Studies on inclusion complexes of 2-(benzothiazolyl-2′)-hydrazono-3-phenyl-5-arylidene-4-thiazolidinone derivatives with β-cyclodextrin

Article abstract of DOI:10.14233/ajchem.2016.20116

A series of 2-(benzothiazolyl-2′)-hydrazono-3-phenyl-5-arylidene-4-thiazolidinone derivatives have been synthesized starting from 2-hydrazinobenzothiazole.To enhance the solubility and bioaccessibility of these synthesized pharmacophores the inclusion com

Full text of DOI:10.14233/ajchem.2016.20116

Asian Journal of Chemistry; Vol. 28, No. 12 (2016), 2764-2768
A
SIAN
J
OURNAL OF HEMISTRY
C
http://dx.doi.org/10.14233/ajchem.2016.20116
Studies on Inclusion Complexes of 2-(Benzothiazolyl-2')-hydrazono-3-
phenyl-5-arylidene-4-thiazolidinone Derivatives with β-Cyclodextrin
*
S. DASH, R. SAHU and B.K. GARNAIK
P.G. Department of Chemistry, Berhampur University, Bhanja Bihar-760 007, India
*Corresponding author: E-mail: bama_61@rediffmail.com
Received: 31 May 2016;
Accepted: 11 July 2016;
Published online: 1 September 2016;
AJC-18077
A series of 2-(benzothiazolyl-2')-hydrazono-3-phenyl-5-arylidene-4-thiazolidinone derivatives have been synthesized starting from
2-hydrazinobenzothiazole.To enhance the solubility and bioaccessibility of these synthesized pharmacophores the inclusion complexes
have been prepared with β-cyclodextrin. The synthesis of compounds and their inclusion complexes have been ascertained from their
changes in physical, thermal and spectral characteristics (UV, IR and NMR). The stability constant and free energy change of the inclusion
complexes have also been determined. The study suggests that inclusion complexes are appreciably stable and thermodynamically allowed.
The synthesized compounds and their inclusion complexes have been screened for their possible antibacterial and antioxidant activities.
The results revealed that compounds show better antibacterial and antioxidant activities after inclusion complex formation.
Keywords: 4-Thiazolidinone, β-Cyclodextrin, Phase solubility study, Inclusion complexes, Antibacterial, Antioxidant study.
thiazolidinone derivatives with β-cyclodextrin. The develop-
ment of the compounds and their inclusion complexes have
been established by the study of their physical, thermal and
spectral data (UV, IR and NMR).The thermodynamic stability
constants and the free energy change of the inclusion comp-
lexes are determined. The impact of naked compounds and
their inclusion complexes on antibacterial and antioxidant
activities have also been studied.
INTRODUCTION
Due to the need of present society, the research has been
carried out with the important heterocycles with active
pharmacophore moiety. Thiazolidinones and their derivatives
have importance in the field of medicinal chemistry due to
their wide range of chemotherapeutic uses. The substituted
thiazolidinones are well known for their biological activities
such as antimicrobial [1,2], antioxidant [3], anti-HIV [4],
antihistaminic [5], anticonvulsant [6,7], anti-inflammatory
[8-10]. The present work has emphasized on the synthesis
of a series of 2-(benzothiazolyl-2')hydrazono-3-phenyl-
5-arylidene-4-thiazolidinone derivatives starting from
2-hydrazinobenzothiazoles. Due to the poor solubility of the
compounds, they are unable to show significant bioaccessi-
bility. The drugs are encapsulated in the hydrophobic cavity
of cyclodextrin [11] and this leads to an increase in the biological
activities. The cavity shape of the cyclodextrins are considered
as the most appropriate synthetic model host cavities, which
make available water insoluble guests for encapsulation,
thereby making them water soluble [12]. Among various
cyclodextrins, β-cyclodextrin is the suitable one for inclusion
complex formation because the cavity size of the β-cyclodextrin
is appropriate for heterocyclic compounds [13]. Inclusion
complexes are prepared by encapsulating the synthesized
(2-benzothiazolyl-2')-hydrazono-3-phenyl-5-arylidene-4-
EXPERIMENTAL
All the chemicals used are procured with analytical reagent
grade. Double distilled water is used as the solvent for dilution
was prepared in the laboratory. The electronic spectra were
recorded on Shimadzu UV-1700 Spectrophotometer while
IR-spectra were recorded in KBr pellets in 4000-400 cm-1
1
region on a Shimadzu 8400 FTIR Spectrophotometer. H
NMR spectra (CDCl3) are scanned on a DRX-300 (300 MHz)
spectrophotometer using TMS as internal standard and
chemical shifts are expressed in δ scale. Purity of synthesized
compounds has been checked by sulphur detection and
homogeneity has been checked by TLC using silica gel.
Melting points are recorded by open capillary method and are
uncorrected.
Synthesis of compounds: The compounds were synthe-
sized as describe by Garnaik and Mishra [14] (Scheme-I).

Vol. 28, No. 12 (2016)
Studies of Inclusion Complexes of 4-Thiazolidinone Derivatives with β-Cyclodextrin 2765
2-(benzothiazolyl-2')-hydrazono-3-phenyl-4-thiazolidinone
(0.35 g, 2 mmol), benzaldehyde (0.22 g, 2 mmol), fused
sodium acetate (1 g) in glacial acetic acid (15 mL) was heated
under reflux for 4 h. The pale yellow solution after cooling to
room temperature was poured into ice cold water when yellow
solids separated out. The crude product was filtered, washed
with water and recrystallized from ethanol, m.p. 122 °C, yield-
0.28 g (63 %). (Found: S, 14.07 % C23H17N4OS2 requires S,
14.91 %). Similarly the other compounds of the series were
prepared by using p-chloro benzaldehyde (compound B) and
p-methoxy benzaldehyde (compound C), respectively.
Aqueous phase solubility study: The aqueous phase
solubility of all the compounds have been studied with different
concentration of β-cyclodextrin (0-10 mM) with accurately
weighed compound in different conical flasks as per Higuchi
Connors method [15].
N
NHNH2
S
C6H5NCS
EtOH
N
S
NHNHCSNHC6H5
CH
COONa
3
,EtOH
N
NH
N
S
S
Synthesis of inclusion complexes: The inclusion
complexes of the synthesized compounds (A, B and C) with
β-cyclodextrin were prepared as per co-precipitation method
N
O
[16-18].
C6H5
Evaluation of antibacterial activity: As per cup-plate
method [19,20] the antibacterial activity of compounds was
carried out. Dimethyl sulphoxide at 500 µg/mL were taken
and solutions of synthesized compounds and inclusion
complex is prepared with a conc. of 500 µg/mL. Three types
of bacteria namely E. coli, S. aureus and P. vulgaris were inocu-
C6H5CHO,
a,
COON
CH3
H COOH
C
3
N
NH
N
S
HC
Ar
lated into 100 mL of the sterile nutrient broth and incubated
for 24 h at at 37 °C. Uniform diameter of agar plates were
used to inoculate them one by one with the test organisms
aseptically. With the help of micropipette drug and test
compounds solution is taken and then plates were placed in
the refrigerator at 8-10 °C for right dispersal of drug into the
media. The Petri plates were transferred to incubator after 2 h
and maintained at 38 °C for 22 h. Then the Petri plates were
observed for zone of inhibition by using vernier scale and the
data were observed.
S
N
O
C6H5
Ar = phenyl(compound-
A
)
=
=
p
p
-chloro phenyl(compound -B)
-methoxy phenyl(compound-C)
Scheme-I
Evaluation of antioxidant activity: As suggested by
Tagashira and Ohtake [21], the antioxidant activity of the
synthesized compounds was studied. 2,2-Diphenyl-1-picryl-
hydrazyl (DPPH) method is used for screening the compound.
Ethanolic DPPH having 100 µg/mL concentration is used to
prepare sample solution for test. The mixture is incubated for
10 min at room temperature After vortexing with 100 µg/mL
concentration. The absorbances of the samples are calculated
at 517 nm. The difference of absorbance between a test sample
and a control is the activity of the sample. Here the reference
substance used is butylated hydroxyl toluene (BHT).
Step-I: 1-(Benzothiazolyl-2')-4-phenyl thiosemicarba-
zide: A mixture of 2-hydrazinobenzothiazole (1.65 g, 10
mmol) in ethanol (10 mL), phenyl isothiocyanate (1.35 g, 10
mmol) was added with stirring during a period of 5 min. The
resulting solution was refluxed with stirring with 0.5 h and
cooled. The crystals obtained were filtered and recrystallized
from ethanol. m.p. 179 °C, yield 2.1 g (70 %), (Found S, 21.2 %,
C14H22N4S2 requires S, 21.4 %)
Step-II: 2-(Benzothiazolyl-2')-hydrazono-3-phenyl- 4-
thiazolidinone: A mixture of 1-(benzothiazolyl-2')-4-phenyl
thiosemicarbazide (0.06 g, 2 mmol), monochloroacetic acid
(0.25 g, 2 mmol) and anhydrous sodium acetate (0.2 g) in
absolute ethanol (10 mL) were refluxed for 3 h. The excess of
solvent was removed and poured into cold water. The solid
obtained was filtered, washed with hot water, dried and
recrystallized from ethanol, m.p. 166 °C, yield 0.3 g (44 %),
(Found: S, 18.80 % C16H12N4OS2 requires S,18.95 %). IR (KBr,
RESULTS AND DISCUSSION
The encapsulation of the compounds in the cavity of β-
cyclodextrin is confirmed from the changes in melting point,
colour and spectral characteristics with respect to their
compounds (Tables 1 and 2). From the melting point data it is
observed that inclusion complexes are having higher value
than that of compounds due to the fact that it requires an addi-
tional thermal energy to carry the compounds from the cavity
of the β-cyclodextrin.
ν
max, cm-1): 746.45 (C-S str), 1487.12 (C=C str) 1556.55 (C=N
str), 1714.72 (C=O str), 3030.17 (Ar-H str), 3226.91 (N-H
str).
Step-III: 2-(Benzothiazolyl-2')-hydrazono-3-phenyl-5-
arylidene-4-thiazolidinone (Compound-A): A mixture of

2766 Dash et al.
Asian J. Chem.
TABLE-1
PHYSICAL PROPERTIES OF COMPOUNDS AND THEIR INCLUSIONS
Compound/Complex
Compound A
Compound A with β-cyclodextrin
Compound B
Compound B with β-cyclodextrin
Compound C
Substituent
Phenyl
Colour
m.p. (°C)
122
145
190
205
Yield (%)
Yellow
63
45
65
50
63
48
Yellowish white
p-Chloro phenyl
Brown
Pale brown
Yellow
Yellowish white
p-Methoxy phenyl
201
225
ompound C with β-cyclodextrin
TABLE-2
SPECTRAL DATA OF SYNTHESIZED COMPOUNDS AND THEIR INCLUSIONS
IR (KBr, νmax, cm-1)
742.59 (C-S str), 1492.60 (C=C str), 1589.34 (C=N
str), 1645.28 (C=O str), 3194.12 (N-H str)
Compound/complexes
Compound-A
1H NMR
UV λmax
1H NMR (CDCl3): δ 6.8-8.2 (d, 6H, Ar-H), 4.2 (s,
275
1H, C-NH), 7.58 (s, 1H, C-H), 7.3-7.6 (t, 8H, Ar-H)
1H NMR (CDCl3): δ 6.1-7.8 (d, 6H, Ar-H), 3.8 (s,
1H, C-NH), 7.11 (s, 1H, C-H), 6.8-7.2 (t, 8H, Ar-H)
746.45 (C-S str), 1494.83 (C=C str), 1581.83 (C=N
str), 1714.12 (C=O str), 3224.34 (N-H str)
278
265
Compound-A with β-CD
1H NMR (CDCl3): δ 6.95-8.6 (d, 6H, Ar-H), 4.4 (s,
1H, C-NH), 7.80 (s, 1H, C-H), 7.56-7.9 (t, 8H, Ar-
H)
692.44 (C-Cl str), 744.52 (C-S str), 1487.12 (C=C
str), 1583.56 (C=N str), 2916.37 (Ar-H str)
1701.22, 1645.28 (C=O str), 3197.89 (N-H str)
Compound-B
692.44 (C-Cl str), 746.45 (C-S str), 1489.05 (C=C
str), 153 9.20 (C=N str), 1714.72 (C=O str),
3030.17 (Ar-H str), 3325.28, 3194.12 (N-H str)
748.38 (C-S str), 1425.40 (C=N str), 1494.83 (C=C
str), 1593.20 (C=N str), 1712.97 (C=O), 3062.96
(Ar-H str)
748.38 (C-1417.60 (C-N str), 1456.26 (C=C str)
1508.33 (C=N str), 1699.29, 1637.56 (C=O str),
3331.07 (N-H str)
1H NMR (CDCl3): δ 6.3 -7.45 (d, 6H, Ar-H), 3.9 (s,
267
296
299
Compound-B with β-CD
Compound-C
1H, C-NH), 7.25 (s, 1H, C-H), 6.9-7.3 (t, 8H, Ar-H)
1H NMR (CDCl3): δ 6.6-8.5 (d, 6H, Ar-H), 4.3 (s,
1H, C-NH), 7.65 (s, 1H, C-H), 7.3-7.6 (t, 8H, Ar-
H), 3.95 (s, 3H, OCH3)
1H NMR (CDCl3): δ 6.1-7.8 (d, 6H, Ar-H), 3.7 (s,
1H, C-NH), 7.5 (s, 1H, C-H), 6.6-7.1 (t, 8H, Ar-H)
3.65 (s, 3H, OCH3)
Compound-C with β-CD
1.0
In case of IR data of compound A it is seen that the IR
frequencies are found at 742.59 (C-S str), 1492.60 (C=C str),
1589.34 (C=N str), 1645.28 (C=O str), 3194.12 (N-H str)
indicating the presence of C-S, C=C, C=N, C=O and N-H in
the compound as expected and similarly the IR data of inclu-
sion complexes of compound A show characteristics absorption
at 746.45 (C-S str), 1494.83 (C=C str), 1581.83 (C=N str)
1714.12 (C=O str), 3224.34 (N-H str) indicating the presence
of C-S, C=C, C=N, C=O and N-H in the compounds.
Absorption at suitable characteristic frequencies of IR data of
compounds B, C and their inclusion complexes are shown in
Table-2. For compounds C, the IR frequency of carbonyl group
(C=O) shifted towards lower energy side. For all inclusion
complexes there is a remarkable change in the IR spectrum
(broader and smoother) as the compounds are encapsulated
into the cavity of β-cyclodextrin. The host and guest molecules
are interacted with each other through H-bonding and van der
Waals forces [22]. It can be concluded that the δ values of the
inclusion complexes are having low value as compare to their
respective compounds. This means PMR signals are shifted
towards up field in the inclusion complex due to the notable
shielding factor which arise through encapsulation within the
cavity of β-cyclodextrin.
Compound
Compound
Compound
A
B
C
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
-0.001 0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007
-CD concentration
β
Fig. 1. Variation of absorption with concentration
1/∆A = 1/∆C + 1/KT [Guest]o ∆C · [β-CD]o
where ∆A is change in absorbance, ∆C is change in molar
extension coefficient, [Guest]o is concentration of compound
in inclusion complex and [β-CD]o is molar concentration of
β-cyclodextrin.
Plot of 1/∆A versus 1/[β-CD]o for compounds show appre-
ciable linear correlations (Fig. 2). Using the equation KT =
Intercept/Slope, the values of thermodynamic stability constant
KT are determined. The KT values of the inclusion complexes
of compounds with β-cyclodextrin were found to be 526.13,
399.66 and 533.94 M-1, respectively (Table-3). All the data
were remaining within the ideal range of 100 to 1000 M-1 signi-
fying stabilities for the inclusion complexes through weak
molecular interactions [23-25].
From the graphs of aqueous phase solubility studies, it
can be concluded that there is a linear increase in solubility of
the compounds with respect to concentration of β-cyclodextrin
(Fig. 1). The stoichiometry of these complexes may be 1:1 as
the values of all the slopes of plots were less than unity. In
order to calculate the thermodynamic stability constants (KT)
of inclusion complexes, Benesi-Hilderband relation is used
[20].

Vol. 28, No. 12 (2016)
Studies of Inclusion Complexes of 4-Thiazolidinone Derivatives with β-Cyclodextrin 2767
16
Compound
Inclusion
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
14
Compound
Compound
Compound
A
B
C
12
10
8
6
4
2
0
A
B
C
Fig. 4. Antibacterial activity of the tested compounds and their inclusions
0
200
400
1/
600
800
1000
1200
against E. coli
β
-CD concentration
Fig. 2. Variation of 1/absorption with 1/concentration
16
Compound
Inclusion
TABLE-3
14
12
10
8
EQULIBRIUM CONSTANT AND FREE ENERGY
CHANGE OF INCLUSION COMPLEXES
Inclusion complex
of compound
Equlibrium
constant (KT)
526.123
399.666
533.941
∆G (kJ/mol)
-15.627
-14.941
-15.756
Inclusion complex A
Inclusion complex B
Inclusion complex C
6
The ∆G value can be calculated at 298 K using the equation:
∆G = –2.303RT log K
4
The value of free energy of activation has been calculated
and found to be -15.627, -14.941 and -15.756 kJ/mol (Table-3)
for the inclusion complexes of Compound A, B and C, respec-
tively. In all cases we obtained negative values of ∆G, which
make the process thermodynamically favourable.
From the graphs of antibacterial studies against three
bacterial strains namely E. coli, S. aureus and P. vulgaris, it is
found that the diameter of the zone of inhibition of inclusion
complexes noticeably high as compare to the compounds
shown in Figs. 3-5. Among the tested substances the inclusion
2
0
A
B
C
Fig. 5. Antibacterial activity of the compound and inclusion complex
against P. vulgaris
complex of compound C exhibited maximum activity against
S. aureus than that of other complexes whereas compound B
shows maximum activity against E. coli and P. vulgaris with
respect to other complexes. The remarkable enhancement of
antibacterial activity of the inclusion complexes due to their
solubility in the aqueous medium which makes them more
bio-accessible and effective towards specific tissues thereby
increasing drug efficiency. After encapsulation, the radical
scavenging activity of the compound increases significantly
(Table-4). This can be associated with higher solubility
16
Compound
Inclusion
14
12
10
8
TABLE-4
ANTIOXIDANT ACTIVITY OF SYNTHESIZED
COMPOUNDS AND THEIR INCLUSIONS
6
Conc. (500 µg/mL)
% of inhibition
Conc. (100 µg/mL)
% of inhibition
Compound/Complex
4
Compound-A
Inclusion with β-CD
Compound-B
Inclusion with β-CD
Compound-C
Inclusion with β-CD
Ascorbic acid
34.6
47.8
28.7
44.4
36.5
51.6
90.0
28.80
35.87
22.60
31.80
27.60
36.80
74.30
2
0
A
B
C
Fig. 3. Antibacterial activity of the compound and inclusion complex
against S. aureus

2768 Dash et al.
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