Bioactive heteroleptic Bismuth(V) carboxylates: Synthetic Stratagem, characterization and binding pattern validation

Article abstract of DOI:10.1016/j.jorganchem.2020.121357

A series of heteroleptic triorganobismuth(V) carboxylates (1–8) of general formula Ar₃Bi(COOR)₂; where Ar = C₆H₅ (1–4), p-CH₃C₆H₄ (5–8) and R = C₁₀H₇ (1, 5), 2-CH₃C₆H₄ (2, 6), 3, 4- (OCH₂CH₃)C₆H₃ (3, 7), 2-ClC₆H₄ (4, 8); were synthesized by a stoichiometric reaction between the precursor, Ar₃BiBr₂, and the respective carboxylic acidusing triethylamine as a base in dry toluene. They were characterized by FT-IR, NMR spectroscopy and X-ray diffraction technique to get unequivocal evidence for their structural motifs. The single crystal XRD data for (2 & 5) revealed the existence of five coordinated bismuth centre having distorted trigonal bipyramidal molecular geometry, whereas (6) described weakly hexacoordinated bismuth including a unique anisobidentate interaction of one carboxyl group with the resultant distorted octahedral molecular geometry. The molecular docking studies demonstrate that compounds (1, 2 and 7) give significant GOLD fitness scores of 60.09, 62.65 and 56.30 against EGFR tyrosine kinase, human pancreatic alpha amylase and H. pylori urease respectively. The synthesized compounds were also preliminary screened for their antimicrobial, α-amylase inhibition and protein kinase inhibition activities to determine their biological efficacy. The antibacterial activity profile for (2) looks good with MIC value 6.25 μg/mL against E. coli whereas, (1, 2 and 5) show significant antifungal activity against A. flavus having MIC value of 6.25 μg/mL and the values are comparable to the reference drug(s). Compound (6) displays significant % alpha amylase inhibition of 34.80, whereas (2) exhibit 30 mm bald inhibition zone for protein kinase inhibition study, thus, proving their worth as moderate enzyme inhibitors. The molecular docking studies for (1–8) demonstrate strong interactions between the receptor and the molecule and a firm protein-ligand complex formation described their effective role in enzymes’ inhibition. The bioactivity data obtained from both in silico analysis and in vitro studies are quite promising ones and the synthesized compounds may find a leading role in future drug discovery programs.

Full text of DOI:10.1016/j.jorganchem.2020.121357

Journal Pre-proof
Bioactive heteroleptic Bismuth(V) carboxylates: Synthetic Stratagem, characterization
and binding pattern validation
Mehwish Mehmood, Imtiaz-ud-Din, Sumaira Abbas, Syed Sikander Azam, Ihsan-ul-
Haq, Muhammad Nawaz Tahir, Nousheen Parvaiz, Asim Tameez-Ud Din
PII:
S0022-328X(20)30259-X
DOI:
https://doi.org/10.1016/j.jorganchem.2020.121357
JOM 121357
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 10 March 2020
Revised Date: 23 May 2020
Accepted Date: 25 May 2020
Please cite this article as: M. Mehmood, Imtiaz-ud-Din, S. Abbas, S.S. Azam, Ihsan-ul-Haq, M.N. Tahir,
N. Parvaiz, A. Tameez-Ud Din, Bioactive heteroleptic Bismuth(V) carboxylates: Synthetic Stratagem,
characterization and binding pattern validation, Journal of Organometallic Chemistry (2020), doi: https://
doi.org/10.1016/j.jorganchem.2020.121357.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition
of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of
record. This version will undergo additional copyediting, typesetting and review before it is published
in its final form, but we are providing this version to give early visibility of the article. Please note that,
during the production process, errors may be discovered which could affect the content, and all legal
disclaimers that apply to the journal pertain.
©
2020 Published by Elsevier B.V.

Bioactive Heteroleptic Bismuth(V) Carboxylates: Synthetic Stratagem,
Characterization and Binding Pattern Validation
a
a*
a
b
c
Mehwish Mehmood , Imtiaz-ud-Din , Sumaira Abbas , Syed Sikander Azam , Ihsan-ul-Haq
d
b
e
Muhammad Nawaz Tahir , Nousheen Parvaiz , Asim Tameez-Ud Din
a
Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan.
Computational Biology Lab, National Center for Bioinformatics, Quaid-i-Azam University,
b
Islamabad 45320, Pakistan
c
Department of Pharmacy, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad
4
5320, Pakistan.
d
Department of Physics, University of Sargodha, Sargodha 40100, Pakistan.
e. Rawalpindi Medical University, Rawalpindi, Pakistan
Corresponding Author: drimtiazuddin@yahoo.com
Abstract
A series of heteroleptic triorganobismuth(V) carboxylates (1-8) of general formula
Ar Bi(COOR) ; where Ar = C H (1-4), p-CH C H (5-8) and R = C H (1, 5), 2-CH C H (2,
3
2
6
5
3
6
4
10
7
3
6
4
6
2 3 6 3 6 4
), 3, 4- (OCH CH )C H (3, 7), 2-ClC H (4, 8); were synthesized by a stoichiometric reaction
between the precursor, Ar BiBr and the respective carboxylic acid, using triethylamine as a base
3
2
in dry toluene. They were characterized by FT-IR, NMR spectroscopy and X-ray diffraction
technique to get unequivocal evidence for their structural motifs. The single crystal XRD data for
(2 & 5) revealed the existence of five coordinated bismuth centre having distorted trigonal
bipyramidal molecular geometry, whereas (6) described weakly hexacoordinated bismuth
including a unique anisobidentate interaction of one carboxyl group with the resultant distorted
octahedral molecular geometry. The molecular docking studies demonstrate that compounds (1,
2
and 7) give significant GOLD fitness scores of 60.09, 62.65 and 56.30 against EGFR tyrosine
kinase, human pancreatic alpha amylase and H. pylori urease respectively. The synthesized
compounds were also preliminary screened for their antimicrobial, α-amylase inhibition and
protein kinase inhibition activities to determine their biological efficacy. The antibacterial
activity profile for (2) looks good with MIC value 6.25 µg/mL against E.coli whereas, (1, 2 and
5
) show significant antifungal activity against A.flavus having MIC value of 6.25 µg/mL and the
values are comparable to the reference drug(s). Compound (6) displays significant % alpha
amylase inhibition of 34.80, whereas (2) exhibit 30 mm bald inhibition zone for protein kinase
1

inhibition study, thus, proving their worth as moderate enzyme inhibitors. The molecular
docking studies for (1-8) demonstrate strong interactions between the receptor and the molecule
and a firm protein-ligand complex formation described their effective role in enzymes’ inhibition
.The bioactivity data obtained from both in silico analysis and in vitro studies are quite promising
ones and the synthesized compounds may find a leading role in future drug discovery programs.
Keywords: Bismuth carboxylates, X-ray Structure, H. pylori, Enzyme inhibition, Molecular
docking.
1
. INTRODUCTION
Bismuth is considered to be the least toxic heavy metal which is stable and possesses medicinal
importance since 1900 especially when a mixture of bismuth nitrate (or chloride) with common
hydroxyl carboxylic acid began to be used in wide range of medicinal capacities [1, 2]. Being a
green element and having lowest toxicity level, most of its’ compounds are used in some
commercially available medicines [3, 4]. The important derivatives of bismuth, being currently
used as medicinal products, are colloidal bismuth subcitrate (CBS) with the trade name of De-
®
®
Nol and bismuth subsalicylate (BSS) trade named as Pepto-Bismol [5-10]. These medicines
are used worldwide to control dyspepsia, diarrhea, duodenal and peptic ulcers caused by
bacterial strain named Helicobacter pylori. The organometallic complexes of bismuth are of
extraordinary interest due to their chemically well-defined structure and possibility of tuning
their both activity & toxicity [11, 12]. Over the past few years, bismuth derivatives of
carboxylates, thiocarboxylates, amides, sulfamates and sulfonates have also been explored for
their possible in vitro activity against H. pylori and found promising results [13-17].
Urea amino-hydrolase, commonly known as urease, is a nickel containing enzyme which is
responsible for the synthesis of urea into carbamic acid and ammonia. The carbamic acid further
hydrolyses under the action of urease to form carbonic acid and a molecule of ammonia.
Ammonia, being strong base, is responsible for elevation of pH and consequently it creates
feasible scenario for the survival of H. pylori in stomach that have harsh acidic conditions.
Moreover additional production of ammonia also leads to the formation of certain cytotoxins like
monochloramine which is responsible for causing peptic ulcer and gastric carcinoma [18, 19].
The epidermal growth factor receptor (EGFR) tyrosine kinases are considered to be responsible
2

for cell growth and its irregular behavior may lead to the development of tumors in body organs
like lungs, breast, ovary and colon. It has been reported that blocking of EGFR tyrosine kinases
may serve as a tool to prevent the growth of cancerous cells [20]. The human pancreatic alpha
amylase is responsible for cleaving bulky starch molecules into glucose so as to enable them to
cross the blood brain barrier; however, an excessive conversion of starch into glucose may cause
hyperglycemia or diabetes mellitus which is an endocrine disorder [21].
In continuation to our previous work [22-24], we report here the synthesis, structural
characterization and biological applications of triarylbismuth(V) derivatives (1-8). The
synthesized compounds were preliminary assayed for their possible agentive role as
antimicrobial, alpha amylase and protein kinase inhibitors besides checking their level of toxicity
using brine shrimp lethality assay. One of the methods of computer-aided drug design (CADD),
known as molecular docking, was also carried out to validate the binding pattern of H. pylori
urease, EGFR tyrosine kinase and human pancreatic alpha amylase with the synthesized
compounds. In recent times, the application of in silico tools provide an additional support to the
experimental data for the development and discovery of new drugs [25, 26]. The molecular
docking approach has been used to model the interactions between the selected drug receptors
and the synthesized bismuth(IV) compounds to unravel their behavior in active sites of the target
protein(s).
2
2
. Experimental Section
.1 Materials and methods
The commercially available chemicals were purchased from Sigma Aldrich (USA). Some of
which are; 2-napthoic acid, o-toluic acid, 3,4-diethoxybenzoic acid and 2-chlorobenzoic acid and
were used as received. Tri-phenylbismuth(V) / tri-p-tolylbismuth(V) dibromide were prepared by
a reported methodology [27]. All the solvents used were of analytical grade and dried before use
[28]. The melting point of the compounds were determined by using electro thermal melting
point apparatus (model MP-D Mitamura Riken Kogyo Japan). The IR spectra were recorded with
1
13
Bio-Rad Excalibur (model FTS 3000 MX), as KBr discs. The multinuclear ( H, C) NMR
spectra were recorded on Bruker Advance Digital 300 MHz FT-NMR spectrometer
(
Switzerland) in deuterated chloroform as solvent relative to Me Si as internal reference. The
4
single crystal X-ray diffraction analysis was performed on Bruker Kappa APEXII CCD
3

diffractometer equipped with a four-circle goniometer. The X-ray structures were solved with the
ShelXT structure solution program using Direct Methods and refined with the ShelXL-1997
refinement package using Least squares minimization.
2
.2 Synthesis
The compounds (1-8) were synthesized using the procedure as reported earlier with slight
modification [17, 29, 30]. Firstly triarylbismuth(III) species,symbolized as Ar Bi(III) (where, Ar
C H -, CH -C H ), were synthesized by reacting the respective Grignard’s reagent with BiCl
3
3
=
6
5
3
6
4
o
in dry THF under argon at 0 C, and the reaction mixture was stirred for 8-10 hours followed by
extraction in chloroform. The oxidative addition of the respective Ar Bi(III) species was
3
accomplished by drop wise addition of liquid bromine into the solution to achieve the precursor
as Ar
The second step involves the preparation of target compounds (1-8) by using stoichiometric
amounts of the respective carboxylic acid (1 mmole), Ar BiBr (0.5 mmole) and triethylamine (1
3 2
Bi(V) Br [31].
3
2
mmole) as base in 20 mL toluene. The reaction mixture was refluxed for 3-4 hours at room
temperature under argon gas. The triethylammonium bromide salt, thus formed, was filtered off
and the clear filtrate was allowed to evaporate at room temperature for solidification which was
subsequently recrystallized in a mixture of chloroform and pet-ether (3:1) to get the pure
compound(s) as illustrated in Scheme-1.
Scheme-1: Synthetic Stratagem for 1-8
4

The physico-analytical and spectroscopic data pertaining to the synthesized compounds are
summarized as follows:
Bis(2-napthoato)triphenylbismuth(V)
(1)
Quantities used; 2-napthoic acid (0.17 g, 1 mmole), triphenylbismuth dibromide (0.3 g, 0.5
o
mmole), triethylamine (0.14 mL, 1 mmole), crystalline product, yield: 75%, m.p: 159 C, Anal.
Calcd. for C40
H29BiO
4
(782.64g/mole), C, 61.39, H, 3.73%, Found, C, 61.36, H, 3.74%; FT-IR
-1
data (ν, cm , KBr) C-H
(3052), COOasym (1555), COOsym (1323), ∆ν (232), Bi-C (469), Bi-
aromatic
1
O (444); H NMR data (300 MHz, CDCl , ppm) δ 8.56 (s, 2H, Ar-H ), 8.42-8.40 (d, 2H,
3
d
J=7.2Hz, Ar-H ), 8.08-8.05 (d, 2H, J=7.5Hz, Ar-H ), 7.93-7.91 (d, 4H, J=7.5Hz, Ar-He = e’),
h
g
7
.85-7.79 (t, 4H, J=7.8Hz, Ar-Hf = f’), 7.66 -7.61 (t, 9H, J=7.5Hz, Ar- Hb = b’= c), 7.55-7.53 (d, 6H,
13
J=6.9Hz, Ar-Ha = a’); C NMR data (75MHz, CDCl
3
, ppm) δ 160.7 (COO),134.1 (Bi-Cipso), 131.3
(o-CHaromatic), 130.8 (m-CHaromatic), 129.1 (C-COO), 127.6 (p-CHaromatic).
Bis(2-methylbenzoato)triphenylbismuth(V)
(2)
Quantities used; 2-methylbenzoic acid (0.14 g, 1 mmole), triphenylbismuth dibromide (0.3 g, 0.5
o
mmole), triethylamine (0.14 mL, 1 mmole), crystalline product, yield: 81%, m.p: 128 C, Anal.
Calcd. for C H BiO (710.57g/mole), C, 57.47, H, 4.11%, Found, C, 57.48, H, 4.12%; FT-IR
3
4
29
4
-1
data (ν, cm , KBr) C-Haromatic (3052), C-Haliphatic (2962), COOasym (1547), COOsym (1336), ∆ν
1
(
211), Bi-C (488), Bi-O (444); H NMR data (300 MHz, CDCl , ppm) δ 8.37-8.35 (d, 6H,
3
J=7.2Hz, Ar- Ha = a’), 7.74-7.72 (d, 2H, J=7.5 Hz, Ar-H ), 7.64-7.59 (t, 6H, J=7.5Hz, Ar-Hb = b’),
d
7
c e
.51-7.46 (t, 3H, J=7.2Hz, Ar-H ), 7.28 -7.24 (t, 2H, J=7.5Hz, Ar- H ), 7.17-7.11 (t, 4H,
1
3
J=7.5Hz, Ar- H ), 2.41 (s, 6H, -CH ); C NMR data (75 MHz, CDCl , ppm) δ 174.8 (COO),
f, g
3
3
1
2
3
61.5 (Bi-Cipso), 138.6 (C-CH ), 133.3 (C-COO), 134.1 (o-CHaromatic), 131.0 (m,p-CHaromatic),
1.4 (-CH3).
Bis(3,4-diethoxybenzoato)triphenylbismuth(V)
(3)
Quantities used; 3,4-diethoxybenzoic acid (0.21 g, 1 mmole), triphenylbismuth dibromide (0.3 g,
o
0
.5 mmole), triethylamine (0.14 mL, 1 mmole), crystalline product, yield: 82%, m.p: 170 C,
Anal. Calcd. for C H BiO (858.73 g/mole), C, 55.95, H, 4.81%, Found, C, 55.93, H, 4.80%;
4
0
41
8
5

-1
FT-IR data (ν, cm , KBr) C-Haromatic (3051), C-Haliphatic (2982), COOasym (1558), COOsym (1327),
1
∆
ν (231), Bi-C (510), Bi-O (443); H NMR data (300 MHz, CDCl , ppm) δ 8.32-8.30 (d, 6H,
3
J=7.5 Hz, Ar-Ha = a’), 7.63-7.61 (t, 6H, J=4.8 Hz, Ar-H b = b’), 7.59 (s, 2H, Ar-H ), 7.57-7.48 (t,
f
3
c d
H, J=13.2 Hz, Ar- H ), 7.45-7.43 (d, 2H, J=7.2 Hz, Ar- H ), 6.83 -6.81 (d, 2H, J=8.4 Hz, Ar-
1
3
H ), 4.15-4.08 (q, 8H, J=6.6Hz, -CH ), 1.47-1.43 (t, 12H, J=6.6 Hz, -CH ); C NMR data (75
e
2
3
MHz, CDCl
3
, ppm) δ 172.4 (COO),161.1 (Bi-Cipso), 151.7 (C
3
4
-OEt), 147.7 (C -OEt), 133.9 (o-
CHaromatic), 131.2 (m-CHaromatic), 130.6(p-CHaromatic), 64.5 (-CH ), 14.8 (-CH ).
2
3
Bis(2-chlorobenzoato)triphenylbismuth(V)
(4)
Quantities used; 2-chlorobenzoic acid (0.16 g, 1 mmole), triphenylbismuth dibromide (0.3 g, 0.5
o
mmole), triethylamine (0.14 mL, 1 mmole), crystalline product, yield: 75%, m.p: 138 C, Anal.
Calcd. for C H BiCl O (750.41g/mole), C, 51.15, H, 3.09%, Found, C, 51.17, H, 3.06%; FT-
3
2
23
2
4
-1
IR data (ν, cm , KBr) C-H
(3062), COOasym (1587), COOsym (1347), ∆ν (240), Bi-C (464),
aromatic
1
Bi-O (405); H NMR data (300 MHz, CDCl , ppm) δ 8.40-8.37 (d, 6H, J=7.2 Hz, Ar- Ha = a’),
3
7
.69-6.70 (d, 6H, J=6.9Hz, Ar-Hb = b’), 7.65-7.62 (d, 2H, J=6.9Hz, Ar- H ), 7.53-7.50 (m, 6H, Ar-
d
1
3
H
c 3
e, f, g), 7.31-7.26 (t, 3H, J=8.7Hz, Ar-H ); C NMR data (75 MHz, CDCl , ppm) δ 172.2
(COO), 159.7 (Bi-Cipso), 134.3 (o-CHaromatic), 133.9 (C-Cl), 131.7 (C-COO), 131.4 (m,p-
CHaromatic).
Bis(2-napthoato)tri(p-tolyl)bismuth(V)
(5)
Quantities used were 2-napthoic acid (0.17 g, 1 mmole), p-tritolylbismuth dibromide (0.31 g, 0.5
o
mmole), triethylamine (0.14 mL, 1 mmole), crystalline product, yield: 78%, m.p: 232 C, Anal.
4
Calcd. for C43H35BiO (824.72g/mole), C, 62.62, H, 4.28%, Found, C, 62.62, H, 4.27%; FT-IR
-1
Data (ν, cm , KBr) C-H
(3055), C-Haliphatic (2961), COOasym (1562), COOsym (1326), ∆ν
aromatic
1
(
236), Bi-C (470), Bi-O (415); H NMR Data (300 MHz, CDCl , ppm) δ 8.56 (s, 2H, Ar-H ),
3
d
8
h g
.29-8.27 (d, 2H, J=8.1Hz, Ar-H ), 8.08-8.06 (d, 2H, J=7.8 Hz, Ar-H ), 7.93-7.91 (d, 4H,
J=6.3Hz, Ar-He = e’), 7.85-7.79 (t, 4H, J=7.8 Hz, Ar- Hf = f’), 7.52-7.49 (d, 6H, J=8.1 Hz, Ar-Ha =
13
a’), 7.44-7.41 (d, 6H, J=8.1Hz, Ar-Hb = b’), 2.41(s, 9H, -CH ); C NMR Data (75 MHz, CDCl ,
3
3
ppm) δ 157.1 (COO), 1401.0 (Bi-Cipso), 133.9 (o-CHaromatic), 131.8 (m-CHaromatic), 130.8 (CCOO),
27.4 (p-CHaromatic), 21.4 (-CH3).
1
Bis(2-methylbenzoato)tri(p-tolyl)bismuth(V)
(6)
6

Quantities used; 2-methylbenzoic acid (0.14 g, 1 mmole), p-tritolylbismuth dibromide (0.31 g,
o
0
.5 mmole), triethylamine (0.14 mL, 1mmole), crystalline product, yield: 75%, m.p: 151 C,
Anal. Calcd. for C H BiO (752.65 g/mole), C, 59.04, H, 4.69%, Found, C, 59.02, H, 4.71%;
3
7
35
4
-1
FT-IR data (ν, cm , KBr) C-Haromatic (3053), C-Haliphatic (2964), COOasym (1588), COOsym (1338),
1
∆
ν (250), Bi-C (474), Bi-O (434); H NMR data (300 MHz, CDCl , ppm) δ 8.24-8.22 (d, 6H,
3
d
J=8.4Hz, Ar- Ha = a’), 7.75-7.31 (d, 2H, J=6 Hz, Ar-H ), 7.46-7.39 (t, 6H, J=8.1Hz, Ar-Hb = b’),
1
3
7
.42-7.39 (d, 2H, J=8.1Hz, Ar- H ), 7.28-7.12 (t, 4H, J=9Hz, Ar- H ), 2.41 (s, 15H, -CH ); C
g
e,f
3
NMR data (75 MHz, CDCl , ppm) δ174.5 (COO), 170.4 (Bi-C ), 158.0 (C-CH ), 141.5 (p-
3
ipso
3
CH
3
), 140.8 (C-COO), 133.9 (o-CHaromatic), 131.0 (m-CHaromatic), 22.0 (CH
3
-CHaromatic), 21.4
(
CH -p-CHaromatic).
3
Bis(3,4-diethoxybenzoato)tri(p-tolyl)bismuth(V)
(7)
Quantities used; 3,4-Diethoxybenzoic acid (0.21 g, 1 mmole), p-tritolylbismuth dibromide (0.31
o
g, 0.5 mmole), triethylamine (0.14 mL, 1 mmole), crystalline product, yield: 75%, m.p: 201 C,
Anal. Calcd. for C H BiO (900.81 g/mole), C, 57.33, H, 5.26%, Found, C, 57.34, H, 45.26%;
4
3
47
8
-1
FT-IR data (ν, cm , KBr) C-Haromatic (2984), C-Haliphatic (2922), COOasym (1549), COOsym (1351),
1
∆
ν (198), Bi-C (474), Bi-O (434); H NMR data (300 MHz, CDCl , ppm) δ 8.19-8.16 (d, 6H,
3
J=8.1Hz, Ar-Ha = a’), 7.62-7.59 (t, 2H, J=4.8 Hz, Ar-H ), 7.52 (s, 2H, Ar-H ), 7.40-7.37 (d, 6H,
d
f
J=8.1Hz, Ar-Hb = b’), 6.82-6.80 (d, 2H, J=8.1 Hz, Ar- H
e
2
), 4.15-4.08 (q, 8H, J=6.6 Hz, -CH ),
1
3
2
1
.37(s, 9H, p-CH ), 1.47-1.43 (t, 12H, J=6.9Hz, -CH ); C NMR data (75 MHz, CDCl , ppm) δ
3
3
3
3 4
72.1 (COO), 154.4 (C -OEt), 151.5 (C -OEt), 140.8 (p-CHaromatic), 133.8 (o-CHaromatic), 132.1
(
m-CHaromatic), 64.5 (-CH ), 21.4 (p-CH3aromatic), 14.6 (-CH3).
2
Bis(2-chlorobenzoato)tri(p-tolyl)bismuth(V)
(8)
Quantities used; 2-chlorobenzoic acid (0.16 g, 1 mmole), p-tritolylbismuth dibromide (0.31 g,
o
0
.5 mmole), triethylamine (0.14 mL, 1 mmole), crystalline product, yield: 75%, m.p: 110 C,
Anal. Calcd. for C H BiCl O (793.49 g/mole), C, 52.98, H, 3.68%, Found, C, 52.95, H,
3
5
29
2
4
-1
3
.70%; FT-IR data (ν, cm , KBr) C-H
(3068), C-Haliphatic (2917), COOasym (1585), COOsym
aromatic
1
(
1353), ∆ν (232), Bi-C (472), Bi-O (426); H NMR data (300 MHz, CDCl , ppm) δ 8.26-8.24 (d,
3
6
2
H, J=8.1Hz, Ar- Ha = a’), 7.52-7.42 (m, 8H, Ar- Hd, e, f, g), 7.27-7.24 (d, 6H, J=8.1Hz, Ar- Hb=b’),
1
3
.41 (s, 9H, -CH
3
); C NMR data (75 MHz, CDCl
3
, ppm) δ 156.2 (COO), 154.1 (Bi-Cipso), 141.7
7

(C-Cl), 141.2 (p-CHaromatic), 138.2 (CCOO), 134.1 (o-CHaromatic), 132.1 (m-CHaromatic), 21.4 (-
CH3).
2
.3 X-ray Crystallography
Single crystal XRD analyses for 2, 5 and 6 were performed by mounting a suitable size crystal
on a thin glass fiber and kept at 296(2) K. All the reflections were collected on Kappa APEXII
CCD (Bruker) diffractometer equipped by graphite monochromatic radiation MoKα (λ=
o
0
.71073A ) [32]. For structural refinement, SHELXL 2014/7 (Sheldrick, 2014) program was
used. All the crystallographic details and structural refinement parameters are given in Tables 1
and 2.
2
2
.4 Biological Activities
.4.1 Antibacterial activity
To evaluate the antibacterial activity for (1-8), the refreshed bacterial cultures of Staphylococcus
aureus (ATCC-6538), Bacillus subtilis (ATCC-6633), Escherichia coli (ATCC-25922) and
Klebsiella pneumoniae (ATCC-1705) were employed in order to determine their minimum
inhibitory concentration (MIC) by using Broth dilution technique and the detailed procedure has
been given as supplementary files [33].
2
.4.2 Antifungal activity
The antifungal activity of the synthesized compounds was explored by using agar disc diffusion
technique. The spores of four fungal strains, namely Aspergillus fumigatus (FCBP-66), A. niger
(
FCBP-0198), Mucor species (FCBP-0300) and Aspergillus flavus (FCBP-0064) were used in
order to determine MIC and for details see supplementary files [34].
2
.4.3 Alpha amylase inhibition assay
The alpha amylase inhibition assay was performed to evaluate the antidiabetic potential of
synthesized complexes as well as the precursors by using a reported method [35]. Acarbose (250
µM) and DMSO was used as positive and negative control respectively. Absorbance was
measured at 540 nm and percentage inhibition of alpha amylase enzyme was calculated, and for
detailed procedure sees supplementary files.
8

2
.4.4 Protein kinase inhibition assay
Protein kinase inhibition assay was executed by utilizing Streptomyces 85E bacterial strain and
surfactin and DMSO were used as positive and negative controls respectively. The protocol
details for the assay have been given as supplementary files [36].
2
.4.5 Brine shrimp lethality assay
Brine shrimp lethality assay was performed according to the standard protocol with little
modifications [34]. The doxorubicin (4 mg/ml DMSO) and DMSO were used as positive and
negative standards respectively. The degree of lethality induced by each compound was
quantified after 24 hours. The median lethal doses (LD50) of the compounds with ≥ 50%
mortality was calculated using table curve 2D vs. 5.01 software and for procedural details see
supplementary files.
2
.4.6 Computational Studies
Molecular docking studies were performed using Genetic Optimization for Ligand Docking
GOLD) program to explore the antibacterial, antidiabetic and anticancer potential of the
(
synthesized compounds [37, 38]. The GOLD implements a genetic algorithm for docking
flexible lead compounds into the active pocket of the selected receptor. The crystal structures of
Helicobacter Pylori urease (PDB ID: 1E9Y), Human Pancreatic Alpha Amylase (PDB ID:
5
U3A), and Epidermal Growth Factor Receptor tyrosine kinase (PDB ID: 1M17) were retrieved
from RCSB Protein Data Bank (PDB) for molecular docking studies. It is crucial to identify the
active pocket of the protein for targeted inhibition. The binding site of the selected target proteins
was taken from the literature studies [39-41] and for more details see elsewhere [42]. Gold
fitness function was selected to rank active compounds according to their binding affinity with
the active site residues of the selected receptors. Compounds exhibiting greater Gold fitness
score will be considered as having better binding affinity with the receptor [43].
3
3
. Results and discussion
.1 Chemistry
9

The salt metathesis method was employed to prepare the pure products from the reaction
mixture. The triarylbismuth(V) carboxylates (1-8) were synthesized by a stoichiometric reaction
between the substituted benzoic acid and appropriate triarylbismuth(V) dibromide in dry toluene,
using triethylamine as a base (Scheme 1). They are stable in moist air and for their stability tests
see elsewhere [27] and were characterized by FT-IR, NMR spectroscopy and single crystal XRD
technique. The data have already been mentioned in the experimental section.
3
3
.2 Spectroscopic Studies
.2.1 FTIR Data
-1
The IR absorption band for hydroxyl stretching frequency, νOH, appeared around 3400 cm in the
free carboxylic acid (ligand), whereas it disappeared in complexes (1-8) which clearly indicate
deprotonation of acid and successful coordination to the organobismuth moiety through its
oxygen(s). The stretching frequencies for carboxyl group appeared in range 1547-1588 & 1323-
-1
1
353 cm for νasym (COO) and νsym (COO) respectively. The ∆ν [= νasym (COO) – νsym (COO)]
-1
for carboxyl group(s) has been determined to be greater than 200 cm for all the synthesized
complexes [44, 45] which depict its monodentate and/or anisobidentate mode of coordination
with the metal centre which was further authenticated by single crystal XRD data for (2, 5 and
6
). Another indication for the deprotonation of the carboxylic acid(s) came from lowering of
-1
values of symmetric and asymmetric stretching frequency by 30-40 cm in the complexes than in
-1
free acids. The presence of two new stretching bands in range 462-510 and 405-444 cm
demonstrate the bismuth linkages to carbon ((Bi-C) and oxygen (Bi-O) respectively in the
synthesized compounds when compared with the spectra of the free ligands [27]. The other
characteristic vibrational bands attributable to certain organic groups, present in the compounds,
-1
-1
are; 2984-3068 cm for ν (C-Haromatic) and 2917-2982 cm for ν (C-Haliphatic).
The IR absorption bands appeared for (6) are, ν C-Haromatic (3053), ν C-Haliphatic (2964), νasym
COO (1588), νsym COO (1338), ν Bi-C (474), ν Bi-O (434). The characteristic ∆ν value for this
-1
particular carboxyl group is 250 cm , which qualified the ligand for anisobidentate mode of
chelation with the organobismuth moiety [27]. Thus IR data fully support the proposed structural
motifs for the synthesized compounds and are in accordance to the earlier reports [27, 46].
3
.2.2 NMR Data
10

1
The chemical structures assigned to (1-8) were further ascertained by their multinuclear ( H and
1
3
C) NMR spectral data which were recorded in CDCl as solvent. The data explicitly determine
3
magnetically non-equivalent protons present in the synthesized organobismuth dervatives along
1
with their coupling constant values. The H NMR data for these compounds revealed the
successful coordination of the appropriate carboxylic acid to the metal centre by its
deprotonation as indicated by absence of resonance around 11 ppm which was present in the free
acids. The resonances for all the aromatic protons were observed in range 8.30-7.30 ppm as
reported earlier [22, 23]. The ethoxy protons of (3, 7) show quartet and triplet signals for -CH2-
3
and -CH groups that resonate in range 4.15-4.08 and 1.47-1.43 ppm respectively [27].
1
3
The C NMR data for (1-8) clearly manifested the presence of all the unique carbons in their
structural motifs. The characteristic resonance peak pertaining to C=O functionality appears in
range 174.8-156.2 ppm for the compounds. The methyl carbon of p-tolyl group resonate around
2
1 ppm as for (5-8) which further confirmed attachment of the respective arylbismuth moiety to
the substituted carboxylic acid. The aromatic carbons appear in their usual region such as; Cipso
Bi (161.5-134.1), o-CHaromatic (131.3-134.3), o-CHaromatic (130.8-132.1), p-CHaromatic (141.2-
27.4), C -OEt (151.7-154.4), C -OEt (147.7-151.5) [30]. The -CH and -CH carbons of ethoxy
-
1
3
4
2
3
group present in compounds (3, 7) appear at 64.5 and 14.8 ppm respectively [30]. The coupling
constants provide useful structural information as well as about precise location of the
substituent on the aromatic ring.
3
.3 X-ray Crystallography
Three synthesized compounds; [BiPh (O CC H (2-CH )) ] (2), [Bi(p-tol) (O CC H ) ] (5) and
3
2
6
4
3
2
3
2
10 7 2
3 2 6 4 3 2
[Bi(p-tol) (O CC H (2-CH )) ] (6), were also analyzed by single crystal XRD technique and
their ORTEP diagrams are shown in Figures 1-3 whereas the selected bond lengths and bond
angles are presented in Tables 1 and 2. The XRD data for (2 & 5) revealed the existence of five
coordinated bismuth centre having distorted trigonal bipyramidal molecular geometry whereas
compound (6) described hexacoordination for bismuth atom including a unique anisobidentate
interaction of one carboxyl group that rendered the molecular geometry as distorted octahedral. It
is worth mentioning here that the lability of Bi-O interaction is sensitive to the basicity of the
donor species and the reactions, involving multifunctional ligands, are very dependent on
11

reaction conditions. Moreover, flexibility of the ligand backbone may result in structural
variability in terms of chelation and bridging.
As mentioned earlier the compounds (2 & 5) are isostructural with each other having slight
changes in bond lengths and bond angles. They emerging out five coordinated metal centre
occupies carboxylates at axial positions and phenyl or p-tolyl moiety fits in equatorial positions
[12, 29]. The Bi-C bond lengths for phenyl and p-tolyl groups appear in range 2.206(4) -
o
2
.223(5) and 2.185(4) - 2.209(5) with average bond length of 2.247 and 2.197 A respectively
and the data are compatible with the reported ones [29, 30, 47]. The bond lengths for Bi1-O1 and
o
Bi1-O3 appear at 2.276(4) and 2.292(4) A for (2), whereas these values fall at 2.288(3) and
o
2
.293(3) A respectively for (5). The XRD data for two compounds are in accordance to IR
findings that described monodentate binding behavior for the two carboxylates with the metal
centre. However the Bi-C bond lengths for phenyl and p-tolyl groups are found in range 2.185(4)
o
-
2.288(4) with the average bond length of 2.236 A for compound (6). The bond lengths for Bi1-
o
O1 and Bi1-O3 in the complex are determined as 2.294(3) and 2.286(3) A respectively, whereas
o
the bond length for (Bi1-O2) is determined to be 2.729(3) A indicating lengthening of the bond
that compel the carboxyl group to coordinate with the bismuth centre via anisobidentate manner
and the molecule assumed overall distorted octahedral geometry [27].
12

Table-1: Crystallographic data and refinement details for 2, 5 and 6
Identification Codes
2
5
6
Empirical formula
C H O Bi
C H BiO4
43 35
C H O Bi
3
4
29
4
37 35
4
Formula weight
7
10.55
96(2)
824.69
296(2)
752.63
296(2)
Temperature/K
2
Crystal system
Triclinic
P-1
Monoclinic
Monoclinic
Space group
P2 /n
1
P2 /c
1
a/Å
b/Å
c/Å
α/°
β/°
8
.7736(16)
12.9031(9)
12.2299(9)
22.6797(18)
90
14.412(3)
1
0.672(2)
6.635(3)
9.948(4)
10.6492(19)
1
22.286(3)
9
90
1
1
03.612(4)
02.951(5)
100.520(3)
90
105.089(9)
γ/°
90
3302.5(11)
4
3
Volume/Å
1
432.9(4)
2
3518.8(5)
4
Z
-1
ꢀ/mm
6
6
.189
96.0
5.052
5.375
F(000)
Crystal size/mm
Radiation
1632.0
1488.0
3
0
.400 × 0.320 × 0.160
0.420×0.230×0.180
MoKα (λ = 0.71073)
0.380 × 0.260 × 0.220
MoKα (λ = 0.71073)
MoKα (λ = 0.71073)
2
θ range for data
collection/°
5.29 - 56.344
4.9°- 53.9°
4.816 - 55.92
Index ranges
-11 ≤ h ≤ 11,
-16 ≤ h ≤ 15,
-14 ≤ k ≤ 15,
-28 ≤ l ≤ 26
-18 ≤ h ≤ 18,
-14 ≤ k ≤ 12,
-29 ≤ l ≤ 27
-
14 ≤ k ≤ 14,
16 ≤ l ≤ 21
-
Reflections collected
1
8133
23550
22673
Independent
reflections
6711
7671
7879
Rint
6
1
.189
.022
0.0571
0.968
0.0528
1.014
Goodness of Fit
Final R
indexes[I>=2σ (I)]
R
wR
1
= 0.0354,
R = 0.0349,
1
R = 0.0365,
1
= 0.0685
wR
= 0.0708
2
2
wR = 0.0878
2
Final R indexes [all
data]
R
1
= 0.0643,
1
R = 0.0628,
R = 0.0476,
1
wR = 0.0787
wR = 0.0807
2
2
wR = 0.0931
2
13

Table-2 : Selected bond lengths (Å) and bond angles (°) for 2, 5 and 6
2
Bi1—C29 2.206 (4)
C23—Bi1—O1 91.84° (16)
C17—Bi1—O1 84.88° (16)
C29—Bi1—O3 93.01° (16)
C23—Bi1—O3 89.36° (17)
C17—Bi1—O3 84.27° (17)
O1—Bi1—O3 168.91° (13)
C1—O1—Bi1 105.7° (3)
C9—O3—Bi1 108.0° (3)
Bi1—C23 2.210 (4)
Bi1—C17 2.223 (5)
Bi1—O1 2.276 (4)
Bi1—O3 2.292 (4)
C29—Bi1—C23 147.3° (2)
C29—Bi1—C17 104.41° (17)
C23—Bi1—C17 108.23° (18)
C29—Bi1—O1 91.92° (15)
5
Bi1—C37 2.185 (4)
C23—Bi1—O3 89.41 (14)
C30—Bi1—O3 85.70 (15)
C37—Bi1—O1 92.42 (14)
C23—Bi1—O1 92.51 (14)
C30—Bi1—O1 86.19 (15)
O3—Bi1—O1 171.87 (12)
C1—O1—Bi1 107.6 (3)
C12—O3—Bi1 109.5 (3)
Bi1—C23 2.202 (4)
Bi1—C30 2.209 (5)
Bi1—O1 2.293 (3)
Bi1—O3 2.288 (3)
C37—Bi1—C23 142.77 (19)
C37—Bi1—C30 109.47 (18)
C23—Bi1—C30 107.67 (17)
C37—Bi1—O3 90.82 (14)
6
Bi1—C17 2.198 (4)
C17—Bi1—O3 88.50° (14)
C31—Bi1—O3 90.69° (14)
C24—Bi1—O3 87.08° (14)
C17—Bi1—O1 89.49 ° (14)
C31—Bi1—O1 93.90° (14)
C24—Bi1—O1 87.95° (14)
O3—Bi1—O1 173.92° (10)
C1—O1—Bi1 103.7° (3)
C1—O1—Bi1 103.7° (3)
Bi1—C31 2.202 (4)
Bi1—C24 2.218 (4)
Bi1—O1 2.294 (3)
Bi1—O2 2.729 (3)
Bi1—O3 2.286 (3)
C17—Bi1—C31 150.27° (16)
C17—Bi1—C24 105.76° (16)
C31—Bi1—C24 103.88° (15)
14

Fig.1 ORTEP view showing 50 % probability ellipsoids for 2, with atom numbering scheme
Fig.2 ORTEP diagram for 5, showing 50 % probability ellipsoids with atom numbering scheme
15

Fig.3 ORTEP view for 6, showing 50 % probability ellipsoids with atom numbering scheme
16

3
.4 Biological Studies
Organobismuth(V) compounds have been considered to be potentially bioactive species owing
to their biocidal properties and low toxicity [3, 4]. They were preliminary screened for their
antimicrobial, alpha amylase and protein kinase inhibition activity so as to find out their
biological significance in medicinal chemistry.
3
.4.1 Antimicrobial assay
Compounds (1-8) were screened in vitro to determine their antimicrobial potential against four
bacterial as well as four fungal strains using the standard drugs cefixime or roxithromycin and
clotrimazole as the case may be and the data are given in Table-3. The compound 2, has shown
significant antibacterial activity against E.coli, having MIC value of 6.25 µg/mL, whereas 1, 5
and 8, with MIC value 12.5 µg/mL for each also exhibit good activity against the two bacterial
strains, namely B.subtilus and E.coli. The antifungal activity profile for 1, 2 and 5 described their
significant activity against A.flavus with MIC value of 6.25 µg/mL. The results are encouraging
when compare with relevant standard drug and data demonstrate that antimicrobial activity of the
target compounds became enhanced when appropriate carboxylic acids were complexed with
respective triarylbismuth moiety as evinced by their least MIC values (lesser the MIC value for
the compound, more it will be effective).
The increased antimicrobial activity of the compounds may be attributed to the effect of
pentavalent bismuth metal ion and the current data can be interpreted in light of Tweedy’s theory
of chelation [48]. The polarity of metal ion becomes generally reduced due to chelation because
of the partial sharing of positive charge of bismuth with the donor carboxylate moiety. The
delocalization of π electrons on the aromatic ring may also contribute in enhancing the
antimicrobial potential of the compounds when compared with the reported data [49]. The
presented work demonstrate that compounds 1, 2 and 5 showed significant MIC value of
6
.25µg/mL which have naphthalene and methyl substituents (electron donating group) in their
structural motifs that seem to facilitate the delocalization of π electrons within the system. The
delocalization further increase lipophilic character of the synthesized complexes that aids in
gaining entry into the lipid bilayer of bacterial and fungal cell membrane with ultimate increase
in their antimicrobial properties [50, 51].
17

Table.3 Antimicrobial activity data for (1-8)
MIC(µg/mL)
Number of
compounds
Antibacterial Strains
Antifungal Strains
Bacillus
Subtilis
Staphylococcus
Aureus
Klebsiella
Escherichia
coli
Aspergillus
Flavus
Aspergillus
Niger
Aspergillus
Mucor
Fumigatus
Pneumoniae
1
2
3
4
5
6
7
8
12.5
25
50
12.5
50
25
25
6.25
50
6.25
6.25
25
25
12.5
25
12.5
12.5
12.5
12.5
25
50
˃50
˃50
˃50
˃50
50
50
50
50
25
50
25
25
12.5
6.25
25
50
12.5
25
25
25
50
50
25
50
25
25
12.5
25
50
50
50
25
25
50
˃50
˃50
12.5
12.5
-
25
25
25
12.5
25
25
50
50
Ph
3
BiBr
2
50
25
25
12.5
12.5
-
12.5
12.5
-
12.5
12.5
-
(
p-tolyl) BiBr
25
25
12.5
0.334
12.5
1.11
3
2
Cefixime*
1.11
0.334
Roxithromycin*
0.334
0.334
0.334
0.334
-
-
-
-
Clotrimazole*
DMSO
-
-
-
-
-
-
-
-
10
-
5
-
5
-
2.5
-
*
-
Standard drug
No activity
3
.4.2 Alpha amylase inhibition
The compounds (1-8) were bioassayed for their chromogenic alpha amylase inhibition activity.
The reported percentage inhibition of alpha amylase has been observed at 100µg/mL, using
acarbose as a positive control and DMSO as a negative control and the data are presented in
Table 4. The data shows that (2) and (6) exhibit highest percentage inhibition of 31.49 and 34.80
%
respectively, as both compounds contain an electron donating group (-CH ) in their structures.
3
The activity of the complexes were also compared with the precursors, [Ph
3 2
BiBr and (p-
tolyl) BiBr ] and found the least % age inhibition of -33.54 and -33.70 % respectively for them,
3
2
but on derivatization with substituted carboxylic acids, the percent inhibition became enhanced
about 15 to 35 % for the metal complexes [27]. Hence greater the percentage inhibition value for
alpha amylase enzyme, more it will be effective against hyperglycemia or diabetes mellites. The
18

data are presented with the prospects that the reported compounds may prove themselves as
potent candidates in future drug development and delivery processes.
3
.4.3 Protein kinase inhibition assay
To evaluate the protein kinase inhibitory potential for (1-8) surfactin and DMSO were used as
positive and negative control and data are presented in Table 4. The non-toxic effect of DMSO
was verified by the absence of growth inhibition zone. A significant inhibition zone of 30 mm
bald phenotype corresponds to (2) which is equivalent to the standard drug (surfactin; 100 µg
/
disc) whereas (7) and (8) show bald zone at 20 mm for each. The zones of inhibition greater
than 20 mm bald and clear (zones) are attributable to significant activity and cytotoxic nature
respectively for the under trialed compounds. The electron donating group (-CH ) attached to the
3
carboxylic moiety in compound (2) is responsible for this exceptional percentage inhibition of
protein kinase enzyme at 100 µg disc loading. The assay involves Streptomyces 85E strain to
envisage the protein kinase inhibition, as it resembles with the eukaryotic cells that readily
provides evidence about anticancer and cytotoxic nature of the synthesized products. The protein
kinases are involved in phosphorylation of various eukaryotic cells, whereas the protein kinase
inhibitors are specifically involved in blocking them in order to stop the proliferation of
cancerous cells. The kinase inhibition data for some of the organobismuth compounds are
encouraging and may prove suitable agents in futuristic drug discovery projects [27].
3
.4.4 Brine shrimp lethality assay
The brine shrimp lethality assay is a simple, robust and least expensive technique for assessing
the cytotoxic nature of the synthesized organobismuth(V) complexes , so as to develop a toxicity
appraisal for them in comparison to the reference drug (doxorubicin). The results were
documented in term of LD50 value, which refer to the dose required to kill half of the tested
population in specific time duration (Table 4). The percentage mortality of Artemia salina was
tested in serial dilutions as 200, 100, 50 and 25 µg/mL. The least LD value for 1, 4 and 7 were
5
0
found to be 18.61, 5.25 and 19.05 µg/mL respectively, describing their toxic nature whereas 5
show the least toxic nature having the value of 114.39 µg/mL,. The data suggest that the
synthesized compounds are moderately toxic and can be further optimized for future drug
discovery processes by altering their structural motifs [24].
19

Table.4 Alpha amylase and Protein kinase inhibition activity data for (1-8) with LD50 values
Alpha amylase
inhibition assay
Protein kinase inhibition
assay
Brine shrimp lethality assay
% age Mortality
Number of
compounds
Zones (mm) at 100µg/disc
%
age inhibition
LD50
2
00
100
50
25
1
00 (µg/mL)
(µg/mL)
Clear zone
Bald zone
(mm)
(µg/mL)
(µg/mL)
(µg/mL)
(µg/mL)
(
mm)
25
-
1
18.58
31.49
11.65
27.40
21.10
34.80
14.64
23.50
-33.54
-33.70
69.29
-
100
100
100
100
100
100
100
100
100
100
80
60
70
50
50
80
0
60
40
20
80
0
18.61
44.45
56.95
5.25
2
30
18
-
3
22
30
-
60
4
90
5
-
10
114.39
24.77
19.05
42.54
30.31
25.01
6
-
15
20
20
20
-
90
80
80
60
90
90
50
60
30
30
50
7
8
-
90
25
-
70
Ph BiBr
100
100
3
2
(
p-tolyl)
3
BiBr
2
24
Acarbose*
Surfactin*
-
-
30
-
Doxorubicin*
DMSO
90
-
80
-
60
-
30
-
5.93
-
-
*
Standard drug
-
No activity
3
.5 Computational Studies
Molecular docking studies of the synthesized compounds against various enzymes were carried
out to find out their biological potential as the CADD tools are diagnostic in this regards.
3
.5.1 H. pylori Urease
The molecular docking data for (1-8), presented in Table 5, suggest that compound (7) exhibit
the highest GOLD fitness score of 56 and could serve as a lead compound in the present study.
The active site residues of protein that interact directly with (7) include Asp403, Ala407, His459,
Cys559, His560, Arg576, Val558, Met555, Asp554, Glu551, Arg606, Gly605, Gln602, Ile376,
20

Ser601, Val607, and Thr408 (Fig.4). The binding pattern analysis of the docked complex depicts
strong hydrogen bonding between oxygen atoms of the ligand with the Arg606 and Cys559
residues of the receptor. The amide-pi stacking interactions play an important role towards
improved binding affinity in receptor-ligand complexes [52]. Moreover the binding orientation
analysis demonstrates that multiple aromatic interactions such as amide-pi and alkyl-pi, in
docked complexes, are playing a crucial role in anchoring the ligand within the binding pocket of
the protein (Fig.5). For instance, protein residues Arg606, Val558, Cys559, and Asn406 are
stabilizing the complex by forming aromatic interactions with the benzene ring of the ligand. The
results of the docking studies suggest that reported compounds are potentially active against H.
pylori urease that could find place for themselves as potent inhibitors in future drug discovery
and development projects.
Table-5 : GOLD fitness score against various enzymes* for (1-8)
GOLD Fitness Score
Compound
H. pylori Urease*
Tyrosine kinase*
Human pancreatic
alpha amylase*
1
2
3
4
5
6
7
8
40.49
29.38
55.99
41.10
44.25
28.45
56.30
42.2
64.09
46.28
40.51
40.72
41.82
41.91
58.85
17.44
55.69
62.65
57.15
57.19
60.91
58.64
62.1
45.79
21

Fig.-4 Preferred binding mode for (7) in the active site of H. pylori urease
Fig.-5 Two-dimensional depiction of docked lead compound within the binding pocket of urease
protein through DS Visualizer.
22

3
.5.2 Tyrosine kinase
The molecular docking studies for (1-8) against the receptor tyrosine kinase were accomplished
as the studies widely suggests that kinases play an important role in the onset of cancer by
increasing cell proliferation [53, 54]. The data show that compound (1) with the GOLD fitness
score of 64.09 has the higher binding potential to kinase, whereas rest of the compounds also
demonstrates substantial binding affinity with the enzyme structure (Table 5). The active site
residues of protein that involved in binding with the ligand include; Ala27, Lys180, Pro182,
S
Gly26, Asp160, Asp105, Leu149, Leu104, Asn147, Arg146, Thr159, and Phe28 (Fig.14 ). The
strong hydrogen bondings have been observed between protein residues (Asp160, Asn147, and
S
Arg146) and the oxygen atoms of the ligand (Fig.15 ). It is worth to be mentioned here, that
compound (7) in addition to (1) may prove as a potential candidate for “lead compound” against
receptor tyrosine kinase in future studies as it’s in silico binding interactions with the enzyme are
also significant.
3
.5.3 Human Pancreatic Alpha Amylase
Molecular docking studies were performed to analyze the amylase inhibitory potential of the
synthesized compounds and the data are given in Table 5. The highest GOLD fitness score of
6
2.65 was determined for (2) which suggest its firm binding affinity in the protein active site and
may be regarded as lead compound in the present study. The GOLD fitness scores for other
compounds are also impressive and may be considered for their possible role as amylase
inhibitors in future drug discovery processes. The active site residues involved in receptor-ligand
interactions include Trp59, Gln63, Thr163, Leu162, Leu165, His201, Ala198, Glu233, Asp300,
and Ile235 as illustrated in Fig.6. A strong hydrogen bond interaction has been observed between
Thr163 and oxygen atom of the ligand. The major role of anchoring and stabilizing the ligand
within the binding pocket has been played by several pi-pi and pi-alkyl interactions of benzene
ring of the ligand with the protein residues (Fig.7).
23

Fig 6 Preferred binding modes for (2) in active sites of human pancreatic alpha amylase
Fig.7. 2-D depiction for (2) showing interactions within the binding pocket of alpha amylase
protein (through DS Visualizer).
24

Conclusions
Eight new triarylbismuth(V) carboxylates (1-8) were successfully synthesized and were well
characterized by FTIR, NMR spectroscopy and single crystal X-ray diffraction techniques. The
X-ray structure for (6) described anisobidentate nature of one (of the two) carboxyl group that
ultimately leads to hexa-coordination for bismuth with distorted octahedral molecular geometry,
while for (2), and (5) the bismuth center is five coordinated with having distorted trigonal
bipyramidal molecular geometry. They were preliminary assayed to check their biocidal
properties like anti-microbial, antidiabetic, protein kinase inhibition and brine shrimp lethality
assay in order to develop a limited structure to activity relationship (SAR). In silico molecular
docking studies of these compounds were also conducted against three enzyme systems namely;
H. pylori urease, EGFR tyrosine kinase and human pancreatic alpha amylase; to investigate their
binding potential in the active sites of target protein receptors. The Gold fitness scores for 1, 2
and 7 against EGFR tyrosine kinase, human pancreatic alpha amylase and H. pylori urease are
6
0.09, 62.65 and 56.30 respectively which placed them lead compounds in their respective
biological study domains. The hydrogen bonding and aromatic interactions (such as pi-pi
stacked, pi-sigma, and pi-alkyl) have played a crucial role in anchoring the ligands within the
binding pockets of the receptor. The outcomes of the docking studies demonstrate the inhibitory
potential of the compounds against the selected drug targets that may provide a basic scaffold for
discovering new therapeutic agents in future drug discovery processes. Furthermore the docking
data manifest that tolyl group of tritolylbismuth derivatives provide the best fit for the binding
pockets of the receptor proteins that may rendered them as potent enzyme inhibitors whereas
triphenylbismuth compounds show strong antimicrobial character in particular to those having
carboxylate moiety with aromatic ring bear electron donating groups. The results obtained from
experimental and computational studies suggest that the organobismuth carboxylates,
particularly 1, 2, 5 and 8 have promising biocidal activity profiles that could provide a clue to the
development of even more potent antimicrobial agents besides improving their anti-diabetic,
anti-cancer and gastrointestinal properties by altering/modifying their chemical structures.
Acknowledgements
The authors are thankful to Higher Education Commission of Pakistan, and Quaid-I-Azam
University Islamabad, Pakistan, for providing financial assistance and granting funds for the
project 6182/Federal/NRPU/R&D/HEC/2016.
25

Appendix - Supplementary data
The CCDC numbers for the reported compounds are 1969180, 1969182 and 1969184. The data
can be downloaded from CCDC data base which can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
Abbreviations
LD50 : Lethal dose 50%, BSLA : Brine shrimp lethality assay, EGFR : Epidermal growth factor
receptor, NMR : Nuclear magnetic resonance, THF : Tetrahydrofuran, XRD : X-ray diffraction.
SAR : Structure to activity relationship, GOLD : Genetic Optimization for Ligand Docking,
CADD : Computer-aided drug design, ATCC : American type culture collection, FCBP :
Fungal Culture Bank of Pakistan.
References
[
[
[
[
[
(
[
1] G.G. Briand, N. Burford, Chem. Rev, 99 (1999) 2601-2658.
2] P.J. Sadler, H. Li, H. Sun, Coord. Chem., 185 (1999) 689-709.
3] R. Mohan, Nat. Chem, 2 (2010) 336.
4] H. Sun, H. Li, P.J. Sadler, Chem. Ber., 130 (1997) 669-681.
5] K. Goh, N. Parasakthi, S. Peh, N. Wong, Y. Lo, S. Puthucheary, Scand. J. Gastroenterol., 26
1991) 1123-1131.
6] P. Malfertheiner, F. Bazzoli, J.-C. Delchier, K. Celiñski, M. Giguère, M. Rivière, F.
Mégraud, P.S. Group, Lancet, 377 (2011) 905-913.
7] G.E.G. Felga, F.M. Silva, R.C. Barbuti, T. Navarro-Rodriguez, S. Zaterka, J.N. Eisig, World
J Gastroenterol, 14 (2008) 6224.
8] P.C. Andrews, G.B. Deacon, C.M. Forsyth, P.C. Junk, I. Kumar, M. Maguire, Angew. Chem,
5 (2006) 5638-5642.
[
[
4
[
(
[
[
9] J. Gilster, K. Bacon, K. Marlink, B. Sheppard, C. Deveney, M. Rutten, Dig. Dis. Sci., 49
2004) 370-378.
10] E.V.D. Wouden, A.V. ZWET, Aliment Pharmacol Ther, 13 (1999) 297-302.
11] P.T. Reynolds, K.C. Abalos, J. Hopp, M.E. Williams, Int. J. Clin. Med., 3 (2012) 46.
26

[
12] A. Islam, J. Da Silva, F. Berbet, S. da Silva, B. Rodrigues, H. Beraldo, M. Melo, F. Frézard,
C. Demicheli, Molecules, 19 (2014) 6009-6030.
13] P.C. Andrews, M. Busse, G.B. Deacon, R.L. Ferrero, P.C. Junk, J.G. MacLellan, A. Vom,
Dalton Trans., 41 (2012) 11798-11806.
14] P.C. Andrews, M. Busse, G.B. Deacon, R.L. Ferrero, P.C. Junk, K.K. Huynh, I. Kumar, J.G.
MacLellan, Dalton Trans., 39 (2010) 9633-9641.
15] P.C. Andrews, G.B. Deacon, R.L. Ferrero, P.C. Junk, A. Karrar, I. Kumar, J.G. MacLellan,
Dalton Trans., (2009) 6377-6384.
16] P.C. Andrews, R.L. Ferrero, C.M. Forsyth, P.C. Junk, J.G. Maclellan, R.M. Peiris,
Organometallics, 30 (2011) 6283-6291.
17] P.C. Andrews, V.L. Blair, R.L. Ferrero, P.C. Junk, L. Kedzierski, R.M. Peiris, Dalton
Trans., 43 (2014) 1279-1291.
18] S. Mahbubul Hasan, A. Chowdhury, C.A. Keya, J Gastroenterol Hepatol, 23 (2001) 1175-
181.
19] S. Andleeb, Imtiaz-ud-Din, M.K. Rauf, S.S. Azam, A. Badshah, H. Sadaf, A. Raheel, M.N.
Tahir, S. Raza, RSC Adv., 6 (2016) 79651-79661.
20] P. Ballard, R.H. Bradbury, C.S. Harris, L.F. Hennequin, M. Hickinson, P.D. Johnson, J.G.
Kettle, T. Klinowska, A.G. Leach, R. Morgentin, Bioorg. Med. Chem., 16 (2006) 1633-1637.
[
[
[
[
[
[
1
[
[
[21] D.C. Whitcomb, M.E. Lowe, Digest. Dis. Sci, 52 (2007) 1-17.
[22] A. Raheel, Imtiaz-ud-Din, S. Andleeb, S. Ramadan, M.N. Tahir, Appl. Organomet. Chem.,
3
1 (2017) e3632.
23] Imtiaz-ud-Din, K.C. Molloy, M. Mazhar, S. Dastgir, S. Ali, M.F. Mahon, Appl. Organomet.
Chem., 17 (2003) 781-787.
24] M. Mehmood, Imtiaz-ud-Din, M.N. Tahir, I.-u. Haq, S.S. Zahra, Inorganica Chim. Acta,
86 (2019) 387-394.
[
[
4
[25] S.P. Leelananda, S. Lindert, Beilstein J. Org. Chem., 12 (2016) 2694-2718.
[26] P.V. Payghan, I. Bera, D. Bhattacharyya, N. Ghoshal, Front. Phys., 6 (2018) 52.
[27] S. Andleeb, Imtiaz‐ud‐Din, M.K. Rauf, S.S. Azam, I.u. Haq, M.N. Tahir, S. Ahmad,
Applied Organometallic Chemistry, 33 (2019) e5061.
28] A.B. Pangborn, M.A. Giardello, R.H. Grubbs, R.K. Rosen, F.J. Timmers, Organometallics,
5 (1996) 1518-1520.
[
1
27

[29] Y.C. Ong, V.L. Blair, L. Kedzierski, K.L. Tuck, P.C. Andrews, Dalton Trans., 44 (2015)
1
8215-18226.
[
[
[
[
30] Y.C. Ong, V.L. Blair, L. Kedzierski, P.C. Andrews, Dalton Trans., 43 (2014) 12904-12916.
31] J. Supniewski, R. Adams, J. Am. Chem. Soc, 48 (1926) 507-517.
32] A. Bruker, A. Bruker, Madison, WI, 53711 (2007).
33] A. Ihsan-Ul-Haq, I. Ahmed, I. Hussain, M. Jamil, B. Mirza, Pak J Bot, 44 (2012) 1487-
1
490.
[
34] M. Ahmed, H. Fatima, M. Qasim, B. Gul, BMC Complement Altern Med, 17 (2017) 386.
35] S.S. Zahra, M. Ahmed, M. Qasim, B. Gul, M. Zia, B. Mirza, I.-u. Haq, BMC Complement
[
Altern Med 17 (2017) 443.
36] H. Fatima, K. Khan, M. Zia, T. Ur-Rehman, B. Mirza, I.-u. Haq, BMC Complement Altern
Med 15 (2015) 376.
[
[
[
[
[
[
37] S. Wajid Abbasi, S. Sikander Azam, Curr. Cancer Drug Targets, 15 (2015) 822-835.
38] S.S. Azam, A. Abro, F. Tanvir, N. Parvaiz, Med Chem Res, 23 (2014) 3765-3783.
39] J. Stamos, M.X. Sliwkowski, C. Eigenbrot, J. Biol. Chem., 277 (2002) 46265-46272.
40] A.B. Casey, C.E. Canal, ACS Chem. Neurosci., 8 (2017) 1135-1146.
41] N.-C. Ha, S.-T. Oh, J.Y. Sung, K.A. Cha, M.H. Lee, B.-H. Oh, Nat. Struct. Biol., 8 (2001)
5
05-509.
[
[
[
[
[
[
42] J.H. Lii, N.L. Allinger, J. Comput. Chem., 19 (1998) 1001-1016.
43] S.T. Baby, S. Sharma, S. Enaganti, P.R. Cherian, Bioinformation, 12 (2016) 149.
44] G. Deacon, R. Phillips, Coord. Chem., 33 (1980) 227-250.
45] J.O. Adeyemi, D.C. Onwudiwe, Molecules, 23 (2018) 2571.
46] G. Deacon, R. Phillips, Coord Chem Rev, 33 (1980) 227-250.
47] V. Sharutin, I. Egorova, O. Sharutina, T. Ivanenko, Y.V. Gatilov, N. Adonin, V.
Starichenko, Russ. J. Coord., 29 (2003) 462-467.
[
48] N. Dharmaraj, P. Viswanathamurthi, K. Natarajan, Transit. Met. Chem., 26 (2001) 105-109.
49] A. Islam, J.G. Da Silva, F.M. Berbet, S.M. Da Silva, B.L. Rodrigues, H. Beraldo, M.N.
[
Melo, F. Frézard, C. Demicheli, Molecules, 19 (2014) 6009-6030.
[50] A.A. Al-Amiery, A.A.H. Kadhum, A.B. Mohamad, Bioinorg. Chem. Appl., 2012 (2012).
[51] R. Nagarajan, S.I. Mehtaa, S.R. Naik, W. Fabry, Arzneimittelforschung, 49 (1999) 951-954.
[52] R.F. de Freitas, M. Schapira, Medchemcomm, 8 (2017) 1970-1981.
28

[53] K.S. Bhullar, N.O. Lagarón, E.M. McGowan, I. Parmar, A. Jha, B.P. Hubbard, H.V.
Rupasinghe, Mol Cancer, 17 (2018) 48.
[
54] S. Gross, R. Rahal, N. Stransky, C. Lengauer, K.P. Hoeflich, Clin. Drug Investig., 125
2015) 1780-1789.
(
29