Synthesis and anticancer activity study of indolyl hydrazide-hydrazones

Article abstract of DOI:10.1007/s00044-016-1522-1

A series of N'-((1-(substituted)-1H-indol-3-yl)methylene)hydrazides were synthesized and evaluated for their in vitro antiproliferative activities against various cancer cell lines. Formation of indole hydrazide-hydrazones was accomplished by the reaction of indole 3-carboxaldehyde with aryl/alkyl hydrazides in the presence of acetic acid. Out of synthesized twenty-two compounds, some of the analogs exhibited specificity toward breast (18b, 18d, 18f and 18j) and prostate (18t and 18v) cancer cells. Among the prepared derivatives, compounds 18b, 18d and 18j were most cytotoxic (IC₅₀ = 0.9, 0.4 and 0.8 μM, respectively) against the screened cancer cell lines. Exposure of PC3 cells to either 18d or 18j resulted in increased levels of cleaved PARP1, indicating that indolyl hydrazide-hydrazones induce apoptosis in PC3 cells.

Full text of DOI:10.1007/s00044-016-1522-1

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-016-1522-1
ORIGINAL RESEARCH
Synthesis and anticancer activity study of indolyl hydrazide–
hydrazones
Swapna Sundaree1 Buchi Reddy Vaddula2 Mukund P. Tantak1 Santosh B. Khandagale1 Chun Shi3
•
•
•
•
•
Kavita Shah3 Dalip Kumar1
•
Received: 4 April 2015 / Accepted: 3 February 2016
Ó Springer Science+Business Media New York 2016
Abstract A series of N0-((1-(substituted)-1H-indol-3-
yl)methylene)hydrazides were synthesized and evaluated
for their in vitro antiproliferative activities against various
cancer cell lines. Formation of indole hydrazide–hydra-
zones was accomplished by the reaction of indole 3-car-
boxaldehyde with aryl/alkyl hydrazides in the presence of
acetic acid. Out of synthesized twenty-two compounds,
some of the analogs exhibited specificity toward breast
(18b, 18d, 18f and 18j) and prostate (18t and 18v) cancer
cells. Among the prepared derivatives, compounds 18b,
18d and 18j were most cytotoxic (IC50 = 0.9, 0.4 and
0.8 lM, respectively) against the screened cancer cell
lines. Exposure of PC3 cells to either 18d or 18j resulted in
increased levels of cleaved PARP1, indicating that indolyl
hydrazide–hydrazones induce apoptosis in PC3 cells.
Introduction
Indole is an important pharmacophore found in a large
number of molecules with significant biological activity
including anti-inflammatory, anticancer, antinociceptive,
antipsychotic, antileishmanial and antiviral activities
(Adam et al., 2010; Choppara et al., 2015; Gupta et al.,
2007; Zhang et al., 2015). Since indole scaffolds have
shown promising results in anticancer drug discovery
research, they have constantly garnered the attention of
researchers (El-Sayed et al., 2014; Kamal et al., 2012;
Panathur et al., 2013; Singh et al., 2009). Literature survey
revealed that in the recent past, several indole-based syn-
thetic as well as natural products exhibited potent anti-
cancer activity. For example, natural products camalexin
(1), labradorins (2), nortopsentins (3), topsentins (4) and
meridianin (5), isolated from Arabidopsis thaliana, Pseu-
domonas syringae pv. Coronafaciens, Spongosorites ruet-
zleri, Topsentia genitrix and Aplidium meridianum,
respectively, are found to be effective against various
cancer cell lines (Diana et al., 2010; Kumar et al., 2014;
Pettit et al., 2002). Recently, many indole-containing small
molecules have been identified as potent anticancer agents.
The 3-aroylindole (6) and indibulin (7) are endowed with
interesting anticancer activity via modulation of tubulin
polymerization in clinical trials (Brancale and Silvestri,
2007; Wienecke and Bacher, 2009). Similarly, 2-aryl-4-
benzoylimidazole (8) showed anticancer activity through
the inhibition of tubulin polymerization with typical IC50
values around 3.8 nm (Chen et al., 2012). Moreover, Sil-
vestri and coworkers described 2-heteroarylthioindole (9)
as tubulin-targeting anticancer agent with IC50 = 1.0 nM
in MCF-7 cells (Fig. 1) (La Regina et al., 2012).
Keywords Antiproliferative activity Á
Indole hydrazide–hydrazones Á MTT assay
& Kavita Shah
shah23@purdue.edu
& Dalip Kumar
dalipk@pilani.bits-pilani.ac.in
1
Department of Chemistry, Birla Institute of Technology and
Science, Pilani, Rajasthan 333031, India
2
Sustainable Technology Division, National Risk
Management Research Laboratory, U.S. Environmental
Protection Agency, 26 West Martin Luther King Drive, MS
483, Cincinnati, OH 45268, USA
3
On the other hand, hydrazide–hydrazones have been
received significant attention due to their diverse biological
Department of Chemistry and Purdue Cancer Center, Purdue
University, 560 Oval Drive, West Lafayette, IN 47907, USA
123

Med Chem Res
S
N
N
R
N
O
N
R
R
H
N
N
N
N
H
H
H
H
Nortopsentins A-C (3)
R = 5/6-Br/OCH3
Camalexin (1)
Labradorins (2)
OCH3
N
O
O
R
N
OCH3
OCH3
R
NH2
N
H
N
R
R
N
H
N
R
N
H3CO
N
H
H
H
R
3-Aroylindole (6)
Topsentins (4)
Meridianins (5)
OCH3
O
OCH3
H
O
OCH3
OCH3
N
N
S
N
OCH3
N
H
O
N
N
OCH3
N
N
H
N
H
2-Indolyl-4-benzoylimidazole (8)
Indibulin (7)
Arylthioindole (9)
Cl
Fig. 1 Representative indole-based anticancer agents
properties including anticancer, antimicrobial, anticonvul-
sant, anti-inflammatory, antimalarial and antitubercular
(Nasr et al., 2014). Literature survey revealed that the
hydrazide–hydrazone moiety plays a crucial role in anti-
cancer activity of nitrogen-containing heterocycles (Salum
et al., 2015).
et al., 2014). Keeping in view the aforementioned
anticancer potency of functionalized indoles and
hydrazide–hydrazones, we have designed and synthe-
sized indolyl hydrazide–hydrazones by tethering indole
with hydrazide–hydrazone moiety into a single mole-
cule (Fig. 2).
In the recent past, several functionalized indoles were
found to be effective against various cancer cells. The N-
4-chlorobenzyl-3-formylindole, oncrasin-1 (10) (Wu
et al., 2011), was found to be effective against K-Ras
mutant cancer cells. Our studies on the conversion of
indole to indolyl chalcones (11) (Kumar et al., 2010a) and
bis(indolyl)hydrazide–hydrazones (13) (Kumar et al.,
2012b) showed promising activity against a panel of
cancer cell lines. Also, Sato et al. isolated rhopaladins
A * D (12) from marine tunicate Rhopalaea sp. with
inhibitory activity against CDK4 (IC50 = 12.5 lg/mL)
and c-erbb-2 (IC50 = 7.4 lg/mL) kinases (Sato et al.,
1998). Recently, we have also synthesized several indole-
based small molecules as promising anticancer agents.
For example, 5-(30-indolyl)-1,3,4-thiadiazoles (Kumar
et al., 2010b), 5-(30-indolyl)-1,3,4-oxadiazoles (Kumar
et al., 2009), indolyl-1,2,4-triazoles (Kumar et al., 2011),
2-arylamino(indolyl)-1,3,4-thiadiazoles (Kumar et al.,
2012a), 2-arylamino-5-(30-indolyl)-1,3,4-oxadiazoles (Tantak
et al., 2013), a-cyano bis(indolyl)chalcones (Kumar
Taking cue from the literature, we have attempted
to synthesize a series of hydrazide–hydrazones that
derive from the reaction of indole 3-carboxaldehyde
(16) with various aromatic/aliphatic acid hydrazides (17)
(Scheme 1). Initially, N-alkyl indoles 15 were prepared
from the reaction of indole (14) with alkyl halides in
the presence of a base (Kumar et al., 2012c). Subse-
quently, treatment of 15 with phosphorus oxychloride in
dimethylformamide led to 3-carboxaldehyde (16) (James
and Snyder, 1959). On the other hand, aromatic/aliphatic
acid hydrazides 17 were prepared by following the liter-
ature procedures (Palace-Berl et al., 2013; Sadek et al.,
2014). Synthesized hydrazide–hydrazones 18a–v were
studied for their in vitro antiproliferative activities in
different cancer cell lines: prostate (PC3, DU145 and
LnCaP), breast (MCF-7 and MDA-MB-231) and pancreas
(PaCa2). Also, in an attempt to study the role of indolyl
N–H, we substituted the proton at first position of indole
ring with methyl (18m–q) and p-chlorobenzyl moieties
(18r–v).
123

Med Chem Res
O
CHO
R
R
N
N
R
Oncrasin-1 (10)
Indolyl chalcones (11)
O
Cl
NH
H
O
O
H
N
N
R
N
N
N
O
O
N
N
R
N
HO
N
H
H
Indolyl hydrazid-hydrazones
Rhopaladin B (12)
Cl
Indibulin (7)
H
N
NH
N
O
N
H
Bis(indolyl)hydrazide-hydrazones (13)
Fig. 2 Rational design for indolyl hydrazide–hydrazones
H
H
N
CHO
R
POCl3
DMF
R1X, NaH
(17)
RCONHNH2
N
EtOH, AcOH,
reflux
DMF, 0 °C-rt
N
N
H
N
O
N
R1
16
R1
15
R1
,
18a-v
14
Scheme 1 Synthesis of a library of indolyl hydrazide–hydrazones 18a–v
ethanol (5 mL) in the presence of glacial acetic acid
(0.3 mL) for 4 h. On cooling the reaction mixture to room
temperature, the crude product was precipitated, filtered
and dried. Further recrystallization of the crude products in
ethanol allowed to obtain pure products in 85–95 % yields.
Materials and methods
Chemistry
Infrared (IR) spectra were recorded on a Jasco FTIR-4100
spectrometer in the wave number range of 4000–400 cm-1
.
N0-((1H-Indol-3-yl)methylene)acetohydrazide (18a) White
solid, yield 85 %; FTIR (KBr) mmax 3210, 3101, 1605,
Nuclear magnetic resonance (1H and 13C) spectra were
recorded on a Bruker AM-400 MHz spectrometer using
CDCl3 or DMSO-d6 as solvent and tetramethylsilane as an
internal standard. The chemical shifts are expressed in d
values and the following abbreviations are used: s (singlet),
d (doublet), t (triplet), q (quartet) and m (multiplet). Purity
of the crude compounds was qualitatively analyzed by thin-
layer chromatography (TLC). Silica gel column chro-
matography was performed using MerckÒ silica gel
(60–120 mesh). All the reagents and solvents were pur-
chased from SpectrochemÒ or Sigma-AldrichÒ.
1574, 1444, 1354 cm-1 1H NMR (CDCl3, 400 MHz):
;
d = 2.12 (s, 3H, CH3), 7.31–7.34 (m, 2H, Ar–H), 7.42
(d, 1H, J = 7.3 Hz, Ar–H), 7.49 (d, 1H, J = 2.6 Hz,
Ar–H), 7.96 (s, 1H, azomethine-CH), 8.09 (d, 1H, J =
7.3 Hz, Ar–H), 9.69 (s, 1H, hydrazine-NH), 11.27 (brs,
1H, NH); 13C NMR (CDCl3, 101 MHz) d = 171.73
(CONH), 155.22 (C=NH), 137.50 (C, C-8), 131.16 (C,
C-9), 125.08 (CH, C-2), 122.80 (CH, C-6), 122.47 (CH,
C-4), 120.71 (CH, C-5), 112.55 (CH, C-7), 111.99 (C,
C-3), 20.73 (CH3); LCMS m/z (pos) 201.1 C11H11N3O
(calcd 201.0); HRMS m/z (pos); 201.0910 C11H11N3O
(calcd. 201.0902).
General procedure for the synthesis of N0-((1-(substituted)-
1H-indol-3-yl)methylene)hydrazides (18a–v)
N0-((1H-Indol-3-yl)methylene)-2,2,2-trifluoroacetohydrazide
(18b) White solid, yield 87 %; FTIR (KBr) mmax 3214,
Indole-3-aldehyde 16 (1 mmol) and the corresponding
alkyl/aryl acid hydrazide 17 (1.05 mmol) were refluxed in
1
3107, 1608, 1577, 1454, 1360 cm-1; H NMR (CDCl3,
123

Med Chem Res
400 MHz): d = 7.26–7.29 (m, 2H, Ar–H), 7.47 (d, 1H,
J = 7.2 Hz, Ar–H), 7.52 (d, 1H, J = 2.4 Hz, Ar–H), 7.99
(d, 1H, J = 7.2 Hz, Ar–H), 8.02 (s, 1H, azomethine-CH),
9.69 (s, 1H, hydrazine-NH), 11.32 (brs, 1H, NH); 13C
NMR (CDCl3, 101 MHz): d = 154.81 (CONH), 134.90
(C, C-8), 134.39 (C, C-2), 131.42 (C, C-9), 127.19 (CH,
C-6), 121.26 (CH, C-4), 120.32 (CH, C-5), 114.13 (CF3, q),
113.26 (CH, C-7), 105.72 (C, C-3); HRMS m/z (pos):
256.0912 C11H9F3N3O (calcd 256.0698).
C-50), 112.29 (CH, C-7), 112.26 (C, C-3), 55.86 (CH3,
OCH3); HRMS m/z (pos): 294.1204 C17H16N3O2 (calcd
294.1243).
N0-((1H-Indol-3-yl)methylene)-2-phenylacetohydrazide (18f)
White solid, yield 89 %; 1H NMR (CDCl3400, MHz):
d = 4.24 (s, 2H, CH2, Ar–H), 7.19–7.21 (m, 5H, Ar–H),
7.32–7.34 (m, 2H, Ar–H), 7.44 (d, 1H, J = 7.2 Hz, Ar–H),
7.52 (d, 1H, J = 2.6 Hz, Ar–H), 8.02 (d, 1H, J = 7.2 Hz,
Ar–H), 8.10 (s, 1H, azomethine-CH), 9.74 (s, 1H, hydra-
zine-NH), 11.35 (brs, 1H, NH); 13C NMR (CDCl3,
101 MHz): d = 168.61 (CONH), 134.84 (C=NH), 134.81
(C, C-8), 134.54 (C, C-10), 133.72 (C, C-9), 129.45 (CH,
C-20, C-60), 129.18 (CH, C-30, C-50), 128.42 (CH, C-40),
127.16 (CH, C-2), 121.39 (CH, C-5), 120.77 (CH, C-6),
118.42 (CH, C-4), 113.45 (CH, C-7), 105.72 (C, C-3),
40.81 (CH2, CH2Ph); LCMS m/z (pos): 277.2 C17H15N3O:
(calcd 277.1); HRMS m/z (pos): 277.1231 C17H15N3O
(calcd 277.1221).
N0-((1H-Indol-3-yl)methylene)benzohydrazide (18c) White
solid, yield 89 %, mp 239–241 °C; FTIR (KBr) mmax
3209, 3040, 1605, 1574, 1443, 1358, 1319, 1250 cm-1; 1H
NMR (CDCl3, 400 MHz): d = 7.16–7.18 (m, 5H, Ar–H),
7.27–7.30 (m, 2H, Ar–H), 7.38 (d, 1H, J = 7.4 Hz, Ar–H),
7.50 (d, 1H, J = 2.4 Hz, Ar–H), 8.05 (s, 1H, azomethine-
CH), 8.09 (d, 1H, J = 7.4 Hz, Ar–H), 9.71 (s, 1H, hydra-
zine-NH), 11.29 (brs, 1H, NH); 13C NMR (DMSO-d6,
101 MHz): d = 163.01 (CONH), 145.44 (C=NH), 137.51
(CH, C-8), 134.54 (C, C-9), 131.79 (C, C-10), 130.81 (CH,
C-40), 128.87 (CH, C-30, C-50), 127.95 (CH, C-20, C-60),
124.83 (CH, C-2), 123.11 (CH, C-5), 122.52 (CH, C-6),
120.87 (CH, C-4), 112.29 (CH, C-7), 112.20 (C, C-3);
HRMS m/z (pos): 264.1421 C16H14N3O (calcd 264.1137).
N0-((1H-Indol-3-yl)methylene)-3,4-dimethoxybenzohydrazide
(18g) White solid, yield 90 %; 1H NMR (CDCl3,
400 MHz): d = 3.62 (s, 3H, OCH3), 3.68 (s, 3H, OCH3),
7.25–7.27 (m, 3H, Ar–H), 7.38–7.40 (m, 2H, Ar–H), 7.43
(d, 1H, J = 7.2 Hz, Ar–H), 7.50 (d, 1H, J = 2.6 Hz, Ar–
H), 8.04 (s, 1H, azomethine-CH), 8.10 (d, 1H, J = 7.2 Hz,
Ar–H), 9.68 (s, 1H, hydrazine-NH), 11.35 (brs, 1H, NH);
13C NMR (DMSO-d6, 101 MHz): d = 166.11 (CONH),
152.06 (C, C-40), 148.74 (C, C-30), 136.49 (C=NH), 128.70
(C, C-8), 126.77 (C, C-9), 125.43 (C, C-10), 124.07 (CH,
C-2), 122.58 (CH, C-5), 121.36 (CH, C-6), 121.32 (CH,
C-60), 121.12 (CH, C-4), 112.41 (CH, C-7), 111.47 (CH,
C-20), 111.09 (CH, C-50), 108.70 (C, C-3), 56.09 (CH3,
OCH3), 56.03 (CH3, OCH3); HRMS m/z (pos): 324.1321
C18H18N3O3 (calcd 324.1348).
N0-((1H-Indol-3-yl)methylene)-4-chlorobenzohydrazide (18d)
White solid, yield 87 %, mp 226–227 °C; FTIR (KBr)
mmax 3340, 3194, 1605, 1558, 1450, 1358, 1103,
1
758 cm-1; H NMR (CDCl3, 400 MHz): d = 7.12–7.14
(m, 4H, Ar–H), 7.29–7.32 (m, 2H, Ar–H), 7.38 (d, 1H,
J = 7.2 Hz, Ar–H), 7.49 (d, 1H, J = 2.4 Hz, Ar–H), 8.02
(s, 1H, azomethine-CH), 8.07 (d, 1H, J = 7.2 Hz, Ar–H),
9.79 (s, 1H, hydrazine-NH), 11.35 (brs, 1H, NH); 13C
NMR (DMSO-d6, 101 MHz): d = 161.87 (CONH), 145.75
(C=NH), 137.51 (C, C-8), 136.58 (C, C-40), 133.23 (C,
C-10), 130.99 (C, C-9), 129.88 (CH, C-30, C-50), 128.96
(CH, C-20, C-60), 124.80 (CH, C-2), 123.12 (CH, C-5),
122.49 (CH, C-6), 120.90 (CH, C-4), 112.30 (CH, C-7),
112.12 (C, C-3); HRMS m/z (pos): 298.1202 C16H13ClN3O
(calcd 298.0747).
N0-((1H-Indol-3-yl)methylene)-4-(hydroxy)-3-methoxyben-
zohydrazide (18h) White solid, yield 93 %; FTIR (KBr)
mmax 3320, 3154, 1606, 1554, 1358, 1268, 1140 cm-1; 1H
NMR (CDCl3, 400 MHz): d = 3.78 (s, 3H, OCH3),
7.25–7.28 (m, 3H, Ar–H), 7.32–7.35 (m, 2H, Ar–H), 7.44
(d, 1H, J = 7.5 Hz, Ar–H), 7.52 (d, 1H, J = 2.6 Hz, Ar–
H), 8.00 (d, 1H, J = 7.5 Hz, Ar–H), 8.09 (s, 1H, azome-
thine-CH), 9.72 (s, 1H, hydrazine-NH), 11.31 (brs, 1H,
NH); 13C NMR (CDCl3, 101 MHz): d = 164.25 (CONH),
150.12 (C, C-40), 149.09 (C, C-30), 134.80 (C=NH), 134.51
(C, C-8), 133.02 (C, C-9), 127.12 (C, C-10), 126.03 (CH,
C-2), 125.00 (CH, C-60), 121.37 (CH, C-5), 120.72 (CH,
C-6), 118.39 (CH, C-4), 114.37 (CH, C-20), 113.21 (CH,
C-7), 112.42 (CH, C-50), 105.68 (C, C-3), 56.80 (OCH3);
HRMS m/z (pos): 310.1231 C17H16N3O3 (calcd 310.1192).
N0-((1H-Indol-3-yl)methylene)-4-methoxybenzohydrazide
(18e) White solid, yield 92 %, mp 253–255 °C; FTIR
(KBr) mmax 3240, 3115, 1605, 1558, 1512, 1450, 1358,
1
1296, 1265 cm-1; H NMR (CDCl3, 400 MHz): d = 3.62
(s, 3H, OCH3), 7.18–7.21 (m, 4H, Ar–H), 7.34–7.36 (m,
2H, Ar–H), 7.48 (d, 1H, J = 7.4 Hz, Ar–H), 7.54 (d, 1H,
J = 2.3 Hz, Ar–H), 8.00 (d, 1H, J = 7.4 Hz, Ar–H), 8.10
(s, 1H, azomethine-CH), 9.79 (s, 1H, hydrazine-NH), 11.26
(brs, 1H, NH); 13C NMR (DMSO-d6, 101 MHz):
d = 162.44 (CONH), 162.16 (C, C-40), 144.88 (C=NH),
137.49 (C, C-8), 130.55 (C, C-9), 129.78 (CH, C-20, C-60),
126.57 (C, C-10), 124.84 (CH, C-2), 123.06 (CH, C-5),
122.52 (CH, C-6), 120.80 (CH, C-4), 114.10 (CH, C-30,
N0-((1H-Indol-3-yl)methylene)-4-(benzyloxy)-3-methoxy-
1
benzohydrazide (18i) White solid, yield 87 %; H NMR
123

Med Chem Res
(CDCl3, 400 MHz): d = 3.60 (s, 3H, OCH3), 5.10 (s, 2H,
CH2), 7.19–7.22 (m, 3H), 7.29–7.34 (m, 2H), 7.36–7.39
(m, 5H, ArH), 7.42 (d, 1H, J = 7.3 Hz), 7.49 (d, 1H,
J = 2.4 Hz), 8.07 (s, 1H, azomethine-CH), 8.10 (d, 1H,
J = 7.3 Hz), 9.69 (s, 1H, hydrazine-NH), 11.29 (brs, 1H,
NH); 13C NMR (CDCl3, 101 MHz): d = 167.91 (CONH),
155.32 (C, C-40), 153.91 (C, C-30), 149.59 (C, C=NH),
142.00 (C, C-8), 141.39 (C, C-9), 133.54 (C, C-100), 133.37
(CH, C-300, C-500), 132.82 (CH, C-200, C-600), 132.27 (CH,
C-400), 131.86 (C, C-10), 129.64 (CH, C-2), 127.55 (CH,
C-5), 127.05 (CH, C-6), 125.49 (CH, C-4), 125.45 (CH,
C-60), 117.42 (CH, C-7), 116.96 (CH, C-4), 116.52 (CH,
C-60), 116.36 (C, C-3), 75.34 (CH2, OCH2Ph), 60.83 (CH3,
OCH3); HRMS m/z (pos): 400.1621 C24H22N3O3 (calcd
400.1661).
(m, 2H, Ar–H), 7.29–7.31 (m, 4H, Ar–H), 7.38 (d, 1H,
J = 7.4 Hz, Ar–H), 7.52 (d, 1H, J = 2.6 Hz, Ar–H), 7.97
(d, 1H, J = 7.4 Hz, Ar–H), 8.12 (s, 1H, azomethine-CH),
9.68 (s, 1H, hydrazine-NH), indole NH was not observed;
13C NMR (DMSO-d6,101 MHz): d = 161.46 (CONH),
152.37 (CH, C-40), 148.95 (CH, C-20), 146.04 (C, C=NH),
137.52 (CH, C-2), 135.75 (C, C-8), 131.18 (C, C-9), 130.21
(C, C-10), 124.79 (CH, C-60), 124.02 (CH, C-50), 123.15
(CH, C-5), 122.47 (CH, C-6), 120.95 (CH, C-4), 112.33
(CH, C-7), 112.02 (C, C-3); HRMS m/z (pos): 265.1103
C15H13N4O (calcd. 265.1089).
N0-((1-Methyl-1H-indol-3-yl)methylene)acetohydrazide
(18m) White solid, yield 91 %; FTIR (KBr) mmax 3194,
1605, 1566, 1381, 1327, 1196, 748 cm-1 1H NMR
;
(CDCl3, 400 MHz,): d = 2.47 (s, 3H, CH3), 3.89 (s, 3H,
N-CH3), 7.27–7.32 (m, 2H, Ar–H), 7.47 (d, 1H,
J = 7.3 Hz, Ar–H), 7.52 (s, 1H, Ar–H), 7.92 (d, 1H,
J = 7.3 Hz, Ar–H), 8.08 (s, 1H, azomethine-CH), 9.71 (s,
1H, hydrazine-NH); 13C NMR (DMSO-d6, 101 MHz):
d = 155.14 (CONH), 138.19 (C, C-8), 135.82 (C, C-9),
125.61 (CH, C-2), 123.20 (CH, C-6), 122.71 (CH, C-4),
121.30 (CH, C-5), 111.56 (CH, C-7), 110.80 (C, C-3),
33.37 (N-CH3), 20.90 (CH3); HRMS m/z (pos): 216.1102
C15H13N4O (calcd. 216.1137).
N0-((1H-Indol-3-yl)methylene)-3,4,5-trimethoxybenzohy-
drazide (18j) White solid, yield 95 %, mp 231–232 °C;
FTIR (KBr) mmax 3271, 3163, 2932, 1612, 1582, 1551,
1458, 1335, 1234, 1126, 764 cm-1 1H NMR (CDCl3,
;
400 MHz): d = 3.62 (s, 3H, OCH3), 3.68 (s, 3H, OCH3),
3.72 (s, 3H, OCH3), 7.28 (s, 1H, Ar–H), 7.32 (s, 1H, Ar–
H), 7.36–7.39 (m, 2H, Ar–H), 7.45 (d, 1H, J = 7.4 Hz, Ar–
H), 7.54 (d, 1H, J = 2.4 Hz, Ar–H), 7.99 (d, 1H,
J = 7.4 Hz, Ar–H), 8.08 (s, 1H, azomethine-CH), 9.72 (s,
1H, hydrazine-NH),; 13C NMR (DMSO-d6, 101 MHz):
d = 162.44 (CONH), 153.13 (2C, C-30, C-50), 145.54 (C,
C-40), 140.52 (C, C=NH), 137.51 (C, C-8), 130.75 (C, C-9),
129.69 (CH, C-2), 124.82 (CH, C-5), 123.11 (CH, C-6)
122.45 (CH, C-4), 120.87 (CH, C-10), 112.31 (CH, C-7),
112.15 (C, C-20, C-60), 105.48 (C, C-3), 60.58 (CH3,
OCH3), 56.53 (CH3, 2OCH3); LCMS m/z (pos): 353.2
C19H19N3O4 (calcd 353.1); HRMS m/z (pos): 400.1621
C24H22N3O3 (calcd 400.1661).
2,2,2-Trifluoro-N0-((1-methyl-1H-indol-3-yl)methylene)ace-
tohydrazide (18n) White solid, yield 94 %; 1H NMR
(CDCl3, 400 MHz): d = 3.91 (s, 3H, CH3), 7.24–7.28 (m,
2H, Ar–H), 7.40 (d, 1H, J = 7.4 Hz, Ar–H), 7.49 (s, 1H,
Ar–H), 8.04 (s, 1H, azomethine-CH), 8.11 (d, 1H,
J = 7.4 Hz, Ar–H), 9.74 (s, 1H, hydrazine-NH); 13C NMR
(CDCl3, 101 MHz): d = 153.97 (CONH), 137.63 (C, C-8),
134.98 (C, C-9), 125.41 (CH, C-2), 124.58 (CH, C-6),
123.00 (CH, C-4), 122.03 (CH, C-5), 121.21 (C, C-CF3, q),
110.55 (CH, C-7), 109.72 (C, C-3), 33.15 (CH3, N-CH3);
HRMS m/z (pos): 270.0921 C12H11F3N3O (calcd.
270.0854).
N0-((1H-Indol-3-yl)methylene)isonicotinohydrazide (18k)
White solid, yield 91 %, mp 208–210 °C; FTIR (KBr)
mmax 3340, 3194, 1605, 1558, 1450, 1358, 1103,
756 cm-1 1H NMR (CDCl3,400 MHz): d = 7.21–7.23
;
4-(Benzyloxy)-3-methoxy-N0-((1-methyl-1H-indol-3-yl)
methylene)benzohydrazide (18o) White solid, yield
89 %; 1H NMR (CDCl3, 400 MHz): d = 3.52 (s, 3H,
OCH3), 3.89 (s, 3H, CH3), 5.14 (s, 2H, CH2), 7.14–7.16 (m,
2H, Ar–H), 7.19–7.23 (m, 2H, Ar–H), 7.27 (d, 1H,
J = 7.4 Hz, Ar–H), 7.34–7.38 (m, 5H, Ar–H), 7.42 (s, 1H,
Ar–H), 7.49 (s, 1H, Ar–H), 8.09 (d, 1H, J = 7.4 Hz, Ar–
H), 8.12 (s, 1H, azomethine-CH), 9.63 (s, 1H, hydrazine-
NH); 13C NMR (DMSO-d6, 101 MHz): d = 162.44
(CONH), 150.82 (C, C-40), 149.09 (C, C-30), 144.44 (C,
C=NH), 137.99 (CH, C-2), 137.19 (C, C-100), 134.17 (C,
C-8), 128.93 (C, C-9), 128.44 (CH, C-300, C-500), 128.36
(CH, C-200, C-600), 126.89 (CH, C-400), 125.22 (C, C-10),
123.14 (CH, C-6), 122.58 (CH, C-5), 121.07 (CH, C-4),
121.05 (CH, C-60), 113.00 (CH, C-20), 111.54 (CH, C-50),
(m, 2H, Ar–H), 7.27–7.29 (m, 4H, Ar–H), 7.41 (d, 1H,
J = 7.2 Hz, Ar–H), 7.49 (d, 1H, J = 2.3 Hz, Ar–H), 7.94
(d, 1H, J = 7.2 Hz, Ar–H), 8.05 (s, 1H, azomethine-CH),
9.63 (s, 1H, hydrazine-NH); 13C NMR (DMSO-d6,
101 MHz,): d = 161.31(CONH), 150.70 (CH, C-30, C-50),
149.90 (C, C-10), 146.60 (C, C=NH), 141.54 (C, C-8),
137.53 (C, C-9), 131.39 (CH, C-2), 124.77 (CH, C-20,
C-60), 123.35 (CH, C-5), 123.18 (CH, C-6), 122.45 (CH,
C-4), 112.34 (CH, C-7), 111.96 (C, C-3); HRMS m/z (pos):
265.1092 C15H13N4O (calcd. 265.1089).
N0-((1H-Indol-3-yl)methylene)nicotinohydrazide (18l) White
solid, yield 89 %, mp 150–152 °C; FTIR (KBr) mmax
3433, 3209, 1605, 1551, 1450, 1366, 1250, 1119,
1
795 cm-1; H NMR (CDCl3, 400 MHz): d = 7.24–7.26
123

Med Chem Res
111.26 (CH, C-7), 110.65 (C, C-3), 70.29 (CH2, –OCH2–),
56.14 (CH3, OCH3), 33.24 (CH3, N-CH3); HRMS m/z
(pos): 414.1810 C25H24N3O3 (calcd. 414.1818).
N0-((1-(4-chlorobenzyl)-1H-indol-3-yl)methylene)-2,2,2-tri-
fluoroacetohydrazide (18s) Pale yellow solid, yield 92 %;
1H NMR (CDCl3, 400 MHz): d = 5.11 (s, 2H, CH2),
7.22–7.25 (m, 4H, Ar–H), 7.38–7.40 (m, 2H, Ar–H), 7.50
(s, 1H, Ar–H), 7.53 (d, 1H, J = 7.4 Hz, Ar–H), 7.98 (s, 1H,
azomethine-CH), 8.02 (d, 1H, J = 7.4 Hz, Ar–H), 9.76 (s,
1H, hydrazine-NH); 13C NMR (CDCl3, 101 MHz):
d = 154.65 (CONH), 141.09 (C, C=NH), 136.90 (C, C-10),
135.52 (C, C-8), 132.68 (C, C-9), 132.07 (CH, C-2), 130.00
(CH, C-30, C-50), 129.97 (CH, C-20, C-60), 128.94 (C, C-40),
128.39 (CH, C-6), 123.34 (CH, C-5), 122.94 (CH, C-4),
120.52 (CH, C-7), 114.09 (C, C-CF3, q), 108.62 (C, C-3),
53.04 (CH2, –NCH2–); HRMS m/z (pos): 380.0714 C18-
H14ClF3N3O (calcd. 380.0777).
4-Chloro-N0-((1-methyl-1H-indol-3-yl)methylene)benzohy-
drazide (18p) Pale yellow solid, yield 90 %, mp
275–277 °C; FTIR (KBr) mmax 3194, 1605, 1565, 1381,
1
1327, 748, cm-1; H NMR (CDCl3, 400 MHz): d = 3.87
(s, 3H, CH3), 7.15–7.19 (m, 2H, Ar–H), 7.22–7.25 (m, 2H,
Ar–H), 7.31–7.33 (m, 2H, Ar–H), 7.40 (d, 1H, J = 7.3 Hz,
Ar–H), 7.49 (s, 1H, Ar–H), 7.97 (d, 1H, J = 7.3 Hz, Ar–
H), 8.09 (s, 1H, azomethine-CH), 9.69 (s, 1H, hydrazine-
NH); 13C NMR (DMSO-d6, 101 MHz): d = 161.83
(CONH), 145.19 (C=NH), 138.02 (C, C-40), 136.60 (C,
C-8), 134.58 (C, C-9), 133.18 (C, C-10), 129.86 (CH, C-30,
C-50), 128.95 (CH, C-20, C-60), 125.18 (CH, C-2), 123.18
(C, C-6), 122.58 (CH, C-5), 121.16 (CH, C-4), 111.11 (CH,
C-7), 110.68 (C, C-3), 33.27 (CH3, N-CH3); HRMS m/z
(pos): 312.0913 C17H15ClN3O (calcd. 312.0904).
N0-((1-(4-Chlorobenzyl)-1H-indol-3-yl)methylene)-4-(ben-
zyloxy)-3-methoxybenzohydrazide (18t) Pale yellow
1
solid, yield 89 %; H NMR (CDCl3, 400 MHz): d = 3.69
(s, 3H, OCH3), 5.10 (s, 2H, CH2), 5.16 (s, 2H, CH2),
7.16–7.18 (m, 4H, Ar–H), 7.21–7.24 (m, 5H, Ar–H),
7.27–7.30 (m, 2H, Ar–H), 7.35–7.37 (m, 2H, Ar–H), 7.41
(s, 1H, Ar–H), 7.46 (d, 1H, J = 7.3 Hz, Ar–H), 7.51 (s, 1H,
Ar–H), 7.99 (d, 1H, J = 7.3 Hz, Ar–H), 8.07 (s, 1H,
azomethine-CH), 9.72 (s, 1H, hydrazine-NH); 13C NMR
(DMSO-d6, 101 MHz): d = 162.50 (CONH), 150.85 (C,
C-40), 149.11 (C, C-30), 144.24 (C, C=NH), 137.23 (CH,
C-2), 137.19 (C, C-100), 137.10 (C, C-1¢¢¢), 133.45 (C, C-8),
132.63 (C, C-9), 129.48 (CH, C-2¢¢¢, C-6¢¢¢), 129.09 (CH,
C-300, C-500), 128.93 (CH, C-3¢¢¢, C-5¢¢¢), 128.44 (C, C-4¢¢¢),
128.36 (CH, C-200, C-600), 126.86 (CH, C-400), 125.56 (CH,
C-6), 123.38 (CH, C-5), 122.74 (CH, C-4), 121.30 (CH,
C-60), 121.06 (CH, C-20), 113.00 (CH, C-20), 112.08 (CH,
C-50), 111.59 (C, C-7), 111.08 (C, C-3), 70.29 (CH2,
–OCH2–), 56.14 (CH3, OCH3), 49.05 (CH2, –NCH2–);
HRMS m/z (pos): 524.1720 C31H27ClN3O3 (calcd.
524.1741).
3,4,5-Trimethoxy-N0-((1-methyl-1H-indol-3-yl)methylene)ben-
zohydrazide (18q) Pale yellow solid, yield 95 %, mp
224–226 °C; FTIR (KBr) mmax 3047, 1582, 1504, 1466,
1335, 1126, 748 cm-1 1H NMR (CDCl3, 400 MHz):
;
d = 3.68 (s, 3H, OCH3), 3.73 (s, 3H, OCH3), 3.79 (s, 3H,
OCH3), 3.83 (s, 3H, CH3), 7.27 (s, 1H, Ar–H), 7.30 (s, 1H,
Ar–H), 7.42–7.45 (m, 2H, Ar–H), 7.52 (s, 1H, Ar–H),
7.72–7.79 (m, 2H, Ar–H), 7.99 (s, 1H, azomethine-CH),
9.77 (s, 1H, hydrazine-NH); 13C NMR (DMSO-d6,
101 MHz): d = 162.38 (CONH), 153.12 (C, C-30, C-50),
144.92 (C, C-40), 140.50 (C, C=NH), 138.01 (C, C-8),
134.32 (C, C-9), 129.65 (C, C-10), 125.20 (CH, C-2),
123.17 (CH, C-6), 122.53 (CH, C-5), 121.12 (CH, C-4),
111.14 (CH, C-7), 110.69 (C, C-3), 105.44 (CH, C-20,
C-60), 60.58 (OCH3), 56.53 (CH3, 2OCH3), 33.26 (CH3,
N-CH3); LCMS m/z (pos): 367.1 C20H21N3O4 (calcd.
367.1); HRMS m/z (pos): 367.1542 C20H21N3O4 (calcd.
367.1532).
N0-((1-(4-Chlorobenzyl)-1H-indol-3-yl)methylene)-4-
chlorobenzohydrazide (18u) Pale yellow solid, yield
92 %; 1H NMR (CDCl3, 400 MHz): d = 5.18 (s, 2H,
CH2), 7.21–7.24 (m, 4H, Ar–H), 7.32–7.35 (m, 4H, Ar–H),
7.38 (d, 1H, J = 7.2 Hz, Ar–H), 7.40–7.43 (m, 2H, Ar–H),
7.52 (s, 1H, Ar–H), 8.03 (d, 1H, J = 7.2 Hz, Ar–H), 8.08
(s, 1H, azomethine-CH), 9.65 (s, 1H, hydrazine-NH); 13C
NMR (CDCl3, 101 MHz): d = 166.85 (CONH), 149.60
(C, C=NH), 141.91 (C, C-40), 141.68 (CH, C-2), 141.03 (C,
C-400), 137.77 (C, C-8), 137.69 (C, C-9), 137.61 (CH, C-200,
C-600), 134.37 (C, C-10), 133.70 (C-100), 133.68 (CH, C-20,
C-60), 133.37 (CH, C-300, C-500), 130.37 (CH, C-6), 128.06
(CH, C-30, C-50), 127.57 (CH, C-5), 126.01 (CH, C-4),
116.87 (CH, C-7), 115.29 (C, C-3), 54.14 (CH2, –NCH2–);
HRMS m/z (pos): 422.0935 C23H18Cl2N3O (calcd.
422.0827).
N0-((1-(4-Chlorobenzyl)-1H-indol-3-yl)methylene)acetohy-
1
drazide (18r) Pale yellow solid, yield 92 %; H NMR
(CDCl3, 400 MHz): d = 2.53 (s, 3H, CH3), 5.08 (s, 2H,
CH2), 7.19–7.22 (m, 4H, Ar–H), 7.35–7.37 (m, 2H, Ar–H),
7.43 (d, 1H, J = 7.2 Hz, Ar–H), 7.49 (s, 1H, Ar–H), 7.99
(d, 1H, J = 7.2 Hz, Ar–H), 8.03 (s, 1H, azomethine-CH),
9.69 (s, 1H, hydrazine-NH); 13C NMR (DMSO-d6,
101 MHz): d = 155.04 (CONH), 137.34 (CH, C-2),
136.41 (C, C=NH), 134.62 (C, C-8), 132.94 (C, C-40),
129.13 (C, C-9), 128.96 (C, C-10), 125.97 (CH, C-30, C-50),
123.33 (CH, C-20, C-60), 122.92 (CH, C-6), 121.44 (CH,
C-5), 121.39 (CH, C-4), 112.35 (CH, C-7), 110.79 (C,
C-3), 49.39 (CH2, -N-CH2-), 23.05 (CH3, CH3); HRMS
m/z (pos): 326.1103 C18H17ClN3O (calcd. 326.1060).
123

Med Chem Res
N0-((1-(4-Chlorobenzyl)-1H-indol-3-yl)methylene)-3,4,
5-trimethoxybenzohydrazide (18v) Pale yellow solid,
yield 94 %; 1H NMR (CDCl3, 400 MHz): d = 3.62 (s, 3H,
OCH3), 3.66 (s, 3H, OCH3), 3.70 (s, 3H, OCH3), 5.14 (s, 2H,
CH2), 7.19–7.20 (m, 4H, Ar–H), 7.24 (s, 1H, Ar–H), 7.28 (s,
1H, Ar–H), 7.32–7.34 (m, 2H, Ar–H), 7.42 (d, 1H, J =
7.4 Hz, Ar–H), 7.49 (s, 1H, Ar–H), 8.02 (s, 1H, azomethine-
CH), 8.10 (d, 1H, J = 7.4 Hz, Ar–H), 9.68 (s, 1H, hydrazine-
NH); 13C NMR (CDCl3, 101 MHz): d = 167.73 (CONH),
157.68 (C, C-30, C-50), 149.16 (C, C-40), 145.29 (C=NH),
141.85 (CH, C-2), 140.65 (C, C-8), 137.95 (C, C-9), 136.92
(C, C-100), 134.12 (C, C-400), 133.67 (CH, C-200, C-600), 133.47
(CH, C-300, C-500), 130.45 (C, C-10), 128.06 (CH, C-6),
127.48 (CH, C-5), 126.02 (CH, C-4), 116.98 (CH, C-7),
115.06 (C, C-3), 110.10 (CH, C-20, C-60), 65.38 (2CH3,
OCH3), 61.08 (CH3, OCH3), 54.28 (CH2, NCH2); HRMS
m/z (pos): 478.1518 C26H25ClN3O4 (calcd. 478.1534).
according to the literature procedures (James and Snyder,
1959; Knaack et al., 2001; Roy et al., 2006; Yu et al.,
2008). The condensation of aldehydes 16 with hydrazides
17 was achieved in the presence of acetic acid in refluxing
ethanol. The products 18a–v were obtained in good to
excellent yields. All the synthesized molecules were
characterized by using IR, NMR (1H and 13C) and LC/
HRMS.
We have investigated the cytotoxic effects of the syn-
thesized compounds 18a–v against various cancer cell
lines: prostate (PC3, DU145 and LnCaP), breast (MCF-7
and MDA-MB-231) and pancreas (PaCa2). A tentative
comparison of the structure of compound and its activity
was helpful to understand the structure–activity relation-
ships (SAR). The cytotoxicity results of 18a–v are sum-
marized in Table 1. Some of the compounds decreased cell
viability significantly as established by colorimetric MTT
mitochondrial assay with IC50 values ranging from 100 nM
to 1 mM concentration. In addition, some compounds
exhibited more specificity toward one cell type versus the
others.
Antiproliferative activity of indolyl hydrazide–
hydrazones
Initial screening was carried out for indolyl hydrazide–
hydrazones (18a–l) with free N–H indole ring. Compounds
18a and 18b with alkyl substituents including methyl and
trifluoromethyl exhibited remarkable antiproliferative
activity with IC50 values of 0.97 and 0.99 lM against
PaCa2 and MCF-7, respectively. Further, we synthesized
derivatives (18c–l) of indolyl hydrazide–hydrazones with
substituted phenyl ring. Compound 18c with a phenyl ring
was found to be moderately cytotoxic against the tested
cancer cell lines. Introduction of a chloro substituent at
para position of phenyl ring led to compound 18d with
significantly enhanced activity. Compound 18d
(IC50 = 0.42) was found to be 173-fold selectively cyto-
toxic against MCF-7 cells when compared to 18c.
Replacement of a chloro group in 18d by a methoxy group
resulted in derivative 18e with reduced cytotoxicity against
the tested cell lines. Replacement of the phenyl group in
compound 18c with benzyl group led to compound 18f
with increased cytotoxicity (IC50 = 6.94 lM), when
compared to its homologue 18c (IC50 = 73.22 lM),
against MCF-7 cell line. Introduction of an additional
methoxy group in 18e resulted in compound 18g with
improved cytotoxicity against MCF-7 cell line. Compound
18h bearing 4-hydroxy-3-methoxyphenyl moiety exhibited
moderate activity against MCF-7 and PaCa2 cells. Pro-
tection of hydroxy group as in compound 18h by a benzyl
group gave compound 18i showed improved activity
against all the tested cancer cell lines, except DU-145 and
MDA-MB-231 cells. Also, compound 18i was selectively
cytotoxic to PaCa2 cells with an IC50 of 0.89 lM.
Biology
Cell lines and culture conditions
The human cancer cell lines for screening were cultured in
RPMI 1640 medium containing 5 % fetal bovine serum.
Cells were seeded in 96-well microtiter plate, at an expected
target cell density of 5000–10,000 cells per well, based on
cell growth. Inoculates were allowed to pre-incubate for
12 h at 37 °C for stabilization. Test compounds were eval-
uated at different concentrations ranging from 1 mM to
100 nM. Incubation lasted for 36 h in 5 % CO2 atmosphere.
The anticancer activity was determined for each cell line
using formazan dye (MTT) conversion (assay).
Cleaved PARP1 assay
PC3 cells plated on polylysine-coated coverslips were
treated with compounds 18d and 18j (10 mM) for 48 h.
The cells were lysed, separated on SDS-PAGE, transferred
to PVDF membrane and analyzed using cleaved PARP1
and actin antibodies. Antibodies against PARP1 (sc-56196)
and actin (sc-8432) were purchased from Santa Cruz
Biotechnology (Santa Cruz, CA).
Results and discussion
In the present study, we have synthesized a series of
twenty-two indolyl hydrazide–hydrazone derivatives as
shown in scheme 1. Compounds 15 and 16 were prepared
In view of beneficial cytotoxic effects of 3,4,5-tri-
methoxyphenyl fragment in antimitotic agents known
123

Med Chem Res
Table 1 In vitro cytotoxicity data of indolyl hydrazide–hydrazones
18a–v
R1
R
Cytotoxicity (IC50 lM)a
PC3
DU145
LnCaP
MDA-MB-
231
MCF-
7
PaCa2
18a
18b
18c
18d
18e
18f
18g
18h
18i
H
H
H
H
H
H
H
H
H
CH3
89.65
6.33
[103
122.4
[103
491.6
[103
115.1
[103
[103
155.6
[103
17.96
[103
160.9
[103
51.63
758.5
[103
9.16
999.8
799.9
[103
563.5
[103
300.8
[103
[103
[103
181.9
0.99
0.97
4.06
CF3
C6H5
95.83
15.34
[103
[103
[103
[103
2.54
73.22
236.9
4-ClC6H4
4-CH3OC6H4
CH2C6H5
3,4-(CH3O)2C6H3
4-OH-3-CH3OC6H3
0.42
2.27
[103
6.94
[103
91.18
24.82
58.88
0.89
22.16
21.88
2.34
4-BnO-3-
CH3OC6H3
18j
H
3,4,5-(CH3O)3C6H2
4-Pyridyl
3-Pyridyl
CH3
3.89
[103
[103
80.9
170.1
[103
[103
74.7
5.31
[103
19.53
44.9
[103
[103
718
0.87
[103
535.6
91.3
6.62
[103
[103
40.7
18k
18l
H
H
18m
18n
18o
CH3
CH3
CH3
148.1
166.7
36.9
CF3
150.8
174.1
121.2
40.7
48.7
34.1
88.2
4-BnO-3-
CH3OC6H3
55.5
200.6
74.2
18p
18q
18r
18s
18t
CH3
4-ClC6H4
251.4
315.1
55.4
165.2
44.8
92.8
54.6
76.3
78.3
5.9
264.1
104.9
39.8
37.4
106.2
512.4
40.4
320
CH3
3,4,5-(CH3O)3C6H2
305.2
28.7
4-ClC6H4CH2
4-ClC6H4CH2
4-ClC6H4CH2
CH3
CF3
88.6
416.2
149.3
242.3
18.1
205.3
89.8
179.6
13.6
4-BnO-3-
CH3OC6H3
11.8
18u
18v
a
4-ClC6H4CH2
4-ClC6H4CH2
4-ClC6H4
91.4
59.9
82.9
12.6
45.5
234
25.7
113
52.1
12.4
3,4,5-(CH3O)3C6H2
6.8
40.9
Data obtained for each compound were analyzed in triplicates, and IC50 values given in micromolar concentrations were obtained using a
dose–response curve by nonlinear regression using a curve fitting program, GraphPad Prism 5.0
* Bold values indicate IC50 [ 10 lM
(Negi et al., 2015), compound 18j was synthesized with
significant cytotoxicity when compared to parent com-
pound 18c. Also, compound 18j showed 83-fold selective
cytotoxicity against breast cancer cells (MCF-7;
IC50 = 0.87 lM). Introduction of heteroaryl moieties, e.g.,
4-pyridyl and 3-pyridyl (compounds 18k and 18l), resulted
in complete loss of cytotoxicity against all the tested cancer
cell lines, except in LnCaP (compound 18l).
interested to study the effect of this substituent on nitrogen
atom of indole ring. Therefore, we synthesized another
series of indolyl hydrazide–hydrazones possessing N-
methyl indole (compounds 18m–q) and N-(4-chloroben-
zyl)indole (compounds 18r–v). The cytotoxic activities of
compounds 18m–q were found to be moderate. Hydrazide–
hydrazones (compounds 18r–v) with N-(4-chloroben-
zyl)indole moiety demonstrated low cytotoxicity, except
compounds 18t and 18v which displayed selective cyto-
toxicity against LnCaP cancer cell line with IC50 values of
5.9 and 6.8 lM, respectively. Thus, it demonstrates a
Based on our initial anticancer activity data for indolyl
hydrazide–hydrazones and importance of 4-chlorobenzyl
group in indibulin (9) and oncrasin-1 (10), we were
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Med Chem Res
and position of the substituents on indole and hydrazide
moieties is in progress. Also, compounds N0-((1H-indol-3-
yl)methylene)acetohydrazide 17a, N0-((1H-indol-3-yl)me-
thylene)-4-chlorobenzohydrazide 17d and N0-((1H-indol-3-
yl)methylene)-4-(benzyloxy)-3-methoxybenzohydrazide 17i
are proved to be potential leads for further cytotoxic activity
studies.
Fig. 3 Exposure of PC3 cells to 18d and 18j for cleavage of PARP1
level
Acknowledgments We are grateful to CSIR and UGC, New Delhi,
for financial support to perform the research work. This work was
performed during the association of Swapna Sundaree and Buchi
Reddy Vaddula with Birla Institute of Technology and Science,
Pilani, India.
diverse mechanism of action for this library of compounds
18a–v.
Anticancer screening results showed that compounds
18a–v affect the cell proliferation (Table 1) at concentra-
tions ranging from 100 nM to 1 mM. We observed that
the newly synthesized indolyl hydrazide–hydrazones 18
exhibited improved cytotoxicity when compared to repor-
ted bis(indolyl)hydrazide–hydrazones (Kumar et al.,
2012c). The IC50 values were calculated based on the
MTT assay. Most of the derivatives showed IC50 values
\100 lM. At present, a molecular target responsible for
the observed cytotoxicity of this series of N0-((1-(substi-
tuted)-1H-indol-3-yl)methylene)hydrazides has not been
identified and a reasonable explanation of SAR described
above is not yet possible. These results suggest that the
antiproliferative activity depends both on the substitution
on indole nitrogen atom and hydrazide moiety.
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