Monoamine Oxidase Inhibitory Activity of Ferulic Acid Amides: Curcumin-Based Design and Synthesis

Article abstract of DOI:10.1002/ardp.201500317

Ferulic acid has structural similarity with curcumin which is being reported for its monoamine oxidase (MAO) inhibitory activity. Based on this similarity, we designed a series of ferulic acid amides 6a-m and tested for their inhibitory activity on human MAO (hMAO) isoforms. All the compounds were found to inhibit the hMAO isoforms either selectively or non-selectively. Nine compounds (6a, 6b, 6g-m) were found to inhibit hMAO-B selectively, whereas the other four (6c-f) were found to be non-selective. There is a gradual shift from hMAO-B selectivity (6a,b) to non-selectivity (6c-f) as there is an increase in chain length at the amino terminus. In case of compounds having an aromatic nucleus at the amino terminus, increasing the carbon number between N and the aromatic ring increases the potency as well as selectivity toward hMAO-B. Compounds 6f, 6j, and 6k were subjected to membrane permeability and metabolic stability studies by in vitro assay methods. They were found to have a better pharmacokinetic profile than curcumin, ferulic acid, and selegiline. In order to understand the structural features responsible for the potency and selectivity of 6k, we carried out a molecular docking simulation study.

Full text of DOI:10.1002/ardp.201500317

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Arch. Pharm. Chem. Life Sci. 2016, 349, 9–19
Archiv der Pharmazie
Full Paper
Monoamine Oxidase Inhibitory Activity of Ferulic Acid Amides:
Curcumin-Based Design and Synthesis
1
2
2
3
1
_
€
Vishnu N. Badavath , Ipek Baysal , Gulberk Uc¸ar *, Susanta K. Mondal , Barij N. Sinha ,
and Venkatesan Jayaprakash1
1
Department of Pharmaceutical Sciences and Technology, Birla Institute of Technology, Mesra, Ranchi,
Jharkhand, India
Department of Biochemistry, Faculty of Pharmacy, Hacettepe University, Sıhhiye, Ankara, Turkey
TCG Lifesciences Ltd, Block-EP&GP, BIPL, Tower-B, Saltlake, Sector-V, Kolkata, West Bengal, India
2
3
Ferulic acid has structural similarity with curcumin which is being reported for its monoamine oxidase
(MAO) inhibitory activity. Based on this similarity, we designed a series of ferulic acid amides 6a–m
and tested for their inhibitory activity on human MAO (hMAO) isoforms. All the compounds were
found to inhibit the hMAO isoforms either selectively or non-selectively. Nine compounds (6a, 6b,
6g–m) were found to inhibit hMAO-B selectively, whereas the other four (6c–f) were found to be
non-selective. There is a gradual shift from hMAO-B selectivity (6a,b) to non-selectivity (6c–f) as there
is an increase in chain length at the amino terminus. In case of compounds having an aromatic
nucleus at the amino terminus, increasing the carbon number between N and the aromatic ring
increases the potency as well as selectivity toward hMAO-B. Compounds 6f, 6j, and 6k were subjected
to membrane permeability and metabolic stability studies by in vitro assay methods. They were found
to have a better pharmacokinetic profile than curcumin, ferulic acid, and selegiline. In order to
understand the structural features responsible for the potency and selectivity of 6k, we carried out a
molecular docking simulation study.
Keywords: Ferulic acid amides / hMAO inhibitors / Metabolic stability studies / Molecular docking /
Permeability studies
Received: September 10, 2015; Revised: October 27, 2015; Accepted: October 30, 2015
DOI 10.1002/ardp.201500317
Additional supporting information may be found in the online version of this article at the publisher’s web-site.
:
depression (MAO-A selective) and neurodegenerative disor-
ders (MAO-B selective) [1]. Development of new generation
1 Introduction
The “cheese effect” was mainly due to the non-specific
inhibition of MAO-A in gut (peripheral) that warranted brain-
specific MAO inhibitors. Although brain specific inhibitor
reduces “cheese effect”, isoform selective inhibitors are to be
developed for their therapeutic potential in treatment of
of MAO inhibitors that specifically inhibits brain-MAO in
isoform selective and reversible mode has renewed the
research interest on MAO inhibitors [2, 3].
The current study explores the synthesis, hMAO-inhibitory
activity, and binding mode analysis of few ferulic acid
amides. The design strategy utilized the structural features
in curcumin,
a natural compound with proven hMAO
inhibitory activity [4–10]. Due to poor bioavailability [11]
Correspondence: Dr. Venkatesan Jayaprakash, Department of
Pharmaceutical Sciences and Technology, Birla Institute of
Technology, Mesra, Ranchi, Jharkhand 835 215, India.
E-mail: drvenkatesanj@gmail.com
ꢀ
€
Additional correspondence: Prof. Gulberk Uc¸ar,
Fax: þ91-6512275290
E-mail: gulberk@hacettepe.edu.tr
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and metabolic stability, curcumin has never been recognized
as a good antidepressant. In an effort to improve its activity,
permeability, and metabolic stability, we designed few
ferulic acid amide derivatives. They contain one half of
the curcumin, i.e., an aryl-a,b-unsaturated carbonyl portion
attached with amines (Fig. 1). They were tested for their
hMAO-inhibitory activity and also for their membrane
permeability and metabolic stability in an in vitro assay
system. Molecular docking studies were also carried out to
understand the interactions that are crucial for their potency
and selectivity.
compounds 6b–m. Formation of ferulic acid 2 (mp: 172°C;
Lit. 168–172°C) [12], acetylated ferulic acid 3 (mp: 200°C; Lit.
199–200°C) [13], and isoferulic acid 2a (mp: 130°C; Lit. 128–
129°C) [14] were confirmed by matching their mp with
reported values.
All the final compounds 6a–m were characterized by using
1H NMR and ESI-MS spectra. The Ar-OCH3 protons appear
between d: 3.70 and 3.84 ppm. The Ar-OH peak appeared
between d: 9.21 and 9.55 ppm. For all the compounds, the
–NH– protons peak appeared between d: 7.84 and 12.22 ppm.
The olefinic protons appeared between d: 6.39 and 6.83 ppm
with coupling constant between J ¼ 16.0 and 16.4 Hz, whereas
other olefinic protons appeared between d: 7.29 and 7.59 ppm
with coupling constants between J ¼ 15.6 and 16.0 Hz. ESI-MS
spectra of all the final compounds displayed the characteristic
molecular ion peak (M)þ or (Mþ1)þ. 13C NMR of compounds
Results and discussion
Chemistry
–
Compounds 6a–m were synthesized according to the reac-
tions outlined in Scheme 1. Ferulic (2) and isoferulic (2a) acids
were prepared by the reaction of appropriately substituted
aromatic aldehydes (1 and 1a) with malonic acid, in the
presence of pyridine and aniline in toluene. Protection of
hydroxyl group of 2 and 2a was achieved by reacting them
with acetic anhydride and DMAP (as a base) that provided
acetylated ferulic (3) and isoferulic (3a) acids, respectively.
Further, they were chlorinated using oxalyl chloride and a
catalytic amount of dimethylformamide in dry dichloro-
showed that amide carbonyl carbon peak (NHC O) between
–
d: 165.875 and 168.95 ppm; this peak indicates the formation
of amide bond. The Ar-OCH3 peak appears between d: 55.917
and 56.92 ppm.
Biochemistry
Compounds 6a–m were screened for their hMAO inhibitory
activity using recombinant hMAO-A and hMAO-B. MAO
inhibitory activity was determined by measuring the produc-
tion of H2O2 from p-tyramine, the common substrate for
both hMAO-A and hMAO-B, using the Amplex Red MAO assay
kit. The compounds and reference inhibitors did not react
directly with the Amplex Red reagent indicating that they
do not interfere with the measurements. The compounds
also were confirmed as they did not interact with resorufin
by treating the maximum concentration of compounds
with various concentrations of resorufin in order to detect
if the fluorescence signal is the same with or without our
compounds in the medium. No significant quenching of
resorufin was observed.
methane at 0–10°C to yield acid chlorides
4 and 4a,
respectively. Amidation of acid chlorides should be carried
out without any delay as they are highly unstable leading to
poor yields.
Reaction of 4 with 28% aqueous ammonium solution in
dry DCM provided 5a, which upon deprotection of acetyl
group with 28% sodium ethoxide in methanol provided 6a,
whereas reaction of 4 and 4a with appropriate amines in dry
DCM and triethylamine (as a base) provided 5b–m. Upon
deprotection of acetyl group with hydrazine monohydrate in
acetonitrile for 15–30 min at room temperature provided final
The results of hMAO-A and hMAO-B inhibition studies with
compounds 6a–m are presented in Table 1 together with their
selectivity indexes. Curcumin and ferulic acid were found to
inhibit hMAO-A selectively, whereas, the synthesized ferulic
acid amide derivatives inhibited hMAO-B selectively with SI
values between 1.58 and 17.73 (Table 1), and reversibly in a
competitive mode. Compounds 6c, 6d, 6e, and 6f were found
to be non-selective inhibitors. The most potent hMAO-B
inhibitor in this series was compound 6k which is carrying
a phenylethyl group at amino-terminal and 4-methoxy-3-
hydroxy phenyl (isovanilinyl) at benzylidene end. Compound
6k inhibited hMAO-B isoform potently and selectively with a
Ki value of 0.11 ꢁ 0.01 mM which is lower than the Ki value of
selegiline, a known selective MAO-B inhibitor (Ki value
of selegiline for hMAO-B was estimated as 0.13 ꢁ 0.09)
(Fig. 2). According to the selectivity index, compound 6k also
appeared as the most selective hMAO-B inhibitor (SI ¼ 17.73)
in this series.
All tested compounds inhibited the hMAO isoforms
reversibly. Table 2 presents the reversibility of hMAO-B
Figure 1. Design strategy adopted for designing hMAO
inhibitors (6a–m).
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Arch. Pharm. Chem. Life Sci. 2016, 349, 9–19
Design and Synthesis of Monoamine Oxidase Inhibitors
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Scheme 1. Reagents and conditions: (a) Malonic acid, pyridine, toluene, aniline, reflux, 4 h; (b) Ac2O, DMAP, 0–10°C; (c) dry DCM,
DMF, oxalyl chloride, 0°C, 2 h; (d) dry DCM, 28% aq. ammonium solution, 0°C; (e) methanol, 28% sodium methoxide in methanol
15 min, 0°C; (f) TEA, dry DCM, R-NH2, 0°C, 2 h; (g) 4% NH2NH2 ꢂ H2O in acetonitrile, 15–30 min, rt; (h) TEA, dry DCM, C6H5-CH2-CH2-NH2,
0°C, 2 h; (i) TEA, dry DCM, pyrrolidine, 0°C, 2 h; (j) TEA, dry DCM, morpholine, 0°C, 2 h.
inhibition with the novel compounds and selegiline, which
inhibits MAO-B by acting as a “suicide” substrate for the
enzyme combining irreversibly with the enzyme active site
and/or the enzyme’s essential FAD cofactor. MAO inhibitors
are classified as reversible or irreversible, according to their
interaction with the isoform. MAO irreversible inhibitors
previously have been used as clinical drugs. However, this type
of inhibition has been shown to induce significant toxic
effects, mainly provoked by the inhibition of the peripheral
MAO located in the gut, liver, and endothelium. On the other
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Table 1. Experimental Ki values corresponding to the inhibition of hMAO isoforms by compounds.
Ki value (mM)a)
Mol.
weight
Mol.
formula
Inhibition
type
Compound
hMAO-A
hMAO-B
SIb)
Reversibility
MAO selectivity
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
193.20
207.23
221.25
235.28
235.28
249.31
275.34
269.30
283.32
297.14
297.14
247.29
263.29
194.18
368.38
–
C
10H11NO3
79.50 ꢁ 2.80
28.55 ꢁ 1.87
22.85 ꢁ 1.05
21.30 ꢁ 1.87
15.75 ꢁ 1.22
10.22 ꢁ 0.78
1.55 ꢁ 0.12
4.55 ꢁ 1.90
3.22 ꢁ 0.14
3.20 ꢁ 0.21
1.95 ꢁ 0.10
5.30 ꢁ 0.33
5.04 ꢁ 0.40
7.55 ꢁ 0.49
0.71 ꢁ 0.04
6.32 ꢁ 1.33
0.013 ꢁ 0.009
21.90 ꢁ 9.13
10.36 ꢁ 0.95
23.56 ꢁ 1.10
15.66 ꢁ 1.07
15.00 ꢁ 1.09
10.98 ꢁ 0.85
0.59 ꢁ 0.03
1.39 ꢁ 0.20
0.78 ꢁ 0.20
0.55 ꢁ 0.03
0.11 ꢁ 0.01
2.13 ꢁ 0.17
3.19 ꢁ 0.25
24.00 ꢁ 1.98
21.50 ꢁ 1.19
0.13 ꢁ 0.09
1.35 ꢁ 0.20
3.63
2.76
0.97
1.36
1.05
0.94
2.63
3.27
4.13
5.82
17.73
2.49
1.58
0.315
0.033
48.62
0.01
Competitive
Competitive
Competitive
Competitive
Competitive
Competitive
Competitive
Competitive
Competitive
Competitive
Competitive
Competitive
Competitive
Competitive
Competitive
Suicide inhibitor
Competitive
Reversible
Reversible
Reversible
Reversible
Reversible
Reversible
Reversible
Reversible
Reversible
Reversible
Reversible
Reversible
Reversible
Reversible
Reversible
Irreversible
Reversible
B
B
C11H13NO3
C12H15NO3
C13H17NO3
Non-selective
Non-selective
Non-selective
Non-selective
C13H17NO3
C14H19NO3
C16H21NO3
C16H15NO3
C17H17NO3
C13H17NO3
C13H17NO3
C14H17NO3
C14H17NO4
C10H10O4
C21H20O6
–
B
B
B
B
B
B
B
A
A
B
A
6m
Ferulic acid
Curcumin
Selegiline
Moclobemide
–
–
b)
a) Each value represents the mean ꢁ SEM of three independent experiments. Selectivity index was calculated as Ki (MAO-A)/
Ki(MAO-B). Selectivity toward MAO-A increases as the corresponding SI decreases whereas selectivity toward MAO-B increases
as the corresponding SI increases.
hand, competitive reversible inhibitors have less influence in
the enzyme recovery after withdrawal as the ingested
tyramine is able to displace the inhibitor from the MAO
active site and be metabolized in the normal way by the
peripheral enzyme in the gut and liver [15]. Besides, the slow
and variable enzyme recovery following the withdrawal of
irreversible inhibitors is a disadvantage in clinical use, as the
turnover rate for MAO biosynthesis in the human brain seems
to require about 40 days. Thus, newly synthesized reversible
MAO-B inhibitors may have a value in this aspect.
The potent and selective inhibitors of hMAO-B (6j and 6k)
and the non-selective inhibitor 6f were further subjected to
in vitro permeability studies (Caco-2, MDCK-II) [16–20], and
metabolic stability studies [18, 21–23]. All the three were
Table 2. Reversibility of hMAO-B inhibition by compounds
6a–m.
hMAO-B inhibition (%)
Compounds
(0.50 mM)
After repeated
washing
Before washing
Selegiline
48.02 ꢁ 3.21
89.06 ꢁ 5.33
85.55 ꢁ 6.00
74.45 ꢁ 4.62
87.00 ꢁ 6.01
76.85 ꢁ 5.30
77.49 ꢁ 4.98
86.55 ꢁ 5.22
82.60 ꢁ 6.17
85.90 ꢁ 5.23
88.75 ꢁ 5.40
90.25 ꢁ 7.20
81.60 ꢁ 6.00
92.81 ꢁ 5.00
47.99 ꢁ 4.55
8.01 ꢁ 0.59
12.73 ꢁ 1.16
21.88 ꢁ 1.20
9.76 ꢁ 0.67
19.11 ꢁ 1.24
22.03 ꢁ 1.19
10.11 ꢁ 0.99
11.84 ꢁ 1.10
11.75 ꢁ 1.00
9.89 ꢁ 0.75
8.165 ꢁ0.54
12.05 ꢁ 1.10
8.05 ꢁ 0.78
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
Figure 2. Experimental and calculated Ki values corresponding
to the inhibition of hMAO-A and -B with compounds 6a–m; EXP
hMAO-A: experimental hMAO-A; EXP hMAO-B: experimental
hMAO-B; CALC hMAO-A: calculated hMAO-A; CALC hMAO-B:
calculated MAO-B.
6m
Each value represents the mean ꢁ SEM of three experiments.
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Table 3. In vitro Caco-2 permeability data.
Avg Papp ꢃ10ꢄ6 cm/s; n ¼ 2
Efflux ratio
(B > A/A > B)
Compound
A–B
B–A
Permeability rank
6f
6j
6k
7.0
19.1
6.1
4.1
0.0
14.3
51.2
19.3
6.3
2.05
2.7
3.16
1.55
NA
High
High
High
Low
Low
Ferulic acid
Curcumin
0.0
All permeability values are represented as ꢃ10ꢄ6 cm/s, permeability ranking based on following criteria (in hours): low, Papp A–
B < 5 ꢃ 10ꢄ6 cm/s; high, Papp A–B ꢅ 5 ꢃ 10ꢄ6 cm/s; NA, not applicable.
found to be highly permeable (Tables 3 and 4) and are falling
in Class-I of BCS (biopharmaceutics classification system), i.e.,
highly soluble and highly permeable, whereas curcumin
seems to fall in Class-IV, i.e., low soluble and low perme-
able [24]. The modification rendered seems to impart good
permeability characteristics to the designed compound.
Compound 6k was found to be the best among the three
evaluated; all the three fall in the same BCS class as selegiline.
Curcumin bioavailability and pharmacokinetic studies have
been carried out in rodents [25] and humans [26]. Due to poor
aqueous solubility, the absorption of curcumin is poor and
due to which it has a very poor bioavailability [11]. The half-
life (t1/2) of curcumin in phosphate-buffered saline (PBS) at pH
7.2 was less than 10 min due to extensive metabolism [27]. In
humans, moclobemide is rapidly and almost completely
absorbed and totally metabolized via the liver [28]; about
44% of the drug is lost due to the first pass effect through the
liver [29]. The elimination half-life is around 2 h [30]. Selegiline
has a low oral bioavailability, which increases to moderate
when ingested together with a high-fat meal, the molecule
beingfatsoluble[31]. Selegilineoralbioavailabilityisdrastically
increased in females taking oral contraceptives (10- to 20-fold)
[32]. This could lead to loss of MAO-B selectivity in favor of
an MAO-A selectivity, which in turn would make patients
susceptible to the usual risks of unselective MAOIs such as
tyramine-induced hypertensive [32].
parameters when compared with curcumin and ferulic acid
(Table 5). As they are reversible, they may also be devoid
of adverse effects related to the irreversible inhibition of
hMAO-B, as in the case of selegiline as discussed above.
Molecular docking simulation
Molecular docking simulation was carried out to understand
the interaction of synthesized compounds with hMAO
isoforms (Table 6). Compounds 6a–f were found to orient
in a similar fashion inside the active site of both hMAO-A
(except 6a) and hMAO-B. 4-Hydroxy-3-methoxy phenyl ring
(head) is accommodated in the aromatic cage of hMAO-B and
the amide portion (tail) in the narrow cavity between
aromatic cage and entrance, whereas in hMAO-A the tail
portion completely gets accommodated in Pocket 2 (lined by
GLY71, GLN74, ARG206, ILE207, PHE208, GLU216, TRP441)
while the head portion occupies the junction of all the three
pockets leaving Pocket 1 (aromatic cage: FAD, TYR407,
TYR447) and Pocket 3 (lined by ILE180, ILE335, LEU337,
MET350, PHE352) totally unoccupied. Compound 6a was
totally present in the junction of three pockets and seems
freely moving in-and-out, thus having reduced potency in
inhibiting hMAO-A. Analysis of component energy of 6a–f
with hMAO-A revealed a steady increase in VdW interaction
with an increase in carbon from C1–C4 in the side chain
(Table 7). Calculated Ki value for hMAO-A correlates well with
the experimental Ki value for hMAO-A. A similar trend was
observed in the case of hMAO-B for compounds 6a–f. For
Current research provided two potential and selective
inhibitors of hMAO-B that are having better pharmacokinetic
Table 4. In vitro MDCK-II permeability data.
Papp ꢃ10ꢄ6 cm/s
Compounds
AVG A > B
AVG B > A
Ratio
6f
6j
6k
13.59
24.79
5.68
5.38
0.00
14.61
23.41
2.67
3.07
0.00
1.1
0.9
0.5
0.6
NA
Ferulic acid
Curcumin
Cell growth media, MEM-alpha with MEM NEAA þ glutamine þ penicillin–streptomycin; test conc: 2 mM; incubation period,
150 min; apical/donor pH, 7.4 /7.4; NA, not applicable.
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Arch. Pharm. Chem. Life Sci. 2016, 349, 9–19
V. N. Badavath et al.
Archiv der Pharmazie
Table 5. In vitro human liver microsomal stability study
data.
on the other hand, orients reversibly and occupies the same
area within the active site. Analysis of component energies
revealed a steady increase in VdW interaction from com-
pound 6h to compound 6k. However, experimental result
suggested the decreased potency for compound 6j. We
observed number of clusters in docking log for this molecule
was higher with each having less than ten conformers. This
shows that the molecule has less favorable interaction within
the active site and this may be the reason why it is showing
decreased potency in in vitro analysis.
T-half
(min)
CLint, app
(mL/min/mg)
Compounds
6f
6j
6k
85.4
308.0
50.1
120.0
7.7
16.22
4.5
27.68
11.60
180.33
Ferulic acid
Curcumin
CLint, app range: 11.6–462.0 mL/min/mg, T-half range: 3–120 min,
LM conc: 0.5 mg/mL.
Experimental
Chemistry
General
compounds 6a–f, VdW interaction was found to determine
the selectivity toward hMAO-B.
In case of compounds 6h–k with hMAO-B, two molecules,
6h and 6i, were found to have the 4-hydroxy-3-methoxy-
phenyl ring in the aromatic cage (similar to 6a–f) whereas
compounds 6j,k were found to have the reversed orientation.
Analysis of component energy reveals a steady increase in
VdW interaction from compounds 6h–k (Table 7). This
correlates well with increase in potency as well as selectivity
toward hMAO-B. Comparing 6g with 6h, cyclohexyl replacing
phenyl, both are having similar orientation in the active site of
hMAO-B. Compound 6g was found to be potent among the
two as it was having a better VdW interaction compared with
6h. As compound 6k exhibited potent hMAO-B inhibitory
activity in in vitro assay, the binding pose of 6k with hMAO-B
is presented in Fig. 3. In the active site of hMAO-A, compounds
6h, 6j, and 6k have similar orientation. Aryl ring of these three
are completely accommodated in Pocket 2 and the tail portion
is kept at the junction of all the three pockets. This leaves
Pocket 1 and Pocket 3 completely unoccupied. Compound 6i,
All the chemicals and solvents for synthesis were purchased
from Aldrich. Unless otherwise mentioned, the solvents were
used without purification. Curcumin (98.0%) and trans-ferulic
acid (99%) were purchased from Sigma–Aldrich. Reactions
were monitored by TLC on precoated silica gel plates
(Kieselgel 60 F 254, Merck) and the spots were detected
under UV light. Purification was performed by column
chromatography using silica gel (particle size 100–200 mesh,
CDH). Melting points were determined using Optimelt
(Stanford Research Systems, Sunnyvale, CA, USA) by capillary
method and are uncorrected. 1H NMR spectra were recorded
on Varian 400 MHz instrument in DMSO-d6 as a solvent.
Chemical shifts are reported in parts per million (d) downfield
with respect to tetramethylsilane (TMS, d ¼ 0.0) as an internal
standard. Coupling constants (J) are given in hertz. Mass
spectra were recorded by the ESI-MS electro spray ionization
technique. hMAO-A and hMAO-B (both recombinant,
expressed in baculovirus-infected BTI insect cells), and other
Table 6. Calculated Ki values corresponding to the inhibition of hMAO isoforms.
Ki value (mM)
Compound
hMAO-A (2BXR)
hMAO-B (2BYB)
SIa)
MAO selectivity
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
97.33
23.66
17.77
18.58
15.90
7.73
1.09
2.64
2.64
2.01
1.27
6.73
7.41
4.15
40.10
15.65
19.57
11.49
12.58
6.67
0.61
1.38
0.88
0.64
0.27
3.16
5.91
20.33
2.43
1.51
0.91
1.61
1.26
1.16
1.79
1.91
3.00
3.14
4.70
2.13
1.25
0.20
0.03
B
B
Non-selective
B
B
B
B
B
B
B
B
B
B
A
A
6m
Ferulic acid
Curcumin
0.602
16.40
a) Selectivity index was calculated as Ki(MAO-A)/Ki(MAO-B).
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Arch. Pharm. Chem. Life Sci. 2016, 349, 9–19
Design and Synthesis of Monoamine Oxidase Inhibitors
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Table 7. Component energy of the docked compounds with hMAO-isoforms.
Enzyme
Compound
#ESTAT
#HB
#VDW
#DSOLV
hMAO-A (PDB: 2BXR)
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
6m
ꢄ0.6245
ꢄ0.2988
ꢄ0.3121
ꢄ0.3128
ꢄ0.2695
ꢄ0.1646
ꢄ0.2043
ꢄ0.4151
ꢄ0.147
ꢄ1.5697
ꢄ1.5476
ꢄ1.5553
ꢄ1.5339
ꢄ0.8523
ꢄ0.3201
ꢄ0.8183
ꢄ1.4069
ꢄ0.6375
ꢄ1.0888
ꢄ0.76
ꢄ7.7701
ꢄ8.1902
ꢄ8.5988
ꢄ9.0446
ꢄ9.2218
ꢄ9.6808
ꢄ9.2826
ꢄ9.7253
ꢄ11.1756
ꢄ10.6112
ꢄ10.976
ꢄ8.8426
ꢄ9.8403
-7.2073
2.2869
2.2629
2.2776
2.3011
2.2628
2.1638
2.0469
2.2329
2.4257
2.2866
2.1543
1.7106
1.9263
2.1745
2.4513
ꢄ0.1889
ꢄ0.1476
ꢄ0.2877
ꢄ0.3222
ꢄ2.0400
ꢄ0.2413
ꢄ1.2896
ꢄ1.5303
ꢄ1.4742
ꢄ0.8357
Ferulic acid
Curcumin
ꢄ12.5707
hMAO-B(PDB: 2BYB)
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
6m
ꢄ0.1354
ꢄ0.0964
ꢄ0.1329
ꢄ0.061
ꢄ1.1236
ꢄ8.0929
ꢄ8.5791
ꢄ8.2115
ꢄ9.4516
ꢄ9.0696
ꢄ9.9677
ꢄ10.543
ꢄ10.425
ꢄ11.19
1.8562
1.7074
1.4057
1.4864
1.4201
1.4032
1.2281
1.4802
1.6371
1.4766
1.4335
1.2959
1.6144
1.9533
2.4587
ꢄ0.799
ꢄ0.9617
ꢄ0.7257
ꢄ0.5413
ꢄ0.7196
ꢄ0.7204
ꢄ0.5877
ꢄ0.5933
ꢄ0.3217
ꢄ0.8049
ꢄ0.5128
ꢄ0.0005
ꢄ0.7503
ꢄ0.7946
ꢄ0.0633
ꢄ0.0601
ꢄ0.0475
ꢄ0.0716
ꢄ0.0635
ꢄ0.0382
ꢄ0.0945
ꢄ0.0646
0.0167
ꢄ11.414
ꢄ11.443
ꢄ9.2712
ꢄ9.6412
ꢄ7.9670
ꢄ12.2710
Ferulic acid
Curcumin
ꢄ1.0042
ꢄ0.2676
chemicals were purchased from Sigma–Aldrich (Munich,
Germany). The Amplex1-Red hMAO assay kit was purchased
from Cell Technology Inc. Mountain View, CA, USA. Molecular
docking studies were carried out on RHEL-5.0 operating
system installed on Dell Precision workstation with Intel Core
2 quad processor and 8 GB RAM, using AutoDock 4.2
molecular modeling software [33].
1H, J ¼ 16 Hz), 7.43 (s, 1H), 9.47 (s, 1H, –OH); ESI-MS (m/z):
Calcd. 193.20, Observed 193.60.
N-Methyl-3-(4-hydroxy-3-methoxyphenyl)-acrylamide (6b)
Yield: 48%; mp: 170°C (Lit. 169–170°C) [37]; 1H NMR (400 MHz,
DMSO-d6): d (ppm) 2.26 (s, 3H, –CH3), 3.82 (s, 3H, –OCH3),
6.59 (d, 1H, J ¼ 16.4 Hz), 7.12 (d, 1H, J ¼ 7.6 Hz), 7.25 (d, 1H,
J ¼ 8 Hz), 7.48 (s, 1H), 7.58 (d, 1H, J ¼ 16 Hz), 12.4 (s, 1H).
Synthesis of compounds 6a–m
Synthesis of ferulic and isoferulic acids (2 and 2a) was achieved
by following the procedures reported by Xia et al. [34]
Conversion of 2 and 2a to 3 and 3a was achieved by following
the reactions reported by Galey and Terranova [13]. Inter-
mediates 4 and 4a were derived from 3 and 3a by adopting
the procedures reported by Ergan et al. [35]. Compounds 5a–
m and 6a–m were synthesized according to the procedure
reported earlier [36].
N-Ethyl-3-(4-hydroxy-3-methoxyphenyl)-acrylamide (6c)
Yield: 70%; mp: 185°C (Lit. 187–188°C) [37]; 1H NMR
(400 MHz, DMSO-d6):
d (ppm) 1.08 (t, 3H, –CH3), 3.20
(q, 2H, –CH2–), 3.8 (s, 3H, –OCH3), 6.6 (d, 1H, J ¼ 16.4 Hz),
7.13 (m, 2H), 7.3 (s, 1H), 7.41 (d, 1H, J ¼ 16 Hz), 8.1 (t, 1H,
–NH–), 9.4 (s, 1H, –OH).
N-Propyl-3-(4-hydroxy-3-methoxyphenyl)-acrylamide (6d)
Yield: 68%; mp: 163°C (Lit. 165–166°C) [37]; 1H NMR (400 MHz,
DMSO-d6): d (ppm) 0.86 (t, 3H, –CH3), 1.44 (sixet, 2H), 3.1 (q,
2H), 3.79 (s, 3H, –OCH3), 6.43 (d, 1H, J ¼ 16 Hz), 6.78 (d, 1H,
J ¼ 12 Hz), 6.97 (d, 1H, J ¼ 4 Hz), 7.1 (s, 1H), 7.3 (d, 1H,
J ¼ 16 Hz), 7.95 (t, 1H, J ¼ 4 Hz, 8 Hz, –NH–), 9.46 (s, 1H, –OH).
3-(4-Hydroxy-3-methoxyphenyl)-acrylamide (6a)
Yield: 69%; mp: 153°C (Lit. 151–153°C) [36]; 1H NMR (400 MHz,
DMSO-d6): d (ppm) 3.7 (s, 3H, OCH3), 6.42 (d, 1H, J ¼ 12 Hz),
6.78 (d, 1H, J ¼ 8 Hz), 6.98 (d, 2H, J ¼ 8 Hz), 7.12 (s, 1H), 7.31 (d,
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Figure 3. Interaction of compound 6k with the hMAO-B (PDB: 2BYB) active site; H-bonds are shown as green dots.
N-Isopropyl-3-(4-hydroxy-3-methoxyphenyl)-acrylamide (6e)
Yield:70%;mp:178.5°C(Lit. 175–176°C)[37];1HNMR(400 MHz,
DMSO-d6): d (ppm)1.08 (d, 6H, (–CH3)2). 3.79 (s, 3H, –OCH3), 3.93
1H), 7.5 (d, 1H), 7.59 (d, 1H, J ¼ 16 Hz), 7.7 (t, 2H), 9.55 (s, 1H,
–OH), 10.23 (s, 1H, –NH–); ESI-MS (m/z): Calcd. 269.30,
Observed 269.60.
–
(m, 1H, CH–), 6.4 (d, 1H, J ¼ 16 Hz), 6.78 (d, 1H), 6.96 (m, 1H),
–
7.09 (s, 1H), 7.29 (d, 1H, J ¼ 16 Hz), 7.84 (d, 1H, J ¼ 8 Hz, –NH–),
9.42 (s,1H, OH); ESI-MS (m/z): Calcd. 235.28, Observed 235.70.
N-Benzyl-3-(4-hydroxy-3-methoxyphenyl)-acrylamide (6i)
Yield: 50%; mp: 155°C (Lit. 152–154°C) [37]; 1H NMR (400 MHz,
DMSO-d6): d (ppm) 3.79 (s,3H, –OCH3), 4.38 (d, 2H), 6.52 (d, 1H,
J ¼ 16Hz), 6.79 (d, 1H, J ¼ 8 Hz), 7 (d, 1H, J ¼ 8 Hz), 7.13 (s, 1H),
7.22–7.39 (m, 6H), 8.49 (t, 1H, –NH–), 9.49 (s, 1H, –OH); 13C NMR
(400 MHz, DMSO-d6): d (ppm) 42.713, 55.917, 111.207, 116.094,
119.198, 121.990, 126.809, 127.234, 128.759, 127.773, 139.831,
140.013, 148.740, 148.247, 165.875; ESI-MS (m/z): Calcd. 283.32,
Observed 283.70.
N-Butyl-3-(4-hydroxy-3-methoxyphenyl)-acrylamide (6f)
Yield: 65%; mp: 129°C (Lit. 126–128°C) [36]; 1H NMR (400 MHz,
DMSO-d6): d (ppm) 0.87 (t, 3H, –CH3), 1.30 (pentate, 2H,
–CH2–), 1.42 (m, 2H, –CH2–), 3.15 (q, 2H, –CH2–), 3.79 (s, 3H,
–OCH3), 6.43 (d, 1H, J ¼ 16 Hz), 6.78 (d, 1H, J ¼ 8), 6.97 (m, 1H),
7.1 (s, 1H), 7.3 (d, 1H, J ¼ 16 Hz), 7.93 (t, 1H, J ¼ 8 Hz, 12 Hz,
–NH–), 9.42 (s, 1H, –OH); ESI-MS (m/z): Calcd. 249.31, Observed
249.70.
N-Phenethyl-3-(4-hydroxy-3-methoxyphenyl)-acrylamide
(6j)
N-Cyclohexyl-3-(4-hydroxy-3-methoxyphenyl)-acrylamide
(6g)
Yield: 65%; mp: 155°C; 1H NMR (400 MHz, DMSO-d6): d (ppm)
2.73(t, 2H, –CH2–), 3.37(t, 2H, –CH2–), 3.76 (s, 3H, Ar-OCH3), 6.39
(d, 1H, J ¼ 16 Hz), 6.75(d, 1H, J ¼ 8 Hz), 6.94 (d, 1H, J ¼ 8 Hz), 7.07
(s, 1H), 7.14–7.20 (m, 3H), 7.24–7.30 (m, 3H), 8.01 (t, 1H, –NH–),
9.40 (s, 1H, –OH); 13C NMR (400 MHz, DMSO-d6): d (ppm) 35.648,
39.298, 55.924, 111.124, 116.064, 119.357, 121.960, 126.528,
126.817, 129.078, 128.782, 139.383, 139.960, 148.672, 148.232,
165.799; ESI-MS (m/z): Calcd. 297.14, Observed 297.70.
Yield: 90%; mp: 160°C; 1H NMR (400 MHz, DMSO-d6): d (ppm)
1.17(m,3H),1.27(m,2H),1.56(m, 1H),1.68(m, 2H),1.77(m, 2H),
3.63 (m, 1H), 3.79 (s, 3H, Ar-OCH3), 6.43 (d, 1H, J ¼ 15.6 Hz), 6.78
(d, 1H, J ¼ 7.6 Hz), 6.96 (d, 1H, J ¼ 8 Hz), 7.10 (s, 1H), 7.29 (d, 1H,
J ¼ 15.6 Hz), 7.84(d, 1H, J ¼ 8 Hz, –NH–), 9.42(s,1H, –OH);ESI-MS
(m/z): Calcd. 275.34, Observed 276 (Mþ1)þ.
N-Phenyl-3-(4-hydroxy-3-methoxyphenyl)-acrylamide (6h)
Yield: 40%; mp: 151°C (Lit. 152–154°C) [38]; 1H NMR (400 MHz,
DMSO-d6): d (ppm) 3.84 (s, 3H, –OCH3), 6.05 (d, 1H), 6.83 (d, 1H,
J ¼ 16 Hz), 7.06 (t, 1H), 7.22–7.14 (m, 1H), 7.33 (m, 1H), 7.37 (s,
N-Phenethyl-3-(3-hydroxy-4-methoxyphenyl)-acrylamide
(6k)
Yield: 45%; mp: 110°C; 1H NMR (400 MHz, DMSO-d6): d (ppm)
2.78 (t, 2H, –CH2–), 3.8 (m, 5H, –OCH3 and merged –CH2–),
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Archiv der Pharmazie
6.39 (d, 1H, J ¼ 16 Hz), 6.5 (d, 1H, J ¼ 16 Hz), 6.96 (dd, 2H),
7.16–7.38 (m, 5H), 7.45 (d, 1H), 8.11 (t, 1H, –NH–), 9.21
(s, 1H, –OH); 13C NMR (100 MHz, DMSO-d6): d (ppm) 20.86,
35.67, 56.43, 113.46, 119.96, 120.70, 121.29, 126.57,
127.26, 128.32, 129.04, 139.16, 139.95, 139.97, 147.14,
152.31, 165.47, 168.98; ESI-MS (m/z): Calcd. 297.35, Observed
298 (Mþ1)þ.
experimental conditions, this background activity was
negligible.
Control experiments were carried out by replacing the
compound and reference inhibitors. The possible capacity of
compounds to quench the fluorescence generated in the
reaction mixture was determined by adding these compounds
to solutions containing only the Amplex Red reagent or
resorufin in a sodium phosphate buffer. The new compounds
and reference inhibitors themselves did not react directly
with Amplex1 Red reagent or did not affect the fluorescence
generated in the reaction mixture. Newly synthesized
compounds did not cause any inhibition on the activity of
HRP in the test medium.
3-(4-Hydroxy-3-methoxyphenyl)-1-(pyrrolidin-1-yl)-prop-
2-en-1-one (6l)
Yield: 75%; mp: 175°C (Lit. 170–172) [36]; H NMR (400 MHz,
1
DMSO-d6): d (ppm) 1.825 (m, 2H, –CH2–), 1.91 (m, 2H, –CH2–),
2.51 (t, 2H, –CH2–, merged with DMSO solvent peak), 3.65
(t, 2H, –CH2–), 3.83 (s, 3H, –OCH3), 6.59 (d, 1H, J ¼ 16 Hz), 6.99
(d, 1H, J ¼ 16 Hz), 7.13–7.10 (m, 1H, Ar-H), 7.27 (m, 1H, Ar-H),
7.48 (m, 1H, Ar-H), 7.58 (d, 1H, Ar-H).
Kinetic experiments
The synthesized compounds were dissolved in DMSO with a
maximum concentration of 1% (w/v) and used in the concentra-
tion range of 0.10–50 mM. Kinetic data for the interaction of
the enzymes with the compounds were analyzed with the
Microsoft Excel package program. The specificity index was
expressed as SI ¼ Ki(hMAO-A)/Ki(hMAO-B). Protein was de-
termined according to Bradford [40] using bovine serum
albumin as the standard.
3-(4-Hydroxy-3-methoxyphenyl)-1-morpholinoprop-2-en-
1-one (6m)
Yield: 80%; mp: 165°C (167–169°C) [39]; 1H NMR (400 MHz,
DMSO-d6): d (ppm) 3.62 (m, 8H), 3.84 (s, 3H, –OCH3), 6.59 (d,
1H, J ¼ 16 Hz), 7.10–7.13 (m, 1H), 7.23–7.30 (m, 1H), 7.50 (s,
1H), 7.59 (d, 1H, J ¼ 16 Hz), 9.5 (s, 1H, –OH); ESI-MS (m/z): Calcd.
263.29, Observed 264 (Mþ1)þ.
Reversibility experiments
Biochemistry
Reversibility was assessed using a centrifugation-ultrafiltration
method previously reported [41]. Recombinant enzymes
were incubated with the compounds or standard inhibitors
in 0.05 M sodium phosphate buffer, pH 7.4, for 1 h at 37°C.
An aliquot was stored at 4°C for hMAO activity measure-
ment. Another sample was placed in an Ultrafree-0.5
centrifuge tube (Nalgene1, NY, USA) with a 30-kDa Biomax
membrane (Millipore Corp., Bedford, MA, USA) and
centrifuged at 9000g for 20 min at 4°C. The enzyme
retained in the 30-kDa membrane was resuspended in
the buffer at 4°C and centrifuged, and this process was
repeated once more. The enzyme retained in the mem-
brane was resuspended in buffer and used for hMAO
determination. Control experiments were performed by
replacing the test drugs with appropriate vehicle dilutions.
The corresponding values of percent hMAO inhibition were
separately calculated for the samples with and without
repeated washing.
Determination of hMAO-A and hMAO-B activities
The activities of hMAO-A and hMAO-B were determined
using p-tyramine (0.05–1.00 mM) as a common substrate.
Specific activity was calculated as 147.16 ꢁ 8.55 pmol/mg/min
(n ¼ 3) for hMAO-A and 129.30 ꢁ 9.12 pmol/mg/min (n ¼ 3) for
hMAO-B. The interactions of the synthesized compounds with
hMAO isoforms were determined by a fluorimetric method
described and modified previously [14, 15].
Briefly, study medium contained 0.1 mL of sodium
phosphate buffer (0.05 M, pH 7.4), various concentrations
of the newly synthesized compounds or reference com-
pounds, and adequate amounts of recombinant hMAO-A
or hMAO-B. This mixture was incubated for 15 min at
37°C in 96-well microplates, placed in the dark fluorimeter
chamber. After this incubation period, reaction was
started by adding 200 mM Amplex Red reagent, 1 U/mL
horseradish peroxidase (HRP), and p-tyramine (concentra-
tion range 0.05–1.00 mM). The production of H2O2 cata-
lyzed by hMAO isoforms was detected using Amplex1-Red
reagent; a non-fluorescent probe that reacts with H2O2
in the presence of HRP to produce the fluorescent
product resorufin was quantified at 37°C in a multi-
detection microplate fluorescence reader based on the
fluorescence generated with excitation at 545 nm, and
emission at 590 nm, over a 15 min period, in which the
fluorescence increased linearly. The specific fluorescence
emission was calculated after subtraction of the back-
ground activity, which was determined from wells con-
taining all components except the enzymes, which were
replaced by a sodium phosphate buffer solution. In our
In vitro permeability and metabolic stability studies
In vitro permeability studies using Caco-2 and MDCK-II cell
lines and metabolic stability studies using human liver
microsomal enzymes were carried out as per the procedure
reported by Mondal et al. [23, 42].
Molecular docking simulation
In order to understand the interaction at the molecular level,
compounds 6a–m were docked with X-ray crystal structure
of hMAO-A (PDB: 2BXR) and hMAO-B (PDB: 2BYB) using
AutoDock 4.2. Docking protocol employed was reported
already by our group [43–45]. For docking, grid parameter
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V. N. Badavath et al.
Archiv der Pharmazie
file (.gpf) and docking parameter files (.dpf) were written
[17] L. Kellard, M. Engelstein, J. Assoc. Lab. Autom. 2007, 12,
104–109.
[18] P. V. Kaplita, H. Hu, L. Liu, T. M. Farrell, H. Grbic,
D. M. Spero, JALA – J. Assoc. Lab. Autom. 2005, 10,
140–148.
[19] P. V. Balimane, Y.-H. Han, S. Chong, AAPS J. 2006, 8,
E1–E13.
[20] P. V. Balimane, S. Chong, Drug Discov. Today 2005, 10,
335–343.
using MGL Tools-1.5.6. Receptor grids were generated using
̊
60 ꢃ 60 ꢃ 60 grid points in xyz with a grid spacing of 0.375 A.
Grid box was centered on N5 atom of FAD. Map types were
generated using Autogrid 4.2. Docking was carried out
with following parameters: number of runs: 50; population
size: 150; number of evaluations: 2500000; and number of
generations: 27000, using Autodock 4.2. Analysis of docking
results was done using MGL Tools-1.5.6. Top scoring molecule
in the largest cluster was analyzed for its interaction with
the protein.
[21] L. Di, E. H. Kerns, Y. Hong, T. A. Kleintop, O. J. McConnell,
D. M. Huryn, J. Biomol. Screen. Off. J. Soc. Biomol.
Screen. 2003, 8, 453–462.
Authors acknowledge Birla Institute of Technology for
providing Institute fellowship to the first author. Authors
acknowledge Dr. Reddy’s Institute of Life Science, Hyderabad,
India for spectral characterization of compounds.
[22] K. M. Jenkins, R. Angeles, M. T. Quintos, R. Xu,
D. B. Kassel, R. A. Rourick, J. Pharm. Biomed. Anal.
2004, 34, 989–1004.
[23] S. K. Mondal, U. K. Mazumdar, N. B. Mondal, S. Banerjee,
J. Biol. Sci. 2008, 6, 1110–1114.
The authors have declared no conflicts of interest.
[24] B. Wahlang, Y. B. Pawar, A. K. Bansal, Eur. J. Pharm.
Biopharm. 2011, 77, 275–282.
[25] K. Y. Yang, L. C. Lin, T. Y. Tseng, S. C. Wang, T. H. Tsai, J.
Chromatogr. B Anal. Technol. Biomed. Life Sci. 2007,
853, 183–189.
References
[1] M. B. H. Youdim, M. Weinstock, Neuro Toxicol. 2004, 25,
243–250.
[2] G. Lavian, J. P. Finberg, M. B. Youdim, Clin. Neuro-
pharmacol. 1993, 16(Suppl 2), S1–S7.
[3] M. Da Prada, H. H. Keller, R. Kettler, Psychiatr. Prax. 1989,
16(Suppl 1), 18–24.
[4] Y. Xu, B. S. Ku, H. Y. Yao, Y. H. Lin, X. Ma, Y. H. Zhang,
X. Li, J. Pharmacol. Biochem. Behav. 2005, 82, 200–
206.
[5] S. K. Kulkarni, M. K. Bhutani, M. Bishnoi, Psychophar-
macology 2008, 201, 435–442.
[6] A. Rajeswari, M. Sabesan, Inflammopharmacology 2008,
16, 96–99.
[7] L. Zhang, J. Luo, M. Zhang, W. Yao, X. Ma, S. Y. Yu, Int. J.
Neuropsychopharmacol. 2014, 17, 793–806.
[8] R. Wang, Y. Xu, H. L. Wu, Y. B. Li, Y. H. Li, J. B. Guo, X. Li,
Eur. J. Pharmacol. 2008, 578, 43–50.
[26] R. A. Sharma, S. A. Euden, S. L. Platton, D. N. Cooke,
A. Shafayat, H. R. Hewitt, T. H. Marczylo, B. Morgan,
D. Hemingway, S. M. Plummer, M. Pirmohamed, A. J.
Gescher, W. P. Steward, Clin. Cancer Res. 2004, 10,
6847–6854.
[27] Y. J. Wang, M. H. Pan, A. L. Cheng, L. I. Lin, Y. S. Ho,
C. Y. Hsieh, J. K. Lin, J. Pharm. Biomed. Anal. 1997, 15,
1867–1876.
[28] M. Mayersohn, T. W. Guentert, Clin. Pharmacokinet.
1995, 29, 292–332.
[29] J. Raaflaub, P. Haefelfinger, K. H. Trautmann, Arznei-
mittelforschung 1984, 34, 80–82.
[30] N. P. V. Nair, S. K. Ahmed, N. M. K. Ng Ying Kin, J.
Psychiatry Neurosci. 1993, 18, 214–225.
[31] J. S. Barrett, P. Szego, S. Rohatagi, R. J. Morales, K. E.
DeWitt, G. Rajewski, Ireland J. Pharm. Res. 1996, 13,
1535–1540.
[9] Y. Xu, B. S. Ku, H. Y. Yao, Y. H. Lin, X. Ma, Y. H. Zhang,
X. Li, Eur. J. Pharmacol. 2005, 518, 40–46.
[10] S. Carradori, M. D. Ascenzio, P. Chimenti, D. Secci,
A. Bolasco, Mol. Divers. 2014, 18, 219–243.
[11] H. H. Tonnesen, M. Masson, T. Loftsson, Int. J. Pharm.
2002, 244, 127–135.
[12] M. L. Salum, C. J. Robles, R. Erra-Balsells, Org. Lett. 2010,
12, 4808–4811.
[13] B. Galey Jean, E. Terranova, U.S. Patent 5536500, July 16,
1996.
[32] K.Laine,M.Anttila,A.Helminen,H.Karnani,R.Huupponen,
Br. J. Clin. Pharmacol. 1999, 47, 249–254.
[33] G. M. Morris, R. Huey, W. Lindstrom, M. F. Sanner,
R. K. Belew, D. S. Goodsell, A. J. Olson, J. Comput. Chem.
2009, 30, 2785–2791.
[34] C. N. Xia, H. B. Li, F. Liu, W. X. Hu, Bioorg. Med. Chem.
Lett. 2008, 18, 6553–6557.
[35] B. C. Ergun, T. Coban, F. K. Onurdag, E. Banoglu, Arch.
Pharm. Res. 2011, 34, 1251–1261.
[36] E. Nomura, A. Kashiwada, A. Hosoda, K. Nakamura,
H. Morishita, T. Tsuno, H. Taniguchi, Bioorg. Med. Chem.
2003, 11, 3807–3813.
[14] H. R. Arthur, W. H. Hui, C. N. Ma, J. Chem. Soc. 1956,
632–635.
[15] M. B. H. Youdim, Y. S. Bakhle, Br. J. Pharmacol. 2006, 147,
S287–S296.
[16] E. H. Kerns, L. Di, S. Petusky, M. Farris, R. Ley, P. Jupp, J.
Pharm. Sci. 2004, 93, 1440–1453.
[37] Y.-Y. Lai, L.-J. Huang, H.-C. Lin, T. Wu, C.-M. Teng,
S.-C. Kuo, Chin. Pharm. J. 2002, 54, 41–52.
[38] K. Freudenberg, R. Dillenburg, Chem. Ber. 1951, 84,
67–70.
ß 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com
18

RCHH HARM
A P
Arch. Pharm. Chem. Life Sci. 2016, 349, 9–19
Design and Synthesis of Monoamine Oxidase Inhibitors
Archiv der Pharmazie
€
€
[39] E. A. Correa, E. D. Hogestatt, O. Sterner, F. Echeverri,
P. M. Zygmunt, Bioorg. Med. Chem. 2010, 18, 3299–
3306.
[43] B.VishnuNayak,S.Ciftci-Yabanoglu,S.S.Jadav,M.Jagrat,
B. N. Sinha, G. Ucar, V. Jayaprakash, Eur. J. Med. Chem.
2013, 69, 762–767.
[40] M. M. Bradford, Anal. Biochem. 1976, 72, 248–254.
[41] F. Chimenti, S. Carradori, D. Secci, A. Bolasco, B. Bizzarri,
[44] A. Sahoo, S. Yabanoglu, B. N. Sinha, G. Ucar, A. Basu,
V. Jayaprakash, Bioorg. Med. Chem. Lett. 2010, 20,
132–136.
ꢀ~
P. Chimenti, A. Granese, M. Yanez, F. Orallo, Eur. J. Med.
Chem. 2010, 45, 800–804.
[42] S. K. Mondal, N. B. Mondal, S. Banerjee, U. K. Mazumder,
Indian J. Pharmacol. 2009, 41, 176–181.
[45] M. Jagrat, J. Behera, S. Yabanoglu, A. Ercan, G. Ucar,
B. N. Sinha, V. Sankaran, A. Basu, V. Jayaprakash, Bioorg.
Med. Chem. Lett. 2011, 21, 4296–4300.
ß 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com
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