Benzimidazole bearing oxadiazole and triazolo-thiadiazoles nucleus: Design and synthesis as anticancer agents

Article abstract of DOI:10.1016/j.bmcl.2012.07.038

Two new series of benzimidazole bearing oxadiazole[1-(1H-benzo[d]imidazol- 2-yl)-3-(5-substituted-1,3,4-oxadiazol-2-yl)propan-1-ones (4a-l)] and triazolo-thiadiazoles[1-(1H-benzo[d]imidazol-2-yl)-3-(6-(substituted)-[1,2,4] triazolo[3,4-b][1,3,4]thiadiazol

Full text of DOI:10.1016/j.bmcl.2012.07.038

Bioorganic & Medicinal Chemistry Letters 22 (2012) 5438–5444
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Benzimidazole bearing oxadiazole and triazolo-thiadiazoles nucleus: Design
and synthesis as anticancer agents
Asif Husain a, Mohd Rashid a, , Ravinesh Mishra a,c, Shama Parveen a, Dong-Soo Shin b, Deepak Kumar b
⇑
a Department of Pharmaceutical Chemistry, Faculty of Pharmacy, JamiaHamdard (Hamdard University), Hamdard Nagar, New Delhi 110062, India
b Research Institute of Natural Sciences, Department of Chemistry, Changwon National University, Changwon 641773, Republic of Korea
c Institute of Pharmacy & Emerging Sciences, Baddi University of Emerging Science &Technology, Baddi, Solan, Himachal Pradesh 173205, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Two new series of benzimidazole bearing oxadiazole[1-(1H-benzo[d]imidazol-2-yl)-3-(5-substituted-
1,3,4-oxadiazol-2-yl)propan-1-ones (4a–l)] and triazolo-thiadiazoles[1-(1H-benzo[d]imidazol-2-yl)-3-
(6-(substituted)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazol-3-yl)propan-1-one (7a–e)] have been synthesized
successfully from4-(1H-benzo[d]imidazol-2-yl)-4-oxobutanehydrazide (3) with an aim to produce prom-
ising anticancer agents. In vitro anticancer activities of synthesized compounds were screened at the
National Cancer Institute (NCI), USA, according to their applied protocol against full NCI 60 human cell
lines panel; results showed good to remarkable anticancer activity. Among them, compound (4j, NCS:
761980) exhibited significant growth inhibition and further screened at 10-fold dilutions of five different
Received 2 April 2012
Revised 24 May 2012
Accepted 10 July 2012
Available online 17 July 2012
Keywords:
Benzimidazole
Oxadiazole
Triazolo-thiadiazoles
Cancer
concentrations (0.01, 0.1, 1, 10 and 100 lM) with GI50 values ranging from 0.49 to 48.0 lM and found
superior for the non-small cell lung cancer cell lines like HOP-92 (GI50 0.49, TGI 19.9,LC50 >100 and
Log10GI50 ꢀ6.30, Log10TGI ꢀ4.70, Log10LC50 >ꢀ4.00).
Ó 2012 Elsevier Ltd. All rights reserved.
The searching of a new agent for the treatment of cancer is an
important tool of medicinal chemistry. It is a disease of cell cycle,
in which abnormal cells divide mitosis without control and being
heterocyclic ring with
1H-benzimidazole-2-butanoicacid-5-[bis(2-chloroethyl)amino]-
1methyl- monohydrochloride, rationally designed purine
a butyric acid substituent, chemical,
a
one of the major health problems in the world from decades.1,2
A
analog and alkylation hybrid of chlorambucil chemotherapeutic
drug shown in Figure 1. On March 20, 2008, it was approved by
the FDA (U.S.) for the treatment of chronic lymphocytic leukemia
(CLL) and about 6 months later, on October 31, 2008, this also ap-
proved for patients with indolent B-cell non-Hodgkin’s lym-
phoma (NHL).26–28 The chemically drawn of newly prepared
targeted compound as rationally designed with bendamustine
along with chlorambucil, represented in Figure 1.
In view of these points, it was thought worthwhile to prepare a
new type of hybrid that clubbed both of benzimidazole as well as
oxadiazole/(1,2,4)triazolo(3,4-b)(1,3,4)thiadiazole ring systems
with a view to produce promising anticancer agents. Therefore,
several hybrids were synthesized and screened for their in vitro
anticancer activities at Development Therapeutic Program, Na-
tional Cancer Institute (NCI), Chemotherapeutic Research division,
USA, against full NCI 60 cell line panel according their applied pro-
tocol. The selected compounds were submitted to NCI and granted
NCS codes shown in Table 1.
lot of chemical classes of heterocyclic and fused heterocyclic com-
pounds have been identified through molecular biology, empirical
screening and rational drug development for evaluation of antican-
cer agents during the past decades. In terms of searching, it could be
considered that the benzimidazole heterocyclics are great impor-
tance in their biological as well as synthetic approach of medicinal
chemistry. From worldwide reported literature, the various substi-
tuted derivatives of benzimidazole nucleus showed remarkable
biological activity as antitumor/antiproliferative/anticanceractivi-
ty,3–12 antimicrobial including anti-HIV,13–16 antioxidant17 and cys-
ticidal activities.18 Similarly, oxadiazole and triazolo-thiadiazoles
are a class of heterocyclic’s, which have attracted significant inter-
est in medicinal chemistry as they have a wide range of pharmaceu-
tical and biological activities including antitumor and antimicrobial
activities.19–25Here light on some rationally designed targeted
compounds with biologically active antitumor agents having benz-
imidazole and other heterocyclic moiety, for example Treanda
(bendamustine hydrochloride), made up by Cephalon Inc. USA
and comprises by mechlorethamine group and benzimidazole
4-(1H-benzo[d]imidazol-2-yl)-4-oxobutanoic acid (1) was
synthesized by reacting o-phenylenediamine and
a-ketoglutaric
acid in presence of 4 N HCl. 4-(1H-benzo[d]imidazol-2-yl)-4-
oxobutanehydrazide (3) was obtained by treating the compound
(1) with hydrazine hydrate through an ethyl–ester intermediate
(2). The compound 3 was treated with CS2/KOH using ethanol as
⇑
Corresponding author. Tel.: +91 1126059681/26059688x5647, mobile: +91
9911609781; fax: +91 1116988874.
E-mail address: rashidpharm2008@gmail.com (M. Rashid).
0960-894X/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2012.07.038

A. Husain et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5438–5444
5439
Cl
O
C
OH
Cl
N
Chlorambucil drug
(NSC: 3088)
Mean GI50 : 52µM
Mean TGI >100
Mean LC50 >100
Mechlorethamine group
Butyric acid
+
Cl
O
C
OH
N
N
Cl
N
.HCl
N
N
Br
O
N
Bendamustine Structure
C
(NSC : 138783)
NH2
Benzimidazole
ring
O
NH
CH2 CH2
: 60µM
Mean GI50
Mean TGI >100
>100
Br
Mean LC50
Targeted compound (4j)
(NCS: 761980)
Mean GI50 : 12.62µM
Mean TGI >100
Mean LC50 >100
Figure 1. Structure of biologically active agent of benzimidazoleheterocyclic’sas anticancer and rationally designed template for targeted compound.
Table 1
NSC: code, sensitivity, growth percent, mean growth percent of NCI cancer cell lines treated with synthesized compounds (10
lM)
Compd.
NSC: Code
The most sensitive cell line
Growth % of the most
sensitive cell line
Range of growth, (%)
Mean
Range
Activity
4i
4j
4l
7c
7d
7e
761979/1
761980/1
761981/1
761984/1
761985/1
761986/1
UO-31 (Renal cancer)
MDA-MB-435 (Melanoma)
K-562 (Leukemia)
K-562 (Leukemia)
K-562 (Leukemia)
62.25
5.71
24.57
8.30
7.05
2.17
62.25–125.99
5.71–104.44
24.57–116.54
8.30–116.26
7.05–124.02
2.17–118.42
97.16
70.36
87.22
96.71
95.24
85.93
63.74
98.73
91.97
110.46
116.97
116.25
Active
Active
Active
Active
Active
Active
K-562 (Leukemia)
The tested compounds, which showed growth inhibition 632% is called as active for that particular cell lines. Percent cell growth reduction following 48 h incubation with
test compounds (used sulphorhodamine B procedure).
solvent to get 1-(1H-benzo[d]imidazol-2-yl)-3-(5-mercapto-1,3,4-
oxadiazol-2-yl)propan-1-one (5) and 3-(4-amino-5-mercapto-4H-
1,2,4-triazol-3-yl)-1-(1H-benzo[d]imidazol-2-yl)propan-1-one (6)
was obtained by reacting hydrazine hydrate with compound (4).
After that different types of aromatic/aliphatic acids were reacted
with compound 3 and 5 in presence of POCl3 to produce newly
1-(1H-benzo[d]imidazol-2-yl)-3-(5-substituted-1,3,4-oxadiazol-2-
yl)propan-1-ones (4a-l) (Scheme 1) and 1-(1H-benzo[d]imidazol-
2-yl)-3-(6-(substituted)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazol-3-yl)
propan-1-one (7a–e), respectively (Scheme 2). The purity of com-
pounds was checked by single-spot TLC using T/E/F (toluene/ethyl-
acetate/formic acid, 5:4:1) and benzene/acetone (9:1) as solvent
systems and spots located under iodine vapors/UV light and sharp
melting point. The final products were purified by recrystallization
with suitable solvent. The structures assigned to all the synthe-
sized compounds were supported by the results of elemental anal-
ysis as well as IR, 1H NMR, 13C NMR and Mass spectral data and
found in full agreement with the proposed structures.
Melting points were determined in open capillary tubes and are
uncorrected. Thin-layer chromatography (TLC) was carried out to
monitor the progress of the reactions using silica gel G (Merck
No. 5554) as stationary phase and solvent systems—toluene/ethyl
acetate/formic acid (5:4:1) and benzene/acetone (9:1). The spots
were located by exposure to iodine vapors or under UV-light. IR
spectra were measured as potassium bromide pellets using Per-
kin–Elmer 1725X spectrophotometer. 1H NMR and 13C NMR spec-
tra were recorded on Brukerspectropsin DPX-300 MHz in CDCl3/
DMSO-d6 using tetramethylsilane as internal reference; chemical
shift (d) values are reported in parts per million (ppm). The split-
ting pattern abbreviations are as follows: s, singlet; bs, broad sin-
glet; d, doublet; dd, double doublet; t, triplet; m, multiplet. Mass
spectra were recorded on LCMS/MS (Perkin–Elmer and LABINDIA,
Applied Biosystem) model no. API 3000 presented as m/z. Elemen-
tal analyses were performed on Perkin–Elmer 240 analyzer and
was in range of 0.4% for each element analyzed (C, Hand N). Dry
solvents were used throughout.

5440
A. Husain et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5438–5444
O
C
N
O
C
O
C
NH2
NH2
i
+
OH
HO
OH
NH
O
O
1
ii
Compd.
4a
-R
O
C
N
NH2
C2H5
C
CH3
O
H
N
H
O
O
O
2
3
4b
4c
C
H2
C
CH3
Cl
iii
O
C
H2
C
N
4d
4e
4f
NH2
NH2
N
H
CH2-CH2-CH2 NH2
CCl3
N
H
O
4g
iv
C
R
+
N
H
HO
N
N
4h
N
N
OH
R
O
OH
N
H
4i
4j
O
OH
Br
4a-l
NH2
Reactions and conditions:
Br
O
C
(i) 4NHCl, methanol,water, reflux, r.t. (ii) Abs. ethanol, conc.
H2SO4 (iii) NH2NH2.H2O, ethanol (iv) POCl3
4k
4l
H
, reflux.
CH CH
Scheme 1. Synthetic pathway for compounds (4a–l).
The newly compounds were prepared as outlined in Schemes 1
and 2. In general, IR spectra of the compounds showed peaks at
3341 and 2599 cmꢀ1 for NH and SH, respectively. In 1H NMR spec-
tra, there appeared a singlet at around d 12.1 indicative of ring
H–N and another singlet at d13.4 for S–H, both disappeared by
addition of D2O as confirmation for these groups. The appeared
peak in IR spectra at around 1716 and 1648 cmꢀ1 accounted for
C@O and C@N. The chemical shift in 13C NMR spectra at d 174.3
and 155.8 could be accounted for C@O and C@N. The characteristic
peaks at around 1384 and 1263 cm-1 for N@C–S and N–N@C as
indicative the formation of thiadiazole and triazole ring. All the
synthetic compounds showed two triplets at appropriate signals
All the selected compounds (14 in no.) were submitted to Na-
tional Cancer Institute (NCI), USA for evaluating their in vitro anti-
cancer activity at single dose (10 lM) against full NCI 60 cell lines
panels representing on full nine human systems as leukemia, mel-
anoma and cancers of lung, colon, brain, breast, ovary, kidney and
prostate. The compounds added at a concentration (10 lM) and
the culture incubated for 48 h. End point determinations made
with a protein binding dye, sulforhodamine B.31 Results for each
compound were reported as mean graph of the percent growth
of the treated cells when compared with untreated control
cells.32,33 The compounds which reduced the growth of the cell
lines to 32% or less (negative number indicate kills) is considered
in vitro activity shown in Table 1.34 Compound (4j, NCS:
761980)satisfied pre-determined threshold growth inhibition
criteria and further selected for NCI full panel five dose assay at
10-fold dilutions of five different concentrations (0.01, 0.1, 1, 10
and chemical shifts in 1H NMR spectra at around
d 3.3
(J = 7.2 Hz) and d 2.8 (J = 6.9 Hz) and 13C NMR spectra showed at
around d 30.3 and 28.1 which could be accounted for two methy-
lene groups (–CH2-CH2–) forming a linker chain through which
benzimidazole nuclei attached with oxadiazole/triazole/thiadia-
zole ring, made up the complete back bone of synthetic com-
pounds. The presence of doublet, triplet at around d 7.7, 7.4 and
7.2 (7.8, 7.5, 7.5 Hz) indicated benzimidazole hydrogen. The sig-
nals in 13C NMR spectra which appeared at around d 172.8 could
be for thiadiazole carbon ring and other signals at d 160.7, 159.8
indicative of triazole carbon ring. Other peaks were observed at
appropriate d values supporting the structure. The mass spectra
(ESI MS) showed the presence of peak at definite m/z value in
accordance to the molecular ion peak. In case of aryl groups hav-
ing chloro-substituent (s) the molecular ion peak appeared as
cluster of peaks. The elemental analysis results were within
0.4% deviation from the theoretical values.
and 100 lM). The result of tested compound is given by three re-
sponse parameters (GI50, TGI and LC50) for each cell line from log
concentration versus % growth inhibition curves on nine cancer
disease. The GI50 value (growth inhibitory activity) corresponds
to the concentration of the compound causing 50% decrease in
net cell growth, the TGI value (cytostatic activity) is the concentra-
tion of the compound resulting in total growth inhibition and LC50
value (cytotoxic activity) is the concentration of the compound
causing net 50% loss of initial cells at the end of the incubation
period of 48 h. Furthermore, a mean graph midpoint (MG-MID) is
calculated giving an averaged activity parameter over all cell lines.
The title compound (4j, NCS: 761980) under investigation
exhibited remarkable anticancer activity against all the tested cell

A. Husain et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5438–5444
5441
N
N
N
O
C
N
v
NH2
O
SH
N
H
N
H
O
N
H
O
5
3
vi
-R
CH2CN
Compd.
N
N
N
7a
7b
N
SH
O
N
H
O
C
H
NH2
6
OH
OH
OH
7c
vii
Br
N
N
N
7d
7e
NH2
N
S
N
H
Br
O
N
R
H
7a-e
C C
H
Reactions and conditions:
(v) CS2, KOH, ethanol (vi) Hydrazine hydrate, ethanol (vii) R-
COOH, POCl3, reflux
Scheme 2. Synthetic pathway for compounds (7a-e).
lines representing nine different subpanels with GI50 values be-
tween 0.49 and 48.0 M except HCT-15 (GI50 >100) under sensitive
for each of parameters, giving as log GI50 (ꢀ5.13), log TGI (ꢀ4.23)
and log LC50 (ꢀ4.02) and insensitive cell lines are also included
with the highest concentration (Table 3). The criterion for selectiv-
ity of a compound depends upon a ratio called as selective index,
which is obtained by dividing the full panel MIDa (the average sen-
sitivity of all cell lines towards the test agent) by their individual
subpanel MIDb (the average sensitivity of all cell lines of a particu-
lar subpanel towards the test agent). The ratios between 3 and 6
refer to moderate selectivity; ratios greater than 6 indicate high
selectivity towards the corresponding cell line, while compounds
not meeting either of these criteria rated non-selective.35 As per
this criterion, compound 4j, in the study was found to be moderate
selective towards Leukemia cancer subpanel with selective index
3.23.
l
range an outstanding activity (Table 2). With regard to the sensitiv-
ity against some individual cell lines the compound showed high
activity against Non-Small Cell Lung Cancer cell lines like HOP-
92 (GI50 0.49, TGI 19.9, LC50 >100 and Log10GI50 ꢀ6.30, Log10TGI
ꢀ4.70, Log10LC50 >ꢀ4.00). Obtained data revealed an obvious sen-
sitivity profile towards Ovarian Cancer subpanel (GI50 value rang-
ing from 2.60 to 29.4 lM), least for OVCAR-3and maximum for
OVCAR-5 cell line. The compound proved to be sensitive towards
all the tested Leukemia cancer cell lines with not more than
4.94
lM concentrations. All the tested Prostate cancer cell lines
were sensitive with not more than GI50 5.40
l
M concentrations
of the tested compound. The highest growth inhibitory activity
was observed against the HOP-92 cell line of Non-Small Cell Lung
The human tumor cell lines were grown in RPMI 1640 medium
Cancer with GI50 value 0.49
activity against ACHN cell line of Renal Cancer with GI50 value
48.0 M. The all remaining subpanel cell line showed maximum
sensitive towards tested compound with not more than 36.5
concentrations (Table 2). Over all the GI50 values of the screening
process resulted in a sensitive range inferior of 48.0 M denoting
an outstanding activity and the values of LC50 are in most of the cell
lines >100 M except COLO 205 (80.1 M) and MDA-MB-435
(8.83 M) cell line (Table 2).The log molar concentration of the re-
l
M and minimum growth inhibitory
containing 5% fetal bovine serum and 2 mM L-glutamine. After cell
inoculation, the micro titer plates incubated at 37 °C, 5% CO2, 95%
air and 100% relative humidity for 24 h prior to addition of tested
compounds. After 24 h, two plates of each cell line fixed in situ
with TCA, to represent a measurement of the cell population for
each cell line at the time of sample addition (Tz). The sample
solubilized in DMSO at 400-fold the desired final maximum test
concentration and stored frozen prior to use. At the time of com-
pounds addition, an aliquot of frozen concentrate was thawed
and diluted to twice, the desired final maximum test concentration
l
lM
l
l
l
l
sulted screening as log GI50 ranged from ꢀ6.30 to ꢀ4.32 except
HCT-15(>ꢀ4.00), minimum concentration for HOP-92 cell line
(ꢀ6.30) of Non-Small Cell Lung Cancer and maximum for ACHN
with complete medium containing 50 lg/ml gentamicin. Addi-
tional four, 10-fold or ½ log serial dilutions are made to provide
a total of five drug concentrations plus control. Aliquots of
cell line (ꢀ4.32
lM) of Renal Cancer, log TGI value for most cell
lines showed more than >ꢀ4.00 and mostly cell lines showed log
LC50 >ꢀ4.00 except COLO 205 (ꢀ4.10 M) and MDA-MB-435
(ꢀ5.05 M) cell line. A mean graph midpoint (MG-MID) calculated
100
micro titer wells already containing 100
the required final sample concentrations.31 The tested compounds
lL of these different sample dilutions added to the appropriate
l
lL of medium, resulting in
l

5442
A. Husain et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5438–5444
Table 2
Calculated values of GI50, TGI, LC50 of the cell lines, NCI: full cell lines panel, MG-MID and selectivity index of the compound (4j, NCS: 761980/1)
Panel
Cell line
GI50
(lM)
TGI (lM) LC50 (lM)
Concentration per cell line Subpanel
Subpanel MIDb Selectivity index
concentration
Leukemia
CCRF-CEM
HL-60(TB)
K-562
MOLT-4
RPMI-8226
SR
3.81
3.44
2.89
4.94
4.21
4.20
27.6
23.1
23.7
0.499
22.6
3.26
8.15
3.99
2.90
11.8
11.0
8.26
>100
19.2
3.71
3.28
5.14
9.78
17.3
20.1
2.96
3.50
3.25
2.06
17.5
1.56
4.30
6.30
14.2
7.63
5.37
5.87
2.60
5.49
29.4
21.6
22.6
22.3
21.0
0.662
48.0
19.8
13.0
29.5
36.5
4.06
2.90
5.40
3.06
10.1
>100
>100
>100
>100
>100
>100
>100
>100
>100
19.9
>100
36.4
>100
20.1
16.9
30.8
42.5
>100
>100
83.5
18.0
>100
81.6
35.6
60.8
>100
20.5
>100
46.4
17.2
55.5
3.71
>100
79.0
>100
>100
>100
62.7
6.98
78.2
>100
>100
>100
80.5
61.7
10.5
>100
>100
58.6
>100
>100
>100
>100
53.5
>100
86.8
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
80.1
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
8.83
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
23.49
3.91
3.23
0.98
Non-small cell lung cancer A549/ATCC
EKVX
HOP-62
HOP-92
115.799
12.86
NCI-H226
NCI-H23
NCI-H322M
NCI-H460
NCI-H522
COLO 205
HCC-2998
HCT-116
HCT-15
HT29
KM12
SW-620
SF-268
SF-295
SF-539
SNB-19
SNB-75
U251
LOX IMVI
MALME-3M
M14
MDA-MB-435
SK-MEL-2
SK-MEL-28
SK-MEL-5
UACC-257
UACC-62
IGROV1
OVCAR-3
OVCAR-4
OVCAR-5
OVCAR-8
NCI/ADR-RES
SK-OV-3
786-0
A498
ACHN
CAKI-1
RXF 393
SN12C
TK-10
UO-31
PC-3
DU-145
MCF7
MDA-MB-231/
ATCC
HS 578T
BT-549
T-47D
MDA-MB-468
60
Colon cancer
22.46
0.56
157.25
CNS cancer
Melanoma
9.79
6.90
1.29
1.83
58.78
62.17
Ovarian cancer
Renal cancer
15.69
0.80
109.86
21.56
4.15
8.17
0.58
3.04
1.54
172.522
8.3
Prostate cancer
Breast cancer
3.75
6.82
23.4
1.93
12.62
49.06
31.7
>100
>100
6.97
>100
>100
>100
>100
MIDa
757.231
MID = mean graph midpoint, arithmetical mean value of treated cancer cell lines. Full panel (MIDa)—the average sensitivity of all cell lines towards the test agent in
Subpanel (MIDb)—the average sensitivity of all cell lines of a particular subpanel towards the test agent in
M.
lM,
l
addition, the plates was incubated for an additional 48 h at 37 °C,
dried. Sulforhodamine B (SRB) solution (100lL) at 0.4 % (w/v) in
5% CO2, 95% air, and 100% relative humidity. Cells fixed in situ by
the gentle addition of 50 lL of cold 50% (w/v) TCA (final concentra-
tion, 10% TCA) and incubated for 60 min at 4 °C. The supernatant
discarded and plates washed five times with tap water and air
1 % acetic acid added to each well and plates incubated for
10 min at rt. Bound stain subsequently solubilized with 10 mM tri-
zma base and the absorbance was read on an automated plate
reader at a wavelength of 515 nm. Using the seven absorbance

A. Husain et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5438–5444
5443
Table 3
Values of the log molar concentration of response parameter (Log10GI50, Log10TG and Log10LC50) of test compound (4j, NCS: 761980/1)
Cancer disease
Leukemia
Used cell lines
Log10 GI50
Log10 TGI
Log10 LC50
CCRF-CEM
HL-60 (TB)
K-562
MOLT-4
RPMI-8226
SR
ꢀ5.42
ꢀ5.46
ꢀ5.54
ꢀ5.31
ꢀ5.38
ꢀ5.38
ꢀ4.56
ꢀ4.64
ꢀ4.63
ꢀ6.30
ꢀ4.65
ꢀ5.49
ꢀ5.09
ꢀ5.40
ꢀ5.54
ꢀ4.93
ꢀ4.96
ꢀ5.08
>ꢀ4.00
ꢀ4.72
ꢀ5.43
ꢀ5.48
ꢀ5.29
ꢀ5.01
ꢀ4.76
ꢀ4.70
ꢀ5.53
ꢀ5.46
ꢀ5.49
ꢀ5.69
ꢀ4.76
ꢀ5.81
ꢀ5.37
ꢀ5.20
ꢀ4.85
ꢀ5.12
ꢀ5.27
ꢀ5.23
ꢀ5.58
ꢀ5.26
ꢀ4.53
ꢀ4.67
ꢀ4.65
ꢀ4.65
ꢀ4.68
ꢀ6.18
ꢀ4.32
ꢀ4.70
ꢀ4.89
ꢀ4.53
ꢀ4.44
ꢀ5.39
ꢀ5.51
ꢀ5.27
ꢀ5.51
ꢀ4.99
ꢀ5.43
ꢀ5.17
ꢀ4.63
ꢀ5.71
ꢀ5.13
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
ꢀ4.70
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
ꢀ4.10
Non-small cell lung cancer
A549/ATCC
EKVX
HOP-62
HOP-92
NCI-H226
NCI-H23
NCI-H322M
NCI-H460
NCI-H522
COLO 205
HCC-2998
HCT-116
HCT-15
HT29
KM12
SW-620
SF-268
SF-295
SF-539
SNB-19
SNB-75
U251
LOX IMVI
MALME-3M
M14
MDA-MB-435
SK-MEL-2
SK-MEL-28
SK-MEL-5
UACC-257
UACC-62
IGROV1
OVCAR-3
OVCAR-4
OVCAR-5
OVCAR-8
NCI/ADR-RES
SK-OV-3
786-0
A498
ACHN
CAKI-1
RXF 393
SN12C
TK-10
UO-31
PC-3
DU-145
MCF7
>ꢀ4.00
ꢀ4.44
>ꢀ4.00
ꢀ4.70
ꢀ4.77
Colon cancer
ꢀ4.51
ꢀ4.37
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
-5.05
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
ꢀ4.02
>ꢀ4.00
>ꢀ4.00
ꢀ4.08
ꢀ4.74
>ꢀ4.00
ꢀ4.09
CNS cancer
Melanoma
ꢀ4.45
ꢀ4.22
>ꢀ4.00
ꢀ4.69
v4.00
ꢀ4.33
ꢀ4.76
ꢀ4.26
ꢀ5.43
>ꢀ4.00
ꢀ4.10
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
ꢀ4.20
Ovarian cancer
Renal cancer
ꢀ5.16
ꢀ4.11
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
ꢀ4.09
-4.21
ꢀ4.98
>ꢀ4.00
>ꢀ4.00
ꢀ4.23
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
>ꢀ4.00
ꢀ4.27
Prostate cancer
Breast cancer
>ꢀ>ꢀ4.00
ꢀ4.06
MDA-MB-231/ATCC
HS 578T
BT-549
T-47D
MDA-MB-468
ꢀ4.50
>ꢀ4.00
>ꢀ4.00
ꢀ5.16
MID
ꢀ4.23
measurements [time zero, (Tz), control growth (C) and test growth
in the presence of sample at the five concentration levels (Ti)]. Per-
centage growth inhibition calculated as:
the drug concentration resulting in a 50% reduction in the net pro-
tein increase), Total growth inhibition (TGI) calculated from Ti = Tz
(concentration at which the total growth inhibition is 100%) and
LC50 calculated from [(TiꢀTz)/Tz] ꢂ 100 = ꢀ50 (concentration of
drug resulting in a 50% reduction in the measured protein at the
end of the drug treatment as compared to that at the beginning)
indicating a net loss of the cells. Values were calculated for each
of these three parameters if the level of activity was reached; how-
ever, if the effect was not reached or was exceeded, the value for
that parameter was expressed as greater or less than the maximum
½ðTi ꢀ TzÞ=ðC ꢀ TzÞꢁ ꢂ 100for concentrations for whichTi > = ¼ Tz
½ðTi ꢀ TzÞ=Tzꢁ ꢂ 100for concentrations for whichTi < Tz
Three dose–response parameters (GI50, TGI and LC50) were cal-
culated for each experimental agent. Growth inhibition of 50 %
(GI50) calculated from [(TiꢀTz)/(CꢀTz)] ꢂ 100 = 50 (which was

5444
A. Husain et al. / Bioorg. Med. Chem. Lett. 22 (2012) 5438–5444
or minimum concentration tested.31,32 The logs molar concentra-
tion also calculated of individual GI50, TGI and LC50 and repre-
sented as log10GI50, log10TGI and log10LC50, respectively. The
lowest values of response parameter were obtained with the most
sensitive cell lines.
References and notes
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On the basis of structure activity relationships, it could be con-
cluded that benzimidazole bearing oxadiazole ring were found to
have better anticancer activity than those of benzimidazole bear-
ing triazolo-thiadiazole nucleus. The anticancer activity was influ-
enced by the presence of electron withdrawing group like bromo
on ortho, meta or para position of aromatic ring. As obtained result,
the compound (4j) substituted by bromo group on ortho position
(2,6-dibromo) of phenyl ring, chemically as 3-(5-(4-amino-2,6-dib-
romophenyl)-1,3,4-oxadiazol-2-yl)-1-(1H-benzo[d]imidazol-2-
yl)propan-1-one increases the sensitivity of cell line (70.36%) and
similarly group substituted on ortho position (2,6-dibromo)of com-
pound (7d),chemically as3-(6-(4-amino-2,6-dibromophenyl)-
[1,2,4]triazolo[3,4-b][1,3,4]thiadiazol-3-yl)-1-(1H-benzo[d] imid
azol-2-yl)propan-1-one decrease the sensitivity of cell line
(95.24%). On the other hand the electron releasing group like hy-
droxyl group attached with phenyl ring decrease the sensitivity
(96.71%) and (97.16%) as exhibited by compound (7c), 1-(1H-
benzo[d]imidazol-2-yl)-3-(6-(3,4,5-trihydroxyphenyl)-[1,2,4]triaz-
olo[3,4-b][1,3,4]thiadiazol-3-yl)propan-1-one
and
compound
(4i),1-(1H-benzo[d]imidazol-2-yl)-3-(5-(3,4,5-trihydroxyphenyl)-
1,3,4-oxadiazol-2-yl)propan-1-one, respectively. Finally, unsubsti-
tution phenyl rings observed in compounds 4l and 7e showed
the sensitivity of cell line (87.22%) and (85.93%), respectively.
Two series of benzimidazole bearing [1,3,4]oxadiazole and
[1,2,4]triazolo[3,4-b] [1,3,4] thiadiazole moieties comprising of 20
new compounds were successfully synthesized and among them
14 compounds were selected and evaluated for their in vitro anti-
cancer screening at the NCI, USA. Compounds showed good to
remarkable and broad-spectrum anticancer activity. The com-
pound (4j), namely 3-(5-(4-amino-2,6-dibromophenyl)-1,3,4-oxa-
diazol-2-yl)-1-(1H-benzo[d]imidazol-2-yl)propan-1-one emerged
as lead compound with broad spectrum of anticancer activities
on tumor cell lines (MG-MID 12.62 of GI50 and ꢀ5.13, ꢀ4.23,
ꢀ4.02 value of Log10GI50, Log10TGI, Log10LC50, respectively). Based
on these observations, it could be subject of further investigations
for searching potential antitumor agents. Finally it’s conceivable
that further derivatization of such compounds can be serve as no-
vel templates for anticancer chemotherapy and could be possibly
lead to more active molecules in the field of cancer chemotherapy.
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We are thankful to Dr. Thelma Dizon (Project Manager), Devel-
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(NCI), Chemotherapeutic Agents Repository, Fisher Bio Services,
Rockville, MD, USA, for in vitro anticancer screening of the com-
pounds. Thanks are also to UGC, New Delhi, Government of India,
for financial assistance in the form of Major Research Project [file
No. 36-107/2008 (SR)].
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Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2012.07.
038.