Docking, synthesis, and pharmacological evaluation of isoindoline derivatives as anticonvulsant agents

Article abstract of DOI:10.1007/s00044-012-0256-y

Eleven analogs of N-arylisoindoline pharmacophore were synthesized and evaluated for their anticonvulsant activities. The in vivo screening data acquired indicate that all the analogs have the ability to protect against pentylenetetrazole-induced seizure. Compounds 2, 6, and 11 elevated clonic seizure thresholds at 30 min which were more active than reference drug phenytoin, and compounds 2, 7, and 11 showed marked anticonvulsant activity on tonic seizure. The most potent compounds were 2 and 11 which had comparative activity to the phenytoin. Using a model of the open pore of the Na channel, we have docked all compounds. Docking studies have revealed that these compounds interacted mainly with residues II-S6 of NaV1.2 by making hydrogen bonds and have additional hydrophobic interactions with other domains in the channel's inner pore.

Full text of DOI:10.1007/s00044-012-0256-y

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-012-0256-y
ORIGINAL RESEARCH
Docking, synthesis, and pharmacological evaluation of isoindoline
derivatives as anticonvulsant agents
•
Asghar Davood Mohsen Amini Leila Azimidoost
•
•
•
Somaieh Rahmatpour Ali Nikbakht Maryam Iman
•
•
•
Hamed Shafaroodi Abdollah Ansari
Received: 15 July 2012 / Accepted: 21 September 2012
Ó Springer Science+Business Media New York 2012
Abstract Eleven analogs of N-arylisoindoline pharma-
cophore were synthesized and evaluated for their anticon-
vulsant activities. The in vivo screening data acquired
indicate that all the analogs have the ability to protect
against pentylenetetrazole-induced seizure. Compounds 2,
6, and 11 elevated clonic seizure thresholds at 30 min
which were more active than reference drug phenytoin, and
compounds 2, 7, and 11 showed marked anticonvulsant
activity on tonic seizure. The most potent compounds were
2 and 11 which had comparative activity to the phenytoin.
Using a model of the open pore of the Na channel, we have
docked all compounds. Docking studies have revealed that
these compounds interacted mainly with residues II-S6 of
NaV1.2 by making hydrogen bonds and have additional
hydrophobic interactions with other domains in the chan-
nel’s inner pore.
Introduction
Epilepsy is a brain disorder involving repeated, spontaneous
seizures of any type. Seizures are the physical findings or
changes in behavior that occur after an episode of abnormal
electrical activity in the brain (Chang and Lowenstein,
2003). Epilepsy affecting 0.5–1 % of the population world-
wide, and every year new cases are added to this figure
(Loscher, 1998; Leppik, 2008; Chen et al., 2007). Antiepi-
leptic drugs (AEDs) are used to reduce or prevent the
occurrence of epileptic seizures, but up to 30 % of patients
are resistant to the available medical therapies (Kubota and
Sakakihora, 2000; French, 1999) and treatment of epilepsy
still remains inadequate and patients suffer from a number of
unfavorable side effects. Some types of seizures are still not
adequately treated with AEDs (Ilangovan et al., 2010;
Malawska, 2005); phenytoin, carbamazepine, oxcarbaze-
pine, and lamotrigine are effective in the control of partial
and generalized tonic–clonic seizures and are ineffective in
the treatment of generalized absence seizures (Rogawski,
2002). Therefore, in response to these limitations, the search
for new anticonvulsant drugs continuesto be an active area of
investigation in medicinal chemistry.
Keywords Anticonvulsant ꢀ Docking ꢀ Isoindoline ꢀ
Na channel ꢀ Seizure
A. Davood (&) ꢀ L. Azimidoost ꢀ S. Rahmatpour
Department of Medicinal Chemistry, Pharmaceutical Sciences
Branch, Islamic Azad University, No 99, Yakhchal ave. Shariatie
Street, 19419 Tehran, Iran
Studies with mixtures of phenytoin, carbamazepine, and
lamotrigine have revealed that these drugs bind to a com-
mon recognition site on sodium channels (Kuo, 1998).
Although these three compounds are structurally dissimi-
lar, they do contain a common motif of two phenyl groups
separated by one to two C–C or C–N single bonds (1.5–3 A)
(Fig. 1). These two phenyl groups probably are critical ele-
ments in binding (Rogawski, 2002). The proposed binding
site is domain IV-S6 in the channel’s inner pore (Lipkind and
Fozzard, 2010, 2005). Docking studies of these drugs
revealed that they show a common pharmacophore, includ-
ing an aromatic ring that has an aromatic–aromatic
e-mail: adavood@iaups.ac.ir; adavood2001@yahoo.com
M. Amini
Department of Medicinal Chemistry, Faculty of Pharmacy,
Tehran University of Medical Sciences, Tehran, Iran
A. Nikbakht ꢀ H. Shafaroodi ꢀ A. Ansari
Department of Pharmacology, Pharmaceutical Sciences Branch,
Islamic Azad University, Tehran, Iran
M. Iman
Chemical Injuries Research Center, Baqiyatallah University of
Medical Sciences, Tehran, Iran
123

Med Chem Res
Fig. 1 Structure of antiepileptic
drugs phenytoin,
carbamazepine, and lamotrigine
interaction with Tyr-1771 of NaV1.2 and a polar amide or
imides that interacts with the aromatic ring of Phe-1764 by
a low energy amino-aromatic hydrogen bond. The second
aromatic ring is almost at the right angle to the pharma-
cophore and fills the pore lumen, probably interacting with
the other S6 segments and physically occluding the inner
pore to block the Na permeation. The hydrophobic inter-
actions with this second aromatic ring maybe an important
contribution to the binding abilities of these anticonvul-
sants (Lipkind and Fozzard, 2010, 2005).
Recently, N-phenylisoindoline derivatives were designed
by molecular hybridization approach based on ameltolide
and thalidomide (Fig. 2) as they possess a similar degree of
anticonvulsant potency due to their phenytoin-like profile
(Vamecq et al., 2000, 1998; Davood et al., 2012). The ability
of isoindolines to interact with the neuronal voltage-
dependent sodium channels was studied in the batrachotoxin
affinity assay (Vamecq et al., 2000). The presence of
hydrophobic interactions of second aromatic ring (Chen
et al., 2007) and a polar amide in the middle mainly con-
tributes to the binding abilities of anticonvulsants and known
properties of isoindoline derivatives (Vamecq et al., 2000,
1998; Davood et al., 2012). Therefore, we explored this idea
further based on SAR studies of N-arylisoindoline and their
drug–receptor interaction profiles (Davood et al., 2012).
Ultimately, the new series of N-arylisoindoline derivatives
were docked and synthesized to investigate the pharmaco-
logical activities.
Fig. 2 Rational design of isoindoline pharmacophore by molecular
hybridization approach
the respective aromatic amine (homocycle or heterocycle) with
phthalic anhydride in acetic acid at reflux temperature (Vamecq
et al., 2000; Davood et al., 2012) (Scheme 1). Compound 10
was reduced to compound 11 using Pd/C and cyclohexene in
2-propanol at reflux temperature.
Reagents and solvents were obtained from Merck
(Darmstadt, Germany). Pentylenetetrazole (PTZ) was pur-
chased from Sigma (UK).
Materials and methods
Spectroscopy and analytical procedures
Chemistry
Melting points were determined using a Thomas-Hoover
1
capillary apparatus and were uncorrected. HNMR spectra
A group of N-aryl derivatives of the isoindoline (1–11), pos-
sessing a variety of substituent at the 20-, 30-, 40-, and 50-posi-
tions of the isoindole ring, were synthesized by condensation of
wererecordedonaBrukerFT-500spectrometerandTMSwas
used as an internal standard. Infrared spectra were acquired on
a Nicolet 550-FT spectrometer. Elemental analysis was
123

Med Chem Res
Scheme 1 Reagents and
conditions: (a) acetic acid
glacial, reflux (b) 2-propanol,
cyclohexene, Pd/C, reflux
carried out using a Perkin-Elmer model 240-C apparatus. The
results of elemental analysis (C, H, and N) were within 0.4 %
of the calculated amounts. Molecular modeling studies were
carried out by HYPERCHEM and Autodock 4.2.3.
3098 (CH-aromatic), 1778, 1726 (CO), 1521, 1388 (NO2);
1H NMR (CDCl3): d 8.13 (d, J = 8.43 Hz, 1H, H3-phenyl),
7.57–7.91 ppm (m, 7H, aromatic); Mass m/z (rel.int): 268
(M?, 8), 220 (100), 164 (21), 103 (21), 75 (43); Anal.
Calcd. for C14H8N2O4: C, 62.69; H, 3.01; N, 10.44. Found:
C, 62.60; H, 3.02; N, 10.41.
General procedure for the preparation isoindoline
derivatives (1–11)
2-(3-Nitrophenyl) isoindoline-1,3-dione (2)
A solution of phthalic anhydride (0.5 g, 3.73 mmol) and
arylamine (3.73 mmol) in glacial acetic acid (5 mL) was
stirred and heated under reflux. The product of this reaction
was precipitated by addition of water, filtered, dried, and
recrystallized to give desired compounds.
By means of the general procedure, 3-nitroaniline provided
the title compound after 20 h of reflux: White crystals,
yield 88.5 %; mp 174–176 °C (ethanol). IR (KBr): m cm-1
,
3093 (CH-aromatic), 1721, 1735 (CO), 1526, 1378 (NO2);
1H NMR (CDCl3): d 8.79 (d, J = 2.46 Hz, 1H, H2-phenyl),
8.62 (dd, J = 8.15, 2.47 Hz, 1H, H4-phenyl), 7.75–8.04
(m, 5H, aromatic), 7.43 ppm (dd, J = 8.16, 4.98 Hz, 1H,
H5-phenyl); Mass m/z (rel.int): 268 (M?, 6), 222 (50), 179
(44), 153 (7), 103 (35), 75 (100), Anal. Calcd. for
C14H8N2O4: C, 62.69; H, 3.01; N, 10.44. Found: C, 62.74;
H, 3.02; N, 10.46.
2-(2-Nitrophenyl) isoindoline-1,3-dione (1)
By means of the general procedure, 2-nitroaniline provided
the title compound after 19 h of reflux: yellow crystals,
yield 56 %; mp 204–207.5 °C (ethanol). IR (KBr): m cm-1
,
123

Med Chem Res
2-(4-Nitrophenyl) isoindoline-1,3-dione (3)
N-(4-(1,3-Dioxoisoindolin-2-yl) phenyl) acetamide (7)
Preparation of this compound has been reported already
(Vamecq et al., 2000). By means of the general procedure,
3-nitroaniline provided the title compound after 10 h of
reflux: yellow crystals, yield 81.5 %; mp 262–264 °C
(ethanol). IR (KBr): m cm-1, 3119 (CH-aromatic), 1780,
1731 (CO), 1521, 1347 (NO2); 1H NMR (CDCl3): d 8.35(d,
J = 9.18 Hz, 2H, H3,5-phenyl), 7.71–7.94(m, 6H, aro-
matic); Mass m/z (rel.int): 268 (M?, 43), 237 (21), 165
(14), 103 (36), 74 (100), Anal. Calcd. for C14H8N2O4: C,
62.69; H, 3.01; N, 10.44. Found: C, 62.57; H, 3.00; N,
10.42.
By means of the general procedure, N-(4-aminophenyl)
acetamide provided the title compound after 20 h of reflux:
violet crystals, yield 85 %; mp 228–231 °C (methanol). IR
(KBr): m cm-1, 3318 (NH), 3020 (CH-aromatic), 2919 (CH-
aliphatic), 1787, 1710, 1675 (CO); 1HNMR (DMSO-d6): d
9.87(br, 1H, NH), 7.79–7.89(m, 4H, aromatic), 7.70(d,
J = 8.78 Hz, 2H, H3,5-phenyl), 7.28 (d, J = 8.9 Hz, 2H,
H
2,6-phenyl), 2.12 ppm (s, 3H, CH3); Mass m/z (rel.int): 280
(M?, 22), 238 (29), 236 (43), 177 (14), 130 (6), 103 (50), 75
(100); Anal. Calcd. for C16H12N2O3: C, 68.56; H, 4.32; N,
9.99. Found: C, 68.49; H, 4.33; N, 9.97.
2-(1, 3-Dioxoisoindolin-2-yl) benzoic acid (4)
4-(1,3-Dioxoisoindolin-2-yl) benzene sulfonamide (8)
By means of the general procedure, 2-aminobenzoic acid
provided the title compound after 8 h of reflux: White
crystals, yield 61 %; mp 217–221 °C (chloroform). IR
(KBr): m cm-1, 3200 (OH), 3083 (CH-aromatic), 1721,
By means of the general procedure, 4-aminobenzenesulf-
onamide provided the title compound after 55 h of reflux:
yellow crystals, yield 89 %; mp 185–187 °C (methanol).
IR (KBr): m cm-1, 3365, 3257 (NH2), 1721, 1680 (CO),
1
1698 (CO); H NMR (DMSO-d6): d 8.16 (dd, J = 6.60,
1
1301, 1157(SO2); H NMR (DMSO-d6): d 7.96–8.09 (m,
2.30 Hz, 1H, H3-phenyl)), 7.41–7.95 ppm (m, 7H, aro-
matic); Mass m/z (rel.int): 268 (M? ?1, 18), 266(M?- 1,
100), 221 (100), 195 (50), 177 (100), 102 (48), 139 (28),
104 (100), 74 (100), 49 (100); Anal. Calcd. for C15H9NO4:
C, 67.42; H, 3.39; N, 5.24. Found: C, 67.51; H, 3.40; N,
5.23.
6H, aromatic), 7.68 (d, J = 8.27 Hz, 2H, H2,6-phenyl),
7.28 ppm (s, 2H, NH2); Mass m/z (rel.int): 302(M?, 29),
301 (M?-1, 36), 237 (14), 222 (78), 166 (21), 103 (50), 75
(100); Anal. Calcd. for C14H10N2O4S: C, 55.62; H, 3.33; N,
9.27. Found: C, 55.72; H, 3.34; N, 9.25.
5-(1,3-Dioxoisoindolin-2-yl)-1,3,4-thiadiazole-2-
sulfonamide (9)
4-(1,3-Dioxoisoindolin-2-yl) benzoic acid (5)
By means of the general procedure, 4-aminobenzoic acid
provided the title compound after 17 h of reflux: White
crystals, yield 80 %; mp 282–289.5 °C (ethanol). IR
(KBr): m cm-1, 3225–3310 (OH), 3067 (CH-aromatic),
By means of the general procedure, 5-amino-1,3,4-thia-
diazole-2-sulfonamide provided the title compound after
5 h of reflux: White crystals, yield 47 %; mp 264–274 °C
(ethanol). IR (KBr): m cm-1, 3329, 3180 (NH2), 3078 (CH-
aromatic), 1792, 1736 (CO); 1H NMR (DMSO-d6): d
7.90–8.02(m, 4H, aromatic); Mass m/z (rel.int): 310 (M?,
14), 308 (30), 244 (25), 188 (9), 170 (33), 156 (10), 102
(58), 74 (100); Anal. Calcd. for C10H6N4O4S2: C, 38.71; H,
1.95; N, 18.06. Found: C, 38.82; H, 1.94; N, 18.04.
1
1726, 1695 (CO); H NMR (DMSO-d6): d 8.42–9.51 (brs,
1H, COOH), 8.17 (d, J = 8.58 Hz, 2H, H3,5-phenyl),
7.75–8.03 (m, 4H, aromatic), 7.56 ppm (d, J = 8.58 Hz,
2H, H2,6-phenyl);. Anal. Calcd. for C15H9NO4: C, 67.42;
H, 3.39; N, 5.24. Found: C, 67.55; H, 3.40; N, 5.25.
2-Hydroxy-4-(1,3-dioxoisoindolin-2-yl) benzoic acid (6)
2-(4-Methoxy-2-nitrophenyl) isoindoline-1,3-dione (10)
By means of the general procedure, 4-amino-2-hydroxy-
benzoic acid provided the title compound after 2 h of reflux:
White crystals, yield 40 %; mp 293–295 °C (methanol–
chloroform). IR (KBr): m cm-1 2750–3700 (OH), 1716,
By means of the general procedure, 4-methoxy-2-nitroan-
iline provided the title compound after 7 h of reflux: yellow
crystals, yield 62.5 %; mp 148–153 °C (ethanol). IR
(KBr): m cm-1, 3080 (CH-aromatic), 2938 (CH-aliphatic),
1
1676 (CO); HNMR (DMSO-d6): d 11.25–1155 (brs, 1H,
1
1781, 1723 (CO), 1540, 1387(NO2); H NMR (CDCl3): d
COOH), 7.75–8.12 (m, 5H, aromatic), 7.06–7.39 ppm (m,
2H, H2,6-phenyl); Mass m/z (rel.int): 283 (M?, 25), 265
(60), 237 (19), 192(10), 132 (31), 103 (65), 76 (72), 75
(100).; Anal. Calcd. for C15H9NO5: C, 63.61; H, 3.20; N,
4.95. Found: C, 63.70; H, 3.21; N, 4.96.
7.69–7.93 (m, 4H, aromatic), 7.60 (d, J = 2.56 Hz, 1H,
H3-phenyl), 7.24(d, J = 8.5 Hz, 1H, H6-phenyl), 7.16 (dd,
J = 8.70, 2.6 Hz, 1H, H5-phenyl), 3.83 ppm (s, 3H,
OCH3); Mass m/z (rel.int): 298 (M?, 38), 252 (100), 209
123

Med Chem Res
(13), 153 (10); Anal. Calcd. for C15H10N2O5: C, 60.41; H,
3.38; N, 9.39. Found: C, 60.52; H, 3.39; N, 9.38.
only once, and each treatment group consisted of at least
eight animals.
2-(2-Amino-4-methoxyphenyl) isoindoline-1,3-dione (11)
Determination of clonic and tonic seizure thresholds
2-(4-Methoxy-2-nitrophenyl) isoindoline-1,3-dione (10)
(2.7 g, 5.7 mmol) was dissolved in 2-propanol (30 ml) and
then 10 % palladium on charcoal (500 mg) and cyclohexene
(150 ml) were added. The mixture was heated under reflux for
20 h and then filtered. The solvent was evaporated in vacuo,
and the residue was recrystallized from an ethanol 96° to give
the desired compound as a yellow crystal. (0.65 g, 43.3 %
yield). mp 188–190 °C. IR (KBr): m cm-1, 3441, 3365(NH2),
The infusion pump was adjusted to pump PTZ (0.5 %) with
constant rate (1 ml/min) in all the experiments (NE 1000,
New Era Pump System, Inc.). A 30-gauge butterfly needle
allowing access to the tail vein of mice was connected to a
pump by a flexible tube which made it possible to infuse
PTZ (0.5 %) at a constant rate of 1 ml/min to unrestrained
freely moving animals. Time was measured when forelimb
clonus (clonic seizure) followed by forelimb extension
(tonic seizure) were observed and the doses of PTZ
administered (mg/kg of mice weight) were measured as an
index of clonic and tonic seizure threshold (Loscher and
Rundfeldt, 1991).
1
1716, 1695 (CO); H NMR (CDCl3) d 7.72–7.98 (m, 4H,
aromatic), 7.00(d, J = 8.88 Hz, 1H, H6-phenyl), 6.43 (d,
J = 8.80 Hz, 1H, H5-phenyl), 6.38 (s, 1H, H3-phenyl),
3.78 ppm (s, 3H, OCH3); Anal. Calcd. for C15H12N2O3: C,
67.16; H, 4.51; N, 10.44. Found: C, 67.30; H, 4.52; N, 10.46.
Molecular modeling and docking
Results and discussion
Conformational analysis of the phenytoin and compound 8
was performed by Semi-empirical molecular orbital cal-
culations (PM3) method by means of the HYPERCHEM
software. Among all energy minima conformers, the global
minimum was used in docking calculations.
Chemistry
Eleven derivatives of N-arylisoindoline analogs were syn-
thesized in 40–89 % yield based on the method that is
shown in Scheme 1. All the compounds were characterized
by TLC followed by IR, Mass, elemental analysis, and
proton NMR.
Using a model of the open pore of the Na channel that
has been developed by homology with the crystal struc-
tures of K channels (Lipkind and Fozzard, 2005), we have
docked compounds 1–11 and phenytoin as a reference
drug. Docking calculations were performed by means of
Autodock software (version 4.2.3) and the implemented
Lamarckin GL. The docking log (dlg) files were analyzed
by the AutoDock Tools, graphical user interface of Auto-
dock. The docked conformations of each ligand were
ranked into clusters based on the binding energy. The top
ranked conformations were visually analyzed.
Molecular modeling and docking
Flexible docking was carried out on the active site of the
open pore of the Na channel. The binding energies,
hydrogen bonding, and Ki of all the compounds studied
have been tabulated (Table 1). Lowest energy and maxi-
mum number of conformations per cluster was set as the
criteria to predict the binding modes of the compounds.
Our docking studies reveal while phenytoin interacted with
the domain IV-S6 of NaV1.2 (Davood et al., 2012) but
compounds 1–11, interacted mainly with the domain II-S6
(Fig. 3). There is a hydrogen binding and additional
hydrophobic interaction with domain I and II in the chan-
nel’s inner pore. Oxygen of oxygen-containing functional
group like as carbonyl, nitro, or carboxyl groups play main
role in making hydrogen binding interaction with the OH
of THR87 and SER84 or NH3 of LYS7. In the compounds
5 and 6 which contain p-COOH, there is a hydrogen
bonding interaction between oxygen of OH and NH3 of
LYS7. In the compounds 1, 4, 7, 8, 10, and 11, there is a
hydrogen bond between oxygen of carbonyl of imide and
OH of THR87 or SER84 (Fig. 4); in the compounds 2
and 9, there is a hydrogen bond between oxygen of nitro
and nitrogen of NH2 with the OH of THR87 (Fig. 3).
Pharmacology and determination of anticonvulsant
activity
Pharmacology
Male Swiss mice weighing 22–28 g (Pasteur Institute)
were used throughout the study. Animals were housed in
groups of 4–5 and were allowed free access to food and
water except for the short time when animals were
removed from their cages for testing. All behavioral
experiments were conducted during the period between
10:00 and 13:00 with normal room light (12-h regular light/
dark cycle) and temperature (22 1 °C). All procedures
were carried out in accordance with the institutional
guidelines for animal care and use. Each mouse was used
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Med Chem Res
Table 1 The ability of isoindoline derivatives (1–11) to the protection against PTZ-induced seizure
Comp.
CST (mg/kg)a
TST (mg/kg)b
Binding
energy
Ki (lM)
Atoms in
hydrogen bonds
logPc
1
2
46.34 3.51
64.89 9.25
65.66 5.87
-5.29
-6.36
133.56
21.8
Sod:G:THR87 (OH)
with O (keton)
2.63
2.63
96.84
9.91
Sod:G:THR87
(OH) with O (NO2)
3
4
41.12 3.85
42.95 3.1
61.6 5.76
-5.71
-4.74
65.56
337.8
No H.B formed
2.63
2,37
58.08 4.39
Sod:G:THR87
(OH) with O (keton)
5
46.65 5.5
52.1 4.32
40.37 1.39
33.40 2.85
45.14 1.55
49.4 7.31
56.34 4.3
79.94 1.31
64.97 8.46
86.37 8.37
60.56 2.44
62.35 1.44
61.92 5.96
98.12 12.44
-5.86
-5.6
50.4
78.42
18.27
16.01
61.07
108.07
20.3
Sod:LYS7 (NH3)
with O (COOH)
2,37
2.09
1.52
1.56
2.22
2.37
1.64
2.26
6
Sod:LYS7 (NH3)
with O (COOH)
7
-6.46
-6.54
-5.75
-5.41
-6.4
Sod:G:THR87 (OH)
with O (keton)
8
Sod:G:THR87 (OH)
with O (keton)
9
Sod:G:THR87 (OH)
with N (NH2)
10
11
Sod:G:THR87 (OH)
with O (keton)
Sod:G:SER84 (OH)
with O (keton)
Phenytoin
Vehicle
a
49.20 1.09
38.9 1.01
115.00 1.85
59.58 1.01
-5.83
53.37
Sod:E:SER83:O:H
Colonic seizure threshold—it was calculated as mg of PTZ which induced clonic seizure/weight of mouse (kg)
Tonic seizure threshold—it was calculated as mg of PTZ which induced clonic seizure/weight of mouse (kg)
logP values have been calculated by HYPERCHEM software
b
c
Aryl part of isoindoline pharmacophore forms a hydro-
control. The single doses of all compounds (40 mg/kg) were
administered 15, 30 or 60 min prior to distinct groups of mice.
Further analysis showed that most of the compounds and
phenytoin exerted their maximal effects 30 min after
administration. The in vivo screening data indicated that
except compound 8, all the analogs have the ability to
protection against PTZ-induced seizure (Table 1).
phobic interaction with the hydrophobic pocket of receptor
that mainly created by domains I, II (Fig. 3).
Binding energy analysis of compounds 1–11 (Table 1) has
led us to similar structures for their complexes with the two
domain IIS6 residues in the open inner pore of the Na channel
that are known from mutagenesis studies to be criticalfor their
blockingaction (Davoodetal., 2012). Basedonthe predicated
binding energies (Table 1), some designed compounds, like
compounds 7, 8, and 11, should be more potent than phenyt-
oin; however, the experimental data did not confirm this
possibly due to low logP of these compounds.
Phenytoin as a standard did not inhibit clonic seizure
evoked by PTZ in lower doses (10, 20 mg/kg). Compounds
2, 6, and 11 elevated the clonic seizure thresholds at 30 min
which were more active than phenytoin as a reference drug,
and compounds 2, 7, and 11 showed marked anticonvulsant
activity on tonic seizure. The most potent compounds were 2
and 11 that had comparative activity to the reference drug
phenytoin. In the nitro series, compounds 1, 2, and 3, meta
derivative (comp. 2) is more potent than ortho (comp. 1) and
para (comp. 3) derivatives, reactivity in nitro analogs is
according to meta [ ortho [ para. In the carboxylic acid
series (compounds 4–6), para analog is more potent then
ortho analog. Reduction of nitro (comp. 10) to amine (comp.
11) increases the clonic and tonic activity.
Protection against PTZ-induced seizure
The ability of the compounds 1–11 to protect against PTZ-
induced seizure, tonic and colonic, was determined by an in
vivo assay, and the results are summarized in Table 1. Each
compound was dissolved in DMSO, injected intraperitone-
ally, and screened for anticonvulsant activities at doses of 10,
20, and 40 mg/kg compared with phenytoin as a positive
123

Med Chem Res
Fig. 3 Docked structure of 2 in
the model of sodium channel
(Nav1.2) (top view). The
backbones of S6 a-helices of
domains I–IV are shown by red,
green, yellow, and violet,
correspondingly. Hydrogen
˚
bond (distance 1.754 A) is
represented with dashed green
lines (Color figure online)
Fig. 4 Docked structure of 11
in the model of sodium channel
(Nav1.2). Hydrogen bond
˚
(distance = 1.6 A,
energy = 1.724) is represented
with dashed green lines (Color
figure online)
Statistical analysis
Conclusion
The results are presented as mean SEM and the statis-
tical significance between the groups was analyzed by
means of variance followed by one-way ANOVA test.
P values \0.05 were considered as indicative of signifi-
cance.
Eleven analogs of N-arylisoindoline derivatives were syn-
thesized, characterized by TLC followed by IR, Mass,
elemental analysis, and proton NMR and tested for their
ability to protection against PTZ-induced seizure in vivo in
mice. The in vivo screening data acquired indicate that all
123

Med Chem Res
Davood A, Shafaroodi H, Amini M, Nematollahi A, Shirazi M, Iman
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seizure. These compounds exerted their maximal effects
30 min after administration. The most potent compounds
were 2 and 11.
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Acknowledgments We are grateful to the Azad University for
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