Synthesis and in vitro evaluation of some isatin-thiazolidinone hybrid analogues as anti-proliferative agents

Article abstract of DOI:10.2174/157340610793358909

A range of isatin-thiazolidinone hybrid analogues were synthesized and their cytotoxicity was evaluated against several cancer cell lines in vitro. The acute toxicity studies in mice models revealed that these analogues possess low systemic toxicity and are safe up to 1600mg/Kg. Among the compounds synthesized, 5-(2-nitrobenzylidene)-2-(isatin-3- azino)-thiazolidin-4-one (CI) has been shown to be the most active, highly promising compound which induced S phase arrest in cell cycle in a time dependent manner. Our initial analysis indicate that incorporation of electron withdrawing group at ortho position of the ring favors over the meta and para positions for eliciting its cytostatic effect. Overall, the in vitro biological evaluation suggests that the growth inhibitory effect of CI is promising and can be studied further.

Full text of DOI:10.2174/157340610793358909

306
Medicinal Chemistry, 2010, 6, 306-312
Synthesis and In Vitro Evaluation of Some Isatin-Thiazolidinone Hybrid
Analogues as Anti-Proliferative Agents
P.K. Ramshid1, Sankar Jagadeeshan2, Anand Krishnan2, Mary Mathew1,†, S. Asha Nair2,†,* and
M. Radhakrishna Pillai2
1Department of Pharmaceutical Chemistry, College of Pharmaceutical Sciences, Thiruvananthapuram, India;
2Integrated Cancer Research Programme, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
Abstract: A range of isatin-thiazolidinone hybrid analogues were synthesized and their cytotoxicity was evaluated against
several cancer cell lines in vitro. The acute toxicity studies in mice models revealed that these analogues possess low sys-
temic toxicity and are safe up to 1600mg/Kg. Among the compounds synthesized, 5-(2-nitrobenzylidene)-2-(isatin-3-
azino)-thiazolidin-4-one (CI) has been shown to be the most active, highly promising compound which induced S phase
arrest in cell cycle in a time dependent manner. Our initial analysis indicate that incorporation of electron withdrawing
group at ortho position of the ring favors over the meta and para positions for eliciting its cytostatic effect. Overall, the in
vitro biological evaluation suggests that the growth inhibitory effect of CI is promising and can be studied further.
Keywords: Isatin, thiazolidinone, cancer, cytotoxicity, cell cycle arrest.
1. INTRODUCTION
aberrant functions of other kinases has been observed to be
one of the responsible mechanisms underlying pathological
hyperproliferation [5]. Consequently, inhibition of these
kinases is considered to be one of the therapeutic options for
combating cancer [6,7]. The success of “bcr-abl” kinase in-
hibitor, imatinib, in chronic myeloid leukemia (CML) ther-
apy has already proven the importance of kinase inhibitors in
cancer chemotherapy.
Surgical removal of cancerous tissue followed by radio-
therapy and chemotherapy is the standard front line treat-
ment modality of cancer diseases. However, this approach is
always not feasible depending on severity of the disease and,
in such conditions, the patients mainly rely on long term
chemotherapy to maintain the quality of life. Though chemo-
therapy with conventional anti-tumor drugs offers promising
control over tumor associated problems, by inhibiting its
progression and metastasis, the drug itself, at most of the
times, renders undesirable systemic toxicity. These undesir-
able effects are usually because of the indiscriminate cyto-
toxic effect of these drugs to normal cells. Drug resistance is
another well known hurdle in chemotherapy. Use of combi-
nation chemotherapy, which is the administration of several
drugs with different and complementary mechanism of ac-
tion, is regarded as an effective approach to evade drug resis-
tance. However administration of multiple cytotoxic drugs at
a time brings in more serious deleterious systemic effects.
Therefore design and synthesis of new anti-cancer agents,
with low systemic toxicity and ability to evade different drug
resistance mechanisms, is highly desirable and demanding in
the field of medicinal chemistry.
1H-indole-2,3-diones (Isatins) and its derivatives have
shown a variety of biological effects including antibacterial,
antifungal and antiviral activities [8]. In addition, antiprolif-
erative and proapoptotic actions of isatin have been reported
in different cancer cell lines at concentrations lower than
10-6mol/L [9]. These previous studies have shown good cor-
relation between the anti-proliferative effects of synthetic
oxindoles with their inhibitory effects on ATP binding pock-
ets associated with biomolecules. To be more specific, some
of the derivatives were earlier reported to target protein
kinases associated with growth factor receptors [10-12] to
elicit the anti-proliferative effects. C3-substituted synthetic
oxindoles are a major research focus area and, so far, they
were developed as specific inhibitors of protein tyrosine
kinases (PTKs) associated epidermal growth factor, platelet
derived growth factor, vascular endothelial growth factor and
insulin like growth factor receptors by different research
groups [13]. The synthetic feasibility of isatin has led to an
extensive use of this compound in organic synthesis to con-
jugate isatin with a variety of other potent molecules to im-
prove the efficacy and versatility of action.
Phosphorylation of serine / threonine / tyrosine residues
is identified to be one of the main post translational modifi-
cations employed by cells to fine tone their metabolic and
regulatory pathways [1,2]. Abnormal phosphorylation may
sometimes become a cause of initiation or progression of
different diseases like cancer, Alzheimer’s and atherosclero-
sis [3,4]. Excessive activity of cyclin-dependent kinases or
Strikingly, a large number of literatures indicate presence
of thiazole moiety in the structure of several naturally occur-
ring molecules with important antibiotic, immunosuppres-
sive and antitumor activities [14]. Studies have shown that
thiazolidinone moiety has potential to inhibit tyrosine
kinases [15] and its synthetic analog 5-benzylidene-2-
*Address correspondence to this author at the Integrated Cancer Research
Programme, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram,
India; Tel: +91 471 2529501; Fax No. +91 471 2348096;
E-mail: sasha@rgcb.res.in
†Both authors contributed equally
1573-4064/10 $55.00+.00
© 2010 Bentham Science Publishers Ltd.

Synthesis and in vitro Evaluation of some Isatin-Thiazolidinone Hybrid Analogues
Medicinal Chemistry, 2010, Vol. 6, No. 5 307
phenylimnio-1,3-thiazolidin-4-one has been shown to induce
apoptosis in cancer cells sparing normal ones [16]. More
interestingly, thiazolidinone analogs are not p-glycoprotein
substrates and thus may act as promising molecules in treat-
ing p-glycoprotein over-expressing refractory cancers.
2.2.1. Synthesis of Isatin-3-Thiosemicarbazone
Equimolar quantity of Isatin and Thiosemicarbazone was
dissolved in warm ethanol. pH was adjusted to 4 - 5 with
glacial acetic acid and heated under reflux for 40 minutes.
The reaction mixture was allowed to stand for 24h at room
temperature and the products were separated by filtration and
recrystallized from 90% aqueous ethanol. Yield: 55%; mp:
198-200oC; Rf [benzene: chloroform (5.5 : 4.5)] 0.81; UV
ꢁmax: 220 nm in methanol; IR: (KBr ꢂcm-1) 3420cm-1&
Cytotoxic
ꢀ electron delocalized lipophilic cations
(DLCs) possess marked and selective anti-tumor activity.
This effect of DLCs is because of their selective accumula-
tion in negatively charged mitochondria in carcinoma cells
due to electrochemical proton gradient [17-23]. Structural
requirements of 4-oxothiazolidine and double conjugate sys-
tem has been reported to be essential for the ꢀ electron delo-
calization activity [24,25]. Altogether, considering the tumor
therapeutic potential of oxindole and thiazole groups, in the
present study, a hybrid molecule has been synthesized, com-
bining these two central molecules and maintaining the
unique double conjugate structure. This was followed by
synthesis of a range of hybrid analogues and their pharma-
cological evaluation was done for their cytotoxic and cy-
tostatic activities.
3162cm-1 NH str, 1700cm-1CO str, 1131cm-1CS str; HNMR
1
(DMSO) ꢃppm 6.4-6.1 (Ar-H, 9H); MS, m/z: 220(M+).
2.2.2. Synthesis of 2-(Isatin-3-azino)-4-thiazolidinone
A mixture of Isatin-3-thiosemicarbazone (0.01 mol),
monochloroacetic acid (0.01 mol) and anhydrous sodium
acetate (0.02 mol) in ethanol (100 ml) was heated under re-
flux for 10 hrs with occasional shaking. The excess solvent
was distilled off under vaccum and poured into crushed ice,
filtered and recrystallized from 90% aqueous ethanol to give
orange crystals. Yield: 60%; mp:210-212oC; Rf [benzene:
chloroform (5.5 : 4.5)] 0.85; UV ꢁmax: 220 nm in methanol;
IR: (KBr ꢂcm-1) 3174cm-1 NH str, 1702cm-1 CO str; 1HNMR
(DMSO) ꢃppm 7.1-6.5 (Ar-H, 9H); MS, m/z: 260(M+)
2. MATERIALS AND METHODS
2.1. General
2.1.1. Chemistry
2.2.3.
Synthesis
of
5-Arylidene-2-(Isatin-3-azino)-
thiazolidin-4-one Derivatives
All solvents were of AR grade and compounds were puri-
fied by crystallization from absolute alcohol. Reactions were
monitored using thin-layer chromatography (TLC) on alumi-
num backed precoated silica gel plates. In general isatins are
highly colored and were visible on a TLC plate; colorless
compounds were detected using UV light and/ or iodine va-
por. All solvents ratio are quoted as vol/vol. Melting points
were determined in one end open capillary tubes on a Buchi
530 melting point apparatus and are uncorrected. Infra red
(IR) spectra were recorded using FT-IR spectrophotometer
2-(isatin-3-azino)-4-thiazolidinone (0.001 mol), appro-
priate aromatic aldehyde (0.3 gm) and anhydrous sodium
acetate (0.006 mol) in glacial acetic acid (10 ml) were re-
fluxed for 5h, cooled and poured into crushed ice and left
overnight. The orange solid thus obtained was filtered,
washed several times with cold distilled water and recrystal-
lized from hot ethanol.
2.2.3.1. 5-(2-Nitrobenzylidene)-2-(Isatin-3-azino)-thiazoli-
din-4-one (CI)
1
(6200 Jasco) in KBr. H nuclear magnetic resonance (1H
NMR) spectra were recorded for the compounds on Bruker
(360 MHz) instrument. Chemical shifts are reported in parts
per million (ppm) using tetramethylsilane (TMS) as an inter-
nal standard.
The reaction of 2-(isatin-3-azino)-4-thiazolidinone with
2-nitrobenzaldehyde led to the target compound (CI) in 65%
yield. Rf [benzene: methanol (9.4 : 0.6)] 0.71. Yield: 65%;
mp: 345 - 347oC; UV ꢁmax: 249 nm in methanol; IR: (KBr
ꢂcm- 1) 2918cm-1 C-H, Ar-H str, 1530cm-1& 1350 cm-1 NO2
2.1.2. Cell Culture and Chemicals
1
str, 1709 cm-1 CO str, 1613 cm-1 CN str; HNMR (DMSO)
ꢃ
ppm 8.5-7.2 (Ar-H, 9H); MS, m/z: 394(M+).
Human cancer cell lines MDA MB 231, MDA MB 435,
MCF 7, T47D and SiHa were purchased from ATCC, USA.
NCI ADR Res cell line was obtained from National Cancer
Institute (NCI, USA). The cells were maintained in DMEM
(Sigma, USA) containing 10% heat inactivated FBS
(GIBCO, USA) and 1% antibiotic-antimycotic cocktail
(GIBCO, USA).
2.2.3.2. 5-(4-Fluorobenzylidene)-2-(Isatin-3-azino)-thiazo-
lidin-4-one (CII)
The reaction of 2-(isatin-3-azino)-4-thiazolidinone with
4-fluorobenzaldehyde led to the target compound (CII) in
67% yield. Rf [benzene: methanol (9.4 : 0.6)] 0.72. Yield:
67%; mp:348-50 oC; UV ꢁmax: 249 nm in methanol; IR: (KBr
ꢂcm-1) 2918cm-1 C-H, Ar-H str, 1530cm-1& 1350 cm-1 NO2
str, 1709 cm-1 CO str, 1613 cm-1 CN str; 1HNMR (DMSO)
ꢃppm 8.0-7.1 (Ar-H, 9H); MS, m/z: 366(M+).
Propidium Iodide, RNAse, DMSO and MTT were pur-
chased from Sigma, USA. All the compounds were dissolved
in DMSO for the experiments. The final concentration of
DMSO used for the cell culture experiment is 0.1%.
2.2.3.3. 5-(4-Hydroxybenzylidene)-2-(Isatin-3-azino)-thia-
zolidin-4 -one (CIII)
2.1.3. Animal Experiment
Acute toxicity studies were carried out in Swiss albino
mice of both sexes weighing between 20-25g.
The reaction of 2-(isatin-3-azino)-4-thiazolidinone with
4-hydroxybenzaldehyde led to the target compound (CIII) in
65% yield. Rf [benzene: methanol (9.4 : 0.6)] 0.74. Yield:
65%; mp:294-95 oC;UV ꢁmax: 251 nm in methanol; IR: (KBr
ꢂcm-1) 3182cm-1 OH str, 1711cm-1 CO str, 1614cm-1 CN str;
2.2. Chemistry
Synthesis of 5-arylidene-2-(isatin-3-azino)-thiazolidin-4-
one derivatives were performed by the following steps.

308 Medicinal Chemistry, 2010, Vol. 6, No. 5
Ramshid et al.
1HNMR (DMSO) ꢀppm 8.5-7.6 (Ar-H, 9H); MS, m/z:
cold ethanol for 30 minutes. Fixed cells were washed twice
and treated with 200 ꢃg/ml of RNase A at 37°C for 1h. Fi-
nally propidium iodide was used to stain the cells. Analysis
was done in FACS Aria (BD, Mountain View, CA, USA)
using BD FACS Diva software.
364(M+).
2.2.3.4. 5-(2,4-Dihydroxybenzylidene)-2-(Isatin-3-azino)-
thiazolidin-4-one (CIV)
The reaction of 2-(isatin-3-azino)-4-thiazolidinone with
2,4-dihydroxybenzaldehyde led to the target compound
(CIV) in 65% yield. Rf [benzene: methanol (9.4 : 0.6)] 0.71.
3. RESULTS AND DISCUSSION
3.1. Chemistry
o
Yield: 68%; mp:298-300 C;UV ꢁmax: 249 nm in methanol;
IR: (KBr ꢂcm-1) 2917cm-1 C-H, Ar-H str, 1701cm-1 CO str,
The schematic representation of the synthesis of com-
pounds is shown in Scheme 1. Isatin-3-thiosemicarbazide
was synthesized by condensation reaction between isatin and
thiosemicarbazide leading to hydrazone formation. pH was
adjusted ranging between 4-5 with glacial acetic acid to get
2, 3-dihydro-2-oxo-3-substituted indole. Further, S-
alkylation followed by cyclocondensation of this product
with monochloroacetic acid yielded 2-(Isatin-3-azino)-
thiazolidin-4-one. Different aromatic aldehydes were reacted
with 2-(Isatin-3-azino)-thiazolidin-4-one to attain the desired
5-arylidene-2-(Isatin-3-azino)-thiazolidin-4-one derivatives
(CI-CV). Thin layer chromatography (TLC) was run
throughout the reaction for checking the purity and comple-
1
1615cm-1 CN str, 1182cm-1 CS str; HNMR (DMSO) ꢀppm
8.1-7.0 (Ar-H, 9H); MS, m/z: 380(M+).
2.2.3.5.
5-(4-Dimethylaminobenzylidene)-2-(Isatin-3-
azino)-thiazolidin-4-one (CV)
The reaction of 2-(isatin-3-azino)-4-thiazolidinone with
4-dimethylaminobenzaldehyde led to the target compound
(CV) in 66% yield. Rf [benzene: methanol (9.4 : 0.6)] 0.77.
Yield: 66%; mp:278-80oC;UV ꢁmax: 249 nm in methanol; IR:
(KBr ꢂcm-1) 2917cm-1 C-H, Ar-H str, 1719cm-1 CO str,
1
1166cm-1 CS str; HNMR (DMSO) ꢀppm 8.2-7.4 (Ar-H, 9H);
MS, m/z: 391(M+).
1
tion. Melting point, Rf value, UV, IR, H NMR and mass
2.3. Biological Assays
spectral analysis were done to characterize the compounds.
Physical data of these synthesized hybrid compounds are
given in Table 1.
2.3.1. Acute Toxicity Assay
The new derivatives obtained from the reaction sequence
were evaluated for acute toxicity studies [26-28] using stair-
case method [29,30]. Albino mice of both sexes, weighing
between 20 and 25g were starved overnight. They were di-
vided randomly into 6 groups of two mice each. The first
group served as the control and was given 0.1% CMC orally
at a dose of 10ml/Kg body weight. The selected analogues at
doses of 60mg/Kg, 120mg/Kg, 240mg/Kg, 480mg/Kg,
960mg/Kg and 1600mg/Kg body weight was given orally as
a suspension in CMC (0.1%) to the remaining groups. All
the animals were observed continuously for 2 hours, then
intermittently for another 4 hours and also at the end of 24
hours. All the experiments were carried out according to the
protocols approved by the Institutional Animal Ethical
Committee.
3.2. Biological activity and SAR
Acute toxicity studies were performed in mice for all the
analogues and all of them were found to be safe up to the
dose of 1600 mg/Kg.
Cytotoxic effects of all the thiazolidinone derivatives
synthesized (CI-CV) was assessed in five different cell lines
using MTT assay (Table 2 & Fig. (1)). Among the deriva-
tives, 5-(2-nitrobenzylidene)-2-(isatin-3-azino)-thiazolidin-4-
one (CI) induced potent dose dependent and reproducible
cytotoxicity in all the cell lines tested compared to others. CI
was more effective in breast cancer cell lines (MDA MB 231
and MDA MB 435) with IC50 values ranging from 51μM to
63μM whereas in T47D it was observed to be slightly higher
than 100μM. Similarly, the cytotoxic potential was observed
to be lower in drug resistant NCI ADR Res as well as SiHa
cells. However, the cytotoxic effect was dose dependant in
these cell lines as well. Introduction of electron withdrawing
nitro group at ortho position of benzylidene ring in CI might
have resulted in greater dose dependent response due to the
selective accumulation of DLCs in negatively charged mito-
chondria in carcinoma cells because of the electrochemical
proton gradient. Further, introduction of electron withdraw-
ing substituent in CI established a highly stable conjugated
system and subsequently the inhibitory activity. CIV showed
good cytotoxic effect in MDA MB 231 cells but failed to
elicit a cytotoxic response in other cell lines. However, a
moderate and dose dependant cytotoxic effect was observed
with CIV in MDA MB 435 and T47D cells. Presence of OH
radical in ortho and para position of benzylidene ring in CIV
appeared to confer greater potency than CIV with OH at para
position alone. Interestingly, potent growth stimulatory ef-
fect was observed with the compounds CII, CIII and CV in
SiHa cells. The growth stimulatory effect of CII and CV was
evident in MDA MB 435 cells as well. Electron rich halogen
2.3.2. Cell Viability Assay
Briefly, cells (5000 cells/well) were seeded into a 96 well
plate and incubated for 24h. After 24 h, cells were replen-
ished with fresh medium containing different concentration
of compounds or 0.1% DMSO. After 48h of incubation,
MTT (500ꢃg/ml final concentration) was added to each well
and incubated for 4h in order to allow the conversion of
MTT to formazan crystals. Finally, the formazan crystals
formed was dissolved in isopropyl alcohol and the OD
measured at 570 nm using ELISA microplate reader (Bio
Rad). The amount of formazan crystals formation is directly
proportional to the viability of cells and the percentage
growth inhibition by the compounds was calculated and
tabulated.
2.3.3. Cell Cycle Analysis
Cell cycle status was identified by measuring the DNA
content. Briefly, cells after treatment (CI; 100ꢃM) were
trypsinized, washed twice in PBS and fixed using 70% of ice

Synthesis and in vitro Evaluation of some Isatin-Thiazolidinone Hybrid Analogues
Medicinal Chemistry, 2010, Vol. 6, No. 5 309
Scheme 1. Scheme for synthesis of 5-Arylidene-2-(isatin-3-azino)-thiazolidin-4-one derivatives (CI - CV).
Table 1. Physical Data of 5-Arylidene-2-(isatin-3-azin)-thiazolidin-4-one Derivatives (CI - CV)
Code No
X
Yield (%)
MP( oC)
Mol. Formula
Mol. weight
CI
CII
o-NO2
p-F
65
67
65
68
66
345
348
294
300
278
CI8H11N5O4S
C18H11FN4O2S
C18H12N4O3S
CI8H12N4O4S
C20H17N5O2S
394.384
366.377
364.386
380.385
391.456
CIII
CIV
CV
p-OH
o,p-OH
p-N(CH3)2
Table 2. Percentage Growth Inhibition Induced by the Derivatives in Different Cell Lines Based on MTT Assay
Cell lines
Conc. in ꢀM
CI
CII
CIII
CIV
CV
25
50
26.1
49.24
70.36
2.63
-3.96
2.59
10.02
8.41
-3.13
-0.28
54.36
-12.1
7.4
7.6
MDA MB 231
14.75
17.97
-28.27
-5.99
7.51
100
25
-0.73
-30.31
-1.1
12.65
-0.91
-2.45
-6.69
-0.07
2.15
MDA MB 435
NCI ADR Res
T47D
50
19.89
74.69
4.34
100
25
8.69
20.17
-18.04
-6.5
-0.98
3.15
-12.62
-5.68
1.12
50
10.93
29.55
19.56
33.04
46.11
-3.24
3.91
100
25
8.98
3.01
-2.79
-6.85
5.91
-1.34
3.55
-9.8
-11.63
-7.09
1.53
50
-8.81
4.3
100
25
5.41
18.42
-12.65
-13.78
-31.24
-16.02
-57.29
-63.3
-18.89
-27.78
-46.55
-20.35
-26.3
-55.72
SiHa
50
100
28.27

310 Medicinal Chemistry, 2010, Vol. 6, No. 5
Ramshid et al.
Fig. (1). Graphical representation of MTT assay results. Cells were treated with different concentration of compounds or 0.1% DMSO for 48h
and the percentage growth inhibition was calculated and the corresponding graph was plotted using %growth inhibition vs concentration.
substitution at para position of benzylidene ring in CII and
introduction of electron rich (N (CH3)2) at the para position
of benzylidene ring in CV might have resulted in compounds
with potent growth stimulatory effects.
ing and can be utilized in combination therapy to circumvent
advanced/ metastatic cancers.
C3 substituted isatins have already been shown to selec-
tively target and inhibit PTKs. SAR studies on previously
synthesized different compounds have shown that the oxin-
dole core occupies a site where the adenine of ATP binds,
while substituent at C3 of various isatins contact residues in
the hinge region of growth factor receptors [35]. The in vitro
growth inhibitory activity of CI and its ability to arrest cells
at S phase indicate that CI may have an affinity to ATP bind-
ing pockets associated PTKs and may probably be the mode
of action by which it elicits its biological effect.
Several N-alkylindole derivatives have been reported to
trigger apoptosis [31] through induction of G2/M arrest [32-
34]. Since CI possess potent cytotoxic activity compared to
other derivatives, we profiled its effect during cell division
cycle to investigate whether the cytotoxic effect precedes
growth arrest at any particular phase of cell cycle. A time
dependant FACS analysis was performed in all the five cell
lines treatment with CI (Fig. (2)). Our results showed a time
dependant accumulation of cells at S-phase, at the onset of
12hr post treatment, in all the tested cell lines. This selective
and time dependent cell cycle arrest might be attributed to
inhibition of cyclin dependent kinases by CI and supported
by the previous literatures suggesting the ability of isatins
and thiazolidinones to target different kinases. Interestingly,
a reversal in the S phase arrest was quite evident in SiHa
cells at 36h. The cells were observed to be relieved from S
phase arrest and were shown gradually entering into M
phase. This reversibility might be due to the predominant
cytostatic, not cytotoxic, effect of the treatment in SiHa cells
at early time intervals and attributed to the low toxicity ob-
served in SiHa and NCI ADR Res cells in MTT assay.
Therefore, it can be speculated that CI acts as more of cy-
tostatic than cytotoxic agent at low doses or at highly resis-
tant conditions. The predominant cytostatic property of CI at
a single dose may benefit to reduce systemic toxicity under
in vivo conditions as evidenced from the acute toxicity re-
sults. The cytostatic effect of CI on resistant cells is promis-
4. CONCLUSIONS
A range of isatin derivatives have been synthesized and
1
were characterized by their MS, H NMR, UV and IR data.
Cytotoxicity screening in different cell lines revealed CI to
be most active among the different compounds synthesized.
Cell cycle analysis revealed induction of S phase arrest in CI
treated cells. CI acts as more of a cytostatic than cytotoxic
agent, especially at low doses and resistant conditions. How-
ever, the structural similarity it shares with other isatins that
competitively bind at ATP catalytic sites suggests that the
molecular mode of action may be via inhibition of protein
kinases associated with S phase transition. CI can be sub-
jected to more detail pharmacological screening, under spe-
cific conditions, for elucidation of its specific target. Also
structural modifications can be attempted in other analogues
to improve their activity in order to convert them to prospec-
tive drug candidates.

Synthesis and in vitro Evaluation of some Isatin-Thiazolidinone Hybrid Analogues
Medicinal Chemistry, 2010, Vol. 6, No. 5 311
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ACKNOWLEDGEMENT
The authors acknowledge the assistance of Mr. Bineesh,
National Institute of Interdisciplinary Science and Technol-
ogy, Trivandrum, India for spectral analysis.
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Received: June 20, 2010
Revised: August 25, 2010
Accepted: August 28, 2010