Synthesis of 2-methoxybenzoylhydrazone and evaluation of their antileishmanial activity

Article abstract of DOI:10.1016/j.bmcl.2013.03.051

Compounds 1-25 showed varying degree of antileishmanial activities with IC₅₀ values ranging between 1.95 and 88.56 μM. Compounds 2, 10, and 11 (IC₅₀ = 3.29 ± 0.07 μM, 1.95 ± 0.04 μM, and 2.49 ± 0.03 μM, respectively) were found to be more active than standard pentamidine (IC₅₀ = 5.09 ± 0.04 μM). Compounds 7 (IC₅₀ = 7.64 ± 0.1 μM), 8 (IC₅₀ = 13.17 ± 0.46 μM), 18 (IC₅₀ = 13.15 ± 0.02 μM), and 24 (IC ₅₀ = 15.65 ± 0.41 μM) exhibited good activities. Compounds 1, 3, 4, 5, 9, 12, 15, 18, and 19 were found to be moderately active. Compounds 13, 14, 16, 17, 20-25 showed weak activities with IC₅₀ values ranging between 57 and 88 μM.

Full text of DOI:10.1016/j.bmcl.2013.03.051

Bioorganic & Medicinal Chemistry Letters 23 (2013) 3463–3466
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis of 2-methoxybenzoylhydrazone and evaluation of their
antileishmanial activity
a
b
c
Muhammad Taha a, , Mohd Syukri Baharudin , Nor Hadiani Ismail , Khalid Mohammed Khan ,
⇑
Faridahanim Mohd Jaafar b, Samreen c, Salman Siddiqui c, M. Iqbal Choudhary c
a Atta-ur-Rahman Institute for Natural Product Discovery, Universiti Teknologi MARA (UiTM), Puncak Alam Campus, 42300 Bandar Puncak Alam, Selangor, Malaysia
b Faculty of Applied Science UiTM, 40450 Shah Alam, Selangor, Malaysia
c H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 75270, Pakistan
a r t i c l e i n f o
a b s t r a c t
Article history:
Compounds 1–25 showed varying degree of antileishmanial activities with IC50 values ranging between
Received 4 January 2013
Revised 11 March 2013
Accepted 14 March 2013
Available online 31 March 2013
1.95 and 88.56
respectively) were found to be more active than standard pentamidine (IC50 = 5.09 0.04
pounds (IC50 = 7.64 0.1 M), (IC50 = 13.17 0.46 M), 18 (IC50 = 13.15 0.02 M), and 24
(IC50 = 15.65 0.41 M) exhibited good activities. Compounds 1, 3, 4, 5, 9, 12, 15, 18, and 19 were found
to be moderately active. Compounds 13, 14, 16, 17, 20–25 showed weak activities with IC50 values rang-
ing between 57 and 88 M.
l
M. Compounds 2, 10, and 11 (IC50 = 3.29 0.07
l
M, 1.95 0.04
l
M, and 2.49 0.03
lM,
lM). Com-
7
l
8
l
l
l
Keywords:
l
2-Methoxybenzoylhydrazone
Antileishmanial activity
Pentamidine
Ó 2013 Elsevier Ltd. All rights reserved.
Leishmania promestigotes
Applications of Schiff bases are reported in a broad range of
fields, for example, inorganic, biological and analytical chemis-
try.1–3 A number of heterocyclic hydrazones were reported to pos-
Cutaneous leishmaniasis produces permanent wounds on the
face, arms and feet.31,32 Due to its high occurrence in many coun-
tries, the discovery of potential drugs is highly desirable.33,34 Drugs
currently used include antimonial, glucantine, pentamidine, bis-
amidines, and stilbamidine. Many of these drugs show high toxic-
ities, produce clinical resistance and contribute to an increase in
co-infections such as leishmaniasis–AIDS.34,35 In addition, these
drugs are costly and require long-term treatment.36 Therefore,
there is an urgent need to work and discover molecules having po-
tential antileishmanial properties.
We previously reported the antileishmanial activities of acy-
lhydrazides and disulfides37 and in continuation of our research
on acylhdrazides and leishmaniasis, we have synthesized a library
of Schiff bases of 2-methoxybenzoyl hydrazide by condensing it
with twenty five (25) aromatic aldehydes and screening them for
their antileishmanial activities.
sess antimicrobial,4 antiglycation,5 and antifungal, anti-HIV,
antibacterial,6,7 and thymidine phosphorylase inhibitory activi-
ties.8 Metal complexes of Schiff bases have also shown various bio-
logical activities.9–12 Numerous hydrazones have shown
interesting bioactivities, such as antiinflammatory, anticancer,
antiplatelets, antibacterial, cytotoxic, antifungal, anticonvulsant,
and analgesic activities.13–20 N-Cyanoethyl hydrazide analogues
were reported to be b-glucuronidase inhibitory agents.21 In addi-
tion, these have also been reported to have a range of bioactivities,
including antibacterial, antiviral, antifungal,22 and GSK-3 inhibi-
tory activities.23,24 Substituted hydrazines have also found signifi-
cant commercial applications.25 A variety of heterocycles can easily
be synthesized by hydrazide derivatives.26 For example diacylhyd-
razides can be cyclized to 1,3-oxa- and thiadiazoles, and 1,2,4-
triazoles.27
The results of the current study are promising and deserve to be
investigated further to develop more active, safe and cost-effective
antileishmanial agents.
Leishmaniasis is a protozoan disease with large global distribu-
tion which causes a huge number of mortalities every year. Leish-
maniasis is classified as cutaneous, visceral (Kala Azar), mucosal or
mucocutaneous and diffused cutaneous on the basis of cellular im-
mune systems of the patients and parasite.28–30
2-Methoxybenzoylhydrazones 1–25 were synthesized from
2-methoxybenzoylhydrazide which was obtained from methyl-2-
methoxybenzoate by refluxing with hydrazine hydrate for 2 h which
was then crystallized from methanol. 2-Methoxybenzoylhydraz-
ones were prepared by condensing 2-methoxybenzoylhydrazide
with different aromatic aldehydes in refluxing ethanol for 3–4 h
(Scheme 1) in high yield. The products so obtained were crystallized
from methanol and most were obtained as needle-like crystals. The
⇑
Corresponding author. Tel.: +60 193098141; fax: +60 32584770.
E-mail addresses: muhamm9000@puncakalam.uitm.edu.my, taha_hej@yahoo.
com (M. Taha).
0960-894X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2013.03.051

3464
M. Taha et al. / Bioorg. Med. Chem. Lett. 23 (2013) 3463–3466
OMeO
OMeO
OMeO
R
NH2
R
N2H2 H2O
N
Methanol
Reflux 3 h
H
OMe
N
H
N
H
Methanol
O
Reflux 6 h
1-25
Scheme 1. Synthesis of 2-methoxybenzoylhydrazones 1–25.
Table 1
In vitro antileishmanial activities of acylhyrazide and % yield of 2-methoxybenzoylhydrazide1 1–25
Compd no.
R
Yield (%)
IC50
(lM
SEMa)
Compd no.
R
Yield (%)
IC50
(lM
SEMa)
1'
1'
OH
OH
2'
6'
6'
1
82
31.47 0.23
3.29 0.07
28.24 1.44
33.22 1.28
14
83
91
92
90
68.05 1.74
34.85 0.48
88.56 2.7
57.41 0.93
5'
HO
OH
4'
OH
1'
1'
OH
6'
5'
6'
2'
2
3
4
5
85
84
87
86
15
16
17
18
3'
'
HO
OH
4
OH
1'
1'
OH
6'
5'
6'
2'
3'
HO
OH
4'
OH
1'
1'
'
6'
5'
6'
5'
2'
2
3'
OH
4'
1'
OH
1'
OH
OH
6'
5'
6'
5'
35.41 0.53
78
80
82
83
13.15 0.02
45.67 1.09
63.36 2.11
53.13 1.56
3'
6'
3'
4'
OCH3
1'
1'
2'
OH
6'
5'
6
7
8
81
90
91
>100
19
20
21
3'
H3CO
4'
OH
OCH3
1'
1'
6'
6'
5'
2'
I
7.64 0.10
13.17 0.46
5'
Br
OCH3
OH
OCH3
1'
1'
6'
5'
6'
2'
2'
H3CO
OH3
4'
OCH3
OCH3
1'
1'
6'
2'
3'
6'
5'
N
9
92
88
40.07 0.55
1.95 0.04
22
23
84
86
59.97 0.6
3'
5'
4'
OCH3
1'
1'
6'
2'
2'
3'
6'
5'
10
75.89 0.89
N
5'
N
4'
1'
1'
6'
S
2'
3'
2'
5'
11
84
2.49 0.03
24
5'
85
15.65 0.41
3'
4'
O
O

M. Taha et al. / Bioorg. Med. Chem. Lett. 23 (2013) 3463–3466
3465
Table 1 (continued)
Compd no.
R
Yield (%)
85
IC50
(
l
M
SEMa)
Compd no.
R
Yield (%)
87
IC50
(
l
M
SEMa)
1'
1'
2'
3'
6'
5'
6'
5'
2'
12
31.56 0.32
68.53 2.30
25
77.36 0.58
5.09 0.04
F
NO2
Br
1'
2'
3'
6'
5'
13
89
Pentamidinec
Cl
a
SEM is the standard error of the mean, Pentamidine is the standard drug.
structures of 2-methoxybenzoylhydrazones were elucidated by
using NMR spectroscopy. All synthetic compounds gave satisfactory
CHN analyses.
bonding is not as effective as in case of compound 2. The decline in
activities of compounds 4, 5 and 6 may also be due to the altera-
tions in positions of dihydroxy groups at ring A. The compound
4 has 2,5-dihydroxy, compound 5 has 3,5-dihydroxy and com-
pound 6 has 2,4-dihydroxy and chances of intramolecular bonding
are not as effective as in the case of compound 2 and 3. The mono-
hydroxy substituent show varying degrees of activities and the
activity mainly depends upon the position of hydroxyl group at
ring A. This suggests that monohydroxy group at ring A along with
2-methoxy at ring B are responsible for activity. Compound 7
(7.64 0.10 lM) is the most active among monohydroxy
analogues having a hydroxyl at position 3 of ring A, however, if
the hydroxy residue shifts to position 4, its activity decreases as
in compound 8 (13.17 0.46 lM). Interestingly, if the hydroxyl
Compounds 1–25 showed varying degrees of antileishmanial
activities with IC50 values ranging between 1.95 and 88
compared to standard pentamidine (IC50 = 5.09 0.04 M) (Ta-
ble 1). Compounds 10 (IC50 = 1.95 0.04 M), 11 (IC50 = 2.49
0.03 M), and 2 (IC50 = 3.29 0.07 M) were found to be more ac-
tive than standard pentamidine (IC50 = 5.09 0.04 M). Com-
pounds 7 (IC50 = 7.64 0.10 M), 8 (IC50 = 13.17 0.46 M), 18
(IC50 = 13.15 0.02 M), and 24 (IC50 = 15.65 0.41 M) exhibited
good activities. Compounds 3 (IC50 = 28.24 1.44 M), 1 (IC50
31.47 0.23 M), 12, (IC50 = 31.56 0.32 M), (IC50 = 33.22
1.28 M), 15 (IC50 = 34.85 0.48 M), 5 (IC50 = 35.41 0.53 M),
9 (IC50 = 40.07 0.53 M), and 19 (IC50 = 45.67 1.09 M) were
lM, as
l
l
l
l
l
l
l
l
l
l
=
l
l
4
l
l
l
l
l
shifts to position 2 as in compound 9 (40.07 0.55 lM) the activity
found to be moderately active. Compounds 13, 14, 16, 17, 20–23
drops by almost 5 times.
and 25 showed weak activities with IC50 values between 57.41
If ring A is replaced by a pyridine ring then interesting results
are observed and the activities of the compounds vary according
to the position of nitrogen of the pyridine. The most active among
and 88.56
lM. Only compound 6 was found to be completely inac-
tive Table 1.
Limited SAR suggests that the activity mainly depends upon the
presence of hydroxyl and methoxy groups and their respective
positions at ring A. If we compare the activity of the most active
the pyridine derivatives is compound 18 (13.15 0.02 lM), with
the nitrogen at position 2. Interestingly, when the nitrogen atom
of pyridine goes away from the hydrazine bridge as in compound
19 to position 3 and compound 20 to position 4, the activity
decreases sharply almost fourfold and sixfold, respectively. The
compounds that have the halogenated analogues of hydrazones
along with other substituent’s show weak activities. In conclusion,
it can be said that the antileishmanial activity of this class of com-
pounds mainly depends upon the suitable substitution on rings A
and B. Suitable combinations of substituent’s at rings A and B are
found to be 2-hydroxy-4-methoxy for ring A and 2-methoxy for
ring B as in compound 10. Several other compounds demonstrated
remarkable antileishmanial activities. However, compound 10 is
found to be the most active antileishmanial molecule and may
serve as a lead compound for further studies. In summary it can
be concluded that the 2-methoxybenzohydrazones with the ut-
most antileishmanial activities bear 2-hydroxy along with meth-
oxy residue. From the present study it is concluded that
compounds having 2-hydroxy along with methoxy residue are po-
tential lead compounds for further research
member of the series, compound 10 (IC50 = 1.95 0.04
its analogous compounds 11 (IC50 = 2.49 0.03 M), and 12
(IC50 = 31.56 0.32 M) we find that both the positions of methoxy
lM) with
l
l
and hydroxyl groups at ring
A affect the activities of the
compounds.
Compound 10 showed excellent activity having 2-hydroxy-4-
methoxy substituents at ring A, however, when the methoxy group
shifted to position 5 as in compound 11 its activity decreases
slightly. A sharp decline (ꢀ16-fold) in the activity of compound
12 was observed when the hydroxyl changed from position 2 to
3. This difference in activity suggested that the 2-hydroxy substitu-
tion at ring A is vital for antileishmanial activity for this type of
compounds along with methyl group. The other meth-
oxybenzoylhydrazones, compounds 15, 16, and 17 showed moder-
ate to weak activities. This difference in activity may be due to a
hydroxyl residue along with a methoxy group which play signifi-
cant role in antileishmanial activity of this type of compounds.
Compound 2 (IC50 = 3.29 0.07 lM) having 3,4-dihydroxy sub-
Acknowledgements
stitution at ring A was found to be the third most active compound
in the series. The other analogous compounds 3, 4, 5, showed
moderate activities but surprisingly, compound 6 was found to
be completely inactive.
The difference in activities of dihydroxy-containing compounds
is controlled by the intramolecular hydrogen bonding at ring A and
methoxy group at position 2 at ring B. 3,4-Dihydroxy substitution
at ring A and 2-methoxy at ring B seemingly control the antileish-
manial activity of compound 2. However, changing the position of
the dihydroxy from 3, 4 to 2, 3 in compound 3 decreases its
activity by about eight times because the intramolecular hydrogen
Authors would like to acknowledge Research Management
Institute of UiTM for the financial support under Dana Kecemerlan-
gan Grant Scheme.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2013.03.
051.

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M. Taha et al. / Bioorg. Med. Chem. Lett. 23 (2013) 3463–3466
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