Novel hybrids of benzothiazole-1,3,4-oxadiazole-4-thiazolidinone: Synthesis, in silico ADME study, molecular docking and in vivo anti-diabetic assessment

Article abstract of DOI:10.1016/j.bioorg.2018.10.025

A series of new benzothiazole-1,3,4-oxadiazole-4-thiazolidinone hybrid analogs (Tz1-Tz28) were synthesized in search of potential anti-diabetic agents. Molecular docking study was conducted with binding pocket of peroxisome proliferator activated receptor-gamma to elucidate the binding interactions of newly synthesized targets. Seven selected compounds with best docking scores were further screened for in vivo anti-hyperglycemic efficacy by oral glucose tolerance test in non-diabetic rats and on streptozotocin induced diabetic rat models. All the tested compounds demonstrated excellent to moderate reduction in blood glucose levels. Three of the compounds (Tz21, Tz7 and Tz10) showed excellent anti-diabetic effect by reducing concentration of glucose to 157.15 ± 1.79 mg/dL, 154.39 ± 1.71 mg/dL, 167.36 ± 2.45 mg/dL, respectively better than the standard drug, pioglitazone, 178.32 ± 1.88 mg/dL. Moreover, three derivatives Tz21, Tz4 and Tz24 with IC50 values of 0.21 ± 0.01 μM, 9.03 ± 0.12 μM and 11.96 ± 0.40 μM respectively also showed better inhibitory activities on alpha-glucosidase even more than the standard acarbose (IC50 = 18.5 ± 0.20 μM), indicating Tz21 has the highest inhibitory effect among the seven tested derivatives. Prediction of Drug like properties using molinspiration online software suggests that all the synthesized compounds have potential of becoming the orally active molecules. Thus, these novel hybrids could serve as potential candidates to become leads for the development of new drugs eliciting anti-hyperglycemic effect orally.

Full text of DOI:10.1016/j.bioorg.2018.10.025

Accepted Manuscript
Novel Hybrids of Benzothiazole-1,3,4-oxadiazole-4-thiazolidinone: Synthesis,
in silico ADME study, molecular docking and in vivo anti-diabetic assessment
Rubina Bhutani, Dharam Pal Pathak, Garima Kapoor, Asif Husain, Md. Azhar
Iqbal
PII:
S0045-2068(18)30815-0
DOI:
https://doi.org/10.1016/j.bioorg.2018.10.025
YBIOO 2559
Reference:
To appear in:
Bioorganic Chemistry
Received Date:
Revised Date:
Accepted Date:
3 August 2018
10 October 2018
12 October 2018
Please cite this article as: R. Bhutani, D. Pal Pathak, G. Kapoor, A. Husain, Md. Azhar Iqbal, Novel Hybrids of
Benzothiazole-1,3,4-oxadiazole-4-thiazolidinone: Synthesis, in silico ADME study, molecular docking and in
vivo anti-diabetic assessment, Bioorganic Chemistry (2018), doi: https://doi.org/10.1016/j.bioorg.2018.10.025
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Novel Hybrids of Benzothiazole-1,3,4-oxadiazole-4-thiazolidinone: Synthesis,
in silico ADME study, molecular docking and in vivo anti-diabetic assessment.
Rubina Bhutani a*, Dharam Pal Pathak , Garima Kapoor , Asif Husain , Md. Azhar
a
a
b
Iqbal b
a
Department of Pharmaceutical Chemistry, Delhi Institute of Pharmaceutical Sciences and Research, New
Delhi, India.
b
Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Hamdard University, New Delhi, India.
*Author for correspondence
Address: Department of pharmaceutical chemistry, Delhi institute of pharmaceutical
sciences and research, PushpVihar, Sector-3, New Delhi-110017, India.
Phone: +91-995-829-6439.
E-mail addresses: rubinabhutani23@gmail.com (R. Bhutani), drasifhusain@yahoo.com (A.
Husain).

ABSTRACT
A series of new benzothiazole-1,3,4-oxadiazole-4-thiazolidinone hybrid analogs (Tz1-Tz28)
were synthesized in search of potential anti-diabetic agents. Molecular docking study was
conducted with binding pocket of peroxisome proliferator activated receptor-gamma to elucidate
the binding interactions of newly synthesized targets. Seven selected compounds with best
docking scores were further screened for in vivo anti-hyperglycemic efficacy by oral glucose
tolerance test in non-diabetic rats and on streptozotocin induced diabetic rat models. All the
tested compounds demonstrated excellent to moderate reduction in blood glucose levels. Three
of the compounds (Tz21, Tz7 and Tz10) showed excellent anti-diabetic effect by reducing
concentration of glucose to 157.15±1.79 mg/dL, 154.39±1.71 mg/dL, 167.36±2.45 mg/dL,
respectively better than the standard drug, pioglitazone, 178.32±1.88 mg/dL. Moreover, three
derivatives Tz21, Tz4 and Tz24 with IC50 values of 0.21 ± 0.01 µM, 9.03 ± 0.12 µM and 11.96
±
0.40 µM respectively also showed better inhibitory activities on alpha-glucosidase even more
than the standard acarbose (IC50 = 18.5 ± 0.20 µM), indicating Tz21 has the highest inhibitory
effect among the seven tested derivatives. Prediction of Drug like properties using molinspiration
online software suggests that all the synthesized compounds have potential of becoming the
orally active molecules. Thus, these novel hybrids could serve as potential candidates to become
leads for the development of new drugs eliciting anti-hyperglycemic effect orally.
Keywords: Anti-diabetic; Benzothiazole; Hybrid analogues; Molecular Docking; Oxadiazole;
PPAR-gamma; 4-thiazolidinone.

1
. INTRODUCTION
Various compounds incorporating heterocyclic and fused heterocyclic ring plays major role in
designing and synthesis of anti-diabetic pharmaceuticals. Among them, nitrogen, sulphur and
oxygen containing heterocyclic compounds have attracted the interest of medicinal chemists due
to their innumerable biological applications. 1,3,4-oxadiazole derivatives among the family of
heterocycles showed many promising pharmaceutical applications. Extensive literature report
reveals the anticancer [1-3], antioxidant [4], anti-hyperglycaemic [5-7] anti-tubercular [8]
properties of 1,3,4-oxadiazole scaffold. Large number of medicinal drugs used clinically contain
1
,3,4-oxadiazole moiety as pharmacophore such as raltegravir an antiretroviral drug for HIV
infection, antibiotic furamizole, zibotentan, an antineoplastic agent, tiodazosin and nesapidil as
antihypertensive drugs. [9]
On the other hand, the benzothiazole (a benzo-heterocycle) scaffold represents an important core
template for a vast variety of pharmacologically active compounds, having many pharmaceutical
activities. The versatile biological functions shown by benzothiazole nucleus include anti-
diabetic [10-11], anti-convulsant [12], anticancer [13] and anti-viral properties [14].
Moreover, 4-thiazolidinone, a 4-carbonyl derivative of tetrahydro form of thiazole, has been
found as a basic structure in diverse synthetic pharmaceutical drugs [15-16]. The presence of
th
keto group at 4 position and N-C-S linkage was found accountable for the pharmacological
activity of thiazolidinones [17]. 4-thiazolidinone derivatives exhibited abundance of applications
such as anti-diabetic [18], antimicrobial [19], antiviral [20], anti-tubercular [21] and
anticonvulsant [22].

Diabetes or Diabetes Mellitus is a chronic progressive metabolic disorder characterized by
increased levels of blood glucose/impaired insulin secretion/liver or peripheral insulin resistance
[23, 24]. Type-I, Type-II and gestational diabetes are different types of diabetes, among which
Type-II diabetes mellitus or non-insulin dependent diabetes mellitus is the most prevalent
diabetes occurring in 80% of the affected patients worldwide [25]. The World Health
Organization reported that the global prevalence of diabetes has been increased from 108 million
people in 1980 which increased to 422 million people in 2014 [26]. The medicinal agents used in
the therapy of Diabetes Mellitus comprise insulin and oral anti-hyperglycaemic agents
(thiazolidinediones, biguanides, sulphonylureas and α-glucosidase inhibitors [27]. Peroxisome
proliferator-activated receptors (PPARs), ligand-activated transcription factors, consisting of
three distinct subtypes PPAR-α, PPAR-δ and PPAR-γ, are members of nuclear hormone receptor
superfamily (NR1C3) [28]. Among these subtypes, Peroxisome proliferator-activated receptor-γ
(PPAR-γ) agonists have come up with a prominent role for an orally effective anti-
hyperglycaemic agent [29]. Thiazolidinediones (TZDs), such as rosiglitazone and pioglitazone,
PPAR-γ agonists, are able to improve insulin sensitization and glucose metabolism in the
treatment of type II diabetes, but they have also been related with various side effects [30]. The
diverse synthetic oral anti-hyperglycemic medicines exist but most of them are linked with
miscellaneous side effects and toxicity [31].
Latest trends in pharmaceutical chemistry research indicated the increased popularity of
molecular hybridization for medical drug development, which is based on the combination of
two or more pharmacophoric moieties of different biologically active substances to make a new
potent hybrid molecule with enhanced efficiency and affinity when compared to standard drug
[32].

Recently our research batch has reported the hybrid analogue of oxadiazole clubbed
benzothiazole mannich bases as anti-diabetic agents [33]. In view of the aforementioned findings
and as a continuation of our effort in exploring hybrid analogues, we hereby in the present study
report the synthesis, in vitro alpha-glucosidase inhibition study [34] and in vivo anti-diabetic
evaluation of novel series of hybrid compounds incorporating the benzothiazole, oxadiazole and
4
-thiazolidinone heterocyclic ring systems in a single molecule, with an aim to obtain new, safer,
potent and relatively low-cost anti-hyperglycemic agents. Molecular docking studies were also
done to understand the binding interactions of synthesized hybrids to a receptor (PPAR-γ, PDB
ID-1FM9). Also, the comparison of stabilizing energy of compounds against alpha-glucosidase
(PDB ID-2QMJ) and inhibiton activity was done.
2
2
. EXPERIMENTAL SECTION
.1 General
All chemicals and solvents utilized were obtained from commercial sources and were used in
their original form without further purification. Thin layer chromatography (TLC) was run on
pre-coated silica gel G 60 F254 plates (Merck, Germany) using toluene: ethyl acetate (3:1) and
n-hexane: ethyl acetate (6:4) as solvent systems. The melting points of synthesized compounds
were determined by the open capillary method in an electric melting point apparatus of Icon
Instruments, India and are uncorrected. All the IR spectra were recorded on a Bruker Optics
1
13
Spectrophotometer. H (300 MHz) and C (75 MHz) Nuclear Magnetic Resonance spectra were
recorded on a Bruker advanced model DPX-300 spectrometer in CDCl /DMSO-d . Chemical
3
6
shifts (δ) are expressed in parts per million (ppm) with reference to Tetra methyl silane (TMS) as
an internal standard. The mass spectra of synthesized analogs were recorded using ESI technique
on LCMS/LCQ (Agilent, Advantage-Max) instrument. Elemental analysis (C, H, and N) were

conducted using Flash 2000 organic elemental analyzer was used for and the values were found
within ±0.4% of theoretical values.
2
.2 Synthesis
2
.2.1 Synthesis of 5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-amine, 3
A solution of benzothiazole-2-carboxyhydrazide (0.01 mol) synthesized according to the
previously reported protocol [35] and cyanogen bromide (0.01mol) in methanol (50 mL) was
stirred at 40 °C for 1.5 h. The solution was then refluxed on parallel synthesizer (Carousel Tech,
Radleys, Germany) for 5 h at 70 °C. The reaction mixture was then poured into crushed ice and
neutralized with sodium bicarbonate solution. The resultant precipitate obtained was filtered,
dried and recrystallised from methanol to give compound, 3 [36]. Yield: 70%.
2
.2.2 General procedure for synthesis of Schiff bases, Sb(1-28)
Compound 3 (0.02 mol) was dissolved in ethanol. To this solution appropriate aromatic
aldehydes (0.02 mol) were added. 2-3 mL of glacial acetic acid was added to the above reaction
mixture and the mixture was refluxed for 14 h. After the completion of reaction, the solvent
(ethanol) was distilled off and the residue thus obtained were poured into ice and stirred for 20
min. The resulting precipitates were filtered, washed occasionally with ice cold water, dried and
recrystallized from alcohol [37]. Yield: 65-68%.
2
.2.3 General procedure for synthesis of 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-
substituted thiazolidin-4-one, Tz(1-28)
A reaction mixture of appropriate Schiff base (4a-z) (0.1mol) and mercaptoacetic acid (0.1mol)
in dimethylformamide (25-30 mL), containing a catalytic amount of zinc chloride was refluxed
with stirring for 15 h. After the completion of reaction, the mixture was cooled and poured into
crushed ice. The resultant product was filtered, washed with an excess of 10% sodium

bicarbonate solution followed by several times washing with cold water, dried and recrystallised
from ethanol to get the desired product, Tz1-Tz28 [38].
2
.2.3.1 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(4-hydroxyphenyl)thiazolidin-4-one
-1
(
Tz1). Yield: 75%; M.p. 155–156°C, R = 0.71. IR (KBr, cm ); 3046 (Ar, C-H), 1604 (C=N),
f
1
1
706 (C=0). H NMR (DMSO-d , δ, ppm): 4.01 (2H, s, SCH ); 4.62 (1H, s, N-CH-S); 5.23 (1H,
6
2
s, OH), 6.62-7.07 (4H, m, Ar-CH of phenyl); 7.42-7.79 (2H, m, Ar-CH); 8.02 (1H, m, Ar-CH);
1
3
8
1
.17(1H, m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 33.4, 65.4, 115.7, 121.3, 121.8, 125.2,
6
+
26.1, 130.2, 131.8, 135.4, 153.5, 156.0, 156.6, 171.8. ESI MS (m/z): 397 (M+H) . Calcd. Anal.
for C H N O S : C, 54.53; H, 3.05; N, 14.13; found C, 54.76; H, 3.33; N, 14.41.
1
8
12
4
3 2
2
.2.3.2
3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(4-fluorophenyl)thiazolidin-4-one
-1
(
Tz2). Yield: 63%; M.p. 209–210°C, R = 0.63. IR (KBr, cm ); 3236 (Ar, C-H), 1564 (C=N),
f
1
1
720 (C=0). H NMR (DMSO-d , δ, ppm): 3.75 (2H, s, SCH ); 4.87 (1H, s, N-CH-S); 6.85-7.04
6
2
(4H, m, Ar-CH of phenyl); 7.34-7.86 (2H, m, Ar-CH); 8.07 (1H, m, Ar-CH); 8.14(1H, m, Ar-
1
3
CH). C NMR (75 MHz, DMSO-d ): δ 34.1, 65.2, 115.3, 121.6, 121.9, 125.4, 125.6, 130.7,
6
+
1
34.8, 135.7, 153.0, 156.4, 161.4, 171.1. ESI MS (m/z): 399 (M+H) . Calcd. Anal. for
C H FN O S : C, 54.26; H, 2.78; N, 14.06; found C, 54.60; H, 2.35; N, 14.30.
1
8
11
4
2 2
2
.2.3.3
3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(4-chlorophenyl)thiazolidin-4-one
-1
(
Tz3). Yield: 65%; M.p. 188–189°C, R = 0.60. IR (KBr, cm ); 3220 (Ar, C-H), 1540 (C=N),
f
1
1
667 (C=0). H NMR (DMSO-d , δ, ppm): 3.56 (2H, s, SCH ); 5.21 (1H, s, N-CH-S); 6.98-7.28
6
2
(4H, m, Ar-CH of phenyl); 7.43-7.60 (2H, m, Ar-CH); 8.03 (1H, m, Ar-CH); 8.15 (1H, m, Ar-
1
3
CH). C NMR (75 MHz, DMSO-d ): δ 33.4, 66.0, 121.4, 121.6, 121.7, 125.6, 125.9, 128.8,
6
+
1
30.4, 132.1, 135.0, 137.8, 153.9, 156.0, 171.8. ESI MS (m/z): 415 (M+H) . Calcd. Anal. for
C H ClN O S : C, 52.11; H, 2.67; N, 13.50; found C, 52.44; H, 2.45; N, 13.69.
1
8
11
4
2 2

2
.2.3.4
3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(4-nitrophenyl)thiazolidin-4-one
-1
(
Tz4) Yield: 72%; M.p. 231–232°C, R = 0.58. IR (KBr, cm ); 3116 (Ar, C-H), 1602 (C=N),
f
1
1
685 (C=0). H NMR (DMSO-d , δ, ppm): 3.76 (2H, s, SCH ); 5.26 (1H, s, N-CH-S); 7.32-8.07
6
2
(4H, m, Ar-CH of phenyl); 7.34 -7.65 (2H, m, Ar-CH); 8.02 (1H, m, Ar-CH); 8.17 (1H, m, Ar-
1
3
CH). C NMR (75 MHz, DMSO-d ): δ 33.9, 66.2, 121.4, 121.4, 121.9, 125.4, 125.7, 129.77,
6
+
1
35.2, 145.2, 146.6, 153.0, 156.7, 172.1. ESI MS (m/z): 426 (M+H) . Calcd. Anal. for
C H N O S : C, 50.82; H, 2.61; N, 16.46; found C, 50.47; H, 2.55; N, 16.34.
1
8
11
5
4 2
2
.2.3.5
3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(4-bromophenyl)thiazolidin-4-one
-1
(
Tz5). Yield: 68%; M.p. 198–199°C, R = 0.70. IR (KBr, cm ); 3136 (Ar, C-H), 1610 (C=N),
f
1
1
735 (C=0). H NMR (DMSO-d , δ, ppm): 3.85 (2H, s, SCH ); 5.02 (1H, s, N-CH-S); 6.95-7.14
6
2
(4H, m, Ar-CH of phenyl); 7.23-7.68 (2H, m, Ar-CH); 8.09 (1H, m, Ar-CH); 8.12(1H, m, Ar-
1
3
CH). C NMR (75 MHz, DMSO-d ): δ 33.2, 64.9, 121.0, 121.7, 121.9, 124.9, 125.9, 131.2,
6
+
1
31.8, 135.0, 138.2, 153.4, 156.0, 161.4, 171.6. ESI MS (m/z): 460 (M+H) . Calcd. Anal. for
C H BrN O S : C, 47.07; H, 2.41; N, 12.20; found C, 47.30; H, 2.12; N, 12.36.
1
8
11
4
2 2
2
4
.2.3.6 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(3,4,5-trimethoxyphenyl)thiazolidin-
-1
-one (Tz6). Yield: 68%; M.p. 168–169°C, R = 0.71. IR (KBr, cm ); 3145 (Ar, C-H), 1570
f
1
(
C=N), 1680 (C=0). H NMR (DMSO-d , δ, ppm): 3.42 (2H, s, SCH ); 3.84 (9H, s, 3×OCH );
6
2
3
5
.12 (1H, s, N-CH-S); 6.08-6.18 (2H, m, Ar-CH of phenyl); 7.34-7.60 (2H, m, Ar-CH); 8.07
(
1H, m, Ar-CH); 8.14 (1H, m, Ar-CH). 13C NMR (75 MHz, DMSO-d ): δ 34.1, 56.2, 56.5, 65.9,
6
1
06.4, 121.4, 120.8, 121.7, 125.0, 125.6, 128.8, 133.7, 135.6, 150.9, 153.7, 156.4, 171.5. ESI MS
+
(
m/z): 471 (M+H) . Calcd. Anal. for C H N O S : C, 53.61; H, 3.86; N, 11.91; found C, 55.36;
2
1
18
4
5 2
H, 3.98; N, 11.65.

2
.2.3.7 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(3-hydroxyphenyl)thiazolidin-4-one
-1
(
Tz7). Yield: 60%; M.p. 200–201°C, R = 0.69. IR (KBr, cm ); 3034 (Ar, C-H), 1612 (C=N),
f
1
1
718 (C=0). H NMR (DMSO-d6, δ, ppm): 3.80 (2H, s, SCH ); 5.10 (1H, s, N-CH-S); 5.0 (1H,
2
s, OH), 6.53-6.98 (4H, m, Ar-CH of phenyl); 7.52-7.68 (2H, m, Ar-CH); 8.08 (1H, m, Ar-CH);
1
3
8
1
.27(1H, m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 34.2, 65.8, 114.4, 114.6, 121.8, 121.9,
6
25.4, 125.9, 130.8, 135.7, 140.6, 153.9, 155.9, 158.4, 171.1. ESI MS (m/z): 397 (M+H) +.
Calcd. Anal. for C H N O S : C, 54.53; H, 3.05; N, 14.13; found C, 54.10; H, 3.28; N, 14.26.
1
8
12
4
3 2
2
.2.3.8 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(3,4-dimethoxyphenyl)thiazolidin-4-
-1
one (Tz8). Yield: 72%; M.p. 175–176°C, R = 0.72. IR (KBr, cm ); 3152 (Ar, C-H), 1571
f
1
(
C=N), 1672(C=0). H NMR (DMSO-d6, δ, ppm): 3.78 (2H, s, SCH ); 3.61 (6H, s, 2×OCH );
2
3
5
.05 (1H, s, N-CH-S); 6.46-6.94 (3H, m, Ar-CH of phenyl); 7.24-7.72 (2H, m, Ar-CH); 8.10
1
3
(
1H, m, Ar-CH); 8.18 (1H, m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 32.9, 56.6, 65.8,
6
1
13.8, 115.2, 121.7, 121.8, 122.4, 125.7, 125.9, 132.8, 135.6, 148.6, 149.7, 153.0, 156.6, 172.0.
+
ESI MS (m/z): 441 (M+H) . Calcd. Anal. for C H N O S : C, 54.53; H, 3.66; N, 12.72; found
1
9
14
4
3 2
C, 54.35; H, 3.96; N, 12.52.
.2.3.9 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(4-hydroxy-3-methoxyphenyl)
2
-1
thiazolidin-4-one (Tz9). Yield: 76%; M.p. 212–213°C, R = 0.61. IR (KBr, cm ); 3267 (Ar, C-
f
1
H), 1610 (C=N), 1728 (C=0). H NMR (DMSO-d , δ, ppm): 3.86 (2H, s, SCH ); 3.74 (3H, s,
6
2
OCH ); 4.96 (1H, s, N-CH-S); 6.47-6.84 (3H, m, Ar-CH of phenyl); 7.21-7.45 (2H, m, Ar-CH);
3
8
1
.09 (1H, m, Ar-CH); 8.12 (1H, m, Ar-CH). 13C NMR (75 MHz, DMSO-d ): δ 34.1, 56.3, 66.2,
6
14.8, 116.3, 121.4, 121.6, 122.4, 125.6, 125.9, 132.7, 135.6, 144.2, 151.3, 153.4, 156.8, 170.8.
+
ESI MS (m/z): 427 (M+H) . Calcd. Anal. for C H N O S : C, 53.51; H, 3.31; N, 13.14; found
1
9
14
4
4 2
C, 53.24; H, 3.27; N, 13.34.

2
.2.3.10
3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-[(4-dimethylamino)phenyl]
-1
thiazolidin-4-one (Tz10). Yield: 67%; M.p. 109–110°C, R = 0.68. IR (KBr, cm ); 3134 (Ar, C-
f
1
H), 1560 (C=N), 1705 (C=0). H NMR (DMSO-d6, δ, ppm): 3.40 (2H, s, SCH ); 6.10 (1H, s, N-
2
CH-S); 6.65-6.83 (4H, m, Ar-CH of phenyl); 7.51-7.60 (2H, m, Ar-CH); 8.09 (1H, m, Ar-CH);
1
3
8
1
.18 (1H, m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 33.8, 40.5, 64.0, 114.4, 121.1, 121.9,
6
24.9, 126.2, 128.1, 129.4, 135.4, 145.0, 152.9, 156.6, 171.4. ESI MS (m/z): 424 (M+H) +.
Calcd. Anal. for C H N O S : C, 56.72; H, 4.05; N, 16.54; found C, 56.94; H, 3.88; N, 16.41.
2
0
17
5
2 2
2
.2.3.11
3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(furan-2-yl)thiazolidin-4-one
-1
(
Tz11). Yield: 74%; M.p. 165–166°C, R = 0.62. IR (KBr, cm ); 3010 (Ar, C-H), 1636 (C=N),
f
1
1
745 (C=0). H NMR (DMSO-d , δ, ppm): 3.92(2H, s, SCH ); 5.60 (1H, s, N-CH-S); 6.26-6.28
6
2
(
4H, d, 2×CH of furan), 7.29 (2H, d, CH of furan); 7.54-7.74 (2H, m, Ar-CH); 8.10 (1H, m, Ar-
2 2
1
3
CH); 8.24(1H, m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 31.2, 55.6, 57.7, 106.4, 110.6,
6
+
1
16.4, 126.0, 130.2, 135.4, 142.2, 151.8, 163.6, 171.3. ESI MS (m/z): 371 (M+H) . Calcd. Anal.
for C H N O S : C, 51.88; H, 2.72; N,15.13; found C, 51.40; H, 2.98; N, 15.42.
1
6
10
4
3 2
2
.2.3.12 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(2,4-dimethylphenyl)thiazolidin-4-
-1
one (Tz12). Yield: 73%; M.p. 220–221°C, R = 0.72. IR (KBr, cm ); 3132 (Ar, C-H),
f
1
1
570(C=N), 1695 (C=0). H NMR (DMSO-d6, δ, ppm): 2.35 (6H, s, 2×CH3), 3.74 (2H, s,
SCH ); 5.88 (1H, s, N-CH-S); 6.74-6.90 (3H, m, Ar-CH of phenyl); 7.32 -7.67 (2H, m, Ar-CH);
2
8
.02 (1H, m, Ar-CH); 8.15 (1H, m, Ar-CH). 13C NMR (75 MHz, DMSO-d ): δ 17.6, 24.6, 33.2,
6
5
8.8, 121.8, 121.9, 125.2, 125.7, 126.0, 128.2, 130.7, 135.2, 136.0, 136.4, 136.8, 153.2, 156.5,
+
1
71.4. ESI MS (m/z): 409 (M+H) . Calcd. Anal. for C H N O S : C, 58.80; H, 3.95; N, 13.72;
2
0
16
4
2 2
found C, 58.68; H, 3.74; N, 13.89.

2
.2.3.13 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(3-chlorophenyl)thiazolidin-4-one
-1
(
Tz13) Yield: 67%; M.p. 132–133°C, R = 0.68. IR (KBr, cm ); 3225 (Ar, C-H), 1598 (C=N),
f
1
1
676 (C=0). H NMR (DMSO-d , δ, ppm): 3.66 (2H, s, SCH ); 5.30 (1H, s, N-CH-S); 6.94-7.06
6
2
(4H, m, Ar-CH of phenyl); 7.43-7.60 (2H, m, Ar-CH); 8.09 (1H, m, Ar-CH); 8.12 (1H, m, Ar-
1
3
CH). C NMR (75 MHz, DMSO-d ): 34.2, 65.9, 121.8, 122.2, 121.7, 125.1, 126.0, 126.8, 127.4,
6
+
1
28.3, 134.1, 135.8, 140.6, 153.4, 156.6, 171.2. ESI MS (m/z): 415 (M+H) . Calcd. Anal. for
C H ClN O S : C, 52.11; H, 2.67; N, 13.50; found C, 51.84; H, 2.88; N, 13.14.
1
8
11
4
2 2
2
.2.3.14 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(3-methoxyphenyl)thiazolidin-4-one
-1
(
Tz14). Yield: 64%; M.p. 187–188°C, R = 0.53. IR (KBr, cm ); 3165 (Ar, C-H), 1594 (C=N),
f
1
1
686 (C=0). H NMR (DMSO-d , δ, ppm): 3.56 (2H, s, SCH ); 3.71 (3H, s, OCH ); 5.16 (1H, s,
6
2
3
N-CH-S); 6.57-7.06 (4H, m, Ar-CH of phenyl); 7.38-7.65 (2H, m, Ar-CH); 8.07 (1H, m, Ar-
1
3
CH); 8.13 (1H, m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 33.4, 55.9, 65.6, 112.7, 112.8,
6
1
4
3
2
21.1, 121.8, 121.9, 125.1, 126.2, 129.8, 135.2, 140.6, 153.6, 156.2, 160.4, 171.4. ESI MS (m/z):
+
11 (M+H) . Calcd. Anal. for C H N O S : C, 55.60; H, 3.44; N, 13.65; found C, 55.41; H,
1
9
14
4
3 2
.16; N, 13.49.
.2.3.15 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(3-nitrophenyl)thiazolidin-4-one
-1
(
Tz15). Yield: 72%; M.p. 232–233°C, R = 0.74. IR (KBr, cm ); 3120 (Ar, C-H), 1571 (C=N),
f
1
1
677 (C=0). H NMR (DMSO-d , δ, ppm): 3.36 (2H, s, SCH ); 5.10 (1H, s, N-CH-S); 7.80-7.98
6
2
(4H, m, Ar-CH of phenyl); 7.40-7.59 (2H, m, Ar-CH); 8.04 (1H, m, Ar-CH); 8.15 (1H, m, Ar-
1
3
CH). C NMR (75 MHz, DMSO-d ): δ 33.2, 65.1, 119.4, 120.3, 121.7, 124.2, 125.1, 126.2,
6
+
1
29.2, 134.2, 135.6, 140.2, 147.8, 153.6, 156.4, 171.4. ESI MS (m/z): 411 (M+H) . Calcd. Anal.
for C H N O S : C, 50.82; H, 2.61; N, 16.46; found C, 50.48; H, 2.75; N, 16.59.
1
8
11
5
4 2

2
.2.3.16 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-p-tolylthiazolidin-4-one (Tz16).
-1
Yield: 69%; M.p. 224-225°C, R = 0.66. IR (KBr, cm ); 3104 (Ar, C-H), 1606 (C=N), 1705
f
1
(
C=0). H NMR (DMSO-d , δ, ppm): 2.35 (3H, s, CH3), 4.00 (2H, s, SCH ); 5.02 (1H, s, N-CH-
6
2
S); 6.84-6.92 (4H, m, Ar-CH of phenyl); 7.24 -7.60 (2H, m, Ar-CH); 8.08 (1H, m, Ar-CH);
1
3
8
1
.12(1H, m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 24.2, 33.8, 65.3, 121.3, 121.8, 125.7,
6
25.9, 128.7, 129.1, 135.5, 136.4, 136.7, 153.6, 156.0, 171.1. ESI MS (m/z): 395 (M+H) +.
Calcd. Anal. for C H N O S : C, 57.85; H, 3.58; N, 14.20; found C, 57.70; H, 3.82; N, 14.44.
1
9
14
4
2 2
2
.2.3.17 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(4-methoxyphenyl)thiazolidin-4-one
-1
(
Tz17). Yield: 69%; M.p. 208-209°C, R = 0.71. IR (KBr, cm ); 3260 (Ar, C-H), 1584 (C=N),
f
1
1
690 (C=0). H NMR (DMSO-d , δ, ppm): 3.60 (2H, s, SCH ); 3.76 (3H, s, OCH ); 4.81 (1H, s,
6
2
3
N-CH-S); 6.90-7.18 (4H, m, Ar-CH of phenyl); 7.48-7.59 (2H, m, Ar-CH); 8.06 (1H, m, Ar-
1
3
CH); 8.18 (1H, m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 33.8, 55.1, 64.8, 114.4, 120.8,
6
1
20.9, 125.6, 125.9, 128.8, 130.8, 134.7, 151.2, 155.8, 158.6, 170.8. ESI MS (m/z): 411 (M+H)
+.
Calcd. Anal. for C H N O S : C, 55.60; H, 3.44; N, 13.65; found C, 55.38; H, 3.10; N,
1
9
14
4
3 2
1
2
3.51.
.2.3.18 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(2,4-dichlorophenyl)thiazolidin-4-
-1
one (Tz18). Yield: 73%; M.p. 198-199°C, R = 0.62. IR (KBr, cm ); 3230 (Ar, C-H), 1588
f
1
(
C=N), 1647 (C=0). H NMR (DMSO-d , δ, ppm): 3.90 (2H, s, SCH ); 4.94 (1H, s, N-CH-S);
6
2
6
.93-7.18 (3H, m, Ar-CH of phenyl); 7.34-7.65 (2H, m, Ar-CH); 8.08 (1H, m, Ar-CH); 8.10 (1H,
1
3
m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 33.9, 56.0, 100.6, 121.9, 122.4, 125.1, 125.8,
6
1
26.8, 130.8, 131.5, 134.1, 135.4, 135.8, 153.0, 156.6, 171.2. ESI MS (m/z): 434 (M+H) +.
Calcd. Anal. for C H Cl N O S : C, 46.91; H, 1.85; N, 12.87; found C, 46.64; H, 1.66; N,
1
7
8
2
4
2 2
1
2.96.

2
.2.3.19
3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(4-trifluoromethylphenyl)
-1
thiazolidin-4-one (Tz19). Yield: 76%; M.p. 222–223°C, R = 0.57. IR (KBr, cm ); 3314 (Ar, C-
f
1
H), 1610 (C=N), 1703(C=0). H NMR (DMSO-d , δ, ppm): 3.72 (2H, s, SCH ); 5.00 (1H, s, N-
6
2
CH-S); 7.06-7.34 (4H, m, Ar-CH of phenyl); 7.20-7.56 (2H, m, Ar-CH); 8.01 (1H, m, Ar-CH);
1
3
8
1
.16 (1H, m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 33.1, 65.5, 121.6, 121.7, 123.3, 124.6,
6
25.2, 125.7, 126.4, 129.0, 130.6, 132.5, 135.2, 139.3, 153.5, 156.0, 171.8. ESI MS (m/z): 449
+
(
M+H) . Calcd. Anal. for C H F N O S : C, 50.89; H, 2.47; N, 12.49; found C, 50.37; H,
1
9
11
3
4
2 2
2
2
.76; N, 12.62.
.2.3.20
3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(5-chloro-2-hydroxyphenyl)
-1
thiazolidin-4-one (Tz20). Yield: 63%; M.p. 208-210°C, R = 0.58. IR (KBr, cm ); 3142 (Ar, C-
f
1
H), 1602 (C=N), 1707 (C=0). H NMR (DMSO-d , δ, ppm): 3.90 (2H, s, SCH ); 5.00(1H, s,
6
2
OH); 5.26(1H, s, N-CH-S); 6.54-6.92 (3H, m, Ar-CH of phenyl); 7.32-7.74 (2H, m, Ar-CH);
1
3
8
1
.01 (1H, m, Ar-CH); 8.18(1H, m, Ar-CH). C NMR (75 MHz, DMSO-d ): 33.8, 54.5, 117.4,
6
19.5, 121.7, 121.9, 125.8, 125.9, 126.2, 128.6, 130.2, 135.4, 153.7, 154.0, 156.9, 170.8. ESI MS
+
(
m/z): 431 (M+H) . Calcd. Anal. for C H ClN O S : C, 50.17; H, 2.57; N, 13.00; found C,
1
8
11
4
3 2
5
2
0.42; H, 2.76; N, 12.84.
.2.3.21 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(4-diethylamino-2-hydroxyphenyl)
-1
thiazolidin-4-one (Tz21). Yield: 69%; M.p. 230–231°C, R = 0.68. IR (KBr, cm ); 3265 (Ar, C-
f
1
H), 1640 (C=N), 1721 (C=0). H NMR (DMSO-d , δ, ppm): 3.71 (2H, s, SCH ); 4.98(1H, s, N-
6
2
CH-S); 5.08 (1H, s, OH); 1.29(6H, t, 2×CH ); 3.18(4H, m, 2×CH ); 6.02-6.24 (3H, m, Ar-CH of
3
2
phenyl); 7.50-7.79 (2H, m, Ar-CH); 8.08 (1H, m, Ar-CH); 8.22(1H, m, Ar-CH). 13C NMR (75
MHz, DMSO-d ): 13.7, 33.9, 44.8, 55.2, 99.1, 106.6, 107.4, 121.0, 121.5, 125.1, 125.6, 131.4,
6

+
1
35.7, 149.2, 153.0, 156.0, 156.1, 171.6. ESI MS (m/z): 468 (M+H) . Calcd. Anal. for
C H N O S : C, 56.51; H, 4.53; N, 14.98; found C, 56.78; H, 4.20; N, 14.60.
2
2
21
5
3 2
2
.2.3.22 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-m-tolylthiazolidin-4-one (Tz22).
-1
Yield: 73%; M.p. 205-206°C, R = 0.72. IR (KBr, cm ); 3120 (Ar, C-H), 1624 (C=N),
f
1
1
740(C=0). H NMR (DMSO-d , δ, ppm): 2.50 (3H, s, CH ), 3.98 (2H, s, SCH ); 5.07 (1H, s, N-
6
3
2
CH-S); 6.72-7.04 (4H, m, Ar-CH of phenyl); 7.14 -7.60 (2H, m, Ar-CH); 8.01 (1H, m, Ar-CH);
1
3
8
1
.20(1H, m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 24.6, 33.2, 65.4, 121.6, 121.9, 125.2,
6
25.6, 125.9, 127.4, 128.6, 130.6, 135.1, 138.4, 139.7, 153.5, 156.7, 171.0. ESI MS (m/z): 395
+
(
M+H) . Calcd. Anal. for C H N O S : C, 57.85; H, 3.58; N, 14.20; found C, 57.98; H, 3.32;
1
9
14
4
2 2
N, 14.38.
2
4
.2.3.23 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(4-chloro-3-nitrophenyl)thiazolidin-
-1
-one (Tz23). Yield: 68%; M.p. 215-216°C, R = 0.61. IR (KBr, cm ); 3134 (Ar, C-H), 1595
f
1
(
C=N), 1676 (C=0). H NMR (DMSO-d , δ, ppm): 3.73 (2H, s, SCH ); 5.94 (1H, s, N-CH-S);
6
2
7
.39-7.43 (4H, m, Ar-CH of phenyl); 7.24-7.72 (2H, m, Ar-CH); 8.06 (1H, m, Ar-CH); 8.20 (1H,
1
3
m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 34.1, 64.2, 121.8, 121.9, 125.1, 125.7, 125.9,
6
1
27.4, 129.4, 135.1, 136.3, 138.3, 148.6, 153.5, 156.2, 171.3. ESI MS (m/z): 459 (M+H) +.
Calcd. Anal. for C H ClN O S : C, 47.01; H, 2.19; N, 15.23; found C, 47.34; H, 2.04; N,
1
8
10
5
4 2
1
2
5.56.
.2.3.24
4-{3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-4-oxothiazolidin-2-yl}
-1
benzaldehyde (Tz24). Yield: 73%; M.p. 202-203°C, R = 0.56. IR (KBr, cm ); 3116 (Ar, C-H),
f
1
1
635 (C=N), 1727(C=0). H NMR (DMSO-d6, δ, ppm): 3.71(2H, s, SCH ); 4.92 (1H, s, N-CH-
2
S); 9.50 (1H, s, CHO); 7.10-7.42 (4H, m, Ar-CH of phenyl); 7.55-7.67 (2H, m, Ar-CH); 8.08
1
3
(
1H, m, Ar-CH); 8.14(1H, m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 33.4, 65.2, 121.4,
6

1
21.8, 125.1, 125.7, 129.3, 129.8, 135.2, 135.6, 145.0, 153.0, 156.7, 171.8, 191.2. ESI MS
+
(
m/z): 409 (M+H) . Calcd. Anal. for C H N O S : C, 55.87; H, 2.96; N, 13.72; found C, 55.49;
1
9
12
4
3 2
H, 2.67; N, 12.8.
2
.2.3.25 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(3-fluorophenyl)thiazolidin-4-one
-1
(
Tz25). Yield: 60%; M.p. 214-215°C, R = 0.66. IR (KBr, cm ); 3312 (Ar, C-H), 1564 (C=N),
f
1
1
738 (C=0). H NMR (DMSO-d , δ, ppm): 3.90 (2H, s, SCH ); 5.06 (1H, s, N-CH-S); 6.77-7.12
6
2
(4H, m, Ar-CH of phenyl); 7.52-7.84 (2H, m, Ar-CH); 8.12 (1H, m, Ar-CH); 8.22 (1H, m, Ar-
1
3
CH). C NMR (75 MHz, DMSO-d ): δ 33.9, 65.8, 113.8, 115.4, 121.8, 121.9, 124.4, 125.4,
6
+
1
25.9, 130.6, 135.7, 140.8, 153.5, 156.1, 171.2. ESI MS (m/z): 399 (M+H) . Calcd. Anal. for
C H FN O S : C, 54.26; H, 2.78; N, 14.06; found C, 54.10; H, 2.98; N, 14.40.
1
8
11
4
2 2
2
.2.3.26 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(3-bromophenyl)thiazolidin-4-one
(Tz26). Yield: 69%; M.p. 189-190°C, Rf = 0.75. IR (KBr, cm-1); 3124 (Ar, C-H), 1608 (C=N),
1
1
702 (C=0). H NMR (DMSO-d , δ, ppm): 3.60 (2H, s, SCH ); 4.86 (1H, s, N-CH-S); 7.00-7.24
6
2
(4H, m, Ar-CH of phenyl); 7.32-7.56 (2H, m, Ar-CH); 8.07 (1H, m, Ar-CH); 8.10(1H, m, Ar-
1
3
CH). C NMR (75 MHz, DMSO-d ): δ 33.0, 64.6, 121.5, 121.7, 123.0, 125.3, 125.8, 127.7,
6
+
1
30.2, 130.8, 133.8, 135.2, 141.2, 153.8, 156.7, 171.9. ESI MS (m/z): 460 (M+H) . Calcd. Anal.
for C H BrN O S : C, 47.07; H, 2.41; N, 12.20; found C, 47.36; H, 2.76; N, 12.42.
1
8
11
4
2 2
2
.2.3.27 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-phenylthiazolidin-4-one (Tz27).
-1
Yield: 74%; M.p. 198-199°C, R = 0.63. IR (KBr, cm ); 3065 (Ar, C-H), 1624 (C=N), 1712
f
1
(
C=0). H NMR (DMSO-d , δ, ppm): 4.23 (2H, s, SCH ); 4.98 (1H, s, N-CH-S); 6.82-7.14 (4H,
6
2
m, Ar-CH of phenyl); 7.48-7.78 (2H, m, Ar-CH); 8.00 (1H, m, Ar-CH); 8.22(1H, m, Ar-CH).
1
3
C NMR (75 MHz, DMSO-d ): δ 33.3, 65.6, 121.3, 122.0, 125.9, 127.1, 128.6, 128.5, 135.2,
6

+
1
5
2
39.6, 153.6, 156.6, 171.1. ESI MS (m/z): 381 (M+H) . Calcd. Anal. for C H N O S : C,
18 12 4 2 2
6.83; H, 3.18; N, 14.73; found C, 54.72; H, 3.37; N, 14.52.
.2.3.28 3-[5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-(2-hydroxyphenyl)thiazolidin-4-one
-1
(
Tz28). Yield: 62%; M.p. 188–189°C, R = 0.56. IR (KBr, cm ); 3126 (Ar, C-H), 1610 (C=N),
f
1
1
726 (C=0). H NMR (DMSO-d , δ, ppm): 3.98 (2H, s, SCH ); 5.00 (1H, s, N-CH-S); 5.4 (1H, s,
6
2
OH), 6.60-6.92 (4H, m, Ar-CH of phenyl); 7.21-7.60 (2H, m, Ar-CH); 8.05 (1H, m, Ar-CH);
1
3
8
1
.16(1H, m, Ar-CH). C NMR (75 MHz, DMSO-d ): δ 33.7, 55.4, 115.6, 121.4, 121.6, 121.9,
6
25.3, 125.8, 128.5, 130.4, 135.6, 153.2, 155.8, 156.2, 171.7. ESI MS (m/z): 397 (M+H) +.
Calcd. Anal. for C H N O S : C, 54.53; H, 3.05; N, 14.13; found C, 54.82; H, 3.22; N, 14.32.
1
8
12
4
3 2
2
.3 In silico methods
.3.1 Absorption, Distribution, Metabolism and Excretion (ADME) study.
2
We estimated the pharmacokinetic parameters (ADME) of the novel synthesized compounds for
prediction of oral bioavailability using molinspiration online program in compliance with
Lipinski’s rule of five [39]. According to the rule, for oral absorption of newly designed
molecule, it should have a molecular weight < 500, Log P (Octanol-water partition coefficient) <
5
, hydrogen bond donors ≤ 5, hydrogen bond acceptors ≤ 10, number of rotatable bonds ≤ 10, the
topological polar surface area ≤ 160 [40]. Drug candidates showing violation of more than one of
this rule will lead to difficulty in oral absorption [22]. The percentage of absorption (% Abs) was
calculated using topological polar surface area (TPSA) by the formula, % Abs = 109 - [0.345 ×
TPSA] [41].
2
.3.2 Molecular docking study with Peroxisome Proliferator-Activated Receptor Gamma and
alpha glucosidase.

Molecular Docking analysis was carried out using X-ray crystal structure of peroxisome
proliferator-activated receptor-gamma (PDB code: 1FM9, resolution: 2.1A°) and alpha
glucosidase (PDB code: 2QMJ, resolution: 1.9 A°) obtained from Research Collaboratory
Structural Bioinformatics protein data bank [42, 43]. PPAR gamma receptor is the chief target in
the discovery of successful anti-diabetic agents. All the steps of docking i.e. protein selection,
protein preparation, grid generation, ligand preparation, docking and docking study analysis were
performed by Maestro 9.0 Schrodinger suite [44]. The protein structure was constructed using
protein preparation wizard proceeded by optimization and minimization of protein with the 0.3 Å
root mean square deviation. Structures of synthesized ligands were drawn and prepared using Lig
Prep module. The Optimized Potentials for Liquid Simulations (OPLS) 2005 force field was
used for minimization of both the synthesized molecules and protein. The grid box accounting
the active site residues was generated. The docking studies of prepared and minimized molecules
into the prepared and minimized protein were carried out using glide software with extra
precision. The docking score, hydrogen bonding with surrounding amino acids and binding free
energy of all the synthesized hits were anticipated to elucidate the binding affinity into the active
sites of PPAR gamma.
2
.3.3 Prime molecular mechanics-generalized born surface area (MM-GBSA) assessment [45]
The Prime molecular mechanics-generalized born surface area assay, Maestro 9.0, was used to
estimate the binding free energy for the set of synthesized small molecules (ligands) to a receptor
(PPAR-γ) and alpha-glucosidase enzyme. Protein and ligands were prepared using protein
preparation wizard and Lig Prep tool respectively. The results of MM-GBSA may also be
obtained by running the MM-GBSA model directly in the document acquired by running the
procedure of molecular docking.

2
.3.4 Alpha glucosidase assay [46, 47]
The inhibitory potential of seven selected analogues was determined by inhibition assay against
the standard acarbose [48]. Alpha Glucosidase enzyme was purchased from Sigma-Aldrich
which was prepared in potassium phosphate buffer (pH 7.2, 2 mM). The p-nitrophenol-α-D-
glucopyranoside substrate (100μL of pNPG substrate, 2mM, pH 7.2), various concentrations of
synthesized entities and 0.5 IU/mL enzyme were taken in the 96-well plate and incubated at 37°
C for 10 min. The reaction was stopped by the addition of Na CO solution (50μL, 2N).
2
3
Microplate reader was used to measure the absorbance of the reaction mixture at 405 nm. The
percentage of inhibition was calculated according to the formula: % inhibition = (Ac - At)/Ac ×
1
00, where Ac is the absorbance of control and At is the absorbance of the test sample. IC50
values were determined using non-linear regression curve.
.3.5 Enzyme inhibition kinetics study
2
To determine the mode of inhibition of the synthesized derivatives, kinetics studies were carried
out on the highest potent compound Tz21. Different concentrations (0.2, 0.4, 0.6, 0.8 and 1.0
µM) of most potent compound Tz21 was added to 20 mL of the enzyme (0.5 IU/mL) and
incubated with for 30°C for 10 min. pNPG at different concentrations (2, 4, and 6mM) was
added as substrate to initiate the reaction. Change in absorbance was noted for 50min at 405nm.
The type of inhibition is determined by Lineweaver burk plot (1/V versus 1/[푆]) where V is
reaction velocity and [푆] is substrate concentration was. Ki (EI dissociation constant) and Ki’
(ESI dissociation constant) was calculated using the secondary plots of slope versus
concentration of inhibitor and secondary plot of intercept versus concentration of inhibitor
respectively.
2
.4 In vivo Biological Evaluation

2
.4.1 Animals
Albino Wistar rats of either sex weighing 180-240 gm were used for the anti-diabetic study. The
animals were acquired from our institute’s (Delhi Institute of Pharmaceutical Sciences and
Research, New Delhi, India) animal housing facility after the approval by Institutional Animal
Ethics Committee (Protocol No.6, 2016-I). All the animals were housed in polypropylene cages
under 12 h light/12 h dark cycle with standard conditions of temperature (24±1°C) and relative
humidity (35-60%). The rats were given standard food and water ad libitum.
2
.4.2 Experimental procedure of Oral Glucose Tolerance Test [49]
On the basis of glide scores obtained from molecular docking study, seven compounds (Tz4,
Tz10, Tz17, Tz19, Tz21, Tz23 and Tz24) with higher docking scores as compared to the
standard drug were selected for in vivo hypoglycemic activity by Oral Glucose Tolerance Test in
normal rats. Overnight fasted (16 h) normal rats were divided into nine groups of six animals
each. Rats of normal control group (Group I) were administered orally with 0.25% (w/v) aqueous
carboxymethyl cellulose solution (5 mL/kg). Standard group (Group II) received pioglitazone as
a suspension of 0.25% carboxymethyl cellulose at a dose of 36mg/kg. Groups III-IX was orally
fed with selected compounds as 0.25% carboxymethyl cellulose suspension at a dose of
3
6mg/kg. Glucose solution (2g/kg body weight) was given orally to all groups after 30 min of
dosing of carboxymethyl cellulose, pioglitazone and tested compounds. Plasma glucose level of
each rat in every group was measured at 0h, 2h and 6h using Accu-chek Active TM Test
glucometer (Roche Diagnostics, Mannheim, Germany).
2
2
.4.3 Anti-hyperglycemic study on streptozotocin (STZ) induced diabetic rat model [50]
.4.3.1 Streptozotocin instigation of diabetes: Hyperglycemia was induced in overnight fasted
rats by injecting freshly prepared solution of streptozotocin in 0.1 M citrate buffer (pH 4.5) (60

mg/kg bodyweight) intraperitoneally. To overcome the streptozotocin induced hypoglycemic
condition the rats were permitted to drink 5% glucose solution whole night and their blood
glucose levels were then checked by glucometer. The animals with blood glucose level more
than 260 mg/dL after 48 h of STZ injection were considered as diabetic rats and used for the
anti-diabetic evaluation.
2
.4.3.2 Experimental design: The diabetic animals were classified into nine groups with six rats
in each group. Diabetic control group (Group I) received 0.25% (w/v) aqueous carboxymethyl
cellulose solution (5 mL/kg). Group II diabetic rats received oral dose (36 mg/kg) of standard as
0
.25% carboxymethyl cellulose suspension. Groups III-IX was treated with oral dosing (36
mg/kg) of the derivatives (Tz4, Tz10, Tz17, Tz19, Tz21, Tz23, Tz24) (as 0.25% suspension) ,
selected on the basis of higher docking scores.
2
.4.3.3 Blood glucose level estimation: Blood sample was acquired from the retro orbital plexus
of the rat eye utilizing capillary tube. At the 0h, 2h, 4h and 6h intervals, the blood glucose levels
of the rat in every group was monitored by Accu-check Active TM Test meter of Roche
Diagnostics.
2
.5 Statistical Analysis
All the results obtained from in vivo study were represented as mean ± SEM. Statistical
significance were estimated between the tested derivatives and control by one-way ANOVA
followed by Dunnett’s multiple comparison test. The values were considered as significant when
p is less than 0.01.
3
3
. Results and discussion
.1 Chemistry

A library of twenty-eight title compounds (Tz1-Tz28) was synthesized as depicted in scheme 1.
Refluxing of 2-mercaptoaniline with diethyl oxalate proceeded by pouring the solution into
mixture of water, hydrochloric acid and ethanol results in compound 1 which on treatment with
hydrazine monohydrate yields intermediate 2. Compound 3 was prepared by cyclization reaction
of 5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-amine with methanolic cyanogen bromide. Schiff
bases (Sb1-Sb28) were afforded by reaction of compound 3 with different substituted aromatic
aldehydes. Reaction of appropriate Schiff base and mercaptoacetic acid (0.1mol) in
dimethylformamide (25-30ml), containing a catalytic amount of zinc chloride lead to synthesis
of titled derivatives, [5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl]-2-substituted thiazolidin-4-
one (Tz1-Tz28). The purity of the compounds was checked by thin layer chromatography and all
the compounds were obtained in good yield.
The structure of all the synthesized hybrids was confirmed by IR, NMR, Mass and elemental
-1
analysis data. The IR spectra displayed bands of aromatic C-H in the region of 3010-3314 cm ,
-1
-1
bands at 1520-1640 cm due to C=N group and 1647-1748 cm due to carbonyl group of 4-
thiazolidinone ring. The mass spectra of the targets exhibited the molecular ion peaks at [M+1]
+.
The H NMR spectra showed the signal at δ 3.36-4.23 ppm due to –SCH and at δ 4.62-6.10
1
2
ppm due to N-CH-S indicating the generation of 4-thiazolidinone heterocycle. In C13 NMR
signals appears at appropriate values. C, H and N analysis results were within ±0.4% for the
theoretical values.

O
SH
+
O
O
N
N
S
O
(b)
O
(a)
CONHNH2
S
1
NH2
O
2
benzo[d]thiazole-2-carbohydrazide
ethyl benzo[d]thiazole-2-carboxylate
(
c)
N
S
N
O
N
NH2
3
R CHO (d)
N
S
N
O
N
O
N
S
N
O
R
S
(e)
N
N
N C R
Tz(1-28)
Sb(1-28)
H
R= Tz1 = 4-hydroxyphenyl; Tz2 = 4-fluorophenyl; Tz3 = 4-chlorophenyl; Tz4 = 4-nitrophenyl; Tz5 = 4-bromo; Tz6 =
,4,5-trimethoxyphenyl; Tz7 = 3-hydroxyphenyl; Tz8 = 3,4-dimethoxy; Tz9 = 4-hydroxy-3-methoxyphenyl; Tz10 = 4-
3
dimethylamine phenyl; Tz11 = furan-2-yl; Tz12 = 2,4-dimethylphenyl; Tz13 = 3-chlorophenyl; Tz14 = 3-methoxyphenyl;
Tz15 = 3-nitrophenyl; Tz16 = 4-methylphenyl; Tz17 = 4-methoxyphenyl; Tz18 = 2,4-dichlorophenyl; Tz19 = 3-
trifluoromethylphenyl; Tz20 = 5-chloro-2-hydroxyphenyl; Tz21 = 4-diethylamine-2-hydroxyphenyl; Tz22 = 3-
methylphenyl; Tz23 = 4-chloro-3-nitrophenyl; Tz24 = 4-oxophenyl; Tz25 = 3-fluorophenyl; Tz26 = 3-bromophenyl;
Tz27= phenyl; Tz28= 2-hydroxyphenyl
Scheme 1: Synthetic protocol for synthesis of title compounds (Tz1-Tz28). Reagent and
conditions: (a) 10 h, 130 °C; (b) Hydrazine hydrate, ethanol, 9h, 80 °C; (c) Cyanogen Bromide,
methanol, stirring,1.5h, 40 °C; reflux, 11h, 70 °C; (d) Glacial acetic acid, ethanol, 10-12h, 80 °C;
(e) Mercaptoacetic acid, dimethylformamide, 15h.
3
.2 Computer simulation
3
.2.1 ADME Evaluation
Oral bioavailability is accounted as a crucial characteristic for the discovery of efficacious
medicinal drugs. Drug likeliness properties of the prepared benzothiazole-oxadiazole-
thiazolidinone hybrids (Tz1-Tz28) were calculated by the help of molinspiration online software.
The results are presented in table 1. Molecular weight of all the designed derivatives was found
to be less than 500 and thus predicting their easy movement, diffusion and absorption. Molecular

aquaphobicity is measured by Log P (Octanol-water partition coefficient) [41]. Log P value of all
the synthesized hits were found less than five except Tz18 (Log P = 5.15), demonstrating good
membrane permeability of the compounds. Number of hydrogen bond donors and number of
hydrogen bond acceptors in all the hybrid analogues were determined less than 5 and 10
respectively. Topological polar surface area (TPSA) is a very useful parameter for prediction of
°
transport of drug molecule [51] and was observed less than 160 A i.e. in the range of 72.12-
°
1
17.95 A . It can be noticed that all the titled derivatives displayed percentage absorption ranging
from 68.31 to 84.12% indicating significant oral bioavailability. All these pharmacokinetic
properties, as shown in table 1, are in accordance with Lipinski’s rule of five and thus making all
the titled compounds as good orally active anti-diabetic agents.
Table 1: ADME study of synthesized compounds
%Abs1
TPSA
2
n-rotb3
MW4
MV5
miLog
Po/w
n-OHNH7
n-ON8
nviolation
Compound
0
6
(A )
Rule
Tz1
<500
396.45
<5
3.39
<5
1
<10
7
≤1
0
77.14
84.12
92.35
72.12
3
3
311.36
308.28
Tz2
398.44
4.03
0
6
0
Tz3
Tz4
84.12
68.31
72.12
3
4
414.90
425.45
316.88
326.68
4.54
3.83
0
0
6
9
0
0
117.95
Tz5
Tz6
Tz7
84.12
74.56
77.14
72.12
99.83
92.35
3
6
3
459.35
470.53
396.45
321.23
379.98
311.36
4.68
3.50
3.36
0
0
1
6
9
7
0
0

0
0
Tz8
77.75
73.95
83.00
79.58
84.12
84.12
80.93
68.31
84.12
80.93
84.12
84.12
77.14
76.02
84.12
68.31
78.23
84.12
90.59
101.59
75.36
85.27
72.12
72.12
81.36
117.95
72.12
81.36
72.12
72.12
92.35
95.59
72.12
117.95
89.20
72.12
5
4
4
3
3
3
4
4
3
4
3
4
3
6
3
4
4
3
440.51
426.48
423.52
370.42
408.51
414.90
410.48
425.45
394.48
410.48
449.34
448.45
430.90
467.58
394.48
459.90
408.46
398.44
354.44
336.91
349.25
284.91
336.47
316.88
328.89
326.68
319.91
328.89
330.42
334.64
324.90
390.87
319.91
340.22
322.33
308.28
3.51
3.21
3.97
3.12
4.69
4.52
3.90
3.80
4.32
3.92
5.15
4.74
4.46
4.64
4.29
4.43
3.66
4.01
0
1
0
0
0
0
0
0
0
0
0
0
1
1
0
0
0
0
8
8
7
7
6
6
7
9
6
7
6
6
7
8
6
9
7
6
Tz9
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
Tz10
Tz11
Tz12
Tz13
Tz14
Tz15
Tz16
Tz17
Tz18
Tz19
Tz20
Tz21
Tz22
Tz23
Tz24
Tz25
Tz26
Tz27
84.12
84.12
72.12
72.12
3
4
459.35
448.45
321.23
334.64
4.65
4.74
0
0
6
6
0
0
Tz28
77.14
92.35
3
396.45
311.36
3.81
1
7
0
1
2
3
4
5
Percentage of absorption.
Topological polar surface area.
Number of rotatable bonds.
Molecular weight.
Molecular volume.

6
7
8
Logarithm of octanol/water partition coefficient.
Number of hydrogen bond donors.
Number of hydrogen bond acceptors.
3
.2.2 Docking study
The molecular docking study was performed to understand the binding mode of all the
synthesized analogs into the active site of PPAR-γ receptor. The docking scores, binding
energies and interaction with amino acids of the prepared hits are presented in Table 2. All the
compounds in the series were active. Three compounds Tz21, Tz17 and Tz10 showed the
highest docking scores (-9.85, -9.11 and -8.85 respectively) among all the compounds which is
higher than pioglitazone (-8.46) in the binding site of the PPAR-γ receptor. Here we discuss the
binding mode of three most active compounds (Tz21, Tz17 and Tz10). Docking study of
compounds Tz21, Tz17and Tz10 into the active site of target indicated that several molecular
interactions were supposed to be accountable for the remarkable affinity of these compounds.
Tz21 is the most active compound in the synthesized library. Tz21 forms four hydrogen bonds
with Leu340, Ser342 and Glu343. Oxygen of 4-thiazolidinone ring forms two hydrogen bonds
with Glu343 and Ser342. Third hydrogen bond was formed between oxygen of oxadiazole and
Ser342 and fourth hydrogen bond was observed between hydrogen of hydroxyl group of benzene
and Leu340. In addition, the compound showed hydrophobic interactions with Leu330, Met334,
Val339, Met364, Leu356, Ile281, Ala278, Phe260, Phe262, Cys285, Tyr327, Ile326, Leu453,
Leu469 and Tyr473. The oxadiazole ring was found to have π-π interaction with Hie449 while
the thiazolidinone ring showed polar interaction with Ser289. (Fig. 1.).

(a)
(b)
Fig. 1. (a) 3D docked pose of compound Tz21 showing hydrogen bonds in black dotted line with
Leu340, Ser342 and Glu343. Coloured by atom: Carbons: brown; Nitrogen: blue; Oxygen: red;
Hydrogen: white. (b) 2D docked pose of compound Tz21 denoting hydrophobic interactions by
green amino acid residues and pie-pie interactions by green solid line.

In compound Tz17, oxygen of thiazolidinone ring showed two hydrogen bonds formation with
amino acids Hip323 and Tyr473, in which interaction with Hip323 is similar to the standard
drug, pioglitazone. Moreover, third hydrogen bond was observed between nitrogen of oxadiazole
ring and Tyr473 amino acid. Additionally it forms hydrophobic contact with Met364, Phe282,
Leu356, Phe363, Cys285, Leu330, Leu465, Leu453, and Leu469. π-π stacking appears between
the oxadiazole ring and Hie449 and the oxadiazole core also shows polar interaction with Gln286
and Ser289. (Fig. 2.)
(a)

(b)
Fig. 2. (a) 3D docked pose of compound Tz17 showing hydrogen bonds in black dotted line with
Hip323 and Tyr473. Coloured by atom: Carbons: brown; Nitrogen: blue; Oxygen: red;
Hydrogen: white. (b) 2D docked pose of compound Tz17 denoting hydrophobic interactions by
green amino acid residues and pie-pie interactions by green solid line.
Compound Tz10 (third most active compound) shows three hydrogen bond interactions. One
hydrogen bond was formed between nitrogen of oxadiazole ring and amino acid Ser342 which is
similar to the standard drug, pioglitazone. Second hydrogen bond was observed between nitrogen
of oxadiazole ring with amino acid Glu343 and third hydrogen bond was formed between
hydrogen of methyl group and Ile326. Futhermore, compound form hydrophobic cloud with
Leu255, Ile281, Met348, Met364, Ile341, Leu 340, Leu 340, Leu 333, Val 339, Cys285, Tyr327.
(Fig. 3.)

(a)
(
b)
Fig. 3. (a) 3D docked pose of compound Tz10 showing hydrogen bonds in black dotted line with
Ser342, Glu343 and Ile326. Coloured by atom: Carbons: brown; Nitrogen: blue; Oxygen: red;
Hydrogen: white. (b) 2D docked pose of compound Tz10 denoting hydrophobic interactions by
green amino acid residues.
3
.2.3 MM-GBSA Assay