Potent α-amylase inhibitors and radical (DPPH and ABTS) scavengers based on benzofuran-2-yl(phenyl)methanone derivatives: Syntheses, in vitro, kinetics, and in silico studies

Article abstract of DOI:10.1016/j.bioorg.2020.104238

Thirty benzofuran-2-yl(phenyl)methanones 1–30 were synthesized and characterized their structures by spectroscopic techniques. Substituted phenacyl bromide and different derivatives of 2-hydroxy-benzaldehyde treated in the presence of anhydrous K₂

Full text of DOI:10.1016/j.bioorg.2020.104238

BioorganicChemistry104(2020)104238
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Bioorganic Chemistry
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Potent α-amylase inhibitors and radical (DPPH and ABTS) scavengers based
on benzofuran-2-yl(phenyl)methanone derivatives: Syntheses, in vitro,
kinetics, and in silico studies
⁎
Irfan Alia, Rafaila Rafiquea, Khalid Mohammed Khana,b, , Sridevi Chigurupatic, Xingyue Jid,
Abdul Wadoode, Ashfaq Ur Rehmane, Uzma Salarf, Muhammad Shahid Iqbalg, Muhammad Tahab,
Shahnaz Perveenh, Basharat Alia
a H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological, Sciences, University of Karachi, Karachi 75270, Pakistan
b Department of Clinical Pharmacy, Institute for Research and Medical Consultations (IRMC), Imam Abdulrahman Bin Faisal University, P.O. Box 31441, Dammam, Saudi
Arabia
c Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, Qassim University, Buraidah 52571, Saudi Arabia
d Department of Medicinal Chemistry, College of Pharmaceutical Science, Soochow University, Suzhou, China
e Department of Biochemistry, Shankar Campus, Abdul Wali Khan University, Mardan, Khyber Pukhtoonkhwa, Pakistan
f Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi 75270,
Pakistan
g Department of Clinical Pharmacy, College of Pharmacy, Prince Sattam bin Abdulaziz University, Alkharj, Saudi Arabia
h PCSIR Laboratories Complex, Karachi, Shahrah-e-Dr. Salimuzzaman Siddiqui, Karachi 75280, Pakistan
A R T I C L E I N F O
A B S T R A C T
Keywords:
Synthesis
Benzofuran
In vitro
Thirty benzofuran-2-yl(phenyl)methanones 1–30 were synthesized and characterized their structures by spec-
troscopic techniques. Substituted phenacyl bromide and different derivatives of 2-hydroxy-benzaldehyde treated
in the presence of anhydrous K2CO3 in acetonitrile at room temperature to afford the desired benzofurans 1–30.
All compounds were screened for their in vitro α-amylase inhibitory and radical scavenging (DPPH and ABTS)
activities. Results revealed that para substituted compounds were found to be more active than the others with
IC50 values ranges for α-amylase inhibition (IC50 = 18.04–48.33 µM), DPPH (IC50 = 16.04–32.33 µM) and ABTS
(IC50 = 16.99–33.01 µM) radical scavenging activities. Activities results were compared with the standards
α-amylase
Radical scavengers
DPPH
ABTS
acarbose (IC50 = 16.08
0.07 µM) for α-amylase, ascorbic acid (IC50 = 15.08
0.03 and 15.09
0.17 µM)
Kinetics
for DPPH and ABTS radical scavenging activities, respectively. Kinetic studies predicted that all compounds
followed non-competitive mechanism of inhibition. Molecular docking results showed good protein–ligand in-
teractions profile against the corresponding target. To the best of our knowledge, out of thirty molecules, ten
compounds 18–20, 22, and 25–30 were structurally new.
Docking studies
1. Introduction
chemotherapeutic and physiological characteristics as well as for their
wide-range occurrence in nature [4]. Benzofurans are usually colorless
Heterocyclic compounds are considered to be powerful scaffolds for
many biological evaluations [1,2]. They play a vital role in the fields of
chemical and life sciences as well as in the discovery of new pharma-
cologically active molecules. In this context, oxygen based heterocycles
possess distinct pharmacological and biological activities as they are
the integral part of many synthetic and natural molecules with known
biological activities [3]. Benzofurans (oxygen based heterocycles) have
attracted medicinal and natural product chemist due to their excellent
liquids obtained from coal tar, containing a benzene ring fused with
furan ring [5,6]. For example, benzofuran derivatives as shown in Fig. 1
possess potent, nonselective aromatase inhibitory effect [7] and selec-
tive toxicity against a tumorigenic cell line [8].
Benzofuran derivatives gained special interest to researchers due to
their wide range of pharmacological activities including antiviral [9],
anti-inflammatory [10], antimicrobial [11], anti-hyperglycemic [12],
anti-oxidative [13], analgesic [14], antitumor [15], antifungal [16],
⁎ Corresponding authors at: H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological, Sciences, University of Karachi, Karachi
75270, Pakistan.
E-mail address: khalid.khan@iccs.edu (K.M. Khan).
https://doi.org/10.1016/j.bioorg.2020.104238
Received 5 December 2019; Received in revised form 3 May 2020; Accepted 10 August 2020
Availableonline28August2020
0045-2068/©2020ElsevierInc.Allrightsreserved.

I. Ali, et al.
BioorganicChemistry104(2020)104238
Current study deals with the synthesis of benzofurans 1–30 derivatives.
Here, we chose the starting material bearing hydroxy and halogen with
other substitutions, to synthesize compounds 1–30. Furthermore, well-
reported fact of the bioisosterism of oxadiazoles for a variety of car-
bonyl containing compounds such as esters, hydroxamic esters, amides,
and carbamates [47–49] leads us to incorporate the carbonyl group in
newly synthesized compounds. In addition to that the ligancy potential
of carbonyl group as a pharmacophore encouraged us to explore these
synthetic molecules for α-amylase inhibitory activity. Thus, the close
structural resemblance of the newly synthesized derivatives with the
already identified α-glucosidase inhibitors [46] prompted us to in-
vestigate their antidiabetic potential. Therefore, the aim of the present
research is to investigate α-amylase and antioxidative inhibitory ac-
tivities of a library of synthetic benzofuran derivatives 1–30 (Fig. 2).
Fig. 1. Naturally occurring benzofurans.
antiparasitic [17], and antineoplastic properties [18]. In addition, they
are also used as androgen biosynthesis modulator (furanosteroids) [19],
fluorescent sensors [20], and many others.
Diabetes is considered as a metabolic syndrome which is char-
acterized by elevated blood sugar due to relative to absolute deficiency
of insulin. Both type of diabetes has similar physio-pathological prop-
erties but different in etiology [21]. There are almost 430 million dia-
betic patients worldwide and expected to reach 630 million by 2045
with type II diabetes which is the most expressive form of this disease
[22,23]. One of the strategies for the management of type II diabetes is
the inhibition of the degradation of saccharides into glucose by in-
hibiting α-amylase, exists in gastrointestinal tract [24–27]. Scientific
evidences showed that oxidative stress also plays a vital role in the
pathogenesis of chronic disorder [28,29] and increased oxidative load
may affect the anti-oxidative defense system [30]. Some studies showed
that people with low concentrations of antioxidants are at risk of dia-
betes complications [29,31,32]. In addition to that, type II diabetes
related with endothelial dysfunctions [33]. These conditions lead to the
progression of many micro and macro vascular disorders such as ne-
phropathy, coronary artery, retinopathy, lower extremity amputations,
and cardiovascular disorders [34,35] which are the major reason of
death and morbidity all over the world [23].
2. Results and discussion
2.1. Chemistry
Substituted phenacyl bromide were treated with different deriva-
tives of 2-hydroxy-benzaldehyde in acetonitrile in the presence of an-
hydrous K2CO3. The reaction mixture was stirred at room temperature
for 4–5 h. In this reaction, 2-hydroxybenzaldehyde with anhydrous
K2CO3 forms phenolate which displaces the bromide group from phe-
nacyl bromide to afford an intermediate. Enolate was generated from
intermediate in basic condition which undergo intramolecular con-
densation reaction to afford the desired benzofurans 1–30 (Scheme 1;
Scheme 2). The overall reaction progress was monitored through TLC
analysis (Hex/EtOAc, 7:3). Structures of expected products (1–30) were
confirmed by different spectroscopic techniques including 1H NMR, 13
C
NMR, EIMS and HREI-MS. Ten compounds 18–20, 22, and 25–30 are
structurally new derivatives.
Antioxidants are the entities those can inhibit or slow down the
oxidative damage, caused by free radicals [36]. The main characteristic
of the antioxidant is to trap a free radical and to alter the mechanism of
oxidation that causes degenerative diseases [37]. Oxidative stress is
also a risk factor of several disorders such as diabetes, asthma, in-
flammatory, arthropathies, Alzheimer’s and Parkinson’s disease
[38,39]. It is well understood that diabetes and oxidative stress have
connections with each other. So, there is an upmost need to discover
new compounds which possess dual properties against diabetes and free
radicals. Our group has reported a number of lead molecules as α-glu-
cosidase and α-amylase enzyme inhibitors [40–45]. We have also re-
ported 5-aryl-2-(6-nitrobenzofuran-2-yl)-1,3,4-oxadiazoles as potent α-
glucosidase inhibitors, where, compounds containing hydroxyl and
halogens substituents were identified as potent molecules based on the
results obtained by in vitro studies. Besides the participation of aromatic
part through π-π interactions, in silico study validated the active par-
ticipation of hydroxyl and halogen substituents making important in-
teractions (hydrogen bonding) with the active site of enzyme [46].
2.2. Structure elucidation of the most active compound 4
2.2.1. 1H NMR and 13C NMR
The 1H NMR spectrum of the most active compound 4 was recorded
on a Bruker AM (CDCl3, 300 MHz). The spectrum shows the char-
acteristic singlet at δH 7.58 for H-2, of the benzofuran moiety. Two
doublet of doublet at δH 7.87 and 7.50, appeared for aromatic H-4 and
H-7, respectively, showing ortho and meta couplings (J4,5/4,6 and J7,6/
7,5). The spectrum also shows two triplets of H-5 and H-6 at δH 7.02 for
H-6, and at δH 6.99 for H-5, while the most downfield signals for the
phenyl protons appeared as doublets at δH 8.81 and δH 8.24 for H-3′/5′
and H-2′/6′, respectively (Fig. 3A).
The 13C NMR spectrum of compound 4 characteristic signals of the
benzofuran carbons at δc 151.8 (C-1), 117.7 (CH-2), 130.6 (C-3) and
156.4 (C-8). Other signals of benzofuran ring appeared at δc 123.5 (CH-
4), 123.8 (CH-5), 126.9 (CH-6) and 112.8 (CH-7). The spectrum also
shows the characteristic signal for carbonyl carbon at δc 182.4 (C-1′’).
Fig. 2. Rational of the current study.
2

I. Ali, et al.
BioorganicChemistry104(2020)104238
Scheme 1. Synthesis of benzofuran derivatives 1–30.
Scheme 2. Proposed mechanism for the synthesis of compound 1–30.
Signals for the aromatic system appeared at δc 142.2 (C-1′), 129.3 (CH-
2′/6′), 124.4 (CH-3′/5′) and a signal for carbon directly attached to
nitro group at δc 150.3 (C-4′) (Fig. 3B).
2.2.3. Structure-activity relationship (SAR) for α-amylase inhibition
activity
Apparently, the inhibitory effect is the result of cordial participation
of all structural features of compounds 1–30 including benzofuran ring,
carbonyl moiety, phenyl ring, and different substitutions. Among all
structural features, benzofuran ring, carbonyl moiety, and phenyl ring
are constant in every structure. So, by assuming that the variations in
the inhibtory activity in terms of IC50 values is due to the varying
features e.g. positions and nature of the substituents attached on ben-
zofuran and aryl rings (Fig. 5), a limited SAR is established. A close look
on the IC50 values given in Table 1 gave a perception that the com-
pounds having attachment at para position showed IC50 values com-
parable to the standard. In order to simplify the SAR, compounds were
divided in A, B, C, and D categories.
In EI-MS spectrum, molecular ion peak [M+] was observed at m/z
267, corresponds to the molecular formula of the desired product
C15H9NO4. EI-MS fragmentation pattern of compound 4 is given in
Fig. 4.
2.2.2. In vitro biological screening
All the derivatives of benzofurans 1–30 were screened for their
antioxidant (DPPH and ABTS) and α-amylase inhibitory activities, as
shown in Table 1. Compounds 4, 6, 8, 15, 16, and 20 showed com-
parable DPPH and ABTS radical scavenging activities with the standard
(DPPH, IC50 = 15.08
0.03 µM; ABTS, IC50 = 15.09
0.17 µM).
Category A consist of compounds 1–10 which possess different
substitutions at meta and para positions of phenyl moiety. Compound 1
Along with DPPH and ABTS, many compounds also possess sig-
nificant and comparable α-amylase inhibitory activity with IC50 values
(IC50 = 56.52
0.08 µM) having no substitutions, showed weak
range 16.04
0.12–48.33
0.02 µM to the standard acarbose
activity as compared to the standard acarbose (IC50 = 16.08
0.07 μM). Attachment of the methyl group at para position as in the
case of compound 2 did not show inhibition, however, introduction of
(IC50 = 16.08
0.07 µM) except compounds 2, 25–29 which were
found to be completely inactive against α-amylase enzyme.
methoxy group at the same position made the compound
3
Fig. 3. 1H- and 13C NMR chemical shift of the most active compound 4.
3

I. Ali, et al.
BioorganicChemistry104(2020)104238
Fig. 4. EI-MS fragmentation of the most active compound 4.
(IC50 = 62.17
0.14 µM) weakly active. Inactivity of compound 2
2.2.4. Structure activity relationship (SAR) for DPPH and ABTS radical
scavenging activities
might be due to not well fit within the active site of the enzyme.
Compounds 4 and 5 are positional isomers, among them, compound 4
From category A, para substituted compounds
4
(DPPH,
(IC50 = 18.04
0.05 µM) with nitro group at para position was much
IC50 = 16.04
IC50 = 25.86
0.12 μM: ABTS, IC50 = 16.99
0.73 μM: ABTS, IC50 = 25.71
0.09 μM), 6 (DPPH,
0.72 µM) and 8
more active than its meta isomer 5 (IC50 = 76.7
0.06 µM) which is
the least active in this category as well. It is noted that compound 4
exhibit the most active inhibition among this series. Similarly, com-
pounds 6 and 7 are positional isomers of bromo group. It was found that
(DPPH, IC50 = 25.86
0.73 μM: ABTS, IC50 = 25.71
0.72 µM)
were the most active scavengers against both DPPH and ABTS which
showed scavenging activities close to standard ascorbic acid (DPPH,
compound 6 (IC50 = 28.84
0.13 µM) with para substitution is much
IC50 = 15.08
parent analog
IC50 = 59.27
0.03 μM: ABTS, IC50 = 15.09
0.17 µM). The
more active than meta substituted compound 7 (IC50 = 52.7
1
(DPPH, IC50
=
57.527
0.08 μM: ABTS,
0.06 µM). Compound 8 (IC50 = 19.46
0.03 µM) with para chloro
0.18 µM) without any substitution, showed weak
substituted displayed activity comparable to the standard. The attach-
antioxidant activity. At para position the presence of electron donating
ment of chloro at meta position as in the case of compound 9
group in compound 2 (DPPH, IC50 = 62.13
IC50 = 62.79 0.17 µM) again lowered the activity. Substitution of
methoxy group in compound 3 (DPPH, IC50 = 52.17 0.14 µM:
ABTS, IC50 = 52.01 0.09 µM) increased the activity as compared to
compound 1 and 2 which might be due to the efficiently scavenged the
radicals. Compound 5 (DPPH, IC50 = 75.7 0.16 μM: ABTS,
IC50 = 76.97 0.14 µM) with nitro substitution at meta position is the
least active analog of this category. Another meta bromo substituted
compound (DPPH, IC50 42.7 0.06 µM: ABTS,
0.08 µM: ABTS,
(IC50 = 65.46
0.03 µM), lowered the activity. Decreased activity of
meta substituted analogs might be due to the attainment of conforma-
tion which didn’t well fit into the active site of the enzyme. Compound
10 (IC50 = 65.84
0.11 µM) with para phenyl substitution exhibited
almost the same activity than other para substituted analogs (Fig. 6).
Category B possesses compounds 11–19 having chloro groups on
benzofuran ring. In this category, compounds 15 and 16 were the most
active analogs with IC50 = 28.04
0.02 µM and IC50 = 29.86
7
=
0.13 µM, respectively. Comparison of activities of compounds 15
and 16 with analogs 7 and 8 reveals that attachment of an electron
withdrawing (EWG) choro group on benzofuran moiety increases the
IC50 = 44.97
0.19 µM) exhibited moderate antioxidant activity
against both DPPH and ABTS radicals. This showed that substitutions at
meta positions have moderate roles in stabilizing the reactive species.
inhibitory potential. Similarly, compound 14 (IC50
0.23 µM) as compared to compound 5 (IC50 = 76.7
=
32.846
Similarly, in compound 9 (DPPH, IC50 = 63.84
0.03 µM: ABTS,
0.06 µM) of
IC50 = 64.61
0.11 µM) having two adjacent chloro group showed
category A, gave better activity due to the incorporation of chloro at
weak scavenging potential which might be due to these both groups
benzofuran ring. The least active compound in this category is com-
were decreasing the electron density of each other. However, para
pound 18 (IC50 = 70.7
0.06 µM) with aromatic substitution at para
substituted
phenyl
substituted
compound
10
(DPPH,
position. Less activity of compound 18 might be due to being bulky
IC50 = 63.01
0.07 μM: ABTS, IC50 = 63.11
0.15 µM) also
group as compared to other analogs. Other compounds which have
showed weak scavenging potential (Fig. 10).
weak inhibition potentials are compounds 17 (IC50
0.06 µM) with two chloro groups and 19 (IC50 = 66.65
with nitro substitution, respectively (Fig. 7).
=
60.7
In category B, attachment of chloro group at C-5 of benzofuran also
effect the antioxidant activity. As observed previously, para substituted
0.03 µM)
analogs 15 (DPPH, IC50
=
20.04
0.02 μM: ABTS,
0.73 μM:
0.72 µM), appeared as the most active com-
pounds of this category. Dichloro substitutions at aryl ring as in case of
compound 17 (DPPH, IC50 55.7 0.06 μM: ABTS,
IC50 = 55.97 0.19 µM) decreased the scavenging activities.
Compound 12 (DPPH, IC50 35.33 0.02 μM: ABTS,
IC50 = 36.01 0.12 µM) with para methoxy substitution, was found
to be good scavengers than other para substituted analogs such as para
nitro substituted compound 13 (DPPH, IC50 = 67.33 0.02 μM:
ABTS, IC50 = 68.01 0.12 µM) and para phenyl substituted com-
50.7 0.06 μM: ABTS,
0.19 µM). Meta substituted analog 14 (DPPH,
Category C comprises five compounds 20–24 having ethoxy group
at benzofuran ring. Out of them, compound 20 (IC50 = 48.33
0.02 µM) was only molecule which displayed some inhibitory ac-
tivity as compared to compound 2 from category A, without ethoxy
group which showed no activity. The variation between these two
compounds is only the attachment of the ethoxy group at C-7 which
increased the inhibition activity. Compounds 21 (IC50 = 50.33
IC50 = 21.99
0.09 µM) and 16 (DPPH, IC50 = 21.86
ABTS, IC50 = 21.71
=
=
0.02 µM) and 23 (IC50 = 59.93
0.11 µM) also showed weak
activity with para substitution. On contrary to the categories A and B,
para bromo substituted compound 22 (IC50 = 71.7 0.06 µM)
showed less inhibition. Again para phenyl substituted compound 24
pound 18 (DPPH, IC50
=
(IC50 = 70.7
0.06 µM) showed weak inhibition (Fig. 8).
IC50 = 51.97
IC50 = 25.86
Category D consist of compound 25–30, having two hydroxy groups
at C-5 and C-7 of benzofuran moiety, showed weak inhibition might be
due to not fulfilling the substitution conditions to interact with enzyme
except compound 30 which have weak α-amylase inhibition (Fig. 9).
0.43 µM: ABTS, IC50 = 27.71
0.13 µM) appeared
more active than compound 5 of category A. Introduction of second
chloro group at C-7 of benzofuran ring as in compound 19 (DPPH,
IC50 = 76.65
0.03 μM: ABTS, IC50 = 77.47
0.13 µM) further
4

I. Ali, et al.
BioorganicChemistry104(2020)104238
Table 1
Different structures, In vitro α-amylase inhibitory and radicals (DPPH and ABTS) scavenging activities of benzofuran derivatives 1–30.
S. No.
Structures
α-Amylase inhibitory activity
DPPH radical scavenging activity
ABTS radical scavenging activity
IC50
SEMa
IC50
SEMa
IC50
SEMa
Category “A”
1
56.52
0.08
57.52
0.08
59.27
0.18
2
3
4
NAb
62.13
52.17
16.04
0.08
0.14
0.12
62.79
52.01
16.99
0.17
0.09
0.09
62.17
18.04
0.14
0.05
5
6
76.7
0.06
0.13
75.7
0.16
0.73
76.97
25.71
0.14
0.72
28.84
25.86
7
8
52.7
0.06
0.03
42.7
0.06
0.03
44.97
17.71
0.19
0.71
19.46
17.86
9
65.46
65.84
0.03
0.11
63.84
63.01
0.03
0.07
64.61
63.11
0.11
0.15
10
Category “B”
11
73.33
0.02
63.33
0.02
65.01
0.12
(continued on next page)
5

I. Ali, et al.
BioorganicChemistry104(2020)104238
Table 1 (continued)
S. No.
Structures
α-Amylase inhibitory activity
DPPH radical scavenging activity
ABTS radical scavenging activity
IC50
SEMa
0.02
IC50
SEMa
0.02
IC50
SEMa
0.12
12
13
39.33
35.33
36.01
67.33
0.02
67.33
0.02
68.01
0.12
14
15
32.84
28.04
0.23
0.02
25.86
20.04
0.43
0.02
27.71
21.99
0.13
0.09
16
29.86
0.13
21.86
0.73
21.71
0.72
17
18
60.7
70.7
0.06
0.06
55.7
50.7
0.06
0.06
55.97
51.97
0.19
0.19
19
66.65
0.03
76.65
0.03
77.47
0.13
Category “C”
20
48.33
50.33
0.02
0.02
32.33
37.33
0.02
0.02
33.01
38.01
0.12
0.12
21
(continued on next page)
6

I. Ali, et al.
BioorganicChemistry104(2020)104238
Table 1 (continued)
S. No.
Structures
α-Amylase inhibitory activity
DPPH radical scavenging activity
ABTS radical scavenging activity
IC50
SEMa
0.06
IC50
SEMa
0.18
IC50
SEMa
0.18
22
23
24
71.70
87.63
89.79
59.93
70.70
0.11
0.06
59.93
65.7
0.11
0.06
50.79
65.97
0.27
0.19
Category “D”
25
NAb
NAb
59.33
50.70
0.02
0.06
58.01
51.97
0.12
0.19
26
27
NAb
66.65
0.03
67.47
0.13
28
29
NAb
NAb
59.33
89.63
0.02
0.18
58.01
88.79
0.12
0.18
30
75.46
0.03
63.84
0.03
62.71
0.11
(continued on next page)
7

I. Ali, et al.
BioorganicChemistry104(2020)104238
Table 1 (continued)
S. No.
Structures
α-Amylase inhibitory activity
DPPH radical scavenging activity
ABTS radical scavenging activity
IC50
SEMa
IC50
SEMa
0.03
IC50
SEMa
0.17
Standards
Ascorbic acidc
Acarbosed
–
15.08
–
15.09
–
16.08
0.07
SEMa (standard error mean); NAb (Not active), Ascorbic acidc (Standard for DPPH and ABTS radical scavenging activity); Acarbosed (standard inhibitor for α-amylase
inhibitory activity).
Out of category D having two hydroxyl groups at benzofuran ring,
compounds 25 (DPPH, IC50
=
59.33
0.02 µM; ABTS,
IC50 = 58.01
IC50 51.97
IC50 = 59.33
moderate scavenging activities. Other analogs 27 (DPPH,
IC50 = 66.65 0.03 μM: ABTS, IC50 = 67.47 0.13 µM) and 30
(DPPH, IC50 = 63.84 0.11 µM)
0.12 M), 26 (DPPH, IC50 = 50.70 0.06 μM: ABTS,
=
0.19 µM) and compound 28 (DPPH,
0.02 μM: ABTS, IC50 = 58.01
0.12 µM), displayed
0.03 μM: ABTS, IC50 = 62.71
exhibited slightly decreased potential which might be due to the nature
and position of the attached group that make them less capable to
scavenged radicals. Similarly, dichloro substituted compound 29
(DPPH, IC50 = 89.63
0.18 µM; ABTS, IC50 = 88.79
0.18 µM)
Fig. 5. Structure of benzofurans.
found to be the least active analogs in the whole library (Fig. 13).
decreased the radical scavenging potential and found to be the least
active analog of this category (Fig. 11).
2.2.5. Kinetic studies for α-amylase enzyme inhibitory activity
Compounds 4, 6, 8, 15, 16, and 20 were analyzed to interpret the
inhibition mechanism of synthesized compounds. Kinetic studies were
performed by Sigma-Plot enzyme kinetic software version 14.0 via
graph fitting analysis. Through various kinetic plots such as Line
Weaver-Burk (Fig. 14A), Hill (Fig. 14B), Hanes-Woolf (Fig. 14C), Eadie-
Hofstee (Fig. 14D), Dixon (Fig. 14E), and Scatchard models (Fig. 14F).
Values of parameters Vmax, Km, AICc, and R2 were represented in
Table 2. On the Basis of low AICc value, and curve fitting model shown
that all compounds were non-competitive type.
Among category C having ethoxy group at C-7 of benzofuran nu-
cleus, para methyl substituted analog 20 (DPPH, IC50 = 32.33
0.02 µM; ABTS, IC50 = 33.01
0.12 µM) appeared as the most
active analog of this category. Replacement of methyl with nitro and
chloro groups as in compounds 21 (DPPH, IC50 = 37.33
0.02 μM:
ABTS, IC50 = 38.01
0.12 µM) and compound 23 (DPPH,
IC50 = 59.93
0.11 μM: ABTS, IC50 = 50.79
0.27 µM), respec-
tively, displayed slightly decreased activity. However, the replacement
with bromo group as in compound 22 (DPPH, IC50 = 87.63
0.18 µM: ABTS, IC50 = 89.79
0.18 µM) was weak scavenger.
0.06 µM: ABTS, IC50 = 65.97
Compound 24 (DPPH, IC50 = 65.7
2.3. Molecular docking studies
0.19 µM) having para phenyl showed moderate scavenging activity
(Fig. 12).
To the best of our knowledge, we have performed blind docking
Fig. 6. α-Amylase inhibitory activity of compounds 1–10 (Category A).
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BioorganicChemistry104(2020)104238
Fig. 7. α-Amylase inhibitory activity of compounds 11–19 (Category B).
choosing the whole structure of the α-amylase enzyme as an active site
due to the non-competitive nature of the synthetic compounds to ex-
plore the possible binding mode of these synthetic compounds against
the target enzyme. We have observed that these synthetic compounds
bind to the site (cryptic) apart from the substrate-binding site, which
also might support their non-competitive nature (Fig. 15A). We have
noticed while performing blind docking study that compounds bearing
electron-withdrawing group (EWG) such as NO2, Cl, and Br, etc., at
various position showed good inhibitory activity against the targeted
enzyme, while bearing electron-donating groups (EDG) showed less
inhibitory activity. However, EWG might make aromatic ring electron-
poor (δ + ) relative to benzene. Therefore, these groups strongly de-
activate the ring and further compel the compounds to adopt favorable
interactions with different binding affinities; hence, they might be
raised the inhibitory activity. The high potency of compounds 4, 8, 17,
and 20 that is bearing EWG (i.e., NO2, Cl, Br) might be due to the
variation in the magnitude of withdrawal of electrons from the benzene
ring at a certain level and subsequently, increase the enzyme activity.
In detail, the results of blind docking revealed that in the cryptic
site, most of the residues adopted interactions with the 1-(4,5-dihy-
drofuran-2-yl) ethanone and nitrobenzene moiety of the synthetic
compounds. In case of compound 4 in the series showed best inhibitory
activity against α-amylase enzyme not only in vitro but also observed
good protein–ligand-interaction (PLI) profile; including arene-arene
interaction by Trp388, the basic Arg322, and Arg343 which adopted
side-chain H-donor interactions with both the oxygen of NO2 group
(Fig. 15B). While in the case of compound 8 in the series, we noticed
similar interaction with the cryptic site residues, but the only difference
found is in the interaction by the basic residue Arg343. In contrast, in
case of compound 4, it makes two interactions with both oxygen but
only one in case of compound 8 of category B with the chlorine group
(Fig. 15C).
These results delineate that the high potency of the compound 4
against the targeted enzyme might be due to the substantial
Fig. 8. α-Amylase inhibitory activity of compounds 20–24 (Category C).
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BioorganicChemistry104(2020)104238
Fig. 9. α-Amylase inhibitory activity of compounds 25–30 (Category D).
withdrawing magnitude of the nitro group which had the energetic EW-
inductive-effect. As discussed previous paragraph, that due EWG, the
aromatic ring become electron-poor relative to benzene and therefore,
de-activate the ring and hence that benzene ring searching further for
making interactions with critical residue to let gains the stability and
this way they migh be enhanced the inhibitory potential. While other
compounds also showed good inhibitory potentials at a different level,
it might be due to their magnitude of withdrawing of an electron from
the same benzene ring and hence benzene unable to make interactions
with others. Our experimental activity correlate with the blind docking
results, as shown in Fig. 17. The PLI profile enlisted in Table 3.
In order to further validate our results based on the inhibitory po-
tential of the compounds, where the compounds showed the best in-
hibitory potential but showed conflict with the kinetic study, where
their nature is non-competitive. The blind docking study revealed that
all the compounds bind to the cryptic site which is distant from the
substrate-binding site. Therefore, to further validate the inhibitory
potential, we have performed molecular dynamics (MD) simulation
study of the high potent compound 4 in complex with the α-amylase
enzyme. We simulated a fully solvated atomistic model of the α-amylase
enzyme both in the presence and absence of compound. We have
analyzed the root-mean-square-deviation (RMSd) in order to check the
stability of the overall conformation both in the absence and presence
of the potent compound. The dynamics results in the absence of potent
compound revealed a very unstable behavior while upon binding of the
compound in the cryptic site stabilized the enzyme (Fig. 16a)
throughout MD simulation. Moreover, we have root-mean-square-fluc-
tuation (RMSf) to check the impact of the individual residue. The re-
sults revealed that in the absence of compound, some of the regions
showed high fluctuation, while the same regions showed less fluctua-
tion upon binding of the compound which might indicate the role of
these regions in the enzyme function (i.e. inhibitory activity) as shown
in Fig. 16b. Furthermore, to corroborate the overall displacement in the
conformation of the enzyme, we have analyzed the dynamics-cross-
Fig. 10. DPPH and ABTS radical scavenging activity of compounds 1–10 (Category A).
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BioorganicChemistry104(2020)104238
Fig. 11. DPPH and ABTS radical scavenging activity of compounds 11–19 (Category B).
Fig. 12. DPPH and ABTS radical scavenging activity of compounds 20–24 (Category C).
correlation-map (DCCM), as shown in Fig. 16c, and −16d. Interest-
ingly, we have observed that in the absence of the compound, the active
site (substrate binding site) and the site where our synthetic compound
bonded showed distinct behavior. The active site region showed zero
correlation, while the cryptic site showed a strong negative correlation
which supports that dynamically, this enzyme might possess the hidden
cryptic site apart from the active site which is also our supportive in-
formation regarding our blind docking results. One the other hand, in
the presence of the compound, we have observed that a robust positive
correlation in the active region, which indicates the compactness of this
site comprised residues (closing event), while the negative correlation
diminished in the presence of a compound in the cryptic site. These
results delineate that binding of the compound in the cryptic site bring
significant conformational changes which might be functional and will
give us clue toward the inhibitory event of the corresponding enzyme
and might support the potential of the synthetic compound.
3. Conclusion
A library of thirty benzofurans were synthesized and screened for
their inhibitory activity against α-amylase, and radical scavenging
(DPPH and ABTS) activities. Based on the results obtained from the in
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BioorganicChemistry104(2020)104238
Fig. 13. DPPH and ABTS radical scavenging activity of compounds 25–30 (Category D).
vitro screening and structure–activity relationship (SAR) showed that
the positions of the substituted analogs play a significant role. The para
substituted compounds founds to be the most active in both α-amylase
enzyme inhibitory and radical scavenging activities. Kinetic studies
reveal that all compounds were non-competitive type inhibitors.
Docking results of the most active compound 4 reveals good pro-
tein–ligand-interaction (PLI) profile against the corresponding target
which was tuned by serval key residues including arene-arene inter-
action by Trp388, the basic Arg322, and Arg343 which adopted side-
chain H-donor interactions with both the oxygen of NO2 group. In this
study, we have recognized a library of lead compounds having great
potential against α-amylase enzyme as well as potent antioxidants
which would be helpful in future for the designing and development of
drugs against diabetes and oxidative stress in patients.
4.2.1. Benzofuran-2-yl(phenyl)methanone (1) [50]
White powder; Yield: 75%; M.P.: 88–90 °C; 1H NMR (CD3OD,
300 MHz): δH 7.96 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 7.87 (dd,
J
4,5 = 9 HZ, J4,6 = 3 Hz, 1H, H-4), 7.76 (m, 1H, H-4′), 7.65 (d, J3′,2′/
5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.59 (s, 1H, H-2), 7.46 (dd, J7,6 = 9 HZ,
J7,5 = 6 Hz, 1H, H-7), 7.04 (t, J6(5,7) = 6 Hz, 1H, H-6), 6.96 (t,
J
5(4,6) = 6 Hz, 1H, H-5); 13C NMR (CDCl3, 75 MHz): δC 184.5, 156.1,
152.3, 137.2, 133.1, 129.7, 129.7, 128.7, 128.7, 128.3, 127.1, 124.1,
123.4, 116.6, 111.3; EI-MS m/z (% rel. abund): 222 (M+, 45), 145 (17),
121 (33), 118 (35), 105 (100), 77 (42).
4.2.2. Benzofuran-2-yl(p-tolyl) methanone (2) [50]
White powder; Yield: 87%; M.P.: 60–62 °C; 1H NMR (CDCl3,
300 MHz): δH 7.92 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 7.87 (dd,
J
4,5 = 9HZ, J4,6 = 3 Hz, 1H, H-4), 7.58 (s, 1H, H-2), 7.47 (dd, J7,6 = 9
4. Experimental
HZ, J7,5 = 3 Hz, 1H, H-7), 7.42 (d, J3′,2′/5′,6′ = 9 Hz, 2H, H-3′, H-5′),
7.04 (t, J6(5,7) = 6 Hz, 1H, H-6), 6.96 (t, J5(4,6) = 6 Hz, 1H, H-5), 2.34
(s, 3H, H-1′'); 13C NMR (CDCl3, 75 MHz): δ 184.2, 155.8, 152.6, 143.9,
134.7, 129.8, 129.8, 128.9, 128.9, 128.2, 127.2, 124.6, 123.8, 116.2,
112.7, 21.7; EI-MS m/z (% rel. abund.): 236 (M+, 89), 221 (45), 145
(27), 121 (66), 118 (41), 91 (77), 65 (22).
4.1. Materials and methods
All reagents were purchased from Sigma-Aldrich, USA. α-Amylase
enzyme from Aspergillus oryzae was obtained from Sigma-Aldrich Co.
LLC (St. Louis, MO). The NMR (300, 400, and 500 MHz) spectra were
recorded on Bruker AM spectrometers. Mass spectra (EI) and HR-MS
(EI) were recorded on MAT 312 and MAT 113D mass spectrometer
(Germany) mass spectrometer. Melting points were determined by
using Büchi Melting Point-560 apparatus and are uncorrected. Thin
layer chromatography was carried out using pre-coated silica gel-254
Merck, Germany. Spots were visualized under UV light at 366 and
254 nm or iodine vapors. Chemical shift values are presented in ppm
with respect to TMS as internal standard and coupling constant are
presented in Hz.
4.2.3. Benzofuran-2-yl(4-methoxyphenyl) methanone (3) [50]
White powder; Yield: 91%; M.P.: 97–99 °C; 1H NMR (CDCl3,
300 MHz): δH 7.96 (d, J2′,3′/6′,5′= 9 Hz, 2H, H-2′, H-6′), 7.86 (dd,
J
4,5 = 9, J4,6 = 3 Hz, 1H, H-4), 7.58 (s, 1H, H-2), 7.49 (dd, J7,6 = 9 HZ,
J7,5 = 3 Hz, 1H, H-7), 7.43 (d, J3′,5′/2′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.07 (t,
J
6(5,7) = 6 Hz, 1H, H-6), 6.94 (t, J5(4,6) = 6 Hz, 1H, H-5), 3. 83 (s, 3H,
O-CH3); 13C NMR (CDCl3, 75 MHz): δC 182.9, 163.7, 155.9, 152.8,
132.1, 129.9, 129.9, 128.1, 127.2, 123.9, 123.1, 115.6, 113.9, 113.9,
112.6, 55.7; EI-MS m/z (% rel. abund.): 252 (M+, 88), 221 (15), 135
(100), 107 (7), 77 (9).
4.2. General procedure for the synthesis of compounds 1–30
In an oven dried round-bottomed flask, a mixture of substituted
salicylaldehyde (1 mmol), phenacyl bromide derivatives (1 mmol) and
K2CO3 (1 mmol) in acetonitrile (10 mL) were stirred at room tem-
perature for 4–5 h. After completion of the reaction, the mixture was
poured onto ice resulting in precipitate. Precipitate were filtered and
washed thoroughly with excess distilled water and hexane to afford
pure products. The solids were crystallized from ethanol. The overall
reaction was monitored through TLC analysis. Compounds 1–30
(Table 1) were characterized by different spectroscopic techniques in-
cluding 1H-, 13C NMR, EI-MS, HREI-MS, and IR.
4.2.4. Benzofuran-2-yl(4-nitrophenyl) methanone (4) [51]
Pale yellow; Yield: 96%; M.P.: 200–202 °C; 1H NMR (CDCl3,
300 MHz): δH 8.81 (d, J3′,5′/2′,6′ = 9 Hz, 2H, H-3′, H-5′), 8.24 (d, J2′,3′/
6′,5′= 9 Hz, 2H, H-2′, H-6′), 7.87 (dd, J4,5 = 9 HZ, J4,6 = 3 Hz, 1H, H-4),
7.58 (s, 1H, H-2), 7.50 (dd, J7,6 = 9 HZ, J7,5 = 3 Hz, 1H, H-7), 7.02 (t,
J6(5, 7) = 6 Hz, 1H, H-6), 6.99 (t, J5(4,6) = 6 Hz, 1H, H-5); 13C NMR
(CDCl3, 75 MHz): δC 182.4, 156.4 151.8, 150.3, 142.2, 130.6, 129.3,
129.3, 126.9, 124.4, 124.4, 123.8, 123.5, 117.7, 112.8; EI-MS m/z (%
rel. abund.): 267 (M+, 100), 165 (10), 150 (11), 145 (92), 89 (19).
12

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BioorganicChemistry104(2020)104238
Lineweaver-Burk
Hill
0.030
0.025
0.020
0.015
0.010
0.005
1000
100
10
1
0.1
0.01
-10
0
10
20
30
40
50
60
1.2
0.6
0.01
0.1
1
10
1/[Substrate] (µM)
[Substrate] (µM)
I = 0
I = 0
I = 0.0625
I = 0.125
I = 0.2
I = 0.0625
I = 0.125
I = 0.2
A
B
I = 0.4
I = 0.4
Hanes-Woolf
Eadie-Hofstee
0.005
0.004
0.003
0.002
0.001
1000
800
600
400
200
0
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
0
1000
2000
3000
4000
5000
6000
7000
[Substrate] (µM)
Rate (µmol/min/mg)/[Substrate] (µM)
I = 0
I = 0
I = 0.0625
I = 0.125
I = 0.2
I = 0.0625
I = 0.125
I = 0.2
D
C
I = 0.4
I = 0.4
Dixon
Scatchard
0.035
0.030
0.025
0.020
0.015
0.010
0.005
7000
6000
5000
4000
3000
2000
1000
0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0
200
400
600
800
1000
[Inhibitor] (µM)
Rate (µmol/min/mg)
S = 0.02
S = 0.2
S = 0.4
S = 0.8
S = 1
I = 0
I = 0.0625
I = 0.125
I = 0.2
E
F
I = 0.4
Fig. 14. (A): Lineweaver-Burk plot of 1/[S] vs 1/Rate in the different concentration of non-competitive type inhibitor. (B): Hill plot of different concentration of [S]
vs Rate (Vmax-Rate) in the different concentration of non-competitive type inhibitor. (C): Hanes-Woolf plot of compound 4 at different concentration of [S] vs [S]/
Rate in the different concentration of noncompetitive type inhibitor. (D): Eadie-Hofstee plot of compound 4 by rate/[S] vs Rate in the different concentration of non-
competitive type inhibitor. (E): Dixon plot of compound 4 at different concentration of non-competitive Inhibitor vs 1/Rate. (F): Scatchard plot of compound 4 by
Rate vs Rate/[S] in the different concentration of non-competitive type inhibitor.
4.2.5. Benzofuran-2-yl(3-nitrophenyl) methanone (5) [50]
m/z (% rel. abund.): 267 (M+, 44), 150 (100), 145 (32), 121 (23), 104
Pale yellow powder; Yield: 81%; M.P.: 134–136 °C; 1H NMR (CDCl3,
300 MHz): δH 8.53 (d, J2,6 = 3 Hz, 1H, H-2′), 8.47 (dd, J4′,5′ = 9 HZ,
J4′,6′ = 3 Hz, 1H, H-4′), 8.33 (dd, J6′,5′ = 9 HZ, J6′,2′ = 3 Hz, 1H, H-6′),
7.99 (t, J5′(4′,6′) = 9 Hz, 1H, H-5′), 7.84 (dd, J4,5 = 9 HZ, J4,6 = 3 Hz,
1H, H-4), 7.58 (s, 1H, H-2), 7.47 (dd, J7,6 = 9 HZ, J7,5 = 3 Hz, 1H, H-7),
(33), 76 (23), 43 (23).
4.2.6. Benzofuran-2-yl(4-bromophenyl) methanone (6) [50]
White powder; Yield: 93%; M.P.: 170–172 °C; 1H NMR (CDCl3,
300 MHz): δH 7.95 (d, J3′,2′/5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.87 (dd,
7.04 (t, J6(5,7) = 6 Hz, 1H, H-6), 6.96 (t, J5(4,6) = 6 Hz, 1H, H-5); 13
C
J
4,5 = 9 HZ, J4,6 = 3 Hz, 1H, H-4), 7.69 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′,
NMR (CDCl3, 75 MHz): δC 181.6, 156.3, 151.7, 148.4, 138.4, 135.2,
H-6′), 7.58 (s, 1H, H-2), 7.50 (dd, J7,6 = 9 HZ, J7,5 = 3 Hz, 1H, H-7),
129.9, 129.1, 127.3, 126.8, 124.6, 124.3, 123.7, 117.2, 112.8; EI-MS
7.04 (t, J6(5,7) = 6 Hz, 1H, H-6), 6.96 (t, J5(4,6) = 6 Hz, 1H, H-5); 13
C
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BioorganicChemistry104(2020)104238
Table 2
Kinetic study of the active compounds 4, 6, 8, 15, 16, and 20.
Compounds
Vmax (µM/min)
Km (mM)
AICc
R2
Type of inhibition
4
898.9
742.2
805.1
795.4
814.6
820.4
0.60
0.60
0.59
0.59
0.59
0.60
264.6
289.3
302.5
288.5
270.4
280.6
0.987
0.915
0.944
0.902
0.915
0.912
Non-competitive type
Non-competitive type
Non-competitive type
Non-competitive type
Non-competitive type
Non-competitive type
6
8
15
16
20
Fig. 15. The Protein-Ligand Interaction (PLI) profiles against α-amylase. (A-C) indicates the surface representation of the α-amylase enzyme and represent the PLI
profile for compound 4 and 8.
Fig. 16. (a) represents the RMSd both in the pre-
sence (red) and absence (black) of compound 4. (b)
represents the RMSf for both the active site and
cryptic site residues were labeled with an arrow. (c)
and (d) represent the DCCM plot, the active and
cryptic sites were labeled with a black box. (For
interpretation of the references to color in this
figure legend, the reader is referred to the web
version of this article.)
NMR (CDCl3, 75 MHz): δC 183.2, 156.2, 152.2, 135.9, 131.9, 131.9,
131.1, 131.1, 128.7, 128.2, 126.9, 124.3, 123.5, 116.7, 112.7; EI-MS
m/z (% rel. abund.): 300 (M+, 100), 302 (M+2, 96), 221 (30), 185
(37), 183 (39), 155 (12), 145 (44).
1H, H-4′), 7.96 (dd, J6′,5′ = 9 HZ, J6′,2′= 3 Hz, 1H, H-6′), 7.84 (dd,
4,5 = 9 HZ, J4,6 = 3 Hz, 1H, H-4), 7.68 (t, J5′(4′,6′) = 9 Hz, 1H, H-5′),
J
7.58 (s, 1H, H-2), 7.49 (dd, J7,6 = 9 HZ, J7,5 = 3 Hz, 1H, H-7), 7.02 (t,
J
6(5,7) = 6 Hz, 1H, H-6), 6.99 (t, J 5(4, 6) = 6 Hz, 1H, H-5); 13C NMR
(CDCl3, 75 MHz): δC 182.7, 156.1, 151.8, 138.9, 135.8, 132.3, 130.1,
128.7, 128.0, 126.9, 124.2, 123.4, 122.8, 116.9, 112.6; EI-MS m/z (%
rel. abund.): 300 (M+, 73), 302 (M+2, 75), 221 (26), 185 (72), 183
(87), 155 (26), 145 (78), 118 (100), 89 (15).
4.2.7. Benzofuran-2-yl (3-bromophenyl) methanone (7) [50]
White powder; Yield: 90%; M.P.: 125–127 °C; 1H NMR (CDCl3,
300 MHz): δH 8.19 (d, J2′,6′ = 3 Hz, 1H, H-2′), 8.03 (d, J4′,5′ = 9 Hz,
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BioorganicChemistry104(2020)104238
1H, H-2), 7.54 (d, J4,6 = 3 Hz, 1H, H-4), 7.51 (dd, J6,7 = 9 Hz,
J
6,4 = 3 Hz, 1H, H-6), 3.88 (s, 3H, H-1′'); 13C NMR (CDCl3, 75 MHz): δC
182.5, 164.2, 157.3, 154.3, 132.2, 131.0, 130.8, 130.8, 129.1, 128.6,
122.7, 115.6, 114.9, 114.9, 113.6, 56.5; EI-MS m/z (% rel. abund.): 286
(M+, 81), 288 (M+2, 58), 271 (21), 255 (45), 152 (47), 135 (100), 107
(39), 92 (33), 77 (53), 44 (50).
4.2.13. (5-Chlorobenzofuran-2-yl) (4-nitrophenyl) methanone (13) [51]
Pale yellow; Yield: 82%; M.P.: 188–190 °C; 1H NMR (CDCl3,
300 MHz): δH 8.40 (d, J3′,2′/5′,6′ = 9 Hz, 2H, H-3′, H-5′), 8.22 (d, J2′,3′/
6′,5′ = 9 Hz, 2H, H-2′, H-6′), 7.73 (d, J7,6 = 9 Hz, 1H, H-7), 7.58 (s, 1H,
H-2), 7.55 (d, J4,6 = 3 Hz, 1H, H-4), 7.48 (dd, J6,7 = 9 Hz, J6,4 = 3 Hz,
1H, H-6); 13C NMR (CDCl3, 75 MHz): δC 182.2, 154.2, 152.8, 150.6,
141.6, 130.5, 129.5, 129.5, 127.9, 123.8, 123.8, 123.6, 122.8, 116.3,
113.8; EI-MS m/z (% rel. abund.): 301 (M+, 100), 303 (M+2, 77), 179
(88), 150 (61), 123 (34), 104 (27), 76 (20).
Fig. 17. A correlation graph for IC50 values vs predicted docking score (S) for α-
amylase.
4.2.8. Benzofuran-2-yl(4-chlorophenyl) methanone (8) [50]
White powder; Yield: 80%; M.P.: 150–152 °C; 1H NMR (CDCl3,
300 MHz): δH 8.21 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 7.96 (d, J3′,2′/
5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.84 (dd, J4,5 = 9 HZ, J4,6 = 3 Hz, 1H, H-
4), 7.58 (s, 1H, H-2), 7.47 (dd, J7,6 = 9 HZ, J7,5 = 3 Hz, 1H, H-7), 7.07
(t, J6(5,7) = 6 Hz, 1H, H-6), 6.99 (t, J5(4,6) = 6 Hz, 1H, H-5); 13C NMR
(CDCl3, 75 MHz): δC 183.1, 156.1, 152.2, 139.6, 135.5, 131.1, 131.1,
128.9, 128.9, 128.7, 126.9, 124.2, 123.5, 116.6, 112.7; EI-MS m/z (%
rel. abund.): 256 (M+, 62), 258 (M+2, 25), 221 (16), 145 (24), 141
(35), 139 (100), 118 (72), 111 (26).
4.2.14. (5-Chlorobenzofuran-2-yl) (3-nitrophenyl) methanone (14) [51]
Pale yellow; Yield: 86%; M.P.: 106–108 °C; 1H NMR (MeOD,
300 MHz): δH 8.85 (d, J2′,6′ = 9 Hz, H, H-2′), 8.54 (dd, J4′,5′ = 9 Hz,
J4′,6′ = 3 Hz, 1H, H-4′), 8.44 (d, J7,6 = 9 Hz, 1H, H-7), 8.17 (t,
J
5′(4′,6′) = 9 Hz, 1H, H-5′), 7.87 (dd, J6′,5′ = 9, J6′,5′ = 3 Hz, 2H, H-6′),
7.78 (s, 1H, H-2), 7.70 (d, J4,6 = 3 Hz, 1H, H-4), 7.56 (dd, J6,7 = 9 Hz,
J6,4 = 3 Hz, 1H, H-6); 13C NMR (CDCl3, 75 MHz): δC 181.5, 154.4,
152.8, 148.2, 137.8, 135.1, 132.7, 129.9, 129.4, 127.9, 127.4, 124.5,
122.8, 116.0, 113.7; EI-MS m/z (% rel. abund.): 301 (M+, 100), 303 (M
+2, 70), 181 (47), 179 (86), 150 (49), 123 (41), 104 (28), 76 (24).
4.2.9. Benzofuran-2-yl(3,4-dichlorophenyl) methanone (9) [52]
Light brown; Yield: 82%; M.P.: 139–141 °C; 1H NMR (CDCl3,
300 MHz): δH 7.92 (dd, J6′,5′ = 9 HZ, J6′,2′ = 3 Hz, 1H, H-6′), 7.84 (dd,
4.2.15. (4-Bromophenyl) (5-chlorobenzofuran-2-yl) methanone (15) [51]
White powder; Yield: 94%; M.P.: 211–213 °C; 1H NMR (CDCl3,
300 MHz): δH 7.81 (d, J3′,2′/5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.73 (d,
J
4,5 = 9 HZ, J4,6 = 3 Hz, 1H, H-4), 7.78 (d, J2′,6′ = 6 Hz, 1H, H-2′), 7.65
(d, J5′,6′ = 9 Hz, 1H, H-5′), 7.58 (s, 1H, H-2), 7.47 (dd, J7,6 = 9 HZ,
J7,5 = 6 Hz, 1H, H-7), 7.04 (t, J6(5,7) = 6 Hz, 1H, H-6), 6.96 (t,
J
7,6 = 9 Hz, 1H, H-7), 7.58 (s, 1H, H-2), 7.55 (d, J4,6 = 3 Hz, 1H, H-4),
7.49 (dd, J6,7 = 9 Hz, J6,4 = 3 Hz, 1H, H-6), 7.36 (d, J2′,3′/6′,5′ = 9 Hz,
2H, H-2′, H-6′); 13C NMR (CDCl3, 75 MHz): δC 182.1, 154.5, 152.7,
141.6, 130.5, 130.5, 130.1, 130.1, 129.5, 127.9, 123.8, 123.6, 122.9,
116.3, 113.7; EI-MS m/z (% rel. abund.) 334 (M+, 85), 336 (M+2, 93),
338 (M+4, 25), 255 (30), 185 (98), 183 (100), 179 (41), 155 (46), 123
(18), 76 (17).
J
5(4,6) = 6 Hz, 1H, H-5); 13C NMR (CDCl3, 75 MHz): δC 181.8, 156.2,
151.8, 137.7, 136.6, 133.3, 131.5, 130.8, 128.9, 128.6, 126.9, 124.4,
123.6, 116.9, 112.7; EI-MS m/z (% rel. abund.): 290 (M+, 100), 292 (M
+2, 63), 294 (M+4, 12), 254 (24), 172 (36), 145 (75).
4.2.10. [1,1′-Biphenyl]-4-yl(benzofuran-2-yl) methanone (10) [53]
White powder; Yield: 90%; M.P.: 148–150 °C; 1H NMR (CDCl3,
300 MHz): δH 8.35 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 8.19 (d, J3′,2′/
5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.90 (d, J8′',9′'/12′',11′' = 9 Hz, 2H, H-8′',
H-12′'), 7.84 (dd, J4,5 = 9 HZ, J4,6 = 3 Hz, 1H, H-4), 7.76 (d, J9′',8′'/
11′',12′' = 9 Hz, 2H, H-9′', H-11′'), 7.63 (m, 1H, H-10′'), 7.58 (s, 1H, H-
2), 7.49 (dd, J7,6 = 9 HZ, J7,5 = 6 Hz, 1H, H-7), 7.04 (t, J6(5,7) = 6 Hz,
1H, H-6), 6.96 (t, J5(4,6) = 6 Hz, 1H,H-5); 13C NMR (CDCl3, 75 MHz): δC
183.9, 156.1, 152.5, 145.9, 139.9, 135.8, 130.3, 130.3, 129.1, 129.1,
128.6, 128.5, 128.5, 127.4, 127.4, 127.3, 127.2, 124.1, 123.4, 116.4,
112.7; EI-MS m/z (% rel. abund.): 298 (M+, 100), 281 (20), 270 (28),
181 (90), 153 (58), 152 (69), 145 (25), 135 (35), 118 (23).
4.2.16. (5-Chlorobenzofuran-2-yl) (4-chlorophenyl) methanone (16) [54]
White powder; Yield: 86%; M.P.: 185–187 °C, 1H NMR (CDCl3,
300 MHz): δH 8.09 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 7.90 (d, J3′,2′/
5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.73 (d, J7,6 = 9 Hz, Hz, 1H, H-7), 7.57 (s,
1H, H-2), 7.55 (d, J4,6 = 3 Hz, 1H, H-4), 7.49 (dd, J6,7 = 9 Hz,
J6,4 = 3 Hz, 1H, H-6); 13C NMR (CDCl3, 75 MHz): δC 182.3, 154.8,
153.1, 142.1, 130.8, 130.8, 130.3, 129.7, 129.7, 127.6, 123.8, 123.4,
122.9, 116.5, 113.7; EI-MS m/z (% rel. abund.): 290 [M+, 100), 255
(30), 179 (31), 139 (93), 111 (27), 75 (10).
4.2.17. (5-Chlorobenzofuran-2-yl) (3,4-dichlorophenyl) methanone (17)
[55]
White powder; Yield: 90%; M.p.: 139–141 °C; 1H NMR (CDCl3,
300 MHz): δH 7.89 (dd, J6′, 5′ = 9 Hz, J6′,2′ = 3 Hz, 1H, H-6′), 7.78 (d,
J2′,6′ = 3 Hz, 1H, H-2′), 7.69 (d, J7,6 = 9 Hz, 1H, H-7), 7.62 (d,
4.2.11. (5-Chlorobenzofuran-2-yl) (phenyl)methanone (11) [54]
White powder; Yield: 88%; M.P.: 161–163 °C; 1H NMR (MeOD,
300 MHz): δH 8.11 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 8.04 (d, J3′,2′/
5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.66 (m, 1H, H-4′), 7.56 (s, 1H, H-2), 7.52
(d, J7,6 = 9 Hz, 1H, H-7), 7.33 (dd, J6,7 = 9 Hz, J6,4 = 3 Hz, 1H, H-6),
7.25 (d, J4,6 = 3, 1H, H-4); 13C NMR (CDCl3, 75 MHz): δC 184.1, 154.3,
153.4, 136.9, 133.2, 129.7, 129.7, 129.5, 128.7, 128.7, 128.6, 128.3,
122.7, 115.5, 113.7; EI-MS m/z (% rel. abund.): 256 (M+, 90), 258 (M
+2, 32), 179 (21), 150 (49), 152 (88), 105 (100), 77 (86), 51 (16).
J
5′,6′ = 9 Hz, 1H, H-5′), 7.59 (s, 1H, H-2), 7.54 (d, J4,6 = 3 Hz, Hz, 1H,
H-4), 7.30 (dd, J6,7 = 9 Hz, J6,4 = 3 Hz, 1H, H-6); 13C NMR (CDCl3,
75 MHz): δC 182.31, 158.6, 155.2, 137.3, 133.5, 132.8, 131.7, 131.1,
130.3, 129.2, 128.7, 124.6, 120.5, 116.6, 112.9; EI-MS m/z (% rel.
abund.): 324 (M+, 100), 326 (M+2, 94), 328 (M+4, 328), 289 (40),
179 (72), 173 (91), 145 (42), 123 (25), 109 (13), 44 (45).
4.2.12. (5-Chlorobenzofuran-2-yl) (4-methoxyphenyl) methanone (12)
[54]
4.2.18. [1,1′-Biphenyl]-4-yl(5-chlorobenzofuran-2-yl) methanone (18)
1
White powder; Yield: 91%; M.P.: 133–135 °C; H NMR (DMSO‑d6,
Yellow pink; Yield: 94%; M.P.: 136–138 °C; 1H NMR (MeOD,
300 MHz): δH 8.07 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 8.00 (d,
300 MHz): δH 8.10 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 7.87 (d, J3′,2′/
5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.77 (d, J8′',9′'/12′',11′' = 9 Hz, 2H, H-8′', H-
12′'), 7.66 (d, J9′',8′'/11′',12′' = 9 Hz, 2H, H-9′', H-11′'), 7.62 (d,
J
7,6 = 9 Hz, 1H, H-7), 7.72 (d, J3′,2′/5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.79 (s,
15

I. Ali, et al.
BioorganicChemistry104(2020)104238
Table 3
The protein–ligand interaction (PLI) detail for all synthesized compounds against α-amylase enzyme.
S. No.
Interaction details
Docking score
Ligands
Receptor
5-ring
Interaction
π-π
Distance
4.00
E cal/mol
-0.0
Residue
1
2
3
4
5-ring
NA
TRP388 (A)
-4.58380985
NA
6-ring
O 12
O 19
O 19
O 20
O 20
6-ring
5-ring
6-ring
6-ring
O 12
6-ring
6-ring
5-ring
6-ring
6-ring
O 12
O 12
CL 18
6-ring
6-ring
O 7
N
π-H
3.62
3.23
3.34
3.44
3.41
2.94
3.77
3.55
3.90
3.83
3.50
3.73
3.98
3.57
3.85
3.76
3.55
3.92
3.47
3.71
3.58
3.40
3.18
3.29
3.54
3.56
3.77
3.41
3.39
3.53
3.80
3.42
3.72
3.56
3.60
3.22
2.87
3.39
3.15
3.84
3.72
3.32
3.41
3.42
3.86
3.67
3.03
3.63
3.50
3.79
-1.1
-8.6
-2.9
-0.8
-0.8
-1.5
-0.0
-0.0
-0.0
-0.0
-4.4
-0.0
-0.0
-0.0
-0.0
-0.0
-0.7
-0.7
-0.7
-0.0
-0.0
-0.6
-1.8
-2.6
-0.0
-0.6
-1.9
-0.9
-1.8
-0.0
-0.0
-0.0
-0.0
-0.0
-0.0
-7.2
-0.7
-0.0
-1.9
-1.5
-1.2
-2.5
-0.0
-0.0
-0.0
-0.0
-0.5
-0.6
-1.0
-0.0
-5.03079653
LYS322 (A)
ARG343 (A)
ARG343 (A)
ARG343 (A)
ARG343 (A)
TRP388 (A)
TRP388 (A)
TRP388 (A)
TRP388 (A)
LYS322 (A)
TRP388 (A)
TRP388 (A)
TRP388 (A)
TRP388 (A)
TRP388 (A)
LYS322 (A)
LYS322 (A)
ARG343 (A)
TRP388 (A)
TRP388 (A)
ARG392 (A)
ARG392 (A)
ARG343 (A)
TRP388 (A)
LYS322 (A)
LYS322 (A)
ARG392 (A)
ARG392 (A)
TRP388 (A)
TRP388 (A)
TRP388 (A)
TRP388 (A)
TRP388 (A)
TRP388 (A)
LYS322 (A)
THR376 (A)
TRP388 (A)
ARG389 (A)
ARG389 (A
ARG389 (A
ARG343 (A)
TRP388 (A)
TRP388 (A)
TRP388 (A)
TRP388 (A)
ARG392 (A)
ARG392 (A)
ARG392 (A)
TRP388 (A)
NZ
H-acceptor
H-acceptor
H-acceptor
H-acceptor
H-acceptor
π-π
-6.00995398
NH1
NH2
NH1
NH2
6-ring
5-ring
6-ring
5-ring
NZ
5
6
7
8
π-π
-4.90942192
-4.86930895
-4.90942192
-5.89942932
π-π
π-π
H-acceptor
π-π
6-ring
5-ring
5-ring
6-ring
5-ring
CD
π-π
π-π
π-π
π-π
H-acceptor
H-acceptor
H-acceptor
π-π
NZ
NH2
6-ring
5-ring
NH2
NH2
NH2
5-ring
CD
9
π-π
-4.85125828
-5.3188076
10
H-acceptor
H-acceptor
H-acceptor
π-π
O 12
CL 18
5-ring
O 12
O 12
O 21
O 20
5-ring
6-ring
5-ring
6-ring
6-ring
6-ring
O 12
O 21
5-ring
O 11
O 11
6-ring
O 20
6-ring
5-ring
6-ring
6-ring
O 7
11
12
-4.90383196
-5.0564127
H-acceptor
H-acceptor
H-acceptor
H-acceptor
π-π
NZ
13
14
15
NH2
NH2
5-ring
5-ring
5-ring
6-ring
5-ring
5-ring
NZ
-5.02815676
-5.4013834
-5.63663254
π-π
16
π-π
-5.56192898
π-π
π-π
17
18
19
π-π
-5.09705925
-5.46022463
-5.33724403
H-acceptor
H-acceptor
π-π
OG1
5-ring
NH1
NH2
N
20
H-acceptor
H-acceptor
π-H
-5.10037518
21
22
NH2
5-ring
5-ring
6-ring
5-ring
NH2
NH2
NH
H-acceptor
π-π
-5.31678343
-5.06391668
π-π
π-π
π-π
23
24
H-acceptor
H-acceptor
H-acceptor
π-π
-4.94170952
-5.38447266
O 12
O 11
6-ring
NA
6-ring 2
25
26
27
28
29
30
NA
NA
NA
NA
NA
NA
NA
NA
NA
O 11
O 11
CB
CB
H-acceptor
H-acceptor
3.35
3.38
-0.6
-0.6
CYS384
-5.2860343
ARG387 (A)
J7,6 = 9 Hz, 1H, H-7), 7.57 (s, 1H, H-2), 7.54 (d, J4,6 = 3 Hz, 1H, H-4),
4.2.19. (5,7-Dichlorobenzofuran-2-yl) (4-nitrophenyl) methanone (19)
White powder; Yield: 82%; M.P.: 206–208 °C; 1H NMR (CDCl3,
300 MHz): δH 8.41 (d, J3′,2′/5′,6′ = 9 Hz, 2H, H-3′, H-5′), 8.30 (d, J2′,3′/
6′,5′ = 9 Hz, 2H, H-2′, H-6′), 7.65 (d, J4,6 = 3 Hz, 1H, H-4), 7.62 (s, 1H,
H-2), 7.54 (d, J6,7 = 9 Hz, J6,4 = 3 Hz, 1H, H-6); 13C NMR (DMSO‑d6,
100 MHz): δC 181.9, 159.6, 155.8, 152.4, 145.8, 135.9, 130.6, 130.6,
129.3, 126.2, 123.7, 123.7, 119.1, 117.6, 117.3; EI-MS m/z (% rel.
abund.): 335 (M+, 100), 337 (M+2, 90), 339 (M+3, 39), 226 (19), 215
7.45 (m, 1H, H-10′'), 7.28 (dd, J6,7 = 9 Hz, J6,4 = 3 Hz, 1H, H-6); 13
C
NMR (DMSO‑d6, 100 MHz): δC 186.1, 158.2, 156.6, 145.4, 141.7,
136.8, 133.9, 130.5, 130.5 129.9, 129.9, 129.0, 129.0, 128.8, 128.6,
127.9, 127.9, 125.5, 123.1, 116.9, 114.1; EI-MS m/z (% rel. abund.):
332 (M+, 100), 332 (M+2, 77), 289 (30), 179 (60), 173 (75), 145 (42),
123 (46), 109 (24); HREI-MS calcd for C21H13ClO2: m/z = 332.0601,
Found 332.0604.
16

I. Ali, et al.
BioorganicChemistry104(2020)104238
(65), 213 (75), 157 (32), 150 (76),120 (24), 104 (36); HREI-MS calcd
4.2.25. (4,6-Dihydroxybenzofuran-2-yl) (phenyl)methanone (25)
for C15H7Cl2NO4: m/z = 335.9734, Found 335.9752.
White powder; Yield: 92%; M.P.: 122–124 °C; 1H NMR (CD3OD,
300 MHz): δH 7.91 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 7.75 (d, J3′,2′/
5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.58 (s, 1H, H-2), 7.50 (m, 1H, H-4′), 6.99
(d, J7,5 = 3 Hz, 1H, H-7), 6.50 (d, J5,7 = 3 Hz, 1H, H-5); 13C NMR
(DMSO‑d6, 100 MHz): δC 183.0, 160.7, 158.7, 156.0, 152.9, 139.7,
134.1, 133.9, 133.9, 132.0, 132.0, 116.4, 114.2, 107.7, 90.36; EI-MS
4.2.20. (7-Ethoxybenzofuran-2-yl) (p-tolyl) methanone (20)
Light brown powder; Yield: 81%; M.P.: 108–110 °C; 1H NMR
(DMSO‑d6, 300 MHz): δH 7.81 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′),
7.63 (d, J3′,2′/5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.62 (s, 1H, H-2), 7.44 (dd, ,
m/z (% rel. abund.): 254 (M+, 62), 106 (36), 105 (100), 91 (22), 77
J
4,5 = 9 Hz, J4,6 = 3 Hz, 1H, H-4), 7.36 (dd, J6,5 = 9 Hz, J6,4 = 3 Hz,
+
(78), 65 (18), 51 (12); HR-MS (EI) calcd for C15H10O4 ([M+H]
254.0731, found 254.0736.
)
2H, H-6), 7.17 (t, J5(4,6) = 9 Hz, 1H, H-5), 4.05 (q, 2H, H-1′'), 2.36 (s,
3H, 3′'), 1.27 (t, J2′',1′' = 9 Hz, 3H, H-2′'); 13C NMR (DMSO‑d6,
100 MHz): δC 185.0, 156.7, 152.0, 146.2, 143.6, 135.3, 131.7, 129.3,
129.3, 129.2, 129.2, 127.7, 123.9, 119.6, 115.20, 64.3, 21.1, 14.4; EI-
MS m/z (% rel. abund.): 280 (M+, 97), 252 (99), 237 (20), 160 (37),
119 (100), 91 (59); HREI-MS calcd for C18H16O3: m/z = 280.1095,
Found 280.1099.
4.2.26. (4,6-Dihydroxybenzofuran-2-yl) (p-tolyl) methanone (26)
Brown powder; Yield: 92.%; M.P.: 173–175 °C; 1H NMR (CD3OD,
300 MHz): δH 7.97 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 7.68 (d, J3′,2′/
5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.59 (s, 1H, H-2), 6.66 (d, J7,5 = 3 Hz, 1H,
H-7), 6.51 (d, J5,7 = 3 Hz, 1H, H-5), 2.34 (s, 3H, H-1′'); 13C NMR
(DMSO‑d6, 100 MHz): δC 182.9, 159.9, 157.7, 155.3, 153.2, 144.4,
136.1, 129.9, 129.9, 129.3, 129.3, 116.8, 114.9, 105.8, 92.5, 21.2; EI-
MS m/z (% rel. abund.): 268 (M+, 76), 235 (29), 119 (100), 105 (07),
91 (30); HREI-MS calcd for C16H12O4: m/z = 268.0730, Found
268.0736.
4.2.21. (7-Ethoxybenzofuran-2-yl) (4-nitrophenyl) methanone (21) [56]
Brown powder; Yield: 83%; M.P.: 164–166 °C; 1H NMR (CD3OD,
300 MHz): δH 8.44 (d, J3′,2′/5′,6′ = 9 Hz, 2H, H-3′, H-5′), 8.25 (d, J2′,3′/
= 9 Hz, 2H, H-2′, H-6′), 7.74 (s, 1H, H-2), 7.35 (d, J4,5 = 9 Hz,
6′,5′
J4,6 = 6 Hz, 1H, H-4), 7.30 (t, J5(4,6) = 9 Hz, 1H, H-5), 7.12 (d,
J6,5 = 9 Hz, J6,4 = 3 Hz, 1H, H-6), 4.30 (q, 2H, H-1′'), 1.49 (t,
J2′',1′' = 6 Hz,3H, H-2′'); 13C NMR (CDCl3, 125 MHz): δC 182.3, 155.5,
151.9, 151.4, 146.1, 140.9, 132.1, 129.4, 129.4, 125.4, 124.2, 124.2,
116.5, 112.8, 109.3, 65.0, 14.9; EI-MS m/z (% rel. abund.): 311 (M+,
78), 283 (100), 237 (23), 150 (31), 104 (23), 76 (18).
4.2.27. (4,6-Dihydroxybenzofuran-2-yl) (4-nitrophenyl) methanone (27)
Brown powder; Yield: 86%; M.P.: 138–140 °C; 1H NMR (CD3OD,
300 MHz): δH 8.29 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 8.06 (d, J3′,2′/
5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.59 (s, 1H, H-2), 6.96 (d, J7,5 = 3 Hz, 1H,
H-7), 6.52 (d, J5,7 = 3 Hz, 1H, H-5); 13C NMR (DMSO‑d6, 100 MHz): δC
185.8, 161.4, 158.2, 153.8, 152.4, 150.3, 143.3, 131.1, 131.1, 129.9,
129.9, 123.1, 116.9, 107.8, 92.7; EI-MS m/z (% rel. abund.): 299 (M+,
100), 269 (15), 252 (29), 150 (21), 139 (13), 120 (13); HREI-MS calcd
for C15H9NO6: m/z = 299.0423, Found 299.0430.
4.2.22. (4-Bromophenyl) (7-ethoxybenzofuran-2-yl) methanone (22)
1
White powder; Yield: 91%; M.P.: Above 400 °C; H NMR (CD3OD,
300 MHz): δH 8.03 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 7.99 (d, J3′,2′/
5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.56 (s, 1H, H-2), 7.47 (dd, J4,5 = 9 Hz,
J4,6 = 3 Hz, 1H, H-4), 7.37 (dd, J6,5 = 9 Hz, J6,4 = 3 Hz, 2H, H-6),
7.17 (t, J5(4,6) = 9 Hz, 1H, H-5), 4.10 (q, 2H, H-1′'), 1.33 (t,
J2′',1′' = 6 Hz, 3H, H-2′'); 13C NMR (DMSO‑d6 100 MHz): δC 183.2,
156.2, 151.6, 142.9, 137.5,132.1, 131.8, 131.8, 131.1, 131.1, 127.7,
124.9, 117.7, 115.2, 111.1, 64.2, 14.9; EI-MS m/z (% rel. abund.): 344
(M+, 66), 346 (M+2, 64), 237 (37), 183 (100), 161 (67), 155 (40), 105
(20), 76 (37), 44 (24); HREI-MS calcd for C17H13BrO3: m/
z = 344.0046, Found 344.0048.
4.2.28. (4,6-Dihydroxybenzofuran-2-yl) (3-nitrophenyl) methanone (28)
Pale yellow powder; Yield: 90%; M.P.: 192–194 °C; 1H NMR
(CD3OD, 300 MHz): δH 8.27 (dd, J4′,5′ = 9 Hz, J4′,6′ = 3 Hz, 1H, H-4′),
8.17 (d, J2′,6′ = 6 Hz, 1H, H-2′), 8.03 (dd, J6′,5′ = 9 Hz, J6′,5′ = 3 Hz,
1H, H-6′), 7.90 (t, J5′(4′,6′) = 6 Hz, 1H, H-5′), 7.59 (s, 1H, H-2), 6.97 (d,
J7,5 = 6 Hz, 1H, H-7), 6.50 (d, J5,7 = 6 Hz, 1H, H-5); 13C NMR
(DMSO‑d6, 100 MHz): δC 184.4, 160.9, 162.6, 157.7, 153.4, 152.2,
148.0, 137.2, 135.2, 128.0, 126.9, 120.3, 112.8, 109.8, 93.0; EI-MS m/z
(% rel. abund.): 299 (M+, 100), 255 (24), 226 (23), 177 (34), 163 (27),
150 (52), 104 (23), 76 (24); HREI-MS calcd for C15H9 NO6: m/
z = 299.0427, Found 299.0430.
4.2.23. (4-Chlorophenyl) (7-ethoxybenzofuran-2-yl) methanone (23) [56]
White powder: Yield: 93%; M.P.: 108–110 °C; 1H NMR (CD3OD,
300 MHz): δH 7.98 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 7.84 (d, J3′,2′/
5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.55 (s, 1H, H-2), 7.37 (dd, J4,5 = 9 Hz,
4.2.29. (3,4-Dichlorophenyl) (4,6-dihydroxybenzofuran-2-yl) methanone
(29)
J
4,6 = 3 Hz, 1H, H-4), 7.29 (dd, J6,5 = 9 Hz, J6,4 = 3 Hz, 2H, H-6),
Light brown powder; Yield: 94%; M.P.: 116–118 °C; 1H NMR
(CD3OD, 300 MHz): δH 7.94 (dd, J6′,5′ = 9 Hz, J6′,2′ = 3 Hz, 1H, H-6′),
7.88 (d, J2′,6′ = 6 Hz, 1H, H-2′), 7.63 (d, J5′,6′ = 9 Hz, 1H, H-5′), 7.53
(s, 1H, H-2), 6.96 (d, J7,5 = 6 Hz, 1H, H-7), 6.52 (d, J5,7 = 6 Hz, 1H,
H-5); 13C NMR (DMSO‑d6, 100 MHz): δC 186.1, 160.7, 157.8, 155.8,
153.2, 136.6, 134.2, 132.3, 131.8, 131.1, 129.9, 116.5, 114.8, 107.7,
90.4; EI-MS m/z (% rel. abund.): 322 (M+, 82), 324 (M+2, 79), 326 (M
+4, 16), 177 (54), 174 (91), 172 (100), 145 (57), 109 (16), 65 (20);
HREI-MS calcd for C15H8 Cl2O4: m/z = 323.9968, Found 323.9978.
7.14 (t, J5(4,6) = 9 Hz, 1H, H-5), 4.08 (q, 2H, H-1′'), 1.33 (t,
J2′',1′' = 6 Hz, 3H, H-2′'); 13C NMR (CDCl3, 125 MHz): δC 182.5, 155.5,
151.7, 142.8, 139.1, 136.8, 132.2, 131.3, 131.5, 128.7, 128.7, 125. 2,
116.8, 112.9, 109.2, 64.8, 14.8; EI-MS m/z (% rel. abund.): 300 (M+,
67), 272 (91), 179 (32), 165 (58), 164 (51), 141 (50), 139 (100), 136
(27), 111 (38).
4.2.24. [1,1′-Biphenyl]-4-yl(7-ethoxybenzofuran-2-yl) methanone (24)
[56]
White powder; Yield: 91%; M.P.: 88–90 °C; 1H NMR (CD3OD,
300 MHz): δH 8.35 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 8.19 (d, J3′,2′/
5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.91 (d, J8′',9′'/12′',11′' = 9 Hz, 2H, H- 8′', H-
12′'), 7.72 (d, J9′',8′'/11′',12′' = 9 Hz, 2H, H-9′', H-11′'), 7.51 (s, 1H, H-
2), 7.47 (m, 1H, H-10′'), 7.41 (dd, J4,5 = 9 Hz, J4,6 = 3 Hz, 1H, H-4),
7.30 (dd, J6,5 = 9 Hz, J6,4 = 3 Hz, 1H, H-6), 7.17 (t, J5(4,6) = 9 Hz,
1H, H-5), 4.10 (q, 2H, H-1′'), 1.33 (t, J2′',1′' = 6 Hz, 3H, H-2′'); 13C NMR
(CDCl3, 125 MHz): δC 183.3, 155.8, 152.3, 144.9, 141.9, 140.6, 138.2,
132.5, 130.7, 130.7, 129.5, 129.5, 128.4, 128.4, 127.9, 127.9, 127.6,
125.3, 116.7, 112.7, 109.1, 65.8, 14.9; EI-MS m/z (% rel. abund.): 342
(M+, 74), 315 (18), 314 (67), 181 (100), 160 (15), 152 (44), 44 (21).
4.2.30. [1,1′-Biphenyl]-4-yl(4,6-dihydroxybenzofuran-2-yl)
(30)
methanone
Light brown powder; Yield: 88%; M.P.: 154–156 °C; 1H NMR
(CD3OD, 300 MHz): δH 8.35 (d, J2′,3′/6′,5′ = 9 Hz, 2H, H-2′, H-6′), 8.19
(d, J3′,2′/5′,6′ = 9 Hz, 2H, H-3′, H-5′), 7.88 (d, J8′',9′'/12′',11′' = 9 Hz, 2H,
H- 8′', H-12′'), 7.72 (d, J9′',8′'/11′',12′' = 9 Hz, 2H, H- 9′', H-11′'), 7.58 (s,
1H, H-2), 7.49 (m, 1H, H-10′'), 6.99 (d, J7,5 = 6 Hz, 1H, H-7), 6.53 (d,
J5,7 = 6 Hz, 1H, H-5); 13C NMR (DMSO‑d6, 100 MHz): δC 183.9, 159.6,
157.1, 155.0, 152.6, 145.2, 142.1, 138.7, 132.9, 132.9, 129.1, 129.1,
128.6, 128.6, 127.5, 127.5, 127.0, 116.8, 114.5, 104.8, 92.6; EI-MS m/z
17

I. Ali, et al.
BioorganicChemistry104(2020)104238
MMFF94X). The crystal structure for the α-amylase was retrieved from
the protein databank using PDB codes 3BAJ. Later the structure co-
ordinates were subjected to MOE for preparation.
(% rel. abund.): 330 (M+, 100), 302 (7), 181 (30), 153 (13), 152 (12),
44 (32); HREI-MS calcd for C21H14O4: m/z = 330.0890, Found
330.0892.
Further, the protonation was done using default parameters for the
structure preparation module of MOE. Furthermore, the structure was
subjected to energy minimization to get minimal energy conformation.
Finally, the refined structure was used for docking study using the de-
fault parameters of MOE; Placement: Triangle Matcher, rescoring 1:
London dG, Refinement: Forcefield, rescoring 2: GBVI/WSA. We have
selected the overall enzyme structure as an active site due to the non-
competitive nature of the active compounds. Before running the
docking protocol, we have selected a total of five conformations for the
ligand. The top-ranked conformations based on docking score (S) and
protein–ligand interaction (PLI) profile were selected for analysis.
Moreover, we have performed molecular dynamics simulation of the
potent compound 4 in order to check the dynamic stability of the en-
zyme in a watery environment. The detailed protocol for MD simulation
has been described in our previous article [61].
4.2.31. α-Amylase inhibition assay
A 500 µL of α-amylase enzyme solution (0.5 mg/mL) in 0.2 mM
phosphate buffer (pH 6.9) with different volume of test sample (100,
200, 400, 800, 1000 µg/mL) were incubated at 25 ˚C for 10 min. After
pre-incubation, 500 μL of 1% starch solution in 0.02 M sodium phos-
phate buffer (pH 6.9) added into each test tube and incubated for
10 min at 25 ˚C. Then the reaction was arrested with color reagent 1 mL
of dinitrosalicylic acid and tubes were then kept incubated in boiling
water for 5 min and cooled to room temperature. The absorbance was
measured at 540 nm after dilution of solution by adding 10 mL distilled
water [57,58].
The percentage inhibition was calculated as follows:
%Inhibition = (Absorbancecontrol Absorbancesample)/Absorbancecontrol × 100
4.2.32. DPPH radical scavenging assay
Declaration of Competing Interest
DPPH (1,1-diphenyl-2-picryl hydrazyl) free radical scavenging assay
was performed using following protocol. DPPH radical solution in
ethanol (0.3 mM) was reacted with different test sample (0.5 mM) for
30 min at 37 °C. The violet color of DPPH solution disappeared when it
was reduced by test samples. The decrease in absorbance was recorded
by multiplate reader (Spectra max-384, USA) at 517 nm [57,58]. Re-
sults were shown in terms of IC50 values means minimum concentration
of compounds required to scavenge 50% of DPPH radicals. All test re-
actions were done in triplicate.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influ-
ence the work reported in this paper.
Acknowledgements
The authors are thankful to Pakistan Academy of Sciences, Pakistan
for providing financial support to project No. 5-9/PAS/440.
4.2.33. ABTS radical scavenging assay
Appendix A. Supplementary material
The (ABTS + ) 2,2ʹ-azino-bis(3-ethylbenzothiazoline-6-sulphonic
acid) free radical cation scavenging ability protocol of the compounds
was performed by the standard method [57,58]. 7 mM concentration of
ABTS solution which was dissolved in distilled water and 2.45 mM
concentrated potassium persulfate was added to the ABTS solution.
After adding potassium persulfate in ABTS solution then kept the so-
lution in the dark place for 12–16 h at room temperature. The sample
solutions of test compounds were prepared in absolute alcohol ranging
from 0.01 to 1 mg/mL. Then the test samples added with ABTS solution
and incubated for 30 min. The absorbance was recorded at 734 nm
wavelength and the same protocol was repeated for ascorbic acid as a
standard.
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.bioorg.2020.104238.
References
[1] V. Polshettiwar, R.S. Varma, Greener and sustainable approaches to the synthesis of
pharmaceutically active heterocycles, Curr. Opin. Drug Discov. Devel. 10 (6) (2007)
723–737.
[2] G. Eren, S. Ünlü, M.T. Nuñez, L. Labeaga, F. Ledo, A. Entrena, E. Banoğlu,
M.F. Costantino, M.F. Şahin, Synthesis, biological evaluation, and docking studies
of novel heterocyclic diaryl compounds as selective COX-2 inhibitors, Bioorg. Med.
Chem. 18 (17) (2010) 6367–6376.
[3] R.W. DeSimone, K.S. Currie, S.A. Mitchell, J.W. Darrow, D.A. Pippin, Privileged
structures: applications in drug discovery, Comb. Chem. High T. Scr. 7 (5) (2004)
473–493.
4.2.34. Kinetic studies
[4] S. Alper-Hayta, M. Arisoy, Ö. Temiz-Arpaci, I. Yildiz, E. Aki, S. Özkan, F. Kaynak,
Synthesis, antimicrobial activity, pharmacophore analysis of some new 2-(sub-
stitutedphenyl/benzyl)-5-[(2-benzofuryl) carboxamido] benzoxazoles, Eur. J. Med.
Chem. 43 (11) (2008) 2568–2578.
To determine the mechanism of enzyme inhibition, the kinetic
studies were performed by using varying concentration of α-amylase
inhibitors (0.0625, 0.125, 0.2, and 0.4 mM) with varying concentra-
tions of inhibitor substrate (p-nitrophenyl R-D-maltoside (NPM)) such as
0.02, 0.2, 0.4, 0.8 and 1.0 mM. The enzyme was dissolved in de-ionized
water to produce the concentration 0.2 mg/mL for each well. PIPES
buffer was used as adjusted the pH of 7.0 [44]. The reaction mixture
was incubated for the period of 30 min at 25 °C for 1-minute interval.
The absorbance was measured using ELISA reader by keeping the 96-
well plate (BioTek XL-800, USA) [59]. The kinetic parameters Vmax,
Km, AICc and R2 values of all the α-amylase inhibitors were determined
by graph fitting analysis using Sigma-Plot enzyme kinetic software 14.0
version.
[5] J. ApSimon, D.J. Goldsmith, The total synthesis of natural products, vol. 2, Wiley,
New York, 1973, pp. 641–725.
[6] D.M.X. Donnelly, M.J. Meegan, in: A.R. Katrizky (Ed.), Comprehensive heterocyclic
chemistry, vol. 4, Pergamon Press, N.-Y., 1984, pp. 657.
[7] R. Whomsley, E. Fernandez, P.J. Nicholls, H.J. Smith, P. Lombardi, V. Pestellini,
Substituted 1-[(benzofuran-2-yl)-phenylmethyl]-imidazoles as potent inhibitors of
aromatase in vitro and in female rats in vivo, J. Steroid Biochem. Mol. Biol. 44 (4–6)
(1993) 675–676.
[8] I. Hayakawa, R. Shioya, T. Agatsuma, H. Furukawa, S. Naruto, Y. Sugano, 4-
Hydroxy-3-methyl-6-phenylbenzofuran-2-carboxylic acid ethyl ester derivatives as
potent anti-tumor agents, Bioorg. Med. Chem. Lett. 14 (2) (2004) 455–458.
[9] G.A. Kraus, I. Kim, Synthetic approach to malibatol A, Org. Lett. 5 (8) (2003)
1191–1192.
[10] M. Sun, C. Zhao, G.A. Gfesser, C. Thiffault, T.R. Miller, K. Marsh, J. Wetter,
M. Curtis, R. Faghih, A.T. Esbenshade, A.A. Hancock, Synthesis and SAR of 5-
amino-and 5-(aminomethyl) benzofuran histamine H3 receptor antagonists with
improved potency, J. Med. Chem. 48 (20) (2005) 6482–6490.
4.2.35. Molecular docking
The blind docking approach was performed by using the Molecular
Operating Environment (MOE) [60] to explore the possible binding
mode of synthetic compounds against the α-amylase enzymes. First, the
3D coordinates for all the synthesized compounds were generated via
MOE-builder wizards and were protonated, and energy minimized by
using the default parameters of the MOE (gradient: 0.05, Force Field:
[11] M. Koca, S. Servi, C. Kirilmis, M. Ahmedzade, C. Kazaz, B. Özbek, G. Ötük, Synthesis
and antimicrobial activity of some novel derivatives of benzofuran: part 1.
Synthesis and antimicrobial activity of (benzofuran-2-yl) (3-phenyl-3-methylcy-
clobutyl) ketoxime derivatives, Eur. J. Med. Chem. 40 (12) (2005) 1351–1358.
[12] B. Cottineau, P. Toto, C. Marot, A. Pipaud, J. Chenault, Synthesis and hypoglycemic
evaluation of substituted pyrazole-4-carboxylic acids, Bioorg. Med. Chem. Lett. 12
18

I. Ali, et al.
BioorganicChemistry104(2020)104238
(16) (2002) 2105–2108.
[41] K.M. Khan, S. Qurban, U. Salar, M. Taha, S. Hussain, S. Perveen, A. Hameed,
N.H. Ismail, M. Riaz, A. Wadood, Synthesis, in vitro α-glucosidase inhibitory activity
and molecular docking studies of new thiazole derivatives, Bioorg. Chem. 68 (2016)
245–258.
[13] H. Lu, G.T. Liu, Anti-oxidant activity of dibenzocyclooctene lignans isolated from
Schisandraceae, Planta Med. 58 (04) (1992) 311–313.
[14] Y.S. Xie, D. Kumar, V.V. Bodduri, P.S. Tarani, B.X. Zhao, J.Y. Miao, K. Jang,
D.S. Shin, Microwave-assisted parallel synthesis of benzofuran-2-carboxamide de-
rivatives bearing anti-inflammatory, analgesic and antipyretic agents, Tetrahedron
Lett. 55 (17) (2014) 2796–2800.
[42] R. Rafique, K. M. Khan, S. Chigurupati, A. Wadood, A. U. Rehman, A. Karunanidhi,
S. Hameed, M. Taha, M. al-Rashida, Synthesis of new indazole based dual inhibitors
of α-glucosidase and α-amylase enzymes, their in vitro, in silico and kinetics stu-
dies. Bioorg. Chem. 94 (2020) 103195.
[15] S. Erber, R. Ringshandl, 2-Phenylbenzo [b] furans: relationship between structure,
estrogen receptor affinity and cytostatic activity against mammary tumor cells,
AntiCancer Drug Des. 6 (5) (1991) 417–426.
[43] U. Salar, K.M. Khan, S. Chigurupati, S. Syed, S. Vijayabalan, A. Wadood,
M. Ghufran, S. Perveen, New hybrid scaffolds based on hydrazinyl thiazole sub-
stituted coumarin; As novel leads of dual potential; In vitro α-amylase inhibitory and
antioxidant (DPPH and ABTS radical scavenging) activities, Med. Chem. 15 (1)
(2019) 87–101.
[16] G. McAllister, R. Hartley, M. Dawson, A. Knaggs, Total synthesis of moracin C, J.
Chem. Soc. Perkin Transactions 1. 1 (20) (1998) 3453–3458.
[17] M. Thévenin, S. Thoret, P. Grellier, J. Dubois, Synthesis of polysubstituted benzo-
furan derivatives as novel inhibitors of parasitic growth, Bioorg. Med. Chem. 21
(17) (2013) 4885–4892.
[44] S. Yousuf, K.M. Khan, U. Salar, S. Chigurupati, M.T. Muhammad, A. Wadood,
M. Aldubayan, V. Vijayan, M. Riaz, S. Perveen, 2ʹ-Aryl and 4ʹ-arylidene substituted
pyrazolones: As potential α-amylase inhibitors, Eur. J. Med. Chem. 159 (2018)
47–58.
[18] E. Navarro, S.J. Alonso, J. Trujillo, E. Jorge, C. Pérez, General behaviour, toxicity,
and cytotoxic activity of elenoside, a lignan from Justicia hyssopifolia, J. Nat. Prod.
64 (1) (2001) 134–135.
[45] S. Hameed, Kanwal., F. Seraj, R. Rafique, S. Chigurupati, A. Wadood, A.U. Rehman,
V. Venugopal, U. Salar, M. Taha, K.M. Khan, Synthesis of benzotriazoles derivatives
and their dual potential as α-amylase and α-glucosidase inhibitors in vitro:
Structure-activity relationship, molecular docking, and kinetic studies. Eur. J. Med.
Chem. 183 (2019) 11167.
[19] V. Kumar, J.H. Ackerman, M.D. Alexander, M.R. Bell, R.G. Christiansen, J.S. Dung,
E.P. Jaeger, J.L. Herrmann Jr, M.E. Krolski, Androgen receptor affinity of 5'-acyl
furanosteroids, J. Med. Chem. 37 (24) (1994) 4227–4236.
[20] O. Oter, K. Ertekin, C. Kirilmis, M. Koca, M. Ahmedzade, Characterization of a
newly synthesized fluorescent benzofuran derivative and usage as a selective fiber
optic sensor for Fe (III), Sensors Actuat. B: Chem. 122 (2) (2007) 450–456.
[21] O. Evliyaoğlu, L. Kebapçılar, N. Uzuncan, N. Kılıçaslan, B. Karaca, R. Kocaçelebi,
N. Yensel, Correlations of Serum Cu, Zn, Mg and HbA 1c in Type 2 and Type 2
Diabetes Mellitus, Turk J. Endocrinol. Metab. 2 (2004) 75–79.
[46] M. Taha, N.H. Ismail, S. Imran, A. Wadood, F. Rahim, S.M. Saad, K.M. Khan,
A. Nasir, Synthesis, molecular docking and α-glucosidase inhibition of 5-aryl-2-(6-
nitrobenzofuran-2-yl)-1,3,4-oxadiazoles, Bioorg. Chem. 66 (2016) 117–123.
[47] G.A. Patani, E.J. LaVoie, Bioisosterism: a rational approach in drug design, Chem.
Rev. 96 (1996) 3147–3176.
[22] American Diabetes Association. Standards of medical care in diabetes-2009.
Diabetes Care, (Suppl. 1), 32 (2009) S13.
[48] M.D. McBriar, J.W. Clader, I. Chu, R.A. Del Vecchio, L. Favreau, W.J. Greenlee,
L.A. Hyde, A.A. Nomeir, E.M. Parker, D.A. Pissarnitski, L. Song, L. Zhang, Z. Zhao,
Discovery of amide and heteroaryl isosteres as carbamate replacements in a series of
orally active γ-secretase inhibitors, Bioorg. Med. Chem. Lett. 18 (2008) 215–219.
[49] J.S. Warmus, C. Flamme, L.Y. Zhang, S. Barrrett, A. Bridges, M. Kaufman, H. Tecle,
R. Gowan, J. Sebolt-Leopold, W. Leopold, R. Merriman, S. Przybranowski, H. Valik,
J. Chen, J. Ohren, A. Pavlovsky, C. Whithead, E. Ahang, 2-Alkylamino-and alkoxy-
substituted 2-amino-1,3,4-oxadiazoles-O-Alkyl benzohydroxamate esters replace-
ments retain the desired inhibition and selectivity against MEK (MAP ERK kinase),
Bioorg. Med. Chem. Lett. 18 (2008) 6171–6174.
[23] D. Atlas, International diabetes federation. IDF Diabetes Atlas, 7th edn.,
International Diabetes Federation, Brussels, Belgium, 2015.
[24] P.M. Sales, P.M. Souza, L.A. Simeoni, P.O. Magalhães, D. Silveira, α-Amylase in-
hibitors: a review of raw material and isolated compounds from plant source, J.
Pharm. Pharm. Sci. 15 (1) (2012) 141–183.
[25] I. Funke, M.F. Melzig, Traditionally used plants in diabetes therapy: phytother-
apeutics as inhibitors of α-amylase activity, Rev. Bras. Farmacogn. 16 (1)
(2006) 1–5.
[26] S.A. Tucci, E.J. Boyland, J.C. Halford, The role of lipid and carbohydrate digestive
enzyme inhibitors in the management of obesity: a review of current and emerging
therapeutic agents, Diabet. Metab. Synd. Ob.: Targets Therapy. 3 (2010) 125.
[27] M.L. Barrett, J.K. Udani, A proprietary α-amylase inhibitor from white bean
(Phaseolus vulgaris): a review of clinical studies on weight loss and glycemic con-
trol, Nutr. J. 10 (1) (2011) 24.
[50] P. Gouthami, L.N. Chavan, R. Chegondi, S. Chandrasekhar, Syntheses of 2-aroyl
benzofurans through cascade annulation on arynes, J. Org. Chem. 83 (6) (2018)
3325–3332.
[51] Y. Shang, C. Wang, X. He, K. Ju, M. Zhang, S. Yu, J. Wu, DMAP-catalyzed cascade
reaction: one-pot synthesis of benzofurans in water, Tetrahedron. 66 (50) (2010)
9629–9633.
[28] L.W. Oberley, Free radicals and diabetes, Free Radic. Biol. Med. 5 (2) (1988. 1988,)
113–124.
[52] K. Neog, B. Das, P. Gogoi, 2, 3-Diaroyl benzofurans from arynes: sequential
synthesis of 2-aroyl benzofurans followed by benzoylation, Org. Biomol. Chem. 16
(17) (2018) 3138–3150.
[29] A. Ceriello, R. Testa, S. Genovese, Clinical implications of oxidative stress and po-
tential role of natural antioxidants in diabetic vascular complications, Nutr. Metab.
Cardiovasc. Dis. 26 (4) (2016) 285–292.
[53] C. Aswathanarayanappa, E. Bheemappa, Y.D. Bodke, V.K. Bhovi, R. Ningegowda,
M.C. Shivakumar, S.K. Peethambar, S. Telkar, 5-Phenyl-1-benzofuran-2-yl deriva-
tives: synthesis, antimicrobial, and antioxidant activity, Med. Chem. Res. 22 (1)
(2013) 78–87.
[30] P. Manna, S.K. Jain, Obesity, oxidative stress, adipose tissue dysfunction, and the
associated health risks: causes and therapeutic strategies, Metab. Syndr. Relat. D. 13
(10) (2015) 423–444.
[54] S. Bhargava, D. Rathore, A Tandem and one-pot access to 2-aroylbenzofuran and its
derivatives using ionic liquid as an efficient and recyclable reaction media, CBI. 6
(1) (2016) 19–26.
[31] M. Sankhla, T.K. Sharma, K. Mathur, J.S. Rathor, V. Butolia, A.K. Gadhok,
M. Vardey, M. Sinha, G.G. Kaushik, Relationship of oxidative stress with obesity and
its role in obesity induced metabolic syndrome, Clin. Lab. 58 (5–6) (2012) 385–392.
[32] J. Kositsawat, V.L. Freeman, Vitamin C and A1c relationship in the national health
and nutrition examination Survey (NHANES) 2003–2006, J. Am. Coll. Nutr. 30 (6)
(2011) 477–483.
[55] J.P. Bachelet, P. Demerseman, R. Royer, R. Cavier, J. Lemoine, Comparison of
antibacterial properties of halogeno aroylbenzofurans and corresponding alcohols,
Eur. J. Med. Chem. 17 (4) (1982) 323–325.
[56] V. Pestellini, A. Giolitti, F. Pasqui, L. Abelli, C. Cutrufo, G. De Salvia, S. Evangelista,
A. Meli, Synthesis and hypolipidemic activity of new substituted (benzofuran-2-yl)-
phenyl-carbinols, Eur. J. Med. Chem. 23 (1988) 203–206.
[33] J. Calles-Escandon, M. Cipolla, Diabetes and endothelial dysfunction: A clinical
perspective, Endocr. Rev. 22 (1) (2001) 36–52.
[34] U. Hink, N. Tsilimingas, M. Wendt, T. Münzel, Mechanisms underlying endothelial
dysfunction in diabetes mellitus, Treat. Endocrinol. 2 (5) (2003) 293–304.
[35] S. Sasaki, T. Inoguchi, The role of oxidative stress in the pathogenesis of diabetic
vascular complications, Diabetes Metab. J. 36 (4) (2012) 255–261.
[36] S.I. Yamagishi, T. Matsui, Nitric oxide, a Janus-faced therapeutic target for diabetic
microangiopathy-Friend or foe, Pharmacol. Res. 64 (3) (2011) 187–194.
[37] Y.Y. Wu, W. Li, Y. Xu, E.H. Jin, Y.Y. Tu, Evaluation of the antioxidant effects of four
main theaflavin derivatives through chemiluminescence and DNA damage analyses,
J. Zhejiang Univ. Sci. B. 12 (9) (2011) 744.
[57] U. Salar, K.M. Khan, S. Chigurupati, M. Taha, A. Wadood, S. Vijayabalan,
S. Perveen, New hybrid hydrazinyl thiazole substituted chromones: as potential α-
amylase inhibitors and radical (DPPH & ABTS) scavengers, Sci. Rep. 7 (1) (2017)
16980.
[58] R. Rafique, K.M. Khan, S. Arshia, A. Chigurupati, A.U. Wadood, U. Rehman,
V. Salar, S. Venugopal, M. Shamim, S. Perveen Taha, Synthesis, in vitro α-amylase
inhibitory, and radicals (DPPH & ABTS) scavenging potentials of new N-sulfono-
hydrazide substituted indazoles, Bioorg. Chem. 94 (2020) 103410.
[59] M. Ramírez-Escudero, M. Gimeno-Pérez, B. González, D. Linde, Z. Merdzo,
M. Fernández-Lobato, J. Sanz-Aparicio, Structural analysis of β-fructofuranosidase
from Xanthophyllomyces dendrorhous reveals unique features and the crucial role of
N-glycosylation in oligomerization and activity, J. Biolog. Chem. 291 (13) (2016)
6843–6857.
[38] J.R. Kanwar, R.K. Kanwar, H. Burrow, S. Baratchi, Recent advances on the roles of
NO in cancer and chronic inflammatory disorders, Curr. Med. Chem. 16 (19) (2009)
2373–2394.
[39] V. Chiavaroli, C. Giannini, S. De Marco, F. Chiarelli, A. Mohn, Unbalanced oxi-
dant–antioxidant status and its effects in pediatric diseases, Redox Rep. 16 (3)
(2011) 101–107.
[60] Molecular Operating Environment (MOE); Chemical Computing Group Inc., 1010
Sherbrooke St. West, Suite #910, Montreal, QC, Canada, H3A 2R7. 08 (2016).
[61] A.U. Rehman, M.U. Rahman, S. Lu, H. Liu, J.-Y. Li, T. Arshad, A. Wadood, H. Leung
Ng, H.-F. Chen, Decoding allosteric communication pathways in protein lysine
acetyltransferase, Int. J. Biolog. Macromol. 149 (2020) 70–80.
[40] T. Arshad, K.M. Khan, N. Rasool, U. Salar, S. Hussain, T. Tahir, M. Ashraf,
A. Wadood, M. Riaz, S. Perveen, M. Taha, Syntheses, in vitro evaluation and mo-
lecular docking studies of 5-bromo-2-aryl benzimidazoles as α-glucosidase in-
hibitors, Med. Chem. Res. 25 (9) (2016) 2058–2069.
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