Novel approach of multi-targeted thiazoles and thiazolidenes toward anti-inflammatory and anticancer therapy—dual inhibition of COX-2 and 5-LOX enzymes

Article abstract of DOI:10.1007/s00044-020-02655-9

It is well established that cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) play a vital role in the initiation and progression of inflammatory reactions. Hence, thiazole and thiazolidene-based pharmacophore molecules were synthesized to obtain dual C

Full text of DOI:10.1007/s00044-020-02655-9

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MEDICINAL
CHEMISTRY
RESEARCH
Medicinal Chemistry Research
https://doi.org/10.1007/s00044-020-02655-9
ORIGINAL RESEARCH
Novel approach of multi-targeted thiazoles and thiazolidenes
toward anti-inflammatory and anticancer therapy—dual inhibition
of COX-2 and 5-LOX enzymes
Jaismy Jacob P1 Manju S L1
●
Received: 3 August 2020 / Accepted: 15 October 2020
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
It is well established that cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) play a vital role in the initiation and
progression of inflammatory reactions. Hence, thiazole and thiazolidene-based pharmacophore molecules were synthesized
to obtain dual COX-2 and 5-LOX inhibitory activity. The synthesis of target compounds has been achieved by a novel green
strategy. In vitro COX-1, COX-2, and 5-LOX evaluation of these molecules have shown the potential for an improved anti-
inflammatory profile. Most promising compound among the series (2-(diphenylamino)-4-(4-nitrophenyl)thiazol-5-yl)
(naphthalen-1-yl)methanone 7h (IC50 = 0.07 0.02 μM) showed equivalent COX-2 inhibitory potency as that of positive
control etoricoxib (IC50 = 0.07 0.01 μM) and an enhanced selectivity index of 115.14. Compound 7h exhibited 5-LOX
IC50 of 0.29 0.09 μM and reference drug zileuton showed IC50 of 0.15 0.05 μM. In vivo studies of 7h including
carrageenan-induced paw edema assay (63% inhibition of paw edema), antiulcer studies, biochemical assays, qRT-PCR
analysis, and anticancer studies indicated that the present study has identified a good lead compound for the development of
a potential anti-inflammatory drug having improved gastric safety profile.
Graphical Abstract
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Keywords Thiazole Cyclooxygenase-2 5-Lipoxygenase Anti-inflammatory
Introduction
The significance of chronic inflammation in the pathophy-
siology of cancer, rheumatoid arthritis, cardiovascular, and
neurological disorders is of serious therapeutic concern
[1, 2]. Tumor microenvironments enclose a variety of
inflammatory mediators, such as growth factors, chemo-
kines, and cytokines that trigger extravasations of tumor
cells [3]. Biologically, the protective response of the body
to extrinsic and intrinsic stimuli is associated with altera-
tions in arachidonic acid (AA) metabolism leading to
Supplementary information The online version of this article (https://
doi.org/10.1007/s00044-020-02655-9) contains supplementary
material, which is available to authorized users.
* Manju S L
slmanju@vit.ac.in
1
Department of Chemistry, School of Advanced Sciences, Vellore
Institute of Technology, Vellore, Tamil Nadu, India

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Fig. 1 Bioactive molecules with
thiazole ring
Fig. 2 General structures of the novel molecules 7a–r including previously reported 5-LOX inhibitors, 1, 2, 3, and dual COX-2/5-LOX inhibitor,
4, considered as the starting scaffolds for the design of new molecules.
inflammation. Cyclooxygenases (COX) and lipoxygenases
(LOX) are two important enzymes involved in the AA
cascade. COX include two isoenzymes, COX-1/COX-2,
which produce prostaglandins (PGs), prostacyclin (PGI2),
and thromboxanes from AA. Among the COXs, COX-1 is
intrinsic and responsible for homeostatic function whereas
COX-2 is an inducible enzyme and is over expressed in
inflammation and tissue damage. Evidence showed that
leukotriene metabolites produced by LOX especially 5-
LOX are associated with cardiovascular diseases and cancer
[4, 5]. The significance of dual inhibition of COX-2 and 5-
LOX is further underscored as they have been reported to be
upregulated in various tumor types, including colon cancer,
prostate cancer, breast cancer, and pancreatic cancer [6, 7].

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Scheme 1 Synthesis of 4-
substituted-N-(amino-1-
carbonothioyl)-1-naphthamide
(5a–c) derivatives
Table 1 Reaction
optimizationa,b
Entry
Catalyst (equiv)
Solvent
Temp (°C)
Time (h)
Yield (%)b
1
–
Neat
RT
100
RT
60
80
100
80
80
80
80
80
80
80
80
80
80
80
80
80
24
11
20
56
75
94
86
62
94
94
46
42
37
69
55
57
87
82
76
0
2
–
Neat
24
3
TBAF(0.1)
TBAF(0.1)
TBAF(0.1)
TBAF(0.1)
TBAF(0.05)
TBAF(0.2)
TBAF(0.4)
NaF
Neat
12
4
Neat
5
5
Neat
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
6
Neat
7
Neat
8
Neat
9
Neat
10
11
12
13
14
15
16
17
18
19
Neat
KF
Neat
CsF
Neat
TBAB
Neat
TBAHSO4
CTAB
Neat
Neat
TBAF(0.1)
TBAF(0.1)
TBAF(0.1)
TBAF(0.1)
Water
Ethanol
Acetonitrile
DMF
aReagents and conditions: 1a (1.0 mmol), 2a (1.0 mmol), under solvent-free condition
bIsolated yields
Epidemiologic investigations recommended that COX-2
inhibitors radically reduced the risk of these dreadful dis-
eases [8]. Hence, multi-targeted ligands that inhibit both
COX-2 and 5-LOX enzymes hold great promise in opti-
mizing anti-inflammatory activity with minimal side effects
[9]. Thus we have found the rationale for the extension of
our research on COX-2/5-LOX inhibitors to cancer
cell lines.
Thiazoles are important constituents of many naturally
occurring biomolecules such as thiamine and synthetic
drugs with a variety of therapeutic properties for instance
analgesic, antipyretic, anti-inflammatory, anticancer, and
antiviral activities [10–12]. Antiretroviral agent ritonavir
[13], antimicrobial agent sulfathiazole [14], antifungal agent
abafungin [15], anti-inflammatory drug meloxicam [16],
antiparkinson’s drug pramipexole [17], and antineoplastic
drug tiazofurin [18] and bleomycin [19] are few examples
of clinically used thiazole-based drugs (Fig. 1). Interest-
ingly, thiazol-4(5H)-one derivative darbufelone and 1,3-
thiazolidine-2,4-dione derivative CI-987 are reported to
possess dual COX/LOX inhibition [20]. Woods et al.
reported the synthesis of thiazole analogues of indometha-
cin having selectivity toward COX-2, IC50 ~ 0.3 nM [21].
Thiazolo-celecoxib analogues have been reported for COX-
1/COX-2/15-LOX activity with IC50 ~ 6.0, 2.0, and 5.0 µM,
respectively [22]. Purine-pyrazole hybrids containing

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Scheme 2 Synthesis of 2-
(substituted)-4-(4-substituted
phenyl)thiazol-5-yl)
(naphthalene-1-yl)methanone
(7a–l) and N-(3-phenyl-4-(4-
(substituted)phenyl)thiazol-2
(3H)-ylidene)-1-naphthamide
(7m–r) derivatives
thiazoles, thiazolidinones, and rhodanines, were reported to
have 15-LOX IC50 = 1.76–6.12 μM and potential anticancer
and antioxidant activity [23].
Our group had reported 2-amino-4-aryl thiazoles [24], 1,
2-amino-4-aryl thiazole-5-phenylmethanones [25], 2, and
N-(5-(3-substituted acryloyl)-4-methylthiazol-2-yl) benza-
mides [26], 3 as potent inhibitors of 5-LOX (Fig. 2).
intended to design and synthesis 2-amino-4-arylthiazol-5-
ylnaphthalen-1-yl methanone derivatives. Naphthoyl moi-
ety was introduced to the C5 of thiazole ring, as the inclu-
sion of a large aromatic ring would increase the bulkiness of
the moiety, and henceforth it can fit well selectively within
the large Val523 side pocket of the COX-2 active site. The
key intermediate 5a–c was synthesized with minor mod-
ification as per the earlier report [25]. Briefly, 1-naphthoyl
thioureas (5a–c) in the first step were synthesized by
treating 1-naphthoyl chloride with potassium thiocyanate in
Recently, we have developed
a new series of 2-
carbonylthiophene substituted at the 5th position of thia-
zoles, 4 and thiazolidenes as potent dual inhibitors of COX-
2/5-LOX with enhanced gastrointestinal tolerance and
excellent in vivo anti-inflammatory activity [27] (Fig. 2).
Encouraged by these results, it is envisaged that substitution
of a bulky 1-naphthoyl moiety at 5th position of thiazoles
would produce lead molecules with superior COX-2 inhi-
bition and improved anti-inflammatory activities. We
hereby report green synthesis of some (2-(alkyl/aromatic
amino)-4-(4-substituted phenyl)thiazol-5-yl)(naphthalen-1-
yl)methanone and N-(4-(4-substituted phenyl)-3-phe-
nylthiazol-2(3H)-ylidene)-1-naphthamide and their in vitro
evaluation for COX-1/COX-2 and 5-LOX inhibitory activ-
ity. Compounds with promising dual inhibitory activity
were investigated for in vitro PGE2 and LTB4 inhibition.
Besides, we conducted in vivo anti-inflammatory, antiulcer,
qRT-PCR, and molecular docking studies on the most
active compound. In the current study, the most active
compound was also investigated for the anticancer activity
on various cell lines.
a
toluene-water system in the presence of tetra-
butylammonium fluoride (TBAF), followed by the reaction
with substituted amines (Scheme 1). Initially, we optimized
the reaction conditions for thiazole synthesis using the
substrates, N-(diphenylcarbamothioyl)-1-naphthamide and
2-bromo-1-phenylethan-1-one to study the catalytic effi-
ciency of TBAF. The results are shown in Table 1. Because
of the low thermal stability of TBAF, reactions involving
these were carried out below 100 °C [28]. Under SFC and in
the absence of catalyst at RT, the reaction of N′-naph-
thoylthiourea with phenacyl bromide was negligible. Even
after 24 h, the yield obtained was 11% (Table 1 entry 1).
Then the temperature was raised to 100 °C, but there was no
significant improvement in the reaction, 20% yield (Table 1
entry 2). However, after mixing of N′-naphthoylthiourea
with phenacyl bromide in the presence of 0.1 equiv of
TBAF at RT, thiazole was indeed formed in 1.5 h, 56%
yield (Table 1 entry 3). Then, reaction at different tem-
peratures such as 60, 80, and 100 °C was examined and the
yield of product was gratifyingly increased to 75%, 94%,
and 82%, respectively (Table 1 entries 4–6). These results
emphasized the role of TBAF as a catalyst for cycloaddi-
tion. Further, we studied the effect of other fluoride catalysts
such as NaF, KF, and CsF, which exhibited less catalytic
activity compared to TBAF (Table 1 entries 10–12).
Meanwhile, the study of other phase transfer catalysts like
Results and discussion
Chemistry
Since thiazoles are associated with various biological
activities and inspired by our earlier studies [25], here, we