Design, synthesis and biological evaluation of some novel hexahydroquinoline-3-carbonitriles as anticancer and antimicrobial agents

Article abstract of DOI:10.14233/ajchem.2014.17616

The synthesis of ten novel 3-cyano-8-methyl-2-oxo-1,4-disubstituted-1,2,5,6,7,8-hexahydro-quinolines supported with benzensulfonyl and phenylthiocarbamoyl pharmacophores that are known to contribute to potential chemotherapeutic effects is described. They were evaluated in vitro for their antimicrobial activity against eight different microorganisms and for their cytotoxic effects against three different human tumor cell lines. The results revealed that nine compounds displayed variable inhibitory effects on the growth of the tested Gram-positive and Gram-negative bacteria with special pronounced activity against S. aureus and E. coli bacterial strains, in addition to a moderate antifungal activity against C. albicans. On the other hand, six compounds were able show remarkable cytotoxic efficiency against human colon carcinoma HT29, hepatocellular carcinoma Hep-G2 and Caucasian breast adenocarcinoma MCF7 cell lines. Collectively, the results would suggest that compounds 15 and 16 could be considered as possible dual antimicrobial-anticancer agents.

Full text of DOI:10.14233/ajchem.2014.17616

Asian Journal of Chemistry; Vol. 26, No. 23 (2014), 8139-8144
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.17616
Design, Synthesis and Biological Evaluation of Some Novel
Hexahydroquinoline-3-carbonitriles as Anticancer and Antimicrobial Agents
*
HASSAN M. FAIDALLAH , ALAA A. SAQER, KHALID. A. ALAMRY, KHALID A. KHAN, MOHIE A.M. ZAYED and SALMAN A. KHAN
Department of Chemistry, P O Box 80203, Faculty of Science, King Abdulaziz University, Jeddah-21589, Saudi Arabia
*Corresponding author: Tel: +966 567743180; E-mail: hfaidallahm@hotmail.com
Received: 18 March 2014;
Accepted: 21 May 2014;
Published online: 15 November 2014;
AJC-16312
The synthesis of ten novel 3-cyano-8-methyl-2-oxo-1,4-disubstituted-1,2,5,6,7,8-hexahydro-quinolines supported with benzensulfonyl
and phenylthiocarbamoyl pharmacophores that are known to contribute to potential chemotherapeutic effects is described. They were
evaluated in vitro for their antimicrobial activity against eight different microorganisms and for their cytotoxic effects against three
different human tumor cell lines. The results revealed that nine compounds displayed variable inhibitory effects on the growth of the
tested Gram-positive and Gram-negative bacteria with special pronounced activity against S. aureus and E. coli bacterial strains, in
addition to a moderate antifungal activity against C. albicans. On the other hand, six compounds were able show remarkable cytotoxic
efficiency against human colon carcinoma HT29, hepatocellular carcinoma Hep-G2 and Caucasian breast adenocarcinoma MCF7 cell lines.
Collectively, the results would suggest that compounds 15 and 16 could be considered as possible dual antimicrobial-anticancer agents.
Keywords: Synthesis, N-benzensulfonyl, N-phenylthiocarbamoyl, cytotoxic agents, antimicrobial agents.
INTRODUCTION
EXPERIMENTAL
Quinolines are well known and important nitrogen-
containing heterocyclic compounds1. Quinoline derivatives
have been established to possess considerable biological
activities, which stimulated the research activity in this field2.
They have several prominent effects, such as antimicrobial3,
antimycobacterial4, antiinflammatory5, analgesic6 and anti-
depressant7 activities. Bi-functional quinoline derivatives
dramatically increase the biological activity8,9.Various methods
have been reported for their synthesis bi-fungsanal quinoline
derivative10,11. It is used as intermediates for the formation of
fused heterocyclic compounds such as pyrazolo quinoline
pyrimidoquinolines12,13. The molecules having the quinolines
framework have been largely investigated for optical-electrical
applications for photophysical studies such as non-linear
optical properties14, photonic materials15, devices, optical
limiting16, electrochemical sensing17, light-emitting devices18,
Langmuir film19 and solar cell materials20. However, the quino-
lines has been used extensively for the photo-alignment and
photo-crosslinking unit in polymers21. Encouraged by these
facts and in continuation with the wok related to the synthesis,
spectral studies and biological properties of quinolines, herein
is reported the synthesis of some novel hexahydro-quinoline-
3-carbonitriles and their anticancer and antibacterial activities
were investigated.
Melting points were determined on a Gallenkamp melting
point apparatus and are uncorrected. The infrared (IR) spectra
were recorded on Shimadzu FT-IR 8400S infrared spectro-
photometer using the KBr pellet technique. 1H and 13C NMR
spectra were recorded on a Bruker DPX-400 FT NMR spectro-
meter using tetramethylsilane as the internal standard and
DMSO-d6 as a solvent (Chemical shifts in δ, ppm). Elemental
analyses were performed on a 2400 Perkin Elmer Series 2
analyzer and the found values were within 0.4 % of the
theoretical values. Follow up of the reactions and checking
the homogeneity of the compounds were made by TLC on
silica gel-protected aluminum sheets (Type 60 F254, Merck)
and the spots were detected by exposure to UV-lamp at λ 254.
3-Cyano-8-methyl-2-oxo-4-substituted 1,2,5,6,7,8-
hexahydroquinolines (1, 2, 4, 6, 7 and 8) and 3-cyano-8-
methyl-2-oxo-4-substituted 1,2,4,4a,5,6,7-octahydroquino-
lines (3 and 5): A mixture of the appropriate aldehyde (10
mmol), 2-methylcyclohexanone (1.46 g, 10 mmol), ethyl cyano-
acetate (1.1 g, 10 mmol) and ammonium acetate (6.2 g, 80
mmol) in absolute ethanol (50 mL) was refluxed for 6 h. The
reaction mixture was allowed to cool and the formed precipitate
was filtered, washed with water, dried and recrystallized.
In case of bromo- and chloro benzaldehydes two products
were obtained (3 and 5) which were separated by fractional

8140 Faidallah et al.
Asian J. Chem.
recrystallization. Physicochemical and analytical data are listed
in Table-1. 1H NMR spectral data are recorded in Table-2.
IR (KBr, νmax, cm-1): 3378-3264 (NH), 2239-2220 (CN),
1672-1668 (C=O). 13C NMR (δ-ppm) for 1: 15.1 (CH3), 27.7,
27.9, 34.4, 34.9 (cyclohexyl C), 117.2 (CN), 95.7, 119.5, 132.7,
165.9 (CO), 169.4 (pyridine C), 126.2, 127.7, 128.4, 134.9
(Ar C). 2: 15.4 (CH3), 27.6, 28.1, 32.4, 34.5 (cyclohexyl C),
117.2 (CN), 96.7, 119.0, 133.0, 163.0 (CO), 169.4 (pyridone
C), 122.2, 128.4, 131.7, 133.9 (Ar C). 3 : 18.2 (CH3), 23.4,
23.6, 31.2 (C-5,6,7), 34.2 (C-4), 39.4 (C-3), 41.4 (C-4a), 116.8
(CN), 120.2, 126.8, 131.4,132.2, 132.6, 138.1 (Ar C) 171.2.0
(CO). 4: 15.2 (CH3), 27.8, 28.0, 34.6, 34.8 (cyclohexyl C),
117.6 (CN), 96.8, 119.4, 132.8, 162.9 (CO), 169.6 (pyridone
C), 127.6, 128.8, 133.0, 133.2 (Ar C). 5: 18.1 (CH3), 23.2,
23.5, 31.0 (C-5,6,7), 34.1 (C-4), 39.6 (C-3), 41.2 (C-4a), 116.6
(CN), 126.9, 128.6, 129.4, 131.4, 132.2, 137.1 (Ar C), 171.3
(CO). 6: 15.2 (CH3), 27.8, 28.6, 34.4, 34,8 (cyclohexyl C),
56.0 (OCH3), 117.3 (CN), 96.6, 120.2, 133.4, 164.7 (CO), 169
(pyridone C), 114.0, 127.2, 127.3, 161.2 (Ar C). 7: 15.1 (CH3),
20.5 (CH3), 27.6, 27.8, 33.3, 34.2 (cyclohexyl C), 117.5 (CN),
96.0, 119.5, 133.0, 163.0 (CO), 169.2 (pyridone C), 125.9,
127.8, 128.6, 134.9 (Ar C). 8: 15.3 (CH3), 27.7, 28.0, 30.1,
34.2 (cyclohexyl C), 118.2 (CN), 101.6, 119.7, 132.7, 163.0
(CO), 169.3 (pyridone C), 126.4, 127.6, 130.6, 136.7 (thiophene
C).
1-Benzensulfonyl-3-cyano-8-methyl-2-oxo-4-
substituted 1,2,5,6,7,8-hexahydroquinolines (9-13): A
mixture of the appropriate starting compound (1, 2, 6-8) (10
mmol) and benzenesulfonyl chloride (10 mmol, 1.77 g) in
pyridine (10 mL) was heated under reflux for 4-6 h. After
cooling the reaction mixture to room temperature, it was
poured on crushed ice and the separated solid product was
TABLE-1
CHARACTERIZATION DATA OF COMPOUNDS 1-18
R1, R2
or R3
Calcd. (%)
H
Found (%)
H
Yield
(%)
m.p.
(ºC)
Compd.
R
m.f.
C
N
C
N
C6H5
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
86
79
12
78
14
85
82
78
72
70
80
82
82
80
84
83
79
78
248-249 C17H16N2O
289-290 C17H15N2OBr
238-240 C17H17 N2OBr
233-235 C17H15N2OCl
220-222 C17H17N2OCl
250-252 C18H18N2O2
246-248 C18H18N2O
253-255 C15H14N2OS
233-234 C23H20N3O3S
223-224 C23H19N3O3SBr
202-204 C24H22N3O4S
186-188 C24H22N2O3S
224-226 C21H18N2O3S2
234-236 C24H21N3OS
138-140 C24H20 BrN3OS
210-212 C25H23N3O2S
122-124 C25H23N3OS
128-130 C22H19N3OS2
77.25
59.49
59.14
68.34
67.88
73.45
77.67
66.64
68.30
57.15
66.34
68.88
61.44
72.15
60.25
69.91
72.61
65.16
6.10
4.41
4.96
5.06
5.70
6.16
6.52
5.22
4.98
3.96
5.10
5.30
4.42
5.30
4.21
5.40
5.61
4.72
10.60
8.16
8.11
9.38
9.31
9.52
10.06
10.36
6.93
5.80
6.45
6.69
6.82
10.52
8.78
9.78
10.16
10.36
77.36
59.50
59.25
68.44
67.98
73.34
77.73
66.77
68.10
57.21
66.44
69.24
61.32
72.22
60.33
70.02
72.66
65.02
6.22
4.42
5.02
5.13
5.62
6.02
6.45
5.43
5.11
3.87
5.12
3.98
4.62
5.42
4.39
5.34
5.82
4.77
10.72
8.24
8.30
9.41
9.39
9.66
10.21
10.54
7.10
5.90
6.61
8.87
6.90
10.68
8.62
9.84
10.12
10.23
1
2
4-BrC6H4
4-BrC6H4
4-ClC6H4
4-ClC6H4
4-CH3OC6H4
4-CH3C6H4
2-Thienyl
C6H5
3
4
5
6
7
8
9
4-BrC6H4
4-CH3OC6H4
4-CH3C6H4
2-Thienyl
C6H5
10
11
12
13
14
15
16
17
18
4-BrC6H4
4-CH3OC6H4
4-CH3C6H4
2-Thienyl
TABLE-2
1H NMR SPECTRAL DATA (δ/ppm)a OF COMPOUNDS 1-18
CH3
(d, 3H)
1.26
1.18
1.71
1.16
1.74
1.22
1.16
1.20
1.16
1.18
1.21
1.19
1.17
1.15
1.16
1.18
1.14
1.16
H-5, 6, 7, 8
(2m, 7H)
Compound
R
R’
Ar-H
Others
C6H5
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
1.85, 2.29
1.90, 2.23
1.74, 2.33
1.78, 2.13
1.80, 2.21
1.98, 2.28
1.61, 2.19
1.65, 2.27
1.68, 2.21
1.66, 2.10
1.65, 2.16
1.68, 2.18
1.70, 2.16
1.69, 2.18
1.65, 2.13
1.75, 2.14
1.81, 2.22
1.76, 2.21
6.92-7.68 (5H)
7.19-7.38 (4H)
7.02-7.35 (4H)
7.22-7.34 (4H)
7.07-7.19 (4H)
6.99-7.26 (4H)
7.01-7.55 (4H)
7.31-7.64 (3H)
7.14-7.85 (10H)
7.04-7.38 (4H)
6.97-7.29(4H)
7.11-7.52 (4H)
7.33-7.62 (3H)
6.49-7.32 (10H)
6.64-7.42 (9H)
6.47-7.19 (9H)
6.52-6.18 (9H)
7.33-7.67 (8H)
8.21 (s, 1H, NH)
8.16 (s, 1H, NH)
8.05 (s, 1H, NH)
8.10(s, 1H, NH)
8.25 (s, 1H, NH)
1
4-BrC6H4
4-BrC6H4
4-ClC6H4
4-ClC6H4
2
3b
4c
5
4-CH3OC6H4
4-CH3C6H4
2-Thienyl
C6H5
8.14 (s, H, NH), 3.73 (s, CH3O)
6
8.09 (s, 1H, NH), 2.34 (s, CH3)
7
8.11 (s, 1H, NH)
8
-
9
4-BrC6H4
4-CH3OC6H4
4-CH3C6H4
2-Thienyl
C6H5
-
10
11
12
13
14
15
16
17
18
3.76 (s, CH3O)
2.34 (s, CH3)
-
6.23 (s, NH)
4-BrC6H4
4-CH3OC6H4
4-CH3C6H4
2-Thienyl
6.31 (s, NH)
3.75 (s, CH3O), 6.42 (s, NH)
2.35(s, CH3), 6.57 (s, NH)
6.24 (s, NH)

Vol. 26, No. 23 (2014)
Design, Synthesis and Biological Evaluation of Some Novel Hexahydroquinoline-3-carbonitriles 8141
filtered, washed with water, dried and recrystallized from
ethanol.
136.8, 139.5 (Ar C). 18: 15.7 (CH3), 27.8, 28.2, 32.2, 35.1
(cyclohexyl C), 117.1 (CN), 95.5, 119.4, 132.6, 162.7(CO),
169.4 (pyridone C), 117.1(CN), 124.5, 125.3, 126.4, 127.5,
128.9, 130.2, 136.3, 139.4 (Ar C).
IR (KBr, νmax, cm-1): 2236-2224 (CN), 1676-1668 (C=O
pyridone), 1378-1372 and 1198-1172 (SO2). 13C NMR (δ-ppm)
9: 15.1 (CH3), 27.6, 27.9, 31.3, 34.4 (cyclohexyl C), 95.9,
119.8, 133.0, 163.2 (CO), 169.5 (pyridone C), 117.6 (CN),
125.6, 126.2, 127.7, 128.4, 128,8, 131.7, 134.9, 139.3 (Ar
C).10: 14.9 (CH3), 27.5, 27.7, 34.1, 34.4 (cyclohexyl C), 95.9,
119.8, 133.0, 163.2 (CO), 169.5 (pyridone C), 117.6 (CN),
123.1, 128.2, 131.7, 128.4, 128,8, 131.7, 134.9, 139.8 (Ar C).
11: 15.3 (CH3), 27.3, 27.8, 31.0, 34.2 (cyclohexyl C), 56.1
(OCH3), 95.7 119.4, 132.7, 163.4 (CO), 169.7 (pyridone C),
117.2(CN), 114.1, 125.6, 127.2, 127.3, 128.8, 131.7, 139.3,
161.5 (Ar C). 12: 15.7 (CH3), 20.8 (CH3), 27.8, 28.2, 32.3,
34.6 (cyclohexyl C), 117.4 (CN), 95.5, 119.2, 133.1, 164.2
(CO), 169.4 (pyridone C), 125.4, 126.1, 128.7, 129.0, 131.7,
131.9, 136.9, 139.4 (Ar C). 13: 15.2 (CH3), 27.1, 27.5, 31.3,
34.5 (cyclohexyl C), 95.2 119.6, 132.5, 163.2 (CO), 169.6
(pyridone C), 117.1(CN), 125.5, 126.5, 127.8, 128.7, 130.3,
131.6, 136.4, 139.1 Ar C).
Biological activity
in vitro MTT cytotoxicity assay: All the newly synthe-
sized compounds were investigated for their in vitro cytotoxic
effect via the standard MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-
diphenyltetrazolium bromide] method against a panel of three
human tumour cell lines namely; Caucasian breast adenocar-
cinoma MCF7, hepatocellular carcinoma Hep-G2 and colon
carcinoma HT29. The results are presented in Table-3 as LC50
(µg/mL, µM) which is the lethal concentration of the compound
which causes death of 50 % of the cells in 24 h.
in vitro Antibacterial and antifungal activities
Minimal inhibitory concentration (MIC) measurement:
The MIC of the most active compounds were measured using
the twofold serial broth dilution method22. The MIC values in
µg/mL (µM) of the compounds are listed in Table-4.
3-Cyano-8-methyl-2-oxo-1-(phenylthiocarbamoyl)-4-
substituted 1,2,5,6,7,8-hexahydroquinolines (14-18): A
mixture of the appropriate quinoline derivative (1, 2, 6-8) (10
mmol) and the phenyl isothiocyanate (1.35 g, 10 mmol) in
pyridine (10 mL) was heated under reflux for 6-8 h. After
being cooled to room temperature, the reaction mixture was
poured on ice cold water and the separated solid product was
filtered, washed with water, dried and recrystallized from
ethanol as needles.
IR (KBr, νmax, cm-1): 2232-2220 (CN), 1670-1665 (C=O
pyridone), 1242-1228 (C=S). 13C NMR (δ-ppm) 14: 15.7
(CH3), 27.9, 28.3, 32.4, 35.0 (cyclohexyl C), 117.5 (CN), 98.6,
120.2, 132.9, 162.7 (CO), 168.3 (pyridone C), 124.5, 125.3,
126.2, 127.7, 128.4, 128.8, 134.9, 139.4 (Ar C), 175.4 (CS).
15: 15.6 (CH3), 28.0, 28.2, 32.6, 34.9 (cyclohexyl C), 117.4
(CN), 99.2, 119.8, 132.7, 163.0 (CO) 169.4 (pyridone C),
122.5, 125.6, 127.5, 128.3, 128.8, 133.0, 133.3, 140.1 (Ar C),
175.0 (CS). 16: 15.5 (CH3), 27.8, 28.2, 32.3, 34.6 (cyclohexyl
C), 56.1 (CH3O), 118.2 (CN), 95.8, 119.6, 133.3, 164.0 (CO),
169.4 (pyridone C), 114.4, 126.5, 127.6, 128.4, 129.5, 130.5,
141.9, 160.5 (Ar C). 17: 15.5 (CH3), 27.9, 28.3, 32.3, 35.0
(cyclohexyl C), 117.3 (CN), 95.8, 119.3, 132.7, 162.9 (CO),
169.1 (pyridone C), 124.5, 125.2, 126.2, 128.7, 129.1, 131.9,
RESULTS AND DISCUSSION
The synthetic strategies adopted for the preparation of
the intermediate and target compounds are described in
Schemes-I. The key intermediates 3-cyano-8-methyl-2-oxo-
4-substituted hexahydro- and octahydroquinolines 1-8 were
synthesized via one-pot multicomponent reaction (MCR) of
the appropriate aromatic aldehyde and 2-methylcyclo-
hexanone, an excess of ammonium acetate and ethyl cyano-
acetate in boiling ethanol. Such type of reactions has received
considerable interest since it is easier to perform, gives higher
yields and less time consuming, when compared with the
traditional procedure that involved the formation of the 2-
arylidene-6-methylcyclohexanones (chalcones) via Claisen-
Schmidt condensation followed by cyclocondensation with
ethyl cyanoacetate and ammonium acetate23. It is worthy to
mention here, that when the aromatic aldehyde is bromo- or
chloro benzaldehyde two products were isolated one is the
expected quinoline derivatives (2 and 4) which is the major
product and a side product (3 and 5) represent the reduced
formula of 2 and 4, respectively. This may be attributed to the
electron withdrawing character of the halogen atoms. The IR
spectra of the cyanoquinolines 1-8 exhibited absorption bands
TABLE-3
CYTOTOXIC EFFECTS LC50; µg/mL (µM)a OF THE ACTIVE COMPOUNDS
ON SOME HUMAN TUMOR CELL LINES USING THE MTT ASSAY
Compound
HT29b
65.8 (220.2)
47.1 (160)
33.2 (68.6)
29.6 (68)
8.4 (19)
Hep-G2c
57.2 (191.5)
66.3 (226.8)
22.4 (46.3)
18.5 (64)
20.6 (47)
11.6 (25)
48.7 (131)
31.8 (70)
1.69 (3)
MCF 7d
46.3 (155)
34.1 (116)
24.8 (51.3)
25.2 (58)
12.1 (28)
9.7 (21)
64.9 (175)
-
2
6
10
11
15
14.9 (32)
26.3 (70)
34.9 (77)
21.1 (40)
16
17
18
Doxorubicinf
2.14 (4)
aLC50: Lethal concentration of the compound which causes death of 50 % of cells in 24 h µg/mL(µM); bHT29 (Human colon carcinoma cell line);
cHep-G2 (Human hepatocellular carcinoma cell line); dMCF7 (Human breast cancer cell line); eTotally inactive against this cell line; fPositive
control cytotoxic agent

8142 Faidallah et al.
Asian J. Chem.
TABLE-4
MINIMAL INHIBITORY CONCENTRATIONS [MIC, µg/mL (µM)] OF THE TESTED COMPOUNDS
Compound no.
S. aureus
50 (135.2)
50 (169.8)
50 (123.6)
12.5 (28.5)
12.5 (28.8)
25 (57.5)
6.25 (13.3)
25 (60)
B. subtilis
100 (257.8)
100 (339.7)
100 (247.2)
25 (57)
M. luteus
E. coli
P. aeruginosa
100 (-)
K. pneumoniae
C. albicans
-
-
-
50 (-)
-
2
25 (84.9)
100 (247.2)
6.25 (14.2)
12.5 (28.8)
25 (57.5)
6.25 (13.3)
12.5 (60)
12.5 (27.6)
6.25 (18)
-
100 (339.7)
100 (247.2)
25 (57)
-
-
6
-
-
-
9
100 (228)
100 (230.4)
200 (460)
25 (53.4)
50 (120)
-
100 (228)
25 (57)
25 (57.6)
100 (230.4)
12.5 (26.7)
50 (120)
12.5 (27.6)
-
10
50 (115.2)
100 (230)
25 (53.4)
50 (120)
50 110.6)
12.5 (36)
-
25 (57.6)
50 (115)
12.5 (26.7)
100 (240)
50 (110.6)
12.5 (36)
-
-
11
-
14
50 (106.8)
15
16
-
100 (221.2)
12.5 (36)
-
12.5 (27.6)
6.25 (18)
-
18
Ampicillin
Clotrimazole
12.5 (36)
6.25 (18)
aMIC > 200 (600) µg/mL (µM)
O
O
O
phenyl-thiocarbamoyl analogs 22-26. The IR spectra of these
compounds showed C=S absorption at 1242-1228 cm-1 as well
as a C=O and CN absorptions in the regions 1670-1665 and
2232-2220 cm-1. The structures were further supported from
(i)
R
+
H
R
(ii)
(ii)
1
their H NMR (Table-2) and 13C NMR spectral data which
R
R
CN
O
CN
exhibited beside the expected number of aliphatic and aromatic
carbons, two signals at δ 162.7-163.0 and δ 175.0-175.4 for
the CO and CS, respectively .
+
N
H
N
H
O
1: R = C H ;
6
5
Biological evaluation
3: R = 4-BrC H ;
6
4
2: R = 4-BrC H ;
6
4
5: R = 4-ClC H
6
4
6: R = 4-CH OC H ;
6 4
3
in vitro MTT cytotoxicity assay: The data obtained
(Table-3) revealed that eight compounds namely 2, 6, 10, 11,
15, 16, 17 and 18 were able to affect cell viability of the tested
tumour cell lines particularly the human colon carcinoma
HT29 cell line whereas the rest of the compounds were totally
inactive. In addition, the three tested human tumour cell lines
exhibited variable degree of sensitivity profiles towards the
active compounds. In terms of µg/mL concentration, the human
colon carcinoma HT29 cell line showed pronounced sensitivity
against compounds 15 and 16 (LC50 8.4 and 14.9 µg/mL,
respectively) even higher than that of doxorubicin (LC50 21.1
µg/mL). Moreover, a remarkable cytotoxic potential was
displayed by compounds 11 and 17 against the same cell line
(LC50 29.6 and 26.3 µg/ mL respectively) comparable to that
of doxorubicin. The rest of the active compounds showed
moderate to weak activity profiles against the same cell line
with LC50 range of 33.2-34.9 µg/mL. On the other hand, the
growth of the human hepatocellular carcinoma Hep-G2 cell
line was found to be moderately inhibited by six of the active
compounds with LC50 values range of 11.6-48.7 µg/ mL, among
which compounds 11 and 15 (LC50 values 18.5 and 11.6 µg/mL,
respectively) revealed the highest cytotoxic activity as com-
pared to doxorubicin (LC50 1.69 µg/mL). Regarding the human
breast cancer MCF7, it was proved to be the least sensitive
among the tested cell lines, as its growth was inhibited by
only seven of the tested compounds. However, a remarkable
growth inhibitory potential was shown by compounds 15 and
16 as evidenced from their LC50 values (12.1 and 9.7 µg/mL,
respectively) when compared to doxorubicin (LC50 2.14 µg/mL).
A close examination of the structure of the active compounds
showed that the 4-bromo and 4-methoxy groups at the C-4
aryl ring are the most favourable substituents. Although the
key precursors 2 and 6 possessed moderate cytotoxic profiles,
7: R = 4-CH C H ;
3 6 4
8: R = 2-Theinyl
R
N
R
CN
CN
O
(iii)
(iv)
O
H
N
S
N
O2S
Ph
Ph
9 : R = C H ;
6
5
14: R = C H ;
6
5
10: R = 4-BrC H ;
6
4
15: R = 4-BrC H ;
6
4
11: R = 4-CH OC H ;
6 4
3
16: R = 4-CH OC H ;
3 6 4
12: R = 4-CH C H ;
3 6 4
17: R = 4-CH C H ;
3 6 4
13: R = 2-Theinyl
18: R = 2-Theinyl
Scheme-I:Reagent and reaction conditions: (i) NaOH; (ii) CNCH2COOEt/
NH4OAc, absolute EtOH, reflux, 6 h. (iii) PhSO2Cl in Pyridine,
reflux 4-6 h; (iv) PhNCS in Pyridine, reflux 6-8 h
at 2239-2220 and 1672-1668 cm-1 for the CN and CO groups,
1
respectively. Their H NMR showed beside the aromatic
protons two multiplets at δ 2.26-2.88 and 2.54-2.90 ppm
corresponding to the protons of the cyclohexyl moiety in the
quinoline derivatives 2, 6, 7 and 8 while in case of compounds
3 and 5, the 1H NMR exhibited beside the aromatic protons,
two multiplets at δ 1.61-1.94 (6H), δ 2.30-2.38 (1H), a triplt
at 3.12-3.24 (1H) and a doublet at δ 3.54-3.85 (1H, J = 9Hz)
for the H-5,6,7, H-4a, H-4 and H-3, respectively (Table-2).
The structures were further supported by 13C NMR data. The
hexahydroquinolines 1, 2, 6, 7 and 8 obtained from Scheme-
I were utilized as key intermediates for the synthesis of the
target compounds 9-18. In this respect, reacting compounds
1, 2, 6, 7 and 8 with benzenesulfonyl chloride in a pyridine
medium resulted in the introduction of a benzenesulfonyl
moiety at position-1 to yield compounds 9-13. Moreover,
condensation of the same compounds with phenyl isothio-
cyanate in alkaline medium afforded the corresponding N-

Vol. 26, No. 23 (2014)
Design, Synthesis and Biological Evaluation of Some Novel Hexahydroquinoline-3-carbonitriles 8143
yet sulfonylation as in (10, 11), led to a noticeable enhancement
in both the cytotoxic spectrum and potential. On the other hand,
great improvement of the cytotoxic potential was linked to
the introduction of a thiocarbamoyl substituent at position-1
(15-18). It could be clearly recognized that the bromo and
methoxy derivatives (15 and 16) showed distinctive cytotoxic
activities, whereas 17 and 18 were moderately active. Among
these, the analogs 15 and 16 proved to be the most active
members in this study with a broad spectrum of activity against
the tested cell lines.
display a noticeable growth inhibitory potential against
C. albicans, among which compounds 15 and 18 (MIC 12.5
µg/mL) were the most active members when compared with
clotrimazole (MIC 6.25 µg/mL). A close examination of the
structures of the active compounds revealed that, their antimi-
crobial activity is strongly bound to the nature of the substituent
of the aryl ring at C-4, together with the substituent linked to
position-1 of the ring structure. In general, it could be clearly
recognized that potential antibacterial activity was connected
with the brominated derivatives (R = 4-Br C6H4), whereas
moderate activities were displayed by the methoxylated
analogs (R = 4-CH3O C6H4). In this context, the key hexahydro
quinoline precursors 2 and 6 showed moderate antimicrobial
potential, with particular effectiveness against S. aureus and
E. coli. Introducing a benzenesulfonyl moiety at position-1
gave rise to three active compounds 9-11, among which the
bromo derivative 10 showed equipotent activity to ampicillin
against E. coli and 50 % of its activity against S. aureus,
B. subtilis and P. aeruginosa, together with an appreciable
antifungal activity against C. albicans. Moreover, incorporating
a substituted thiocarbamoyl counterpart as in compounds
14,15,16 and 18, resulted in an obvious enhancement in both
the antimicrobial potential and spectrum. It could be clearly
recognized that the activity of these analogs is connected with
the aryl substituent in position-4. Within this series, compound
15 (R = 4-Br-C6H4) was the most active member as it displayed
a fourfold increase in the antimicrobial activity against
S. aureus, E. coli and P. aeruginosa (MIC 6.25, 6.25 and 12.5
µg/mL, respectively), together with a remarkable antifungal
activity (12.5 µg/mL), when compared with the parent 2.
in vitro Antibacterial and antifungal activities: All of
the newly synthesized target compounds were evaluated for
their in vitro antibacterial activity against Staphylococcus
aureus (ATCC 6538), Bacillus subtilis (ATCC 6633) and
Micrococcus luteus (ATCC 21881) as examples of Gram-
positive bacteria and Escherichia coli (ATCC 25922), Pseudo-
monas aeruginosa (ATCC 27853) and Klebsiella pneumonia
(clinical isolate) as examples of Gram-negative bacteria. They
were also evaluated for their in vitro antifungal potential against
Candida albicans (ATCC 10231) and Aspergillus niger
(recultured) fungal strains. Agar-diffusion method was used
for the determination of the preliminary antibacterial and
antifungal activities. Ampicillin trihydrate and clotrimazole
were used as reference drugs. The results were recorded for
each tested compound as the average diameter of inhibition
zones (IZ) of bacterial or fungal growth around the discs in
mm. The minimum inhibitory concentration (MIC) measure-
ment was determined for compounds that showed significant
growth inhibition zones (= 13 mm) using the two-fold serial
dilution method18. As revealed from MIC data recorded in
Table-4, [MIC expressed in both concentration units µg/mL
(µM)], nine out of the twelve synthesized compounds 1, 2, 6,
8 and 9-18 displayed variable inhibitory effects on the growth
of the tested Gram-positive and Gram-negative micro-
organisms with pronounced activity against S. aureus and
E. coli bacterial strains. In addition, some members exhibited
moderate antifungal activity against C. albicans, whereas, all
the tested compounds lacked antifungal potential against
Aspergillus niger.
Conclusion
Six compounds were able show remarkable cytotoxic
efficiency against human colon carcinoma HT29, hepato-
cellular carcinoma Hep-G2 and Caucasian breast adenocar-
cinoma MCF7 cell lines. The results revealed that compounds
11, 15, 16 and 17 showed considerable broad spectrum
cytotoxic activity against the three tested cell lines, among
which the analogs 15 and 16 proved to be the most active
members in this study with special effectiveness against the
human colon carcinoma HT29 and human breast cancer MCF7
cell lines even higher than that of doxorubicin, the reference
standard cytotoxic agent utilized in this test. On the other hand,
seven 1,2,5,6,7,8-hexahydro-quinoline derivatives displayed
very good activity against S. aureus and E. coli bacterial strains,
in addition to moderate antifungal activity against C. albicans.
Compounds 10, 11 and 15 could be considered as the most
active broad spectrum antimicrobial members identified in this
study. Among these, compound 15 proved to be the most active
candidate as it showed equipotency to ampicillin against
S. aureus, E. coli and P. aeruginosa, in addition to an obvious
antifungal activity comparable with clotrimazole. The best
antifungal activity was demonstrated by compounds 15 and
18 which possessed almost half the activity of clotrimazole
against C. albicans.
In terms of µg/mL concentration, among the tested Gram-
positive bacterial strains, two organisms namely; S. aureus
and B. subtilis showed relatively high sensitivity towards the
active compounds. In this view, compound 15 was equipotent
to ampicillin (MIC 6.25 µg/mL) against S. aureus, whereas
the analogs 10,11 and 18 (MIC 12.5 µg/mL) were 50 % less
active than ampicillin. With regard to the activity against
B. subtilis, compounds 10 and 15 (MIC 25 µg/mL) showed
half the activity of ampicillin. Concerning the antibacterial
activity against the three tested Gram-negative strains, three
analogs namely 10 and 15 were able to produce a distinctive
growth inhibitory profile against E. coli (MIC 6.25 µg/mL)
which was equipotent to ampicillin, whereas, compounds 11
and 18 (MIC 12.5 µg/mL), were 50 % less active than ampi-
cillin against the same organism. Meanwhile, the tested
P. aeruginosa strain showed moderate sensitivity towards most
of the active compounds, particularly compound 15 (MIC 12.5
µg/mL) which was equipotent to ampicillin. On the other hand,
only six compounds 10, 11, 14, 15, 16 and 18 were able to
Finally, the obtained antimicrobial and anticancer data
makes such type of compounds a fruitful matrix for further
development of more potent and selective cytotoxic and/or

8144 Faidallah et al.
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This article was funded by the Deanship of Scientific
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