Multifunctional quinoxaline-hydrazone derivatives with acetylcholinesterase and monoamine oxidases inhibitory activities as potential agents against Alzheimer’s disease

Article abstract of DOI:10.1007/s00044-020-02541-4

Multitarget molecules are considered as an effective way for the treatment of AD, instead of the classic one-drug-one-target strategy because of the multifactorial nature of AD. A variety of studies indicate that several enzymes inhibitors can be useful in the treatment of AD, including acetylcholinesterase (AchE), butyrylcholinesterase (BuChE) and monoamine oxidase (MAO). Various substituted quinoxaline-hydrazone derivatives were synthesized, and their activity in vitro were investigated, including AChE/BuChE inhibitory activity and MAOA/B inhibitory activity. Based on the experimental results, compound 5l exhibited good inhibitory potency on both AchE (IC₅₀ = 0.028 ± 0.001 μM) and monoamine oxidase B (IC50 = 0.046 ± 0.002 μM). Molecular modeling studies showed that 5l could bind to the active site of AChE and MAO-B. Taken together, these results suggested that compound 5l might be a potential multifunctional agent for the treatment of AD.

Full text of DOI:10.1007/s00044-020-02541-4

MEDICINAL
CHEMISTRY
RESEARCH
Medicinal Chemistry Research
https://doi.org/10.1007/s00044-020-02541-4
ORIGINAL RESEARCH
Multifunctional quinoxaline-hydrazone derivatives with
acetylcholinesterase and monoamine oxidases inhibitory activities
as potential agents against Alzheimer’s disease
Ulviye Acar Çevik1,2 Derya Osmaniye
1,2 ●
Begüm Nurpelin Sağlik
1,2 ●
Betül Kaya Çavuşoğlu
1,2 ●
Serkan Levent
1,2 ●
●
3 ●
3 ●
1 ●
1,2 ●
1 ●
Abdullah Burak Karaduman Sinem Ilgin Ahmet Çağrı Karaburun Yusuf Özkay
Zafer Asım Kaplancikli
Gülhan Turan1
Received: 19 January 2020 / Accepted: 31 March 2020
©
Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
Multitarget molecules are considered as an effective way for the treatment of AD, instead of the classic one-drug-one-
target strategy because of the multifactorial nature of AD. A variety of studies indicate that several enzymes inhibitors
can be useful in the treatment of AD, including acetylcholinesterase (AchE), butyrylcholinesterase (BuChE) and
monoamine oxidase (MAO). Various substituted quinoxaline-hydrazone derivatives were synthesized, and their activity
in vitro were investigated, including AChE/BuChE inhibitory activity and MAOA/B inhibitory activity. Based on the
experimental results, compound 5l exhibited good inhibitory potency on both AchE (IC50 = 0.028 ± 0.001 μM) and
monoamine oxidase B (IC50 = 0.046 ± 0.002 μM). Molecular modeling studies showed that 5l could bind to the active
site of AChE and MAO-B. Taken together, these results suggested that compound 5l might be a potential multifunctional
agent for the treatment of AD.
●
●
●
●
Keywords Quinoxaline-hydrazone Acetylcholinesterase Butyrylcholinesterase Monoamine oxidases Enzyme inhibition
Introduction
treatment might provide improved symptomatic efficacy
and eliminate the use of several drugs with potentially
different degrees of bioavailability, pharmacokinetics, and
metabolism (Youdim and Buccafusco 2005; Li et al. 2017).
The ethology of AD is not completely known, but low
levels of acetylcholine (ACh), β-amyloid deposits, dysho-
meostasis of biometals and oxidative stress have been
thought to play significant roles in the pathogenesis of the
disease (Scarpini et al. 2003). The cholinergic hypothesis
suggests that the inhibition of acetylcholinesterase (AchE)
increase the levels of ACh and treat some symptoms of AD
patients (Xiao et al. 2017). Therefore, AchE inhibitors such
as donepezil, rivastigmine, and galantamine are the clinical
first-line drugs in the therapy of AD. Though these drugs
provide improvement in memory and cognitive function,
fail to achieve a comprehensive and satisfactory therapeutic
solution (Takeda et al. 2006; Raina et al. 2008).
The potential targets have been comprehensively studied for
several years in the therapy of psychiatric and neurode-
generative diseases with complex and variable underlying
mechanisms. Current therapeutic strategies have favored
drugs that act on a single molecular target while new
pharmacological approaches aim candidate compounds
designed to interact with multiple neural and biochemical
targets. Since the multifactorial nature of Alzheimer’s dis-
ease (AD), the administration of a multi-targeted drug in the
*
Ulviye Acar Çevik
uacar@anadolu.edu.tr
1
2
3
Department of Pharmaceutical Chemistry, Faculty of Pharmacy,
Anadolu Universty, Eskişehir, Turkey
Monoamine oxidase (MAO) is responsible for catalysing
the oxidative deamination of a variety of biogenic and
xenobiotic amines and considered to be also an important
target in the treatment of AD (Youdim et al. 2006). The
inhibition of MAO prevents the formation of neurotoxic
Doping and Narcotic Compounds Analysis Laboratory, Faculty of
Pharmacy, Anadolu Universty, Eskişehir, Turkey
Department of Pharmaceutical Toxicology, Faculty of Pharmacy,
Anadolu Universty, Eskişehir, Turkey

Medicinal Chemistry Research
products, such as hydrogen peroxide and aldehydes, which
are known to be related with neurodegenerative diseases,
thus MAO inhibitors protect the nerve cells from oxidative
damage and neurotoxicity (Xu et al. 2018) MAOs are flavin
adenine dinucleotide (FAD)-containing enzymes and have
two functional isozymic forms, namely, MAO-A and
MAO-B, based on their substrate and inhibitor specificities
Material and methods
Chemistry
All chemicals used in the syntheses were purchased either
from Merck Chemicals (Merck KGaA, Darmstadt, Germany)
or Sigma-Aldrich Chemicals (Sigma-Aldrich Corp., St. Louis,
MO, USA). The reactions and the purities of the compounds
were observed by thin layer chromatography (TLC) on silica
gel 60 F254aluminum sheets obtained from Merck (Darm-
stadt, Germany). Melting points of the synthesized com-
pounds were recorded by MP90 digital melting point
apparatus (Mettler Toledo, OH, USA) and were presented as
(
Edmondson et al. 2004). MAO-A inhibitors are used as
clinical antidepressants and antianxiety agents, while MAO-
B inhibitors are employed in the therapy of neurodegen-
erative disorders such as AD and Parkinson’s diseases (PD)
(
Wouters 1998; Youdim et al. 2006). Selegiline, an irre-
versible and selective MAO-B inhibitor, has been reported
as an effective drug in individuals with AD due to its
neuroprotective property (Bar-Am et al. 2010).
1
13
uncorrected. H NMR and C NMR spectra were recorded
by a Bruker 300 MHz and 75 MHz digital FT-NMR spec-
trometer (Bruker Bioscience, Billerica, MA, USA) in DMSO-
d6, respectively. In the NMR spectra splitting patterns were
designated as follows: s: singlet; d: doublet; t: triplet; m:
multiplet. Coupling constants (J) were reported as Hertz. LC-
MS-MS studies were performed on a Schimadzu, 8040
LCMSMS spectrophotometer (Shimadzu, Tokyo, Japan).
The strategy targeting the simultaneously inhibition of
MAO and AChE represents one of the promising
approaches due to the multifactorial pathogenesis of AD.
Lately, ladostigil was designed via the combination of
pharmacophores of rivastigmine (an AChE inhibitor) and
rasagiline (an MAO inhibitor) to give a novel dual AChE
and MAO-B inhibitor for the therapy of AD and approved
for Phase II clinical trials by the FDA (Fig. 1) (Sterling
et al. 2002). Attempts to design a molecule with anti-
MAO and anti-AChE activities have previously been
reported (Sterling et al. 2002; Sang et al. 2017a, 2017b).
Quinoxalines has become an important construction
motif for the development of new drugs. In particular,
quinoxaline derivatives have multitude of pharmacologi-
cal actions including MAO and AChE inhibitory proper-
ties (Khattab et al. 2015, 2010; Huang et al. 2011). On the
other hand, hydrazone derivatives have been also docu-
mented as promising scaffold to design anti-MAO and
anti-AChE agents (Evranos-Aksöz et al. 2015; Tripathi
and Ayyannan 2016; D’Ascenzio et al. 2015; Dias Viegas
et al. 2018; Karaman et al. 2016). In an attempt to develop
novel MAO and AChE inhibitory agents, in present study,
we combined hydrazone moiety and quinoxaline ring to
synthesize multifunctional agents for the potential treat-
ment of AD. The mode of inhibition and interaction
modes of the most active inhibitors were explored via
kinetic and reversibility studies along with docking
studies.
Microwave-assisted synthesis of quinoxaline-2(1H)-one (1)
1,2-Phenylenediamine (5.4 g, 0.05 mol) and ethyl glyox-
alate (6.2 mL, 0.06 mol) were reacted in a vial (30 mL) of
microwave synthesis reactor (Anton-Paar Monowave 300)
in ethanol. The reaction was maintained under the condi-
tions of 200 °C and 25 bar for 15 min. After this time, the
reaction mixture was cooled and the solvent was evapo-
rated. The residue was washed with water, dried and
recrystallized from ethanol (Yan-Yan 2010).
Synthesis of 2-chloroquinoxaline (2)
Quinoxaline-2(1H)-one (1) (5.6 g, 0.038 mol) was refluxed
for 3 h in POCl (100 mL). After cooling, excessive of
3
POCl was evaporated and crude product was held for
3
further reaction without recrystallization (Becker 2008).
Microwave-assisted synthesis of quinoxaline-2-hydrazine (3)
2-Chloroquinoxaline (2) (4.7 g, 0029 mol) were reacted
with hydrazine hydrate (99%) (3.5 mL) in tetrahydrofuran
Fig. 1 Chemical structures of
rivastigmine, rasagiline and
ladostigil

Medicinal Chemistry Research
(
(
THF) (10 mL) at 170 °C and 10 bar for 15 min in a vial
30 mL) of microwave synthesis reactor (Anton-Paar
3.25 (4H, br s, piperidine-H), 6.97 (2H, d, J = 8.7 Hz, 1,4-
disubstituted benzene), 7.42–7.48 (1H, m, quinoxaline),
7.58 (2H, d, J = 8.7 Hz, 1,4-disubstituted benzene),
7.64–7.66 (2H, m, quinoxaline), 7.89 (1H, d, J = 8.1 Hz,
quinoxaline), 8.03 (1H, s, quinoxaline), 9.03 (1H, s,
N=CH), 11.43 (1H, s, NH). C NMR (75 MHz, DMSO-d6,
ppm) δ 24.39, 25.48, 49.08, 115.34, 124.51, 125.12,
Monowave 300). In the end of reaction, the solvent and
excessive of hydrazine hydrate were evaporated, the residue
was washed with water, dried and recrystallized from
ethanol (Chen et al. 2008).
1
3
Synthesis of benzaldehyde derivatives (4a–4m)
126.43, 128.17, 129.21, 130.67, 136.96, 138.14, 141.63,
+
143.06, 150.83, 152.42. HRMS (m/z): [2M+2H] calcd for
Appropriate seconder amines (5 mmol) and 4-
fluorobenzaldehyde (5 mmol, 0.62 g) were refluxed in
dimethylformamide (10 mL) with the presence of potassium
carbonate (6 mmol, 0.83 g). After TLC screening, the mix-
ture was poured into ice water and filtered. The products
were recrystallized from ethanol (Osmaniye et al. 2019).
C H N : 166.5971; found: 166.5966.
20 21 5
2-[2-(4-(2-Methylpiperidin-1-yl)benzylidene)hydrazineyl]
quinoxaline (5c) Yield 72%, m.p. 225.9–227.4 °C. IR ν
max
−
1
(cm ): 3199 (N–H) 3043 (aromatic C–H), 2935 (aliphatic
1
C–H), 1606–1490 (C=N, C=C), 1307–1109 (C–N). H
NMR (300 Mhz, DMSO-d , ppm) δ 1.01 (3H, d, J =
6
General synthesis of N-(4-substitutedbenzylidene)-N’-
quinoxalin-2-yl-hydrazine derivatives (5a–5m)
6.7 Hz, CH ), 1.57–1.76 (6H, m, piperidine-H), 2.89 (1H, t,
3
J = 12.2 Hz, piperidine-H), 3.47 (1H, d, J = 12.7 Hz,
piperidine-H), 4.18–4.21 (1H, m, piperidine-H), 6.93 (2H,
d, J = 8.9 Hz, 1,4-disubstituted benzene), 7.42–7.48 (1H,
m, quinoxaline), 7.57 (2H, d, J = 8.9 Hz, 1,4-disubstituted
benzene), 7.64–7.65 (2H, m, quinoxaline), 7.88 (1H, d, J =
8.1 Hz, quinoxaline), 8.02 (1H, s, quinoxaline), 9.03 (1H, s,
Quinoxaline-2-hydrazine (3) (0.32 g, 2 mmol) and appro-
priate benzaldehyde derivatives (4a–4m) (2 mmol) in etha-
nol (25 mL) were refluxed for 1 h with catalytic amount of
acetic acid. The precipitate was filtered, dried and recrys-
tallized from ethanol (Kaya Çavuşoğlu et al. 2018a).
1
3
N=CH), 11.42 (1H, s, NH). C NMR (75 MHz, DMSO-d6,
ppm) δ 13.35 (CH ), 18.74, 25.86, 30.90, 42.04, 49.32,
115.22, 124.03, 125.09, 126.42, 128.24, 129.20, 130.66,
3
2
-[2-(4-(Pyrrolidin-1-yl)benzylidene)hydrazineyl]quinoxa-
−
1
line (5a) Yield 79%, m.p. 276.2–278.0 °C. IR νmax (cm ):
3
1
136.96, 138.13, 141.65, 143.13, 150.84, 151.74. HRMS (m/z):
+
685 (N–H) 3035 (aromatic C–H), 2972 (aliphatic C–H),
[M+H] calcd for C H N : 346.2026; found: 346.2016.
2
1
23
5
1
610–1427 (C=N, C=C), 1350–1020 (C–N). H NMR
(
300 Mhz, DMSO-d , ppm) δ 1.96 (4H, br.s, pyrrolidin-H),
2-[2-(4-(3-Methylpiperidin-1-yl)benzylidene)hydrazineyl]
6
3
.27 (4H, br s, pyrrolidine-H), 6.57 (2H, d, J = 8.6 Hz, 1,4-
disubstituted benzene), 7.40–7.47 (1H, m, quinoxaline),
.55 (2H, d, J = 8.6 Hz, aromatic-H, 1,4-disubstituted
quinoxaline (5d) Yield 69%, m.p. 218.2–219.7 °C. IR ν
(cm ): 3211 (N–H) 3055 (aromatic C–H), 2951 (aliphatic
C–H), 1608–1492 (C=N, C=C), 1246–1132 (C–N). H
max
−
1
1
7
benzene), 7.63 (2H, d, J = 3.7 Hz, quinoxaline), 7.87 (1H,
d, J = 8.2 Hz, quinoxaline), 8.01 (1H, s, quinoxaline), 9.02
NMR (300 Mhz, DMSO-d , ppm) δ 0.92 (3H, d, J =
6
6.7 Hz, CH ), 1.04–1.13 (1H, m, piperidine-H), 1.50–1.79
3
13
(
1H, s, N=CH), 11.35 (1H, s, NH). C NMR (75 MHz,
(4H, m, piperidine-H), 2.39 (1H, t, J = 11.2 Hz, piperidine-
H), 2.69 (1H, t, J = 12.2 Hz, piperidine-H), 3.68–3.75 (2H,
m, piperidine-H), 6.96 (2H, d, J = 8.9 Hz, 1,4-disubstituted
benzene), 7.42–7.47 (1H, m, quinoxaline), 7.57 (2H, d, J =
8.8 Hz, 1,4-disubstituted benzene), 7.63–7.65 (2H, m, qui-
noxaline), 7.88 (1H, d, J = 8.3 Hz, quinoxaline), 8.02 (1H,
s, quinoxaline), 9.03 (1H, s, N=CH), 11.42 (1H, s, NH).
DMSO-d , ppm) δ 25.43 (pyrolidine-CH ), 47.70 (pyr-
6
2
olidine-CH2), 112.08 (1,4-disubstituted benzene-CH),
21.90 (quinoxaline-CH), 124.96 (1,4-disubstituted ben-
1
zene-C), 126.35 (quinoxaline-CH), 128.42 (quinoxaline-
CH), 129.19 (1,4-disubstituted benzene-CH), 130.64 (qui-
noxaline-CH), 136.99 (quinoxaline-CH), 138.05 (quinoxa-
line-C), 141.71 (quinoxaline-C), 143.72 (CH=N), 148.86
1
3
C NMR (75 MHz, DMSO-d , ppm) δ 19.68 (CH ), 24.92,
6
3
(
1,4-disubstituted benzene-C), 150.84 (quinoxaline-C).
30.56, 32.98, 48.46, 55.95, 115.26, 124.37, 125.11, 126.42,
+
HRMS (m/z): [M+H] calcd for C H N : 318.1713;
found: 318.1699.
128.20, 129.20, 130.66, 136.96, 138.14, 141.64, 143.08,
19
19
5
+
150.83, 152.19. HRMS (m/z): [M+H] calcd for C H N :
21
23
5
346.2026; found: 346.2011.
2
-[2-(4-(Piperidin-1-yl)benzylidene)hydrazineyl]quinoxaline
−
1
(
5b) Yield 75%, m.p. 252.1–254.2 °C. IR νmax (cm ):
2-[2-(4-(4-Methylpiperidin-1-yl)benzylidene)hydrazineyl]
3
1
176 (N–H) 3057 (aromatic C–H), 2935 (aliphatic C–H),
606–1450 (C=N, C=C), 1307–1111 (C–N). H NMR
quinoxaline (5e) Yield 65%, m.p. 232.5–234.2 °C. IR ν
(cm ): 3201 (N–H) 3089 (aromatic C–H), 2920 (aliphatic
C–H), 1606–1492 (C=N, C=C), 1307–1093 (C–N). H
max
1
−1
1
(
300 Mhz, DMSO-d , ppm) δ 1.59 (6H, s, piperidine-H),
6

Medicinal Chemistry Research
NMR (300 Mhz, DMSO-d , ppm) δ 0.93 (3H, d, J =
2-[2-(4-(Morpholine-4-yl)benzylidene)hydrazineyl]quinoxa-
line (5h) Yield 67%, m.p. 258.3–260.1 °C. IR νmax (cm ):
6
−
1
6
.4 Hz, CH ), 1.13–1.26 (2H, m, piperidine-H), 1.49–1.57
3
(
1H, m, piperidine-H), 1.69 (2H, d, J = 12.6 Hz, piperidine-
H), 2.73 (1H, t, J = 12.4 Hz, piperidine-H), 3.79 (2H, d, J =
2.8 Hz, piperidine-H), 6.96 (2H, d, J = 8.9 Hz, 1,4-dis-
ubstituted benzene), 7.42–7.47 (1H, m, quinoxaline), 7.57
2H, d, J = 9.0 Hz, 1,4-disubstituted benzene), 7.64–7.65
2H, m, quinoxaline), 7.88 (1H, d, J = 8.1 Hz, quinoxaline),
3207 (N–H) 3084 (aromatic C–H), 2993 (aliphatic C–H),
1
1612–1492 (C=N, C=C), 1309–1111 (C–N, C–O).
H
1
NMR (300 Mhz, DMSO-d , ppm) δ 3.20 (4H, t, J = 4.7 Hz,
6
morpholine-H), 3.75 (4H, t, J = 5.0 Hz, morpholine-H),
7.00 (2H, d, J = 9.0 Hz, 1,4-disubstituted benzene),
7.43–7.48 (1H, m, quinoxaline), 7.60–7.65 (2H, m, qui-
noxaline), 7.89 (1H, d, J = 8.3 Hz, 1,4-disubstituted benzene),
8.05 (1H, s, quinoxaline), 9.04 (1H, s, N=CH), 11.47 (1H, s,
(
(
8
.02 (1H, s, quinoxaline), 9.03 (1H, s, N=CH), 11.42 (1H, s,
1
3
NH). C NMR (75 MHz, DMSO-d , ppm) δ 22.23 (CH ),
6
3
13
3
1
1
3
0.71, 33.74, 48.40, 115.34, 124.48, 125.12, 126.43,
NH). C NMR (75 MHz, DMSO-d , ppm) δ 48.12, 66.45,
6
28.18, 129.20, 130.67, 136.96, 138.14, 141.63, 143.06,
115.02, 125.20, 125.61, 126.46, 128.11, 129.21, 130.69,
+
50.83, 152.19. HRMS (m/z): [M+H] calcd for C H N :
136.96, 138.18, 141.60, 142.84, 150.83, 152.14. HRMS (m/z):
21
23
5
+
46.2026; found: 346.2011.
[M+H] calcd for C H N O: 334.1662; found: 334.1646.
1
9 19 5
2
-[2-(4-(3,5-Dimethylpiperidin-1-yl)benzylidene)hydrazi-
2-[2-(4-(4-Methylpiperazin-1-yl)benzylidene)hydrazineyl]
neyl]quinoxaline (5f) Yield 66%, m.p. 191.1–193.6 °C. IR
νmax (cm ): 3201 (N–H) 3055 (aromatic C–H), 2989 (ali-
quinoxaline (5i) Yield 60%, m.p. 221.9–224.3 °C. IR ν
(cm ): 3207 (N–H) 3057 (aromatic C–H), 2926 (aliphatic
C–H), 1577–1481 (C=N, C=C), 1246–1132 (C–N). H
max
−
1
−1
1
phatic C–H), 1614–1456 (C=N, C=C), 1342–1105 (C–N).
1
H NMR (300 Mhz, DMSO-d , ppm) δ 0.66–0.78 (1H, m,
NMR (300 Mhz, DMSO-d , ppm) δ 2.22 (3H, s, CH ), 2.45
6
6
3
piperidine-H), 0.93 (6H, d, J = 6.5 Hz, CH ), 1.61–1.78
(4H, t, J = 4.9 Hz, piperazine-H), 3.23 (4H, t, J = 4.7 Hz,
piperazine-H), 6.98 (2H, d, J = 8.9 Hz, 1,4-disubstituted
benzene), 7.42–7.48 (1H, m, quinoxaline), 7.59 (2H, d, J =
8.9 Hz, 1,4-disubstituted benzene), 7.64–7.65 (2H, m, qui-
noxaline), 7.88 (1H, d, J = 8.1 Hz, quinoxaline), 8.03 (1H, s,
3
(
3H, m, piperidine-H), 2.25 (2H, t, J = 11.7 Hz, piperidine-
H), 3.77 (2H, d, J = 12.3 Hz, piperidine-H), 6.96 (2H, d, J =
.7 Hz, 1,4-disubstituted benzene), 7.42–7.47 (1H, m, qui-
8
noxaline), 7.56 (2H, d, J = 8.8 Hz, 1,4-disubstituted ben-
zene), 7.63–7.65 (2H, m, quinoxaline), 7.88 (1H, d, J =
13
quinoxaline), 9.04 (1H, s, N=CH), 11.45 (1H, s, NH).
C
8
.1 Hz, quinoxaline), 8.02 (1H, s, quinoxaline), 9.03 (1H, s,
NMR (75 MHz, DMSO-d , ppm) δ 46.21 (CH ), 47.74, 54.91,
6
3
13
N=CH), 11.42 (1H, s, NH). C NMR (75 MHz, DMSO-d6,
ppm) δ 19.60 (CH ), 27.23, 30.50, 42.29, 55.45, 115.18,
115.18, 125.14, 125.17, 126.43, 128.11, 129.21, 130.68,
136.97, 138.16, 141.60, 142.94, 150.82, 152.04. HRMS (m/z):
3
+
1
24.25, 125.11, 126.42, 128.24, 129.20, 130.66, 136.95,
[M+H] calcd for C H N : 347.1979; found: 347.1973.
2
0 22 6
1
38.14, 141.64, 143.10, 150.83, 151.83. HRMS (m/z):
+
[
M+H] calcd for C H25l5: 360.2183; found: 360.2167.
2-[2-(4-(4-Ethylpiperazin-1-yl)benzylidene)hydrazineyl]qui-
22
noxaline (5j) Yield 69%, m.p. 212.0–213.9 °C. IR ν
(cm ): 3167 (N–H) 3057 (aromatic C–H), 2967 (aliphatic
C–H), 1612–1489 (C=N, C=C), 1244–1128 (C–N). H
max
−
1
2
-[2-(4-(4-Benzylpiperidin-1-yl)benzylidene)hydrazineyl]
1
quinoxaline (5g) Yield 78%, m.p. 248.9–251.1 °C. IR ν
max
−
1
(
cm ): 3213 (N–H) 3082 (aromatic C–H), 2967 (aliphatic
NMR (300 Mhz, DMSO-d , ppm) δ 1.02 (3H, t, J = 7.1 Hz,
6
1
C–H), 1612–1492 (C=N, C=C), 1307–1099 (C–N). H
CH ), 2.35 (2H, q, J = 7.2 Hz, CH ), 2.46–2.49 (4H, m,
3
2
NMR (300 Mhz, DMSO-d , ppm) δ 1.21–1.32 (2H, m,
piperidine-H), 1.63–1.74 (3H, m, piperidine-H), 2.55 (2H,
piperazine-H), 3.21 (4H, t, J = 4.9 Hz, piperazine-H), 6.97
(2H, d, J = 8.7 Hz, 1,4-disubstituted benzene), 7.42–7.47
(1H, m, quinoxaline), 7.59 (2H, d, J = 8.7 Hz, 1,4-dis-
ubstituted benzene), 7.64–7.65 (2H, m, quinoxaline), 7.88
(1H, d, J = 8.1 Hz, quinoxaline), 8.03 (1H, s, quinoxaline),
6
d, J = 7.0 Hz, CH ), 2.70 (2H, t, J = 12.4 Hz, piperidine-H),
2
3
8
.80 (2H, d, J = 12.7 Hz, piperidine-H), 6.96 (2H, d, J =
.8 Hz, 1,4-disubstituted benzene), 7.19–7.21 (3H, m,
1
3
Monosubstituted benzene), 7.27–7.32 (2H, m, Mono-
substituted benzene), 7.42–7.47 (1H, m, quinoxaline), 7.56
9.04 (1H, s, N=CH), 11.46 (1H, s, NH). C NMR
(75 MHz, DMSO-d , ppm) δ 12.44 (CH ), 47.86 (CH ),
6
3
2
(
(
8
2H, d, J = 8.9 Hz, 1,4-disubstituted benzene), 7.64–7.65
2H, m, quinoxaline), 7.88 (1H, d, J = 8.2 Hz, quinoxaline),
52.08, 52.67, 115.12, 125.11, 125.16, 126.43, 128.10,
129.21, 130.67, 136.96, 138.16, 141.61, 142.94, 150.83,
152.07. HRMS (m/z): [M+H]+ calcd for C H N :
.02 (1H, s, quinoxaline), 9.02 (1H, s, N=CH), 11.42 (1H,
21
24
6
1
3
s, NH). C NMR (75 MHz, DMSO-d , ppm) δ 31.58,
361.2135; found: 361.2122.
6
3
1
1
7.77, 42.70, 48.33, 115.36, 124.52, 125.13, 126.26,
26.43, 128.17, 128.62, 129.21, 129.49, 130.67, 136.95,
2-[2-[4-(4-(4-Methoxyphenyl)piperazin-1-yl)benzylidene]
hydrazineyl]quinoxaline (5k) Yield 65%, m.p.
260.8–263.1 °C. IR νmax (cm ): 3196 (N–H) 3062 (aro-
matic C–H), 2956 (aliphatic C–H), 1606–1510 (C=N,
38.14, 140.65, 141.63, 143.03, 150.83, 152.14. HRMS (m/
+
−1
z): [M+H] calcd for C H N : 422.2339; found:
27
27
5
4
22.2321.

Medicinal Chemistry Research
C=C), 1296–1020 (C–N, C–O). 1H NMR (300 Mhz,
Activity studies
DMSO-d , ppm) δ 3.16 (4H, t, J = 5.0 Hz, piperazine-H),
6
3
.38 (4H, t, J = 4.1 Hz, piperazine-H), 3.69 (3H, s, OCH3),
.84 (2H, d, J = 9.0 Hz, 1,4-disubstituted benzene), 6.96
Monoamine oxidase activity assay
6
(
2H, d, J = 9.0 Hz, 1,4-disubstituted benzene), 7.05 (2H, d,
The inhibitory activities of the obtained compounds against
MAO-A and MAO-B enzymes were evaluated in black
bottom 96-well plates by method as defined in our previous
studies (Can et al. 2017, 2018). All pipetting procedures in
the enzyme inhibition assay were carried out using a robotic
system, Biotek Precision XS (Winooski, VT, USA). Sele-
giline and chlorgiline were used as reference drugs. The
IC50 values were calculated from a dose-response curve
gained by plotting the percentage inhibition versus the log
concentration with the use of GraphPad PRISM software
J = 8.9 Hz, 1,4-disubstituted benzene), 7.43–7.48 (1H, m,
quinoxaline), 7.61–7.66 (4H, m, 1,4-disubstituted benzene,
quinoxaline), 7.89 (1H, d, J = 8.1 Hz, quinoxaline), 8.05
(
1H, s, quinoxaline), 9.05 (1H, s, N=CH), 11.47 (1H, s,
1
3
NH). C NMR (75 MHz, DMSO-d , ppm) δ 48.09, 50.15,
6
5
1
1
5.65, 114.77, 115.46, 118.22, 125.20, 125.45, 126.46,
28.16, 129.22, 130.70, 136.98, 138.18, 141.61, 142.88,
45.70, 150.83, 151.97, 153.66. HRMS (m/z): [M+H]+
calcd for C H N O: 439.2241; found: 439.2234.
2
6
26
6
(version 5.0, GraphPad Software Inc., La Jolla, CA, USA).
2
-[2-[4-(4-(2-(N,N-Dimethylamino)ethyl)piperazin-1-yl)ben-
The results are showed as the mean ± standard deviation.
The inhibitory capacity of the obtained compounds on
AChE and BChE biological activities was assessed using a
modified Ellman’s spectrometric method, as described in
our previous studies (Acar Çevik et al. 2019; Özkay et al.
2016; Sağlık et al. 2016; Hussein et al. 2018; Tok et al.
2019). Donepezil was used as a reference drug. All pipet-
ting procedures in the enzyme inhibition assay were carried
out via a robotics system, Biotek Precision XS (Winooski,
VT, USA). A BioTek-Synergy H1 microplate reader
(Winooski, VT, USA) was used to carry out measurements
of percent inhibition at 412 nm, and the IC50 values of the
selected compounds were performed as previously
described.
zylidene]hydrazineyl] quinoxaline (5l): Yield 64%, m.p.
1
matic C–H), 2954 (aliphatic C–H), 1608–1492 (C=N,
C=C), 1305–1107 (C–N). H NMR (300 Mhz, DMSO-d ,
ppm) δ 2.14 (6H, s, 2CH ), 2.32–2.44 (4H, m, CH -CH ),
2
CH ), 6.96 (2H, d, J = 8.9 Hz, 1,4-disubstituted benzene),
7
−
1
90.3–192.2 °C. IR νmax (cm ): 3201 (N–H) 3053 (aro-
1
6
3
2
2
.51–2.53 (4H, m, piperazine-H), 3.20 (4H, t, J = 4.2 Hz,
3
.42–7.47 (1H, m, quinoxaline), 7.58 (2H, d, J = 8.6 Hz,
1,4-disubstituted benzene), 7.64–7.65 (2H, m, quinoxa-
1
line), 7.88 (1H, d, J = 8.3 Hz, quinoxaline), 8.03 (1H, s,
quinoxaline), 9.04 (1H, s, N=CH), 11.46 (1H, s, NH).
NMR (75 MHz, DMSO-d , ppm) δ 46.01, 47.88, 53.40,
1
3
C
6
5
6.30, 57.11, 115.12, 125.13, 126.43, 128.10, 129.21,
1
30.67, 136.96, 138.16, 141.61, 142.93, 150.83, 152.05.
+
HRMS (m/z): [M+H] calcd for C H N : 404.2557;
Molecular docking studies
23
29
7
found: 404.2541.
Molecular docking studies were performed to discover the
binding modes of compound 5 l to active sites of AChE and
MAO-B enzymes, respectively. The crystal structures of
AChE (PDB code: 4EY7) (Cheung et al. 2012) and MAO-B
(PDB code: 2V5Z) (Claudia et al. 2007) were retrieved
from the Protein Data Bank server (www.pdb.org). Docking
procedures were followed as reported previously (Tok et al.
2019; Sağlık et al. 2016; Kaya Çavuşoğlu et al.
2018a, 2018b; Can et al. 2017; Sağlık et al. 2019).
2
-[2-[4-(4-(3-(N,N-Dimethylamino)propyl)piperazin-1-yl)
benzylidene]hydrazineyl] quinoxaline (5m): Yield 72%,
m.p. 194.8–196.9 °C. IR νmax (cm ): 3201 (N–H) 3053
−
1
(
(
aromatic C–H), 2941 (aliphatic C–H), 1610–1492
C=N, C=C), 1228–1107 (C–N). H NMR (300 Mhz,
1
DMSO-d , ppm) δ 1.57 (2H, p, J = 7.1 Hz, CH -CH -
CH ), 2.11 (6H, s, 2CH ), 2.21 (2H, t, J = 7.5 Hz, CH ),
2
6
2
2
2
3
2
.32 (2H, t, J = 7.5 Hz, CH ), 2.47 (4H, t, J = 4.9 Hz,
2
piperazine-H), 3.22 (4H, t, J = 4.9 Hz, piperazine-H),
6
7
1
.97 (2H, d, J = 8.9 Hz, 1,4-disubstituted benzene),
.43–7.48 (1H, m, quinoxaline), 7.59 (2H, d, J = 8.7 Hz,
,4-disubstituted benzene), 7.64–7.65 (2H, m, quinoxa-
Results and discussion
line), 7.88 (1H, d, J = 8.1 Hz, quinoxaline), 8.03 (1H, s,
quinoxaline), 9.04 (1H, s, N=CH), 11.47 (1H, s, NH).
Chemistry
1
3
C NMR (75 MHz, DMSO-d , ppm) δ 24.99, 45.71,
Target compounds (5a–5m) were efficiently synthesized
according to the protocol outlined in Scheme 1. The che-
mical structure of the compounds is organized in Table 1.
Following the microwave supported synthesis of quinoxa-
line-2(1H)-one (1), 2-chloroquinoxaline (2) was synthesized
6
4
1
1
7.89, 53.14, 56.50, 57.78, 115.14, 125.12, 125.16,
26.43, 128.11, 129.21, 130.68, 136.97, 138.15, 141.61,
+
42.95, 150.83, 152.07. HRMS (m/z): [M+H] calcd for
C H N : 418.2714; found: 418.2695.
2
4
31
7

Medicinal Chemistry Research
Scheme 1 The reaction
sequence for the synthesis of the
compounds (5a–5m). Reagents
and conditions: (i) EtOH, MW,
2
00 °C, 25 bar, 15 min; (ii)
POCl3, reflux, 3 h; (iii)
NH2NH2.H2O, THF, MW,
1
0 bar, 170 °C, 15 min; (iv)
DMF, K2CO3, reflux, 24 h; (v)
CH3COOH, EtOH, reflux, 1 h
Table 1 The synthesized compounds (5a–5m)
amount of acetic acid gave the designed compounds (5a–
5m).
Compound
Seconder amine
The IR, H NMR, 13C NMR and MS spectral data of the
compounds provided evidence for the formation of the
expected structures. In the IR spectra of all compounds,
1
5
5
5
5
5
5
5
5
5
5
5
5
5
a
b
c
d
e
f
pyrolidine
piperidine
2-metilpiperidine
−1
Broad peaks at 3150–3370 cm indicated N–H stretching
3-metilpiperidine
vibrations of hydrazine. The C=N and C=C stretching
4-metilpiperidine
vibration bands were observed in the expected region:
−
1
3,5-dimetilpiperidine
4-benzylpiperidine
morpholine
1
630–1667 cm . In 1H NMR spectrum of compounds,
g
h
i
protons belonging to pyrrolidine, piperidine, piperazine, and
morpholine rings resonated at 0.66–4.21 ppm. The azo-
methine (N=CH) protons of hydrazone were observed at
9.02–9.05 ppm as a singlet. The protons belonging to the
phenyl and quinoxaline rings and the other aliphatic groups
were observed with the expected chemical shift and integral
values. The NH protons were appeared at 11.42–11.47 ppm
4-metilpiperazine
j
4-ethylpiperazine
k
l
4-(4-methoxyphenyl)piperazine
4-(dimethylaminoethyl)piperazine
4-(dimethylaminopropyl)piperazine
m
1
3
as singlet peak. In C NMR spectra of compounds, aro-
matic carbons were resonated a large area between
114.77–153.66 ppm. The mass spectra of compounds
via the reaction of compound 1 and phosphoryl chloride.
The intermediate compound 2 was reacted hydrazine
hydrate to gain quinoxaline-2-hydrazine (3). In order to
obtain several benzaldehyde derivatives (4a–4m), appro-
priate seconder amines and 4-fluorophenylbenzaldehyde
were refluxed in dimethylformamide. Finally, the treatment
of quinoxaline-2-hydrazine (3) with the synthesized ben-
zaldehyde derivatives (4a–4m) in ethanol with catalytic
showed [M + 1] peaks, in agreement with their molecular
formula.
Monoamine oxidase activity assay
The synthesized compounds were evaluated for their
hMAO-A and hMAO-B inhibitory activities. In addition,
selegiline and moclobemide were evaluated as reference

Medicinal Chemistry Research
Table 2 % Inhibition of compounds 5a–5m, moclobemide and selegiline against hMAO-A and hMAO-B
Comp.
hMAO-A inhibition %
hMAO-B inhibition %
10−3
1
0−
3
M
10−4
M
M
10−4
M
5
5
5
5
5
5
5
a
b
c
d
e
f
77.798 ± 1.252
72.068 ± 1.329
82.554 ± 1.096
85.454 ± 1.136
83.816 ± 1.018
82.443 ± 1.114
49.619 ± 0.992
94.125 ± 2.760
81.170 ± 1.007
60.153 ± 1.066
58.168 ± 0.952
53.893 ± 0.962
54.504 ± 0.976
48.050 ± 0.823
–
49.020 ± 0.833
48.460 ± 0.604
23.359 ± 0.708
48.016 ± 0.539
37.405 ± 0.647
47.786 ± 0.788
36.800 ± 0.851
82.143 ± 2.694
39.847 ± 0.631
20.695 ± 0.475
22.137 ± 0.455
34.952 ± 0.671
29.313 ± 0.411
26.209 ± 0.529
–
98.338 ± 1.467
98.826 ± 1.244
94.216 ± 1.538
52.528 ± 0.875
93.138 ± 1.148
94.516 ± 1.007
75.150 ± 0.877
–
94.226 ± 1.108
96.240 ± 1.066
39.846 ± 0.632
48.586 ± 0.611
44.473 ± 0.975
89.326 ± 1.106
41.902 ± 0.319
–
g
Moclobemide
5
5
5
5
5
5
h
76.864 ± 1.028
83.676 ± 1.244
69.152 ± 0.955
66.581 ± 0.819
99.531 ± 1.116
87.295 ± 1.259
98.912 ± 1.281
45.501 ± 0.871
46.015 ± 0.905
38.303 ± 0.417
20.280 ± 0.332
95.631 ± 1.085
48.806 ± 0.511
96.882 ± 1.313
i
j
k
l
m
Selegiline
Table 3 IC50 values of compounds 5a, 5b, 5f, 5l and selegiline against
MAO-B
compounds. The results, expressed as % inhibition and IC50
values are summarized in Tables 2 and 3. In the first step,
the synthesized compounds were prepared at concentrations
Compound
hMAO-B IC50 (µM)
−
3
−4
of 10 ve 10 M and inhibition values of hMAO A and
hMAO B were calculated. The compounds showing >50%
inhibition were selected for the second stage according to
the first step results. In this second step, inhibition values
and IC values of the selected compounds at concentrations
5
5
5
5
a
b
f
0.098 ± 0.003
0.075 ± 0.002
0.113 ± 0.004
0.046 ± 0.002
0.039 ± 0.001
l
5
5
0
−
−9
Selegiline
of 10 –10 M were calculated. Considering Table 2, only
compound 5l passed the second step hMAO-B enzyme
inhibition assay.
Generally, the compounds showed higher activity against
hMAO-B than hMAO-A. In particular compound 5l has a
significant activity value against hMAO-B. Compound 5l
efficient inhibition against hMAO-B with IC50 value of
the 10− M concentration. Then, the IC50 values of the
4
−
3
−9
active compounds were determined using 10 –10
M
concentrations against AChE along with the reference drug
donepezil (Table 5). The IC50 values of the compound 5l
were calculated as 0.028 ± 0.001 µM for AChE. Compared
with the reference drug, it is clear that it shows similar
activity with donepezil.
0
.046 ± 0.002 μM. Compared with the reference drug sele-
giline, it is clear that it shows significant activity.
Anticholinesterase activity assay
To determine the potential interest of the quinoxaline-
hydrazone synthesized, AChE and BChE inhibitory potency
was assessed according to modified Ellman method with
commercially obtainable donepezil as the reference stan-
dard. Initially, all the obtained compounds were tested at
Molecular docking studies
Docking studies were performed in order to gain more
insight into the binding modes of compound 5l to AChE
and MAO-B enzymes. Studies were carried out by using the
X-ray crystal structures of Homo sapiens AChE (hAChE
PDB ID:4EY7) (Cheung et al. 2012) and MAO-B (PDB ID:
2V5Z) (Claudia et al. 2007) obtained from Protein Data
Bank server (www.pdb.org).
−
3
−4
1
0
M and 10 M concentrations and The ChE inhibitory
results are outlined in Table 4. With respect to the activity
results, it was determined that most of the tested compounds
showed better inhibitory activity against AChE than BChE
activity. Compound 5l indicated more than 50% activity at

Medicinal Chemistry Research
Table 4 % Inhibition of compounds 5a–5m, donepezil and tacrine against AChE and BChE
Comp.
AChE inhibition %
BChE inhibition %
10−3
1
0−
3
M
10−4
M
M
10−4
M
5
5
5
5
5
5
5
a
b
c
d
e
f
55.411 ± 0.994
58.837 ± 0.905
49.550 ± 0.529
47.007 ± 0.808
42.678 ± 0.429
53.178 ± 0.994
39.618 ± 0.825
99.258 ± 1.168
41.362 ± 0.318
95.280 ± 1.299
96.750 ± 1.106
68.871 ± 1.062
99.625 ± 1.297
98.147 ± 1.062
–
48.165 ± 0.754
42.629 ± 0.623
41.307 ± 0.872
38.824 ± 0.621
36.458 ± 0.337
47.869 ± 0.420
33.460 ± 0.525
98.542 ± 1.095
35.060 ± 0.479
88.256 ± 1.011
85.248 ± 1.126
44.674 ± 0.718
97.662 ± 1.268
95.336 ± 1.108
–
39.921 ± 0.898
28.078 ± 0.545
34.512 ± 0.806
42.926 ± 0.623
38.306 ± 0.629
29.835 ± 0.599
33.431 ± 0.488
–
30.456 ± 0.641
21.826 ± 0.711
27.146 ± 0.455
30.674 ± 0.477
31.134 ± 0.558
20.660 ± 0.318
30.167 ± 0.320
–
g
Donepezil
5
5
5
5
5
5
h
38.658 ± 0.759
44.396 ± 0.298
29.893 ± 0.411
35.346 ± 0.782
48.067 ± 0.520
36.869 ± 0.525
98.248 ± 1.019
27.507 ± 0.605
36.125 ± 0.355
22.627 ± 0.359
31.104 ± 0.699
30.020 ± 0.498
31.661 ± 0.417
96.275 ± 1.471
i
j
k
l
m
Tacrine
Table 5 IC50 values of compounds 5i, 5j, 5l, 5m and donepezil
against AChE
The docking poses of compound 5l for AChE enzyme
are presented in Figs 2 and 3. According to these poses, it is
clearly understood that compound 5l binds to AChE
enzyme in a similar position with donepezil due to the dual
binding sites. The quinoxaline ring of compound forms the
lipophilic part, whereas the polar basic center is consisted of
dimethylaminoethylpiperazine moiety. The docking poses
specify that lipophilic group of the structure bind to PAS
region of AChE, while CAS region of the enzyme interacts
with the polar basic center.
Compound
AChE IC50 (µM)
5
5
5
5
i
0.106 ± 0.003
0.187 ± 0.007
0.028 ± 0.001
0.042 ± 0.002
0.026 ± 0.001
j
l
m
Donepezil
It is observed that the quinoxaline ring is in interaction
with indole of Trp286 by π-π interaction. Other π-π interac-
tions are identified between the phenyl ring in the middle of
the structure and phenyl rings of Phe338 and Tyr341. Also,
hydrazone moiety of the structure is essential for polar
interactions. Amine moiety of hydrazone group interacts with
carbonyl of Arg296 by forming a hydrogen bond. Another
hydrogen bond is related to nitrogen of imine group. The
nitrogen atom of imine forms a hydrogen bond with amino of
Phe295. An efficient binding is also provided by the forma-
tion of cation-π interaction between the nitrogen atom of
dimethylaminoalkyl group and indole of Trp86. Furthermore,
this nitrogen atom creates salt bridge with Glu202. Docking
results also show that extended carbon chain enhances the van
der Waals interactions with the amino acids in the active site
and intensifies the proper bonding.
near the FAD cofactor. According to docking poses, the
quinoxaline ring creates a π- π interaction with phenyl of
Tyr435. There is another π- π interaction between phenyl
ring near to piperazine and phenyl of Tyr326. The amine
group of hydrazone moiety in the structure interacts with
carbonyl of Glu206 by the formation of a hydrogen bond.
Another hydrogen bond is observed between the nitrogen
atom of dimethylaminoalkyl chain and carbonyl of Pro102.
It is thought that this interaction is answer to why com-
pound 5l is the most active derivative in the series.
Conclusion
Three-dimensional poses of compound 5l in the active
site of MAO-B are presented in Figs 4 and 5. The com-
pound 5l adequately binds to amino acid residues, lining the
cavity by overlapping at the same site and, locating very
To develop biologically active derivatives, the presence of a
pharmacophore group in the compounds that synthesis is
planned is a basic approach in pharmaceutical chemistry.
Based on this approach, quinoxaline and hydrazone in

Medicinal Chemistry Research
Fig. 2 Three-dimensional pose
of compound 5l (orange colored)
in the enzyme active site (AChE
PDB Code: 4EY7)
Fig. 3 The interacting mode of
compound 5l in the active region
of AChE. The inhibitor, colored
with orange, and the important
residues, colored with turquoise,
in the active site of the enzyme
are presented by tube model
which we reported MAO and ChE inhibitor activities in
previous studies were combined at the same molecule.
MAO and ChE inhibitor activities of the obtained com-
pounds were performed. Generally obtained compounds
showed more activity against hMAO-B and AChE
enzymes. According to the results of the in vitro MAO and
ChE enzyme inhibition assay, it was found that the com-
pound 5l is the most active derivative against both enzymes.
Compound 5l bearing dimethylaminoethyl moiety is similar
acetylcholine molecule. High activity in this compound
suggests that it acts as acetylcholine and inhibits the
enzyme.

Medicinal Chemistry Research
Fig. 4 Three-dimensional pose
of compound 5l in the enzyme
active site (MAO-B PDB
Code: 2V5Z)
Fig. 5 The interacting mode of
compound 5l in the active region
of MAO-B. The inhibitor and
the important residues in the
active site of the enzyme are
presented by tube model. The
inhibitor is colored with orange.
The FAD molecule is colored
white with ball and stick model
Publisher’s note Springer Nature remains neutral with regard to
jurisdictional claims in published maps and institutional affiliations.
Acknowledgements This study was financially supported by Anadolu
University Scientific Projects Fund, Project No: 1805S190 and
1
905S033.
References
Compliance with ethical standards
Acar Çevik U, Sağlık BN, Levent S, Osmaniye D, Kaya Çavuşoğlu B,
Özkay Y, Kaplancıklı ZA (2019) Synthesis and AChE-inhibitory
activity of new benzimidazole derivatives. Molecules 24(5):861
Conflict of interest The authors declare that they have no conflict of
interest.

Medicinal Chemistry Research
Bar-Am O, Amit T, Weinreb O, Youdim MB, Mandel S (2010)
Propargylamine containing compounds as modulators of proteo-
lytic cleavage of amyloid-beta protein precursor: involvement of
MAPK and PKC activation. J Alzheimer’s Dis 21(2):361–371
Becker I (2008) Preparation of derivatives of 1-(2-pyrimidinyl)
piperazine as potetial antianxiety, antideppessant, and anti-
psycotic agents. J Het Chem 45:1005–1022
Can ÖD, Osmaniye D, Demir Özkay Ü, Sağlık BN, Levent S, Ilgın S,
Baysal M, Özkay Y, Kaplancıklı ZA (2017) MAO enzymes
inhibitory activity of new benzimidazole derivatives including
hydrazone and propargyl side chains. Eur J Med Chem
Karaman N, Sıcak Y, Taşkın-Tok T, Öztürk M, Karaküçük-İyidoğan
A, Dikmen M, Koçyiğit-Kaymakçıoğlu B, Oruç-Emre EE (2016)
New piperidine-hydrazone derivatives: synthesis, biological
evaluations and molecular docking studies as AChE and BChE
inhibitors. Eur J Med Chem 124:270–283
Kaya Çavuşoğlu B, Sağlık BN, Osmaniye D, Levent S, Acar Çevik U,
Karaduman A, Özkay Y, Kaplancıklı Z (2018a) Synthesis and
biological evaluation of new thiosemicarbazone derivative schiff
bases as monoamine oxidase inhibitory agents. Molecules 23:60
Kaya Çavuşoğlu B, Sağlık BN, Özkay Y, İnci B, Kaplancıklı ZA
(2018b) Design, synthesis, monoamine oxidase inhibition and
docking studies of new dithiocarbamate derivatives bearing
benzylamine moiety. Bioorg Chem 76:177–187
1
31:92–106
Can NÖ, Osmaniye D, Levent S, Sağlık BN, Korkut B, Atlı Ö, Özkay
Y, Kaplancıklı ZA (2018) Design, synthesis and biological
assessment of new thiazolylhydrazine derivatives as selective and
reversible hMAO-A inhibitors. Eur J Med Chem 144:68–81
Chen CY, Lin TP, Chen CK, Lin SC, Tseng MS, Wen YS, Sun SS
Khattab SN, Abdel Moneim SA, Bekhit AA, El Massry AM, Hassan
SY, El-Faham A, Ali Ahmed HE, Amer A (2015) Exploring new
selective 3-benzylquinoxaline-based MAO-A inhibitors: design,
synthesis, biological evaluation and docking studies. Eur J Med
Chem 93:308–320
(
2008) New chromogenic and fluorescent probes for anion
detection: formation of a [2+2] supramolecular complex on
addition of fluoride with positive homotropic cooperativity. J Org
Chem 73(3):900–911
Khattab SN, Hassan SY, Bekhit AA, El Massry AM, Langer V, Amer
A (2010) Synthesis of new series of quinoxaline based MAO-
inhibitors and docking studies. Eur
J Med Chem 45
Cheung J, Rudolph MJ, Burshteyn F, Cassidy MS, Gary EN, Love J,
Matthew CF, Height JJ (2012) Structures of human acet-
ylcholinesterase in complex with pharmacologically important
ligands. J Med Chem 55:10282–10286
Claudia B, Wang J, Pisani L, Caccia C, Carotti A, Salvati P,
Edmondson DE, Mattevi A (2007) Structures of human mono-
amine oxidase B complexes with selective noncovalent inhibi-
(10):4479–4489
Li Y, Qiang X, Luo L, Yang X, Xiao G, Zheng Y, Cao Z, Sang Z, Su
F, Deng Y (2017) Multitarget drug design strategy against Alz-
heimer’s disease: homoisoflavonoid mannich base derivatives
serve as acetylcholinesterase and monoamine oxidase B dual
inhibitors with multifunctional properties. Bioorg Med Chem 25
(2):714–726
tors: safinamide and coumarin analogs.
0:5848–5852
J
Med Chem
Osmaniye D, Sağlık BN, Acar Çevik U, Levent S, Kaya Çavuşoğlu B,
Özkay Y, Kaplancıklı ZA, Turan G (2019) Synthesis and AChE
inhibitory activity of novel thiazolylhydrazone derivatives.
Molecules 24(13):2392
5
D’Ascenzio M, Chimenti P, Gidaro MC, De Monte C, De Vita D,
Granese A, Scipione L, Di Santo R, Costa G, Alcaro S, Yáñez M,
Carradori S (2015) (Thiazol-2-yl)hydrazone derivatives from
acetylpyridines as dual inhibitors of MAO and AChE: synthesis,
biological evaluation and molecular modeling studies. J Enzyme
Inhib Med Chem 30(6):908–919
Dias Viegas FP, de Freitas Silva M, Divino da Rocha M, Castelli MR,
Riquiel MM, Machado RP, Vaz SM, Simões de Lima LM,
Mancini KC, Marques de Oliveira PC, Morais ÉP, Gontijo VS, da
Silva FMR, D’Alincourt da Fonseca Peçanha D, Castro NG,
Neves GA, Giusti-Paiva A, Vilela FC, Orlandi L, Camps I,
Veloso MP, Leomil Coelho LF, Ionta M, Ferreira-Silva GA,
Pereira RM, Dardenne LE, Guedes IA, de Oliveira Carneiro Jr W,
Quaglio Bellozi PM, Pinheiro de Oliveira AC, Ferreira FF,
Pruccoli L, Tarozzi A, Viegas C (2018) Design, synthesis and
pharmacological evaluation of N-benzyl-piperidinyl-aryl-acylhy-
drazone derivatives as donepezil hybrids: discovery of novel
multi-target anti-alzheimer prototype drug candidates. Eur J Med
Chem 147:48–65
Özkay ÜD, Can ÖD, Sağlık BN, Cevik UA, Levent S, Özkay Y, Ilgın S,
Atlı Ö (2016) Design, synthesis, and AChE inhibitory activity of new
benzothiazole–piperazines. Bioorg Med Chem Lett 26:5387–5394
Raina P, Santaguida P, Ismaila A, Patterson C, Cowan D, Levine M,
Booker L, Oremus M (2008) Effectiveness of cholinesterase
inhibitors and memantine for treating dementia: evidence review
for a clinical practice guideline. Ann Intern Med 148:379–397
Sağlık BN, Ilgın S, Özkay Y (2016) Synthesis of new donepezil
analogues and investigation of their effects on cholinesterase
enzymes. Eur J Med Chem 124:1026–1040
Sağlık BN, Kaya Çavuşoğlu B, Osmaniye D, Levent S, Acar Çevik U,
Ilgın S, Özkay Y, Kaplancıklı ZA, Öztürk Y (2019) In vitro and
in silico evaluation of new thiazole compounds as monoamine
oxidase inhibitors. Bioorg Chem 85:97–108
Sang Z, Pan W, Wang K, Ma Q, Yu L, Liu W (2017a) Design,
synthesis and biological evaluation of 3,4-dihydro-2(1H)-quino-
line-O-alkylamine derivatives as new multipotent cholinesterase/
monoamine oxidase inhibitors for the treatment of Alzheimer’s
disease. Bioorg Med Chem 25(12):3006–3017
Edmondson DE, Mattevi A, Binda C, Li M, Hubálek F (2004)
Structure and mechanism of monoamineoxidase. Curr Med Chem
1
1:1983–1993
Sang Z, Wang K, Wang H, Wang H, Ma Q, Han X, Ye M, Yu L, Liu
W (2017b) Design, synthesis and biological evaluation of 2-
acetyl-5-O-(aminoalkyl)phenol derivatives as multifunctional
agents for the treatment of Alzheimer’s disease. Bioorg Med
Chem Lett 27:5046–5052
Evranos-Aksöz B, Baysal İ, Yabanoğlu-Çiftçi S, Djikic T, Yelekçi K,
Uçar G, Ertan R (2015) Synthesis and screening of human
monoamine oxidase-A inhibitor effect of new 2-pyrazoline and
hydrazone derivatives. Arch Pharm Chem Life Sci 348
(
10):743–756
Scarpini E, Scheltens P, Feldman H (2003) Treatment of Alzheimer’s
disease: current status and new perspectives. Lancet Neurol 2
(9):539–547
Sterling J, Herzig Y, Goren T, Finkelstein N, Lerner D, Goldenberg
W, Miskolczi I, Molnar S, Rantal F, Tamas T, Toth G, Zagyva A,
Zekany A, Finberg J, Lavian G, Gross A, Friedman R, Razin M,
Huang W, Krais B, Chorev M, Youdim MB, Weinstock M
(2002) Novel dual inhibitors of AChE and MAO derived from
hydroxy aminoindan and phenethylamine as potential treatment
for Alzheimer’s disease. J Med Chem 45(24):5260–5279
Huang W, Tang L, Shi Y, Huang S, Xu L, Sheng R, Wu P, Li J, Zhou
N, Hu Y (2011) Searching for the Multi-Target-Directed Ligands
against Alzheimer’s disease: discovery of quinoxaline-based
hybrid compounds with AChE, H3R and BACE 1 inhibitory
activities. Bioorg Med Chem 19(23):7158–7167
Hussein W, Saglık BN, Levent S, Korkut B, Ilgın S, Özkay Y,
Kaplancıklı ZA (2018) Synthesis and biological evaluation of
new cholinesterase inhibitors for Alzheimer’s disease. Molecules
2
3:2033

Medicinal Chemistry Research
Takeda A, Loveman E, Clegg A, Kirby J, Picot J, Payne E, Green C
2006) A systematic review of the clinical effectiveness of
luation of 4′-aminochalcone-rivastigmine hybrids as multi-
functional agents for the treatment of Alzheimer’s disease. Bioorg
Med Chem 25(3):1030–1041
(
donepezil, rivastigmine and galantamine on cognition, quality of
life and adverse events in Alzheimer’s disease. Int J Geriatr
Psychopharmacol 21(1):17–28
Xu YX, Wang H, Li XK, Dong SN, Liu WW, Gong Q, Wang TD, Tang
Y, Zhu J, Li J, Zhang HY, Mao F (2018) Discovery of novel
propargylamine-modified 4-aminoalkyl imidazole substituted pyr-
imidinylthiourea derivatives as multifunctional agents for the treat-
ment of Alzheimer’s disease. Eur J Med Chem 143:33–47
Yan-Yan H (2010) An efficient synthesis of 3-(indol-3-yl)quinoxalin-
2-ones with TfOH- Catalyzed Friedel–Crafts type coupling
reaction in air. Tetrahedron Lett 51(15):2023–2028
Youdim MB, Buccafusco JJ (2005) Multi-functional drugs for various
CNS targets in the treatment of neurodegenerative disorders.
Trends Pharm Sci 26(1):27–35
Youdim MB, Edmondson D, Tipton KF (2006) The therapeutic
potential of monoamine oxidase inhibitors. Nat Rev Neurosci 7
(4):295–309
Tripathi RK, Ayyannan SR (2016) Design, synthesis, and evaluation
of 2-amino-6- nitrobenzothiazole-derived hydrazones as MAO
inhibitors: role of the methylene spacer group. ChemMedChem
1
1(14):1551–1567
Tok F, Koçyigit Kaymakçıoglu B, Saglık BN, Levent S, Özkay Y,
Kaplancıklı ZA (2019) Synthesis and biological evaluation of
new pyrazolone Schiff bases as monoamine oxidase and choli-
nesterase inhibitors. Bioorg Chem 84:41–50
Wouters J (1998) Structural aspects of monoamine oxidase and its
reversible inhibition. Curr Med Chem 5(2):137–162
Xiao G, Li Y, Qiang X, Xu R, Zheng Y, Cao Z, Luo L, Yang X, Sang
Z, Su F, Deng Y (2017) Design, synthesis and biological eva-