Novel fatty acid-thiadiazole derivatives as potential antimycobacterial agents

Article abstract of DOI:10.1111/cbdd.13634

The discovery of antibiotics around the middle twentieth century led to a decrease in the interest in antimycobacterial fatty acids. In order to re-establish the importance of naturally abundant fatty acid, a series of fatty acid-thiadiazole derivatives were designed and synthesized based on molecular hybridization approach. In vitro antimycobacterial potential was established by a screening of synthesized compounds against Mycobacterium tuberculosis H37Rv strain. Among them, compounds 5a, 5d, 5h, and 5j were the most active, with compound 5j exhibiting minimum inhibitory concentration of 2.34?μg/ml against M.tb H37Rv. Additionally, the compounds were docked to determine the probable binding interactions and understand the mechanism of action of most active molecules on enoyl-acyl carrier protein reductases (InhA), which is involved in the mycobacterium fatty acid biosynthetic pathway.

Full text of DOI:10.1111/cbdd.13634

Received: 15 June 2019
Revised: 20 August 2019
Accepted: 21 September 2019
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DOI: 10.1111/cbdd.13634
R E S E A R C H A R T I C L E
Novel fatty acid‐thiadiazole derivatives as potential
antimycobacterial agents
Jaishree K. Mali
Vikas N. Telvekar
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Yogesh B. Sutar
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Akshata R. Pahelkar
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Preeti M. Verma
|
Department of Pharmaceutical Sciences
and Technology, Institute of Chemical
Technology, Mumbai, India
Abstract
The discovery of antibiotics around the middle twentieth century led to a decrease in
the interest in antimycobacterial fatty acids. In order to re‐establish the importance
of naturally abundant fatty acid, a series of fatty acid‐thiadiazole derivatives were
designed and synthesized based on molecular hybridization approach. In vitro an-
timycobacterial potential was established by a screening of synthesized compounds
against Mycobacterium tuberculosis H37Rv strain. Among them, compounds 5a, 5d,
5h, and 5j were the most active, with compound 5j exhibiting minimum inhibitory
concentration of 2.34 μg/ml against M.tb H37Rv. Additionally, the compounds were
docked to determine the probable binding interactions and understand the mecha-
nism of action of most active molecules on enoyl‐acyl carrier protein reductases
Correspondence
Vikas N. Telvekar, Department of
Pharmaceutical Sciences and Technology,
Institute of Chemical Technology, N.
Parekh Marg, Matunga, Mumbai‐400 019,
India.
Email: vikastelvekar@rediffmail.com
Funding information
University Grants Commission
(
InhA), which is involved in the mycobacterium fatty acid biosynthetic pathway.
K E Y W O R D S
docking, fatty acid, Mycobacterium tuberculosis, resazurin microtiter assay, thiadiazole
1
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INTRODUCTION
Bagade, Bonde, Sharma, & Saraogi, 2018). The molecular
hybridization strategy is a rational design of new ligands or
prototypes with better efficacy and physicochemical proper-
ties (Viegas‐Junior, Danuello, da Silva Bolzani, Barreiro, &
Fraga, 2007).
The emergence of multidrug‐resistant and extensively drug‐
resistant strains of Mycobacterium tuberculosis (Mtb), to-
gether with various other challenges in the development
of new antitubercular agents (Gagneux, 2018; Laurenzi,
Ginsberg, & Spigelman, 2007), has flooded the drug dis-
covery pipeline with several antituberculosis drugs. Despite
this, tuberculosis infection is the tenth leading cause of
morbidity and mortality ranking above HIV/AIDS making
it major health problem worldwide with a large number of
MDR/RR‐TB incident cases being in India, China, and the
Russian Federation. After more than 50 years, two new drugs
bedaquiline and delamanid have recently been approved and
released for drug‐resistant TB (World Health Organization,
The antitubercular effects of free fatty acids on mam-
malian tubercle bacilli and various species of mycobacteria
have been determined historically (Dubos, 1950; Kondo &
Kanai, 1972). Before the advent of antibiotics, cod liver
(a mixture of saturated and unsaturated fatty acids), chaul-
moogra (cyclopentyl alkanoic acids), palm kernel, and tur-
tle oil (10‐, 12‐, and 14‐carbon saturated fatty acids) were
used as a remedy for the treatment of tuberculosis (Grad,
2004; Nieman, 1954). Kondo and Kanai in 1972 reported
that among saturated fatty acids, lauric and myristic acids
were highly active in killing both H37Ra and H37Rv of Mtb
at 20 μg/ml (Kondo & Kanai, 1972). Later, H Saito et al.
established the cytotoxicity of a series of fatty acids against
seventy‐one strains of rapidly growing mycobacteria.
2
018). This rising problem of resistance to antituberculosis
agents and the current situation can be solved by designing of
a new molecular scaffold with the novel mechanism of action
and with the ease of tailoring to the medicinal chemist (Patil,
Chem Biol Drug Des. 2019;00:1–8.
wileyonlinelibrary.com/journal/cbdd
© 2019 John Wiley & Sons A/S
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1

2
MALI et AL.
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Amidst saturated fatty acid, lauric acid (C12:0) showed the
maximum MIC’s 6.25–25 μg/ml and capric acid (C10:0)
was the next best active with MIC’s 50–100 μg/ml. The
lethal effects of fatty acids were due to disorganization of
the bacterial cell membrane culminating into the change
in membrane permeability. Fatty acids are naturally abun-
dant, renewable, biodegradable, biocompatible, and cost‐
effective (Carballeira, 2008; Muniyan & Jayaraman, 2016;
Saito, Tomioka, & Yoneyama, 1984).
These observations rekindled our interest in exploring fatty
acids in tuberculosis infection. Fatty acids have high log P,
and Rodrigues and Biava et al. demonstrated its importance
that high values of log P represent an increase in drug perme-
ability through the lipid‐rich mycobacterial cell wall leading
to increased antimycobacterial potency (Biava et al., 2006;
Rodrigues et al., 2013). However, fatty acids are a less potent
surface‐active agent as they ionize into anionic form at physi-
ological pH. Various authors have demonstrated the antituber-
cular effect of various fatty acids alone or in combination with
the heterocyclic ring (Figure 1; Chatzipanagiotou et al., 2005;
D’Oca et al., 2010; Menendez et al., 2012; Morbidoni et al.,
antioxidant, anti‐inflammatory, anticonvulsants, antidepres-
sant, anxiolytic, antihypertensive, anticancer, and antifungal
activity. The biological activity of thiadiazoles is attributed to
their meso‐ionic nature and liposolubility which makes them
capable of crossing the cellular membranes (Haider, Alam, &
Hamid, 2015; Hu, Li, Wang, Yang, & Zhu, 2014; Jain, Sharma,
Vaidya, Ravichandran, & Agrawal, 2013; Krátký & Vinsova,
2016). Keeping in perspective the promising antimycobac-
terial activity of 1, 3, 4‐thiadiazoles and fatty acids, we de-
signed novel series of mycobacterium inhibitors by merging
medium (lauric acid) and long‐chain fatty acids (myristic acid)
with 1, 3, 4‐thiadiazole through molecular hybridization tech-
nique and their antitubercular activity was evaluated against
Mycobacterium tuberculosis H37Rv strain using resazurin mi-
crotiter plate assay (REMA; Figure 2). We speculated that fatty
acid‐thiadiazole derivatives might inhibit fatty acid biosynthe-
sis, as mycolic acid, the major component of the cell wall of
mycobacteria, is made from FabH (β‐ketoacyl carrier protein
synthase III) that catalyzes the extension of fatty acids such
as lauroyl, myristoyl, and palmitoyl groups (Morbidoni et al.,
2006). Based on similarities in the structure, we docked these
molecules on InhA (enoyl‐acyl carrier protein enzyme) to get
insights into their interaction profiles and mechanism of action.
2
006; Rodrigues et al., 2013; Venepally & Reddy Jala, 2017).
The physicochemical and pharmacokinetic properties of fatty
acids can be improved by merging it with heterocycles or any
molecule with relatively lower lipophilicity. Azaheterocycle
derivatives have been widely explored as antimycobacterial
agents (Danac & Mangalagiu, 2014; Mantu, Luca, Moldoveanu,
Zbancioc, & Mangalagiu, 2010; Olaru, Vasilache, Danac, &
Mangalagiu, 2017). Out of them 1, 3, 4‐thiadiazoles are well‐
known privileged structures with remarkable pharmacological
activities such as antimicrobial, antituberculosis (Figure 1),
2
METHODS AND MATERIALS
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All the chemicals were purchased from Sigma‐Aldrich and
1
S. D. Fine Chemicals, India. H NMR was recorded on
1
3
400 MHz and C NMR at 101 MHz on Agilent Technology
MR400 spectrometer. Merck silica gel 60 F‐254 aluminum
FIGURE 1 Fatty acid and thiadiazole
derivatives with antimycobacterial activity
FIGURE 2 Pictorial representation of
designed fatty acid derivatives

MALI et AL.
3
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sheets were used for analytical thin‐layer chromatography
with brine (20 ml), dried over Na SO , and then evaporated
2
4
(
TLC), and silica gel 60–120 mesh was used for column
under reduced pressure to give compound 1k (yield 75%) as
a white solid with melting point 159–161°C matched with
literature was used directly for the next step without further
purification (Yang et al., 2012).
chromatography. Mass spectra were recorded by Shimadzu
instrument in electrospray ionization in both positive and
negative modes.
2
.1
General procedure for the synthesis of
2.3
General procedure for the synthesis of
|
|
compounds 2a‐k
compounds 4a and 4b
A mixture of appropriate carboxylic acid (1.0 g, 0.1 mol),
Dodecanoic (3a)/tetradecanoic acid (3b) (1g, 1.0 eq.) was
dissolved in dry chloroform (20 ml/g), and a catalytic amount
of DMF was added followed by slow addition of thionyl chlo-
ride (1.2 eq.). The reaction mixture was heated under reflux
for 4 hr. The solvent was removed evaporated in vacuo to get
the crude acid chlorides. The crude acid chlorides (colorless
liquids) were used directly for next step without further puri-
fication (García‐Barrantes et al., 2013).
thiosemicarbazide (0.1 mol), and POCl (0.3 mol) was heated
3
to 75°C for 0.5 hr. The reaction mixture was cooled to room
temperature, and then, water (9 ml) was added to it, and the
mixture was refluxed for a further 4 hr. The mixture was
cooled and basified to pH 8 with 50% NaOH solution. The
mixture was filtered, and the residue was recrystallized from
ethanol to afford the corresponding compounds characterized
by melting point similar to reported compounds (Guan et al.,
2
014).
2
.4
General procedure for the synthesis of
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compounds 5a‐k and 6a‐k
2
.2
General procedure for the synthesis of
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Thiadiazole amines (1 equiv) were dissolved in pyridine
compound 1k
(20 ml/g) and stirred at 0°C under an inert atmosphere. After
To a solution of 4‐fluorobenzoic acid (5 g, 0.04 moles)
in ethanol (50 ml), concentrated sulfuric acid (5 ml) was
added, and the reaction mixture was refluxed for 16 hr. The
reaction was monitored by TLC. After the consumption of
starting material, the solvent was evaporated under reduced
15 min, 1.2 equiv of dodecanoyl/tetradecanoyl chloride was
added to the above stirred solution. The mixture was stirred
at room temperature for 4 hr, and completion of the reac-
tion was monitored by TLC. After completion of the reaction,
the reaction mixture was diluted with water and ethyl acetate
followed by the addition of 2 N HCl to neutralize the mix-
ture. The precipitate obtained was then washed with water
and stirred in saturated bicarbonate solution to remove acid
impurities. (Wherever the residue was soluble in the organic
layer, the organic layer was washed with water and saturated
bicarbonate solution sequentially. The organic layer was
dried over anhydrous Na SO , and then evaporated under re-
pressure. Saturated NaHCO was added, and the resultant
3
solution was extracted with ethyl acetate. The organic layer
was washed with water and then with brine solution. The
organic layer was dried over anhydrous Na SO and evapo-
2
4
rated under reduced pressure to obtain the desired product
(
ii) as yellow oil matched with the previously reported re-
sults (90%). A reaction mixture of ethyl 4‐fluorobenzoate
1.00 g, 5.95 mmol), phenol (1.11 g, 6.55 mmol), and dry
K CO (1.64 g, 11.9 mmol) in DMSO (8 ml) was heated at
2
4
(
duced pressure to afford corresponding amides.) The crude
compounds were purified either by column chromatography
or by recrystallization from chloroform and methanol. The
2
3
1
10°C for 18 hr. The mixture was poured into water and
1
extracted with EtOAc several times. The organic layer was
washed with water and brine and dried over anhyd·Na SO .
compounds were characterized by melting point, H NMR,
1
3
C NMR, and mass spectrometer (Figures S3–S53).
2
4
The solvent was evaporated in vacuo, and the residue was
purified by silica gel column chromatography (n‐hexane/
AcOEt) to give 1.47 g of iii (78% yields), to obtain color-
less oil in 78% yield (boiling point = 150–152°C; Li et al.,
2
.5
In vitro antitubercular activity
|
Resazurin microtiter assay protocol (Palomino et al., 2002)
was used to determine the minimum inhibitory concentra-
tion (MIC) of all the synthesized N‐(5‐aryl‐1, 3, 4‐thiadia-
zole‐2‐yl) alkanamide derivatives (5a–5k & 6a–6k). The
synthesized compounds were screened against Mtb H37Rv
25177 using serial dilution technique in Middlebrook
7H9‐S broth medium. Mtb H37Rv was grown in media till
the cells reached mid log phase. Each compound (2 mg)
was dissolved in 1 ml of DMSO. The serial dilution of each
compound was prepared using 96‐well microtiter plate and
2
015; Palmer et al., 2015).
Ethyl 4‐phenoxybenzoate (iii) (1.85 mmol), sodium hy-
droxide (80 mg, 2.0 mmol) in ethanol (4 ml), and water
(
4 ml) were stirred under reflux for 3 hr. The reaction mixture
was allowed to cool to ambient temperature and concentrated
in vacuo. The residue was partitioned between ethyl acetate
(
3 × 10 ml) and water (20 ml). The aqueous layer was sepa-
rated and made acidic with 2 M HCl and then extracted with
dichloromethane (3 × 10 ml). The organic layer was washed

4
MALI et AL.
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SCHEME 1 Synthesis of
unsubstituted and substituted 5‐aryl‐1, 3, 4‐
thiadiazol‐2‐amine derivatives (2a–k)
1
00 μl of Mtb H37Rv cell suspension in nutrient media was
3
RESULTS AND DISCUSSION
Chemistry
|
added to each well. The pellicle was vortexed with glass
beads in sealed tube in Middlebrook 7H9broth to obtain
homogeneous suspension. The supernatant formed after
standing the suspension for 15 min was taken in fresh tube,
3.1
|
The novel series of N‐(5‐aryl‐1, 3, 4‐thiadiazole‐2‐yl)
alkanamide derivatives were synthesized according to
Schemes 1, 2 and 3. The intermediates, 5‐sub and unsub
aryl‐1, 3, 4‐thiadiazol‐2‐amine, were synthesized as de-
picted in Scheme 1. Acylthiosemicarbazides were prepared
in situ by heating the carboxylic acid and thiosemicar-
bazide in the acidic medium and cyclized subsequently.
Various aryl and heteroaryl acid were reacted with thio-
7
and optical density at 540 nm was adjusted to 0.1 (~10
cells/ml). 100 µl of Mtb H37Rv culture suspension was
4
seeded in 96‐well microtiter plates at a density of 10 cells
per well and serially diluted with compounds to a final vol-
ume of 200 µl. Equivalent amount of DMSO was to the
controls instead of compounds. The plates were incubated
at 37°C for 7 days, after that 30 μl of the resazurin dye
semicarbazide in the presence of POCl to form in situ
3
(
0.02% w/v dissolved in distilled water) was added to all
2
‐acyl thiosemicarbazides which later underwent cyclode-
the wells and, the plates were again sealed and re‐incu-
bated for 48 hr. The MIC values were calculated by visual
inspection for each well displaying change in color of the
resazurin from blue to pink. Isoniazid (INH) was used as
the standard drug.
hydration to afford corresponding amine intermediates. 1k
was synthesized by esterification of 4‐flourobenzoic acid
followed by nucleophilic aromatic substitution of ethyl‐4‐
flourobenzoate with phenol in the presence of K CO as a
2
3
base in DMSO at 110°C; then, subsequent hydrolysis of the
ester with aqueous NaOH gave the 4‐phenoxybenzoic acid
(1k) as depicted in Scheme 2. As described in Scheme 3,
the lauric and myristic acid was treated with thionyl chlo-
ride to obtain the corresponding acyl chloride and was re-
acted with various amines, 2a–k in the presence of pyridine
to afford the target compounds, 5a–k, and 6a–k (Scheme
2
.6
Docking studies and in silico
|
ADME prediction
The docking studies were performed using Glide mod-
ule (version 7.1, Schrödinger, LLC, NY) installed on
Linux workstation, and in silico ADME was predicted
by Qikprop module as described in the Supplementary
Information.
3
). The structures of 5a–k and 6a–k were characterized
1 13
by H NMR, C NMR, and mass spectroscopic analysis.
1
In H NMR spectra, the aromatic protons resonated at δ
SCHEME 2 Synthesis of 4‐phenoxybenzoic acid (1k)

MALI et AL.
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SCHEME 3 Synthesis of N‐(5‐
aryl‐1, 3, 4‐thiadiazole‐2‐yl) alkanamide
derivatives (5a–k) and (6a–k)
TABLE 1 Antitubercular activity of
N‐(5‐aryl/heteroaryl)‐1, 3, 4‐thiadiazol‐2‐yl)
dodecanamide derivatives
Compound
Ar
QPlogPo/wa
Mol. weight
MIC in μg/ml (μM)
5
5
5
5
5
5
5
5
5
5
5
a
b
c
d
e
f
g
h
i
Ph
4‐F‐Ph
3‐NO ‐Ph
3,5‐diNO ‐Ph
3,4‐diOMePh
4‐MePh
5.393
5.633
4.686
3.987
5.52
5.749
6.094
6.043
5.836
4.427
7.018
359.529
377.519
404.526
449.524
419.581
373.555
468.451
385.566
393.974
360.516
451.626
4.69 (13.04)
150 (397.32)
9.38 (23.18)
4.69 (10.43)
18.75 (44.67)
18.75 (50.1)
9.38 (20.02)
4.69 (12.16)
75 (190.37)
2.34 (6.49)
2
2
3‐Br‐4‐OMePh
C H ‐CH=CH‐
6
5
2‐Cl‐Ph
4‐pyridinyl
Ph‐O‐Ph
j
k
37.5 (83.03)
aDetermined by QikProp analysis.
TABLE 2 Antitubercular activity of
N‐(5‐aryl/heteroaryl)‐1, 3, 4‐thiadiazol‐2‐yl)
tetradecanamide derivatives
Compound
Ar
QPlogPo/wa
Mol. weight
MIC in μg/ml (μM)
6
6
6
6
6
6
6
6
6
6
6
a
b
c
d
e
f
g
h
i
Ph
4‐F‐Ph
3‐NO ‐Ph
3,5‐diNO ‐Ph
3,4‐diOMePh
4‐MePh
6.172
6.409
5.456
4.744
6.307
5.749
6.852
6.815
6.615
5.185
7.686
—
387.582
405.573
432.58
477.577
447.635
401.609
496.504
413.62
9.38 (24.20)
>150 (>369.84)
18.75 (43.34)
9.38 (19.64)
37.5 (83.77)
37.5 (93.37)
9.38 (18.89)
18.75 (45.33)
>150 (>355.43)
18.75 (48.25)
75 (156.34)
2
2
3‐Br‐4‐OMePh
C H ‐CH=CH‐
6
5
2‐Cl‐Ph
4‐pyridinyl
Ph‐O‐Ph
—
422.027
388.57
479.679
j
k
INH
0.4 (2.91)
Rifampicin
—
—
0.60 (0.729)
aDetermined by QikProp analysis.
7
.10–9.50 ppm. Resonance signals of the aliphatic regions
C‐2 of the ring. Further structural confirmation was done
using mass spectrometric data analysis (Supplementary
Information).
were seen in the range of δ 0.88–2.37 ppm. The terminal
methyl group was seen at 0.85–0.89 ppm. Broad singlet be-
tween δ 12.0 and 13.5 ppm confirmed the presence of pro-
1
3
ton of ‐CONH group. In C NMR spectra, aromatic carbon
resonated between δ 111 and 160 ppm with many overlaps
in these regions, while the C=O carbon resonated around
δ171–173 ppm. The C‐5 of the 1, 3, 4‐thiadiazole nucleus
appeared downfield in the NMR spectra in comparison to
3
.2
Biological Screening
|
All 22 novel, N‐(5‐aryl‐1, 3, 4‐thiadiazole‐2‐yl) alkanamide
derivatives were evaluated in a whole‐cell assay against Mtb
strain H37Rv using REMA (Palomino et al., 2002). The

6
MALI et AL.
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synthesized compounds exhibited interesting activity with
MIC ranging from 2.34 to 150 μg/ml against Mtb H37Rv,
as seen in Tables 1 and 2. INH was used as a standard drug.
The results of in vitro antimycobacterial evaluation revealed
that substitution at the para position with electron withdraw-
ing group such as fluoro was deleterious for the activity (5b,
3
.4
In Silico ADME prediction
|
Fatty acids being lipophilic imparted distinct lipophilicity to
the designed molecules and hence imparted distinct MIC’s.
QikProp analysis data reveal that three compounds follow the
Lipinski rule of five, and others have varying Log P values
which range from 3.987 to 7.686 (Table S1), as increase in
the lipophilicity could ease the entrance of these molecules
through the lipid‐enriched bacterial membrane (Biava et al.,
2008; Navarrete‐Vázquez et al., 2007).
6
b). Introduction of the weaker electron‐releasing group such
as methyl at the para position of phenyl ring (5f) displayed
a decrease in the potency as compared to the unsubstituted
phenyl ring in dodecanamide series (5a). Similarly, in tet-
radecanamide series, methyl substituted ring (6f) was least
active as compared to its unsubstituted counterparts (6a). The
presence of bulkier groups at para position resulted in com-
pounds with reduced antitubercular activity in both the series
4
CONCLUSION
|
(5k, 6k) may be due to high steric hindrance. Halogen sub-
In summary, a new series of N‐(5‐aryl‐1, 3, 4‐thiadia-
zole‐2‐yl) alkanamides were designed successfully through
molecular hybridization approach based on the inherent an-
titubercular activity of abundant fatty acids. The synthesized
derivatives exhibited good to moderate in vitro inhibitory
activity against Mtb H37Rv strain (ATCC 25177). These
fatty acid‐thiadiazole derivatives were synthesized from
readily accessible reactants and reagents by simple and ef-
ficient synthetic protocols. Out of 22 fatty acid‐thiadiazole
derivatives, compounds 5a, 5d, and 5h showed in vitro in-
hibitory activity with MIC 4.69 μg/ml and 5j with 4‐pyridi-
nyl moiety displayed maximum Mtb inhibitory activity with
MIC 2.34 µg/ml. The structure–activity relationship revealed
that electron withdrawing group such as nitro on phenyl ring
(mono‐ and disubstitution) enhanced the inhibitory activity
of the compounds as compared to electron donating groups.
Lauric acid derivatives showed higher activity as compared
to myristic acid derivatives. SAR revealed that the increase
in log P did not improve the inhibitory activity toward my-
cobacteria. Additionally, docking and MM‐GBSA studies on
the enzyme InhA were carried out with the most active mole-
cules to examine the putative interactions responsible for bi-
ological activity. Docking studies revealed that compounds
5a and 5j bind to the enzyme InhA. However, the biological
target for compounds 5d and 5h needs to be defined. Further
studies are underway to improve antitubercular potency and
to elucidate the precise mechanism of action.
stitution at ortho position was unfavorable in both dodecana-
mide and tetradecanamide series (5i, 6i). In general, halogen
substitution was detrimental for the activity. Substitution at
meta position with nitro was favorable for activity (5c, 6c).
Disubstitution at 3, 5 positions with electron withdrawing
group such as nitro showed an improved biological profile as
compared to monosubstituted nitro at 3‐position indicating
that the presence of both nitro groups in dodecanamide series
is requisite for the high efficacies (5d, 6d). Disubstitution at
3
, 4 positions with one electron withdrawing and one elec-
tron donating have shown equal potency in dodecanamide
(
5g) and tetradecanamide (6g) series and showed better
activity as compared to electron donating groups. (5e, 6e)
Disubstitution was favorable over monosubstitution. Styryl
group in case of dodecanamide (5h) series exhibited good
antitubercular activity as compared to tetradecanamide series
(
6h). Replacement of phenyl ring with heteroaryl ring such
as 4‐pyridinyl resulted in compounds with the highest anti-
mycobacterial activity in dodecanamide series (5j, 6j). The
above finding revealed that the potency decreased with the
increase in the carbon chain. Overall, dodecanamide series
displayed greater antitubercular potency as compared to tet-
radecanamide series.
3
.3
Molecular docking studies
|
The mycobacterial cell wall biosynthetic pathway (FAS II) is
distinct from mammalian (FAS‐I) multienzyme complex. So in-
hibition of InhA enzyme, involved in mycobacterium cell wall
biosynthesis, is an attractive target. As per previous reports on
the antitubercular activity of some alkanamide and thiadiazole
derivatives (Martínez‐Hoyos et al., 2016; Saha, Alam, & Akhter,
ACKNOWLEDGMENTS
Authors would like to thank UGC (University Grant
Commissions), New Delhi, India, for providing a Basic
Science Research (BSR) fellowship. Authors also thank
Infexn Laboratories Pvt. Ltd, Thane, for providing antituber-
cular activity.
2015; Shirude et al., 2013; Šink et al., 2015), molecular dock-
ing was carried out on the basis of the similarity of the struc-
tures with the bound ligand in the target. All the molecules were
docked into the active site of the crystal structure of enoyl‐ACP
reductase (5JFO) target enzymes to determine the possible mode
of action and binding orientations, as seen in Figures S1 and S2.
CONFLICT OF INTEREST
The authors declare no conflict of interest.

MALI et AL.
7
|
DATA AVAILABILITY STATEMENT
Guan, P., Wang, L., Hou, X., Wan, Y., Xu, W., Tang, W., & Fang, H.
(
2014). Improved antiproliferative activity of 1,3,4‐thiadiazole‐
The data that support the findings of this study are available
from the corresponding author upon reasonable request.
containing histone deacetylase (HDAC) inhibitors by introduction
of the heteroaromatic surface recognition motif. Bioorganic and
Medicinal Chemistry, 22(21), 5766–5775. https://doi.org/10.1016/j.
bmc.2014.09.039
ORCID
Haider, S., Alam, M. S., & Hamid, H. (2015). 1,3,4‐Thiadiazoles: A
potent multi targeted pharmacological scaffold. European Journal
of Medicinal Chemistry, 92, 156–177. https://doi.org/10.1016/j.
ejmech.2014.12.035
Vikas N. Telvekar
org/0000-0002-2074-1186
https://orcid.
Hu, Y., Li, C. Y., Wang, X. M., Yang, Y. H., & Zhu, H. L. (2014). 1,3,4‐
Thiadiazole: Synthesis, reactions, and applications in medicinal,
agricultural, and materials chemistry. Chemical Reviews, 114(10),
5572–5610. https://doi.org/10.1021/cr400131u
REFERENCES
Biava, M., Porretta, G. C., Poce, G., De Logu, A., Saddi, M., Meleddu,
R., … Botta, M. (2008). 1.5‐Diphenylpyrrole derivatives as an-
timycobacterial agents. Probing the influence on antimycobacte-
rial activity of lipophilic substituents at the phenyl rings. Journal
of Medicinal Chemistry, 51, 3644–3648. https://doi.org/10.1021/
jm701560p
Jain, A. K., Sharma, S., Vaidya, A., Ravichandran, V., & Agrawal, R.
K. (2013). 1,3,4‐Thiadiazole and its derivatives: A review on re-
cent progress in biological activities. Chemical Biology and Drug
Design, 81(5), 557–576. https://doi.org/10.1111/cbdd.12125
Kondo, E., & Kanai, K. (1972). The lethal effect of long‐chain fatty
acids on mycobacteria. Japanese Journal of Medical Science and
Biology, 25, 1–13. https://doi.org/10.7883/yoken1952.25.1
Krátký, M., & Vinsova, J. (2016). Sulphur‐containing heterocycles
as antimycobacterial agents: Recent advances in thiophene and
thiadiazole derivatives. Current Topics in Medicinal Chemistry,
16(26), 2921–2952. https://doi.org/10.2174/156802661666616
0506131118
Laurenzi, M., Ginsberg, A., & Spigelman, M. (2007). Challenges asso-
ciated with current and future TB treatment. Infectious Disorders
‐ Drug Targets, 7(2), 105–119. https://doi.org/10.2174/1871526077
81001817
Li, C., Liu, J. C., Li, Y. R., Gou, C., Zhang, M. L., Liu, H. Y., & Piao,
H. R. (2015). Synthesis and antimicrobial evaluation of 5‐aryl‐1,2,4‐
Biava, M., Porretta, G. C., Poce, G., Supino, S., Deidda, D., Pompei,
R., … Botta, M. (2006). Antimycobacterial agents. Novel dia-
rylpyrrole derivatives of BM212 endowed with high activity to-
ward Mycobacterium tuberculosis and low cytotoxicity. Journal of
Medicinal Chemistry, 49(16), 4946–4952. https://doi.org/10.1021/
jm0602662
Carballeira, N. M. (2008). Newadvancesinfattyacidsasantimalarial, an-
timycobacterial and antifungals agents. Progress in Lipid Research,
4
7(1), 50–61. https://doi.org/10.1016/j.plipres.2007.10.002
Chatzipanagiotou, S., Ioannidou, V., Ioannidis, A., Nicolaou, C.,
Papavasileiou, E., Chaniotaki, S., & Legakis, N. J. (2005). Absence
of the plasmid‐mediated quinolone resistance qnrA gene among
Campylobacter jejuni clinical isolates from Greece. International
Journal of Antimicrobial Agents, 26(3), 261–262. https://doi.
org/10.1016/j.ijantimicag.2005.06.008
triazole‐3‐thione derivatives containing
a rhodanine moiety.
Bioorganic and Medicinal Chemistry Letters, 25(15), 3052–3056.
D’Oca, C. D. R. M., Coelho, T., Marinho, T. G., Hack, C. R. L., Da
Costa Duarte, R., Da Silva, P. A., & D’Oca, M. G. M. (2010).
Synthesis and antituberculosis activity of new fatty acid amides.
Bioorganic and Medicinal Chemistry Letters, 20(17), 5255–5257.
https://doi.org/10.1016/j.bmcl.2010.06.149
Danac, R., & Mangalagiu, I. I. (2014). Antimycobacterial activ-
ity of nitrogen heterocycles derivatives. European Journal of
Medicinal Chemistry, 74, 664–670. https://doi.org/10.1016/j.
ejmech.2013.09.061
Dubos, R. J. (1950). Effect of organic acids on mammalian tubercle ba-
cilli. Journal of Experimental Medicine, 92(4), 319–332. https://doi.
org/10.1084/jem.92.4.319
Gagneux, S. (2018). Ecology and evolution of Mycobacterium tuber-
culosis. Nature Reviews Microbiology, 16(4), 202–213. https://doi.
org/10.1038/nrmicro.2018.8
García‐Barrantes, P. M., Lamoureux, G. V., Pérez, A. L., García‐
Sánchez, R. N., Martínez, A. R., & San Feliciano, A. (2013).
Synthesis and biological evaluation of novel ferrocene‐naph-
thoquinones as antiplasmodial agents. European Journal of
Medicinal Chemistry, 70, 548–557. https://doi.org/10.1016/j.
ejmech.2013.10.011
Grad, R. (2004). Cod and the consumptive: A brief history of cod‐
liver oil in the treatment of Pulmonary Tuberculosis. Pharmacy in
History, 46(3), 106–120.
https://doi.org/10.1016/j.bmcl.201504.081
Mantu, D., Luca, M. C., Moldoveanu, C., Zbancioc, G.,
&
Mangalagiu, I. I. (2010). Synthesis and antituberculosis activity
of some new pyridazine derivatives. Part II. European Journal of
Medicinal Chemistry, 45, 5164–5168. https://doi.org/10.1016/j.
ejmech.2010.08.029
Martínez‐Hoyos, M., Perez‐Herran, E., Gulten, G., Encinas, L.,
Álvarez‐Gómez, D., Alvarez, E., … Mendoza‐Losana, A. (2016).
Antitubercular drugs for an old target: GSK693 as a promis-
ing InhA direct inhibitor. EBioMedicine, 8, 291–301. https://doi.
org/10.1016/j.ebiom.2016.05.006
Menendez, C., Chollet, A., Rodriguez, F., Inard, C., Pasca, M. R.,
Lherbet, C., & Baltas, M. (2012). Chemical synthesis and biological
evaluation of triazole derivatives as inhibitors of InhA and antitu-
berculosis agents. European Journal of Medicinal Chemistry, 52,
275–283. https://doi.org/10.1016/j.ejmech.2012.03.029
Morbidoni, H. R., Vilchèze, C., Kremer, L., Bittman, R., Sacchettini, J.
C., & Jacobs, W. R. (2006). Dual inhibition of mycobacterial fatty
acid biosynthesis and degradation by 2‐alkynoic acids. Chemistry
and Biology, 13(3), 297–307. https://doi.org/10.1016/j.chemb
iol.2006.01.005
Muniyan, R., & Jayaraman, G. (2016). Lauric acid and myristic acid
from Allium sativum inhibit the growth of Mycobacterium tuber-
culosis H37Ra: In silico analysis reveals possible binding to protein

8
MALI et AL.
|
kinase B. Pharmaceutical Biology, 54(12), 2814–2821. https://doi.
org/10.1080/13880209.2016.1184691
unsaturated fatty acids. Antimicrobial Agents and Chemotherapy,
26(2), 164–169. https://doi.org/10.1128/AAC.26.2.164
Navarrete‐Vázquez, G., Molina‐Salinas, G. M., Duarte‐Fajardo, Z. V.,
Vargas‐Villarreal, J., Estrada‐Soto, S., González‐Salazar, F., …
Said‐Fernández, S. (2007). Synthesis and antimycobacterial activity
of 4‐(5‐substituted‐1,3,4‐oxadiazol‐2‐yl)pyridines. Bioorganic and
Medicinal Chemistry, 15(16), 5502–5508. https://doi.org/10.1016/j.
bmc.2007.05.053
Nieman, C. (1954). Influence of trace amounts of fatty acids on the
growth of microorganisms. Bacteriology Reviews, 18(2), 147–163.
Olaru, A. M., Vasilache, V., Danac, R., & Mangalagiu, I. I. (2017).
Antimycobacterial activity of nitrogen heterocycles derivatives: 7‐
Shirude, P. S., Madhavapeddi, P., Naik, M., Murugan, K., Shinde, V.,
Nandishaiah, R., … Read, J. A. (2013). Methyl‐Thiazoles: A novel
mode of inhibition with the potential to develop novel inhibitors tar-
geting InhA in Mycobacterium tuberculosis. Journal of Medicinal
Chemistry, 56(21), 8533–8542. https://doi.org/10.1021/jm4012033
Šink, R., Sosič, I., Živec, M., Fernandez‐Menendez, R., Turk, S., Pajk,
S., … Gobec, S. (2015). Design, synthesis, and evaluation of new
thiadiazole‐based direct inhibitors of enoyl acyl carrier protein reduc-
tase (InhA) for the treatment of tuberculosis. Journal of Medicinal
Chemistry, 58(2), 613–624. https://doi.org/10.1021/jm501029r
Venepally, V., & Reddy Jala, R. C. (2017). An insight into the bi-
ological activities of heterocyclic–fatty acid hybrid molecules.
European Journal of Medicinal Chemistry, 141, 113–137. https://
doi.org/10.1016/j.ejmech.2017.09.069
Viegas‐Junior, C., Danuello, A., da Silva Bolzani, V., Barreiro, E. J.,
& Fraga, C. A. (2007). Molecular hybridization: A useful tool in
the design of new drug prototypes. Current Medicinal Chemistry,
14(17), 1829–1852. https://doi.org/10.2174/092986707781058805
World Health Organization. (2018). Global tuberculosis report. http://
apps.who.int/iris/bitstream/handle/10665/274453/9789241565646-
eng.pdf/ (accessed 23.05.19).
(
pyridine‐4‐yl)‐indolizine derivatives. Part VII. Journal of Enzyme
Inhibition and Medicinal Chemistry, 32(1), 1291–1298. https://doi.
org/10.1080/14756366.2017.1375483
Palmer, B. D., Sutherland, H. S., Blaser, A., Kmentova, I., Franzblau,
S. G., Wan, B., & Thompson, A. M. (2015). Synthesis and struc-
ture‐activity relationships for extended side chain analogues of
the antitubercular drug (6 S)‐2‐nitro‐6‐{[4‐(trifluoromethoxy)ben-
zyl]oxy}‐6,7‐dihydro‐5H‐imidazo[2,1‐b][1,3]oxazine
(PA‐824).
Journal of Medicinal Chemistry, 58(7), 3036–3059. https://doi.
org/10.1021/jm501608q
Palomino, J. C., Martin, A., Camacho, M., Guerra, H., Swings,
J., & Portaels, F. (2002). Resazurin microtiter assay plate:
Simple and inexpensive method for detection of drug resis-
tance in Mycobacterium tuberculosis. Antimicrobial Agents
and Chemotherapy, 46(8), 2720–2722. https://doi.org/10.1128/
AAC.46.8.2720-2722.2002
Yang, Y., Wang, Z., Yang, J., Yang, T., Pi, W., Ang, W., … Wei, Y.
(2012). Design, synthesis and evaluation of novel molecules with a
diphenyl ether nucleus as potential antitubercular agents. Bioorganic
and Medicinal Chemistry Letters, 22(2), 954–957. https://doi.
org/10.1016/j.bmcl.2011.12.022
Patil, K., Bagade, S., Bonde, S., Sharma, S., & Saraogi, G. (2018).
Recent therapeutic approaches for the management of tu-
berculosis: Challenges and opportunities. Biomedicine and
Pharmacotherapy, 99, 735–745. https://doi.org/10.1016/j.
biopha.2018.01.115
SUPPORTING INFORMATION
Additional supporting information may be found online in
the Supporting Information section at the end of the article.
Rodrigues, M. O., Cantos, J. B., D’Oca, C. R. M., Soares, K. L., Coelho,
T. S., Piovesan, L. A., … D’Oca, M. G. M. (2013). Synthesis and
antimycobacterial activity of isoniazid derivatives from renewable
fatty acids. Bioorganic and Medicinal Chemistry, 21(22), 6910–
How to cite this article: Mali JK, Sutar YB, Pahelkar
AR, Verma PM, Telvekar VN. Novel fatty acid‐
thiadiazole derivatives as potential antimycobacterial
agents. Chem Biol Drug Des. 2019;00:1–8. https://doi.
org/10.1111/cbdd.13634
6
914. https://doi.org/10.1016/j.bmc.2013.09.034
Saha, R., Alam, M. M., & Akhter, M. (2015). Novel hybrid‐pyrrole
derivatives: Their synthesis, antitubercular evaluation and dock-
ing studies. RSC Advances, 5(17), 12807–12820. https://doi.
org/10.1039/c4ra14440f
Saito, H., Tomioka, H., & Yoneyama, T. (1984). Growth of group
IV mycobacteria on medium containing various saturated and