Design, synthesis, biological evaluation, and docking study of acetylcholinesterase inhibitors: New acridone-1,2,4-oxadiazole-1,2,3-triazole hybrids

Article abstract of DOI:10.1111/cbdd.12609

In this study, novel acridone-1,2,4-oxadiazole-1,2,3-triazole hybrids were designed, synthesized, and evaluated for their acetylcholinesterase and butyrylcholinesterase inhibitory activity. Among various synthesized compounds, 10-((1-((3-(4-methoxyphenyl)-1,2,4-oxadiazol-5-yl)methyl)-1H-1,2,3-triazol-4-yl)methyl)acridin-9(10H)-one 10b showed the most potent anti-acetylcholinesterase activity (IC₅₀ = 11.55 μm) being as potent as rivastigmine. Also docking outcomes were in good agreement with in vitro results confirming the dual binding inhibitory activity of compound 10b. A novel series of acridone-1,2,4-oxadiazole-1,2,3-triazole hybrids were synthesized and evaluated in vitro for their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities.

Full text of DOI:10.1111/cbdd.12609

Chem Biol Drug Des 2015; 86: 1425–1432
Research Article
Design, Synthesis, Biological Evaluation, and Docking
Study of Acetylcholinesterase Inhibitors: New
Acridone-1,2,4-oxadiazole-1,2,3-triazole Hybrids
Maryam Mohammadi-Khanaposhtani1,
cholinergic neurotransmission, the decline of which leads
to AD (2). In spite of the fact that physiological function
Mohammad Mahdavi2, Mina Saeedi3,4
,
Reyhaneh Sabourian4, Maliheh Safavi5,
Mahnaz Khanavi6, Alireza Foroumadi2,
Abbas Shafiee2 and Tahmineh Akbarzadeh1,4,
of AChE at cholinergic synapses is well known, the
function of BChE has not been fully recognized (3).
Koelle demonstrated that contrary to AChE, BChE could
be more active at high concentrations of ACh (4). In
another study, Li et al. (5) found that it may act as
backup to AChE when the AChE activity has been
decreased.
*
1Department of Medicinal Chemistry, Faculty of Pharmacy,
Tehran University of Medical Sciences, Tehran 14176, Iran
2Department of Medicinal Chemistry, Faculty of Pharmacy
and Pharmaceutical Sciences Research Center, Tehran
University of Medical Sciences, Tehran 14176, Iran
3Medicinal Plants Research Center, Faculty of Pharmacy,
Tehran University of Medical Sciences, Tehran 14176, Iran
4Persian Medicine and Pharmacy Research Center,
Tehran University of Medical Sciences, Tehran 14176, Iran
5Department of Biotechnology, Iranian Research Organization
for Science and Technology, Tehran 14176, Iran
There is no definite cure for Alzheimer’s disease and cur-
rent investigations continue to treat symptoms (2,6). At
present, the neuroprotective effect is one of the most
important aspects of the currently marketed anti-Alzheimer
agents (7–9)
6Department of Pharmacognosy, Tehran University of
Medical Sciences, Tehran 14176, Iran
*Corresponding author: Tahmineh Akbarzadeh,
akbarzad@tums.ac.ir
Two main binding sites are involved in the structure of
AChE: the catalytic binding site (CS) and the peripheral
anionic binding site (PAS) (10,11). Recently, dual binding
site inhibitors (binding to both CS and PAS) have attracted
lots of attention and in this field, heterocyclic compounds
play crucial role. They can interact with both sites
efficiently and in this regard, indolinones (12), huperzine
A-tacrine (13), quinolone–benzylpiperidine (14), thiazolo-
1,2,4-triazinones (15), and oxoisoaporphines (16) have
shown remarkable activities.
In this study, novel acridone-1,2,4-oxadiazole-
1,2,3-triazole hybrids were designed, synthesized, and
evaluated for their acetylcholinesterase and butyrylcho-
linesterase
inhibitory
activity.
Among
various
synthesized compounds, 10-((1-((3-(4-methoxyphenyl)-
1,2,4-oxadiazol-5-yl)methyl)-1H-1,2,3-triazol-4-yl)methyl)
acridin-9(10H)-one 10b showed the most potent anti-
acetylcholinesterase activity (IC50 = 11.55 lM) being as
potent as rivastigmine. Also docking outcomes were in
good agreement with in vitro results confirming the dual
binding inhibitory activity of compound 10b.
As an extension of our continuous investigation on the
design and synthesis of anti-AChE agents (12,17–19),
herein, we decided to investigate AChEI activity of
novel
acridone-1,2,4-oxadiazole-1,2,3-triazole
hybrids
(Scheme 1). Latterly, in view of the efficiency of 1,2,3-triaz-
oles in the inhibition of AChE (20), we reported synthesis
and in vitro evaluation of acridone linked to 1,2,3-triazoles
(21). Most of the synthesized derivatives showed good
activity in comparison with rivastigmine as the reference
drug and among them, 10-((1-(4-chlorobenzyl)-1H-1,2,3-
Key words: acetylcholinesterase, acridone-1,2,4-oxadiazole-
1,2,3-triazole, Alzheimer’s disease, docking study
Received 26 January 2015, revised 24 May 2015 and
accepted for publication 3 June 2015
triazol-4-yl)methyl)-2-methoxyacridin-9(10H)-one
A
was
found to be more potent than rivastigmine (IC50 = 7.31 lM)
(Figure 1A). Considering the fact that 1,2,4-oxadiazoles
exhibited a wide variety of biological properties (22) and
have not been extensively considered in anti-AChE
research (23), we decided to insert 1,2,4-oxadiazole moi-
ety to acridone-1,2,3-triazole moiety and investigate AChEI
activity (Figure 1).
Alzheimer’s disease (AD) has emerged as the main
cause of dementia in elderly people affecting cognitive
characteristics including intelligence, memory, language,
and speech (1). It is known that two cholinesterases
(ChEs), acetylcholinesterase (AChE) and butyrylcholinest-
erase (BChE), are responsible for the regulation of
ª 2015 John Wiley & Sons A/S. doi: 10.1111/cbdd.12609
1425

Mohammadi-Khanaposhtani et al.
Scheme 1: Synthesis of acridone-1,2,4-oxadiazole-1,2,3-triazole derivatives 10.
General procedure for the synthesis of acridone-
1,2,4-oxadiazole-1,2,3-triazole derivatives 10
Methods and Materials
In the beginning, azide derivatives 9 were prepared in situ.
For this purpose, a solution of 3-aryl-5-(chloromethyl)-
1,2,4-oxadiazole derivative 7 (1.1 mmol), sodium azide 8
(0.9 mmol), and Et3N (1.3 mmol) in the mixture of water
(4 mL)/t-BuOH (4 mL) was stirred at room temperature for
1 h. Subsequently, mixture of 10-(prop-2-yn-1-yl) acridin-
9-one derivative 6 (1 mmol) and CuI (7 mol %) was added
to the freshly prepared azide derivative 9 and the reaction
mixture was stirred at room temperature for 24–56 h. Upon
completion of the reaction, monitored by TLC, the reaction
mixture was diluted with water, poured into crushed ice,
and the precipitated product was filtered off, washed with
cold water, and purified by flash chromatography on silica
gel using petroleum ether/ethyl acetate (4:1).
General chemistry
Melting points were determined on a Kofler hot stage
apparatus and are uncorrected. 1H and 13C NMR spec-
tra were recorded on a Bruker FT-500, using TMS as
an internal standard. IR spectra were obtained with a
Nicolet Magna FTIR 550 spectrophotometer (KBr disks).
MS values were recorded on an Agilent Technology (HP)
mass spectrometer operating at an ionization potential of
70 eV. Elemental analysis was performed with an Ele-
mentar Analysensystem GmbH VarioEL CHNS mode.
A
B
AChE and BChE inhibition assay
Acetylcholinesterase (AChE, E.C. 3.1.1.7, Type V-S, lyoph-
ilized powder, from electric eel, 1000 unit), butylcholinest-
erase (BChE, E.C. 3.1.1.8, from equine serum),
acetylthiocholine iodide (ATCI), and 5,5-dithiobis-(2-nitro-
benzoic acid) (DTNB) were obtained from Sigma-Aldrich.
Figure 1: The structure of 10-((1-(4-chlorobenzyl)-1H-1,2,3-
triazol-4-yl)methyl)-2-methoxyacridin-9(10H)-one as a potent anti-
AChE (IC50 = 7.31 lM) (A) and acridone-1,2,4-oxadiazole-1,2,3-
triazole hybrids (B).
1426
Chem Biol Drug Des 2015; 86: 1425–1432

Acridone-1,2,4-oxadiazole-1,2,3-triazoles
Potassium dihydrogen phosphate, dipotassium hydrogen
phosphate, potassium hydroxide, and sodium hydrogen
carbonate were purchased from Fluka. The acridone-
1,2,4-oxadiazole-1,2,3-triazole derivatives 10a-p were dis-
solved in a mixture of DMSO (5 mL) and methanol (5 mL)
and diluted in 0.1 M KH2PO4/K2HPO4 buffer (pH 8.0) to
obtain final assay concentrations. All experiments were
achieved at 25 °C, and four different concentrations were
tested for each compound in triplicate to obtain the range
of 20–80% inhibition for AChE.
structure of 1EVE was taken from the Brookhaven pro-
tein database (http://www.rcsb.org) as a complex bound
with inhibitor E2020 (donepezil). Subsequently, the water
molecules and the original inhibitors were removed from
the protein structure. The 3D structure of the com-
pounds 10b, 10c, 10m, and 10n were provided using
MARVINESKETCH
5.8.3,
2012,
ChemAxon
(http://
www.chemaxon.com) and converted to pdbqt co-ordi-
nate by AUTODOCK 4.2 program. Also, the autodock for-
mat of protein was provided using the same software.
Polar hydrogen atoms were added to amino acid resi-
dues using AUTODOCK TOOLS (ADT; version 1.5.6), Koull-
man charges were assigned to all atoms of the enzyme,
and the obtained enzyme structure was used as an
input for the AUTOGRID program. AUTOGRID performed a
precalculated atomic affinity grid maps for each atom
type in the ligand, plus an electrostatics map and a
separate desolation map presented in the substrate mol-
ecule. All maps were calculated with 0.375 A° spacing
between grid points. The center of the grid box was
To evaluate in vitro AChE activity, modified Ellman’s
method was performed (24) using a 96-well plate reader
(BioTek ELx808, Highland Park, IL, USA). Each well con-
tained 50 lL potassium phosphate buffer (KH2PO4/
K2HPO4, 0.1 M, pH 8), 25 lL sample dissolved in 50%
methanol and 50% DMSO, and 25 lL enzyme (final con-
centration 0.22 U/mL in buffer). They were preincubated
for 20 min at room temperature, and then, 125 lL DTNB
(3 mM in buffer) was added. Characterization of the
hydrolysis of ATCI catalyzed by AChE was performed
spectrometrically at 405 nm followed by the addition of
substrate (ATCI 3 mM in water). The change in absor-
bance was measured at 405 nm after 20 min. The IC50
values were determined graphically from inhibition curves
(log inhibitor concentration versus percent of inhibition). A
control experiment was performed under the same condi-
tions without inhibitor and the blank contained buffer,
DMSO, DTNB, and substrate. The described method
was also used for BChE inhibition assay.
placed
at
the
center
of
donepezil
with
co-ordinates x = 2.023, y = 63.295, and z = 67.062. The
dimensions of the active site box were set at
40 9 40 9 40 9 A. Flexible ligand docking was accom-
plished for the compounds 10b, 10c, 10m, and 10n.
Each docked system was carried out by 100 runs of
the AUTODOCK search by the Lamarckian genetic algorithm
(LGA). Other than the above-mentioned parameters, the
other parameters were accepted as default. The lowest
energy conformation of ligand–enzyme complex was
considered for analyzing the interactions between AChE
and the inhibitor. The results were visualized using
DISCOVERY STUDIO 4.0 CLIENT (Figures 1 and 2).
DPPH radical scavenging activity (DPPH)
Antioxidant activity of compounds 10a-d, 10k, and 10n
were assessed using DPPH (1,1-diphenyl-2-picrylhydrazyl)
(25). Several concentrations of the above-mentioned com-
pounds in DMSO were prepared. The compound solution
(0.5 mL) was added to the methanolic DPPH solution
(1.0 mL, 0.1 mM), and the mixture was kept in the dark for
30 min. Then, the absorbance at 517 nm was measured
by an UV/visible spectrophotometer. The percent scaveng-
ing activity was calculated using the following formula: inhi-
bition (%) = 100À[100 9 (Abssample – Abscontrol)⁄Absblank].
Results and Discussion
Chemistry
The synthetic pathways for the synthesis of novel acri-
done-1,2,4-oxadiazole-1,2,3-triazoles 10 have been
shown in Scheme 1. Our approach was started from the
Ullmann condensation reaction of 2-bromobenzoic acid 1
and different anilines 2 (26) using potassium carbonate
and copper in refluxing EtOH leading to the formation of
2-arylamino benzoic acids 3. Compound 3 easily partici-
pated in the cyclization reaction in the presence of PPA
at 100 °C and afforded acridones 4 (27). Acridone deriva-
tive 4 reacted with propargyl bromide 5 using potassium
Molecular docking study
Docking studies were carried out using the AUTODOCK 4.2
program (La Jolla, CA, USA). For this purpose, the pdb
Scheme 2: Synthesis of 3-aryl-5-(chloromethyl)-1,2,4-oxadiazole derivatives 7.
Chem Biol Drug Des 2015; 86: 1425–1432
1427

Mohammadi-Khanaposhtani et al.
presence of potassium carbonate in dry acetone gave
N’-(2-chloroacetoxy)-4-substituted benzimidamide 15
which underwent the further cyclization reaction in reflux-
ing toluene to give 3-aryl-5-(chloromethyl)-1,2,4-oxadiaz-
ole derivative 7. Then, compound 7 and sodium azide 8
reacted in the presence of Et3N in the mixture of H2O/t-
BuOH at room temperature for 1 h. After that, mixture of
10-(prop-2-yn-1-yl) acridin-9-one derivative
6 and CuI
was added to the freshly prepared azide derivative 8 and
the reaction was continued at room temperature for 24–
56 h to give the corresponding product 10 in good yields
(68–86%).
Pharmacology
Figure 2: Superimposition of the most potent compound 10b
(cyan) and donepezil (pink) in the active site of AChE.
The anti-AChE activity of acridone-1,2,4-
oxadiazole-1,2,3-triazole derivatives
In vitro AChE and BChE inhibition assays were accompa-
nied according to the Ellman’s method (24), and all results
were compared to rivastigmine as the reference drug
(Table 1). Among sixteen newly synthesized acridone-
1,2,4-oxadiazole-1,2,3-triazoles 10a-p, compounds 10a-d,
10k, and 10n (IC50 = 11.55–77.79 lM) showed anti-AChE
activity and 10b (IC50 = 11.55 lM) was found as potent as
rivastigmine (IC50 = 11.07 lM).
tert-butoxide in DMSO at room temperature. The resulting
10-(prop-2-yn-1-yl) acridin-9-one derivative
6 tolerated
click reaction through the method described by Sharpless
et al. to construct 1,2,3-triazole ring (28). For this
purpose, different 3-aryl-5-(chloromethyl)-1,2,4-oxadiazole
derivatives 7 were prepared as approached in Scheme 2
(29). Accordingly, benzonitrile derivative 11 and hydroxyl-
amine hydrochloride 12 reacted in refluxing EtOH in the
presence of sodium hydroxide to obtain 13. The reaction
of compound 13 and chloroacetyl chloride 14 in the
According to our results, compound 10b possessing
unsubstituted acridone and 4-methoxyphenyl-1,2,4-
Table 1: The IC50 values of the compounds 10 against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE)a
O
8
1
9
R1
7
6
3
10N
5
R2
O
N
N
N
N
N
10
Ar
AChE inhibition
IC50 (lM)
BChE inhibition
IC50 (lM)
Entry
Compound 10
R1
R2
Ar
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
10a
10b
H
H
H
H
H
H
H
Me
OMe
OMe
OMe
Cl
Cl
Cl
Br
Br
H
H
H
H
OMe
OMe
Cl
H
H
H
H
H
4-Me-C6H4
4-MeO-C6H4
4-Cl-C6H4
49 Æ 0.04
11.55 Æ 0.08
24.72 Æ 0.53
67.44 Æ 0.17
>100
>100
>100
>100
>100
>100
>100
88.86 Æ 0.24
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
>100
N.D
10c
10d
4-Br-C6H4
10e
10f
4-Me-C6H4
4-MeO-C6H4
4-MeO-C6H4
4-Cl-C6H4
4-Me-C6H4
4-MeO-C6H4
4-Cl-C6H4
4-Me-C6H4
4-MeO-C6H4
4-Cl-C6H4
4-MeO-C6H4
4-Cl-C6H4
10g
10h
10i
10j
>100
10k
10l
77.79 Æ 0.01
>100
10m
10n
H
H
H
H
>100
44.93 Æ 0.06
10o
10p
>100
>100
11.07 Æ 0.01
Rivastigmine
aData are expressed as mean Æ SE (three independent experiments).
1428
Chem Biol Drug Des 2015; 86: 1425–1432

Acridone-1,2,4-oxadiazole-1,2,3-triazoles
oxadiazole moieties showed the most potent activity
(IC50 = 11.55 lM). However, AChE inhibition disappeared
when the acridone moiety was substituted at C-2 or C-4
position by methoxy, chlorine, and bromine in compounds
10f, 10g, 10j, 10l, and 10o. In the series of compounds
10, compound 10c was found as the second active deriva-
tive (IC50 = 24.72 lM). It consisted of unsubstituted acri-
done and 4-chlorophenyl-1,2,4-oxadiazole moieties.
Introduction of chlorine or methoxy group to the C-2 posi-
tion of acridone moiety led to the reduction of AChE activity
in compounds 10n and 10k (IC50 = 44.93 and77.79 lM,
respectively), and AChE inhibition activity was canceled out
when the hydrogen at C-2 was replaced by methyl or bro-
mine (10h and 10p). Our results showed that compounds
10a and 10d having 4-methyphenyl/4-bromophenyl-1,2,
4-oxadiazole moiety were less active (IC50 = 49.46 and
67.44 lM, respectively) than compounds 10b and 10c.
However, compound 10a presented more potency in com-
parison with its counterparts 10e, 10i, and 10l.
diphenyl-2-picrylhydrazyl radical scavenging activity (DPPH)
assay based on the method described in the literature
(25). In this colorimetric method, 1,1-diphenyl-2-pic-
rylhydrazyl radical has an absorption band at 515 nm
which is disappeared upon reduction by an antioxidant
agent. The inhibition percentage values were determined
by comparison with butylated hydroxyanisole (BHA) as a
standard antioxidant. As can be seen in Table 2, among
tested compounds, 10d was found to be more potent
antioxidant agent (inhibition percentage: 84.16) in compari-
son with BHA (inhibition percentage: 95.70).
Docking studies
We also performed docking studies parallel to the synthe-
sis and in vitro evaluation of acridone-1,2,4-oxadiazole-
1,2,3-triazoles to gain a more exhaustive perception of the
interactions and binding to the active site of AChE. They
were obtained using AUTODOCK TOOLS (1.5.6) and DISCOVERY
STUDIO 4.0 CLIENT. Several ligand-bounded crystallographic
structures of AChE were obtained from the RCSB protein
data bank (http://www.rcsb.org/pdb/home/home.do). In
this study, PDB structure of 1EVE was retrieved for dock-
ing purpose.
Other instructive results were obtained from derivatives
having substituted acridone moieties (10e-p). In this series
of compounds, only 10k and 10n (IC50 = 77.79 and
44.93 lM, respectively) possessing 4-chlorophenyl-1,2,4-
oxadiazole moiety exhibited relatively good anti-AChE
effects. It should be noted that 10k and 10n had methoxy
and chlorine at C-2 position of acridone moiety, respec-
tively.
As it is clear in Figure 2, the orientation of the most potent
compound 10b in the active site of AChE was the same
as donepezil. Our results related to the most active com-
pound 10b, relatively good active compounds including
10c and 10n, and inactive compound 10m are shown in
Figure 3. The most active compound 10b is located in the
binding site of AChE as shown in Figure 3. It confirms the
dual binding site activity. It is clear that the acridone moi-
ety is linked to the bottom of active site through p–p inter-
action with Trp84 in the catalytic anionic site (CAS). Also
there is another interaction between acridone and Phe331.
Indeed, compound 10b depicted a hydrogen-bond inter-
action between carbonyl group of acridone and hydroxyl
group of Ser200 in catalytic triad site. In addition, 1,2,4-
oxadiazole moiety exhibited p–p interaction with a phenyl
group of Tyr121 in the peripheral anionic site (PAS). It
should be noted that there was an interaction via hydro-
To sum up, the electronic properties of substituents on all
three heterocyclic moieties play crucial role in anti-AChE
activity. As can be seen in Table 1, the satisfactory results
with anti-AChE effects were related to derivatives possess-
ing unsubstituted acridone moiety and it is strongly con-
firmed by compounds 10b and 10c. At this juncture,
substituted 1,2,4-oxadiazole ring was perceived to be
important and the AChEI activity in the unsubstituted
acridone series was observed in the order of
10b>10c>10a>10d. It seems that methoxy group imparted
a higher activity in comparison with chlorine, methyl, and
bromine substituents (OMe>Cl>Me>Br). It should be note
that the anti-AChEI activity of compounds 10 was in good
agreement with those reported in the literature as the
efficiency of methoxy and chlorine groups to establish suit-
able interactions has been well documented, the ability of
formation of a hydrogen bond between methoxy oxygen
and amino acids NH protons (30) as well as interaction
between chlorine and backbone carbonyl group (31).
Table 2: DPPH antioxidant activities of the compounds 10a–d,
10k, and 10na
Entry Compound 10 Inhibition (%) (700 lg/mL) EC50 (lg/mL)
To determine selectivity toward AChE and BChE enzymes,
all compounds 10 were evaluated for their BChEI activity,
and there were no significant activities.
1
2
3
4
5
6
7
10a
10b
10c
10d
10k
10n
BHA
30.68 Æ 0.92
38.06 Æ 0.94
43.44 Æ 0.27
84.16 Æ 0.53
35.37 Æ 0.65
67.19 Æ 0.20
95.70 Æ 0.50
>700
>700
>700
299
>700
400
1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical
scavenging activity
1.27
aData are expressed as mean Æ SE (three independent experi-
The total antioxidant activity of the six AChEI active com-
pounds 10a–d, 10k, and 10n were evaluated using 1,1-
ments).
Chem Biol Drug Des 2015; 86: 1425–1432
1429

Mohammadi-Khanaposhtani et al.
Figure 3: Docking study of compounds
10b, 10c, 10m, and 10n. p–p interactions
and hydrogen bonds are represented as
dashed lines and green lines, respectively.
gen bond between methoxy group of aryl and backbone
NH atom. The docking study was also performed for two
other active compounds 10c and 10n (Figure 3). Both
compounds exhibited p–p interaction of acridone moiety
with Trp84 and lacked the interaction between acridone
carbonyl group and Ser200 as well as the interaction of
1,2,4-oxadiazole ring with Tyr121 in PAS. It suggested that
these interactions play vital role in anti-AChE activity.
Docking study of compounds 10c and 10n depicted two
extra interactions including p–p interaction of 1,2,3-triazole
with Phe330 and the p–p interaction of aryl group with
Trp279, which were not observed in the docking study of
compound 10b. Also p–p interaction between 1,2,4-ox-
adiazole ring and Phe331 was observed for compounds
10c and 10n. Docking study of inactive AChEI compound
10m showed significant difference lacking desirable inter-
actions with active sites of enzyme. It seems that the inter-
action of acridone moiety with Phe330 and Tyr121 did not
lead to the AChEI activity.
1,2,4-oxadiazol-5-yl)methyl)-1H-1,2,3-triazol-4-yl)methyl)
acridin-9(10H)-one 10b showed the highest activity for
the inhibition of AChE (IC50 = 11.55 lM) being as potent
as reference drug, rivastigmine. Comparing with our
recent report on the anti-AChE activity of acridone linked
to 1,2,3-triazoles [18], insertion of 1,2,4-oxadiazole moi-
ety to acridone-1,2,3-triazole system did not lead to
higher potency but presented dual binding site AChE
inhibitors.
Acknowledgment
This work was supported by grant from the Research
Council of Tehran University of Medical Sciences under
grant No. 94-01-33-28706.
References
Consequently, the high activity of compound 10b is
indebted to multilateral interactions with the active site of
AChE including catalytic site CS (both CAS and catalytic
triad) and peripheral anionic site (PAS).
1. Goedert M., Spillantini M.G. (2006) A century of Alzhei-
mer’s disease. Science;311:777–781.
2. Francis P.T., Palmer A.M., Snape M., Wilcock G.K. (1999)
The cholinergic hypothesis of Alzheimer’s disease: A review
of progress. J Neurol Neurosurg Psychiatry;66:137–147.
3. Chatonnet A., Lockridge O. (1989) Comparison of
butyrylcholinesterase and acetylcholinesterase. Biochem
J;260:625–634.
Conclusion
In conclusion, we have designed, synthesized, and
evaluated novel acridone-1,2,4-oxadiazole-1,2,3-triazole
hybrids as efficient anti-AChE agents. Among sixteen
synthesized compounds, 10-((1-((3-(4-methoxyphenyl)-
4. Koelle G.B.J. (1950) The histochemical differentiation
of types of cholinesterases and their localization in
tissues of the cat. J Pharmacol Exp Ther;100:158–
179.
1430
Chem Biol Drug Des 2015; 86: 1425–1432

Acridone-1,2,4-oxadiazole-1,2,3-triazoles
5. Li B., Stribley J.A., Ticu A., Xie W., Schopfer L.M.,
Hammond P., Brimijoin S., Hinrichs S.H., Lockridge O.
(2000) Abundant tissue butyrylcholinesterase and its
possible function in the acetylcholinesterase knockout
mouse. J Neurochem;75:1320–1331.
6. Dunnett S.B., Fibiger H.C. (1993) Chapter 49: role of
forebrain cholinergic systems in learning and memory:
relevance to the cognitive deficits of aging and Alzhei-
mer’s dementia. Prog Brain Res;98:413–420.
[3,2-c]chromene derivatives as acetylcholinesterase
and butyrylcholinesterase inhibitors. Eur J Med Chem;68:
260–269.
18. Asadipour A., Alipour M., Jafari M., Khoobi M., Emami
S., Nadri H., Sakhteman A., Moradi A., Sheibani V.,
Moghadam F.H., Shafiee A., Foroumadi A. (2013)
Novel coumarin-3-carboxamides bearing N-benzylpi-
peridine moiety as potent acetylcholinesterase inhibi-
tors. Eur J Med Chem;70:623–630.
7. Munoz-Torrero D. (2008) Acetylcholinesterase inhibitors
as disease-modifying therapies for Alzheimer’s disease.
Curr Med Chem;15:2433–2455.
8. Soreq H., Seidman S. (2001) Acetylcholinesterase-new
roles for an old actor. Nat Rev Neurosci;2:294–302.
9. Hashimoto M., Kazui H., Matsumoto K., Nakano Y.,
Yasuda M., Mori E. (2005) Does donepezil treatment
slow the progression of hippocampal atrophy in
19. Alipour M., Khoobi M., Moradi A., Nadri H., Moghad-
am F.H., Emami S., Hasanpour Z., Foroumadi A., Sha-
fiee A. (2014) Synthesis and anti-cholinesterase activity
of new 7-hydroxycoumarin derivatives. Eur J Med
Chem;82:536–544.
ꢀ
20. Lewis W.G., Green L.G., Grynszpan F., Radic Z., Car-
lier P.R., Taylor P., Finn M.G., Sharpless K.B. (2002)
Click chemistry in situ: acetylcholinesterase as a reac-
tion vessel for the selective assembly of a femtomolar
inhibitor from an array of building blocks. Angew Chem
Int Ed Engl;41:1053–1057.
patients with Alzheimer’s disease. Am
J Psychia-
try;162:676–682.
ꢀ
10. Bourne Y., Taylor P., Radic Z., Marchot P. (2003)
Structural insights into ligand interactions at the acetyl-
cholinesterase peripheral anionic site. EMBO J;22:1–
12.
21. Khanaposhtani M.M., Saeedi M., Mahdavi M., Zafarg-
handi N.S., Sabourian R., Razkenari E.K., Alinezhad
H., Khanavi M., Foroumadi A., Shafiee A., Akbarzadeh
T. (2015) Potent acetylcholinesterase inhibitors: design,
synthesis, biological evaluation, and docking study of
acridone linked to 1,2,3-triazole derivatives. Eur J Med
Chem;92:799–806.
11. Johnson G., Moore S.W. (2006) The peripheral anionic
site of acetylcholinesterase: structure, functions and
potential role in rational drug design. Curr Pharm
Des;12:217–225.
12. Akrami H., Mirjalili B.F., Khoobi M., Nadri H., Moradi
A., Sakhteman A., Emami S., Foroumadi A., Shafiee A.
(2014) Indolinone-based acetylcholinesterase inhibitors:
synthesis, biological activity and molecular modeling.
Eur J Med Chem;84:375–381.
13. Carlier P.R., Du D.-M., Han Y.-F., Liu J., Pang Y.-P.
(1999) Potent, easily synthesized huperzine A-tacrine
hybrid acetylcholinesterase inhibitors. Bioorg Med
Chem Lett;9:2335–2338.
22. Bora R.O., Dar B., Pradhan V., Farooqui M. (2014) [1,
2, 4]-Oxadiazoles: synthesis and biological applica-
tions. Mini Rev Med Chem;14:355–369.
23. Takasugi H., Kuno A., Ohkubo M. (1997) Oxadiaz-
ole derivatives having acetylcholinesterase-inhibitory
and muscarinic agonist activity. US Patent
5622976.
24. Ellman G.L., Courtney K.D., Andres V. Jr, Feather-
Stone R.M. (1961) A new and rapid colorimetric deter-
mination of acetylcholinesterase activity. Biochem
Pharmacol;7:88–95.
25. Yassa N., Beni H.R., Hadjiakhoondi A. (2008) Free
radical scavenging and lipid peroxidation activity of
the Shahani black grape. Pak J Biol Sci;11:2513–
2516.
€
14. Pudlo M., Luzet V., Ismaıli L., Tomassoli I., Iutzeler A.,
Refouvelet B. (2014) Quinolone–benzylpiperidine deriv-
atives as novel acetylcholinesterase inhibitor and anti-
oxidant hybrids for Alzheimer Disease. Bioorg Med
Chem;22:2496–2507.
15. Liu S., Shang R., Shi L., Wan D.C.-C., Lin H. (2014)
Synthesis and biological evaluation of 7H-thiazolo[3,2-
b]-1,2,4-triazin-7-one derivatives as dual binding site
acetylcholinesterase inhibitors. Eur J Med Chem;81:
237–244.
26. Wolf C., Liu S., Mei X., August A.T., Casimir M. (2006)
Regioselective copper-catalyzed amination of bromo-
benzoic acids using aliphatic and aromatic amines. J
Org Chem;71:3270–3273.
16. Tanga H., Weia Y.-B., Zhanga C., Ninga F.-X.,
Qiaob W., Huanga S.-L., Mab L., Huanga Z.-S., Gu
L.-Q. (2009) Synthesis, biological evaluation and
molecular modeling of oxoisoaporphine and oxoapor-
phine derivatives as new dual inhibitors of acetylcho-
27. Hedge R., Thimmaiah P., Yerigeri M.C., Krishnegowda
G., Thimmaiah K.N., Houghton P.J. (2004) Anti-cal-
modulin acridone derivatives modulate vinblastine
resistance in multidrug resistant (MDR) cancer cells.
Eur J Med Chem;39:161–178.
linesterase/butyrylcholinesterase.
Eur
J
Med
28. Kolb H.C., Finn M.G., Sharpless K.B. (2001) Click
Chem;44:2523–2532.
chemistry: diverse chemical function from a few
17. Khoobi M., Alipour M., Sakhteman A., Nadri H.,
Moradi A., Ghandi M., Emami S., Foroumadi A.,
Shafiee A. (2013) Design, synthesis, biological evalua-
tion and docking study of 5-oxo-4,5-dihydropyrano
good reactions. Angew Chem Int Ed Engl;40:2004–
2021.
29. Kumar D., Patel G., Johnson E.O., Shah K. (2009)
Synthesis and anticancer activities of novel 3,5-disub-
Chem Biol Drug Des 2015; 86: 1425–1432
1431

Mohammadi-Khanaposhtani et al.
stituted-1,2,4-oxadiazoles. Bioorg Med Chem Lett;19:
2739–2741.
Supporting Information
30. Kuhn B., Mohr P., Stahl M. (2010) Intramolecular
Additional Supporting Information may be found in the
online version of this article:
hydrogen bonding in medicinal chemistry.
J Med
Chem;53:2601–2611.
31. Bissantz C., Kuhn B., Stahl M. (2010) A medicinal
Appendix S1. It includes all required procedures as
well as 1H NMR and 13C NMR full characterization and
spectra.
chemist’s guide to molecular interactions.
J Med
Chem;53:5061–5084.
1432
Chem Biol Drug Des 2015; 86: 1425–1432