Synthesis, antimicrobial activity and cytotoxicity of some new carbazole derivatives

Article abstract of DOI:10.3109/14756366.2011.622273

In this work, some N-(9-Ethyl-9H-carbazole-3-yl)-2-(phenoxy)acetamide derivatives were synthesised and evaluated for their antimicrobial activity and cytotoxicity. The structural elucidation of the compounds was performed by IR, ¹H-NMR, ¹³

Full text of DOI:10.3109/14756366.2011.622273

Journal of Enzyme Inhibition and Medicinal Chemistry, 2012; 27(6): 868–874
© 2012 Informa UK, Ltd.
ISSN 1475-6366 print/ISSN 1475-6374 online
DOI: 10.3109/14756366.2011.622273
RESEARCH ARTICLE
Synthesis, antimicrobial activity and cytotoxicity of some
new carbazole derivatives
Zafer Asim Kaplancikli1, Leyla Yurttaş1, Gülhan Turan-Zitouni1, Ahmet Özdemir1, Rasime Özic2,
and Şafak Ulusoylar-Yıldırım3
1Department of Pharmaceutical Chemistry, Anadolu University, Eskişehir, Turkey, 2Department of Biology,
Anadolu University, Eskişehir, Turkey, and 3Department of Pharmacology, Anadolu University, Eskişehir, Turkey
Abstract
In this work, some N-(9-Ethyl-9H-carbazole-3-yl)-2-(phenoxy)acetamide derivatives were synthesised and evaluated
for their antimicrobial activity and cytotoxicity. The structural elucidation of the compounds was performed by IR,
1H-NMR, 13C-NMR and FAB+-MS spectral data and elemental analyses. The title compounds were obtained by reacting
2-chloro-N-(9-ethyl-9H-carbazole-3-yl)acetamide with some substituted phenols. The synthesised compounds were
investigated for their antibacterial and antifungal activities against Micrococcus luteus, Bacillus subtilis, Pseudomonas
aeruginosa, Staphylococcus aureus, Escherichia coli, Listeria monocytogenes and Candida albicans. The compounds
N-(9-Ethyl-9H-carbazole-3-yl)-2-(4-ethylphenoxy)acetamide (2c) and N-(9-Ethyl-9H-carbazole-3-yl)-2-(quinolin-8-
yloxy)acetamide (2n) showed notable antimicrobial activity. The compounds were also studied for their cytotoxic
effects using MTT assay, and it was seen that 2n had the lowest cytotoxic activity against NIH/3T3 cells.
Keywords: Carbazole, phenol, antibacterial activity, antifungal activity, cytotoxicity
Introduction
and possesses desirable electronic and charge-transport
e alarming rates of emerging and reemerging micro-
bial threats coupled with the rapid development of
multi-drug-resistant microbial pathogens are major
escalating concerns to the public health, particularly
during the past decades1,2. Despite a large number of
antibiotics and chemotherapeutics available for medical
use, at the same time, the emergence of old and new anti-
biotic resistance created revealed a substantial medical
need for new classes of antimicrobial agents3. ere is no
doubt that the existing arsenal of antimicrobial agents we
have in hand for the treatment of infectious diseases is
insufficient to protect us over the long term4–7. us there
is a need to search for new and efficacious antimicrobial
agents8,9. Nevertheless, there is a continuing effort among
the scientists especially in the pharmaceutical industry
to develop new antimicrobial agents for the treatment of
resistant infections10.
properties, as well as large p-conjugated system, and
the various functional groups are easily introduced into
the structurally rigid carbazole ring. ese character-
istics result in the extensive potential applications of
carbazole-based derivatives in the field of chemistry and
medicinal chemistry11.
Carbazole and its derivatives are a considerable
structural unit which have been isolated from differ-
ent sources such as some genera of higher plants, blue
green algae, actinomycetes and filamentous fungi12–14
.
It is known that natural origin carbazoles especially for
those complex carbazoles fusing with a heterocyclic frag-
ment show well-known pharmacological activities15,16
.
Accordingly, to the present, a large number of natural
and synthetic carbazole derivatives have been reported to
exhibit diverse biological activities such as antituber-
culosis17, antiproliferative14, antibacterial18,19, antiviral20,
antifungal21,22, antitumour23, anti-inflammatory24, anti-
oxidant12 and antihistaminic activities25.
e tricyclic carbazole nucleus is an important type
of nitrogen-containing aromatic heterocyclic compound
Address for Correspondence: Zafer Asim Kaplancikli, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, Anadolu University,
26470 Eskişehir, Turkey. E-mail: zakaplan@anadolu.edu.tr
(Received 18 August 2011; revised 06 September 2011; accepted 07 September 2011)
868

New carbazole derivatives 869
It is known that the phenol and phenol derivatives are
in use as potential antimicrobial agent26. Several studies
demonstrated the antimicrobial activity of phenols and/
or phenolic compounds making them a good alterna-
tive to antibiotics and chemical preservatives27. Also the
alkoxy and aryloxy moiety, which is containing phenol
residue, has low toxicity and active against the growth of
derivatives (1.98 mmol) and K2CO3 (1.98 mmol, 0.3 g) in
acetonitrile was refluxed for 6 hours. e cooled mixture
was filtered and recrystallised from alcohol. Some char-
acteristics of the compounds are given in Table 1.
N-(9-Ethyl-9H-carbazole-3-yl)-2-(o-tolyloxy)acetamide (2a)
IR (KBr) νmax (cm−1): 3332 (amide N-H), 3050 (aromatic
C-H), 2922, 2850 (aliphatic C-H), 1683 (amide C=O),
1604, 1556, 1442 (C=C), 1000–1300 (C-N), 1245 (C-O-C).
1H NMR (400 MHz, DMSO-d6): 1.31 (3H, t J= 6 Hz,
CH3), 2.29 (3H, s, Ar-CH3), 4.43 (2H, q J= 7 Hz, N-CH2),
4.75 (2H, s, O-CH2), 6.91–7.60 (9H, m, Ar-H), 8.07
(H, d, J=8 Hz, carbazole C5-H), 8.44 (H, s, carbazole C4-H),
10.04 (H, s, NH).
various yeasts and bacteria28–30
.
In the view of these observations, we designed and
synthesised carbazole-based aryloxy compounds as
potential antimicrobial agent.
Experimental
Chemistry
13C NMR (100MHz, DMSO-d6): 13.65 (CH3), 16.16
(CH3), 36.95 (CH2), 67.52 (CH2), 108.98 (CH), 109.16 (CH),
111.50 (CH), 111.88 (CH), 118.57 (CH), 119.39 (CH),
120.19 (CH), 120.85 (CH), 125.78 (CH), 130.23 (2C), 130.58
(2CH), 136.39 (2C), 139.96 (2C), 156.10 (C), 166.27 (C).
For C23H22N2O2 calculated: 77.07% C, 6.19% H, 7.82%
N; found: 77.02% C, 6.18% H, 7.80% N.
All chemicals were purchased from Sigma-Aldrich
Chemical Co. All melting points (m.p.) were determined
by Electrothermal 9100 digital melting point apparatus
and are uncorrected. Spectroscopic data were recorded
with the following instruments: 1H-NMR, Bruker 400 MHz
spectrometer; 13C-NMR, Bruker 100 MHz spectrometer;
and MS-FAB, VG Quattro Mass spectrometer. Elemental
analyses were performed on a Perkin Elmer EAL 240
elemental analyzer.
MS (FAB) [M+1]+: m/z 359
N-(9-Ethyl-9H-carbazole-3-yl)-2-(m-tolyloxy)acetamide (2b)
IR (KBr) νmax (cm−1): 3299 (amide N-H), 3030 (aromatic
C-H), 2904 (aliphatic C-H), 1665 (amide C=O), 1610, 1557
(C=C), 1000–1300 (C-N), 1247 (C-O-C).
General procedure for the synthesis of the compounds
2-Chloro-N-(9-ethyl-9H-carbazole-3-yl)acetamide (1)
9-Ethyl-9H-carbazole-3-amine (0.05mol) and triethylam-
ine (0.06mol) were dissolved in THF with a constant stir-
ring at 0–5°C, then chloroacetyl chloride (0.06mol) was
added dropwise gradually to this solution. e reaction
mixture thus obtained was further agitated for 1h at room
temperature. After the solvent was evaporated to dryness,
the solid was filtered and washed with water.
1H NMR (400MHz, DMSO-d6): 1.31 (3H, t, J=8 Hz, CH3),
2.31 (3H, s, Ar-CH3), 4.43 (2H, q, J=7 Hz, N-CH2), 4.71 (2H,
s, O-CH2), 6.85–7.65 (9H, m, Ar-H), 8.07 (H, d, J=8 Hz, car-
bazole C5-H), 8.44 (H, s, carbazole C4-H), 10.06 (H, s, NH).
13C NMR (100 MHz, DMSO-d6): 13.65 (CH3), 21.10
(CH3), 36.95 (CH2), 67.20 (CH2), 108.94 (CH), 109.16
(CH), 111.62 (CH), 115.47 (CH), 118.57 (3CH), 121.80
(C), 125.78 (C), 129.22 (2CH), 130.17 (2C), 136.42 (CH),
138.97 (2C), 139.96 (CH), 157.88 (C), 166.20 (C).
For C23H22N2O2 calculated: 77.07% C, 6.19% H, 7.82%
N; found: 77.04% C, 6.19% H, 7.82% N.
N-(9-Ethyl-9H-carbazole-3-yl)-2-(substituted phenoxy)
acetamide derivatives (2a-n)
A
mixture of 2-chloro-N-(9-ethyl-9H-carbazole-3-yl)
acetamide (1) (1.65 mmol, 0.5 g), the appropriate phenol
MS (FAB) [M+1]+: m/z 359
Table 1. Some characteristics of the synthesised compounds.
Compound
Ar
Yield (%)
70
Melting point (°C)
Molecular formula
C23H22N2O2
C23H22N2O2
C24H24N2O2
C22H19ClN2O2
C22H19ClN2O2
C22H19N3O4
C22H19N3O4
C22H19N3O4
C24H24N2O2
C24H24N2O2
C24H24N2O2
C24H24N2O2
C28H24N2O2
Molecular weight
2a
2b
2c
2d
2e
2f
2-Methylphenyl
3-Methylphenyl
4-Ethylphenyl
146
173
166
159
186
198
178
175
165
191
146
178
183
358
358
372
378.5
378.5
389
389
389
372
372
372
372
420
72
75
2-Chlorophenyl
4-Chlorophenyl
2-Nitrophenyl
80
81
73
2g
2h
2i
3-Nitrophenyl
75
4-Nitrophenyl
80
2,3-Dimethylphenyl
3,4-Dimethylphenyl
2,4-Dimethylphenyl
3,5-Dimethylphenyl
76
2j
72
2k
2l
74
75
2m
70
1,1′-Biphenyl]-4-yl
2n
Quinolin-8-yl
71
85
C25H21N3O2
395
© 2012 Informa UK, Ltd.

870 Z. A. Kaplancikli et al.
N-(9-Ethyl-9H-carbazole-3-yl)-2-(4-ethylphenoxy)
acetamide (2c)
N-(9-Ethyl-9H-carbazole-3-yl)-2-(2-nitrophenoxy)
acetamide (2f)
IR (KBr) νmax (cm−1): 3354 (amide N-H), 3042, 3015
(aromatic C-H), 2987, 2889 (aliphatic C-H), 1691
(amide C=O), 1554, 1486 (C=C), 1000–1300 (C-N), 1230
(C-O-C).
IR (KBr) νmax (cm−1): 3317 (amide N-H), 3100 (aromatic
C-H), 2980 (aliphatic C-H), 1687 (amide C=O), 1525, 1442
(C=C), 1000–1300 (C-N), 1239 (C-O-C).
1H NMR (400 MHz, DMSO-d6): 1.30 (3H, t, J= 8 Hz,
CH3), 4.42 (2H, q, J= 8 Hz, N-CH2), 4.99 (2H, s, O-CH2),
7.18–7.96 (9H, m, Ar-H), 8.08 (H, d, J= 8 Hz, carbazole
C5-H), 8.44 (H, s, carbazole C4-H), 10.10 (H, s, NH).
13C NMR (100 MHz, DMSO-d6): 13.64 (CH3), 36.95
(CH2), 67.87 (CH2), 109.11 (CH), 109.17 (C), 111.55 (C),
115.44 (2C), 118.61 (2C), 121.20 (CH), 125.26 (CH), 125.84
(2CH), 130.05 (2CH), 134.57 (CH), 136.42 (CH), 139.46
(CH), 139.98 (CH), 150.92 (C), 165.04 (C).
1H NMR (400 MHz, DMSO-d6): 1.15 (3H, t, J= 7.4,
Hz, C-CH2CH3) 1.31 (3H, t, J= 7.1 Hz, CH3), 2.31 (2H,
q, J= 7 Hz C-CH2), 4.43 (2H, q, J= 7.2 Hz, N-CH2), 4.71
(2H, s, O-CH2), 6.96–7.65 (9H, m, Ar-H), 8.07 (H, d, J= 7.5
Hz, carbazole C5-H), 8.44 (H, s, carbazole C4-H), 10.06
(H, s, NH).
13C NMR (100 MHz, DMSO-d6): 13.82 (CH3), 16.8
(CH3), 28.0 (CH2), 37.09 (CH2), 68.35 (CH2), 109.63
(CH), 111.51 (2CH), 115.72 (CH), 119.75 (CH), 120.94
(CH), 121.76 (2CH), 123.78 (C), 124.02 (CH), 128.81 (C),
132.42 (2CH), 134.34 (C), 137.17 (C), 141.63 (2C), 156.75
(C), 167.77 (C).
For C22H19N3O4 calculated: 67.86% C, 4.92% H, 10.79%
N; found: 67.85% C, 4.90% H, 10.75% N.
MS (FAB) [M+1]+: m/z 390
For C24H24N2O2 calculated: 77.39% C, 6.49% H, 7.52%
N; found: 77.39% C, 6.47% H, 7.56% N.
N-(9-Ethyl-9H-carbazole-3-yl)-2-(3-nitrophenoxy)
acetamide (2g)
MS (FAB) [M+1]+: m/z 373
IR (KBr) νmax (cm−1): 3440 (amide N-H), 3012 (aromatic
C-H), 2980 (aliphatic C-H), 1695 (amide C=O), 1602,
1543, 1551 (C=C), 1000–1300 (C-N), 1245 (C-O-C).
1H NMR (400 MHz, DMSO-d6): 1.31 (3H, t, J=8 Hz,
CH3), 4.43 (2H, q, J= 8 Hz, N-CH2), 4.92 (2H, s, O-CH2),
7.19–7.89 (9H, m, Ar-H), 8.08 (H, d, J= 8 Hz, carbazole
C5-H), 8.43 (H, s, carbazole C4-H), 10.20 (H, s, NH).
13C NMR (100MHz, DMSO-d6): 13.66 (CH3), 36.96
(CH2), 67.46 (CH2), 108.99 (CH), 109.17 (CH), 109.52
(2CH), 112.11 (C), 116.01 (C), 118.60 (CH), 120.18 (2C),
121.91 (2C), 125.81 (CH), 130.02 (CH), 130.72 (CH), 136.48
(CH), 139.97 (CH), 148.62 (CH), 158.43 (C), 165.47 (C).
For C22H19N3O4 calculated: 67.86% C, 4.92% H, 10.79%
N; found: 67.81% C, 4.90% H, 10.78% N.
N-(9-Ethyl-9H-carbazole-3-yl)-2-(2-chlorophenoxy)
acetamide (2d)
IR (KBr) νmax (cm−1): 3413 (amide N-H), 3012 (aromatic
C-H), 2989, 2876 (aliphatic C-H), 1698 (amide C=O),
1610, 1564 (C=C), 1000–1300 (C-N), 1218 (C-O-C),
1H NMR (400 MHz, DMSO-d6): 1.31 (3H, t,
J= 6 Hz, CH3), 4.43 (2H, q, J= 6 Hz, N-CH2), 4.88 (2H, s,
O-CH2), 7.01–7.60 (9H, m, Ar-H), 8.08 (H, d, J= 8
Hz, carbazole C5-H), 8.45 (H, s, carbazole C4-H), 10.14
(H, s, NH).
13C NMR (100 MHz, DMSO-d6): 13.65 (CH3), 36.95
(CH2), 67.80 (CH2), 109.06 (2CH), 109.16 (CH), 111.59
(CH), 114.11 (2C), 118.58 (CH), 120.20 (2C), 122.07 (CH),
125.81 (2CH), 128.25 (CH), 130.06 (CH), 130.22 (C),
136.38 (C), 139.97 (CH), 153.51 (C), 165.50 (C).
For C22H19ClN2O2 calculated: 69.75% C, 5.05% H, 7.39%
N; found: 70.02% C, 5.03% H, 7.41% N.
MS (FAB) [M+1]+: m/z 390
N-(9-Ethyl-9H-carbazole-3-yl)-2-(4-nitrophenoxy)
acetamide (2h)
IR (KBr) νmax (cm−1): 3298 (amide N-H), 3017 (aromatic
C-H), 2980, 2875 (aliphatic C-H), 1669 (amide C=O),
1556, 1510 (C=C), 1000–1300 (C-N), 1236 (C-O-C).
1H NMR (400 MHz, DMSO-d6): 1.31 (3H, t, J=8 Hz,
CH3), 4.43 (2H, q, J= 8 Hz, N-CH2), 4.95 (H, s, O-CH2),
7.19–8.42 (11H, m, Ar-H), 10.27 (H, s, NH).
13C NMR (100 MHz, DMSO-d6): 13.66 (CH3), 43.61
(CH2), 67.42 (CH2), 109.00 (CH), 109.09 (CH), 109.18
(CH), 111.60 (CH), 115.35 (C), 118.61 (C), 119.44 (CH),
121.86 (CH), 125.81 (CH), 130.05 (CH), 130.29 (CH),
136.45 (CH), 139.97 (2C), 141.22 (2C), 163.21 (CH), 164.21
(C), 165.16 (C).
MS (FAB) [M+1]+: m/z 379
N-(9-Ethyl-9H-carbazole-3-yl)-2-(4-chlorophenoxy)
acetamide (2e)
IR (KBr) νmax (cm−1): 3249 (amide N-H), 3079 (aromatic
C-H), 2908 (aliphatic C-H), 1683 (amide C=O), 1612, 1594
(C=C), 1000–1300 (C-N), 1274 (C-O-C).
1H NMR (400 MHz, DMSO-d6): 1.31 (3H, t, J= 8 Hz,
CH3), 4.43 (2H, q, J= 7 Hz, N-CH2), 4.75 (2H, s, O-CH2),
7.09–7.61 (9H, m, Ar-H), 8.07 (H, d, J= 8 Hz, carbazole
C5-H), 8.43 (H, s, carbazole C4-H), 10.11 (H, s, NH).
13C NMR (100 MHz, DMSO-d6): 13.65 (CH3), 36.95
(CH2), 67.42 (CH2), 108.95 (CH), 109.16 (2CH), 112.05
(2C), 116.53 (C), 118.58 (CH), 120.17 (2C), 124.84 (C),
129.24 (2CH), 130.10 (CH), 136.44 (2CH), 139.96 (2CH),
156.77 (C), 165.83 (C).
For C22H19N3O4 calculated: 67.86% C, 4.92% H, 10.79%
N; found: 67.82% C, 4.89% H, 10.80% N.
MS (FAB) [M+1]+: m/z 390
N-(9-Ethyl-9H-carbazole-3-yl)-2-(2,3-dimethylphenoxy)
acetamide (2i)
For C22H19ClN2O2 calculated: 69.75% C, 5.05% H, 7.39%
N; found: 69.78% C, 5.06% H, 7.40% N.
IR (KBr) νmax (cm−1): 3356 (amide N-H), 3059 (aro-
matic C-H), 2932, 2879 (aliphatic C-H), 1689 (amide
MS (FAB) [M+1]+: m/z 379
Journal of Enzyme Inhibition and Medicinal Chemistry

New carbazole derivatives 871
C=O), 1601, 1557, 1444 (C=C), 1000–1300 (C-N), 1215
(C-O-C).
N-(9-Ethyl-9H-carbazole-3-yl)-2-(3,5-dimethylphenoxy)
acetamide (2l)
1H NMR (400 MHz, DMSO-d6): 1.31 (3H, t, J= 8 Hz,
CH3), 2.16 (3H, s, Ar-CH3) 2.21 (3H, s, Ar-CH3), 4.42 (2H,
q, J= 8 Hz, N-CH2), 4.66 (2H, s, O-CH2), 6.97–7.76 (8H, m,
Ar-H), 8.04 (H, d, J= 8.2 Hz, carbazole C5-H), 8.42 (H, s,
carbazole C4-H), 10.02 (H, s, NH).
IR (KBr) νmax (cm−1): 3412 (amide N-H), 3053 (aromatic
C-H), 2962, 2858 (aliphatic C-H), 1635 (amide C=O),
1504, 1482 (C=C), 1000–1300 (C-N), 1287 (C-O-C).
1H NMR (400MHz, DMSO-d6): 1.31 (3H, t, J=8.2 Hz, CH3),
2.26 (6H, s, 2CH3), 4.43 (2H, q, J=8.1 Hz, N-CH2), 4.67 (2H, s,
O-CH2), 6.64–7.65 (8H, m, Ar-H), 8.07 (H, d, J=8 Hz, carba-
zole C5-H), 8.43 (H, s, carbazole C4-H), 10.02 (H, s, NH).
13C NMR (100 MHz, DMSO-d6): 13.66 (CH3), 21.05
(2CH3), 36.95 (CH2), 67.17 (CH2), 108.94 (CH), 109.16
(CH), 112.05 (CH), 112.46 (CH), 118.57 (2C), 119.54 (CH),
120.16 (C), 122.77 (C), 125.78 (C), 130.17 (2CH), 136.42
(2CH), 138.62 (CH), 139.96 (2C), 157.89 (C), 166.25 (C).
For C24H24N2O2 calculated: 77.39% C, 6.49% H, 7.52%
N; found: 77.34% C, 6.46% H, 7.49% N.
13C NMR (100 MHz, DMSO-d6): 13.56 (CH3), 18.82
(CH3), 19.65 (CH3), 35.54 (CH2), 67.12 (CH2), 108.92
(CH), 110.16 (CH), 115.18 (2C), 113.51 (2C), 117.26 (CH),
117.512 (CH), 121.18 (CH), 126.78 (CH), 128.67 (C), 132.54
(CH), 135.40 (2C), 137.58 (CH), 140.94 (2CH), 155.45 (C),
166.34 (C).
For C24H24N2O2 calculated: 77.39% C, 6.49% H, 7.52%
N; found: 77.34% C, 6.48% H, 7.56% N.
MS (FAB) [M+1]+: m/z 373
MS (FAB) [M+1]+: m/z 373
N-(9-Ethyl-9H-carbazole-3-yl)-2-(3,4-dimethylphenoxy)
acetamide (2j)
N-(9-Ethyl-9H-carbazole-3-yl)-2-([1,1′-biphenyl]-4-yloxy)
acetamide (2m)
IR (KBr) νmax (cm−1): 3346 (amide N-H), 3013
(aromatic C-H), 2984, 2750 (aliphatic C-H), 1687
(amide C=O), 1650, 1556 (C=C), 1000–1300 (C-N), 1254
(C-O-C),
IR (KBr) νmax (cm−1): 3346 (amide N-H), 3084 (aromatic
C-H), 2978, 2880 (aliphatic C-H), 1673 (amide C=O),
1650, 1589, 1442 (C=C), 1000–1300 (C-N), 1238 (C-O-C),
1H NMR (400 MHz, DMSO-d6): 1.31 (3H, t, J= 7.2 Hz,
CH3), 4.44 (2H, q, J= 7.6 Hz, N-CH2), 4.80 (2H, s, O-CH2),
7.14–7.67 (14H, m, Ar-H), 8.09 (H, d, J= 7.8 Hz, carbazole
C5-H), 8.46 (H, s, carbazole C4-H), 10.20 (H, s, NH).
13C NMR (100 MHz, DMSO-d6): 14.24 (CH3), 37.95
(CH2), 67.87 (CH2), 109.11 (CH), 109.17 (CH), 112.55
(C), 116.44 (2C), 118.61 (2C), 121.20 (CH), 123.26 (CH),
125.84 (2CH), 127.05 (2CH), 128.57 (CH), 129.42 (CH),
130.46 (CH), 131.98 (CH), 134.92 (C), 137.04 (C), 141.04
(2CH), 141.27 (2CH), 158.96 (C), 167.72 (C).
1H NMR (400 MHz, DMSO-d6): 1.31 (3H, t, J= 8 Hz,
CH3), 2.16 (3H, s, Ar-CH3) 2.21 (3H, s, Ar-CH3), 4.43 (2H,
q, J= 8 Hz, N-CH2), 4.66 (2H, s, O-CH2), 6.77–7.65 (8H, m,
Ar-H), 8.07 (H, d, J= 8.1 Hz, carbazole C5-H), 8.43 (H, s,
carbazole C4-H), 10.02 (H, s, NH).
13C NMR (100 MHz, DMSO-d6): 13.66 (CH3), 18.42
(CH3), 19.65 (CH3), 36.94 (CH2), 67.32 (CH2), 108.93
(CH), 109.16 (CH), 111.58 (2C), 112.03 (2C), 116.16 (CH),
118.57 (CH), 120.17 (CH), 125.78 (CH), 128.67 (C), 130.15
(CH), 136.40 (2C), 137.28 (CH), 139.94 (2CH), 155.94 (C),
166.34 (C).
For C28H24N2O2 calculated: 79.98% C, 5.75% H, 6.66%
N; found: 79.96% C, 5.76% H, 6.68% N.
For C24H24N2O2 calculated: 77.39% C, 6.49% H, 7.52%
N; found: 77.35% C, 6.50% H, 7.53% N.
MS (FAB) [M+1]+: m/z 421
MS (FAB) [M+1]+: m/z 373
N-(9-Ethyl-9H-carbazole-3-yl)-2-(quinolin-8-yloxy)
acetamide (2n)
N-(9-Ethyl-9H-carbazole-3-yl)-2-(2,4-dimethylphenoxy)
acetamide (2k)
IR (KBr) νmax (cm−1): 3411 (amide N-H), 3056 (aromatic
C-H), 2987, 2850 (aliphatic C-H), 1659(amide C=O), 1652,
1587, 1498 (C=C), 1000–1300 (C-N), 1247(C-O-C).
1H NMR (400 MHz, DMSO-d6): 1.31 (3H, t, J= 8, CH3),
4.42 (2H, q, J = 8.3 Hz, N-CH2), 5.01 (2H, s, O-CH2),
7.19–9.04 (13H, m, Ar-H), 10.65 (H, s, NH).
IR (KBr) νmax (cm−1): 3381 (amide N-H), 3059 (aro-
matic C-H), 2927, 2874 (aliphatic C-H), 1694 (amide
C=O), 1600, 1556, 1448 (C=C), 1000–1300 (C-N), 1224
(C-O-C).
1H NMR (400 MHz, DMSO-d6): 1.31 (3H, t, J= 8 Hz,
CH3), 2.21 (3H, s, Ar-CH3) 2.26 (3H, s, Ar-CH3), 4.43 (2H,
q, J= 8.3 Hz, N-CH2), 4.70 (2H, s, O-CH2), 6.83–7.59 (8 H,
m, Ar-H), 8.07 (H, d, J= 8 Hz, carbazole C5-H), 8.43 (H, s,
carbazole C4-H), 10.01 (H, s, NH).
13C NMR (100 MHz, DMSO-d6): 13.66 (CH3), 16.11
(CH3), 20.05 (CH3), 36.94 (CH2), 67.71 (CH2), 108.97 (C),
109.16 (C), 111.53 (C), 111.87 (CH), 118.57 (2C), 119.39
(2C), 120.19 (CH), 121.96 (CH), 125.78 (CH), 129.49 (CH),
130.22 (CH), 131.29 (2CH), 136.37 (CH), 139.94 (CH),
154.01 (C), 166.40 (C).
13C NMR (100 MHz, DMSO-d6): 13.65 (CH3), 18.52
(CH2), 36.95 (CH2), 56.00 (CH), 70.12 (CH), 109.13 (CH),
111.40 (C), 113.06 (C), 118.58 (2C), 118.93 (2C), 120.25
(CH), 121.39 (CH), 125.83 (CH), 129.18 (CH), 130.24
(2CH), 136.24 (CH), 136.39 (CH), 139.97 (CH), 140.05
(CH), 149.55 (C), 154.21 (C), 166.40 (C).
For C25H21N3O2 calculated: 75.93% C, 5.35% H, 10.63%
N; found: 75.92% C, 5.36% H, 10.60% N.
MS (FAB) [M+1]+: m/z 396
For C24H24N2O2 calculated: 77.39% C, 6.49% H, 7.52%
N; found: 77.40% C, 6.51% H, 7.47% N.
Antimicrobial activity
e antimicrobial activities of compounds (2a-n) were
MS (FAB) [M+1]+: m/z 373
tested using the microbroth dilution method31. Tested
© 2012 Informa UK, Ltd.

872 Z. A. Kaplancikli et al.
microorganism strains were Micrococcus luteus (NRLL
B-4375), Bacillus subtilis (NRS-744), P. aeroginosa
(ATCC-254992), Staphylococcus aureus (NRRL B-767),
Escherichia coli (ATCC-25922), Listeria monocytogenes
(ATCC-7644) and Candida albicans (ATCC-22019).
Microbroth dilution-susceptibility assay was used for
antimicrobial evaluation of the compounds. Stock solu-
tions of the samples were prepared in dimethylsulfoxide.
Dilution series using sterile distilled water were pre-
pared from 0.65–4 mg/mL to 0.000633–0.0039 mg/mL in
micro test tubes that were transferred to 96-well micro-
titre plates. Overnight-grown bacterial and C. albicans
suspensions in double-strength Mueller–Hinton broth
were standardised to 108 CFU/mL using McFarland No:
0.5 standard solutions. 100 µL of each microorganism
suspension were then added into the wells. e last well
chain without a microorganism was used as a negative
control. Sterile distilled water and the medium served
as a positive growth control. After incubation at 37°C for
18–24 h, antimicrobial activity was detected by spray-
ing of 0.5% TTC (triphenyl tetrazolium chloride, Merck)
aqueous solution. MIC was defined as the lowest con-
centration of compounds that inhibited visible growth,
as indicated by the TTC staining. Streptomycin was used
as standard antibacterial agent, whereas ketoconazole
was used as an antifungal agent.
Scheme 1. e synthetic protocol of the compounds (2a-n).
(1) which was then reacted with some phenol derivatives
to get N-(9-ethyl-9H-carbazole-3-yl)-2-(substituted phe-
noxy)acetamide derivatives (2a-n).
e structure elucidation of the compounds was
1
determined by IR, H-NMR, 13C-NMR, FAB+-MS spectral
data and elemental analyses results.
In the IR spectra of all compounds, characteristic
amide function was observed in the region 1659–
1698 cm−1 because of the amide C=O vibration. In addi-
tion, the amide N-H vibration of the compounds were
seen at 3249–3440 cm−1 region as expected.
e 1H-NMR spectral data were also consistent
1
with the assigned structures. In the 400 MHz H-NMR
Cytotoxicity
spectrum of compounds, the O-CH2 protons resonated
at 4.6–5.01 ppm as a singlet and also N-H protons
were observed at 10.01–10.65 ppm. For ethyl substitu-
tion, CH3 protons were observed at about 1.31 ppm as
triplet and CH2 protons at 4.42–4.43 ppm as quartet. In
aromatic region, the signal of the carbazole C4-H and
carbazole C5-H protons was observed much further
from upfield at about 8.06–8.46 ppm34 and the other
characteristic aromatic protons were observed at
expected regions.
e cytotoxic activities of the tested compounds were
determined by cell proliferation analysis using standard
3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium
bromide (MTT) assay32,33. Mouse embryonic fibroblast
(NIH/3T3) cells were cultured in 96-well flat-bottom
plates at 37°C for 24 h (2 × 104 cells per well). All of
the compounds were dissolved in dimethyl sulfoxide
(DMSO) individually and added to culture wells at vary-
ing concentrations (0.5–500 µg/mL); the highest final
DMSO concentration was under 0.1%. After 24-hour
drug incubation at 37°C, 20 µl MTT solution (5 mg/
mL MTT powder in PBS) was added to each well. en
3-hour incubation period was maintained in the same
conditions. Purple formazan was occurred at the end of
the process which is the reduction product of MTT agent
by the mitochondrial dehydrogenase enzyme of intact
cells. Formazan crystals were dissolved in 100 µL DMSO,
and the absorbance was read by ELISA reader (OD570nm).
e percentage of viable cells was calculated based on
the medium control.
In the 13C-NMR spectra of the compounds, the signal
of characteristic carbonyl carbon appeared at 166.27 ppm
and O-CH2 at 67.52 ppm, respectively.
In the MS spectra, the electron-spraying technique
with positive polarity mode was applied and M+1 peaks
were detected as base peak.
All compounds gave satisfactory elemental analysis
results.
Antimicrobial activity and toxicity
Antimicrobial activity was investigated by finding mini-
mum inhibitory concentration (MIC) of the synthe-
sised compounds against S. aureus, L. monocytogenes,
E. coli, Pseudomonas aeruginosa, M. luteus, B. subtilis
and C. albicans comparing with streptomycin and keto-
conazole as standard drug. e MIC value of the com-
pounds and control drugs are summarised in Table 2.
e MIC values were generally within the range of
31.25–500 μg/mL. Most of the compounds showed sig-
nificant antifungal activity against C. albicans. In con-
sideration of synthesised compounds’ MIC values with
Result, discussion and conclusion
Chemistry
Inthisstudy, aseriesofcarbazole-basedcompoundswere
synthesised via an easy, convenient and efficient syn-
thetic route. e synthesis of the compounds is shown in
Scheme 1. To obtain final compounds, 3-amino-9-ethyl-
carbazole was reacted with chloroacetyl chloride to pro-
duce 2-chloro-N-(9-ethyl-9H-carbazole-3-yl)acetamide
Journal of Enzyme Inhibition and Medicinal Chemistry

New carbazole derivatives 873
Table 2. Antimicrobial activities of the compounds (µg/mL).
Compound
A
B
C
D
E
187.5
250
F
187.5
250
G
2a
187.5
250
93.75
93.75
93.75
187.5
250
2b
125
40.625
250
125
40.625
250
125
40.625
250
2c
81.25
500
81.25
500
81.25
500
81.25
500
2d
2e
500
250
250
250
500
500
500
2f
500
250
250
250
250
500
250
2g
281.25
393.75
500
140.625
196.875
250
140.625
196.875
250
140.625
196.875
250
281.25
196.875
250
281.25
393.75
500
281.25
393.75
500
2h
2i
2j
393.75
337.5
500
196.875
168.75
250
196.875
168.75
250
196.875
168.75
250
196.875
337.5
500
393.75
337.5
500
393.75
337.5
500
2k
2l
2m
500
250
250
250
250
500
500
2n
31.25
31.25
–
250
250
250
250
31.25
15.625
–
125
Reference 1
Reference 2
7.81
31.25
–
125
15.625
–
–
–
–
250
Reference 1: Sytreptomycin; Reference 2: Ketoconazole.
A: Staphylococcus aureus (NRRL B-767), B: Listeria monocytogenes (ATCC-7644), C: Escherichia coli (ATCC-25922), D: P. aeroginosa
(ATCC-254992), E: Micrococcus luteus (NRLL B-4375), F: Bacillus subtilis (NRS-744), G: Candida albicans (ATCC-22019).
standard drug, compounds 2a, 2c and 2n had more and
2g had less antifungal activity than did ketoconazole
and also 2b and 2f had similar antifungal activity to
ketoconazole.
It was also observed that all compounds had anti-
microbial activity against all tested bacteria according
to standard drug streptomycin. Especially, compounds
2c and 2n are highly active against all of the evaluating
bacterial strains. Compound 2n, which includes qui-
nolinoxy moiety, exhibited equipotent activity to stan-
dard drug with an MIC value of 31.25 μg/mL against
S. aureus.
Compounds 2a, 2c and 2b had satisfying activ-
ity against P. aeruginosa. Compound 2c was the most
effective against this bacteria with an MIC value of
40.25 μg/mL, whereas streptomycin had an MIC value
of 125 μg/mL.
Compounds were also studied for their cytotoxic
properties using MTT assay. e IC50 (μg/mL) values
of the compounds against NIH/3T3 cells are shown in
Table 3. e biological study indicated that compounds
2a, 2c, 2e, 2j and 2l possessed the highest cytotoxicity,
whereas the other compounds exhibited moderate cyto-
toxicity except 2n. e IC50 concentration of compound
2n was 300 μg/mL, which was greater than all MIC
values observed against all tested bacteria and fungi for
this compound.
Table 3. In vitro cytotoxicity of the compounds.
Compound
IC50 (µg/mL)a
15.7 0.6
120.7 22.0
11.0 1.7
76.7 25.2
20.1 0.2
78.9 2.5
76.0 8.7
74.7 8.1
122.7 4.6
16.7 1.2
37.5 13.0
23.7 7.5
65.0+5.0
300+50
2a
2b
2c
2d
2e
2f
2g
2h
2i
2j
2k
2l
2m
2n
aCytotoxicity of the compounds to mouse fibroblast (NIH/3T3)
cell line. Incubation for 24 hours. IC50 is the drug concentration
required to inhibit 50% of the cell growth. e values represent
mean SD of triplicate determinations.
Declaration of interest
e authors report no conflicts of interest.
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