Design, synthesis, and biological evaluation studies of novel quinazolinone derivatives as anticonvulsant agents

Article abstract of DOI:10.1007/s00044-013-0569-5

In view of their expected anticonvulsant activity, some novel derivatives of 6,8-diiodo-2-methyl-3-substituted-quinazolin-4(3H)-ones (4-14) were synthesized, evaluated for their anticonvulsant activity by the maximal electroshock-induced seizure and subcutaneous pentylenetetrazole tests. The neurotoxicity was assessed using rotorod test. All the tested compounds showed considerable anticonvulsant activity in at least one of the anticonvulsant tests. Compounds 5, 6, and 8 proved to be the most potent compounds of this series with relatively low neurotoxicity and low toxicity in the median lethal dose test when compared with the reference drugs. The obtained results showed that the most potent compounds could be useful as a template for future design, optimization, and investigation to produce more active analogs.

Full text of DOI:10.1007/s00044-013-0569-5

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-013-0569-5
ORIGINAL RESEARCH
Design, synthesis, and biological evaluation studies of novel
quinazolinone derivatives as anticonvulsant agents
•
Mohamed F. Zayed Hany E. A. Ahmed
•
•
•
Abdel-Sattar M. Omar Adel S. Abdelrahim
Khaled El-Adl
Received: 8 December 2012 / Accepted: 2 March 2013
Ó Springer Science+Business Media New York 2013
Abstract In view of their expected anticonvulsant activ-
ity, some novel derivatives of 6,8-diiodo-2-methyl-3-sub-
stituted-quinazolin-4(3H)-ones (4–14) were synthesized,
evaluated for their anticonvulsant activity by the maximal
electroshock-induced seizure and subcutaneous pentylen-
etetrazole tests. The neurotoxicity was assessed using
rotorod test. All the tested compounds showed considerable
anticonvulsant activity in at least one of the anticonvulsant
tests. Compounds 5, 6, and 8 proved to be the most potent
compounds of this series with relatively low neurotoxicity
and low toxicity in the median lethal dose test when com-
pared with the reference drugs. The obtained results showed
that the most potent compounds could be useful as a tem-
plate for future design, optimization, and investigation to
produce more active analogs.
Keywords Quinazolin-4(3H)-one Á Epilepsy Á
Neurotoxicity Á Synthesis Á Anticonvulsant
Introduction
Epilepsy is ubiquitous disease characterized by recur-
rent seizures and inflicts [60 million people worldwide
according to epidemiological studies (Leppik, 1994). Every
year *250,000 new cases are added to this figure. About
28–30 % of epilepsy patients have a multidrug resistance
and develop refractory epilepsy (RE). This particular
refractoriness is now attributed to overexpression and
upregulation of p-glycoprotein in brain, leading to impaired
access of antiepileptic drugs to CNS targets. These findings
were documented in both human as well as in experimental
models of RE after the biological examination of brain
capillary endothelial cells from cerebral cortex biopsies
from normal and drug-resistant epileptic patients (Chen
et al., 2007).
M. F. Zayed (&) Á H. E. A. Ahmed
Pharmaceutical Chemistry Department, College of Pharmacy,
Taibah University, Al-madinah Al-munawarah,
Kingdom of Saudi Arabia
Despite the development of several new anticonvulsants,
the treatment of epilepsy remains still inadequate and the
patients suffer from many side effects like neurotoxicity,
depression, and other CNS disorders. Therefore, it is nec-
essary to search for safer and more effective anticonvul-
sants (French, 1999).
e-mail: mohamad2zayed@yahoo.com; mfzayed@taibah.edu.sa
A.-S. M. Omar
Pharmaceutical Chemistry Department, Faculty of Pharmacy,
King AbdulAziz University, Jeddah, Kingdom of Saudi Arabia
The sedative-hypnotic (neurotoxicity) properties of 4(3H)-
quinazolinone are well documented (Jatav et al., 2008). A
literature survey revealed that the presence of aromatic or
aliphatic group at position 2 and a substituted aromatic ring
at position 3 are essential requirements for CNS activities
of quinazolinone moiety predominantly anticonvulsant
properties (Nagwa et al., 2011). 2-Methyl-3-O-tolyl 4(3H)-
quinazolinone (methaqualone) is an important landmark in
the field of synthetic anticonvulsant and prototype
A. S. Abdelrahim
Pharmaceutical Chemistry Department, Faculty of Pharmacy,
Jazan University, Jazan, Kingdom of Saudi Arabia
M. F. Zayed Á A.-S. M. Omar Á A. S. Abdelrahim Á K. El-Adl
Pharmaceutical Chemistry Department, Faculty of Pharmacy,
Al-Azhar University, Cairo, Egypt
H. E. A. Ahmed
Organic Chemistry Department, Faculty of Pharmacy,
Al-Azhar University, Cairo, Egypt
123

Med Chem Res
sedative-hypnotic containing quinazolinone ring system
(Wolfe et al., 1990). Many quinazolinones structurally
related to compound methaqualone were synthesized and
biologically tested for their anticonvulsant activity. None
of those compounds are clinically used (Aziza, 1997)
because of the fact that, nearly every derivative tested in
combined neurotoxicity and anticonvulsant screenings
exhibited neurotoxicity values (TD50’s) that are less than or
only slightly higher than the effective doses (ED50’s)
consequently, the protective index (PI) corresponding to
environments to study the SAR of these compounds and
the effect of each substituent on their anticonvulsant
activity. Quinazolinone moiety joined with aromatic unit
through an aliphatic linker (CH2) to form group of novel
compounds maintaining basic features of the lead structure
methaqualone. All the target compounds contain iodine.
Iodine was selected because it has received considerable
attention in organic synthesis due to its high tolerance to air
and moisture, low-cost, nontoxic nature, and ready avail-
ability (Laznicek et al., 1985; Wang et al., 2003). The
presence of iodine at 6th and 8th positions increases the
lipophilicity of the molecules, the hydrophobic surface of
contact the absorption and the distribution (Ugale et al.,
2012). This study was carried out in hope of developing
potent, safe, new and effective anticonvulsant agents with
low dose-related toxicity and without idiosyncratic side
effects.
`
(TD50/ED50) is too low (Zappala et al., 2003).
Results and discussion
Rationale and structure-based design
Various reported facts were analyzed before the chemical
synthesis of our target compounds. First fact was: modifi-
cations at second and third positions of methaqualone have
led to the generation of many CNS active agents as
afaqualone and mecloqualone. Mecloqualone was found to
possess a significant anticonvulsant action 1.5 times more
potent than phenytoin against MES-induced convulsions
and ten times more potent than troxidone against PTZ-
Chemistry
The synthetic strategy to prepare the target compounds
(4–14) is depicted in Scheme 1: it includes two simple
reactions, first one is acetylation/benzoylation followed by
ring closure reaction for 2-amino-3,5-diiodobenzoic acid
(1) when refluxed with acetic anhydride for 1 h, converted
to benzoxazinone. This reaction afforded quantitative yield
of 6,8-diiodo-2-methyl-4H-benzo[d][1,3]oxazin-4-one (2).
Second reaction is a nucleophilic displacement reaction for
the oxygen of benzoxazinone with the nitrogen of amino
group upon treating with substituted aromatic amines.
These amines were selected following a second manual
method of the Hansch approach to drug design suggested
by Topliss (1977). Hansch approach is a procedure in
which an initial small group of compounds are selected,
tested, and ordered according to potency.
`
induced seizures (Zappala et al., 2003). Second fact
explained that substitution of the quinazolinone ring with
halogens or electron rich group at 6th or 8th positions
greatly enhanced the anticonvulsant activity as in com-
pound (A) which has been reported to posses better
activity, longer duration and lower toxicity than phenytoin
and ethosuximide (Saravanan et al., 2012). Figure (1)
represents the structural similarities and pharmacophoric
features of some reported anticonvulsants quinazolinones
and our designed compounds. Based on the previously
mentioned facts, it appeared to us that considerable
promise for discovering of new anticonvulsants might be
found through the synthesis of structural analogs of these
compounds.
The title compounds were designed to contain unsub-
stituted, monosubstituted, and disubstituted aromatic ring
with different kinds of halogens and other hydrophobic and
hydrophilic groups of different electronic environment
either electronic rich or electronic deficient groups to study
SAR of these compounds and compare the differences in
their anticonvulsant activity. The second reaction was done
by refluxing compound (2) with the appropriate aromatic
amine in dry conditions for 6 h to give target compounds
of 6,8-diiodo-2-methyl-3-substituted-quinazolin-4(3H)-one
(4–14).
Figure (1) showed that structure of the title compounds
(4–14) fulfilled all the pharmacophoric structural require-
ments. These requirements include: the presence of qui-
nazolin-4(3H)-one moiety as hydrophobic portion, N as
electron donor system, the presence of carbonyl group and
another hydrophobic distal aryl ring responsible for con-
trolling the pharmacokinetic properties of the antiepileptic
activity.
Biological screening
The present study was carried out to prepare the target
compounds as hybrid molecules. These molecules formed
of quinazolinone ring system joined with aromatic amine
derivatives. The target compounds were also designed to
contain different substituents with different electronic
The anticonvulsant activity of the target compounds were
evaluated by the use of standard techniques (Krall et al.,
1968; Yogeeswari et al., 2005), while the acute neurotox-
icity was done according to the method described by
123

Med Chem Res
Fig. 1 Structural similarities
and pharmacophoric features of
reported and designed
quinazolinones (4–14) as
anticonvulsants
O
N
O
N
H2N
N
N
F
Afaqualone
Methaqualone
Cl
O
N
R
N
O
Br
N
Mecloqualone
N
Br
Hydrogen bonding site
(A)
R
O
I
N
Hydrophobic domain
N
I
Hydrophobic domain
Electron donor moiety
Title compounds
O
N
been proven to be a good predictor of clinical efficacy
against generalized spike-wave epilepsies which are known
as the absence seizures. Thus, the MES and scPTZ screens
have become the most widely employed seizure models
for initial identification of candidate anticonvulsants
(Rogawski, 2006). The initial anticonvulsant evaluation
showed that all of the target compounds were active in
mice i.p. against PTZ at 0.5 mmol/kg, among which
compounds 5, 6, 8, 9, and 13 showed 100 % protection,
compounds 4, 7, 10, and 14 showed 66 % protection while
compounds 11 and 12 showed 50 % protection. For the
MES test, compounds 5, 6, and 8 showed 100 % protec-
tion, compounds 7, 9, 13, and 14 showed 66 % protection,
compound 4 showed 50 % protection while compounds
10, 11, and 12 presented 33 % protection. The results
explained in Table (1).
COOH
I
I
(CH3CO)2O
reflux 1hr
O
NH2
I
I
(2)
(1)
R
NH2
O
R
I
N
dry pyridine
reflux 6hrs
N
I
(3)
4) R = H
5) R = 4Cl
6) R = 4F
7) R = 4I
8) R = 4Br
9) R = 3NO2
10)R= 4OCH3
11)R= 4CH3
12)R= 3CF3
13)R= 3Cl
14)R= 3,4Cl2
From the result of preliminary screening, the most active
compounds 5, 6, and 8 were subjected to further investiga-
tions in mice i.p. at different doses for quantification of their
anticonvulsant activity which indicated by the effective dose
causing protection for 50 % of mice (ED50) and neurotox-
icity which indicated by median toxic dose producing
minimal neurological toxicity in 50 % of mice (TD50).
As demonstrated in Table (2), the selected compounds 5,
6, and 8 exhibited anticonvulsant activity against PTZ-
induced seizure with (ED50) values of 150, 160, and
138 mg/kg, respectively. Methaqualone and valproate were
used as reference drugs produced (ED50) values of 200 and
300 mg/kg, respectively. The (ED50) values of the selected
compounds were found to be smaller than the reference
anticonvulsant drugs at molar doses. The protective
index (PI) = (TD50/ED50) is defined to be an index rep-
resenting the margin of safety and tolerability between
Scheme 1 Synthesis of target compounds 4–14
Dunham and Miya (1957). The preliminary screening was
performed at 0.5 mmol/kg of all synthesized compounds
(4–14) by chemical induction of the convulsions using of
pentylenetetrazole (PTZ) and electrical induction of con-
vulsions using maximal electroshock (MES) models of
seizures (Crivori et al., 2000). The MES model has served
to identify the anticonvulsants that are functionally similar
to phenytoin. Activity in this model seems highly predic-
tive of the ability of those anticonvulsants to protect against
generalized tonic–clonic seizures. The scPTZ model has
123

Med Chem Res
the most potent compounds 6 and 8 were found to be
higher than that of the reference anticonvulsant drugs as
shown in Table (2). The results of the anticonvulsion
screening methods in the present study showed that some
new quinazolinones were effective in controlling the sei-
zures induced by PTZ and MES. From the MES test, one
can suggest that the anti-seizure effects of agents or drugs
that suppress tonic–clonic seizures through raising sei-
zure’s threshold and/or possessing the ability to prevent the
spread of seizure discharge throughout neuronal tissues
(Dunham and Miya, 1957).
Table 1 Preliminary anticonvulsant activity of the newly synthesized
compounds and C log P values of the most potent compounds,
comparing compounds (0.5 mmol/kg), methaqualone (0.8 mmol/kg),
and valproate (1.8 mmol/kg)
Compound
PTZ (% protection) MES (% protection) C log P
4
66
100
100
66
50
100
100
66
–
5
6.03844
6
5.88844
7
–
8
100
100
66
100
66
5.31844
9
–
Concerning their partial effectiveness, our newly syn-
thesized compounds can control the seizures induced by
PTZ and MES indicating that these compounds exhibited a
broad spectrum of anticonvulsant activity in animal models
of partial and generalized epilepsy. The high lipid solu-
bility of the target compounds might account for their good
activity, in addition, more detailed study on the GABA
pathways, neurotransmitter levels and MDR of our newly
synthesized compounds might be interesting and might
provide us with more insights for the anticonvulsant effects
of the newly synthesized quinazolinones which will be
considered extensively in our future study. However, at
present, some of our newly synthesized compounds have
relatively significant anticonvulsant effects combined with
relatively low neurotoxicity. Structure activity relationship
(SAR) studies indicated that different substitution on the
aromatic ring, exerted varied anticonvulsant activities. The
electronic nature of the substituent group attached to
the aromatic ring led to a significant variation in anticon-
vulsant activity. From the data shown above, it is clear that
the presence of electron withdrawing group at aromatic
ring enhanced the activity when compared to unsubstituted
or electron donating group in the phenyl ring. For example,
electronic withdrawing groups (mainly bromo substitution)
enhanced the anticonvulsant activity whereas non-bromo
analogs showed less activity and the order of analogs
activity was monobromo analog (8) [ monochloro analog
(5) [ monofluoro analog (6) [ monochloro and mononitro
analogs (13, 9) [ monoiodo and dichloro analogs (7, 14) [
unsubstituted analog (4) [ monomethoxy analog (10) [
monomethyl and trifluromethyl analogs (11, 12).
10
11
12
13
14
21
22
23
33
–
50
33
–
50
33
–
100
66
66
–
66
–
66
66
3.777
4.91335
6.26531
3.64597
2.76
66
66
100
66
Methaqualone 100
Valproate 100
100
100
anticonvulsant doses and doses of anticonvulsant drugs
exerting acute adverse effects like sedation, motor coor-
dination impairment, ataxia, or any other neurotoxic
manifestations (Loscher and Nolting, 1991). The most
potent compounds 5, 6, and 8 had (TD50) values of 280,
360, and 330 mg/kg. These values revealed that these
agents exerted low neurological disorders. From the results
of ED50 and TD50, compounds 5, 6, and 8 had (PI) values
of 1.87, 2.25, and 2.39, which means that compounds 6 and
8 had higher (PI) values than the reference drugs meth-
aqualone and valproate as shown in Table (2). The present
results are implying high safety margin of the synthesized
compounds when compared with the reference drugs. The
therapeutic index (TI) = (LD50/ED50) is a comparison of
the amount of a therapeutic agent that causes the thera-
peutic effect to the amount that causes death in mice
`
(Zappala et al., 2003). Compounds 5, 6, and 8 had (LD50)
values of 600, 420, and 565 mg/kg with (TI) values of 4,
2.62, and 4.09. It is worthwhile to note that (TI) values of
Table 2 ED50, TD50, LD50, therapeutic index (TI) and protective index (PI) for the most active compounds 5, 6, and 8 compared to reference
drugs methaqualone and valproate
Compound
ED50 (mg/kg)
TD50 (mg/kg)
LD50 (mg/kg)
Therapeutic index (TI)
Protective index (PI)
5
150
160
138
200
300
280
360
330
400
450
600
420
565
500
500
4
1.87
2.25
2.39
2
6
2.62
4.09
2.5
8
Methaqualone
Valproate
1.66
1.5
123

Med Chem Res
Scheme 2 Synthesis of the
comparing compounds (21–23)
O
N
R1
N
Br
H2N
R2
21) R1= H, R2= H
22) R1= I, R2= H
e
n
i
d
i
O
N
s
r
COOH
(CH3CO)2O
reflux 1hr
r
R1
y
Br
h
6
y p
R1
x
r
u
d
l
O
f
e
r
NH2
R2
d
f
r
y
r
R2
e
p
y
l
u
r
15) R1= H, R2= H
16) R1= I, R2= H
17) R1= I, R2= I
i
x
d
18) R1= H, R2= H
19) R1= I, R2= H
20) R1= I, R2= I
i
n
H2N
6
h
e
r
s
Br
O
N
Br
I
N
I
(23)
From the structure of newly synthesized compounds, we
can notice that there are two major differences between
them and the related lead structure methaquolane, first
difference is substitution at 6th and 8th position with diiodo
substituent and second difference is the presence of (CH2)
linker between aromatic moiety and quinazolinone moiety.
For practical assessment of these two differences and for
determination the role of them, the highest potent com-
pound (8) which was selected for further investigations and
quantitative study of target compounds and had best ED50,
was synthesized again with unsubstituted quinazolinone
moiety (compound 21), monoiodo substitution (compound
22) and without (CH2) linker (compound 23) as shown in
Scheme (2).
with their biological activity, an attempted correlation of
anticonvulsant activity with C log P data were calcd. for
measurement the lipophilicity factor which could be
attributed in their anticonvulsant activity. For antiepileptic
agents to be effective, they have to cross the blood brain
barrier (BBB) (Crivori et al., 2000). Crossing the brain is
therefore a crucial step in developing effective drug ther-
apies for treatment of neurological disorders. Lipophilic
substances are able to permeate into the brain interstitium
in a relatively easy way (Bhaduri et al., 1964). Deter-
mination of brain-blood partitioning in vitro is difficult,
time-consuming, expensive, not always available and not
suitable to screen a large collection of new chemicals.
Therefore, an alternative method was used based on com-
puterized models (Cambridge software). So, the C log P
values were calcd. for some compounds to reflect the
overall lipophilicity of these compounds and compare
between them. It is postulated that a C log P value of at
least 2.0 is required by a specific compound to cross the
BBB (Shank et al., 2000). The C log P data for all selected
anticonvulsant compounds (5, 6, 8, 21, 22, and 23)
explained in Table (1) and ranged from 3.777 to 6.26531.
All the compounds were found to have C log P values
above 2 which required for effective penetration in the
brain. It is worthwhile to note that the C log P values for
compounds 5, 6, and 8 which had higher potency were
higher than that of the other two compounds 21 and 22
which might explain the significant variation in their bio-
logical activity in correlation with their lipophilicity. While
compound 23 had higher C log P value than other com-
pounds and had no correlation with the lipophilicity factor.
Interestingly, the values of C log P for the selected potent
compounds agree with their potency levels, compound (8)
All of the comparing compounds were tested the same
way under the same conditions of testing target compounds
to measure their anticonvulsant activity and compare it to
that of the target compounds. The initial anticonvulsant
evaluation of these three compounds showed that com-
pounds 21 and 22 were active against PTZ and MES at
0.5 mmol/kg and they presented 66 % protection against
chemical and electrical convulsants while compound 23
presented 100 % protection in PTZ and 66 % in MES at
0.5 mmol/kg. The initial activity of these compounds were
less than that of the title compounds which indicated and
confirmed the role of diiodo substitution and (CH2) linker
in enhancement the activity of our target compounds as
anticonvulsant agents.
C log P correlation
As a trial for interpretation the correlation between
chemical structure of compounds 5, 6, 8, 21, 22, and 23
123

Med Chem Res
which had the highest activity, had also highest C log P
value (6.03844), while compound 5 which had the medium
activity, had medium C log P value (5.88844) and com-
pound (9) had lowest C log P value as its activity
(5.31844). In general, it was found that compounds having
more C log P values having higher potency as anticon-
vulsant agents.
compounds gave materials of good purity, as evidenced by
their spectral analyses and by thin layer chromatography.
All m.p. were above 300 °C.
3-Benzyl-6,8-diiodo-2-methylquinazolin-4(3H)-one (4)
1
Yield 73 %, HNMR (DMSO-d6): d 1.05 (s, 3H, CH3),
4.91 (s, 2H, CH2), 6.96–8.17 (m, 7H, Ar–H). 13C NMR
(DMSO-d6): d 21, 41, 82, 91, 122, 124., 125, 127, 128, 132,
145, 149, 155, 157, 164. Anal. Calcd. for C16H12I2N2O
(501.9): C, 38.27; H, 2.41; N, 5.58. Found C, 38.51; H,
2.61; N, 5.39. MS (EI) m/z 502.9 [M?1].
Experimental
General
All chemicals used for synthesis were purchased from
(Sigma-Aldrich). All m.p. were measured on a Griffin
melting point apparatus (Griffin) and were uncorrected.
The Infrared spectra were recorded as KBr disks on a
3-(4-Chlorobenzyl)-6,8-diiodo-2-methylquinazolin-
4(3H)-one (5)
1
Yield 70 %, HNMR (DMSO-d6): d 2.34 (s, 3H, CH3),
Nicolet IR 200 (Thermo Fisher Scientific).1HNMR and 13
C
4.69 (s, 2H, CH2), 7.01–8.23 (m, 6H, Ar–H). 13C NMR
(DMSO-d6): d 21, 44, 82, 93, 123, 126., 127, 128, 129,
132, 135, 153, 155, 162. Anal. Calcd. for C16H11ClI2N2O
(535.86): C, 35.82; H, 2.07; N, 5.22. Found C, 35.61; H,
2.31; N, 5.17. MS (EI) m/z 536.8 [M?1].
NMR was recorded in DMSO-d6 and/or CDCl3 on a Jeol
500 MHz instrument using TMS as internal standard
(chemical shifts in d ppm). MS were obtained on a JEOL-
SX-102 instrument using electron impact ionization. Sol-
vent evaporation was done under reduced pressure using
Buchi rotary evaporator. Elemental analyses (C, H, N)
were performed on a Perkin-Elmer 240C analyzer (Perkin-
Elmer). All compounds were within 0.4 % of the theo-
retical values. The elemental analyses indicated that purity
of the synthesized compounds was above 99.6 %.
3-(4-Florobenzyl)-6,8-diiodo-2-methylquinazolin-
4(3H)-one (6)
1
Yield 68 %, HNMR (DMSO-d6): d 2.43 (s, 3H, CH3),
4.87 (s, 2H, CH2), 7.11–8.43 (m, 6H, Ar–H). 13C NMR
(DMSO-d6): d 21, 44, 82, 94, 110, 117, 123, 126, 134, 142,
153, 156, 160, 164. Anal. Calcd. for C16H11FI2N2O
(519.89): C, 36.95; H, 2.13; N, 5.39. Found C, 36.71; H,
2.37; N, 5.54. MS (EI) m/z 520.8 [M?1].
6,8-Diiodo-2-methyl-4H-benzo[d][1,3]oxazin-4-one (2)
It was prepared by refluxing (3.88 g, 0.01 mol) of 2-amino-
3,5-diiodobenzoic acid (1) with appropriate amount of
acetic anhydride for 1 h. The residue obtained was evap-
orated tell complete dryness, left to cool, washed with
petroleum ether many times, collected, filtered, and dried
well in the absence of moisture.
6,8-Diiodo3-(4-iodobenzyl)-2-methylquinazolin-
4(3H)-one (7)
1
1
Yield 65 %, HNMR (DMSO-d6): d 2.49 (s, 3H, CH3),
Yield 85 %, mp: 245–247 °C; HNMR (DMSO-d6): d
4.72 (s, 2H, CH2), 7.08–8.23 (m, 6H, Ar–H). 13C NMR
(DMSO-d6): d 21, 45, 82, 93, 96, 126, 134, 138, 139, 140,
146, 153, 156, 164. Anal. Calcd. for C16H11I3N2O (627.8):
C, 30.60; H, 1.77; N, 4.46. Found C, 36.42; H, 1.93; N,
4.57. MS (EI) m/z 628.8 [M?1].
1.21(s, 3H, CH3) 7.21–8.19 (m, 2H, Ar–H). 13C NMR
(DMSO-d6): d 24, 90, 118, 138, 149, 150, 154, 158.Anal.
Calcd. For C9H5I2NO2 (412.84): C, 26.18; H, 1.22; N, 3.39.
Found C, 26.32; H, 1.01; N, 3.74. MS (EI) m/z 412.8 [M?1].
General method for preparation of test compounds (4–14)
3-(4-Bromobenzyl)-6,8-diiodo-2-methylquinazolin-
4(3H)-one (8)
They were prepared in a conical flask by mixing (0.01 mol,
4.13 g) of compound (2) with the appropriate amount
(0.01 mol) of aromatic amine derivatives in 100 ml dry
pyridine, refluxed for 6 h, cooled then treated with few
amount of 10 % hydrochloric acid and poured on crushed
ice. The obtained crystals collected by filtration and
recrystallized from ethanol or glacial acetic acid. The
method used for the preparation and isolation of the
1
Yield 62 %, HNMR (DMSO-d6): d 2.34 (s, 3H, CH3),
4.86 (s, 2H, CH2), 7.01–8.23 (m, 6H, Ar–H). 13C NMR
(DMSO-d6): d 21, 44, 82, 93, 123, 127, 128, 129, 132, 135,
138, 153, 155, 162. Anal. Calcd. for C16H11BrI2N2O
(579.81): C, 33.08; H, 1.91; N, 4.82. Found C, 32.96; H,
2.01; N, 5.11. MS (EI) m/z 580.8 [M?1].
123

Med Chem Res
6,8-Diiodo3-(3-nitrobenzyl)-2-methylquinazolin-
4(3H)-one (9)
3-(3,4-Dichlorobenzyl)-6,8-diiodo-2-methylquinazolin-
4(3H)-one (14)
1
1
Yield 58 %, HNMR (DMSO-d6): d 2.46 (s, 3H, CH3),
Yield 61 %, HNMR (DMSO-d6): d 2.19 (s, 3H, CH3),
4.92 (s, 2H, CH2), 7.14–8.41 (m, 6H, Ar–H). 13C NMR
(DMSO-d6): d 24, 45, 84, 98, 120, 123, 128, 129, 132, 137,
143, 145, 148, 152, 158, 164. Anal. Calcd. for
C16H11I2N3O3 (546.89): C, 35.13; H, 2.03; N, 7.68. Found
C, 35.41; H, 2.24; N, 7.57. MS (EI) m/z 547.8 [M?1].
4.72 (s, 2H, CH2), 6.93–8.01 (m, 5H, Ar–H). 13C NMR
(DMSO-d6): d 24, 36, 88, 98, 125, 129, 129, 132, 132, 136,
138, 145, 149, 156, 158, 165. Anal. Calcd. for
C16H10Cl2I2N2O (569.83): C, 33.66; H, 1.77; N, 4.91.
Found C, 33.87; H, 1.92; N, 5.04. MS (EI) m/z 570.8
[M?1].
6,8-Diiodo-3-(4-methoxybenzyl)-2-methylquinazolin-
4(3H)-one (10)
3-(4-Bromobenzyl)-2-methylquinazolin-4(3H)-one (21)
1
1
Yield 60 %, HNMR (DMSO-d6): d 2.31 (s, 3H, CH3),
Yield 68 %, HNMR (DMSO-d6): d 2.21 (s, 3H, CH3),
4.68 (s, 2H, CH2), 7.03–7.98 (m, 8H, Ar–H). 13C NMR
(DMSO-d6): 2 d 4, 46, 121, 123, 124, 127, 128, 130, 132,
136, 145, 149, 158, 164. Anal. Calcd. for C16H13BrN2O
(328.02): C, 58.38; H, 3.98; N, 8.51. Found C, 58.55; H,
4.21; N, 8.37. MS (EI) m/z 329 [M?1].
3.28 (s, 3H, OCH3), 4.51 (s, 2H, CH2), 7.11–8.33 (m, 6H,
Ar–H). 13C NMR (DMSO-d6): d 23, 46, 58, 85, 96, 114,
122, 130, 137, 143, 149, 156, 158, 162, 164. Anal. Calcd.
for C17H14I2N2O2 (531.91): C, 38.37; H, 2.65; N, 5.26.
Found C, 38.21; H, 2.81; N, 5.19. MS (EI) m/z 532.9
[M?1].
3-(4-Bromobenzyl)-6-iodo-2-methylquinazolin-
4(3H)-one (22)
6,8-Diiodo-2-methyl-3-(4-methylbenzyl)quinazolin-
4(3H)-one (11)
1
Yield 64 %, HNMR (DMSO-d6): d 2.19 (s, 3H, CH3),
1
Yield 65 %, HNM R (DMSO-d6): d 2.16 (s, 3H, CH3),
4.53 (s, 2H, CH2), 7.13–8.24 (m, 7H, Ar–H). 13C NMR
(DMSO-d6): d 24, 48, 96, 122, 127, 128, 132, 134, 137,
142, 146, 148, 158, 163. Anal. Calcd. for C16H12BrIN2O
(453.92): C, 42.23; H, 2.66; N, 6.16. Found C, 42.51; H,
2.81; N, 6.34. MS (EI) m/z 454.9 [M?1].
2.34 (s, 3H, CH3), 4.67 (s, 2H, CH2), 7.09–8.24 (m, 6H,
Ar–H). 13C NMR (DMSO-d6): d 21, 23, 47, 85, 96, 124,
129, 130, 133, 135, 138, 149, 154, 157, 162. Anal. Calcd.
for C17H14I2N2O (515.91): C, 39.56; H, 2.73; N, 5.43.
Found C, 39.71; H, 2.89; N, 5.61. MS (EI) m/z 516.9
[M?1].
3-(4-Bromophenyl)-6,8-diiodo-2-methylquinazolin-
4(3H)-one (23)
6,8-Diiodo-2-methyl-3-(3-trifluoromethyl)benzyl)
quinazolin-4(3H)-one (12)
1
Yield 60 %, HNMR (DMSO-d6): d 2.27 (s, 3H, CH3),
7.23–8.31 (m, 6H, Ar–H). 13C NMR (DMSO-d6): d 24, 87,
121, 126, 128, 136, 138, 138, 149, 154, 158, 162. Anal.
Calcd. for C15H9BrI2N2O (565.8): C, 31.78; H, 1.60; N,
4.94. Found C, 31.91; H, 1.89; N, 5.19. MS (EI) m/z 566.8
[M?1].
1
Yield 55 %, HNMR (DMSO-d6): d 2.34 (s, 3H, CH3),
4.78 (s, 2H, CH2), 7.19–8.31 (m, 6H, Ar–H). 13C NMR
(DMSO-d6): d 24, 48, 86, 98, 122, 124, 126, 128, 129, 132,
134, 138, 138, 149, 156, 158, 164. Anal. Calcd. for
C17H11F3I2N2O (569.89): C, 35.82; H, 1.94; N, 4.91.
Found C, 35.63; H, 2.21; N, 5.22. MS (EI) m/z 570.9
[M?1].
Pharmacological tests
3-(3-Chlorobenzyl)-6,8-diiodo-2-methylquinazolin-
4(3H)-one (13)
Adult male white Swiss albino mice weighing 20–30 g
(10–12 weeks old) were obtained from Experimental Ani-
mal Care Centre, King Abdul-Aziz University. The ani-
mals were maintained under standard conditions of
humidity, temperature (23 2 °C), and light (12 h light/
12 h dark). They were fed with a standard mice pellet diet
and had free access to water. The protocol adopted for the
testing of animals was approved by Institutional Animal
Ethics Committee (approval No: 409/432). All the trials
1
Yield 68 %, HNMR (DMSO-d6): d 2.37 (s, 3H, CH3),
4.63 (s, 2H, CH2), 7.06–8.41 (m, 6H, Ar–H). 13C NMR
(DMSO-d6): 2 d 1, 43, 84, 92, 122, 124, 126, 128, 129, 129,
132, 135, 152, 155, 161. Anal. Calcd. for C16H11ClI2N2O
(535.86): C, 35.82; H, 2.07; N, 5.22. Found C, 35.57; H,
2.28; N, 5.41. MS (EI) m/z 536.8 [M?1].
123

Med Chem Res
were carried out according to the respective internationally
valid guidelines. Each test group and vehicle control group
included six animals.The anticonvulsant activities of all
title compounds were evaluated by two models, pentylen-
tetrazole (PTZ), and maximal electroshock (MES) models
according to the reported procedures (Vogel and Vogel,
2002). The test compounds were dissolved 10 % DMSO
and injected i.p. at dose of 0.5 mmol/kg 30 min before
seizures induction. Methaqualone (0.8 mmol/kg) and
sodium valproate (1.8 mmol/kg) were used as reference
drugs. In the MES test, the electrical stimulus produced
from electroconvulsiometer was 50 mA, 60 Hz. The cur-
rent was applied for 0.2 s via auricular electrodes. Pro-
tection against the spread of MES-induced seizures
identified by the abolition of the hind leg and tonic maxi-
mal extension component of the seizure (Woodbury and
Davenport, 1952). The PTZ test was performed by the i.p.
injection of a convulsing dose of PTZ (100 mg/kg). Sei-
zures and tonic–clonic convulsions, hypnosis and death
were recorded. The highest potent compounds 5, 6, and 8
were further evaluated at different doses in PTZ model to
determine their protective and therapeutic indexes. Groups
of 6 mice each were given a range of i.p. doses of the
selected drug until at least four points were established in
the range of 10–90 % seizure protection or minimal
observed neurotoxicity. From the plots of these data,
(ED50) was determined, slopes of the regression line and
the standard error were calcd. using a computer program
based on the method described by Finney (1971). The
animals considered to be protected if showed no convul-
sion within 1 h after convulsive drug administration
(Everett and Richards, 1952). Neurological toxicity (NT)
was determined by rotrod test in mice using the method
reported by Dunham and Miya (1957). In brief, group of
animals (mice) were trained to balance on a rotating rod
(3 cm diameter and 6 rpm speed) and they allowed three
attempts to remain on the rotating rod for 20 s. The trained
animals were treated with the tested compounds at a vari-
ous dose levels by i.p. administration. The tested com-
pounds considered to be neurotoxic at a particular dose
level if the trained animal showed lack of Rolling Roller
Performance. The trained animals were tested in this
manner at 30 min and 4 h after the drug administration and
then the neurotoxic effect was recorded in terms of median
toxic dose (TD50). The protective index was determined
from the equation (PI = TD50/ED50). The median lethal
dose (LD50), the dose that causes 50 % mortality in mice
was determined from dose-response curves with at least
four doses according to the reported method by Litchfield
and Wilcoxon (1949). Therapeutic index was determined
from the equation (TI = LD50/ED50).
Conclusions
New derivatives of 4(3H)-quinazolinones were synthesized
and evaluated for their anticonvulsant activity and acute
neurotoxicity in mice. The results of this study demon-
strated that some 6,8-diiodo-2-methyl-3-substituted-4(3H)-
quinazolinones derivatives possess a good anticonvulsant
activity, specially, compounds 5, 6, and 8 showed better
anticonvulsant activity and much lower toxicity compared
with the reference drugs. The obtained results showed that
compounds 5, 6, and 8 could be useful as a template for
future design, optimization, and investigation to produce
more active analogs.
Acknowledgments The authors extend their appreciation to the
Deanship of Scientific Research at Taibah University, Al-madinah
Al-munawarah, KSA for funding the whole work through the research
group Project No. 409/432.
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