Imidazopyridine linked triazoles as tubulin inhibitors, effectively triggering apoptosis in lung cancer cell line

Article abstract of DOI:10.1016/j.bioorg.2018.07.026

A library of new imidazopyridine linked triazole hybrid conjugates (8a-r) were designed, synthesized and evaluated for their cytotoxicity against four cancer cell lines namely, human lung (A549), human prostate (DU-145), human colon (HCT-116) and breast (

Full text of DOI:10.1016/j.bioorg.2018.07.026

Accepted Manuscript
Imidazopyridine linked triazoles as tubulin inhibitors, effectively triggering
apoptosis in lung cancer cell line
Ibrahim Bin Sayeed, M.V.P.S. Vishuwardhan, Apoorva Nagarajan, Srinivas
Kantevari, Ahmed Kamal
PII:
S0045-2068(18)30421-8
DOI:
https://doi.org/10.1016/j.bioorg.2018.07.026
YBIOO 2445
Reference:
To appear in:
Bioorganic Chemistry
Received Date:
Revised Date:
Accepted Date:
29 April 2018
21 July 2018
23 July 2018
Please cite this article as: I. Bin Sayeed, M.V.P.S. Vishuwardhan, A. Nagarajan, S. Kantevari, A. Kamal,
Imidazopyridine linked triazoles as tubulin inhibitors, effectively triggering apoptosis in lung cancer cell line,
Bioorganic Chemistry (2018), doi: https://doi.org/10.1016/j.bioorg.2018.07.026
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Imidazopyridine linked triazoles as tubulin inhibitors, effectively triggering
apoptosis in lung cancer cell line
a,b
a
b,d
b,d
Ibrahim Bin Sayeed, M.V.P.S. Vishuwardhan, Apoorva Nagarajan, Srinivas Kantevari,
*a,b,c
Ahmed Kamal.
a
Medicinal Chemistry and Pharmacology Division, CSIR - Indian Institute of Chemical Technology, Hyderabad
5
00007, India
b
Academy of Scientific and Innovative Research (AcSIR), CSIR - Indian Institute of Chemical Technology,
Hyderabad 500007, India
c
School of Pharmaceutical Education and Research, Jamia Hamdard University, New Delhi 110062, India
d
Department of Crop Protection Chemicals, CSIR- Indian Institute of Chemical Technology, Hyderabad
5
00007, India
Abstract: A library of new imidazopyridine linked triazole hybrid conjugates (8a-r) were
designed, synthesized and evaluated for their cytotoxicity against four cancer cell lines
namely, human lung (A549), human prostate (DU-145), human colon (HCT-116) and breast
(
MDA-MB 231) cancer. These conjugates exhibited good to moderate activity against the
tested human cancer cell lines. Two of the conjugates (8g and 8j) showed significant
antitumor activity against human lung cancer cell line (A549) with IC50 values of 0.51µM and
0
.63µM respectively. Flow cytometry analysis revealed that these conjugates arrested the cell
cycle at G /M phase in human lung cancer cell line (A549). Immune-histochemistry and
2
tubulin polymerization assay suggest inhibition of tubulin. Hoechst staining, annexin V and
DNA fragmentation by tunnel assay suggested that these compounds induce cell death by
apoptosis. Overall, the current study demonstrates that the synthesis of imidazopyridine
linked triazole conjugates as promising anticancer agents causing G
inducing ability.
2
/M arrest and apoptotic-
Keywords: imidazopyridine, triazoles, tubulin, apoptosis, lung cancer
Introduction
Microtubules are important part of endoskeleton and play a key role in diverse cellular
processes such as cell formation, cell division, regulation of motility; maintenance of cell
shape, secretion and cytoplasmic transport, thus making microtubules an important target for
anticancer drugs [1-3]. Furthermore, microtubules play a significant role in cell signalling
pathways which are accountable for cellular apoptosis. The dynamics of this heterodimeric
polymer is regulated by various important proteins such as dynein and kinesin [4]. Various

reports have established the indispensible role of microtubule in chromosomal translocation
and spindle formation [5]. Colchicines bind to the soluble hetero dimers of tubulin at
colchicine binding site which accommodate the diverse similar ligand structures. However,
colchicine binding affinity varies depending on the source of tubulin; vinblastin in presence
of increases the colchicine binding site affinity. Further, colchicine-tubulin complex
decreases dimer dissociation constant by reducing the GTPase activity. Any aberration in
dynamics of this protein results in the hindrance of cell division at metaphase; as a result,
various efforts are made to block mitosis, like inhibition of tubulin polymerization by tubulin
targeting agents has emerged as an effective approach for cancer treatment [6-7]. Many
reports in literature recognise tubulin polymerization inhibition with subsequent arrest of
cells during mitosis leading to apoptosis [8]. Microtubule binding agents are effective in the
treatment of lung, breast, ovarian and other cancers. Colchicines (I) and nocodazole (II) are
the prominent examples of compounds (Figure 1) that inhibit assembly of microtubule by
binding to tubulin [9-10].
Nitrogen-bridge head fused heterocycles containing an imidazole ring is common scaffold in
various pharmacologically important lead molecules, exhibiting a wide range of biological
activities by binding on different targets. The most widely implied heterocyclic scaffold from
this group is imidazopyridine [11]. This bi-nitrogen fused heterocycle have a broad spectrum
of biological activities such as, inhibitors of aromatase estrogen production suppressors
[
12a,b], potential positive inotropic agents [13], platelet aggregation, thromboxane synthetase
inhibitors [14a,b], antiviral [15], and anticancer [16] being important amongst them.
Imidazopyridine-guanylhydrazone (III) showed potent activity against various human cancer
cell lines and it is considered as a promising lead. Imidazopyridine scaffold exhibit different
types of molecular mechanisms in cancer chemotherapy such as down regulation of cell
regulatory proteins like cyclin-D1, CDK2, up regulation of P27 and activation of Caspase-3
[
17,18]. Similarly one of the imidazopyridine derivative namely 2,2,2-trifluoro-N-(6-(2-
fluoro-5-methylbenzoyl)imidazo[1,2-a]pyridin-2-yl)acetamide (IV) induced cell cycle arrest
at G /M phase suggesting tubulin arrest [19]. In this regard, we recently reported
2
imidazopyridine-propenones [20] (V) as apoptosis inducers that inhibit assembly of tubulin
by binding at the colchicines binding site of tubulin.

Figure 1: Chemical structures of microtubule targeting agents: colchicine (I), nocodazole
II), imidazopyridine guanylhydrazones (III), 2,2,2-trifluoro-N-(6-(2-fluoro-5-
(
methylbenzoyl)imidazo[1,2-a]pyridin-2-yl)acetamide (IV), imidazopyridine-propenones (IV)
and imidazopyridine linked triazole hybrids 8 (a-r).
Similarly, 1,2,3-triazole derivatives have attracted the medicinal chemists worldwide, due to
their wide range of biological activities, such as antifungal [21], antitubercular [22] and
antitumor activity [23-25]. 1,2,3-Triazoles are also serve as building blocks for the synthesis
of important bioorganic-conjugates. Moreover, triazoles possess a high dipole moment and
are highly capable of forming hydrogen bonding. Considering the above biological
significance about triazole scaffold, researchers have used this nucleus in the development of
numerous biologically active compounds. Triazole hybrids of biological importance have
been developed by various research groups across the globe.
Our continued efforts to discover new and effective anticancer agents targeting tubulin
through the combination of biologically important pharmacophores prompted us to design
synthesize and evaluate imidazopyridine linked triazole conjugates by combining two
biologically significant pharmacophores such as imidazopyridine and triazole scaffold
respectively. Our designed scaffold constitutes of three rings. In addition, a comprehensive
structure activity relationship has been described by varying the substitutions on the rings.
These synthesized conjugates were evaluated for their cytotoxic effect in human lung cancer
cell line (A549). The two most active conjugates from the library namely (8g and 8j) were
further investigated for their ability to inhibit tubulin assembly and for their ability to induce
apoptosis. The results of our investigation in this direction are presented in this work.

Figure 2: Design concept for Imidazopyridine linked triazole derivatives
Results and Discussions
Chemistry
Synthesis of the imidazopyridine linked triazoles (8a-r) is shown in Scheme 1. To
obtain 2-arylimidazopyridine (4a-c), equimolar mixtures of substituted 2-
bromoacetophenones and 2-aminopyridine were refluxed for 4-5h followed by 2N HCl
under reflux conditions. The intermediates, imidazopyridine aldehydes (5a–c) were
prepared by means of Vilsmeier-Haack reaction on the corresponding 2-
arylimidazopyridine (4a–c). These aldehydes (5a-c) were further treated with
ethynylmagnesium bromide in THF to obtain the intermediates (6a-c) followed by
oxidation with 2-iodoxybenzoic acid (IBX) in DMSO providing the corresponding
precursors (7a-c). Subsequently, the desired compounds (8a-r) were prepared by
reaction of corresponding precursors (7a-c) with benzyl azide in tertiary butanol and
water using click chemistry. The list of substitutions along with their corresponding
yields and respective melting points are listed in Table1
.

Scheme 1: Synthesis of imidazopyridine-triazole hybrids
Table 1: Structures of compounds 8(ar) and their yields
Compound
R
2
R
1
Yield %
77%
75%
85%
83%
81%
78%
86%
78%
77%
82%
84%
77%
77%
79%
81%
82%
80%
82%
8
8
8
a
b
c
3,4,5-trimethoxyphenyl OCH
3
3
3
3
3
3
3,4-dimethoxyphenyl
4-methoxyphenyl
4-flourophenyl
OCH
OCH
OCH
OCH
OCH
H
H
H
H
H
H
Cl
Cl
Cl
8
d
8
e
4-chlorophenyl
8
f
4-bromophenyl
8
8
8
g
h
i
j
3,4,5-trimethoxyphenyl
3,4-dimethoxyphenyl
4-methoxyphenyl
4-chlorophenyl
8
8
k
4-flourophenyl
8
l
4-bromophenyl
8
8
8
8
8
m
3,4,5-trimethoxyphenyl
3,4-dimethoxyphenyl
4-methoxyphenyl
4-flourophenyl
n
o
p
q
Cl
Cl
Cl
4-chlorophenyl
8
r
4-bromophenyl

Biological evaluation
Table 2: IC50 (µM) values for compounds 8(a-r) on selected human cancer cell lines
a
b
c
d
e
f
g
Compound
A549
DU-145
HCT 116
MDA MB-231
HEK 293
SI
2
1
1
1
1
2.41±0.27 47.64±0.08 12.50±0.63
2.75±0.35 19.17±1.67 20.55±0.09
2.15±0.88 14.09±0.07 19.40±0.59
0.22±0.95 5.02±0.92 14.46±0.08
6.16±2.74 15.11±0.17 6.16±0.38
19.10±0.37
86.53±0.58
65.32±0.57
77.35±0.37
99.12±1.04
87.35±0.81
3.86
5.12
6.37
9.70
5.41
8
8
a
6.30±0.95
15.75±0.88
15.28±0.59
3.09±0.67
10.51±0.07
1.75±0.33
3.16±0.92
1.62±0.88
3.98±1.05
1.94±0.16
8.88±0.37
25.84±0.46
10.90±0.27
11.07±0.82
15.40±0.73
12.84±0.61
10.13±0.71
1.56±0.54
0.005±0.08
0.3±0.95
b
8
c
8
d
8
e
1
.17±0.52
1.47±0.63 22.55±0.44
1.04±0.51 1.05±0.19
75.45±0.43 64.50
63.53±1.33 124.57
8
f
0
.51±0.32
8
8
g
1
2.86±0.49 8.91±0.88 19.53±0.71
72.54±0.94
5.64
h
1
.91±0.76
.63±0.49
.93±0.08
1.30±0.13
1.11±0.84
9.48±0.81
2.83±0.35
88.68±0.72 46.43
91.25±2.18 144.84
93.26±0.94 48.32
8
i
0
1
8
j
1.71±0.73 10.62±0.06
8
k
1
1
2
4
2
1
4.63±0.55 11.4±0.39 18.96±0.22
4.13±1.18 26.99±1.58 10.67±0.86
3.79±0.58 18.15±0.16 16.53±0.17
7.92±0.19 14.73±0.99 35.05±0.17
6.40±0.86 11.14±0.42 32.78±0.93
1.13±0.94 12.99±0.67 10.37±1.06
98.65±0.82
77.65±0.94
64.28±0.17
73.56±0.67
79.62±0.39
59.65±1.18
6.74
5.49
2.70
1.54
3.02
5.36
8
l
8
m
8
n
o
p
q
8
8
8
3
.79±0.73
.47±0.14
8.14±0.29 11.53±0.84
1.38±0.16 1.65±0.94
90.36±1.83 23.84
8
r
1
0
-
-
-
-
-
-
Nocodazole
Taxol
.04±0.07 0.009±0.04 0.015±0.09
.1±0.03 0.7±0.02 0.5±0.83
0
Colchicine

a
b
c
5
0% Inhibitory concentration after 48 h of drug treatment; human lung cancer; human
d
e
f
prostate cancer; human colon cancer; human breast cancer; Human embryonic kidney cells
g
(
normal cell line); SI-selective index corresponding to A549 cell line
Cytotoxic activity
To better understand the structure activity relationships of imidazopyridine linked triazole
hybrid congeners 8(a-r), the IC50 values were obtained by employing MTT cytotoxicity assay
[
26]. Our designed scaffold consists of 3 rings as depicted in the Figure 3. For convenience
the rings are labeled A, B and C. For SAR study, changes were made at rings B and C
respectively whereas ring A was kept unchanged. The cytotoxicity of the synthesized
congeners was evaluated against four human cancer cell lines namely lung (A549), prostate
(
DU-145), colon (HCT116) and breast (MDA-MB-231) cancer cells. The assay was
performed using taxol and colchicine as reference drugs. The results are summarized in
Table 2. The IC50 values of these conjugates shows considerable cytotoxic activity ranging
from 0.51µM – 47.94 µM. Particularly congener 8g, having an H atom at ring B and 3,4,5-
trimethoxy group at ring C posses significant activity against human lung cancer and prostate
cancer cells with IC50 values of 0.51µM and 1.04µM respectively. Another congener 8j
th
th
having H atom at 4 position of ring B and chlorine atom at 4 position on ring C, displayed
IC50 value 0.63µM and 1.11µM respectively. An overview on the substituents on ring B
shows that the potency is high when the ring is unsubstituted followed by good profile with
an electron withdrawing halogen (chlorine) and less with an electron donating substituent
(
methoxy) is present on ring B. Similarly on ring C trimethoxy group was showed to have
maximum potency among the donating group and in case of withdrawing groups, chlorine
atom showed maximum potency on ring C.
Figure 3: Structure activity relationship of imidazopyridine linked triazole hybrids
Cell cycle analysis

Cell cycle analysis plays an important role in studies for anticancer screening, mechanism
and cytokinetic research [27]. To gain further insight into the mode of action of 8g and 8j as
the most potent compounds, we examined their effect on the cell cycle by flow cytometry in
A549 cells. These results clearly demonstrate that the treatment of cells for 48h with 1 µM of
compound 8g and 8j causes cell cycle arrest at G2/M phase as seen in Figure 4 (see
supplementary information file) and Table 3.
Table 3: Cell cycle distribution of A549 cells (%) for 8g and 8j
S.No
Sub G
7.5
1
G
1
S
G /M
5.7
2
Control
78.2
18.8
19.5
8.6
7.5
6.5
8
8
g
j
3.5
70.2
68.5
5.5
Effect on microtubule network
To substantiate the observed cytotoxic effects of these conjugates 8g and 8j on the inhibition
of tubulin polymerization to functional microtubules, immunocytochemistry studies have
been carried further to examine the insitu effects of conjugates 8g and 8j on cellular
microtubules. Therefore, A549 cancer cells were treated with 8g and 8j at 1µM concentration
for 48h. From the data, the results revealed that untreated human lung cancer cells displayed
normal distribution of microtubules as seen in Figure 5. However, cells treated with 8g and
8
j showed disrupted microtubule organization as observed thereby demonstrating the
inhibition of tubulin polymerization. However, the positive control nocodazole showed
disrupted microtubule organization. This immunocytochemistry study indicated that the level
of tubulin polymerization inhibition was similar to that of standard nocodazole for these
conjugates 8g and 8j on lung cancer cells.

Figure 5: Immunocytochemistry (ICC) analyses of compounds on the microtubule network;
A549 cells were treated with compounds 8g and 8j and nocodazole at 1µM concentration for
4
8 h followed by staining with α-tubulin antibody with nocodazole as positive control.
Effect of compounds on tubulin polymerization
To elucidate whether the antiproliferative activities of these conjugates 8g and 8j were related
to the interaction with tubulin, we studied their effects on the tubulin polymerization in a cell-
free system [28,29]. As tubulin subunits heterodimerize and self-assemble to form
microtubules in a time dependent manner, we investigated the progression of tubulin
polymerization by monitoring the increase in fluorescence emission at 420 nm (excitation
0
wavelength is 360 nm) in a 384 well plate for 30 min at 37 C with and without the
compounds at 3µM concentration. Conjugates 8g and 8j inhibited tubulin polymerization by
5
9.46%, 56.08% respectively, compared to the control Figure 6, (supplementary information
file). Tubulin polymerization inhibition was also observed in the case of the standard like
nocodazole (54.73%).
Effect on DNA (tunel assay and hoechst staining)
A terminal transferase dUTP nick end labelling assay was carried out with a view to
understand the effect of 8g and 8j on DNA integrity by treating A549 cells at 1µM for 24 h.

Figure 7 (given in supplementary information file) illustrates that DNA fragmentation (green
FITC staining) was observed in the treated cells whereas there is no fragmentation in the
untreated cells, thereby suggesting apoptotic cell death. Moreover, Hoechst DNA staining
also indicated the formation of apoptotic bodies (blebbing) in cells treated with conjugate 8g
and 8j, which is more prominent than untreated cells, as apparent in Figure 7 and the results
demonstrated that 8g and 8j have apoptotic-inducing ability.
Apoptosis, with its classic characteristics of chromatin condensation and fragmented nuclei,
is one of the major pathways that lead to the process of cell death. The study was performed
on A549 cell line by Hoechst staining [30] (H33258) method. In the study, A549 cells were
treated with the test compounds at 1µM concentrations for 48 h. Manual field quantification
of apoptotic cells based on cytoplasm condensation, presence of apoptotic bodies, nuclear
fragmentation and relative fluorescence of the test compounds (8g and 8j) revealed that the
compounds exerted apoptotic activity as evident from the increase in the percentage of
apoptotic cells (Figure 8, see supplementary file).
Measurement on reactive oxygen species (ROS)
Accumulation of ROS in human lung cancer (A549) cells treated with compound 8g and 8j
was estimated. Therefore we investigated whether ROS production has increased after
treatment with the test compounds. Apoptosis can be initiated by oxidative stress which may
be mediated by the generation of reactive oxygen species (ROS). As these conjugates 8g and
8
j is cytotoxic and induces apoptosis in A549 cells, it was considered of interest to
understand its effect of conjugates on the generation of ROS [31]. Therefore, cells were
incubated with 8g and 8j for 24 h at 1µM concentration and the intracellular generation of
ROS was examined using DCFH-DA dye by fluorescent microscopy. As shown in Figure 9,
there was a significant increase in DCF positive cell population by 8g and 8j as compared to
the control which reveals that it induces apoptosis through intracellular ROS in A549 cells.
Altogether, these results indicate that this compound induced apoptosis through the
mitochondrial pathway.

Figure 9: Effect of conjugates 8g and 8j on reactive oxygen species in Lung cancer cells.
Annexin v-fitc for apoptosis
The apoptotic inducing ability is also investigated by Annexin V FITC/PI (AV/PI) dual
staining [32] assay to examine the occurrence of phosphatidylserine externalization and also
to understand whether it is due to physiological apoptosis or nonspecific necrosis. In this
study A549 cells were treated with compounds 8g and 8j for 48 h at 1µM concentration to
examine (Figure 10) the apoptotic effect. It was observed that these compounds showed
significant apoptosis against A549 cells as shown in. Results indicated that compounds 8g
and 8j showed 57.6% and 62.7% of apoptosis, respectively whereas 14.4% of apoptosis was
observed in control (untreated cells). From this experiment it was suggested that these
conjugates significantly induce apoptosis in A549 cells.
Molecular docking studies
Insilico docking studies were performed to gather information about the binding profile of
the two most potent molecules of the series, viz., compounds 8g and 8j in the colchicine
binding site of tubulin dimer. The three-dimensional crystal structure of tubulin was taken
from RCSB Protein Data Bank (PDB ID: 3E22) [33] for docking studies. Auto dock 4.2 [34]

was used for the docking study. Docking results were viewed in Discovery Studio 2016 [35].
The study indicated that both these compounds bind at the interface of α/β chains of the
tubulin dimer. Compound 8g exhibited various interactions with the residues in the binding
pocket. Conventional hydrogen bonds were seen between the carbonyl oxygen and Thr 349,
nitrogen atom of imidazopyridine ring and Ile332, nitrogen atom of the triazole ring and
Gly350. The oxygen atoms in the methoxy substituents were also involved in hydrogen
bonding with amino acid residues Asp179, Asn329 and Ile341. Other bonds stabilizing the
compound in the binding site include π-alkyl stacking between the phenyl substituent and
Ala333, imidazopyridine ring and Lys336. The docking image is shown in Figure 11.
Figure 11: Binding interaction of compound 8g (left) and binding interactions of compound
8
j (right)
Compound 8j showed substantial interactions such as hydrogen bonding between nitrogen on
triazole ring and Lys336 and Ile341. Pro348 and Pro175 were seen to form π-π interactions
with the phenyl substituent on the imidazole ring. More such bonds were seen between
Ile332, Ile335 and imidazopyridine ring and the benzyl ring bearing the chloro- substituent
respectively. Phe226 and Tyr312 formed similar kinds of bonds with the chloro- substituent.
The docking image is shown in Figure 11.
Conclusion
In the present study, we synthesized 18 hybrid conjugates of imidazopyridine linked triazole
8
(a-r) and evaluated for their cytotoxic activity against four human cancer cell lines namely
prostate (DU-145), lung (A549), HCT-116 (Colon) and breast (MCF-7) cancer. Among
them, compounds 8g and 8j showed significant cytotoxic activity (IC50, 0.51 µM and 0.63

µM respectively) against human lung cancer cell line (A549). Flow cytometry analysis
revealed that these conjugates caused cell cycle arrest at G /M phase suggesting inhibition of
2
tubulin polymerization, Hoechst 33258 staining and DNA fragmentation by tunnel, ROS and
Annexin V also suggests that 8g and 8j induces cell death by apoptosis. Overall, the current
study demonstrates that these new imidazopyridine linked triazolehybrids, particularly 8g and
8
j have the potential to be developed as new class of anticancer agents by further structural
modifications.
Notes
Refer to the supplementary information file for experimental procedures, spectral data and
biological assay procedures and the relevant figures.
Conflicts of interest
There are no conflicts of interest to declare.
Acknowledgements
I.B.S acknowledges CSIR, New Delhi for the award of senior research fellowship. We
th
also acknowledge CSIR, New Delhi, for financial support under the 12 Five Year
plan project “Affordable Cancer Therapeutics (ACT)” (CSC0301).
References
[
[
[
1] L. Amos, Org. Biomol. Chem., 2004, 2, 2153; C.E. Walczak, Curr. Opin. Cell. Biol.,
000, 12, 52.
2] P.K. Sarger, M. Dobles, R. Tournebize, A.A. Hyman, Curr. Opin. Cell. Biol., 1997, 9,
07.
2
8
3] S. Honore, E. Pasquier, D. Braguer, Cell. Mol. Life Sci., 2005, 62, 3039; L.A. Amos,
Org. Biomol. Chem., 2004, 2, 2153; K.H. Downing, E. Nogales, Curr. Opin. Struct.
Biol., 1998, 8, 785.
[
4] Z. Chen, P.J. Merta, N.H. Lin, S.K. Tahir, P. Kovar, H.L. Sham, H. Zhang, Mol. Cancer
Ther., 2005, 4, 562.
[
[
[
5] R.D. Vale, Cell., 2003, 112, 467.
6] J. Howard, A.A. Hyman, Curr. Opin. Cell. Biol., 2007, 19, 31.
7] T.J. Mitchison, E.D. Salmon, Nat. Cell. Biol., 2001, E17-21. Review. Erratum in: Nat.
Cell. Biol., 2001, 3, 530.
[
[
8] R.O. Carlson, Expert Opin. Invest. Drugs., 2008, 17, 707.
9] F. D. Boyer, J. Dubois, S. Thoret, M.E. Dau, I. Hanna, Bioorg. Chem., 2010, 38, 149.

[
[
10] R.W. Beswick, H.E. Ambrose, S.D. Wagner, Leuk. Res., 2006, 4, 427.
11] A.C. Humphries, E. Gancia, M.T. Gillian, S. Goodacre, D. Hallett, K.J. Merchant, S.R.
Thomas, Bioorg. Med. Chem. Lett., 2006, 16, 1518.
[
12] (a) L.J. Browne, Eur. Pat. Appl., 1985, 165, 904 (Chem. Abstr. 165 (1986) 6507d). (b)
L.J. Browne, C. Gude, H. Rodriguez, R.E. Steele, A. Bhatnager, J. Med. Chem,. 1991,
3
4, 725.
[
[
13] D. Davey, P.W. Erhardt, W.C. Lumma, J. Wiggins, M. Sullivan, D. Pang, J. Med.
Chem., 1987, 30, 1337.
14] (a) N. Ford, US Pat. 4,444,775, 1984 (Chem. Abstr. 101 (1984) 110920m). (b) N.F.
Ford, L.J. Browne, T. Campbell, C. Gemenden, R. Goldstein, C. Gude, W.F. Wasley, J.
Med. Chem., 1985, 28, 164.
[
[
15] C. Hamdouchi, J.D. Blas, M.D. Prado, J. Gruber, B.A. Heinz, V.J. Vance, J. Med.
Chem., 1999, 42, 50.
16] A. Kamal. V.S. Reddy, S. Karnewar, S.S. Chourasiya, A.B. Shaikh, G.B. Kumar, C.
Kishor, M.K. Reddy, M.P.N. Rao, A. Nagabhushana. K.V. Ramakrishna, A. Addlagatta,
S. Kotamraju, Chem.Med.Chem., 2013, 12, 2015.
[
[
[
[
[
[
[
17] A. Kamal, J.S. Reddy, M.J. Ramaiah, D. Dastagiri, E.V. Bharathi, V.M. Prem sagar,
S.N.V.C.L. Pushpavalli, P. Ray, M.P. Bhadra, MedChemComm., 2010, 1, 355.
18] M.A. Martinez-Urbina, A. Zentella, M.A. Vilchis-Reyes, A. Guzman, O. Vargas, M.T.
R. Apan, J.L.V. Gallegos, E. Diaz, Eur. J. Med. Chem., 2010, 45, 1211.
19] A. Kamal, G.B. Kumar, V.L. Nayak, V.S. Reddy, A.B. Shaikh, M.K.R. Reddy,
MedChemCommun., 2015, 6, 606.
20] I.B. Sayeed, V.L. Nayak, M.A. Shareef, N.K. Chouhan, A. Kamal, MedChemCommun.,
2
017, 8, 1000.
21] N.G. Aher, V.S. Pore, N.N. Mishra, A. Kumar, P.K. Shukla, A. Sharma, Bioorg. Med.
Chem. Lett., 2009, 19, 759.
22] S.R. Patpi, L. Pulipati, P. Yogeswari, D. Sriram, N. Jain, B. Sridhar, R. Murthy, D.T.
Anjana, S.V. Kalivendi, S. Kantevari, J. Med. Chem., 2012, 55, 3911.
23] A. Kamal, S. Prabhakar, M.J. Ramaiah, P.V. Reddy, C.R. Reddy, A. Malla Reddy, N.
Shankaraiah, T.L.N. Reddy, S.N.C.V.L. Pushpavalli, M.P. Bhadra, Eur. J. Med. Chem.,
2
011, 46, 3820.
[
24] K.D. Thomas, A.V. Adhikari, I.H. Chowdhury, E. Sumesh, N.K. Pal, Eur. J. Med.
Chem., 2011, 46, 2503.

[
[
[
25] R. He, Y. Chen, Y. Chen, A.V. Ougolkov, J.S. Zhang, D.N. Savoy, D.D. Billadeau, A.P.
Kozikowski, J. Med. Chem., 2010, 53,1347.
26] M. Botta, S. Armaroli, D. Castagnolo, G. Fontana, P. Perad, E. Bombardelli, Bioorg.
Med. Chem. Lett., 2007, 17, 1579.
27] (a) K.T. Chan, F.Y. Meng, Q. Li, C.Y. Ho, T.S. Lam, Y. To, W.H. Lee, M. Li, K.H. Chu,
M. Toh, Cancer Lett., 2010, 294, 24; (b) J.K. Shen, H.P. Du, M. Yang, Y.G. Wang, J.
Jin, Ann. Hematol., 2009, 88, 52.
[
[
[
28] C. Kanthou, O. Greco, A. Stanford, I. Cook, R. Knight, O. Benzakour, G. Tozer, Am. J.
Pathol., 2004, 165, 1401.
29] K. Huber, P. Patel, L. Zhang, H. Evans, A.D. Westwell, P.M. Fischer, S. Chan, S.
Martin, Mol. Cancer. Ther., 2008, 7, 143.
30] R. Shankar, B. Chakravarti, U.S. Singh, M.I. Ansari, S. Deshpande, S.K.D. Dwivedi,
H.K. Bid, R. Konwar, G. Kharkwal, V. Chandra, A. Dwivedi, K. Hajela, Bioorg. Med.
Chem., 2009, 17, 3847.
[
[
[
[
[
[
31] Y. Sanchez, G.P. Simon, E. Calvino, E. de Blas, P. Aller, J. Pharmacol. Exp. Ther.,
2
010, 335, 114.
32] N.M. Weir, K. Selvendiran, V.K. Kutala, L. Tong, S. Vishwanath, M. Rajaram, S.
Tridandapani, S. Anant, P. Kuppusamy, Cancer Biol. Ther., 2007, 6, 178.
33] A. Cormier, M. Marchand, R.B.G. Ravelli, M. Knossow, B. Gigant, EMBO Rep., 2008,
9
, 1101.
34] G.M. Morris, R. Huey, W. Lindstrom, M.F. Sanner, R.K. Belew, D.S. Goodsell, A.J.
Olson, J. Comput. Chem., 2009, 16, 2785.
35] Dassault Systèmes BIOVIA, Discovery Studio Modeling Environment, Release 2017,
San Diego: Dassault Systèmes, 2016.
36] K. Gonda, H. Tsuchiya, T. Sakabe, Y. Akechi, R. Ikeda, R. Nishio, K. Terabayashi, K.
Ishii, Y. Matsumi, A.A. Ashla, H. Okamoto, K. Takubo, S. Matsuoka, Y. Watanabe, Y.
Hoshikawa, A. Kurimasa, G. Shiota, Biochem. Biophys. Res. Commun. 2008, 370, 629.
37] M. Szumilak, M.A. Szulawska, K. Koprowska, M. Stasiak, W. Lewgowd, A. Stanczak,
M. Czyz, Eur. J. Med. Chem. 2010, 45, 5744.
[
[
38] R. Shankar, B. Chakravarti, U.S. Singh, M.I. Ansari, S. Deshpande, S.K.D. Dwivedi,
H.K. Bid, R. Konwar, G. Kharkwal, V. Chandra, A. Dwivedi, K. Hajela, Bioorg. Med.
Chem. 2009, 17, 3847.

Research Highlights

Imidazopyridine-triazole conjugates 8(a-r) were synthesized and evaluated for their anti-
proliferative activity.



Conjugates 8g and 8j showed IC50 values 0.51 & 0.63µm respectively
Conjugates arrest cell growth in G
2
/M phase indicating tubulin arrest.
Triggering of apoptosis was confirmed through Hoescht staining and annexin V assay.

Imidazopyridine linked triazoles as tubulin inhibitors, effectively triggering
apoptosis in lung cancer cell line
a,b
a
b,d
b,d
Ibrahim Bin Sayeed, M.V.P.S. Vishuwardhan, Apoorva Nagarajan, Srinivas Kantevari,
*a,b,c
Ahmed Kamal.
a
Medicinal Chemistry and Pharmacology Division, CSIR - Indian Institute of Chemical
Technology, Hyderabad 500007, India
b
Academy of Scientific and Innovative Research (AcSIR), CSIR - Indian Institute of Chemical
Technology, Hyderabad 500007, India
c
School of Pharmaceutical Education and Research, Jamia Hamdard University, New Delhi
1
10062, India
d
Department of Crop Protection Chemicals, CSIR- Indian Institute of Chemical Technology,
Hyderabad 500007, India