Synthesis and anticonvulsant activity of 4-bromophenyl substituted aryl semicarbazones

Article abstract of DOI:10.1016/S0223-5234(00)01169-7

A number of 4-bromophenyl semicarbazones were synthesised and evaluated for anticonvulsant and sedative-hypnotic activities. After intraperitoneal injection to mice, the semicarbazone derivatives were examined in the maximal electroshock seizure (MES), subcutaneous pentylenetetrazole (scPTZ), subcutaneous strychnine (scSTY) and neurotoxicity (NT) screens. All the compounds showed anticonvulsant activity in one or more test models. Compound 12 showed greatest activity, being active in all the screens with very low neurotoxicity and no sedative-hypnotic activity. All the compounds except 7 had lower neurotoxicity compared to phenytoin. Three compounds (6, 11 and 14) showed greater protection than Sodium valproate. The essential structural features responsible for interaction with receptor site are established within a suggested pharmacophore. (C) 2000 Editions scientifiques et medicales Elsevier SAS.

Full text of DOI:10.1016/S0223-5234(00)01169-7

Eur. J. Med. Chem. 35 (2000) 879–886
´
© 2000 Editions scientifiques et me´dicales Elsevier SAS. All rights reserved
Original article
PII: S0223-5234(00)01169-7/FLA
Synthesis and anticonvulsant activity of 4-bromophenyl substituted aryl
semicarbazones
Surendra N. Pandeyaa*, Perumal Yogeeswaria, James P. Stablesb
aDepartment of Pharmaceutics, Institute of Technology, Banaras Hindu University, Varanasi-221005, India
bPreclinical Pharmacology Section, Epilepsy Branch, National Institutes of Health, Bethesda, MD 20892-9020, USA
Received 17 February 2000; revised 25 April 2000; accepted 26 April 2000
Abstract – A number of 4-bromophenyl semicarbazones were synthesised and evaluated for anticonvulsant and sedative–hypnotic
activities. After intraperitoneal injection to mice, the semicarbazone derivatives were examined in the maximal electroshock seizure
(MES), subcutaneous pentylenetetrazole (scPTZ), subcutaneous strychnine (scSTY) and neurotoxicity (NT) screens. All the
compounds showed anticonvulsant activity in one or more test models. Compound 12 showed greatest activity, being active in all
the screens with very low neurotoxicity and no sedative–hypnotic activity. All the compounds except 7 had lower neurotoxicity
compared to phenytoin. Three compounds (6, 11 and 14) showed greater protection than sodium valproate. The essential structural
´
features responsible for interaction with receptor site are established within a suggested pharmacophore. © 2000 Editions
scientifiques et me´dicales Elsevier SAS
semicarbazones / electroshock / pentylenetetrazole / strychnine / neurotoxicity / pentobarbitone
1. Introduction
If the aryl semicarbazones displaying activity in the
MES screen interact at a specific binding site, it is
likely that the semicarbazone group and the aryl ring
align at complimentary areas on a macromolecular
complex in vivo; these areas have been referred to as
the hydrogen bonding area and the aryl binding site,
respectively [8]. In the initial studies on aryl semicar-
bazones, it was found to possess potent anticonvul-
sant activity and the importance of the terminal
amino group of semicarbazone was implicated in hy-
drogen bonding [9–11]. The presence of electron-rich
atom/group attached at the para position of the aryl
ring showed increased potency in the MES screen.
Substitution in the aryl ring by halogens led to a
number of semicarbazones with low ED50 values in
the rat oral MES screen accompanied by high protec-
tive index values [12]. In the present study, 4-bro-
mophenyl group was considered an important aryl
group. In a study of 3-aminopyrroles for anticonvul-
More than half of a century has elapsed since the
anticonvulsant properties of phenytoin were first evi-
denced in laboratory animal models [1] with success-
ful therapeutic administration in epileptic patients [2,
3]. Current drug therapy for epilepsy suffers from a
number of disadvantages including the fact that the
convulsions of approximately 25 % of epileptics are
inadequately controlled by medication [4]. In recent
years, the field of antiepileptic drug development has
become quite dynamic, affording many promising re-
search opportunities. Mechanistic approaches are in-
creasingly being facilitated by ‘the new wave of
research in the epileptics’ [5]. Semicarbazones have
documented consistent advances in the design of
novel anticonvulsant agents, through the work of
Dimmock and his colleagues [6]. A number of (aryl-
oxy)aryl semicarbazones possessed greater protection
in the maximal electroshock seizure (MES) screen [7].
sant
activity,
4-(4-bromophenyl)-3-morpholino-
pyrrole-2-carboxylic acid methyl ester proved to be
the most active compound with an oral ED50 of 2.5
mg/kg in MES screen and with no neurotoxicity up to
* Correspondence and reprints:
E-mail address: snpande@banaras.ernet.in (S.N. Pandeya).

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S.N. Pandeya et al. / European Journal of Medicinal Chemistry 35 (2000) 879–886
500 mg/kg [13]. Moreover 4-bromobenzaldehyde semi-
carbazone displayed high potency in the MES test
with very low neurotoxicity resulting in high protec-
tive index [14]. Thus the aim of the present study was
to prepare a series of 4-bromophenyl semicarbazones
with a view to confirm their chemical features which
contribute to interactions at a binding site. The 4-bro-
mophenyl group has been attached at the terminal
amino function of the semicarbazone in contrast to
the compounds synthesised by Dimmock et al. [7].
The 4-bromo derivatives have shown significant anti-
convulsant activity in the MES screen, which would
serve as prototypic molecule for subsequent molecular
modification. The compounds were also tested against
subcutaneous strychnine (scSTY) test, a test that
throws light for the interaction with glycine receptors.
2. Chemistry
The preparation of 4-bromophenyl semicarbazones
was achieved as depicted in figure 1. 4-Bromoaniline
was treated with sodium cyanate in presence of glacial
acetic acid according to the known urea preparation
method, to yield 4-bromophenyl urea. The urea
derivative on condensation with hydrazine hydrate in
ethanol in the presence of sodium hydroxide gave the
4-bromophenyl semicarbazide. The semicarbazones
were prepared by reaction of the appropriate aldehyde
or ketone with 4-bromophenyl semicarbazide. The
products (table II) were identified by spectral data. In
general, IR spectra showed the CꢀN peak at 1610–
1590 cm−1 and the NH streching vibrations at 3450
cm−1. The semicarbazone derivatives exhibited char-
Figure 1. Synthetic protocol of the 4-bromophenyl semicarbazones.

S.N. Pandeya et al. / European Journal of Medicinal Chemistry 35 (2000) 879–886
881
acteristic amide bonds at 3300–3240 cm−1 and 1700–
1670 cm−1 and absorption band at 820 cm−1 was
characteristic of a para-substituted phenyl ring. The
1H-NMR spectrum revealed that the hydrazino
(ꢀNꢁNH) proton attached to the phenyl ring at 9.1–
9.8 and the aryl NH proton which showed a singlet at
5.7–6.9 were D2O exchangeable.
4-bromo substituted phenyl semicarbazones were ac-
tive in the MES test at a dose of 300 mg/kg, indicative
of their ability to prevent seizure spread. At a dose of
100 mg/kg, compounds that showed protection in half
or more of the tested mice were 2 (2 h), 3 (0.25 h, 1 h),
4 (2 h), 12 (1 h) and 17 (1 h). Compound 8 did not
show any protection at 0.5 h interval but showed
protection at 4 h at a dose of 300 mg/kg. All of the
compounds except 1, 5, 9 and 17 were active in the
scPTZ test, a test used to identify compounds that
elevate seizure threshold. The most active compound
in scPTZ test was 12, which showed activity compara-
ble with carbamazepine and potency greater than
sodium valproate. Compounds 2, 3, 10, 11, 15 and 16
showed activity only at 0.5 h and compounds 7 and
14 showed activity only at 4 h. The activity of com-
pounds 2, 6 and 9–15 in scSTY test showed that
semicarbazones could also act through inhibitory
glycine receptors. The compounds 2 and 6 were found
to possess activity at 100 mg/kg. In the NT screen, all
the compounds showed neurotoxicity at a higher dose
level (300 mg/kg) except 7 (100 mg/kg). Compounds
1, 2, 3, 11 and 15 showed neurotoxicity only up to 0.5
h and not at 4 h. All compounds were less neurotoxic
than phenytoin except compound 7. Mice were unable
to grasp rotorod after administration of the following
compounds, viz. 3 (300, 0.5 h), 4 (300, 0.5 h), 5 (300,
0.5 h, 4 h), 6 (300, 0.5 h, 4 h), 8 (300, 0.5 h, 4 h), 10
(300, 0.5 h), 11 (300, 0.5 h), 12 (300, 0.5 h), 13 (300,
0.5 h, 4 h), 15 (300, 0.5 h) and 17 (300, 0.5 h).
Some selected compounds (2, 4, 6, 7, 12 and 17)
were examined for activity in the rat oral MES screen
and these data are presented in table I. Initially a
dose of 30 mg/kg was employed. Compounds af-
forded complete protection against seizures confirm-
ing their potential utility as prototypic molecules and
compounds 2, 6 and 7 emerged as the most active
compounds in the oral MES screen. In the sedative
hypnotic evaluation (table V), compounds 1, 3, 4, 8,
9, 13, 15 and 16 were found to potentiate the pento-
barbitone induced narcosis and compounds 2 and 6
did not induce sleep. Compounds 6, 10, 11, 12 and 14
hence emerged as the most promising anticonvulsant
agents with low neurotoxicity and no sedative
activity.
3. Pharmacology
Initial anticonvulsant evaluation of the 4-bromo-
phenyl semicarbazones was undertaken by following
the anticonvulsant drug development (ADD) pro-
gram protocol [15, 16]. The profile of anticonvulsant
activity was established after i.p. injections by one
electrical and two chemical tests. The electrical test
employed was the MES pattern test. The chemical
tests employed were the subcutaneous pentylenetetra-
zole (scPTZ) seizure threshold test and scSTY seizure
threshold test. Minimal motor impairment was mea-
sured by the rotorod (neurotoxicity, NT) test. Some
compounds were administered orally to rats and ex-
amined in the MES screen. The compounds were also
evaluated for the sedative hypnotic activity by using
pentobarbitone induced narcosis in rats.
4. Results
The evaluations of the semicarbazones in the mouse
i.p. MES, scPTZ, scSTY and NT screens are sum-
marised in table IV along with the literature data on
phenytoin, carbamazepine, sodium valproate, pento-
barbital and ethosuximide [7, 16, 17]. All of the
Table I. Evaluation of selected compounds in the MES test
after oral administration (30 mg/kg) to rats.
Compound
Oral administration to ratsa
0.25 h
0.5 h
1 h
2 h
4 h
2
4
2
1
2
1
1
1
1
3
2
3
2
–
3
2
3
3
–
2
4
2
4
3
3
3
4
3
3
4
2
3
6
7
12
17
5. Discussion
a The figures indicate the number of rats out of four which
were protected. The dash (–) means that no activity was
demonstrated.
The bioevaluation led to an understanding of the
importance of the size of the group at the carbimino

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S.N. Pandeya et al. / European Journal of Medicinal Chemistry 35 (2000) 879–886
Table II. Elemental analyses for reviewersa.
Compound
Molecular formula
Found (%) (calc. %) C H N
C
H
N
1
3
C14H11N3OBrCl
C16H17N4OBr
C16H16N3O3Br
C15H14N3OBr
C16H17N3OBr
C20H16N3OBr
C10H12N3OBr
C16H14N3OBr
C12H10N3O2Br
C17H24N3OBr
47.57 (47.68)
53.23 (53.19)
50.84 (50.81)
54.36 (54.23)
55.43 (55.34)
61.10 (60.92)
44.58 (44.46)
55.78 (55.83)
46.83 (46.77)
55.94 (55.74)
3.12 (3.14)
4.78 (4.74)
4.32 (4.26)
4.29 (4.25)
4.91 (4.94)
4.11 (4.09)
4.48 (4.47)
4.16 (4.10)
3.30 (3.27)
6.64 (6.60)
11.98 (11.92)
15.49 (15.51)
11.16 (11.11)
12.71 (12.65)
12.13 (12.10)
10.35 (10.66)
15.64 (15.56)
12.21 (12.21)
13.59 (13.64)
11.50 (11.47)
5
6
8
11
12
13
15
17
a Elemental analyses were determined with Perkin Elmer model 240C analyser.
carbon atom. Replacement of the proton on the car-
bimino carbon atom by methyl (6–10) or phenyl (11)
or cinnamylidene (13) leading to increase in the size of
the group at this position of the molecule has shown
variation in activity. This modification might increase
the anticonvulsant activity due to additional van der
Waals bonding or alternatively steric impedance to
alignment at a binding site leading to a reduction or
abolition of activity [18]. The introduction of a third
phenyl group led to compound 11 which was active in
MES, scPTZ and showed moderate activity in scSTY
screens.
substituents at the distal aryl ring was found to affect
the biological activity. The distal aryl ring is expected
to get p-hydroxylated during metabolism. Introduc-
tion of o-nitro group (2) showed protection in all the
screens compared to the o-chloro substituted com-
pound (1) or a p-N,N-dimethyl substituted compound
(3). Replacement of the phenyl ring with furyl (15) or
cyclohexanone derivatives (16, 17) showed less or no
activity in scSTY screen. 3,4-Methylenedioxyphenyl
compounds like stiripentol [20] and 7,8-methylene-
dioxy-2,3-benzodiazepines [21] were found to possess
longer-lasting anticonvulsant activity. Likewise, com-
pound 14 showed higher protection in the scSTY
screen compared to the standard drugs. Since bio-
activity is considered to be influenced by the rate and
extent of the passage of a drug to its site of action, the
partition coefficients between chloroform and buffer
pH 7.4 of all the compounds were determined (table
III). The data support the concept that the com-
pounds align at a specific binding site and are not
structurally non-specific. The pharmacophore model
of these aryl semicarbazones resemble that of the
standard anticonvulsants as depicted in figure 2 and
the 4-bromophenyl semicarbazones largely resemble
the structure of desmethyl diazepam. Hence these
semicarbazones could emerge as bioisosteres of
desmethyl diazepam (CH2 replaced with NH).
In terms of interaction at the binding site, as pro-
posed previously by Dimmock et al. [7, 18], the phar-
macophoric descriptors were thought to be
a
lipophilic aryl ring and a hydrogen bonding semicar-
bazone moiety. The attachment of a second aryl ring
designated as the distal ring to the proximal aryl ring
to increase the van der Waals bonding at binding site
and to increase potency have been studied [12]. In all
these studies, the terminal amino function was found
to be free. In our approach, 4-bromophenyl group
has been attached at the terminal amino function in
contrast to Dimmock’s study, to reveal the impor-
tance of the terminal amino function for anticonvul-
sant activity. It is conceivable from our study that the
structural features essential to interact at the binding
site were a lipophilic moiety (4-bromophenyl ring)
and a hydrogen bonding domain (amide function,
NHCO) as proposed by Cook and co-workers [19].
The distal aryl ring at the carbimino terminal (benzyl-
idene ring) may be essential for the pharmacokinetic
properties of the compounds since variation in the
In conclusion, the present results indicate that the
terminal amino function of the semicarbazone is not
essential for activity and can be substituted with a
lipophilic aryl ring. This is a new aspect, which led to
prototypic molecules with potential activity in the
preliminary studies.

S.N. Pandeya et al. / European Journal of Medicinal Chemistry 35 (2000) 879–886
Table III. Physical data of the semicarbazone derivatives.
883
Compound
Yield ( %)
Mp ( °C)
Molecular formulaa
Rfb
Pc
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
62
52
74
69
88
85
55
59
55
65
55
57
68
83
52
59
56
210
183
172
253
144
229
200
222
196
167
179
201
158
184
112
193
245
C14H11N3OBrCl
C14H11N4O3Br
C16H17N4OBr
C15H14N3O3Br
C16H16N3O3Br
C15H14N3OBr
C15H15N3O2Br
C16H17N3OBr
C15H15N4OBr
C15H14N4O3Br
C20H16N3OBr
C10H12N3OBr
C16H14N3OBr
C15H12N3O3Br
C12H10N3O2Br
C13H16N3OBr
C17H24N3OBr
0.66
0.67
0.71
0.48
0.73
0.61
0.58
0.64
0.78
0.63
0.72
0.77
0.83
0.50
0.51
0.68
0.42
0.51
0.72
0.86
2.10
0.94
2.15
2.95
0.43
0.77
1.23
1.05
2.26
1.48
0.59
1.82
0.46
2.53
a Elemental analyses for C,H,N were within 0.4 % of the theoretical values.
b Eluants for TLC were benzene–ethanol (9.8:0.2) for all compounds except 3–5, 9, 11–15 and 17 for which only benzene was used.
c Partition coefficient at 25 °C [chloroform–phosphate buffer system, pH 7.4].
6. Experimental protocols
has been described previously [10]. Equimolar quantities
(0.1 mol) of 4-bromophenyl urea (21.5 g) and hydrazine
hydrate (5 mL) in ethanol were refluxed for 3 h in the
presence of 0.1 mol sodium hydroxide. The resultant
precipitate was filtered, dried and recrystallised from
95 % ethanol to give 4-bromophenyl semicarbazide, mp
6.1. Chemistry
Melting points were determined in open capillary
tubes on a Thomas Hoover melting point apparatus and
are uncorrected. Infrared (IR) and proton nuclear mag-
netic resonance (1H-NMR) spectra were recorded for
the compounds on Jasco IR Report 100 (KBr) and
JEOL Fx 90Q (Fourier Transform) instruments, respec-
tively. Chemical shifts are reported in ppm (l) using
tetramethylsilane (TMS) as internal standard. All ex-
changeable protons were confirmed by addition of D2O.
Elemental analyses (C,H,N) undertaken with Perkin
Elmer Model 240C analyser on compounds 1, 3, 5, 6, 8,
11–13, 15 and 17 were within 0.4 % of the calculated
values. The homogeneity of the compounds was moni-
tored by ascending thin layer chromatography (TLC) on
silica-G (Merck) coated glass plates, visualised by iodine
vapour. Developing solvents were either benzene or
benzene–ethanol (9.8:0.2). The partition coefficients
were determined using a chloroform–phosphate buffer
(pH 7.4) system by UV method.
1
278–280 °C in 78 % yield. H-NMR (CDCl3) 5.6 (s, 2H,
NH2, D2O exchangeable), 6.15 (s, 1H, ArNH, D2O
exchangeable), 7.2–7.46 (m, 4H, ArH), 9.6 (bs, 1H,
NHNH2).
6.1.2. Synthesis of 4-bromophenyl semicarbazones
To a solution of 4-bromophenyl semicarbazide (0.69
g, 0.003 mol) in ethanol was added an equimolar quan-
tity of the appropriate aldehyde or ketone. The pH of
the reaction mixture was adjusted between 5 and 6 by
adding glacial acetic acid. The reaction mixture was
refluxed for 1–2 h. The product obtained after cooling
was filtered and recrystallised from 95% ethanol. The
physical data of the semicarbazones are presented in
table III. The IR spectra of the compounds were
identical in the following aspects: 3450 (NH), 3300–
3240 (CONH), 1640 (CꢀO), 1590 (CꢀN) and 840 cm−1
1
(ArꢁCH); H-NMR (90 MHz, l) spectra of some repre-
6.1.1. Synthesis of 4-bromophenyl semicarbazide
sentative compounds were as follows: 1 (DMSO-d6): 5.8
(s, 1H, ArNH, D2O exchangeable), 6.84 (s, 1H, Car-
bimino H) 7.2–7.6 (m, 8H, ArꢁH), 8.89 (s, 1H, CONH,
D2O exchangeable); 3 (CDCl3): 3.0 (s, 6H, N (CH3)2),
The 4-bromophenyl urea was prepared from p-bro-
moaniline by a reported procedure [22] and converted
into 4-bromophenyl semicarbazide by a method which

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S.N. Pandeya et al. / European Journal of Medicinal Chemistry 35 (2000) 879–886
Table IV. Anticonvulsant activity and minimal motor impairment of 4-bromophenyl semicarbazone derivatives.
Compound
Intraperitoneal injection in micea
MES screen
0.5 h
scPTZ screen
scSTY screenb
0.5 h
Toxicity screen
0.5 h
4 h
0.5 h
4 h
4 h
4 h
1
300
300
300c
300
300
100
300
–
300
300
300
300
300
300
300
300
300
30
300
–
–
–
–
300
–
300
300
300
–
–
–
300
300
300
–
–
–
–
300
–
30
–
–
300
–
–
–
100
–
–
300
300
100
300
100
100
300
–
–
–
–
300
–
–
300
–
–
–
100
–
–
300
300
300d
300
300
100
300
–
–
100
–
–
100
–
300
300
300
300
300
300
100
300
300
300
300
300
300
300
300
300
300
100
100
—
–
–
–
2
300c
300
300
300
–
300
–
300
–
300
300
100
300
–
c
3
–
4
300c
300
300
300
300
300
300
300
300c
300
300
300
300
300c
30
300
300
300
300
300
300
300
–
300
300
300
–
300
300
100
300
—
300
—
5
6
7
8
9
10
11
12
13
14
15
300
300
–
16
17
Phenytoine
Carbamazepinee
Na. Valproatee
Phenobarbitalf
Ethosuximidef
–
30
100
–
30
100
300
30
300
100
–
100
—
–
300
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 animals were examined 0.5 and 4 h after injections were made. The dash (−) indicates
an absence of activity at maximum dose administered (300 mg/kg).
b In scSTY screen, rats were used.
c In the MES screen, at a dose of 100 mg/kg, compounds that showed protection were 2 (2 h), 3 (0.25, 1 h), 4 (2 h), 12 (1 h) and
17 (1 h).
d Compound 11 showed protection at a dose of 100 mg/kg up to 1 h in the scSTY screen.
e Data from references [7, 16].
f Data from reference [17].
5.9 (s, 1H, ArNH, D2O exchangeable), 6.91 (s, 1H,
Carbimino H), 7.2–7.5 (m, 4H, p-bromophenyl), 7.6–
7.8 (m, 4H, p-dimethylaminophenyl), 8.75 (s, 1H,
CONH, D2O exchangeable); 4 (CDCl3): 3.63 (s, 3H,
OCH3), 5.89 (s, 1H, ArNH, D2O exchangeable), 6.94 (s,
1H, Carbimino H), 7.23–7.43 (m, 7H, ArH), 9.66 (s,
1H, CONH, D2O exchangeable), 10.95 (s, 1H, OH); 8
(CDCl3): 2.3 (s, 3H, CH3), 2.35 (s, 3H, NꢀC(CH3)), 6.1
(s, 1H, ArNH, D2O exchangeable), 7.3–7.6 (m, 8H,
ArH), 8.71 (s, 1H, CONH, D2O exchangeable); 11
(CDCl3): 5.82 (s, 1H, ArNH, D2O exchangeable), 7.2–
8.12 (m, 14H, ArH), 8.88 (s, 1H, CONH, D2O ex-
changeable); 12 (CDCl3): 2.29 (s, 6H, 2×CH3), 5.81 (s,
1H, ArNH, D2O exchangeable), 7.2–7.56 (m, 4H, ArH),
8.75 (s, 1H, CONH, D2O exchangeable); 14 (CDCl3):
5.88 (s, 1H, ArNH, D2O exchangeable), 6.05 (m, 2H,
OCH2O), 6.77 (s, 1H, Carbimino H), 7.18–7.62 (m, 7H,
ArH), 8.86 (s, 1H, CONH, D2O exchangeable); 15
(CDCl3): 5.83 (s, 1H, ArNH, D2O exchangeable), 6.75
(s, 1H, Carbimino H), 6.46–7.49 (m, 7H, ArH), 8.82 (s,
1H, CONH, D2O exchangeable); 16 (CDCl3): 2.54 (m,
4H, o-position of cyclohexane ring), 3.26–3.4 (m, 6H,
m- and p-positions of cyclohexane ring), 5.9 (s, 1H,
ArNH, D2O exchangeable), 7.21–7.43 (m, 4H, ArH),
8.91 (s, 1H, CONH, D2O exchangeable).
6.2. Pharmacology
The anticonvulsant evaluations were undertaken by
the National Institute of Neurological Disorders and

S.N. Pandeya et al. / European Journal of Medicinal Chemistry 35 (2000) 879–886
885
Table V. Evaluation of compounds for the potentiation or
antagonism of pentobarbitone induced narcosisa.
Compoundsb
Mean sleeping timec (min)
1
196.6949.80
141.16915.75
147.3094.67
23.6097.18
34.6094.25
160.40910.78
69.4098.02
23.6092.82
34.1697.82
20.3396.18
107.60927.84
14.3091.55
132.0996.26
182.7911.95
28.00910.74
49.3091.36
3
4
5
7
8
9
10
11
12
13
14
15
16
17
Pentobarbitone (control)
a Compounds were tested at a dose of 30 mg/kg (i.p.).
b Compounds 2 and 6 did not induce sleep in rats.
c Each value represents the mean SEM of six rats significantly
different from the control (PB0.5) (student’s t-test).
Figure 2. Development of a pharmacophore model. R-hydro-
phobic unit; HBD-hydrogen bonding domain; D-electron
donor.
mals were given i.p. injection of the test compounds in
doses of 30, 100 and 300 mg/kg. Neurotoxicity was
indicated by the inability of the animal to maintain
equilibrium on the rod for at least 1 min in each of the
three trails.
Strokes, NIH (USA) using their reported procedures
[15, 16, 23]. Male albino mice (CF-1 strain, 18–25 g)
and male albino rats (Sprague–Dawley, 100–150 g)
were used as experimental animals. The semicarbazones
were suspended in 0.5 % methylcellulose/water mixture
or in polyethylene glycol (PEG).
6.2.3. Sedati6e–hypnotic acti6ity
This test was performed with the test substances in a
dose of 30 mg/kg only by the method reported previ-
ously [10]. The compounds in PEG were administered
i.p. to a group of six rats. After 30 min, rats were
injected i.p. with a solution of pentobarbitone (in PEG)
in a dose of 30 mg/kg. The rats were then placed on
their back and loss of righting reflex was taken as onset
of sleep. The time taken by rats to awake was noted. A
control was also performed after pre-treatment with test
substance vehicle (PEG) and injected pentobarbitone.
6.2.1. Anticon6ulsant screening
Initially all the compounds were administered i.p. in a
volume of 0.01 mL/g body weight for mice and 0.004
mL/g body weight for rats at doses of 30, 100 and 300
mg/kg to one to four animals. Activity was established
using the MES, scPTZ and scSTY tests and these data
are presented in table IV. Some selected semicarbazone
derivatives described in this study were examined for
oral activity in the MES screen. The results are pre-
sented in table I.
Acknowledgements
6.2.2. Neurotoxicity (NT) screen
Minimal motor impairment was measured in mice by
the rotorod test. The mice were trained to stay on an
accelerating rotorod that rotates at 10 revolutions per
minute. The rod diameter was 3.2 cm−1. Trained ani-
The authors deeply appreciate the assistance of the
Antiepileptic Drug Development program, Epilepsy
Branch, Preclinical Pharmacology Section, NIH, USA
in the testing of the compounds.

886
S.N. Pandeya et al. / European Journal of Medicinal Chemistry 35 (2000) 879–886
[12] Dimmock J.R., Sidhu K.K., Tumber S.D., Basran S.K., Chen
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