Design and synthesis of some new quinazolin-4-(3H)-ones as anticonvulsant and antidepressant agents

Article abstract of DOI:10.1007/s12272-013-0004-y

A series of 3-[(4-substituted-benzylidene)-amino]-2-phenyl-3H-quinazolin-4- ones (5a-k) were synthesized by reacting 3-amino-2-phenyl-1H-quinazolin-4-one with p-hydroxybenzaldehyde, and then further with various alkyl/benzyl halides or substituted phenacy

Full text of DOI:10.1007/s12272-013-0004-y

Arch. Pharm. Res. (2013) 36:61–68
DOI 10.1007/s12272-013-0004-y
RESEARCH ARTICLE
Design and synthesis of some new quinazolin-4-(3H)-ones
as anticonvulsant and antidepressant agents
•
Mohd Amir Israr Ali Mohd Zaheen Hassan
•
Published online: 17 January 2013
Ó The Pharmaceutical Society of Korea and Springer Science+Business Media Dordrecht 2013
Abstract A series of 3-[(4-substituted-benzylidene)-amino]-
2-phenyl-3H-quinazolin-4-ones (5a–k) were synthesized
by reacting 3-amino-2-phenyl-1H-quinazolin-4-one with
p-hydroxybenzaldehyde, and then further with various alkyl/
benzyl halides or substituted phenacyl bromides. The structures
of the compounds were confirmed on the basis of IR, NMR, MS
and elemental analysis. Anticonvulsant activities were evalu-
ated using the MES and scPTZ tests. Some of the selected
compounds were evaluated for antidepressant activity by
forced swim pool test. Compound 3-[(4-butoxy-benzylidene)-
amino]-2-phenyl-3H-quinazolin-4-one was emerged as the
most promising anticonvulsant agent without any motor
impairment effect. The whole brain GABA estimation of brain
homogenate indicated that the anticonvulsant activity of above
mentioned quinazolinone derivatives might be due to an
increased GABA concentration.
(AEDs) of diverse classes such as phenytoin, carbamaze-
pine, phenobarbital, valproate, lamotrigine, vigabatrin,
tiagabine, topiramate, gabapentin and levetiracetam (White
2003). These drugs, however, do carry adverse side effects
such as drowsiness, ataxia, gastrointestinal disturbance,
hepatotoxicity, megaloblastic anemia, leading to life
threatening conditions (Nicholas et al. 1998). Therefore,
there is a pressing need for safer and effective antiepileptic
drugs.
Quinazolinones are important benz-fused pyrimidone
heterocyclic compounds. A number of quinazolin-4(3H)-
ones derivatives possess vital pharmacological properties
like antihypertensive (Alagarsamy and Pathak 2007), anti-
inflammatory (Kumar et al. 2007; Alagarsamy et al. 2008),
anticonvulsant (Archana 2002; Zappala et al. 2003; Jatav
et al. 2008; Kashaw et al. 2009), antimicrobial (Grover and
Kini 2006; Pandeya et al. 2009), antitumor (Bavetsias et al.
2002; Al-Rashood et al. 2006) and antidiabetic (Malamas
and Millen 1991) and therefore, they are considered as
valuable scaffolds in drug research. In the past decades,
various quinazolin-4-(3H)-ones structurally related to
methaqualone have also been reported to exhibit potential
anticonvulsant and antidepressant properties. Moreover,
several interactions have been reported between anticon-
vulsant and antidepressant drugs and many anticonvulsants
like oxcarbazepine, piperine, and lamotrigine etc. have
displayed intrinsic antidepressant properties (Wang et al.
2009). Recently Schiff bases have also gained huge interest
due to its seizure protective action (Shaquiquzzaman et al.
2012).
Keywords Quinazolinone ꢀ Schiff base ꢀ Anticonvulsant ꢀ
Antidepressant ꢀ GABA
Introduction
Epilepsy is one of the most prevalent CNS disorder in
which brain experiences episodes of irregular electrical
discharge. The disease has affected more than 60 million
people across the globe, according to the epidemiological
studies of WHO (Loscher 1998). The present pharmaco-
therapy of epilepsy covers more than 20 antiepileptic drugs
Encouraged by these observations and in continuation of
our ongoing research program on anticonvulsants (Amir
et al. 2010, 2012), herein we plan to synthesize some new
quinazolin-4-(3H)-one derivatives by incorporating Schiff
base pharmacophore, in a hope to get better anticonvulsant
M. Amir (&) ꢀ I. Ali ꢀ M. Z. Hassan
Department of Pharmaceutical Chemistry, Faculty of Pharmacy,
Hamdard University, Hamdard Nagar, New Delhi 110062, India
e-mail: mamir_s2003@yahoo.co.in
123

62
M. Amir et al.
and antidepressant agents. The designed molecules have all
the pharmacophoric fragments to meet the structural
requirements essential for anticonvulsant activity (Fig. 1).
ethanol gave white powdery solid (yield: 75 %; m.p:
120–122 °C).
3-Amino-2-hydroxy-2-phenyl-2,3-dihydroquinazolin-
4(1H)-one (2)
Materials and methods
A mixture of compound 1 (12.55 mmol) and hydrazine
hydrate (99 %) (15 mmol) in absolute ethanol (20 mL) was
refluxed for 2 h. After completion of the reaction, ethanol
was removed by evaporation. The reaction mixture was
then diluted with ethyl acetate and washed with brine
(30 mL). The organic extract was dried over anhydrous
sodium sulphate, filtered and evaporated to dryness. The
white colored product thus formed gives yellow color with
ninhydrine reagent.
All the chemicals used in the synthesis were supplied by E.
Merck and S.D. Fine Chemicals. Melting points were
determined by open capillary tube method and are uncor-
rected. Purity of the compounds was checked on silica gel
G plates using iodine vapors as visualizing agents. IR
spectra were obtained on a Perkin-Elmer 1720 FT-IR
spectrometer (KBr pellets). The 1H-NMR spectra were
measured on a Bruker Avance-400 instrument (400 MHz).
Chemical shifts are reported in ppm downfield from tetr-
amethysilane (TMS) as the internal standard. Mass spectra
were recorded at Waters Synapt Mass spectrometer,
UPLC-MS/MS.
Yield: 70 %; m.p: 160–162 °C; IR (KBr) mmax cm-1
:
3,367 (NH), 3,405 (br, OH), 1,680 (C=O); 1H-NMR
(400 MHz, DMSO-d6): d 12.53 (s, 1H, OH, D2O
exchangeable), 10.17 (br s, 1H, NH, D2O exchangeable),
8.64–7.12 (m, 9H, ArH), 4.68 (br s, 2H, NH2, D2O
exchangeable); MS: m/z 256 (M ? 1)?.
Synthesis
As depicted in scheme 1, a series of 3-[(4-aryl/alkyloxy-ben-
zylidene)-amino]-2-phenyl-3H-quinazolin-4-ones (5a–k) was
prepared starting from anthranillic acid.
3-Amino-2-phenyl-1H-quinazolin-4-one (3)
To a solution of 2 (1 g, 10 mmol) in ethanol (20 mL) was
added glacial acetic acid (2 mL) at room temperature and
the reaction mixture was refluxed for 4 h. After completion
of the reaction, it was poured into ice cold water. The white
precipitate thus obtained was filtered, dried and recrystal-
lized from ethyl acetate which gives orange color with
ninhydrine reagent.
2-Phenyl-benzo[d][1,3]oxazin-4-one (1)
A mixture of anthranilic acid (36.5 mmol) and benzoyl
chloride (54.7 mmol) in pyridine (15 mL) was stirred for
1 h maintaining the temperature 0–5 °C. The semi solid
that was formed on stirring was washed with NaHCO3
solution and air dried. Recrystallization from absolute
Yield: 72 %; m.p: 171–173 °C; IR (KBr) mmax cm-1
:
1
3,354 (NH), 1,692 (C=O); H-NMR (400 MHz, CDCl3):
Fig. 1 Development of four-
R O
point pharmacophore model,
R-aryl ring center or lipophilic
group; D an electron donor
D
O
D
O
HD
H
atom; HA a hydrogen bond
acceptor; HD a hydrogen bond
donor
D O
H O
N
N
H
HD
N
A
A
HA
N
N N
S
A
H
HA
N
Cl HD H
HA
Aryl semicarbazone
Quinazolone-Schiff base derivatives
Ralitoline
HA
D
O
D
H
D
N
O
S
O
OH N
N
H
A
A
HD
N
H
H
HD
A
N
H N
HD
2
Cl
O
HA
O
HA
F
Carbamazipine
Zonisamide
Progabide
123

Design and synthesis
63
O
O
O
O
NH2
OH
NH2
Ph
N
OH
NH2
NH2NH2 .H2O
EtOH
GAA
N
O
PhCOCl
Pyridine
EtOH
N
H
2
N
3
N
1
Ph
Ph
Anthranilic acid
OH
O
O
O
N
R
N
N
4-OH - PhCHO
GAA, EtOH
N
DMF,K2CO3
RX
N
N
Ph
Ph
5(a-k)
4
R = 5a: methyl; 5b: ethyl; 5c: allyl; 5d: propyl; 5e: isopropyl; 5f: butyl; 5g: benzyl; 5h: CH2COC6H5;
5i: CH2CO-C6H4-p-OCH3; 5j: CH2CO-C6H4-p-F; 5k: CH2CO-C6H4-p-NO2
Scheme 1 Synthesis of quinazolinone Schiff base derivatives (5a–k)
d 8.33–7.50 (m, 9H, ArH), 5.03 (br s, 2H, NH2, D2O
exchangeable); MS: m/z 238 (M ? 1)?.
8.34–6.87 (m, 13H, ArH), 3.99 (s, 3H, OCH3); Mass m/z,
356 (M ? 1)?; Anal. Calcd for C22H17N3O2: C, 74.35, H,
4.82, N, 11.82; Found: C, 74.31; H, 4.79; N, 11.78 %.
3[(4-Hydroxybenzylidene)-amino]-2-phenyl-3H-
quinazolin-4-one (4)
3-[(4-Ethoxybenzylidene)amino]-2-phenyl-3H-quinazolin-
4-one (5b) Yield: 75 %; m.p: 150–152 °C; IR (KBr) mmax
1
A mixture of compound 3 (2.1 mmol), 4-hydroxybenzal-
dehyde (2.1 mmol), concentrated HCl (1 mL) and glacial
acetic acid (2 mL) in ethanol (25 mL) was refluxed on a
steam bath for 2 h. The solution was then cooled and solid
thus separated out was filtered, washed with water, air
dried, and recrystallized from absolute ethanol. Yield:
75 %; m.p: 163–165 °C. IR (KBr) mmax cm-1: 3,354 (NH),
cm-1: 1,682 (C=O), 1,651 (N=C), 1,249 (C–O); H-NMR
(400 MHz, CDCl3): d 8.87 (s, 1H, N=CH), 8.31–6.91 (m,
13H, ArH), 3.98 (q, 2H, J = 6.6 Hz, OCH2), 1.72 (t, 3H,
J = 7.2 Hz, CH3); Mass m/z, 370 (M ? 1)?; Anal. Calcd
for C23H19N3O2: C, 74.78, H, 5.18, N, 11.37; Found: C,
74.72; H, 5.21; N, 11.39 %.
1
1,643 (N=C), 1,692 (C=O); H-NMR (400 MHz, CDCl3):
3-[(4-Allyloxybenzylidene)amino]-2-phenyl-3H-quinazo-
lin-4-one (5c) Yield: 70 %; m.p: 117–119 °C; IR (KBr)
d 10.37 (s, 1H, OH, D2O exchangeable), 8.83 (s, 1H,
N=CH), 8.25–6.87 (m, 13H, ArH); MS: m/z 342 (M ? 1)?.
1
mmax cm-1: 1,678 (C=O), 1,651 (N=C), 1,249 (C–O); H-
NMR (400 MHz, CDCl3): d 8.86 (s, 1H, N=CH),
8.31–6.97 (m, 13H, ArH), 6.13–6.04 (m, 1H, CH=CH2),
5.48–5.32 (m, 2H, CH=CH2), 4.64–4.60 (q, 2H,
J = 5.2 Hz, OCH2); Mass m/z, 382 (M ? 1)?; Anal. Calcd
for C24H19N3O2: C, 75.57, H, 5.02, N, 11.02; Found: C,
75.53; H, 5.04; N, 11.06 %.
3-[(4-Substituted-benzylidene)-amino]-2-phenyl-3H-
quinazolin-4-one (5a–k)
To a mixture of 3[(4-hydroxybenzylidene)-amino]-2-phe-
nyl-3H-quinazolin-4-one (4, 1.45 mmol) and anhydrous
potassium carbonate (2.17 mmol) in DMF (15 mL), the
corresponding Alkyl/benzyl halides or substituted phenacyl
bromides (0.00145 mol) were added drop-wise while stir-
ring and maintaining the temperature of the reaction mix-
ture at 0–5 °C. Stirring was continued for 4 h at this
temperature and then 2 h at room temperature. After
completion of reaction, the reaction mixture was poured
into ice cooled water, neutralized with acetic acid and the
precipitate obtained was filtered, dried and recrystallized
from ethyl acetate.
2-Phenyl-3-[(4-propoxybenzylidene)amino]-3H-quinazo-
lin-4-one (5d) Yield: 72 %; m.p: 125–127 °C; IR (KBr)
1
mmax cm-1: 1,679 (C=O), 1,653 (N=C), 1,240 (C–O); H-
NMR (400 MHz, CDCl3): d 8.85 (s, 1H, N=CH),
8.37–6.89 (m, 13H, ArH), 3.97 (t, 2H, J = 6.6 Hz, OCH2),
1.88–1.78 (m, 2H, CH2), 1.04 (t, 3H, J = 7.2 Hz, CH3);
Mass m/z, 384 (M ? 1)?; Anal. Calcd for C24H21N3O2: C,
75.18, H, 5.52, N, 10.96; Found: C, 75.03; H, 5.50; N,
10.98 %.
3-[(4-Methoxybenzylidene)amino]-2-phenyl-3H-quinazo-
lin-4-one (5a) Yield: 70 %; m.p: 190–192 °C; IR (KBr)
3-[(4-Iso-propoxybenzylidene)amino]-2-phenyl-3H-qui-
nazolin-4-one (5e) Yield: 65 %; m.p: 109–111 °C; IR
(KBr) mmax cm-1: 1,684 (C=O), 1,650 (N=C), 1,247 (C–O);
1H-NMR (400 MHz, CDCl3): d 8.83 (s, 1H, N=CH),
1
mmax cm-1: 1,672 (C=O), 1,644 (N=C), 1,241 (C–O); H-
NMR (400 MHz, CDCl3) : d 8.82 (s, 1H, N=CH),
123

64
M. Amir et al.
1
8.3–6.98 (m, 13H, ArH), 4.70–4.64 (m, 1H, OCH),1.39 (d,
6H, J = 6.0 Hz, 2CH3); Mass m/z, 384 (M ? 1)?; Anal.
Calcd for C24H21N3O2: C, 75.18, H, 5.52, N, 10.96; Found:
C, 75.07; H, 5.55; N, 10.95 %.
(N=C), 1,247 (C–O); H-NMR (400 MHz, CDCl3): d 8.81
(s, 1H, N=CH), 8.20–6.90 (m, 17H, ArH), 5.28 (s, 2H,
CH2); Mass m/z, 505 (M ? 1)?; Anal. Calcd for
C29H20N4O5: C, 69.04, H, 4.00, N, 11.11; Found: C, 69.10;
H, 4.02; N, 11.15 %.
3-[(4-Butoxybenzylidene)amino]-2-phenyl-3H-quinazolin-
4-one (5f) Yield: 64 %; m.p: 89–91 °C; IR (KBr) mmax
1
cm-1: 1,679 (C=O), 1,643 (N=C), 1,245 (C–O); H-NMR
Pharmacology
(400 MHz, CDCl3): d 8.86 (s, 1H, N=CH), 8.38–6.90 (m,
13H, ArH), 4.01 (t, 2H, J = 6.4 Hz, OCH2), 1.82–1.75 (m,
2H, OCH2CH2), 1.53–1.48 (m, 2H, CH2CH3), 0.99 (t, 3H,
J = 7.2 Hz, CH3); Mass m/z, 398 (M ? 1)?; Anal. Calcd
for C25H23N3O2: C, 75.54, H, 5.83, N, 10.57; Found: C,
75.50; H, 5.87; N, 10.53 %.
The anticonvulsant activity of all the synthesized com-
pounds (5a–k) was performed as per the protocol of An-
tiepiletic Drug Development (ADD) program by National
Institute of Neurological Disorders and Stroke (NINDS).
The preliminary anticonvulsant screening was carried out
by maximal electroshock (MES) (Krall, et al. 1978) and
subcutaneous pentylenetetrazole tests (scPTZ) (Swinyard
1989). Minimal motor impairment was assessed by rotarod
method (Dunham and Miya 1957). Compounds were
administered intra-peritoneal as a solution in polyethyl-
eneglycol (PEG) and tested using three graded doses of 30,
100 and 300 mg/kg at two different time intervals
(Table 1). Antidepressant activity was carried out by
forced swim test (Porsolt et al. 1978) and the results are
presented in Table 2. All the pharmacological experiments
were conducted in compliance with ethical principles after
Institutional Animal Ethics Committee (IAEC) approval
and the animals were obtained from the Central Animal
House Facility, Hamdard University, New Delhi (Form no.
460; Registration number 173/CPCSEA; Registration date;
28 January 2000).
3-[(4-Benzyloxybenzylidene)amino]-2-phenyl-3H-quinazo-
lin-4-one (5g) Yield: 65 %; m.p: 95–97 °C; IR (KBr)
mmax cm-1: 1,685 (C=O), 1,643 (N=C), 1,246 (C–O);
1H-NMR (400 MHz, CDCl3): d 8.88 (s, 1H, N=CH),
8.32–6.94 (m, 18H, ArH), 5.10 (s, 2H, OCH2); Mass m/z,
384 (M ? 1)?; Anal. Calcd for C28H21N3O2: C, 77.94, H,
4.91, N, 9.74; Found: C, 77.99; H, 4.95; N, 9.71 %.
2-Phenyl-3[(4-(2-oxo-2-phenylethoxy)benzylidene)-amino]-
3H-quinazolin-4-one (5h) Yield: 65 %; m.p: 158–160 °C;
IR (KBr) mmax cm-1: 1,734, 1,667 (C=O), 1,645 (N=C),
1
1,247 (C–O); H-NMR (400 MHz, CDCl3): d 8.93 (s, 1H,
N=CH), 8.38–6.95 (m, 18H, ArH), 5.36 (s, 2H, CH2); Mass
m/z, 460 (M ? 1)?; Anal. Calcd for C29H21N3O3: C, 75.80,
H, 4.61, N, 9.14; Found: C, 75.45; H, 4.63; N, 9.12 %.
3-[(4-(2-(4-Methoxyphenyl)-2-oxo-ethoxy)benzylidene)-amino]-
2-phenyl-3H-quinazolin-4-one (5i) Yield: 62 %; m.p:
191–193 °C; IR (KBr) mmax cm-1: 1,737, 1,677 (C=O),
Maximal electroshock seizure (MES) test
1
1,646 (N=C), 1,242 (C–O); H-NMR (400 MHz, DMSO-
Maximal seizures were induced by the application of
electrical current to the brain via corneal electrodes. For all
tests based on MES convulsions, 60 Hz of alternating
current (50 mA) was delivered for 0.2 s by corneal elec-
trodes which had been primed with an electrolyte solution
containing an anesthetic agent (0.5 % tetracaine HCl).
Abolition of the hind limb tonic extensor was recorded as a
measurement of anticonvulsant activity (Krall et al. 1978).
d6): d 8.80 (s, 1H, N=CH), 8.23–6.86 (m, 17H, ArH), 5.32
(s, 2H, CH2), 3.91(s, 3H, OCH3); Mass m/z, 490 (M ? 1)?;
Anal. Calcd for C30H23N3O4: C, 73.61, H, 4.74, N, 8.58;
Found: C, 73.65; H, 4.72; N, 8.57 %.
3-[(4-(2-(4-Fluorophenyl)-2-oxo-ethoxy)benzylidene)-amino]-2-
phenyl-3H-quinazolin-4-one (5j) Yield: 63 %; m.p: 180–
182 °C; IR (KBr) mmax cm-1: 1,739, 1,679 (C=O), 1,644
1
(N=C), 1,257 (C–O); H-NMR (400 MHz, CDCl3): d 8.93
Subcutaneous PTZ seizure (scPTZ) test
(s, 1H, N=CH), 8.38–6.94 (m, 17H, ArH), 5.30 (s, 2H,
CH2); Mass m/z, 478 (M ? 1)?; Anal. Calcd for
C29H20FN3O3: C, 72.95, H, 4.22, N, 8.80; Found: C, 72.91;
H, 4.24; N, 8.78 %.
A PTZ dose of 85 mg/kg administered subcutaneously to
mice causes seizures in more than 97 % of the animals
(CD97: 85 mg/kg). The animals were pretreated with var-
ious doses of the test compounds and control group
received only subcutaneous PTZ solution (in 0.9 % sodium
chloride) in the posterior midline of the mice and the onset
and severity of convulsion was noted (Swinyard 1989).
3-[(4-(2-(4-Nitrophenyl)-2-oxo-ethoxy)benzylidene)-amino]-2-
phenyl-3H-quinazolin-4-one (5k) Yield: 60 %; m.p: 135–
137 °C; IR (KBr) mmax cm-1: 1,729, 1,671 (C=O), 1,638
123

Design and synthesis
65
Table 1 Anticonvulsant and neurotoxicity screening of synthesized compounds (4, 5a–k)
Compound
R
C Log P
MESa
scPTZa
0.5 h
Motor impairment
0.5 h
4.0 h
4.0 h
0.5 h
4.0 h
4
H
3.00
3.37
3.90
4.17
4.43
4.25
4.96
5.02
–
300
300
100
100
100
100
30
300
–
–
–
–
–
–
–
–
–
–
300
–
5a
5b
5c
5d
5e
5f
–CH3
–
300
300
100
100
100
100
–
–C2H5
–
–
–
–CH2–CH=CH2
–CH2CH2CH3
–CH(CH3)2
–CH2CH2CH2CH3
100
30
–
100
100
–
–
–
–
30
–
30
–
–
5g
100
–
CH2
O
5h
4.44
100
100
100
300
–
–
CH2
O
5i
5j
4.52
4.50
–
–
300
–
–
–
300
–
–
–
–
O
CH2
O
300
F
CH2
O
5 k
4.20
–
–
–
–
300
300
NO2
CH2
Phenytoinb
Ethosuximideb
Carbamazepineb
Valproic acidb
a
–
–
–
–
–
–
–
–
30
–
30
–
–
–
–
–
–
100
–
100
–
300
100
300
30
–
–
100
–
300
–
–
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 mice. The animals were examined 0.5 and 4.0 h after injection was made. The dash (–) indicates an absence of activity at
maximum dose administered
b
Reported activity (show 100 % protection at respective dose)
Motor impairment test
then given an i.p. injection (100 mg/kg) of the test com-
pounds 60 min before the test session. The duration of
passive floating without struggling was recorded during the
last 4 min of the 6 min testing period as the immobility
time (Porsolt et al. 1978).
Neurotoxicity of all the test compounds was evaluated
using rotarod test. Mice were trained to balance on the
rotating rod (3.2 cm diameter) that rotates at 6 rpm.
Trained animals were treated with test compounds at gra-
ded doses of 30, 100 and 300 mg/kg administered intra-
peritoneally. Neurotoxicity was determined by the inability
of the animal to remain on the rod for 1 min (Dunham and
Miya 1957).
Brain GABA estimation
The whole brain GABA estimation was performed after 2 h
of drug administration (100 mg/kg, i.p.) in mouse brain by
spectrophotometric method as described earlier (Gokani
et al. 1979). After the dosing the animals were decapitated
and their brains were dropped into vials and rinsed with
ice-cold isotonic saline followed by homogenization with
0.1 mmol/L phosphate buffer (pH 7.4). The homogenate
(10 % w/v) was then centrifuged at 20,000 9 g for 30 min
Porsolt’s swim test
Antidepressant activity was evaluated using the forced
swim test (FST). Before starting the test the animals were
trained to swim (24 h before). These trained animals were
123

66
M. Amir et al.
Table 2 Antidepressant activities of some selected compounds in FST
Compounda
R
Duration of Immobility (s)c
Change from control (%)
4
H
166.83 6.41 NS
121.16 6.81**
133.0 5.69*
?2.87
–25.28
–17.98
–27.02
–15.41
5c
5d
5f
5g
–CH2–CH=CH2
–CH2CH2CH3
–CH2CH2CH2CH3
118.33 6.72**
137.16 6.06*
CH2
5h
109.66 6.09**
–32.37
O
CH2
Fluoxetineb
–
–
64.50 5.90**
162.16 6.04
–60.22
–
Control
a
The compounds were tested at a dose of 100 mg/kg (i.p.)
Standard drug was tested at a dose of 20 mg/kg (i.p.)
b
c
Each value represents the mean SEM of six mice. The CNS depressant effect was compared with respect to standard drug
* p \ 0.05, ** p \ 0.01, NS p [ 0.05. Data was analyzed by unpaired student’s t test
1
FT-IR, H-NMR and mass spectrum. FT-IR spectrum of
and the supernatant so formed was used for the biochem-
ical estimations.
compound 5a revealed three bands for C=O, N=C, and
C–O at 1,672, 1,644, and 1,241 cm-1, respectively. The
1H-NMR spectrum of compound 5a showed a singlet for
OCH3 protons at d 3.99 ppm. A singlet for N=CH proton
was obtained at d 8.82 ppm and aryl ring protons resonated
at d 6.87–8.34.
Results and discussion
3-[(4-Substituted-benzylidene)-amino]-2-phenyl-3H-qui-
nazolin-4-ones (5a–k) were synthesized by the method
outlined in Scheme 1. 3-Amino-2-phenyl-1H-quinazolin-4-
one (3) was prepared according to the procedure earlier
reported which involved the condensation of anthranillic
acid with benzoyl chloride, followed by refluxing with
hydrazine hydrate, and dehydrated in the presence of gla-
cial acetic acid and ethanol. FT-IR spectra showed bands at
3,354 and 1,692 cm-1 which confirms the presence of NH
Pharmacology
The protocols of Antiepileptic Drug Development (ADD)
program of NINDS, US were followed when the anticon-
vulsant screenings of the titled compounds 5(a–k) were
carried out. All the synthesized compounds were admin-
istered intraperitoneally into mice using doses of 30, 100
and 300 mg/kg and the observations were noted at two
different time intervals (0.5 and 4 h). Table 1 shows the
results of phase I pharmacological screening, comprising
MES, scPTZ and neurotoxicity. Selected compounds were
also screened for their antidepressant effect in mice using
forced swim test (FST). Preliminary anticonvulsant
screening showed that most of the compounds were active
against convulsant stimuli, indicating the anticonvulsant
potential of Schiff base derivatives.
1
and C=O stretching vibrations, respectively. The H-NMR
spectrum showed a D2O exchangeable broad singlet at d
5.03 ppm due to NH2 protons. Reaction of compound 3
with 4-hydroxybenzaldehyde in the presence of glacial
acetic acid in ethanol afforded 3[(4-hydroxybenzylidene)-
amino]-2-phenyl-3H-quinazolin-4-one (4). FT-IR spectra
of compound 4 showed bands at 3,354, 1,692 and
1,643 cm-1 due to NH, C=O and C=N groups. In 1H-
NMR, the appearance of two singlets at d 10.37 ppm (OH)
and d 8.83 ppm (N=CH) and the disappearance of NH2
protons confirm the formation of Schiff base derivative (4).
The final compounds 3-[(4-substituted-benzylidene)-
amino]-2-phenyl-3H-quinazolin-4-ones (5a–k) were syn-
thesized by the reaction of compound 4 with appropriate
alkyl/benzyl halides or substituted phenacyl bromides in
the presence of anhydrous K2CO3 in DMF. The synthe-
sized compounds were characterized by elemental analysis,
In the MES test at a dose of 30 mg/kg, compounds 5d
(R = propyl) and 5f (R = butyl) showed protection
against the electric shock induced seizure after 0.5 h.
Among them, only compound 5f retained the protection
after 4 h at the same dose, whereas compound 5d showed
protection at a higher dose of 100 mg/kg. These results
showed their rapid onset and long duration of action. In
scPTZ test, compound 5f raised the seizure threshold
123

Design and synthesis
67
against the chemoshock induced convulsion (30 mg/kg,
0.5 h; 100 mg/kg, 4 h). The promising results of 5f against
both the MES and scPTZ models are indicative of possible
involvement of sodium channel and/or GABAA receptor
complex. Other compounds showed moderate to good
anticonvulsant activity except compounds 5j and 5k, which
were found to be inactive against both the seizure tests.
The anticonvulsant activities of various alkyloxy, ben-
zyloxy and oxyarylethanone derivatives of quinazolinone
Schiff base (5a–k), were compared and the following
structure–activity relationship was obtained. Among the
3-[(4-alkyloxy-benzylidene)-amino]-2-phenyl-3H-quinazo-
lin-4-ones (5a–f), the alkyl substitution and length of the
alkyl chain at the alkyloxy group appeared to have a direct
relationship with anticonvulsant activities of these com-
pounds. With the increase in alkyl chain length, anticon-
vulsant protections also increase (5f, butyl [ 5d, propyl [
5c, allyl [ 5e, isopropyl [ 5b, ethyl [ 5a, methyl). It was
also noted that replacement of alkyloxy groups with a ben-
zyloxy group (5g) resulted in decreased anticonvulsant
activity. In the late 19th century acetophenone (an ingredient
of herbal drug Anise) was a clinically available anticonvul-
sant under the drug named hypnone (Bartholow 1899).
Therefore, it would be worthwhile to introduce an aceto-
phenone like pharmacophore into the benzylidene moiety to
get oxy-arylethanone derivatives (5h–k).
Partition coefficient (Log P) is an imperative physico-
chemical marker of drug permeability across the blood
brain barrier (BBB) for inadequate drug concentration in
crucial brain areas (Kwan and Brodie 2005). Therefore,
partition coefficients of all the compounds were calculated
to establish the correlation between C Log P and anticon-
vulsant activity (Table 1). The lipophilicity of compounds
4 (C Log P 3.0) and 5a–f (C Log P 3.37–4.96) was
increased with increasing the length of aliphatic chain from
–H to n-butyl, which consequently enhanced the anticon-
vulsant potency due to increased BBB crossing capacity.
However, on replacement with bulkier benzyl and aryl-
ethanone groups (5g–k), the potency might be decreased
due to steric hindrance at the receptor site. Moreover,
electron withdrawing groups like F and NO2 at the aryl
ethanones resulted in the loss of activity due to reduction in
their BBB crossing capacity.
Antidepressant study
Due to the several reports regarding the interactions among
antidepressant and AEDs, only selected compounds (4, 5c,
5d, 5f, 5g and 5h) were evaluated for antidepressant activity
by forced swimming test in mice at a dose of 100 mg/kg,
and compared with the standard drug fluoxetine (20 mg/kg)
(Table 2). Results of FST revealed that compounds 5c
(-25.28 %), 5f (-27.02 %) and 5h (-32.37 %) exhibited
significant (p \ 0.01) reduction in the immobility time
compared to the control, while compounds 5d (-17.98 %)
and 5g (-15.41 %) showed moderate antidepressant
activity (p \ 0.05), whereas compound 2 (HBQ) did not
show any antidepressant activity. Therefore, derivatization
of HBQ into its alkyloxy/oxy-phenylethanone derivatives
also resulted in the enhanced antidepressant activity.
Among the oxy-arylethanone derivatives, compound
having unsubstituted phenyl ring (5h) was found to be
active in both MES and scPTZ tests. When an electron
releasing group was introduced in the phenyl ring (5i)
activity was found to be decreased, whereas substitution
with an electron withdrawing groups like F (5j) and NO2
(5k) resulted in the loss of anticonvulsant activity. The
anticonvulsant activity revealed on comparison that com-
pounds having alkyloxy groups (5a–f) were found to be
more active than compounds having oxy-arylethanone
groups (5h–k).
Estimation of GABA level in the mice brain
To further explore the effects of alkyloxy and oxy-
phenylethanone substitution on Schiff base derivatives,
activity of these compounds were compared with that of
intermediate 3-[(4-hydroxybenzylidene)-amino]-2-phenyl-
3H-quinazolin-4-ones (4, HBQ). HBQ (R=H) showed
protection only at a maximum dose of 300 mg/kg in both
MES and scPTZ screenings, indicating that derivatization
of HBQ into its alkyloxy/oxy-phenylethanone derivatives
resulted in enhanced anticonvulsant activity.
To further explore the seizure protection mechanism of the
most potent anticonvulsant compounds 5d and 5f (active
against both MES and scPTZ), whole brain GABA esti-
mation was also carried out (Table 3). The standard drug
Table 3 GABA estimation of some selected compounds in mice
whole brain
S. no. Compound GABA Conc. (lg/100 mg tissue)a % Increase
1.
2.
3.
4.
a
5d
5f
58.33 3.70 NS
71.5 3.57**
9.37
34.07
83.12
–
Results from the rotarod motor impairment test (Table 1)
demonstrated that compounds 4 (R=H), 5j (R=CH2COC6H4-
p-F) and 5k (R=CH2COC6H4-p-NO2) showed motor
impairment at maximum dose of 300 mg/kg, whereas the
rest of the compounds were without motor impairment,
indicating that the effect may be due to presence of electron
withdrawing groups like OH, F and NO2 in the phenyl ring.
Clobazam 97.66 3.98**
Control 53.33 3.12
Each value represents the mean SEM of six rats, significantly
different from the control at NS, p [ 0.05 **, p \ 0.01 (Student’s
t test)
123

68
M. Amir et al.
Grover, G., and S.G. Kini. 2006. Synthesis and evaluation of new
quinazolone derivatives of nalidixic acid as potential antibacte-
rial and antifungal agents. European Journal of Medicinal
Chemistry 41: 256–262.
Jatav, V., P. Mishra, S. Kashaw, and J.P. Stables. 2008. CNS
depressant and anticonvulsant activities of some novel 3-[5-
substituted 1,3,4-thiadiazole-2-yl]-2-styryl quinazoline-4(3H)-
ones. European Journal of Medicinal Chemistry 43: 1945–1954.
Kashaw, S.K., V. Kashaw, P. Mishra, N.K. Jain, and J.P. Stables.
2009. CNS depressant and anticonvulsant activities of some
novel 3-[5-substituted 1,3,4-thiadiazole-2-yl]-2-styryl quinazo-
line-4(3H)-ones. European Journal of Medicinal Chemistry 44:
4335–4343.
Krall, R.L., J.K. Penry, B.G. White, H.J. Kupferbeng, and E.A.
Swinyard. 1978. Antiepileptic drug development: II. Anticon-
vulsant drug screening. Epilepsia 19: 409–428.
Kumar, A., C.S. Rajput, and S.K. Bhati. 2007. Synthesis of 3-[40-(p-
chlorophenyl)-thiazol-20-yl]-2-[(substituted azetidinonethiazoli-
dinone)-aminomethyl]-6-bromoquinazolin-4-ones as anti-inflam-
clobazam (83.12 %) and tested compound 5f (34.07 %)
were found to significantly increase the GABA concen-
tration (p \ 0.01) as compared to control. These results
suggest that the anticonvulsant activities of the synthesized
compounds might be through a GABA-mediated mecha-
nism and 3-[(4-butoxybenzylidene)-amino]-2-phenyl-3H-
quinazolin-4-one (5f) could serve as a lead compound for
the development of anticonvulsant agents.
Acknowledgments One of the authors, Israr Ali is thankful to
University Grant Commission (UGC) New Delhi, India, for financial
assistance. The authors are also grateful to the Dr. M. S. Zaman and
Mr. Niyaz Ahmad, Central instrumentation Facilities (CIF), Faculty
of Pharmacy, Hamdard University for carrying out the NMR and
Mass spectra.
matory agent. Bioorganic
3089–3096.
&
Medicinal Chemistry 15:
References
Kwan, P., and M.J. Brodie. 2005. Potential role of drug transporters in
the pathogenesis of medically intractable epilepsy. Epilepsia 46:
224–235.
Loscher, W. 1998. New visions in the pharmacology of anticonvul-
sion. European Journal of Pharmacology 342: 1–13.
Malamas, M.S., and J. Millen. 1991. Quinazoline acetic acids and
related analogues as aldose reductase inhibitors. Journal of
Medicinal Chemistry 34: 1492–1503.
Nicholas, D.P.C., I.A. McDonald, and E.J. Schweiger. 1998. Recent
progress in antiepileptic drug research. Annual Reports in
Medicinal Chemistry 43: 61–70.
Pandeya, S.K., A. Singh, A. Singh, and Nizamuddin. 2009.
Nizamuddin, Antimicrobial studies of some novel quinazolinon-
es fused with [1,2,4]-triazole, [1,2,4]-triazine and [1,2,4,5]-
tetrazine rings. European Journal of Medicinal Chemistry 44:
1188–1197.
Alagarsamy, V., and U.S. Pathak. 2007. Synthesis and antihyperten-
sive activity of novel 3-benzyl-2-substituted-3H-[1,2,4]triazol-
o[5,1-b]quinazolin-9-ones. Bioorganic & Medicinal Chemistry
15: 3457–3462.
Alagarsamy, V., R. Solomon, M. Murugan, K. Dhanabal, P.
Parthiban, and G.V.J. Anjana. 2008. Design and synthesis of
3-(4-ethylphenyl)-2-substituted amino-3H-quinazolin-4-ones as
a novel class of analgesic and anti-inflammatory agents. Journal
of Enzyme Inhibition and Medicinal Chemistry 23: 839–847.
Al-Rashood, S.T., I.A. Aboldahab, M.N. Nagi, L.A. Abouzeid,
A.A.M. Abdel-Aziz, S.G. Abdel-hamide, K.M. Youssef, A.M.
Al-Obaid, and H.I. El-Subbagh. 2006. Synthesis, dihydrofolate
reductase inhibition, and molecular modeling study of some new
4(3H)-quinazolinone analogues. Bioorganic & Medicinal Chem-
istry 14: 8608–8621.
Amir, M., M.J. Ahsan, and I. Ali. 2010. Syntheis of N1-(3-chloro-4-
fluorophenyl)-N4-substituted semicarbazones as novel anticon-
vulsant agents. Indian Journal of Chemistry 49B: 1509–1514.
Amir, M., S. Asif, I. Ali, and M.Z. Hassan. 2012. Synthesis of
benzothiazole derivatives having acetamido and carbothioamido
pharmacophore as anticonvulsant agents. Medicinal Chemistry
Research 21: 2661–2670.
Archana, V.K. Srivastava, and A. Kumar. 2002. Synthesis of newer
thiadiazolyl and thiazolidinonyl quinazolin-4(3H)-ones as poten-
tial anticonvulsant agents. European Journal of Medicinal
Chemistry 37: 873–882.
Porsolt, R.D., G. Anton, N. Blanet, and M. Jalfer. 1978. Behavioral
despair in rats:
a new model sensitive to antidepressant
treatments. European Journal of Pharmacology 47: 379–386.
Shaquiquzzaman, M., S.A. Khan, M. Amir, and M.M. Alam. 2012.
Synthesis and anticonvulsant activity of some 2-(2-{1-[substi-
tuted phenyl]ethylidene}hydrazinyl)-4-(4-methoxy-phenyl)-6-
oxo-1,6-dihydro-pyrimidine-5-carbonitrile. Journal of Enzyme
Inhibition and Medicinal Chemistry 27: 825–831.
Swinyard, E.A., Woodhead, J.H., White, H.S., Franklin, M.R. (1989)
General principles: experimental selection, quantification, and
evaluation of anticonvulsants. In Antiepileptic Drugs. Eds. Levy
R., Mattson R., Meldrum B., Penry J.K., Dreifuss F.E., 3rd ed.
Raven Press: New York.
Bartholow, R. 1899. A practical treatise on materia medica and
therapeutics. New York: D. Appleton.
Bavetsias, V., L.A. Skelton, F. Yafai, F. Mitchell, S.C. Wilson, B.
Allan, and A.L. Jackman. 2002. The design and synthesis of
water-soluble analogues of CB30865, a quinazolin-4-one based
antitumor agent. Journal of Medicinal Chemistry 45: 3692–3702.
Dunham, N.W., and T.S. Miya. 1957. A note on a simple apparatus
for detecting neurological deficit in rats and mice. Journal of the
American Pharmacists Association 46: 208–209.
Wang, H.J., C.X. Wei, X.Q. Deng, F.L. Li, and Z.S. Quan. 2009.
Synthesis and evaluation on anticonvulsant and antidepressant
activities of 5-alkoxy-tetrazolo[1,5- a]quinazolines. Arch Pharm
(Weinheim) 342: 671–675.
White, H.S. 2003. Preclinical development of antiepileptic drugs:
past, present, and future directions. Epilepsia 44: 2–8.
`
Zappala, M., S. Grasso, N. Micale, G. Zuccala, F.S. Menniti, G.
Gokani, V.N., M.U. Thakker, J.G. Patel, S.K. Ghosh, and S.K.
Chatterjee. 1979. Thin layer chromatographic method for
estimation of c-aminobutyric acid from brain. Indian Journal
of Physiology and Pharmacology 23: 101–104.
Ferreri, G. De Sarro, and C. De Micheli. 2003. 1-Aryl-6,7-
methylenedioxy-3H-quinazolin-4-ones as anticonvulsant agents.
Bioorganic & Medicinal Chemistry Letters 13: 4427–4433.
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