Design, synthesis, molecular docking and biological evaluation of novel coumarin-oxime ether derivatives as COX-2 inhibitors

Article abstract of DOI:10.14233/ajchem.2017.20865

Coumarin-oxime ether derivatives (14-25) were synthesized by an efficient and straight forward procedure from the reaction of 3-acetyl coumarin (1) and o-substituted benzyl hydroxyl amines (2-13) in pyridinium p-toluenesulfonate/dichloromethane (PPTS/DCM)

Full text of DOI:10.14233/ajchem.2017.20865

Asian Journal of Chemistry; Vol. 29, No. 11 (2017), 2559-2564
ASIAN JOURNAL OF CHEMISTRY
https://doi.org/10.14233/ajchem.2017.20865
Design, Synthesis, Molecular Docking and Biological Evaluation of
Novel Coumarin-Oxime Ether Derivatives as COX-2 Inhibitors
2
1
2
M. VIJAYA BHARGAVI1,2,*, P. SHASHIKALA , M. SUMAKANTH and SHRAVAN KUMAR GUNDA
1RBVRR Women's College of Pharmacy, 3-4-343, Barkathpura, Hyderabad-500 027, India
2Department of Pharmacy, Faculty of Technology, Osmania University, Hyderabad-500 007, India
*Corresponding author: E-mail: mvijayabhargavi@gmail.com
Received: 15 June 2017;
Accepted: 28 August 2017;
Published online: 29 September 2017;
AJC-18591
Coumarin-oxime ether derivatives (14-25) were synthesized by an efficient and straight forward procedure from the reaction of 3-acetyl
coumarin (1) and o-substituted benzyl hydroxyl amines (2-13) in pyridinium p-toluenesulfonate/dichloromethane (PPTS/DCM) at reflux
temperature. High yields and simple operations are important features of this methodology. The method is very useful for the construction
of many biologically active oxime ether derivatives. The structures of the synthesized compounds are established based on IR, NMR and
MASS spectrometry. Molecular docking studies were performed against selective COX-2 enzyme using Discovery Studio v3.5. The
compounds with good LibDock score were screened for their in vivo anti-inflammatory activity by paw edema method, employing
indomethacin as a reference standard.
Keywords: 3-Acetyl coumarin, Benzyl hydroxylamines, Oxime ethers, Docking, COX-2.
OR
H
INTRODUCTION
OR
N
N
Coumarin and its derivatives are some of the most impor-
tant oxygen heterocycles and are extensively found in various
natural and synthetic products [1]. These compounds are broadly
classified as, simple coumarins, furanocoumarins, pyranocou-
marins, biscoumarins, triscoumarins and coumarinolignans.
They are effective pharmacophores, widely used in the drug
design and synthesis of novel bioactive compounds [2]. They
possess different biological activities such as anticoagulant
and cardiovascular activities [3], antimicrobial activities [4],
anticancer [5], anti-inflammatory and antioxidant [6], antiviral
[7] and enzyme-inhibition effect [8]. At this juncture, fused
coumarin derivatives have attracted attention because of their
biological properties [9], like antiproliferative [10], anti-
inflammatory [11] activities.
R1
R1 R2
b
a
Fig. 1. General structure of aldoximes (a) and ketoxime o-ethers (b)
However, up to date, oxime-ethers containing coumarin
moiety has not been reported much. With the aim to seek new
oxime-ether with high anti-inflammatory activity, here we
introduced oxime-ether moiety into coumarin structure
according to the sub-structure link way and synthesized twelve
novel coumarin oxime-ethers. The structures of the synthesized
compounds were assigned on the basis of spectral analysis
and elemental analysis. The compounds were evaluated for
their anti-inflammatory activity.
The oxime ether name is an abbreviation of oxy-imine
ether. The oxime ether moiety (Fig. 1) is a privileged group in
chemistry due to its presence in a large number of medicinal
scaffolds that exhibit a broad range of biological and pharma-
ceutical properties, such as antifungal [12] antibacterial [13],
anti-enteroviral [14], antiprotozoal [15], anti-inflammatory
[16,17], anticonvulsant [18], anticancer [19], antitumor [20]
activities. Therefore, oxime-ether moiety is usually chosen as
an efficiently active group in the drug discovery.
EXPERIMENTAL
There are two methods for the synthesis of oxime-ethers
[21,22]. In the present study, we have synthesized a novel series
of coumarin-oxime ethers (14-25) via condensation reaction
of 3-acetyl coumarin (1) and o-substituted benzylhydroxyl-
amines (2-13) in PPTS/DCM (pyridinium p-toluenesulfonate/
dichloromethane) at reflux temperature in a single step shown
in Scheme-I.

2560 Bhargavi et al.
Asian J. Chem.
O
O
N
3-(1-(4-Bromobenzyloxyimino)ethyl)coumarin (16):
NH2
O
Yield: 95 %; white solid; m.p.: 213-214 °C; IR (KBr, νmax
,
CH3
O
PPTS/DCM
Reflux
O
O
O
cm–1): 2884-2892, 1725 (-C=O), 1604 (-C=N), 1042 (N-O);
1H NMR (CDCl3, 400 MHz): δ 2.27 (s, -CH3), 5.17 (s, -OCH2),
7.26-7.34 (m, H-2', H-6' & H-6, H-8), 7.48-7.56 (m, H-5, H-
3' & H-7, H-5'), 7.83 (s, H-4); 13C NMR (CDCl3, 100.6 MHz):
δ 11.6 (-CH3), 77.2 (-OCH2), 115.1 (C-4a), 116.1 (C-8), 118.1
(C-8a), 122.0 (C-4'), 125.4 (C-6), 125.5 (C-3), 127.9 (C-5), 128.3
(C-7), 129.0 (C-6'), 129.3 (C-2' & C-6'), 131.8 (C-3' & C-5'),
136.3 (C-1'), 137.0 (C-4), 162.8 (-C=N), 166.0 (C-2); DIPMS:
m/z at 373.2 (M+1), 375.2 (M+3); Anal. calcd. (%) for
C18H14NO3Br: C, 58.08; H, 3.79; N, 3.76. Found: C, 58.11; H,
3.83; N, 3.79.
+
CH3
R
R
1
2-13
14-25
4, 16) R = 4-Br
3, 15) R = 4-Cl
2, 14) R = 2-F
5, 17) R = 2-Cl
6, 18) R = 4-F 7, 19) R = 2,4-Dichloro
10, 22) R = 4-CN
9, 21) R = 4-OCH3
8, 20) R = 2-OCH3
11, 23) R = 2-CN 12, 24) R = 3-CN
13, 25) R = 3-OCH3
Scheme-I: Synthesis of coumarin oxime ethers (14-25)
Initially, 3-acetyl coumarin (1) was synthesized from the
reaction of salicyaldehyde and ethyl acetoacetate in the pre-
sence of pyridine and ethyl alcohol. N-Hydroxy phthalimide
was alkylated with substituted benzyl halides in the presence
of K2CO3 and DMF at room temperature. These intermediates
are reacted with hydrazine hydrate in ethanol at reflux temperature
to give o-(substituted benzyl)hydroxylamines (2-13) [23].
Coumarin oxime ethers (14-25) were synthesized from the
reaction of 3-acetyl coumarin (1)and o-substitutedbenzylhydroxyl-
amines (2-13) in PPTS/DCM at reflux temperature.
General procedure for the synthesis of compounds (14-
25): To a stirred solution of 3-acetyl coumarin (1) (150 mg,
0.79 mmol) in DCM (15 mL) was added to PPTS (240 mg,
0.95 mmol) along with O-(2-fluorobenzyl)hydroxylamine (2)
(134 mg, 0.95 mmol) and refluxed continued for 3 h. After
completion of the reaction by TLC detection, Water (30 mL)
and DCM (15 mL) were added and layers separated, dried
over Na2SO4 and concentratedto yield the crude oxime ether,
which was further purified by column chromatography using
silca gel (60 × 120) by eluting with pet. ether:ethyl acetate
(9:1) to yield pure compound.
3-(1-(2-Fluorobenzyloxyimino)ethyl)coumarin (14):
Yield: 90 %; white solid; m.p.: 137-138 °C; IR (KBr, νmax, cm–1):
2890-2910, 1721 (-C=O), 1609 (-C=N), 1039 (N-O); 1H NMR
(CDCl3, 400 MHz) δ 2.28 (s, -CH3), 5.30 (s, -OCH2), 7.16-
7.17 (m, H-5' & H-6'), 7.28-7.30 (m, H-6, H-3' & H-8), 7.42-
7.46 (m, H-7), 7.52-7.54 (m, H-5 & H-4'), 7.87 (s, H-4); 13C
NMR (CDCl3, 100.6 MHz): δ 11.5 (-CH3), 70.2 (-OCH2), 115.2
(C-3'), 115.3 (C-4a), 116.1 (C-8), 118.1 (C-8a), 124.5 (C-5'),
125.2 (C-3), 125.4 (C-6), 127.9 (C-5), 128.4 (C-7), 128.7 (C-6'),
128.9 (C-1'), 129.2 (C-4'), 137.0 (C-4), 159.5 (C-2'), 163.2 (-C=N),
166.0 (C-2), DIPMS: m/z at 312.3 (M+1),Anal. calcd. (%) for
C18H14NO3F: C, 69.45; H, 4.53; N, 4.50. Found: C, 69.54; H,
4.51; N, 4.56.
3-(1-(2-Chlorobenzyloxyimino)ethyl)coumarin (17):
Yield: 90 %; white solid; m.p.: 175-176 °C; IR (KBr, νmax
,
cm–1): 2892-2912, 1720 (-C=O), 1610 (-C=N), 1038 (N-O);
1H NMR (CDCl3, 400 MHz): δ 2.28 (s, -CH3), 5.30 (s, -OCH2),
7.16-7.17 (m, H-5' & H-6'), 7.28-7.30 (m, H-6, H-3' & H-8),
7.42-7.46 (m, H-7), 7.52-7.54 (m, H-5 & H-4'), 7.87 (s, H-4);
13C NMR (CDCl3, 100.6 MHz): δ 11.5 (-CH3), 71.9 (-OCH2),
115.3 (C-4a), 116.1 (C-8), 118.1 (C-8a), 125.2 (C-3), 125.4 (C-6),
127.0 (C-5'), 127.9 (C-5), 128.3 (C-7), 128.5 (C-6'), 129.0 (C-3'),
128.9 (C-4'), 130.7 (C-2'), 137.0 (C-4), 138.2 (C-1'), 163.2 (-C=N),
166.0 (C-2), DIPMS: m/z at 328.7 (M+1),Anal. calcd. (%) for
C18H14NO3ClF: C, 65.96; H, 4.31; N, 4.27. Found: C, 65.54;
H, 4.41; N, 4.26.
3-(1-(4-Fluorobenzyloxyimino)ethyl)coumarin (18):
Yield: 95 %; white solid; m.p.: 191-192 °C; IR (KBr, νmax
,
cm–1): 2896-2918, 1725 (-C=O), 1609 (-C=N), 1045 (N-O);
1H NMR (CDCl3, 400 MHz): δ 2.26 (s, -CH3), 5.18 (s, -OCH2),
7.04-7.08 (m, H-5' & H-6'), 7.33-7.39 (m, H-6, H-3' & H-8),
7.52-7.54 (H-7 & H-2'), 7.64-7.69 (m, H-5), 7.86 (s, H-4); 13C
NMR (CDCl3, 100.6 MHz): δ 11.5 (-CH3), 77.0 (-OCH2), 115.3
(C-4a), 115.7 (C-3' & C-5'), 116.1 (C-8), 118.1 (C-8a), 125.4 (C-6),
125.2 (C-3), 127.9 (C-5), 128.3 (C-7), 128.7 (C-6'), 128.7 (C-2'
& C-6'), 132.9 (C-1'), 137.0 (C-4), 161.8 (C-4'), 163.2 (-C=N),
166.1 (C-2); DIPMS: m/z at 328.7 (M+1), Anal. calcd. (%)
for C18H14NO3F: C, 69.45; H, 4.53; N, 4.50. Found: C, 69.55;
H, 4.43; N, 4.46.
3-(1-(2,4-Dichlorobenzyloxyimino)ethyl)coumarin
(19): Yield: 90 %; white solid; m.p.: 215-216 °C; IR (KBr,
νmax, cm–1): 2890-2910, 1729 (-C=O), 1611 (-C=N), 1031 (N-O);
1H NMR (CDCl3, 400 MHz): δ 2.29 (s, -CH3), 5.31 (s, -OCH2),
7.26-7.29 (m, H-8, H-5' & H-6'), 7.35-7.41 (m, H-3' & H-7),
7.52-7.57 (m, H-5 & H-6), 7.86 (s, H-4); 13C NMR (CDCl3,
100.6 MHz): δ 11.5 (-CH3), 71.9 (-OCH2), 115.3 (C-4a), 116.1
(C-8), 118.1 (C-8a), 125.2 (C-3), 125.4 (C-6), 127.1 (C-5'),
127.9 (C-5), 128.3 (C-7), 129.9 (C-6'), 130.6 (C-3'), 133.8
(C-2'), 134.6 (C-4'), 136.3 (C-1'), 137.0 (C-4), 163.2 (-C=N),
166.0 (C-2), DIPMS: m/z at 363.2 (M+1),Anal. calcd. (%) for
C18H13NO3Cl2: C, 59.69; H, 3.62; N, 3.87. Found: C, 59.54;
H, 3.61; N, 3.96.
3-(1-(4-Chlorobenzyloxyimino)ethyl)coumarin (15):
Yield: 95 %; white solid; m.p.: 173-174 °C; IR (KBr, νmax
,
cm–1): 2892-2912, 1723 (-C=O), 1607 (-C=N), 1041 (N-O);
1H NMR (CDCl3, 400 MHz): δ 2.31 (s, -CH3), 5.24 (s, -OCH2),
7.28-7.41 (m, H-2' to H-6', H-6 & H-8), 7.52-7.54 (m, H-5 &
H-7), 7.87 (s, H-4); 13C NMR (CDCl3, 100.6 MHz): δ 11.5 (-CH3),
77.0 (-OCH2), 115.3 (C-4a), 116.1 (C-8), 118.1 (C-8a), 125.4
(C-6), 125.5 (C-3), 127.9 (C-5), 128.3 (C-7), 129.0 (C-6'),
128.9 (C-3' & C-5'), 129.7 (C-2' & C-6'), 133.2 (C-4'), 135.4
(C-1'), 137.0 (C-4), 163.2 (-C=N), 166.0 (C-2); DIPMS: m/z at
328.7 (M+1), Anal. calcd. (%) for C18H14NO3Cl: C, 65.96; H,
4.31; N, 4.27. Found: C, 65.95; H, 4.33; N, 4.26.
3-(1-(2-Methoxybenzyloxyimino)ethyl)coumarin (20):
Yield: 85 %; white solid; m.p.: 142-144 °C; IR (KBr, νmax
,
cm–1): 2892-2912, 1723 (-C=O), 1610 (-C=N), 1041 (N-O);
1H NMR (CDCl3, 400 MHz): δ 2.38 (s, -CH3), 3.83 (s, -OCH3),
5.30 (s, -OCH2), 6.92-6.96 (m, H-3', H-4' & H-5'), 7.25 (m,
H-6'), 7.40-7.44 (m, H-6), 7.51 (dd, J = 1.09 Hz, 8.05Hz, H-8),
7.65 (m, H-7), 7.54 (s, H-4), 7.84 (dd, J = 1.61 Hz, 7.72 Hz,

Vol. 29, No. 11 (2017)
Synthesis and Biological Evaluation of Novel Coumarin-Oxime Ether Derivatives as COX-2 Inhibitors 2561
H-5); 13C NMR (CDCl3, 100.6 MHz): δ 11.5 (-CH3), 71.1 (-OCH2),
115.3 (C-4a), 116.1 (C-8), 118.1 (C-8a), 124.0 (C-5'), 125.2
(C-3), 125.4 (C-6), 127.2 (C-1'), 127.9 (C-5), 128.3 (C-7),
128.6 (C-4'), 129.0 (C-3'), 129.7 (C-6'), 137.0 (C-4), 156.7
(C-2'), 163.2 (-C=N), 166.0 (C-2); DIPMS: m/z at 324.3 (M+1),
Anal. calcd. (%) for C19H17NO4 : C, 70.58; H, 5.30; N, 4.33.
Found: C, 70.54; H, 5.41; N, 4.36.
137.0 (C-4), 141.9 (C-1'), 163.4 (-C=N), 166.0 (C-2); DIPMS:
m/z at 319.3 (M+1),Anal. calcd. (%) for C19H14N2O3 : C, 71.69;
H, 4.43; N, 8.80. Found: C, 71.53; H, 4.51; N, 8.74.
3-(1-(3-Methoxybenzyloxyimino)ethyl)coumarin (25):
Yield: 85 %; white solid; m.p.: 211-212 °C; IR (KBr, νmax
,
cm–1): 2895-2915, 1728 (-C=O), 1610 (-C=N), 1041 (N-O);
1H NMR (CDCl3, 400 MHz): δ 2.32 (s, -CH3), 3.83 (s, -OCH3),
5.31 (s, -OCH2), 6.87-6.97 (m, H-2' & H-4'), 7.05-7.23 (m, H-
5' & H-6'), 7.33-7.42 (m, H-6 & H-8), 7.68 (td, H-7, J = 8.05
Hz, J = 1.61Hz, J = 7.52 Hz), 8.01-8.03 (m, H-4 & H-5); 13C
NMR (CDCl3, 100.6 MHz): δ 11.6 (-CH3), 55.8 (-OCH3), 77.3
(-OCH2), 113.2 (C-4'), 113.5 (C-2'), 115.7 (C-4a), 116.1 (C-8),
119.4 (C-6'), 119.8 (C-8a), 125.3 (C-3), 125.4 (C-6), 127.9 (C-5),
128.3 (C-7), 129.9 (C-5'), 137.0 (C-4), 142.2 (C-1'), 160.8 (C-3'),
163.2 (-C=N), 166.5 (C-2); DIPMS: m/z at 324.3 (M+1),Anal.
calcd. (%) for C19H17NO4 : C, 70.58; H, 5.30; N, 4.33. Found:
C, 70.53; H, 45.31; N, 4.43.
3-(1-(4-Methoxybenzyloxyimino)ethyl)coumarin (21):
Yield: 95 %; white solid; m.p.: 213-214 °C; IR (KBr, νmax
,
cm–1): 2888-2908, 1721 (-C=O), 1609 (-C=N), 1042 (N-O);
1H NMR (CDCl3, 400 MHz): δ 2.34 (s, -CH3), 5.21 (s, -OCH2),
6.96-7.01 (m, H-2', H-3' & H-5', H-6'), 7.42-7.46 (m, H-6 &
H-8), 7.54 (s, H-4), 7.65-7.69 (m, H-7), 7.84 (dd, J = 1.61 Hz,
7.72 Hz, H-5); 13C NMR (CDCl3, 100.6 MHz): δ 11.5 (-CH3),
77.0 (-OCH2), 114.5 (C-3' & C-5'), 115.3 (C-4a), 116.1 (C-8),
118.1 (C-8a), 125.2 (C-3), 125.4 (C-6), 127.9 (C-5), 128.3 (C-7),
129.3 (C-2' & C-6'), 129.6 (C-1'), 137.0 (C-4), 159.5 (C-4'),
163.2 (-C=N), 166.0 (C-2); DIPMS: m/z at 324.3 (M+1),Anal.
calcd. (%) for C19H17NO4 : C, 70.58; H, 5.31; N, 4.33. Found:
C, 70.65; H, 5.33; N, 4.26.
Molecular docking studies: Computational studies of
the novel coumarin oxime ether derivatives were done using
Discovery studio v 3.5. The three dimensional structure of
celecoxib bound at the COX-2 active site (PDB ID: 3LN1)
was retrieved from the Brookhaven Protein Data Bank (PDB),
USA (http://www.rcsb.org/pdb). Protein preparation and ligand
preparation wizard were used for protein and ligand prep-
aration respectively. Initially, ions, water molecules, all the
internal ligands were removed and missing atoms were inserted
before minimization of the target protein. Alternate conform-
ations (disorder) were removed.
The bioactive binding poses of inhibitors in the active
site of the enzyme was generated by using a LibDock program
of Discovery Studio. The ligand poses were placed in to polar
and apolar interactions site. MMFF force field was used for
energy minimization of the ligands. ‘Hotspots’are the binding
site features. The hotspot map counts for polar and apolar cluster
in the active site of the protein which is further used for the
alignment of the ligand conformations to the interaction sites
of the protein.All the minimized ligand poses and their rankings
are based on the ligands score. In accordance with the LibDock
score, each pose is assessed for binding energy, by a simple pair-
wise method.The ligands with high LibDock scores are considered
for estimating binding energies of the protein-ligand complex.
The complex pose with the best binding energy is used for
further binding mode analysis. For the docking validation, the
co-crystallized ligand CEL in the Musmusculus COX-2 binding
site is redocked. The binding affinities of the synthesized comp-
ounds were compared and analyzed in reference to celecoxib
to identify structural characteristics of the complexes formed
by these compounds and the protein.
3-(1-(4-Cyanobenzyloxyimino)ethyl)coumarin (22):
Yield: 85 %; white solid; m.p.: 223-224 °C; IR (KBr, νmax
,
cm–1): 2892-2912, 1723 (-C=O), 1607 (-C=N), 1041 (N-O),
1
2230 (-CN); H NMR (CDCl3, 400 MHz): δ 2.37 (s, -CH3),
5.22 (s, -OCH2), 7.32-7.39 (m, H-2', H-6', & H-6), 7.44 (dd,
J = 1.09 Hz, J = 8.05 Hz, H-5 & H-7), 7.65-7.71 (m, H-7),
7.82 (dd, J = 2.23 Hz, J = 8.29 Hz, H-3' & H-5'), 7.87 (s, H-4),
8.03 (dd, J = 1.61 Hz, 7.72Hz, H-5); 13C NMR (CDCl3, 100.6
MHz): δ 11.5 (-CH3), 77.0 (-OCH2), 111.5 (C-4'), 115.3 (C-4a),
116.1 (C-8), 118.1 (C-8a), 118.6 (4'-CN), 125.4 (C-6), 125.5
(C-3), 127.9 (C-5), 128.3 (C-7), 127.9 (C-2' & C-6'), 132.4 (C-3'
& C-5'), 141.6 (C-1'), 137.0 (C-4), 163.2 (-C=N), 166.0 (C-2);
DIPMS: m/z at 319.3 (M+1), Anal. calcd. (%) for C19H14N2O3 :
C, 71.69; H, 4.43; N, 8.80. Found: C, 71.95; H, 4.41; N, 8.82.
3-(1-(2-Cyanobenzyloxyimino)ethyl)coumarin (23):
Yield: 80 %; white solid; m.p.: 153-155 °C; IR (KBr, νmax
,
cm–1): 2895-2915, 1727 (-C=O), 1607 (-C=N), 1041 (N-O),
1
2233 (-CN); H NMR (CDCl3, 400 MHz): δ 2.30 (s, -CH3),
5.31 (s, -OCH2), 7.16-7.17 (m, H-5' & H-6'), 7.28-7.31 (m,
H-6, H-3' & H-8), 7.42-7.46 (m, H-7), 7.51-7.56 (m, H-5 & H-4'),
7.89 (s, H-4); 13C NMR (CDCl3, 100.6 MHz): δ 11.9 (-CH3),
70.6 (-OCH2), 115.3 (C-3'), 115.7 (C-4a), 116.1 (C-8), 119.8 (C-8a),
124.7 (C-5'), 125.3 (C-3), 125.8 (C-6), 127.9 (C-5), 128.3 (C-7),
128.7 (C-6'), 128.9 (C-1'), 129.6 (C-4'), 137.3 (C-4), 159.6
(C-2'), 163.4 (-C=N), 166.0 (C-2), DIPMS: m/z at 319.3 (M+1),
Anal. calcd. (%) for C19H14N2O3 : C, 71.69; H, 4.43; N, 8.80.
Found: C, 71.54; H, 4.49; N, 8.76.
3-(1-(3-Cyanobenzyloxyimino)ethyl)coumarin (24):
Yield: 75 %; white solid; m.p.: 192-193 °C; IR (KBr, νmax
,
Anti-inflammatory activity-carrageenan-induced rat
paw edma assay: Anti-inflammatory activity of synthesized
compounds was assessed by carrageenan-induced rat paw edema
method which was described by Winter et al. [24]. Carrageenan
(0.1 mL, 1 %) was administered into the plantar surface of the
right hind paw of the animals to induce edema. Wistar rats
weighing between 190 and 260 g, were used in the current
study.
cm–1): 2891-2911, 1729 (-C=O), 1608 (-C=N), 1049 (N-O),
1
2236 (-CN); H NMR (CDCl3, 400 MHz): δ 2.31 (s, -CH3),
5.33 (s, -OCH2), 7.33-7.42 (m, H-6 & H-8), 7.50-7.55 (m, H-5'
& H-6'), 7.68 (td, H-7, J = 8.05 Hz, J = 1.61Hz, J = 7.52 Hz),
7.97 (m, H-4'), 8.01-8.03 (m, H-4 & H-5), 8.07 (d, H-2', J = 1.55
Hz, J = 1.55 Hz); 13C NMR (CDCl3, 100.6 MHz): δ 11.5 (-CH3),
76.5 (-OCH2), 112.8 (C-3'), 116.1 (C-8), 115.7 (C-4a), 118.6
(3-CN), 119.8 (C-8a), 125.3 (C-3), 125.4 (C-6), 127.7 (C-5),
128.3 (C-7), 129.7 (C-5'), 131.1 (C-4'), 131.3 (C-2'), 131.4 (C-6'),
Indomethacin was used as a reference drug. The rats were
divided into eight groups, each group consist of five animals.

2562 Bhargavi et al.
Asian J. Chem.
Group-1 referred as control (animals received carrageenan
along with the vehicle [0.5 % carboxy methyl cellulose (CMC)]
and Group-2 received standard reference (indomethacin) along
with the vehicle prior to the administration of carrageenan.
Group 3-8 received the test compounds.All the test compounds
were suspended in 0.5 % of CMC and administered orally (10
mg/kg) 60 min prior to the injection of 0.1 mL of freshly
prepared carrageenan (1 %) in physiological solution (154 mM
NaCl) into the sub-planter tissue of hind paw of each rat.
Plethysmometer apparatus was used to measure the volume
prior to the administration of carrageenan, 2 and 4 h after the
injection. The increase in volume of the rat paw was adopted
as a measure of edema. The antiedematous effects of the com-
pounds were estimated as percentage inhibition of the induced
inflammation in comparision with control. Statistical analysis
was also carried out using a one-way analysis of variance
(ANOVA). A significance level of p < 0.001 denoted signifi-
cance in all cases.
RESULTS AND DISCUSSION
Docking: Molecular docking studies are used to study
the binding modes and affinities of our synthesized compounds
with Musmusculus COX-2 (PDB ID: 3LN1). All the ligands
were targeted to celecoxib bound at the COX-2 site. The best
ligand conformation is chosen on the base of LibDock score
and highly interacting amino acid residues. Of the ten confor-
mations generated for each compound, the compound with
the highest LibDock score is taken for interaction analysis of
the hydrogen bonding. LibDock scores of all the compounds
along with their hydrogen bond interactions and bond lengths
are depicted in Table-1. The interaction of amino acid residues
with bound ligands as represented by different colours e.g.,
pink indicates electrostatic interaction, purple indicates covalent
bond and green colour indicates vander waals molecular inter-
action (Fig. 2). From the overall docking and interaction analysis,
the best conformation of the compound 23 docked complex
shows high LibDock score of 141.261 kcal/mol and forms
hydrogen bonds with the protein COX-2. Hydrogen bonds are
formed between the H12 of arginine 106 with the N24 atom
of compound 23 with a hydrogen bond distance of 2.303000
Å and the second hydrogen bond is formed with the same
amino acid arginine 106 between H22 with the N24 atom of
compound 23 with a hydrogen bond distance of 1.976000.
The percentage inhibition of edema was calculated using
the formula given below:
(Vc – Vt/Vc) × 100
Vc is the increase in paw volume of control; Vt is the increase
in paw volume after administration of the test compound.
(a)
(b)
(c)
(d)
Fig. 2. Molecular interaction of 3LN1 with (a) compound 14, (b) compound 17, (c) compound 20 and (d) compound 23

Vol. 29, No. 11 (2017)
Synthesis and Biological Evaluation of Novel Coumarin-Oxime Ether Derivatives as COX-2 Inhibitors 2563
TABLE-1
INTERACTION OF LIGAND AND AMINO ACIDS
Compound No.
Interacting amino acids
Interacting atoms
H-Distance
A:ARG106:HH11- Comp14:O9
A:ARG106:HH11 -Comp14:O7
Gln178, Arg499, Arg106, Leu517 A:ARG106:HH12 -Comp14:O7
Leu338, Phe504His75, Val509
A:LEU517:HN - Comp14:N13
Val335, Ala513, Leu345, Leu517 Comp14:H28 - A:LEU345:CD2
Comp14:H30 - A:LEU345:CD1
2.490000
2.467000
2.256000
1.836000
1.996000
2.133000
Tyr371, Trp373, Phe504, Gly512
14
A:ARG106:HH11 - Comp15:O9
2.299000
2.315000
1.951000
2.099000
2.182000
2.028000
Tyr371, Trp373, Phe504, Gly512
Gln178, Arg499, Arg106, Leu517 A:ARG106:HH12 - Comp15:O9
Leu338, Phe504His75, Val509
A:ARG106:HH12 - Comp15:N13
A:ARG106:HH11 - Comp15:N13
15
Val335, Ala513, Leu345, Leu517 Comp15:H30 - A:TYR341:CE2
Comp15:H36 - A:VAL509:CG1
Tyr371, Trp373, Phe504, Gly512
Gln178, Arg499, Arg106, Leu517 A:ARG106:HH12 - Comp16:O9
Leu338, Phe504His75, Val509 A:ARG106:HH11 - Comp16:O9
A:ARG106:HH12 - Comp16:N13
2.289000
1.722000
2.214000
2.211000
2.458000
2.195000
1.637000
2.572000
2.388000
16
17
Val335, Ala513, Leu345, Leu517 A:ARG106:NH1 - Comp16:O9
A:ARG106:HH12 - Comp17:N13
Tyr371, Trp373, Phe504, Gly512
A:ARG106:HH11 - Comp17:O9
Gln178, Arg499, Arg106, Leu517
A:ARG106:HH12 - Comp17:O9
Leu338, Phe504His75, Val509
Val335, Ala513, Leu345, Leu517
Comp17:C12 - A:LEU517:CD1
Comp17:C14 - A:LEU517:CG
A:ARG106:HH11 - Comp18:O7
Tyr371, Trp373, Phe504, Gly512
2.418000
2.030000
2.457000
1.942000
1.935000
A:ARG106:HH12 - Comp18:O7
Gln178, Arg499, Arg106, Leu517
Leu338, Phe504His75, Val509
Val335, Ala513, Leu345, Leu517
A:ARG106:HH12 - Comp18:O9
Comp18:H25 - A:LEU345:CD2
18
19
20
Comp18:H35 - A:LEU338:CD2
Tyr371, Trp373, Phe504, Gly512
Gln178, Arg499, Arg106, Leu517 A:TYR371:HH - Sc1_Comp19:Cl23
Leu338, Phe504His75, Val509
Val335, Ala513, Leu345, Leu517
2.342000
2.158000
Comp19:H25 - A:TYR341:CE2
A:ARG106:HH22 - Sc1_Comp20:O9
A:ARG106:HH12 - Sc1_Comp20:O9
A:ARG106:HH12 - Sc1_Comp20:N13
A:TYR341:CE2 - Comp20:H34
2.393000
2.391000
2.322000
1.959000
2.186000
Tyr371, Trp373, Phe504, Gly512
Gln178, Arg499, Arg106, Leu517
Leu338, Phe504His75, Val509
Val335, Ala513, Leu345, Leu517
A:LEU338:CB - Comp20:H28
Tyr371, Trp373, Phe504, Gly512
Gln178, Arg499, Arg106, Leu517
Leu338, Phe504His75, Val509
Val335, Ala513, Leu345, Leu517
A:ARG106:HH12 - Comp21:N13
A:ARG106:HH11 - Comp21:N13
A:TYR341:CE2 - Comp21:H31
2.378000
2.018000
1.999000
21
22
23
Tyr371, Trp373, Phe504, Gly512
A:TYR371:HH - Comp22:N24
2.344000
2.003000
1.508000
2.141000
2.366000
1.976000
2.303000
1.977000
Gln178, Arg499, Arg106, Leu517 A:ARG106:HH11 - Comp22:O9
Leu338, Phe504His75, Val509 A:ARG106:HH12 - Comp22:O9
Val335, Ala513, Leu345, Leu517 Comp22:H30 - A:LEU345:CD2
Tyr371, Trp373, Phe504, Gly512 A:TYR341:HH - Comp23:N24
Gln178, Arg499, Arg106, Leu517 A:ARG106:HH22 - Comp23:N24
Leu338, Phe504His75, Val509 A:ARG106:HH12 - Comp23:N24
Val335, Ala513, Leu345, Leu517 Comp23:C23 - A:ARG106:HH12
A:ARG106:HH12 - Comp24:N13
2.158000
2.341000
2.018000
1.875000
1.733000
Tyr371, Trp373, Phe504, Gly512
A:ARG106:HH12 - Comp24:O15
Gln178, Arg499, Arg106, Leu517
A:ARG499:HH22 - Comp24:N24
Leu338, Phe504His75, Val509
24
25
A:LEU517:HN - Comp24:O9
Val335, Ala513, Leu345, Leu517
Comp24:H38 - A:TYR341:OH
A:LEU517:HN - Comp25:O15
Tyr371, Trp373, Phe504, Gly512
A:LEU517:HN - Comp25:N13
2.279000
2.270000
2.148000
1.984000
1.977000
Gln178, Arg499, Arg106, Leu517
A:ARG106:HH12 - Comp25:O7
Leu338, Phe504His75, Val509
Val335, Ala513, Leu345, Leu517
A:LEU345:CD2 - Comp25:H26
A:LEU517:CD1 - Comp25:C11
Leu345, Leu157, Arg106,
Val335, Tyr341, Leu338
Ser339, Gln178, Ala513
Gly512, Tyr371, Val509
His75, Trp373, Phe504
Gln178
Celecoxib:H28 - A:HIS75:NE2
Celecoxib:H28 - A:SER339:O
A:ARG499:HH11 - Celecoxib:O6
Celecoxib:H28 - A:HIS75:NE2
A:PHE504:HN - Celecoxib:N9
Celecoxib:H28 - A:PHE504:HN
2.387000
2.413000
2.308000
2.387000
2.081000
1.396000
Celecoxib

2564 Bhargavi et al.
Asian J. Chem.
Antiinflammatory activity: The compounds with good
Libdock scores (Table-2) were selected for antiinflammatory
activity using carrageenan-induced rat paw edema model and
exhibited protection against carrageenan-induced edema. The
protection ranged up to 70 %, while the reference drug (indo-
methacin) showed 76 % at an equivalent dose. Among all the
tested compounds, 3-(1-(2-cyanobenzyloxyimino)ethyl)coumarin
showed remarkable antiinflammatory activity compared to other
derivatives. This compound has cyano group at the ortho-position
of aromatic ring showed enhanced activity compared to other
aromatic analogues (Table-3).
Management of RBVRR Women’s College of Pharmacy for
their constant support and for providing necessary facilities.
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energy
van der
Waals energy
LibDock
score
Compd. No.
14
15
3.562
-2.752
-1.316
2.997
-4.282
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4.079
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3.938
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3.635
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4.465
3.861
3.359
3.297
4.745
3.059
5.172
4.555
3.847
3.836
4.81
137.534
130.704
130.123
135.833
135.833
133.259
139.171
120.812
124.802
141.261
133.009
138.151
145.691
16
17
18
19
20
21
22
23
24
3.647
3.572
4.762
25
Celecoxib
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TABLE-3
ANTI-INFLAMMATORY ACTIVITY
OF THE TESTED COMPOUNDS*
Volume of Paw edema (mL)
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Treatment
2 h
0.93 0.01
4 h
0.89 0.02
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Indomethacin
0.22 0.01 (76.06)
0.36 0.03 (60.87)
0.37 0.03 (59.78)
0.39 0.02 (57.61)
0.35 0.01 (61.96)
0.28 0.01 (68.30)
0.38 0.02 (59.76)
0.19 0.02 (78.64)
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Herewith, we report the simple and efficient method for
synthesis of novel coumarin-oxime ether derivatives (14-25).
The present methodology used to synthesize oxime ether deriv-
atives which is the first example in coumarin chemistry can
be further explored for the synthesis of various heterocycle-
coumarin oxime ether derivatives.All the synthesized compounds
were docked with 3LN1 and Libdock scores are measured.
The compounds which got the good libDock score evaluated
for their in vivo anti-inflammatory activity. The compound 3-
(1-(2-cyanobenzyloxyimino)ethyl)coumarin (23) exhibited
good antiinflammatory activity.
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ACKNOWLEDGEMENTS
The authors express their thanks to The Head, Department
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