Molecular docking, synthesis and anticonvulsant activity of some novel 3-(2-substituted)-4-oxothiazolidine-3-yl)-2-phenylquinazoline-4(3H)-ones

Article abstract of DOI:10.1007/s11164-018-3612-9

As the therapeutic potential of quinazolinone and thiazolidinone is well mentioned in literature for their versatile biological activities, their related toxicological profiles cannot be ignored. So, the purpose of this study is to synthesize 3-(2-substit

Full text of DOI:10.1007/s11164-018-3612-9

Research on Chemical Intermediates
https://doi.org/10.1007/s11164-018-3612-9
Molecular docking, synthesis and anticonvulsant activity
of some novel 3‑(2‑substituted)‑4‑oxothiazolidine‑3‑yl)‑2
‑phenylquinazoline‑4(3H)‑ones
Sampada S. Jangam1 · Sagar B. Wankhede1 · Sohan S. Chitlange1
Received: 2 August 2018 / Accepted: 24 September 2018
© Springer Nature B.V. 2018
Abstract
As the therapeutic potential of quinazolinone and thiazolidinone is well mentioned
in literature for their versatile biological activities, their related toxicological profles
cannot be ignored. So, the purpose of this study is to synthesize 3-(2-substituted)-
4-oxothiazolidine-3-yl)-2-phenylquinazoline-4(3H)-ones (3a–3k) and evaluate them
as anticonvulsant agents. Novel series of 3a–3k were synthesized and their struc-
tures elucidated on the basis of elemental and spectral analyses. A hybrid scafold
containing quinazolinone and thiazolidinone moieties was synthesized to get the title
compounds, and their in vivo anticonvulsant activities were performed by maximal
electro-shock (MES) induced convulsion model at a dose of 25 mg/kg body weight.
Six compounds, 3b, 3c, 3d, 3e, 3f and 3i, were found to have signifcant anticonvul-
sant activities with their durations of tonic hind limb extension ranging from 13.117
to 16.450 s and animal protection from 83 to 100%. The results were compared with
the standard. All compounds exhibited good binding energies ranging from −5.15
to −6.13 kcal/mol with sodium channel IIA inactivation gate (PDB ID: 1BYY) in
molecular docking study; amongst them, 3d has shown signifcant binding energy
of −6.13 kcal/mol. The obtained result showed that biologically active compounds
could be used as a template for future design, optimization and investigation for pro-
ducing more active analogs.
Keywords Synthesis · 4-oxothiazolidine · Quinazoline-4(3H)-ones · Epilepsy ·
Anticonvulsant activity · Molecular docking
*
Sampada S. Jangam
samjangam@gmail.com
Sagar B. Wankhede
sbw.ccopr@gmail.com
Sohan S. Chitlange
sohanchitlange@redifmail.com
1
Dr. D. Y. Patil Institute of Pharmaceutical Sciences and Research, Sant Tukaram Nagar,
Pimpri, Pune 411018, Maharashtra, India
Vol.:(0123456789)
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S. S. Jangam et al.
Introduction
Epilepsy is a syndrome of various cerebral disorders of the central nervous sys-
tem (CNS) is characterized by paroxysmal, excessive, and hypersynchronous dis-
charges of large numbers of neurons [1, 2]. It afects a large section of the popula-
tion (45–100 million people) worldwide [3, 4]. The poor tolerability and reported
side efects of the antiepileptic drugs have afected the quality of life of the epilepsy
patients [5, 6]. Therapeutic failure in 20–25% of patients and serious side efects of
the available antiepileptic drugs have stimulated intensive research on novel antiepi-
leptic drugs [7–10].
The quinazolinone nucleus and its derivatives have been found to be efective
as antihypertensive [11–13], anti-infammatory [14], antihyperglycemic [15], anti-
cancer [16], antimalarial [17, 18], neuroprotective [19] and anticonvulsant [20, 21]
agents. The presence of a substituted aromatic ring at position 3 of quinazolinone
is a necessary requirement for the CNS depression and anticonvulsant activities
of such derivatives as methaqualone, ethaqualone and mecloqualone (Fig. 1) [22].
Medicinal chemists over the years have substituted diferent heterocyclic rings at
position 3 of 4(3H)-quinazolinone to get potent CNS acting drugs [21]. Literature
searches reveal that 4-oxo thiazolidine derivatives exhibit antitubercular [23], cyto-
toxic [24], anti-infammatory [25, 26] and anticonvulsant [27] activities. Therefore,
in the present study, 2-substituted thiazolidinone moiety was connected to position
3 of the quinazolinone ring, as the combination of diferent pharmacophores in one
frame may lead to signifcant anticonvulsant agents. Stabilization of the sodium
channel IIA inactivation gate may be useful in disrupting prolonged neuronal sei-
zure discharge, and has been an important target for a number of anticonvulsant
drugs [28].
In the present work, compounds (3a–3k) were synthesized by stirring 3-amino-
2-phenylquinazoline-4(3H)-one with substituted aromatic aldehydes using thio-
glycolic acid (TGA) and N, N-dicyclohexylcarbodiimide (DCC) in N, N-dimethyl
formamide (DMF) as a solvent. The purity and completion of the reaction was
monitored by using thin layer chromatography (TLC). All the synthesized com-
pounds were characterized by spectral (IR, 1H NMR, MS) and elemental analyses. A
series of 3-(2-substituted)-4-oxothiazolidine-3-yl)-2-phenylquinazoline-4(3H)-ones
(3a–3k) were evaluated for their anticonvulsant activity with the maximal electro-
shock (MES) test using Swiss albino mice.
O
O
O
N
N
N
N
CH3
CH3
Cl
CH3
CH2 CH3
CH3
N
N
Ethaqualone
Methaqualone
Mecloqualone
Fig. 1 Quinazolinone derivatives as potential CNS depressant agents [22]
1 3

Molecular docking, synthesis and anticonvulsant activity…
A docking program, such as AutoDock, when used prior to experimental screen-
ing, can be a powerful computational flter to reduce labor and cost needed for the
development of efective medicinal compounds [29]. Molecular docking studies
were executed against 3D crystal structure of sodium channel IIA inactivation gate
(PDB ID: 1BYY).
Experimental
Materials and methods
All the chemicals used for synthesis were of laboratory reagent (LR) and analyti-
cal reagent (AR) grade procured from Sigma-Aldrich, Sisco Research Laboratories
(SRL), SD fne chemicals (India). To monitor the reactions as well as to establish
the identity and purity of reactants and products, TLC was performed on pre-coated
silica gel G plates (0.2 mm thickness, Merck, India) using chloroform : ethyl acetate
(7 : 3) as a solvent system; the spots were visualized by exposure to iodine vapors
or ultra-violet (UV) light cabinet (254 nm). Melting points were determined in open
capillary tubes and are uncorrected. Infrared (IR) spectra of synthesized compounds
were recorded on a Fourier-transform infrared (FT-IR) spectrophotometer (Shi-
1
madzu 8400-S) using potassium bromide (KBr) as an internal standard. H nuclear
magnetic resonance (NMR) spectra were measured on NMR (500 MHz) spectrom-
eter (Bruker, India) in dimethyl sulfoxide (DMSO-d6) and CDCl3 and chemical
shifts (δ) values were given in parts per million (ppm), downfeld from tetramethyl
silane (TMS) as an internal standard. Mass spectra were measured on a high-res-
olution mass spectrometer (HRMS) (Bruker, India). The elemental analyzer was
used for elemental (C, H and N) analyses and results obtained were within 0.4%
of the theoretical values. The three-dimensional structure of the sodium channel IIA
inactivation gate (PDB ID: 1BYY) was selected from the RCSB Protein Data Bank,
which contains information about experimentally determined protein structures. CS
ChemDraw Ultra 8.0 was used for ligand preparation. AutoDock 1.5.6 was used for
molecular docking studies. Discovery Studio 3.5 visualizer was employed for visu-
alization and further analyses of results.
Synthesis of 3‑(2‑Substituted)‑4‑oxothiazolidin‑3yl)‑2‑phenyluinazolin‑4(3H)‑one
(3a–3k) 0.01 mol of 3-amino-2-phenylquinazolin-4(3H)-one was added to 25 ml
of DMF. To this, diferent aromatic aldehydes (0.012 mol) were added. The reac-
tion mixture was stirred under ice cold condition for 5 min, followed by addition of
thioglycolic acid (0.02 mol). After 5 min, DCC (0.012 mol) was added to the reac-
tion mixture at 0 °C and the reaction mixture was stirred for 5 h. The resulting mix-
ture was fltered to remove the insoluble product of dicyclohexylurea. To the fltrate,
25 ml of cold water was added; product was fltered and recrystallised from acetone.
3‑(4‑Oxo‑2‑phenylthiazolidin‑3‑yl)‑2‑phenylquinazolin‑4(3H)‑one (3a) Mol.
Wt:
399.46; Yield: 79%; mp: 216–218 °C; IR (KBr) cm−1: 1653.05 (C=O str in amide),
1 3

S. S. Jangam et al.
1311.64 (C=N str), 1282.71 (N–N str), 3063.06 (C–H str in arom), 1595.18 (C=O
str in thiazolidinone), 1444.73 (C–N str), 752.26 (C–S–C str); 1H NMR (500 MHz,
CDCl3, δ ppm): 7.31–7.42 (m, 5H, phenyl of thiazolidinone), 7.42–7.53 (m, 5H,
phenyl), 7.53–7.57 (m, 3H, heterocyclic arom), 7.60 (d, J=5 Hz, 1H, arom near
C=O), 3.71 (s, 2H, CH2 of thiazolidinone), 3.47 (s, 1H, CH of thiazolidinone); MS:
m/z 399 (M); Anal. Calcd. for C23H17N3O2S: C, 69.15; H, 4.29; N, 10.52. Found: C,
68.94; H, 4.28; N, 10.54.
3‑(2‑(4‑Hydroxyphenyl)‑4‑oxothiazolidin‑3‑yl)‑2‑phenylquinazolin‑4(3H)‑one
(3b) Mol. Wt: 415.46; Yield: 72%; mp: 198–200 °C; IR (KBr) cm−1: 1645.33
(C=O str in amide), 1315.50 (C=N str), 1282.71 (N–N str), 3053.42 (C–H str in
arom), 1599.04 (C=O str in thiazolidinone), 1442.80 (C–N str), 702.11 (C–S–C str),
1369.50 (O–H str in phenol); 1H NMR (500 MHz, DMSO-d6, δ ppm): 7.06 (dd, 4H,
phenyl of thiazolidinone), 7.64–7.65 (m, 3H, heterocyclic arom), 7.92 (d, J=5 Hz,
1H, heterocyclic arom near C=O), 7.59–7.63 (m, 5H, phenyl), 2.73 (s, 2H, CH2 of
thiazolidinone), 2.51 (s, 1H, CH of thiazolidinone), 10.01 (s, 1H, -OH); MS: m/z
416 (M+1); Anal. Calcd. for C23H17N3O3S: C, 66.49; H, 4.12; N, 10.11. Found: C,
66.27; H, 4.10; N, 10.13.
3‑(2‑(4‑Methoxyphenyl)‑4‑oxothiazolidin‑3‑yl)‑2‑phenylquinazolin‑4(3H)‑one
(3c) Mol. Wt: 429.49; Yield: 79%; mp: 250–252 °C; IR (KBr) cm−1: 1651.12 (C=O
str in amide), 1305.85 (C=N str), 3026.41 (C–H str in arom), 1637.62 (C=O str in
thiazolidinone), 1442.80 (C–N str), 1174.69 (N–N str), 750.33 (C–S–C str), 1257.63
1
(C–O str in arylalkyl), 2956.97 (C–H str in alkyl); H NMR (500 MHz, DMSO-
d6, δ ppm): 7.15 (dd, 4H, phenyl of thiazolidinone), 7.65–7.66 (m, 3H, heterocyclic
arom), 7.96 (d, J = 5 Hz, 1H, heterocyclic arom near C=O), 7.28–7.62 (m, 5H, phe-
nyl), 2.52 (s, 2H, CH2 of thiazolidinone), 3.35 (s, 1H, CH of thiazolidinone), 3.82
(s, 3H, –OCH3); MS: m/z 430 (M+1); Anal. Calcd. for C24H19N3O3S: C, 67.12; H,
4.46; N, 9.78. Found: C, 67.02; H, 4.45; N, 9.82.
3‑(2‑(4‑Nitrophenyl)‑4‑oxothiazolidin‑3‑yl)‑2‑phenylquinazolin‑4(3H)‑one (3d) Mol.
Wt: 444.46; Yield: 75%; mp: 222–224 °C; IR (KBr) cm−1: 1656.91 (C=O str in
amide), 1334.78 (C=N str), 3061.13 (C–H str in arom), 1597.11 (C=O str in thiazo-
lidinone), 1444.73 (C–N str), 1269.20 (N–N str), 761.91 (C–S–C str), 1519.96 (Ar–
1
NO2 str); H NMR (500 MHz, DMSO-d6, δ ppm): 7.29 (d, J=5 Hz, 2H, phenyl of
thiazolidinone), 7.92 (d, J=5 Hz, 2H, phenyl of thiazolidinone), 7.64–7.67 (m, 3H,
heterocyclic arom), 7.96 (d, J=5 Hz, 1H, heterocyclic arom near C=O), 7.30–7.62
(m, 5H, phenyl), 2.51 (s, 2H, CH2 of thiazolidinone), 3.38 (s, 1H, CH of thiazolidi-
none); Mass: m/z 445 (M+1); Anal. Calcd. for C23H16N4O4S: C, 62.15; H, 3.63; N,
12.61. Found: C, 61.95; H, 3.64; N, 12.58.
3‑(2‑(3‑Hydroxyphenyl)‑4‑oxothiazolidin‑3‑yl)‑2‑phenylquinazolin‑4(3H)‑one
(3e) Mol. Wt: 415.46; Yield: 77%; mp: 230–232 °C; IR (KBr) cm−1: 1728.28
(C=O str in amide), 1340.57 (C=N str), 3059.20 (C–H str in arom), 1662.69 (C=O
str in thiazolidinone), 1444.73 (C–N str), 1265.35 (N–N str), 700.18 (C–S–C str),
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Molecular docking, synthesis and anticonvulsant activity…
1
1166.97 (O–H str in phenol); H NMR (500 MHz, DMSO-d6, δ ppm): 6.85–6.93
(m, 4H, phenyl of thiazolidinone), 7.60–7.63 (m, 3H, heterocyclic arom), 7.92 (d,
J=5 Hz, 1H, heterocyclic arom near C=O), 7.12–7.21 (m, 5H, phenyl), 2.51 (s, 2H,
CH2 of thiazolidinone), 3.36 (s, 1H, CH of thiazolidinone), 9.67 (s, 1H, –OH); MS:
m/z 416 (M+1); Anal. Calcd. for C23H17N3O3S: C, 66.49; H, 4.12; N, 10.11. Found:
C, 66.27; H, 4.13; N, 10.07.
3‑(2‑(3‑Nitrophenyl)‑4‑oxothiazolidin‑3‑yl)‑2‑phenylquinazolin‑4(3H)‑one (3f) Mol.
Wt: 444.46; Yield: 78%; mp: 232–234 °C; IR (KBr) cm−1: 1687.77 (C=O str in
amide), 1338.64 (C=N str), 3059.20 (C–H str in arom), 1620.26 (C=O str in thia-
zolidinone), 1446.66 (C–N str), 1298.14 (N–N str), 744.55 (C–S–C str), 1587.47
1
(Ar–NO2 str); H NMR (500 MHz, DMSO-d6, δ ppm): 7.91–7.97 (m, 4H, phenyl
of thiazolidinone), 7.62–7.66 (m, 3H, heterocyclic arom), 7.79 (d, J=5 Hz, 1H, het-
erocyclic arom near C=O), 7.31–7.61 (m, 5H, phenyl), 2.51 (s, 2H, CH2 of thiazoli-
dinone), 3.36 (s, 1H, CH of thiazolidinone); MS: m/z 445 (M+1); Anal. Calcd. for
C23H16N4O4S: C, 62.15; H, 3.63; N, 12.61. Found: C, 62.03; H, 3.64; N, 12.56.
3‑(2‑(4‑(Dimethylaminophenyl)‑4‑oxothiazolidin‑3‑yl)‑2‑phenylquinazolin‑4(3H)‑one
(3g) Mol. Wt: 442.53; Yield: 70%; mp: 210–212 °C; IR (KBr) cm−1: 1620.26
(C=O str in amide), 1309.71 (C=N str), 3037.99 (C–H str in arom), 1579.75 (C=O
str in thiazolidinone), 1440.87 (C–N str), 1242.20 (N–N str), 819.77 (C–S–C
1
str), 2926.11 (C–H str in alkyl); H NMR (500 MHz, DMSO-d6, δ ppm): 6.78 (d,
J=5 Hz, 2H, phenyl of thiazolidinone), 7.57 (d, J=5 Hz, 2H, phenyl of thiazolidi-
none), 7.95–7.97 (m, 3H, heterocyclic arom), 8.0 (d, J=5 Hz, 1H, heterocyclic arom
near C=O), 7.61–7.66 (m, 5H, phenyl), 2.51 (s, 2H, CH2 of thiazolidinone), 3.34 (s,
1H, CH of thiazolidinone), 5.58 (s, 6H, –CH3); MS: m/z 443 (M+1); Anal. Calcd.
for C25H22N4O2S: C, 67.85; H, 5.01; N, 12.66. Found: C, 67.75; H, 4.99; N, 12.63.
3‑(2‑(3‑Chlorophenyl)‑4‑oxothiazolidin‑3‑yl)‑2‑phenylquinazolin‑4(3H)‑one (3h) Mol.
Wt: 433.91; Yield: 80%; mp: 245–247 °C; IR (KBr) cm−1: 1683.16 (C=O str in
amide), 1310.75 (C=N str), 3069.80 (C–H str in arom), 1698.70 (C=O str in thiazo-
lidinone), 1442.50 (C–N str), 1245.50 (N–N str), 735.20 (C–S–C str), 750.52 (C–Cl
1
str in arom); H NMR (500 MHz, DMSO-d6, δ ppm): 7.13–7.42 (m, 4H, phenyl of
thiazolidinone), 7.82–7.92 (m, 3H, heterocyclic arom), 7.96 (d, J=5 Hz, 1H, het-
erocyclic arom near C=O), 7.52–7.65 (m, 5H, phenyl), 2.51 (s, 2H, CH2 of thiazoli-
dinone), 3.93 (s, 1H, CH of thiazolidinone); MS: m/z 434 (M+1); Anal. Calcd. for
C23H16ClN3O2S: C, 63.66; H, 3.72; N, 9.68. Found: C, 63.43; H, 3.71; N, 9.72.
3‑(2‑(3,4‑Dimethoxyphenyl)‑4‑oxothiazolidin‑3‑yl)‑2‑phenylquinazolin‑4(3H)‑one
(3i) Mol. Wt: 459.52; Yield: 79%; mp: 282–284 °C; IR (KBr) cm−1: 1660.15 (C=O
str in amide), 1316.86 (C=N str), 3060.53 (C–H str in arom), 1640.72 (C=O str in
thiazolidinone), 1444.80 (C–N str), 1180.59 (N–N str), 720.44 (C–S–C str), 1259.65
1
(C–O str in arylalkyl), 2950.88 (C–H in alkyl); H NMR (500 MHz, DMSO-d6, δ
ppm): 6.93–7.05 (m, 3H, phenyl of thiazolidinone), 7.62–7.65 (m, 3H, heterocy-
clic arom), 7.90 (d, J=5 Hz, 1H, heterocyclic arom near C=O), 7.23–7.60 (m, 5H,
1 3

S. S. Jangam et al.
phenyl), 2.55 (s, 2H, CH2 of thiazolidinone), 3.37 (s, 1H, CH of thiazolidinone),
3.98 (s, 6H, –OCH3); MS: m/z 460 (M+1); Anal. Calcd. for C25H21N3O4S: C,
65.34; H, 4.61; N, 9.14. Found: C, 65.10; H, 4.60; N, 9.11.
3‑(2‑(2‑Chlorophenyl)‑4‑oxothiazolidin‑3‑yl)‑2‑phenylquinazolin‑4(3H)‑one (3j) Mol.
Wt: 433.91; Yield: 78%; mp: 248–250 °C; IR (KBr) cm−1: 1686.36 (C=O str in
amide), 1320.76 (C=N str), 3070.82 (C–H str in arom), 1696.60 (C=O str in thiazo-
lidinone), 1446.53 (C–N str), 1280.50 (N–N str), 736.20 (C–S–C str), 748.62 (C–Cl
1
str in arom); H NMR (500 MHz, DMSO-d6, δ ppm): 7.29–7.44 (m, 4H, phenyl of
thiazolidinone), 7.87–7.93 (m, 3H, heterocyclic arom), 7.96 (d, J=5 Hz, 1H, het-
erocyclic arom near C=O), 7.45–7.65 (m, 5H, phenyl), 2.55 (s, 2H, CH2 of thiazoli-
dinone), 3.65 (s, 1H, CH of thiazolidinone); MS: m/z 434 (M+1); Anal. Calcd. for
C23H16ClN3O2S: C, 63.66; H, 3.72; N, 9.68. Found: C, 63.40; H, 3.72; N, 9.66.
3‑(2‑(4‑Fluorophenyl)‑4‑oxothiazolidin‑3‑yl)‑2‑phenylquinazolin‑4(3H)‑one (3k) Mol.
Wt: 417.46; Yield: 70%; mp: 220–222 °C; IR (KBr) cm−1: 1682.46 (C=O str in
amide), 1318.86 (C=N str), 3075.82 (C–H str in arom), 1698.65 (C=O str in thiazo-
lidinone), 1448.63 (C–N str), 1285.70 (N–N str), 726.40 (C–S–C str), 1050.60 (C–F
1
str in arom); H NMR (500 MHz, DMSO-d6, δ ppm): 7.22 (d, J=5 Hz, 2H, phe-
nyl of thiazolidinone), 7.29 (d, J=5 Hz, 2H, phenyl of thiazolidinone), 7.64–7.81
(m, 3H, heterocyclic arom), 7.84 (d, J=5 Hz, 1H, heterocyclic arom near C=O),
7.44–7.62 (m, 5H, phenyl), 2.51 (s, 2H, CH2 of thiazolidinone), 3.35 (s, 1H, CH of
thiazolidinone); MS: m/z 418 (M+1); Anal. Calcd. for C23H16FN3O2S: C, 66.17; H,
3.86; N, 10.07. Found: C, 65.97; H, 3.84; N, 10.04.
Pharmacology
Anticonvulsant activity was determined by maximal electro-shock (MES) induced
convulsion test using albino mice of either sex weighing 25–30 g of body mass. The
animals were divided into diferent groups (control, test and standard) containing
six animals each. The animals were housed in standard polypropylene cages under
standard laboratory conditions (12:12 h light/dark cycle at 25 3 °C). They had free
access to standard commercial diet and water. The ethical guidelines for the investi-
gation of animals used in experiments were followed in all tests.
Maximal electro‑shock (MES) induced convulsions
In this test, the mice were subjected to 50 mA alternating current from a convulsi-
ometer for 0.2 s through a pair of electrodes attached to each ear. The duration of
tonic hind limb extensor phase and the number of animals protected from convul-
sions were noted. In this study, the animals were administered 25 mg/kg dose of
the test drugs and standard drug phenytoin. The test and standard drug compounds
were suspended in 0.1% carboxy methyl cellulose (CMC) and administered intra-
peritoneally 30 min prior to testing. The control group animals, instead, received the
10 mg/kg vehicle (0.1% CMC). A complete abolition of tonic hind limb extension
1 3

Molecular docking, synthesis and anticonvulsant activity…
was considered as 100% protection. The ability to prevent this feature was consid-
ered as an indication of anticonvulsant activity.
Statistical analysis
The results were expressed as mean SEM; n represents the number of animals.
Data obtained from pharmacological experiments were analyzed with one-way anal-
ysis of variance (ANOVA) followed by Dunnett’s t-test. A P-value of less than 0.001
was considered statistically signifcant.
Molecular docking study
Protein preparation
The 3D crystal structure of the sodium channel IIA inactivation gate with PDB ID:
1BYY [30] was obtained from the Brookhaven Protein Data Bank (PDB; http://
www.rcsb.org/pdb). and hydrogens were added. The receptor fle was converted to
the pdbqt format, which is pdb plus ‘q’ charges and ‘t’ AutoDock type. To confrm
the AutoDock types, polar hydrogens should be present, whereas non-polar hydro-
gens and the lone pair should be merged; each atom should be assigned Gasteiger
partial charges.
Ligand design
The structure of ligands is one of the most important determinants for successful
docking, thus pre-analysis of the ligand structures is most important. The drugs’ like
properties of ligands were confrmed by manually applying the Lipinski’s Rule of
Five and used for the further studies. ChemDraw Ultra 8.0 (Cambridge Soft.com
100 Cambridge park drive, Cambridge, MA, 02140, USA) was used to draw the
structure of the ligands (3a–3k). The ligands were cleaned in 2D and further in 3D
by addition of explicit hydrogens and the gradient optimization function of Marvin-
Sketch 5.8.1 (Chemaxon Ltd; http://www.chemaxon.com). Original states of ioniza-
tion were retained and chiralities were determined from the 3D structures. All the
structures were written in Tripos mol2 fle format. AutoDock requires that ligands
give partial atomic charges and AutoDock atom types for each atom; it also needs
a description of rotatable bonds in the ligands. AutoDock depends upon the con-
cept of a tree in which the rigid core of the molecule is ‘root’ and fexible parts are
‘branches’ that extends from the root. This set consists of united atoms, aromatic
carbons in a cycle, aliphatic carbons, hydrogen bonded nitrogen, polar hydrogens
and directly hydrogen bonded oxygen, among others, each with partial charges.
Therefore pdbqt format was used for ligands, which were recognized by AutoDock.
The torsional degree of freedom is used in calculating the change in free energy
caused by loss of a torsional degree of freedom upon binding; in AutoDock 1.5.6,
1 3

S. S. Jangam et al.
the torsional degree of freedom value for the ligand is the total number of rotatable
bonds in the ligand.
Molecular docking simulations
AutoDock allows fully fexible modeling of specifc portions of the protein, in a
manner similar to that of ligands [31, 32]. Prior to the actual docking run, AutoGrid
1. 5. 6 was introduced to pre-calculate grid maps of interaction energies of various
atom types [33, 34]. In the present study, the binding site was selected based on the
amino acid residues, which were involved in binding with sodium channel IIA inac-
tivation gate obtained from Protein Data Bank with ID 1BYY. Therefore the grid
was centered at the region including amino acid residues (GLU1492, LYS1502) that
surround the active sites. In the procedure of docking, a grid map with 60×60×60
points, a grid spacing of 0.375Å were used and the maps were centered on the ligand
binding sites with centers x=5.669, y=5.401 and z=−1.697. An afnity grid was
calculated for each type of atom in the substrate, typically carbon, oxygen, nitro-
gen and hydrogens, as well as a grid of electrostatic potential, using point charge of
+1 as the probe [35, 36]. The Lamarckian Genetic Algorithm (LGA) based on an
optimization algorithm [37] was used to fnd the conformers with lowest binding
energy. The docking task was fnally performed by two commands: (i) autogrid4.
exe –p 1BYY.gpf –l 1BYY.glg and (ii) autodock4.exe –p ligand.dpf –l ligand.dlg.
The results of molecular docking studies were obtained in dlg fles in the form of
estimated free energy bindings (kcal/mol) and inhibition constant (Ki in μM) at
298.15 K temperature. The dlg fle was then converted into the pdbqt format. For
visualization and analyses of docking results, Discovery Studio Visualizer version
3.5 was used, which explored hydrogen, hydrophobic and van der Waals contacts.
Results and discussion
Target compounds (3a–3k) were synthesized according to Scheme 1 by a two-com-
ponent reaction using 3-amino-2-phenylquinazolin-4(3H)-one, substituted aromatic
aldehydes, TGA and DCC in N, N-dimethyl formamide as a solvent. The reaction
mixture was stirred for 5 h. This reaction proceeds with initial formation of imine
(the nitrogen of the amino group attacks the carbonyl carbon of the aldehydes) and a
Ar
S
O
N
O
N
NH2
N
DMF, TGA, DCC
Stir, 5hrs
N
N
+
Ar-CHO
O
3-(2-substituted )-4-oxothiazolidin-3-yl)-2-
phenylquinazolin-4(3H)-one
(3a-3k)
Substituted
3-amino-2-phenylquinazolin-
4(3H)-one
aromatic aldehydes
Scheme 1 Synthesis of target compounds (3a–3k)
1 3

Molecular docking, synthesis and anticonvulsant activity…
nucleophilic attack of thiol on imino carbon followed by intramolecular cyclization
by the loss of water. N, N′-dicyclohexyl carbodiimide (DCC) was used as a dehy-
drating agent to accelerate the intramolecular cyclization, resulting in faster reac-
tion and improved yields [38, 39]. All the target compounds were identifed and
confrmed by physical and spectral data. In general, IR (KBr) spectra displayed the
C=O peak in cyclic amide at 1620.26–1728.28 cm−1. The other characteristic peaks,
such as C=O stretching of thiazolidinone, C-H stretching of the aromatic ring, C=N
and C–S–C stretching, were observed at 1579.75–1698.70 cm−1, 3026.41–3075.82,
1305.85–1340.57 cm−1 and 700.18–819.77 cm-1 , respectively. In the nuclear mag-
netic resonance (1H NMR) spectra, the signals of the respective protons of the target
compounds were confrmed on the basis of their chemical shift (δ ppm) values. The
spectra showed CH2 protons of thiazolidinone as a singlet at 2.51–3.71 ppm and
aromatic protons as a multiplet at 7.12–7.61 ppm. In the mass spectra of synthesized
compounds, the molecular ion was evident and its mass was measured. From physi-
cal, spectral and elemental analysis data, all the target compounds were in conform-
ity and structures were envisaged.
All the synthesized 3-(2-substituted)-4-oxothiazolidin-3yl)-2-phenyluinazolin-
4(3H)-one (3a–3k) derivatives were assessed manually against Lipinski’s Rule
of Five [40]. Lipinski’s Rule of Five states that for a chemical compound to be a
successful oral drug, it should fall within following criteria: (i) Number of hydro-
gen bond donors (sum of OHs and NHs) should be≤5, (ii) Number of hydrogen
bond acceptors (sum of Os and Ns) should be≤10, (iii) Its molecular weight should
be≤500, (iv) Its ClogP value should be≤5. All the synthesized compounds were
found within the limits of the parameters described by the Lipinski et al. (Table 1).
Anticonvulsant activity of each of the synthesized compounds (3a–3k) was investi-
gated by the MES model [41] and the results are shown in Table 2. According to the
results of the experiment, it was observed that compounds 3b, 3c, 3d, 3e, 3f and 3i
with substituted p-hydroxy, p-methoxy, p-nitro, m-hydroxy, m-nitro and 3,4-dimeth-
oxy derivatives showed signifcant anticonvulsant activities at dose 25 mg/kg. Com-
pounds 3b, 3d, 3f and 3i demonstrated 100% protection, considered an indication of
anticonvulsant activity.
Analyzing the anticonvulsant activities of synthesized compounds 3b, 3c, 3d, 3e,
3f and 3i the structure-activity relationship (SAR) reveals that presence of electron
withdrawing groups such as -NO2 at p- and m- position increases the anticonvul-
sant activity. Also the presence of electron rich groups such as –OH, –OCH3 shows
signifcant anticonvulsant activity. The compounds 3c, 3e, 3h, 3j, 3k with substi-
tuted m-chloro, o-chloro and p-fuoro derivatives exhibited moderate anticonvulsant
activity with 83% protection, and other compounds 3a with substituted 3,4-dimethyl
amino and 3g derivatives had 67% protection with poor anticonvulsant activity.
To predict possible binding interactions, the proposed ligands (3a–3k) were
docked into the sodium channel IIA inactivation gate by using AutoDock 1.5.6.
Sulfur present in the thiazolidinone ring is an isostere of the nitrogen of Phe-
nytoin containing an imidazolidine-2,4-dione ring, because in nitrogen and sul-
fur peripheral layers of electrons can be considered identical. [42, 43]. Phenytoin
shows anticonvulsant activity by acting as voltage-gated sodium channel blocker
[44, 45]. Hence, for the anticonvulsant activity, the 3D crystal structure of the
1 3

S. S. Jangam et al.
Table 1 Calculation of various descriptors for proposed 3-(2-substituted)-4-oxothiazolidin-3yl)-2-pheny-
luinazolin-4(3H)-one (3a–3k) according to Lipinski’s Rule of Five
Compound
No. of H-bond
donors
No. of H-bond
acceptors
CLogP
Molecular weight Lipinski
violation
3a
3b
3c
3d
3e
3f
3g
3h
3i
0
1
0
0
1
0
0
0
0
0
0
5
6
6
8
6
8
6
5
7
5
5
4.32
3.65
4.24
4.06
3.65
4.06
4.48
5.00
3.98
5.00
4.46
399.46
415.46
429.49
444.46
415.46
444.46
442.53
433.91
459.52
433.91
417.46
0
0
0
0
0
0
0
0
0
0
0
3j
3k
sodium channel IIA inactivation gate with PDB ID 1BYY (Fig. 2) was selected
from the Protein Data Bank. The sodium channel IIA inactivation gate has a helix
structure with a length of 11 amino acid residues including GLU1492, LYS1495,
MET1490 PHE1489 and LYS1502. The grid was centered at the region including
amino acid residues (GlU1492, LYS1502) that surround the active sites as shown
in Fig. 3. The results were expressed in terms of estimated free binding energies
(kcal/mol) and estimated inhibition constants (Ki in μM) as shown in Table 3.
Molecular docking studies indicated that estimated free energy of binding of
docked ligand ranged between − 5.15 and − 6.13 (kcal/mol), while their estimated
inhibition constants (Ki) were found between 32.00 and 166.94 μM. The inter-
acting amino acid residues were found to be GLU1492, MET1490, PHE1489
and LYS1495. Further analyses of results showed that p-nitro substituted deriva-
tives of 3d shown the highest afnity towards sodium channel IIA inactivation
gate, with interacting amino acid residues MET1490, LYS1495 and additionally
PHE1489. In contrast, p-fuoro substituted derivative 3k shown moderate afn-
ity and un-substituted phenyl derivative 3a was found to have the least afnity
towards sodium channel IIA inactivation gate, with interacting amino acid resi-
dues like MET1490, LYS1495 and PHE1489. The docking results were compared
1 3

Molecular docking, synthesis and anticonvulsant activity…
Table 2 Anticonvulsant activity of compounds (3a–3k) using Maximal electro-shock (MES) induced
convulsion model
Group
Dose (mg/kg)
Duration of Tonic Hind Limb Exten- Animals
sion Phase (Sec.) (Mean SEM)
protected
(%)
Normal control (normal saline)
10 ml/kg
25 mg/kg
25 mg/kg
25 mg/kg
25 mg/kg
25 mg/kg
25 mg/kg
25 mg/kg
25 mg/kg
25 mg/kg
25 mg/kg
25 mg/kg
25 mg/kg
25.516 0.5163
18.976 0.3588
15.128 0.4776*
15.542 0.4908*
13.117 0.3578*
16.450 0.5527*
13.226 0.4117*
18.406 0.5074
17.262 0.4547
14.538 0.3684*
17.441 0.3266
17.165 0.4109
6.412 0.4364*
0
67
100
83
100
83
100
67
83
100
83
83
100
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
Standard (Phenytoin)
n=6 in each group
*P<0.001 compared against the control group
Fig. 2 1BYY: Sodium Channel IIA Inactivation Gate
with standard phenytoin with binding energy − 4.56 kcal/mol and interacting
amino acid residues such as GLU1492, MET1490, PHE1489 and LYS1495.
Docking of most active 3d, moderate active 3k, least active 3a and standard phe-
nytoin in 1BYY sodium channel IIA inactivation gate are shown in Figs. 4, 5, 6
and 7.
1 3

S. S. Jangam et al.
Fig. 3 Helix 1 Structure of Sodium Channel IIA Inactivation Gate
Table 3 Molecular docking analysis results of 3-(2-substituted)-4-oxothiazolidin-3yl)-2-phenyluinazolin-
4(3H)-one (3a–3k)
Compound
Binding
Inhibition
No. of hydrogen Interacting atoms of the protein
Energy (kcal/ constant (Ki, bonds involved
mol)
μM)
3a
3b
3c
3d
3e
3f
3g
3h
3i
−5.15
−5.88
−5.79
−6.13
−5.65
−5.97
−5.29
−5.33
−5.97
−5.31
−5.36
166.94
48.82
56.54
32.00
71.95
1
1
2
2
2
1
1
1
2
1
1
1
MET1490
MET1490
MET1490, LYS1495
MET1490, LYS1495
MET1490, LYS1495
LYS1495
MET1490
MET1490
MET1490, LYS1495
LYS1495
MET1490
42.23
133.21
123.05
42.07
128.69
117.23
456.92
3j
3k
Phenytoin (Standard) −4.56
GLU1492
Conclusion
A series of eleven novel 3-(2-substituted)-4-oxothiazolidin-3yl)-2-phenyluinazo-
lin-4(3H)-ones (3a–3k) were synthesized in this study. Synthesized compounds
1
were characterized by physical as well as spectral data including IR, H NMR,
mass spectra and elemental analysis. Their anticonvulsant activities were evalu-
ated using the maximal electro-shock (MES) induced convulsion model. Six com-
pounds, 3b, 3c, 3d, 3e, 3f and 3i, possess signifcant anticonvulsant activity, and
1 3

Molecular docking, synthesis and anticonvulsant activity…
Fig. 4 Docking of most active compound 3d (Binding energy −6.13 kcal/mol) in sodium channel IIA
inactivation gate (PDB ID: 1BYY)
Fig. 5 Docking of moderate active compound 3 k (Binding energy −5.36 kcal/mol) in sodium channel
IIA inactivation gate (PDB ID: 1BYY)
lower activity as compared to the standard drug. The compounds were admin-
istered intraperitoneally at the dose of 25 mg/kg and compared with control
(P < 0.001). Binding energies ranging from − 5.15 to − 6.13 kcal/mol were found
for all synthesized compounds when subjected to molecular docking study with
1 3

S. S. Jangam et al.
Fig. 6 Docking of least active compound 3a (Binding energy −5.15 kcal/mol) in sodium channel IIA
inactivation gate (PDB ID: 1BYY)
Fig. 7 Docking of phenytoin (Binding energy −4.56 kcal/mol) in sodium channel IIA inactivation gate
(PDB ID: 1BYY)
a sodium channel IIA inactivation gate (PDB ID: 1BYY). Compound 3d exhib-
ited signifcant binding energy, − 6.13 kcal/mol, when compared with others and
standard phenytoin. The obtained result showed that active compounds could be
used as a template for future design and investigation to produce more active ana-
logs. However, these compounds should be optimized in order to increase their
efcacy and potency.
1 3

Molecular docking, synthesis and anticonvulsant activity…
Acknowledgement The authors are grateful to the Head, Central Instrumentation Facility (CIF) depart-
ment, Savitribai Phule Pune University, Pune, India for providing the facilities for Spectral Analysis of
compounds.
Compliance with ethical standards
Confict of interest The authors declare that they have no confict of interest.
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