Synthesis, computational studies and enzyme inhibitory kinetics of benzothiazole-linked thioureas as mushroom tyrosinase inhibitors

Article abstract of DOI:10.1080/07391102.2020.1804459

Herein, we report synthesis of a set of benzothiazole-thiourea hybrids with aromatic and aliphatic side chains (BT1 to BT9) using an elegant synthetic strategy. The newly synthesized benzothiazole-thiourea conjugates were subjected to In-vitro tyrosinase inhibition and free radical scavenging activity. Majority of the compounds indicated inhibition considerably improved than the standard; compound (Kojic acid with IC₅₀ = 16.8320 ± 1.1600 μM) BT2 with IC₅₀ = 1.3431 ± 0.0254 μM was found to be the best inhibitor. A non-competitive mode of inhibition of BT2 was disclosed with Ki value of 2.8 μM. In order to study enzyme-inhibitor interactions SAR analysis molecular docking was carried out. The amino groups of thiourea were involved in hydrogen bonding with Glu322 showing the bond length of 1.74 and 2.70 ?, respectively. Moreover, the coupling of π-π was displayed between benzothiazole and benzene rings of His244 and His263, respectively. The outcome of this study might help to develop new inhibitors of melanogenesis, important for cosmetic and food products. Communicated by Ramaswamy H. Sarma.

Full text of DOI:10.1080/07391102.2020.1804459

Journal of Biomolecular Structure and Dynamics
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Synthesis, computational studies and enzyme
inhibitory kinetics of benzothiazole-linked
thioureas as mushroom tyrosinase inhibitors
Rabail Ujan , Aamer Saeed , Saba Ashraf , Pervaiz Ali Channar , Qamar
Abbas , Mahboob Ali Rind , Mubashir Hassan , Hussain Raza , Sung-Yum Seo
& Hesham R. El-Seedi
To cite this article: Rabail Ujan , Aamer Saeed , Saba Ashraf , Pervaiz Ali Channar , Qamar
Abbas , Mahboob Ali Rind , Mubashir Hassan , Hussain Raza , Sung-Yum Seo & Hesham R. El-
Seedi (2020): Synthesis, computational studies and enzyme inhibitory kinetics of benzothiazole-
linked thioureas as mushroom tyrosinase inhibitors, Journal of Biomolecular Structure and
Dynamics, DOI: 10.1080/07391102.2020.1804459
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JOURNAL OF BIOMOLECULAR STRUCTURE AND DYNAMICS
https://doi.org/10.1080/07391102.2020.1804459
Synthesis, computational studies and enzyme inhibitory kinetics of
benzothiazole-linked thioureas as mushroom tyrosinase inhibitors
Rabail Ujana, Aamer Saeedb , Saba Ashrafb,c, Pervaiz Ali Channarb, Qamar Abbasd, Mahboob Ali Rinda,
Mubashir Hassane, Hussain Razaf, Sung-Yum Seof and Hesham R. El-Seedig,h
b
aDr. M. A. Kazi Institute of Chemistry, University of Sindh, Jamshoro, Pakistan; Department of Chemistry, Quaid-I-Azam University,
c
Islamabad, Pakistan; Sulaiman Bin Abdullah Aba Al-Khail-Centre for Interdisciplinary Research in Basic Sciences (SA-CIRBS), International
d
e
Islamic University, Islamabad, Pakistan; Department of Physiology, University of Sindh, Jamshoro, Pakistan; Institute of Molecular Biology
f
and Biotechnology (IMBB), The University of Lahore, Lahore, Pakistan; Department of Biological Sciences, College of Natural Sciences,
Kongju National University, Gongju, Chungnam, Republic of Korea; College of Food and Biological Engineering, Jiangsu University,
Zhenjiang, China; Al-Rayan Colleges, Medina, Saudi Arabia
g
h
Communicated by Ramaswamy H. Sarma
ABSTRACT
ARTICLE HISTORY
Received 1 June 2020
Accepted 28 July 2020
Herein, we report synthesis of a set of benzothiazole-thiourea hybrids with aromatic and aliphatic
side chains (BT1 to BT9) using an elegant synthetic strategy. The newly synthesized benzothiazole-
thiourea conjugates were subjected to In-vitro tyrosinase inhibition and free radical scavenging
activity. Majority of the compounds indicated inhibition considerably improved than the standard;
compound (Kojic acid with IC50 ¼ 16.8320 1.1600 mM) BT2 with IC50 ¼ 1.3431 0.0254mM was
found to be the best inhibitor. A non-competitive mode of inhibition of BT2 was disclosed with Ki
value of 2.8 mM. In order to study enzyme-inhibitor interactions SAR analysis molecular docking was
carried out. The amino groups of thiourea were involved in hydrogen bonding with Glu322 show-
ing the bond length of 1.74 and 2.70 Å, respectively. Moreover, the coupling of p-p was displayed
between benzothiazole and benzene rings of His244 and His263, respectively. The outcome of this
study might help to develop new inhibitors of melanogenesis, important for cosmetic and food
products.
KEYWORDS
Benzothiazoles; aryl
thioureas; docking complex;
kinetics; Tyrosinase
1. Introduction
inhibitors (Deri et al., 2016; Pillaiyar et al., 2017; Zolghadri
et al., 2019).
Tyrosinase (EC 1.14.18.1) is a bifunctional oxidoreductase
involved in monophenolase and diphenolase activity and is
related to melanogenesis and enzymatic browning. Excess of
the pigment melanin is responsible for skin disorders like
freckles, and malignant melanoma. Owing to their skin-
whitening effect by preventing tyrosine inhibitors are an
essential component of the cosmetics. Kojic acid or hydro-
quinone, the well-known inhibitors are found to be precar-
ious for human skin therefore, there remains a continuous
Benzothiazoles represent a promising skeleton in the
pharmaceutical chemistry due to their tremendous applica-
tions. A large number of the marketed drugs contain benzo-
thiazloe nucleus as a part of their structures such as
Ethoxzolomide, the sulfonamide diuretic drug, Frentizole,
antiviral as well as immunosuppressive agent, Riluzole, a glu-
tamate receptor antagonist, used to treat amyotrophic lateral
sclerosis, Pramipexole for Parkinsons disease, restless legs
syndrome thioflavin Amyloid, imaging agent, Zopolrestat,
need for discovering new potent and safe tyrosinase antidiabetic agent and tioxidazole an anthelimintic drug (Gill
CONTACT Aamer Saeed
asaeed@qau.edu.pk; aamersaeed@yahoo.com
Department of Chemistry, Quaid-I-Azam University, Islamabad 45320, Pakistan.
Supplemental data for this article can be accessed online at https://doi.org/10.1080/07391102.2020.1804459.
ß 2020 Informa UK Limited, trading as Taylor & Francis Group

2
R. UJAN ET AL.
Figure 1. Commercial drugs with benzothiazole moiety.
et al., 2015; Gjorgjieva et al., 2018; Mohsen et al., 2015; and the effect of different groups on enzymatic activity was
demonstrated. The results are discussed in the rele-
vant section
Sharma et al., 2013) (Figure 1).
Benzothiazole-based antibacterial compounds inhibit the
enzymes which catalyze the cell-wall synthesis, cell division,
and DNA replication, and the biosynthesis of histidine and
biotin (Saeed et al., 2019).
2. Experimental
Similarly, a wide variety of medicinal and other applica-
tions of acyl thioureas have also been comprehensively
reviewed and updated (Saeed et al., 2008, 2014). Thus, a new
series of benzothiazole thioureas were reported along with
their antibacterial activity (Eshkil et al., 2017). Cytotoxic activ-
ity was checked for a new class of thioureas and N-bisthia-
zoles derivatives and was found to be potent cytotoxic
agents for human and mouse cell lines (Rego et al., 2018).
Several benzothiazole-thiourea derivatives were reported as
urease inhibitors (Zainal et al., 2018) and also been utilized
in complexation reactions with various metals (Dadmal
et al., 2018).
In the pharmacophoric integration approach two or more
pharmacophoric moieties of different bioactive molecules are
combined in a single structural unit to afford hybrids with
improved affinity and efficacy. Furthermore, it can result in
compounds with improved selectivity profile, dual modes of
action and reduced undesired side effects. In furtherance of
our previous findings on thiourea-heterocyclic hybrids,
herein, we report the design and synthesis of a new series of
benzothiazole-thioureas with different alkyl and aryl substitu-
ents (Figure 2). The alkyl/aryl substituents were varied in the
acyl part of thiourea to study the effect of structure on activ-
ity. All the synthesized compounds were subjected to in-vitro
2.1. Methods and materials
The chemicals, potassium thiocyanate, thionyl chloride, sub-
stituted benzoyl chlorides, all synthetic starting materials,
reagents, and solvents were of analytical reagent grade or
of the highest quality commercially available and were pur-
chased from Sigma Aldrich Chemical Co., Merck Germany
and were used without further purification. Acetone was
freshly dried over KMnO4 and distilled. Rf-values were deter-
mined using pre-coated silica gel aluminum plates 60 F254
from Merck (Germany). All Melting points were determined
in open glass capillaries using Stuart SMP3 (UK) melting
point apparatus and are uncorrected. Infrared spectra (IR) of
the compounds were recorded on a Bio-Rad-Excalibur Series
Model No. FTS 300 MX spectrophotometer as pure com-
pounds. 1H and 13C-NMR spectra were obtained on a
Bruker 300 MHz and 75.5 MHz NMR spectrometer and
Elemental analyses were conducted using
CHNS analyzer.
a LECO-183
2.2. Synthesis of benzothiazole-thiourea derivatives
(BT1 to BT9)
The freshly prepared acid chlorides (1.0 mmol) in dry distilled
acetone (20 mL) were added drop wise to a suspension of
inhibition of tyrosinase and free-radical scavenging activities potassium thiocyanate (1.0 mmol) in acetone and refluxed for

JOURNAL OF BIOMOLECULAR STRUCTURE AND DYNAMICS
3
Figure 2. Molecular structural design of Benzothiazole- thioureas.
1.5 h at 50 ꢀC. After cooling, 4-(benzo[d]thiazol-2-yl) aniline linear portion of absorbance up to five minutes after addition of
(1.0 mmol) solution in acetone was added and the resulting the enzyme at a 30 s interval. The inhibition of the enzyme was
mixture was refluxed for 7 h. On completion of the reaction
monitored by TLC (n-Hexane: Ethyl acetate 1: 1), the reaction
mixture was poured onto crushed ice and the precipitates
were collected by filtration, washed with ethanol, dried and
recrystallized from ethanol to yield benzothiazole-thiourea
derivatives (BT1 to BT9). The details of spectral data of all
compounds can be found in the supplementary file.
assayed by Lineweaver-Burk plots of the inverse of velocities (1/V)
versus the inverse of substrate concentration 1/[L-DOPA] mMꢁ1
The EI dissociation constant Ki was determined by the secondary
plot of 1/V versus inhibitors concentrations.
.
2.3. Free radical scavenging assay
Radical scavenging activity was determined by modifying the
already reported method (Friesner et al., 2006; Hassan,
Abbas, Ashraf, et al., 2017) using 2, 2-diphenyl-1-picrylhydra-
zyl (DPPH) assay. The assay solution consisted of 100 mL of
DPPH (150 mM), 20 mL of increasing concentration of test
compounds and the volume was adjusted to 200 mL in each
well with methanol followed by incubation for 30 min at
room temperature. Ascorbic acid (vitamin C) was used as a
reference inhibitor. The measurements were carried out by
using a microplate reader (OPTI Max, Tunable) at 517 nm. The
reaction rates were compared and the percent inhibition
caused by the presence of tested compounds was calculated.
All experiments were repeated thrice.
2.2.1. Anti tyrosinase assay
The inhibition of mushroom tyrosinase was determined by a
modification of the dopachrome method using L-DOPA as a
substrate (Abbas et al., 2017a, 2017b; Larik et al., 2017; Saeed
et al., 2017). In brief, 140 mL of phosphate buffer (20 mM, pH
6.8), 20 mL of mushroom tyrosinase (30 U/mL) and 20 mL of the
inhibitor solution were placed in the wells of a 96-well micro-
plate. After pre-incubation for 10 min at room temperature,
20 mL of L-DOPA (3,4-dihydroxyphenylalanine, Sigma
Chemical, USA) (0.85 mM) was added and the assay plate was
further incubated at 25 ꢀC for 20 min. After incubation time,
the absorbance was read at 475 nm and the inhibition percent-
age calculated in relation to the control. Phosphate buffer and
kojic acid were tested under the same conditions as negative
and positive control, respectively. The amount of inhibition
was expressed as the percentage of concentration necessary
to achieve 50% inhibition (IC50). Each concentration was ana-
lyzed in three independent experiments. IC50 values were cal-
culated by nonlinear regression using GraphPad Prism 5.0.
The % Inhibition of tyrosinase was calculated as following:
2.4. Computational methodology
2.4.1. Retrieval of tyrosinase in protein preparation
wizard
The mushroom tyrosinase structure was retrieved from
Protein Data Bank (PDB) (www.rcsb.org) with PDBID 2Y9X
(Sherman et al., 2006) in protein preparation wizard. The
selected protein structure of tyrosinase was preprocessed
and minimized using default parameters in Maestro interface.
Â
Ã
ð
Þ
Inhibition ð%Þ ¼
Here, the B and S are the absorbance’s for the blank
B ꢁ S =B ꢂ 100
and samples.
2.4.2. Grid generation and molecular docking
The improved tyrosinase structure was prepared using the
€
‘Protein Preparation Wizard’ workflow in Schrodinger Suite.
2.2.2. Kinetic analysis
Bond orders were assigned and hydrogen atoms were added
to the protein. The structure was then minimized to reach
the converged root mean square deviation (RMSD) of 0.30 Å
with the OPLS_2005 force field. The active site of the enzyme
is defined from the co-crystallized ligands as per the Protein
Data Bank and literature data (Reddy et al., 2010).
Additionally, docking experiment was performed against all
On the basis of IC50, the most potent BT2 was selected for kinetic
analysis. A series of experiments were performed to determine the
inhibition kinetics of BT2 by following the already reported meth-
ods (Ashraf et al., 2015; Ismaya et al., 2011; Reddy et al., 2010). The
inhibitor concentrations for BT2 were 0.00, 1.3431, 2.6862 and
5.3724 mM. L-DOPA concentrations were between 0.125 to 2 mM
in all kinetic studies. Pre-incubation and measurement time was
the same as discussed in the mushroom tyrosinase inhibition assay synthesized ligands (BT19) sketched by 2 D sketcher in
protocol. Maximal initial velocity was determined from the initial Maestro and target protein by using Glide docking protocol

4
R. UJAN ET AL.
Scheme 1. Synthesis of benzothiazole thioureas (BT1-BT9)
Figure 3. Structures of benzothiazole thioureas (BT1-BT9).
(Sherman et al., 2006). The predicted binding energies (dock-
ing scores) and conformational positions of ligands within
active region of protein were also performed using Glide
experiment. Throughout the docking simulations, both par-
tial and full flexibility around the active site residues are per-
formed by Glide/SP/XP and induced fit docking (IFD)
approaches (Hassan, Abbas, Raza, et al., 2017; Saeed
et al., 2017).
3. Results and discussion
3.1. Synthesis
Scheme 1 outlines the synthetic pathway adopted for the
synthesis of target molecules. Freshly prepared acid chlorides
were added during to a stirred a solution of potassium
thiocyanate in anhydrous acetone at 50 ꢀC for 1.5 h to yield
corresponding isothiocyanates. On cooling, a solution of

JOURNAL OF BIOMOLECULAR STRUCTURE AND DYNAMICS
5
4-aminobenzothiazole in acetone was added slowly to afford showed potential inhibition and compound BT2 (IC50
¼
1.3431 0.0254) was leading tyrosinase inhibitor as com-
pared to rest of the series. The nature of substituents around
the benzothiazole thiourea moiety greatly affect the tyrosin-
ase inhibition activity. The compound BT2, containing long
alkyl chain, thiourea and benzothiazole moiety, interact
strongly and occupy the whole pocket of receptor. The com-
pound BT3 exhibited least inhibitory activity due to small
size, it poorly interacted with enzyme and unable to occupy
the pocket of receptor. The BT5 compound was the second
potent inhibitor with alkyl chain; conversely, the substitution
of the phenyl ring reduced the inhibitory effect.
benzothiazole-thiourea derivatives (BT1 to BT9) in good
yields. In FT-IR spectra, stretching around 3166 cmꢁ1 were
attributed to N-H, those at 3026 cmꢁ1 belongs to aromatic
CH, and the amidic and lactonic carbonyls appear at
1530 cmꢁ1 and 1694 cmꢁ1 respectively. The aromatic stretch-
ing appeared in the range 1579–1406 cmꢁ1 and thiocarbo-
nylic stretchings at 1157 cmꢁ1. Investigating the 1H-NMR
spectra, the broad signal at 12.77 ppm indicates the N-H
flanked by C ¼ O and C ¼ S, and another at 11.56 ppm for
second N-H, besides the downfield doublet at 8.17-7.44 ppm
due to the aromatic protons. The 13C-NMR showed C ¼ S and
C ¼ O at 179.0 and 175.9 ppm respectively, whereas the
C ¼ N appeared at 166.9 ppm. The complete structures of all
synthesized compounds are shown in Figure 3.
3.3. Kinetic analysis
The strongest compound BT2 was nominated to decide the
inhibition type and inhibition constant on tyrosinase. The
potential to inhibit free enzyme and enzyme substrate com-
plex was firmed in term of EI and ESI constants respectively.
The kinetic studies of the enzyme by the Lineweaver-Burk plot
of 1/V versus 1/[S] in the presence of different compounds
concentrations gave a series of straight lines (Figure 1(A)). The
results of compound BT2 indicated intersection within the
second quadrant. The analysis showed that Vmax decreased to
increasing doses of inhibitors conversely Km remains the same.
This behavior indicates that compound BT2 inhibits the
3.2. Mushroom tyrosinase inhibition assay
The compounds (BT1–9) were screened to authenticate their
implication as tyrosinase inhibitors using Kojic acid as stand-
ard and the half maximal inhibitory concentration (IC50) are
summarized in Table 1. Excitingly, all synthesized compounds
Table 1. IC50 values of compounds (BT1-BT9) were calculated by nonlinear
regression using GraphPad Prism 5.0.
Compound
Tyrosinase activity IC50 SEM (mM)
BT1
BT2
BT3
BT4
BT5
BT6
BT7
BT8
19.0153 1.5744
1.3431 0.0254
54.6311 2.1817
4.7745 0.9975
1.3526 0.0377
2.6841 0.0115
7.8319 0.9916
4.1576 0.7739
6.0986 1.8749
16.8320 1.1600
Table 2. Kinetic parameters of the mushroom tyrosinase of L-DOPA activity in
the presence of various concentration of BT-2.
Concentration (mM) Vmax (DA /Sec) Km (mM)
Inhibition Type
Ki (mM)
0.00
2.05506 ꢂ 10-4
4.6303 ꢂ 10-5
3.58485 ꢂ 10-5
2.93245 ꢂ 10-5
0.3703
0.3703
0.3703
0.3703
Non-Competitive
2.8
1.3431
2.6862
5.3724
BT9
Kojic acid
V
is the reaction velocity, Km is the Michaelis-Menten constant, Ki is the
max
SEM ¼ Standard error of the mean; values are expressed in mean SEM.
EI dissociation constant.
Figure 4. Lineweaver–Burk plots for inhibition of tyrosinase in the presence of Compound BT2. (a) Concentrations of BT2 were 0.00, 1.3431, 2.6862 and 5.3724 mM,
respectively. Substrate L-DOPA Concentrations were 0.125, 0.25, 0.5, 1 and 2 mM, respectively. (b) The insets represent the plot of the slope versus inhibitor BT-2
concentrations to determine inhibition constant. The lines were drawn using linear least squares fit.

6
R. UJAN ET AL.
Figure 5. Free radical % scavenging activity of synthetic compounds, values were represented as mean SEM (Standard error of the mean). All compounds
concentrations were 100 mg/mL.
Figure 6. (A) The overall protein structure tyrosinase and (B) Ramachandran graph.
tyrosinase non-competitively to form enzyme inhibitor com- a-helices, 14% b-sheets and 46% coils. The Ramachandran
plex. Secondary plot of slope against the concentration of plots and values indicated that 95.90% of protein residues
inhibitors showed enzyme inhibitor dissociation constant (Ki)
(Figure 4(B)). The kinetic results are listed in Table 2.
were present in favored region and 100.0% residues were in
allowed region. The Ramachandran graph values exhibited
the good accuracy of phi (u) and psi (w) angles among the
coordinates of receptor and most of residues were plunged
in acceptable region. The complete protein structure and
3.4. Free radical scavenging
The whole BT series was also evaluated for DPPH free radical Ramachandran graphs are mentioned in Figure 6(A,B).
scavenging ability. All compounds did not display significant
radical scavenging potential even at high concentration
(100 mg/mL) relative to the standards, vitamin C (Figure 5).
3.4.2. Molecular docking analysis
3.4.1. Mushroom tyrosinase structural assessment
3.4.3. Glide energy evaluation of synthesized compounds
Mushroom tyrosinase, a copper containing protein comprises Molecular docking predicts the preferred orientation of
391 residues (Friesner et al., 2006) and consists of 39% ligands to target proteins to form a stable complex. (Channar

JOURNAL OF BIOMOLECULAR STRUCTURE AND DYNAMICS
7
Figure 7. A & B. All the docking complexes and their docking energy values.
Figure 8. A & B. Binding interaction of BT2 against tyrosinase protein.
et al., 2018; Hassan et al., 2018). In order to envisage the fin- big energy values variations were observed as the basic
est conformational position of synthesized compounds, all
ligands BT1–9 were docked against tyrosinase separately.
The generated docked complexes were examined on the
basis of glide docking energy values (kcal/mol) and bonding
interaction (hydrogen/hydrophobic) pattern. The results indi-
cated that all the ligands bind within the active region of tar-
get protein with different conformational poses (Figure 7(A)).
The glide docking energy values fluctuated among all
ligands and BT1 and BT5 possessed highest to lowest
energy values of ꢁ5.55 and ꢁ3.13 kcal/mol, respectively.
Furthermore, the compounds BT2, BT6, BT7 and BT9 also
exhibited comparative docking energy values of ꢁ4.99, 5.39,
structures of ligands were similar. All docking energy values
of synthesized ligands are mentioned in Figure 7(B).
3.4.4.
Ligand-Binding
analysis
of
tyrosinase
docked complexes
On the basis of in-vitro results (IC50) BT2 was selected for
binding interaction pattern. The, structure activity relation-
ship (SAR) revealed two H-bonds and p-p interactions in BT2
docking complex. The amino groups of thiourea were
involved in H-bonding with Glu322 having bond length of
1.74 and 2.70 Å, respectively. Likewise, a couple of p-p inter-
5.31 and 5.23 kcal/mol respectively. This indicated that no actions were also observed between benzothiazole and

8
R. UJAN ET AL.
aminobenzothiazole:
776–797. https://doi.org/10.1039/C7NJ03776G
A review. New Journal of Chemistry, 42(2),
benzene rings of BT2 with His244 and His263, respectively.
The His263 is copper bonded residues which ensure the lig-
and binding within the active region of target protein. The
3 D and 2 D graphical representations of BT2 complex is
revealed in Figure 8(A,B). The additional docking complexes
are given in supplementary data (Supplementry material
Figures S1–S8).
Deri, B., Kanteev, M., Goldfeder, M., Lecina, D., Guallar, V., Adir, N., &
Fishman, A. (2016). The unravelling of the complex pattern of tyrosin-
ase inhibition. Scientific Reports, 6, 34993. https://doi.org/10.1038/
srep34993 (2016).
Eshkil, F., Eshghi, H., Saljooghi, A. S., Bakavoli, M., & Rahimizadeh, M.
(2017). Benzothiazole thiourea derivatives as anticancer agents:
Design, synthesis, and biological screening. Russian Journal of
Bioorganic Chemistry, 43(5), 576–582. https://doi.org/10.1134/
S1068162017050065
Friesner, R. A., Murphy, R. B., Repasky, M. P., Frye, L. L., Greenwood, J. R.,
Halgren, T. A., Sanschagrin, P. C., & Mainz, D. T. (2006). Extra precision
glide: Docking and scoring incorporating a model of hydrophobic
enclosure for protein-ligand complexes. J. Med. Chem, 49(21),
6177–6196. https://doi.org/10.1021/jm051256o
4. Conclusion
Suitably substituted benzothiazole-thiourea conjugates
(BT1–BT9) were synthesized and screened for in-vitro mush-
room tyrosinase inhibition potential. Compound BT2 with C-
9
alkyl chain showed remarkably lower IC50 value of
Gill, R. K., Rawal, R. K., & Bariwal, J. (2015). Recent advances in the chem-
istry and biology of benzothiazoles. Archiv Der Pharmazie, 348(3),
155–178. https://doi.org/10.1002/ardp.201400340
1.3431 0.0254 mM compared to standard kojic acid with IC50
value of 16.8320 1.1600 mM. The enzyme inhibitory kinetics
of compound BT2 determined by Lineweaver-Burk plots and
Dixon plots showed non-competitive mode of inhibition with
Ki value of 2.8 mM. The pharmacokinetics showed that the
compounds possess good lead-like properties with little tox-
icity. Molecular docking studies delineated the binding affin-
ity of the strongest derivative BT2 as a lead structure in
evolving most potent mushroom tyrosinase inhibitors.
ꢀ ꢀ
ꢀ ꢀ
Gjorgjieva, M., Tomasic, T., Kikelj, D., & Masic, L. P. (2018). Benzothiazole-
based compounds in antibacterial drug discovery. Current Medicinal
Chemistry,
25(38),
5218–5236.
https://doi.org/10.2174/
0929867324666171009103327
Hassan, M., Abbas, Q., Ashraf, Z., Moustafa, A. A., & Seo, S. Y. (2017).
Pharmacoinformatics exploration of polyphenol oxidases leading to
novel inhibitors by virtual screening and molecular dynamic simula-
tion study. Computational Biology and Chemistry, 68, 131–142. https://
doi.org/10.1016/j.compbiolchem.2017.02.012
Hassan, M., Abbas, Q., Raza, H., Moustafa, A. A., & Seo, S. Y. (2017).
Computational analysis of histidine mutations on the structural stabil-
ity of human tyrosinases leading to albinism insurgence. Molecular
Biosystems, 13(8), 1534–1544. https://doi.org/10.1039/c7mb00211d
Hassan, M., Ashraf, Z., Abbas, Q., Raza, H., & Seo, S. Y. (2018). Exploration
of novel human tyrosinase inhibitors by molecular modeling, docking
and simulation studies. Interdisciplinary Sciences, Computational Life
Sciences, 10(1), 68–80. https://doi.org/10.1007/s12539-016-0171-x
Ismaya, W. T., Rozeboom, H. J., Weijn, A., Mes, J. J., Fusetti, F., Wichers,
H. J., & Dijkstra, B. W. (2011). Crystal structure of Agaricus bisporus
mushroom tyrosinase: Identity of the tetramer subunits and inter-
action with tropolone. Biochemistry, 50(24), 5477–5486. https://doi.
org/10.1021/bi200395t
Acknowledgements
Departments/organizations of all co-authors in this paper are highly
acknowledged for collaborative research work.
Disclosure statement
Authors declare no conflict of interest.
ORCID
Larik, F. A., Saeed, A., Channar, P. A., Muqadar, U., Abbas, Q., Hassan, M.,
Seo, S. Y., & Bolte, M. (2017). Design, synthesis, kinetic mechanism
and molecular docking studies of novel 1-pentanoyl-3-arylthioureas
as inhibitors of mushroom tyrosinase and free radical scavengers.
European Journal of Medicinal Chemistry, 141, 273–281. https://doi.org/
10.1016/j.ejmech.2017.09.059
Aamer Saeed
http://orcid.org/0000-0002-7112-9296
Hesham R. El-Seedi
http://orcid.org/0000-0002-2519-6690
References
€
Mohsen, U. A., Kaplancikli, Z. A., Ozkay, Y., & Yurttas¸, L. (2015). Synthesis
Abbas, Q., Ashraf, Z., Hassan, M., Nadeem, H., Latif, M., Afzal, S., & Seo,
S. Y. (2017a). Development of highly potent melanogenesis inhibitor
by in vitro, in vivo and computational studies. Drug Design,
Development and Therapy, 11, 2029–2046. https://doi.org/10.2147/
DDDT.S137550
Abbas, Q., Raza, H., Hassan, M., Phull, A. R., Kim, S. J., & Seo, S. Y.
(2017b). Acetazolamide inhibits the level of tyrosinase and melanin:
An enzyme kinetic, in vitro, in vivo, and in silico studies. Chemistry &
Biodiversity, 14(9), e1700117. https://doi.org/10.1002/cbdv.201700117
Ashraf, Z., Rafiq, M., Seo, S.-Y., Babar, M. M., & Zaidi, N-u-S S. (2015).
Synthesis, kinetic mechanism and docking studies of vanillin deriva-
tives as inhibitors of mushroom tyrosinase. Bioorganic & Medicinal
Chemistry, 23(17), 5870–5880. https://doi.org/10.1016/j.bmc.2015.06.
068
Channar, P. A., Saeed, A., Shahzad, D., Larik, F. A., Hassan, M., Raza, H.,
Abbas, Q., & Seo, S. Y. (2018). Extending the scope of amantadine
drug by incorporation of phenolic azo Schiff bases as potent selective
inhibitors of carbonic anhydrase II, drug-likeness and binding analysis
. Chemical Biology & Drug Design, 92(3), 1692–1698. https://doi.org/10.
1111/cbdd.13335
and evaluation of anti-acetylcholinesterase activity of some benzo-
thiazole based new piperazine-dithiocarbamate derivatives. Drug
Research, 65(4), 176–183. https://doi.org/10.1055/s-0034-1375613
Pillaiyar, T., Manickam, M., & Namasivayam, V. (2017). Skin whitening
agents: Medicinal chemistry perspective of tyrosinase inhibitors.
Journal of Enzyme Inhibition and Medicinal Chemistry, 32(1), 403–425.
https://doi.org/10.1080/14756366.2016.1256882
Reddy, C. V. K., Sreeramulu, D., & Raghunath, M. (2010). Antioxidant
activity of fresh and dry fruits commonly consumed in India. Food
Research International, 43(1), 285–288. https://doi.org/10.1016/j.foo-
dres.2009.10.006
Rego, Y. F., Queiroz, M. P., Brito, T. O., Carvalho, P. G., de Queiroz, V. T.,
^
ꢁ
de Fatima, A., & Macedo, F. (2018). A review on the development of
urease inhibitors as antimicrobial agents against pathogenic bacteria.
Journal of Advanced Research, 13, 69–100. https://doi.org/10.1016/j.
jare.2018.05.003
€
Saeed, A., Florke, U., & Erben, M. F. (2014). A review on the chemistry,
coordination, structure and biological properties of 1-(acyl/aroyl)-3-
(substituted) thioureas. Journal of Sulfur Chemistry, 35(3), 318–355.
https://doi.org/10.1080/17415993.2013.834904
Dadmal, T. L., Katre, S. D., Mandewale, M. C., & Kumbhare, R. M. (2018).
Contemporary progress in the synthesis and reactions of 2-
Saeed, A., Mahesar, P. A., Channar, P. A., Abbas, Q., Larik, F. A., Hassan,
M., Raza, H., & Seo, S. Y. (2017). Synthesis, molecular docking studies

JOURNAL OF BIOMOLECULAR STRUCTURE AND DYNAMICS
9
of coumarinyl-pyrazolinyl substituted thiazoles as non-competitive Sherman, W., Beard, H. S., & Farid, R. (2006). Use of an induced fit recep-
inhibitors of mushroom tyrosinase. Bioorganic Chemistry, 74, 187–196.
https://doi.org/10.1016/j.bioorg.2017.08.002
tor structure in virtual screening. Chemical Biology & Drug Design,
67(1), 83–84. https://doi.org/10.1111/j.1747-0285.2005.00327.x
Saeed, A., Mustafa, M. N., Zain-Ul-Abideen, M., Shabir, G., Erben, M. F., Sherman, W., Day, T., Jacobson, M. P., Friesner, R. A., & Farid, R. (2006).
€
Florke, U. (2019). Current developments in chemistry, coordination,
Novel procedure for modeling ligand/receptor induced fit effects.
Journal of Medicinal Chemistry, 49(2), 534–553. https://doi.org/10.1021/
jm050540c
structure and biological aspects of 1-(acyl/aroyl)-3-(substituted) thiour-
eas: Advances continue. Journal of Sulfur Chemistry, 40(3), 312–350.
https://doi.org/10.1080/17415993.2018.1551488
Saeed, A., Rafique, H., Hameed, A., & Rasheed, S. (2008). Synthesis and
antibacterial activity of some new 1-aroyl-3-(substituted-2-benzothia-
zolyl) thioureas. Pharmaceutical Chemistry Journal, 42(4), 191–195.
https://doi.org/10.1007/s11094-008-0094-x
Zainal, M. H. B., Mark-Lee, W. F., Mohd Tahir, S., Ahmad, I. B., & Kassim, M. B.
(2018). Experimental and DFT Investigation on the Influence of Electron
Donour/Acceptor on the Hydrogen Bonding Interactions of 1-(1, 3-
Benzothiazol-2-y1)-3-(R-benzoylthiourea). Sains MalaysianaMalaysiana,
47(5), 923–929. https://doi.org/10.17576/jsm-2018-4705-07
Sharma, P. C., Sinhmar, A., Sharma, A., Rajak, H., & Pathak, D. P. (2013). Zolghadri, S., Bahrami, A., Hassan Khan, M. T., Munoz-Munoz, J., Garcia-Molina,
Medicinal significance of benzothiazole scaffold: An insight view.
Journal of Enzyme Inhibition and Medicinal Chemistry, 28(2), 240–266.
https://doi.org/10.3109/14756366.2012.720572
F., Garcia-Canovas, F., & Saboury, A. A. (2019). A comprehensive review on
tyrosinase inhibitors. Journal of Enzyme Inhibition and Medicinal Chemistry,
34(1), 279–309. https://doi.org/10.1080/14756366.2018.1545767