Design and synthesis, biological evaluation of bis-(1,2,3- and 1,2,4)-triazole derivatives as potential antimicrobial and antifungal agents

Article abstract of DOI:10.1016/j.bmcl.2021.128004

A new series of bis-1,2,3- and 1,2,4-triazoles (10a-m) were designed and efficiently synthesized using methyl salicylate as potential antimicrobial agents. All compounds were characterized by their proton & ¹³C NMR, IR, Mass spectral data, and

Full text of DOI:10.1016/j.bmcl.2021.128004

Bioorg. Med. Chem. Lett. 41 (2021) 128004
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Design and synthesis, biological evaluation of bis-(1,2,3- and 1,2,4)-triazole
derivatives as potential antimicrobial and antifungal agents
a
b
c
Sampath Bitla , Akkiraju Anjini Gayatri , Muralidhar Reddy Puchakayala ,
a
d
a
c
Vijaya Kumar Bhukya , Jagadeshwar Vannada , Ramulu Dhanavath , Bhaskar Kuthati ,
Devender Kothula , Someswar Rao Sagurthi , Krisham Raju Atcha
a
b
,
*
a,*
a
Department of Chemistry, Nizam College, Osmania University, Hyderabad, Telangana 500001, India
b
Molecular Medicine Lab, Dept. of Genetics & Biotechnology, Osmania University, Hyderabad, Telangana 500007, India
c
Department of Chemistry, University College of Science, Osmania University, Hyderabad, Telangana 500007, India
d
Department of Chemistry, University College of Science, Saifabad, Osmania University, Hyderabad, Telangana 500004, India
A R T I C L E I N F O
A B S T R A C T
Keywords:
A new series of bis-1,2,3- and 1,2,4-triazoles (10a-m) were designed and efficiently synthesized using methyl
Bis-1,2,3 and 1,2,4-triazole
Antibacterial activity
Antifungal activity
Antimicrobial resistance
Antioxidant
salicylate as potential antimicrobial agents. All compounds were characterized by their proton & 13C NMR, IR,
Mass spectral data, and elemental analysis. The final compounds 10a-m were in vitro screened for antimicrobial
and antifungal activity against gram negative Pseudomonas aeruginosa, Escherichia coli, gram positive Bacillus
subtilis, Staphylococcus aureus strains and Aspergillus niger & Saccharomyces cerevisiae. Majority of the synthesized
compounds exhibited potent antimicrobial activity (MIC 3.9 µg/mL) and promising antifungal activity with the
zone of inhibition (ZOI) 1.5–8.2 mm. Compounds like 10d and 10f exhibited best antimicrobial activity against
S. aureus. The molecular docking analysis revealed that all the synthesized derivatives shown better binding
affinities. Among all, compound 10f exhibited best scores. Hence, there was an assumption that introduction of
para-chloro and bromo-phenyl aromatic groups on triazole moiety could result excellent antimicrobial activity.
This substantial growth inhibitory activity of bis-1,2,3- and 1,2,4-triazole derivatives suggested these compounds
could assist a new way in the development of lead molecules against microbial infection and antimicrobial
resistance investigations.
Molecular docking
Antimicrobial resistance (AMR) has been a worldwide concern that
became a never-ending fight between humans and the micro biome.
Microbial infections are estimated to cause 0.7 million deaths annually
and increasing on an everyday basis.1 Combating antimicrobial resis-
tance has become a major confront for global health, food security and
development hindrance. The rise in resistance of microorganisms
against antimicrobial drugs threatens the successful treatment of
aminoglycosides, tetracycline’s, sulfonamides, quinolines and others
th
developed during the 20 century, failed to control the emerging (AMR)
antimicrobial resistance in some aspects by persisting the ineffective
transmit to microbes. Therefore, in current medicinal chemistry, there is
an urgent requirement of design and developing new strategies to build
up a new effective generation of antimicrobial agents with different
working mechanisms to suppress the antibiotic resistance for future use.
1,2,3-Triazoles are well-known scaffolds, which are when conjugated
2
increasing bacterial and fungal infections and affects people health all
5
–10
over the world. As per WHO reports on global antimicrobial resistance, it
is expected that >10 million people will suffer from the multi-drug
resistance infections with an increased number of human mortality
rates. Further, it is expected to raise in antimicrobial drug resistance.3
Based on these study estimations, it is required to strengthen this
research field to develop new, relatively effective antimicrobial and
antifungal drugs.4 Standard drug treatments like β-lactams,
with other hetero cyclic moieties exhibit useful biological activities.
N-Containing heterocyclic compounds are a major part of the pharma-
ceutical, agrochemical and biological fields.1
1,12
Among them 1,2,3-tri-
azole and 1,2,4-triazoles exhibit a broad range of biological activities,
1
3–15
16
17
18
such as antifungal,
Insomnia,
anticancer,
antineoplastic,
antimicrobial,1
4,19–21,41
antibacterial,
22,30
antioxidant,23,24,13 anti-in-
25,26
27,42
28,29
flammatory,
antiviral,
antimycobacterial,
*
Corresponding authors.
E-mail addresses: drsomeswar@osmania.ac.in (S.R. Sagurthi), krishnamrajua@osmania.ac.in, krishnamrajua@gmail.com (K.R. Atcha).
https://doi.org/10.1016/j.bmcl.2021.128004
Received 23 January 2021; Received in revised form 13 March 2021; Accepted 25 March 2021
Available online 31 March 2021
0
960-894X/© 2021 Elsevier Ltd. All rights reserved.

S. Bitla et al.
Bioorganic & Medicinal Chemistry Letters 41 (2021) 128004
anticonvulsant,31 antidepressant,32 and anticoagulants33 activities
structure was confirmed based on its spectral data where, the singlet
1
(
Fig. 1).
Stimulated by above findings and also as a part of our enduring
–OCH
3
absorption peak δ 3.89 is disappeared in its H NMR spectrum
and followed by the appearance of two new absorptions in its spectra at δ
4.53 (two protons for a singlet) and δ 9.21 (one proton for a singlet) due
research works in lab, we focused to develop novel antimicrobial agents
with potent activity. Here, we described the novel synthesis of bis-1,2,3
and 1,2,4-triazole derivatives 10a-m. All synthesized compounds were
characterized by using 1H NMR and C NMR, EI-MS, FT-IR, Mass and
elementary analyses. All these compounds 10a-m were then studied for
their antimicrobial, antifungal and antioxidant activities (Fig. 2).
The key cyclisation step of compounds 7a-d was carried out in 2N
NaOH solution under reflux temperature for 24hrs to afford the bis-1,2,3
and 1,2,4-triazole-3-thiol 8a-d in 80–85% yield. The compound 8a was
to NH
compound 5a showed absorption bands at 3097 cm and 3394 cm
which could be attributed to NH and NH groups. Additionally, the Mass
2
and NH respectively. The FT-IR spectrum of the particular
ꢀ 1
ꢀ 1
13
2
spectral data of compound 5a is in accordance with its molecular for-
mula which gave its (M + 1) peak at m/z 344. The treatment of ben-
zohydrazides 5a-c with aryl thiocyanates 6a-b in ethanol under reflux
conditions for 12–16hrs afforded the corresponding hydrazine carbo-
thioamide derivatives 7a-d in good yields. Spectral data revealed the
formation of compound 7a where 1H NMR of compound 7a exhibited
one signal for the proton of –CO-NH- as a singlet at δ 10.07, signal of two
1
confirmed by its H NMR spectra which showed the characteristic thiol-
SH and triazole proton absorptions as singlets at δ 11.56 and at δ 9.27
respectively. The absorption of –OCH
2
protons was appeared at δ 5.50 as
protons was observed at δ 4.76
protons corresponding to the Ph-CH
2
- was observed as a doublet at δ
- appeared as a singlet at δ
C NMR spectrum showed absorption signals of >C–
a singlet, and a signal due to benzyl –CH
2
4.71 and absorption of two protons of O-CH
2
5.40. Its 13
as a singlet. This was further confirmed from its mass spectral data with
–
S and
+
–
molecular ion peak at m/z 475 (M + H) .
>C
–
O carbons at δ 184.4 and δ 156.0 respectively. FT-IR spectrum of
–
–
–
S and >C O at
The final target bis-(1,2,3- and-1,2,4)-triazole derivatives 10a-m
were successfully accomplished in quantitative yields by the reaction of
bis-1,2,3-and 1,2,4-triazole-3-thiols 8a-d with phenacyl bromides 9a-
d in the presence of potassium carbonate in dry acetone at reflux tem-
the compound 7a has shown absorption bands of >C
–
ꢀ 1
ꢀ 1
1728 cm and 1600 cm respectively. It also showed a balanced
agreement of elemental analysis and mass spectral data with its calcu-
lated mass of compound 7a.
1
perature. The compounds 10a-m were characterized based on their H
1
3
NMR, C NMR, Infrared, elemental analysis and mass spectral data. The
Antimicrobial activity
1
H NMR spectrum of target compound 10a exhibited singlets at δ 7.78, δ
5
.43, δ 5.02 and δ 4.88 due to 1,2,3-triazole proton, –OCH
CH ,and-S-CH
protons respectively. The 13C NMR spectrum of com-
pound 10a given the (>C
OCH carbon signal at δ 63.2, -N-CH
carbon signal at δ 40.2. The IR spectrum confirmed the presence of
2
protons, -N-
The in vitro assessment of newly synthesized bis-(1,2,3,-and-1,2,4)-
triazole derivatives against two strains of gram-positive and negative
Staphylococcus aureus (S. aureus) MTCC 96, Bacillus subtilis (B. subtilis)
MTCC 441 and Pseudomonas aeruginosa (P. aeruginosa) MTCC 424,
Escherichia coli (E.coli) MTCC 443 was performed. The selection of the
bacterial strains was based on their marked-up ability in developing
drug resistance. Among all, the bacterial growth inhibitory activities of
the synthesized compounds have shown favorable inhibition activity
against gram positive and gram negative bacteria. Though all com-
pounds showed good inhibition against B. subtilis compounds 10d and
10f were endowed with high selectivity against S. aureus species
(Table 1). Therefore, from the in vitro antibacterial assessments, the
compounds 10d and 10f can be promising drugs when compared with
the other existing ampicillin antibiotic drugs (42). Thus the results can
suggest these molecules to be a promising prospect of drugs with analogs
or derivatives. In vitro antimicrobial analysis of synthesized compounds
(Table 1) was done by calculating the particular concentration of com-
pound where there is an initiation of bacterial growth inhibition and
considered as minimal concentration of compound (MIC) required for
bacterial growth inhibition. A comprehensive study of compounds at
molecular level interactions with target protein 1HSK (Responsible for
the bacterial cell wall biogenesis by involving in the peptidoglycan
penta glycine bridge formation) performed using Molegro virtual
docking server to supplement the promising biological activity of com-
pounds (Table 1) as better antibacterial agents.
2
2
–
–
O) keto carbon (phenacyl) signal at δ 191.9,
carbon signal at δ 50.1 and -S-CH
–
2
2
2
–
–
characteristic -C
–
N- & >C
–
O, keto functionalities by exhibiting ab-
ꢀ
1
ꢀ 1
sorption bands at 1592 cm and at 1729 cm . Elemental analysis data
was in good agreement with its structure. Mass spectral data derived for
+
compound 10a has given the (M + H) peak at m/z 593, which shown a
synergic concord with its calculated mass.
The designed final target bis-triazole derivatives (10a-m) were
synthesized efficiently by following the flexible synthetic approach as
detailed in Scheme 1. The synthesis of target compounds 10a-m was
started primarily with propargylation reaction on methyl salicylate 1 by
using the propargyl bromide in presence of potassium carbonate base
and followed by a solvent i.e., dry dimethyl formamide to render cor-
responding alkyne compound 2 with a yield of 85%. The structure of
alkyne group in compound 2 was confirmed by its spectral data.34 By
using copper (I) catalyzed Huisgene 1,3-dipolar cycloaddition of alkyne
2
with azides 3a-c effectively produced triazoles 4a-c in excellent
3
5
yields. The formation of triazole derivatives 4a were confirmed by
1
their analytical data. The data depicts the H NMR spectrum of triazole
4
a where, it’s characteristic triazole proton signal observed as a singlet
at δ 8.02, absorption of –OCH - two protons were noticeable as a singlet
at δ 5.40, then the absorption corresponding to ester –OCH appeared as
2
3
a singlet at δ 3.89. It is then additionally confirmed by following the
mass spectral data which showed up (M + 1) peak at m/z 344. The
obtained triazoles 4a-c were then treated with hydrazine hydrate by
utilizing the 1,4-dioxane as a solvent under reflux conditions for 24 h to
afford benzohydrazides 5a-c in quantitative yields. The 5a compound
Antifungal activity
Synthesized compounds (10a-m) were tested against filamentous
fungi Aspergillus niger (A. niger) MTCC 404 and yeast Saccharomyces
Fig. 1. 1,2,3-Triazole based biologically active agents.
2

S. Bitla et al.
Bioorganic & Medicinal Chemistry Letters 41 (2021) 128004
Fig. 2. 1,2,4-Triazole containing biologically active drugs.
Scheme 1. Synthesis of Bis-(1,2,3,- and 1,2,4)- Triazole Derivatives 10a-m.
3

S. Bitla et al.
Bioorganic & Medicinal Chemistry Letters 41 (2021) 128004
Table 1
cerevisiae (S. cerevisiae) MTCC 1344 strains for antifungal activity. Our
studies identified 10a, 10d, 10f and 10k compounds could show effi-
cient antifungal efficacy among all the other synthesized compounds
Minimal Inhibitory Concentration (MIC
μ
g/ml).* Antimicrobial activities of
synthesized bis-1,2,3-and-1,2,4-Triazole derivatives (10a-m) against growth of
gram-positive and gram-negative bacterial strains by micro dilution method.
(
Table 2).
Antifungal activity of Bis-1,2,3 and-1,2,4-Triazole derivatives (10a-
Compound Sl. No
Gram positive bacteria
MIC g/ml)
Gram negative bacteria
(MIC g/ml)
(
μ
μ
m) against A. niger MTCC 404 and S. cerevisiae MTCC 1344 upon incu-
◦
S. aureus
B. subtilis
P. aeruginosa
E. coli
bation after 2 days at 37 C followed by cross streak plate method.
MTCC 96
MTCC 441
MTCC 424
MTCC 443
Antioxidant activity
1
1
1
1
1
1
1
1
1
1
1
1
1
0a
0b
0c
0d
0e
0f
9.7 ± 0.03
8.5 ± 0.06
8.0 ± 0.05
4.1 ± 0.05
9.5 ± 0.05
3.9 ± 0.05
8.9 ± 0.06
9.8 ± 0.02
8.4 ± 0.05
7.9 ± 0.05
8.7 ± 0.03
8.0 ± 0.05
7.9 ± 0.05
10.0 ± 0.08
5.2 ± 0.00
4.4 ± 0.05
4.0 ± 0.05
6.5 ± 0.05
5.0 ± 0.05
4.2 ± 0.05
4.0 ± 0.05
4.9 ± 0.05
4.0 ± 0.11
4.1 ± 0.05
4.7 ± 0.05
4.1 ± 0.05
5.0 ± 0.05
10.0 ± 0.06
9.0 ± 0.00
8.1 ± 0.03
8.2 ± 0.03
7.3 ± 0.03
8.8 ± 0.03
8.8 ± 0.03
8.7 ± 0.05
9.1 ± 0.03
7.9 ± 0.06
7.5 ± 0.05
8.5 ± 0.05
7.5 ± 0.05
7.5 ± 0.05
10.0 ± 0.08
10.0 ± 0.11
9.0 ± 0.05
8.5 ± 0.11
6.1 ± 0.08
9.1 ± 0.05
4.5 ± 0.05
10.0 ± 0.05
9.8 ± 0.05
>45.4 ± 0.56
10.0 ± 0.06
9.0 ± 0.05
>40.8 ± 0.60
10.0 ± 0.11
3.9 ± 0.03
On considering the DPPH free radical scavenging assay principle, it
was demonstrated that all synthesized compounds (10a-m) were
exhibited negligible potency in clearing the free radicals in the reaction
mixture (Data not shown in manuscript).
0g
0h
0i
Molecular docking analysis
0j
0k
0l
Molecular docking is an in silico tool that follows the manual protocol
to mimic ligand interactions with receptors to find the binding site and
its affinity towards active site conformational changes. During bacterial
inhibition, the existing β-lactam antibiotics are the often targets more
abundantly with more than one penicillin binding protein by their close
structural association. Studies on cell wall biosynthesis inhibitors noted
that, there is an analogous observation between β-lactam antibiotics and
the sugar-amino acid backbone. Soon after the bacterial cell wall
biosynthesis mechanism considers these β-lactam antibiotics as their
own and continues the formation of penta glycine peptidoglycan layers.
In view of these aspects, the current study focused on synthesis of potent
non-β-lactam derivatives called bis-1,2,3 and 1,2,4-triazoles, which can
be successfully and likely targets the MurB protein effectively to inhibit
the bacterial growth in various strains to combat the drug-resistance.
MurB (UDP-N-acetylenol pyruvylglucosamine reductase) (PDB ID:
0m
Ampicillin
Tale 2
Zone of inhibition (mm)* at specified concentrations in parenthesis.
Comp Sl. No Aspergillusniger MTCC 404 Saccharomyces cerevisiae MTCC
1
344
ZOI-mm (Compound Concentration-µM)
1
1
1
1
1
1
1
1
1
1
1
1
1
0a
0b
0c
0d
0e
0f
6.0 ±
.00
16.8)
2.0 ±
.57
14.8)
2.0 ±
.03
15.9)
5.3 ±
.11
17.2)
1.5 ±
.11
16.8)
5.0 ±
.00
15.6)
5.5 ±
.05
18.3)
2.1 ±
.03
18.3)
2.1 ±
.03
17.2)
1.5 ±
.05
16)
7.3 ±
.06
14.9)
2.0 ±
.05
15.9)
2.0 ±
.00
16.8)
8.0 ±
.11
24)
8.0 ±
0.05
8.2 ±
0.05
5.8 ±
0.05
5.7 ±
0.05
7.0 ±
0.00
0
1
HSK) is an attractive target, facilitates a key role in bacterial infections
(
(25.2)
2.0 ±
0.48
(33.7)
3.0 ±
0.11
(16.8)
1.5 ±
0.14
(25.2)
2.0 ±
0.00
(33.7)
3.0 ±
0.11
by involving in cell wall biosynthesis. It plays a vital role in peptido-
glycan biosynthesis mediated with a catalyzing step in continuous pro-
cess of cytoplasmic and membrane-bound reactions. It mediates in
amino sugar metabolism to covert the lipid-I to lipid-II molecule in cell
wall biosynthesis. It helps in reducing the EP-UNAG (enolpyruvyl-uri-
dinediphosphate N-acetyl glucosamine) as an intermediate to relieve m-
A2pm (UNAM-pentapeptide) protein to synthesize cell wall precursor
called UNAM (uridine-diphosphate N-acetyl Muamic acid). In order to
know the binding affinity interactions, the XRD model of S. aureus N-
acetyl enolpyruvylglucosaminereductase (MurB) co-crystal with FAD
(PDB ID: 1HSK) was chosen with high resolution of 2.3 Å (Benson et al.,
0
(
(22.2)
2.0 ±
0.06
(29.7)
3.0 ±
0.11
(14.8)
2.0 ±
0.00
(22.2)
2.0 ±
0.00
(29.7)
3.0 ±
0.11
0
(
(23.9)
6.0 ±
0.00
(31.8)
7.6 ±
0.06
(15.9)
5.0 ±
0.00
(23.9)
7.0 ±
0.05
(31.8)
7.4 ±
0.05
0
(
(25.9)
3.0 ±
0.11
(34.5)
3.0 ±
0.11
(17.2)
2.0 ±
0.00
(25.2)
3.0 ±
0.11
(34.5)
3.0 ±
0.11
0
(
(25.2)
7.4 ±
0.05
(33.7)
7.6 ±
0.08
(16.8)
6.0 ±
0.05
(25.2)
6.5 ±
0.05
(33.7)
7.0 ±
0.00
0
2
001). In dealing with these ligand synthesis and treatment, it directs
(
(23.4)
6.8 ±
0.00
(31.2)
7.0 ±
0.00
(15.6)
6.0 ±
0.08
(23.4)
6.8 ±
0.05
(31.2)
6.7 ±
0.05
bacteria to generate a successful loose imperfect cell wall, which can be
easily destructed by regular or novel antibiotics alone or in combination
therapy to advance antibiotic-resistant bacterial growth. To the model
0g
0h
0i
0
(
(27.5)
3.0 ±
0.11
(36.6)
3.0 ±
0.11
(18.3)
1.5 ±
0.14
(27.5)
2.0 ±
0.00
(36.6)
3.0 ±
0.11
0
Table 3
(
(27.5)
3.0 ±
0.11
(36.6)
3.0 ±
0.11
(18.3)
2.0 ±
0.00
(27.5)
3.0 ±
0.11
(36.6)
3.0 ±
0.11
Docking scores for synthesized compounds against MurB protein (PDB ID:
1HSK).
0
(
(25.9)
2.0 ±
0.06
(34.5)
3.0 ±
0.11
(17.2)
2.0 ±
0.00
(25.9)
2.0 ±
0.00
(34.5)
3.0 ±
0.11
Ligand
MolDock Score
HSK
Rerank Score
1HSK
0j
1
0
(
(24)
(32.1)
7.5 ±
0.05
(16)
(24)
(32.1)
7.4 ±
0.05
10a
10b
10c
10d
10e
10f
ꢀ 205.22
ꢀ 196.55
ꢀ 215.24
ꢀ 204.68
ꢀ 189.45
ꢀ 209.12
ꢀ 225.51
ꢀ 203.06
ꢀ 205.58
ꢀ 202.82
ꢀ 213.56
ꢀ 206.30
ꢀ 213.30
ꢀ 126.57
ꢀ 116.80
ꢀ 114.72
ꢀ 123.06
ꢀ 131.51
ꢀ 143.99
ꢀ 180.47
ꢀ 144.94
ꢀ 121.77
ꢀ 17.60
0k
0l
7.0 ±
0.08
6.2 ±
0.05
6.6 ±
0.05
0
(
(22.3)
2.0 ±
0.06
(29.8)
3.0 ±
0.11
(14.9)
1.5 ±
0.03
(22.3)
2.0 ±
0.00
(29.8)
3.0 ±
0.11
0
(
(23.9)
3.0 ±
0.11
(31.8)
3.0 ±
0.11
(15.9)
2.0 ±
0.00
(23.9)
3.0 ±
0.11
(31.8)
3.0 ±
0.11
10g
10h
10i
0m
0
(
(25.2)
10.0 ±
0.11
(33.7)
12.0 ±
0.05
(16.8)
8.0 ±
0.11
(25.2)
9.0 ±
0.00
(33.7)
12.0 ±
0.05
10j
Miconazole
10k
10l
ꢀ 91.50
0
ꢀ 78.33
(
(36)
(48)
(24)
(36)
(48)
10m
ꢀ 47.42
4

S. Bitla et al.
Bioorganic & Medicinal Chemistry Letters 41 (2021) 128004
PDB’s we have screened the Bis-1,2,3-and-1,2,4-Triazole derivatives at
the binding site specific region of flavin adenine dinucleotide (FAD) and
it is observed that all 10a-10m showed better binding affinities with
potent MolDock score and Rerank score (Table 3) but 10f ligand per-
formed a strong binding affinity and its activity was confirmed by
experimental in vitro approach. The docking results of 10th series
compounds with MurB were regarded as good in relation to in vitro
antibacterial MIC values (as shown in Table 1).
The target binding site of FAD is fully saturated with polar group
amino acids (SER, GLN, ASN, TYR). This formulates the newly synthe-
sized bis-1,2,3-and1,2,4-Triazole derivatives to form hydrogen bond
interactions with target as proton donors or acceptors. In present study,
all compounds displayed a high moldock score with maximum number
of πand hydrogen interactions at binding pocket. On top of it, the Pi-
alkyl and pi-pi, pi-sigma along with other hydrogen interactions are
prevalently found in docking result of ligand–protein structures. These
interactions would contribute a close proximal spatial orientation like
FAD and their interactions with identical amino acid residues on same
positions like FAD. The whole synthesized ligands (10a-m) have shown
a good docking score along with strong binding affinities towards MurB
as shown in Table 3. 2D-visualization of 10f with 1HSK (Fig. 3) shown
an additional H-bond interactions with active site residues. In compar-
ison with the present interactions and earlier literature findings, we
noted that the MurB protein receptor with ligand binding residue posi-
tion atoms at SER82 and 238, ARG188, GLY81 and GLU308 are effective
target sites responsible for receptor active site conformational changes.
The key interaction residues at the binding site are ARG 225, 310, ILE84,
(a)
1
40, GLY146, 153 and PRO141. The active site of MurB was identified
from the earlier studies and also confirmed in Protein ligand server: http
s://projects.biotec.tu-dresden.de/plip-web/plip/index for identifying
the hydrophobic interaction (Pro 141, Leu 231, Phe 274) and water
bridges (Gly 146, Ser 143 and Tyr 77) in 1HSK crystal structure bound
with FAD (Flavin-Adenine Dinucleotide) as inhibitor. Our docking also
showed a broad vicinity of molecular binding at the same active site as
shown in 2D and 3D-images (Fig. 3), and the synthesized compounds
have also shown analogous interactions as found in model PDB struc-
ture. By following the principles and parameters obtained from the
electronic properties & geometry, it is recommended that the compound
with electrostatic interaction plays a key fundamental role in attracting
(
b)
3
6
aromatic and amino acid residues.
Moreover, it is well acknowledged that the collection and display of
heteroatoms, penta-membered rings like triazoles and pyrazoles were
regarded as potential scaffolds in developing antibacterial affinity with
continuation of -N and -O atomic residues in their aromatic rings. The
phenyl groups in molecule showed strong
88 and 225,
–alkyl interactions were observed with ALA, ILE and PHE
at 154, 84 and 997 positions,
–lone pair stabilizing interaction were
observed with SER 238. The phenyl aromatic rings linked to the triazole
group of compounds showed many interactions. The increase in pro-
π
-cation interaction with ARG
1
π
(
c)
Interactions
π
Fig. 3. In silico docking analysis depicts the interaction of 10a-m derivatives
3
7,38
π
with target MurB protein (PDB ID: 1HSK) in protein–ligand complex.
and 2D visualization of 10f molecular interaction with target MurB Protein
PDB ID: 1HSK). (a) Secondary structure and 3D-cartoon-ribbon view of 10f
3D
tein–ligand interactions at aromatic amino acid residues raises the sta-
bility of newly derived ligand binding site conformations.
(
compound with 1HSK. (b) 3D enlarged stick view of compound 10f (green
colour) binding with 1HSK (Grey colour) (c) 2D dock pose and ligand inter-
action of 10f molecule with MurB protein showing molecular binding sites in
active regions.
Structure-activity relationship (SAR) studies
From our previous studies, triazole derivatives are reported with
synthetic feasibility and shown numerous antibacterial activities,
focused on developing bis-triazole moieties as a lead scaffold in the
present study. In addition to this, the collection of aromatic penta rings
like triazole and pyrazole groups, heteroatoms acknowledged a potent
framing in antibacterial action with fixing nitrogen and oxygen atoms in
their aromatic rings. The synthesized series of compounds (10a-10m)
showed better docking scores with good synergy in-vitro biological ac-
tivity. 10f showed better activity against S. aureus MTCC 96 (MIC 3.9 ±
compared with –CH COPh and –COPh assembly alone. Compounds with
2
2
benzyl group substitutions at –R positions improved bacterial growth
inhibition compared with phenyl group replacing alone. Few com-
pounds with the halo group (–Cl) in place of –R group also showed
slightly potent inhibitory activity than compounds devoid of halo group
3
at –R position. Hence, the introduction of more halogens to the aryl
group attached to triazole moiety enhanced the antibacterial efficacy.
On the contrary, few compounds have shown a least activity against
S. aureus even by presence of halogen’s could assess the discrepancy
among binding at various active sites. It may also infer that, larger the
0
.05 µg/ml). It is noticed that–Chloro and –Bromo halogenic substitutes
3
at -para and -meta positions of aryl group attached to –CH
bestowed with pretty good biological inhibitory activities when
2
CO (i.e., –R )
5

S. Bitla et al.
Bioorganic & Medicinal Chemistry Letters 41 (2021) 128004
number of substituents might interfere with the surrounding residues
Radars illustrating oral bioavailability and the drug-likeness of
the compounds
and disturb the sidechain’s suitable confirmation within the active site.
In silico ADME evaluation
The pink area in radar figure represents the appropriate range of
physicochemical space for optimal oral bioavailability (SIZE: MWt,
LIPO: Lipophilicity, INSOLU: Solubility, POLAR: TPSA, INSATU: Insa-
turation, FLEX: Flexivbility). Here in fig. 4, the red line represents the
ability range of compounds tested. The Table 4 shows the outcome of
listed properties and suggested with no significant violations of Lip-
inski’s rule and the calculated physicochemical & pharmacokinetic de-
scriptors are found to be within the projected thresholds (Drug-likeness
acceptance, No. of Violations. Table 5 and predicted hERG-liability
Table 6).
All the synthesized compounds (10a-m) were analyzed for toxicity
and other ADMET properties by using an online web server called
SwissADME (http://www.swissadme.ch) to identify the leads as
bestowed molecules for clinical trials and other management. The
compound toxicity was also established by ProTox-II chemical toxicity
predictions (http://tox.charite.de/protox_II/). After the performance of
synthesized compounds with final conventional biological actions, the
th
1
0
series of compounds were then assessed for the physicochemical
parameters along with the pharmacokinetic properties and drug-
likeness with an aid of freely available SwissADME web source.39,40
As acknowledged in the model study, the compounds were stand
alone as a potent satisfactory with their performance in bioavailability
Discussion
In Summary, we have designed and synthesized a novel series of bis-
(
(
oral). Furthermore, in combination of topological surface polarity
TPSA), lipophilic nature, Molecular Weight and flexibility, solubility,
(1,2,3-and 1,2,4)-triazole derivatives 10a-m. All of these compounds
1
13
were characterized by using their spectral data like H & C NMR, Mass,
FT-IR and elemental analysis and further investigated for their antioxi-
dant, antifungal and antimicrobial activities and derived a noticing wide
saturation shown better drug likeness. The synthesized all compounds
have showed an acceptable range of the above listed parameters and are
graphically displayed in radar plots as mentioned below Fig. 4. Ability of
compounds for drug-likeness was determined by number of free rotat-
able bonds and Lipinski’s rule along with Eagan’s, Veber’s rules. Thus,
these compounds were fulfilled with good pharmacokinetic profiles with
satisfied criterion of drug-likeness. In comparison with above all syn-
thesized compounds, the specific molecules like 10a, 10d, 10f and 10k
were identified as prominent antibacterial agents. Hence, they were also
characterized for further pharmacokinetic analysis for future drug
development.
range of antibacterial activity in 10d (R = Cl-Ph) and 10f (R
3
= p-
BrPhCOCH -S-). Hence, both of these compounds were found to be
2
effective against microbial growth. The rise of interest in inhibiting the
MurB protein by binding analysis gives a clear glance in developing the
inhibitors against antimicrobial resistance. Our findings suggested that
amongst all the synthesized compounds 10a (R = Cl-Ph), 10d (R = Cl-
Ph), 10f (R
3
= p-BrPhCOCH
2
-S-) and 10k (R
3
= m-BrPhCOCH
2
-S-) were
the major compounds exhibited enhanced antifungal activity. From the
principle of DPPH-free radical scavenging assay, it is depicted that none
Fig. 4. Drug likeness in 10a, 10d, 10f and 10k.
6

S. Bitla et al.
Bioorganic & Medicinal Chemistry Letters 41 (2021) 128004
Table 4
List of calculated physicochemical properties using SwissADME web server.
a
b
c
d
e
f
g
2
h
Comp
MW (g/mol)
ClogPo/w
MlogP
nHBA
nHBD
nRB
TPSA (Å )
logS
1
1
1
1
0a
0d
0f
593
5.56
5.41
5.68
6.20
4.87
4.68
4.96
5.41
6
6
6
6
0
0
0
0
11
10
11
11
113.02
113.02
113.02
113.02
ꢀ 7.48
ꢀ 7.49
ꢀ 7.80
ꢀ 8.39
579.07
637.55
671
0k
a-Molecular weight; b, c-Lipophilicity; d-No. of H-bond acceptors; e-No. of H-bond donors; f-No. of rotatable bonds; g-Topological surface area; h-Solubility.
Table 5
Determination of Drug-likeness acceptance, No. of Violations.
Comp
Lipinski
Veber
Egan
Bio-availability score
GI absorption
BBB permeant
CYP1A2
CYP2C19
CYP2C9
CYP2D6
CYP3A4
1
1
1
1
0a
0d
0f
No (2)
No (2)
No (2)
No (1)
N0 (1)
Yes
N0 (1)
N0 (1)
N0 (1)
No (1)
0.17
0.17
0.17
0.17
Low
Low
Low
Low
No
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
Yes
Yes
Yes
Yes
N0 (1)
N0 (1)
0k
for analytical support.
Table 6
Predicted hERG-liability of prominent molecules from LabMol web server for
application capability.
Author contributions
Comp
Potential
Confidence
Applicability domain
(AD)
Weak or
KRA (Corresponding author), SB perceived the idea and provided
critical inputs to the concept. KRA and SB planned the experiment, SB
and RD, KD generated synthesis data. Molecular docking and Biological
assays were carried out by SSR (Co-Corresponding author) and AAG. All
the authors KRA, SB, SSR, AAG, RD, DK, PMR, JV, BK, and BVK
contributed to analyze, interpret data and wrote the manuscript. All
authors contributed to the final reading and approved the submitted
revised version.
cardiotoxic
Moderate
1
1
1
1
0a
0d
0f
+
+
+
+
60%
Yes
60%
50%
50%
50%
(
Value = 0.27 and
limit = 0.26)
70%
70%
60%
Yes
(
Value = 0.28 and
limit = 0.26)
Yes
(
Value = 0.28 and
limit = 0.26)
0k
Yes
Appendix A. Supplementary data
(
Value = 0.27 and
limit = 0.26)
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.bmcl.2021.128004.
of the compounds exhibited their ability in clearing the free radicals in
the reaction mixture. From our current in silico studies, the best dock
scored compounds were further visualized for their active binding re-
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