Dehydrozingerone Inspired Styryl Hydrazine Thiazole Hybrids as Promising Class of Antimycobacterial Agents

Article abstract of DOI:10.1021/acsmedchemlett.6b00088

Series of styryl hydrazine thiazole hybrids inspired from dehydrozingerone (DZG) scaffold were designed and synthesized by molecular hybridization approach. In vitro antimycobacterial activity of synthesized compounds was evaluated against Mycobacterium tuberculosis H₃₇Rv strain. Among the series, compound 6o exhibited significant activity (MIC = 1.5 μM; IC₅₀ = 0.48 μM) along with bactericidal (MBC = 12 μM) and intracellular antimycobacterial activities (IC₅₀ = <0.098 μM). Furthermore, 6o displayed prominent antimycobacterial activity under hypoxic (MIC = 46 μM) and normal oxygen (MIC = 0.28 μM) conditions along with antimycobacterial efficiency against isoniazid (MIC = 3.2 μM for INH-R1; 1.5 μM for INH-R2) and rifampicin (MIC = 2.2 μM for RIF-R1; 6.3 μM for RIF-R2) resistant strains of Mtb. Presence of electron donating groups on the phenyl ring of thiazole moiety had positive correlation for biological activity, suggesting the importance of molecular hybridization approach for the development of newer DZG clubbed hydrazine thiazole hybrids as potential antimycobacterial agents.

Full text of DOI:10.1021/acsmedchemlett.6b00088

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Letter
Dehydrozingerone inspired styryl hydrazine thiazole
hybrids as promising class of anti-mycobacterial agents.
Girish A Hampannavar, Rajshekhar V Karpoormath, Mahesh B.
Palkar, Mahamadhanif S Shaikh, and Balakumar Chandrasekaran
ACS Med. Chem. Lett., Just Accepted Manuscript • DOI: 10.1021/acsmedchemlett.6b00088 • Publication Date (Web): 13 May 2016
Downloaded from http://pubs.acs.org on May 13, 2016
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ACS Medicinal Chemistry Letters
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Dehydrozingerone inspired styryl hydrazine thiazole hybrids as promising class of
anti-mycobacterial agents.
Girish A. Hampannavar,† Rajshekhar Karpoormath,*,† Mahesh B. Palkar,§,† Mahamadhanif S. Shaikh†
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and Balakumar Chandrasekaran†
†Department of Pharmaceutical Chemistry, Discipline of Pharmaceutical Sciences, College of Health Sciences, University of KwaZuluꢀNatal, Westville Campus, Durban – 4000, South Africa
§Department of Pharmaceutical Chemistry, K.L.E. University College of Pharmacy, Vidyanagar, Hubballi – 580031, Karnataka, India
KEYWORDS: Anti-mycobacterial activity, Bactericidal, Dehydrozingerone, NIAID, Thiazole
ABSTRACT: Series of styryl hydrazine thiazole hybrids inspired from dehydrozingerone (DZG) scaffold were designed and synꢀ
thesized by molecular hybridization approach. In vitro antiꢀmycobacterial activity of synthesized compounds was evaluated against
Mycobacterium tuberculosis H37Rv strain. Among the series, compound 6o exhibited significant activity (MIC = 1.5 µM; IC50
=
0.48 µM) along with bactericidal (MBC = 12 µM) and intracellular antiꢀmycobacterial activities (IC50 = < 0.098 µM). Furthermore,
6o displayed prominent antiꢀmycobacterial activity under hypoxic (MIC = 46 µM) and normal oxygen (MIC = 0.28 µM) conditions
along with antiꢀmycobacterial efficiency against isoniazid (MIC = 3.2 µM for INHꢀR1; 1.5 µM for INHꢀR2) and rifampicin (MIC =
2.2 µM for RIFꢀR1; 6.3 µM for RIFꢀR2) resistant strains of Mtb. Presence of electron donating groups on the phenyl ring of thiaꢀ
zole moiety had positive correlation for biological activity, suggesting the importance of molecular hybridization approach for the
development of newer DZG clubbed hydrazine thiazole hybrids as potential antiꢀmycobacterial agents.
Tuberculosis (TB) is a chronic necrotizing bacterial infecꢀ
tion caused by Mycobacterium tuberculosis (Mtb), which has
been a bane of humanity for thousands of years and remains as
one of the rampant health problems in the world. TB is an
ancient enemy and current threat that has been ranked among
the foremost killers of the 21st century.1 According to World
Health Organization (WHO) report, around 9 million people
were found infected and around 1.5 million casualties ocꢀ
curred because of TB. Besides the life threatening strains of
MDRꢀTB (Multi Drug Resistance Tuberculosis) are appearing,
some of which can lead to high mortality rate (e.g., 72ꢀ89%)
with death occurring in short period (4ꢀ16 weeks).2 In 2013
around 480,000 affirmative cases of MDRꢀTB were witꢀ
nessed.3 India, China, the Russian Federation and South Africa
have almost 60 % of the world’s cases of MDRꢀTB. In addiꢀ
tion, the risk becomes even greater if the person is coꢀinfected
with the HIV (human immunodeficiency virus).4 The global
resurgence of TB and development of drug resistance necessiꢀ
tates for an imperative attention of medicinal chemists to deꢀ
velop innovative antiꢀmycobacterial agents as no new classes
of antiꢀTB agents have been developed since the introduction
of rifampin in to clinical practice in 1960s.
pounds resembling cinnamic acid and bearing styryl group or
α,βꢀunsaturated carbonyl groups are reported for antiꢀ
mycobacterial activities (Figure 2).10
Figure 1. Cinnamoylꢀrifamycin derivative.
It is well known fact that transꢀcinnamic acid analogs have
recently drawn back the intentness of medicinal chemists due
to their admirable pharmacological properties like antioxiꢀ
dant,5 antibacterial6 and antitumor.7 Rastogi et al. have demonꢀ
strated the synergistic activity of transꢀcinnamic acid in amalꢀ
gamation with INH, rifamycin and other recognized antimiꢀ
crobial agents against Mtb.8 Further, Reddy et al. have reportꢀ
ed the superior intracellular and in vivo activity of a cinꢀ
namoylꢀrifamycin derivative (Figure 1) in contrast with riꢀ
famycin when tested against susceptible and MDR strains of
Mtb along with M. avium complex (MAC).9 Several comꢀ
Figure 2. Compounds with styryl portion reported against M.
tuberculosis H37RV (I: MIC 6.49 µM)11; (II: MIC 12.5 µg/mL)12;
(III: MIC 6.25 µM)13
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From literature, it was also found that derivatives resulting The thiazole nucleus is a common motif presently found in
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by combining cinnamoyl portion with various chemical clasꢀ
ses of compounds have been reported to possess promising
antiꢀmycobacterial activity.14–16 Besides, various drugꢀlike
heterocycles namely benzimidazoles17 and quinazolinones18
were integrated with cinnamoyl or aryl styryl groups have also
been reported to augment the antiꢀmycobacterial properties.
several FDAꢀapproved drugs, such as the nonsteroidal antiꢀ
inflammatory drug meloxicam20 and the tyrosine kinase inhibiꢀ
tor dasatinib.21 Recently, Meissner et al., have demonstrated
the structureꢀactivity relationships (SAR) of novel series of 2ꢀ
aminothiazole analogs as effective antiꢀmycobacterial agents22
and Carradori et al., have reported microwave assisted methꢀ
od for the synthesis of substitutedꢀthiazolyl hydrazines.23
Therefore, thiazole is an essential scaffold in drug discovery
since its derivatives known to possess wide spectrum of activiꢀ
ties such as antiꢀhypertensive, antiꢀinflammatory, antiꢀHIV,
antiꢀbacterial and antiꢀmycobacterial,24,25 which have tremenꢀ
dously captivated attention of medicinal chemists. Figure 3
highlights the molecular manipulation of DZGꢀthiazole moiety
and their resultant antiꢀmycobacterial activities.
Dehydrozingerone (DZG), also known as feruloylmethane,
a half structural analog of curcumin, is isolated from Curcuma
longa. Chemically DZG is (E)ꢀ4ꢀ(4ꢀhydroxyꢀ3ꢀmethoxy pheꢀ
nyl)butꢀ3ꢀenꢀ2ꢀone and possess an α,βꢀunsaturated carbonyl
(styryl ketone) group that resembles the transꢀcinnamic acid
structure. DZG analogs have been reported to possess broad
range of biological activities like antioxidant, anticancer, antiꢀ
inflammatory, antidepressant, antimalarial, antifungal etc.19
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OCH3
Br
HN
H3CO
O
N
H3CO
O
H3CO
CH3
HO
CH3
H
N
CH3
N
H
N
H3CO
H3CO
N
H3CO
N
NH2
N
R
S
CH3
S
H3CO
N
N
HN
S
N
OCH3
OCH3
NH2
N
O
S
HO
N
S
HN
O
O
NO2
O
Figure 3. The literature reported derivatives containing styryl and thiazoles moieties and their antiꢀmycobacterial activities along with the
designed compounds. Compound 6o exhibited most promising antiꢀmycobacterial compound among the synthesized compounds. A: (E)ꢀ3ꢀ
methoxyꢀ5ꢀstyrylcyclohexaꢀ2,4ꢀdienꢀ1ꢀone (MIC against H37Rv = 32 µg/mL)26; B: (E)ꢀ5ꢀbromoꢀ2ꢀ(3,4ꢀdimethoxystyryl)ꢀ1Hꢀbenzo[d]
imidazole (MIC against H37Rv = > 7.25 µg/mL)17; C: 2ꢀaminoꢀ5ꢀbenzylthiazoleꢀ4ꢀcarboxylate (MIC against H37Rv = 0.06 µg/mL)27; D:
Nitazoxanide (MIC against H37Rv = 16 µg/mL)28; E: Carbazoloꢀthiazole analog (MIC against H37Rv = 21 µM)24
In view of the above facts and in continuation of our reꢀ
search program on the design and development of new antiꢀ
mycobacterial agents19,24,29 it was foreseen to amalgamate two
biologically active pharmacophores (styryl portion of DZG
and thiazole) in one molecular platform to engender a new
scaffold for antiꢀmycobacterial evaluation. As shown in Fig-
ure 3, the designed hybrid analogs possess both DZG (comꢀ
prising styryl) and thiazole motifs connected with each other
via a hydrazine linker. These unifications were suggested as an
effort to explore the possible synergistic influence of such
structural hybridizations on the anticipated activity, hoping to
discover a new lead structure that would have a promising
antiꢀmycobacterial activity.
tuted 2ꢀbromoꢀ1ꢀphenylethanones (5cꢀ5o) were synthesized
from their respective acetophenones. Compound (4) was then
condensed with various freshly synthesized 2ꢀbromoꢀ1ꢀ
(substituted phenyl)ꢀethanones (5aꢀ5o) to yield corresponding
final compounds i.e., 2ꢀ(2ꢀ((2E,3E)ꢀ4ꢀ(3,4ꢀ dimethoxyꢀ
phenyl)butꢀ3ꢀenꢀ2ꢀylidene)hydrazinyl)ꢀ4ꢀ(substituted
pheꢀ
nyl)thiazoles (6aꢀ6o; Scheme 2). The anticipated structures of
the final compounds were in agreement with the spectral (IR,
1H NMR and 13C NMR) data obtained and were further subꢀ
stantiated by HRMS data, which is summarized in supporting
information.
Scheme 1¥
The synthesis of a novel series of styryl hydrazine thiazole
hybrids derived from DZG (6a-6o) was achieved through effiꢀ
cient and versatile synthetic routes. The starting material DZG
(2) was prepared by using commercially available vanillin (1)
by simple Aldol condensation with acetone in presence of
base. Methylation of 2 was done with methyl iodide in presꢀ
ence of potassium carbonate in N,NꢀDimethylformamide to
yield (E)ꢀ4ꢀ(3,4ꢀdimethoxyphenyl)butꢀ3ꢀenꢀ2ꢀone (3). Further,
Schiff base of compound 3 was formed with thiosemicarbaꢀ
zide to yield 4 (Scheme 1). The various appropriately substiꢀ
¥Reaction conditions: (i) Acetone, NaOH; (ii) CH3I, K2CO3,
DMF, reflux, 1.5 h; (iii) Thiosemicarbazide, AcOH, CH3OH,
reflux, 3 h.
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ACS Medicinal Chemistry Letters
Scheme 2§
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§Reaction conditions: (i) Br2, Ether, 0ꢀ5 ˚C for 5c; Br2, CHCl3, reflux, 3 h for 5d and 5g; Br2, CHCl3, 0ꢀ5 ˚C for 5e and 5f; CuBr2, EtOAc,
CHCl3, reflux, 12 h for 5hꢀ5o; (ii) methanol, reflux, 3 h.
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The H NMR spectrum of compound 4 exhibited the presꢀ
ence of distinctive singlet signals at around δ 10.22, 8.22ꢀ7.76,
7.154ꢀ7.150, 3.79ꢀ3.76 and 2.11 for the NꢀH proton, NH2 proꢀ
ton, 2nd proton of phenyl ring, methoxyl (OCH3) protons and
methyl (CH3) protons indicating its formation by a process of
simple carbonꢀnitrogen bond creation with thiosemicarbazide
in the presence of acetic acid as catalyst. In addition, the apꢀ
pearance of most informative doublet signals around δ 6.81ꢀ
6.77 ppm (J = 16.53 Hz) and 7.06ꢀ7.01 (J = 16.84 Hz) conꢀ
firms the presence of olefinic protons.
grown under aerobic conditions by using a dual readꢀout
(OD590 and fluorescence) assay procedure. All the synthesized
compounds exhibited an interesting and noteworthy activity
profiles with MIC ranging from 1.5 to > 200 µM against the
tested mycobacterial strain (Table S3, Supporting infor-
mation).
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Interestingly, it was observed that compound 4 (MIC = 2.1
µM) having thiourea group (without thiazole moiety) disꢀ
played encouraging antiꢀmycobacterial activity with an IC50
value of 0.98 µM. This evidently indicated that the DZG strucꢀ
tural core has greatly contributed for antiꢀmycobacterial activiꢀ
ty. This finding instigated us to explore brief SAR investigaꢀ
tions in order to study the biological effects of various substitꢀ
uents on aromatic ring at 4th position of the thiazole moiety,
which was in turn attached to DZG scaffold through a hydraꢀ
zine linkage. Amongst tested series, compound 6o (MIC = 1.5
µM) with pꢀamino (NH2) group on phenyl ring at 4th position
of thiazole moiety exhibited excellent antiꢀmycobacterial acꢀ
tivity with IC50 value of 0.48 µM, whereas compounds 6d
(MIC = 15 µM), 6g (MIC = 16 µM) and 6i (MIC = 28 µM)
substituted with one or two methoxyl (OCH3) groups on thiaꢀ
zolylphenyl ring exhibited good inhibitory activity with IC50
value of 8.4, 7.4 and 6.6 µM respectively. In the case of comꢀ
pounds 6j (MIC = 40 µM) and 6l (MIC = 88 µM) with hyꢀ
droxyl (OH) group on phenyl ring displayed considerable antiꢀ
mycobacterial activity with IC50 value of 24 µM and 23 µM
respectively. These findings demonstrate that the thiazole core
contributed for enhanced activity and plays significant role in
the action against Mtb. The activity was also considerably
affected by nature of substituent on phenyl ring at 4th position
of the thiazole nucleus. Consistent with our prior report,24 we
found that the presence of electron donating (NH2, OCH3 and
OH) groups on phenyl ring have greatly influenced and conꢀ
ferred good antiꢀmycobacterial activity while the electron
withdrawing (CF3, NO2, F and Br) substituents have caused
decrease in activity. Thus, compounds 6a, 6c, 6h and 6m havꢀ
ing either nitro or halogen groups on phenyl ring were found
to exhibit poor activity with MIC value > 200 µM. (Figure S1,
Supporting information). Compounds with promising antiꢀ
mycobacterial activity profile were further subjected for level
II screening in order to evaluate their broad spectrum efficienꢀ
cy under assorted conditions against relevant drug resistant
isolates of Mtb and other disease causing mycobacterial speꢀ
cies.
1
The H NMR spectrum (400 and 600 MHz, DMSOꢀd6) of
the final compounds (6aꢀ6o) displayed some distinctive singlet
signals at around δ 11.42ꢀ10.22 ppm for NꢀH proton, δ 7.21ꢀ
7.20 for 2nd and δ 7.12ꢀ7.08 for 6th aromatic protons of DZG
scaffold and δ 2.17ꢀ2.08 ppm for methyl (N = CꢀCH3) protons
respectively. In addition, the most informative singlet signal
resonated around δ 7.70ꢀ7.31 ppm, which was attributed to the
aromatic proton at Hꢀ5 of thiazole ring, thus indicating its
formation through cycloꢀcondensation process. Whereas most
characteristic doublet signals around δ 6.83ꢀ6.64 ppm (J =
16.52ꢀ16.24 Hz, PhꢀHC=CHꢀ) and δ 7.57ꢀ6.91 ppm (J =
16.52ꢀ14.76 Hz, PhꢀHC=CHꢀ) evidently indicated the presꢀ
ence of olefinic protons. This observation was found in conꢀ
sistent with previously reported similar type of compounds.30
Further, the unique singlet signals resonating around δ 3.82ꢀ
3.77 ppm indicated the presence of methoxyl protons (OCH3)
on the 3rd and 4th position of the DZG scaffold, while the hyꢀ
droxyl (OH) protons on aromatic ring resonated as singlet
signals around δ 11.24ꢀ10.86 ppm. The various signals apꢀ
peared as either doublets or multiplets around δ 8.29ꢀ6.77 ppm
accounted for aromatic protons. The Eꢀconfiguration was asꢀ
certained for all final derivatives on the basis of 2D NMR
studies. These findings were further corroborated from their
respective 13C NMR spectra of the title compounds. The charꢀ
acteristic signals resonated at around δ 169.53ꢀ156.50 and
108.52ꢀ102.10 ppm were assigned to carbons of Cꢀ2 and Cꢀ5
of thiazole ring. The most prominent carbon signals observed
around δ 149.27ꢀ148.91 and 132.56ꢀ126.23 ppm accounted for
aromatic carbons having methoxyl groups and olefinic (Phꢀ
HC=Cꢀ) carbons respectively. Further, the characteristic carꢀ
bon signals appeared around δ 55.49ꢀ55.47 and 12.35ꢀ12.15
ppm indicated the presence of methoxyl and methyl groups in
the title compounds, while the various aromatic carbons resoꢀ
nated around δ 140.78ꢀ108.03 ppm. Further, the fluorine conꢀ
taining compounds 6k and 6m have been discussed, which
results in a very characteristic NMR spectra and the JCF values
are represented in Table S1 and S2 (Supporting information).
The MIC of test compounds (4, 6d, 6g, 6i and 6o) was asꢀ
sessed against five drug resistant isolates (INHꢀR1, INHꢀR2,
RIFꢀR1, RIFꢀR2 and FQꢀR1) of Mtb strains under aerobic
conditions. The antiꢀmycobacterial activity results are summaꢀ
rized in Table 1. Perusal of the data, we observed that all testꢀ
ed compounds showed excellent antiꢀmycobacterial activity
against INHꢀR1 and INHꢀR2, while two compounds (4 and
6o) exhibited the most promising antiꢀmycobacterial activity
against the tested organisms. In particular, both resistant
strains (R1 and R2) of INH and RIF were found to be extremeꢀ
Both level I and II (in vitro) characterization of antiꢀ
mycobacterial activity of newly synthesized title compounds
(4, 6aꢀ6o) was carried out at Infectious Disease Research Instiꢀ
tute (IDRI) within the National Institute of Allergy and Infecꢀ
tious Diseases (NIAID) screening program, Bethesda, MD,
USA. In the initial studies (Level I), minimum inhibitory conꢀ
centration (MIC) was established against Mtb strain H37Rv
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ly susceptible to compounds 4 and 6o, while these two comꢀ = 2.2 and 6.3 µM; IC50 = 0.54 and 0.76 µM) exhibited signifiꢀ
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3
4
5
6
7
8
pounds had an almost comparable activity with that of
Levofloxacin against FQꢀR1. As compared to reference drug
INH (MIC = > 200 µM; IC50 = > 200 µM), Compound 4 (MIC
= 5.3 and 2.5 µM; IC50 = 1.3 and 0.79 µM) and 6o (MIC = 3.2
and 1.5 µM; IC50 = 0.68 and 0.38 µM) displayed highest antiꢀ
mycobacterial activity against INHꢀR1 and INHꢀR2 respecꢀ
tively. In the case of RIFꢀR1 and RIFꢀR2, compound 6o (MIC
cant antibacterial activity, whereas compounds 4 (MIC = 4 and
4.8 µM; IC50 = 1.1 and 1.2 µM) showed moderate activity
when compared to reference drug RIF (MIC = 2 and > 50 µM;
IC50 = > 50 µM). Nevertheless, the fluoroquinoloneꢀresistant
strain (FQꢀR1) was found to be less susceptible to these comꢀ
pounds.
Table 1. Anti-mycobacterial activity data of newly synthesized compounds (4, 6d, 6g, 6i and 6o) against five drug-resistant
isolates of M. tuberculosis H37Rv
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INHꢀR1a
INHꢀR2b
RIFꢀR1c
RIFꢀR2d
FQꢀR1e
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12
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17
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Compound
MIC
(ꢁM)
IC50
(ꢁM)
IC90
(ꢁM)
MIC
(ꢁM)
IC50
(ꢁM)
IC90
(ꢁM)
MIC
(ꢁM)
IC50
(ꢁM)
IC90
(ꢁM)
MIC
(ꢁM)
IC50
(ꢁM)
IC90
(ꢁM)
MIC
(ꢁM)
IC50
(ꢁM)
IC90
(ꢁM)
4
5.3
15
1.3
12
6.6
> 50
> 200
> 25
3.8
2.5
12
0.79
8
2.9
> 50
12
4
25
1.1
11
4.6
> 50
27
4.8
31
1.2
8.7
5.9
> 50
> 200
>25
9.2
17
22
2.8
23
16
>50
>200
>25
33
6d
6g
24
12
13
7.1
28
9.2
7
46
19
30
18
6i
32
9.1
19
5.6
> 25
1.7
17
19
41
10
33
13
6o
3.2
0.68
0.0084
> 200
0.64
1.5
0.38
0.0047
> 200
0.84
2.2
2
0.54
1.2
0.15
0.59
2.6
6.3
> 50
0.62
1.1
0.76
> 50
0.54
0.6
21
2.3
Rifampicin
Isoniazid
Levofloxacin
0.018
> 200
1.2
0.022
> 200
1.4
0.0065
> 200
1.4
0.012
> 200
1.4
2.3
> 50
0.6
0.027
0.35
20
0.013
0.36
12
0.039
0.47
22
0.17
0.76
0.21
0.91
1.2
aINHꢀR1 was derived from H37Rv and is a katG mutant (Y155* = truncation). INHꢀR2 is strain ATCC35822. RIFꢀR1 was derived from
H37Rv and is a nrpoB mutant (S522L). RIFꢀR2 is strain ATCC35828. FQꢀR1 is a fluoroquinoloneꢀresistant strain derived from H37Rv
and is a gyrB mutant (D94N). (INH – Isoniazid, RIF – Rifampicin and FQ – Fluoroquinolone)
b
c
d
e
In addition, these five promising compounds (4, 6d, 6g, 6i
and 6o) were systematically assessed against Mtb H37Rv
grown under varied conditions. The antimicrobial activity of
these compounds under hypoxic conditions was assessed using
the low oxygen recovery assay (LORA). Further, the bacteriꢀ
cidal (MBC: Minimum Bactericidal Concentration) activity of
these compounds was assessed against Mtb H37Rv grown in
aerobic conditions in 7H9ꢀTwꢀOADC medium. The cytotoxiꢀ
city and intracellular antiꢀmycobacterial activity of compounds
was also determined using the THPꢀ1 human monoocytic cell
line, and THP1 cells infected with Mtb respectively. The reꢀ
sults of all these investigations are represented in Table S4
(Supporting information). A systematic analysis of the data
revealed that compound 4 and 6o exhibited an interesting and
potent antiꢀmycobacterial activity profile as depicted in Fig-
ure 4. All the five title compounds displayed an interesting
cytotoxicity profile with IC50 values ranging from 11 to > 50
ꢀM. Among the series tested, compounds 6o (IC50 = 11 µM)
and 6g (IC50 = 38 µM) showed moderate cytotoxicity, while
other compounds did not show cytotoxic effect upto concenꢀ
tration > 50 µM. The existence of virulent intracellular Mtb in
primary human macrophages compromise it’s functioning and
arrest phagosome maturation thus coping up with various host
threats. The aptitude of the bacteria to assault and survive inꢀ
side cells may be implicated for the persistence of TB. Thereꢀ
fore, it is of greater corollary for an effective tuberculosis
management that these compounds should also be capable of
killing intracellular TB in human macrophages, apart from
their in vitro activity against TB strains. Accordingly, two
compounds (4 and 6o) also displayed effective intracellular
antiꢀmycobacterial activity with IC50 value of < 0.098 ꢁM.
However, oxygen restriction also affects adaptive immune
responses and triggers antimicrobial effector mechanisms in
macrophages and restricts growth of intracellular Mtb.
abscessus and Mycobacterium avium by using MABA methꢀ
od. (Table S5, Supporting information). The results reveal
that compound 6o (MIC = 100 µM) demonstrated a moderate
activity especially against M. avium as compared to the referꢀ
ence drug RIF (MIC = 0.1 µM), while compound 6i displayed
a MIC of > 100 µM against M. abscessus and M. avium. Howꢀ
ever, the remaining compounds showed little or poor activity
(MIC = > 200 µM) against tested organisms.
CH3
H
N
H3CO
H3CO
NH2
N
S
4
CH3
H
N
H3CO
H3CO
N
N
R
S
Figure 4. AntiꢀTB activity profile of most active compounds
6d: R = 4ꢀOCH3; 6g: R = 3,4ꢀOCH3; 6i: R = 2,6ꢀOCH3 and 6o:
4ꢀNH2
In summary, in this work we established the synthesis of a
series of styryl hydrazine thiazole hybrids derived from dehyꢀ
drozingerone and their in vitro antiꢀTB activity. The ease,
simply obtainable reactants and reagents, and practically good
yields (51−74 %) make this synthetic method more attractive
and efficient. Moreover, compound 6o emerged as most promꢀ
ising antiꢀmycobacterial agent since it has demonstrated most
prominent activity under hypoxic condition along with its poꢀ
tential efficiency against drug resistant isolates of Mtb strains
and displayed significant bactericidal and intracellular antiꢀ
The title compounds (4, 6d, 6g, 6i and 6o) were also evaluꢀ
ated for their in vitro antiꢀmycobacterial activity against other
diseaseꢀrelevant Mycobacterial species like Mycobacterium
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Cinnamic Derivatives in Tuberculosis, Understanding Tuberculosis -
New Approaches to Fighting Against Drug Resistance; Cardona, P.ꢀJ.,
Ed.; InTech, 2012.
mycobacterial activity. These findings suggest that the deꢀ
1
2
3
4
5
6
signed compounds highlighted the benefit of incorporating a
hydrazine linkage to combine styryl portion of DZG and thiaꢀ
zole core, thus providing a good starting point for further lead
optimization. The possible enhancement in the antiꢀ
mycobacterial activity can be further accomplished by slender
variation in the ring substituents and/or extensive additional
functionalization warrants further investigations.
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Saffon, N.; Daffé, M.; Baltas, M. Design, Synthesis, and Biological
Evaluation of New Cinnamic Derivatives as Antituberculosis Agents.
J. Med. Chem. 2011, 54 (5), 1449–1461.
(16) Rastogi, N.; Goh, K. S.; Horgen, L.; Barrow, W. W. Synergistic
Activities of Antituberculous Drugs with Cerulenin and Trans ꢀ
Cinnamic Acid against Mycobacterium Tuberculosis. FEMS
Immunol. Med. Microbiol. 1998, 21 (2), 149–157.
(17) Shingalapur, R. V; Hosamani, K. M.; Keri, R. S. Synthesis and
Evaluation of in vitro AntiꢀMicrobial and AntiꢀTubercular Activity of
2ꢀStyryl Benzimidazoles. Eur. J. Med. Chem. 2009, 44 (10), 4244–
4248.
(18) Babu, R. R.; Naresh, K.; Ravi, A.; Madhava Reddy, B.; Harinadha
Babu, V. Synthesis of Novel Isoniazid Incorporated Styryl
Quinazolinones as AntiꢀTubercular Agents against INH Sensitive and
MDR M. Tuberculosis Strains. Med. Chem. Res. 2014, 23 (10), 4414–
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(19) Hampannavar, G. A.; Karpoormath, R.; Palkar, M. B.; Shaikh, M. S.
An Appraisal on Recent Medicinal Perspective of Curcumin
Degradant: Dehydrozingerone (DZG). Bioorg. Med. Chem. 2016, 24
(4), 501–520.
ASSOCIATED CONTENT
Supporting Information
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The Supporting Information is available free of charge on the
ACS Publications website. Synthetic procedures, spectral data and
protocols of bioassay (PDF)
AUTHOR INFORMATION
Corresponding Author
* Phone: +27 31 260 7179; Fax: +27 (0) 31 260 7792. Eꢀmail:
karpoormath@ukzn.ac.za
Author Contributions
The manuscript was written through contributions of all authors.
Funding Sources
This work was supported by funds from the University of KwaZuꢀ
luꢀNatal (UKZN), Westville Campus, Durban, South Africa.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
Authors sincerely thank National Institutes of Health and the Naꢀ
tional Institute of Allergy and Infectious Diseases (NIAID; Conꢀ
tract No.: HHSN272201100009I / HHSN27200002 A14), Bethesꢀ
da, MD, (USA), for in vitro antiꢀmycobacterial activity characterꢀ
ization. Authors are also grateful to Mr. Dilip Jagjivan and Dr.
Caryl Janse Van Rensburg (UKZN, South Africa) for their assisꢀ
tance in the NMR and HRMS experiments.
(20) Luger, P.; Daneck, K.; Engel, W.; Trummlitz, G.; Wagner, K.
Structure and Physicochemical Properties of Meloxicam, a New
NSAID. Eur. J. Pharm. Sci. 1996, 4, 175–187.
(21) Das, J.; Chen, P.; Norris, D.; Padmanabha, R.; Lin, J.; Moquin, R. V.;
Shen, Z.; Cook, L. S.; Doweyko, A. M.; Pitt, S.; Pang, S.; Shen, D.
R.; Fang, Q.; De Fex, H. F.; McIntyre, K. W.; Shuster, D. J.; Gillooly,
K. M.; Behnia, K.; Schieven, G. L.; Wityak, J.; Barrish, J. C. 2ꢀ
Aminothiazole as a Novel Kinase Inhibitor Template. Structureꢀ
Activity Relationship Studies toward the Discovery of Nꢀ(2ꢀChloroꢀ6ꢀ
Methylphenyl)ꢀ2ꢀ[[6ꢀ [4ꢀ(2ꢀHydroxyethyl)ꢀ1ꢀPiperazinyl]ꢀ2ꢀMethylꢀ
4ꢀPyrimidinyl]amino]ꢀ1, 3ꢀThiazoleꢀ5ꢀCarboxamide (Dasatinib,
BMSꢀ354825) as a Potent panꢀSrc Kinase Inhibitor. J. Med. Chem.
2006, 49 (23), 6819–6832.
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CH3
CH3
H
N
H
N
H3CO
H3CO
N
H3CO
H3CO
N
NH2
N
N
R
S
S
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