Synthesis and biological evaluation of fatty imidazolines

Article abstract of DOI:10.1007/s00044-014-0936-x

A series of eight fatty imidazolines were synthesized under microwave-assisted conditions using different fatty acids namely octyl, decyl, dodecyl, tetradecyl and octadecyl, mixed fatty acids prepared from Sterculia foetida (containing cyclopropene-rich fatty acids), coconut (containing medium-chain-rich fatty acids), palm (containing saturated-rich fatty acids) and sunflower (containing unsaturated-rich fatty acids). Coconut, sunflower and non-edible oil S. foetida-based imidazolines were synthesized for the first time. The fatty imidazolines were evaluated for anti-fungal activity and found to be good to excellent (MIC, 4.68-18.75 μg ml^-1) against the tested Candida strains as compared with fluconazole (MIC, 16-64 μg ml ^-1) as standard. The fatty imidazolines also exhibited excellent to moderate anti-bacterial activity (MIC, 4.68-75 μg ml^-1) against Staphylococcus aureus MTCC 96, S. aureus MLS 16 MTCC 2940 and Pseudomonas aeruginosa MTCC 2453 as compared with neomycin (MIC, 18.75 μg ml ^-1) as standard. The cytotoxic evaluation of the imidazolines against different cancer cell lines such as HeLa (Human Cervical Cancer Cell line), A549 (Human Alveolar Adenocarcinoma Cell line), MDA-MB-231& MCF7 (Human Breast Adenocarcinoma Cell line) and Neuro2a (Mouse neuroblastoma cell line) showed excellent cytotoxicity for dodecyl (3b), tetradecyl (3c), octadecyl ( 3d) and coconut (3f)-based imidazolines. Sunflower-based imidazoline (3g) exhibited good anti-cancer activity towards A549, Neuro2a and palm-based imidazoline (3h) towards HeLa, A549 and MCF-7 cell lines. Springer Science+Business Media 2014.

Full text of DOI:10.1007/s00044-014-0936-x

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res
DOI 10.1007/s00044-014-0936-x
ORIGINAL RESEARCH
Synthesis and biological evaluation of fatty imidazolines
•
T. Satyavani Y. Mohini M. S. L. Karuna R. B. N. Prasad
•
•
•
•
C. Ganesh Kumar M. Poornima P. Sujitha
•
Received: 9 October 2013 / Accepted: 3 February 2014
Ó Springer Science+Business Media New York 2014
Abstract A series of eight fatty imidazolines were syn-
thesized under microwave-assisted conditions using dif-
ferent fatty acids namely octyl, decyl, dodecyl, tetradecyl
and octadecyl, mixed fatty acids prepared from Sterculia
foetida (containing cyclopropene-rich fatty acids), coconut
(containing medium-chain-rich fatty acids), palm (con-
taining saturated-rich fatty acids) and sunflower (contain-
ing unsaturated-rich fatty acids). Coconut, sunflower and
non-edible oil S. foetida-based imidazolines were synthe-
sized for the first time. The fatty imidazolines were eval-
uated for anti-fungal activity and found to be good to
excellent (MIC, 4.68–18.75 lg ml-1) against the tested
Candida strains as compared with fluconazole (MIC,
16–64 lg ml-1) as standard. The fatty imidazolines also
exhibited excellent to moderate anti-bacterial activity
(MIC, 4.68–75 lg ml-1) against Staphylococcus aureus
MTCC 96, S. aureus MLS 16 MTCC 2940 and Pseudo-
monas aeruginosa MTCC 2453 as compared with neo-
mycin (MIC, 18.75 lg ml-1) as standard. The cytotoxic
evaluation of the imidazolines against different cancer cell
lines such as HeLa (Human Cervical Cancer Cell line),
A549 (Human Alveolar Adenocarcinoma Cell line), MDA-
MB-231& MCF7 (Human Breast Adenocarcinoma Cell
line) and Neuro2a (Mouse neuroblastoma cell line) showed
excellent cytotoxicity for dodecyl (3b), tetradecyl (3c),
octadecyl (3d) and coconut (3f)-based imidazolines. Sun-
flower-based imidazoline (3g) exhibited good anti-cancer
activity towards A549, Neuro2a and palm-based imidazo-
line (3h) towards HeLa, A549 and MCF-7 cell lines.
Keywords Fatty acids Á Fatty imidazolines Á
Anti-microbial agents Á Cytotoxicity Á Anti-cancer agents
Introduction
There has been a remarkable progress in the prevention,
control and even eradication of infectious diseases with the
development of novel anti-microbial drugs and vaccines.
However, there has been a constant threat to the new drugs
developed due to increase in the microbial resistance and
evolution of newer microbial strains. The impact of the
diseases emerging and re-emerging in tropical countries
like India was found to be more during the past three
decades. Cancer is one such disease, which is increasing
day-by-day globally. The control of cancer requires
effective implementation of knowledge by carrying out
more and more research on bioactive compounds.
Electronic supplementary material The online version of this
article (doi:10.1007/s00044-014-0936-x) contains supplementary
material, which is available to authorized users.
T. Satyavani Á Y. Mohini Á M. S. L. Karuna Á
R. B. N. Prasad (&)
Centre for Lipid Research, CSIR-Indian Institute of Chemical
Technology, Uppal Road, Hyderabad 500 007, India
e-mail: rbnprasad@iict.res.in
In this context, all substituted imidazolines exhibited a
vast array of pharmacological properties such as anti-par-
asitic (Mukherjee et al., 1989; Popa et al., 2001), anti-
fungal (Norman et al., 1986) and anti-microbial (Khabna-
dideh et al., 2003) activities. Their simple structures are
known to possess inhibitory effects on microsomal oxida-
tions (Wilkinson and Hetnarski, 1974), cytotoxic (Miller
C. G. Kumar Á M. Poornima Á P. Sujitha
Medicinal Chemistry and Pharmacology Division, CSIR-Indian
Institute of Chemical Technology, Uppal Road,
Hyderabad 500 007, India
123

Med Chem Res
et al., 1983) and anti-fungal (Norman et al., 1986) activi-
ties. They also act as anti-inflammatory, anti-diabetic and
anti-hypertensive agents (Baltork and Alibeik, 2003).
On the other hand, vegetable oils are good renewable
resources for the synthesis of a wide variety of oleo-
chemicals (Karlheinz, 2000). Further, the presence of im-
idazolines in natural products and pharmacologically active
compounds has instituted a diverse array of synthetic
approaches to develop biologically active heterocycles
(Grammitt et al., 1989). A survey of literature on the
synthesis and applications of imidazoline derivatives
revealed the following published reports. Ismail et al., 2010
synthesized cationic imidazolinium salts by amidation of
lauric, myristic, palmitic, stearic and oleic acids followed
by reaction with chloroacetic acid for 8 h. The salts were
found to exhibit excellent surface-active and anti-corrosion
properties. An efficient method for the synthesis of long-
chain 2-alkyl-1-(2-hydroxy ethyl)-2-imidazolines and their
amide precursors using fatty acids such as lauric, myristic,
palmitic and stearic acids (Palou et al., 2003) and palm
fatty acids (Bajpai and Tyagi, 2007) under solvent-free
microwave conditions were earlier demonstrated, which
resulted in good yields and high purity. The fatty imidaz-
olines also find a wide range of industrial applications,
particularly as corrosion inhibitors in oil field applications
(Ismail et al., 2010). Imidazole-based surfactants were
prepared using ionic liquids for 6–8 h with 70–98 % yield
and the compounds with alkyl amido chains containing
decyl, dodecyl and hexadecyl chain lengths were found to
exhibit good anti-microbial activities (Kanjilal et al.,
2009). A microwave irradiation method was adopted by
Bajpai (Bajpai and Tyagi, 2008) to prepare long-chain
cationic dialkyldiamido imidazolinium salts using dieth-
ylenetriamine (DETA) under solvent-free conditions and
calcium oxide (CaO) as support, followed by quarterniza-
tion. The fatty acids used were stearic, palmitic, myristic
and lauric acids. However, the imidazoline derivatives
synthesized were used for surfactant applications.
Most fatty imidazolines reported were prepared from
fatty acids, which were derived from edible oil sources.
Also there are no literature reports on the synthesis of
imidazolines from non-edible oil-based fatty acids and use
of vegetable oil-based fatty imidazolines as anti-microbial
and cytotoxic agents. The present study involves the syn-
thesis of a series of fatty imidazolines under microwave-
assisted conditions. The fatty acids were selected from
different vegetable oil sources, namely coconut oil (con-
taining medium-chain-rich fatty acids), sunflower oil
(containing unsaturated-rich fatty acids), palm oil (con-
taining saturated-rich fatty acids) and Sterculia foetida seed
oil (containing cyclopropene-rich fatty acids). In addition,
the products were also prepared by employing selected
fatty acids namely octyl (3a), dodecyl (3b), tetradecyl (3c)
and octadecyl (3d) fatty acids. The synthesized fatty imi-
dazolines were further evaluated for anti-bacterial, anti-
Candida and cytotoxic activities.
Results and discussion
The fatty imidazolines were synthesized from selected fatty
acids namely octyl, dodecyl, tetradecyl, octadecyl and fatty
acid mixtures of S. foetida (containing sterulic and malvalic
fatty acids), coconut (containing medium-chain fatty acids),
sunflower (containing unsaturated-rich fatty acids) and palm
fatty acids (containing saturated-rich fatty acids). In the
present study, coconut, sunflower and S. foetida (non-edible
oil) fatty acids-based imidazolines 3a–h were synthesized
for the first time under microwave-assisted conditions
(Scheme 1). The products that were formed in just 4 min
showed an acid value\6 and an amine value\4. The lower
acid and amine values indicated the completion of the
Scheme 1 Microwave-assisted
synthesis of fatty imidazolines
(3a–h). Reagents and
conditions: (a) Calcium oxide
(CaO) as support, 100 °C,
microwave power at 600 W,
reaction time, 4 min
R
O
a
H
N
H
N
+
N
N
R
H2N
NH2
R
OH
O
2
3 (a-h)
1
Fatty Acids
DETA
Fatty Imidazolines
R= octyl, ꢀD
R= dodecyl, ꢀE
R ꢁtetradecylꢂꢁꢀF
R= octadecyl, ꢀG
R= mixture of sterculia foetida fatty acyl,ꢀH
R= mixture of coconut fatty acyl, ꢀI
R= mixture of sunflower fatty acyl, ꢀJ
R= mixture of palm fatty acyl, ꢀK
123

Med Chem Res
aureus MLS 16 MTCC 2940, Pseudomonas aeruginosa
MTCC 2453 as compared with the standard, neomycin (MIC
value of 18.75 lg ml-1) (Table 1). The different fatty acid-
based imidazolines prepared, including dodecyl fatty acid
(3b), which is a medium-chain fatty acid, coconut-based
with medium-chain-rich fatty acid mixture (3f) and Sterculia
(with unusual cyclopropene fatty acid) (3e) exhibited poor
activity which suggested that the medium-chain fatty acids
and cyclopropene fatty acids were poor anti-bacterial agents.
The anti-Candida activity of Sterculia containing
cyclopropene-rich fatty acid-based imidazolines (3e)
Table 1 Anti-bacterial activity of fatty imidazolines 3a–h
Compounds Minimum Inhibitory concentration (MIC, lg ml-1
)
S. aureus
MTCC 96
S. aureus MLS 16
MTCC 2940
P. aeruginosa
MTCC 2453
a
3a
–
–
–
3b
18.75
4.68
18.75
75
37.5
4.68
4.68
–
75
3c
18.75
75
3d
3e
75
3f
75
37.5
4.68
18.75
–
37.5
4.68
18.75
–
showed promising activity (MIC value of 4.68 lg ml-1
)
3g
4.68
4.68
–
towards C. albicans MTCC 183. The activity was found to
be eight times more potent as compared with fluconazole
(MIC value of 32 lg ml-1). While, the compounds 3b, 3c,
3g and 3h exhibited good anti-Candida activity (MIC value
of 18.75 lg ml-1) against the tested C. albicans MTCC
3958, C. albicans MTCC 7315, C. parapsilosis MTCC
1744, C. albicans MTCC 4748, C. glabrata MTCC 3019
3h
Imidazole
Neomycin
18.75
18.75
18.75
a
No activity
reaction between the fatty acid and the amine, resulting in the
formation of fatty imidazoline ring. The synthesized mole-
cules in the present study were further characterized using
and moderate activity (MIC value of 37.5 lg ml-1
)
towards C. albicans MTCC 7315, C. albicans MTCC 1637,
C. albicans MTCC 227, C. parapsilosis MTCC 1744 and
C. glabrata MTCC 3019 as compared with the standard
drug, fluconazole (MIC value of 16–64 lg ml-1; Table 2).
These selected vegetable oils containing medium-chain
fatty acids and long-chain fatty acids exhibited a twofold
increase in activity as compared with the standard drug,
fluconazole. However, the short-chain fatty acid, octyl-
based imidazoline (3a) did not exhibit any activity towards
the tested Candida strains. Therefore, all these tested fatty
acid-based imidazolines can be well-exploited in different
anti-Candida formulations.
1
FTIR, H NMR and ESI–MS studies. Although in some
earlier studies, fatty acids such as lauric, myristic, palmitic
and stearic acids (Palou et al., 2003) and palm fatty acids-
based imidazolines (Bajpai and Tyagi, 2007) were synthe-
sized under microwave-assisted conditions. However, the
biological evaluation of these fatty acid-based imidazolines
was not reported. Hence, in the present study, those com-
pounds having varied chain lengths and nature of the fatty
acids were further evaluated for anti-microbial and anti-
cancer activities for the first time. Among the different fatty
acid-based imidazolines tested, compounds 3c, 3d, 3g and 3h
exhibited excellent anti-bacterial activities (MIC value of
4.68 lg ml-1) towards Staphylococcus aureus MTCC 96, S.
The different fatty acid-based imidazolines were further
screened against different cancer cell lines such as HeLa,
Table 2 Anti-Candida activity of fatty imidazolines 3a–h
Compounds Minimum inhibitory concentration (MIC, lg ml-1
)
Candida
albicans
MTCC 183 MTCC 3018 MTCC 3958 MTCC 7315 MTCC 1744
Candida
albicans
Candida
albicans
Candida
albicans
Candida
parapsilosis
Candida
albicans
Candida
albicans
Candida
albicans
Candida
glabrata
MTCC 4748 MTCC 1637 MTCC 227 MTCC 3019
a
3a
–
–
–
–
–
–
–
–
–
3b
–
75
300
–
150
75
37.5
37.5
75
18.75
18.75
–
75
37.5
–
–
37.5
37.5
300
–
3c
–
18.75
150
150
150
75
–
3d
–
150
18.75
75
–
–
3e
4.68
–
75
75
300
300
–
18.75
37.5
75
18.75
37.5
37.5
37.5
–
37.5
–
37.5
–
3f
150
18.75
18.75
–
3g
–
150
150
–
–
–
3h
–
37.5
–
75
–
–
Imidazole
–
–
–
–
Fluconazole 32
32
64
32
16
32
32
32
64
a
No activity
123

Med Chem Res
Table 3 Cytotoxicity of fatty imidazolines 3a–h
Compounds
IC50 values (lM)
HeLa
A549
MDA-MB-231
MCF-7
Neuro2a
a
3a
–
–
–
44.09 0.02
7.87 0.01
7.56 0.03
7.70 0.03
8.38 0.07
–
3b
10 0.05
23.85 0.04
15 0.05
34 0.04
15 0.08
–
12 0.04
19.62 0.04
74.28 0.05
40 0.03
17.5 0.05
29.71 0.06
8.24 0.05
–
15 0.02
6.27 0.03
12.41 0.06
43 0.02
17 0.04
–
8
0.09
3c
50.2 0.02
3d
–
3e
–
3f
8.45 0.07
6.61 0.04
15.57 0.03
–
3g
–
3h
31.98 0.02
–
–
6.79 0.06
–
Imidazole
Doxorubicin
–
–
0.509 0.01
0.459 0.02
0.91 0.02
1.07 0.02
1.04 0.04
HeLa—human cervical cancer cell line, A549—human alveolar adenocarcinoma cell line; MDA-MB-231 and MCF-7—human breast adeno-
carcinoma cell line, Neuro2a—mouse neuroblastoma cell line
a
No activity
A549, MDA-MB-231, MCF7 and Neuro2a, and the results
to this regard showed that they exhibited promising cyto-
toxicity for medium- and long-chain-based compounds such
as 3b (IC50 values ranging between 7.56 and 15 lM), 3c
(IC50 values ranging between 6.27 and 50.2 lM), 3d (IC50
value of 8.38 lM) and 3f (IC50 values ranging between 6.61
and 17.5 lM). However, the long-chain saturated-rich fatty
acids-containing palm-based imidazoline (3h) showed
excellent activity with IC50 values ranging between 6.79 and
31.9 lM towards A549 and MCF 7 cell lines, while long-
chain unsaturated-rich sunflower fatty acids-containing
imidazoline (3g) exhibited good activity with IC50 values
ranging between 15.5 and 29.7 lM towards A549 and Neuro
2a cell lines (Table 3). However, the shorter chain fatty acid,
octyl-based imidazoline (3a) exhibited promising activity
with IC50 value of 7.87 lM against the neuroblastoma cell
line (Neuro 2a). Based on these results, it was suggested that
all the above tested fatty acid-based imidazolines find
application in a wide range of anti-cancer formulations.
imidazolines (3h) exhibited excellent cytotoxicity against
A549 and MCF 7 cell lines. However, the shorter chain
fatty acid, octyl-based imidazoline (3a) exhibited promis-
ing cytotoxicity against neuroblastoma cell lines (Neu-
ro2a). These results suggest that the above fatty acid-based
imidazolines can find possible application in wide range of
pharmaceutical formulations.
Experimental section
Materials
All chemicals such as sodium hydroxide (NaOH), dieth-
ylenetriamine (DETA), calcium oxide (CaO) and solvents
were procured from different commercial suppliers such as
S.D. Fine Chemicals Limited, Mumbai, India and Avra
Chemicals Pvt. Ltd, Hyderabad, India and were used
without further purification. Pure fatty acids namely octa-
noic, dodecanoic, tetradecanoic and octadecanoic acids
were commercially purchased from S.D. Fine Chemicals
Limited, Mumbai, India, and mixture of fatty acids were
obtained from vegetable oil sources such as coconut, sun-
flower and palm oil. S. foetida oil was obtained from S.
foetida seeds obtained from Indian Institute of Chemical
Technology (IICT) campus. Acid value and amine value of
the synthesized imidazolines were determined according to
the AOCS standard methods (Firestone, 2010).
Conclusions
In conclusion, the fatty imidazolines (3a–h) was synthe-
sized under microwave conditions. Long-chain fatty acid-
based imidazolines exhibited excellent anti-microbial
activity as compared with the standard, neomycin. Ster-
culia containing cyclopropene-rich fatty acids-based imi-
dazolines exhibited promising activity against Candida
albicans MTCC 183 as compared with flucanozole, while
the medium-chain fatty acid-based imidazolines exhibited
good activity against the different Candida strains. Palm
containing-long-chain saturated-rich fatty acids-based
Spectral analysis
1H NMR and 13C NMR spectras were recorded on
AVANCE 300 and 75 MHz, respectively, in CDCl3.
123

Med Chem Res
Chemical shifts relative to TMS as internal standards were
given as d values in ppm. Infrared (IR) spectra were
obtained on a 1600 FTIR Perkin-Elmer Spectrometer
(Norwalk, CT) with a liquid film between NaCl cells. Mass
spectrometry was recorded by electrospray ionization (ESI)
on Shimadzu LC/MS instrument.
(br, –CONH–, 1H); 13C NMR (CDCl3, 75 MHz): d/
ppm 14.1, 21.5, 22.6, 25.8, 28.7, 29.5, 31.8, 36.5, 37.5, 48.
1, 49.2, 56.3, 174.1; MS/ESI (m/z) Calcd: 337 [M?], found
338 [M ?1].
N-(2-(2-Undecyl-4,5-dihydro-1H-imidazol-1-yl)ethyl) dode-
canamide (3b) Yield 89 %; C28H55N3O; FTIR (cm-1
neat): 3,389 (N–H str), 2,927 (CH3, C–H str), 1,715 (–C=O
,
Determination of fatty acid composition
1
str), 1,663 (C–N str), 716 ((CH2)n skeleton, C–H str); H
The composition of the fatty acids was determined using
Agilent 6890N series Gas Chromatograph equipped with a
flame ionization detector (FID); column, DB-225,
30 m 9 0.25 mm 9 0.2 lm). The oven temperature was
kept at 160 °C for 2 min and programmed from 160 to
180 °C at 6 °C/min, kept for 2 min at 180 °C and finally
raised to 230 °C at 4 °C/min which was maintained at
230 °C for 25 min. The injector and detector temperatures
were set at 250 °C.
NMR (CDCl3, 300 MHz): d/ppm 0.87 (t, J = 6.7 Hz,
(CH3)2, 6H), 1.27 (m, –(CH2)16–, 32H), 1.58 (m, –(CH2)2–
, 4H), 1.97 (m, –CH2–NH–CO–, 2H), 2.18 (t, –CH2–CH2–
CO–NH–, 2H), 2.22–2.26 (m, –CH2 attached imidazole
ring, 4H), 3.33–3.60 (m, imidazole ring protons, 4H), 6.09
(br, –CONH–, 1H); 13C NMR (CDCl3, 75 MHz): d/ppm
14.1, 21.6, 22.7, 25.9, 25.8, 28.7, 29.3, 29.4, 29.9, 31.8, 36.
6, 37.5, 49.3, 56.3, 174.2; MS/ESI (m/z) Calcd: 449 [M],
found 450 [M ? 1], 451 [M ? 2].
General procedure for the synthesis of fatty
imidazolines
N-(2-(2-Tridecyl-4,5-dihydro-1H-imidazol-1-yl)ethyl) te-
tradecanamide (3c)
Yield 90 %; C32H63N3O; FT-IR
(cm-1, neat): 3,387 (N–H str), 2,928 (CH3, C–H str),
1,711 (–C=O str), 1,661 (C–N str), 715 ((CH2)n skeleton,
C–H str); 1H NMR (CDCl3, 300 MHz): d/ppm 0.88
(t, J = 6.7 Hz, (CH3)2, 6H), 1.27 (m, –(CH2)20–, 40H), 1.
59 (m, –(CH2)2–, 4H), 1.98 (m, –CH2–NH–CO–, 2H), 2.
19 (t, –CH2–CH2–CO–NH–, 2H), 2.22–2.27 (m, –CH2
attached imidazole ring, 4H), 3.33–3.50 (m, imidazole
ring protons, 4H), 6.17 (br, –CONH–, 1H); 13C NMR
(CDCl3, 75 MHz): d/ppm 14.0, 22.6, 25.6, 26.0, 29.3, 29.
6, 31.8, 36.5, 37.6, 48.1, 49.1, 56.2, 174.2; MS/ESI (m/z)
Calcd: 505 [M?], found 506 [M ? 1], 528 [M ? Na].
Typical procedure for the synthesis of N-[2-(2-Alkyl-4,
5-dihydro-imidazol-1-yl)-ethyl] amide of Sterculia fatty
acid
Sterculia foetida fatty acids (2 mol), DETA (1 mol) and
CaO were mixed and irradiated under a microwave power
of 600 W at 100 °C for 4 min (Bajpai and Tyagi, 2008).
The reaction mixture was allowed to cool to room tem-
perature, dissolved in ethyl acetate and heated until boiling
and filtered off while hot. The filtrate was concentrated
under vacuum to dryness and passed through a silica gel
column chromatography to obtain the corresponding N-[2-
(2-alkyl-4,5-dihydro-imidazol-1-yl)-ethyl] amide of Ster-
culia fatty acid. The product was characterized for acid and
amine values. A similar procedure was followed for the
preparation of the fatty imidazolines of octyl (3a), dodecyl
(3b), tetradecyl (3c), octadecyl (3d), coconut (3f), sun-
flower (3g) and palm fatty acids (3h). All these compounds
N-(2-(2-Heptadecyl-4,5-dihydro-1H-imidazol-1-yl)ethyl)
stearamide (3d)
Yield 91 %; C40H79N3O; FT-IR
(cm-1, neat): 3,397 (N–H str), 2,928 (CH3, C–H str),
1,711 (–C=O str), 1,663 (C–N str), 715 ((CH2)n skeleton,
C–H str); 1H NMR (CDCl3, 300 MHz): d/ppm 0.88 (t,
J = 6.7 Hz, (CH3)2, 6H), 1.27 (m, –(CH2)28–, 56H), 1.59
(m, –(CH2)2–, 4H), 1.97 (m, –CH2–NH–CO–, 2H), 2.18
(t, –CH2–CH2–CO–NH–, 2H), 2.23–2.27 (m, –CH2
attached imidazole ring, 4H), 3.35–3.50 (m, imidazole
ring protons, 4H), 6.18 (br, –CONH–, 1H); 13C NMR
(CDCl3, 75 MHz): d/ppm 14.1, 21.8, 25.6, 26.8, 29.7, 31.
7, 36.7, 37.8, 48.2, 49.3, 56.0, 174.1; MS/ESI (m/z) Calcd:
617 [M?], found 618 [M ? 1].
1
were further characterized for FTIR, H NMR, 13C NMR
and ESI–MS studies.
N-(2-(2-Heptyl-4,5-dihydro-1H-imidazol-1-yl)ethyl)
oc-
tanamide (3a) Yield 87 %; C20H39N3O; FTIR (cm-1
neat) 3,397 (N–H str), 2,928 (CH3, C–H str), 1,711 (–C=O
,
1
str), 1,663 (C–N str), 715 ((CH2)n skeletal, C–H str); H
N-[2-(2-Alkyl-4, 5-dihydro-imidazol-1-yl)-ethyl] amide of
Yield 85 %; FT-IR (cm-1
,
NMR (CDCl3, 300 MHz): d/ppm 0.89 (t, J = 6.7 Hz,
(CH3)2, 6H), 1.26 (m, –(CH2)8–, 16H), 1.59 (m, –(CH2)2–,
4H), 1.96 (m, –CH2–NH–CO–, 2H), 2.18 (t, –CH2–CH2–
CO–NH–, 2H), 2.22–2.26 (m, –CH2 attached to imidazole
ring, 4H), 3.35–3.37 (m, imidazole ring protons, 4H), 6.10
Sterculia fatty acid (3e)
neat) 3,397 (N–H str), 2,928 (CH3, C–H str), 1,711 (–C=
O str), 1,664 (C–N str), 716 ((CH2)n skeleton, C–H str);
1H NMR (CDCl3, 300 MHz): d/ppm 0.78 (s, 2H,
123

Med Chem Res
Biological evaluation
cyclopropene ring protan), 0.88 (t, J = 6.7 Hz, (CH3)2,
6H), 1.26 (m, –(CH2)n), 1.62 (m, –(CH2)2–, 4H), 1.81 (m,
–CH2–NH–CO–, 2H), 2.18 (t, –CH2–CH2–CO–NH–, 2H),
2.74 (m, –CH2 attached imidazole ring, 4H), 3.34 (m,
imidazole ring protons, 4H), 5.34 (m, –CH=CH–, 2H), 6.
16 (br, –CONH–, 1H); 13C NMR (CDCl3, 75 MHz): 8.0,
14.1, 21.6, 23.5, 26.2, 28.4, 28.6, 29.6, 29.9, 31.7, 35.8,
37.2, 49.2, 55.8, 57.5, 112.7, 113.8, 174.6; MS/ESI (m/z)
Calcd: 637 (sterculic, [M?]), found 660 (steruculic,
[M ? Na]).
The prepared fatty imidazolines were evaluated for anti-
microbial activity against different Gram-positive and
Gram-negative bacteria such as S. aureus MTCC 96, S.
aureus MLS16 MTCC 2940 and P. aeruginosa MTCC
2453 and different Candida strains such as Candida albi-
cans MTCC 183, Candida albicans MTCC 3018, Candida
albicans MTCC 3958, Candida albicans MTCC 7315,
Candida parapsilosis MTCC 1744, Candida albicans
MTCC 4748, Candida albicans MTCC 1637, Candida
albicans MTCC 227 and Candida glabrata MTCC 3019
using the well-diffusion method (Amsterdam, 1996). The
pathogenic bacterial and Candida reference strains were
seeded on the surface of the media petri plates, containing
Muller–Hinton agar with 0.1 ml of previously prepared
N-[2-(2-Alkyl-4, 5-dihydro-imidazol-1-yl)-ethyl] amide of
coconut fatty acid (3f) Yield 89 %; FT-IR (cm-1, neat):
3,397 (N–H str), 2,928 (CH3, C–H str), 1,711 (–C=O str),
1
1,663 (C–N str), 715 ((CH2)n skeleton, C–H str); H NMR
(CDCl3, 300 MHz): d/ppm 0.87 (t, J = 6.7 Hz, (CH3)2,
6H), 1.25 (m, –(CH2)n), 1.61 (m, –(CH2)2–, 4H), 1.77 (m,
–CH2–NH–CO–, 2H), 2.17 (t, –CH2–CH2–CO–NH–, 2H),
2.67–2.79 (m, –CH2 attached imidazole ring, 4H), 3.20–3.
32 (m, imidazole ring protons, 4H), 5.30–5.38 (m, –CH=
CH–, 2H), 6.13 (br, –CONH–, 1H); 13C NMR (CDCl3,
75 MHz): 14.1, 21.7, 23.6, 26.1, 28.5, 29.8, 31.6, 37.2, 49.
2, 55.8, 134.5, 135.6, 174.3; MS/ESI (m/z) Calcd:449
[M?], found 450 [M ? 1].
microbial
suspensions
individually
containing
1.5 9 108 cfu ml-1 (equal to 0.5 McFarland). Wells of
6.0 mm diameter were prepared in the media petri plates
using a cork borer, and the synthesized compounds at a
dose range of 300–1.4 lg well-1 were added in each well
under sterile conditions in a laminar air flow chamber.
Standard antibiotic solutions of neomycin and fluconazole
at a dose range of 300–1.4 lg well-1 were used as positive
controls, and the well containing methanol served as neg-
ative control. Imidazole was also run in parallel as a ref-
erence. The plates were incubated for 24 h at 30 °C, and
the well containing the least concentration showing the
inhibition zone was considered as the minimum inhibitory
concentration. All experiments were carried out in dupli-
cates, and mean values are represented.
N-[2-(2-Alkyl-4, 5-dihydro-imidazol-1-yl)-ethyl] amide of
sunflower fatty acid (3g) Yield 86 %; FT-IR (cm-1, neat):
3,395 (N–H str), 2,928 (CH3, C–H str), 1,711 (–C=O str in
amide), 1,663 (C–N str), 715 ((CH2)n skeleton, C–H str); 1H
NMR (CDCl3, 300 MHz): d/ppm 0.88 (t, J = 6.7 Hz, (CH3)2,
6H), 1.26 (m, –(CH2)n), 1.58 (m, –(CH2)2–, 4H), 1.82 (m,
–CH2–NH–CO–, 2H), 2.18 (t, –CH2–CH2–CO–NH–, 2H), 2.
70–2.79 (m, –CH2 attached imidazole ring, 4H), 3.20–3.32 (m,
imidazole ring protons, 4H), 5.30–5.35 (m, –CH=CH–, 2H), 6.
13 (br, -CONH-, 1H); 13C NMR (CDCl3, 75 MHz): 14.1, 21.3,
22.8, 23.7, 26.5, 28.6, 29.7, 29.9, 32.0, 37.5, 49.5, 55.3, 134.2,
135.6, 174.1; MS/ESI (m/z): Calcd: 613 (18:1, [M?]), 609 (18:
2, [M?]), found 636 (18:1, [M ? Na]), 632 (18:2, [M ? Na]).
Cytotoxicity of the products were assessed against a
panel of different cancer cell lines obtained from the
American Type Culture Collection (ATCC), Manassas,
VA, USA, such as HeLa derived from human cervical
cancer cells (ATCC No. CCL-2), A549 derived from
human lung adenocarcinoma epithelial cells (ATCC No.
CCL-185) and MDA-MB-231 derived from human breast
adenocarcinoma cells (ATCC No. HTB-26), MCF-7
derived from human breast adenocarcinoma cells (ATCC
No. HTB-22) and Neuro2a derived from mouse neuro-
blastoma cell line (ATCC No. CCL-131) using the MTT
colorimetric assay (Mosmann, 1983), which is based on the
measurement of in vitro growth of tumour cell lines in
96-well plates by cell-mediated reduction in tetrazolium
salt to water insoluble formazan crystals according to the
literature procedures using doxorubicin as a standard and
imidazole as a reference. After 48 h incubation, the cells
were subjected to MTT colorimetric assay (5 mg ml-1
MTT). The effect of the different test compounds on the
viability of tumour cell lines was measured at the wave-
length of 540 nm on a multimode reader (InfiniteÒ M200,
Tecan, Switzerland). Dose–response curves were plotted
N-[2-(2-Alkyl-4, 5-dihydro-imidazol-1-yl)-ethyl] amide of
Yield 89 %; FT-IR (cm-1, neat)
palm fatty acid (3h)
3,397 (N–H str), 2,928 (CH3, C–H str), 1,712 (–C=O str),
1
1,662 (C–N str), 716 (CH2)n skeleton, C–H str); H NMR
(CDCl3, 300 MHz): d/ppm 0.88 (t, J = 6.9 Hz, (CH3)2, 6H),
1.25 (m, –(CH2)n), 1.61 (m, –(CH2)2–, 4H), 2.00 (m, –CH2
–NH–CO–, 2H), 2.30 (t, –CH2–CH2–CO–NH–, 2H), 2.69–2.
77 (m, –CH2 attached imidazole ring, 4H), 3.20–3.32 (m,
imidazole ring protons, 4H), 5.31–5.37 (m, –CH=CH–, 2H),
6.13 (br, -CONH-, 1H); 13C NMR (CDCl3, 75 MHz): 14.1,
18.4, 22.6, 23.8, 25.9, 29.1, 29.6, 31.8, 37.6, 49.5, 55.2, 134.1,
135.6, 174.2; MS/ESI (m/z): Calcd 561 (16:0, M?), 589 (16:
0 ? 18:0) found 562 (16:0, [M ? H]), 606 [16:0 ? 18:0].
123

Med Chem Res
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