Expeditious synthesis, antileishmanial and antioxidant activities of novel 3-substituted-4-hydroxycoumarin derivatives

Article abstract of DOI:10.1016/j.cclet.2015.10.028

A series of novel 3-substituted-4-hydroxycoumarin derivatives 6(a–l) were synthesized in high yield using one-pot three component coupling reaction catalyzed by ceric ammonium nitrate. These compounds were evaluated for antileishmanial activity against Leishmania donovani promastigotes and antioxidant activity (DPPH-radical scavenging activity). Two compounds, 6h (IC₅₀ = 9.90 μmol/L) and 6i (IC₅₀ = 6.90 μmol/L) displayed potent antileishmanial activity when compared with standard antileishmanial agents pentamidine (IC₅₀ = 16.15 μmol/L) and miltefosine (IC₅₀ = 12.50 μmol/L). Three compounds, 6c (IC₅₀ = 10.79 μmol/L), 6h (IC₅₀ = 10.60 μmol/L), and 6i (IC₅₀ = 10.73 μmol/L) showed significant antioxidant activity favorably with the antioxidant standards butylated hydroxy toluene (IC₅₀ = 16.47 μmol/L) and ascorbic acid (IC₅₀ = 12.69 μmol/L). A molecular docking study of compounds 6(a–l) suggested a possible mode of binding with the Adenine phosphoribosyltransferase enzyme of L. donovani. ADME properties were predicted in silico and support the potential of 6(a–l) to show favorable drug-like properties.

Full text of DOI:10.1016/j.cclet.2015.10.028

G Model
CCLET 3479 1–9
Chinese Chemical Letters xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Chinese Chemical Letters
journal homepage: www.elsevier.com/locate/cclet
1
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Original article
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Expeditious synthesis, antileishmanial and antioxidant activities of
novel 3-substituted-4-hydroxycoumarin derivatives
a
a
b
Q1 Zahid Zaheer a, , Firoz A. Kalam Khan , Jaiprakash N. Sangshetti , Rajendra H. Patil
*
5
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a Dr. Rafiq Zakaria Campus, Y.B. Chavan College of Pharmacy, Aurangabad 431001, MS, India
b Department of Biotechnology, Savitribai Phule Pune University, Pune 411007, MS, India
A R T I C L E I N F O
A B S T R A C T
Article history:
A series of novel 3-substituted-4-hydroxycoumarin derivatives 6(a–l) were synthesized in high yield
using one-pot three component coupling reaction catalyzed by ceric ammonium nitrate. These
compounds were evaluated for antileishmanial activity against Leishmania donovani promastigotes and
Received 10 April 2015
Received in revised form 31 July 2015
Accepted 30 October 2015
Available online xxx
antioxidant activity (DPPH-radical scavenging activity). Two compounds, 6h (IC50 = 9.90
(IC50 = 6.90 mol/L) displayed potent antileishmanial activity when compared with standard
antileishmanial agents pentamidine (IC50 = 16.15 mol/L) and miltefosine (IC50 = 12.50 mol/L). Three
compounds, 6c (IC50 = 10.79 mol/L), 6h (IC50 = 10.60 mol/L), and 6i (IC50 = 10.73 mol/L) showed
significant antioxidant activity favorably with the antioxidant standards butylated hydroxy toluene
(IC50 = 16.47 mol/L) and ascorbic acid (IC50 = 12.69 mol/L). A molecular docking study of compounds
mmol/L) and 6i
m
m
m
Keywords:
m
m
m
4-Hydroxycoumarin
Ceric ammonium nitrate
Antileishmanial activity
Antioxidant activity
Molecular docking study
ADME properties
m
m
6(a–l) suggested a possible mode of binding with the Adenine phosphoribosyltransferase enzyme of L.
donovani. ADME properties were predicted in silico and support the potential of 6(a–l) to show favorable
drug-like properties.
ß 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.
Published by Elsevier B.V. All rights reserved.
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1. Introduction
leishmaniasis-AIDS co-infections in some countries [5]. There- 28
fore, there is an urgent need for development of new, 29
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Leishmaniasis is a family of parasitic diseases caused by
infection of macrophages by obligate intracellular parasites of
genus Leishmania. It is a major health problem worldwide and
over 20 million people in 88 countries have one of the various
forms of the disease [1]. Parasites transmissions occur by way of
female sandflies via anthroponotic or zoonotic cycles [2].
Leishmaniasis is classified as cutaneous, visceral (Kala Azar),
mucosal or mucocutaneous and diffused cutaneous on the basis
of the evaluation of the patients and parasite [3]. Visceral
leishmaniasis (VL or Kala-azar) is the most devastating form and
arises from invasion of the reticuloendothelial system (spleen,
liver and bone marrow) by the haemo flagellate protozoan
parasite Leishmania donovani (L. donovani) [4]. While several drug
treatment strategies are known, these drugs have the drawbacks
of high expense, requirement of prolonged treatment, high
toxicity to liver and heart, and the development of clinical
inexpensive, effective and safe drugs having potential antileish- 30
manial activity. Oxidative and free-radical-mediated processes 31
reactions seem to play an important role in the progression of 32
various diseases, including cancer and coronary heart disease [6]. 33
Radical damage has also been implicated in neurodegeneration 34
occurring both through normal aging processes and in diseases 35
such as Alzheimer’s disease [7]. Thus, there is also a need for 36
development of safe and effective antioxidants to prevent 37
radical-mediated damage.
38
The coumarins are an important heterocyclic core structure 39
that is present in numerous natural products with wide range of 40
biological activities [8]. Flavokavain B, for example, is a natural 41
coumarin derivative that is effective against the promastigote form 42
of L. donovani parasites [9]. Also, many coumarins known to have 43
antioxidant effect [10]. A number of other heterocyclic core 44
structures, such as, indoles, quinolines, and furans, are also present 45
in various biologically active natural products and drugs, including 46
those with potent antileishmanial activity [11–13]. Pleiocarpine 47
(an indole alkaloid) [14], cryptolepine (a quinoline alkaloid) [15], 48
and brasanquinone (a furan derivative) [16] are specific examples 49
of natural antileishmanial agents with activity against L. donovani 50
resistance after
a few weeks of treatment. These issues
contribute to poor treatment outcomes and to an increase in
*
Corresponding author.
parasites (Fig. 1).
51
E-mail address: zahidzresearch@gmail.com (Z. Zaheer).
http://dx.doi.org/10.1016/j.cclet.2015.10.028
1001-8417/ß 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.
Please cite this article in press as: Z. Zaheer, et al., Expeditious synthesis, antileishmanial and antioxidant activities of novel 3-
substituted-4-hydroxycoumarin derivatives, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.10.028

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Z. Zaheer et al. / Chinese Chemical Letters xxx (2015) xxx–xxx
Fig. 1. Structure of some natural antileishmanial compounds active against L. donovani promastigotes and model structure of titled compounds 6(a–l).
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Natural products constitute a large portion of marketed drugs,
particularly in the area of infectious diseases, and often show
remarkable potency, selectivity and drug-like properties [17].
However, the numbers of natural products are limited; hence
incorporating either different natural products or drug fragments
may provide millions of combinations which will be enriched in
biological activity and less toxicity. Taking into account all of the
aforementioned, and as a part of our ongoing effort towards
identifying novel bioactive compounds [18,19], we decided to
explore ways of combining the coumarin nucleus with fragments
present in other antileishmanial agents, heterocycles such as
indoles, quinolines, and furans. We have synthesized a novel series
of 3-substituted-4-hydroxycoumarin hybrids 6(a–l) and evaluated
them as antileishmanial agents against L. donovani (Fig. 1).
Coumarin such as isopimpinellin is reported to act as antileish-
manial agents through the inhibition of enzyme Adenine phosphor-
ibosyltransferase enzyme [20]. Accordingly, we opted to dock our
synthesized compounds against the Adenine phosphoribosyltrans-
ferase of L. donovani to understand features of the molecules that
may be responsible for their antileishmanial activity. Because
coumarins have also found use as antioxidants, the synthesized
compounds were also evaluated for antioxidant activity using
DPPH-radical scavenging method. We have also used in silico
method to predict ADME properties to suggest the suitability of
any of the new compounds for further drug development,
particularly with respect to activity.
2.1.1. General procedure for synthesis of 3-substituted-4-
hydroxycoumarin derivatives 6(a–l)
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A mixture of 4-hydroxycoumarin 3 (1.0 mmol), heterocyclic
aldehydes 4 (1.0 mmol) and secondary amines 5 (1.0 mmol) was
stirred at room temperature (25–30 8C) in ethanol (15 mL) in the
presence of catalytic amount of ceric ammonium nitrate (10 mol%)
for 15–20 min. After completion of the reaction as monitored by
TLC analysis, the reaction mixture was poured into water. The solid
product formed was filtered, dried and recrystallized using
ethanol.
2.2. Biological evaluations
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2.2.1. In vitro antileishmanial activity
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The assay for in vitro antileishmanial activity on culture of L.
donovani promastigotes (NHOM/IN/80/DD8) was carried out in
96-well tissue culture plates using reported procedure [21]. The
promastigotes culture was maintained at 22 8C in modified RPMI
1640 pH 7.4 (without phenol red) with 10% FCS medium. Drug
dilutions were prepared in DMSO and appropriate concentration
of each drug was used in triplicate. Plates were incubated at 22 8C
for 72 h and evaluated using modified MTT assay, where the
conversion of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazo-
lium bromide (MTT) to formazan by mitochondrial enzymes
served as an indicator of cell viability and the amount of
formazan produced was directly proportional to the number of
metabolically active cells. Accordingly, absorbance at 492 nm
represented the number of live cells. The concentration that
decreased cell growth by 50% (IC50) was computed from growth
inhibition curve. Pentamidine and miltefosine were used as
standard drugs.
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2. Experimental
2.1. Chemistry
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All reagents and solvents used were purchased from the Sigma
and Avra synthesis. The completion of reaction was checked by
ascending thin layer chromatography (TLC) on silica gel-G (Merck)
coated aluminum plates, visualized by iodine vapor. Infrared (IR)
spectra were recorded for the compounds on JASCO FTIR (PS 4000)
using KBr pallet. 1H NMR and 13C NMR spectra were recorded using
Brucker Avance II. Multiplicities are recorded as s (singlet), d
(doublet), t (triplet), q (quartet), and m (multiplet). Mass spectra
were taken with Micromass-QUATTRO-II of WATER mass spec-
trometer. Elemental analyses (C, H, and N) were undertaken with a
Shimadzu’s FLASHEA112 analyzer and all analyses were consistent
with theoretical values (within ꢀ0.4%), unless indicated.
2.2.2. Antioxidant activity (DPPH radical scavenging method)
The hydrogen atom or electron donation ability of the
compounds was measured from the bleaching of the purple
colored methanol solution of 1,1-diphenyl-1-picrylhydrazyl
(DPPH) [22]. The spectrophotometric assay uses the stable radical
DPPH as a reagent. 1 mL of various concentrations of the test
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compounds (5, 10, 25, 50 and 100
mg/mL) in methanol was added
to 4 mL of 0.004% (w/v) methanol solution of DPPH. After a 30 min
incubation period at room temperature, the absorbance was read
against blank at 517 nm. The natural antioxidant ascorbic acid and
synthetic antioxidant BHT (butylated hydroxy toluene) were used
Please cite this article in press as: Z. Zaheer, et al., Expeditious synthesis, antileishmanial and antioxidant activities of novel 3-
substituted-4-hydroxycoumarin derivatives, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.10.028

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Z. Zaheer et al. / Chinese Chemical Letters xxx (2015) xxx–xxx
3
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as standards. The percent of inhibition (I%) of free radical
production from DPPH was calculated by the following equation.
and identifying the geometric voids as well as scaling the void for 164
its hydrophobic characteristics using V Life MDS analyze tool. 165
Hence all the cavities that are present in Adenine phosphoribosyl- 166
transferase protein were identified and ranked based on their size 167
and hydrophobic surface area. Considering the dimensions and 168
hydrophobic surface area, ranked-1 cavity was chosen for docking 169
À
ꢀ
Á
ꢁ
AcontrolꢁAsample
% of scavenging ¼
ꢂ100
Ablank
1356
137
138
where Acontrol is the absorbance of the control reaction (containing
all reagents except the test compound) and Asample is the
absorbance of the test compound.
study.
170
2.3.2. ADME prediction
171
A computational study of synthesized compounds 6(a–l) was 172
performed for prediction of ADME properties. In this study, we 173
calculated molecular volume (MV), molecular weight (MW), 174
logarithm of partition coefficient (miLog P), number of hydrogen 175
bond acceptors (n-ON), number of hydrogen bonds donors (n- 176
OHNH), topological polar surface area (TPSA), number of rotatable 177
bonds (n-ROTB) and Lipinski’s rule of five [26] using Molinspiration 178
online property calculation toolkit [27]. Absorption (% ABS) was 179
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2.2.3. In vitro cytotoxicity study
Cytotoxic study of the synthesized compounds on HeLa cell line
was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetra-
zolium bromide (MTT) method [23]. In brief, exponentially
growing Hela cells (1 ꢂ 104 cells/well) were seeded in a 96-well
culture plate and incubated at 37 8C in a 5% CO2 incubator for 24 h.
The drugs were dissolved in 0.1% DMSO and then diluted with the
medium. The cells were then exposed to different concentrations
calculated by: %ABS = 109 ꢁ (0.345 ꢂ TPSA) [28].
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of drug (0–10
mg/mL) and incubated for 72 h. The cells in the
control wells received medium containing the same volume of
DMSO (0.1%). After incubation, 5 mg/mL of MTT reagent was added
in each well and further incubated for additional 4 h. The formazan
produced by the viable cells was stabilized by addition of 0.1 mL
DMSO. The absorbance of each well at 550 nm was determined by a
microplate spectrophotometer. The cells were also seen under the
microscope (Ziess, Germany) at 10ꢂ magnification.
3. Results and discussion
3.1. Chemistry
The starting material 4-hydroxycoumarin (3) was synthesized 183
using 2-hydroxyacetophenone (1) and diethyl carbonate (2) as per 184
reported method [29]. Then a one-pot three component reaction 185
[30] was used to synthesize 3-substituted-4-hydroxycoumarin 186
derivatives 6(a–l) as shown in Scheme 1. These products were 187
obtained via the reaction of 4-hydroxycoumarin (3) with various 188
heterocyclic aldehydes (4) and secondary amines (5) in ethanol at 189
room temperature, using ceric ammonium nitrate (CAN, 10 mol%) 190
as catalyst, through a Mannich type reaction mechanism. CAN has 191
received considerable attention as an relatively inexpensive, non- 192
toxic, water soluble and easily handled catalyst for the construc- 193
tion of carbon-carbon and carbon-heteroatom bonds [31]. The 194
formation of the desired compound indicates that CAN play an 195
important role for the rapid formation of the imine intermediate. 196
155
2.3. Computational studies
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2.3.1. Docking study
Docking study of synthesized compounds 6(a–l) was performed
using VLife MDS 4.3 package [24]. With this purpose, crystal
structure of Adenine phosphoribosyltransferase of L. donovani (PDB
ID: 1QB8) [25] was obtained from the Protein Data Bank in order to
prepare protein for docking study. The cavities in the receptor were
mapped to assign an appropriate active site. The basic features
used to map the cavities were the surface mapping of the protein
Scheme 1. Synthetic protocol for titled compounds 6(a–l).
Please cite this article in press as: Z. Zaheer, et al., Expeditious synthesis, antileishmanial and antioxidant activities of novel 3-
substituted-4-hydroxycoumarin derivatives, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.10.028

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Table 1
Physical data for 3-substituted-4-hydroxycoumarin derivatives 6(a–l).
Entry
Structure
Molecular formula
C22H20N2O4
Reaction time (min)
15
Yield (%)
98
Rf value
Mp (oC)
6a
0.48
180–182
6b
6c
6d
C23H22N2O3
C23H23N3O3
C23H19ClN2O4
15
20
15
96
92
95
0.58
0.54
0.64
166–168
158–160
142–144
6e
C24H21ClN2O3
20
90
0.81
130–132
6f
C24H22ClN3O3
15
93
0.67
170–172
6g
C24H21ClN2O4
20
95
0.69
198–200
6h
C25H23ClN2O3
20
91
0.86
134–136
Please cite this article in press as: Z. Zaheer, et al., Expeditious synthesis, antileishmanial and antioxidant activities of novel 3-
substituted-4-hydroxycoumarin derivatives, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.10.028

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Z. Zaheer et al. / Chinese Chemical Letters xxx (2015) xxx–xxx
5
Table 1 (Continued )
Entry
Structure
Molecular formula
C25H24ClN3O3
Reaction time (min)
15
Yield (%)
98
Rf value
Mp (oC)
6i
0.73
156–158
6j
C18H17NO5
C19H19NO4
C19H20N2O4
20
20
15
90
92
90
0.37
0.53
0.45
110–114
6k
94–96
6l
122–124
Solvent of recrystallization was ethanol; eluants used in TLC were ethyl acetate/n-hexane (9:1) for all compounds.
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The catalyst may induce 4-hydroxy coumarin to act as the Mannich
donor for the very fast formation of 3-substituted-4-hydroxycou-
marin derivatives. The rapid imine generation and subsequent ‘C–
C’ bond formation within a very short time catalyzed by CAN are
the attractive features of this protocol.
any system like chromatography. Melting points were deter- 230
mined in open capillary tubes and are uncorrected. The physical 231
data for the compounds 6(a–l) are presented in Table 1, with 232
characterization by IR, 1H NMR, 13C NMR, Mass and elemental 233
spectroscopic data, with results in agreement with the proposed 234
structures (Supporting information). This type of Mannish 235
adducts are prone to retro-Mannich decomposition to lose the 236
amine and form a Michael acceptor [32]. In order to check the 237
thermal stability of the synthesized compounds 6(a–l), we 238
subjected compound 6i for stress stability testing as per ICHQ1A 239
2.1.2 guidelines [33]. Compound 6i was subjected to forced 240
degradation study at temperatures 105 8C and 157 8C for 1 month. 241
After 1 month of study, compound 6i was again characterized for 242
physical and for spectroscopic data. The data suggested that 243
compound 6i was stable even after 1 month of force degradation 244
To optimize the reaction conditions, we studied a model
reaction of 4-hydroxycoumarin (1.0 mmol), indole-3-carbalde-
hyde (1.0 mmol) and morpholine (1.0 mmol) in ethanol to
synthesize compound 6a. A wide variety of catalysts were
surveyed, including oxalic acid, boric acid, sulphamic acid, p-
toluenesulphonic acid, ZnO, ZnCl2, and ceric ammonium nitrate
(CAN), all at 30 mol%. CAN as the catalyst gave the best results in
terms of yield (98%) and reaction time (15 min) (Table S1 in
Supporting information). Solvent effects were then studied, using
water, toluene, dimethylsulfoxide, ethanol, and dichloromethane.
Ethanol was found to be best among the studied solvents (Table S2
in Supporting information). For the optimization of catalyst
loading, we used CAN as catalyst at 0, 5, 10, 15, 20, and 30 mol%.
The results (Table S3 in Supporting information) revealed that
10 mol% CAN is fully sufficient for obtaining a high yield. This low
catalyst loading contributes to the efficiency and simplicity of the
process.
After optimization of the model reaction, the scope of the
transformation was then studied. We further expanded the series
and synthesized 12 novel derivatives of 3-substituted-4-hydro-
xycoumarins 6(a–l) by reacting 4-hydroxycoumarin 3, heterocy-
clic aldehydes 4, and secondary amines 5 in ethanol using CAN
(10 mol%) as catalyst at room temperature (25–30 8C). The reaction
preceded smoothly under mild reaction conditions. The isolated
yield of synthesized compounds was in the range of 90–98% and
reactions were completed in 15–20 min (monitored by TLC). The
work-up of these reactions was simple, required only a filtration.
The compounds were thus obtained in pure form without aids of
study (stress study).
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3.2. Biological evaluations
3.2.1. In vitro antileishmanial activity
The title compounds 6(a–l) were tested in vitro for their 248
antileishmanial activity against a culture of L. donovani promas- 249
tigotes and data obtained is depicted in Table 2. Most of the 250
synthesized compounds showed promising antileishmanial activ- 251
ity. Compounds 6a, 6c, 6h, 6i, and 6j (IC50 values = 6.90– 252
16.48
to that of standard drugs. Compounds 6b, 6g, 6k, and 6l were less 254
potent in this assay (IC50 values = 22.01–38.50 mol/L). The 255
mmol/L) were most promising, with activity comparable 253
m
compounds 6d, 6e, and 6f (R = 2-chloroquinolinyl) were found 256
to inactive against culture of L. donovani promastigotes. The 257
compounds 6h (IC50 = 9.90
were more potent than standard drugs pentamidine ((IC50 259
= 16.15 mol/L) and miltefosine (IC50 = 12.5 mol/L). 260
mmol/L) and 6i (IC50 = 6.90 mmol/L) 258
m
m
Please cite this article in press as: Z. Zaheer, et al., Expeditious synthesis, antileishmanial and antioxidant activities of novel 3-
substituted-4-hydroxycoumarin derivatives, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.10.028

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Table 2
Biological evaluation and molecular docking statistics of synthesized compounds 6(a–l).
Entry
L. donovani (IC50
Mean ꢀ SEM
m
mol/L)
Antioxidant (IC50
m
mol/L)
Docking result against L. donovani (Adenine phosphoribosyltransferase)
Mean ꢀ SEM
Binding energy (kcal/mol)
Hydrogen bonding
6a
16.48 ꢀ 0.68
38.50 ꢀ 1.25
13.11 ꢀ 0.74
124.40 ꢀ 2.55
136.90 ꢀ 3.48
417.81 ꢀ 5.14
22.01 ꢀ 0.43
9.90 ꢀ 0.33
6.90 ꢀ 0.12
14.67 ꢀ 0.98
33.45 ꢀ 1.33
28.23 ꢀ 0.21
16.15 ꢀ 0.85
12.50 ꢀ 0.90
ND
28.22 ꢀ 0.60
15.23 ꢀ 0.64
10.79 ꢀ 0.69
14.52 ꢀ 0.14
15.46 ꢀ 0.26
22.00 ꢀ 0.35
15.63 ꢀ 0.57
10.60 ꢀ 0.48
10.73 ꢀ 0.61
15.58 ꢀ 0.83
15.47 ꢀ 0.49
25.14 ꢀ 0.53
ND
ꢁ52.88
ꢁ50.88
ꢁ55.01
ꢁ44.01
ꢁ48.12
ꢁ43.25
ꢁ57.64
ꢁ61.81
ꢁ65.40
ꢁ56.71
ꢁ50.87
ꢁ52.92
ND
1 (ARG37–OH)
6b
1(ARG37–OH)
6c
1 (ARG37–O5C)
6d
1 (ARG37–O of coumarin)
1 (GLU120–O of coumarin)
6e
6f
1 (LYS186–O of coumarin)
*
6g
*
6h
6i
2 (ARG37–OH; ARG37–O of coumarin)
*
6j
6k
1 (ARG37–O of coumarin)
6l
1 (ARG37–O of coumarin)
STD 1
STD 2
STD 3
STD 4
ND
ND
ND
ND
ND
ND
16.47 ꢀ 0.18
12.47 ꢀ 0.85
ND
ND
ND
IC50 represents the mean values of three replicates; standard errors were all within 10% of the mean; STD 1: pentamidine; STD 2: miltefosine; STD 3: butylated hydroxy
toluene; STD 4: ascorbic acid.
*
Donates no hydrogen bond interaction of ligands with protein; ND: Not done.
261
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273
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276
277
278
279
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To establish structure-activity relationship (SAR) in the series,
we divided the synthesized compounds into three classes, the
indole class 6(a–c), quinoline class 6(d–i), and furan class 6(j–l).
The activity mainly depends upon the presence of the different
heterocycles and secondary amines at the 3rd position of the 4-
hydroxycoumarin scaffold. The indole class showed promising
which can stabilize an adjacent radical [34]. The higher radical
scavenging activity for compounds 6g, 6h, and 6i (R = 2-chloro-8-
methylquinol-3-yl) can also be explained by noting that the
methyl group also helps stabilize an adjacent unpaired electron
[35].
303
304
305
306
307
activity, particularly when
a
4-methylpiperazine group was
3.2.3. In vitro cytotoxicity study
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313
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315
present at 3rd position of 4-hydroxycoumarin (6c). From the
quinolines 6(d–i), a 2-chloroquinolinyl group at 3rd position of 4-
hydroxycoumarin (compounds 6d, 6e, and 6f) provides much
lower activity towards L. donovani promastigote cultures. Replace-
ment of the 2-chloroquinolinyl group with 2-chloro-8-methylqui-
nolinyl (compounds 6g, 6h, and 6i) increased the activity by 5–70
folds. Adding a methyl group at the 8th position of quinoline
further enhanced activity. Substitution of 2-chloro-8-methylqui-
nolinyl in combination with a 4-methylpiperazinyl group at 3rd
position of the 4-hydroxycoumarin core led to the most potent
compound of the series (6i). From the furan class 6(j–l), the furanyl
nucleus in combination with morpholine group (compound 6j) at
3rd position of the 4-hydroxycoumarin gave the good antileish-
manial activity.
To test for cytotoxicity of titled compounds, we exposed HeLa
cells to the test compounds 6(a–l) and observed the cell
morphology. None of the synthesized compounds showed
cytotoxicity towards the HeLa cell line up to highest tested
concentrations, suggesting the potential for low intrinsic toxicity
toward human cells. The lack of cytotoxicity effects of compound
6i on the HeLa cell line is shown in Fig. 2.
3.3. Computational studies
316
3.3.1. Docking study
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
A molecular docking study of the synthesized compounds 6(a–
l) was performed against the Adenine phosphoribosyltransferase
enzyme of L. donovani to understand the possible binding mode for
the test compounds. Adenine phosphoribosyltransferase, a Leish-
mania enzyme, is responsible for pyrophosphorolysis in sequenc-
ing and amplification of nucleic acids in protein synthesis [36] and
is a potential target for chemotherapeutic intervention. The
docking calculations and hydrogen bonds interactions noted are
shown in Table 2. The modeling results for compounds 6(a–l)
correlate in general with the observed antileishmanial activity. The
docking results indicated that the 3-substituted-4-hydroxycou-
marin core of the compounds 6(a–l) is held in the active site by a
combination of various hydrophobic and van der Waals interac-
tions with the enzyme. Major hydrophobic interactions occur
between the 3-substituted-4-hydroxycoumarin core and with the
active side chain of VAL39, PRO40, GLU120, TYR121, LYS122,
GLU123, ALA124, ALA150, THR151, and LEU181. The various
methylene groups (–CH2–) form strong hydrophobic interactions
with active site hydrophobic residues. H-bonding groups in the
coumarin core (OH, C55O, and –O–) formed hydrogen bonds with
ARG37, GLU120, and LYS186, thus suggesting that the central core
is important for inhibiting of Adenine phosphoribosyltransferase
enzyme of L. donovani.
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
3.2.2. Antioxidant activity (DPPH radical scavenging method)
Antioxidant activity was assessed in vitro by using the DPPH
radical scavenging assay method. The DPPH has an odd electron so
it can accept an electron or hydrogen free radical. In the presence of
antioxidant, this odd electron becomes paired due to H transfer
from antioxidant and hence DPPH absorbance decreases. All the
synthesized compounds 6(a–l) showed interesting antioxidant
activity (IC50 = 10.60–28.22
mmol/L) when compared to the
standards (Table 2). The common antioxidant activity in the series
is likely due to the presence of electron-releasing hydroxy at the
4th position of coumarin nucleus. All the compounds except 6a
(IC50 = 28.22
= 25.14 mol/L) were more active than standard butylated
hydroxy toluene (IC50 = 16.47 mol/L). The most potent antiox-
idants in the series were 6c (IC50 = 10.79 mol/L), 6h
(IC50 = 10.60 mol/L), and 6i (IC50 = 10.73 mol/L), comparing
favorably to the standards BHT (IC50 = 16.47 mol/L) and ascorbic
acid (IC50 = 12.69 mol/L). Among the synthesized compounds,
mmol/L), 6f (IC50 = 22.00 mmol/L), and 6l (IC50
m
m
m
m
m
m
m
quinoline series 6(d–i) had shown better activity than indole 6(a–
c) and furan 6(j–l) series. The higher activity for quinolines may
arise due to the presence of an imine unit in the quinoline moiety,
The most active antileishmanial compound 6i showed the
lowest binding energy in the docking study, -65.40 kcal/mol. The
Please cite this article in press as: Z. Zaheer, et al., Expeditious synthesis, antileishmanial and antioxidant activities of novel 3-
substituted-4-hydroxycoumarin derivatives, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.10.028

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CCLET 3479 1–9
Z. Zaheer et al. / Chinese Chemical Letters xxx (2015) xxx–xxx
7
Fig. 2. Cytotoxic study of compound 6i.
Table 3
Pharmacokinetic parameters important for good oral bioavailability of synthesized compounds 6(a–l).
Entry
% ABS
TPSA (A2)
n-ROTB
MV
MW
miLog P
n-ON acceptors
n-OHNH donors
Lipinski’s violations
Rule
6a
6b
6c
6d
6e
6f
–
–
–
3
3
3
3
3
3
3
3
3
3
3
3
–
ꢃ500
ꢃ5
ꢃ10
6
ꢃ5
2
ꢃ1
0
81.84
85.03
83.91
82.95
86.03
84.91
82.84
86.02
84.91
82.76
85.95
84.83
78.70
69.46
72.70
75.80
66.56
69.80
75.80
66.59
69.80
76.05
66.81
70.05
331.95
339.76
352.31
356.34
364.16
376.70
372.90
380.72
393.26
284.54
292.36
304.90
376.41
3.22
4.29
3.27
4.03
4.89
4.07
4.43
4.79
4.47
2.02
3.08
2.07
374.44
389.45
422.86
420.89
435.91
436.89
434.92
449.93
327.33
325.36
340.37
5
2
0
6
2
0
6
1
0
5
1
0
6
1
0
6g
6h
6i
6
1
0
5
1
0
6
1
0
6j
6
1
0
6k
6l
5
1
0
6
1
0
% ABS: percentage absorption, TPSA: topological polar surface area, n-ROTB: number of rotatable bonds, MV: molecular volume, MW: molecular weight, miLog P: logarithm of
partition coefficient of compound between n-octanol and water, n-ON acceptors: number of hydrogen bond acceptors, n-OHNH donors: number of hydrogen bonds donors.
343
344
345
346
347
348
349
350
351
interactions of compound 6i with enzyme are shown in Fig. 3. The
3.3.2. ADME prediction
352
˚
amino acid ARG37 (2.589 A) forms hydrogen bonds with the –OH
Issues of druggability are also important considerations. As 353
shown in Table 3, all of the synthesized compounds exhibited a 354
good % ABS (81.84–86.03%). Furthermore, none of the compounds 355
violated Lipinski’s rule of five, suggesting promise for development 356
as good drug candidates. A molecule likely to be developed as an 357
orally active drug candidate should show no more than one 358
violation of the following four criteria: log P (octanol–water 359
partition coefficient) ꢃ 5, molecular weight ꢃ 500, number of 360
hydrogen bond acceptors ꢃ 10 and number of hydrogen bond 361
donors ꢃ 5 [37]. All the synthesized compounds 6(a–l) followed 362
the criteria for orally active drug and therefore, these compounds 363
and –O– groups of the 4-hydroxycoumarin nucleus of compound
6i. Also, both methyl groups of compound 6i fit well into the active
site, forming hydrophobic interactions with the THR151 amino
residue. This observation suggests that a 2-chloro-8-methylqui-
nolinyl moiety in combination with 4-methylpiperazinyl group at
3rd position of 4-hydroxycoumarin ring has optimal interactions
with the Adenine phosphoribosyltransferase enzyme.
can be further developed as oral drug candidates.
364
4. Conclusion
365
In conclusion, we have successfully designed compounds 6(a–l) 366
based on a natural product-inspired scaffolds. Also, we have 367
developed an expeditious one-pot three component method for 368
the synthesis of novel 3-substituted-4-hydroxycoumarin deriva- 369
tives 6(a–l) from 4-hydroxycoumarin, heterocyclic aldehydes and 370
secondary amines in ethanol at room temperature using CAN 371
(10 mol%) as catalyst. The advantages of this method include mild 372
reaction conditions, simplicity, short reaction time, easy work up, 373
and high yields. Several compounds have significant antileishma- 374
nial activity against L. donovani promastigotes and many also have 375
antioxidant activity. The compounds 6h (IC50 = 9.90
mmol/L) and 376
6i (IC50 = 6.90 mol/L) from the quinoline class were the most 377
m
active antileishmanial agents. The compound 6i with 2-chloro-8- 378
methylquinolinyl in combination with 4-methylpiperazinyl group 379
at 3rd position of 4-hydroxycoumarin was most potent antileish- 380
manial agent in the series. Three compounds 6c (IC50 = 10.79 m- 381
Fig. 3. Docking study of compound 6i with Adenine phosphoribosyltransferase of L.
donovani (PDB ID: 1QB8). Ligands are shown in green color. (For interpretation of
the references to color in this figure legend, the reader is referred to the web version
of this article.)
Please cite this article in press as: Z. Zaheer, et al., Expeditious synthesis, antileishmanial and antioxidant activities of novel 3-
substituted-4-hydroxycoumarin derivatives, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.10.028

G Model
CCLET 3479 1–9
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Z. Zaheer et al. / Chinese Chemical Letters xxx (2015) xxx–xxx
DB766 analogs modified in the linker region and bis-arylimidamide structure–
activity relationships, Bioorg. Med. Chem. Lett. 22 (2012) 6806–6810.
[14] V. Mun˜oz, C. Morretti, M. Sauvain, et al., Isolation of bis-indole alkaloids with
antileishmanial and antibacterial activities from Perschiera van heurkii (syn.
Tabernaemontana van heurkii), Planta Med. 60 (1994) 455–459.
[15] (a) A.G. Tempone, A.C.M.P. da Silva, C.A. Brandt, et al., Synthesis and antileish-
manial activities of novel 3-substituted quinolines, Antimicrob. Agents Che-
mother. 49 (2005) 1076–1080;
452
453
454
455
456
457
458
459
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477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
382
383
384
385
386
387
388
389
390
391
392
mol/L), 6h (IC50 = 10.60 mmol/L), and 6i (IC50 = 10.73 mmol/L)
were shown potent antioxidants when compared with standards.
None of the synthesized compounds were cytotoxicity to HeLa cell
lines upto their highest tested concentrations. A molecular docking
study suggested the binding interactions of these compounds with
Adenine phosphoribosyltransferase of L. donovani. Furthermore,
analysis of the ADME parameters for synthesized compounds
suggested that they have good drug-like properties with potential
for oral delivery. The lead compounds will be investigated further
in an effort to develop more active, safe and cost-effective
antileishmanial and antioxidant agents.
(b) J.N. Sangshetti, F.A.K. Khan, A.A. Kulkarni, R. Arote, R.H. Patil, Antileishmanial
drug discovery: comprehensive review of the last 10 years, RSC Adv. 5 (2015)
32376–32415.
[16] V.K. Marrapu, M. Mittal, R. Shivahare, S. Gupta, K. Bhandari, Synthesis and
evaluation of new furanyl and thiophenyl azoles as antileishmanial agents,
Eur. J. Med. Chem. 46 (2011) 1694–1700.
[17] O. Kayser, A.F. Kiderlen, H. Laatsch, S.L. Croft, In vitro leishmanicidal activity of
monomeric and dimeric naphthoquinones, Acta Trop. 77 (2000) 307–314.
[18] (a) J.N. Sangshetti, D.B. Shinde, Synthesis of some novel 3-(1-(1-substitutedpi-
peridin-4-yl)-1H-1,2, 3-triazol-4-yl)-5-substituted phenyl-1,2,4-oxadiazoles as
antifungal agents, Eur. J. Med. Chem. 46 (2011) 1040–1044;
393
Acknowledgments
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The authors are thankful to the Mrs. Fatma Rafiq Zakaria,
Chairman, Maulana Azad Educational Trust and Principal, Y.B.
Chavan College of Pharmacy, Dr. Rafiq Zakaria Campus, Auranga-
bad 431 001 (M.S.), India for providing the laboratory facility. The
authors are also thankful to Bar C. (Department of Zoology,
University of Pune) for providing L. donovani culture. The authors
are also thankful to SAIF, Punjab University, Chandigarh, India for
providing NMR spectra.
(b) J.N. Sangshetti, R.R. Nagawade, D.B. Shinde, Synthesis of novel 3-(1-(1-substi-
tuted piperidin-4-yl)-1H-1,2, 3-triazol-4-yl)-1, 2, 4-oxadiazol-5(4H)-one as anti-
fungal agents, Bioorg. Med. Chem. Lett. 19 (2009) 3564–3567;
(c) J.N. Sangshetti, D.B. Shinde, One pot synthesis and SAR of some novel 3-
substituted 5,6-diphenyl-1, 2, 4-triazines as antifungal agents, Bioorg. Med.
Chem. Lett. 20 (2010) 742–745;
(d) J.N. Sangshetti, P.P. Dharmadhikari, R.S. Chouthe, et al., Microwave assisted
nano (ZnO–TiO2) catalyzed synthesis of some new 4,5,6,7-tetrahydro-6-((5-
substituted-1, 3,4-oxadiazol-2-yl)methyl)thieno[2,3-c]pyridine as antimicrobial
agents, Bioorg. Med. Chem. Lett. 23 (2013) 2250–2253;
(e) Z. Zaheer, F.A.K. Khan, J.N. Sangshetti, R.H. Patil, Efficient one-pot synthe-
sis, molecular docking and in silico ADME prediction of bis-(4-hydroxycou-
marin-3-yl) methane derivatives as antileishmanial agents, EXCLI J. 14 (2015)
935–947.
402
Appendix A. Supplementary data
[19] (a) J.N. Sangshetti, A.R. Chabukswar, D.B. Shinde, Microwave assisted one pot
synthesis of some novel 2,5-disubstituted 1,3,4-oxadiazoles as antifungal agents,
Bioorg. Med. Chem. Lett. 21 (2011) 444–448;
403
404
Supplementary material related to this article can be found, in the
online version, at http://dx.doi.org/10.1016/j.cclet.2015.10.028.
(b) J.N. Sangshetti, R.I. Shaikh, F.A.K. Khan, et al., Synthesis, antileishmanial
activity and docking study of N0-substitutedbenzylidene-2-(6,7-dihy-
drothieno[3,2-c]pyridin-5(4H)-yl)acetohydrazides, Bioorg. Med. Chem. Lett. 24
(2014) 1605–1610;
(c) J.N. Sangshetti, F.A.K. Khan, R.S. Chouthe, M.G. Damale, D.B. Shinde, Synthesis,
docking and ADMET prediction of novel 5-((5-substituted-1-H-1,2,4-triazol-3-yl)
methyl)-4,5, 6,7-tetrahydrothieno[3,2-c]pyridine as antifungal agents, Chin.
Chem. Lett. 25 (2014) 1033–1038;
(d) J.N. Sangshetti, F.A.K. Khan, R.H. Patil, et al., Biofilm inhibition of linezolid-like
Schiff bases: synthesis, biological activity, molecular docking and in silico ADME
prediction, Bioorg. Med. Chem. Lett. 25 (2015) 874–880;
(e) F.A.K. Khan, J.N. Sangshetti, Design, synthesis and molecular docking study of
hybrid quinoline-4-YL-oxadiazoles/oxathiadiazoles as potent antifungal agents,
Int. J. Pharm. Pharm. Sci. 7 (2015) 223–229.
405
References
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
[1] (a) J.D. Berman, Human leishmaniasis: clinical, diagnostic, and chemotherapeutic
developments in the last 10 years, Clin. Infect Dis. 24 (1997) 684–703;
(b) M. Khaw, C.B. Panosian, Human antiprotozoal therapy: past, present, and
future, Clin. Microbiol. Rev. 8 (1995) 427–439.
[2] R. Reithinger, J.C. Dujardin, H. Louzir, et al., Cutaneous leishmaniasis, Lancet Infect.
Dis. 7 (2007) 581–596.
[3] World Health Organization (WHO), Tropical Disease Research Progress, World
Health Organization (WHO), 2001.
[4] R.W. Ashford, P. Desjeux, P. DeRaadt, Estimation of population at risk of infection
and number of cases of leishmaniasis, Parasitol. Today 8 (1992) 104–105.
[5] (a) H.W. Murray, Treatment of visceral leishmaniasis in 2004, Am. J. Trop. Med.
Hyg. 71 (2004) 787–794;
(b) S.L. Croft, Recent developments in the chemotherapy of leishmaniasis, Trends
Pharmacol. Sci. 9 (1988) 376–381;
(c) J.D. Berman, Chemotherapy for leishmaniasis: biochemical mechanisms, clin-
ical efficacy, and future strategies, Rev. Infect Dis. 10 (1988) 560–586.
[6] K.F. Gey, The antioxidant hypothesis of cardiovascular disease: epidemiology and
mechanisms, Biochem. Soc. Trans. 18 (1990) 1041–1045.
[20] M. Silva, H.B. Napolitano, J. Ellena, et al., 3-(5,7-Dimethoxy-2,2-dimethyl-2H-
benzo[b]pyran-6-yl) propionic acid: a potential inhibitor against Leishmania, Acta
Cryst. E59 (2003) o1575–o1577.
[21] A. Dutta, S. Bandyopadhyay, C. Mandal, M. Chatterjee, Development of a modified
MTT assay for screening antimonial resistant field isolates of Indian visceral
leishmaniasis, Parasitol. Int. 54 (2005) 119–122.
[22] M. Burits, F. Bucar, Antioxidant activity of Nigella sativa essential oil, Phytother.
Res. 14 (2000) 323–328.
[23] F. Denizlt, R.T. Lang, Rapid colorimetric assay for cell growth and survival:
modifications to the tetrazolium dye procedure giving improved sensitivity
and reliability, J. Immunol. Methods 89 (1986) 271–277.
[7] (a) M.A. Smith, G. Perry, P.L. Richey, et al., Oxidative damage in Alzheimer’s,
Nature 382 (1996) 120–121;
(b) M.N. Diaz, B. Frei, J.A. Vita, J.F. Keaney, Antioxidants and atherosclerotic heart
disease, N. Engl. J. Med. 337 (1997) 408–416.
[8] R.M. Wilson, S.J. Danishefsky, Small molecule natural products in the discovery of
therapeutic agents: the synthesis connection, J. Org. Chem. 71 (2006) 8329–8351.
[9] M.J. Chan-Bacab, L.M. Pen˜a-Rodrı´guez, Plant natural products with leishmanicidal
activity, Nat. Prod. Rep. 18 (2001) 674–688.
[24] VLife, Molecular Design Suite 4.3, VLife Sciences Technologies Pvt. Ltd, 2015
hwww.Vlifesciences.comi.
[25] C.L. Phillips, B. Ullman, R.G. Brennan, C.P. Hill, Crystal structures of adenine
phosphoribosyltransferase from Leishmania donovani, EMBO J. 18 (1999)
3533–3545.
[26] C.A. Lipinski, L. Lombardo, B.W. Dominy, P.J. Feeney, Experimental and computa-
tional approaches to estimate solubility and permeability in drug discovery and
development settings, Adv. Drug Deliv. Rev. 46 (2001) 3–26.
[10] (a) I. Kostova, S. Bhatia, P. Grigorov, et al., Coumarins as antioxidants, Curr. Med.
Chem. 18 (2011) 3929–3951;
(b) I. Kostova, Synthetic and natural coumarins as antioxidants, Mini Rev. Med.
Chem. 6 (2006) 365–374.
[11] (a) L. Gupta, A. Talwar, Nishi, et al., Synthesis of marine alkaloid: 8,9-dihydro-
coscinamide B and its analogues as novel class of antileishmanial agents, Bioorg.
Med. Chem. Lett. 17 (2007) 4075–4079;
[27] Molinspiration Chemoinformatics Brastislava, Slovak Republic, 2015 Available
from hhttp://www.molinspiration.com/cgi-bin/propertiesi.
[28] Y.H. Zhao, M.H. Abraham, J. Le, et al., Rate-limited steps of human oral absorption
and QSAR studies, Pharm. Res. 19 (2002) 1446–1457.
[29] J.C. Jung, Y.J. Jung, O.S. Park, A convenient one-pot synthesis of 4-hydroxycou-
marin, 4-hydroxythiocoumarin, and 4-hydroxyquinolin-2(1H)-one, Synth. Com-
mun. 31 (2001) 1195–1200.
[30] (a) M. Mohsenimehr, M. Mamaghani, F. Shirini, M. Sheykhan, F.A. Moghaddam,
One-pot synthesis of novel pyrido[2,3-d]pyrimidines using HAp-encapsulated-g-
Fe2O3 supported sulfonic acid nanocatalyst under solvent-free conditions, Chin.
Chem. Lett. 25 (2014) 1387–1391;
(b) S.S. Chauhan, L. Gupta, M. Mittal, et al., Synthesis and biological evaluation of
indolyl glyoxylamides as a new class of antileishmanial agents, Bioorg. Med.
Chem. Lett. 20 (2010) 6191–6194.
[12] (a) N.P. Sahu, C. Pal, N.B. Mandal, et al., Synthesis of a novel quinoline derivative,
2-(2-methylquinolin-4-ylamino)-N-phenylacetamide—a potential antileishma-
nial agent, Bioorg. Med. Chem. 10 (2002) 1687–1693;
(b) Z. Dardari, M. Lemrani, A. Bahloul, et al., Antileishmanial activity of a new 8-
hydroxyquinoline derivative designed 7-[50-(30-phenylisoxazolino)methyl]-8-
hydroxyquinoline: preliminary study, Farmaco 59 (2004) 195–199.
[13] (a) A. Tahghighi, S. Emami, S. Razmi, et al., New 5-(nitroheteroaryl)-1,3, 4-
thiadiazols containing acyclic amines at C-2: synthesis and SAR study for their
antileishmanial activity, J. Enzyme Inhib. Med. Chem. 28 (2013) 843–852;
(b) C.S. Reid, A.F. Farahat, X.H. Zhu, et al., Antileishmanial bis-arylimidamides:
(b) J.N. Sangshetti, F.A.K. Khan, C.S. Kute, Z. Zaheer, R.Z. Ahmed, One-pot three-
component synthesis of 3-(a-aminobenzyl)-4-hydroxycoumarin derivatives
using nanocrystalline TiO2 as reusable catalyst, Russ. J. Org. Chem. 51 (2015)
69–73;
(c) M.A. Ameen, S.M. Motamed, F.F. Abdel-latif, Highly efficient one-pot synthesis
of dihydropyran heterocycles, Chin. Chem. Lett. 25 (2014) 212–214;
Please cite this article in press as: Z. Zaheer, et al., Expeditious synthesis, antileishmanial and antioxidant activities of novel 3-
substituted-4-hydroxycoumarin derivatives, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.10.028

G Model
CCLET 3479 1–9
Z. Zaheer et al. / Chinese Chemical Letters xxx (2015) xxx–xxx
9
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
(d) J.N. Sangshetti, F.A.K. Khan, R.S. Chouthe, Z. Zaheer, R.Z. Ahmed, Water-
[33] (a) IFPMA, Stability testing of new drug substances and drug products ICH Q1A 554
(R2), in: International Conference on Harmonization, IFPMA, Geneva, 2003;
mediated oxalic acid catalysed one-pot synthesis of 2-(substituted phenyl)
phthalazin-1(2H)-ones, J. Taibah Univ. Sci. 9 (2015) 548–554.
[31] (a) B. Han, X.D. Jia, X.L. Jin, et al., A CAN-initiated aza-Diels–Alder reaction for a
facile synthesis of 4-amido-N-yl tetrahydroquinolines, Tetrahedron Lett. 47
(2006) 3545–3547;
555
(b) K.K. Hotha, S. Phani, K. Reddy, V.K. Raju, L.K. Ravindranath, Forced degrada- 556
tion studies: practical approach-overview of regulatory guidance and literature 557
for the drug products and drug substances, Int. Res. J. Pharm. 4 (2013) 78–85.
558
[34] M. Sankaran, C. Kumarasamy, U. Chokkalingam, P.S. Mohan, Synthesis, antioxi- 559
dant and toxicological study of novel pyrimido quinoline derivatives from 4- 560
hydroxy-3-acyl quinolin-2-one, Bioorg. Med. Chem. Lett. 20 (2010) 7147–7151. 561
[35] H.Y. Zhang, Structure–activity relationships and rational design strategies for 562
radical-scavenging antioxidants, Curr. Comput. Aided Drug Des. 1 (2005) 257– 563
(b) J.N. Sangshetti, N.D. Kokare, S.A. Kotharkara, D.B. Shinde, Ceric ammonium
nitrate catalysed three component one-pot efficient synthesis of 2,4,5-triaryl-1H-
imidazoles, J. Chem. Sci. 120 (2008) 463–467;
(c) A.P.G. Nikalje, M.S. Ghodke, F.A.K. Khan, J.N. Sangshetti, CAN catalyzed one-
pot synthesis and docking study of some novel substituted imidazole coupled
1,2,4-triazole-5-carboxylic acids as antifungal agents, Chin. Chem. Lett. 26 (2015)
108–112.
273.
[36] R.W. Blakesley, Methods for preventing inhibition of nucleic acid synthesis by 565
pyrophosphate, US6291164.
564
Q2566
[32] B.D. Mather, K. Viswanathan, K.M. Miller, T.E. Long, Michael addition reactions in
macromolecular design for emerging technologies, Prog. Polym. Sci. 31 (2006)
487–531.
[37] P. Ertl, B. Rohde, P. Selzer, Fast calculation of molecular polar surface area as a sum 567
of fragment-based contributions and its application to the prediction of drug 568
transport properties, J. Med. Chem. 43 (2000) 3714–3717.
569
Please cite this article in press as: Z. Zaheer, et al., Expeditious synthesis, antileishmanial and antioxidant activities of novel 3-
substituted-4-hydroxycoumarin derivatives, Chin. Chem. Lett. (2015), http://dx.doi.org/10.1016/j.cclet.2015.10.028