Triazinoindole analogs as potent inhibitors of α-glucosidase: Synthesis, biological evaluation and molecular docking studies

Article abstract of DOI:10.1016/j.bioorg.2014.12.001

A new series of triazinoindole analogs 1-11 were synthesized, characterized by EI-MS and ¹H NMR, evaluated for α-glucosidase inhibitory potential. All eleven (11) analogs showed different range of α-glucosidase inhibitory potential with IC

Full text of DOI:10.1016/j.bioorg.2014.12.001

Accepted Manuscript
Triazinoindole analogs as potent inhibitors of α-glucosidase: Synthesis, biolog-
ical evaluation and molecular docking studies
Fazal Rahim, Khadim Ullah, Hayat Ullah, Abdul Wadood, Muhammad Taha,
Ashfaq Ur Rehman, Imad uddin, Muhammad Ashraf, Ayesha Shaukat, Wajid
Rehman, Shafqat Hussain, Khalid Mohammed Khan
PII:
S0045-2068(14)00127-8
DOI:
http://dx.doi.org/10.1016/j.bioorg.2014.12.001
YBIOO 1778
Reference:
To appear in:
Bioorganic Chemistry
Received Date:
29 September 2014
Please cite this article as: F. Rahim, K. Ullah, H. Ullah, A. Wadood, M. Taha, A.U. Rehman, I. uddin, M. Ashraf,
A. Shaukat, W. Rehman, S. Hussain, K.M. Khan, Triazinoindole analogs as potent inhibitors of α-glucosidase:
Synthesis, biological evaluation and molecular docking studies, Bioorganic Chemistry (2014), doi: http://dx.doi.org/
1
0.1016/j.bioorg.2014.12.001
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Triazinoindole analogs as potent inhibitors of α-glucosidase: Synthesis, biological
evaluation and molecular docking studies
a∗
a
a
b
c,d
Fazal Rahim , Khadim Ullah , Hayat Ullah , Abdul Wadood , Muhammad Taha , Ashfaq Ur
b
a
e
e
a
Rehman , Imad uddin , Muhammad Ashraf , Ayesha Shaukat , Wajid Rehman , Shafqat
Hussain, and Khalid Mohammed Khan
f
f
a
Department of Chemistry, Hazara University, Mansehra-21120, Khyber Pukhtunkhwa, Pakistan
b
Department of Biochemistry, Computational Medicinal Chemistry Laboratory, UCSS, Abdul
Wali Khan University Mardan, Pakistan
c
Universiti Teknologi MARA (UiTM), PuncakAlam Campus, 42300 Bandar PuncakAlam,
Selangor DarulEhsan, Malaysia.
d
Faculty of Applied Science UiTM, 40450 Shah Alam, Selangor, Malaysia
e
Department of Biochemistry and Biotechnology, the Islamia University of Bahawalpur,
Bahawalpur-63100, Pakistan
f
H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological
Sciences, University of Karachi, Karachi-75270, Pakistan
Abstract
A new series of triazinoindole analogs 1-11 were synthesized, characterized by EI-MS and
1
HNMR, evaluated for α-glucosidase inhibitory potential. All eleven (11) analogs showed
different range of α-glucosidase inhibitory potential with IC50 value ranging between 2.46 ±
0
.008 to 312.79 ± 0.06µM when compared with the standard acarbose (IC50, 38.25 ± 0.12 µM).
Among the series, compounds 1, 3, 4, 5, 7, 8, and 11 showed excellent inhibitory potential with
IC50 values 2.46 ± 0.008, 37.78 ± 0.05, 28.91 ± 0.0, 38.12 ± 0.04, 37.43 ± 0.03, 36.89 ± 0.06 and
3
7.11 ± 0.05µM respectively. All other compounds also showed good enzyme inhibition. The
binding modes of these analogs were confirmed through molecular docking.
Keywords: Synthesis, Triazinoindole, α-Glucosidase inhibition, Molecular docking.
*
Corresponding Author: fazalstar@gmail.com, Tel.: 0092-335-9528343

1
. Introduction
Diabetes is a metabolic disease that controls the body’s production and/or utilization of insulin.
In Type-1 diabetes the body fails to produce insulin whereas in Type-2 diabetes the body
produces insulin but due to various reasons the insulin does not function as it should. Glucose is
essential for proper functioning of our brains as well as muscles. Mismanaged or uncontrolled
diabetes can lead to blindness, circulatory problems, nerve conditions, kidney disease/ failure,
leg and foot amputations and even to death. Diabetes is also a major contributing risk factor for
heart disease and stroke [1]. α-Glucosidase enzyme is responsible for catalytic cleavage of a
glycosidic bond [2].
α-Glucosidase (EC 3.2.1.20) enzyme is involved in digestion of carbohydrates significantly
decrease the postprandial increase of blood glucose after a mixed carbohydrate diet and therefore
can be an important strategy in the management of postprandial blood glucose level in type-2
diabetic patients and borderline patients [3]. The intestinal α-glucosidase hydrolyzes complex
carbohydrates to glucose and monosaccharide in small intestine. Inhibition of this enzyme
systems helps to reduce rate of digestion of carbohydrates [4]. In diabetics the short term effect
of enzyme inhibitor drug therapies is to decrease high blood glucose levels [5].
α-Glucosidase has drawn a special interest of the pharmaceutical research community because in
earlier studies it shows the inhibition of its catalytic activity resulted in the retardation of glucose
absorption and decrease in postprandial blood glucose level [6]. α-Glucosidase inhibitors are
expected to cause no hypoglycemic events or other life-threatening events, even at overdoses,
and cause no weight gain [7]. Glucosidase inhibitors are potential bio-tools and highly useful for
medical therapies, such as diabetes, obesity, hyperlipoproteinemia, cancer and HIV [8]. α-
Glucosidase inhibitors have also been observed to block viral infections and proliferation in
HIV-infections [9,10].
Triazinoindole analogs are known to possess important biological activities such as antiviral and
antimalarial activities. Substituted triazinoindole compounds also showed an attractive
antidepressant [11] and antihypertensive activities [12]. The triazinoindole derivatives have
showed considerable interest due to its broad spectrum of antifungal, antibacterial [13], anti-
inflammatory [14] and anti-hypoxic activities [15]. Some of the triazinoindole analogues act as
potential drugs for the treatment of common cold [16-19].

We have planned to synthesize different substituted triazinoindole analogues in continuation of
our research on enzyme inhibition [20]. In this study we are going on to report synthesis, α-
glucosidase inhibitory potential and SAR of triazinoindole derivatives.
2
.0. Result and Discussion
2
.1. Chemistry
Synthesis of triazinoindole analogs were carried out in two steps. In first step isatin (10 mM) was
mixed with thiosemicarbazide (10mM) in distilled water in presence of potassium carbonate. The
reaction mixture was refluxed for 6 hrs. Reaction completion was monitor by TLC. After
completion of reaction the crude mixture was filtered and washed with ethanol and chloroform to
yield pure triazino-indolthione. In second step triazino-indolthione (3 mM) was further treated
and refluxed for 3 hrs with different phenacyl bromide (3 mM) in ethanol in the presence of
triethylamine. The reaction completion was monitored by TLC. After reaction completion the
mixture was filter and wash with hexane and chloroform to yield pure triazino-indole products
1
(
1-11). Different spectroscopic techniques such as EI-MS and H NMR were used to determine
the structure of all analogs.
.
Insert Scheme-1 Here
Insert Table-1 Here
2
.2.Biological activity
Triazino-indole analogs (1-11) exhibited effective α-glucosidase inhibitory potential. Among the
series analogs 1, 3, 4, 5, 7, 8, and 11 with IC50 values 2.46 ± 0.008, 37.78 ± 0.05, 28.91 ± 0.0,
3
8.12 ± 0.04, 38.12 ± 0.04, 36.89 ± 0.06 and 37.11 ± 0.05 showed excellent inhibitory potential
as compared to standard acarbose (IC50 value = 38.25 ± 0.12 µM)(Table-1). All other analogs
also exhibited good enzyme inhibition. The most active analog 1 having 3-hydroxyl substitution,
analog 4 having methoxy substitution, analogs 11 and 3 having 3-bromo and 4-bromo
substitution on the phenyl part of phenacyl bromide showed potent inhibitory activity as
compared to standard acarbose. Analog 8 was unique having no substitution on phenyl group but
exhibited potent inhibitory activity. Analog 5 having 3-flouro on the phenyl part while
compound 7 having coumarin moiety exhibited potent inhibitory activity.

The results showed that analogs 1, 4 with electron donating group’s i.e.hydroxyl or methoxy are
more potent than standard acarbose, while analogs 3, 5, 11 with electron withdrawing groups
exhibit potent inhibition but comparatively low potential compared with analogs 1 and 4. It was
concluded from results that both electron donating groups as well as electron withdrawing
groups play vital role but electron donating groups plays affective role in this assay. The SAR
was established through molecular docking protocol.
2
.3 Molecular Docking simulation
From the docking simulation study, it was observed that the top ranked conformation of all the
compounds were well accommodated inside the active site of the homology model of α-
glucosidase. Computationally most of the synthesized compounds showed interaction with the
hydroxyl group attach to benzene ring, carbonyl oxygen and 1, 2, 4-triazine moiety of the
compounds with the important active site residues. In case of the most active compound-1, four
hydrogen bond interactions and three π-interactions through arene-arene bond were found with
the catalytically active residues Asp68, Asn347, Asp349, Arg439, Tyr71, Phe157 and Phe300 as
shown in (Figure- 01). It was observed that both Asp68 and Asp349 established interaction with
the hydrogen of hydroxyl group attach to benzene ring and same hydrogen interaction with the
oxygen of OH group establish by Arg439, Asn347 was found in interaction with carbonyl
oxygen of the compound-1. Out of three arene-arene interaction, one established with the 1H-
pyrrole group another one was found in π-interaction with the benzene ring and the last third one
with 1, 2,4-triazine group of the compound-1. The highest activity (IC50 value 2.46 ± 0.008) of
compound-1 is due to the presence of hydroxyl group attached to the benzene ring, and both
oxygen and hydrogen of OH-group are involved in hydrogen bonding with the most important
residue Asp349. The hydroxyl group is strong activating groups which polarize the molecule and
enable it to make several interactions with other residues.

Insert Figure-1 Here
Similarly, Compound-4 and 8 also exhibited the good biological activities against the enzyme,
but if compare with the compound-1 these compounds show less activity against the enzyme,
due to compound-1 having OH-group instead of other groups at the same position. In case of
compound-4 having methoxy moiety instead of hydroxyl groups attached to benzene ring and
compound-8 haven’t any group at that position. The docked conformation of compound-4
showed five hydrogen bonds and one arene-arene interaction with active site residues Phe311,
His239, Arg312 and His279 which made it the second active compound in series (Figure-2).
Insert Figure-2 Here
In case of compound-8, the hydroxyl group not exist as in compound-1, similarly several
interactions was observed with active site residues, three hydrogen bonds and two arene-cation
interactions with the Arg439, His348, Arg212 (H-interaction), Arg212 (arene-cation) and
Arg312 which made it the third active compound in series (Figure-3).
Insert Figure-3 Here
Similarly compound-11 and compound-7 also haven’t OH group as seem in compound-1 which
made these compound fourth and fifth active compounds in series of eleven synthesized
compounds. In case of compound-11, two hydrogen, one arene-arene interaction and one arene-
cation interaction were found with the active site residue Tyr313 (two hydrogen interactions),
Arg312 and Phe300 (Figure-4).
Insert Figure-4 Here
Similarly in compound-7, two arene-cation and one arene-arene interaction were found with
residues His279 and Tyr71 (Figure-5).
Insert Figure-5 Here
Similar interaction were found in compound-3, 5 and compound-9 with residue Tyr71, Arg312,
Arg439 and Asn347, these interactions made these compounds 5th, 6th and 7th active
compounds in the series. On the other hand, least active compound-2, 6 and compound-10 show
less potent against enzyme and no interactions were found between these compounds and
binding residues of α-glucosidase.

2
.4 α-glucosidase assay
The inhibitory activities of all the isatin derivatives were measured by using the methods similar
to those described previously [21, 22].Typically, α-glucosidase activity was assayed in 50 mM
phosphate buffer (pH 6.8) containing 5% v/v dimethylsulfoxide and PNP glycoside was used as
0
a substrate. The inhibitors were pre-incubated with enzyme at 37 C for 0.5 hrs. The substrate
0
was then added and the enzymatic reaction was carried out at 37 C for 60 min. The reaction was
monitored spectrophotometrically by measuring the absorbance at 400 nm. The assay was
performed in triplicate with five different concentrations around the IC50 values that were
roughly estimated in the first round of experiments, and the mean values were adopted.
3
. Conclusion
A new sequence of eleven analogs were synthesized and evaluated for α-glucosidase inhibitory
potential. Seven analogs exhibited much potent α-glucosidase inhibitory potential with IC50
value ranging between 2.46 ± 0.008 to 312.79 ± 0.06µM when compared with the standard
acarbose (IC50 38.25 ± 0.12 µM). Compounds 1, 3, 4, 5, 7, 8, 11 with IC50 values 2.46 ± 0.008,
3
7.78 ± 0.05, 28.91 ± 0.0, 38.12 ± 0.04, 38.12 ± 0.04, 36.89 ± 0.06 and 37.11 ± 0.05 showed
excellent inhibitory potential. All other compounds also showed excellent to good enzyme
inhibition.
4
. Materials and methods
NMR spectra were obtained with AVANCE AV 300 MHZ spectrometers. NMR spectra were
recorded by using DMSO and acetone as solvent. TMS was used as internal standard. Finnegan
MAT-311A spectrometer was used for electron impact mass spectra (EI-MS) analysis. Cesium
iodide was used as an internal standard for mass measurement. All the above characterizations
were performed at H.E.J Research Institute of Chemistry, Karachi University Pakistan. Column
chromatography was performed on silica gel (E. Merck, type 60, 70-230 mesh). Pre-coated silica
gel aluminum plates (Kieselgel 60, 20×20 and 0.5 mm thick, E. Merck, Germany) were used for
TLC analysis. Light of wavelength 254 and 365 nm were used to visualize the chromatogram.
4
.1.Computational Methods

The crystallographic structure for α-glucosidase enzyme has not been solved up-to yet. However,
only few homology models have been reported [23-25] so, we build the 3D structure for α-
glucosidase by comparative homology modeling technique using the same propriety as described
by Burke et al [26]. The primary sequence of α-glucosidase was retrieved from UniProt protein
resource data bank (http://www.uniprot.org/) under the access code P53341. Template search
was performed by means of MOE-Search tools against the PDB-database implemented in MOE
2
010.11. The 1.30 Å resolving crystallographic structure of Saccharomyces cerevisiae isomaltase
(
SCI) (PDB code: 3aj7) [27] with 72.4% of sequence identity with the target was selected as the
template for modeling. The 3D structure of α-glucosidase for SCI was built by means of MOE
homology modeling tools. The constructed 3D model was subjected to energy minimization up
to 0.05 gradients. Before docking simulation, ligands and protein were prepared using MOE
2
010.11 software. 3D structure of all synthesized compounds was built by mean of Molecular
Builder program implemented in MOE software. Finally, a database was created in which all the
ligands were converted into their particular 3D structures and this database was used as input file
MOE-docking. Subsequently, the energy of compounds present in the database was minimized
up to 0.05 Gradient using MMFF94x force field. Energy minimization of the database was
followed by the preparation of protein for docking purposes. Most macromolecular crystal
structures contain little or no hydrogen coordinate data due to limited resolution and thus
protonation was accomplish prior to docking using Protonate 3D tools implemented in MOE.
Protonation was followed by energy minimization up to 0.05 Gradient using Amber99 force
field. The database was docked into the active site of protein using the Triangular Matching
docking method and 30 conformations of each Ligand protein complex were generated with
docking score (S). Each complex was analyzed for interactions and their 3D pose was taken.
4
.2.General procedure for synthesis of triazinoindole derivatives
Isatin (4.41g, 30mmol) was reacted with thiosemicarbazide (2.73 g, 30mmol) in 50 mL distilled
water in the presence of potassium carbonate (2.73 g, 30mmol) which afforded
triazinoindolthione. The triazinoindolthione was recystalized in methanol afforded 92% 5.5g
yield. The triazinoindolthione (1 mmol, 0.202g) was treated with different phenacyl bromide (1
mmol) in ethanol in the presence triethylamine (1 mmol) to obtained different substituted

derivatives of triazinoindole moiety. They were purified by recrystalization in methanol. The
1
structures of all compounds were confirmed through EI MS and H NMR.
4
.2.1. 2-(5H-[1,2,4]triazino[5,6-b]indol-3-ylthio)-1-(3-hydroxyphenyl)ethanone (1)
1
M.p. 315 °C, Yield: 70%; H-NMR: (DMSO-d
6
, 300 MHz): δ 12.5 (s, 1H,NH), 9.8 (s, 1H, OH),
8
5
.2(d, J4,5 = 7.8 Hz, 1H, H-4), 7.6 (t, J7/6,5 = 7.8 Hz, 1H,H-7 ), 7.5 (t, J6/7,5 5/4,6 = 9.6 Hz, 2H, H-
/6), 7.4 (m, 3H, H-2′/6′/5′), 7.0 (d, J4′,5′ = 8.4 Hz 1H, H-4′), 4.9 (s, 2H, SCH ); EI-MS: m/z (rel.
2
+
int. %): 336 (M , 45), 303 (27), 215 (51), 202 (45), 121 (100);
4
.2.2.2-(5H-[1,2,4]triazino[5,6-b]indol-3-ylthio)-1-(biphenyl-4-yl)ethanone (2)
1
M.p. 310 °C, Yield: 70%; H-NMR: (DMSO-d
6
, 300 MHz): δ 12.5 (s, 1H,NH), 8.2 (d,J7,6
=
7
.8Hz,1H, H-7), 8.1(d, J4,5 = 8.4 Hz, 1H, H-4), 7.8 (d, J2’,3’ = 8.4 Hz, 1H,H-2’ ), 7.7 (d, J6’,5’ = 7.2
Hz, 1H, H-5’), 7.6 (t, J6/7,5 5/4,6 = 9.6 Hz, 2H, H-5/6), 7.5 (t, J2’’′/3’’,6’’,6’’/2’’,5’’ = 6.9 Hz, 2H, H-
+
2
3
’’/6’’), 7.4 (m, 5H, H-3′/5′/3’’/4’’/5’’), 5.0 (s, 2H, CH
2
); EI-MS: m/z (rel. int. %): 396 (M , 25),
63 (43), 335 (34), 181 (100), 153 (52);
4
.2.3.2-(5H-[1,2,4]triazino[5,6-b]indol-3-ylthio)-1-(4-bromophenyl)ethanone (3)
1
M.p. 298 °C, Yield: 73%; H-NMR: (DMSO-d
6
, 300 MHz): δ 12.5 (s, 1H,NH), 8.2 (d,J7,6
=
7
.8Hz,1H, H-7), 8.0(d, J4,5 = 8.4 Hz, 1H, H-4), 7.8 (d, J2′,3′/ 6′,5′ = 8.4 Hz, 2H, H-2′/6′ ), 7.6 (t, J6/5,7
=
7.5 Hz, 1H, H-6), 7.5 (d, J3′,2′/ 5′,6′ = 8.1 Hz, 1H, H-3’/5’), 7.4 (t, J5/4,6 = 7.5 Hz 1H, H-5), 4.9 (s,
+
2
H, SCH
2
); EI-MS: m/z (rel. int. %): 399 (M , 30), 366 (42), 338 (24), 214 (100), 184 (85);
4
.21.4.2-(5H-[1,2,4]triazino[5,6-b]indol-3-ylthio)-1-(4-methoxyphenyl)ethanone (4)
1
M.p. 306 °C, Yield: 73%; H-NMR: (DMSO-d
6
, 300 MHz): δ 12.5 (s, 1H,NH), 8.2 (d,J7,6
=
=
);
7
7
.5Hz,1H, H-7), 8.0(d, J4,5 = 8.4 Hz, 1H, H-4), 7.6 (t, J6/5,7 = 7.8 Hz, 1H, H-6 ), 7.5 (d, J2′,3′/ 6′,5′
.8 Hz, 2H, H-2′/6′), 7.4 (m, 1H, H-5), 7.1 (d, J3′,2′/ 5′,6′ = 8.4 Hz, 2H, H-3′/5′), 4.9 (s, 2H, SCH
2
+
EI-MS: m/z (rel. int. %): 350 (M , 95),322 (29), 317 (63), 215 (29), 134 (100);

4
.2.5.2-(5H-[1,2,4]triazino[5,6-b]indol-3-ylthio)-1-(3-flourophenyl)ethanone (5)
1
M.p. 290 °C, Yield: 68%; H-NMR: (DMSO-d
6
, 300 MHz): δ 12.5 (s, 1H,NH), 8.2 (d,J2′,6′
=
1
.5Hz,1H, H-2′), 7.9(d, J4′,5′ = 7.5 Hz, 1H, H-4′), 7.8 (d, J6′,5’ = 8.7 Hz, 1H, H-6′ ), 7.6 (t, J4/5,6/
7
/6,5 = 7.2 Hz, 2H, H-4/7), 7.5 (m, 2H, H-5/6), 7.4 (t, J5′/6’.5’ = 7.5 Hz, 1H, H-5′), 4.9 (s, 2H,
+
SCH
2
); EI-MS: m/z (rel. int. %): 338 (M , 21), 215 (100), 173 (27), 123 (88), 95 (32);
4
.2.6.2-(5H-[1,2,4]triazino[5,6-b]indol-3-ylthio)-1-(4-nitrophenyl)ethanone(6)
1
M.p. 320 °C, Yield: 77%; H-NMR: (DMSO-d
6
, 300 MHz): δ 12.5 (s, 1H,NH), 8.4 (d,J3′,2′/5′,6′
=
8
.7Hz,2H, H-3′/5′), 8.3(d, J2′,3′/6′,5′ = 9Hz, 2H, H-2′/6′), 8.2 (d, J4,5 = 7.8 Hz, 1H, H-4 ), 7.6 (t,
J5/4,6 = 7.5 Hz, 1H, H-5), 7.5 (d, J7,6= 8.1Hz, 1H, H-7), 7.4 (t, J6/5,7 = 7.5 Hz, 1H, H-6), 5.0 (s,
+
2
H, SCH
2
); EI-MS: m/z (rel. int. %): 365 (M , 26),332 (41), 215 (100), 173 (37), 150 (67);
4
.1.7.3-(2-(5H-[1,2,4]triazino[5,6-b]indol-3-ylthio)acetyl)-2H-chromen-2-one (7)
1
M.p. 320 °C, Yield: 71%; H-NMR: (DMSO-d
6
, 300 MHz): δ 14.5 (s, 1H,NH), 8.7 (s, 1H, H-4′),
8
7
.2 (d, J7,6 = 7.8Hz, 1H, H-7), 7.9 (d, J4,5 = 7.2 Hz, 1H, H-4 ), 7.7 (t, J5′/6′,7′ = 7.2 Hz, 1H, H-5′),
.6 (m, 1H, H-8′), 7.5 (t, J6/5,7 = 5.1 Hz, 1H, H-6), 7.4 (m, 2H, H-6′/7’), 7.3 (t, J5/4,6 = 7.8 Hz, 1H,
+
H-5), 4.9 (s, 2H, SCH
2
); ; EI-MS: m/z (rel. int. %): 387 (M , 38), 214 (66), 201 (43), 187 (43),
1
73 (100);
4
.2.8.2-(5H-[1,2,4]triazino[5,6-b]indol-3-ylthio)-1-phenylpropane-1-one (8)
1
M.p. 295 °C, Yield: 80%; H-NMR: (DMSO-d
6
, 300 MHz): δ 12.6 (s, 1H,NH), 8.2 (d,J4,5 = 7.2
Hz ,1H, H-4), 8.1(d, J2′,3′/ 6′,5′ = 7.5Hz, 2H, H-2′/6′), 7.6 (m, 2H, H-4′/7 ), 7.5 (t, J3′/2′,4′ 5′/4′,6′ 6/5,7
=
7
.5 Hz, 3H, H-3′/5′/6), 7.4 (t, J5/4,6 = 7.5 Hz, 1H, H-5), 5.8 (s, 2H, SCH ); EI-MS: m/z (rel. int.
2
+
%
): 334 (M , 9), 317 (16), 229 (100), 105 (62), 70 (27);
4
.2.9.2-(5H-[1,2,4]triazino[5,6-b]indol-3-ylthio)-1-(2-methoxyphenyl)ethanone (9)
1
M.p. 327 °C, Yield: 73%; H-NMR: (DMSO-d
6
, 300 MHz): δ 7.4 (d,J4,5/7,6 = 7.5 Hz, 2H, H-4/7),
), 3.1(s, 3H,
), ;EI-MS: m/z (rel. int. %): 350 (M , 100), 322 (54), 289 (43), 131 (54), 118 (39);
7
.3(d, J3’,4’/6’,5’= 7.2Hz, 2H, H-3’/6’), 7.0 (m, 4H, H-4′/5′/5/6 ), 3.8 (s, 2H, SCH
2
+
OCH
3
4
.2.10.2-(5H-[1,2,4]triazino[5,6-b]indol-3-ylthio)-1-(3-methoxyphenyl)ethanone(10)

1
M.p. 302 °C, Yield: 65%; H-NMR: (DMSO-d
6
, 300 MHz): δ 12.5 (s, 1H,NH), 8.2 (d, J4,5 = 8.4
Hz, 1H, H-4), 8.0(d,J7,6 = 7.5Hz,1H, H-7), 7.6 (t, J6/5,7 = 7.8 Hz, 1H, H-6 ), 7.5 (d
,
J
4′,5′/6′,5′
=
7
.3Hz, 2H, H-4′/6′), 7.4 (m, 1H, H-5), 7.1 (m, 2H, H-2′/5′), 4.9 (s, 2H, SCH ); EI-MS: m/z (rel.
2
+
int. %): 350 (M ,81), 329 (35), 310 (45) 249 (33), 122 (100);
4
.2.11.2-(5H-[1,2,4]triazino[5,6-b]indol-3-ylthio)-1-(3-bromophenyl)ethanone (11)
1
M.p. 305 °C, Yield: 51%; H-NMR: (DMSO-d
6
, 300 MHz): δ 12.5 (s, 1H,NH), 8.0 (d,J4′,5′
=
7
.5Hz,1H, H-4′), 7.9(d, J6′,5′ = 7.5 Hz, 1H, H-6′), 7.6 (s, 1H, H-2′ ), 7.6 (t, J4/5, 7/6 = 7.2 Hz, 2H,
H-4/7), 7.5 (m, 2H, H-5/6), 7.4 (m, 1H, H-5′), 4.9 (s, 2H, SCH ); EI-MS: m/z (rel. int. %): 399
2
+
(
M , 34), 243 (49), 169 (100), 91 (70);
Acknowledgment: The authors are thankfull to HEC Pakistan and HEJ ICCBS University of
Karachi, Karachi for providing funding and spectroscopic facilities for this project.
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Captions:
Scheme-1: Protocol for synthesis of triazioindole analogs 1-11
Table-1: Synthesis of triazioindole analogs 1-11 and their α-glucosidase activity
Fig. 1: Docking conformation of Compound-1(most active among all 11 compounds) properly
accommodated into the binding cavity of α-glucosidase enzyme and developed four hydrogen
bond interactions and three arene-arene bond interactions with catalytic residue Asn347, Asp349
and Arg347 and with other residues.
Fig. 2: Binding mode of compound-4 in the active site of α-glucosidase enzyme
Fig. 3: Binding mode of compound-8in the active site of α-glucosidase enzyme
Fig. 4: Binding mode of the compound-11 in the active site of α-glucosidase enzyme
Fig. 5: Binding mode of compound-7 in the active site of α-glucosidase enzyme

Scheme-1:

Figure-1
Figure-2

Figure-3
Figure-4

Figure-5

Triazinoindole analogs as potent inhibitors of α-glucosidase: Synthesis, biological evaluation and
molecular docking studies
a
a
a
b
c,d
b
Fazal Rahim *, Khadim Ullah , Hayat Ullah , Abdul Wadood , Muhammad Taha , Ashfaq Ur Rehman , Imad
a
e
e
a
f
f
uddin , Muhammad Ashraf , Ayesha Shaukat , Wajid Rehman , Shafqat Hussain, and Khalid Mohammed Khan
a
Department of Chemistry, Hazara University, Mansehra-21120, Khyber Pukhtunkhwa, Pakistan
b
Department of Biochemistry, Computational Medicinal Chemistry Laboratory, UCSS, Abdul Wali Khan University
Mardan, Pakistan
c
Universiti Teknologi MARA (UiTM), PuncakAlam Campus, 42300 Bandar PuncakAlam, Selangor DarulEhsan,
Malaysia.
d
Faculty of Applied Science UiTM, 40450 Shah Alam, Selangor, Malaysia
e
Department of Biochemistry and Biotechnology, the Islamia University of Bahawalpur, Bahawalpur-63100,
Pakistan
f
H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of
Karachi, Karachi-75270, Pakistan
_
___________________________________________________________________
H
N
N
O
S
N
N
OH
Compound-1
IC value = 2.46±0.008
Potent inhibitor
5
0

Highlights:
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Synthesis of Triazinoindole Derivatives
In vitro α-glucosidase inhibitory activity
Identification of a novel class of α-glucosidase inhibitors
Structure-activity Relationship established
Molecular docking

Table 1
S.No
Structures
%Yield
IC50 (µM)
2
.46 ± 0.008
1
70
7
3
8.41 ± 0.02
2
70
73
7.78 ± 0.05
3
2
3
8.91 ± 0.01
8.12 ± 0.04
4
5
6
73
68
77
1
24.65 ± 0.09
3
7.43 ± 0.03
7
71

H
N
N
O
O
S
3
5
6.89 ± 0.06
1.57 ± 0.08
8
9
80
73
65
51
N
N
N
H C
3
H
N
N
S
N
H C
3
O
3
12.79 ± 0.06
1
0
1
3
7.11 ± 0.05
8.25 ± 0.12
1
3
Acarbose