Synthesis, characterization, biological screening, ADME and molecular docking studies of 2-phenyl quinoline-4-carboxamide derivatives

Article abstract of DOI:10.14233/ajchem.2020.22583

In this work, some 2-phenyl quinoline-4-carboxamide derivatives (5a-j) were synthesized via base catalyzed Pfitzinger reaction of isatin and acetophenone followed by C-N coupling reaction using POCl3 and assessed them for their in vitro antimicrobial and anticancer activity. The structure of newly synthesized compound were established by FT-IR, ¹H & ¹³C NMR and Mass spectrometric analysis. The synthesized carboxamides were subjected to preliminary in vitro antibacterial activity as well as for antifungal activity. Results of antibacterial activity were compared with standard antibacterial (ciprofloxocin) and antifungal (fluconozole). Among the tested compounds, 5d, 5f and 5h exhibited promising activity with zone of inhibition ranging from 10 to 25 mm. Further, the anticancer activity determined using MTT assay against two cancer cell lines. Compounds 5b, 5d, 5f and 5h showed good anticancer activity among all the other derivatives. In order to correlate the in vitro results, in silico ADME and Molecular docking studies were carried out for (5a-j). ADME properties results showed that all the compounds obey rule of Five rule except 5a, 5e and 5g compound. Molecular docking studies of the synthesized compounds showed good binding affinity through hydrogen bond interactions with key residues on active sites as well as neighboring residues within the active site of chosen target proteins viz. antibacterial, antifungal and anticancer. Comparison of both results of in silico as well as in vitro investigation suggests that the synthesized compounds may act as potential antimicrobial as well as anticancer agents.

Full text of DOI:10.14233/ajchem.2020.22583

Asian Journal of Chemistry; Vol. 32, No. 5 (2020), 1151-1157
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2020.22583
Synthesis, Characterization, Biological Screening, ADME and Molecular
Docking Studies of 2-Phenyl Quinoline-4-Carboxamide Derivatives
1,
1,
1,
1,
2
1,*,
P. RAGHURAMA SHETTY , G. SHIVARAJA , G. KRISHNASWAMY , K. PRUTHVIRAJ , VIVEK CHANDRA MOHAN and S. SREENIVASA
1Department of Studies and Research in Organic Chemistry, Tumkur University, Tumakuru-572103, India
2Department of Biotechnology, Siddaganga Institute of Technology, Tumakuru-572103, India
*Corresponding author: E-mail: drsreenivasa@yahoo.co.in
Received: 10 December 2019;
Accepted: 23 January 2020;
Published online: 29 April 2020;
AJC-19849
In this work, some 2-phenyl quinoline-4-carboxamide derivatives (5a-j) were synthesized via base catalyzed Pfitzinger reaction of isatin
and acetophenone followed by C-N coupling reaction using POCl3 and assessed them for their in vitro antimicrobial and anticancer
activity. The structure of newly synthesized compound were established by FT-IR, 1H & 13C NMR and Mass spectrometric analysis. The
synthesized carboxamides were subjected to preliminary in vitro antibacterial activity as well as for antifungal activity. Results of antibacterial
activity were compared with standard antibacterial (ciprofloxocin) and antifungal (fluconozole). Among the tested compounds, 5d, 5f and
5h exhibited promising activity with zone of inhibition ranging from 10 to 25 mm. Further, the anticancer activity determined using MTT
assay against two cancer cell lines. Compounds 5b, 5d, 5f and 5h showed good anticancer activity among all the other derivatives. In
order to correlate the in vitro results, in silico ADME and Molecular docking studies were carried out for (5a-j). ADME properties results
showed that all the compounds obey rule of Five rule except 5a, 5e and 5g compound. Molecular docking studies of the synthesized
compounds showed good binding affinity through hydrogen bond interactions with key residues on active sites as well as neighboring
residues within the active site of chosen target proteins viz. antibacterial, antifungal and anticancer. Comparison of both results of in silico
as well as in vitro investigation suggests that the synthesized compounds may act as potential antimicrobial as well as anticancer agents.
Keywords: Pfitzinger reaction, 2-Phenyl-quinoline-4-carboxamide, Bioactivity, in silico ADME, Molecular docking studies.
acid derivatives [14] exhibited good antibacterial activity and
they are most suitable for further modifications to obtain more
effective antimicrobial agents as shown in Fig. 1.
Additionally, several drug molecules containing quinoline
motif are known to possess wide variety of pharmacological
activities as shown in Fig. 2.All of these stimulated us to focus
on further structural modification of quinoline-4-carboxylic
acid derivatives in order to find novel molecules with potential
antimicrobial as well as anticancer activity.
INTRODUCTION
Among the important class of nitrogen-containing hetero-
cycles, quinoline is one of the ubiquitous and privileged structural
motifs that occur in bioactive natural products and pharmaceu-
tically active therapeutic agents. The recent estimation reveals
that the average nitrogen atoms in a drug molecule rose to 3.0
from 0.7 atoms. Quinoline skeleton are associated with a range
of biological and pharmaceutical activities such as antibacterial
[1,2], antifungal [3], anthelmintic [4], antileismanial [5], anti-
viral [6], anticancer [7], anti-inflammatory effects [8], tubulin
polymerization inhibitors [9], antioxidant [10], antimalerial
[11], HIV integrate inhibitors [12]. Several quinoline analogues
have anticancer activity against HeLa (human cervix cancer
cell line) and MDA-MB-435 (human breast cancer cell line)
[13]. Furthermore, literature survey revealed that the presence
of an aryl ring at the second position of quinolinec-4-carboxylic
EXPERIMENTAL
All chemicals were purchased from Merck India, Spectro-
chem and Sigma-Aldrich. The solvent and the chemicals used
were LR grade. The purity of the compound was confirmed
using TLC silica gel plate and purification by column chroma-
tography.
This is an open access journal, and articles are distributed under the terms of the Attribution 4.0 International (CC BY 4.0) License. This
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1152 Shetty et al.
Asian J. Chem.
H
O
N
CONHR
N
CONH2
F
N
N
O
N
N
R = Alkyl, Aryl
(B)
(A)
(C)
Fig. 1. Structure of 2-aryl-quinoline-4-carboxylic acid derivatives with antimicrobial activities
Cl
O
O
O
O
F
F
HO
HO
I
N
N
N
NH
OH
N
H3C
H3C
CH3
Pefloxacin
(antibacterial)
Clioquinol
(antifungal)
Ciprofloxacin
(antibacterial)
CH3
N
CH3
N
Cl
O
CH3
N
NH2
CH3
H3C
N
CH3
N
CH3
N
Pyrvinium
(anthelmintic)
Cl
Tipif arnib
(anticancer)
OH
N
OH
N
H
O
N
O
HN
F
OH
Cl
F
F
N
N
N
F
F
F
O
F
H3C
Amodiaquin
(antimalerial)
Mefloquin
(antimalerial)
Moxifloxacin
(antibiotic)
Fig. 2. Pharmacological drugs containing quinoline moiety

Vol. 32, No. 5 (2020) Synthesis, Biological screening, ADME and Molecular Docking Studies of 2-Phenyl Quinoline-4-Carboxamides 1153
Melting points were determined by open capillary method.
FT-IR spectra was recorded on Jasco FT-IR Spectrometer using
KBr pellets. 1H and 13C NMR spectra were recorded on 399.65
MHz and 100.40 MHz, respectively using CDCl3 and DMSO-d6
as solvent. Chemical shift values were reported in ppm. The
LC-MS was recorded using Waters Alliance 2795 separation
module and the Waters Micromass LCT mass detector.
Step-1: Synthesis of compound 2-phenyl quinoline-4-
carboxylic acid (3): Isatin (1.47 g, 10.0 mmol) in 33% alc.
NaOH (15 mL), acetophenone (1.2 g, 10.0 mmol), ethanol
(15 mL) was taken in a round bottom flask. The reaction
mixture was stirred and refluxed for 12 h. The progress of the
reaction was monitored by TLC (ethyl acetate:petroleum ether,
7:3 v/v). After the completion of the reaction, the reaction
mixture was cooled and poured onto ice-water, then acidified
with 10% HCl to achieve pH 2.0-3.0. The precipitate was fil-
tered, washed with water and dried. The acid was recrystallized
from ethanol [15].
Step-2: Synthesis of compound 2-phenyl quinoline-4-
carboxamides (5a-j): 2-Phenyl quinoline-4-carboxylic acid
(0.73 g, 3 mmol) was taken in round bottom flask, to this POCl3
(5 mL) was added slowly. After 2 h of reflux, substituted aro-
matic primary amines (4a-j) (0.32 g, 3 mmol) were added.
Reaction mixture was stirred and heated under reflux for 8 h.
The reaction progress was monitored by TLC (silica gel, ethyl
acetate/petroleum ether 7:3). Upon completion of the reaction
crushed ice was added to the reaction mixture slowly; the
precipitate obtained was filtered, washed with dil. HCl followed
by water and sodium carbonate solution and finally dried
(Scheme-I).
(358.82); IR (KBr, νmax, cm-1): 3426 (NH str.), 1675 (CO str.),
3116 (aromatic CH str.), 2901 (aromatic CH str.), 1586 (C=N
str.), 1416 (C=C str.); H NMR (400 MHz, CDCl3, δ ppm):
8.20 (s, 1H, Ar-H), 8.14-8.12 (d, J = 4.8 Hz, 1H, Ar-H), 8.08-
8.06 (m, 2H, Ar-H), 7.91 (s, 1H, NH), 7.81 (s, 1H, Ar-H),
7.73-7.69 (t, 2H, Ar-H), 7.52-7.48 (t, 1H, Ar-H), 7.46-7.42 (t,
4H, Ar-H), 7.25 (s, 1H, Ar-H), 7.23-7.21 (d, J = 7.6 Hz, 1H,
Ar-H); 13C NMR (100 MHz, CDCl3, δ ppm): 167.82, 158.16,
152.03, 148.37, 145.4, 144.17, 139.2, 138.29, 135.6, 130.90,
130.76, 129.35, 129.19, 128.34, 127.6, 125.92, 123.75, 122.0,
119.7, 118.54.
1
2-Phenyl-N-(p-tolyl)-quinoline-4-carboxamide (5b):
Yield: 65%, m.p.: 186-189 °C, m.f. (m.w.): C23H18N2O (338.40);
IR (KBr, νmax, cm-1): 3305 (NH str.), 1649.50 (CO str.), 3021
(aro-matic CH str.), 2914 (aromatic CH str.), 1585 (C=N str.),
1
1447 (C=C str.); H NMR (400 MHz, CDCl3, δ ppm): 8.20-
8.18 (d, J = 4.8 Hz, 2H, Ar-H), 8.12-8.11 (d, J = 4.8 Hz, 2H,
Ar-H), 7.97 (s, 1H, Ar-H), 7.74-7.72 (t, J = 4.9 Hz, 1H, Ar-
H),7.65-7.63 (m, 4H, Ar-H), 7.56-7.52 (t, J = 5.1 Hz, 1H, Ar-
H), 7.46-7.45 (d, J = 7.4 Hz, 2H, Ar-H), 7.25-7.22 (d, J = 8.0
Hz, 2H,Ar-H), 2.38 (s, 3H, CH3); 13C NMR (100 MHz, CDCl3,
δ ppm): 165.46, 156.04, 148.30, 142.91, 138.15, 135.20,
134.80, 130.3, 129.8, 128.8, 127.38, 124.93, 122.97, 116.15,
21.00.
2-Diphenylquinoline-4-carboxamide (5c):Yield: 56%,
m.p.: 183-185 °C, m.f. (m.w.): C22H16N2O (324.37); IR (KBr,
ν
max, cm-1): 3422.06 (NH str.), 1675.24 (CO str.), 3059 (aro-
matic CH str.), 2976.95 (aromatic CH str.), 1592 (C=N str.),
1491 (C=C str.) 1H NMR (400 MHz, CDCl3, δ ppm): 8.16 (s,
2H, Ar-H), 8.08-8.06 (dd, J = 5.6 Hz, 3H, Ar-H), 7.95 (s, 2H,
Ar-H), 7.75-7.71 (m, 2H, Ar-H), 7.57-7.53 (m, 2H, -NH &
Ar-H), 7.42-7.34 (m, 5H, Ar-H);13C NMR (100 MHz, CDCl3,
2-Phenyl-N-(3-chlorophenyl)-quinoline-4-carboxamide
(5a): Yield: 76%, m.p.: 176-178 °C, m.f. (m.w.): C22H15N2OCl
NH2
R
O
O
OH
R
O
NH
O
4a-j
O
+
i
ii
N
H
1
N
N
5a-j
3
2
Cl
NO2
Cl
CH3
5b
5a
5c
5d
5e
4a-j
CH3
CH3
N
N
N
O
NO2
O
Br
CH3
5i
5g
5h
5j
5f
Scheme-I: Synthetic route for the preparation of 2-phenyl quinoline-4-carboxamides (5a-j); Reagents and conditions: (i) EtOH, 33% NaOH,
80 °C, Reflux 12 h; (ii) POCl3, 70 °C, Reflux 8 h

1154 Shetty et al.
Asian J. Chem.
δ ppm): 165.60, 154.40, 148.16, 142.67, 137.96, 137.85,
130.34, 129.92, 129.26, 128.8, 127.39, 127.29, 125.10, 124.90,
122.86, 120.20, 116.10.
str.), 3098 (aromatic CH str.), 2891 (aromatic CH str.), 1536
(C=N str.), 1408 (C=C str.); H NMR (400 MHz, CDCl3, δ
1
ppm): 8.75 (d, J = 8 Hz, 1H, Ar-H), 8.45 (d, 1H, Ar-H), 8.05-
8.00 (d, J = 4 Hz, 1H, Ar-H), 8.02-7.95 (d, J = 2 Hz, 1H, Ar-
H), 7.83-7.62 (m, 2H, Ar-H), 7.59 (s, 1H, Ar-H), 7.57 (d, J =
7.6, 1H, Ar-H), 7.42-7.40 (t, 1H, Ar-H); 7.11 (d, 1H, Ar-H).
13C NMR (100 MHz, CDCl3, δ ppm): 164.18, 159.38, 152.3,
147.02, 145.53, 136.7, 134.9, 129.9, 128.9, 128.76, 128.08,
127.59, 127.52, 127.2, 125.5, 121.9, 119.1, 118.9, 115.2.
2-Phenyl-N-(3-methoxyphenyl)-quinoline-4-carboxa-
mide (5i): Yield: 64%, m.p.: 193-195 °C, m.f. (m.w.):
C23H18N2O2 (354.40); IR (KBr, νmax, cm-1): 3408 (NH str.),
1625.2 (CO str.), 3196 (aromatic CH str.), 2896 (aromatic CH
str.), 1558 (C=N str.), 1402 (C=C str.); 1H NMR (400 MHz,
CDCl3, δ ppm): 8.72-8.32 (d, J = 8Hz, 1H, Ar-H), 8.23 (s, 1H,
Ar-H), 8.05-8.00 (d, J = 2 Hz, 1H, Ar-H), 8.02-7.95 (d, J =
2Hz, 1H, Ar-H), 7.83-7.62 (m, 2H, Ar-H), 7.61-7.59 (t, 1H,
Ar-H), 7.42-7.40 (t, 1H, Ar-H); 13C NMR (100 MHz, CDCl3,
δ ppm): 165.8, 157.38, 151.8, 142.5, 133.9, 130.4, 128.9,
128.7, 128.43, 127.8, 127.1, 127.0, 124.8, 122.6, 121.89,
121.7, 119.1, 114.4, 50.4.
2-Phenyl-N-(3-nitrophenyl)-quinoline-4-carboxamide
(5j): Yield: 57%, m.p.: 181-183 °C, m.f. (m.w.): C22H15N3O3
(369.37); IR (KBr, νmax, cm-1): 3412 (NH str.), 1640.1 (CO str.),
2930 (aromatic CH str.), 2847 (aromatic CH str.), 1586.6 (C=N
str.), 1557 (C=C str.); 1H NMR (400 MHz, DMSO-d6, δ ppm):
11.09 (s, 1H, NH), 8.23-8.20 (d, J = 8 Hz, 1H, Ar-H), 8.08-
8.06 (m, 3H, Ar-H), 7.82-7.72 (m, 5H, Ar-H), 7.63-7.59 (m,
1H, Ar-H), 7.43-7.40 (d, J = 7.00 Hz, 2H, Ar-H), 7.25-7.22 (t,
1H, Ar-H); 13C NMR (100 MHz, DMSO-d6, δ ppm): 164.60,
150.13, 148.97, 143.49, 143.26, 137.10, 135.4, 131.05, 130.01,
129.29, 129.21, 129.12, 128.38, 128.18, 127.48, 125.42,
123.46, 122.13, 119.4, 116.27.
Antimicrobial activity: Synthesized 2-phenyl quinoline-
4-carboxamides (5a-j) were separately tested against one
Gram-positive (S. aureus), one Gram-negative bacteria (E.coli)
and two mold fungi viz. Candida albicans and Aspergillus
flavus by agar well diffusion method [16]. The microbial
inoculum is spread across the entire agar plate surface. After
the medium had solidified, holes with a diameter of 6 mm was
punched aseptically by a sterile cork-borer and a concentration
of 50 µg/50 µL doses of the test compounds 5a-j, standard
ciprofloxacin for antibacterial and fluconazole for antifungal
(10 µg/mL) along with negative control DMSO was introduced
into the well separately. Then the plates were incubated at 37
°C for 36 h for bacteria and at 28 °C for 72 h for fungal strains.
After the incubation period is over, zone of inhibition diameter
for each well is measured in mm. The experiment was perfor-
med in triplicates and the average values were reported.
Anticancer activity: Anticancer activity of the comp-
ounds 5a-j was carried out by using MTT assay [17,18] against
two cancer lines A549 lung cancer cell line and MCF-7 breast
cancer cell lines. The test was carried out in accordance with
the literature procedure [19,20]. In this assay, the yellow
coloured 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium
bromide (MTT) is reduced by mitochondrial succinate dehy-
drogenase to an insoluble, coloured formazan product that is
dark purple in colour. The cells are then treated with an organic
2-Phenyl-N-(4-nitrophenyl)-quinoline-4-carboxamide
(5d): Yield: 84%, m.p.: 185-187 °C, m.f. (m.w.): C22H15N3O3
(369.37); IR (KBr, νmax, cm-1): 3438.8 (NH str.), 1688.1 (CO
str.), 3027.6 (aromatic CH str.), 2933.03 (aromatic CH str.),
1
1586.6 (C=N str.), 1510 (C=C str.); H NMR (400 MHz,
DMSO-d6, δ ppm): 11.02 (s, 1H, NH), 8.13-8.12 (d, J = 8 Hz,
1H, Ar-H), 8.08-8.02 (m, 3H, Ar-H), 7.84-7.75 (m, 5H, Ar-
H), 7.61-7.57 (m, 1H, Ar-H), 7.45-7.43 (d, J = 7.00 Hz, 2H,
Ar-H), 7.23-7.21 (t, 1H, Ar-H); 13C NMR (100 MHz, DMSO-
d6, δ ppm): 165.60, 152.13, 147.97, 144.49, 143.26, 138.19,
131.01, 130.07, 129.26, 129.19, 129.10, 128.48, 128.23,
127.59, 125.55, 123.49, 122.01, 116.33.
2-Phenyl-N-(4-chlorophenyl)-quinoline-4-carboxamide
(5e): Yield: 69%, m.p.: 172-174 °C, m.f. (m.w.): C22H15N2OCl
(358.82); IR (KBr, νmax, cm-1): 3428.00 (NH str.), 1635.24 (CO
str.), 3090.0 (aromatic CH str.), 2901 (aromatic CH str.), 1564
(C=N str.), 1416.0 (C=C str.); 1H NMR (400 MHz, CDCl3, δ
ppm): 8.18 (s, 1H, NH), 8.12 (s, 1H, Ar-H), 8.0-8.7.95 (m,
4H, Ar-H), 7.75 (s, 1H, Ar-H), 7.73-7.70 (t, J = 4.8 Hz, 1H,
Ar-H), 7.56-7.50 (t, J = 5.1 Hz, 1H, Ar-H), 7.42-7.38(d, J =
8.0 Hz, 2H, Ar-H), 7.34-7.31 (d, J = 8.0 Hz, 2H, Ar-H), 7.25
(s, 1H, Ar-H), 7.20-7.18 (d, J = 7.6 Hz, 1H, Ar-H); 13C NMR
(100 MHz, CDCl3, δ ppm): 164.2, 158.3, 148.57, 145.17,
136.9, 135.3, 131.90, 131.76, 130.8, 129.2, 129.1, 128.04,
127.92, 127.4, 125.5, 121.6, 119.54.
2-Phenyl-N-(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-
1H-pyrazol-4-yl)-quinoline-4-carboxamide (5f): Yield:
70%, m.p.: 185-187 °C, m.f. (m.w.): C27H22N4O2 (434.49); IR
(KBr, νmax, cm-1): 3412 (NH str.), 1640 (CO str.), 2930 (aro-
matic CH str.), 2847 (aromatic CH str.), 1586.6 (C=N str.),
1557 (C=C str.); 1H NMR (400 MHz, CDCl3, δ ppm): 11.9 (s,
N-H, 1H), 8.56-8.54 (d, J = 8 Hz, 1H, Ar-H), 8.14 (s, 1H, Ar-
H), 8.13-8.09 (d, J = 2 Hz, 1H, Ar-H), 8.07-7.97 (d, J = 2 Hz,
1H, Ar-H), 7.85-7.66 (m, 2H, Ar-H), 7.64-7.48 (t, 1H, Ar-H),
7.46-7.4 (t, 1H, Ar-H), 7.36 (t, 1H, Ar-H), 7.34-7.30 (d, 2H,
Ar-H), 6.93-6.52 (m, 2H, Ar-H), 3.097 (s, N-CH3, 3H), 2.422
(s, CH3-H, 3H); 13C NMR (100 MHz, CDCl3, δ ppm) 173.92,
157.14, 152.81, 148.75, 145.81, 139.19, 133.97, 129.64,
129.47, 128.81, 127.45, 126.63, 126.30, 124.04, 120.33,
117.43, 113.26, 77.02, 29.64.
2-Phenyl-N-(4-bromophenyl)-quinoline-4-carboxamide
(5g): Yield: 82%, m.p.: 164-166 °C, m.f. (m.w.): C22H15N2OBr
(403.27); IR (KBr, νmax, cm-1): 3396 (NH str.), 1645 (CO str.),
3096 (aromatic CH str.), 2804 (aromatic CH str.), 1576 (C=N
1
str.), 1402 (C=C str.); H NMR (400 MHz, CDCl3, δ ppm):
8.72 (d, J = 8 Hz, 1H, Ar-H), 8.24 (s, 1H, Ar-H), 8.05-8.01 (d,
J = 1 Hz, 1H, Ar-H), 8.02-7.97 (d, J = 3 Hz, 1H, Ar-H), 7.83
(d, 1H, Ar-H), 7.73-7.59 (t, 1H, Ar-H), 7.62-7.54 (d, 5H, Ar-
H), 7.37 (d, 2H, Ar-H); 13C NMR (100 MHz, CDCl3, δ ppm):
167.1, 156.3, 145.53, 136.4, 132.03, 132.0, 129.98, 128.8,
128.08, 127.7, 127.36, 127.24, 125.5, 121.8, 121.4, 119.1,
116.9.
2-Phenyl-N-(pyridin-2-yl)-quinoline-4-carboxamide
(5h): Yield: 58%, m.p.: 145-147 °C, m.f. (m.w.): C21H15N3O
(325.36); IR (KBr, νmax, cm-1): 3480 (NH str.), 1662.24 (CO

Vol. 32, No. 5 (2020) Synthesis, Biological screening, ADME and Molecular Docking Studies of 2-Phenyl Quinoline-4-Carboxamides 1155
solvent (such as DMSO, isopropanol, etc.) that solubilizes the
cells and releases formazan which was measured spectrophoto-
metrically (570 nm). Since reduction of MTT can only occur
in metabolically active cells the level of activity is a measure
of the viable cells.
After the treatment, the solutions in the wells were dis-
carded and 100 µL of freshly prepared MTT (1 mg/mL PBS)
was added to each well. The plates were shaken gently and
incubated for 4 h at 37 °C in 5% CO2 atmosphere. After 4 h,
the supernatant was removed and the formazan crystals formed
in the cells were solubilized by addition of 100 µL of DMSO.
The absorbance was read using a micro-plate reader (Bio-Tek,
ELX-800 MS) at 570 nm. The assay was done in triplicate for
each compound.
RESULTS AND DISCUSSION
2-Phenyl quinoline-4-carboxamide derivatives (5a-j) were
synthesized by the reaction of chosen aromatic primary amines
with 2-phenyl quinoline-4-carboxylic acid by using conven-
tional method as shown in Scheme-I in good yield (56-86%).
The structures of the all the compounds was established by
both physico-chemical (melting point) as well as spectral studies
13
(FTIR, 1H & C NMR and Mass). Primary evidence for the
formation of amide derivative was obtained from the infrared
spectrum of compounds 5a-j, which showed absence of stret-
ching due to OH group and presence of absorption band in
the range of 3400-3100 cm-1 due to NH-stretching and 1688-
1650 cm-1 due to a carbonyl group. 1H NMR spectrum of 5a-j
showed a singlet at δ 8.54-8.52 ppm indicating NH proton
confirms the coupling of acid with amines. The formation is
further evident from the 13C NMR spectra which showed signal
at 165 ppm due to carbonyl carbon, signals in the range of
133.5 to 148.0 ppm and 118.0-130.7 ppm due to quinoline
and aromatic carbon, respectively.
The growth inhibition was calculated using the formula
below and result were reported in percentage:
Acontrol − Atest
Growth inhibition (%) =
×100
Acontrol
Molecular docking studies
Biological activity: The antibacterial screening of com-
pounds 5a-j reveals that the compound 5d (nitro substituent
at para position), compound 5f (antipyrine group) and comp-
ound 5j (nitro group at meta position) have shown significant
activity compared with standard drug ciprofloxacin, but
compound 5a (chloro group at meta position), compound 5b
(methyl group at para position), compound 5c (unsubstituted),
5e (chloro group at para position), 5g (bromo group at para
position), 5h (Unsubstituted pyridine ring) and 5i (methoxy
group at para position) have shown moderate activity. The
results are tabulated in Table-1.
From the antifungal activity results it is evident that comp-
ound 5d (nitro substituent at para position), 5f (antipyrine
group) and compound 5j (nitro group at meta position) have
shown significant activity compared with standard drug fluco-
nazole but remaining compounds were moderately active against
tested fungal strains. The results are tabulated in Table-1.
From the results of anticancer activity of Schiff bases 5b,
5d, 5f and 5h exhibited anticancer activity whereas compounds
5a, 5c, 5e, 5i and 5j showed weak activity. Among the tested
compound 5b (methyl group at meta position) and compound
5d (nitro group at para position) were emerged as potent agents
with IC50 54.04 µM and 77.29 µM, respectively against A549
cell line and also against MCF-7 cell lines with IC50 66.37 µM
and 60.56 µM, respectively as tabulated in Table-1.
Ligand preparation: The chemical structures of the syn-
thesized compounds were drawn using Chemdraw [21].
Chemistry at Harvard Molecular Mechanics (CHARMm) was
used to perform the ligand optimization and Macro Molecular
Force Field (MMF) followed by energy minimization protocol
[22]. The drug likeliness was evaluated using the Lipinski rule
of 5 via Lipinski drug filter protocol [23,24].
Protein selection: 3D structures of Bacterial target proteins
in S. aureus (PDB ID: 2XCT) [25], Fungal Candida albicans
(PDB ID: 1IYL) [26] and cancer protein (PDB ID: 3OG7)
[27] were retrieved from the Protein Data Bank (PDB) website
www.rcsb.org. Co-crystallized ligand, water molecules and
metal ions were removed from the target structures to obtain
clean protein. The resulting structures were optimized classi-
cally using CHARMm force field implemented in the DS 3.5,
minimized with conjugate gradient energy minimization
protocol and by convergence energy minimization (0.001 kcal/
mol), respectively [28], that readied the structures for docking
and simulations. Active site of the ensemble has been defined
as the collection of residues within 10.0 Å of the bound inhi-
bitor and comprised the union of all ligands of the ensemble.
All atoms located less than 10.0 Å from any ligand atom were
considered.
A flexible docking approach was employed for molecular
docking studies using the Lead IT [28] software in which
targets were considered as receptor proteins.
Active site residues in S. aureus (PDB ID: 2XCT) are
Val30, Ala33, Asp39, Lys42, Arg47, Asn57, Ala67, Val85,
Ile112, Asn148, Ala175 and Gln267 were selected for mole-
cular docking studies.
Active site residues in Candida albicans (PDB ID: 1IYL)
Arg48,Arg92, Tyr100,Val51, Phe66,Arg70 and Gly101, were
selected for molecular docking studies.
Active site residues in (PDB ID: 3OG7), GLN461,
ARG462, ILE463, GLY464, SER465, PHE468, THR470,
VAL471, TYR472, LYS473, ASP479, VAL480, MET484 and
LEV485 were selected for molecular docking studies.
Computational study
ADME properties: The physical properties and theADME
parameters (absorption, distribution, metabolism and excre-
tion) of 2-phenyl quinolie-4-carboxamides were computed
using the freely accessible web server Swiss ADME (http://
swissadme.ch/index.php#undefined). The results of in silico
ADME properties of 5a-j are listed in Table-2. The molecular
weight (MW), the number of hydrogen bond acceptors (nHBA),
donors (nHBD), the number of rotatable bonds (nRB) and the
topological polar surface area (TPSA) for all the compounds
were in accordance with the Lipinski’s rule of five. The lipo-
philicity property (expressed as MLogP ≤ 4.15) was in the
range for all the compounds.

1156 Shetty et al.
Asian J. Chem.
TABLE-1
in vitro BIOLOGICAL ACTIVITY DATA OF 2-PHENYLQUINOLINE-4-CARBOXAMIDES (5a-j)
Antibacterial activity
Antifungal activity
A. niger
Anticancer activity
Compound
S. aureus
E. coli
C. albicans
11.50 0.11
11.21 0.18
11.00 0.19
24.12 0.12
14.00 0.15
19.12 0.19
15.00 0.17
15.50 0.16
13.23 0.16
17.50 0.19
–
A549
107.06 1.1
54.04 1.5
139.63 0.69
77.29 2.1
62.18 1.3
81.41 2.3
No inhibition
85.32 1.4
152.88 1.2
56.76 0.66
–
MCF-7
105.12 0.9
66.37 2.3
206.55 1.8
60.56 1.6
71.38 1.2
77.53 1.2
134.98 2.0
91.01 2.5
181.12 1.5
105.77 1.0
–
17.22 0.32
15.80 0.37
10.92 0.65
18.09 0.52
14.22 0.23
19.28 0.15
15.15 0.42
20.15 0.18
12.95 0.29
20.80 0.16
26.00 0.16
–
14.38 0.56
12.08 0.33
14.18 0.42
19.45 0.25
16.11 0.41
21.78 0.16
12.32 0.22
25.72 0.36
17.38 0.23
22.65 0.17
25.00 0.33
–
12.00 0.12
14.50 0.16
14.00 0.19
22.45 0.14
11.50 0.12
22.56 0.15
11.00 0.19
12.23 0.13
11.24 0.19
19.50 0.12
–
5a
5b
5c
5d
5e
5f
5g
5h
5i
5j
Ciprofloxacin
Fluconozole
Cisplatin
26.00 0.16
–
25.00 0.33
–
–
–
–
–
84.28 0.4
57.33 1.2
TABLE-2
in silico ADME PROPERTIES OF 2-PHENYL QUINOLINE-4-CARBOXAMIDES (5a-j)
Compound
Rule
MW
MLog P
nHBA
nHBD
nRB
TPSA
nViolations
< 500.00
358.82
338.40
324.38
369.37
358.82
434.49
403.27
325.36
354.40
369.37
< 160 Å2
41.99
41.99
41.99
87.81
41.99
68.92
41.99
54.88
51.22
87.81
0
1
0
0
0
1
0
1
0
0
0
≤ 4.15
4.24
3.97
3.75
2.68
4.24
3.95
4.34
3.09
3.39
2.68
≤ 10
2
2
2
4
2
3
2
3
≤ 5
1
1
1
1
1
1
1
1
≤ 10
4
4
4
5
4
5
4
4
5a
5b
5c
5d
5e
5f
5g
5h
5i
3
4
1
1
5
5
5j
TABLE-3
Molecular docking studies: To understand the mecha-
nism of biological activity of newly synthesized compounds,
molecular modelling and docking studies were performed on
X-ray crystal structure of target protein PDB ID: 2XCT for
antibacterial activity, N-myristoyltranferase PDB ID: 1IYL as a
target protein to study the antifungal activity and target protein
PDB ID: 3OG7 was used for anticancer study. The default
spherical Matcher placement method was used for docking.
GBVI/WSA dG scoring function which estimates the free
energy of binding of the ligand from a given pose was used to
rank the final pose. The ligand-enzyme complex with lowest
docking score and binding pattern of compounds were selected.
The antibacterial, antifungal and anticancer docking data of
pyrazole carboxamides 5a-j are tabulated in Table-3. Bind pose
of the active compounds are shown in Fig. 3.
DOCKING ENERGY (kcal/mol) OF 2-PHENYL
QUINOLINE-4-CARBOXAMIDES (5a-j)
Lead IT score
Compound
PDB ID:2XCT
-18.27
PDB ID:1IYL
Lead IT score
-12.46
PDB ID:3OG7
-25.76
5a
5b
5c
5d
5e
5f
5g
5h
5i
-19.482
-19.054
-24.413
-19.742
-21.05
-19.282
-23.335
-16.962
-24.031
-26.391
-25.364
-26.207
-25.39
-30.443
-25.488
-27.794
-24.647
-28.332
-11.723
-12.533
-14.462
-10.283
-13.554
-11.908
-12.277
-10.708
5j
(a)
(b)
(c)
Fig. 3. Binding pose of the title compound 5f with target protein PDB ID:2XCT (a); PDB ID:1IYL (b); and PDB ID: 3OG7 (c)

Vol. 32, No. 5 (2020) Synthesis, Biological screening, ADME and Molecular Docking Studies of 2-Phenyl Quinoline-4-Carboxamides 1157
5. M.A.S. Abdelwahid, T. Elsaman, M.S. Mohamed, S.A. Latif, M.M.
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for activity such as quinoline (nitrogen heterocycles - antimi-
crobial and anticancer agents) which allows its derivatives to
readily interact with a wide variety of enzymes and receptors
in organisms. Further essential substituents like -CH3, -OCH3
(electron donating), -Br, -Cl (halogen) and -NO2 (electron with-
drawing)] groups were varied at meta and para-position of
the phenyl ring to acquire the optimum results. The results
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anticancer activity. In particular, the compounds substituted
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The present study reports the successful synthesis, charac-
terization, cytotoxic, antimicrobial and pharmacokinetic study
of new quinoline carboxamide derivatives.Attempts have been
made to predict in silicoADME of synthesized molecules.All
the compounds were found to be in the acceptable range except
three compounds. Two of the tested compounds 5b and 5d
were effective against A549 with IC50 54.04 µM and 77.29
µM, respectively againstA549 cell line and also against MCF-
7 cell lines with IC50 66.37 and 60.56 µM, respectively. The
results suggest that these compounds may serve as lead chemical
entities for further modification in the search for new classes
of potential antimicrobial and anticancer agents.
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ACKNOWLEDGEMENTS
21. K. Wingen, J.S. Schwed, K. Isensee, L. Weizel, A. •ivkovic, D. Odazic
and H. Stark, Bioorg. Med. Chem. Lett., 24, 2236 (2014);
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The authors are thankful to Tumkur University, Tumakuru
for providing the laboratory facility to carry out this research
work. The authors also thankful to Department of Biotech-
nology, SIT, Tumakuru for providing Docking software to carry
out Docking studies and Sri Siddaganga College of Pharmacy
for providing facility to carry out in vitro study.
24. C.A. Lipinski, F. Lombardo, B.A. Dominy and P.J. Feeney, Adv. Drug
Deliv. Rev., 46, 3 (2001);
CONFLICT OF INTEREST
https://doi.org/10.1016/S0169-409X(00)00129-0
25. B.D. Bax, P.F. Chan, D.S. Eggleston,A. Fosberry, D.R. Gentry, F. Gorrec,
I. Giordano, M.M. Hann, A. Hennessy, M. Hibbs, J. Huang, E. Jones,
J. Jones, K.K. Brown, C.J. Lewis, E.W. May, M.R. Saunders, O. Singh,
C.E. Spitzfaden, C. Shen, A. Shillings, A.J. Theobald, A. Wohlkonig,
N.D. Pearson and M.N. Gwynn, Nature, 466, 935 (2010);
https://doi.org/10.1038/nature09197
The authors declare that there is no conflict of interests
regarding the publication of this article.
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