Facile synthesis, molecular docking and toxicity studies of 4-Phenyl-3-phenylamino-4H-[1,2,4]thiadiazol-5-one analogs as GABAA receptor agonists

Article abstract of DOI:10.1007/s00044-016-1697-5

A series of 4-Phenyl-3-phenylamino-4H-[1,2,4]thiadiazol-5-one derivatives was synthesized by a simple method and their structures were established by physical and spectroscopic methods like infrared, mass and nuclear magnetic resonance spectroscopy. Elemental formulae of all the compounds were determined by elemental analysis and compared with the calculated value. Log P value and in vitro hydrolysis, in simulated gastric fluid and simulated intestinal fluid, for all the compounds were determined by standard methods. Synthesized 1, 2, 4-thiadiazolines were screened for their anticonvulsant activity against maximal electroshock method and isoniazid induced seizures. All the compounds showed good anticonvulsant activity. The compound 4-(3,4-dichloro-phenyl)-3-(3,4-dichloro-phenylamino)-4H-[1,2,4]thiadiazol-5-one (3a) was found to be the most potent member of the series. Molecular docking studies of the synthesized compounds depicted their stable ligand–receptor complex conformation with the typical binding pocket of γ-aminobutyric acid A receptor protein. Compound 3a confined its effect in the molecular docking studies also with non-covalent interactions with Tyr 157, Phe 200 and Tyr 205, the key interacting residues of γ-aminobutyric acid A receptor protein 4COF. In silico absorption, distribution, metabolism and elimination performance of all the compounds also appear to favour anticonvulsant effect. “LAZAR” and “OSIRIS” property explorer predicted nontoxic, nonmutagenic, noncarcinogenic, etc. nature for all the compounds. In conclusion, some γ-aminobutyric acid A receptor agonists have been synthesized in this study with promising drug-like properties, which merit further development.

Full text of DOI:10.1007/s00044-016-1697-5

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-016-1697-5
ORIGINAL RESEARCH
Facile synthesis, molecular docking and toxicity studies of
4-Phenyl-3-phenylamino-4H-[1,2,4]thiadiazol-5-one analogs as
GABAA receptor agonists
Kirti Diwakar1 Pankaj Kumar Sonar1 Mudita Mishra2 Avinash C. Tripathi1
Shailendra K. Saraf1
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Received: 22 April 2016 / Accepted: 18 July 2016
© Springer Science+Business Media New York 2016
Abstract A series of 4-Phenyl-3-phenylamino-4H-[1,2,4]
thiadiazol-5-one derivatives was synthesized by a simple
method and their structures were established by physical
and spectroscopic methods like infrared, mass and nuclear
magnetic resonance spectroscopy. Elemental formulae of all
the compounds were determined by elemental analysis and
compared with the calculated value. Log P value and in
vitro hydrolysis, in simulated gastric fluid and simulated
intestinal fluid, for all the compounds were determined by
standard methods. Synthesized 1, 2, 4-thiadiazolines were
screened for their anticonvulsant activity against maximal
electroshock method and isoniazid induced seizures. All the
compounds showed good anticonvulsant activity. The
compound 4-(3,4-dichloro-phenyl)-3-(3,4-dichloro-pheny-
lamino)-4H-[1,2,4]thiadiazol-5-one (3a) was found to be
the most potent member of the series. Molecular docking
studies of the synthesized compounds depicted their stable
ligand–receptor complex conformation with the typical
binding pocket of γ-aminobutyric acid A receptor protein.
Compound 3a confined its effect in the molecular docking
studies also with non-covalent interactions with Tyr 157,
Phe 200 and Tyr 205, the key interacting residues of γ-
aminobutyric acid A receptor protein 4COF. In silico
absorption, distribution, metabolism and elimination
performance of all the compounds also appear to favour
anticonvulsant effect. “LAZAR” and “OSIRIS” property
explorer predicted nontoxic, nonmutagenic, non-
carcinogenic, etc. nature for all the compounds. In conclu-
sion, some γ-aminobutyric acid A receptor agonists have
been synthesized in this study with promising drug-like
properties, which merit further development.
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Keywords Thiourea Thiadiazole ADME GABAA
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LAZAR OSIRIS
Introduction
Epilepsy is a chronic and often progressive disorder char-
acterized by the periodic and unpredictable occurrence of
epileptic seizures, which are caused by abnormal discharge
of cerebral neurons. Epilepsy is not a disease, but a syn-
drome of different cerebral disorders of the central nervous
system (CNS). This syndrome is characterized by parox-
ysmal, excessive and hyper synchronous discharges of a
large number of neurons that result from too much excita-
tion or too little inhibition in the area in which the abnormal
discharge starts (Barbara, 2008; Rang et al., 2003; Gidal
and Garnett, 1993). Excitation and inhibition of neurons
may be mediated by different neurotransmitters. γ-amino-
butyric acid (GABA) is the principal inhibitory neuro-
transmitter in the cerebral cortex (Schwartz, 1988). GABA
is localized primarily in short-axon interneurons that
synapse on cell bodies and proximal axons, and serves to
maintain inhibitory tone that counterbalances neuronal
excitation. When this balance is perturbed, seizures may
ensue. It is released into the synapse and then acts at one of
* Shailendra K. Saraf
dirpharmniec@gmail.com
1
Division of Pharmaceutical Chemistry, Faculty of Pharmacy, Babu
Banarasi Das Northern India Institute of Technology, Sector-II,
Dr. Akhilesh Das Nagar, Faizabad Road, Lucknow 227105 U.P.,
India
2
Division of Pharmacology, Faculty of Pharmacy, Babu Banarasi
Das Northern India Institute of Technology, Sector-II, Dr.
Akhilesh Das Nagar, Faizabad Road, Lucknow 227105 U.P., India

Med Chem Res
two types of GABA receptors: GABAAreceptors and
GABAB receptors. GABAA receptors are ligand-gated ion
channels that hyperpolarize the neuron by increasing inward
chloride conductance and have a rapid inhibitory effect. The
GABAA-receptor complex is a pentameric hetero-oligomer
that contains binding sites for GABA, barbiturates, benzo-
diazepines, picrotoxin, etc. GABAB receptors are G protein-
coupled receptors, which hyperpolarize the neuron by
increasing potassium conductance. GABAB receptors
decrease calcium entry and have a slow inhibitory effect
(Treiman, 2001).
Heterocyclic compounds are an integral part of the che-
mical and life sciences and constitute a considerable
quantum of the modern research that is being currently
pursued throughout the world (Tripathi et al., 2014). 1, 2, 4-
Thiadiazole is a sulphur and nitrogen containing, π-exces-
sive, aromatic five membered heterocyclic compound,
which shows various types of biological activities. Among
them, 3,5-disubstituted 1, 2, 4-thiadiazoles are associated
with diverse biological activities, probably by virtue of the –
N=C–S group (Gupta et al., 2005).
Material and methods
The chemicals and reagents were procured from S. D. Fine
Chemicals, Mumbai and were used as such. Melting ranges
were determined by open capillary method and are uncor-
rected. Reaction progress was monitored by performing thin
layer chromatography on silica gel G plates 60F254, E.
Merck, Darmstadt, Germany, using iodine vapours and
ultraviolet (UV) light as the visualizing agents. After phy-
sical characterization, the compounds were subjected to
spectral analysis. UV-visible spectra were recorded on a
UV-1700 Pharmaspec-UV-visible spectrophotometer, Shi-
madzu. Infrared (IR) spectra were recorded on Shimadzu
8400S and Perkin Elmer Spectrum RX1 fourier transform
infrared spectroscopy spectrophotometers and the values are
expressed in cm−1. Mass spectra were recorded on a JEOL-
AccuTOF JMS-T100LC spectrometer and nuclear magnetic
resonance (NMR) spectra were recorded on a Bruker DRX-
300 spectrometer and the chemical shifts are reported in
parts per million (δ values) from tetramethylsilane (δ 0 ppm
1
for HNMR) as the internal standard. Elemental analysis
Substituted 1, 2, 4-thiadiazoles have been found to be
active against maximal electroshock (MES) induced sei-
zuresin animal studies and have the potential to be
effective in generalized tonic-clonic seizures. 1, 2, 4-
Thiadiazole derivatives have documented consistent
advances in the design of the novel anticonvulsant agents
because they have the essential features for anticonvulsant
activity, which are (i) a hydrophobic aryl ring, (ii) a
hydrogen binding domain, (iii) an electron donor–accep-
tor system and (iv) another hydrophobic aryl ring of dif-
ferent size responsible for metabolism.Thiadiazole
derivatives have been found to possess potent and wide
spectrum biological activities like anticonvulsant (Kaur
et al., 2010; Siddiqui et al., 2009; Yar and Akhter, 2009),
antibacterial (Lamani et al., 2009; Hagiwara et al., 1992),
anti-inflammatory (Song et al., 1999; Venkatesh and
Pandeya, 2009; Manna and Narang, 2005), antihistaminic
(Xiao et al., 2011) and antidiabetic. Further 1, 2, 4-thia-
diazoles also find use as herbicides, insecticides and
bactericides (Lee et al., 2010; Fadda et al., 2009; Hayat
et al., 2010; Kasimoğullari et al., 2009; Abdel-Hamid
et al., 2007; Patil et al., 2009, Wu and Zhang, 2008). One
of the main objectives of organic and medicinal chemistry
is the design, synthesis and production of molecules
having value as human therapeutic agents (Verma and
Saraf, 2008). On the basis of the above, some new 4-
phenyl-3-phenylamino-4H-[1,2,4]thiadiazol-5-one deri-
vatives were synthesized, which possess two aromatic
rings as the hydrophobic domain, N=C–NH exists as the
hydrogen bonding domain and carbonyl group is the
electron donor group. (Rana et al., 2008; Gupta et al.,
2009; Scott, 2003).
was performed on an Elemental Vario EL III analyzer at
Central Drug Research Institute, Lucknow.
General procedure for the synthesis of aryl thiourea
(1a–i)
To a suspension of (0.30 mol) of aryl amine in 100 mL of
warm water, concentrated hydrochloric acid (HCl) (0.33
mol, 9.16 mL) was added with stirring. The resulting solu-
tion was placed in a large porcelain evaporating dish,
ammonium thiocyanate (0.3 mol, 8.33 g) was added and the
mixture was heated on a steam bath for 1 h. The liquid, from
which a mass of large needles of aryl amine thiocyanate
separated, was allowed to cool, set aside at room tempera-
ture for 1 h and then evaporated slowly to dryness over a
period of 2–3 hrs. The crystalline residue was crushed
finely, 100 mL water was added, and again the mixture was
evaporated slowly. The dry grayish white residual powder
was heated finally on a steam bath for 4–5 hrs. The resulting
mixture of crude substituted phenylthiourea and ammonium
chloride was powdered finely and suspended in 100 mL of
water. The mixture was warmed slowly to 70 °C with stir-
ring, and then allowed to cool to 35 °C and the solid was
filtered with suction. The crude material was dissolved in
absolute ethanol, the solution boiled with decolourizing
carbon for a few minutes and then filtered. The white
crystalline mass of substituted phenylthiourea, which
separated on cooling and standing, was separated by fil-
tration, was washed with light petroleum ether and dried.
Thin layer chromatography was carried out on precoated
silica plates, using the solvent system methanol: chloroform

Med Chem Res
(1:9). Physical and spectral analysis confirmed the forma-
(2-Methoxy-phenyl)-thiourea (1i)
tion of the corresponding thiourea (Rabjohn, 2005).
White crystalline solid; Yield: 28.74 %; Melting range:
184–186 °C; IR (KBr, cm−1) 3446 (N–H), 1409 (C=C),
1064 (C–N), 813 (C=S); ESI-MS m/z = 183.07 [M+1].
(3,4-Dichloro-phenyl)-thiourea (1a)
White crystalline solid; Yield: 29.40 %; Melting range:
180–182 °C; IR (KBr, cm−1) 3419 (N–H), 1465 (C=C),
1064 (C–N), 810(C=S); ESI-MS m/z = 221.0 [M+].
General procedure for the synthesis of (5-imino-4-
phenyl-4,5-dihydro-[1,2,4] thiadiazol-3-yl)-phenyl-amine
derivatives (2a–i)
(4-Chloro-phenyl)-thiourea (1b)
The substituted phenylthiourea (4.18 × 10−3 mol) was
completely dissolved in aqueous sodium hydroxide (2N, 30
mL, 4 × 10−2 mol) at 0 °C. Hydrogen peroxide (30 %, 0.13
mL, 5.51 × 10−3 mol) was then added drop-wise to the
reaction mixture. The mixture was stirred for 3 hrs. at the
same temperature and then it was acidified with con-
centrated HCl to get a pH of 4.5. The resulting colourless
solid was separated and collected by filtration. It was
recrystallized from ethanol to give the pure compound (Cho
et al., 1991). TLC was carried out on precoated silica plate
using the slovent system, methanol: chloroform (1:9).
White crystalline solid; Yield: 32.11 %; Melting range:
150–152 °C; IR (KBr, cm−1) 3415 (N–H), 1400 (C=C),
1081 (C–N), 804 (C=S); ESI-MS m/z = 187.04 [M+1].
(4-Fluoro-phenyl)-thiourea (1c)
White crystalline solid; Yield: 59.90 %; Melting range:
146–148 °C; IR (KBr, cm−1) 3434 (N–H), 1485 (C=C),
1012 (C–N), 823 (C=S); ESI-MS m/z = 171.0 [M+1].
(2-Fluoro-phenyl)-thiourea (1d)
(3,4-Dichloro-phenyl)-[4-(3,4-dichloro-phenyl)-5-imino-
White crystalline solid; Yield: 30.40 %; Melting range:
138–140 °C; IR (KBr, cm−1) 3417 (N–H), 1452 (C=C),
1062 (C–N), 837 (C=S); ESI-MS m/z = 171.06 [M+1].
4,5-dihydro-[1,2,4]thiadiazol-3-yl]-amine (2a)
White crystalline solid; Yield: 36.49 %; Melting range:
134–136 °C; IR (KBr, cm−1) 3438 (N–H),1649 (C=N),
1480 (C=C), 669 (C–S); ESI-MS m/z = 407.29 [M+1].
p-Tolyl-thiourea (1e)
White crystalline solid; Yield: 46.60 %; Melting range:
160–162 °C; IR (KBr, cm−1) 3438 (N–H), 1485 (C=C),
1070 (C–N), 802 (C=S); ESI-MS m/z = 167.07 [M+1].
(4-Chloro-phenyl)-[4-(4-chloro-phenyl)-5-imino-4,5-
dihydro-[1,2,4]thiadiazol-3-yl]-amine (2b)
White crystalline solid; Yield: 25.54 %; Melting range:
164–168 °C; IR (KBr, cm−1): 3110 (N–H),1587 (C=N),
1371 (C=C), 675 (C-S); ESI-MS m/z = 337.16 [M+].
o-Tolyl-thiourea (1f)
White crystalline solid; Yield: 46.60 %; Melting range:
152–154 °C; IR (KBr, cm−1) 3423 (N–H), 1458 (C=C),
1066 (C–N), 825 (C=S); ESI-MS m/z = 167.01 [M+1].
(4-Fluoro-phenyl)-[4-(4-fluoro-phenyl)-5-imino-4,5-
dihydro-[1,2,4]thiadiazol-3-yl]-amine (2c)
(2-Chloro-phenyl)-thiourea (1g)
White crystalline solid; Yield: 74.90 %; Melting range:
120–122 °C; IR (KBr, cm−1) 3448 (N–H),1623 (C=N),
1411 (C=C), 676 (C–S); ESI-MS m/z = 305.16 [M+1].
White crystalline solid; Yield: 37.20 %; Melting range:
128–130 °C; IR (KBr, cm−1) 3348 (N–H), 1411 (C=C),
1058 (C–N), 757 (C=S); ESI-MS m/z = 187.04 [M+1].
(2-Fluoro-phenyl)-[4-(2-fluoro-phenyl)-5-imino-4,5-
dihydro-[1,2,4]thiadiazol-3-yl]-amine (2d)
(4-Bromo-phenyl)-thiourea (1h)
White crystalline solid; Yield: 28.55 %; Melting range:
142–144 °C; IR (KBr, cm−1) 3342 (N–H), 1411 (C=C),
1058 (C–N), 757 (C=S); ESI-MS m/z = 231.0 [M+].
White crystalline solid; Yield: 21.32 %; Melting range:
112–114 °C; IR (KBr, cm−1) 3448 (N–H),1635 (C=N),
1411 (C=C), 669 (C–S); ESI-MS m/z = 304.0 [M+].

Med Chem Res
(5-Imino-4-p-tolyl-4,5-dihydro-[1,2,4]thiadiazol-3-yl)-p-
tolyl-amine (2e)
3.35 (s, 1H), 7.35–7.36 (d, 1H, J=2.4 Hz), 6.91–7.39 (m,
1H), 7.52 (s, 1H), 7.55 (s, 1H), 7.91 (s, 2H); 13C NMR (100
MHz, CDCl3) δ 165.0 (CONH), 162.2 (CN), 146.0 (CH of
Ph) , 137.0 (C of Ph), 135.7 (C of Ph), 135.0 (C of Ph),
133.4 (C of Ph), 130.7 (CH of Ph), 128.9 (C of Ph), 124.8
(C of Ph), 122.3 (CH of Ph), 119.0 (CH of Ph), 115.8 (CH
of Ph), 114.0 (CH of Ph); ESI-MS m/z = 408.11[M+1];
Anal. calcd. for C14H7Cl4N3OS: C, 38.02; H, 2.74; N,
12.67; found: C, 38.05; H, 2.77; N, 12.68.
White crystalline solid; Yield: 31.35 %; Melting range:
176–180 °C; IR (KBr, cm−1): 3350 (N–H),1608 (C=N),
1413 (C=C), 671 (C–S); ESI-MS m/z = 297.81 [M+1].
(5-Imino-4-o-tolyl-4,5-dihydro-[1,2,4]thiadiazol-3-yl)-o-
tolyl-amine (2f)
White crystalline solid; Yield: 41.24 %; Melting range:
130–134 °C; IR (KBr, cm−1): 3446 (N–H),1625 (C=N),
1409 (C=C), 700 (C–S); ESI-MS m/z = 296.06 [M+].
4-(4-Chloro-phenyl)-3-(4-chloro-phenylamino)-4H-[1,2,4]
thiadiazol-5-one (3b)
White crystalline solid; Yield: 33.23 %; Melting range:
(2-Chloro-phenyl)-[4-(2-chloro-phenyl)-5-imino-4,5-
dihydro-[1,2,4]thiadiazol-3-yl]-amine (2g)
136–138 °C; IR (KBr, cm−1): 3232 (N–H),1714 (C=O),
1328 (C=C), 634 (C–S); H-NMR (300 MHz, CDCl3) δ
1
3.37 (s, 1H), 7.19 7.36 (m, 4H), 7.47–7.50 (s, 4H); 13C
NMR (100 MHz, CDCl3) δ 165.6 (CONH), 163.3 (CN),
145.0 (C of Ph), 137.0 (C of Ph), 131.0 (C of Ph), 130.1
(2CH of Ph),129.2 (2CH of Ph), 124.2 (C of Ph), 122.6
(2CH of Ph), 117.7 (2CH of Ph); ESI-MS m/z = 338.19
[M+]; Anal. calcd. for C14H9Cl2N3OS: C, 45.04; H, 3.78; N,
15.0; found: C, 45.02; H, 3.81; N, 15.03.
White crystalline solid; Yield: 50.12 %; Melting range:
108–110 °C; IR (KBr, cm−1): 3360 (N–H),1593 (C=N),
1537 (C=C), 683 (C–S); ESI-MS m/z = 337.16 [M+].
(4-Bromo-phenyl)-[4-(4-bromo-phenyl)-5-imino-4,5-
dihydro-[1,2,4]thiadiazol-3-yl]-amine (2h)
White crystalline solid; Yield: 23.20 %; Melting range:
156–162 °C; IR (KBr, cm−1) 3442 (N–H),1608 (C=N),
1479 (C=C), 669 (C–S); ESI-MS m/z = 337.16 [M+].
4-(4-Fluoro-phenyl)-3-(4-fluoro-phenylamino)-4H-[1,2,4]
thiadiazol-5-one (3c)
Brownish white crystalline solid; Yield: 81.25 %; Melting
range: 184–186 °C; IR (KBr, cm−1): 3220 (N–H), 1623
(C=O), 1515 (C=C), 669 (C–S); 1H-NMR (300 MHz,
CDCl3) δ 3.34 (s, 1H), 7.12–7.17 (s, 4H), 7.37–7.39 (s, 4H);
13C NMR (100 MHz, CDCl3) δ 165.7 (CONH), 163.4 (CN),
158.1 (C of Ph), 153.4 (C of Ph), 142.9 (C of Ph), 134.2 (C
of Ph), 123.1 (2CH of Ph), 117.1 (2CH of Ph), 116.1 (2CH
of Ph), 114.9 (2CH of Ph); ESI-MS m/z = 306.12 [M+1];
Anal. calcd. for C14H9F2N3OS: C, 55.08; H, 2.97; N, 13.76;
found C, 55.05; H, 2.98; N, 13.78.
[5-Imino-4-(2-methoxy-phenyl)-4,5-dihydro-[1,2,4]
thiadiazol-3-yl]-(2-methoxy-phenyl)-amine (2i)
White crystalline solid; Yield: 27.05 %; Melting range:
146–148 °C; IR (KBr, cm−1) 3139 (N–H),1693 (C=N),
1402 (C=C), 619 (C–S); ESI-MS m/z = 329.0 [M+1].
General procedure for the synthesis of 4-phenyl-3-
phenylamino-4H-[1,2,4]thiadiazol-5-one derivatives
(3a–i)
4-(2-Fluoro-phenyl)-3-(2-fluoro-phenylamino)-4H-[1,2,4]
thiadiazol-5-one (3d)
The compounds 2a–i (0.01 mol) were taken separately in a
round-bottomed flask. After adding 10 mL of hydrochloric
acid in 25 mL of ethanol, they were refluxed for 3 h on a
water bath. After cooling, the product was filtered and
recrystallized from ethanol (Gupta et al., 2009). TLC was
carried out on precoated silica plate using the solvent sys-
tem, methanol: chloroform (1:9).
Light yellow amorphous solid; Yield: 45.39 %; Melting
range: 168–170 °C; IR (KBr, cm−1): 3249 (N–H),1730
(C=O), 1585 (C=C), 668 (C–S); 1H-NMR (300 MHz,
CDCl3) δ 3.37–3.44 (s, 1H), 7.12–7.24 (s, 5H), 7.34 (s, H);
7.64–7.69 (s, 2H); 13C NMR (100 MHz, CDCl3) δ 165.9
(CONH), 163.8 (CN), 154.9 (CF of Ph), 147.8 (CF of Ph),
134.2 (C of Ph), 126.1 (CH of Ph), 125.5 (C of Ph), 124.5
(CH of Ph), 123.9 (CH of Ph), 122 (CH of Ph), 119.8 (CH
of Ph), 116.7 (CH of Ph), 115.9 (CH of Ph), 114.6 (CH of
Ph); ESI-MS m/z = 306.03 [M+1]; Anal. calcd. for
C14H9F2N3OS: C, 55.08; H, 2.97; N, 13.76; found C, 55.06;
H, 2.97; N, 13.79.
4-(3,4-Dichloro-phenyl)-3-(3,4-dichloro-phenylamino)-4H-
[1,2,4]thiadiazol-5-one (3a)
White crystalline solid; Yield: 68.47 %; Melting range:
192–194 °C; IR (KBr, cm−1): 3445 (N–H),1724 (C=O),
1
1429 (C=C), 650 (C–S); H-NMR (300 MHz, CDCl3) δ

Med Chem Res
4-p-Tolyl-3-p-tolylamino-4H-[1,2,4]thiadiazol-5-one (3e)
Ph),113.7 (CBr of Ph); ESI-MS m/z = 428.03 [M+1]; Anal.
calcd. for C14H9Br2N3OS: C, 39.37; H, 2.12; N, 9.84; found
C, 39.35; H, 2.11; N, 9.83.
White crystalline solid; Yield: 48.64 %; Melting range:
110–112 °C; IR (KBr, cm−1): 3421 (N–H),1714 (C=O),
1519 (C=C), 669 (C-S); 1H-NMR (300 MHz, CDCl3) δ
2.26 (s, 6H), 3.39 (s, 1H), 7.00–7.34 (m, 8H); 13C NMR
(100 MHz, CDCl3) δ 165.6 (CONH), 163.4 (CN), 144.1 (C
of Ph), 135.7 (C of Ph), 134.1 (C of Ph), 130.6 (2CH of Ph),
129.2 (2CH of Ph), 128.0 (C of Ph), 121.1 (2CH of Ph),
115.4 (2CH of Ph), 21.1 (2CH3); ESI-MS m/z = 298.0
[M+1]; Anal. calcd. for C16H15N3OS: C, 57.80; H, 6.06; N,
16.85; found: C, 57.81; H, 6.04; N, 16.83.
4-(2-Methoxy-phenyl)-3-(2-methoxy-phenylamino)-4H-
[1,2,4]thiadiazol-5-one (3i)
Grey crystalline solid; Yield: 57.14 %; Melting range: 172–
176 °C; IR (KBr, cm−1): 3103 (N–H),1730 (C=O), 1371
1
(C=C), 715 (C–S); H-NMR (300 MHz, CDCl3) δ 3.34 (s,
1H), 3.80 (s, 6H), 6.87–6.92 (s, 2H), 7.01–7.04 (s, 2H),
7.11–7.16 (m, 2H), 7.79–7.81 (s, 2H); 13C NMR (100 MHz,
CDCl3) δ 165.2 (CONH), 164.0 (CN), 154.2 (C–O of Ph),
149.1 (C–O of Ph), 132.9 (C of Ph), 125.7 (CH of Ph),
123.9 (C of Ph), 122.0 (CH of Ph), 121. 6 (CH of Ph), 120.8
(CH of Ph), 119.5 (CH of Ph), 116.8 (CH of Ph), 115.0 (CH
of Ph), 114.4 (CH of Ph), 56.8 (2OCH3); ESI-MS m/z =
330.14 [M+1]; Anal. calcd. for C16H15N3O3S: C, 52.72; H,
5.53; N, 15.37; found: C, 52.70; H, 5.52; N, 15.37.
4-o-Tolyl-3-o-tolylamino-4H-[1,2,4]thiadiazol-5-one (3f)
White amorphous solid; Yield: 37.50 %; Melting range:
144–146 °C; IR (KBr, cm−1): 3247 (N–H),1710 (C=O),
1
1515 (C=C), 611 (C–S); H-NMR (300 MHz, CDCl3) δ
2.18 (s, 6H), 3.42 (s, 1H), 7.00–7.34 (m, 8H); 13C NMR
(100 MHz, CDCl3) δ 165.6 (CONH), 163.4 (CN), 147.9 (C
of Ph), 139.3 (C of Ph), 130.2 (CH of Ph), 129.6 (CF of Ph),
128.9 (CH of Ph), 126.8 (CH of Ph), 125.6 (CH of Ph),
124.9 (CH of Ph), 123.7 (CH of Ph), 120.0 (CH of Ph),
119.0 (CH of Ph), 115.8 (CH of Ph), 12.1 (2CH3); ESI-MS
m/z = 297.02 [M+]; Anal. calcd for C16H15N3OS: C, 57.80;
H, 6.06; N, 16.85; found: C, 57.79; H, 6.10; N, 16.87.
In vitro studies
Determination of partition coefficient
“Shake Flask Method” was adopted for the determination of
partition coefficient of the synthesized compounds (3a–i).
Initially, 2 mg of the synthesized compound(s) were dissolved
in a mixture of water: octanol (1:1, 100 mL). It was then
shaken for 30 min and kept aside for 24 h to achieve equili-
brium. The mixture was separated out in to two phases and
the absorbance of the octanol phase was determined. Finally,
these observed absorbances (Table 2) were extrapolated over
the standard curve so as to obtain the concentration of
the compounds in the octanol phase. The log P value of the
synthesized compounds was then determined from the
obtained concentrations in the octanol phase (Pandey et al.,
2016; Harrold and Yee, 2005; Ashford, 2002).
4-(2-Chloro-phenyl)-3-(2-chloro-phenylamino)-4H-[1,2,4]
thiadiazol-5-one (3g)
White amorphous solid; Yield: 32.64 %; Melting range:
154–156 °C; IR (KBr, cm−1): 3263 (N–H), 1608 (C=O),
1
1411 (C=C), 669 (C–S); H-NMR (300 MHz, CDCl3) δ
3.44 (s, 1H), 7.14–7.34 (m, 4H), 7.46–7.49 (m, 2H), 7.64–
7.66 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 165.2
(CONH), 163.7 (CN), 147.9 (C of Ph), 139.1 (C of Ph),
130.2 (CH of Ph), 129.7 (CH of Ph), 127.7 (CH of Ph),
126.4 (CH of Ph), 125.9 (CCl of Ph), 125.0 (CH of Ph),
122.1 (CH of Ph), 120.2 (CCl of Ph), 119.6 (CH of Ph),
117.1 (CH of Ph); ESI-MS m/z = 338.11 [M+]; Anal. calcd.
for C14H9Cl2N3OS: C, 45.04; H, 3.78; N, 15.01; found: C,
45.08; H, 3.75; N, 15.05.
Hydrolysis studies
10 mg of the synthesized compounds were dispersed/dis-
solved in 100 mL of simulated gastric fluid (SGF)/simulated
intestinal fluid (SIF). The resulting mixture was shaken on
an orbital shaker at a temperature of 37 2 °C. The samples
were withdrawn at regular intervals of 0, 15, 30, 45, 60, 75,
90, 105, 120 min. Samples were suitably diluted, filtered
and analysed spectrophotometrically at the designated
absorption maxima (λmax) of each compound.
4-(4-Bromo-phenyl)-3-(4-bromo-phenylamino)-4H-[1,2,4]
thiadiazol-5-one (3h)
Light brown amorphous solid;Yield: 33.80 %; Melting
range: 162–164 °C; IR (KBr, cm−1): 3271 (N–H), 1622
(C=O), 1467 (C=C), 669 (C–S); 1H-NMR (300 MHz,
CDCl3) δ 3.34–3.47 (m, 1H), 7.39–7.50 (m, 8H); 13C NMR
(100 MHz, CDCl3) δ 165.0 (CONH), 163.8 (CN), 145.1 (C
of Ph), 138.1 (C of Ph), 133.0 (2CH of Ph), 131.8 (2CH of
Ph), 123.2 (2CH of Ph), 119.1 (CBr of Ph), 117.5 (2CH of
Anticonvulsant activity
Male albino mice, weighing 25–30 g each, were used for the
assessment of the anticonvulsant activity of the synthesized

Med Chem Res
1, 2, 4-thiadiazolinone derivatives. Animals were obtained
from the animal house, Faculty of Pharmacy, BBDNIIT,
Lucknow, (U.P.). The animals were housed in poly-
propylene cages with steel net in temperature controlled
room under standard living conditions of 25 5 °C and
relative humidity of 55 5 with regular 12 hrs. light and 12
hrs. dark cycles and allowed free access to standard
laboratory food and water. All the animals were treated
humanely in accordance with the guidelines laid down by
the Institutional Animal Ethics Committee (IAEC No.
BBDGEI/IAEC/12/2011).
phase of convulsions. Therefore, this phase was considered
as an important phase for the activity (Shukla et al., 2016).
Molecular docking studies
The binding modes and binding affinity of the synthe-
sized compounds into GABAA receptor protein crystal
structure (PDB ID: 4COF) was obtained using GLIDE
docking program (version 6.6) of Schrodinger Inc. The
protein–ligand crystal complex was downloaded from
Protein Data Bank (PDB), and optimized using “protein
preparation wizard”. The ligands were prepared by Lig-
Prep module, version 3.3 (Schrödinger, LLC, USA),
which uses optimized potential liquid simulations 2005
force field, to obtain corresponding energy minima. The
default settings were used for all the other parameters. To
validate the docking protocol, re-docking experiment was
performed in which the ligand conformation of co-crystal
ligand was extracted from the crystal structure of the
corresponding GABAA receptor protein/ligand complex
and docked back into its native binding pocket. GLIDE-
XP precision mode perfectly reproduced the experimental
position and accurately predicted the binding conforma-
tion of the ligand. The protein–ligand complex 4COF was
selected on the basis of crystal resolution, R-value, re-
docking GLIDE score and root mean square deviation of
docked pose from the bioactive crystal conformation.
Anticonvulsant activity by maximal electroshock (MES)
method
All the animals were divided in to three main groups, each
group containing six animals (n = 6).
Anticonvulsant activity of the synthesized compounds
was determined by their ability to provide protection from
convulsions in albino mice. The study was started 45 min
after the intraperitoneal injection of 0.5 % aqueous car-
boxymethyl cellulose (CMC) suspension (vehicle)/ test
(3a–i) / standard (Phenytoin, 25 mg/kg b.w.) compounds,
which were suspended vehicle. Convulsions were induced
by MES using the apparatus with corneal electrodes
(Medicraft Electro-Convulsiometer). The intensity of the
applied stimulus was 50 mA, 50 Hz, for 0.2 s, for every
animal. This intensity was enough to produce a character-
istic extensor tonus phase. Animals were observed
approximately for 5 min and the characteristic phases like
flexion, extensor, clonus, stupor and recovery or death were
recorded. Finally, the percentage protection of convulsion
relative to control was calculated for various doses of
synthesized derivatives. All the anticonvulsants shorten or
abolish the extensor tonus phase of convulsion. Therefore,
this phase was considered as an important phase for the
activity (Vogel, 2002).
In silico prediction of pharmacokinetic and toxicity
parameters
Early prediction of ADME (absorption, distribution, meta-
bolism and excretion) inadequacies minimizes the clinical
trial failure risks of the drug candidates, in later stages of
drug discovery and development, and hence reduces
financial burden. QikProp, version 4.3, Schrödinger, LLC,
New York, NY, 2015 program was used for in silico pre-
diction of pharmacokinetic properties of the synthesized
compounds. Furthermore, LAZAR and OSIRIS property
explorer programs were used for the in silico toxicity pre-
dictions (such as acute toxicity, reproductive toxicity, irri-
tancy, carcinogenicity, tumoriogenicity and mutagenicity)
of the synthesized derivatives.
Anticonvulsant activity by isoniazid (INH)-induced seizures
model
All the mice were divided into three groups, each containing
six animals (n = 6), for the study. The study was started
after intraperitonial treatment of 0.5 % aqueous CMC sus-
pension (vehicle) / test compounds (3a–i) / standard
(Diazepam, 4 mg/kg b. w.) in vehicle. After 30 min, seizures
were induced in the animals by using INH (300 mg/kg b.
w.). During the next 120 min, the occurrence of tonic-clonic
seizures and death was recorded. Finally, the percentage
protection of convulsions relative to control was calculated
for various doses of the synthesized derivatives. All the
anticonvulsant agents shorten or abolish the tonus-clonus
Statistical analysis
All the values of the experimental results are expressed as
mean SEM and the statistical significance between the
control and treated groups was calculated by one-way
analysis of variance (ANOVA), followed by Dunnett’s
multiple comparision tests; P < 0.0001 was considered
statistically significant. Statistical analysis was carried out

Med Chem Res
Fig. 1 Synthesis of 3, 4
substituted 1, 2, 4-thiadiazoline
derivatives
S
ArNH2 + NH4SCN + HCl
Ar NH C NH2
Stirring
(1a-i)
H2O2
NaOH
Stirring, 0 °C
Ar
N
Ar
N
HCl
Ar NH
NH
Ar NH
O
Reflux, 3 hr
N
S
N
S
(2a-i)
(3a-i)
Cl
F
Cl
Cl
F
H3C
Ar =
OCH3
Cl
CH3
Br
Table 1 Determination of
partition coefficient of the
synthesized compounds (3a–i)
Comp.
A
Conc. for standard curve in (µg/ml)
B
C
D
Log P
2
4
6
8
10
3a
3b
3c
3d
3e
3f
265.5
271.0
269.0
267.5
270.0
268.0
270.5
275.5
267.5
0.183
0.120
0.069
0.091
0.189
0.151
0.221
0.024
0.111
0.361
0.241
0.146
0.189
0.279
0.303
0.254
0.069
0.161
0.542
0.362
0.227
0.269
0.354
0.444
0.284
0.109
0.206
0.723
0.481
0.325
0.360
0.445
0.599
0.324
0.144
0.262
0.921
0.610
0.403
0.453
0.528
0.755
0.354
0.184
0.313
0.899
0.595
0.394
0.435
0.520
0.743
0.344
0.176
0.285
9.93
9.80
9.85
9.81
9.88
9.90
9.87
9.89
9.04
0.07
0.20
0.15
0.19
0.12
0.10
0.13
0.11
0.96
2.15
1.69
1.81
1.71
1.91
1.99
1.88
1.95
0.97
3g
3h
3i
A = λmax in octanol
B = absorbance of octanol phase after 24 hrs. (y)
C = concentration of compound in octanol (x) (µg/ml)
D = concentration of compound in water (µg/ml)
using Graph pad prism 3.0 (Graph pad software, San
Diego, CA).
were prepared by reacting different aromatic amines with
ammonium thiocyanate, in the presence of concentrated
hydrochloric acid. Compounds 1a–i were oxidatively
cyclized into (5-Imino-4-phenyl-4,5-dihydro-[1,2,4] thia-
diazol-3-yl)-phenyl-amine derivatives, 2a–i. Compounds of
the second step 2a–i, on refluxing with concentrated
hydrochloric acid, gave 4-Phenyl-3-phenylamino-4H-
[1,2,4]thiadiazol-5-one derivatives (3a–i).
Results and discussion
The synthesis of 1,2,4-thiadiazol derivatives were accom-
plished as showed in Fig. 1. Aryl thiourea derivatives 1a–i

Med Chem Res
Table 2 In-vitro hydrolysis
study of the synthesized
compounds (3a–i)
Comp.
λmax 0 min 15 min 30 min 45 min 60 min 75 min 90 min 105 min 120 min Z
3a SGF 246.4 0.659 0.656 0.647 0.645 0.636 0.626 0.617
—
—
6.37
SIF 248.5 0.157 0.150 0.147 0.146 0.141 0.138 0.135 0.131
3b SGF 267.5 0.195 0.190 0.188 0.187 0.186 0.186 0.185
SIF 268.0 0.177 0.176 0.173 0.173 0.171 0.169 0.167 0.165
3c SGF 258.4 0.269 0.262 0.260 0.246 0.244 0.242 0.239
SIF 255.0 0.090 0.089 0.089 0.088 0.079 0.078 0.077 0.076
3d SGF 252.5 0.339 0.337 0.335 0.324 0.324 0.323 0.321
SIF 254.6 0.198 0.196 0.196 0.194 0.190 0.186 0.184 0.184
3e SGF 259.5 0.433 0.429 0.424 0.423 0.417 0.412 0.410
SIF 256.7 0.390 0.388 0.385 0.381 0.377 0.369 0.369 0.362
3f SGF 248.5 0.745 0.744 0.741 0.732 0.710 0.702 0.702
SIF 250.0 0.535 0.532 0.531 0.531 0.525 0.521 0.519 0.519
3g SGF 251.5 0.764 0.764 0.735 0.733 0.727 0.715 0.711
SIF 256.8 0.635 0.632 0.632 0.629 0.610 0.608 0.605 0.604
3h SGF 249.0 0.659 0.638 0.620 0.620 0.610 0.605 0.603
SIF 245.0 0.465 0.460 0.459 0.458 0.452 0.450 0.444 0.432
3i SGF 251.0 0.396 0.380 0.374 0.364 0.360 0.328 0.320
0.131
—
16.56
5.12
6.77
11.15
17.77
5.30
8.08
5.31
8.20
5.7
—
0.165
—
—
0.074
—
—
0.182
—
—
0.358
—
—
0.505
—
5.06
6.9
—
0.602
—
5.19
8.49
11.82
19.19
10.40
—
0.410
—
—
SIF 253.5 0.269 0.264 0.261 0.258 0.248 0.248 0.245 0.243
0.241
SGF simulated gastric fluid, SIF simulated intestinal fluid,
Z = % hydrolysis
Table 3 Anticonvulsant
activity of the synthesized
compounds (3a–i) in the MES
method
Compound Duration of various phases (time in seconds)
Flexor Clonus Stupor
Extensora
Mean % Inhibition of
seizures SEMb
Recovery or
death
Control
3.4 0.24 10.8 0.96 2.6 0.40 118.2 2.97 Death
—
Standard
—
—
—
—
—
—
—
—
1
0.4 0.24
0.6 0.40
1.8 0.26
1.2 0.37
—
—
—
—
—
—
35.2 1.06 Recovery
41.4 1.07 Recovery
41.2 0.80 Recovery
20.8 0.86 Recovery
30.6 0.74 Recovery
28.2 0.80 Recovery
27 0.83 Recovery
72 2.66 Recovery
96.07 2.55
92.54 3.43
81.32 3.49
89.68 3.04
80.57 1.95
91.50 2.33
83.37 3.19
84.50 2.31
87.18 1.62
28.09 1.51
3a
3b
3c
3d
3e
3f
2
1
0.24
0.31
1.8 0.37 0.8 0.58
1.6 0.14 0.8 0.48
3g
3h
3i
0.31
0.31
1.4 0.24 0.8 0.37 77.2 2.51 Recovery
7.6 0.40 0.6 0.24 67.8 1.68 Recovery
2
a Extensor phase considered as an important phase for the anticonvulsant activity in MES model. Therefore,
the data of this phase was considered as activity
b
Mean % inhibition of extensor phase SEM of all the groups were compared with the control group at
95 % confidence limit with P < 0.0001, Dunnet’s test, n = 6
All the synthesized compounds were characterized by
spectroscopic methods like IR, mass and NMR. Elemental
formulae of all the compounds were determined by ele-
mental analysis and compared with the calculated values.
For several classes of CNS active substances, Hansch
and Leo found that the blood–brain barrier (BBB)
penetration is optimal when the log P values are in the range
of 1.5–2.7, with the mean value of 2.1. Hydrogen bonding
approach is also a simple rule for predicting BBB pene-
tration. Because hydrogen bonding is primarily associated
with oxygen and nitrogen moieties in a molecule, then if the
sum of the nitrogen (N) and oxygen (O) atoms in the

Med Chem Res
molecule is five or less (BBB penetration = [N+O] = ≤ 5),
then the molecule has a high probability of entering the
CNS (Pajouhesh and Lenz, 2005). All the synthesized
compounds, except 3i, have log P values in the range of
1.69–2.15 and the sum of N + O is 4. Log P value of the
compound containing 3, 4-dichlorophenyl functionality, at
C-3 and C-4 position of 1, 2, 4-thiadiazolinone ring (3a)
was found to be 2.15, and was found to be the most lipo-
philic compound of the series (Table 1). Compound 3i was
the least lipophilic compound, with a log P value of 0.97.
The synthesized 1, 2, 4-thiadiazolinone derivatives did
not possess any functional group susceptible to hydrolysis.
However, all the synthesized compounds (3a–i) were tested
for in vitro hydrolysis using SGF and SIF to determine their
stability. The stability of the compounds and their probable
bioavailability in SGF was found to be in the order 3b > 3d
> 3e > 3f > 3a > 3g > 3h > 3c > 3i in the series. Similarly,
the stability of the compounds and their possible bioavail-
ability in SIF was in the order 3f > 3g > 3b > 3d > 3e > 3i
> 3h > 3a > 3c in the series. The results of stability in SGF
and SIF indicated that the compounds were stable (Table 2).
All the compounds (3a–i) were screened for their antic-
onvulsant activity against MES-induced seizures and INH-
induced seizures at a dose of 30 mg/kg b.w. intraperitoneal.
The MES test in mice is a suitable model for grand mal epi-
lepsy. INH is regarded as a GABA-synthesis inhibitor and
may be responsible for the induction of petit mal epilepsy like
pentylenetetrazole (Govindu and Adikay, 2014). Antic-
onvulsant activity of all the compounds and standards, against
both the models, were compared with the respective control
groups by one way ANOVA followed by Dunnett’s multiple
comparision tests. All the treated groups were found to be
different from the control group and statistically significant at
p < 0.0001 (Table 3 and Table 4). In the MES method, all the
Table 4 Anticonvulsant activity of the synthesized compounds (3a–i)
in INH-induced seizures model
Compound Duration of various phases
(time in seconds)
Mean % inhibition of
seizures SEMb
Tonus-Clonusa Recovery or
death
Control
74.6 1.030
Death
—
Standard 35 2.049
Recovery
Recovery
Death
53.197 2.07
46.42 2.77
20.04 2.20
26.50 1.21
32.86 3.07
29.07 2.43
26.08 3.70
35.62 2.32
39.54 3.65
19.52 2.33
3a
3b
3c
3d
3e
3f
3g
3h
3i
40 2.258
59.4 1.204
54.8 1.043
50 1.924
52.8 1.90
55 2.049
48 1.673
45 2.324
60 3.742
Death
Recovery
Death
Recovery
Recovery
Recovery
Death
a
Tonus-clonus phase considered as an important phase for the
anticonvulsant activity in INH model. Therefore, the data of this phase
was considered as activity
b
Mean % inhibition of tonus-clonus phase SEM of all the groups
were compared with the control group at 95 % confidence limit with
P < 0.0001, Dunnet’s test, n = 6
Fig. 2 a 3D Ligand receptor interaction diagram of co-crystal ligand at the binding site of GABAA protein (PDB-ID: 4COF). b 3D Ligand receptor
interaction diagram of compound 3a at the binding site of GABAA protein (PDB-ID: 4COF)

Med Chem Res
synthesized compounds showed inhibition of convulsions in
the range of 28.09–92.54 %, in comparison to the standard
drug phenytoin, which completely inhibited the seizures pro-
duced by electroshock in albino mice. In the INH-induced
seizures model, all the compounds showed inhibition of the
convulsions in the range of 19.52–46.42 %, in comparison to
diazepam, which completely inhibited the seizures produced
by isoniazid. Compound 3a exhibited maximum response in
the MES test, as. 92.54 % protection, and in the INH-induced
seizures, as 46.42 % protection and compound 3i shown the
least activity. The compounds 3b, 3c, 3e, 3g and 3i also
showed good activity in the MES test, i.e, 83.33 %, 88.8 %,
90.74 %, 85.18 % and 87.03 % respectively in comparison
to the other substituted compounds. The 3, 4-dichloro group
containing compound (3a) was found to be the most active
compound in this series.
Molecular docking studies of the synthesized compounds
with the GABAA receptor protein displayed good docking
scores (Figs. 2a and 2b). The most active derivative (3a) in
the in vivo study demonstrated best results in molecular
docking studies also. All the synthesized derivatives quali-
fied ADME barrier during in silico studies (Table 5), and
predicted to be nontoxic, nonmutagenic and non-
carcinogenic by “LAZAR” and “OSIRIS” property explorer
programs (Table 6).
The characteristic feature of this series is the substitution
with different moieties at third and fourth position of the 1,
2, 4-thiadiazole ring. All the compounds showed good
anticonvulsant activity.
Binding orientations of the synthesized derivatives, in
the typical binding pocket of GABAA receptor protein
was studied with the help of molecular docking studies.
Non-covalent interactions of the most active derivative,
3a in complex with receptor protein amino acid residues
have been illustrated in Figs. 2a and 2b. Docking simu-
lations clearly demonstrated that, Glu 155, Ser 156, Tyr
157 and Tyr 205 are the key interacting residues of
GABAA receptor protein 4COF. A crucial H-bond inter-
action Tyr 157 amino acid residue was observed with the
-NH group of the compound 3a. Also, the two phenyl
rings of the compound 3a showed conserved pi-pi stach-
ing interactions of 4COF crystal ligand with the Phe 200
and Phe 205 amino acid residues, respectively. Moreover,
favourable in silico ADME performance was observed for
the synthesized derivatives with excellent correlation to
CNS related parameters, which in turn support antic-
onvulsant efficacy, as observed in the in vivo studies. The
in silico toxicity prediction (using LAZAR and OSIRIS
property explorer) results established that most of the
synthesized derivatives were devoid of serious toxic
effects such as acute toxicity, reproductive toxicity, irri-
tancy, carcinogenicity, tumoriogenicity and mutagenicity.

Med Chem Res
Table 6 In silico toxicity
prediction of the synthesized
compounds (3a–i)
Comp. OSIRIS Property Explorer Prediction
LAZAR Prediction
Mutagenic
Tumoriogenic Irritant Reproductive Max.
Acute
daily dose toxicity
Carcinogenic
potency in mouse
(mmol)
(mmol)
3a
3b
3c
3d
3e
3f
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Y
0.0029
0.0091
0.0404
0.0495
0.0433
0.0609
0.0091
0.0746
0.0175
Non-carcinogenic
Non-carcinogenic
Non-carcinogenic
Non-carcinogenic
Carcinogenic
X
Y
X
0.0052
0.0145
0.0088
0.0046
0.0057
0.0052
Y
X
X
X
Non-carcinogenic
Non-carcinogenic
Non-carcinogenic
Non-carcinogenic
3g
3h
3i
Irritant
X
X
High risk
mutagenic
X = non-toxic
Y = not enough similar compounds in training dataset
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Conclusion
From the preliminary in vitro studies, it was concluded that
the compounds, which have high log P value showed less in
vitro hydrolysis and vice versa. Among the nine compounds
used in this study, 3a, 3c, 3e and 3h may be considered to
be potent candidates with promising anticonvulsant prop-
erties. Compound 3a was found to be the most active
anticonvulsant, which was further confirmed by the docking
simulations, as a GABAA receptor agonist. The in silico
toxicity prediction results displayed the nontoxic and non-
carcinogenic nature of most of the compounds. Moreover,
development of this class of compounds may lead to some
interesting chemical entities with improved pharmacologi-
cal profiles. Therefore, this class of compounds may be used
as a template to generate more drugs to suppress
convulsions.
Compliance with ethical standards
Conflict of interest The authors declare that they have no com-
peting interests.
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