Design, synthesis and antimycobacterial activity of cinnamide derivatives: A molecular hybridization approach

Article abstract of DOI:10.1016/j.bmcl.2011.02.022

A series of cinnamide derivatives was designed as potential antimycobacterial agents using molecular hybridization approach. The diamine moiety, a key feature of ethambutol and its other analogs, and certain structural features of cerulenin and cinnamic a

Full text of DOI:10.1016/j.bmcl.2011.02.022

Bioorganic & Medicinal Chemistry Letters 21 (2011) 1997–1999
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Design, synthesis and antimycobacterial activity of cinnamide derivatives:
A molecular hybridization approach
Manoj D. Kakwani a, Prashant Suryavanshi c, Muktikant Ray b, M. G. R. Rajan b, Sharmila Majee c,
Abdul Samad c, Padma Devarajan a, Mariam S. Degani a,
⇑
a Department of Pharmaceutical Sciences & Technology, Institute of Chemical Technology, N. P. Marg, Matunga, Mumbai 400 019, India
b Radiation Medicine Centre, Tata Memorial Hospital, BARC, Parel, Mumbai 400 012, India
c Department of Veterinary Microbiology, Bombay Veterinary College, Parel, Mumbai 400 012, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of cinnamide derivatives was designed as potential antimycobacterial agents using molecular
hybridization approach. The diamine moiety, a key feature of ethambutol and its other analogs, and cer-
tain structural features of cerulenin and cinnamic acid were hybridized to obtain cinnamide derivatives.
The minimum inhibitory concentration (MIC) of all synthesized compounds was determined against M.
tuberculosis H37Rv using Resazurin Microtitre plate Assay (REMA) method. The synthesized molecules
Received 20 September 2010
Revised 25 January 2011
Accepted 7 February 2011
Available online 12 February 2011
showed good to moderate activity with MIC in the range of 5–150
ally, the most potent compound 1a, having MIC 5.1 M exhibited synergy with rifampicin.
Ó 2011 Elsevier Ltd. All rights reserved.
lM and good safety profile. Addition-
Keywords:
Diamine
Cinnamic acid
l
Hybridization
Mycobacterium tuberculosis (Mtb)
Antimycobacterial activity
Synergy
Tuberculosis (TB) is an airborne, contagious disease caused by
Mycobacterium tuberculosis (Mtb) in humans. WHO reported nearly
8–9 million new cases of TB in 2009 including three million deaths
which represent the largest number of incidence of human deaths
attributable to a single etiological agent.1 In particular, the current
concern is the massive problem resulting from extensively drug-
resistant tuberculosis, XDR-TB.2
Ethambutol, a clinically used first line drug for tuberculosis, has
1,2-ethylenediamine as a core structural feature. This scaffold
has been explored extensively, and one of the candidates with this
scaffold, SQ109, has advanced into clinical trials.3 Studies have
shown that replacing the basic scaffold of 1,2-ethylenediamine
by other similar diamine like piperazine or homopiperazine
(e.g., SQ786 and SQ775), still retains useful activity (Fig. 1).
On the other hand, cerulenin and trans-cinnamic acid (Fig. 2)
are traditionally known to have antimycobacterial activity and also
proven to have synergistic action when tested along with known
clinically used drugs.4 Additionally, cinnamyl derivative of rifampi-
cin showed improved intracellular and in vivo activities than by
rifampicin per se.5
Figure 1. Diamine based antimycobacterials.
In our continuous program in the search for new, potent
antimycobacterial agents,6 we have designed a new class of
Figure 2. Traditionally known antimycobacterials having synergistic action.
cinnamide derivatives. The design strategy incorporated the
diamine feature of ethambutol and its analogs along with the
⇑
Corresponding author. Tel.: +91 22 3361 2213; fax: +91 22 3361 1020.
E-mail address: ms.degani@ictmumbai.edu.in (M.S. Degani).
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.02.022

1998
M. D. Kakwani et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1997–1999
Table 1
Cinnamide derivatives with their antimycobacterial activity and toxicity
b
Compound
MICa
(
lM)
CC50
(l
M)
SI
1a
1b
1c
1d
5.1
9.0
17.3
16.7
618
855
708
480
121
95
41
Figure 3. Design concept for cinnamide derivatives.
29
SI—selective index.
a
Compounds were tested against Mtb H37Rv strains using REMA method.
Cytotoxicity studies were done on VERO cell line C1008 using MTT assay.
b
Figure 4. Different diamine linkers used for synthesis.
aromatic
a,b-unsaturated carbonyl moiety, to obtain cinnamide
compounds (Fig. 3). Earlier reports have used similar strategies
where cinnamic acid has been coupled to isoniazid in the search
of potential antimycobacterial agents.7 Also according to recent
reports, the designed cinnamide derivatives may act on the biosyn-
thesis of mycolic acids and more specifically on FAS-II, which uses
Figure 5. General structure of cinnamide derivatives.
Table 2
Cinnamide derivatives with their antimycobacterial activity and toxicity
a
,b-enoyl systems as substrates.8 Moreover, these molecules could
b
Compound
R
MICa
(
lM)
CC50
(l
M)
SI
also have synergy with rifampicin, similar to that exhibited by
cerulenin and trans-cinnamic acid.
1a
1e
1f
1g
1h
1i
1j
1k
1l
Phenyl
5.1
143.7
131.6
128.9
54.8
64.4
68.5
65.8
54.8
618
565
680
788
653
725
615
695
653
683
692
1470
121
4
4-CH3 phenyl
4-OCH3 phenyl
4-Cl phenyl
3,4-diCl phenyl
2-Cl phenyl
3-NO2 phenyl
2-OCH3 phenyl
2,6-diCl phenyl
Furan
Initially, molecules with different diamine linkers were synthe-
sized, that is, 1,2-ethylenediamine, piperazine, and homopiper-
azine (Fig. 4). In addition, 2-(piperazin-1-yl) ethanamine as a
novel diamine scaffold was envisaged. The target compounds, that
is, cinnamide derivatives 1a–1d were synthesized according to
Scheme 1 using the reaction between trans-cinnamic acid and dia-
mine via a mixed anhydride intermediate, formed using methyl
chloroformate in presence of triethylamine.9 Some of the synthe-
sized derivatives are already reported as glycogen phosphorylase
inhibitors10 and hence their spectral data was matched and found
to be in accordance with reported data.
The antimycobacterial activity of all the synthesized com-
pounds was tested against M. tuberculosis H37Rv to determine the
minimum inhibitor concentration (MIC) using REMA (Resazurin
Microtitre Assay) method.11 Ethambutol was used as the reference
drug. The biological results (Table 1) show that the compound hav-
ing a 1,2-ethylenediamine 1a linkage was the most active amongst
5
6
12
11
9
11
12
63
74
96
1m
1n
EMB
10.8
9.41
15.3
Thiophene
—
SI—selective index.
EMB—Ethambutol.
a
Compounds were tested against Mtb H37Rv strains using REMA method.
Cytotoxicity studies were done on VERO cell line C1008 using MTT assay.
b
the synthesized molecules, that is, 1a–1d in this series. Further, to
optimize the potency of the compound derived from 1,2-ethylene-
diamine 1a, the conventional Topliss method was applied.12
Scheme 1. Synthetic scheme for cinnamide derivatives.

M. D. Kakwani et al. / Bioorg. Med. Chem. Lett. 21 (2011) 1997–1999
1999
The biological results of all synthesized molecules are as shown
in (Fig. 5, Table 2). The MIC values of the compounds having sub-
stitution at para-position on the aromatic ring 1e–1h, showed de-
crease in antimycobacterial activity relative to the unsubstituted
compound 1a. Next, the molecules with substitution at ortho- or
meta-position of aromatic ring 1i–1l were synthesized. However
these molecules also did not exhibit increased potency. Further,
heteroaromatic ring system was incorporated as in 1m and 1n in-
stead of phenyl ring. Both these derivatives showed better activity
than substituted aromatic compounds; however they exhibit less
potency than unsubstituted compound 1a.
Department of Biotechnology, India; Grant No. BT/PR7858/Med/
14/1142/2006.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2011.02.022.
References and notes
All the synthesized compounds were tested for cytotoxicity
against mammalian VERO cell line (C1008) using MTT assay.13
All the compounds had low cytotoxicity in this assay, and the po-
tent compounds had a good selective index.
1. http://www.who.int/tb/publications/global_report/2009/en/index.html.
2. Daniel, T. M.; Bates, J. H.; Downes, K. A. Tuberculosis: Pathogenesis, Protection,
and Control; ASM Press: Washington, DC, 1994. pp 13–24.
3. Lee, R. E.; Protopopova, M.; Crooks, E., et al. J. Comb. Chem. 2003, 5, 172.
4. Rastogi, N.; Goh, K. S.; Horgen, L.; Barrow, W. W. FEMS Immunol. Med. Microbiol.
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Antimicrob. Agents Chemother. 1995, 39, 2320.
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R.; Degani, M. S. Bioorg. Med. Chem. Lett. 2010, 20, 1623.
The most potent cinnamide derivative 1a, was further tested for
its synergistic activity with rifampicin.14 The MIC of rifampicin and
1a was found to be 0.125 and 1.625
nation, MIC of rifampicin was reduced to 0.0078
compound 1a to 0.406 g/mL, resulting in 16-fold and 4-fold
lg/mL, respectively. In combi-
lg/mL and of
7. Carvalho, S. A.; da Silva, E. F.; de Souza, M. V. N.; Lourenco, M. C. S.; Vicente, F. R.
Bioorg. Med. Chem. Lett. 2008, 18, 538.
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Med. Chem. Lett. 2009, 19, 341.
l
reduction in MIC of rifampicin and 1a, respectively, which repre-
sents synergism.
9. Guan, L. P.; Wei, C. X.; Deng, Q. X.; Sui, X.; Piao, H. R.; Quan, Z. S. Eur. J. Med.
Chem. 2009, 44, 3654.
In summary, a small library of cinnamide derivatives has been
synthesized using molecular hybridization approach. Among the
synthesized molecules, compound 1a shows promising results as
an antimycobacterial agent. Thus this strategy could prove useful
in design of antimycobacterial agents with inherent activity as well
as synergy with rifampicin.
10. (a) Onda, K.; Shiraki, R.; Yonetoku, Y.; Momose, K.; Katayama, N.; Orita, M.;
Yamaguchi, T.; Ohta, M.; Tsukamoto, S. Bioorg. Med. Chem. Lett. 2008, 16, 8627;
(b) Hill, T.; Odell, L. R.; Edwards, J. K.; Graham, M. E.; Mcgeachie, A. B.; Rusak, J.;
Quan, A.; Abagyan, R.; Scott, J. L.; Robinson, P. J.; McCluskey, A. J. Med. Chem.
2005, 48, 7781.
11. Palomino, J. C.; Martin, A.; Camacho, M.; Guerra, H.; Swings, J.; Portaels, F.
Antimicrob. Agents Chemother. 2002, 46, 2720.
12. Topliss, J. G. J. Med. Chem. 1977, 20, 463.
13. Freshney, R. L. Culture of Animal Cells: A Manual of Basic Techniques, 4th ed.;
Willy-LISS, 2000. p 329.
Acknowledgments
M.K. and P.S. are thankful to Department of Biotechnology
(DBT), India for financial support. This work is funded by
14. Moody, J. A. Clinical Microbiology Procedures Handbook; American Society for
Microbiology: Washington, DC, 1992. pp 5.18.1–28.