Semisynthesis of ursolic acid-2-(2-thienylidene)-oxadiazole hybrid molecule and an evaluation of its COX inhibition property

Article abstract of DOI:10.1002/jhet.3923

A new derivative of ursolic acid containing dual functionality was synthesized. Molecular docking studies and in vitro analysis indicated promising COX inhibition potential for the molecule. The synthesis, characterization, in silico and in vitro studies

Full text of DOI:10.1002/jhet.3923

Received: 22 November 2019
DOI: 10.1002/jhet.3923
Revised: 22 January 2020
Accepted: 23 January 2020
C O M M U N I C A T I O N S
Semisynthesis of ursolic acid-2-(2-thienylidene)-oxadiazole
hybrid molecule and an evaluation of its COX
inhibition property
Ani Deepthi1,2
| Deepa Krishnan1 | Anuroopa Sanju2
1Department of Chemistry, University of
Kerala, Kariavattom Campus,
Abstract
Thiruvananthapuram, Kerala, India
A new derivative of ursolic acid containing dual functionality was synthesized.
Molecular docking studies and in vitro analysis indicated promising COX inhi-
bition potential for the molecule. The synthesis, characterization, in silico and
in vitro studies of the molecule are described here.
2Department of Computational Biology
and Bioinformatics, University of Kerala,
Kariavattom Campus,
Thiruvananthapuram, Kerala, India
Correspondence
Ani Deepthi, Department of Chemistry,
University of Kerala, Kariavattom
Campus, Thiruvananthapuram 65581,
Kerala State, India.
Email: anideepthi@gmail.com
1 | INTRODUCTION
done in order to tackle this problem;[5b] however, there
have not been much reports on the synthesis and
Natural products and their semisynthetic derivatives–
based drugs constitute a large percentage of marketed
drugs that are routinely used today for the treatment of
various diseases.[1] The development of synthetic biology
and genetically engineered biosynthesis[2] are increas-
ingly contributing to the development of natural
product–based drug discovery hand in hand with new
methods for isolation and advanced characterizations.[3]
Pentacyclic triterpenoids constitute a class of secondary
metabolites that could be potential candidates, which can
be used for the treatment of various diseases. For
instance, the pharmacology of ursolic acid (UA, 1) and
oleanolic acid (OA, 2) are well studied in the literature
(Figure 1),[4] and several of their semisynthetic deriva-
tives have been developed and screened.[5]
evaluation of hybrid molecules from UA. Hybrid
molecules refer to structures having two (or more
than two) structural domains having different biologi-
cal functions.[12] It has been reported that Claisen-
Schmidt condensation of 3-oxo-UA with various
aldehydes led to the synthesis of 2-arylidene deriva-
tives, which showed increased α-glucosidase inhibitory
activity.[13] Very recently, it has been reported that
di(2-thienylidene) cyclohexanones exhibited increased
anti-inflammatory activity via COX and LOX inhibition
pathways.[14] Inspired by the above literature reports
and due to our continued interest in the synthesis and
screening of OA and UA derivatives,[15] we have done
the synthesis and evaluation of a novel UA hybrid mole-
cule as discussed below.
UA (3-hydroxy-urs-12-en-28-oic acid) is the main active
component in many traditional Chinese medicines.[6] The
biological effects of UA include anti-inflammatory,[7]
anticancer,[8] antidiabetic,[9] antihepatodamage,[10] and
antibacterial[11] effects. The main concerns regarding
UA is its low water solubility, which leads to limited
bioavailability in human body. Several chemical modifi-
cations of UA at C-3, C-12, and C-28 positions have been
2 | RESULTS AND DISCUSSION
UA was isolated from leaves of Ocimum sanctum Linn by
using standard protocol.[15,16] The crude powder obtained
after extraction was column chromatographed using
silica gel to yield pure UA as a white powder, and the
J Heterocyclic Chem. 2020;1–8.
wileyonlinelibrary.com/journal/jhet
© 2020 Wiley Periodicals, Inc.
1

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DEEPTHI ET AL.
FIGURE 1 Ursolic acid (UA) and oleanolic acid (OA)
SCHEME 1 Oxidation of
ursolic acid (UA) using Jones
reagent (CrO3 in aq.H2SO4)
structure was confirmed based on spectral values, which
was found to be comparable with the literature.[17] Quan-
tification of UA present in O Sanctum Linn was also done
using high-performance thin-layer chromatography
(HPTLC), and the results are presented in the Supporting
Information. The purified UA was then converted to its
3-oxo-derivative (3) by reaction with Jones reagent
(CrO3 in aq.H2SO4) in acetone for 2 hours following lit-
erature procedure (Scheme 1).[18] The resulting product
was purified by column chromatography and was char-
acterized by spectroscopic analysis. From the infrared
(IR) spectrum, the disappearance of the alcoholic group
attached to the C-3 position of UA at 3423 cm−1 and the
appearance of the carbonyl group at 1687 cm−1 indi-
cated the conversion of UA to 3-oxo-urs-12-en-28-oic
acid (3). In the 13C NMR spectrum, the peak at δ
217.7 ppm indicate the presence of carbonyl carbon at
C-3 of 3 while the carbonyl carbon of the acid group was
found at δ 184 ppm.
It was observed that thiophene-2-aldehyde (a) under-
went Claisen-Schmidt condensation with 3 yielding the
product 4 in 68% yield while only lower yields of the con-
densation products 5 to 9 were obtained with the other
aldehydes b to f and therefore 4 was taken up for further
studies. In the IR spectrum of 4, the peak at 1684 cm−1
was attributed to the carbonyl at C-3 conjugated to the
1
thiophene ring. In the H NMR spectrum, the signals
between δ 7.0 and 7.3 ppm indicated the aromatic pro-
tons of the thiophene ring and that at δ 6.8 ppm con-
firmed the presence of the olefin hydrogen in the
conjugated system. The signal at δ 5.7 ppm indicated the
H attached to C-12 of UA. In 13C NMR spectrum, the aro-
matic carbons were observed between δ 137.5 and
126.9 ppm. LC-MS analysis for compound 4 revealed a
peak at m/z 550.350, which confirmed the [M + 2] peak
of the thienylidene derivative 4.
Incorporation of N-heterocycles in the C-28 position
of UA has been proved to be advantageous in generating
anticancer[19] and anti-inflammatory agents.[20] Introduc-
tion of the N atom increases the interaction between the
molecule and the target as N atom can act as an H-bond
donor or acceptor. In particular, studies have shown that
1,3,4-oxadiazoles can facilitate transmembrane diffusion
Compound 3 obtained was then subjected to Claisen-
Schmidt condensation with various heterocyclic alde-
hydes a to f. The reaction was conducted in the presence
of methanolic potassium hydroxide by refluxing the
mixture for 8 hours[13] as shown in Scheme 2.

DEEPTHI ET AL.
3
SCHEME 2 Claisen-Schmidt condensation of 3 with various heterocyclic aldehydes
SCHEME 3 Synthesis of compound 10
by increasing the lipophilicity of the drug.[21] Cyclooxy-
genase (COX) enzymes COX-1 and COX-2 produce pros-
taglandins that induce inflammation, pain, and fever in
which prostaglandins from COX-1 is responsible for the
protection of stomach and intestinal lining. In addition,
COX-1 also activates platelets and is involved in proper
kidney function.[22] COX-2 is an inducible enzyme, found
only in certain conditions, and is responsible for inflam-
matory diseases and carcinogenesis.[23] Inhibition of
COX-2 is necessary while inhibition of COX-1 causes side
effects. Nonselective non-steroidal anti-inflammatory
drugs (NSAID) inhibit the platelet aggregation and
increase the risk of gastrointestinal ulcers as they inhibit
COX-1 also. In this context, it is important to develop
anti-inflammatory drugs that exhibit increased COX-2
inhibition. In silico analysis described below has shown
that compound 10, which incorporates a 1,3,4-oxadiazole
in the C-28 position of UA, shows increased COX-2 inhi-
bition than compound 4.
Compound 10 was obtained by reacting 4 with
2-chloromethyl-5-phenyl-1,3,4-oxadiazole 13 in the pres-
ence of KI/K2CO3 in acetone under reflux following a
reported procedure.[20] Solvent was removed by evapora-
tion, and residue was subjected to column chromatogra-
phy to obtain the desired product. Scheme 3 outlines the
synthetic strategy adopted for synthesis of compound 10.
The IR spectrum of compound 10 showed peaks at
1732 and 1654 cm−1 corresponding to the ester and

4
DEEPTHI ET AL.
TABLE 1 Docking results of compounds 4-10, UA and celecoxib with COX-2 (PDB: 3NTG)
Compound
Libdock Score
107.42
H bond Forming Residues
THR198
No. of Hydrogen Bonds
Hydrogen Bond Distance
4
1
1
1
1
1
1
2
2.40
1.84
2.66
2.48
2.35
1.64
5
93.20
THR198
6
100.99
THR198
7
105.32
THR198
8
118.39
ASN368
9
82.716
GLN440
10
127.48
HIS372
THR198
2.06
1.91
UA
89.54
82.85
TYR134
THR198
ASN368
3
1
2.78
2.45
1.79
Celecoxib
TRP373
2.69
conjugated ketone carbonyls, respectively. In the proton
NMR, aromatic protons of the phenyl ring and thio-
phene were observed between δ 8.06 and 7.31 ppm.
Olefinic proton adjacent to the thiophene ring was observed
at δ 7.1 ppm. The methylene protons adjacent to the ester
carbonyl carbon were found at δ 5.40 to 5.23 ppm. The
absence of peak at 181.8 ppm in the 13C NMR and forma-
tion of a new peak at 175.6 ppm indicated the ester
carbonyl formation. Alkene carbons in the diazole moiety
was found at δ 165.7 and δ 162.6 ppm. The bridged methy-
lene carbon between the ester and oxadiazole moiety is
found at δ 59.5 ppm. Mass spectral analysis also confirmed
the structure of the compound.
Concurrently, an in silico analysis of the COX-2 inhi-
bition by the heteroarylidene products were studied using
BIOVIA, Discovery studio, 2018. The X-ray crystallo-
graphic structure file of COX-2 (PDB Id: 3NTG) with res-
olution 2.19 Å was retrieved from the protein data bank.
Prior to docking, all crystallographic water molecules and
bound ligands were removed manually.[24a] Protonation,
optimization of side chain conformation, and missing
loop modelling were done based on the protein prepara-
tion protocol of Discovery studio.[24b] Compounds 4 to
9 and 10, UA, and standard anti-inflammatory drug
celecoxib were prepared and were docked with target
protein and binding interaction of ligands, and protein
were studied using Ligplot. Table 1 shows the docking
results obtained.
1.84 Å. Compound 6 shows a libdock score of 100.99, and
it was observed that amino acid residue is THR198 with a
hydrogen bond distance of 2.66 Å. The interacting amino
acid residue THR198 for compound 7 with a hydrogen
bond 2.48 Å produces a libdock score of 105.32. For com-
pound 8, docking score observed was 118.39 with a
hydrogen bond (2.35 Å) formed with residue ASN 368.
For compound 9, one direct interaction with the residue
of the binding cavity of COX-2 through GLN440 having a
hydrogen bond with a distance of 1.64 Å was observed.
Celecoxib, which was used as reference drug, showed
libdock score of 82.85, and the hydrogen bond forming
amino acid residue was TRP 373 with a distance of
2.69 Å. The most important finding from the docking
study was that compound 10 shows highest libdock score
(127.48) having two hydrogen bond amino acid residues
(HIS372 and THR198). From the in silico studies, it was
found that most of the molecules have better affinity
towards COX-2 than that of UA and Celecoxib. Interac-
tion of these ligands and proteins is given in Figure 2 in
which A to D show the binding poses of compounds
4 and 10, UA, and celecoxib and E to H show 2-D molec-
ular docking models of compounds 4 and 10, UA, and
celecoxib with COX-2, respectively.
The compounds 4 and 10 along with UA were sub-
jected to in vitro anti-inflammatory analysis.[25] Lipopoly-
saccharide (LPS)-stimulated RAW cells were used for the
study, which were exposed to different concentrations
(25, 50, and 100 μg/mL) of sample solutions and incu-
bated for 24 hours. After incubation, the COX inhibitory
assays were performed using the cell lysate. COX activity
was determined by reading absorbance at 632 nm, and
the results are summarized in Table 2.
UA interacts with COX-2 by forming three hydrogen
bonds with ASN 368, THR198, and TYR134 and was
found to have a libdock score of 89.54. The amino acid
residue THR198 in COX-2 interacts with compound 4 via
a hydrogen bond with 107.42 as the docking score. Com-
pound 5 shows libdock score of 93.20 by forming hydro-
gen bond with THR198, and hydrogen bond distance was
It was also found that the percentage inhibition
increases with increase in concentration of the samples,

DEEPTHI ET AL.
5
FIGURE 2 Docking of compounds 4 and 10, ursolic acid (UA), and celecoxib with COX-2

6
DEEPTHI ET AL.
TABLE 2 COX inhibitory assay of UA, 4, and 10
characterization data of compounds are given below. Ana-
lytical thin-layer chromatography (TLC) was performed on
silica gel coated on aluminum sheets and was monitored
using UV light of wave length 254 nm. Column chroma-
tography was done using silica gel (60-120 and 100-200
mesh). Fourier transform infrared (FTIR) was done using
Concentration
OD at
Compound
(μg/mL)
632 nm
Inhibition (%)
0.00
Control
25
0.2135
0.1537
0.0411
0.1309
0.1946
0.1531
0.1356
0.1216
0.1834
0.1397
0.1267
0.1020
UA
28.01
1
Agilient CARY 630 FTIR instrument. H NMR and 13−C
50
33.91
100
38.69
NMR of the compounds were recorded with Bruker
400-MHz spectrometer using CDCl3 or DMSO-d6 as sol-
vents. LC-MS analysis was performed by SHIMADZU
Triple quadrupole LCMS/MS-8045 coupled with LC-
30AD liquid chromatogram instrument equipped with
electrospray ionization (ESI) mode. Melting points were
recorded on an electrochemical digital melting point
apparatus, Analab Scientific instruments Pvt. Ltd, and
are uncorrected. HPTLC profile was recorded using
DESKTOP-60R1I2G, version 2.5.18053.1. For molecular
docking study, the software used was BIOVIA Discovery
studio, 2018. Anti-inflammatory assay was carried out at
Biogenix Research Center.
Control
25
0.00
4
21.33
50
30.32
100
37.51
Control
25
0.00
10
23.83
50
30.92
100
44.38
Note: Control (italic values) refers to unstimulated RAW cells.
which proves that the compounds acted in a dose-
dependent manner. in vitro studies have showed that
44.38% COX inhibition could be achieved using com-
pound 10 at a concentration of 100 ppm.
4.2 | Plant material
UA was extracted from Tulsi leaf (O Sanctum L) powder
that is purchased from Krishna Ayurvedic Stores,
Trivandrum.
3 | CONCLUSION
Semisynthetic hybrid derivative of UA containing thio-
phene and 1,3,4-oxadiazole was synthesized in the pre-
sent study. From the in silico and in vitro studies, it is
found that the hybrid molecule 10 showed highest dock-
ing score and COX inhibition activity. COX-2 has long
been considered as a target for anticancer drug develop-
ment, and combination treatments of chemotherapy with
COX-2 inhibitors have shown promising results.[26] Tak-
ing into account the tremendous potential for developing
UA as an anticancer agent,[8b] the current study has a sig-
nificance in bringing out a dual role for the semisynthetic
derivative, as a COX inhibitor possessing anticancer
properties. Further studies to find the in vitro selectivity
associated with COX 2 inhibition and in vivo studies are
underway.
4.3 | Extraction and isolation of UA
About 500 g of Tulsi leaf powder was subjected to soxhlet
extraction using hexane and ethyl acetate as solvents suc-
cessively. The ethyl acetate extract was collected, and the
solvent was removed by rotary evaporator. The residue
was purified by column chromatography on silica gel
(60-120 mesh). On elution with a mixture of hexane and
ethyl acetate (80:20), UA was obtained as a white powder
(250 mg of UA was obtained after column chromatogra-
phy of 2-g ethyl acetate extract). The peak at 3432 cm−1
in the IR spectrum of UA corresponded to the OH
stretching vibration while that at 1691 cm−1 was attrib-
uted to the carbonyl stretch of the COOH group.
4 | EXPERIMENTAL
4.1 | Instrumentation
4.4 | Molecular docking study
4.4.1 | Protein preparation
Heterocyclic aldehydes were purchased from Spec-
trochem Pvt. Ltd Mumbai and was used without further
purification. Solvents and other reagents were obtained
from local suppliers. Detailed synthetic procedure and
The X-ray crystallographic structure file of COX-2
(3NTG) with resolution 2.19 Å was retrieved from Protein
Data Bank (PDB). Prior to docking, all crystallographic
water molecules and bound ligands were removed

DEEPTHI ET AL.
7
manually. Protonation, optimization of side chain confor-
mation, and missing loop modelling were done based on
protein preparation protocol of discovery studio.
CO2 incubator (NBS Eppendorf, Germany). The cells were
grown to 60% confluency followed by activation with 1-μL
LPS (1 μg/mL). LPS-stimulated RAW cells were exposed with
different concentrations (25, 50, and 100 μg/mL) of sample
solution and incubated for 24 hours. After incubation, the
anti-inflammatory assays were performed using the cell
lysate.
4.4.2 | Molecular docking
Binding site for target protein was defined using PDB site
records, and site sphere coordinates were set as 24.9159,
34.8601, 40.3226, and 12.6 Å. UA, seven of its derivatives
(4-10), UA, and standard drug celecoxib were prepared
and allowed to dock with target protein. Number of hot-
spots were set as 100, docking tolerance as 0.25. All other
parameters were set as default, and FAST was selected as
conformation method with maximum conformation of
255. Docking results of UA and its seven derivatives were
compared with the standard drug celecoxib and are
reported in the manuscript.
The COX activity was assayed by the method of
Walker and Gierse; 100-μL cell lysate was incubated
with Tris-HCl buffer (pH 8), glutathione 5mM/L, and
hemoglobin 5mM/L for 1 minute at 25ꢀC. The reaction
was initiated by the addition of arachidonic acid
200mM/L and terminated after 20-minute incubation at
37ꢀC, by the addition 200 μL of 10% trichloroacetic acid
in 1 N hydrochloric acid. After the centrifugal separa-
tion and the addition of 200 μL of 1% thiobarbiturate,
the tubes were boiled for 20 minutes. After cooling, the
tubes were centrifuged for 3 minutes. COX activity was
determined by reading absorbance at 632 nm.
Percentage inhibition of the enzyme was calculated as
4.5 | LC-MS analysis
Absorbance of control−Absorbance of test
%inhibition =
× 100:
Absorbance of control
The compound 4 was analyzed by SHIMADZU Triple
quadrupole LCMS/MS-8045 coupled with LC-30AD liquid
chromatogram instrument. Chromatographic separation
performed on Shim-pack GIST C8 column (150 × 2.1 mm,
I.D., 2 μm) using methanol as mobile phase system at a flow
rate of 0.2 mL/min. Column temperature was set at 40ꢀC.
Mass spectrometric analysis was performed with an ESI
source. The Auto MS operation parameters were described
as follows: Nebulizing gas (N2) flow, drying gas flow, and
heating gas flow were set as 3.0, 10.0, and 10.0 L/min,
respectively. Interface voltage set as 3.0 kV having an inter-
face current 6.2 μA and interface temperature maintained at
300ꢀC. Detector voltage is 1.80 kV. Both full scan mode and
single ion monitoring of compound 4 were done at the
range of m/z 50 to 1000 in positive ion mode. A peak at m/z
550.350 confirmed the [M + 2] peak of the thienylidene
derivative 4.
4.6.1 | Procedure for synthesis of
compound 4
To a stirring solution of potassium hydroxide (2 equiv.,
0.35 mmol, 19 mg) in methanol (5 mL), compound
3 (1 equiv., 0.175 mmol, 80 mg) dissolved in methanol
(5 mL) was added drop wise using a pressure equalizer.
Then thiophene-2-aldehyde a (1 equiv., 0.175 mmol,
19 mg) was added to the above solution. The reaction
mixture was stirred for 8 hours at 65ꢀC. The completion
of the reaction was tested by TLC analysis. Solvent was
removed, and reaction mixture was worked up using
methylene dichloride/water; the combined organic layers
were dried over anhydrous sodium sulfate, and the resi-
due was dried in vacuo, and the product 4 obtained was
further purified by column chromatography using silica
gel (100-200 mesh) as stationary phase and mixture of
10% EtOAc-Hexane as mobile phase to obtain amorphous
powder.[6] Yield 68%. Melting point 167-169ꢀC. FTIR
(neat, ν cm−1): 2917, 2850, 1684, 1650, 1456, 1374. 1−H
NMR (400 MHz, CDCl3): 7.31 (d, 1H), 7.02-7.00 (m, 2H),
6.83 (s, 1H), 5.70 (s, 1H), 3.77 (s, 1H), 3.73 (s, 1H), 2.48
(s, 1H), 2.32 (t, 2H), 2.07 (t, 4H), 1.64 (s, 1H), 1.51-1.41
(m, 10H), 1.39-1.32 (t, 5H), 1.29-1.06 (m, 5H), 1.00
(s, 6H), 0.98 (s, 1H), 0.94 (s, 3H), 0.86 (s, 1H), 0.84
(s, 1H). 13C NMR (100 MHz, CDCl3): 206.0, 181.8, 137.5,
133.0, 130.8, 128.6, 128.5, 128.0, 126.9, 49.7, 45.5, 44.9,
4.6 | Anti-inflammatory assay
RAW 264.7 cells were initially procured from National
Centre for Cell Sciences (NCCS), Pune, India, and
maintained Dulbecco's modified Eagle's medium
(DMEM) (Sigma-Aldrich, USA).
The cell line was cultured in 25-cm3 tissue culture flask
with DMEM supplemented with 10% Fetal bovine serum
(FBS), L-glutamine, sodium bicarbonate (Merck, Germany),
and antibiotic solution containing penicillin (100 U/mL),
streptomycin (100 μg/mL), and Amphoteracin B (2.5 μg/
mL). Cultured cell lines were kept at 37ꢀC in a humidified 5%

8
DEEPTHI ET AL.
[8] (a) D. K. Kim, J. H. Baek, C. M. Kang, M. A. Yoo, J. W. Sung,
D. K. Kim, K. W. Kim, Int. J. Cancer. 2000, 87(5), 629.
(b) P. Liu, R. Du, X. Yu, Med. Sci. Monit. 2019, 25, 1283.
[9] P. P. Wu, K. Zhang, Y. J. Lu, P. He, S. Q. Zhao, Eur. J. Med.
Chem. 2014, 80, 502.
42.6, 38.2, 37.7, 37.5, 36.9, 36.7, 32.6, 30.9, 29.6, 28.4, 27.0,
26.3, 24.9, 22.4, 21.6, 20.8, 18.1, 17.7, 16.0, 15.9, 14.4, 13.1.
LC/MS-ESI: m/z calculated for [C35H48O3S + 2]: 550.332;
found: 550.330.
[10] B. Saraswat, P. K. Visen, D. P. Agarwal, Phytother. Res. 2000,
14(3), 163.
4.6.2 | Procedure for synthesis of
compound 10
[11] D. Chattopadhyay, G. Arunachalam, A. B. Mandal, T. K. Sur,
S. C. Mandal, S. K. J. Bhattacharya, Ethnopharmacol. 2002, 82
(2–3), 229.
[12] B. Meunier, Acc. Chem. Res. 2008, 41, 69.
A mixture of compounds 4 (1 equiv., 0.182 mmol, 100 mg)
and 13 (1 equiv., 0.182 mmol, 0.035 mg) was refluxed
in 10-mL acetone at 57ꢀC for 10 hours in the presence
of KI (2 equiv., 0.364 mmol, 60.42 mg)/K2CO3 (2 equiv.,
0.364 mmol, 49.14 mg). Solvent was removed under reduced
pressure, and reaction mixture was worked up using
DCM/brine solution and was dried over Na2SO4. Residue was
purified by silica gel column chromatography, and product
was eluted with 10% EtOAc: hexane solvent in 64% yield.
Melting point 204-207ꢀC. FTIR (neat, ν cm−1): 2928, 2865,
1732, 1654, 1575, 1382. 1−H NMR (400 MHz, CDCl3):
8.06-8.02 (m, 2H), 7.71 (s, 1H), 7.55-7.48 (m, 3H), 7.33-7.31
(m, 1H), 5.74 (s, 1H), 5.40-5.23 (m, 2H), 2.52-2.49 (m, 3H),
2.2381-2.23 (m, 6H), 1.74-1.6 (m, 7H), 1.58-1.40 (m, 5H),
1.39-1.30 (m, 3H), 1.25 (s, 1H), 1.17 (s, 2H), 1.14-1.10 (m, 6H),
1.09-1.06 (m, 4H), 1.01-0.97 (m, 4H), 0.96-0.88 (m, 3H). 13C
NMR (100 MHz, CDCl3): 206.5, 175.6, 165.7, 162.6, 139.4,
133.9, 132.5, 132.0, 131.7, 130.8, 129.8, 129.1, 128.9, 127.4,
126.9, 126.8, 123.9, 123.2, 59.5, 55.2, 54.8, 52.6, 47.9, 47.3, 44.9,
43.8, 38.7, 38.6, 37.7, 35.8, 31.6, 29.7, 29.6, 28.4, 27.3, 23.7, 21.7,
21.0, 20.8, 20.4, 19.0, 18.5, 17.1, 16.9. HRMS-ESI (m/z) calcu-
lated for [C44H54N2O4S -1]: 706.3804; found: [M-1]: 705.3800.
[13] P. -P. Wu, B. -J. Zhang, X.-P. Cui, Y. Yang, Z.-Y. Jiang, Z.-
H. Zhou, Y. Y. Zhong, Y.-Y. Mai, Z. Ouyang, H.-S. Chen,
J. Zheng, S.-Q. Zhao, K. Zhang, Sci. Rep. 2017, 7, 45578.
https://doi.org/10.1038/srep45578.
[14] S. Kar, G. Ramamoorthy, S. Sinha, M. Ramanan, J. K. Pola,
N. R. Golakoti, J. B. Nanubolu, S. K. Sahoo, R. B. Dandamudi,
M. Doble, New J. Chem. 2019, 43, 9012.
[15] N. S. Ratheesh, A. Deepthi, K. Adarsh, S. Ind. J. Chem. Sec B
2016, 55B(5), 598.
[16] J. B. Harborne, Phytochemical Methods - A Guide to Modern
Technique of Plant Analysis, 2nd ed., Dordrecht: Springer
Science & Business Media, 1984.
[17] S. C. Gnoatto, A. Dassonville-Klimpt, S. Da Nascimento, K.;
Gosmann, G.; Moslemi, S. Eur. J. Med. Chem. 2008, 43(9), 1865.
[18] T. Honda, H. J. Finlay, G. W. Gribble, N. Suh, M. B. Sporn,
Chem. Lett. 1997, 7(13), 1623.
[19] S. -X. Hua, R. -Z. Huang, M. -Y. Ye, Y. -M. Pan, G. -Y. Yao,
Y. Zhang, H. -S. Wang, Eur. J. Med. Chem. 2015, 95, 435.
[20] Z. -Y. Wei, K. -Q. Chi, K. -S. Wang, J. Wu, L. -P. Liu, H. -R. Piao,
Bioorg. Med. Chem. Lett. 2018, 28, 1797.
[21] S. Bajaj, V. Asati, J. Singh, P. P. Roy, Eur. J. Med. Chem. 2015,
97, 124.
[22] K. D. Rainsford, S. Tsang, R. H. Hunt, N. Al-Jehani,
Inflammopharmacology. 1995, 3(4), 299.
[23] Y. Li, W. He, T. Liu, Q. Zhang, Mol. Diagn. Ther. 2010, 14(6), 351.
[24] (a)F. C. Bernstein, T. F. Koetzle, G. J. Williams, E. F. Meyer Jr..,
M. D. Brice, J. R. Rodgers, M. J. Tasumi, Mol. Bio. 1977, 112(3),
535; (b)B. I. O. V. I. A. Dassault Systèmes, Discovery Studio Client
v 18.01.100.18065, San Diego, Dassault Systèmes 2018.
[25] M. C. Walker, J. K. Gierse, Mol. Biol. 2010, 644, 131.
[26] J. -B. Méric, S. Rottey, K. Olaussen, J. -C. Soria, D. Khayat,
O. Rixe, J. -P. C. Spano, Rev. Oncol. 2006, 59, 51.
ACKNOWLEDGMENTS
Ms Deepa Krishnan thank Govt. of Kerala for provid-
ing e-grants for her MPhil research project. All authors
thank CLIF, University of Kerala, for providing instru-
mentation facilities and Biogenix Research Center for
in vitro analysis.
ORCID
Ani Deepthi https://orcid.org/0000-0001-6998-5694
SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of this
article.
REFERENCES
[1] D. J. Newman, G. M. Cragg, J. Nat. Prod. 2007, 70, 461.
[2] M. Q. Zhang, Curr. Op. Biotech. 2007, 18, 478.
[3] Q. W. Zhang, L. -G. Lin, W. -C. Ye, Chin. Med. 2018, 13, 20.
[4] J. Liu, J. Ethnopharmacol. 1995, 49(2), 57.
[5] (a) T. B. Ayeleso, M. G. Matumba, E. Mukwevho, Molecules
2017, 22, 1915. (b) S. Mlala, A. O. Oyedeji, M. Gondwe,
O. O. Oyedeji, Molecules 2019, 24, 2751.
[6] M. C. Liu, S. J. Yang, L. H. Jin, D. Y. Hu, W. Xue, B. An Song,
S. Yang, Eur. J. Med. Chem. 2012, 58, 128.
[7] M. K. Shanmugam, X. Dai, A. P. Kumar, B. K. Tan, G. Sethi,
A. Bishayee, Biochem. Pharmacol. 2013, 85(11), 1579.
How to cite this article: Deepthi A, Krishnan D,
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J Heterocyclic Chem. 2020;1–8. https://doi.org/10.
1002/jhet.3923