Design, synthesis, and evaluation of multitarget-directed selenium-containing clioquinol derivatives for the treatment of Alzheimer's disease

Article abstract of DOI:10.1021/cn500119g

A series of selenium-containing clioquinol derivatives were designed, synthesized, and evaluated as multifunctional anti-Alzheimer's disease (AD) agents. In vitro examination showed that several target compounds exhibited activities such as inhibition of metal-induced Aβ aggregation, antioxidative properties, hydrogen peroxide scavenging, and the prevention of copper redox cycling. A parallel artificial membrane permeation assay indicated that selenium-containing clioquinol derivatives possessed significant blood-brain barrier (BBB) permeability. Compound 8a, with a propynylselanyl group linked to the oxine, demonstrated higher hydrogen peroxide scavenging and intracellular antioxidant activity than clioquinol. Furthermore, 8a exhibited significant inhibition of Cu(II)-induced Aβ_1-42 aggregation and was capable of disassembling the preformed Cu(II)-induced Aβ aggregates. Therefore, 8a is an excellent multifunctional promising compound for development of novel drugs for AD. (Chemical Equation Presented).

Full text of DOI:10.1021/cn500119g

Research Article
pubs.acs.org/chemneuro
Design, Synthesis, and Evaluation of Multitarget-Directed Selenium-
Containing Clioquinol Derivatives for the Treatment of Alzheimer’s
Disease
Zhiren Wang, Yali Wang, Wenrui Li, Fei Mao, Yang Sun, Ling Huang,* and Xingshu Li*
Institute of Drug Synthesis and Pharmaceutical Processing, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou
510006, China
*
S Supporting Information
ABSTRACT: A series of selenium-containing clioquinol
derivatives were designed, synthesized, and evaluated as
multifunctional anti-Alzheimer’s disease (AD) agents. In
vitro examination showed that several target compounds
exhibited activities such as inhibition of metal-induced Aβ
aggregation, antioxidative properties, hydrogen peroxide
scavenging, and the prevention of copper redox cycling. A
parallel artificial membrane permeation assay indicated that
selenium-containing clioquinol derivatives possessed signifi-
cant blood-brain barrier (BBB) permeability. Compound 8a,
with a propynylselanyl group linked to the oxine, demonstrated higher hydrogen peroxide scavenging and intracellular
antioxidant activity than clioquinol. Furthermore, 8a exhibited significant inhibition of Cu(II)-induced Aβ1−42 aggregation and
was capable of disassembling the preformed Cu(II)-induced Aβ aggregates. Therefore, 8a is an excellent multifunctional
promising compound for development of novel drugs for AD.
KEYWORDS: Alzheimer’s disease, selenium-containing clioquinol derivatives, antioxidative properties,
inhibition of metal-induced Aβ aggregation
lzheimer’s disease (AD), a multifaceted, progressive
neurodegenerative disorder characterized by progressive
A
cognitive decline and memory loss, results in serious personal
and economic costs due to its high prevalence, mortality, and
1
the elusiveness of efficacious drugs. At present, several factors,
including low levels of acetylcholine, β-amyloid (Aβ) deposits,
τ-protein aggregation, oxidative stress, inflammation, and
dyshomeostasis of biometals, play crucial roles in the
2
pathogenesis of AD.
Biometals, such as Cu(II), Zn(II), and Fe(II, III), are closely
related to several critical aspects of AD, which suggests that the
modulation of these biometals in the brain may be a potential
3
−6
therapeutic strategy. Recently, biometal chelators (Figure 1)
such as desferrioxamine (DFO), ethylenediaminetetraacetate
(
EDTA), clioquinol (CQ), tacrine-8-hydroxyquinoline hybrids,
7,8
and M30 have been investigated.
As is well-known, oxidation-induced apoptosis and tau-
induced neurodegeneration could lead to the generation of Aβ,
and oxidative stress was indicated in the onset and progression
9
of AD pathology. Protection of neurons from oxidative stress
by the detoxification of reactive oxygen species (ROS) is crucial
for AD patients as the efficacy of the endogenous antioxidant
protection system declines sharply with age. It is thought that
these mechanisms coexist and affect each other at multiple
Figure 1. Chemical structures of metal-chelating agents.
1
0
levels. In this respect, multifunctional agents that simulta-
neously inhibit two or several targets (such as cholinesterase,
Aβ aggregation), antioxidation and chelate redox-active metals
Received: May 30, 2014
Revised: July 28, 2014
©
XXXX American Chemical Society
A
dx.doi.org/10.1021/cn500119g | ACS Chem. Neurosci. XXXX, XXX, XXX−XXX

ACS Chemical Neuroscience
Research Article
a
Scheme 1. Synthesis of 2, 3, 4, 5, 6, 7a−7i, and 8a−8i
a
Reagents and conditions: (a) H O, NaNO , H SO , 15−18 °C; (b) H O, HNO , rt; (c) CH Cl /hexane = 1:1, (Boc) O, DIPEA, DMAP, rt, 16 h;
2
2
2
4
2
3
2
2
2
(
d) EtOAc, SnCl ·2H O, rt, 3 h; (e) 10% HCl, H O, NaNO , −3 °C; (f) NaOAc, KSeCN; (g) CH OH, KOH; (h) EtOH, H O, NaBH , alkyl
2
2
2
2
3
2
4
halide; (i) CH Cl , piperidine.
2
2
have been developed as potential agents for the treatment of
AD.
followed by reaction with KSeCN provided the selenocyanate
5. Intermediate 5 was treated with KOH in CH OH to give the
3
Mineral selenium, an essential nutrient, demonstrated
fundamental significance in human biology and fulfilled a
diselenide 6, which was reacted with sodium borohydride and
alkyl halides to afford the corresponding 5-alkylselenenyl-
quinolin derivatives 7. Finally, the deprotection of the Boc
group in the presence of piperidine yielded the target
compounds 8.
11−13
multitude of indispensable health effects.
The redox cycle
of selenium(II)/(IV) is thought to be the most important
mechanism linked to biological systems by the reduction of
1
4,15
ROS,
which are evolved in the oxidative damage of
neurodegenerative diseases, such as AD and Parkinson’s
RESULTS AND DISCUSSION
■
1
1,16−18
disease.
Over the past decades, selenium-containing
In Vitro Antioxidant Activity. To evaluate the antioxidant
activity of the selenium-containing CQ derivatives, the oxygen
radical absorbance capacity assay using fluorescein (ORAC-FL)
was employed, and Trolox (6-hydroxy-2,5,7,8-tetramethyl-
chroman-2-carboxylic acid), a vitamin E analogue, was used
as an internal standard to which the unit value is arbitrarily
compounds have attracted considerable interest in biology and
1
2,19−23
chemistry due to their highly promising function.
The propargyl moiety is known to be responsible for
2
4−26
27−29
providing neuroprotective,
mitochondria-protecting,
30
antioxidant and scavenge peroxynitrite properties. In recent
studies, a series of propargyl moiety containing lead
compounds, including (S)-rasagiline, TVP-1022, M30, and
ladostigil, have been proven to exhibit neuroprotective activty
in cell cultures and animal models of neurodegenerative
40,41
given.
As shown in Table 1, the target compounds
demonstrated better antioxidant activity (ORAC-FL values of
1
0
.53−1.96 Trolox equivalents) than CQ (ORAC-FL value
.62). Specifically, the results indicated that compounds 8a, 8b,
3
1−34
diseases.
Moreover, the hydrophobicity of propargyl
and 8d exhibited best antioxidant activity with 1.94, 1.95, and
.96 Trolox equivalents, respectively, and thus they could be
moiety is beneficial to enhance the BBB penetration ability.
Previously, we designed and synthesized a series of selenium-
containing multifunctional anti-AD agents based on the fusion
of donepezil and ebselen, and they exhibited GPx-like activity
1
considered as potent antioxidant agents.
Hydrogen Peroxide Scavenging Activity. The removal
of ROS, such as hydrogen peroxide, is especially important in
3
5,36
1
5,42,43
and inhibited the activity of AChE.
Herein, we describe the
the elderly and AD patients.
To further evaluate the
design, synthesis, and evaluation of a series of selenium-
containing CQ derivatives as multifunctional anti-AD agents
that exhibit inhibition of metal-induced Aβ aggregation,
antioxidative properties, and hydrogen peroxide scavenging
activity.
antioxidant activity of the selenium-containing CQ derivatives,
compounds 8a, 8b, and 8d were analyzed using the horseradish
44
peroxidase assay (HRPA); CQ and M30 were used as
reference compounds. The results in Figure 2 indicate that all
compounds showed significantly better scavenging activities for
hydrogen peroxide compared to CQ. Compounds 8a, 8b, and
8d exhibited full scale scavenging activities for hydrogen
peroxide at high concentrations of 150−200 μM, but 8a (100
μM, 62% scavenging; 80 μM, 35%; 50 μM, 17%) demonstrated
higher scavenging activity than 8b (100 μM, 44%; 80 μM, 17%;
50 μM, 7%) and 8d (100 μM, 40%; 80 μM, 26%; 50 μM, 10%)
CHEMISTRY
■
Scheme 1 depicts the synthetic route of compounds 2−8. The
synthesis of the intermediates 2 and 3 was conducted as
previously described.
37−39
The reduction of 3 with SnCl ·2H O
2 2
afforded amine 4. Diazotization of 4 with HCl/NaNO2
B
dx.doi.org/10.1021/cn500119g | ACS Chem. Neurosci. XXXX, XXX, XXX−XXX

ACS Chemical Neuroscience
Research Article
Table 1. Oxygen Radical Absorbance Capacity by
Fluorescence (ORAC-FL, Trolox Equivalents) of Selenium-
Containing CQ Derivatives 8a−8i
at lower concentrations. In contrast, CQ (150 μM, 19%; 200
μM, 40%) and M30 (150 μM, 71%; 200 μM, 80%) possess
extremely weak and moderate activity even at high concen-
trations, respectively.
Intracellular Antioxidant Assay. The intracellular anti-
oxidant activity of 8a in human SH-SY5Y cells was evaluated in
a cellular antioxidant assay using dichlorofluorescein diacetate
45,46
(
DCFH-DA)
with CQ and Trolox as the reference
compounds. As reported in Figure 3A, 8a (1 μM, 103% cell
viability; 5 μM, 100%; 10 μM, 100%; 25 μM, 78%; 50 μM,
4
3%) did not affect the cell viability at 10 μM; thus, the
maximum concentration used in the subsequent assay was 10
μM. Figure 3B shows the concentration-dependent protective
effect of compounds against tert-butyl hydroperoxide induced
intracellular oxidative stress. Trolox (5 μM, 95% of control; 10
μM, 88%; 20 μM, 80%) and the tested compounds exhibited
antioxidant activity, and 8a (2.5 μM, 87%; 5 μM, 84%; 10 μM,
7
1
6%) had higher potency than CQ (2.5 μM, 98%; 5 μM, 96%;
0 μM, 93%). These data further suggest the potential of 8a as
an efficient multifunctional anti-AD agent that exhibits
intracellular antioxidant activity.
Metal-Chelating Properties of Compound 8a. The
ability of 8a to binding biometals such as Cu(II), Zn(II),
Fe(II), and Fe(III) was investigated by UV−vis spectrometry,
47−52
and the results are shown in Figure 4.
As shown in Figure
4
A, new optical bands appeared when CuSO , ZnCl , or FeSO
4 2 4
was added to a solution containing 8a; that is, the maximum
absorption (242 nm) shifted to 279, 279, or 259 nm,
2+
respectively. Upon the addition of Cu , a new band associated
with the copper complex appeared at 415 nm. These results
suggest that 8a is able to interact with Cu(II), Zn(II), and
Fe(II). However, upon addition of FeCl , a decrease in
3
absorption was observed, rather than a significant shift, thereby
indicating a possible interaction between 8a and Fe(III). The
binding stoichiometry of 8a with Cu2+ was determined by
measuring the changes in absorption at 415 nm when 8a was
2+
titrated with Cu , as depicted in Figure 4B. The presence of an
2
+
isosbestic point revealed the formation of a unique Cu −8a
complex (Figure 4B), and the titration analysis was consistent
2+
with a 1:2 Cu /ligand molar ratio (Figure 4B, inset).
Prevention of Copper-Based Redox Activity in the
Presence of 8a. An increasing number of studies have
indicated that excessive free radical generation may trigger
a
The mean ± SD of three independent experiments. Data are
expressed as μmole of Trolox equivalent/μmol of tested compound.
15
neuronal cell death in AD patients. Under oxidative stress, the
neurotoxicity of Aβ was caused by the generation of ROS,
•
•− 53
including OH and O2
Cu−ascorbate redox system (Scheme 2)
due to redox-active Cu(II) being implicated in the pathways of
.
The effect of compound 8a on the
54−58
was evaluated
•
−
ROS production. The results in Figure 5 present that OH
produced by copper and ascorbate increased sharply with time
and then stagnated at nearly 14 min. Interestingly, this process
was completely inhibited by 8a and M30, which suggested that
both 8a and M30 were capable of preventing copper redox
cycling.
2
+
Inhibition of Cu -Induced Aβ Aggregation by 8a. To
investigate the effects of the selenium-containing CQ
derivatives to inhibit Cu(II)-induced Aβ1−42 aggregation, we
analyzed 8a using thioflavin T (ThT) fluorescence and
transmission electron microscopy (TEM) (Figure 6), which
depicts Aβ aggregate morphology. CQ was used as a positive
control because it is known to attenuate metal ion-Aβ
Figure 2. Hydrogen peroxide scavenging activity of 8a, 8b, 8d, CQ,
and M30 in the HRPA assay (H O = 100 μM). Values reported are
means ± SD of three independent experiments.
2
2
aggregation. The Aβ
peptide (25 μM) was treated with
1
−42
2+
Cu (25 μM) for 2 min at room temperature followed by
C
dx.doi.org/10.1021/cn500119g | ACS Chem. Neurosci. XXXX, XXX, XXX−XXX

ACS Chemical Neuroscience
Research Article
Figure 3. (A) Effect of 8a on cell viability in SH-SY5Y cells. (B) Intracellular ROS induced by exposure to t-BuOOH without or with compounds
measured using DCFH-DA. The results are reported as the mean of three independent experiments performed in sextuplicate. Statistical significance
was analyzed using ANOVA: *p < 0.05, **p < 0.01, ***p < 0.001, versus control.
Figure 4. (A) UV spectrum of 8a (50 μM) alone and in the presence of CuSO (50 μM), ZnCl (50 μM), or FeSO (50 μM) in buffer (20 mM
4
2
4
2+
HEPES, 150 mM NaCl, pH 7.4). (B) UV−vis titration of 8a with Cu in buffer (20 mM HEPES, 150 mM NaCl, pH 7.4) at room temperature. The
concentrations of Cu2+ and 8a were 0−144 and 80 μM, respectively. A breakpoint is observed at [Cu ]:[8a] = 0.5:1.
2+
Scheme 2. Redox Cycling of Copper in the Presence of
Oxygen and Ascorbate to Produce OH·
incubation with or without a chelator (50 μM) for 24 h at 37
°C. Cu -induced Aβ aggregation was modulated by treatment
2+
with 8a as indicated in Figure 6A. The fluorescence of Aβ
2+
treated with Cu is 160% that of Aβ alone, which demonstrates
that Cu2+ accelerates Aβ aggregation. Conversely, the
2
+
fluorescence of Aβ treated with Cu and the chelator
decreased dramatically (8a, 69% inhibition; CQ, 68%
inhibition; M30, 68% inhibition). The TEM images in Figure
6
B are consistent with the ThT binding assay. Aβ fibrils in the
presence of Cu(II) (Figure 6Bc) showed more definition than
with Aβ alone (Figure 6Bb), and fewer Aβ fibrils were observed
upon addition of 8a (Figure 6Be).
Disaggregation of Metal-Induced Aβ1−42 Aggregation
Fibrils by 8a. To study the disaggregation of metal-induced
Aβ1−42 aggregates, a chelator (50 μM) was added to Aβ fibrils
2
+
generated by reacting Aβ1−42 (25 μM) with 1.0 equiv of Cu
25 μM) for 24 h at 37 °C with constant agitation. TEM images
(
showed that well-structured Aβ1−42 fibrils were formed in the
presence of Cu(II) (Figure 7Bb). Incubation of the Aβ1−42
fibrils with CQ (Figure 7Bc), 8a (Figure 7Bd), or M30 (Figure
7Be) for 24 h resulted in the disassembly of the Aβ1−42 fibrils.
In Vitro Blood-Brain Barrier Permeation Assay. Blood-
brain barrier (BBB) penetration is the first requirement for
successful CNS drugs as they are destined to act within the
central nervous system. To explore whether the selenium-
containing CQ compounds would be able to penetrate into the
brain, a parallel artificial membrane permeation assay was
modified for the blood-brain barrier (PAMPA-BBB), as recently
Figure 5. Fluorescence intensity of 7-hydroxy-coumarin-3-carboxylic
acid (CCA) after incubation of CCA (50 μM) and ascorbate (150
2+
μM) with Cu (5 μM). 8a and M30 (15 μM) was added at t = 0 s,
2+
prior to Cu . Asc is a negative control with buffer and ascorbate only.
All solutions were dissolved and diluted in KH PO /NaCl [20 mM]
2
4
buffer containing desferryl [1 μM] except CuSO (dissolved in Milli-Q
4
water only). Values reported are the means ± SD of three independent
experiments.
59
described by Di et al. The in vitro permeabilities (P ) of
e
newly synthesized compounds 8a−8i and 13 commercial drugs
D
dx.doi.org/10.1021/cn500119g | ACS Chem. Neurosci. XXXX, XXX, XXX−XXX

ACS Chemical Neuroscience
Research Article
Figure 6. (A) Top: Scheme of the inhibition experimental procedure. Bottom: Results of the ThT binding assay. Statistically significant differences
from Aβ1−42 + Cu2 were analyzed by ANOVA: ***p < 0.001. (B) TEM images showing the inhibition of Cu(II)-induced Aβ
+
aggregation
1−42
2+
(
[Aβ ] = 25 μM, [8a] = 50 μM, [CQ] = 50 μM, [M30] = 50 μM, [Cu ] = 25 μM, 37 °C, 24 h; (a) Aβ1−42, 0 h; (b) Aβ1−42 alone; (c) Aβ1−42
+
1
−42
2+
2+
2+
2+
Cu , (d) Aβ
+ Cu + CQ; (e) Aβ1−42 + Cu + 8a; (f) Aβ1−42 + Cu + M30).
1
−42
6
through a lipid extract of porcine brain were determined using a
mixture of of PBS and ethanol in the ratio of 70:30 (Table S1,
Supporting Information). A plot of experimental data versus
moiety, showed outstanding permeability (P = 27.45 × 10−
e
cm/s).
reported values produced the linear correlation P (exp) =
CONCLUSIONS
e
■
2
1
.4574P (bibil) − 1.0773 (R = 0.9427) (see Supporting
e
A new series of multitarget-directed selenium-containing CQ
derivatives were developed as lead compounds for the
treatment of AD. Among the synthesized compounds, 8a
exhibited metal-chelating ability, significant inhibition of
Cu(II)-induced Aβ1−42 aggregation, disaggregation of Aβ fibrils
generated by Cu(II)-induced Aβ aggregation, H O and
intracellular antioxidant activity, and prevention of copper
redox cycling. 8a was also capable of crossing the BBB in a
parallel artificial membrane permeation assay. Based on these
results, 8a is a promising multifunctional candidate for the
treatment of AD. Further investigations of AD therapeutic
candidates based on these results are in progress.
Information Figure S1). According to this equation and taking
into account the described limits by Di et al. for BBB
permeation, we determined that compounds with permeability
above 4.7 × 10− cm/s penetrate into the CNS by passive
diffusion (see Supporting Information Table S2). Analysis of
the target compounds in the PAMPA-BBB assay indicated that
all of the compounds showed permeability values over this limit
6
2
2
(Table 2), demonstrating that all compounds could cross the
BBB and thus can potentially reach their biological targets
within the CNS. The structure−activity relationship study
showed that compounds 8a−8c, which bear alkynyl groups on
the oxine, had much higher permeability; however, for
compounds with alkenyl groups, such as 8d−8h, the
permeabilities were slightly lower. It is worth noting that
compound 8i, which contains a piperidine group on the oxine
METHODS
■
General Remarks. NMR spectra were recorded using TMS as the
internal standard on a Bruker Avance III spectrometer at 400.132 ( H
1
E
dx.doi.org/10.1021/cn500119g | ACS Chem. Neurosci. XXXX, XXX, XXX−XXX

ACS Chemical Neuroscience
Research Article
Figure 7. (A) Top: Scheme of the disaggregation experimental procedure. Bottom: Results of the ThT binding assay. Statistically significant
differences from control were analyzed by ANOVA: ***p < 0.001. (B) TEM images ([Aβ ] = 25 μM, [8a] = 50 μM, [CQ] = 50 μM, [M30] = 50
1
−42
2+
2+
2+
2+
2+
μM, [Cu ] = 25 μM, 37 °C, 24 h; (a) Aβ1−42, 0 h, (b) Aβ1−42 + Cu , (c) Aβ
+ Cu + CQ, (d) Aβ1−42 + Cu + 8a, (e) Aβ1−42 + Cu + M30).
1−42
1
3
NMR) and 100.614 ( C NMR) MHz. MS spectra were obtained on
an Agilent LC−MS 6120 instrument with an ESI and APCI mass
selective detector. The melting points were determined using an SRS-
Opti Melt automated melting point instrument. The reactions were
monitored by thin-layer chromatography (TLC). Flash column
chromatography was performed using silica gel (200−300 mesh)
purchased from Qingdao Haiyang Chemical Co. Ltd. The high-
resolution mass spectra were obtained using a LTQ Orbitrap XL
8.54 (d, J = 8.7 Hz, 1H), 7.88 (dd, J = 8.7, 3.9 Hz, 1H), 7.21 (d, J = 8.8
Hz, 1H).
tert-Butyl (5-Nitroquinolin-8-yl) Carbonate (3). Yellow solid, 94%
1
yield. H NMR (400 MHz, CDCl
) δ 9.06 (d, J = 8.9 Hz, 1H), 9.03 (s,
3
1H), 8.44 (d, J = 8.4 Hz, 1H), 7.68 (dd, J = 5.5, 3.3 Hz, 1H), 7.62 (d, J
= 8.4 Hz, 1H), 1.60 (s, 9H).
Synthesis of 5-Aminoquinolin-8-yl tert-Butyl Carbonate (4). To a
solution of tert-butyl (5-nitroquinolin-8-yl) carbonate (3) (14.0 g, 66.8
mmol) in 200 mL of ethyl acetate was added 8.0 equiv (120 g, 535.1
(
Thermo Scientific) mass spectrometer. The purity (≥95%) of the
samples was determined by HPLC, conducted on a Shimadzu LC-
0AT series system, TC-C18 column (4.6 × 250 mm, 5 μm), eluted
with CH OH/H O, 70/30, at a flow rate of 0.5 mL/min.
mmol) of SnCl
room temperature for 3 h, saturated NaHCO
·2H
O in portions. After the reaction was stirred at
was added to pH 8. The
2
2
2
3
organic phase was separated and the aqueous phase was extracted with
ethyl acetate. The combined organic phase was washed with brine,
3
2
Synthesis of 2 and 3. 2 and 3 were synthesized according to a
37−39
previously described method.
-Nitroquinolin-8-ol (2). Yellow solid, 80% yield. H NMR (400
MHz, DMSO) δ 9.14 (d, J = 8.8 Hz, 1H), 9.02 (d, J = 3.5 Hz, 1H),
dried over anhydrous Na SO , and evaporated to obtain the pure
2 4
1
5
product as a yellow solid. 78% yield. R = 0.32 (CH Cl /CH OH =
f
2
2
3
1
20/1). H NMR (400 MHz, CDCl ) δ 8.90 (s, 1H), 8.20−8.05 (m,
3
F
dx.doi.org/10.1021/cn500119g | ACS Chem. Neurosci. XXXX, XXX, XXX−XXX

ACS Chemical Neuroscience
Research Article
−
6
1
2
3
H), 7.97 (d, J = 7.8 Hz, 1H), 7.52−7.46 (m, 2H), 3.46 (dd, J = 4.6,
Table 2. Permeability (P × 10 cm/s), As Determined by
e
.1 Hz, 2H), 1.69 (t, J = 2.1 Hz, 3H), 1.60 (s, 9H). LC/MS (ESI):
the PAMPA-BBB Assay and Predicted CNS Penetration of
the Target Compounds
+
78.0 [M + H] .
tert-Butyl (5-((2-Methylbut-3-yn-2-yl)selanyl)quinolin-8-yl) Car-
6
a
bonate (7c). Yellow oil, 64% yield. R = 0.41 (petroleum/EtOAc =
compd
P (×10− cm/s)
prediction
f
e
1
5
8
8
1
/1). H NMR (400 MHz, CDCl ) δ 8.92 (dd, J = 4.1, 1.5 Hz, 1H),
.68 (dd, J = 8.5, 1.5 Hz, 1H), 7.89 (d, J = 7.8 Hz, 1H), 7.49 (dd, J =
.6, 4.2 Hz, 1H), 7.46 (d, J = 7.9 Hz, 1H), 5.82 (dt, J = 5.1, 2.5 Hz,
3
8
8
8
8
8
8
8
8
8
a
b
c
d
e
f
18.94 ± 0.32
18.26 ± 1.80
19.30 ± 0.94
16.97 ± 0.96
8.90 ± 1.37
8.56 ± 0.90
6.58 ± 0.65
8.11 ± 1.14
27.45 ± 2.16
6.00 ± 0.30
CNS+
CNS+
CNS+
CNS+
CNS+
CNS+
CNS+
CNS+
CNS+
CNS+
H), 1.60 (s, 9H), 1.39 (d, J = 2.5 Hz, 6H). LC/MS (ESI): 392.1 [M +
+
H] .
5
-(Allylselanyl)quinolin-8-yl tert-Butyl Carbonate (7d). Yellow oil,
1
69% Yield. R = 0.42 (petroleum/EtOAc = 5/1). H NMR (400 MHz,
CDCl ) δ 8.93 (dd, J = 4.1, 1.4 Hz, 1H), 8.75 (dd, J = 8.6, 1.5 Hz, 1H),
7.85 (d, J = 7.8 Hz, 1H), 7.50 (dd, J = 8.6, 4.1 Hz, 1H), 7.45 (d, J = 7.8
Hz, 1H), 5.95−5.82 (m, 1H), 4.85 (dd, J = 9.9, 0.5 Hz, 1H), 4.80 (d, J
=
f
g
h
i
3
16.9 Hz, 1H), 3.52−3.45 (m, 2H), 1.59 (s, 9H). LC/MS (ESI):
+
chlorpromazine
3
66.1 [M + H] .
-(But-3-en-2-ylselanyl)quinolin-8-yl tert-Butyl Carbonate (7e).
aCompounds were dissolved in DMSO at 5 mg mL−1 and diluted with
PBS/EtOH (70:30). Values are expressed as the means ± SD of three
independent experiments.
5
1
Yellow oil, 73% yield. R = 0.41 (petroleum/EtOAc = 5/1). H NMR
f
(400 MHz, CDCl ) δ 8.91 (dd, J = 4.1, 1.4 Hz, 1H), 8.81 (dd, J = 8.5,
3
1
3
.2 Hz, 1H), 7.88 (d, J = 7.8 Hz, 1H), 7.46 (ddd, J = 11.1, 8.0, 4.6 Hz,
H), 5.86 (ddd, J = 17.1, 10.0, 8.4 Hz, 1H), 4.70 (dd, J = 31.5, 13.6 Hz,
1
1
H), 7.38−7.29 (m, 2H), 6.72 (dd, J = 7.9, 3.4 Hz, 1H), 4.12 (s, 2H),
+
2H), 3.89−3.77 (m, 1H), 1.59 (s, 9H), 1.45 (d, J = 6.9 Hz, 3H). LC/
.59 (s, 9H). LC/MS (ESI): 261.1 [M + H] .
+
MS (ESI): 380.1 [M + H] .
Synthesis of tert-Butyl (5-Selenocyanatoquinolin-8-yl) Carbonate
tert-Butyl (5-((2-Methylallyl)selanyl)quinolin-8-yl) Carbonate (7f).
(
5
1
5). To a cold solution (20 mL, −5 °C) of 10% HCl was added 2.0 g of
1
Yellow oil, 75% Yield. R = 0.45 (petroleum/EtOAc = 5/1). H NMR
f
-aminoquinolin-8-yl tert-butyl carbonate (4). Sodium nitrite (0.64 g,
(
400 MHz, CDCl ) δ 8.92 (dd, J = 4.1, 1.6 Hz, 1H), 8.75 (dd, J = 8.6,
3
.2 equiv) was added with stirring, and the reaction mixture was kept
1
7
2
.5 Hz, 1H), 7.83 (d, J = 7.8 Hz, 1H), 7.48 (dd, J = 8.6, 4.1 Hz, 1H),
at −3 °C. Upon completion of the reaction, saturated sodium acetate
was added to pH 6.0. Potassium selenocyanate (1.7 g, 1.5 equiv) in
water (6 mL) was added dropwise. The resulting frothy orange
solution was allowed to stand for 1 h, and the mixture was extracted
with ethyl acetate, washed with brine, and dried over anhydrous
Na SO . The solvent was evaporated under reduced pressure, and the
.44 (d, J = 7.8 Hz, 1H), 4.63−4.59 (m, 1H), 4.45 (s, 1H), 3.47 (s,
+
H), 1.86 (s, 3H), 1.59 (s, 9H). LC/MS (ESI): 380.1 [M + H] .
tert-Butyl (5-((3-Methylbut-2-en-1-yl)selanyl)quinolin-8-yl) Car-
bonate (7g). Yellow oil, 77% yield. R = 0.38 (petroleum/EtOAc =
5
8
f
1
/1). H NMR (400 MHz, CDCl ) δ 8.83 (dd, J = 4.1, 1.4 Hz, 1H),
3
2
4
.68 (dd, J = 8.6, 1.4 Hz, 1H), 7.77 (d, J = 7.8 Hz, 1H), 7.38 (dd, J =
product was purified by silica-column chromatography to afford a
yellow solid. 56% yield. R = 0.44 (petroleum/EtOAc = 3/1). H NMR
1
8.6, 4.1 Hz, 1H), 7.35 (d, J = 7.8 Hz, 1H), 5.22 (t, J = 8.3 Hz, 1H),
.40 (d, J = 8.3 Hz, 2H), 1.51 (s, 9H), 1.46 (s, 3H), 1.11 (s, 3H). LC/
f
3
(
8
400 MHz, CDCl ) δ 9.04−9.00 (m, 1H), 8.59 (d, J = 8.6 Hz, 1H),
3
+
MS (ESI): 394.1 [M + H] .
-(But-3-en-1-ylselanyl)quinolin-8-yl tert-Butyl Carbonate (7h).
Yellow oil, 71% Yield. R = 0.40 (petroleum/EtOAc = 5/1). H NMR
.10 (dd, J = 7.9, 0.6 Hz, 1H), 7.65 (ddd, J = 8.6, 4.1, 0.6 Hz, 1H), 7.57
5
(
dd, J = 7.9, 0.6 Hz, 1H), 1.60 (s, 9H). LC/MS (ESI): 351.0 [M +
1
+
f
H] .
(
400 MHz, CDCl ) δ 8.93 (d, J = 4.1 Hz, 1H), 8.74 (d, J = 8.6 Hz,
3
Synthesis of Di-tert-butyl (5,5′-Diselanediylbis(quinoline-8,5-
1
=
H), 7.87 (d, J = 7.8 Hz, 1H), 7.50 (dd, J = 8.6, 4.1 Hz, 1H), 7.45 (d, J
7.8 Hz, 1H), 5.79 (ddt, J = 16.9, 10.4, 6.5 Hz, 1H), 5.05 (dd, J =
diyl)) Dicarbonate (6). tert-Butyl (5-selenocyanatoquinolin-8-yl)
carbonate (5, 150 mg) was added to potassium hydroxide (60 mg,
1
that was swirled vigorously. The mixture was allowed to stand for 15
min. Water (30 mL) was added, and the pH was adjusted to 8.0 using
1
and dried over anhydrous Na SO , and the solvent was then
evaporated under reduced pressure. The product was purified by
silica-column chromatography to yield a yellow solid. 74% yield. R =
1
2
3.5, 5.1 Hz, 2H), 2.94 (t, J = 7.4 Hz, 2H), 2.40 (dd, J = 14.1, 7.0 Hz,
H), 1.60 (s, 9H). LC/MS (ESI): 380.1 [M + H] .
tert-Butyl (5-((2-(Piperidin-1-yl)ethyl)selanyl)quinolin-8-yl) Car-
.5 equiv) in methanol (4 mL), affording an orange-yellow precipitate
+
bonate (7i). Yellow oil, 56% yield. R = 0.25 (petroleum/EtOAc =
0% HCl. The mixture was extracted with CH Cl , washed with brine,
f
2
2
1
5
8
8
/1). H NMR (400 MHz, CDCl ) δ 8.92 (dd, J = 4.1, 1.4 Hz, 1H),
3
2
4
.73 (dd, J = 8.6, 1.3 Hz, 1H), 7.85 (d, J = 7.8 Hz, 1H), 7.48 (dd, J =
.6, 4.1 Hz, 1H), 7.44 (d, J = 7.8 Hz, 1H), 3.02 (dd, J = 8.5, 6.6 Hz,
f
1
2H), 2.63−2.59 (m, 2H), 2.35 (s, 4H), 1.59 (s, 9H), 1.53 (dt, J = 11.0,
0
.37 (petroleum/EtOAc = 5/1). H NMR (400 MHz, CDCl ) δ 8.83
3
+
5
.7 Hz, 6H). LC/MS (ESI): 437.1 [M + H] .
(
dd, J = 4.1, 1.5 Hz, 2H), 8.22 (dd, J = 8.6, 1.5 Hz, 2H), 7.75 (d, J =
General Procedure for the Synthesis of 8a−8i. Piperidine (1.5
7
1
.8 Hz, 2H), 7.34 (d, J = 7.8 Hz, 2H), 7.22 (dd, J = 8.6, 4.2 Hz, 2H),
.61 (s, 18H). LC/MS (ESI): 649.0 [M + H] .
+
equiv) was added to a solution of 7 (1.0 equiv) in anhydrous DCM (4
mL) at ambient temperature. Upon completion of the reaction, the
solvent was evaporated under reduced pressure and the crude product
was purified by silica-column chromatography to yield the target
product.
General Procedure for the Synthesis of 7a−7i. NaBH (53 mg,
4
6
.0 equiv) was added in portions to diselenide 6 (150 mg, 1.0 equiv) in
ethanol/water (1/1, 8 mL), and the mixture was stirred for 10−15
min. The corresponding alkyl halide (2.0 equiv) was added and the
reaction was stirred at room temperature for 1 h. Water was added,
and the mixture was extracted with CH Cl . The organic phase was
5
-(Prop-2-yn-1-ylselanyl)quinolin-8-ol (8a). Yellow solid, 72%
1
yield. Mp 82.5−83.1 °C. R = 0.25 (CH Cl /CH OH = 20/1). H
f
2
2
3
2
2
NMR (400 MHz, CDCl ) δ 8.84−8.78 (m, 2H), 7.98 (d, J = 7.9 Hz,
washed with brine and dried over anhydrous Na SO . The solvent was
evaporated, and the products were purified using a silica gel column.
3
2
4
1
3
H), 7.54 (dd, J = 8.5, 4.2 Hz, 1H), 7.14 (d, J = 7.9 Hz, 1H), 3.38−
.34 (m, 2H), 2.16 (t, J = 2.7 Hz, 1H). 13C NMR (101 MHz, CDCl )
tert-Butyl (5-(Prop-2-yn-1-ylselanyl)quinolin-8-yl) Carbonate
3
1
(
7a). Yellow oil, 67% yield. R = 0.43 (petroleum/EtOAc = 5/1). H
δ 152.78, 147.01, 137.85, 137.13, 136.14, 129.77, 121.64, 115.24,
f
+
NMR (400 MHz, CDCl ) δ 8.94 (dd, J = 4.1, 1.5 Hz, 1H), 8.77 (dd, J
109.14, 79.77, 71.30, 12.57. [M + H] for C12
263.9922, meas. 263.9921; HPLC purity: 98.68%.
H10NOSe pred.
3
=
8.6, 1.5 Hz, 1H), 8.00 (d, J = 7.8 Hz, 1H), 7.51 (dd, J = 8.3, 3.9 Hz,
1
H), 7.49 (d, J = 7.7 Hz, 1H), 3.45 (d, J = 2.7 Hz, 2H), 2.20 (t, J = 2.7
5-(But-2-yn-1-ylselanyl)quinolin-8-ol (8b). Yellow solid, 65% yield.
+
1
Hz, 1H), 1.60 (s, 9H). LC/MS (ESI): 364.0 [M + H] .
Mp 97.8−98.9 °C. R = 0.23 (CH Cl /CH OH = 20/1). H NMR
f
2
2
3
5
-(But-2-yn-1-ylselanyl)quinolin-8-yl tert-Butyl Carbonate (7b).
(400 MHz, CDCl ) δ 8.82 (dd, J = 8.5, 1.5 Hz, 1H), 8.79 (dd, J = 4.2,
3
1
Yellow oil, 72% yield. R = 0.39 (petroleum/EtOAc = 5/1). H NMR
1.5 Hz, 1H), 7.95 (d, J = 7.9 Hz, 1H), 7.53 (dd, J = 8.5, 4.2 Hz, 1H),
f
(
400 MHz, CDCl ) δ 8.93 (d, J = 4.1 Hz, 1H), 8.78 (d, J = 8.6 Hz,
7.13 (d, J = 7.9 Hz, 1H), 3.39−3.33 (m, 2H), 1.68 (t, J = 2.6 Hz, 3H).
3
G
dx.doi.org/10.1021/cn500119g | ACS Chem. Neurosci. XXXX, XXX, XXX−XXX

ACS Chemical Neuroscience
Research Article
1
3
C NMR (101 MHz, CDCl ) δ 153.63, 147.94, 138.78, 137.92,
stock solution (2000 μM), which was aliquoted into small samples and
stored at −80 °C.
3
1
37.35, 130.92, 122.30, 116.84, 110.25, 80.58, 75.77, 14.85, 3.65. [M +
+
H] for C H NOSe pred. 278.0079, meas. 278.0080; HPLC purity:
For the inhibition of copper-mediated Aβ1−42 aggregation experi-
ment, the Aβ stock solution was diluted in 20 μM HEPES (pH 6.6)
with 150 μM NaCl. The mixture of the peptide (10 μL, 25 μM, final
concentration) with or without copper (10 μL, 25 μM, final
concentration) and the tested compound (10 μL, 50 μM, final
concentration) was incubated at 37 °C for 24 h. Then 20 μL of the
sample was diluted to a final volume of 200 μL with 50 mM glycine−
NaOH buffer (pH 8.0) containing thioflavin T (5 μM). The detection
method was the same as that of self-mediated Aβ1−42 aggregation
experiment.
13
12
9
9.32%.
-((2-Methylbut-3-yn-2-yl)selanyl)quinolin-8-ol (8c). Yellow solid,
yield 68%. Mp 107.4−108.2 °C. R = 0.21 (CH Cl /CH OH = 20/1).
5
f
2
2
3
1
H NMR (400 MHz, CDCl ) δ 8.77 (d, J = 3.0 Hz, 1H), 8.69 (d, J =
.4 Hz, 1H), 7.85 (d, J = 7.9 Hz, 1H), 7.51 (dd, J = 8.4, 4.1 Hz, 1H),
.11 (d, J = 7.8 Hz, 1H), 5.77 (dd, J = 3.2, 1.6 Hz, 1H), 1.33 (d, J = 2.4
3
8
7
13
Hz, 6H). C NMR (101 MHz, CDCl ) δ 153.38, 147.83, 137.46,
1
1
3
37.26, 130.58, 122.36, 116.77, 110.01, 101.17, 97.15, 77.92, 29.66,
9.74. [M + H] for C H NOSe pred. 292.0235, meas. 292.0234;
+
14
14
For the disaggregation of copper-induced Aβ fibrils experiment, the
Aβ stock solution was diluted in 20 μM HEPES (pH 6.6) with 150 μM
NaCl. The mixture of the peptide (10 μL, 25 μM, final concentration)
with copper (10 μL, 25 μM, final concentration) was incubated at 37
HPLC purity: 97.63%.
5
-(Allylselanyl)quinolin-8-ol (8d). Yellow solid, yield 64%. Mp
1
5
2.7−53.3 °C. R = 0.26 (CH Cl /CH OH = 20/1). H NMR (400
f
2
2
3
MHz, CDCl ) δ 8.84−8.71 (m, 2H), 7.83 (d, J = 7.9 Hz, 1H), 7.52
3
°
C for 24 h. The tested compound (10 μL, 50 μM, final
concentration) was then added and incubated at 37 °C for another
4 h. Then 20 μL of the sample was diluted to a final volume of 200
(
9
dd, J = 8.5, 4.2 Hz, 1H), 7.11 (d, J = 7.9 Hz, 1H), 5.87 (ddt, J = 17.6,
.9, 7.7 Hz, 1H), 4.78 (dd, J = 9.9, 0.5 Hz, 1H), 4.68 (dd, J = 16.9, 1.2
13
2
Hz, 1H), 3.42−3.35 (m, 2H). C NMR (101 MHz, CDCl ) δ 153.24,
3
μL with 50 mM glycine−NaOH buffer (pH 8.0) containing thioflavin
1
1
2
47.88, 138.85, 137.74, 137.25, 134.37, 130.80, 122.38, 116.74, 116.64,
10.22, 31.97. [M + H]+ for C H NOSe pred. 266.0079, meas.
T (5 μM). The detection method was the same as above.
1
2
12
34
TEM Assay. For the copper-induced experiment, Aβ stock
solution was diluted with 20 μM HEPES (pH = 6.6) and 150 μM
NaCl. The sample preparation was same as that for the ThT assay.
Aliquots (10 μL) of the samples were placed on a carbon-coated
copper/rhodium grid for 2 min. Each grid was stained with uranyl
acetate (1%, 5 μL) for 2 min. After draining off the excess staining
solution, the specimen was transferred for imaging in a transmission
electron microscope (JEOL JEM-1400). All compounds were
solubilized in the buffer which was used for the experiment.
66.0077; HPLC purity: 96.45%.
-(But-3-en-2-ylselanyl)quinolin-8-ol (8e). Yellow solid, yield 71%.
5
1
Mp 45.9−46.5 °C. R = 0.24 (CH Cl /CH OH = 20/1). H NMR
f
2
2
3
(
1
7
400 MHz, CDCl ) δ 8.80 (dd, J = 8.5, 1.5 Hz, 1H), 8.77 (dd, J = 4.2,
.4 Hz, 1H), 7.83 (d, J = 7.9 Hz, 1H), 7.51 (dd, J = 8.5, 4.2 Hz, 1H),
.11 (d, J = 7.9 Hz, 1H), 5.86 (ddd, J = 17.0, 10.1, 8.3 Hz, 1H), 4.71
3
(
d, J = 10.1 Hz, 1H), 4.61 (d, J = 17.0 Hz, 1H), 3.85−3.66 (m, 1H),
.43 (d, J = 6.9 Hz, 3H). 13C NMR (101 MHz, CDCl ) δ 153.36,
1
1
1
2
3
47.85, 140.23, 138.81, 137.66, 131.34, 128.19, 122.35, 116.89, 113.75,
10.15, 42.16, 20.35. [M + H] for C H NOSe pred. 280.0235, meas.
80.0236; HPLC purity: 97.69%.
62,63
+
Oxygen Radical Absorbance Capacity (ORAC-FL) Assay.
The
1
3
14
tested compound and fluorescein (FL) stock solution were diluted
with 75 mM phosphate buffer (pH 7.4) to 10 μM (or 20 μM) and
0.117 μM, respectively. The solution of (±)-6-hydroxy-2,5,7,8-
tetramethylchroman-2-carboxylic acid (Trolox) was diluted with the
same buffer to 100, 80, 60, 50, 40, 20, and 10 μM. The solution of 2,2′-
azobis(amidinopropane)dihydrochloride (AAPH) was prepared before
the experiment by dissolving 108.4 mg of AAPH in 10 mL of 75 mM
phosphate buffer (pH 7.4) to a final concentration of 40 mM. The
mixture of the tested compound (20 μL) and FL (120 μL; 70 nM, final
concentration) was preincubated for 10 min at 37 °C, and then 60 μL
of the AAPH solution was added. The fluorescence was recorded every
minute for 120 min (excitation, 485 nm; emission, 520 nm). A blank
using phosphate buffer instead of the tested compound was also
carried out. All reaction mixtures were prepared in triplicate, and at
least three independent runs were performed for each sample. The
antioxidant curves (fluorescence versus time) were normalized to the
curve of the blank. The area under the fluorescence decay curve
(AUC) was calculated as following equation:
5
-((2-Methylallyl)selanyl)quinolin-8-ol (8f). Yellow solid, yield
1
6
1%. Mp 59.7−60.3 °C. R = 0.22 (CH Cl /CH OH=20/1). H
f
2
2
3
NMR (400 MHz, CDCl ) δ 8.84−8.67 (m, 2H), 7.81 (d, J = 7.9 Hz,
3
1
4
=
H), 7.51 (dd, J = 8.4, 4.3 Hz, 1H), 7.09 (d, J = 7.9 Hz, 1H), 4.60−
.48 (m, 1H), 4.32 (d, J = 0.8 Hz, 1H), 3.46−3.30 (m, 2H), 1.85 (d, J
0.4 Hz, 3H). 1 C NMR (101 MHz, CDCl ) δ 158.97, 153.05,
3
3
1
4
2
46.33, 144.11, 142.05, 141.52, 135.68, 127.28, 121.51, 118.30, 116.04,
1.73, 25.97. [M + H]+ for C H NOSe pred. 280.0235, meas.
1
3
14
80.0234; HPLC purity: 98.72%.
-((3-Methylbut-2-en-1-yl)selanyl)quinolin-8-ol (8g). Yellow solid,
5
1
yield 66%. Mp 49.6−50.4 °C. R = 0.27 (CH Cl /CH OH = 20/1). H
NMR (400 MHz, CDCl ) δ 8.78 (ddd, J = 6.4, 5.8, 1.5 Hz, 2H), 7.84
f
2
2
3
3
(
d, J = 7.9 Hz, 1H), 7.51 (dd, J = 8.5, 4.2 Hz, 1H), 7.09 (d, J = 7.9 Hz,
H), 5.28 (tdt, J = 8.4, 2.7, 1.3 Hz, 1H), 3.40 (d, J = 8.4 Hz, 2H), 1.52
1
s, 3H), 1.10 (s, 3H). 13C NMR (101 MHz, CDCl ) δ 153.20, 147.80,
(
3
1
2
2
38.69, 137.94, 137.49, 135.60, 131.11, 122.14, 120.54, 117.16, 109.97,
7.40, 25.47, 16.97. [M + H] for C H NOSe pred. 294.0392, meas.
+
14
16
94.0393; HPLC purity: 95.89%.
-(But-3-en-1-ylselanyl)quinolin-8-ol (8h). Yellow solid, yield 59%.
i=1
5
AUC = 1 + ∑ (f /f )
1
i
0
Mp 37.7−38.9 °C. R = 0.29 (CH Cl /CH OH = 20/1). H NMR
f
2
2
3
i=120
(
400 MHz, CDCl ) δ 8.81−8.74 (m, 2H), 7.87 (d, J = 7.9 Hz, 1H),
3
7
1
2
1
1
2
.53 (dd, J = 8.5, 4.2 Hz, 1H), 7.11 (d, J = 7.9 Hz, 1H), 5.83−5.72 (m,
where f0 is the initial fluorescence reading at 0 min and f is the
i
H), 5.04−5.01 (m, 1H), 4.99 (t, J = 1.3 Hz, 1H), 2.83 (t, J = 7.5 Hz,
fluorescence reading at time i. The net AUC was calculated by the
expression: AUCsample − AUCblank. Regression equations between net
AUC and Trolox concentrations were calculated. ORAC-FL values for
each sample were calculated by using the standard curve which means
the ORAC-FL value of tested compound expressed as Trolox
equivalents.
H), 2.34 (tt, J = 8.6, 1.2 Hz, 2H). 13C NMR (101 MHz, CDCl ) δ
3
52.09, 146.88, 137.85, 136.14, 136.04, 136.01, 129.67, 121.35, 115.73,
14.88, 109.25, 33.31, 27.26. [M + H]+ for C H NOSe pred.
1
3
14
80.0235, meas. 280.0235; HPLC purity: 97.43%.
-((2-(Piperidin-1-yl)ethyl)selanyl)quinolin-8-ol (8i). Yellow solid,
5
1
44
yield 56%. Mp 92.1−93.0 °C R = 0.19 (CH Cl /CH OH = 10/1). H
NMR (400 MHz, CDCl ) δ 9.25 (d, J = 8.1 Hz, 1H), 9.07 (d, J = 4.3
Hz, 1H), 8.05 (d, J = 7.2 Hz, 1H), 7.85 (d, J = 6.2 Hz, 1H), 7.74 (d, J
Horseradish Peroxidase Assay. The hydrogen peroxide scaveng-
f
2
2
3
ing property was measured using the horseradish peroxidase assay.
Test compounds of 200 μL of different concentrations were incubated
with 100 μL of 1 mM H O . Then, 0.1 M phosphate buffer (pH 7.4,
3
=
5.7 Hz, 1H), 3.72 (dd, J = 14.0, 7.0 Hz, 2H), 2.98 (dd, J = 10.8, 5.9
2
2
1
3
Hz, 2H), 2.10−1.90 (m, 4H), 1.26−1.21 (m, 6H). C NMR (101
MHz, MeOD) δ 148.75, 144.78, 144.74, 141.71, 140.58, 124.40,
100 μL) and 0.1 M NaCl (50 μL) were added. The solution was
incubated for 10 h at 37 °C. Then, a solution containing red phenol
(0.2 mg/mL) and horseradish peroxidase (0.5 mg/mL) in 0.1 M
phosphate buffer (500 μL) was added. After 15 min, 1 M NaOH
solution (50 μL) was added to quench the reaction, and the
absorbance was recorded at 610 nm. The result is expressed as the
+
1
24.02, 117.38, 117.33, 58.18, 54.02, 32.48, 24.21, 22.64. [M + H] for
C H N OSe pred. 337.0814, meas. 337.0816; HPLC purity: 98.32%.
1
6
21
2
6
0,61
Biological Assays. ThT Assay.
NaOH) was dissolved in ammonium hydroxide (1% v/v) to give a
Aβ1−42 (Millipore, counterion:
H
dx.doi.org/10.1021/cn500119g | ACS Chem. Neurosci. XXXX, XXX, XXX−XXX

ACS Chemical Neuroscience
Research Article
percentage of reduction of H O . The percentage of H O scavenging
5 μM DCFH-DA (a fluorescent probe) in PBS at 37 °C in 5% CO for
2
2
2
2
2
activity was calculated according to the following formula: 1 − (A
30 min. After removal of DCFH-DA and further washing, the cells
were exposed to 0.1 mM t-BuOOH (a compound used to induce
oxidative stress) in PBS for 30 min. At the end of the incubation, the
fluorescence of the cells from each well was measured (λexcitation = 485
nm, λemission = 535 nm) with a multifunctional microplate reader
(Molecular Devices, Flex Station 3). The antioxidant activity was
expressed as percentage of control cells and calculated by the formula
sample
−
A
)/(A
− A ) × 100, where A
is the absorbance of
blank
control
blank
sample
the samples, A
is the absorbance of the blank, and Acontrol is the
blank
absorbance of the control.
In Vitro Blood-Brain Barrier Permeation Assay. The blood-
brain barrier penetration of compounds was evaluated using the
parallel artificial membrane permeation assay (PAMPA) described by
5
9,61,64
Di et al.
Commercial drugs were purchased from Sigma and Alfa
(F
t
− Fnt)/(F
t
′ − Fnt) × 100, where F is the absorbance of treated
t
Aesar. Porcine brain lipid (PBL) was obtained from Avanti Polar
Lipids. The donor microplate (PVDF membrane, pore size 0.45 mm)
and acceptor microplate were both from Millipore. The 96-well UV
plate (COSTAR) was from Corning Incorporated. The acceptor 96-
well microplate was filled with 300 μL of PBS/EtOH (7:3), and the
filter membrane was impregnated with 4 μL of PBL in dodecane (20
mg/mL). Compounds were dissolved in DMSO at 5 mg/mL and
diluted 50-fold in PBS/EtOH (7:3) to a final concentration of 100 μg/
mL. Then, 200 μL of the solution was added to the donor wells. The
acceptor filter plate was carefully placed on the donor plate to form a
sandwich, which was left undisturbed for 10 h at 25 °C. After
incubation, the donor plate was carefully removed, and the
concentration of compounds in the acceptor wells was determined
using the UV plate reader (Flexstation 3). Every sample was analyzed
at five wavelengths in four wells and in at least three independent runs.
P was calculated by the following expression: P = −V V /[(V + V )
neurons with tested compound, F ′ is the absorbance of treated
t
neurons without tested compound, and Fnt is the absorbance of
neurons not treated with t-BuOOH.
6
5
Ascorbate Studies. All of the solutions, except CuSO (Milli-Q
4
water only) and 8a (dissolved in methanol and diluted in PBS), were
mixed and diluted in a phosphate (20 mM), NaCl (100 mM) buffer
(PBS) at pH 7.4 with a final sample volume of 200 μL. Each
experiment was performed in triplicate. Hydroxyl radical production
was measured as the conversion of CCA into 7-hydroxy-CCA (λexcitation
= 395 nm, λemission = 450 nm). The general order of addition was as
follows: CCA [50 μM], ligand [15 μM], or copper [5 μM] and then
ascorbate [150 μM]. All of the test solutions contained 1 μM desferryl
and 0.1% methanol.
Statistical Analysis. The results are expressed as the mean ± SD
of at least three independent experiments. Data were subjected to
Student’s t test or one-way analysis of variance (ANOVA) followed by
Dunnett’s test. P values less than 0.05 were accepted to indicate the
significance.
e
e
d
a
d
a
At] ln(1 − drug
/drug
), where V is the volume of the
acceptor
equilibrium d
donor well, V is the volume in the acceptor well, A is the filter area, t is
a
the permeation time, drugacceptor is the the absorbance obtained in the
acceptor well, and drugequilibrium is the the theoretical equilibrium
absorbance. The results are given as the mean ± standard deviation. In
the experiment, 13 quality control standards of known BBB
permeability were included to validate the analysis set. A plot of the
experimental data versus literature values gave a strong linear
ASSOCIATED CONTENT
Supporting Information
Tables with results of in vitro blood-brain barrier permeation
assay; figure showing linear correlation between experiment
and reported permeability of commercial drugs using the
PAMPA-BBB assay. This material is available free of charge via
the Internet at http://pubs.acs.org.
■
*
S
2
correlation, Pe (exp.) = 1.4574Pe (lit.) − 1.0773 (R = 0.9427)
(
Supporting Information Figure S1). From this equation and the limit
−6
established by Di et al. (P (lit.) = 4.0 × 10 cm/s) for blood-brain
barrier permeation, we concluded that compounds with a permeability
e
−6
greater than 4.7 × 10 cm/s could cross the blood-brain barrier
AUTHOR INFORMATION
Corresponding Authors
Tel: +086-20-3994-3051. Fax: +086-20-3994-3051. E-mail:
huangl72@mail.sysu.edu.cn.
Tel: +086-20-3994-3050. Fax: +086-20-3994-3050. E-mail:
■
*
(Supporting Information Table S2).
Metal-Chelating Study. The chelating studies were performed
with a UV−vis spectrophotometer. All compounds were solubilized in
the buffer which was used for the experiment. The absorption spectra
of compound (50 μM, final concentration) alone or in the presence of
CuSO , FeSO , or ZnCl (50 μM, final concentration) for 30 min in
*
lixsh@mail.sysu.edu.cn.
4
4
2
buffer (20 mM HEPES, 150 mM NaCl, pH 7.4) were recorded at
room temperature.
Author Contributions
Z.W., L.H., and X.L. take charge of the research. Z.W., Y.W.,
and W.L. synthesized compounds. Z.W. and Y.W. carried out
antioxidation and meta bonding related assay. Z.W. and F.M.
performed cell culture. Z.W., Y.W., and Y.S. determined BBB
permeation. Z.W., L.H., and X.L. written the manuscript. All
authors have given approval to the final version of the
manuscript.
For the stoichiometry of the compound-Cu2+ complex, a fixed
amount of 8a (80 μM) was mixed with growing amounts of copper ion
(
0−144 μM), and the difference UV−vis spectra were examined to
investigate the ratio of ligand/metal in the complex.
Determination of Cytotoxicity. The cytotoxicity was evaluated
with the colorimetric MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-
2
H-tetrazolium bromide] assay. Human neuron-like cells, SH-SY5Y,
were routinely grown at 37 °C in a humidified incubator with 5% CO2
in Dulbecco’s modified Eagle’s medium (DMEM, GIBCO)
supplemented with 10% fetal calf serum (FCS, GIBCO), 1 mM
glutamine, 50 mg/μL penicillin, and 50 mg/μL streptomycin. SH-
Funding
We thank the Natural Science Foundation of China (No.
2
1302235, 20972198) and the Ph.D. Programs Foundation of
the Ministry of Education of China (20120171120045) for
4
SY5Y cells were seeded at 5 × 10 cells/well in 96-well plates. After 24
financial support of this study.
Notes
The authors declare no competing financial interest.
h, the medium was removed and replaced with the tested compounds
at different concentrations for 24 h at 37 °C. Then, the cells were
incubated with MTT (2.5 mg/mL) in PBS for 4 h. After the removal
of MTT, the formazan crystals were dissolved in DMSO. The amount
of formazan was measured (570 nm). Cell viability was expressed as
percentage of control cells and calculated by the formula F /F ×100,
ABBREVIATIONS
■
t
nt
AD, Alzheimer’s disease; BBB, blood-brain barrier; DFO,
desferrioxamine; EDTA, ethylenediaminetetraacetate; CQ,
clioquinol; AChE, acetylcholinesterase; GPx, glutathione
peroxidase; ORAC-FL, oxygen radical absorbance capacity
with fluorescein; HRPA, horseradish peroxidase assay; CCA,
coumarin-3-carboxylic acid; DCFH-DA, dichlorofluorescein
where F is the absorbance of treated neurones and F is the
t
nt
absorbance of untreated neurones.
Antioxidant Activity in SH-SY5Y Cells. SH-SY5Y cells were
4
seeded at 1 × 10 cells/well in 96-well plates; After 24 h, the medium
was removed and replaced with tested compounds at 37 °C and kept
for another 24 h. The cells were washed with PBS and incubated with
I
dx.doi.org/10.1021/cn500119g | ACS Chem. Neurosci. XXXX, XXX, XXX−XXX

ACS Chemical Neuroscience
Research Article
diacetate; MTT, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-
tetrazolium bromide; TEM, transmission electron microscopy;
CNS, central nervous system; Aβ, β-amyloid; ROS, reactive
oxygen species; PAMPA-BBB, parallel artificial membrane
permeation assay for the blood-brain barrier; ThT, thioflavin
T; TLC, thin-layer chromatography; PBL, porcine brain lipid
(18) Nordberg, J., and Arner
́
, E. S. J. (2001) Reactive oxygen species,
antioxidants, and the mammalian thioredoxin system. Free Radical Biol.
Med. 31, 1287−1312.
(19) Mugesh, G., du Mont, W.-W., and Sies, H. (2001) Chemistry of
Biologically Important Synthetic Organoselenium Compounds. Chem.
Rev. 101, 2125−2180.
(20) Sarma, B. K., Manna, D., Minoura, M., and Mugesh, G. (2010)
Synthesis, Structure, Spirocyclization Mechanism, and Glutathione
Peroxidase-like Antioxidant Activity of Stable Spirodiazaselenurane
and Spirodiazatellurane. J. Am. Chem. Soc. 132, 5364−5374.
REFERENCES
■
(
1) Walsh, D. M., and Selkoe, D. J. (2004) Deciphering the
Molecular Basis of Memory Failure in Alzheimer’s Disease. Neuron 44,
(21) Sarma, B. K., and Mugesh, G. (2005) Glutathione Peroxidase
(GPx)-like Antioxidant Activity of the Organoselenium Drug Ebselen:
1
(
81−193.
Unexpected Complications with Thiol Exchange Reactions. J. Am.
Chem. Soc. 127, 11477−11485.
2) Scarpini, E., Schelterns, P., and Feldman, H. (2003) Treatment of
Alzheimer’s disease: Current status and new perspectives. Lancet
Neurol. 2, 539−547.
3) Dong, J., Atwood, C. S., Anderson, V. E., Siedlak, S. L., Smith, M.
A., Perry, G., and Carey, P. R. (2003) Metal Binding and Oxidation of
Amyloid-β within Isolated Senile Plaque Cores: Raman Microscopic
Evidence. Biochemistry 42, 2768−2773.
4) Bush, A. I. (2008) Drug Development Based on the Metals
Hypothesis of Alzheimer’s Disease. J. Alzheimer’s Dis. 15, 223−240.
5) Zecca, L., Youdim, H. B. M., Riederer, P., Connor, J. R., and
(22) Zhao, R., Masayasu, H., and Holmgren, A. (2002) Ebselen: A
substrate for human thioredoxin reductase strongly stimulating its
hydroperoxide reductase activity and a superfast thioredoxin oxidant.
Proc. Natl. Acad. Sci. U.S.A. 99, 8579−8584.
(
(23) Nogueira, C. W., Zeni, G., and Rocha, J. B. T. (2004)
Organoselenium and Organotellurium Compounds: Toxicology and
(
Pharmacology. Chem. Rev. 104, 6255−6286.
(24) Bar-Am, O., Amit, T., Weinreb, O., Youdim, M. B. H, and
(
Mandel, S. (2010) Propargylamine containing compounds as
modulators of proteolytic cleavage of amyloid-beta protein precursor:
involvement of MAPK and PKC activation. J. Alzheimer’s Dis. 21, 361−
Crichton, R. R. (2004) Iron, brain ageing and neurodegenerative
disorders. Nat. Rev. Neurosci. 5, 863−873.
6) Mandel, S., Amit, T., Bar-Am, O., and Youdim, M. B. H. (2007)
(
3
(
(
71.
25) Weinreb, O., Amit, T., Bar-Am, O., and Youdim, M. B. H.
2010) Rasagiline: A novel anti-Parkinsonian monoamine oxidase-B
inhibitor with neuroprotective activity. Prog. Neurobiol. 92, 330−344.
26) Maruyama, W., Akao, Y., Carrillo, M. C., Kitani, K.-i., Youdium,
Iron dysregulation in Alzheimer’s disease: Multimodal brain permeable
iron chelating drugs, possessing neuroprotective-neurorescue and
amyloid precursor protein-processing regulatory activities as ther-
apeutic agents. Prog. Neurobiol. 82, 348−360.
(
(
7) Amit, T., Avramovich-Tirosh, Y., Youdim, M. B. H., and Mandel,
M. B. H., and Naoi, M. (2002) Neuroprotection by propargylamines in
Parkinson’s disease: Suppression of apoptosis and induction of
prosurvival genes. Neurotoxicol. Teratol. 24, 675−682.
S. (2008) Targeting multiple Alzheimer’s disease etiologies with
multimodal neuroprotective and neurorestorative iron chelators.
FASEB J. 22, 1296−1305.
(27) Rucins, M., Kaldre, D., Pajuste, K., Fernandes, M. A. S., Vicente,
(
8) Fernandez-Bachiller, M. I., Perez, C., Gonzalez-Munoz, G. C.,
J. A. F., Klimaviciusa, L., Jaschenko, E., Kanepe-Lapsa, I., Shestakova, I.,
Plotniece, M., Gosteva, M., Sobolev, A., Jansone, B., Muceniece, R.,
Klusa, V., and Plotniece, A. (2014) Synthesis and studies of calcium
channel blocking and antioxidant activities of novel 4-pyridinium and/
or N-propargyl substituted 1,4-dihydropyridine derivatives. C. R. Chim.
Conde, S., Lopez, M. G., Villarroya, M., Garcia, A. G., and Rodriguez-
Franco, M. I. (2010) Novel tacrine-8-hydroxyquinoline hybrids as
multifunctional agents for the treatment of Alzheimer’s disease, with
neuroprotective, cholinergic, antioxidant, and copper-complexing
properties. J. Med. Chem. 53, 4927−4937.
9) Bonda, D. J., Wang, X., Perry, G., Nunomura, A., Tabaton, M.,
Zhu, X., and Smith, M. A. (2010) Oxidative stress in Alzheimer
disease: A possibility for prevention. Neuropharmacology 59, 290−294.
10) Von Bernhardi, R., and Eugenin, J. (2012) Alzheimer’s disease:
redox dysregulation as a common denominator for diverse pathogenic
mechanisms. Antioxid. Redox Signaling 16, 974−1031.
11) Rayman, M. P. (2000) The importance of selenium to human
health. Lancet 356, 233−241.
12) Jacob, C., Giles, G. I., Giles, N. M., and Sies, H. (2003) Sulfur
and Selenium: The Role of Oxidation State in Protein Structure and
1
(
7, 69−80.
(
28) Youdim, M. B. H., Bar Am, O., Yogev-Falach, M., Weinreb, O.,
Maruyama, W., Naoi, M., and Amit, T. (2005) Rasagiline: Neuro-
degeneration, neuroprotection, and mitochondrial permeability
transition. J. Neurosci. Res. 79, 172−179.
(
(29) Zheng, H., Weiner, L. M., Bar-Am, O., Epsztejn, S., Cabantchik,
Z. I., Warshawsky, A., Youdim, M. B. H., and Fridkin, M. (2005)
Design, synthesis, and evaluation of novel bifunctional iron-chelators
as potential agents for neuroprotection in Alzheimer’s, Parkinson’s,
and other neurodegenerative diseases. Bioorg. Med. Chem. 13, 773−
(
(
7
(
83.
30) Dragoni, S., Porcari, V., Valoti, M., Travagli, M., and Castagnolo,
Function. Angew. Chem., Int. Ed. Engl. 42, 4742−4758.
13) Kryukov, G. V., Castellano, S., Novoselov, S. V., Lobanov, A. V.,
(
D. (2006) Antioxidant properties of propargylamine derivatives:
assessment of their ability to scavenge peroxynitrite. J. Pharm.
Pharmacol. 58, 561−565.
(31) Bar-Am, Orit, Weinreb, Orly, Amit, Tamar, and Youdim, M. B.
H. (2005) Regulation of Bcl-2 family proteins, neurotrophic factors,
and APP processing in the neurorescue activity of propargylamine.
FASEB J. 19, 1899−1901.
(32) Yu, P. H., Davis, B. A., and Boulton, A. A. (1992) Aliphatic
Propargylamines: Potent, Selective, Irreversible Monoamine Oxidase B
Inhibitors. J. Med. Chem. 35, 3705−3713.
(33) Avramovich-Tirosh, Y., Amit, T., Bar-Am, O., Zheng, H.,
Fridkin, M., and Youdim, M. B. H. (2007) Therapeutic targets and
potential of the novel brain- permeable multifunctional iron chelator−
monoamine oxidase inhibitor drug, M-30, for the treatment of
Alzheimer’s disease. J. Neurochem. 100, 490−502.
(34) Gal, S., Zheng, H., Fridkin, M., and Youdim, M. B. H. (2005)
Novel multifunctional neuroprotective iron chelator-monoamine
oxidase inhibitor drugs for neurodegenerative diseases. In vivo
Zehtab, O., Guigo,
of Mammalian Selenoproteomes. Science 300, 1439−1443.
14) Nascimento, V., Alberto, E. E., Tondo, D. W., Dambrowski, D.,
́
R., and Gladyshev, V. N. (2003) Characterization
(
Detty, M. R., Nome, F., and Braga, A. L. (2012) GPx-Like activity of
selenides and selenoxides: experimental evidence for the involvement
of hydroxy perhydroxy selenane as the active species. J. Am. Chem. Soc.
1
(
34, 138−141.
15) Trippier, P. C., Jansen Labby, K., Hawker, D. D., Mataka, J. J.,
and Silverman, R. B. (2013) Target- and mechanism-based
therapeutics for neurodegenerative diseases: strength in numbers. J.
Med. Chem. 56, 3121−3147.
(
16) Tapiero, H., Townsend, D. M., and Tew, K. D. (2003) The
antioxidant role of selenium and seleno-compounds. Biomed.
Pharmacother. 57, 134−144.
(
17) Magalhae
̃
s, J. P. d., and Church, G. M. (2006) Cells discover
fire: Employing reactive oxygen species in developmentand con-
sequences for aging. Exp. Gerontol. 41, 1−10.
J
dx.doi.org/10.1021/cn500119g | ACS Chem. Neurosci. XXXX, XXX, XXX−XXX

ACS Chemical Neuroscience
Research Article
selective brain monoamine oxidase inhibition and prevention of
(52) Xu, L., Xu, Y., Zhu, W., Yang, C., Han, L., and Qian, X. (2012) A
highly selective and sensitive fluorescence “turn-on” probe for Ag in
+
MPTP-induced striatal dopamine depletion. J. Neurochem. 95, 79−88.
(
35) Luo, Z., Sheng, J., Sun, Y., Lu, C., Yan, J., Liu, A., Luo, H.-b.,
aqueous solution and live cells. Dalton Trans. 41, 7212−7217.
(53) Saharan, S., and Mandal, P. K. (2014) The emerging role of
glutathione in Alzheimer’s disease. J. Alzheimer’s Dis. 40, 519−529.
(54) Bush, A. I. (2003) The metallobiology of Alzheimer’s disease.
Trends Neurosci. 26, 207−214.
Huang, L., and Li, X. (2013) Synthesis and Evaluation of Multi-Target-
Directed Ligands against Alzheimer’s Disease Based on the Fusion of
Donepezil and Ebselen. J. Med. Chem. 56, 9089−9099.
(
36) Luo, Z., Liang, L., Sheng, J., Pang, Y., Li, J., Huang, L., and Li, X.
(55) Gaggelli, E., Kozlowski, H., Valensin, D., and Valensin, G.
(
2014) Synthesis and biological evaluation of a new series of ebselen
(
(
2006) Copper Homeostasis and Neurodegenerative Disorders
Alzheimer’s, Prion, and Parkinson’s Diseases and Amyotrophic
derivatives as glutathione peroxidase (GPx) mimics and cholinesterase
inhibitors against Alzheimer’s disease. Bioorg. Med. Chem. 22, 1355−
Lateral Sclerosis). Chem. Rev. 106, 1995−2044.
56) Barnham, K. J., and Masters, C. L. (2004) Neurodegenerative
diseases and oxidative stress. Nat. Rev. Drug Discovery 3, 205−214.
57) Hardeland, R. (2005) Atioxidative protection by melatonin.
Endocrine 27, 119−130.
58) Lynch, M. A. (2004) Long-Term Potentiation and Memory.
Physiol. Rev. 84, 87−136.
59) Di, L., Kerns, E. H., Fan, K., McConnell, O. J., and Carter, G. T.
2003) High throughput artificial membrane permeability assay for
blood−brain barrier. Eur. J. Med. Chem. 38, 223−232.
60) Rosini, M., Simoni, E., Bartolini, M., Cavalli, A., Ceccarini, L.,
1
361.
(
(
37) Patel, N. B., Patel, J. C., and Modi, S. H. (2011) Synthesis and
antimicrobial activity of carbonyl pyridoquinolones containing urea
(
and piperazine residue. J. Saudi Chem. Soc. 15, 167−176.
(
38) Mazumder, U. K., Gupta, M., Bhattacharya, S., Karki, S. S.,
(
Rathinasamy, S., and Thangavel, S. (2004) Antineoplastic and
antibacterial activity of some mononuclear Ru(II) complexes. J.
Enzyme Inhib. Med. Chem. 19, 185−92.
(
(
(
39) Liu, J. O.; Shim, J., Sup.; Chong, C. R.; Bhat, S. Preparation of
quinoline derivatives for use as human methionine aminopeptidase,
sirT1 and angiogenesis inhibitors. Patent: WO 2010/042163 A2, 2010.
(
Pascu, N., McClymont, D. W., Tarozzi, A., Bolognesi, M. L., Minarini,
A., Tumiatti, V., Andrisano, V., Mellor, I. R., and Melchiorre, C.
2008) Inhibition of Acetylcholinesterase, β-Amyloid Aggregation, and
(
40) Ou, B., Hampsch-Woodill, M., and Prior, R. L. (2001)
Development and Validation of an Improved Oxygen Radical
Absorbance Capacity Assay Using Fluorescein as the Fluorescent
Probe. J. Agric. Food. Chem. 49, 4619−4626.
(
NMDA Receptors in Alzheimer’s Disease: A Promising Direction for
the Multi-target-Directed Ligands Gold Rush. J. Med. Chem. 51, 4381−
(
41) Dav
Extending Applicability of the Oxygen Radical Absorbance Capacity
ORAC−Fluorescein) Assay. J. Agric. Food. Chem. 52, 48−54.
42) Ning, X., Guo, Y., Wang, X., Ma, X., Tian, C., Shi, X., Zhu, R.,
́ ́ ́ ́
alos, A., Gomez-Cordoves, C., and Bartolome, B. (2004)
4
384.
(
61) Camps, P., Formosa, X., Galdeano, C., Mun
̃
oz-Torrero, D.,
(
Ramírez, L., Gomez, E., Isambert, N., Lavilla, R., Badia, A., Clos, M. V.,
Bartolini, M., Mancini, F., Andrisano, V., Arce, M. P., Rodríguez-
Franco, M. I., Huertas, O., Dafni, T., and Luque, F. J. (2009)
́
(
Cheng, C., Du, Y., Ma, Z., Zhang, Z., and Liu, J. (2014) Design,
synthesis, and biological evaluation of (e)-3,4-dihydroxystyryl aralkyl
sulfones and sulfoxides as novel multifunctional neuroprotective
agents. J. Med. Chem. 57, 4302−4312.
́
Pyrano[3,2-c]quinoline−6-Chlorotacrine Hybrids as a Novel Family of
Acetylcholinesterase- and β-Amyloid-Directed Anti-Alzheimer Com-
pounds. J. Med. Chem. 52, 5365−5379.
(
43) Sultana, R., Newman, S., Mohmmad-Abdul, H., Keller, J. N., and
(62) Choi, J.-S., Braymer, J. J., Nanga, R. P. R., Ramamoorthy, A., and
Butterfield, D. A. (2004) Protective Effect of the Xanthate, D609, on
Alzheimer’s Amyloid β-peptide (1−42)-Induced Oxidative Stress in
Lim, M. H. (2010) Design of small molecules that target metal-Aβ
species and regulate metal-induced Aβ aggregation and neurotoxicity.
Proc. Natl. Acad. Sci. U.S.A. 107, 21990−21995.
Primary Neuronal Cells. Free Radical Res. 38, 449−558.
́
(
44) Merino-Montiel, P., Lop
́
ez, O., and Fernan
́
dez-Bolan
̃
os, J. G.
(63) Rodríguez-Franco, M. I., Fernan
́
dez-Bachiller, M. I., Per
́
ez, C.,
(
2012) l-Isofucoselenofagomine and derivatives: Dual activities as
antioxidants and as glycosidase inhibitors. Tetrahedron 68, 3591−3595.
45) Riederer, P., Danielczyk, W., and Grunblatt, E. (2004)
Hernandez-Ledesma, B., and Bartolome,
́
́
B. (2006) Novel Tacrine−
Melatonin Hybrids as Dual-Acting Drugs for Alzheimer Disease, with
Improved Acetylcholinesterase Inhibitory and Antioxidant Properties.
J. Med. Chem. 49, 459−462.
(
̈
Monoamine Oxidase-B Inhibition in Alzheimer’s Disease. Neuro-
toxicology 25, 271−277.
(64) Wohnsland, F., and Faller, B. (2001) High-Throughput
Permeability pH Profile and High-Throughput Alkane/Water log P
with Artificial Membranes. J. Med. Chem. 44, 923−930.
(
46) Oyama, Y., Hayashi, A., Ueha, T., and Maekawa, K. (1994)
Characterization of 2′,7′-dichlorofluorescin fluorescence in dissociated
mammalian brain neurons: estimation on intracellular content of
hydrogen peroxide. Brain Res. 635, 113−117.
(65) Guilloreau, L., Combalbert, S., Sournia-Saquet, A., Mazarguil,
H., and Faller, P. (2007) Redox Chemistry of Copper−Amyloid-β:
The Generation of Hydroxyl Radical in the Presence of Ascorbate is
Linked to Redox-Potentials and Aggregation State. ChemBioChem 8,
(
47) Sharma, A. K., Pavlova, S. T., Kim, J., Finkelstein, D., Hawco, N.
J., Rath, N. P., Kim, J., and Mirica, L. M. (2012) Bifunctional
Compounds for Controlling Metal-Mediated Aggregation of the Aβ42
Peptide. J. Am. Chem. Soc. 134, 6625−6636.
1
317−1325.
(
48) Lee, S., Zheng, X., Krishnamoorthy, J., Savelieff, M. G., Park, H.
M., Brender, J. R., Kim, J. H., Derrick, J. S., Kochi, A., Lee, H. J., Kim,
C., Ramamoorthy, A., Bowers, M. T., and Lim, M. H. (2014) Rational
design of a structural framework with potential use to develop
chemical reagents that target and modulate multiple facets of
Alzheimer’s disease. J. Am. Chem. Soc. 136, 299−310.
(
49) Baum, L., and Ng, A. (2004) Curcumin interaction with copper
and iron suggests one possible mechanism of action in Alzheimer’s
disease animal models. J. Alzheimer’s Dis. 6, 367−377.
(
50) Bolognesi, M. L., Cavalli, A., Valgimigli, L., Bartolini, M., Rosini,
M., Andrisano, V., Recanatini, M., and Melchiorre, C. (2007) Multi-
Target-Directed Drug Design Strategy: From a Dual Binding Site
Acetylcholinesterase Inhibitor to a Trifunctional Compound against
Alzheimer’s Disease. J. Med. Chem. 50, 6446−6449.
(
51) Geng, J., Li, M., Wu, L., Ren, J., and Qu, X. (2012) Liberation of
Copper from Amyloid Plaques: Making a Risk Factor Useful for
Alzheimer’s Disease Treatment. J. Med. Chem. 55, 9146−9155.
K
dx.doi.org/10.1021/cn500119g | ACS Chem. Neurosci. XXXX, XXX, XXX−XXX