Pterostilbene-O-acetamidoalkylbenzylamines derivatives as novel dual inhibitors of cholinesterase with anti-β-amyloid aggregation and antioxidant properties for the treatment of Alzheimer's disease

Article abstract of DOI:10.1016/j.bmcl.2016.02.079

A series of pterostilbene-O-acetamidoalkylbenzylamines were designed, synthesized and evaluated as dual inhibitors of AChE and BuChE. To further explore the multifunctional properties of the new derivatives, their antioxidant activities and inhibitory effects on self-induced Aβ_1-42 aggregation and HuAChE-induced Aβ_1-40 aggregation were also tested. The results showed that most of these compounds could effectively inhibit AChE and BuChE. Particularly, compound 21d exhibited the best AChE inhibitory activity (IC₅₀ = 0.06 μM) and good inhibition of BuChE (IC₅₀ = 28.04 μM). Both the inhibition kinetic analysis and molecular modeling study revealed that these compounds showed mixed-type inhibition, binding simultaneously to the CAS and PAS of AChE. In addition to cholinesterase inhibitory activities, these compounds showed different levels of antioxidant activity. However, the inhibitory activities against self-induced and HuAChE-induced Aβ aggregation of these new derivatives were unsatisfied. Taking into account the results of the biological evaluation, further modifications will be designed in order to increase the potency on the different targets. The results displayed in this Letter can be a new starting point for further development of multifunctional agents for Alzheimer's disease.

Full text of DOI:10.1016/j.bmcl.2016.02.079

Accepted Manuscript
Pterostilbene-O-acetamidoalkylbenzylamines derivatives as novel dual inhibi-
tors of cholinesterase with anti-β-amyloid aggregation and antioxidant proper-
ties for the treatment of Alzheimer’s disease
Yuxing Li, Xiaoming Qiang, Yan Li, Xia Yang, Li Luo, Ganyuan Xiao,
Zhongcheng Cao, Zhenghuai Tan, Yong Deng
PII:
S0960-894X(16)30204-9
DOI:
http://dx.doi.org/10.1016/j.bmcl.2016.02.079
BMCL 23633
Reference:
Bioorganic & Medicinal Chemistry Letters
To appear in:
Received Date:
Revised Date:
Accepted Date:
21 December 2015
17 February 2016
26 February 2016
Please cite this article as: Li, Y., Qiang, X., Li, Y., Yang, X., Luo, L., Xiao, G., Cao, Z., Tan, Z., Deng, Y.,
Pterostilbene-O-acetamidoalkylbenzylamines derivatives as novel dual inhibitors of cholinesterase with anti-β-
amyloid aggregation and antioxidant properties for the treatment of Alzheimer’s disease, Bioorganic & Medicinal
Chemistry Letters (2016), doi: http://dx.doi.org/10.1016/j.bmcl.2016.02.079
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Pterostilbene-O-acetamidoalkylbenzylamines derivatives as novel dual inhibitors of
cholinesterase with anti-β-amyloid aggregation and antioxidant properties for the treatment of
Alzheimer’s disease
Yuxing Lia,#, Xiaoming Qianga,#, Yan Lia, Xia Yanga, Li Luoa, Ganyuan Xiaoa, Zhongcheng Caoa,
Zhenghuai Tanb,* and Yong Denga,*
aDepartment of Medicinal Chemistry, Key Laboratory of Drug Targeting and Drug Delivery System
of the Education Ministry, West China School of Pharmacy, Sichuan University, Chengdu, 610041,
China
bInstitute of Traditional Chinese Medicine Pharmacology and Toxicology, Sichuan academy of
Chinese Medicine Sciences, Chengdu, 610041, China
Abbreviations: AD, Alzheimer’s disease; AChE, acetylcholinesterase ; BuChE, butyrylcholinesterase;
HuAChE, human AChE; EeAChE, Electrophorus electricus AChE; Aβ, β-amyloid peptide; CAS,
catalytic active site; PAS, peripheral anionic site; EDCI, 1-ethyl-3-(3-dimethylaminopropyl)
carbodiimide hydrochloride; PBS, phosphate-buffered saline; DTNB, 5,5’-dithiobis-2-nitrobenzoic
acid; PDB, Protein Data Bank; TcAChE, Torpedo californica AChE; ORAC-FL, Oxygen Radicals
Absorbance Capacity by Fluorescence; ThT, thioflavin T;
# These authors contributed equally to this work.
* Corresponding Author.
Phone, +86-28-85258982; E-mail: tanzhh616@163.com (Zhenghuai Tan)
Phone, +86-28-85503790; E-mail: dengyong@scu.edu.cn (Yong Deng)

Abstract
A series of pterostilbene-O-acetamidoalkylbenzylamines were designed, synthesized and evaluated
as dual inhibitors of AChE and BuChE. To further explore the multifunctional properties of the new
derivatives, their antioxidant activities and inhibitory effects on self-induced Aβ1-42 aggregation and
HuAChE-induced Aβ1-40 aggregation were also tested. The results showed that most of these
compounds could effectively inhibit AChE and BuChE. Particularly, compound 21d exhibited the
best AChE inhibitory activity (IC50 = 0.06 μM) and good inhibition of BuChE (IC50 = 28.04 μM).
Both the inhibition kinetic analysis and molecular modeling study revealed that these compounds
showed mixed-type inhibition, binding simultaneously to the CAS and PAS of AChE. In addition to
cholinesterase inhibitory activities, these compounds showed different levels of antioxidant activity.
However, the inhibitory activities against self-induced and HuAChE-induced Aβ aggregation of these
new derivatives were unsatisfied. Taking into account the results of the biological evaluation, further
modifications will be designed in order to increase the potency on the different targets. The results
displayed in this paper can be a new starting point for further development of multifunctional agents
for Alzheimer’s disease.
Keywords: Alzheimer’s disease; pterostilbene-O-acetamidoalkylbenzylamines; dual cholinesterase
inhibitors; antioxidant; Aβ aggregation inhibitors.

Alzheimer’s disease (AD) is a neurodegenerative disorder that is manifested by progressive loss
of memory and cognitive functions, which inevitably leads to disability and death.1 The disorder is
reaching epidemic proportions, with a large human, social, and economic burden in worldwide
countries.2 Over the past few decades, enormous efforts have been put forth to understand the
complex pathophysiology of AD, but its etiology remains elusive. Many factors, such as low levels
of acetylcholine (ACh), the formation of β-amyloid deposits, oxidative stress and dyshomeostasis of
biometals, are considered to play significant roles in the pathogenesis of AD.3 Currently, the main
therapeutic approach for the treatment of AD is to enhance brain cholinergic activity through
inhibiting acetylcholinesterase (AChE) in pre-synaptic areas.4 However, due to the complex
pathologies of AD, the current AChE inhibitors such as donepezil and galantamine that modulate a
single target can only improve clinical symptoms but cannot mitigate progression of the disease
process underlying the AD.5 As reported in some earlier studies6, inhibition of butyrylcholinesterase
(BuChE) represents an important therapeutic target for AD. It has also been recently reported that
dual inhibition of AChE and BuChE might alleviate AD symptoms owing to the key role of BuChE
in hydrolysis of ACh. It is essential to ensure that the drug inhibits both AChE and BuChE.7
Moreover, converging lines of evidence suggest that accumulation and aggregation of Aβ is also a
pivotal factor to induce AD, as its accumulation in brain may result in a cascade of biochemical
events leading to neuronal dysfunction. Therefore, reducing the aggregation of Aβ in the brain
appears to be a rational therapeutic strategy for AD treatment.5 Recent studies have indicated that
oxidative damage could promote the appearance of amyloid plaques and neurofibrillar tangles in AD
brain.8 Thus, successful protection of neuronal cells from oxidative damage could effectively prevent
AD. Given that the etiology of AD is complex and the decline of ACh may not be the only factor
resulting in AD, a more appropriate therapeutic strategy based on the multi-target-directed ligands

(MTDLs) paradigm has recently been proposed and applied to design multi-target compounds with
the activity not just AChE inhibition.9 Recently, our work is focused on the design of new
multifunctional molecules endowed with AChE and BuChE inhibitory activities, inhibition of Aβ
aggregation properties, and antioxidant activity, by connecting moieties with such properties.
Pterostilbene (trans-3,5-dimethoxy-4’-hydroxystilbene), a naturally occurring dimethylether
analog of resveratrol, was first isolated from P. Santalinus and it is also found in several types of
berries and grapes.10 In vitro and in vivo studies show that pterostilbene and its analogs have a
number of biological activities related to AD including antioxidant, anti-inflammatory and
neuroprotective properties.11 Recently, many researchers demonstrated that pterostilbene analogs can
inhibit self-induced Aβ aggregation, attenuate Aβ-induced toxicity, promote Aβ clearance and reduce
senile plaques.12 Some studies also showed that it has the ability to inhibit monoamine oxidase
(MAO).13 It could be concluded that pterostilbene might be used as a starting compound in the
design of multi-target drugs for the treatment of AD. Our research group has been involved through
the years in the development of multi-target compounds as potential drug candidates for AD. In
particular, our group has reported the synthesis of pterostilbene carbamate derivatives as dual
cholinesterase inhibitors and neuroprotective agents.14 Benzylamines have been proved as essential
cholinesterase inhibitory pharmacophore in our previous work.15-17 As a further development of our
work on the design and synthesis of new multifunctional compounds with better pharmacological
profiles, here we aimed to use a multi-target-directed drug design strategy to combine pterostilbene
with benzylamines using a chain of amide of different lengths.
In this letter, a series of pterostilbene-O-acetamidoalkylbenzylamines derivatives 18-21 were
designed, synthesized and evaluated for their biological activity, including inhibition of AChE and
BuChE, antioxidant, and inhibitory effects on Aβ aggregation.

The synthetic pathways of target compounds were summarized in Scheme 1. The synthesis of
the target compounds applied readily available starting materials and was completed using well
established methods. The starting material pterostilbene was reacted with ethyl bromoacetate in the
presence of K2CO3, followed by hydrolization with LiOH to give carboxylic acid 3. Diamines 14-17
were prepared by Gabriel reaction. Finally, condensation of intermediates 3 with the appropriate
diamines 14-17 in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride
(EDCI) gave the target compounds 18-21.18
Scheme 1. Synthesis of pterostilbene-O-acetamidoalkylbenzylamines derivatives 18-21. Reagents
and conditions: (i) BrCH2COOEt, K2CO3, CH3CN, at 60-65°C, for 8 h; (ii) LiOH, THF/H2O, reflux
for 2 h, then 10% HCl; (iii) KOH, EtOH, reflux, 15 min; (iv) Br(CH2)nBr, PEG-400, acetone, reflux
for 7-8 h; (v) R1R2NH (a-d), K2CO3, KI, CH3CN, at 65°C, for 6-8 h; (vi) H2NNH2.H2O, EtOH,
reflux for 4-5 h; (vii) EDCI, THF, at rt, for 24 h.
To investigate the multipotential profiles of the novel series of pterostilbene derivatives

(18-21a-d), they were first evaluated as inhibitors of AChE and BuChE according to the modified
Ellman’s method.15,19 Their activities were assayed on AChE from electric eel (EeAChE) and BuChE
from rat serum (RatBuChE). Rivastigmine and donepezil were used as reference compounds. The
IC50 values and selectivity index for the inhibition of AChE and BuChE were summarized in Table 1.
The target compounds showed different amounts of inhibitory activity to AChE with IC50 values
ranging from the submicromolar to micromolar range, and exhibited moderate BuChE inhibitory
activities. The results indicated that these derivatives were dual inhibitors of AChE and BuChE.
Compound 21d exhibited the best inhibitory potency for AChE with IC50 value of 0.06 μM, while it
also showed good BuChE inhibition simultaneously with IC50 value of 28.04 μM. Compared with the
previously reported pterostilbene carbamate derivatives14, the results showed that the introduction of
amide on side-chain significantly increased the inhibitory activity. Through analysis and comparison,
we found that the inhibitory potency is associated with length of linker: the increasing length of the
linker may give rise to a better activity. As shown in Table 1, the derivatives with 4- or 6-methylene
linker between benzylamine and amide showed better inhibition of AChE than those with 2- or
3-methylene. Interestingly, the obvious regularity was applicable to BuChE inhibition as well. The
results indicated that these derivatives required side chains of a suitable length to bind to the AChE
and BuChE. The screening data also exhibited that the structure of terminal groups NR1R2 of side
chain effects the inhibitory activities. Generally, the compounds possessing an N-2-methoxybenzyl
group showed better AChE inhibitory activity than compounds with N-benzyl group. And in most
cases, the effect of NR1R2 on BuChE inhibition was similar to that of AChE, except compounds 18c
and 18d. Taken together, N-(2-methoxylbenzyl)ethylamine of this series of derivatives may be the
optimal substitution pattern for cholinesterase inhibition.
Table 1. Inhibition of AChE and BuChE Activity, and Oxygen Radical Absorbance Capacity
(ORAC, Trolox Equivalents) by Pterostilbene Derivatives and Reference Compounds

Compound
IC50 (μM) ± SDa
ORACe
Selectivity
indexd
1.36
AChEb
BuChEc
155.11 ± 19.59
218.11 ± 12.76
30.98 ± 1.58
210.72 ± 15.18
212.75 ± 11.48
326.72 ± 17.09
0.32 ± 0.01
0.15 ± 0.01
0.10 ± 0.01
18a
18b
18c
0.96
10.55
17.46 ± 2.19
13.43 ± 1.41
8.22 ± 0.37
8.52 ± 0.75
2.69 ± 0.36
9.61 ± 0.17
2.86 ± 0.01
0.51 ± 0.03
0.54 ± 0.12
20.72 ± 2.38
3.29 ± 0.04
4.92 ± 0.39
0.06 ± 0.03
4.45 ± 0.37
321.07 ± 30.23
306.97 ± 23.75
262.14 ± 12.72
188.41 ± 12.63
64.00 ± 8.77
278.84 ± 26.67
226.91 ± 11.05
36.74 ± 3.33
26.46 ± 1.49
273.48 ± 22.60
30.93 ± 2.05
27.78 ± 2.26
28.04 ± 1.71
1.32 ± 0.09
18.39
22.86
31.89
22.11
23.79
29.02
79.33
72.04
49.00
13.20
9.40
0.09 ± 0.01
0.20 ± 0.01
0.19 ± 0.01
0.36 ± 0.02
0.37 ± 0.01
0.56 ± 0.03
0.11 ± 0.01
0.79 ± 0.02
0.65 ± 0.04
0.08 ± 0.01
0.68 ± 0.03
0.45 ± 0.02
0.51 ± 0.03
NTf
18d
19a
19b
19c
19d
20a
20b
20c
20d
21a
21b
21c
21d
5.65
467.33
0.30
Rivastigmine
Donepezil
0.015 ± 0.002
20.7 ± 1.36
NTf
1380
NTf
Pterostilbene
Resveratrol
NTf
NTf
-
-
4.32 ± 0.31
5.60 ± 0.42
NTf
a
IC50 values represent the concentration of inhibitor required to decrease enzyme activity by 50%
and are the mean of 3 independent experiments, each performed in triplicate (SD = standard
deviation).
b AChE from electric eel (EeAChE).
c BuChE from rat serum.
d Selectivity index = IC50 (BuChE)/IC50 (AChE).
e
The mean ± SD of the 3 independent experiments. Data are expressed as μM of Trolox
equivalent/μM of tested compound.
f NT = not tested.
To investigate the AChE inhibitory mechanism for this class of pterostilbene-O-acetamidoalkyl
benzylamines derivatives, a kinetic study was carried out with a representative compound 21d using
EeAChE. The Lineweaver-Burk reciprocal plots (Figure 1) exhibited that with increasing
concentrations of 21d, both the slopes (decreased Vmax) and intercepts (higher Km) were increased.

This pattern indicated a mixed-type inhibition and revealed that compound 21d was able to bind at
both the catalytic and peripheral site of AChE.
120
non inhibitor
[21d] = 10.0 μM
[21d] = 5.0 μM
[21d] = 2.5 μM
100
80
60
40
20
0
-25
-20
-15
-10
-5
0
5
10
15
[ATCh]-1 (mM-1)
Figure 1. Kinetic study on the mechanism of EeAChE inhibition by compound 21d. Merged
Lineweaver-Burk reciprocal plots of AChE initial velocity with increasing substrate concentration
(100-400 μM) in the absence or presence of 21d. Lines were derived from a weighted least-squares
analysis of data points.
To further explore the possible interaction mode of these new derivatives with TcAChE (PDB
code: 1EVE), a molecular modeling study was carried out using the docking program AUTODOCK
4.2 with Discovery Studio 2.0.20 As shown in Figure 2, compound 21d occupied the entire
enzymatic catalytic active site (CAS), the mid-gorge sites and the peripheral anionic site (PAS), and
could bind simultaneously to both the catalytic and peripheral site. The phenyl ring without methoxy
groups of pterostilbene was observed to bind to the PAS via π-π stacking with residue Trp279. The
phenyl ring of N-(2-methoxybenzyl)ethylamine moiety could bind to the CAS by establishing a π-π
stacking interaction with the indole ring of Trp84. The long side chain of amide and methylenes
folded in a conformation in the gorge that allowed them to interact with Phe330, Phe331, Tyr121 and
Tyr334 via the hydrophobic interaction. Notably, hydrogen bonds were observed between side chain
and Phe288 and Tyr334. The docking results indicated that compound 21d was a mix-type inhibitor

of AChE, which were consistent with the kinetic analysis result.
Figure 2. Representative compound 21d (colored by atom type) interacting with residues in the
binding site of TcAChE (PDB code: 1EVE), highlighting the protein residues that participate in the
main interactions with the inhibitor.
The antioxidant activities of the synthesized compounds were evaluated by following the
ORAC-FL method.15,21 The antioxidant capacity of pterostilbene derivatives was determined by their
competition with fluorescein in the radical capture. Their abilities to scavenge radicals were provided
as a Trolox (a vitamin E analog) equivalent, with their relative potency at 5 μM compared with
Trolox (Table 1). Pterostilbene and resveratrol were also tested, with an ORAC-FL value of 4.32 and
5.60 trolox equivalents, respectively. Unfortunately, all of the new derivatives exhibited weak
antioxidant activities. When compared the ORAC-FL values of pterostilbene and its derivatives, it
was noticeable that the free 4’-OH was crucial for the radical scavenging ability. And this deficiency

needs to be improved in our follow-on work.
The inhibition of self-induced Aβ1-42 of these pterostilbene derivatives were evaluated using the
thioflavin T (ThT) fluorescence method.15,22 Inhibitory activities are listed in Table 2 as inhibition
ratios at a test concentration of 25 μM. Compared with the reference compound, curcumin (43.1%, at
25 μM) and resveratrol (49.8%, at 25 μM), the target compounds 18-21a-d gave unsatisfied results,
with inhibition ratios from 11.2% to 36.3% (no apparent structure-activity relationship existed). As
many studies reported23, Aβ deposition has been linked to AChE expression. The PAS of AChE can
bind to Aβ, accelerating the formation of amyloid fibrils. Therefore, inhibition of AChE, particularly
the inhibition of PAS of AChE, may reduce Aβ aggregation. The studies as mentioned above have
proved that compounds 20c, 20d and 21d exhibited good AChE inhibition and were able to bind both
CAS and PAS of AChE. Therefore, the abilities of the three new derivatives to inhibit
HuAChE-induced Aβ1-40 aggregation were examined via ThT-based fluorometric assay. Compared
with donepezil (25.0%), compounds 20c, 20d, 21d had lower inhibitory activity (7.5%, 7.8% and
19.3%, respectively) against HuAChE-induced Aβ1-40 aggregation. Due to the poor inhibition of Aβ
aggregation, the inhibitory activities against Aβ aggregation were not deep measured.
Table 2. Inhibition of self-induced Aβ1-42 aggregation and HuAChE-induced Aβ1-40 aggregation
by compound 20c, 20d, 21d and reference compounds
Comp.
%inhibition of Aβ aggregationa
self-inducedb,d
HuAChE-inducedc,d
36.3 ± 1.1
21.9 ± 0.8
11.2 ± 0.2
25.8 ± 1.3
21.2 ± 1.1
11.8 ± 0.2
20.3 ± 1.1
18.3 ± 0.5
17.9 ± 0.8
14.3 ± 0.1
29.6 ± 1.1
NT e
NT e
18a
18b
18c
18d
19a
19b
19c
19d
20a
20b
20c
NT e
NT e
NT e
NT e
NT e
NT e
NT e
NT e
7.5 ± 0.1

28.9 ± 0.8
12.6 ± 0.1
14.6 ± 0.1
22.4 ± 0.7
32.4 ± 1.0
43.1 ± 1.5
49.8 ± 1.7
NT e
7.8 ± 0.1
NT e
20d
21a
21b
21c
NT e
NT e
19.3 ± 0.3
NT e
21d
Curcumin
Resveratrol
Donepezil
NT e
25.0 ± 0.6
a For Inhibition of Aβ aggregation, the thioflavin-T fluorescence method was used.
b Inhibition of self-induced Aβ1-42 aggregation (25 μM) by tested inhibitors at 25 μM.
c
Inhibition of HuAChE-induced Aβ1-40 aggregation. The concentration of tested inhibitor and Aβ1-40
was 100 and 230 μM, respectively, and the Aβ1-40/AChE ratio was equal to 100/1.
d Data are presented as the mean ± SD of 3 independent experiments.
e NT = not tested.
In conclusion, a series of pterostilbene derivatives were designed, synthesized and evaluated as
novel dual inhibitors of cholinesterase with anti-β-amyloid aggregation and antioxidant properties for
the potential treatment of Alzheimer’s disease. Most of these compounds could effectively inhibit
AChE and BuChE. Particularly, compound 21d exhibited the best AChE inhibitory activity (IC50 =
0.06 μM) and good inhibition of BuChE (IC50 = 28.04 μM). Both the inhibition kinetic analysis and
molecular modeling study revealed that these compounds showed mixed-type inhibition, binding
simultaneously to the CAS and PAS of AChE. In addition to cholinesterase inhibitory activities, these
compounds showed different levels of antioxidant activity. With regard to inhibition of Aβ
aggregation, the inhibitory activities against self-induced Aβ aggregation and HuAChE-induced
aggregation of these new derivatives were unsatisfied. Taking into account the results of the
biological evaluation, further modifications will be designed in order to increase the potency on the
different targets. In summary, the results displayed in this paper can be a new starting point for
further development of multifunctional agents for Alzheimer’s disease.
Acknowledgments

This work was supported in part by the Chinese National Natural Science Foundation (20872099),
the Research Fund for the Doctoral Program of Higher Education (20110181110079) and the
National Science and Technology Major Project on “Key New Drug Creation and Manufacturing
Program”(2013ZX09301304-002).
Supplementary data
Supplementary data (the synthesis and characterization of the new compounds as well as the detailed
description of the biological evaluation assays) associated with this article can be found, in the online
version.
References and notes
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18. Synthesis of E-2-(4-(3,5-dimethoxystyryl)phenoxy-N-(6-(ethyl(2-methoxybenzyl)amino)hexyl)
acetamide (21d). A suspension of (1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride
(82 mg, 0.429 mmol) with compound 3 (90 mg, 0.286 mmol) in THF (2 mL) was stirred for 30
min at room temperature, then added the solution of the intermediate 17d (0.343 mmol) in THF (2
mL). The solvent was evaporated after stirring for 24 h. The residue was dissolved in
dichloromethane (40 mL), washed with water (20 mL×2) and saturated aqueous sodium chloride
(20 mL), dried over sodium sulfate, and filtered. After being concentrated, the crude product was
purified by column chromatography (elution with petroleum ether/acetone = 3:1) gave 21d as a
1
colorless oil; 54.1% yield; H NMR (400 MHz, CDCl3) δ 7.47 (d, 3H, J = 8.8 Hz, H-2’, H-6’,
Ar-H), 7.04 (d, 1H, J = 16.4 Hz, =CH-), 6.99-6.86 (m, 6H, 3 × Ar-H, =CH-, H-3’, H-5’), 6.65 (d,
2H, J = 2.0 Hz, H-2, H-6), 6.59 (br s, 1H, CONH), 6.39 (t, 1H, J = 2.0 Hz, H-4), 4.51 (s, 2H,
OCH2), 3.83 (s, 9H, 3 × OCH3), 3.83 (s, 2H, PhCH2), 3.33 (q, 2H, J = 6.8 Hz, NCH2), 2.52-2.67
(m, 4H, 2 × NCH2), 1.56-1.53 (m, 4H, 2 × CH2), 1.29-1.33 (m, 4H, 2 × CH2), 1.15 (br s, 3H, CH3);
13C NMR (100 MHz, CDCl3) δ 167.8, 160.8, 157.5, 156.7, 139.3, 131.2, 129.9, 128.1, 127.9,

127.4, 127.3, 120.1, 114.8, 110.0, 104.3, 99.6, 67.3, 55.2, 53.3, 51.2, 47.6, 38.9, 29.4, 27.1, 26.8,
26.7, 11.7; HRMS (ESI) calcd for C34H45N2O5 [M+H] + m/z: 561.3328, found 561.3329.
19. Zheng, H. L.; Youdim, M.B.H.; Fridkin, M. ACS Chem. Neurosci. 2010, 1, 743.
20. He, Y.; Yao, P. F.; Chen, S. B.; Huang, Z. H.; Huang, S. L.; Tan, J. H.; Li, D.; Gu, L. Q.; Huang,
Z.S. Eur. J. Med. Chem. 2013, 63, 303.
21. Dávalos, A.; Gómez-Cordovés, C.; Bartolomé, B. J. Agric. Food Chem. 2004, 52, 49.
22. Bartolini, M.; Bertucci, C.; Bolognesi, M. L.; Cavalli, A.; Melchiorre, C.; Andrisano, V.
ChemBioChem. 2007, 8, 2159.
23. Bolognesi, M. L.; Andrisano, V.; Bartolini, M.; Banzi, R.; Melchiorre, C. J. Med. Chem. 2005, 48
2.

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