Synthesis of fatty acid Schiff base esters as potential antimicrobial and chemotherapeutic agents

Article abstract of DOI:10.1007/s00044-012-0450-y

Schiff base {4-[(pyridine-3-ylmethylimino)-methyl] phenol} was prepared by reacting 4-hydroxybenzaldehyde with 3-aminomethylpyridine in ethanol for 6 h (85 % yield) followed by their esterification via reaction with fatty acids of varying chain lengths. T

Full text of DOI:10.1007/s00044-012-0450-y

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2013) 22:4360–4366
DOI 10.1007/s00044-012-0450-y
ORIGINAL RESEARCH
Synthesis of fatty acid Schiff base esters as potential antimicrobial
and chemotherapeutic agents
•
Y. Mohini R. B. N. Prasad M. S. L. Karuna C. Ganesh Kumar
•
•
•
•
M. Poornima P. Sujitha
Received: 1 September 2012 / Accepted: 21 December 2012 / Published online: 8 January 2013
Ó Springer Science+Business Media New York 2013
Abstract Schiff base {4-[(pyridine-3-ylmethylimino)-methyl]
phenol} was prepared by reacting 4-hydroxybenzaldehyde with
3-aminomethylpyridine in ethanol for 6 h (85 % yield) followed
by their esterification via reaction with fatty acids of varying chain
lengths. The structure of these Schiff base esters were elucidated
using chromatographic and spectroscopic techniques like GC–
MS, 1H NMR, 13C NMR, and ESI–MS. Schiff base esters with
shorter chain heptanoic (2a) and decanoic acid (2c) showed good
activity against all the tested bacterial and fungal strains. The
synthesized esters were also studied for cytotoxicity toward dif-
ferent human tumor cell lines like HeLa, HepG2, A549, MDA-
MB-231, and MCF 7 and Neuro2a; however, Schiff base esters
with shorter chain (2a, 2b) and medium chain fatty acids (2d, 2i)
exhibited good anticancer activity and selectively toward MDA-
MB-231 and MCF 7, while long chain fatty acid (2g) Schiff base
ester exhibited good anticancer activity selectively toward MDA-
MB-231 as compared to the parent molecule, Schiff base (1).
Introduction
Compounds containing azomethine CH=N structure refer-
red to as Schiff bases are synthesized by the condensation
of primary amines with carbonyl groups (Shi et al., 2007).
These organic compounds find great utility in medicinal,
agricultural, and cosmetic areas (Badawi et al., 2007; Zhu
et al., 2003). They are known to exhibit very good anti-
bacterial (Sridhar et al., 2001; Mladenova et al., 2002;
Panneerselvam et al., 2005; Walsh et al., 1996; Pandeya
et al., 1999a, b) antifungal, and antitumor activities (Liu
et al., 1992; Hodnett and Dunn, 1970). Ha and Win, 2011
synthesized Schiff base esters from 4-formyl-3-hydroxy-
phenyl octadecanoate and 3-substituted-anilines which
exhibited good thermocrystalline behavior.
A series of novel Schiff base cationic surfactants were
prepared by Negm et al., (2011a) by quaternization of
Schiff base-alkyl ketoglutarates. The title molecules
exhibited good anticorrosion and as antibacterial biocides.
Schiff bases derived from 5-chloro-salicylaldehyde by
reacting with primary amines (Shi et al., 2007) exhibited
potential antibacterial and antifungal activities. Novel eco-
friendly Schiff bases vanillin derived cationic surfactants
were prepared by Negm et al., (2011b). These molecules
exhibited good surface-active behavior. Schiff base esters
containing pyridine moiety were prepared and these mol-
ecules were studied for their crystal structure behavior
(Rauf and Parveen, 2005).
Keywords Schiff base esters ꢀ
Vegetable oil based Schiff base esters ꢀ
Antimicrobial agents ꢀ Anticancer agents
Electronic supplementary material The online version of this
article (doi:10.1007/s00044-012-0450-y) contains supplementary
material, which is available to authorized users.
Y. Mohini ꢀ R. B. N. Prasad ꢀ M. S. L. Karuna (&)
Centre for Lipid Research, CSIR-Indian Institute of Chemical
Technology, Uppal Road, Hyderabad 500 607, India
e-mail: karuna@iict.res.in
With increasing number of diseases and alarming
problems of microbial resistance to antibiotics, the dis-
covery of novel bioactive compounds against targeted
diseases has been the need of the hour. In the recent years,
plant-based renewable resources have gained increased
attention. Fatty Acids and their derivatives were found to
exhibit good antimicrobial and antifungal agents (Rauf and
C. Ganesh Kumar ꢀ M. Poornima ꢀ P. Sujitha
Chemical Biology Laboratory, CSIR-Indian
Institute of Chemical Technology, Uppal Road,
Hyderabad 500 607, India
123

Med Chem Res (2013) 22:4360–4366
4361
N
N
N
N
N
N
NH2
CHO
O
C
DCC, DMAP
+
Ethanol
+
R
OH
DCM, 0°C-RT
N
Reflux, 6 h
OH
R
O
OH
OH
O
1
2 (a-k)
1
Scheme 1 Synthesis of Schiff base
Scheme 2 Synthesis of Schiff base esters. R = C6H13 (2a), C7H15
(2b), C9H19 (2c), C11H23 (2d), C13H27 (2e), C15H31 (2f), C17H35 (2g),
Sterculia foetida (2h), coconut (2i), palm (2j), karanja (2k) fatty acids
Parveen, 2005; Sharma et al., 2005). Researchers have
synthesized a wide variety of Schiff base esters (Ha et al.,
2010) and most of them exhibited good antimicrobial
properties. Long chain fatty acids containing Schiff bases
with a polar head group exhibit good surface-active
behavior. However, the fatty acid based alkanoyloxy Schiff
base esters were not studied for antimicrobial and anti-
cancer studies. Keeping this in view, we synthesized a
series of different fatty acid Schiff base esters from pure
and different fatty acid mixtures of vegetable oil origin.
These esters were screened for antimicrobial and antican-
cer activities. The aim of the present study is to check the
effect of alkanoyloxy chain length and nature of fatty acid
mixtures prepared from different vegetable oils attached to
Schiff base on the antimicrobial and anticancer activities.
from different vegetable oils such as Sterculia foetida oil
(containing cyclopropene-rich fatty acids), coconut oil
(containing medium chain-rich fatty acids), palm oil (con-
taining saturated-rich fatty acids), and karanja oil (contain-
ing unsaturated-rich fatty acids).
The Schiff base esters (2) studied exhibited moderate
antibacterial activity which ranged from 75 to 300 lg/ml as
compared to neomycin (18.75 lg/ml) as standard. How-
ever, the compounds with shorter chain, namely hepta-
noyloxy (2a, 37.5 lg/ml), octanoyloxy (2b, 37.5 lg/ml),
decanoyloxy (2c, 37.5 lg/ml) chain lengths exhibited good
activity as compared to the parent compound Schiff base
(1, 75 lg/ml), other long chain (2d–g) and fatty acid
mixture based Schiff base esters (2h–k) (Table 1). Similar
trend was observed by Galbraith et al., (1971); Kabara
et al., (1972); and Feldlaufer et al., (1993) in their studies
on the effect of fatty acid chain length on antimicrobial
activity. However, none of the compounds exhibited
activity against Micrococcus luteus MTCC 2470, Esche-
richia coli MTCC 739 and Klebsiella planticola MTCC
530 strains.
Results and discussion
Chemistry
The Schiff base esters of different fatty acids (2a–k), ele-
ven Schiff base esters were prepared from different fatty
acids. The fatty acids with varied chain lengths were
chosen for the study. The Schiff base esters were prepared
in a two step procedure. 4-hydroxy benzaldehyde and
3-aminomethylpyridine in ethanol were reacted to obtain
Schiff base shown in Scheme 1. The Schiff base (1) was
reacted with fatty acids to obtain the Schiff base esters
2a–k shown in Scheme 2. All the synthesized fatty Schiff
All Schiff base esters (2a–k) exhibited moderate anti-
fungal activity as compared to fluconazole as standard.
However, the shorter chain compounds 2a (75 lg/ml) and
2c (75 lg/ml) exhibited good activity against Candida
aaseri MTCC 1962 (75 lg/ml), Candida albicans MTCC
3018 (75 lg/ml), Issatchenkia hanoiensis MTCC 4755
(75 lg/ml) as compared to standard fluconazole (32–64 lg/ml).
The heptanoyloxy Schiff base ester (2a) exhibited extraor-
dinary activity (75 lg/ml) against Issatchenkia orientalis
MTCC 3020 (128 lg/ml). Kabara et al., (1972) and Bergsson
et al., (2001) also observed similar effect of short chain fatty
acids on antifungal activity. While, other compounds (2b,
2e, 2h, and 2k) showed fairly moderate activity
(75–300 lg/ml) as compared to the standard (16–128 g/ml)
(Table 2). However, the compounds (1, 2d, 2f–g, and 2i–j)
did not show any activity against the tested Candida
strains. Overall, the shorter chain Schiff base esters
1
base esters were characterized by GC–MS, H NMR, 13C
NMR, and ESI–MS. The synthesized Schiff base esters
were screened for antimicrobial and anticancer activities.
Different Schiff base compounds with different alkanoyl-
oxy chain lengths have varied behavior on antibacterial,
antifungal, and anticancer activities. In the present study, we
focused on a series of synthesized Schiff base esters with
different alkanoyloxy chain lengths. The fatty acids used
were shorter chain pure fatty acids (2a–c), longer chain fatty
acids (2d–g), and mixture of fatty acids (2h–k) prepared
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Med Chem Res (2013) 22:4360–4366
Table 1 Anti-bacterial activities of Schiff base (1) and synthesized compounds (2a–k)
Tested strains
Minimum inhibitory concentration (MIC, lg/ml)
1
2a
2b
2c
2d
2e
2f
2g
2h
75
2i
75
2j
75
2k
Neomycin
Staphylococcus aureus MTCC 96
Staphylococcus MLS16 MTCC 2940
Bacillus subtilis MTCC 121
Pseudomonas aeruginosa MTCC 2453
a
75
a
–
37.5
37.5
37.5
150
150
–
75
75
–
–
–
–
–
300
300
–
300
300
–
18.75
18.75
18.75
18.75
150
300
300
300
300
300
–
300
–
150
–
300
–
–
–
37.5
75
–
–
300
–
300
75
–
–
No activity
Table 2 Antifungal activities of synthesized compounds (2a–c, 2e, 2h, 2k)
Test compounds
Minimum inhibitory concentration (lg/ml)
2a
2b
2c
2e
2h
2k
Fluconazole
Candida albicans MTCC 227
Candida albicans MTCC 854
Candida albicans MTCC 7315
Candida albicans MTCC 183
Candida albicans MTCC 3958
Candida albicans MTCC 1637
Candida albicans MTCC 3018
Candida albicans MTCC 3017
Candida parapsilosis MTCC 1744
Candida glabrata MTCC 3019
Candida aaseri MTCC 1962
Issatchenkia orientalis MTCC 3020
Issatchenkia hanoiensis MTCC 4755
75
150
a
300
300
300
300
300
300
75
300
300
300
300
300
300
300
300
–
300
–
300
300
300
300
300
300
300
–
32
32
32
32
64
64
32
64
16
64
64
128
64
300
150
300
150
150
75
–
150
150
150
–
300
300
300
300
300
–
300
–
–
–
300
–
–
150
150
75
150
150
–
150
–
150
300
150
300
–
75
–
–
75
150
75
–
300
150
–
75
–
150
a
No activity
CCL-2), HepG2 derived from human hepatocellular liver
carcinoma cells (ATCC No. HB-8065), A549 derived from
human alveolar adenocarcinoma epithelial cells (ATCC
No. CCL-185), MDA-MB-23 derived from human breast
adenocarcinoma cells (ATCC No. HTB-26), MCF7 derived
from human breast adenocarcinoma cells (ATCC No.
HTB-22) and Neuro2a derived from mouse neuroblastoma
cells (ATCC No. CCL-131). Interestingly, the shorter and
medium chain Schiff base esters 1, 2a, 2b, 2d, 2e, 2g, 2i
exhibited cytotoxicity selectively against MDA-MB-231,
while the parent compound (1), octanoyloxy (2b), and
dodecanoyloxy (2d) based Schiff base esters exhibited
cytotoxicity against MCF7 (Table 3). However, the tested
compounds did not exhibit any cytotoxicity against other
tested cell lines.
Table 3 Anti-cancer activities of Schiff base (1) and synthesized
compounds
Compounds
IC50 (lM)
MDA-MB-231
MCF7
12
1
16.9
14.96
15.80
18.9
a
–
2a
2b
12
17.6
–
2d
2e
26.61
11.5
2g
–
2i
17.2
–
Doxorubicin
\1
1
a
No activity
(2ac) can be well- exploited for antibacterial and antifungal
formulations.
Conclusions
The Schiff base esters studied (2a–k) were also screened
against different human tumor cell lines, namely, HeLa
derived from human cervical cancer cells (ATCC No.
In conclusion, a series of fatty acid-based Schiff base esters
were prepared with varied chain lengths and the effect of
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Med Chem Res (2013) 22:4360–4366
4363
fatty acyl groups on antimicrobial and anticancer activities
was studied. Schiff base esters with shorter chain heptanoic
(2a) and decanoic acid (2c) showed good activity against
the tested bacterial and fungal strains. Schiff base esters
with shorter (2a, 2b) and medium chain fatty acids (2d, 2i)
exhibited good anticancer activity, selectively toward
human breast adenocarcinoma cell lines, MDA-MB-231
and MCF7 and long chain fatty acid (2g) exhibited good
anticancer activity selectively toward MDA-MB-231 as
compared to Schiff base (1).
eluted with 5 % methanol-chloroform as solvent system.
The reaction was cooled and the reaction mixture was
poured into crushed ice with vigorous stirring. The product
was filtered off and then washed with distilled water 2–3
times until it was free of the unreacted amine, followed by
drying in a vacuum desiccator to get the Schiff base
(80–85 % isolated yield).
Schiff base {4-[pyridine-3-ylmethylimino)-methyl]-phe-
nol} (1) Melting point: 143.6 °C; 1H NMR (DMSO-d6,
300 MHz): d/ppm 4.72 (s, 2H, N–CH2–); 6.79 (d, 2H,
J = 8.49 Hz, Ar–H); 7.26 (dd, 1H, J = 7.9 Hz, Ar–H);
7.57 (d, 2H, J = 7.7 Hz, Ar–H); 7.66 (d, 1H, J = 3.58 Hz,
Ar–H); 8.30 (s, 1H, Ar–H); 8.42 (d, 1H, J = 4.7 Hz,
Ar–H); 8.52 (s, 1H, CH=N); 9.6 (s, 1H, OH); 13C NMR
(DMSO-d6, 75 MHz): d/ppm 161.02, 159.15, 147.85,
146.76, 134.43, 130.9, 128.74, 126.13, 122.28, 114.51,
60.68; ESI–MS(m/z): 213.2 [M?H].
Experimental section
Chemistry
Different chemicals such as 4-hydroxybenzaldehyde,
3-aminomethylpyridine, dimethylaminopyridine (DMAP),
dicyclohexylcarbodiimide (DCC), acetonitrile, absolute
ethanol (reagent grade) were procured from different
commercial suppliers like Sigma-Aldrich, St. Louis, MO,
USA, S.D. Fine Chemicals Limited, Mumbai, India and
Avra Chemicals Pvt. Ltd, Hyderabad, India. Pure fatty
acids namely heptanoic, octanoic, decanoic, dodecanoic,
myristic, palmitic, and stearic acids were purchased com-
mercially from S.D. Fine Chemicals Limited, Mumbai,
India. Mixture of fatty acids were obtained from vegetable
oils namely coconut, palm and karanja oils purchased
locally. S. foetida fatty acids were obtained from S. foetida
oil extracted from S. foetida seeds collected from IICT
Campus. The fatty acid composition of the mixture of fatty
acids was determined by GC chromatographic methods.
Melting points were measured by open capillary tubes on
General procedure for the synthesis of Schiff base ester
{4-[(pyridine-3-ylmethylimino)methyl]phenyl alkanoate}
(2a–k)
4-[(Pyridine-3-ylmethylimino)methyl]phenyl alkanoate was
prepared by taking Schiff base (4.7 mmol) dissolved in
2 ml DMF taken in a 100 ml round bottom flask. To this
was added a solution of fatty acids (2a–k) (4.7 mmol) and
4-dimethylamino pyridine; DMAP (0.47 mmol) taken in
dichloromethane; DCM (35 ml). The mixture was mag-
netically stirred in an ice bath at 0 °C. N,N0-dicyclohex-
ylcarbodiimide; DCC (4.7 mmol) dissolved in 10 ml DCM
was added drop wise while stirring in the ice bath for
30 min. The mixture was stirred at room temperature for
12–24 h (Scheme 2). The contents were filtered to remove
the byproduct, dicyclohexylurea; DCU and the excess
solvent were removed from the filtrate by evaporation. The
crude product was dissolved in 50 ml of 50 % hexane–
ethyl acetate and washed with saturated sodium bicarbon-
ate solution and then concentrated. The crude product was
taken in a separating funnel, dissolved in 50 % hexane–
ethyl acetate and to this acetonitrile was added and shaken.
The process was continued 2–3 times to get pure Schiff
base ester with 60–75 % isolated yields.
1
Barnstead Electrothermal apparatus. The H NMR spectra
were recorded at Varian 300 MHz and Innova 500 and
75 MHz for 13C NMR and TMS was used as an internal
standard. All the compounds were dissolved in CDCl3
while, the parent Schiff base (1) was dissolved in DMSO-
d6 and the chemical shifts were recorded at d values in
parts per million (ppm) and tetramethylsilane was used as
internal standard. ESI–MS spectra were recorded on
Waters e2695 Seperators module (Waters, Milford, MA,
USA) mass spectrometer.
{4-[(Pyridine-3-ylmethylimino)-methyl]-phenyl heptano-
1
ate} (2a) H NMR (CDCl3, 500 MHz): d/ppm 0.89 (t, 3H,
General procedure for the synthesis of Schiff base
J = 6.98 Hz, –CH3); 1.30 (m, 6H, CH3–(CH2)3–); 1.78
(quint, 2H, –CH2–CH2–COO); 2.52 (t, 2H, J = 7.0 Hz,
–CH2–COO); 4.78 (s, 2H, –CH2–N=CH–); 6.93 (d, 2H,
J = 8.8 Hz, Ar–H); 7.63 (dd, 1H, J = 8.0 Hz, Ar–H); 7.28
(d, 2H, J = 8.9 Hz, Ar–H); 7.90 (d, 1H, J = 8.5 Hz,
Ar–H); 8.35 (s, 1H, –CH=N–); 8.51 (d, 1H, J = 4.7 Hz,
Ar–H); 8.60 (s, 1H, Ar–H); 13C NMR (CDCl3, 75 MHz):
d/ppm 170.1, 162.03, 161.58, 149.29, 148.18, 135.42,
{4-[(pyridine-3-methylimino) methyl phenol} (1)
4-[(Pyridine-3-ylmethylimino)methyl]phenol was prepared
by taking equimolar ratio of 4-hydroxybenzaldehyde
(0.1 mol) and 3-aminomethyl pyridine (0.1 mol) dissolved
in 100 ml absolute ethanol in a 250 ml round bottom flask
and stirred at 80–85 °C for 6 h magnetically (Scheme 1).
The progress of the reaction was monitored using TLC
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Med Chem Res (2013) 22:4360–4366
134.01, 129.78, 128.47, 123.32, 114.50, 62.18, 31.69, 28.99,
25.89, 22.53, 14.01; ESI–MS (m/z): 325 [M?H].
{4-[(Pyridine-3-ylmethylimino)-methyl]-phenyl hexade-
1
canoate} (2f) H NMR (CDCl3, 500 MHz): d/ppm 0.88 (t,
{4-[(Pyridine-3-ylmethylimino)-methyl]-phenyl octano-
1
3H, J = 6.9 Hz, –CH3); 1.26 (m, 24H, CH3–(CH2)12–);
1.61 (quint, 2H, –CH2–CH2–COO); 2.56 (t, 2H, J =
6.9 Hz, –CH2–COO); 4.82 (s, 2H, –CH2–N=CH–); 7.15
(d, 2H, J = 8.9 Hz, Ar–H); 7.67 (dd, 1H, J = 7.9 Hz, Ar–
H); 7.92 (d, 2H, J = 8.9 Hz, Ar–H); 7.92 (d, 1H,
J = 8.9 Hz, Ar–H); 8.41 (s, 1H, –CH=N–); 8.52 (d, 1H,
J = 4.9 Hz, Ar–H); 8.61 (s, 1H, Ar–H); 13C NMR
(CDCl3, 75 MHz): d/ppm 171.0, 162.13, 161.50, 149.23,
148.21, 135.53, 129.82, 123.36, 114.52, 62.17, 31.86,
29.64, 29.12, 25.95, 22.63, 18.37, 14.07; ESI–MS (m/z):
451 [M?H].
ate} (2b) H NMR (CDCl3, 500 MHz): d/ppm 0.90 (t, 3H,
J = 7.0 Hz, –CH3); 1.31 (m, 8H, CH3–(CH2)4–); 1.42
(quint, 2H, –CH2–CH2–COO); 2.56 (t, 2H, J = 7.0 Hz,
–CH2–COO); 4.82 (s, 2H, –CH2–N=CH–); 7.15 (d, 2H,
J = 9.0 Hz, Ar–H); 7.66 (dd, 1H, J = 8.0 Hz, Ar–H); 7.8
(d, 2H, J = 8.0 Hz, Ar–H); 7.92 (d, 1H, J = 8.0 Hz,
Ar–H); 8.41 (s, 1H, –CH=N–); 8.52 (d, 1H, J = 5.0 Hz,
Ar–H); 8.56 (s, 1H, Ar–H); 13C NMR (CDCl3, 75 MHz): d/
ppm 169.0, 162.01, 161.42, 149.19, 148.14, 135.44,
135.04, 131.85, 129.74, 128.39, 123.28, 114.59, 114.41,
62.09, 31.69, 29.87, 29.08, 29.01, 28.88, 25.86, 13.97;
ESI–MS (m/z): 338.8 [M?H].
{4-[(Pyridine-3-ylmethylimino)-methyl]-phenyl octadec-
anoate} (2g) 1H NMR (CDCl3, 500 MHz): d/ppm 0.88
(t, 3H, J = 6.9 Hz, –CH3); 1.27 (m, 28H, CH3–(CH2)14–);
1.61 (quint, 2H, –CH2–CH2–COO); 2.55 (t, 2H, J =
6.9 Hz, –CH2–COO); 4.82 (s, 2H, –CH2–N=CH–); 7.15
(d, 2H, J = 8.9 Hz, Ar–H); 7.64 (dd, 1H, J = 7.9 Hz, Ar–
H); 7.80 (d, 2H, J = 8.9 Hz, Ar–H); 7.91 (d, 1H,
J = 8.9 Hz, Ar–H); 8.41 (s, 1H, –CH=N–); 8.52 (d, 1H,
J = 4.9 Hz, Ar–H); 8.61 (s, 1H, Ar–H); 13C NMR (CDCl3,
75 MHz): d/ppm 170.0, 162.07, 161.45, 149.24, 148.22,
135.51, 135.10, 131.91, 129.77, 128.44, 123.34, 114.47,
62.16, 31.85, 29.61, 29.29, 29.09, 25.92, 22.60, 14.05;
ESI–MS (m/z): 479 [M?H].
{4-[(Pyridine-3-ylmethylimino)-methyl]-phenyl decano-
1
ate} (2c) H NMR (CDCl3, 500 MHz): d/ppm 0.91 (t, 3H,
J = 7.0 Hz, –CH3); 1.30 (m, 12H, CH3–(CH2)6–); 1.74
(quint, 2H, –CH2–CH2–COO); 2.53 (t, 2H, J = 7.0 Hz,
–CH2–COO); 4.79 (s, 2H, –CH2–N=CH–); 7.11 (d, 2H,
J = 8.5 Hz, Ar–H); 7.63 (dd, 1H, J = 8.0 Hz, Ar–H); 7.76
(d, 2H, J = 8.5 Hz, Ar–H); 7.8 (d, 1H, J = 8.0 Hz, Ar–H);
8.37(s, 1H, –CH=N–); 8.48 (d, 1H, J = 4.0 Hz, Ar–H);
8.56 (s, 1H, Ar–H); 13C NMR (CDCl3, 75 MHz) d/ppm
169.1, 162.07, 149.19, 148.19, 135.44, 135.07, 131.88,
129.7, 123.31, 114.61, 114.44, 62.1, 31.37, 29.44, 29.16,
29.01, 28.98, 25.85, 22.54, 13.98; ESI–MS (m/z): 367
[M?H].
{4-[(Pyridine-3-ylmethylimino)-methyl]-phenyl ester of
1
S. foetida fatty acids} (2h) H NMR (CDCl3, 500 MHz):
{4-[(Pyridine-3-ylmethylimino)-methyl]-phenyl dodecan-
oate} (2d) 1H NMR (CDCl3, 500 MHz): d/ppm 0.88 (t, 3H,
J = 6.7 Hz, –CH3); 1.26 (m, 16H, CH3–(CH2)8–); 1.73
(quint, 2H, –CH2–CH2–COO); 2.56 (t, 2H, J = 7.3 Hz,
–CH2–COO); 4.82 (s, 2H, –CH2–N=CH–); 7.16 (d, 2H,
J = 8.5 Hz Ar–H); 7.7 (dd, 1H, J = 7.9 Hz, Ar–H); 7.76
(d, 2H, J = 8.5 Hz, Ar–H); 7.93 (d, 1H, J = 8.3 Hz, Ar–H);
8.40 (s, 1H, –CH=N–); 8.52 (d, 1H, J = 4.1 Hz, Ar–H);
8.60 (s, 1H, Ar–H); 13C NMR (CDCl3, 75 MHz) d/ppm
170.0, 162.01, 161.40, 149.18, 148.13, 135.42, 135.04,
131.81, 129.72, 123.26, 114.41; ESI–MS (m/z): 394.9
[M?H].
d/ppm 0.88 (t, 3H, J = 6.5 Hz, –CH3); 0.7 (s, 2H, cyclo-
propene ring); 1.26 (m, CH3–(CH2)n–); 1.62 (m, 2H,
–CH2–CH2–COO); 2.02 (t, 2H, methylene protan attached
to cyclopropenoid ring); 2.35 (t, 2H, J = 7.5 Hz, –CH2–
COO); 4.82 (s, 2H, –CH2–N=CH–); 7.11 (d, 2H, J =
8.9 Hz, Ar–H); 7.67 (dd, 1H, J = 7.9 Hz, Ar–H); 7.91
(d, 2H, J = 8.9 Hz, Ar–H); 7.94 (d, 1H, J = 8.9 Hz,
Ar–H); 8.41 (s, 1H, –CH=N–); 8.51 (d, 1H, J = 4.9 Hz,
Ar–H); 8.61 (s, 1H, Ar–H); 13C NMR (CDCl3, 75 MHz):
d/ppm 169, 162.11, 161.70, 149.21, 148.32, 135.62, 135.52,
134.5, 133.7, 131.02, 129.84, 123.38, 114.52, 59.32, 36.43,
34.23, 31.82, 29.63, 29.89, 29.12, 26.13, 23.60, 14.02.
{4-[(Pyridine-3-ylmethylimino)-methyl]-phenyl ester of
coconut fatty acids} (2i) 1H NMR (CDCl3, 500 MHz):
d/ppm 0.88 (t, 3H, J = 6.9 Hz,–CH3); 1.26 (m, CH3–
(CH2)n–); 1.61 (quint, 2H, –CH2–CH2–COO); 2.56 (t, 2H,
J = 6.9 Hz, –CH2–COO); 4.80 (s, 2H, –CH2–N=CH–);
5.36 (m, 2H, –CH=CH–); 7.16 (d, 2H, J = 8.9 Hz, Ar–H);
7.68 (dd, 1H, J = 7.9 Hz, Ar–H); 7.92 (d, 2H, J = 8.9 Hz,
Ar–H); 7.94 (d, 1H, J = 8.9 Hz, Ar–H); 8.41(s, 1H,
–CH=N–); 8.52 (d, 1H, J = 4.9 Hz, Ar–H); 8.60 (s, 1H,
Ar–H); 13C NMR (CDCl3, 75 MHz): d/ppm 169.1, 162.17,
161.89, 149.25, 148.32, 135.67, 134.52, 133.9, 131.02,
129.84, 123.48, 114.53, 63.32, 34.23, 31.92, 29.55, 29.63,
29.89, 28.12, 26.12, 23.60, 14.03.
{4-[(Pyridine-3-ylmethylimino)-methyl]-phenyl tetrade-
1
canoate} (2e) H NMR (CDCl3, 500 MHz): d/ppm 0.88
(t, 3H, J = 6.79 Hz, –CH3);1.26 (m, 20H, CH3–(CH2)10);
1.76 (quint, 2H, –CH2–CH2–COO); 2.56 (t, 2H, J =
8.3 Hz, –CH2–COO); 4.82 (s, 2H, –CH2–N=CH–); 7.15
(d, 2H, J = 8.4 Hz, Ar–H); 7.68 (dd, 1H, J = 7.7 Hz,
Ar–H); 7.81 (d, 2H, J = 8.4 Hz, Ar–H); 7.92 (d, 1H, J =
8.3 Hz, Ar–H); 8.42 (s, 1H, –CH=N–); 8.53 (d, 1H, J =
4.1 Hz, Ar–H); 8.60 (s, 1H, Ar–H); 13C NMR (CDCl3,
75 MHz) d/ppm 170.02, 162.07, 161.45, 149.24, 148.22,
135.50, 129.77, 123.24, 114.47, 62.16, 31.85, 29.52,
29.29, 29.09, 25.92, 22.60, 14.06; ESI–MS (m/z): 423
[M?H].
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Med Chem Res (2013) 22:4360–4366
4365
{4-[(Pyridine-3-ylmethylimino)-methyl]-phenyl ester of
palm fatty acids} (2j) 1H NMR (CDCl3, 500 MHz): d/ppm
0.89 (t, 3H, J = 7.0 Hz, –CH3); 1.25 (m, CH3–(CH2)n–);
1.77 (quint, 2H, –CH2–CH2–COO); 2.56 (t, 2H, J =
7.0 Hz, –CH2–COO); 4.81 (s, 2H, –CH2–N=CH–); 5.35
(m, 2H, –CH=CH–); 7.15 (d, 2H, J = 9.0 Hz, Ar–H); 7.67
(dd, 1H, J = 8.0 Hz, Ar–H); 7.80 (d, 2H, J = 9.0 Hz,
Ar–H); 7.92 (d, 1H, J = 8.9 Hz, Ar–H); 8.41(s, 1H,
–CH=N–); 8.52 (d, 1H, J = 3.0 Hz, Ar–H); 8.61 (s, 1H,
Ar–H); 13C NMR (CDCl3, 75 MHz): d/ppm 170.01,
162.11, 161.70, 149.21, 148.32, 135.62, 135.52, 133.9,
131.02, 129.84, 123.38, 114.52, 62.32, 34.23, 31.92, 29.63,
29.89, 29.12, 26.12, 23.60, 14.02.
dose range of 300–1.4 lg well-1 in each well under sterile
conditions in a laminar air flow chamber. Standard antibiotic
solutions of neomycin (antibacterial) and fluconazole (anti-
fungal) at a dose range of 300–1.4 lg well-1 and the well
containing methanol served as positive and negative con-
trols, respectively. The plates were incubated for 24 h at
30 °C and the well containing the least concentration
showing the inhibition zone is considered as the minimum
inhibitory concentration. All experiments were carried out in
duplicates and mean values are represented.
Cytotoxicity assay
{4-[(Pyridine-3-ylmethylimino)-methyl]-phenyl ester of
1
Cytotoxicity of the Schiff base (1) and synthesized esters
(2) was determined on the basis of measurement of in vitro
growth inhibition of tumor cell lines in 96-well plates by
cell-mediated reduction of tetrazolium salt to water insol-
uble formazan crystals using doxorubicin as a standard.
The cytotoxicity as assessed against a panel of four dif-
ferent human tumor cell lines: A549 derived from human
alveolar adenocarcinoma epithelial cells (ATCC No. CCL-
185), HeLa derived from human cervical cancer cells
(ATCC No. CCL-2), MDA-MB-231 derived from human
breast adenocarcinoma cells (ATCC No. HTB-26) and
MCF7 derived from human breast adenocarcinoma cells
(ATCC No. HTB-22) using the MTT assay (Mosmann,
1983). The IC50 values (50 % inhibitory concentration)
were calculated from the plotted absorbance data for the
dose–response curves. IC50 values (in lM) are expressed as
the average of two independent experiments.
karanja fatty acids} (2k) H NMR (CDCl3, 500 MHz): d/
ppm 0.88 (t, 3H, J = 7.0 Hz, –CH3,); 1.28 (m, 6H, CH3–
(CH2)3–); 1.74 (quint, 2H, –CH2–CH2–COO); 2.54 (t, 2H,
J = 7.0 Hz, –CH2–COO); 4.80 (s, 2H, –CH2–N=CH–);
5.34 (m, 2H, –CH=CH–); 7.16 (d, 2H, J = 9.0 Hz, Ar–H);
7.63 (dd, 1H, J = 8.0 Hz, Ar–H); 7.78 (d, 2H, J = 8.5 Hz,
Ar–H); 7.9 (d, 1H, J = 8.9 Hz, Ar–H); 8.40 (s, 1H,
–CH=N), 8.53 (d, 1H, J = 4.0 Hz, Ar–H); 8.56 (s, 1H,
Ar–H). 13C NMR (CDCl3, 75 MHz): d/ppm 169.02,
162.11, 161.71, 149.25, 148.32, 135.67, 134.52, 133.9,
131.02, 129.84, 123.38, 114.55, 63.32, 34.23, 31.92, 29.55,
29.63, 29.89, 29.12, 26.12, 23.60, 14.1.
Biological evaluation
Assay for antibacterial and antifungal activities: The anti-
bacterial and antifungal activities of the Schiff base (1) and
synthesized esters (2) were determined using modified
microtiter broth dilution method (Amsterdam, 1996) against
different pathogenic bacterial reference strains like Bacillus
subtilis MTCC 2940, Staphylococcus aureus MTCC 96,
S. aureus MLS16 MTCC 2970, M. luteus MTCC 2470,
E. coli MTCC 739, K. planticola MTCC 530, and Pseudo-
monas aeruginosa MTCC 2453 and pathogenic Candida
reference strains such as C. albicans MTCC 227, C. albicans
MTCC 854, C. albicans MTCC 7315, C. albicans MTCC
183, C. albicans MTCC 3958, C. albicans MTCC 1637,
C. albicans MTCC 3017, C. albicans MTCC 3018, Candida
parapsilosis MTCC 1744, Candida glabrata MTCC 3019,
C. aaseri MTCC 1962, I. orientalis MTCC 3020 and
I. hanoiensis MTCC 4755 procured from the Microbial Type
Culture Collection (MTCC), CSIR-Institute of Microbial
Technology, Chandigarh, India. The 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 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 plates
using a cork borer and the test compounds were loaded at a
Acknowledgments One of the author Y. M. thanks to the Director,
Indian Institute of Chemical Technology, Hyderabad, India and
thanks to the Head, Centre for Lipid Research, IICT for giving the
financial support.
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