Alzheimer’s disease (AD), the most common cause of dementia
in the elderly, is affecting millions of people worldwide. The ailment
is characterized by a complex neurodegenerative process occurring
in the central nervous system which leads to progressive cognitive
decline and memory loss. [1] The etiology of AD is not fully known,
although factors including the low levels of acetylcholine (ACh),
accumulation of abnormal proteins namely -amyloid and -protein,
homeostasis irregularity of biometals, and oxidative stress are
considered to play significant roles in the pathophysiology of AD.[2]
At the present , clinical therapy for AD patients is primarily
established upon the cholinergic hypothesis which suggests that the
decline of the ACh level might lead to cognitive and memory
deficits, and drugs with the ability of inhibiting acetylcholinesterase
(AChE) would control symptoms of the disease.[1]
Chalcone is a sub-group of flavonoid and is the intermediary in
the synthesis process of other flavonoids, pyrazoline, isoxazole, and
quinolinylpyrimidine. There are a lot of chalcone compounds which
are reported to have a diverse array of bioactivities such as
antibacterial, antifungal, antiviral, antioxidant, antitumoral, and other
characteristics such as anti-inflammatory, analgesic, antiulce. Recent
studies on the bioactivities of chalcone compounds have also
revealed their abilities in inhibiting enzymes including urease, -
glucosidase, lipoxygenase, acetylcholinesterase, mammalian alphaamylase, xanthine oxidase58, monoamine oxidase (MAO), and -
secretase. In addition, it was reported that chalcone derivatives
exhibit high binding affinity to A aggregates in vitro, and they2
could serve as a useful mean for in vivo imaging of A plaques in
Alzheimer’s brain.[2-4] The studies on bioactivities of chalcone
derivatives on the function of human brain promise the finding of
new drugs for the treatment of many diseases including AD.
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TP Hồ Chí Minh - Năm 2017
MINISTRY OF EDUCATION
AND TRAINING
VIETNAM ACADEMY OF
SCIENCE AND TECHNOLOGY
GRADUATE UNIVERSITY SCIENCE AND
TECHNOLOGY
-----------------------------
Nguyen Thi Cam Vi
DESIGN, SYNTHESIS AND EVALUATION OF
ACETYLCHOLINESTERASE INHIBITORY ACTIVITY
OF CHALCONE DERIVATIVES FOR THE DISCOVERY
OF NEW ANTI-ALZHEIMER DRUGS
Major: Organic chemistry
Code: 9.44.01.14
SUMMARY OF ORGANIC CHEMISTRY DOCTORAL
THESIS
Ho Chi Minh – 2018
Công trình được hoàn thành tại Viện Công Nghệ Hóa Học
Viện Khoa Học và Công Nghệ Việt Nam
Người hướng dẫn khoa học
1. PGS. TS. TRẦN THÀNH ĐẠO
2. PGS. TS. THÁI KHẮC MINH
Phản biện 1: TS. Nguyễn Thụy Việt Phương
Phản biện 2: GS. TS. Phan Thanh Sơn Nam
Luận án sẽ được bảo vệ trước Hội đồng đánh giá luận án
cấp cơ sở họp tại Viện Công Nghệ Hóa Học, Viện Khoa Học
và Công Nghệ Việt Nam.
Vào hồi.. giờ ngày . tháng .
năm 2017
Có thể tìm hiểu luận án tại: Viện Công Nghệ Hóa Học và
Thư Viện quốc gia.
The doctoral thesis was finished at: Graduate University Science and
Technology - Vietnam Academy of Science and Technology.
The 1st supevisor: Ass c. Prof. Dr. Tran Thanh Dao
The 2nd supevisor: Assoc. Prof. Dr. Thai Khac Minh
The 1st doctoral thesis reviewer:
The 2nd doctoral thesis reviewer:
The 3rd doctoral thesis reviewer: .
The doctoral thesis will be protected at the evaluation coucil of PhD
dissertation (Academy degree), meeted at Graduate University
Science and Technology - Vietnam Academy of Science and
Technology, at am (pm), day month year 201.
Read the doctoral thesis:
- Graduate University Science and Technology Library
- National Library of Vietnam
1
INTRODUCTION
1. The urgency of the thesis
Alzheimer’s disease (AD), the most common cause of dementia
in the elderly, is affecting millions of people worldwide. The ailment
is characterized by a complex neurodegenerative process occurring
in the central nervous system which leads to progressive cognitive
decline and memory loss.
[1]
The etiology of AD is not fully known,
although factors including the low levels of acetylcholine (ACh),
accumulation of abnormal proteins namely -amyloid and -protein,
homeostasis irregularity of biometals, and oxidative stress are
considered to play significant roles in the pathophysiology of AD.[2]
At the present , clinical therapy for AD patients is primarily
established upon the cholinergic hypothesis which suggests that the
decline of the ACh level might lead to cognitive and memory
deficits, and drugs with the ability of inhibiting acetylcholinesterase
(AChE) would control symptoms of the disease.
[1]
Chalcone is a sub-group of flavonoid and is the intermediary in
the synthesis process of other flavonoids, pyrazoline, isoxazole, and
quinolinylpyrimidine. There are a lot of chalcone compounds which
are reported to have a diverse array of bioactivities such as
antibacterial, antifungal, antiviral, antioxidant, antitumoral, and other
characteristics such as anti-inflammatory, analgesic, antiulce. Recent
studies on the bioactivities of chalcone compounds have also
revealed their abilities in inhibiting enzymes including urease, -
glucosidase, lipoxygenase, acetylcholinesterase, mammalian alpha-
amylase, xanthine oxidase
58
, monoamine oxidase (MAO), and -
secretase. In addition, it was reported that chalcone derivatives
exhibit high binding affinity to A aggregates in vitro, and they
2
could serve as a useful mean for in vivo imaging of A plaques in
Alzheimer’s brain.[2-4] The studies on bioactivities of chalcone
derivatives on the function of human brain promise the finding of
new drugs for the treatment of many diseases including AD.
From the above scientific bases, the research project "Design,
synthesis and acetylcholinesterase inhibitory activity evaluation of
chalcone derivatives for the discovery of new anti-alzheimer drugs"
was conducted.
2. The objectives of the thesis
Molecular docking studies on acetylcholinesterase were performed to
predict the chalcone structure has good in silico AChE
acetylcholinesterase inhibitory activity. The potential chalcone
compounds were synthesized and studied for their in vitro and in
vivo AChE inhibitory activities.
3 . The main contents of the thesis
- The molecular binding abilities of chalcone derivatives with ACHE
were elucidated by docking procedure to predict the chalcone
structure has good in silico AChE acetylcholinesterase inhibitory
activity.
- The potential chalcone compounds were synthesized and studied
for their in vitro and in vivo AChE inhibitory activities.
Chapter 1. OVERVIEW
1.1. Alzheimer disease
Alzheimer’s disease (AD), the most common cause of dementia
in the elderly, is affecting millions of people worldwide. The ailment
is characterized by a complex neurodegenerative process occurring
3
in the central nervous system which leads to progressive cognitive
decline and memory loss.
[1]
The etiology of AD is not fully known,
although factors including the low levels of acetylcholine,
accumulation of abnormal proteins namely -amyloid and -protein,
homeostasis irregularity of biometals, and oxidative stress are
considered to play significant roles in the pathophysiology of AD.[12]
At the present , clinical therapy for AD patients is primarily
established upon the cholinergic hypothesis which suggests that the
decline of the ACh level might lead to cognitive and memory
deficits, and drugs with the ability of inhibiting acetylcholinesterase
(AChE) would control symptoms of the disease.
[1]
1.2. Acetylcholinesterase (AChE)
Acetylcholinesterase (acetycholine acetylhydrolase, E.C. 3.1.1.7)
[11]
is involved in the hydrolysis of acetylcholine, an essential
neurotransmitter of the central nervous system, into choline. This
enzyme catalyzes the hydrolysis of the neurotransmitter
acetylcholine at neuronal synapses, and at neuromuscular junctions,
at the end of the signaling process. In certain neurological disorders
such as Alzheimer’s disease, acetylcholinesterase is overactivated in
the synapses so that levels of acetylcholine in the brains is
significantly diminished, which leads to weakened neurotransmission
and thereby memory loss and other adverse effects.
1.3. Chalcone
Chalcones (1,3-diphenyl-2-propen-1-one) are open chain flavonoids
with a 15-carbon structure arranged in a C6-C3-C6 configuration.
They consist in two phenolic rings (A and B rings) connected by a
3C bridge with a double bond between α- and β-positions, which
confers them a particularly singular structure.
[16]
4
Figure 1.7. Structure and numbering of chalcone
1.4. Molecular Docking
Molecular docking is an attractive scaffold to understand
drugbiomolecular interactions for the rational drug design and
discovery, as well as in the mechanistic study by placing a molecule
(ligand) into the preferred binding site of the target specific region of
the DNA/protein (receptor) mainly in a non-covalent fashion to form
a stable complex of potential efficacy and more specificity. The
information obtained from the docking technique can be used to
suggest the binding energy, free energy and stability of complexes.
At present, docking technique is utilized to predict the tentative
binding parameters of ligand-receptor complex beforehand.
[21]
1.5. In vitro screening for acetylcholinesterase inhibition
AChE inhibitory activity was determined spectrophotometrically
using the Ellman's colorimetric method. ACHE hydrolyzes the
substrate ATCI to thiocholine and acetic acid. Thiocholine is allowed
to react with DTNB, and this reaction resulted in the development of
a yellow color. The color intensity of the product is measured at 405
nm, and it is proportional to the enzyme activity.
[27]
1.6. Short-term memory impairment models
Loss of memory is among the first symptoms reported by patients
suffering from Alzheimer's disease (AD) and by their caretakers.
5
Currently, short-term memory impairment models are widely used in
the treatment of AD.
[27]
The Y-maze model and Novel Object Recognition model are quick
and useful initial tests to study short-term memory.
Chapter 2. CONDITION AND EXPERIMENTAL METHOD
2.1. Time and place of study
Time: 1 11 2011 01/05/2017
Place: Labs of Department of Pharmacology, Department of
Pharmaceutical, Department of Microbiology, Faculty of Pharmacy,
Ho Chi Minh City Medicine and Pharmacy University.
2.2. Experimental content and method
2.2.1. Experimental content
The molecular binding abilities of chalcone derivatives with ACHE
were elucidated by docking procedure to predict the chalcone
structure has strong in silico AChE acetylcholinesterase inhibitory
activity. The potential chalcone compounds were synthesized by
Claisen-Schmidt condensation reaction. These chalcone compounds
are studied for their in vitro and in vivo AChE inhibitory activities.
2.2.2. Experimental method
Molecular Docking Study
The Protein Data Bank crystallographic structure of TcAChE(-)-
Galantamine complex (pdb 1DX6)
67
was used as receptor model in
this study. The 3D structure of the crystallographic complex was
rendered by means of BioSolveIT LeadIt. The active site was defined
as all the important amino acid residues enclosed within a radius
sphere of 6.5 Å centered by the bound ligand, galantamine. All
unbound water molecules were eliminated and the structures of
6
amino acid residues were checked before re-establishing the active
site of the enzyme.
Docking process of 107 chalcone derivatives (35 normal chalcone
derivatives, 24 heterocyclic chalcone derivatives, 32
benzylaminochalcone derivatives and 16 promazine chalcone
derivatives) was performed in BioSolveIT LeadIt with the following
options: the method in which base fragment placed in binding pocket
was Triangle Matching; the maximum number of solutions per
iteration was set to 1 000; the maximum number of solutions per
fragmentation was set to 200; the number of poses to keep for further
analysis of interaction was set to 10. The best conformation is the
one that has the most minus docking score. This score was the total
energy emitted from the formation of binding between the molecules
and the active site.
General Procedures for the Preparation of chalcone derivatives
Claisen-Schmidt condensation reaction was applied to synthesize
chalcone derivatives (Scheme 2.1). The reaction of acetophenone and
benzaldehyde derivatives in KOH/MeOH was followed by an
acidification with concentrated HCl provided chalcone derivatives
with satisfactory yields after recrystallized from appropriate solvents.
The structures and purities of the target compounds were confirmed by
UV, MS, IR,
1
H-NMR and
13
C-NMR spectra.
Scheme 2.1. Claisen-Schmidt condensation reaction in chalcones
synthesis
[18]
7
In vitro Acetylcholinesterase inhibitory activity assay
AChE inhibitory activities of chalcones were determined using
purified acetylcolinesterase from electric eel (Sigma, Type VI) and
acetylthiocholine iodide (Sigma) as a substrate with the colourimetric
method of Ellman66. Galantamine, ATCI (acetylthiocholin iodide),
and DTNB (5,5’-dithio-bis-nitro benzoic acid) were purchased from
Sigma. This assay was performed in 96-well microtiter plates in the
same condition for both chalcones and control substance
(galantamine).
In vivo Acetylcholinesterase inhibitory activity assay
The best ACHE inhibitory chalcone derivative is tested for their
ability to improve memory dysfunction in mice using two short-term
memory impairment models: Y - maze model and Novel Object
Recognition model based on Tran Phi Hoang Yen model (2007).
[28]
Chapter 3. RESULTS AND DISCUSSION
3.1. Molecular Docking Study
3.1.1. Re-docking result of co-crystallized ligand
Re-docking results of galantamine showed that interactions made
by re-docked conformations with the active site were resemble those
of the original bound ligand in 1DX6. The RMSD values of re-
docked conformations were < 1.5 Å (Table 3.1) indicated that the
molecular model could be applied to explain the interactions of new
ligands with the active site.
8
Table 3.1. Results of re-docking processes with co-crystallized
ligands
Ligand RMSD (Å)
(1) separated from the complex (native form, not
prepared).
0,4912
(2) separated from the complex and re-prepared using
mentioned appropriate procedure.
0,5184
(3) built and prepared from the beginning. 0,5021
3.1.2 Docking results of chalcone derivatives
3.1.2.1 Docking results of 35 normal chalcone derivatives
The docking process was performed successfully with all
chalcone derivatives. The ways of change which are beneficial for
the binding ability to acetylcholinesterase of chalcones are
summarized and displayed in Fig 3.5.
Fig 3.5. The ways of change which are beneficial for the binding
ability to acetylcholinesterase of chalcones
9
The molecular docking studies elucidated the binding modes
of chalcones to the active site of AChE quite precisely, and from
which a structure – activity relationship was then drawn out.
Thenceforward, we have the direction to design and synthesize new
compounds that have high acetylcholinesterase inhibitory activities.
3.1.2.2. Docking results of 24 heterocyclic chalcone derivatives
The docking results showed that chalcones containing
thiophen moiety may increase the acetylcholinesterase inhibitory
activity compaire with other heterochalcone. Beside, the substitution
methoxy group(s) on B-ring (benzen ring) also lead to improve the
bioactivity of the heterochalcone.
Hình 3.11. The ways of change which are beneficial for the binding
ability to acetylcholinesterase of heterocyclic chalcones
This study was published in "Evaluation of
acetylcholinesterase inhibitory activity of heterochalcones
derivaties" in Journal of Medicine, Ho Chi Minh city, 2015.
3.1.2.3 Docking results of 32 benzylaminochalcone derivatives
The docking process was performed successfully with all
benzylaminochalcone derivatives. The ways of change which are
beneficial for the binding ability to acetylcholinesterase of
benzylaminochalcone derivatives are summarized and displayed in
Fig 3.8.
X: thiophen moiety
more beneficial than
pyridin, furan
moiety.
-OCH3
groups
10
Fig 3.18. The ways of change which are beneficial for the binding
ability to acetylcholinesterase of benzylamino chalcones
From the docking results as fig 3.18, we have the direction to
design and synthesize new benzylamino chalcones that have high
acetylcholinesterase inhibitory activities.
3.1.2.4. Docking results of promazine chalcone derivatives
Promazine chalcones are chalcone derivatives that ring A is replaced
acepromazine. The docking process was performed with 16
promazine chalcone derivatives by BioSovelIT LeadIT.
The ways of change which are beneficial for the binding ability to
acetylcholinesterase of promazine chalcone derivatives are
summarized and displayed in Fig 3.22.
- OH (necessary for a
high activity)
- OH at position 2 or 3
g tốt
N or O
heterocyclic
-OCH3 or -NO2 group on
ring B affect the binding
orientation to the target.
11
Fig 3.22. The ways of change which are beneficial for the binding
ability to acetylcholinesterase of promazine chalcone derivatives
3.2. Synthesis of chalcone derivatives
3.2.1. Synthesis of normal chalcone derivatives
20 Normal chalcone derivatives based on the orientation of
docking results are synthesized by Claisen-Schmidt condensation
reaction.
Derivatives Name of derivatives
Yield
(%)
ST1 (E)-2-chloro-2’-hydroxychalcone 68
ST2 (E)-4-chloro-2’-hydroxychalcone 74
ST3 (E)-2,4-dichloro-2’-hydroxychalcone 74
ST4 (E)-2,3-dichloro-2’-hydroxychalcone 67
ST5 (E)-2’-hydroxy-2,4-dimethoxychalcone 71
ST6 (E)-2’-hydroxy-2,3-dimethoxychalcone 48
ST7 (E)-2’-hydroxy-3,4,5-trimethoxychalcone 67
ST8 (E)-2’-hydroxy-4-dimethylaminochalcone 87
ST9 (E)-2’-hydroxy-2,3,4’-trimethoxychalcone 58
ST10 (E)-2’-hydroxy-3,4,4’-trimethoxychalcone 62
-Cl group
-Br group
-F group which have -Cl at
position ortho
-OCH3 group
12
ST11 (E)-2’-hydroxy-3,4,4’,5-tetramethoxychalcone 63
ST12 (E)-4-chloro-2’-hydroxy-4’-methoxychalcone 68
ST13 (E)-2’-hydroxy-2,4,4’,6’-tetramethoxychalcone 55
ST14 (E)-2’-hydroxy-3,4,4’,6’-tetramethoxychalcone 66
ST15
(E)-2’-hydroxy-2,3,4,4’,6’-
pentamethoxychalcone
72
ST16
(E)-4-chloro-2’-hydroxy-4’,6’-
dimethoxychalcone
69
ST17 (E)-4’-amino-2-chlorochalcone 66
ST18 (E)-4’-amino-4-chlorochalcone 70
ST19 (E)-4’-amino-4-nitrochalcone 76
ST20 (E)-3’,4-dinitrochalcone 60
Structure of all synthesized chalcone derivatives were
confirmed by UV, IR, 1H-NMR spectra and showed in addendum 6.
3.2.2. Synthesis of heterocyclic chalcone derivatives
24 heterocyclic chalcone derivatives are synthesized by Claisen-
Schmidt condensation reaction.
Derivatives Name of derivatives
Yield
(%)
D1
(E)-1-(pyridin-2-yl)-3-[2-(hydroxy)phenyl]-2-
propen-1-one
56
D2
(E)-1-(pyridin-2-yl)-3-[4-(hydroxy)phenyl]-2-
propen-1-one
65
D3
(E)-1-(pyridin-2-yl)-3-[3-(hydroxy)phenyl]-2-
propen-1-one
62
D4
(E)-1-(pyridin-2-yl)-3-[4-
(dimethylamino)phenyl]-2-propen-1-one
58
D5
(E)-1-(pyridin-2-yl)-3-[3,4-(dimethoxy)phenyl]-2-
propen-1-one
52
D6
(E)-1-(pyridin-2-yl)-3-[3,4,5-(trimethoxy)phenyl]-
2-propen-1-one
76
13
D7
(E)-1-(pyridin-2-yl)-3-[2,4-(dimethoxy)phenyl]-2-
propen-1-one
63
D8
(E)-1-(furan-2-yl)-3-[3,4-(dimethoxy)phenyl]-2-
propen-1-one
51
D9
(E)-1-(furan-2-yl)-3-[4-(methoxy)phenyl]-2-
propen-1-one
64
D10
(E)-1-(furan-2-yl)-3-[3,4,5-(trimethoxy)phenyl]-2-
propen-1-one
68
D11
(E)-1-(furan-2-yl)-3-[4-(hydroxy)phenyl]-2-
propen-1-one
50
D12
(E)-1-(furan-2-yl)-3-[3-(hydroxy)phenyl]-2-
propen-1-one
54
D13
(E)-1-(furan-2-yl)-3-[2-(hydroxy)phenyl]-2-
propen-1-one
52
D14
(E)-1-(furan-2-yl)-3-[3-(nitro)phenyl]-2-propen-1-
one
54
D15
(E)-1-(furan-2-yl)-3-[4-(dimethylamino)phenyl]-
2-propen-1-one
62
D16
(E)-1-(thiophen-2-yl)-3-[4-(hydroxy)phenyl]-2-
propen-1-one
56
D17
(E)-1-(thiophen-2-yl)-3-[3-(hydroxy)phenyl]-2-
propen-1-one
52
D18
(E)-1-(thiophen-2-yl)-3-[2-(hydroxy)phenyl]-2-
propen-1-one
54
D19
(E)-1-(thiophen-2-yl)-3-[4-(methoxy)phenyl]-2-
propen-1-one
66
D20
(E)-1-(thiophen-2-yl)-3-[2,4-(dimethoxy)phenyl]-
2-propen-1-one
52
D21
(E)-1-(thiophen-2-yl)-3-[3,4,5-
(trimethoxy)phenyl]-2-propen-1-one
74
D22
(E)-1-(thiophen-2-yl)-3-[3-(nitro)phenyl]-2-
propen-1-one
52
D23
(E)-1-(thiophen-2-yl)-3-[3-(nitro)phenyl]-2-
propen-1-one
56
14
D24
(E)-1-(thiophen-2-yl)-3-[4-
(dimethylamino)phenyl]-2-propen-1-one
60
3.2.3. Synthesis of benzylaminochalcone derivatives
The Claisen-Schmidt condensation reaction of 4'-
aminoacetophenone and benzaldehyde derivatives provided 10
benzylaminochalcones.
Derivatives Name of derivatives
Yield
(%)
A1
(E)-1-(4-((2-hydroxylbenzyl)amino)phenyl)-3-
phenyl)prop-2-ene-1-one
80,88
A2
(E)-3-(2-chlorophenyl)-1-(4-((2-
hydroxylbenzyl)amino)phenyl)prop-2-ene-1-one
88
A3
(E)-3-(4-chlorophenyl)-1-(4-((2-
hydroxylbenzyl)amino)phenyl)prop-2-ene-1-one
81,60
A4
(E)-3-(4-nitrophenyl)-1-(4-((2-
hydroxylbenzyl)amino)phenyl)prop-2-ene-1-one
60
A5
(E)-3-(2,3-dimethoxyphenyl)-1-(4-((2-
hydroxylbenzyl)amino)phenyl)prop-2-ene-1-one
81,51
A6
(E)-3-(3,4-dimethoxyphenyl)-1-(4-((2-
hydroxylbenzyl)amino)phenyl)prop-2-ene-1-one
58,85
A7
(E)-3-(2,4-dimethoxyphenyl)-1-(4-((2-
hydroxylbe