Design & synthesis of N′-[substituted] pyridine-4-carbohydrazides as potential anticonvulsant agents

Article abstract of DOI:10.1016/j.ejmech.2010.11.030

A series of N′-[substituted] pyridine-4-carbohydrazides were designed and synthesized keeping in view the structural requirement of pharmacophore and evaluated for anticonvulsant activity and neurotoxicity. The anticonvulsant activity of the titled compounds was established after intraperitoneal administration in three seizure models, which include MES, scMET and 6 Hz model. The most active compound of the series was N′-[4-(4-fluorophenoxy) benzylidene]pyridine-4-carbohydrazide PCH 6, which showed a MES ED₅₀ value of 128.3 mg/kg and 6 Hz ED₅₀ value of 53.3 mg/kg in mice. The median toxic dose (TD₅₀) was 343.6 mg/kg, providing compound PCH 6 with a protection index of 2.67 in the MES test and 6.44 in 6 Hz test. A computational study was also carried out, including calculation of pharmacophore pattern, prediction of pharmacokinetic properties and docking studies.

Full text of DOI:10.1016/j.ejmech.2010.11.030

European Journal of Medicinal Chemistry 46 (2011) 509e518
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Design & synthesis of N0-[substituted] pyridine-4-carbohydrazides as potential
anticonvulsant agents
,
a
b
Laxmi Tripathi a , Ranjit Singh , James P. Stables
*
a School of Pharmaceutical Sciences, Shobhit University, Meerut 250110, India
b Preclinical Pharmacology Section, Epilepsy Branch, National Institute of Health, Bethesda, MD 20892-9020, USA
a r t i c l e i n f o
a b s t r a c t
A series of N0-[substituted] pyridine-4-carbohydrazides were designed and synthesized keeping in view
the structural requirement of pharmacophore and evaluated for anticonvulsant activity and neurotox-
icity. The anticonvulsant activity of the titled compounds was established after intraperitoneal admin-
istration in three seizure models, which include MES, scMET and 6 Hz model. The most active compound
of the series was N0-[4-(4-fluorophenoxy)benzylidene]pyridine-4-carbohydrazide PCH 6, which showed
a MES ED50 value of 128.3 mg/kg and 6 Hz ED50 value of 53.3 mg/kg in mice. The median toxic dose
(TD50) was 343.6 mg/kg, providing compound PCH 6 with a protection index of 2.67 in the MES test and
6.44 in 6 Hz test. A computational study was also carried out, including calculation of pharmacophore
pattern, prediction of pharmacokinetic properties and docking studies.
Article history:
Received 16 October 2010
Received in revised form
16 November 2010
Accepted 18 November 2010
Available online 24 November 2010
Keywords:
N’-[substituted]pyridine-4-carohydrazides
Anticonvulsant activity
Neurotoxicity
Ó 2010 Elsevier Masson SAS. All rights reserved.
Computational study
1. Introduction
N-iso-propyl derivative of isoniazid has mood-elevating effects in
patients due to its monoamine oxidase inhibitor activity.
Epilepsy is a collective term that includes over 40 different types
of human seizure disorders [1]. Approximately 1% of the world
population at any one time (z50 million people world wide) is
afflicted with this serious neurological disorder [2]. Although the
current drugs provide adequate seizure control in many patients, it
is roughly estimated that up to 28e30% of patients are poorly
treated with the available antiepileptic drugs (AEDs). Moreover, the
current drug therapy is associated with adverse side effects such as
drowsiness, ataxia, gastrointestinal disturbances, gingival hyper-
plasia, hirsutism and megaloblastic anaemia [3,4] and life long
medication may be required. These facts necessitate the search for
the development of novel anticonvulsant drugs with greater effi-
cacy and fewer side effects.
Hydrazones possessing an azomethine eNHN]CHe proton
constitute an important class of compounds for new drug devel-
opment. In the past decade, hydrazones have been designed
as potential anticonvulsants that were structurally dissimilar from
very common anticonvulsants containing the dicarboximide func-
tion (CONRCO), which may contribute to toxic side effects [5e7].
Isonicotinyl hydrazones were mostly reported as antitubercular
[8,9], antidepressant [10] and antimalarial [11]. Iproniazide, a
Consistent advances in the design of novel anticonvulsant
agents have been obtained through the works of Dimmock and his
collegues [12e15], which includes various semicarbazones and
hydrazones. Earlier two-dimensional (2D) modeling on anticon-
vulsants has identified that at least one aryl unit, one or two elec-
tron donor atoms, and/or an NH group in a spatial arrangement are
to be recommended for anticonvulsant activity [16e18]. Unverferth
et al. identified a common pharmacophore model based on some
well known voltage-gated sodium channel blockers including
phenytoin and lamotrigine [19].
Based on the literature review, we are the first to report the
synthesis and anticonvulsant activities of N0-[substituted] pyridine-
4-carbohydrazides. Their chemical structures were characterized
using IR, 1H NMR, MS and elemental analysis techniques. All the
synthesized titled compounds comprised of the essential phar-
macophoric elements (Fig. 1) that are necessary for good antic-
onvulsant activity as suggested by Unverferth et al. [19]. The
essential structural features which could be responsible for an
interaction with the active site of voltage-gated sodium channels
were a hydrophobic HP unit (R), an electron donor (D) group, and
a hydrogen donor/acceptor (HBD) unit [20]. In addition, their
anticonvulsant activity was evaluated by using experimental
epilepsy models, i.e., maximal electroshock (MES), subcutane-
ous metrazole (scMET) and psychomotor seizure (6 Hz) test in
mice. The rotorod assay was performed in mice to evaluate the
* Corresponding author. Tel.: þ91 9897112288.
E-mail address: tripathilaxmi@rediffmail.com (L. Tripathi).
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.11.030

510
L. Tripathi et al. / European Journal of Medicinal Chemistry 46 (2011) 509e518
D
N
D
CH3
A
D
S
H
H
HD
OH
CH3
A
N
O HA
HD
N
N
H
A
S HA
HA
O
HD H2N
Albutoin
Carbamazepine
Gabapentin
D
HA
O
D
N
H
H
N
O
A
H
NH
HD
N
Cl
HD
C2H5
O
Cl
N
H
N
N
O
N
N
O
HA
D
H
HD
HA
CH3
H
Lamotrignine
Mephobarbital
Phenytoin
HA
O
N
O
A
OH
D
H
HD
H3C
O
S
N
O
HA
D
HD
H
N
H
N
N
A
F
HA
O
H
H
N
H
H
Zonisamide
HD
A
Remacemide
Progabide
Cl
HD
H
O
H3C
D
CH3
O
D
O
H
N
CH3
A
C
N
N
C
HA
S
HA
N
H
A
O
Cl
H
N
HD
PCH 3
Ralitoline
HD
H
D
O
H
F
C
N
N
C
HA
A
O
N
PCH 6
Fig. 1. Pharmacophoric pattern of well-known anticonvulsants.
neurotoxicity of the compounds. Computational study was also
carried out to highlight the pharmacophore distance mapping,
miLog P calculation and prediction of pharmacokinetic parameters.
In this study, we have used AutoDock 4.0 along with its LGA algo-
rithm for automated flexible ligand docking of compounds with six
established epilepsy molecular targets and evaluated docking
affinity and count of probable hydrogen bonds.
throughout the reactions to optimize the reactions for purity and
completion. The physical data for the newlysynthesized compounds
are presented in Table 1.
The structural assignments to new compounds were based on
their elemental analysis and spectral (FT-IR, 1H NMR and mass)
data. The formation of 4-substituted benzaldehydes 3aei from 4-
substituted phenols was confirmed by its IR and 1H NMR spectral
studies. The IR spectrum of 4-(4-fluorophenoxy) benzaldehydes 3f
showed bands at 1665, 3035 and 1240 cmꢀ1 indicating the pres-
ence of C]O str, CeH str and diaryl ether linkage (eOe). The
absence of broad band of phenolic eOH at 2900e3000 cmꢀ1
confirm the conversion of 4-fluoro phenol 1f to 3f. In its 1H NMR
2. Chemistry
The reaction sequence leading to the formation of the titled
compounds, viz. N0-(substituted) pyridine-4-carbohydrazide PCH
1e10 is shown in Scheme 1. The 4-substituted benzaldehydes 3aei
were prepared by refluxing various substituted phenol 1aei with
4-fluorobenzaldehyde 2 in N,N0-DMF in presence of potassium
carbonate. The pyridine-4-carbohydrazide 4 was refluxed with
various 4-substituted benzaldehyde 3aei and isatin 3j in the pres-
ence of catalytic amount of glacial acetic acid to yield the titled
compounds PCH 1e10. Thin layer chromatography (TLC) was run
spectrum a singlet at
group, where as absence of a singlet around
phenolic eOH confirm the conversion of 1f to 3f.
d
9.87 ppm indicating the presence of eCHO
d
9.288 ppm for
The IR spectrum of the titled compound PCH 6 showed C]O str
at 1651 cmꢀ1, NeH str (associated) at 3252 and 3080 cmꢀ1, CH]N
str at 1605 cmꢀ1 and diaryl ether linkage (eOe) at 1255 cmꢀ1. Its 1H
NMR spectrum showed a singlet of imine (CH]N) proton at

L. Tripathi et al. / European Journal of Medicinal Chemistry 46 (2011) 509e518
511
O
F
K2CO3, N,N'-DMF
reflux
+
Ar OH
Ar
CHO
CHO
3a-i
1a-i
2
C NHN C
H
O Ar
O
O
O
O
Ar
OR
C
NHNH2
CHO
O
N
N
H
3a-i
3j
PCH 1-9
Ethanol, Glacial acetic acid, reflux
N
4
C NHN
O
NH
O
N
PCH 10
PCH 6: Ar =
F
PCH 1: Ar =
PCH 2: Ar =
CH3
NO2
CH3
Cl
Cl
PCH 7: Ar =
PCH 8: Ar =
PCH 9: Ar =
PCH 3: Ar =
PCH 4: Ar =
PCH 5: Ar =
O
O
Br
Scheme 1. Synthesis of N0-(substituted) pyridine-4-carbohydrazide PCH 1e10.
d
8.359 ppm, two doublet of pyridine protons at
6.98 ppm and eNHe proton resonated as a broad singlet at
9.86 ppm that was D2O exchangeable. Aromatic protons appeared
as a multiplet in the region 7.001e7.885 ppm. The presence
of CH]N str at 1605 cmꢀ1 in IR spectrum and a singlet for imine
(CH]N) proton at 8.359 ppm confirm the formation of PCH 6.
d
8.76 and
Model and In-vitro Hippocampal Slice Culture Neuroprotection
Assay (NP) and results are shown in Tables 6e8.
d
d
4. Computational study
d
The pharmacophore pattern studies in which distance between
the various groups postulated as essential for anticonvulsant
activity were done on the 3D optimized structures using ACD/3D
viewer version 12.0 and Argus Lab 4.0 Mark A. Thompson Planaria
Software LLC. A computational study of all compounds was per-
formed for prediction of ADME properties such as absorption
(%ABS), polar surface area (TPSA), miLog P, number of rotatable
bonds, and violations of Lipinski’s rule of five by using Molinspi-
ration online property calculation toolkit. Calculated miLog P for
synthesized compounds were then compared with the experi-
mental Log P data of these compounds. Docking study of titled
compounds was performed with six established epilepsy molecular
targets namely GABA (A) alpha-1 receptor, GABA (A) delta receptor,
glutamate receptor, Na/H exchanger, Na channel receptor, T-type
calcium channel receptor by using AutoDock 4.0 along with its LGA
algorithm for automated flexible ligand docking and affinity (Kcal/
mol) and count of probable hydrogen bonds were evaluated.
Further mass spectrum confirmed their purity and molecular
weight.
3. Pharmacology
The newly synthesized N0-(substituted) pyridine-4-carbohy-
drazides PCH 1e10 were subjected to anticonvulsant screening by
the anticonvulsant drug development (ADD) program protocol. The
profile of anticonvulsant activity was established after i.p. injec-
tions into mice and evaluated in the maximal electroshock (MES)
and subcutaneous metrazole (scMET) using doses of 30, 100 and
300 mg/kg at two different time intervals. Neurotoxicity was
observed by minimal motor impairment which was measured by
the rotorod test. The results are shown in Table 2. Compound
showing significant protection was examined for its oral activity in
rat MES screen and result is shown in Table 3. Some compounds
were screened in 6 Hz model to identify their activity at five
different time points, i.e., 0.25 h, 0.5 h, 1.0 h, 2.0 h and 4.0 h after i.p.
administration in mice. The results are shown in Table 4. Potential
compounds were also subjected to quantification studies in one or
more models i.e. MES, scMET, neurotoxicity and 6 Hz test and the
corresponding ED50 and TD50 reported in Table 5. Some compounds
were screened in Pilocarpine Induced Status Prevention (PISP)
5. Results and discussion
5.1. Anticonvulsant and neurotoxicity evaluation
Some of the synthesized compounds showed protection against
MES test, indicative of their ability to inhibit the seizure spread. The

512
L. Tripathi et al. / European Journal of Medicinal Chemistry 46 (2011) 509e518
Table 1
Compounds showed more promising results when tested in
6 Hz model and the results are shown in Table 4. Compound PCH 6
was the most active one in this series with protection at three
different time points, i.e. 100% (4/4, 0.5 h), 75% (3/4, 0.25 h) and 50%
(2/4, 1.0 h) at a dose of 100 mg/kg. Compound PCH 3 showed 75%
protection (3/4, 1.0 h) and 50% protection (2/4, 2.0 h) at a dose of
100 mg/kg. Compound PCH 10 showed 50% protection (2/4, 0.5 h)
at a dose of 100 mg/kg.
Physical data of N0-(substituted) pyridine-4-carbohydrazides PCH 1e10.
C
N
NHN C
O Ar
O
H
C NHN
N
O
NH
O
PCH 10
PCH 1-9
Compounds PCH 3 and PCH 6 were subjected to quantification
studies in MES, scMET, neurotoxicity and 6 Hz test. The results are
shown in Table 5. Compound PCH 6 showed an ED50 (95% confi-
dence interval) of 128.3 mg/kg (95e155.9) at a time of peak effect
(TPE) of 1h in quantitative MES test. It showed an ED50 (95%
confidence interval) of >250 mg/kg at a time of peak effect (TPE) of
1 h in quantitative scMET test. It showed a TD50 (95% confidence
interval) of 343.6 mg/kg (258.6e474.5) at a time of peak effect (TPE)
of 8 h in quantitative toxicity test. Compound PCH 6 showed an
ED50 (95% confidence interval) of 53.3 mg/kg (28.4e81.4) at a time
of peak effect (TPE) of 0.25 h in quantitative 6 Hz evaluation.
Compound PCH 3 was subjected to quantitative 6 Hz evaluation.
Compound PCH 3 showed an ED50 of >200 mg/kg at a time of peak
effect (TPE) of 1.0 h.
Compounds PCH 6 and PCH 10 were subjected to Pilocarpine
Induced Status Prevention (PISP) Model. The results are shown in
Tables 6 and 7. In acute toxicity test, compound PCH 10 did not
show any toxicity up to 600 mg/kg, but compound PCH 6 showed
toxicity at a dose of 300 mg/kg. Compounds PCH 6 and PCH 10 did
not exhibit any protection against Pilocarpine Induced Status
Prevention model. Compound PCH 3 was evaluated in the primary
screen experiment of In-vitro Hippocampal Slice Culture Neuro-
protection Assay (NP) and result is shown in Table 8. No significant
protection was observed against either KA- or NMDA-induced
cytotoxicity.
Compounds Ar
Phenyl
Yield (%) Melting
point (ꢁC) (Mol. Wt.)
108 19H15N3O2
Mol. Formula Rf
PCH 1
PCH 2
PCH 3
PCH 4
PCH 5
PCH 6
PCH 7
PCH 8
PCH 9
PCH 10
76
74
77
80
79
82
76
81
C
0.52
0.44
0.54
(317.34)
C19H14N4O4
(362.34)
C20H17N3O2
(331.37)
4-NO2-Phenyl
4-CH3-Phenyl
4-Cl-Phenyl
4-Br-Phenyl
4- F-Phenyl
224
152
176
185
156
222
205
118
292
C
19H14ClN3O2 0.43
(351.79)
19H14BrN3O2 0.41
(396.24)
19H14FN3O2 0.45
(335.33)
20H16ClN3O2 0.48
(365.81)
23H17N3O2
(367.40)
20H15N3O4
(361.35)
14H10N4O2
(266.25)
C
C
3-Methyl-4-chloro
phenyl
Naphthalene-2-yl
C
C
0.40
0.47
0.50
1,3-benzodioxol-5-yl 74
84
C
e
C
results are shown in Table 2. Compounds PCH 3 and PCH 6 were
active in MES test. The compound PCH 3 showed 100% protection
(1/1, 4.0 h) at a dose of 300 mg/kg where as compound PCH 6
showed 100% protection (1/1, 4.0 h) and 67% protection (2/3, 2.0 h)
at a dose of 100 mg/kg. None of the compounds showed protection
in scMET test, a test used to identify compounds that elevate
seizure threshold. Minor toxicity shown as motor impairment was
observed in PCH 4 (1/2, 4 h) at a dose of 300 mg/kg. None of the
other compounds showed neurotoxicity in the highest adminis-
tered dose (300 mg/kg). Compound PCH 6 was examined for its oral
activity in rat MES screen and showed 25% protection (1/4, 2.0 h) at
a dose of 30 mg/kg orally in rats (115e150 g). The results are shown
in Table 3.
5.2. Computational study
5.2.1. Distance mapping
The present work involves the correlation of the structural
requirement of well known and structurally different anticonvul-
sant compounds with the titled compounds. The two-dimensional
(2D) modeling on anticonvulsants has identified that at least one
aryl unit, one or two electron donor atoms, and/or an NH group in
a special spatial arrangement is recommended for anticonvulsant
activity. In the present study, the 10 well known and structurally
Table 2
Anticonvulsant activity and neurotoxicity of N0-(substituted) pyridine-4-carbohydrazides PCH 1e10.
Compound
Intraperitoneal injection in micea
MES screen (h)
scMET screen (h)
0.5
Neurotoxicity screen (h)
0.5
2.0
4.0
4.0
0.5
4.0
PCH 1
PCH 2
PCH 3
PCH 4
PCH 5
PCH 6
PCH 7
PCH 8
e
e
e
e
e
e
e
e
e
e
30
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
300b
e
e
e
e
e
e
e
300c
e
e
e
e
e
100b
e
300b
e
e
e
e
e
e
e
e
e
e
e
e
PCH 9
e
e
e
e
e
PCH 10
Phenytoin
Sodium valproate
e
e
e
e
e
30
e
30
e
e
100
e
100
e
300
a
Doses of 30, 100 and 300 mg/kg were administered. The figures in the table indicate the minimum dose whereby bioactivity was demonstrated in half or more of the mice.
The dash (e) indicates an absence of activity at maximum dose administered (300 mg/kg).
b
In the MES screen, compound PCH 3 showed protection (1/1, 4 h) at a dose of 300 mg/kg. Compound PCH 6 showed protection (2/3, 2 h) at a dose of 100 mg/kg and
protection (1/1, 4 h) at a dose of 300 mg/kg.
c
Minor toxicity (1/2, 4 h) at a dose of 300 mg/kg was observed with compound PCH 4.

L. Tripathi et al. / European Journal of Medicinal Chemistry 46 (2011) 509e518
513
Table 3
Table 5
Evaluation of compound PCH 6 in the MES test after oral administration (30 mg/kg)
Quantification studies of PCH 3 and PCH 6: ED50 and TD50 value.
to rats.
Compound Test Time (h) ED50 95%
Slope STD Err PI Valuea
Compound
Test
Oral administration to ratsa (h)
(mg/kg) Confidence
Interval
0.25
0.5
1.0
2.0
4.0
PCH 6
MES
scMET 1.0
TOX
6 Hz
6 Hz
1.0
128.3 95e155.9
6.4
e
1.7
e
2.67
e
PCH 6b
MES
TOX
0/4
0/4
0/4
0/4
0/4
0/4
1/4
0/4
0/4
0/4
>250
e
8.0
0.25
1
343.6 258.6e474.5 4.4
1.5
0.8
e
e
a
53.3 28.4e81.4
>200
3
e
6.44
e
Figure indicate the number of rats out of four which were protected.
In the rat p.o.(test 2), compound PCH 6 exhibited activity in one animal out of
b
PCH 3
e
four at 2.0 h.
a
PI Value was determined by TD50/ED50.
different compounds with anticonvulsant activity- albutoin, car-
bamazepine, gabapentin, lamotrigine, mephobarbital, phenytoin,
progabide, ralitoline, remacemide and zonisamide (Fig. 1) with
different mechanisms of action, were selected so as to propose
a generalized pharmacophore model. The pharmacophore group’s
distance estimation was done by molecular mechanics calculation
with the force fields based on both CHARMm force fields and MM3
parametrization. In the present work, energy minimization was
performed on above mentioned ten well known anticonvulsants
and N0-[substituted] pyridine-4-carbohydrazides using Argus Lab
4.0. Distance between the various structural components essential
for activity was determined by ACD/3D viewer. The crucial struc-
tural components that were included in the four-point pharmaco-
phore model (Fig. 2) were the aryl ring center or the lipophilic
group (A), an electron donor atom (D), a hydrogen bond acceptor
(HA), and a hydrogen bond donor (HD). An average distance range
for every point was obtained and compared to the N0-[substituted]
pyridine-4-carbohydrazides. Now it may be interesting to examine
whether the N0-[substituted] pyridine-4-carbohydrazides reflect
the conditions of the derived pharmacophore model. Our analyses
of the distance relationship showed that N0-[substituted] pyridine-
4-carbohydrazides did fulfill the essential demands of the phar-
macophore when compared to the average distance requirement
(Table 9).
bloodebrain barrier (BBB), thus potency has been correlated with
optimum lipophilicity (Log P) near 2. In this study, we attempted to
correlate the anticonvulsant activity of congeners with their
calculated Log P value. The experimental Log P values were deter-
mined using the octanol-phosphate buffer method. The data is
presented in Table 11. As observed some of the experimental values
were in good agreement with the theoretical values. All the titled
compounds showed lipophillic character.
5.2.4. Docking study
In this study, we have used AutoDock 4.0 along with its LGA
algorithm for automated flexible ligand docking of compounds PCH 3
and PCH 6 with six established epilepsy molecular targets namely
GABA (A) alpha-1 receptor, GABA (A) delta receptor, glutamate
receptor, Na/H exchanger, Na channel receptor, T-type calcium
channel receptor and evaluated docking affinity (Kcal/mol) and count
of probable hydrogen bonds. Compound PCH 3 have exhibited good
binding properties with glutamate receptor (Affinity value ꢀ6.1 kcal/
mol and 3 H-bonds), GABA (A) delta (Affinity value ꢀ6.0 kcal/mol and
2 H-bonds) and GABA (A) alpha-1 receptor (Affinity value ꢀ6.3 kcal/
mol and 1 H-bonds). The docking images are given in Fig. 3.
Compound PCH 3 does not exhibit binding properties with Na/H
exchanger, Na channel receptor and T-type calcium channel receptor.
Compound PCH 6 does not exhibit binding properties with receptors
used in the study. The results are shown in Table 12.
5.2.2. Prediction of ADME properties
A computational study for prediction of ADME properties of
titled compounds was performed. Topological polar surface area
(TPSA), i.e., surface belonging to polar atoms, is a descriptor that
was shown to correlate well with passive molecular transport
through membranes and, therefore, allows prediction of transport
properties of drugs in the intestines and bloodebrain barrier
crossing [21]. The percentage of absorption (%ABS) was calculated
using TPSA. From all these parameters, it can be observed that all
titled compounds exhibited a great %ABS ranging from 71.3 to 87%
(Table 10). None of the compounds violated Lipinski’s parameters,
making them potentially promising agents for epilepsy therapy.
6. Conclusion
A series of N0-[substituted] pyridine-4-carbohydrazides were
designed, synthesized, and their anticonvulsant activity and
neurotoxicity were evaluated after intraperitoneal administration
in three seizure models, which include the MES, scMET and 6 Hz
model. A computational study was also carried out, including
calculation of pharmacophore pattern, prediction of pharmacoki-
netic properties and docking studies. The compound PCH 6 dis-
played significant protection and emerged as a lead in this series.
Further, compound PCH 3 came out as a potential candidate for
further investigation. Furthermore, none of the compounds
violated Lipinski’s parameters, making them potentially promising
agent for epilepsy therapy. Docking study results shows that the
5.2.3. Log P determination
Titled compounds showed dependence of biological activity on
lipophillic character in a congeneric series. In particular, for drugs
acting on central nervous system to be potent, they have to cross
Table 4
Table 6
Results of anticonvulsant activity of some N0-(substituted) pyridine-4-carbohy-
Results of Pilocarpine Induced Status Prevention (PISP) Model (Test 71, Acute
drazides by 6 Hz model.
Toxicity Test) of PCH 6 and PCH 10.
Compound
Dose
Time (h) to peak effect (N/F)*
Test
Dose (mg/kg)
Compound
Time (h) (N/F)*
(mg/kg)
0.25
0.5
1.0
2.0
4.0
0.25
0.5
1.0
2.0
4.0
PCH 3
PCH 5
PCH 6
PCH 7
PCH 10
100
100
100
100
100
1/4
0/4
3/4
1/4
1/4
1/4
0/4
4/4
0/4
2/4
3/4
0/4
2/4
0/4
1/4
2/4
1/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
0/4
TOX
TOX
TOX
100
300
600
PCH 6
PCH 10
PCH 6
PCH 10
PCH 10
0/2
0/2
2/2
0/2
0/2
0/2
0/2
2/2
0/2
0/2
0/2
0/2
2/2
0/2
0/2
0/2
0/2
2/2
0/2
0/2
0/2
0/2
1/2
0/2
0/2
*N/F ¼ number of animals active or toxic over the number tested.
*N/F ¼ number of animals toxic over the number tested.

514
L. Tripathi et al. / European Journal of Medicinal Chemistry 46 (2011) 509e518
Table 7
A- Hydrophobic Unit
D- Electron Donor Group
Results of Pilocarpine Induced Status Prevention (PISP) Model (Test 71, Response
HA- Hydrogen Bond Acceptor Unit
HD- Hydrogen Bond Donor Unit
data) of PCH 6 and PCH 10.
D
Compound
Dose
Time
(h)a
N/F
Deaths
Avg.Weight Change
(mg/kg)
(g) ꢂ S.E.Mb
4.30
(3.01-5.38)
Protected
rats
Non- protected
rats
4.86
(2.43-6.79)
C
C
C
C
4.37
(2.52-6.72)
PCH 6
PCH 10
200
600
0.0
0.0
0/7
0/8
1
5
e
e
24.2 ꢂ 1.3
20.0 ꢂ 0.0
A
C
C
a
Post first Stage III seizure.
Weight change 24 h Post first Stage III seizure.
b
6.05
(3.78-9.51)
5.86
(2.72-9.23)
compounds exhibited good binding properties with glutamate,
GABA (A) delta and GABA (A) alpha-1 receptor. The docking study
data strongly support the assumption that these receptors may be
involved in observed anticonvulsant activity of N0-[substituted]
pyridine-4-carbohydrazides. However, further studies need to be
carried out to ascertain the precise mechanism of action of anti-
convulsant activity of these molecules.
HA
2.54
(1.78-3.87)
HD
Fig. 2. Four-point 3D pharmacophore model for anticonvulsants derived by using
MM3 and CHARMm parametrization (Argus Lab 4.0 and ACD/3D viewer).
7. Experimental protocols
was washed with ethanol and recrystallized from 90% ethanol. The
physical, elemental analysis and spectral data of the titled
compounds PCH 1e10 are given below.
7.1. Chemistry
All the chemicals and solvents, purchased from Merck (India),
Spectrochem (India), Himedia (India) and S. d. Fine were used
without further purification. The progress of reaction was moni-
tored by thin layer chromatography, performed on a silica gel 60
F254 coated aluminium sheet. The melting points were determined
by using Thomas- Hoover melting point apparatus and are uncor-
rected. The FT-IR spectra were recorded on PerkineElmer Spectrum
BX-II Spectrophotometer. The 1H NMR spectra were recorded on
Bruker 300 MHz High Resolution NMR spectrometer using TMS as
7.1.2.1. N0-(4-phenoxybenzylidene)pyridine-4-carbohydrazide (PCH
1). IR (KBr, cmL1) v: 3250, 3081 (NHstr associated), 1657 (C¼Ostr),
1597 (CH]Nstr), 1240 (eOe). 1H NMR (CDCl3, 300 MHz)
d in ppm:
6.943 and 8.712 (d, 4H, pyridine protons), 7.10e7.87 (m, 9H, Ar-H),
8.353 (s, 1H, CH]N), 10.13 (s, 1H, NH, D2O exchangeable). MS (m/z,
%): 318.17 (Mþþ1, 94.16). Anal. Calcd.: C, 71.91; H, 4.76; N, 13.24.
Found: C, 71.87; H, 4.73; N, 13.23.
an internal standard. Chemical shifts were reported in ppm (d) and
7.1.2.2. N0-[4-(4-nitrophenoxy)benzylidene]pyridine-4-carbohydrazide
(PCH 2). IR (KBr, cmL1) v: 3256, 3085 (NHstr associated), 1657
(C]Ostr), 1603 (CH]Nstr), 1525 (N]O), 1241 (eOe). 1H NMR
signals were described as singlet (s), doublet (d), triplet (t) and
multiplet (m). All exchangeable protons were confirmed by addi-
tion of D2O. The mass spectra were recorded on a Waters Micro-
mass ZQ 2000 mass spectrometer. Elemental analysis (C, H, N) was
undertaken with PerkineElmer Model 240C analyzer.
(CDCl3, 300 MHz)
d in ppm: 6.943 and 8.721 (d, 4H, pyridine
protons), 7.13e7.87 (m, 8H, Ar-H), 8.354 (s, 1H, CH]N), 10.17 (s, 1H,
NH, D2O exchangeable). MS (m/z, %): 363.13 (Mþþ1, 89.17). Anal.
Calcd: C, 62.98; H, 3.89; N, 15.46. Found: C, 62.92; H, 3.86; N, 15.44.
7.1.1. Synthesis of 4-substituted benzaldehyde (3aei)
A mixture of substituted phenol 1aei (37.4 mmol), 4-fluoro-
benzaldehyde 2 (37.4 mmol) and potassium carbonate (38.8 mmol)
in N,N-dimethylformamide (30 ml) was refluxed for 16e18 h under
nitrogen. After cooling, the product was extracted from the reaction
mixture and purified by chromatography.
7.1.2.3. N0-[4-(4-methylphenoxy)benzylidene]pyridine-4-carbohydrazide
(PCH 3). IR (KBr, cmL1) v: 3253, 3083 (NHstr associated), 1655
(C]Ostr), 1599 (CH]Nstr), 1243 (eOe). 1H NMR (CDCl3, 300 MHz)
d
in ppm: 2.348 (s, 3H, CH3), 6.941 and 8.717 (d, 4H, pyridine
protons), 7.11e7.89 (m, 8H, Ar-H), 8.357 (s, 1H, CH]N), 10.20 (s, 1H,
NH, D2O exchangeable). MS (m/z, %): 332.26 (Mþþ1, 100.00). Anal.
Calcd.: C, 72.49; H, 5.17; N, 12.68. Found: C, 72.47; H, 5.17; N, 12.61.
7.1.2. Synthesis of N0-(substituted) pyridine-4-carbohydrazide
(PCH 1e10)
Equimolar quantities (0.01 mol) of 4-substituted benzaldehydes
3aei/isatin 3j and pyridine-4-carbohydrazide 4 were dissolved in
warm ethanol containing 0.5 ml of glacial acetic acid. The reaction
mixture was refluxed for 4e6 h and set aside. The resultant solid
7.1.2.4. N0-[4-(4-chlorophenoxy)benzylidene]pyridine-4-carbohydrazide
(PCH 4). IR (KBr, cmL1) v: 3257, 3081 (NHstr associated), 1653
(C]Ostr), 1601 (CH]Nstr), 1241 (eOe). 1H NMR (CDCl3, 300 MHz)
d
in ppm: 6.938 and 8.721 (d, 4H, pyridine protons), 7.13e7.91 (m,
8H, Ar-H), 8.352 (s, 1H, CH]N), 9.891 (s, 1H, NH, D2O exchange-
able). MS (m/z, %): 352.13 (Mþþ1 for 35Cl,100.00), 354.11 (Mþþ1 for
37Cl, 34.3). Anal. Calcd.: C, 64.87; H, 4.01; N, 11.94. Found: C, 64.81;
H, 4.03; N, 11.93.
Table 8
Results of In-vitro Hippocampal Slice Culture Neuroprotection Assay (Test 76) of
PCH 3.
Compound
Excitotoxin
Insult
Duration
(h)
Primary Screen
Results
7.1.2.5. N0-[4-(4-bromophenoxy)benzylidene]pyridine-4-carbohydrazide
(PCH 5). IR (KBr, cmL1) v: 3258, 3086 (NHstr associated), 1662
(C]Ostr), 1609 (CH]Nstr), 1244 (eOe). 1H NMR (CDCl3, 300 MHz)
PCH 3
N-methyl-D-aspartate
(NMDA)
Kainic acid (KA)
4
No neuroprotection
observed
No neuroprotection
observed
d
in ppm: 6.945 and 8.719 (d, 4H, pyridine protons), 7.13e7.81 (m,
4
8H, Ar-H), 8.355 (s, 1H, CH]N), 9.921 (s, 1H, NH, D2O exchange-
able). MS (m/z, %): 396.12 (Mþþ1, 100.00), 398.13 (Mþþ1, 97.3).

L. Tripathi et al. / European Journal of Medicinal Chemistry 46 (2011) 509e518
515
Table 9
Distance range between the essential structural elements A, D and HA e HD.a
Compounds
A-HA
A-HD
A-D
HA-HD
HD-D
HA-D
Albutoin
5.37
4.28
4.26
5.30
3.78
6.20
9.51
8.30
7.51
6.02
6.05
(3.78e9.51)
4.80
2.72
4.28
4.93
7.42
5.50
4.01
9.23
5.55
8.75
6.22
5.86
(2.72e9.23)
4.19
4.51
4.25
3.83
4.54
4.81
4.35
3.79
4.56
5.38
3.01
4.30
(3.01e5.38)
3.99
2.72
2.33
2.23
2.42
2.34
2.63
2.41
2.75
3.87
1.78
2.54
(1.78e3.87)
1.44
4.03
5.75
3.57
4.94
4.63
3.88
6.72
2.52
3.96
3.71
4.37
(2.52e6.72)
2.39
5.40
5.67
4.50
4.25
5.23
5.17
6.79
4.85
2.43
4.31
4.86
Carbamazepine
Gabapentin
Lamotrigine
Mephobarbital
Phenytoin
Progabide
Ralitoline
Remacemide
Zonisamide
Av distance
(Range)
(2.43e6.79)
3.77
PCH 3
PCH 6
4.79
4.187
4.00
1.43
2.38
3.77
a
Distances calculated for 3D optimized structures using MM3 and CHARMm parametrization (Argus Lab 4.0 and ACD/3D viewer).
Anal. Calcd.: C, 57.59; H, 3.56; N, 10.60. Found: C, 57.56; H, 3.54; N,
NMR (CDCl3, 300 MHz) d in ppm: 5.989 (s, 2H, CH2), 6.943 and
10.57.
8.717 (d, 4H, pyridine protons), 7.14e7.87 (m, 7H, Ar-H), 8.349 (s,
1H, CH]N), 10.02 (s, 1H, NH, D2O exchangeable). MS (m/z, %):
362.15 (Mþþ1, 89.11). Anal. Calcd.: C, 66.48; H, 4.18; N, 11.63.
Found: C, 66.41; H, 4.17; N, 11.60.
7.1.2.6. N0-[4-(4-fluorophenoxy)benzylidene]pyridine-4-carbohydrazide
(PCH 6). IR (KBr, cmL1) v: 3252, 3080 (NHstr associated), 1651
(C]Ostr), 1605 (CH]Nstr), 1255 (-O-). 1H NMR (CDCl3, 300 MHz)
d
in ppm: 6.986 and 8.760 (d, 4H, pyridine protons), 7.016e7.885
7.1.2.10. N0-[(3Z)-2-oxo-1,2-dihydro-3H-indol-3-ylidene]pyridine-4-
carbohydrazide (PCH 10). IR (KBr, cmL1) v: 3258, 3080 (NHstr
associated), 1680 (C]Ostr), 1590 (C]Nstr). 1H NMR (CDCl3,
(m, 8H, Ar-H), 8.359 (s, 1H, CH]N), 9.863 (s, 1H, NH, D2O
exchangeable). MS (m/z, %): 336.17 (Mþþ1, 68.10). Anal. Calcd.: C,
68.05; H, 4.21; N, 12.53. Found: C, 68.01; H, 4.20; N, 12.55.
300 MHz)
d in ppm: 6.940 and 8.711 (d, 4H, pyridine protons),
7.19e7.71 (m, 4H, Ar-H), 10.07 (s, 1H, NH, D2O exchangeable), 12.81
(s, 1H, NH of isatin, D2O exchangeable). MS (m/z, %): 267.13 (Mþþ1,
95.12). Anal. Calcd.: C, 63.15; H, 3.79; N, 21.04. Found: C, 63.11; H,
3.77; N, 21.01.
7.1.2.7. N0-[4-(4-chloro-3-methylphenoxy)benzylidene]pyridine-4-
carbohydrazide (PCH 7. IR (KBr, cmL1) v: 3255, 3081 (NHstr
associated), 1659 (C]Ostr), 1607 (CH]Nstr), 1237 (eOe). 1H NMR
(CDCl3, 300 MHz)
d in ppm: 2.362 (s, 3H, CH3), 6.938 and 8.711 (d,
4H, pyridine protons), 7.13e7.85 (m, 7H, Ar-H), 8.356 (s, 1H, CH]N),
10.09 (s, 1H, NH, D2O exchangeable). MS (m/z, %): 366.15 (Mþþ1 for
35Cl, 100.00), 368.11 (Mþþ1 for 37Cl, 33.7). Anal. Calcd.: C, 65.67; H,
4.41; N, 11.49. Found: C, 65.66; H, 4.38; N, 11.46.
7.2. Pharmacology
The evaluation of anticonvulsant activity and neurotoxicity was
carried out by the Epilepsy Branch, National Institute of Neuro-
logical Disorder and Stroke, National Institute of Health, Bethesda,
USA following the reported procedures.
7.1.2.8. N0-[4-(naphthalen-2-yloxy)benzylidene]pyridine-4-carbohy-
drazide (PCH 8). IR (KBr, cmL1) v: 3247, 3081 (NHstr associated),
Male albino mice (CF-1 strain, 18e25 g) and male albino rats
(Sprague Dawley, 100e150 g) were used as experimental animals.
The synthesized derivatives were suspended in 0.5% methyl cellu-
lose and the test compound is usually manipulated with a mortar
pestle to help preparation of suspension. In the preliminary
screening by MES and scMET tests, each compound was adminis-
tered as an i.p. injection at three dose levels (30, 100 and 300 mg/
kg) and anticonvulsant and neurotoxic effects were assessed at
30 min and 4 h intervals after administration. Selected derivatives
were examined for the oral activity in rat MES screen. Further
compounds were also tested for their activity in 6 Hz model at five
1661 (C]Ostr), 1597 (CH]Nstr), 1238 (eOe), 836, 821 (
b-naphthyl).
1H NMR (CDCl3, 300 MHz)
d
in ppm: 6.939 and 8.707 (d, 4H,
pyridine protons), 7.09e7.89 (m, 11H, Ar-H), 8.359 (s, 1H, CH]N),
10.12 (s, 1H, NH, D2O exchangeable). MS (m/z, %): 368.17 (Mþþ1,
92.38). Anal. Calcd.: C, 75.19; H, 4.66; N, 11.44. Found: C, 75.16; H,
4.65; N, 11.41.
7.1.2.9. N0-{(Z)-[4-(1,3-benzodioxol-5-yloxy)phenyl]methylidene}
pyridine-4-carbohydrazide (PCH 9). IR (KBr, cmL1) v: 3246, 3077
(NHstr associated), 1654 (C]Ostr), 1601 (CH]Nstr), 1239 (eOe). 1H
Table 10
Pharmacokinetic parameters important for good oral bioavailability of compounds PCH 1e10a.
Compound
% ABS
TPSA (A2)
n-ROTB
MW
MV
n-OHNH donors
n-ON acceptors
Lipinski’s violations
Rule
e
e
e
5
6
5
5
5
5
5
5
5
2
<500
331.4
e
<5
1
1
1
1
1
1
1
1
<10
5
8
5
5
5
5
5
5
ꢃ1
0
0
0
0
0
0
0
0
PCH 1
PCH 2
PCH 3
PCH 4
PCH 5
PCH 6
PCH 7
PCH 8
PCH 9
PCH 10
87.0
71.3
87.0
87.0
87.0
87.0
87.0
87.0
80.6
78.9
63.58
302.896
326.23
319.457
316.432
320.782
307.828
332.993
346.888
326.826
226.486
109.412
63.588
63.588
63.588
63.588
63.588
63.588
82.056
87.216
376.372
345.402
365.82
410.271
349.365
379.847
381.435
375.384
266.26
1
2
7
6
0
0
a
%ABS, percentage of absorption; TPSA, topological polar surface area; n-ROTB, number of rotatable bonds; MW, molecular weight; MV, molecular volume; n-OHNH,
number of hydrogen bond donors; n-ON, number of hydrogen bond acceptors.

516
L. Tripathi et al. / European Journal of Medicinal Chemistry 46 (2011) 509e518
Table 11
7.2.4. Minimal clonic seizure (6 Hz) test
Log P value for compounds PCH 1-10.
Minimal clonic seizure (6 Hz) test was used to assess
compound’s efficacy against electrically induced seizures but used
a lower frequency (6 Hz) and longer duration of stimulation (3 s).
Test compounds were pre-administered to mice via i.p. injection. At
varying times, individual mice (four mice per time point) were
challenged with sufficient current delivered through corneal elec-
trodes to elicit a psychomotor seizure in 97% animals (32 mA for
3 s). The untreated mice would display seizure characterized by
a minimal clonic phase followed by stereotyped, automatistic
behaviours, described originally as being similar to the aura of
human patients with partial seizure. Animals not displaying this
behavior are considered to be protected. Most potent derivatives
were tested quantitatively in the 6 Hz study and ED50 reported.
Compounds
Experimental Log P
Theoretical Log P (miLog Pa)
Rule
e
ꢃ5
PCH 1
PCH 2
PCH 3
PCH 4
PCH 5
PCH 6
PCH 7
PCH 8
PCH 9
PCH 10
3.373
3.23
3.477
3.436
3.926
4.155
4.286
3.641
4.532
4.661
3.367
1.045
3.652
3.948
4.029
3.496
4.215
4.521
3.197
1.124
a
miLog P, logarithm of compound partition coefficient between n-octanol and
water calculated as per Molinspiration Online Property Toolkit.
7.2.5. Pilocarpine Induced Status Prevention (PISP) model
Compounds were assessed for pharmacological evaluation of
potential activity against nerve agents using the pilocarpine model
of epilepsy as an introductory screen. The pilocarpine models are
one of the most recognized animal models of status epilepticus
(SE).
A. Acute Toxicity: To determine acute motor impairment usual
starting doses of 100 and 300 mg/kg were administered via the i.p.
route to groups of Sprague Dawley rats over several time points.
The behavior of the animals was closely observed and recorded
over a 4 h period. A minimum number of four (4) rats, two per dose
was employed in the acute screen.
B. Status Prevention: To determine if the test substance can
prevent acute pilocarpine induced status an initial qualitative
efficacy screen was performed. Administration of the candidate
drug was given to male albino Sprague Dawley rats (150e180 g) via
the i.p. route of administration. Then a challenge dose of pilocar-
pine was administered observing for treatment-effects of the
candidate drug. The outcome measures were determined as
“protection” or “no protection”. The seizure severity was deter-
mined using the well established Racine scale.
different time points i.e. 0.25 h, 0.5 h, 1.0 h, 2.0 h and 4.0 h at a dose
of 100 mg/kg administered i.p. Compounds showing significant
protection were evaluated for quantification studies in 6 Hz test and
ED50 reported. Selected derivatives were also evaluated in Pilocar-
pine Induced Status Prevention (PISP) model and In-vitro Hippo-
campal Slice Culture Neuroprotection Assay.
7.2.1. Maximal electroshock (MES) test
For MES test, 60 Hz of alternating current (50 mA in mice,
150 mA in rats) is delivered for 0.2 s by corneal electrodes which
have been primed with an electrolyte solution containing anes-
thetic agent (0.5% tetracaine HCl). An animal is considered pro-
tected from MES-induced seizures upon abolition of hind limb
tonic extensor component of the seizure. One compound des-
cribed in this study was examined for the oral activity in rat MES
screen.
7.2.2. Subcutaneous metrazol seizure threshold (scMET) test
For scMET test animals are pretreated with various doses of the
test compound. At a previously determined TPE of the test
compound the dose of metrazol which will induce convulsion in
97% of animals is injected into a loose fold of skin in the midline of
the neck. The animals are placed in isolation cage to minimize
stress and observed for the next 30 min to see the absence of
seizure. An episode of clonic spasms, approximately 3e5 s of the
fore and/or hind limbs, jaws or vibrissae was taken as the end
point. Animals which do not meet this criterion were considered
protected.
7.2.6. In-vitro hippocampal slice culture neuroprotection assay
(NP): primary screen experiment
The “Primary Screen Experiment” is a qualitative assessment of
the ability of a compound to prevent excitotoxic cell death. Orga-
notypic hippocampal slice cultures are treated with N-methyl-D-
aspartate (NMDA) or kainic acid (KA) to induce neuronal cell death.
Propidium iodide (PI), a membrane-impermeant compound, is
included in all wells of the culture plate. Dying cells have
compromised cell membranes, thus PI may diffuse into the cell,
intercalate with DNA and fluoresce. Thus, the intensity of the PI
fluorescence is proportional to the amount of cell death in the
individual slices. Hippocampal slice cultures are treated with the
excitotoxin alone, or where indicated above, with the excitotoxin
and either one or two investigational compounds at the concen-
trations indicated. If neuroprotection occurs as a consequence of
7.2.3. Neurotoxicity- minimal motor impairment (MMI)
Minimal motor impairment was measured by the rotorod
(neurotoxicity) test. When a mouse is placed on a rod that rotates at
a speed of 6 rpm, the animal can maintain its equilibrium for a long
period of time. The compound was considered toxic if the treated
animal falls off this rotating rod 3 times during 1 min period.
Fig. 3. Docking images (a) PCH 3 with GABA(A) alpha-1, (b) PCH 3 with GABA(A) delta, (c) PCH 3 with Glutamate receptor.

L. Tripathi et al. / European Journal of Medicinal Chemistry 46 (2011) 509e518
517
Table 12
Results of docking study of compounds PCH 3 and PCH 6.a
Ligand
Receptor
Affinity (Kcal/mol)
H-bonds
H- Binding Ligand
H- Binding Receptor
Element
Atom No.
Type
Residue
Element
Atom No.
Type
PCH 3
GABA(A) alpha-1
GABA (A) delta
ꢀ6.3
ꢀ6.0
01
02
N
N
N
N
N
N
e
e
e
e
e
e
e
e
e
23
23
23
23
02
04
e
Acceptor
Acceptor
Acceptor
Acceptor
Donor
Acceptor
e
e
e
e
e
e
e
e
e
Thr
Arg
Arg
Arg
Leu
Leu
e
O
N
N
N
O
N
e
e
e
e
e
e
e
e
e
71
165
164
247
201
198
e
Both
Donor
Donor
Donor
Acceptor
Donor
e
e
e
e
e
e
e
e
e
Glutamate
ꢀ6.1
03
Na/H exchanger
Na channel
T-type calcium
GABA(A) alpha-1
GABA (A) delta
Glutamate
Na/H exchanger
Na channel
T-type calcium
ꢀ5.6
ꢀ0.0
ꢀ0.0
ꢀ5.8
ꢀ5.4
ꢀ6.2
ꢀ5.5
ꢀ0.0
ꢀ0.0
NIL
NIL
NIL
NIL
NIL
NIL
NIL
NIL
NIL
e
e
e
e
e
e
PCH 6
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
a
Affinity and H-bonds calculations were determined by docking studies using AutoDock 4.0 software.
the added compound, slice cultures will have a visibly reduced
fluorescent intensity when compared to the slice cultures that have
been treated with the excitotoxin alone.
channel and T-type calcium channel receptor. These receptors are
among the most important targets in the design and discovery of
successful antiepileptic drugs [27]. In present study, AutoDock 4.0
with its Lamarckian genetic algorithm (LGA) was used for auto-
mated flexible ligand docking of PCH 3 and PCH 6 with above
mentioned receptors and docking affinity (Kcal/mol) and count of
probable H-bonds were evaluated.
7.3. Computational study
7.3.1. Distance mapping
The pharmacophore pattern studies in which distance between
the various groups postulated as essential for anticonvulsant
activity were done on the 3D optimized structures using ACD/3D
viewer version 12.01 and Argus Lab 4.0 Mark A. Thompson Planaria
Software LLC. In conformational analysis of the ten clinically
effective, well known and structurally different anticonvulsant
drugs such as albutoin, carbamazepine, gabapentin, lamotrigine,
mephobarbital, phenytoin, progabide, ralitoline, remacemide,
zonisamide; a molecular model was suggested on the basis of
molecular dynamics distance estimations [22].
Acknowledgements
The authors would like to express their gratitude to IIT, Delhi
and CDRI, Lucknow for providing the spectral and elemental data.
One of the authors (Laxmi Tripathi) is thankful to S. D. College of
Pharmacy and Vocational Studies, Muzaffarnagar, India for
providing research facilities. The authors also appreciate the help
and support by Mr. Om Prakash during docking study.
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