Design, synthesis, biological screenings and docking simulations of novel carvacrol and thymol derivatives containing acetohydrazone linkage

Article abstract of DOI:10.1007/s11164-017-2919-2

Abstract: Carvacrol and thymol are well-known phenolic monoterpenoids present as functional ingredients in numerous products. Keeping the diverse therapeutic activities of phenolic monoterpenes in mind, we attempted to synthesize a new series of acetohydrazone linkage containing carvacrol and thymol derivatives. All synthesized derivatives were characterized by spectroscopic techniques. Finally, all the derivatives were screened for their anti-oxidant activities by using DPPH assay, and anticancer activities by using SRB assay against pancreatic cancer with the MIAPaCa-2 cell line and colon cancer with the HCT-15 cell line. Themolecular docking studies of all the synthesized derivatives were carried out on the cyclooxygenase-2 (COX-2) protein enzyme. In the anti-oxidant test, EC₅₀ values of all the compounds showed excellent anti-oxidant potency, and similarly the values of GI₅₀ in the anticancer test displayed that most of the compounds possess good anticancer potency. Total docking results suggested that all the synthesized compounds exhibit good binding affinity towards receptors.

Full text of DOI:10.1007/s11164-017-2919-2

Res Chem Intermed
DOI 10.1007/s11164-017-2919-2
Design, synthesis, biological screenings and docking
simulations of novel carvacrol and thymol derivatives
containing acetohydrazone linkage
Jamatsing D. Rajput1 Suresh D. Bagul1
•
•
Ratnamala S. Bendre1
Received: 3 November 2016 / Accepted: 23 February 2017
Ó Springer Science+Business Media Dordrecht 2017
Abstract Carvacrol and thymol are well-known phenolic monoterpenoids present as
functional ingredients in numerous products. Keeping the diverse therapeutic activities
of phenolic monoterpenes in mind, we attempted to synthesize a new series of aceto-
hydrazone linkage containing carvacrol and thymol derivatives. All synthesized
derivatives were characterized by spectroscopic techniques. Finally, all the derivatives
were screened for their anti-oxidant activities by using DPPH assay, and anticancer
activities by using SRB assay against pancreatic cancer with the MIAPaCa-2 cell line
and colon cancer with the HCT-15 cell line. Themolecular docking studies of all the
synthesized derivatives were carried out on the cyclooxygenase-2 (COX-2) protein
enzyme. In the anti-oxidant test, EC50 values of all the compounds showed excellent
anti-oxidant potency, and similarly the values of GI50 in the anticancer test displayed
that most of the compounds possess good anticancer potency. Total docking results
suggested that all the synthesized compounds exhibit good binding affinity towards
receptors.
Electronic supplementary material The online version of this article (doi:10.1007/s11164-017-2919-
2) contains supplementary material, which is available to authorized users.
&
Ratnamala S. Bendre
bendrers@gmail.com
1
School of Chemical Sciences, North Maharashtra University, Jalgaon, Maharashtra 425001,
India
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J. D. Rajput et al.
Graphical Abstract
Keywords Cyclooxygenase-2 Á Molecular docking Á HCT-15 Á MIAPaCa-2 Á
SRB protocol Á DPPH assay Á Anti-oxidant and anticancer
Introduction
Organic syntheses are key tools for supplying rare compounds and are helping in
the transformation of bioactive natural compounds into more drug-like deriva-
tives [1, 2]. Some novel synthetic tactics have been developed in an effort to
yield potential compounds with medicinal value [3–5]. Mainly, structural
modifications of the natural core structures are achieved to increase selectivity
and potency to provide other properties [6, 7] and to help their synthesis [8]. In
addition, many novel synthetic approaches have been developed to increase
structural diversity; in other words, to enlarge the chemical space of investigated
molecules [9–11].
Thymol (2-iso-propyl- 5-methylphenol) and its isomer carvacrol (5-iso-propyl-2-
methyl-phenol) are the most frequently occurring constituents of thyme plants,
which possess a wide range of biological and pharmacological properties [12–14].
The rich essential oils present in thyme species are used for the treatment of several
diseases as well as for the preservation of food [15]. These two naturally occurring
phenolic monoterpenoids are outstanding resourceful molecules incorporated as
functional ingredients in numerous products [16, 17]. Carvacrol and thymol have
been used as precursors for the synthesis of various molecules, and their analogs are
part of many biologically active molecules known to exhibit interesting biological
activities [18, 19].
Hence, in the present investigation, we have synthesized six new carvacrol-
and thymol-based hydrazone derivatives by the condensation of ortho formyl
carvacrol, thymol and eugenol with substituted 2-acetohydrazide of carvacrol
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Design, synthesis, biological screenings and docking…
and thymol as previously reported [20, 21]. Finally, all the synthesized
derivatives were screened for their anti-oxidant activity by using DPPH assay,
and anticancer activity by using SRB assay against pancreatic cancer and colon
cancer with MIaPaCa-2 and HCT-15 cell lines, respectively. The molecular
docking studies of all the synthesized derivatives were performed on the COX-2
protein enzyme.
Materials and methods
Experimental
All the chemicals and reagents necessary for the reactions were procured from
Sigma-Aldrich and Fisher with purity 98% and used without further purification.
The products were characterized using 1H NMR, 13C NMR, IR spectra and LC–MS.
IR spectra were recorded on a Shimadzu FTIR spectrometer using KBr disks. The
NMR spectra (CDCl3) were recorded on a Bruker AC-400 MHz spectrometer with
TMS as an internal standard.
Synthesis of acetate of carvacrol and thymol [22]
A mixture of carvacrol or thymol (0.02 mol), dry acetone (50 ml), and
anhydrous K2CO3 (0.03 mol) in a 100-ml round-bottom flask was heated to
reflux for 6 h. Upon cooling to room temperature, and the drop-wise addition of
ethyl chloroacetate (0.02 mol) during 1 h, refluxing was continued for 4 h. The
reaction mixture was kept overnight, the excess of solvent was recovered, and
the residue was quenched onto crushed ice. The contents were then stirred for
30 min and extracted with diethyl ether. The organic layer was washed with
water and dried with Na2SO4. The solvent was recovered under vacuum to obtain
yellowish oils (yield: 79.55%), and the product was used in the next step without
purification.
Synthesis of acetohydrazide of carvacrol and thymol [23]
Acetate of carvacrol or thymol (0.015 mol) and 99% hydrazine hydrate
(0.023 mol) in ethanol (15 ml) were charged to a 50-ml round-bottom flask
and refluxed for 2 h. Progress of the reaction was monitored by TLC. The
resulting clear solution was concentrated under vacuum and the suspension
formed was poured onto crushed ice. The product separated was filtered, washed
with cold water, dried and recrystallized from ethanol–water (yield: 84%; m.p.
78–81 °C).
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J. D. Rajput et al.
Synthesis of Acetohydrazone of carvacrol acetohydrazide and thymol
acetohydrazide [24]
Acetohydrazone of carvacrol and thymol were conveniently synthesized via the
condensation of acetohydrazide of carvacrol and thymol with ortho formyl
carvacrol, thymol and eugenol [20]. The acetohydrazide of carvacrol or thymol
(160 mg, 0.0103 mol) was treated with ortho formyl carvacrol or thymol or eugenol
(120 mg, 0.01 mol) in anhydrous ethanol (20 mL). The reaction mixture was
refluxed for 2 h. After cooling, the solid was collected and washed with anhydrous
ethanol followed by drying to get a solid, which was dried and recrystallized from
ethanol (yield: 78%).
Results and discussion
Chemistry
The synthesis schemes involved a multi-step pathway leading to the formation of ix
novel substituted acetohydrazones of carvacrol and thymol in excellent yields. The
structures of the compounds obtained are shown in Schemes 1 and 2. Their
analytical and spectroscopic data are in agreement with the predicted structures. The
synthesis of acetohydrazone analogs of carvacrol and thymol by using 2-acetohy-
drazide prepared from carvacrol and thymol, which react with aldehyde of
carvacrol, thymol and eugenol, has been previously reported by our group [24, 25].
Reaction Scheme 1 Synthesis of carvacrol hydrazones derivatives. Reaction condition: (i) K2CO3 in
acetone and bromoethylaceate reflux at 60 °C for 4 h, (ii) NH2NH2:H2O, ethanol, reflux at 80 °C for 2 h,
(iii) respective aldehyde in ethanol, reflux at 80 °C for 2 h
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Design, synthesis, biological screenings and docking…
Reaction Scheme 2 Synthesis of thymol hydrazones derivatives. Reaction condition: (i) K2CO3 in
acetone and bromoethylaceate reflux at 60 °C for 4 h, (ii) NH2NH2:H2O, ethanol, reflux at 80 °C for 2 h,
(iii) respective aldehyde in ethanol, reflux at 80 °C for 2 h
The synthesis route of substituted acetohydrazones of carvacrol and thymol is
shown in Schemes 1 and 2.
Spectroscopic Characterizations and Physical Properties of Synthesized
Derivatives
(E)-N-(2-hydroxy-6-isoproyl-3-methylbenzylindine)-2-(5-isopropyl-2-methylphenoxy)
acetohydrazide, carvacrylacetohydrazone of carvacrol (IIIA) Color creamy, mp-
110 °C. 1H NMR (CDCl3) d 1.21–1.24 (d, J = 4.0 Hz, 6H), d 1.25–1.27 (d,
J = 4.0 Hz, 6H), 2.16 (s, 3H), 2.31 (s, 3H), 2.84–2.89 (m, J = 4.0 Hz, 1H),
3.19–3.25 (m, J = 4.0 Hz, 1H), 4.69 (s, 2H), 6.71 (d, J = 8.0 Hz, 1H), 6.7 (s, 1H),
6.85 (d, 1H), 7.12–7.25 (d, J = 8.0 Hz, 2H), 8.90 (s, 1H for imine), 9.38 (s, 1H for
OH ? D2O Exchangeable), 11.89 (s, 1H for NH ? D2O Exchangeable) 13C NMR
(CDCl3) d 15.75, 16.08, 24.01, 24.06, 28.46, 34.04, 67.86, 110.70, 112.98, 115.32,
120.32, 123.94, 124.01, 131.13, 133.61, 146.72, 148.81, 150.20, 155.27, 157.91,
164.27, LC–MS (methanol), m/z: [M ? 1] ? 383.43, [M ? Na?] ? 405.40.
(E)-N-(2-hydroxy-3-isoproyl-6-methylbenzylindine)-2-(5-isopropyl-2-methylphenoxy)
acetohydrazide, carvacryl acetohydrazone of thymol (IIIB) Color white, mp-
1
100 °C. H NMR (CDCl3) d 1.22 (d, J = 4.0 Hz, 6H), d 1.24 (d, J = 4.0 Hz, 6H),
2.31 (s, 3H), 2.40 (s, 3H), 2.84–2.91 (m, J = 4.0 Hz, 1H), 3.35–3.42 (m,
J = 4.0 Hz, 1H), 4.70 (s, 2H), 6.68 (d, J = 8.0 Hz, 1H), 6.71 (s, 1H), 6.86 (d,
2H), 7.12–7.16 (d, J = 8.0 Hz, 2H), 8.71 (s, 1H for imine), 9.35 (s, 1H for OH D2O
Exchangeable), 11.72 (s, 1H for NH ? D2O Exchangeable), 13C NMR (CDCl3) d
16.07, 19.18, 22.40, 24.05, 26.50, 34.04, 67.79, 110.60, 114.52, 120.30, 121.00,
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J. D. Rajput et al.
123.95, 129.08, 131.13, 134.80, 135.61, 148.82, 150.22, 155.25, 157.07, 164.13,
LC–MS (methanol), m/z: [M ? 1] ? 383.43, [M ? Na?] ? 405.40.
(E)-N-(5-allyl-2-hydroxy-3-methoxybenzylindine)-2-(5-isopropyl-2-methylphenoxy)
acetohydrazide, carvacrylacetohydrazone of eugenol (IIIC) Color yellow, mp-
1
108 °C. H NMR (CDCl3) d 1.19 (d, J = 4.0 Hz, 6H), 2.11 (s, 3H), 2.21–2.85 (m,
J = 4.0 Hz, 1H), 3.31–3.32 (d, 2H), 3.90 (s, 3H), 4.67 (s, 2H), 5.05–5.10 (m, 2H),
5.89–5.90 (m, 1H), 6.69 (s, 1H), 6.74 (d, J = 8.0 Hz, 1H), 6.77 (d, J = 8.0 Hz, 1H),
6.84 (d, 1H), 7.11–7.13 (d, 1H), 8.45 (s, 1H for imine), 9.41 (s, 1H for OH ? D2O
Exchangeable), 10.50 (s, 1H for NH ? D2O Exchangeable), 13C NMR (CDCl3) d
16.02, 24.06, 34.04, 39.57, 56.26, 67.57, 110.40, 114.18, 116.07, 117.04, 120.20,
121.99, 123.85, 13090, 131.10, 137.25, 146.63, 148.21, 148.76, 151.95, 155.13,
164.25. LC–MS (methanol), m/z: [M ? 1] ? 397.40, [M ? Na?] ? 419.36.
(E)-N-(2-hydroxy-3-isoproyl-6-methylbenzylindine)-2-(2-isopropyl-5-methylphenoxy)
acetohydrazide, thymylacetohydrazone of thymol (VIA) Color creamy, mp-
112 °C. 1H NMR (CDCl3) d 1.20–1.22 (d, J = 4.0 Hz, 6H), d 1.24–1.297 (d,
J = 4.0 Hz, 6H), 2.33 (s, 3H), 2.39 (s, 3H), 3.30–3.33 (m, J = 4.0 Hz, 1H),
3.37–3.40 (m, J = 4.0 Hz, 1H), 4.68 (s, 2H), 6.66–6.68 (d, J = 8.0 Hz, 2H),
6.68–6.88 (s, 1H), 7.14–7.25 (d, 2H), 8.70 (s, 1H for imine), 9.34 (s, 1H for OH
D2O ? Exchangeable), 11.70 (s, 1H for NH ? D2O Exchangeable). 13C NMR
(CDCl3) d 19.12, 21.26, 22.41, 23.96, 26.51, 26.89, 68.10, 113.51, 114.50, 121.03,
123.48, 126.51, 129.11, 134.10, 134.79, 135.60, 137.26, 150.60, 154.26, 157.06,
164.22, LC–MS (methanol), m/z: [M ? 1] ? 383.43, [M ? Na?] ? 405.40.
(E)-N-(2-hydroxy-6-isoproyl-3-methylbenzylindine)-2-(2-isopropyl-5-methylphenoxy)
acetohydrazide, thymyl acetohydrazone of carvacrol (VIB) Color white, mp-
102 °C. 1H NMR (CDCl3) d 1.21–1.24 (d, J = 4.0 Hz, 6H), d 1.26–1.29 (d,
J = 4.0 Hz, 6H), 2.25 (s, 3H), 2.29 (s, 3H), 3.17–3.21 (m, J = 4.0 Hz, 1H),
3.22–3.28 (m, J = 4.0 Hz, 1H), 4.68 (s,2H), 6.68 (s, 1H), 6.73 (d, J = 8.0 Hz, 1H),
7.15–7.25 (d, 2H), 8.90 (s, 1H for imine), 9.35 (s, 1H for OH ? D2O Exchange-
able), 11.84 (s, 1H for ? NH D2O Exchangeable). 13C NMR (CDCl3) d 15.14,
21.26, 22.97, 23.96, 26.91, 28.53, 68.14, 112.96, 113.58, 115.35, 123.50, 123.95,
126.51, 133.63, 134.12, 137.27, 146.67, 150.37, 154.27, 157.90, 164.31, LC–MS
(methanol), m/z: [M ? 1] ? 383.43, [M ? Na?] ? 405.40.
(E)-N-(5-allyl-2-hydroxy-3-methoxybenzylindine)-2-(2-isopropyl-5-methylphenoxy)
acetohydrazide, thymyl acetohydrazone of eugenol (VIC) Color yellow, mp-
1
108 °C. H NMR (CDCl3) d 1.18 (d, J = 4.0 Hz, 6H), 2.13 (s, 3H), 2.20–2.80 (m,
J = 4.0 Hz, 1H), 3.31–3.32 (d, 2H), 3.90 (s, 3H), 4.67 (s,2H), 5.05–5.10 (m, 2H),
5.89–5.90 (m, 1H), 6.69 (s, 1H), 6.74 (d, J = 8.0 Hz, 1H), 6.77 (d, J = 8.0 Hz, 1H),
6.84 (d, 1H),7.11–7.13 (d, 1H), 8.40 (s, 1H for imine), 9.41 35 (s, 1H for OH ? D2O
Exchangeable), 10.50 (s, 1H for NH ? D2O Exchangeable), 13C NMR (CDCl3) d
16.08, 24.16, 34.14, 39.50, 56.20, 67.60, 110.40, 114.18, 116.07, 117.04, 120.20,
121.99, 123.85, 130.90, 131.10, 137.25, 146.63, 148.21, 148.76, 151.95, 155.13,
164.25. LC–MS (methanol), m/z: [M ? 1] ? 397.40, [M ? Na?] ? 419.36.
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Design, synthesis, biological screenings and docking…
Bioassay
Anticancer activity
In vitro anticancer activities of synthesized derivatives were performed using
sulforhodamine B (SRB) assay on a panel of human cancer cell lines HCT-12 (colon
cancer) and MIPaCa-2 (pancreatic cancer) [25]. The cell lines were grown in RPMI
1640 medium containing 10% fetal bovine serum and 2 mM L-glutamine. For the
present screening experiment, cells were inoculated into 96-well microtiter plates in
90 lL at 5000 cells per well. After cell inoculation, the micro-titer plates were
incubated at 37 °C, 5% CO2, 95% air and 100% relative humidity for 24 h prior to
addition of the experimental drugs, which were solubilized in an appropriate solvent
to prepare stock of 10-2 concentration. At the time of experiment, four 10-fold
serial dilutions were made using complete medium. Aliquots of 10 ll of these
different drug dilutions were added to the appropriate micro-titer wells already
containing 90 ll of medium, resulting in the required final drug concentrations.
After addition of the compound, the plates were incubated in standard conditions for
48 h and the assay was terminated by the addition of cold TCA. Cells were fixed
in situ by the gentle addition of 50 ll of cold 30% (w/v) TCA (final concentration,
10% TCA) and incubated for 60 min at 4 °C. The supernatant was discarded and the
plates were washed five times with tap water and air-dried. Sulforhodamine B
(SRB) solution (50 ll) at 0.4% (w/v) in 1% acetic acid was added to each of the
wells, and the plates were incubated for 20 min at room temperature. After staining,
unbound dye was recovered and the residual dye was removed by washing five
times with 1% acetic acid, and the plates were air-dried. Bound stain was
subsequently eluted with 10 mM trizma base, and the absorbance was read on an
Elisa plate reader at a wavelength of 540 nm with 690-nm reference wavelength.
The GI50 values, defined as the drug concentration required for inhibiting the growth
of cell proliferation by 50%, were calculated from the percent growth and were
expressed as the ratio of average absorbance of the test well to the average
absorbance of the control wells 9 100. Using the six absorbance measurements
[time zero (T), control growth (C), and test growth in the presence of drug at the
four concentration levels (Ti)], the percentage growth was calculated at each of the
drug concentration levels. The results are expressed as GI50 (growth inhibitory
concentration at 50%), i.e. the concentration of the compound which inhibits the
tumor cell growth by 50%, and the data are presented in Table 1 and Figs. 1 and 2.
Cell growth inhibition was investigated by SRB assay and the results indicate
that the some of compounds show an inhibitory effect on the proliferation of HCT-
15 and MIAPaCa-2 cells in a dose-dependent manner (Table 1). Compound IIC is
found to exhibit excellent cytotoxic potency (10 lg/ml) which is comparable with
of adriamycin (10 lg/ml) against the HCT-15 cell. Similarly, the compounds IIIB
and IIC were found to possess excellent cytotoxic potency (10 lg/ml) compared
with adriamycin (10 lg/ml) against MIAPaCa-2. Of note is that the derivatives
IIIA, IIIC and IIIC derived from 2-acetohydrazide of carvacrol show better activity
than those derived from 2-acetohydrazide of thymol.
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J. D. Rajput et al.
Table 1 Anti-oxidant and anticancer activity of synthetized compounds
Sr.
no.
Name of derivatives
Anti-oxidant test
EC50 in lg/ml
Anticancer test
Colon cancer
GI50 in lg/ml
Pancreatic cancer
GI50 in lg/ml
1.
Carvacryl acetohydrazone
0.1602
80
80
of carvacrol (IIIA)
2.
3.
4.
5.
6.
7.
Carvacryl acetohydrazone
of Thymol (IIIB)
0.2011
0.1224
18.22
80
10
80
80
80
10
10
10
80
80
80
10
Carvacryl acetohydrazone
of Eugenol (IIIC)
Thymyl acetohydrazone
of Thymol (VIA)
Thymyl acetohydrazone
of carvacrol (VIB)
4.652
Thymyl acetohydrazone
of Eugenol (VIC)
0.1348
STD
0.1203
Butylated hydroxy
toluene ([BHT)
Adriamycin
(ADR)
Adriamycin
(ADR)
* All calculations related to EC50 and GI50 are performed from graphpad prism (http://www.graphpad.
com/scientific-software/prism/)
Fig. 1 Cytotoxicity effects of acetohydrazones measured against colon cancer on the HCT-15 cell line
Anti-oxidant activity
DPPH radical-scavenging activity was performed by the reported method [26]. For
each determination, the stock solution (1 mg/ml) was diluted by serial dilution
(25 lg–500 lg/ml) with 60% (v/v) ethanol. An aliquot of each dilution (0.5 mL)
was mixed with a methanolic solution of DPPH (5 mL, 0.06 mM). The mixtures
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Design, synthesis, biological screenings and docking…
Fig. 2 Cytotoxicity effects of acetohydrazones measured against pancreatic cancer on the MIAPaCa cell
line
were shaken vigorously and incubated at 37 °C in the dark for 30 min. At the same
time, a control containing 60% (v/v) ethanol (0.5 mL) and methanolic solution of
DPPH (5 mL, 0.06 mM) was run. The absorbance was measured at 517 nm. The
percentage of DPPH scavenging versus concentration of samples was plotted. The
concentration of the sample necessary to decrease the DPPH concentration by 50%
was obtained by interpolation from linear regression analysis and denoted as the
EC50 value (lg/mL). All determinations were carried out in triplicate. Butylated
hydroxy toluene (BHT) was used as the reference compound. Figure 3 demonstrates
the % radical scavenging against the concentration of the entity.
DPPH radical scavenging activity of the compounds was found to be good to
outstanding as compared to the standard BHT. In particular, compounds IIIA, IIIB,
IIIE and VIC showed outstanding EC50 values which are comparable with STD,
while VIA and VIB demonstrated a decrease in % anti-oxidant activity with higher
EC50 values. The lowest activity was noted for VIA at every concentration; perhaps
Fig. 3 Anti-oxidant activity of acetohydrazones determined by the DPPH free radical method at various
concentrations
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J. D. Rajput et al.
due to the phenolic OH present in the steric crow. The anti-oxidant activity of the
compounds is related to their electron or hydrogen radical releasing abilities to
DPPH so that they become stable diamagnetic molecules. This might be the reason
for the higher or lower anti-oxidant activity. IIIC showed the highest anti-oxidant
activity with a remarkable EC50 value which is comparatively lower than STD. All
EC50 values for synthesized derivatives are shown in Table 1.
Molecular docking studies
The docking study was performed by FRED (Open Eye) and used to determine the
orientation of inhibitors bound in the active site of cyclooxygenases-2 (COX-2,
PDB code: 4PH9). The PDB files were downloaded from the Protein Data Bank
(www.rsc.org). The ligands were drawn in Chem Draw Ultra 12.0 (Freeware) and
the FRED docking programme was used to perform molecular docking [27]. The
docking of ligand molecules with COX-2 indicated that all the inhibitor compounds
exhibit bonding with more than one amino acid in the active pocket (Fig. 4) and that
they may be considered as good inhibitors of cyclooxygenases-2 (COX-2). The
study also showed that the phenolic monoterpenoids-based scaffolds are attached to
the key residues , i.e. TYR356, ARG121, IBP601 and SER354 of the active pocket
of cyclooxygenases (COX-2). Moreover, all the compounds have a minimum
binding energy and docking scores comparable with Ibuprofen from Tables 2 and 3,
and hence could be considered as having a good affinity with cyclooxygenases
(COX-2). The theoretical outcome highlighted that the minimum binding energy of
the molecules with the targeted enzyme suggests that the synthesized carvacrol- and
thymol-based scaffolds are good inhibitors ofto cyclooxygenases-2 (COX-2).
Therefore, it is striking to state that the docking studies have extended the scope of
developing carvacrol and thymol derivatives as promising anti-oxidant and anti-
cancer agents.
On the basis of the EC50 values, all the compounds have been found to possess
excellent anti-oxidant potency, and similarly the values of GI50 in anticancer test
indicated good anticancer potency for some of the compounds. The molecular
docking study was done by FRED (Open Eye) on cyclooxygenases-2. Overall
docking results suggested that the synthesized compounds exhibit good binding
affinity towards receptors.
Conclusion
In conclusion, six novel derivatives of carvacrol and thymol moieties containing an
acetohydrazone linkage have been synthesized by a multistep pathway with good
practical yields of the synthesized compounds. Anticancer and anti-oxidant
activities were tested in vitro. The obtained results indicated that the free hydroxy
group in a given scaffold has significantly improved anti-oxidant potency. All the
synthesized compounds displayed extensive in vitro anti-oxidant activities by DPPH
assay. In the anticancer test using SRB assay against pancreatic cancer with the
MIAPaCa-2 cell line and colon cancer with the HCT-15 cell line, the GI50 values of
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Design, synthesis, biological screenings and docking…
Fig. 4 a General molecule in the active pocket site of cyclooxygenases-2 (COX-2). b Binding mode of
all inhibitors in active site of cyclooxygenases (COX-2). c Interaction of IIIA with cyclooxygenases
(COX-2). d Binding of IIIA with amino acids of cyclooxygenases (COX-2). e Binding of IIIC with
amino acids of cyclooxygenases (COX-2). f Binding of VIA with amino acids of cyclooxygenases (COX-
2). g Binding of VIB with amino acids of cyclooxygenases (COX-2). h Binding of VIC with amino acids
of cyclooxygenases (COX-2)
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Table 3 Docking score, steric score and structural parameters of synthesized derivatives
Sr. No.
Name
Docking
score
Steric
score
Desolvation
Hydrogen
bond acceptor
Hydrogen
bond donor
1
2
3
4
5
6
7
IIIA
-64.18
-79.40
-67.96
-78.71
-49.92
-82.45
-81.28
-76.85
-82.73
-75.08
-87.63
-57.09
-85.69
-82.91
13.21
12.95
14.82
13.06
12.01
14.90
10.35
-0.54
-9.29
-6.22
-2.30
-4.59
-9.47
-8.72
0.00
-0.32
-1.48
-1.85
-0.25
-2.19
0.00
IIIB
IIIC
VIA
VIB
VIC
Ibuprofen
two compounds, i.e. IIIB and IIIC, indicated their good anticancer efficacy. The
entire results of the molecular docking studies of the synthesized derivatives carried
on the COX-2 enzyme suggested that all the synthesized derivatives exhibit
excellent binding affinity towards it.
Acknowledgements RSB thanks UGC-SAP (DSA-I) and Jamatsing D. Rajput gratefully thanks UGC,
New Delhi, for the BSR Fellowship of Ph.D Candidates. We are also are grateful to Dr. Davinder Tuli for
the molecular docking studies.
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