.651
7.474
5.909
9.811
4.827
5.304
5.554
2.497
4.598
6.729
5.209
2.948
6.635
1.497
Carbamazepine
Phenytoin
Lamotrigine
Zonisamide
Rufinamide
Dezinamide
Remacemide
Diazepam
a
Distance calculated for 3D optimized structures using ACD/Chemsketch/3-D viewer 2.0 version program.

N. Siddiqui, W. Ahsan / European Journal of Medicinal Chemistry 45 (2010) 1536–1543
1541
spectra were taken on a Bruker 400 Ultra shieldÔ (400 MHz) NMR
spectrometer. Chemical shifts ( ) are expressed in ppm relative to
30 mL of 2% aq. NaOH solution was refluxed for 6 h. After
completion of reaction, the reaction mixture was filtered and the
filtrate was neutralized with conc. HCl dropwise till pH was
adjusted to 7. The mixture was kept aside for few minutes. A
distinctive precipitate thus obtained was filtered, washed with
water, and recrystallized from ethanol to get the titled compounds
(7a–t).
d
tetramethylsilane (TMS) as an internal standard. The homogeneity
of the compounds was checked by thin layer chromatography (TLC)
on silica gel G (Merck) coated plates by using toluene: ethyl acetate:
formic acid (5:4:1) as solvent system. Iodine chamber and UV lamp
were used for the visualization of TLC spots. For the molecular
mechanics calculations, the ACD/Chemsketch/3-D viewer Freeware
version program was used for employing the Chemistry at Harvard
Macromolecular Mechanics (CHARMM) force field. The three-
dimensional structural analysis of the synthesized compounds was
performed using the software Ortep3v2.
6.1.1.7.1. 3-[4-(4-Chlorophenyl)-1,3-thiazol-2-ylamino]-4-(2-methyl-
phenyl)-4,5-dihydro-1H-1,2,4-triazole-5-thione (7a). Yield 84%, mp
238 ꢁC. IR (KBr) nmax cmꢂ1: 3316 (NH str.), 2889 (Ar-CH str.), 1395
(C]N), 1064 (C]S), 819 (C–Cl); 1H NMR (CDCl3)
d 2.31 (s, 3H, CH3),
5.35 (s, 1H, ArH-thiazole), 6.95–7.73 (m, 8H, ArH), 10.61 (bs, 1H, NH,
D2O exchangeable).
6.1.1. General procedure for the synthesis of titled compounds
(7a–t)
6.1.1.7.2. 3-[4-(4-Chlorophenyl)-1,3-thiazol-2-ylamino]-4-(4-methyl-
phenyl)-4,5-dihydro-1H-1,2,4-triazole-5-thione (7b). Yield 76%, mp
251 ꢁC. IR (KBr) nmax cmꢂ1: 3341 (NH str.), 2991 (Ar-CH str.), 1405
6.1.1.1. 2-Bromo-1-(substituted phenyl)ethanones (1a–d). To the
solution of substituted acetophenones (0.1 mol) in chloroform
(50 mL), was added bromine previously dissolved in chloroform
(0.11 mol in 50 mL) dropwise for a period of 15 min. The reaction
mixture was stirred for an additional 2 h at room temperature.
When the reaction was complete, the reaction mixture was
concentrated and cooled to get the crystals of brominated aceto-
phenones (1a–d).
(C]N), 1051 (C]S), 807 (C–Cl); 1H NMR (CDCl3)
d 2.38 (s, 3H, CH3),
5.39 (s, 1H, ArH-thiazole), 6.98–7.86 (m, 8H, ArH), 10.55 (bs, 1H, NH,
D2O exchangeable).
6.1.1.7.3. 3-[4-(4-Chlorophenyl)-1,3-thiazol-2-ylamino]-4-(2-meth-
oxyphenyl)-4,5-dihydro-1H-1,2,4-triazole-5-thione (7c). Yield 62%,
mp 209 ꢁC. IR (KBr) nmax cmꢂ1: 3343 (NH str.), 2893 (Ar-CH str.),
1415 (C]N), 1059 (C]S), 831 (C–Cl); 1H NMR (CDCl3)
d 3.56 (s, 3H,
OCH3), 5.42 (s, 1H, ArH-thiazole), 6.89–7.89 (m, 8H, ArH), 10.57 (bs,
1H, NH, D2O exchangeable).
6.1.1.2. 4-(Substituted phenyl)-1,3-thiazol-2-amines (2a–d). A solu-
tion of compound (1a–d, 0.1 mol) in 150 mL of acetic acid was
refluxed with thiourea (0.1 mol) for 2 h and cooled to get thiazoles
as crystals, which were filtered, washed with water and recrystal-
lized with ethanol.
6.1.1.7.4. 3-[4-(4-Chlorophenyl)-1,3-thiazol-2-ylamino]-4-(4-meth-
oxyphenyl)-4,5-dihydro-1H-1,2,4-triazole-5-thione (7d). Yield 74%,
mp 245 ꢁC. IR (KBr) nmax cmꢂ1: 3314 (NH str.), 2994 (Ar-CH str.),
1407 (C]N), 1084 (C]S), 864 (C–Cl); 1H NMR (CDCl3)
d 3.52 (s, 3H,
OCH3), 5.49 (s, 1H, ArH-thiazole), 6.99–7.79 (m, 8H, ArH), 10.51 (bs,
1H, NH, D2O exchangeable).
6.1.1.3. Ethyl [4-(substituted phenyl)-1,3-thiazol-2-yl]carbamates
(3a–d). To the substituted thiazoles (2a–d, 0.1 mol) in benzene
were added ethylchloroformate (0.11 mol) and triethylamine
(25 mL), and the reaction mixture was refluxed for 3 h. After cooling
the reaction mixture was poured into cold dil. HCl (50%) and the
carbamate thus formed was recrystallized from benzene.
6.1.1.7.5. 3-[4-(4-Chlorophenyl)-1,3-thiazol-2-ylamino]-4-phenyl-
4,5-dihydro-1H-1,2,4-triazole-5-thione (7e). Yield 73%, mp 194 ꢁC.
IR (KBr) nmax cmꢂ1: 3319 (NH str.), 2987 (Ar-CH str.), 1426 (C]N),
1087 (C]S), 846 (C–Cl); 1H NMR (CDCl3)
d 5.42 (s, 1H, ArH-thia-
zole), 6.81–7.71 (m, 9H, ArH), 10.43 (bs, 1H, NH, D2O exchangeable).
6.1.1.7.6. 3-[4-(4-Bromophenyl)-1,3-thiazol-2-ylamino]-4-(2-
6.1.1.4. 1-(Substituted phenyl)thioureas (4a–e). Substituted anilines
(0.1 mol) were taken in water and warmed with dilute hydrochloric
acid (5 mL) until a clear solution was obtained. To this solution was
added ammonium thiocyanate (0.11 mol) dissolved in water
(25 mL) gradually. The reaction mixture was boiled and evaporated
to less than half of the volume. It was then cooled to get the
precipitate of phenyl thiourea which were filtered, washed with
water and recrystallized from ethanol to get the target compounds.
methylphenyl)-4,5-dihydro-1H-1,2,4-triazole-5-thione
65%, mp 179 ꢁC. IR (KBr) nmax cmꢂ1: 3318 (NH str.), 3015 (Ar-CH str.),
1478 (C]N), 1135 (C]S), 563 (C–Br); 1H NMR (CDCl3)
2.27 (s, 3H,
CH3), 5.40 (s, 1H, ArH-thiazole), 6.98–7.95 (m, 8H, ArH), 10.37 (bs,
1H, NH, D2O exchangeable).
(7f). Yield
d
6.1.1.7.7. 3-[4-(4-Bromophenyl)-1,3-thiazol-2-ylamino]-4-(4-methyl-
phenyl)-4,5-dihydro-1H-1,2,4-triazole-5-thione (7g). Yield 71%, mp
186 ꢁC. IR (KBr) nmax cmꢂ1: 3334 (NH str.), 2918 (Ar-CH str.), 1454
(C]N), 1054 (C]S), 556 (C–Br); 1H NMR (CDCl3)
d 2.31 (s, 3H, CH3),
6.1.1.5. N-(substituted phenyl)hydrazinecarbothioamides (5a–e). To
the solution of substituted phenylthioureas (4a–e, 0.1 mol) in
ethanol was added hydrazine hydrate (0.11 mol) and the reaction
mixture was refluxed for 16 h. It was then concentrated, cooled and
poured over crushed ice to get the precipitate which was filtered,
washed with water and recrystallized from ethanol to get hydra-
zinecarbothioamides (5a–e).
5.51 (s, 1H, ArH-thiazole), 7.08–7.96 (m, 8H, ArH), 10.41 (bs, 1H, NH,
D2O exchangeable).
6.1.1.7.8. 3-[4-(4-Bromophenyl)-1,3-thiazol-2-ylamino]-4-(2-meth-
oxyphenyl)-4,5-dihydro-1H-1,2,4-triazole-5-thione (7h). Yield 76%,
mp 226 ꢁC. IR (KBr) nmax cmꢂ1: 3345 (NH str.), 2934 (Ar-CH str.),
1405 (C]N), 1085 (C]S), 559 (C–Br); 1H NMR (CDCl3)
d 3.51 (s, 3H,
OCH3), 5.65 (s, 1H, ArH-thiazole), 7.15–8.03 (m, 8H, ArH), 10.43 (bs,
1H, NH, D2O exchangeable).
6.1.1.6. 2-[(Substituted phenyl)carbamothioyl]-N-[4-(substituted ph-
enyl)-1,3-thiazol-2-yl]hydrazinecarboxamides (6a–t). The solution
of carbamates (3a–d, 0.01 mol) and hydrazinecarbothioamides (5a–
e, 0.01 mol) in ethanol (25 mL) was refluxed for 4 h. The residue was
concentrated, cooled and poured over crushed ice to the precipitate
which was filtered, washed with water, dried and recrystallized
from ethanol to get the targeted compounds (6a–t).
6.1.1.7.9. 3-[4-(4-Bromophenyl)-1,3-thiazol-2-ylamino]-4-(4-meth-
oxyphenyl)-4,5-dihydro-1H-1,2,4-triazole-5-thione (7i). Yield 69%, mp
238 ꢁC. IR (KBr) nmax cmꢂ1: 3351 (NH str.), 2884 (Ar-CH str.), 1398
(C]N), 1074 (C]S), 564 (C–Br); 1H NMR (CDCl3)
d 3.57 (s, 3H,
OCH3), 5.66 (s, 1H, ArH-thiazole), 7.09–7.89 (m, 8H, ArH), 10.14 (bs,
1H, NH, D2O exchangeable).
6.1.1.7.10. 3-[4-(4-Bromophenyl)-1,3-thiazol-2-ylamino]-4-phenyl-
4,5-dihydro-1H-1,2,4-triazole-5-thione (7j). Yield 61%, mp 198 ꢁC. IR
(KBr) nmax cmꢂ1: 3325 (NH str.), 2875 (Ar-CH str.),1385 (C]N),1081
6.1.1.7. 4-(Substituted phenyl)-5-[{4-(substituted phenyl)-1,3-thia-
zol-2-yl}amino]-2,4-dihydro-3H-1,2,4-triazole-3-thiones (7a–t). A
mixture of substituted hydrazinecarboxamides (6a–t, 0.01 mol) and
(C]S), 561 (C–Br); 1H NMR (CDCl3)
d
5.42 (s, 1H, ArH-thiazole),
6.95–7.83 (m, 9H, ArH), 10.39 (bs, 1H, NH, D2O exchangeable).

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N. Siddiqui, W. Ahsan / European Journal of Medicinal Chemistry 45 (2010) 1536–1543
6.1.1.7.11. 4-(2-Methylphenyl)-3-[4-(4-nitrophenyl)-1,3-thiazol-
cage. All the experimental protocols were carried out with the
permission from Institutional Animal Ethics committee (IAEC),
form no. 502. Animals were obtained from Central Animal House
Facility, Hamdard University, New Delhi-62. Registration no. and
date of registration is 173/CPCSEA, 28 Jan., 2000.
2-ylamino]-4,5-dihydro-1H-1,2,4-triazole-5-thione (7k). Yield 62%,
mp 209 ꢁC. IR (KBr) nmax cmꢂ1: 3315 (NH str.), 2956 (Ar-CH str.), 1449
(C]N), 1339 (NO2), 1041 (C]S); 1H NMR (CDCl3)
d 2.29 (s, 3H, CH3),
5.49 (s, 1H, ArH-thiazole), 7.21–8.29 (m, 8H, ArH), 10.69 (bs, 1H, NH,
D2O exchangeable).
6.1.1.7.12. 4-(4-Methylphenyl)-3-[4-(4-nitrophenyl)-1,3-thiazol-
2-ylamino]-4,5-dihydro-1H-1,2,4-triazole-5-thione (7l). Yield 76%,
mp 245 ꢁC. IR (KBr) nmax cmꢂ1: 3364 (NH str.), 3016 (Ar-CH str.),
6.2.1. Anticonvulsant activity
6.2.1.1. Maximal electroshock test (MES). The maximal electroshock
seizure test was carried out according to the standard protocol [16].
Albino mice were stimulated through corneal electrodes to 50 mA
current at a pulse of 60 Hz applied for 0.25 s. Animals were
previously administered with the test drug i.p. Abolition of hind
limb tonic extension spasm was recorded as the anticonvulsant
activity. The test compounds were dissolved in polyethylene glycol
(PEG). In the preliminary screening, each compound was admin-
istered as an i.p. injection at three dose levels (30, 100 and 300 mg/
kg body mass) and the anticonvulsant activity assessed after 0.5 h
and 4.0 h intervals of administration.
1467 (C]N), 1347 (NO2), 1029 (C]S); 1H NMR (CDCl3)
d 2.26 (s, 3H,
CH3), 5.51 (s, 1H, ArH-thiazole), 7.16–8.12 (m, 8H, ArH), 10.71 (bs,
1H, NH, D2O exchangeable).
6.1.1.7.13. 4-(2-Methoxyphenyl)-3-[4-(4-nitrophenyl)-1,3-thiazol-
2-ylamino]-4,5-dihydro-1H-1,2,4-triazole-5-thione (7m). Yield 58%,
mp 216 ꢁC. IR (KBr) nmax cmꢂ1: 3316 (NH str.), 3048 (Ar-CH str.),
1451 (C]N), 1336 (NO2), 1045 (C]S); 1H NMR (CDCl3)
d 3.54 (s, 3H,
OCH3), 5.46 (s, 1H, ArH-thiazole), 7.19–8.24 (m, 8H, ArH), 10.69 (bs,
1H, NH, D2O exchangeable).
6.1.1.7.14. 4-(4-Methoxyphenyl)-3-[4-(4-nitrophenyl)-1,3-thiazol-
2-ylamino]-4,5-dihydro-1H-1,2,4-triazole-5-thione (7n). Yield 73%,
mp 263 ꢁC. IR (KBr) nmax cmꢂ1: 3349 (NH str.), 3013 (Ar-CH str.),
6.2.1.2. Subcutaneous pentylenetetrazole induced seizure test
(scPTZ). The subcutaneous pentylenetetrazole test was performed
according to the known protocol [17]. This method utilizes penty-
lenetetrazole (75 mg/kg) that produces seizures in >95% of animals
as a 0.5% solution subcutaneously in the posterior midline. The
animal was observed for 30 min, failure to observe even a threshold
seizure (a single episode of clonic spasms of at least 5 s duration)
was defined as protection.
The pharmacological parameters estimated in phase I screening
was quantified in phase II screening (Table 3). Anticonvulsant
activity was expressed in terms of the median effective dose (ED50),
and neurotoxicity was expressed as the median toxic dose (TD50).
For the determination of ED50 and TD50 values, groups of 10 mice
were given a range of intraperitoneal doses of the test drug until at
least three points were established in the range of 10–90% seizure
protection or minimal observed neurotoxicity. From the plot of
these data, the respective ED50 and TD50 values, 95% confidence
intervals, slope of the regression line, and the standard error of the
slope were calculated by means of the computer program by
Litchfield and Wilcoxon’s method [18].
1464 (C]N), 1329 (NO2), 1019 (C]S); 1H NMR (CDCl3)
d 3.57 (s, 3H,
OCH3), 5.41 (s, 1H, ArH-thiazole), 7.02–8.16 (m, 8H, ArH), 10.58 (bs,
1H, NH, D2O exchangeable).
6.1.1.7.15. 3-[4-(4-Nitrophenyl)-1,3-thiazol-2-ylamino]-4-phenyl-
4,5-dihydro-1H-1,2,4-triazole-5-thione (7o). Yield 59%, mp 186 ꢁC.
IR (KBr) nmax cmꢂ1: 3346 (NH str.), 3046 (Ar-CH str.), 1449 (C]N),
1329 (NO2), 1037 (C]S); 1H NMR (CDCl3)
d
5.51 (s, 1H, ArH-thia-
zole), 7.27–8.16 (m, 9H, ArH), 10.57 (bs, 1H, NH, D2O exchangeable).
6.1.1.7.16. 4-(2-Methylphenyl)-3-(4-phenyl-1,3-thiazol-2-ylamino)-
4,5-dihydro-1H-1,2,4-triazole-5-thione (7p). Yield 67%, mp 194 ꢁC.
IR (KBr) nmax cmꢂ1: 3306 (NH str.), 3008 (Ar-CH str.), 1445 (C]N),
1045 (C]S); 1H NMR (CDCl3)
d 2.29 (s, 3H, CH3), 5.43 (s, 1H, ArH-
thiazole), 6.74–7.79 (m, 9H, ArH), 10.41 (bs, 1H, NH, D2O
exchangeable).
6.1.1.7.17. 4-(4-Methylphenyl)-3-(4-phenyl-1,3-thiazol-2-ylamino)-
4,5-dihydro-1H-1,2,4-triazole-5-thione (7q). Yield 76%, mp 229 ꢁC.
IR (KBr) nmax cmꢂ1: 3318 (NH str.), 3026 (Ar-CH str.), 1458 (C]N),
1034 (C]S); 1H NMR (CDCl3)
d 2.27 (s, 3H, CH3), 5.41 (s, 1H, ArH-
thiazole), 6.69–7.62 (m, 9H, ArH), 10.39 (bs, 1H, NH, D2O
exchangeable).
Phase III screening comprises of the assessment of general
behavior of mice at regular time intervals up to 24 h following the
i.p. administration of the test compounds at doses equivalent to
TD50, 2TD50 and 4TD50. The median hypnotic dose was assessed by
loss of righting reflex and the 24 h median lethal dose was deter-
mined by using the procedure described previously for evaluation
of ED50 and TD50 values in phase II screening.
In phase IV screening the same procedure was followed as dis-
cussed in phase II screening except the fact that the test compounds
and standard drugs are administered orally (p.o.). The test
compounds were converted to their respective hydrochloride salt,
dissolved in water and given orally to groups of mice and the ED50
and TD50 values of the compounds were determined.
6.1.1.7.18. 4-(2-Methoxyphenyl)-3-(4-phenyl-1,3-thiazol-2-ylamino)-
4,5-dihydro-1H-1,2,4-triazole-5-thione (7r). Yield 73%, mp 209 ꢁC.
IR (KBr) nmax cmꢂ1: 3371 (NH str.), 2976 (Ar-CH str.), 1429 (C]N),
1017 (C]S); 1H NMR (CDCl3)
d 3.53 (s, 3H, OCH3), 5.51 (s, 1H, ArH-
thiazole), 6.86–7.83 (m, 9H, ArH), 10.29 (bs, 1H, NH, D2O
exchangeable).
6.1.1.7.19. 4-(4-Methoxyphenyl)-3-(4-phenyl-1,3-thiazol-2-ylamino)-
4,5-dihydro-1H-1,2,4-triazole-5-thione (7s). Yield 68%, mp 267 ꢁC.
IR (KBr) nmax cmꢂ1: 3356 (NH str.), 2937 (Ar-CH str.), 1415 (C]N),
1048 (C]S); 1H NMR (CDCl3)
d 3.46 (s, 3H, OCH3), 5.47 (s, 1H, ArH-
thiazole), 6.81–7.76 (m, 9H, ArH), 10.37 (bs, 1H, NH, D2O
exchangeable).
6.1.1.7.20. 4-Phenyl-3-(4-phenyl-1,3-thiazol-2-ylamino)-4,5-di-
hydro-1H-1,2,4-triazole-5-thione (7t). Yield 79%, mp 174 ꢁC. IR
(KBr) nmax cmꢂ1: 3319 (NH str.), 2961 (Ar-CH str.), 1467 (C]N), 1039
d 5.47 (s, 1H, ArH-thiazole), 6.81–7.78 (m,
10H, ArH), 10.46 (bs, 1H, NH, D2O exchangeable).
6.2.2. Neurotoxicity screening (NT)
The minimal motor impairment was measured in mice by the
rotorod test. The mice were trained to stay on an accelerating rotorod
of diameter 3.2 cm that rotates at 10 rpm. Trained animals were
given i.p. injection of the test compounds 30, 100 and 300 mg/kg.
Neurotoxicity was indicated by the inability of the animal to main-
tain equilibrium on the rod for at least 1 min in each of the trials [19].
(C]S); 1H NMR (CDCl3)
6.2. Pharmacology
The investigations were conducted on albino mice of either sex
(25–30 g). The albino mice were kept under standard conditions at
an ambient temperature of 25 ꢀ 2 ꢁC and allowed free access to
food and water except at the time they were brought out of the
6.3. Log P determination
The partition coefficient between octanol and phosphate buffer
was determined at room temperature (29 ꢁC) using a procedure

N. Siddiqui, W. Ahsan / European Journal of Medicinal Chemistry 45 (2010) 1536–1543
1543
described elsewhere [20]. 10 mL of octanol and 10 mL phosphate
buffer (pH ¼ 7.4) were taken in a glass stoppered graduated tube
and 5 mg of accurately weighed drug was added. The mixture was
then shaken with the help of mechanical shaker for 24 h at room
temperature. The mixture was then transferred to a separating
funnel and allowed to equilibrate for 6 h. The aqueous and octanol
phase were separated and filtered through membrane filter and
drug content in aqueous phase was analyzed by UV spectroscopy.
Partition coefficient was calculated by;
Research Fellowship (SRF) as financial assistance. We are also
thankful to Shrenik Pharma Ltd., Mumbai, India for providing
pentylenetetrazole as gift sample.
References
[1] C. Wasterlain, in: G. Siegel, G. Agranoff, R.W. Albers, P. Molinof (Eds.), Basic
Neurochemistry: Molecular, Cellular and Medical Aspects, fourth ed. Raven
Press, New York, 1989, pp. 797–810.
[2] J.J. Coatsworth, NINDS Monograph No. 12. HEW Publication No. (NIH), U.S.
Government Printing Office, 1971, pp. 51–73.
[3] N. Siddiqui, S.N. Pandeya, A.P. Sen, G.S. Singh, Pharmakeftiki 5 (1992) 121–125.
[4] N. Siddiqui, S.N. Pandeya, S.A. Khan, J.P. Stables, Bioorg. Med. Chem. Lett. 17
(2007) 255–259.
[5] N. Siddiqui, A. Rana, S.A. Khan, Bioorg. Med. Chem. Lett. 17 (2007) 4178–4182.
[6] A. Rana, N. Siddiqui, S.A. Khan, S.E. Haque, M.A. Bhat, Eur. J. Med. Chem. 43
(2008) 1114–1122.
PC ¼ (Ct ꢂ Ca)/Ca.
PC ¼ Partition coefficient, Ct ¼ Concentration of total drug,
Ca ¼ Concentration of the drug in aqueous phase.
6.4. In silico studies
[7] M. Bachir, J.P. Riffaud, J. Lacolle, J. Lemoine, A.D. Almeida, P. Houziaux,
B. Danree, Eur. J. Med. Chem. 25 (1990) 71–74.
6.4.1. Distance mapping
[8] G.B. DeSarro, M. Zapalla, S. Grasso, A. Chimirri, A. DeSarro, Gen. Pharmacol. 24
(1993) 877–884.
[9] A. Almasirad, S.A. Tabatabai, M. Faizi, Bioorg. Med. Chem. Lett. 14 (2004) 6057–
6059.
[10] M.R. Shiradkar, M. Ghodake, K.G. Bothara, S.V. Bhandari, A. Nikalje, K.C. Akula,
N.C. Desai, P.J. Burange, Arkivoc 14 (2007) 58–74.
[11] S.N. Pandeya, P. Yogeeswari, J.P. Stables, Eur. J. Med. Chem. 35 (2000) 879–886.
[12] P. Yogeeswari, D. Sriram, L.R.J. Suniljit, S.S. Kumar, J.P. Stables, Eur. J. Med.
Chem. 37 (2002) 231–236.
[13] Anticonvulsant Screening Project, Antiepileptic Drug Development
Program. National Institute of Health, DHEW Publ (NIH), (US), 1978,
pp. 78–1093.
[14] E.J. Lien, R.C.H. Liao, H.G. Shinouda, J. Pharm. Sci. 68 (1979) 463–465.
[15] N.D. Eddington, D.S. Cox, R.R. Roberts, R.J. Butcher, I.O. Edafiogho, J.P. Stables,
N. Cooke, A.M. Goodwin, C.A. Smith, K.R. Scott, Eur. J. Med. Chem. 37 (2002)
635–648.
In the conformational analysis of the older generation clinically
active anticonvulsant drugs such as phenytoin, carbamazepine,
lamotrigene, rufinamide, remacemide and phenobarbitone,
a molecular model was suggested on the basis of molecular
dynamics distance estimations [21]. According to which an electron
´
ꢀ
donor (D) should be in a distance range of 3:2—5:1A to an aryl ring
´
ꢀ
or any other hydrophobic unit (R) and of 3:9—5:5Ato the hydrogen
bonding domain (HBD). For the molecular mechanics calculations,
the ACD/Chemsketch/3-D viewer 2.0 version program was used for
employing the CHARMM force field [22].
6.4.2. Three-dimensional structure analysis
This is performed to define the role of three-dimensional
structures of synthesized compounds to their anticonvulsant
activity. Compound 4-phenyl-3-(4-phenyl-1,3-thiazol-2-ylamino)-
4,5-dihydro-1H-1,2,4-triazole-5-thione (7t) which represents the
prototype structure of the synthesized compounds was chosen for
the study. It was performed using software Ortep3v2.
[16] R.L. Krall, J.K. Penry, B.G. White, H.J. Kupferberg, E.A. Swinyard, Epilepsia 19
(1978) 409–428.
[17] C.R. Clark, M.J.M. Wells, R.T. Sansom, G.N. Norris, R.C. Dockens, W.R. Ravis,
J. Med. Chem. 27 (1984) 779–782.
[18] J.T. Litchfield, F. Wilcoxon, J. Pharmacol. Exp. Ther. 96 (1949) 99–113.
[19] P. Yogeeswari, D. Sriram, V. Saraswat, R.J. Vaigunda, K.M. Mohan,
S. Murugesan, R. Thirumurugan, Eur. J. Pharm. Sci. 20 (2003) 341–346.
[20] V.A. Farrar, M. Ciechanowicz-Rutkowska, J. Grochowski, P. Serda, T. Pilati,
G. Filippini, C.N. Hinko, A. El-Assadi, J.A. Moore, I.O. Edafiogho,
C.W. Andrews, M. Cory, J.M. Nicholson, K.R. Scott, J. Med. Chem. 36 (1993)
3517–3525.
Acknowledgments
[21] M.G. Wong, J.A. Defina, P.R. Andrews, J. Med. Chem. 29 (1986) 562–572.
[22] B.R. Brooks, R.E. Bruccoleri, B.D. Olafson, D.J. States, S. Swaminathan,
M. Karplus, J. Comput. Chem. 4 (1983) 187–217.
One of the authors (W.A.) is thankful to Council of Scientific and
Industrial Research (CSIR), Government of India for the Senior