Nicotinic acid hydrazones: A novel anticonvulsant pharmacophore

Article abstract of DOI:10.1007/s00044-010-9396-0

A series of aryl acid hydrazones of substituted aromatic acid hydrazides (D₁ to D₂₀) were synthesised and evaluated for anticonvulsant activity. Aryl acid hydrazones of Nicotinic acid hydrazide (D₈, D₉, and D

Full text of DOI:10.1007/s00044-010-9396-0

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2011) 20:1499–1504
DOI 10.1007/s00044-010-9396-0
ORIGINAL RESEARCH
Nicotinic acid hydrazones: a novel anticonvulsant pharmacophore
•
Reema Sinha U. V. Singh Sara R. L. Khosa
•
•
•
James Stables Jainendra Jain
Received: 15 January 2010 / Accepted: 22 July 2010 / Published online: 3 August 2010
Ó Springer Science+Business Media, LLC 2010
Abstract A series of aryl acid hydrazones of substituted
aromatic acid hydrazides (D1 to D20) were synthesised and
evaluated for anticonvulsant activity. Aryl acid hydrazones
of Nicotinic acid hydrazide (D8, D9, and D10) have dis-
played excellent protection in maximal electroshock
screen. These compounds have also exhibited excellent
binding properties with Lys 329 residue of gamma amino
butyrate amino transferase (GABA-AT) in Lamarckian
genetic algorithm based flexible docking studies. Com-
pound D8, N1-(4-chlorobenzylidene) nicotinohydrazide
was found to be the most potent analog with ED50 value of
16.1 mg/kg and protective index (PI = TD50/ED50) value
of[20, which was much greater than that of the prototype
drug phenytoin (PI = 6.9). It has shown free binding
energy value of -10.20 kcal/mol and inhibition constant
(Ki) value of 33.30 nM for GABA-AT, indicating that aryl
acid hydrazones of nicotinic acid hydrazide could be con-
sidered as a new pharmacophore in the design of novel
anticonvulsant drugs.
Keywords Aryl acid hydrazones Á Anticonvulsant
activity Á Antiepileptic drug design Á Maximal electroshock
test Á scPTZ Á Docking Á GABA-AT
Introduction
Epilepsy is not a disease, but a syndrome of different
cerebral disorders of central nervous system and is char-
acterized by paroxysmal, excessive, and hyper synchronous
discharges of large number of neurons. Epilepsy is a
common neurological condition, affecting 60 million peo-
ple worldwide according to epidemiological studies
(Loscher, 1998). In India, the prevalence rate of epilepsy
varies from 1,710 to 9,780 cases per million populations
(Gupta and Malhotra, 2000). Nearly, 95% of clinically
approved drugs for epilepsy treatment were approved
before 1985, and they can provide satisfactory seizure
control for 60–70% of patients. These drugs, however, also
causes notable adverse side effects such as drowsiness,
ataxia, gastrointestinal disturbance, hepato-toxicity and
megaloblastic anemia (Perucca, 1996; Lin and Kadaba,
1997), and even life threatening conditions (Al-Soud et al.,
2003). These facts make the field of anticonvulsant drug
discovery, a high priority. Structures of clinically estab-
lished drugs concluded that anticonvulsant properties have
been displayed by various hydrazones (=NNH), amides
(CONH2), carbamides (NHCONH), and semicarbazido
(=NNHCONH) groups. Semicarbazones have acquired an
important place as anticonvulsants and can be considered
as a new class of anticonvulsants with oral activity
(Yogeeswari et al., 2004, 2005). Aryl semicarbazones are
believed to interact at a specific binding site called as
hydrogen bonding area and aryl binding site (Dimmock
et al., 1995). Aryl acid hydrazones, similar to
R. Sinha Á J. Jain (&)
RamEesh Institute of Vocational and Technical Education,
3, Knowledge Park I, Greater Noida 201308, Uttar Pradesh,
India
e-mail: jainendrem@yahoo.com
U. V. S. Sara
D J College of Pharmacy, Niwari Road, Modinagar,
Ghaziabad 201202, Uttar Pradesh, India
R. L. Khosa
Department of Pharmacy, Bharat Institute of Technology,
Partapur Bypass, Meerut 250103, Uttar Pradesh, India
J. Stables
Preclinical Pharmacology, National Institute of Neurological
Disorders and Stroke (NINDS), National Institute of Health
(NIH), Bethesda, MD 20892-9020, USA
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Med Chem Res (2011) 20:1499–1504
semicarbazones, contains large hydrophobic group in close
proximity to two electron donor nitrogen atoms, thus ful-
filling the structural requirements of maximal electroshock
(MES) screen (Jones and Woodbury, 1982). Gamma amino
butyrate amino transferase (GABA-AT) is a pyridoxal
phosphate dependent enzyme mainly responsible for deg-
radation of inhibitory neurotransmitter, gamma amino
butyric acid. It is one of the most important targets in the
design and discovery of successful antiepileptic drugs
(Sowa et al., 2005). Automated flexible docking is an
important emerging technology for rational lead discovery
based on the receptor structure which is considered as rigid
(Abagyan and Totrov, 2001). The challenge of docking a
flexible ligand into a rigid receptor has been taken up by a
number of groups; one particularly good outcome is the
Autodock with its Lamarckian genetic algorithm (LGA)
(Morris et al., 1998). In this study, we have used Autodock
4.0 along with its LGA algorithm for automated flexible
ligand docking of 20 aryl acid hydrazones and evaluated
free binding energies and inhibition constant values for Lys
329 residue of GABA-AT (pdb code: 10HV).
scPTZ screen, which is used to identify compounds that
elevate seizure threshold. In neurotoxicity screen, except
for compound D2, all other aryl acid hydrazones were
found non-toxic. In addition to these tests, compound dis-
playing activity in MES screen, were also evaluated in
minimal clonic seizure model where smaller amount of
electric current (6 Hz) was given for longer duration of
time (3 s) (Table 3). In this screen, compounds D8, D9, and
D10 exhibited strong anticonvulsant activity with lower
neurotoxicity. Compounds D8 and D9 were the most potent
analogs (D8, ED50 = 16.1 mg/kg, protective index
(PI) [ 20 and D9, ED50 = 47.2 mg/kg, PI [ 11.0) at
0.25 h interval. Both compounds were found to be more
potent than the prototype drug Phenytoin (PI = 6.9).
Compound D10 also exhibited strong anticonvulsant
activity with ED50 value of 80.0 mg/kg and PI [ 6.25 in
6 Hz studies. In addition, compounds were also evaluated
by oral route for anticonvulsant effect. In this screen,
compound D8 has shown strong activity with ED50 of
31.4 mg/kg and PI [ 10. Thus, from series of compounds
synthesised, aryl acid hydrazones of Isonicotinic acid
hydrazide (compounds D2 and D4), Nicotinic and hydra-
zide (compounds D8, D9, and D10) and Toluic acid
hydrazide (compound D17) exhibited protection in the MES
screen while aryl acid hydrazones of Benzoic acid hydra-
zide were found to be totally inactive. Compounds D8, D9,
and D10 from the series of Nicotinic acid hydrazide were
found to be the most potent analogs. All active compounds
were found to possess halogen substituent either at meta or
para position of benzene ring further proving that halogens
have prominent contribution in anticonvulsant effect. Acid
hydrazones of Nicotinic acid hydrazide (compounds D8,
D9, and D10) exhibited strong anticonvulsant effect as
compared to the corresponding analogs of Isonicotinic acid
hydrazide (compounds D2, D4, and D6) in 6 Hz screen,
indicating that position of nitrogen in the ring must be
playing important role in controlling seizures. Compounds
D8, D9, and D10 were also studied for their binding prop-
erties with GABA-AT enzyme, since it is the most
important targets in the design and discovery of successful
antiepileptic drugs. These studies were carried out at
Lys329 residue of GABA-AT using LGA-based flexible
docking (Autodock 4.0) method. As shown in Table 6,
these molecules exhibited high selectivity for GABA-AT
and their interaction appears to be in close proximity.
Compound D8 displayed excellent free binding energy
value of -10.20 kcal/mol and inhibition constant (Ki)
value of 33.30 nm, indicating that it would be preventing
seizure through inhibition of GABA-AT enzyme. These
studies have also indicated that halogen (para) substituted
aryl acid hydrazones of nicotinic acid hydrazide could be
considered as a new pharmacophore in the design of novel
anticonvulsant drugs.
The principal aim of synthesizing and evaluating aryl
acid hydrazones was to investigate the anticonvulsant
activity in comparison to semicarbazones and to study their
binding properties with GABA-AT.
Results and discussion
Synthesis
Aryl acid hydrazones (D1 to D20) were synthesised by
condensing aromatic acid hydrazides with substituted aro-
matic aldehydes in absolute alcohol. Structures of syn-
1
thesised compound were confirmed by FTIR and H NMR
spectral data.
Pharmacology
The new derivatives (D1 to D20) were injected intraperi-
toneally into mice and evaluated in the MES, subcutaneous
pentylene tetrazole (scPTZ), and neurotoxicity screens
using doses of 30, 100, and 300 mg/kg. Observations were
carried out at two different time intervals (0.5 and 4.0 h) at
60 Hz current.
As shown in Table 2, compounds D2, D4, D8, D9, D10,
and D17 exhibited anti-MES activity, which indicate that
these compounds had the ability to prevent the spread of
seizure at 100 mg/kg, compounds D2, D8, D9, and D17
showed protection at 0.5 h duration. In addition, com-
pounds D2 and D17 also showed activity at 4 h indicating
that these compound must have longer duration of action.
However, none of the compound was found to be active in
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Med Chem Res (2011) 20:1499–1504
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Experimental
Table 1 Physicochemical properties of compounds D1–D20
Ar1
NH
All chemicals were purchased from Sigma-Aldrich Cor-
poration, USA. Compounds D1–D20 were synthesised
according to the synthetic Scheme 1. Melting points were
determined in open capillary tubes and are reported
uncorrected. Purity of compounds was confirmed by thin
layer chromatography using silica gel G as stationary phase
and mixture of chloroform: ethyl acetate (1:1) as mobile
phase. Infrared (IR) spectra were recorded (in KBr) on a
SHIMADZU Fourier-Transform IR instrument FTIR-
8400S; 1H nuclear magnetic resonance (NMR) spectra
were measured on a BRUKER-300 spectrometer, and
chemical shifts were expressed in ppm relative to tetra-
methylsilane as an internal standard.
N
Ar2
O
Compounds D1-D20
Comp. no. Ar1
Ar2
Mol. formula Raf
D1
Pyridine-4-yl
Pyridine-4-yl
2-nitrophenyl
4-chlorophenyl
2-fluorophenyl
3-chlorophenyl
2-bromophenyl
3-bromophenyl
4-nitrophenyl
4-chlorophenyl
3-bromophenyl
3-chlorophenyl
C13H10N4O3 0.38
C13H10N3OCl 0.26
C13H10N3OF 0.46
C13H10N3OCl 0.25
C13H10N3OBr 0.42
C13H10N3OBr 0.52
C13H10N4O3 0.48
C13H10N3OCl 0.39
C13H10N3OBr 0.43
C13H10N3OCl 0.35
D2
D3
Pyridine-4-yl
Pyridine-4-yl
Pyridine-4-yl
Pyridine-4-yl
Pyridine-4-yl
Pyridine-3-yl
Pyridine-3-yl
Pyridine-3-yl
Pyridine-3-yl
Phenyl
D4
D5
D6
D7
Synthesis of substituted aryl acid hydrazones
D8
derivatives (D1–D20) (Scheme 1)
D9
D10
D11
D12
D13
D14
D15
D16
D17
D18
D19
D20
a
Equimolar quantities of substituted benzaldehydes
(50 mmol) and substituted aromatic acid hydrazides
(50 mmol) were dissolved in absolute ethanol (40 ml) in a
100 ml round-bottomed flask equipped with a reflux con-
denser. The reaction mixture was refluxed for 3.0 h, and
completion of reaction was confirmed by thin layer chro-
matography using silica gel G layers. After being cooled
and concentrated, the product was added to iced water. The
precipitate was collected through filtration and dried in
oven at low temperature. The crude products were re-
crystallized from 95% v/v ethanol to give desired products.
Physicochemical properties of synthesised compounds are
given in Table 1.
4-hydroxy phenyl C13H11N3O2 0.42
3-bromophenyl
4-chlorophenyl
3-chlorophenyl
2-fluorophenyl
C14H11N2OBr 0.49
C14H11N2OCl 0.59
C14H11N2OCl 0.27
C14H11N2OF 0.39
Phenyl
Phenyl
Phenyl
Phenyl
4-hydroxy phenyl C14H12N2O2 0.35
4-methyl phenyl 3-chlorophenyl
4-methyl phenyl 3-bromophenyl
4-methyl phenyl 4-nitrophenyl
4-methyl phenyl 4-chlorophenyl
C15H13N2OCl 0.30
C15H13N2OBr 0.27
C15H13N3O3 0.41
C15H13N2OCl 0.57
Rf calculated in chloroform: ethyl acetate (1:1)
N1-(2-nitrobenzylidene) isonicotinohydrazide (D1)
J = 6.9 Hz, 2H, ArH), 7.74 (S, 2H, pyridin-H), 8.39 (S,
2H, pyridin-H), 8.68 (S, 1H, CH), 12.10 (S, 1H, NH), IR
(KBr) cm-1: 3166 (NH), 1670 (C=O), 1552 (C=N), 690
(C–Cl).
1
Yield: 68%, yellow crystals, m.p: 234–236°C. H NMR
(DMSOd6): 7.66 (m, 1H, ArH), 7.81 (d, J = 6.4 Hz, 2H,
ArH), 8.13 (d, J = 6.9 Hz, 1H, ArH), 8.22 (d, J = 7.1 Hz,
1H, pyridin-H), 8.52 (d, J = 8.1 Hz, 2H, pyridin-H), 8.68
(m, 1H, pyridin-H), 8.78 (S, 1H, CH), 12.31 (S, 1H, NH).
IR (KBr) cm-1: 3207 (NH), 1668 (C=O), 1581 (C=N),
1352 (NO2).
N1-(2-fluorobenzylidene) isonicotinohydrazide (D3)
Yield: 78%, white crystals, m.p: 206–208°C. 1H NMR
(DMSOd6): 7.22 (m, 2H, ArH), 7.27(d, J = 7.2 Hz, 2H,
ArH), 7.47 (d, J = 6.7 Hz, 2H, pyridin-H), 7.89 (d,
J = 7.1 Hz, 2H, pyridin-H), 8.69 (S, 1H, CH), 12.10 (S,
1H, NH), IR (KBr) cm-1: 3193 (NH), 1664 (C=O), 1581
(C=N), 1299 (C–F).
N1-(4-chlorobenzylidene) isonicotinohydrazide (D2)
1
Yield: 82%, white creamy crystals, m.p: 216–218°C. H
NMR (DMSOd6): 7.42 (d, J = 6.7 Hz, 2H, ArH), 7.67 (d,
Scheme 1 Synthesis of
compounds D1–D20
Ar1
NH
Ar1
NH
O
Abs. EtOH
NH2
N
Ar2
+
Ar2
H
O
O
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Med Chem Res (2011) 20:1499–1504
N1-(3-bromobenzylidene) nicotinohydrazide (D9)
Table 2 Anticonvulsant activity of compounds D1–D20
Comp. no. Intraperitoneal injection in micea
Yield: 72%, white crystals, m.p: 128–130°C. 1H NMR
(DMSOd6): 7.42 (m, 2H, ArH), 7.62 (m, 2H, ArH), 7.92 (s,
1H, pyridin-H), 8.24 (d, J = 7.9 Hz, 1H, pyridin-H), 8.40
(S, 1H, pyridin-H), 8.75 (s, 1H, pyridin-H), 9.07 (s, 1H,
CH), 12.14 (S, 1H, NH), IR (KBr) cm-1: 3151 (NH), 1670
(C=O), 1569 (C=N), 574 (C–Br).
MES screen
scPTZ screen
Neurotoxicity test
0.5
4.0
0.5
4.0
0.5
4.0
D1
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
D2
100
–
100
–
100
–
100
–
D3
D4
300
–
–
–
–
N1-(3-chlorobenzylidene) nicotinohydrazide (D10)
D5
–
–
–
Yield: 80%, white crystals, m.p: 130–132°C. 1H NMR
(DMSOd6): 7.45 (s, 2H, ArH), 7.55 (m, 1H, ArH), 7.67 (s,
1H, ArH), 7.76 (s, 1H, pyridine-H), 8.24 (d, J = 6.9 Hz,
1H, pyridin-H), 8.40 (S, 1H, pyridin-H), 8.75 (s, 1H,
pyridin-H), 9.07 (s, 1H, CH), 12.14 (s, 1H, NH). IR (KBr)
cm-1: 3155 (NH), 1670 (C=O), 1560 (C=N), 682 (C–Cl).
D6
–
–
–
–
D7
–
–
–
–
D8
100
100
300
–
–
–
–
D9
–
–
–
D10
D11
D12
D13
D14
D15
D16
D17
D18
D19
D20
Phenytoin
–
–
–
–
–
–
–
–
–
–
N1-(2-fluorobenzylidene) benzhydrazide (D15)
–
–
–
–
–
–
–
–
Yield: 86%, white shiny crystals, m.p: 197–199°C. 1H
NMR (CDCl3): 7.21 (d, J = 6.9 Hz, 1H, ArH), 7.45 (d,
J = 7.1 Hz, 3H, ArH), 7.71 (s, 1H, fluorophenyl-H), 7.86
(s, 3H, fluorophenyl-H), 8.62 (s, 1H, CH), 11.92 (s, 1H,
NH). IR (KBr) cm-1: 3217 (NH), 1643 (C=O), 1556
(C=N), 1290 (C–F).
–
–
–
–
–
–
–
–
–
100
–
–
–
–
–
–
–
–
–
–
–
–
–
–
30
30
100
100
N1-(3-chlorobenzylidene) tolylhydrazide (D17)
The figures in the table indicate the minimum dose whereby bioac-
tivity was demonstrated in half or more of the mice. – indicates
absence of activity at maximum dose administered (300 mg/kg)
Yield: 72%, white shiny crystals, m.p: 175–177°C. 1H
NMR (CDCl3): 2.36 (s, 3H, CH3), 7.31 (d, J = 6.7 Hz, 2H,
tolyl-H), 7.48 (s, 2H, tolyl-H), 7.67 (s, 1H, ArH), 7.83 (m,
3H, ArH), 8.42 (s, 1H, CH), 11.90 (s, 1H, NH). IR (KBr)
cm-1: 3394 (NH), 3091 (CH), 1656 (C=O), 1571 (C=N),
680 (C–Cl).
a
Doses of 30, 100, and 300 mg/kg were administered
Barton et al., 2001). Compounds D1–D20 were dissolved in
polyethylene glycol 400 and evaluated for anticonvulsant
activity with both sexes of C57B/6 mice in the 18–22 g
weight range and Sprague–Dawley rats in the 120–125 g
weight range in both qualitative and quantitative screening
methods. In quantitative screening, groups of eight mice
were given a range of intraperitoneal doses (per oral for
rats) 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 plots of these
data, the respective ED50 and TD50 values, 95% confidence
intervals, slope of the regression line, and the standard
error of the slopes were calculated by means of a computer
program written by the NINDS. Qualitative screening
results are specified in Table 2 whereas quantitative
screening results are given in Tables 3, 4, and 5.
N1-(3-bromobenzylidene) tolylhydrazide (D18)
Yield: 88%, white crystals, m.p: 142–144°C. 1H NMR
(CDCl3): 2.36 (s, 3H, CH3), 7.42 (d, J = 6.8 Hz, 2H, tolyl-
H), 7.60 (s, 2H, tolyl-H), 7.70 (d, J = 7.2 Hz, 2H, ArH),
7.82 (d, J = 7.4 Hz, 2H, ArH), 7.91(s, 1H, ArH), 8.40 (s,
1H, CH), 11.19 (s, 1H, NH). IR (KBr) cm-1: 3390 (NH),
3089 (CH), 1635 (C=O), 1571 (C=N), 514 (C–Br).
Pharmacology
Maximal electroshock seizures, scPTZ, minimal clonic
seizure (6 Hz), and rotarod test were carried out by the
Antiepileptic Drug Development Program, Epilepsy
Branch, National Institute of Neurological Disorders and
Stroke (NINDS) program following previously described
testing procedures (Krall et al., 1978; Porter et al., 1984;
Maximal electroshock seizure
Seizures were elicited in mice with (50 mA) or in rats
(150 mA) 60 Hz alternating current. The current was
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Med Chem Res (2011) 20:1499–1504
1503
after administration of the compounds, activities were
evaluated in the scPTZ test.
Table 3 Anticonvulsant activity of compounds D8, D9, and D10 at
6 Hz
Comp. no.
MES screena
0.25 h
Rotarod test
0.5 h
D8
D9
D10
a
12.5
35.0
–
12.5
35.0
40.0
At 30 min after the administration of test compounds, the
animals were tested on a 1-in. diameter knurled plastic rod
rotating at 6 rpm for 1 min. Neurotoxicity was indicated by
the inability of an animal to maintain equilibrium in each
of three trials.
Figures in the table indicate the minimum active dose (mg/kg) of
the compound
Minimal clonic seizure test
Table 4 Quantitative anticonvulsant data in mice at 6 Hz (test drug
administered i.p)
The minimal clonic seiure test is used to assess a com-
pound’s efficacy against electrically induced seizures but
uses low freqency (6 Hz) and longer duration of stimula-
tion (3 s). Test compounds are pre-administered to mice
via i.p injection. At varying times, individual mice are
challenged with sufficient current delivered through cor-
neal electrodes to elicit a psychomotor seizure in 97% of
animals (32 mA for 3 s). Protection was defined as the
absence of minimal clonic phase with stereotyped, au-
tomatistic behaviors. This behavior is described as being
similar to the aura of human patients with partial seizures.
Comp. no.
EDa50
TDb50
PI (TD50/Ed50)
D8
16.1 (11.5–21.5)c
47.2 (38.9–53.5)
80.0 (54–113.5)
9.5 (8.0–10.4)
[325.0
[520.0
[500
65.5
[20.0
[11.0
[6.25
6.9
D9
D10
Phenytoin
a
Dose measured in mg/kg
b
Minimal neurotoxicity was determined by the rotarod test after the
test compounds were administered
c
95% confidence limit
Table 5 Quantitative anticonvulsant data in rat at 6 Hz (test drug
administered orally)
Docking studies
Comp. no.
EDa50
TDb50
PI (TD50/Ed50)
LYS 329 was included as flexible residue structure, using it
flexible and rigid files prepared. The grid maps were cal-
culated using AutoGrid (Goodford, 1985). In all dockings, a
grid map with 60 9 60 9 60 points, a grid spacing of
D8
D9
D10
a
31.4 (18.3–64.3)c
[320
[10.0
d
–
–
–
–
–
–
˚
0.375 A (roughly a quarter of the length of a carbon–carbon
Dose measured in mg/kg
single bond) were used, and the mps were centered on the
ligand binding site. In an AutoGrid procedure, the protein is
embedded in a 3D grid, and a probe atom is placed at each
grid point. The energy of interaction of this single atom with
the protein is assigned to the grid point. An affinity grid is
calculated for each type of atoms in the substrate, typically
carbon, oxygen, nitrogen, and hydrogens as well as grid of
electrostatic potential using a point charge of ?1 as the
probe (Sharp et al., 1987; Allison et al., 1998). Of the three
different search algorithms offered by AutoDock 4.0, the
LGA; LGA, based on the optimization algorithm (Solis
and Wets, 1981) was used, which utilizes (discredited)
Lamarckian notation that an adaptations of an individual to
its environment can be inherited by its offspring. For all
dockings, 100 independent run with, an initial population of
random individuals with a population size of 150 individu-
als, a maximum number of 2.5 9 106 energy evaluations,
maximum number of generations of 27,000, an elitism value
of 1, a number of active torsion of 9 were used. Auto Dock
4.0 was used to generate both grid and docking parameter
files (i.e., .gpf and .dpf files) (Table 6).
b
Minimal neurotoxicity was determined by the rotarod test after the
test compounds were administered
c
95% confidence limit
d
Not tested
applied via corneal electrodes for 0.2 s. Protection against
the spread of MES-induced seizures was defined as the
abolition of the hind leg tonic maximal extension compo-
nent of the seizure. At 0.5 h and 4.0 h after administration
of the test compounds, activities were evaluated in the
MES test.
Subcutaneous pentylene tetrazole-induced seizures
Seizures were produced in mice and rats with subcutaneous
administration of pentylene tetrazole (85 mg/kg for mice
and 70 mg/kg for rats). The test compounds were admin-
istered intraperitoneally in mice and orally in rats followed
by subcutaneous injection of pentylene tetrazole. Protec-
tion against the spread of scPTZ-induced seizures was
defined as the absence of clonic spasm. At 0.5 h and 4.0 h
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Gupta YK, Malhotra J (2000) Epidemiology of epilepsy in India. Ind J
Physiol Pharmacol 44(1):8–23
Table 6 Binding energy data of compounds D8, D9, and D10
Comp. no.
Estimated free
binding energya
(kcal/mol)
Estimated inhibition
constantb, Ki (nM)
Jones GL, Woodbury DM (1982) Anticonvulsant structure–activity
relationships: historical development and probable causes of
failure. Drug Dev Res 2(4):333–355
Krall RJ, Penry JK, White BG, Kupferberg HJ, Swinyard EA (1978)
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D8
D9
D10
a
-10.20
-9.36
33.30
22.91
19.25
-10.12
Free binding energy calculations were determined by docking
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b
Inhibition constant values were calculated for Lys 329 residue of
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