Structure-based design, synthesis, and molecular modeling studies of 1-(benzo[d]thiazol-2-yl)-3-(substituted aryl)urea derivatives as novel anti-Parkinsonian agents

Article abstract of DOI:10.1007/s00044-011-9786-y

1-(Benzo[d]thiazol-2-yl)-3-(substituted aryl)urea derivatives were designed and synthesized as our efforts to discover novel anti-Parkinsonian agents with improved pharmacological profile in haloperidol-induced catalepsy and oxidative stress in mice. All of the compounds were found to be active in alleviating haloperidol-induced catalepsy in mice. Furfuryl, 2- and/or 3-methoxy substituted phenyl derivatives emerged as potent agents. With exception of 2-chloro,5-trifluoromethyl-substituted analog, halogensubstituted derivatives exhibited moderate anti-Parkinsonian activity. Biochemical estimations of malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) from brain homogenate were carried out to highlight the neuroprotective properties associated with them. Molecular docking studies of these compounds with adenosine A_2A receptor exhibited very good binding interactions and warrants further studies to confirm their binding with human A_2A receptor for the design and development of potent antagonists. Parameters for Lipinski's rule of 5 were calculated computationally because pharmacokinetic and metabolic behaviors in the body often are linked to the physical properties of a compound. None of the synthesized compounds violated Lipinski's rule, making them suitable drug candidate for the treatment of Parkinson's disease. Springer Science+Business Media, LLC 2011.

Full text of DOI:10.1007/s00044-011-9786-y

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2012) 21:2630–2643
DOI 10.1007/s00044-011-9786-y
ORIGINAL RESEARCH
Structure-based design, synthesis, and molecular modeling studies
of 1-(benzo[d]thiazol-2-yl)-3-(substituted aryl)urea derivatives
as novel anti-Parkinsonian agents
•
Faizul Azam Medapati Vijaya Vara Prasad
•
Neelaveni Thangavel
Received: 20 May 2011 / Accepted: 16 August 2011 / Published online: 10 September 2011
Ó Springer Science+Business Media, LLC 2011
Abstract 1-(Benzo[d]thiazol-2-yl)-3-(substituted aryl)urea
derivatives were designed and synthesized as our efforts to
discover novel anti-Parkinsonian agents with improved
pharmacological profile in haloperidol-induced catalepsy
and oxidative stress in mice. All of the compounds were
found to be active in alleviating haloperidol-induced cata-
lepsy in mice. Furfuryl, 2- and/or 3-methoxy substituted
phenyl derivatives emerged as potent agents. With exception
of 2-chloro,5-trifluoromethyl-substituted analog, halogen-
substituted derivatives exhibited moderate anti-Parkinso-
nian activity. Biochemical estimations of malondialdehyde
(MDA), glutathione (GSH), superoxide dismutase (SOD),
and glutathione peroxidase (GSH-Px) from brain homoge-
nate were carried out to highlight the neuroprotective prop-
erties associated with them. Molecular docking studies of
these compounds with adenosine A2A receptor exhibited
very good binding interactions and warrants further studies
to confirm their binding with human A2A receptor for the
design and development of potent antagonists. Parameters
for Lipinski’s rule of 5 were calculated computationally
because pharmacokinetic and metabolic behaviors in the
body often are linked to the physical properties of a com-
pound. None of the synthesized compounds violated Lipin-
ski’s rule, making them suitable drug candidate for the
treatment of Parkinson’s disease.
Keywords Parkinson’s disease ꢀ Benzothiazole ꢀ
Urea derivatives ꢀ Neuroprotection ꢀ Docking
Introduction
Parkinson’s disease (PD) is a chronic neurodegenerative
disorder characterized by massive and progressive degen-
eration of the nigrostriatal dopaminergic system which
results in abnormal motor behaviors such as muscular
rigidity, postural abnormality, and tremor (Lang, 2011). The
etiopathogenesis of dopaminergic loss is not yet clear and
continues to be an enigma for the science world (Sulzer,
2007). Various mechanisms—including mitochondrial
defects, oxidative stress, glutamate toxicity, and genetic
factors—are likely to contribute to the degenerative process.
The substantia nigra is involved in the breakdown of
catecholamines (dopamine, norepinephrine, and epineph-
rine), a process that produces free radicals as by-products.
These free radicals are very reactive atoms or molecular
fragments typically having a single unpaired electron, are
neutralized by endogenous antioxidants such as glutathione
(GSH) and antioxidant enzymes, e.g., superoxide dismu-
tase (SOD), glutathione peroxidase (GSH-Px), catalase,
etc. Disturbances in the balance of these processes increase
the number of free radicals, causing a state of oxidative
stress. The hypothesis of oxidative stress proposes that free
radicals damage a neuron and cause its death. Post-mortem
studies in PD brains and studies illustrating the capacity of
oxidizing toxins to induce nigral cell degeneration support
a role for oxidative stress-induced cell death in PD (Jenner
and Olanow, 1998). In addition, some evidences suggest
that compounds that act as antioxidants (e.g., coenzyme-
Q10, vitamin E, glutathione, etc.) may be protective in PD
(Azam, 2010).
F. Azam (&)
Department of Pharmaceutical Chemistry,
NIMS Institute of Pharmacy, NIMS University,
Jaipur 303121, Rajasthan, India
e-mail: faizulazam@gmail.com; azamfaizul@yahoo.co.in
F. Azam ꢀ M. V. V. Prasad ꢀ N. Thangavel
CMR College of Pharmacy, Medchal Road,
Kandlakoya (V) 501401, Hyderabad, India
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Med Chem Res (2012) 21:2630–2643
2631
Currently available medications for PD provide good
symptomatic relief in the early to middle stages of the
disease, but they lose their effectiveness as the disease
progresses because they do not have disease-modifying
properties. Consequently, although PD patients experi-
ence an improved quality of life when they are properly
medicated, both their disease and their response to drug
therapy progressively worsen. Levodopa, the direct pre-
cursor of dopamine, is still the ‘‘gold standard’’. How-
ever, long-term therapy with levodopa is associated with
significant side effects. Therefore, there is a dire need for
new therapeutic strategies aimed at relieving motor
symptoms and slowing the progression of neuronal
degeneration.
During the past few years, our research group has been
focusing on developing neuroprotective agents for the
therapy of various neurological diseases (Azam, 2009;
Azam et al., 2009a, b, c, 2010a, b). In this regard, we have
found 2-aminothiazole ring system as a useful structural
element having application in drug development for the
treatment of PD (Azam, 2009; Azam et al., 2009a). In
particular, urea or thiourea derivatives bearing thiazole
nucleus has been found to confer neuroprotection by
boosting up endogenous antioxidative mechanisms as well
as ameliorating deleterious processes of oxidative stress in
experimental animals (Fig. 1C; Azam, 2009, 2010; Azam
et al., 2009a, b, c, 2010a, b). Several urea-substituted
benzothiazoles (Fig. 1a, b) have also been patented for
R1
R1
N
N
NH
R3
R4
NH
O
S
N
S
N
O
OH
R2
R2
B
A
OCF3
O
C
N
R
N
N
S
H
H
N
N
S
R =
S
D
C
R
NH
NH
NH2
O
O
Synthesized compounds 1-19
R
Hydrogen bond
donor/acceptor
moiety
Electron rich
motiff
Lipophilic group
Pharmacophore model for adenosine A2A receptor antagonists (Ye et al. 2008)
Fig. 1 Design of the title compounds based on pharmacophore model of adenosine A2A receptor antagonists and some known anti-Parkinsonian
agents. A (Flohr et al., 2006, 2007), B (Malefyt and Pickford, 2010), C (Azam 2009), D (Araki et al., 2001)
123

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Med Chem Res (2012) 21:2630–2643
their use in control or prevention of PD (Flohr et al., 2006,
2007; Malefyt and Pickford, 2010). 2-Amino-6-trifluoro-
methoxy benzothiazole (Fig. 1d), a Na? channel blocker
with antiglutamatergic activity is effective against MPTP-
induced neurodegeneration of the nigrostriatal dopaminer-
gic neuronal pathway (Araki et al., 2001). Furthermore,
Hoffmann–La Roche discovered benzothiazole derivatives
as novel scaffold for adenosine A2A receptor antagonists
(Alanine et al., 2006). These antagonists afford neuropro-
tective and antidyskinetic benefits (Schwarzschild et al.,
2006) as well as increase the therapeutic index ratio
between the therapeutic and unwanted side effects of
L-dopa and other D2 receptor agonists (Bara-Jimenez et al.,
2003; Hauser et al., 2003).
8201 PC FT-IR spectrophotometer and wave numbers are
given in cm-1. The mass spectra were recorded on Jeol
1
SX-102 (FAB). H NMR spectra, in CDCl3 solution, were
recorded on a Bruker DRX-300 instrument at 298 K.
Chemical shifts are reported as ppm relative to TMS as
internal standard. Melting points (°C) were determined
with an open glass capillary tube and are uncorrected.
Elemental analyses were performed on Elementar Vario
EL III instrument. The found values for C, H, and N were
always 0.4% of the theoretical ones.
Synthesis of the compounds
Synthesis of benzo[d]thiazol-2-amine. It was synthesized
from aniline and potassium thiocyanate as described pre-
viously (Jimonet et al., 1999).
In addition to these, a large number of compounds
having thiazole skeleton are potent adenosine A2A receptor
antagonists (Azam et al., 2009d; Cole et al., 2009; Nak-
ajima et al., 2010; Sams et al., 2010) which have been
shown to produce an increase in locomotor activity, a
decrease of neuroleptic-induced catalepsy, a decrease of
MPTP-induced motor disability, and several indications of
neuroprotection in response to brain injury (Schwarzschild
et al., 2003; Jenner et al., 2009; Nakajima et al., 2010). The
importance of urea functionality can also be evidenced by
its presence in potent A2A receptor antagonists as well as in
many biologically active compounds including neuropro-
tectants (Di Fabio et al., 1999; Choi et al., 2007).
General procedure for the synthesis of urea derivatives
1–19. To a solution of benzo[d]thiazol-2-amine (0.2 g,
0.002 mol) in 25 ml of dry acetonitrile, a 1.5 M quantity of
appropriate isocyanate in 5 ml dry acetonitrile was added
dropwise at room temperature. The mixture was stirred for
1–4 h until the completion of the reaction and the resultant
precipitate was filtered, washed with acetonitrile and dried.
The product was recrystallized from 95% ethanol.
1-(Benzo[d]thiazol-2-yl)-3-(o-tolyl)urea (1) % Yield: 92;
m.p: 344°C; IR (KBr) mmax 3205, 3096, 2944, 1708, 1624,
1595, 1533, 1441, 1319, 1273, 1190, 1120, 1049, 1016,
938, 756, 743, 695 cm-1; 1H NMR (CDCl3) d 10.81 (s, 1H,
NH), 8.81 (s, 1H, NH), 7.00–7.99 (d, 1H, J = 7.89 Hz),
7.74–7.76 (d, 1H, J = 7.77 Hz), 7.67–7.69 (d, 1H,
J = 8.01 Hz), 7.00–7.53(m, 5H, ArH), 2.36 (s, 3H, CH3);
MS (FAB) m/z 284 (M ? 1)?.
Based on these observations and in view of the structural
requirements for the adenosine A2A receptor antagonism
(Ye et al., 2008), benzothiazolyl urea derivatives were
designed (Fig. 1) and synthesized to obtain better agents
for the treatment of PD. All of the newly synthesized
compounds were biologically evaluated for their ability to
antagonize neuroleptic-induced catalepsy as well as oxi-
dative stress in mice. Flexible ligand docking studies were
performed to assess the molecular interaction of these
compounds with adenosine A2A receptor.
1-(Benzo[d]thiazol-2-yl)-3-(p-tolyl)urea (2) % Yield: 81;
m.p: 326°C; IR (KBr) mmax 3295, 3192, 3056, 1722, 1597,
1512, 1451, 1405, 1312, 1279, 1242, 1185, 1019, 896, 817,
1
752, 726 cm-1; H NMR (CDCl3) d 10.41 (s, 1H, NH),
8.90 (s, 1H, NH), 7.74–7.77 (d, 1H, J = 7.81 Hz),
7.68–7.70 (d, 1H, J = 8.03 Hz), 7.21–7.45 (m, 4H, ArH),
7.11–7.14 (d, 2H, J = 8.07 Hz), 2.32 (s, 3H, CH3); MS
(FAB) m/z 284 (M ? 1)?.
Materials and methods
Chemistry
Synthetic starting material, reagents, and solvents were of
analytical reagent grade or of the highest quality com-
mercially available and were purchased from Aldrich
Chemical Co., Merck Chemical Co. and were dried when
necessary. The progress of the reactions was monitored by
thin layer chromatography with F254 silica-gel precoated
sheets (Merck) using chloroform/ethylacetate (90:10) as
eluent; UV light and iodine vapors were used for detection.
IR spectra were recorded, as KBr pellets, on a Schimadzu
1-(Benzo[d]thiazol-2-yl)-3-(2-methoxyphenyl)urea (3) %
Yield: 62; m.p: 320°C; IR (KBr) mmax 3365, 3100, 2953,
2873, 1773, 1683, 1598, 1566, 1541, 1457, 1441, 1339,
1315, 1276, 1254, 1224, 1195, 1120, 1048, 1030, 940, 746,
1
718, 700 cm-1; H NMR (CDCl3) d 11.08 (s, 1H, NH),
9.04 (s, 1H, NH), 8.23–8.25 (d, H, J = 7.22 Hz), 7.75–7.77
(d, 1H, J = 7.81 Hz), 7.67–7.70 (d, 1H, J = 8.02 Hz),
6.92–7.40 (m, 5H, ArH), 3.94 (s, 3H, OCH3); MS (FAB)
m/z 300 (M ? 1)?.
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2633
%
1-(Benzo[d]thiazol-2-yl)-3-(4-methoxyphenyl)urea (4)
Yield: 87; m.p: 302°C; IR (KBr) mmax 3291, 3056, 1720,
1599, 1551, 1512, 1455, 1413, 1307, 1281, 1249, 1176,
1111, 1031, 899, 828, 802, 755, 729, 681 cm-1; H NMR
%
1-(Benzo[d]thiazol-2-yl)-3-(2-bromophenyl)urea (10)
Yield: 90; m.p: 308°C; IR (KBr) mmax 3327, 3215, 2963,
1670, 1594, 1534, 1434, 1275, 1189, 1023, 935, 888, 848,
750, 721, 667 cm-1; H NMR (CDCl3) d 11.26 (s, 1H,
1
1
(CDCl3) d 10.39 (s, 1H, NH), 8.85 (s, 1H, NH), 7.74–7.76
(d, 1H, J = 7.77 Hz), 7.67–7.69 (d, 1H, J = 8.0 Hz),
7.20–7.49 (m, 4H, ArH), 6.85–6.88 (d, 2H, J = 8.84 Hz),
3.79 (s, 3H, OCH3); MS (FAB) m/z 300 (M ? 1)?.
NH), 9.32 (s, 1H, NH), 8.23–8.26 (d, 1H, J = 7.95 Hz),
6.96–7.77 (m, 7H, ArH); MS (FAB) m/z 349 (M ? 1)?.
1-(Benzo[d]thiazol-2-yl)-3-(4-bromophenyl)urea (11)
%
Yield: 94; m.p: 300°C; IR (KBr) mmax 3231, 3033, 2943,
1710, 1618, 1594, 1540, 1489, 1443, 1400, 1310, 1280,
1247, 1193, 1118, 1075, 1006, 943, 821, 809, 751,
722 cm-1; 1H NMR (CDCl3) d 10.68 (s, 1H, NH), 9.15 (s,
1H, NH), 7.76–7.79 (d, 1H, J = 7.78 Hz), 7.65–7.68 (d,
1H, J = 8.02 Hz), 7.21–7.49 (m, 6H, ArH); MS (FAB) m/z
349 (M ? 1)?.
1-(Benzo[d]thiazol-2-yl)-3-(2,4-dimethoxyphenyl)urea
(5) % Yield: 95; m.p:[350°C; IR (KBr) mmax 3310, 2945,
2826, 1717, 1618, 1541, 1445, 1417, 1276, 1215, 1181,
1
1159, 1132, 1041, 919, 843, 785, 748, 724, 681 cm-1; H
NMR (CDCl3) d 10.93 (s, 1H, NH), 8.85 (s, 1H, NH),
8.04–8.07 (d, 1H, J = 8.75 Hz), 7.74–7.77 (d, 1H,
J = 7.76 Hz), 7.67–7.69 (d, 1H, J = 7.97 Hz), 6.46–7.39
(m, 3H, ArH), 3.92 (s, 3H, OCH3), 3.81 (s, 3H, OCH3); MS
(FAB) m/z 330 (M ? 1)?.
1-(Benzo[d]thiazol-2-yl)-3-(2-fluorophenyl)urea (12)
Yield: 94; m.p: 334°C; IR (KBr) mmax 3258, 3056, 1722,
1619, 1598, 1545, 1454, 1316, 1296, 1277, 1181, 1107,
%
1-(Benzo[d]thiazol-2-yl)-3-(3,4,5-trimethoxyphenyl)urea
(6) % Yield: 93; m.p: 262°C; IR (KBr) mmax 3213, 3110,
2940, 1686, 1620, 1598, 1568, 1505, 1452, 1414, 1355,
1316, 1270, 1232, 1186, 1126, 1029, 1007, 929, 849, 831,
799, 748, 707, 652 cm-1; 1H NMR (CDCl3) d 10.52 (s, 1H,
NH), 8.92 (s, 1H, NH), 7.75–7.77 (d, 1H, J = 7.69 Hz),
7.67–7.70 (d, 1H, J = 7.99 Hz), 7.21–7.41 (m, 4H, ArH),
3.88 (s, 6H, OCH3), 3.79 (s, 3H, OCH3); MS (FAB) m/z
360 (M ? 1)?.
1047, 1018, 935, 896, 854, 818, 787, 756, 726, 691 cm-1
;
1H NMR (CDCl3) d 10.69 (s, 1H, NH), 9.07 (s, 1H, NH),
8.28–8.33 (m, 1H, ArH), 7.01–7.78 (m, 7H, ArH); MS
(FAB) m/z 288 (M ? 1)?.
1-(Benzo[d]thiazol-2-yl)-3-(4-fluorophenyl)urea (13)
Yield: 86; m.p: [350°C; IR (KBr) mmax 3364, 3137, 3062,
2754, 1690, 1600, 1568, 1511, 1444, 1403, 1300, 1272,
%
1
1207, 1156, 1014, 894, 838, 808, 757, 731, 679 cm-1; H
NMR (CDCl3) d 10.50 (s, 1H, NH), 9.05 (s, 1H, NH),
7.75–7.78 (d, 1H, J = 7.73 Hz), 7.67–7.70 (d, 1H,
J = 7.95 Hz), 6.99–7.63 (m, 6H, ArH); MS (FAB) m/z 288
(M ? 1)?.
1-(Benzo[d]thiazol-2-yl)-3-(4-phenoxyphenyl)urea (7)
%
Yield: 91; m.p: 302°C; IR (KBr) mmax 3322, 3062, 2893,
2761, 1688, 1599, 1570, 1508, 1485, 1446, 1408, 1302,
1275, 1229, 1166, 1105, 1069, 1020, 899, 876, 837, 791,
750, 733, 693, 681 cm-1; 1H NMR (CDCl3) d 10.39 (s, 1H,
NH), 9.06 (s, 1H, NH), 6.97–7.77 (m, 13H, ArH); MS
(FAB) m/z 362 (M ? 1)?.
1-(Benzo[d]thiazol-2-yl)-3-(2-chlorophenyl)urea (14)
Yield: 96; m.p: [350°C; IR (KBr) mmax 3374, 3215, 3096,
2950, 1709, 1609, 1528, 1444, 1277, 1194, 1058, 1037,
%
1
1016, 938, 852, 807, 746, 679 cm-1; H NMR (CDCl3) d
1-(Benzo[d]thiazol-2-yl)-3-(naphthalen-1-yl)urea (8)
%
11.19 (s, 1H, NH), 8.82 (s, 1H, NH), 8.29–8.32 (d, 1H,
J = 8.13 Hz), 8.29–8.32 (d, 1H, J = 8.11 Hz), 7.01–7.78
(m, 6H, ArH); MS (FAB) m/z 305 (M ? 1)?.
Yield: 98; m.p: 312°C; IR (KBr) mmax 3292, 3231, 3049,
1720, 1538, 1511, 1452, 1402, 1345, 1268, 1255, 1188,
1171, 1133, 1007, 896, 800, 770, 757, 729 cm-1; 1H NMR
(CDCl3) d 10.86 (s, 1H, NH), 9.48 (s, 1H, NH), 8.13–8.18
(m, 1H, ArH), 7.23–7.90 (m, 10H, ArH); MS (FAB) m/z
320 (M ? 1)?.
1-(Benzo[d]thiazol-2-yl)-3-(3-chlorophenyl)urea (15)
Yield: 86; m.p: 348°C; IR (KBr) mmax 3396, 2959, 1691,
1594, 1531, 1479, 1427, 1409, 1317, 1293, 1245, 1193,
%
1
1098, 1076, 894, 870, 809, 753, 735, 674 cm-1; H NMR
1-(Benzo[d]thiazol-2-yl)-3-(furan-2-ylmethyl)urea (9)
Yield: 29; m.p: 248°C; IR (KBr) mmax 3335, 3056, 2952,
1710, 1601, 1536, 1447, 1307, 1277, 1199, 1144, 1078,
%
(CDCl3) d 10.55 (s, 1H, NH), 9.16 (s, 1H, NH), 7.22–7.78
(m, 7H, ArH), 7.02–7.04 (d, 1H, J = 7.59 Hz); MS (FAB)
m/z 305 (M ? 1)?.
1005, 914, 877, 813, 754, 728, 711, 598 cm-1; H NMR
1
(CDCl3) d 10.28 (s, 1H, NH), 7.72–7.74 (d, 1H, J =
7.66 Hz), 7.64–7.67 (d, 1H, J = 7.88 Hz), 6.06–7.45
(m, 5H, ArH), 6.32 (t, 1H, NH), 4.48 (s, 2H, CH2); MS
(FAB) m/z 274 (M ? 1)?.
1-(Benzo[d]thiazol-2-yl)-3-(4-chlorophenyl)urea (16) %
Yield: 88; m.p: [350°C; IR (KBr) mmax 3231, 3033, 2944,
1713, 1621, 1564, 1542, 1494, 1443, 1405, 1311, 1279,
;
1249, 1197, 1091, 1011, 943, 823, 752, 723 cm-1 1H
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Med Chem Res (2012) 21:2630–2643
Measurement of catalepsy
NMR (CDCl3) d 10.53 (s, 1H, NH), 9.11 (s, 1H, NH),
7.75–7.78 (d, 1H, J = 7.81 Hz), 7.68–7.70 (d, 1H,
J = 7.99 Hz), 7.22–7.56 (m, 6H, ArH); MS (FAB) m/z 305
(M ? 1)?.
Haloperidol-induced catalepsy was measured with the
standard bar test (Sanberg et al., 1988), in a wooden
chamber (length, 23 cm; width, 10.5 cm; height, 9 cm)
with a horizontal metal bar (diameter, 0.4 cm; length,
10.5 cm) fixed at 9 cm above the floor, and at 4 cm from
the back of the box. All experiments were carried out
between 8:00 and 15:30 h in a room with controlled tem-
perature (23 1°C), and light intensity of 20 lux. Cata-
lepsy was measured every 30 min during the whole session
that lasted 3 h after haloperidol injection. To measure
catalepsy, the mouse was gently lifted until its forepaws
firmly grasped the metal bar. Then, the mouse body was
released and simultaneously a stopwatch was started. The
time elapsed until the animal released both forepaws from
the bar, up to a maximum of 300 s, was defined as the
descent time. The sum of the descent time values measured
every 30 min during the 3 h after haloperidol or vehicle
was defined as the cumulative descent time (CDT [3 h]).
The mean CDTs measured in animals treated by the vehicle
in which haloperidol was dissolved were subtracted from
the mean CDTs recorded in mice treated with haloperidol.
This difference was taken as 100% of catalepsy, and served
as a reference value to calculate the percent inhibition of
drugs on catalepsy intensity.
1-(Benzo[d]thiazol-2-yl)-3-(2-chloro-5-(trifluoro-
methyl)phenyl)urea (17) % Yield: 40; m.p: 342°C; IR
(KBr) mmax 3375, 3236, 3117, 2970, 1797, 1694, 1604,
1541, 1427, 1332, 1279, 1259, 1175, 1115, 1082, 1003,
1
900, 812, 757, 715, 683 cm-1; H NMR (CDCl3) d 11.34
(s, 1H, NH), 8.74 (s, 1H, NH), 7.76–7.79 (d, 1H,
J = 7.72 Hz), 7.69–7.73 (d, 1H, J = 7.89 Hz) 7.53–7.55
(d, 1H, J = 7.01 Hz), 7.24–7.43 (m, 4H, ArH); MS (FAB)
m/z 373 (M ? 1)?.
1-(Benzo[d]thiazol-2-yl)-3-(2-nitrophenyl)urea (18)
%
Yield: 83; m.p: [350°C; IR (KBr) mmax 3336, 3286, 3128,
3056, 2869, 1719, 1662, 1609, 1585, 1563, 1499, 1432,
1338, 1319, 1263, 1192, 1148, 1089, 1043, 894, 808, 779,
1
740, 687, 664 cm-1; H NMR (CDCl3) d 11.94 (s, 1H,
NH), 10.18 (s, 1H, NH), 8.62–8.65 (d, 1H, J = 8.47 Hz),
7.16–7.77 (m, 7H, ArH); MS (FAB) m/z 315 (M ? 1)?.
1-(Benzo[d]thiazol-2-yl)-3-(4-nitrophenyl)urea (19)
%
Yield: 72; m.p: 296°C; IR (KBr) mmax 3368, 3215, 2972,
1713, 1622, 1578, 1545, 1517, 1460, 1444, 1413, 1371,
1332, 1306, 1285, 1258, 1193, 1109, 1018, 942, 868, 850,
749, 733, 705, 685 cm-1; 1H NMR (CDCl3) d 10.78 (s, 1H,
NH), 9.63 (s, 1H, NH), 8.18–8.21 (d, 2H, J = 9.11 Hz),
7.24–7.79 (m, 6H, ArH); MS (FAB) m/z 315 (M ? 1)?.
Biochemical evaluation
Mice were killed by decapitation 4 h after the last injection.
The brains were quickly removed and were washed twice
with ice-cold saline solution, placed into glass bottles,
labeled, and stored in a deep freeze (-30°C) until processing
(maximum 10 h). Tissues were homogenized in four vol-
umes of ice-cold Tris–HCl buffer (50 mM, pH 7.4) using a
glass Teflon homogenizer (Ultra Turrax IKA T18 Basic,
USA) after cutting up the brain into small pieces with scis-
sors (for 2 min at 5000 rpm). Malondialdehyde (MDA) and
protein levels were carried out at this stage. The homogenate
was then centrifuged at 10,5009g for 20 min to remove
nuclear debris. Clear supernatant fluid was taken and GSH-
Px activity was carried out in this stage. The supernatant
solution was then extracted with an equal volume of an
ethanol/chloroform mixture (5:3, v/v). After centrifugation
at 5,0009g for 30 min, the clear upper layer (the ethanol
phase) was taken and used in the SOD activity. All prepa-
ration procedures were performed at ?4°C.
Biological activity
Animals and drugs
Adult male pathogen-free Swiss albino mice weighing
18–25 g were used. All animal experimentation was con-
ducted in accordance with the National Guidelines on the
‘Proper Care and Use of Animals in Laboratory Research’
(Indian National Science Academy, New Delhi, 2000) and
was approved by the Animal Ethics Committee of the
Institute. The procedures adhered to the NIH Guidelines for
the Care and Use of Laboratory Animals. Haloperidol
(Sigma-Aldrich) was administered in dose of 5 mg/kg in
order to induce catalepsy. Each test compound was tested
at the dose of 100 mg/kg. All the drugs including synthe-
sized compounds were suspended in 0.5% gum acacia in
redistilled water and administered intraperitoneally at a
volume of 0.1 ml/100 g. Thirty minutes after the admin-
istration of the test compounds, mice were injected with
haloperidol dose. Five mice were taken in each group and
each mouse was used only once.
Lipid peroxidation (LPO) assay
The extent of LPO in mice brain homogenate was deter-
mined by measuring the release of thiobarbituric acid
123

Med Chem Res (2012) 21:2630–2643
2635
GSH-Px activity determination
reactive substance (TBARS) in terms of MDA equivalent
using a molar extinction coefficient of 1.56 9 105/min/cm
as described by Ohkawa et al., (1979). Briefly, the
homogenate was centrifuged at 3,0009g for 15 min and
supernatant was used for assay. Samples of 0.1 ml
homogenate was mixed with 0.2 ml of 8.1% SDS, 1.5 ml
20% glacial acetic acid and 1.5 ml of 0.8% thiobarbituric
acid (TBA). Following these additions, tubes were mixed
and heated at 95°C for 1 h on a water bath and cooled
under tap water before mixing 1 ml of distilled water and
5 ml mixture of n-butanol and pyridine (15:1). The mixture
was centrifuged at 2,2009g for 10 min. The amount of
MDA formed was measured by the absorbance of upper
organic layer at a wavelength of 532 nm in Perkin Elmer
spectrophotometer using appropriate controls. The results
are expressed as nmol MDA/mg protein.
The GSH-Px activity was measured by the method of
Paglia and Valentine (1967). The enzymatic reaction was
conducted in 3 ml quartz cuvettes of 1 cm path length in a
Perkin-Elmer spectrophotometer. Each 3 ml assay volume
contained 50 mM potassium phosphate buffer (pH 7.0),
1 mM EDTA, 1 mM sodium azide, 0.2 mM NADPH, 1 U
glutathione reductase, and 1 mM reduced GSH. The sam-
ple (0.2 ml of the tissue homogenate), after its addition,
was allowed to equilibrate for 5 min at 25°C. The reaction
was initiated by adding 0.1 ml of 2.5 mM H2O2. Changes
in absorbance were recorded at 340 nm for 5 min. Values
were expressed as units of NADPH oxidized to NADP by
using the extinction coefficient of 6.22 mM-1 cm-1 at
340 nm. All samples were assayed in duplicate. GSH-Px
activity was expressed as U/mg protein.
GSH determination
Total protein determinations
The amount of GSH in mice brain was measured according
to the method of Sedlak and Lindsay (1968). Briefly, brain
tissue was deproteinized with an equal volume of 10%
TCA and was allowed to stand at 4°C for 2 h. The contents
were centrifuged at 20009g for 15 min. The supernatant
was added to 2 ml of 0.4 M Tris buffer (pH 8.9) containing
0.02 M EDTA (pH 8.9) followed by the addition of 0.01 M
DTNB [5,50-dithiobis(2-nitrobenzoic acid)]. Finally, the
mixture was diluted with 0.5 ml of distilled water, to make
the total mixture to 3 ml and absorbance was read in a
spectrophotometer at 412 nm and results are expressed as
lg GSH/gm tissue.
Total protein concentration of brain homogenates was
determined by folin–phenol reaction as described by
Lowry et al. (1951). The bovine serum albumin was used
as a standard.
Molecular modeling studies
Molecular docking
The crystal structures of human adenosine A2A receptor,
PDB code: 3EML (Jaakola et al., 2008) was downloaded
from the protein data bank (www.rcsb.org/pdb). For
docking experiments with AutoDock 4.2, ligand molecules
were drawn in ChemBioDraw Ultra 12.0 and converted to
their three-dimensional structures in ChemBio3D Ultra
12.0, energy minimized by PM3 method using MOPAC
Ultra 2009 program (MOPAC2009) and saved as in pdb
format. The prepared ligands were used as input files for
AutoDock 4.2 in the next step. Lamarckian genetic algo-
rithm method (Morris et al., 1998) was employed for
docking simulations. The standard docking procedure was
used for a rigid protein and a flexible ligand whose torsion
angles were identified (for 10 independent runs per ligand).
A grid of 60, 60, and 60 points in x, y, and z directions was
SOD activity determination
Cu,Zn-SOD activity was determined according to the
method of Sun et al. (1988). In this method, a xanthine–
xanthine oxidase complex produces superoxide radicals,
which react with nitrobluetetrazolium (NBT) to form the
farmazan compound. In brief, a reactive was prepared with
0.1 mM of xanthine, 0.1 mM of EDTA, 50 mg of bovine
serum albumin, 25 lM of NBT, and 40 mM of Na2CO3
(pH 10.2). To 2.45 ml of reactive was added 0.5 ml of a
ethanol/chloroform (5:3, v/v) extract, previously prepared
from brain homogenate. Subsequently, 50 ll of 9.9 nM of
xanthine oxidase solution was added, the mixture was kept
in a water bath of 25°C for 20 min, and the reaction was
terminated using 1 ml of CuCl2. The absorbance of the
samples was read at 560 nm. In the control sample the
amount of the ethanol supernatant was replaced by equiv-
alent volume of PBS buffer. One unit SOD activity was
defined as the amount of enzyme causing 50% inhibition of
NBT reduction to formazan. SOD activity was expressed as
U/mg protein.
˚
built with a grid spacing of 0.375 A and a distance-
dependent function of the dielectric constant were used for
the calculation of the energetic map. The default settings
were used for all other parameters. At the end of docking,
the best poses were analyzed for hydrogen bonding/p–p
interactions and root mean square deviation (RMSD) cal-
culations using Discovery Studio Visualizer 2.5 (Accelrys
Software Inc.) and Pymol (The PyMOL Molecular
123

2636
Med Chem Res (2012) 21:2630–2643
Graphics System) programs. From the estimated free
energy of ligand binding (DGbinding, kcal/mol), the inhibi-
tion constant (Ki) for each ligand was calculated (Table 3).
in Scheme 1. Benzo[d]thiazol-2-amine was synthesized
from aniline and potassium thiocyanate as described pre-
viously (Jimonet et al., 1999). Compounds 1–19 were
prepared by nucleophilic substitution from a primary
amine, benzo[d]thiazol-2-amine and the corresponding
aromatic isocyanate. Reaction was carried out at room
temperature in acetonitrile, and the derivatives were
obtained in good yields. All compounds showed a single
spot on TLC and had spectral data in accord with their
anticipated structure.
Calculation of ADME parameters
Absorption (%ABS) was calculated by: %ABS =
109 - [0.345 9 Topological polar surface area (TPSA)]
according to the method of Zhao et al. (2002). TPSA (Ertl
et al., 2000), miLogP, and violations of Lipinski’s rule of
five (Lipinski et al., 2001) were calculated using Molin-
spiration online property calculation toolkit (Molinspira-
tion Cheminformatics, 2010).
Biological evaluation
Haloperidol-induced catalepsy
Statistical analysis
Impairment of movement caused by neuroleptic-induced
blockade of the dopamine D2 receptor is used as an
animal model to screen potential compounds for their
anti-Parkinsonian activity (Crocker and Hemsley, 2001;
Sanberg et al., 1988). Haloperidol, a neuroleptic agent,
antagonizes the postsynaptic dopamine D2 receptors and
produces catalepsy as an extra pyramidal symptom of
PD. Catalepsy is a behavioral condition characterized by
muscular rigidity and shares some similarity to human
PD. A cataleptic animal is unable to correct an externally
imposed posture while catalepsy-free animal, i.e., those
without haloperidol, should be able to come down from
the horizontal bar within certain time period. Blockade of
adenosine A2A receptors produces motor stimulant effects
and reverses catalepsy induced by haloperidol in rodents
and primates (Chen et al., 2001; Varty et al., 2008).
Data were expressed as the mean standard error (SE) of
the means. For a statistical analysis of the data, group
means were compared by one-way analysis of variance
(ANOVA) with post hoc analysis. The post hoc Bonferroni
multiple comparison test was applied to identify signifi-
cance among groups. P \ 0.05 was considered to be sta-
tistically significant.
Results and discussion
Chemistry
In the present study 1-(substituted aryl)-3-(benzo[d]thiazol-
2-yl)urea derivatives (1–19) were synthesized as presented
NH2
N
N
KCNS
R
NCO
NH
O
NH2
Br2
Acetonitrile
S
NH
S
1 19
-
R
Comp R
Comp R
Comp
R
1
2
3
4
5
6
7
2-CH3-C6H4
4-CH3-C6H4
2-OCH3-C6H4
4- OCH3-C6H4
2,4-OCH3-C6H3
8
9
10
11
12
1-Naphthyl
14
15
16
17
18
19
2-Cl-C6H4
3-Cl-C6H4
4-Cl-C6H4
2-Cl,5-CF3-C6H3
2-NO2-C6H4
4-NO2-C6H4
2-Furfuryl
2-Br-C6H4
4-Br-C6H4
2-F-C6H4
4-F-C6H4
3,4,5-OCH3-C6H2 13
4-Phenoxyphenyl
Scheme 1 Synthetic protocol of 1-(benzo[d]thiazol-2-yl)-3-(substituted aryl)urea derivatives
123

Med Chem Res (2012) 21:2630–2643
2637
Table 1 Mean descent time observed at different time intervals
Compound
Mean descent time (s) SEM at time (min)a
Mean CDT [3 h]
Reduction in
catalepsy (%)
30
66 3.2
60
90
120
150
180
1
101 4.6
97 4.9
34 3.1
69 3.6
41 3.1
46 2.9
67 1.7
31 2.4
29 2.4
128 2.4
132 3.9
145 4.4
131 4.6
134 6.1
155 6.1
65 3.8
117 5.9
78 4.9
81 3.6
126 2.6
49 4.4
72 4.4
156 4.1
178 3.8
193 4.7
188 5.2
134 5.8
169 3.6
166 3.1
114 3.9
77 3.2
181 4.1
264 4.7b
99 2.2
36 1.6
166 4.7
160 4.6
72 2.7
180 6.1
171 5.3
95 4.8
198 4.9
845
840
46.9
47.2
75.9
53.1
69.8
70.1
50.5
69.6
77.3
36.7
35.4
30.8
29.8
37.1
35.6
37.4
56.3
71.4
30.5
-
2
72 3.2
32 1.9
43 2.6
26 2.6
37 2.2
51 2.9
25 2.3
18 1.7
118 4.3
87 2.3
81 3.7
70 3.1
57 2.2
101 3.9
78 1.2
77 3.6
23 1.9
90 2.9
155 4b
32 0.2
185
5
3
103 4.8
181 3.8
149 6.7
122 6.5
196 8.2
178 8.7
95 5.9
401
4
160 6.8
94 2.2
180 5.7
107 4.2
115 6.5
189 5.2
123 4.6
85 3.3
750
5
495
6
89 4.5
490
7
161 8.4
92 4.2
790
8
498
9
81 3.9
380
10
173 4.9
196 5.4
207 6.4
219 8.1
205 7.3
182 6.2
190 6.2
118 4.7
85 2.6
201 5.3
211 5.6
223 7.7
234 4.4
224 4.7
216 5.8
241 4.4
263 5.1
289 4.6
230 4.4
220 7.2
1000
1020
1090
1105
995
11
12
13
14
98
5
212
8
15
144 3.3
129 4.8
89 2.5
56 2.3
138 3.7
242 4.2b
49 0.5
191 3.9
207 5.9
129 5.1
99 4.6
1017
990
16
17
173
4
700
18
130 3.8
253 7.5
300 4.8b
137 2.3
72 2.49
470
19
199 5.5
300 5.4b
119 1.9
45 0.84
234 6.6
300 5.2b
122 2.2
1095
1561
558
Haloperidol
Levodopac
SCH58261
Control
65.6
86.4
–
11
4
1
19
7
1
58
5
2
241
0.71
0.71
5
0.45
6
0.45
0.55
6
0.55
33
Data is presented as mean descent time (s) SEM. Number of animals per group (n) = 5, Haloperidol (5 mg/kg), Compounds 1–19 admin-
istered i.p. at the dose of 100 mg/kg 30 min prior to haloperidol injection. The sum of the descent time values measured every 30 min during the
2 h after haloperidol or vehicle is defined as the cumulative descent time (CDT [3 h]). Data was analyzed by one-way ANOVA followed by
Bonferroni post hoc analysis
a
P \ 0.001 as compared with haloperidol group
b
P \ 0.001 as compared with control group
Data taken from reference (Azam, 2009)
c
Haloperidol (5 mg/kg) produced a profound increase in
catalepsy as shown by a progressive increase in the latency
to step down the rod over time as compared with controls
(P \ 0.001). Efficacious compounds were defined as those
that allowed the mice to come down from the bar within
300 s. The results obtained from acute administration of
haloperidol are in agreement with previous studies of our
research group (Azam, 2009; Azam et al., 2009a, c, 2010b)
as well as report from other laboratory (Correa et al.,
2004). Acute subcutaneous administration of compounds
(1–19) at a dose of 100 mg/kg significantly antagonized
haloperidol-induced catalepsy as evident from the decrease
in mean descent time in treated animals when compared to
mice injected with haloperidol alone. The cataleptic score
was significantly reduced throughout the period of obser-
vations, till 3 h in all animal groups pretreated with title
compounds. Compounds 3, 5, 6, 8, 9, and 18 showed
better anticataleptic activity than standard drug levodopa
whereas none of the compounds was superior to the
standard adenosine A2A receptor antagonist, SCH58261.
Compound 9 having furfuryl moiety was the most active
whereas 4-fluorophenyl substituted derivative (compound
13) was observed to be least active among the series
exhibiting 77.3 and 29.8% reduction in catalepsy,
respectively. Generally, halogen substitution in the phe-
nyl ring produced less effective molecules (compounds
10–16) in terms of anti-Parkinsonian activity, except
2-chloro,3-trifluoromethyl-substituted derivative (com-
pound 17), which exhibited 56.3% reduction in catalepsy
probably because of the lipophilic groups. The effect of
title compounds and standard drugs in terms of mean
descent time observed at different time intervals, mean
CDT [3 h] and % reduction in catalepsy are presented in
Table 1.
123

2638
Med Chem Res (2012) 21:2630–2643
Table 2 Biochemical estimation from brain homogenate
Compound
LPO (nmol MDA/mg protein)
GSH (lg/gm tissue)
GSH-Px (U/g protein)
SOD (U/mg protein)
3
2.99 1.01a
3.12 1.12a
4.92 0.53b
0.958 0.11
12.34 2.06a
16.53 1.84a
5.57 1.02b
21.16 2.94
1.65 0.95a
1.36 0.86a
0.68 0.08b
2.01 0.34
2.12 0.85a
1.87 0.77a
0.85 0.19b
2.71 0.27
9
Haloperidol
Control
The data are expressed as mean SEM (n = 5)
a
P \ 0.001 compared with corresponding value for haloperidol-treated mice
P \ 0.001 compared with corresponding value for control mice
b
Oxidative stress parameters
development of neurological disorders (Azam, 2009; Azam
et al., 2009a, b, c, 2010a, b).
The brain is highly susceptible to oxidative damage
because it consumes a large amount of oxygen and gen-
erates reactive oxygen species (ROS) as normal products of
cellular metabolism (Escames et al., 2010). In particular,
nigrostriatal neurons utilize endogenous neurochemical
redox reaction, such as dopamine oxidation leading to
generation of ROS and neurodegeneration (Jana et al.,
2011). Although the antioxidant defense system responds
to an increase in the production of ROS under normal
conditions, it gives rise to oxidative stress in the brain if an
imbalance occurs between the production of ROS and the
cellular defense capability. Because ROS may have an
impact upon a number of PD pathologies, we tested if
synthesized compounds ameliorate Parkinsonian symptoms
by decreasing oxidative stress in mice. Several oxidative
stress parameters such as LPO, reduced GSH, GSH-Px, and
SOD were analyzed in brain homogenate of mice to
emphasize the role of title compounds in suppressing the
catalepsy and oxidative stress induced by haloperidol
administration. The results so obtained are summarized in
Table 2.
Molecular docking studies
Molecular docking is a widely used computational tool for
the study of molecular recognition, which aims to predict
the binding mode and binding affinity of a complex formed
by two or more constituent molecules with known struc-
tures (Huang and Zou, 2010). Nowadays, pharmaceutical
companies analyze very large numbers of compounds with
docking. Those compounds that have the best docking
results will be synthesized if necessary, and analyzed in the
laboratory. By using the knowledge gained from the
docking study, fewer compounds need be synthesized and
assayed, and a higher percentage of compounds assayed are
found to be active (Young, 2009).
All of the synthesized compounds were docked into the
active site of adenosine A2A receptor (PDB code: 3EML)
to study the possible mode of interaction of 1-(benzo[d]
thiazol-2-yl)-3-(substituted aryl)urea derivatives (1–19).
Docking of these compounds into inhibitor binding cavity
(IBC) of adenosine A2A receptor confirms that these
compounds dock in a similar binding modus like native co-
crystallized ligand, ZM-241385 (Fig. 2). IBC of adenosine
In the present study, a consistent decrease in reduced
GSH, antioxidant enzymes (SOD and GSH-Px) activities
and marked increase in MDA level in brain homogenate of
haloperidol-treated mice clearly implicates the role of
oxidative stress in the development of Parkinsonian
symptoms. Haloperidol, administered at 5 mg/kg induces
an abnormal increase in free radical production that com-
promises GSH-Px and SOD activity, further increasing free
radicals occurrence in experimental animals (Azam, 2009;
Azam et al., 2009a, c, 2010b). Compounds 3 and 9,
administered prior to haloperidol injection stops this
destructive cycle allowing recovery of detoxifying enzyme
activities and controlling free radical production, suggest-
ing a potential role of the drug in the treatment of neuro-
degenerative disorders such as PD. Present investigation
continues to support our previous findings related to
the involvement of oxidative stress component in the
A
2A receptor is outlined by residues Ile-66, Ala-81, Leu-85,
Phe-168, Glu-169, Met-177, Trp-246, Leu-249, His-250,
Asn-253, His-264, Leu-267, Met-270, Tyr-271, Ser-277,
and His-278.
Both hydrophobic as well as hydrophilic interactions
contribute to the binding of docked compounds within IBC.
In addition to be involved in formation of H-bonds with
most docked compounds, Phe-168 contributes to p–p
stacking interactions in compounds 3, 5, 6, 7, 9, 10, 13, 14,
17, and 18. Residue Asn-253, which is involved in H-bond
formation of native co-crystallized ligand ZM-241385, also
interacts with compounds 1, 6, 12, 13, and 15 in identical
manner. Methoxy- or nitro-groups substituted at ortho or
meta positions of the phenyl ring (compounds 3, 5, 6,
and 18) accommodates better in the IBC and furnish better
123

Med Chem Res (2012) 21:2630–2643
2639
bioavailability, toxicity, and other factors present in the
body (Young, 2009).
Prediction of pharmacokinetic properties
Oral bioavailability is considered to play an important role
for the development of bioactive molecules as therapeutic
agents. Lipinski et al. (2001) identified common chemical
properties that recur in FDA-approved molecules, pre-
senting the familiar ‘rule of 5’ for drug-like molecules (B5
hydrogen bond donors and 10 acceptors, molecular weight
\500 Da, and logPoctanol/water coefficient lower than 5) and
is employed to predict pharmacokinetic properties of drug
candidates.
Fig. 2 Compound 9 (shown in yellow) docked in the active site of
adenosine A2A receptor (PDB code: 3EML) along with the native co-
˚
crystallized ligand ZM-241385 (RMSD 1.37 A) (Color figure online)
anti-Parkinsonian activity (Fig. 3). However, when these
groups are present only at para position (compounds 4 and
19), activity decreases because compound 4 do not show any
interaction within IBC while compound 19 exhibits only
hydrophilic interaction with high RMSD value (Table 3).
All of the potent compounds demonstrated lower energy
of binding, estimated inhibition constant and hydrophilic as
well as hydrophobic interactions (Table 3). Compound 9,
being the most potent anti-Parkinsonian and antioxidant
agent among the series, exhibited higher energy of binding
in molecular docking. However, this compound accom-
modates well in the IBC by participating in hydrophobic as
well as hydrophilic interactions with RMSD value of 1.37
To check the suitability of synthesized compounds for
good oral bioavailability, a computational study for pre-
diction of ADME properties of the urea derivatives was
performed by determination of lipophilicity, TPSA, %ABS
and simple molecular descriptors used by Lipinski in
formulating his ‘rule of 5’. Calculations were performed
using Molinspiration online property calculation toolkit,
http://www.molinspiration.com (Molinspiration Chemin-
formatics, 2010). Results are summarized in Table 4.
Percentage of absorption (%ABS) was estimated using the
equation: %ABS = 109 - 0.345 9 TPSA, according to
Zhao et al. (2002). TPSA was also calculated using Mol-
inspiration online property calculation toolkit (Molinspi-
ration Cheminformatics, 2010) according to the fragment-
˚
A (Fig. 2). Although, docking calculations simulate the
interaction between a compound and a protein’s active site
and the results are comparable to those of biochemical
assays/animal experiments, it does not take into account of
Fig. 3 The lowest energy
configuration of docking result
of compound 3 with binding
pocket of human adenosine A2A
receptor. The residues of
binding pocket are shown as
stick in gray color while
compound 6 is presented as ball
and stick style in cyan color.
Dashed lines in green indicate
H-bonds while p–p stacking
interactions are shown in
orange. Sulfur is presented in
dark yellow, nitrogens in blue,
and oxygens in red. Bond
˚
distances are given in A
(Color figure online)
123

2640
Med Chem Res (2012) 21:2630–2643
Table 3 Docking results of 1-(benzo[d]thiazol-2-yl)-3-(substituted aryl)urea derivatives with adenosine A2A receptor (PDB code: 3EML)
Comp
DGab
Kib
RMSDc
Hydrogen bonds
AAd
p-Interactions
Atom
Diste
Type
AAd
Diste
–
f
1
-7.49
3.25
1.56
O
H
Asn-253
Asn-253
–
1.74
2.15
–
–
–
f
f
2
3
-7.34
-7.72
4.19
2.20
4.93
5.79
–
–
–
–
O
N
Ser-277
His-278
–
1.76
2.19
–
p–p
Phe-168
5.73
f
f
4
5
-7.37
-7.25
3.97
4.88
5.16
5.14
–
–
–
–
O
His-278
2.13
p–p
p–p
p–p
p–p
Phe-168
Phe-168
Phe-168
Phe-168
3.93
3.75
4.27
4.90
6
-7.26
4.75
0.71
O
S
Glu-169
Asn-253
Asn-253
–
2.02
2.33
2.14
–
H
f
7
8
-8.11
-8.26
1.14
0.88
2.66
4.29
–
p–p
p–p
p–p
p–p
p–p
p–p
Phe-168
Tyr-271
Tyr-271
Phe-168
Phe-168
Phe-168
5.03
4.59
6.07
3.86
3.85
5.85
f
–
–
–
9
-6.80
-8.13
-7.71
-7.08
-7.54
10.30
1.11
2.23
6.45
2.98
1.37
5.99
6.58
1.54
5.99
O
H
O
N
O
S
Phe-168
Glu-169
Ser-277
His-278
Ser-277
His-278
Asn-253
Asn-253
Asn-253
Ser-277
His-278
Ser-277
His-278
Asn-253
Asn-253
–
1.88
2.13
1.75
2.22
1.86
2.29
1.78
2.15
2.42
1.85
2.26
1.71
2.14
1.74
2.16
–
10
11
12
13
f
–
–
–
f
O
H
F
–
–
–
p–p
p–p
Phe-168
5.88
O
N
O
N
O
H
14
15
-7.93
-7.62
1.55
2.60
6.01
1.63
Phe-168
–
5.73
–
f
–
f
f
16
17
-7.38
-8.09
3.90
1.18
4.91
6.15
–
–
–
–
F
His-250
Ser-277
His-278
Ser-277
His-278
His-278
His-278
Tyr-271
2.45
2.02
2.21
1.84
2.38
2.33
2.17
2.23
p–p
Phe-168
6.08
O
S
18
19
-7.56
-7.63
2.85
2.56
5.90
4.43
O
N
O
O
H
p–p
Phe-168
–
6.07
–
f
–
a
Binding free energy (kcal/mol)
b
c
d
e
f
Inhibition constant estimated by docking (in lM)
˚
Root mean square deviation (in A)
Amino acid
˚
Bond distance (in A)
No H-bond or p-interaction
123

Med Chem Res (2012) 21:2630–2643
2641
Table 4 Pharmacokinetic
Comp
%ABS
TPSA
2
(A )
MW
miLogP
n-OHNH
donors
n-ON
acceptors
Lipinski’s
violations
parameters important for good
oral bioavailability of
1-(benzo[d]thiazol-2-yl)-3-
(substituted aryl)urea
˚
Rule
1
–
–
\500
B5
\5
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
\10
4
B1
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
1
0
0
90.36
90.36
87.18
87.18
83.99
80.81
87.18
90.36
85.83
90.36
90.36
90.36
90.36
90.36
90.36
90.36
90.36
74.55
74.55
54.02
54.02
63.25
63.25
72.49
81.72
63.25
54.02
67.16
54.02
54.02
54.02
54.02
54.02
54.02
54.02
54.02
99.84
99.84
283.36
4.1
derivatives (1–19)
2
283.36
299.36
299.36
329.38
359.41
361.43
319.39
273.32
348.23
348.23
287.32
287.32
303.77
303.77
303.77
371.77
314.33
314.33
4.15
3.71
3.76
3.74
3.33
5.45
4.86
2.66
4.46
4.51
3.82
3.86
4.33
4.35
4.38
5.20
3.61
3.66
4
3
5
4
5
5
6
6
7
7
5
8
4
9
5
10
11
12
13
14
15
16
17
18
19
4
4
4
4
%ABS percentage of absorption,
TPSA topological polar surface
area, MW molecular weight,
miLogP logarithm of compound
partition coefficient between
n-octanol and water, n-OHNH
number of hydrogen bond
donors, n-ON number of
4
4
4
4
7
7
hydrogen bond acceptors
based method of Ertl et al. (2000). Polar surface area,
together with lipophilicity, is an important property of a
molecule in transport across biological membranes. Too
high TPSA values give rise to a poor bioavailability and
absorption of a drug. According to the above criterions,
calculated percentages of absorption for compounds 1–19
ranged between 74.55 and 90.36%. The lipophilicity study
showed that most of compounds possess optimum lipo-
philicities (miLogP 2.66–5.45) required for oral absorption
and biomembrane penetration. From all these parameters, it
is evident that all 1-(substituted aryl)-3-(benzo[d]thiazol-2-yl)
urea derivatives (1–19) showed no obvious indications
that they would not be active orally, as none of the
compounds violated Lipinski’s parameters, making them
potentially promising drug candidates for the treatment of
PD.
role in the pathophysiological mechanisms underlying
PD. Molecular docking studies of these compounds with
adenosine A2A receptor exhibited very good binding
interactions and warrants further studies to confirm their
binding with human A2A receptor for the design and
development of better therapy for PD.
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