Synthesis and biological evaluation of novel flavanone derivatives as potential antipsychotic agents

Article abstract of DOI:10.1111/cbdd.12843

In this study, a series of novel flavanone derivatives were designed and synthesized, and the antipsychotic activities of the target compounds were evaluated in vitro and in vivo. The results showed that synthesized compounds 7a–7g decreased the activity of dopamine D₂ receptors in HEK293 cells co-transfected with D₂ receptor/G protein α16a, with IC₅₀ values of 0.051–0.35?μm. Compounds 7a–7g inhibited the over-production of nitric oxide stimulated by lipopolysaccharide/interferon-γ in BV-2 microglial cells. In mice, intragastric administration of 7d, 7e, and 7g reversed the increase in locomotor activity induced by MK-801 (an antagonist of NMDA receptors) and decreased the hyperactivity of climbing behavior induced by apomorphine (a dopamine receptor agonist). These results suggest that some of the novel flavanone derivatives have potential antipsychotic effects and may be useful in the treatment of schizophrenia.

Full text of DOI:10.1111/cbdd.12843

Received Date : 17-Feb-2016
Revised Date : 20-Jun-2016
Accepted Date : 13-Aug-2016
Article type
: Research Article
Synthesis and biological evaluation of novel flavanone derivatives as
potential antipsychotic agents
Hong-shun Gu1, Xi Chen1, Jian-wei Zhang2, Lan Zhang1,*, Lin Li1,*
1 Department of Pharmacology, Xuanwu Hospital of Capital Medical University; Beijing
Institute for Brain Disorders; Beijing Engineering Research Center for Nerve System
Drugs; Key Laboratory for Neurodegenerative Diseases of Ministry of Education, Beijing
100053, China.
2School of Chemical Biology and Pharmaceutical Sciences, Capital Medical University,
Beijing 100069, China.
*Corresponding author:
Professor Lin Li, Department of Pharmacology, Xuanwu Hospital of Capital Medical
University, 45 Chang-chun Street, Beijing 100053, China.
Tel.: +86-10-83198886; Fax: +86-10-63042809;
E-mail address: linlixw@126.com
This article has been accepted for publication and undergone full peer review but has not
been through the copyediting, typesetting, pagination and proofreading process, which
may lead to differences between this version and the Version of Record. Please cite this
article as doi: 10.1111/cbdd.12843
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Professor Lan Zhang, Department of Pharmacology, Xuanwu Hospital of Capital Medical
University, 45 Chang-chun Street, Beijing 100053, China.
Tel.: +86-10-63132779;
E-mail: lanizhg@hotmail.com
Abstract: In the present study, a series of novel flavanone derivatives were designed and
synthesized, and the antipsychotic activities of the target compounds were evaluated in
vitro and in vivo. The results showed that synthesized compounds 7a−7g decreased the
activity of dopamine D2 receptors in HEK293 cells co-transfected with D2 receptor/G
protein α16a, with IC50 values of 0.051–0.35 μM. Compounds 7a−7g inhibited the
over-production of nitric oxide stimulated by lipopolysaccharide/interferon-γ in BV-2
microglial cells. In mice, intragastric administration of 7d, 7e, and 7g reversed the increase
in locomotor activity induced by MK-801 (an antagonist of NMDA receptors), and
decreased the hyperactivity of climbing behavior induced by apomorphine (a dopamine
receptor agonist). These results suggest that some of the novel flavanone derivatives have
potential antipsychotic effects, and may be useful in the treatment of schizophrenia.
Key words: flavanone derivatives; schizophrenia; dopamine D2 receptor; apomorphine;
MK-801; neuroinflammation
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Schizophrenia is a chronic and complex neuropsychiatric illness, afflicting approximately
1% of the population worldwide (1). Typical antipsychotics antagonize dopamine receptors
and mainly ameliorate the positive symptoms of schizophrenia, but they fail to manage the
negative symptoms and cognitive impairment. Moreover, serious side effects such as
extrapyramidal symptoms and hyperprolactinemia limit the use of these drugs (2). Atypical
antipsychotics (e.g., clozapine, ziprasidone, risperidone, quetiapine, and olanzapine)
potently antagonize the serotonin 2A receptor (5-HT2A receptor) along with a dopamine D2
receptor blockade. A major advantage of atypical antipsychotics is their effectiveness in
suppressing negative and cognitive symptoms. However, it has been proven that atypical
antipsychotics cause numerous side effects, such as substantial weight gain and the time
from the start of QRS waves to end point of T wave (QT) interval prolongation.
Recently, some studies have found that people with schizophrenia have increased blood
concentrations of inflammatory cytokines (3). There exist several randomized clinical trials
of the non-steroidal anti-inflammatory drugs (such as celecoxib (4) and aspirin (5,6) as
adjuncts to antipsychotics, and one trial found that adjunctive treatment with the
antioxidant N-acetylcysteine significantly reduced psychopathology in schizophrenic
patients (7). The evidence from first-degree relatives of patients with schizophrenia
supports the idea that increased inflammation is associated with schizophrenia (8−10).
Flavanones are a series of naturally occurring compounds present in natural medicine and
plant-based foods. They possess a broad range of pharmacological properties including
radical-scavenging, anti-inflammatory, anti-cancer, and anti-mutagenic properties (11). An
increasing number of reports have shown that flavanones (such as hesperidin (12),
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naringenin (13, 14), nobiletin (15), and tangeretin (16)) inhibit inflammation caused by
activated microglia. However, the low content of these flavanones in natural products
limits further research and development, and it is not easy to obtain them by separation and
purification. On the other hand, chemical synthesis may reduce the waste of resources.
Meanwhile, it has been reported that some synthesized antipsychotic agents containing an
arylpiperazine (piperidine) group have antagonistic effects on dopamine receptors (17−22).
Therefore, in the present study, we designed and synthesized a series of new compounds
with the arylpiperazine (piperidine) group linked to flavanones. We then investigated the
preliminary antipsychotic effects of the target compounds on the dopamine D2 receptor and
on neuroinflammation in vitro, and on hyperactive behavior in mouse models of
schizophrenia (induced by MK-801 and by apomorphine) in vivo.
Materials and methods
Chemical synthesis
General information
Optical rotations were measured on a JASCO P-2000 automatic digital polarimeter (Japan).
Ultraviolet (UV) spectra were obtained on a JASCO V650 spectrophotometer (Japan).
Infrared (IR) spectra were recorded on a Nicolet 5700 FT-IR microscope instrument (USA).
1D Nuclear magnetic resonance (NMR) spectra were recorded at 300 MHz on a Bruker
Avance spectrometer (Germany) in CDCl3 solution. Chemical shifts were given in δ values
(ppm) using tetramethylsilane (TMS) as the internal standard. Electrospray ionization mass
spectrometry (ESIMS) data were measured on a Waters Micromass Quattro Micro API
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LC/MS/MS mass spectrometer (USA). High-resolution ESIMS (HRESIMS) data were
recorded on an Agilent Technologies 6250 Accurate-Mass Q-TOF LC/MS spectrometer
(USA). Analytical thin layer chromatography (TLC) was performed on silica gel GF254
(Qingdao Marine Chemical Inc., China). Column chromatographic purification was carried
out using silica gel. Reagents were all of analytical grade or of chemical purity.
General synthesis for novel flavanone derivatives is shown in Fig. 1.
Procedure for synthesis of 1-[2-Hydroxy-4,6-bis(methoxymethoxy)phenyl] ethanone (2)
A flame-dried flask was charged with acetone (30 mL), anhydrous potassium carbonate
(8.28 g, 60 mmol), and ketone 1 (5.04 g, 30 mmol). The mixture was stirred at room
temperature (RT) for 5 min, and MOMCl (5.93 g, 75 mmol) was added dropwise. The
mixture was maintained at RT for 1.5 h, and then filtered to remove the anhydrous
potassium carbonate. The organic layer was concentrated under reduced pressure to give
thick yellow oil. Column chromatography of the crude product on silica gel using 10%
EtOAc in petroleum ether yielded 2 (4.33 g, 56%) as a colorless oil.
Procedure
for
synthesis
of
1-(4,6-bis(methoxymethoxy)-2-hydroxy-phenyl)-
3-(4-methoxy-phenyl)-propenone 4 (a–c)
A mixture of 10 mmol of sodium hydroxide, 15 mmol of 2, and 25 mmol of corresponding
substituted benzaldehyde in 50 mL of methanol was refluxed for 3 h, acidified (2 N HCl),
and extracted with ethyl acetate (3×25 mL). The combined organic layers were evaporated
under reduced pressure, and the crude products 3 (a–c) were then directly used for the next
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step.
Sodium acetate (5.0 g, 0.4 mmol) was added to a stirring solution of crude 3 (a–c) in
methanol (50 mL). The solution was refluxed for 14 h, and then evaporated under reduced
pressure. The crude product was washed with distilled water (50 mL) and extracted with
ethyl acetate (3×25 mL). The combined organic layers were dried over Na2SO4, filtered,
and then concentrated. The crude materials were purified on a silica gel column using 25%
EtOAc in petroleum ether to yield 4 (a–c) as yellow oils.
5,7-Bis(methoxymethoxy)-2-(4-methoxyphenyl)chroman-4-one (4a):
Yield: 72%. 1H NMR δ ppm (300 MHz, CDCl3): 7.43 (d, 2H, J＝ 8.7 Hz), 6.99 (d, 2H, J＝
8.7 Hz), 6.36 (d, 1H, J＝ 2.1 Hz), 6.33 (d, 1H, J＝ 2.1 Hz), 5.50 (dd, 1H, J＝ 13.2, 2.7 Hz),
5.23 (s, 2H), 5.22 (s, 2H), 3.77 (s, 3H), 3.41 (s, 3H), 3.78 (s, 3H), 3.11 (dd, 1H, J＝ 16.5,
13.2 Hz), and 2.61 (dd, 1H, J＝ 16.5, 3.0 Hz). ESIMS m/z 375.2 [M+H]+.
5,7-Bis(methoxymethoxy)-2-(4-methylphenyl)chroman-4-one (4b):
Yield: 75%. 1H NMR δ ppm (300 MHz, CDCl3): 7.37 (d, 2H, J＝ 7.8 Hz), 7.26 (d, 2H, J＝
7.8 Hz), 6.45 (d, 1H, J＝ 2.4 Hz), 6.41 (d, 1H, J＝ 2.4 Hz), 5.40 (dd, 1H, J＝ 13.2, 2.7 Hz),
5.32 (s, 2H), 5.20 (s, 2H), 3.55 (s, 3H), 3.49 (s, 3H), 3.04 (dd, 1H, J＝ 16.5, 13.2 Hz), 2.72
(dd, 1H, J＝ 16.51, 2.7 Hz), and 2.39 (s, 3H). ESIMS m/z 359.1 [M+H]+.
5,7-Bis(methoxymethoxy)-2-(4-fluorophenyl)chroman-4-one (4c):
Yield: 81%. 1H NMR δ ppm (300 MHz, CDCl3): 7.60 (d, 2H, J＝ 8.7 Hz), 7.29 (d, 2H, J＝
8.7 Hz), 6.37 (d, 1H, J＝ 2.1 Hz), 6.35 (d, 1H, J＝ 2.1 Hz), 5.61 (dd, 1H, J＝ 13.2, 3.0 Hz),
5.23 (s, 2H), 5.22 (s, 2H), 3.42 (s, 3H), 3.79 (s, 3H), 3.12 (dd, 1H, J＝ 16.2, 13.2 Hz), and
2.60 (dd, 1H, J＝ 16.2, 3.0 Hz). ESIMS m/z 363.1 [M+H]+.
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Procedure for the preparation of 5 (a–c)
A mixture of 10 mmol of 4 (a–c) and 1 mL of concentrated HCl in 15 mL of MeOH was
refluxed for 0.5 h. After the solvent was evaporated under vacuum, the residue was
dissolved in ice-cold water, and the precipitate was filtered off, washed with water, and
recrystallized from absolute ethanol to give 5 (a–c).
5,7-Dihydroxy-2-(4-methoxyphenyl)chroman-4-one (5a):
Yield: 82%. [α]2D0 −17.4 (c 0.1, MeOH). 1H NMR δ ppm (300 MHz, DMSO-d6): 12.14 (br
s, 1H), 10.78 (br s, 1H), 7.44 (d, 2H, J＝ 8.7 Hz), 6.97 (d, 2H, J＝ 8.7 Hz), 5.90 (d, 1H, J＝
2.1 Hz), 5.89 (d, 1H, J＝ 1,8 Hz), 5.53 (dd, 1H, J＝ 12.6, 2.7 Hz), 3.77 (s, 3H), 3.28 (dd, 1H,
J＝ 14.1, 12.6 Hz), and 2.72 (dd, 1H, J＝ 14.1, 3.0 Hz). ESIMS m/z 287.1 [M+H]+.
5,7-Dihydroxy-2-(4-methylphenyl)chroman-4-one (5b):
Yield: 82%. [α]2D0 −13.5 (c 0.1, MeOH). 1H NMR δ ppm (300 MHz, DMSO-d6): 12.13 (br
s, 1H), 10.81 (br s, 1H), 7.40 (d, 2H, J＝ 7.8 Hz), 7.23 (d, 2H, J＝ 7.8 Hz), 5.91 (d, 1H, J＝
2.4 Hz), 5.90 (d, 1H, J＝ 2.4 Hz), 5.54 (dd, 1H, J＝ 12.3, 2.4 Hz), 3.23 (dd, 1H, J＝ 17.1,
12.4 Hz), 2.72 (dd, 1H, J＝ 17.1, 3.0 Hz), and 3.32 (s, 3H). ESIMS m/z 271.1 [M+H]+.
5,7-Dihydroxy-2-(4-fluorophenyl)chroman-4-one (5c):
Yield: 86%. [α]2D0 −3.1 (c 0.1, MeOH). 1H NMR δ ppm (300 MHz, DMSO-d6): 12.12 (br s,
1H), 10.85 (br s, 1H), 7.58 (d, 2H, J＝ 8.4 Hz), 7.27 (d, 2H, J＝ 8.7 Hz), 5.93 (d, 1H, J＝
2.1 Hz), 5.91 (d, 1H, J＝ 2.1 Hz), 5.60 (dd, 1H, J＝ 12.6, 2.7 Hz), 3.25 (dd, 1H, J＝ 17.1,
12.6 Hz), and 2.77 (dd, 1H, J＝ 17.1, 3.0 Hz). ESIMS m/z 275.0 [M+H]+.
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Procedure for the preparation of 6 (a–c)
1,4-Dibromobutane (10 mmol) was added to a solution of 5 (a–c) (5 mmol) and potassium
carbonate in acetone (30 mL), and the mixture was refluxed for 3 h. After cooling to room
temperature, the mixture was filtered, solvent was evaporated, and residue was purified by
column chromatography (petroleum ether/EtOAc 15:1) to yield 6 (a–c) as yellow oils.
7-(4-Bromobutoxy)-5-hydroxy-2-(4-methoxyphenyl)chroman-4-one (6a):
1
Yield: 52%. H NMR δ ppm (300 MHz, CDCl3): 12.04 (s, 1H), 7.40 (d, 2H, J＝ 8.7 Hz),
6.97 (d, 2H, J＝ 8.7 Hz), 6.07 (d, 1H, J＝ 2.4 Hz), 6.04 (d, 1H, J＝ 2.4 Hz), 5.38 (dd, 1H, J
＝ 12.9, 3.0 Hz), 4.02 (t, 2H, J＝ 6.0 Hz), 3.85 (s, 3H), 3.49 (t, 2H, J＝ 6.0 Hz), 3.11 (dd, 1H,
J＝ 17.1, 12.9 Hz), 2.80 (dd, 1H, J＝ 17.1, 3.0 Hz), 2.08–2.03 (m, 2H), and 2.01–1.93 (m,
2H). ESIMS m/z 423.1 [M + H]+ .
7-(4-Bromobutoxy)-5-hydroxy-2-(4-methylphenyl)chroman-4-one (6b):
1
Yield: 45%. H NMR δ ppm (300 MHz, CDCl3): 12.05 (s, 1H), 7.35 (d, 2H, J＝ 8.1 Hz),
7.25 (d, 2H, J＝ 8.1 Hz), 6.07 (d, 1H, J＝ 2.4 Hz), 6.04 (d, 1H, J＝ 2.4 Hz), 5.40 (dd, 1H, J
＝ 12.9, 3.0 Hz), 4.04 (t, 2H, J＝ 6.0 Hz), 3.47 (t, 2H, J＝ 6.0 Hz), 3.11 (dd, 1H, J＝ 17.1,
12.9 Hz), 2.81 (dd, 1H, J＝ 17.1, 3.0 Hz), 2.38 (s, 3H), 2.09–2.03 (m, 2H), and 2.02–1.93
(m, 2H). ESIMS m/z 405.2 [M + H]+ .
7-(4-Bromobutoxy)-5-hydroxy-2-(4-fluorophenyl)chroman-4-one (6c):
Yield: 47%. 1H NMR δ ppm (300 MHz, CDCl3): 12.04 (br s, 1H), 7.75 (d, 2H, J＝ 8.7 Hz),
7.46 (d, 2H, J＝ 8.7 Hz), 6.08 (d, 1H, J＝ 2.1 Hz), 6.05 (d, 1H, J＝ 2.4 Hz), 5.51 (dd, 1H, J
＝ 12.6, 2.7 Hz), 4.03 (t, 2H, J＝ 6.0 Hz), 3.45 (t, 2H, J＝ 6.0 Hz), 2.85 (dd, 1H, J＝ 17.1,
3.0 Hz), 2.08–2.01 (m, 2H), and 2.00–1.90 (m, 2H). ESIMS m/z 409.1 [M + H]+.
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Procedure for the preparation of 7 (a–c)
For the preparation of 7 (a–c), 1-(2-methoxyphenyl)piperazine (2.5 mmol) and a catalytic
amount of KI were added to a suspension of 6 (a–c) (2 mmol) and K2CO3 (1.22 mmol) in
acetonitrile (15 mL). The resulting mixture was refluxed for 1 h. After filtration, the
resulting filtrate was evaporated to dryness under reduced pressure. The residue was
evaporated under reduced pressure, and the crude product was purified by means of
chromatography (petroleum ether/EtOAc 2:1) to yield 7 (a–c).
5-hydroxy-2-(4-methoxyphenyl)-7-(4-(4-(2-methoxyphenyl)piperazin-1-yl)butoxy)chr
oman-4-one (7a):
Compounds 7a was obtained as yellow sticky residue, with yield 26%. The molecular
formula was established as C31H36N2O6 by HR-Q-TOFMS at m/z 533.2712 [M + H]+
(calcd 533.2646) and the 1D NMR spectroscopic data, representing fourteen indices of
hydrogen deficiency. The 1H NMR spectrum exhibited one hydroxy protons [δH 12.04 (br s,
1H)], six aromatic protons, 7.40 (d, 2H, J＝ 8.7 Hz), 7.04–6.86 (m, 2H), 6.08 (d, 1H, J＝
2.1 Hz), 6.05 (br s, 1H, J＝ 1.8 Hz), 5.38 (dd, 1H, J＝ 12.9, 2.7 Hz), 3.85 (s, 3H), 3.16–3.06
(m, 1H), 2.80 (dd, 1H, J＝ 17.1, 3.0 Hz) indicated that 7a with the same skeletal structure
of flavanones as that observed for 5a. The proton signals at 4.03 (t, 2H, J＝ 6.0 Hz), 2.49 (t,
2H, J＝ 7.2 Hz), 1.87–1.82 (m, 2H), and 1.75–1.68 (m, 2H) suggesting that 7a possessing
the butoxy fragment as that observed for 6a, furthermore, the other proton signals at
3.16–3.06
(m,
4H),
2.68
(m,
4H)
suggesting
the
presence
of
4-(4-(2-methoxyphenyl)piperazin-1-yl) fragment. [α]2D0 −5.3 (c 0.1, MeOH). UV (MeOH):
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λmax (log ε ) 208.5 (4.73), and 287.5 (4.36) nm. IR (KBr): νmax 2939, 2833, 1641, 1574,
1
1514, 1503, 1448, 1302, 1242, 1163, and 829 cm−1. H NMR δ ppm (300 MHz, CDCl3):
12.04 (br s, 1H), 7.40 (d, 2H, J＝ 8.7 Hz), 7.04–6.86 (m, 6H), 6.08 (d, 1H, J＝ 2.1 Hz), 6.05
(br s, 1H, J＝ 1.8 Hz), 5.38 (dd, 1H, J＝ 12.9, 2.7 Hz), 4.03 (t, 2H, J＝ 6.0 Hz), 3.88 (s, 3H),
3.85 (s, 3H), 3.16–3.06 (m, 5H), 2.80 (dd, 1H, J＝ 17.1, 3.0 Hz), 2.68 (m, 4H), 2.49 (t, 2H,
J＝ 7.2 Hz), 1.87–1.82 (m, 2H), and 1.75–1.68 (m, 2H). 13C NMR δ ppm (75 MHz, CDCl3):
195.9, 167.5, 164.1, 162.9, 160.1, 152.3, 141.4, 130.5, 127.7, 122.9, 121.0, 118.2, 114.2,
111.3, 103.1, 95.6, 94.6, 79.0, 68.3, 58.1, 55.4, 53.4, 50.6, 43.2, 27.0, and 23.2. ESIMS m/z
532.9 [M + H]+; HR-Q-TOFMS: 533.2712 [M + H]+ (calcd for C31H36N2O6, 533.2646).
5-hydroxy-2-(4-methylphenyl)-7-(4-(4-(2-methoxyphenyl)piperazin-1-yl)butoxy)chro
man-4-one (7b):
Yellow sticky residue, yield: 20%. [α]20 −3.4 (c 0.1, MeOH). UV (MeOH): λmax (log ε )
D
210 (4.48), and 287 (4.14) nm. IR (KBr): νmax 2941, 2820, 1638, 1578, 1506, 1452, 1368,
1299, 1165, 826, and 743 cm−1. 1H NMR δ ppm (300 MHz, CDCl3): 12.03 (br s, 1H), 7.36
(d, 2H, J＝ 8.1 Hz), 7.26 (d, 2H, J＝ 7.8 Hz), 7.05–6.87 (m, 4H), 6.08 (d, 1H, J＝ 2.7 Hz),
6.06 (br s, 1H, J＝ 2.4 Hz), 5.40 (dd, 1H, J＝ 12.9, 3.0 Hz), 4.03 (t, 2H, J＝ 6.3 Hz), 3.88 (s,
3H), 3.16–3.06 (m, 5H), 2.82 (dd, 1H, J＝ 17.1, 3.0 Hz), 2.69 (m, 4H), 2.49 (t, 2H, J＝ 7.2
13
Hz), 2.40 (s, 3H), 1.87–1.80 (m, 2H), and 1.76–1.68 (m, 2H). C NMR δ ppm (75 MHz,
CDCl3): 195.8, 167.5, 164.1, 162.9, 152.3, 141.4, 138.8, 135.5, 129.5, 126.2, 122.9, 121.0,
118.2, 111.3, 103.1, 95.6, 94.6, 79.1, 68.3, 58.1, 55.4, 53.4, 50.6, 43.3, 27.0, 23.2, and 21.2.
ESIMS m/z 517.2 [M + H]+; HR-Q-TOFMS: 517.2766 [M + H]+ (calcd for C31H36N2O5,
517.2697).
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5-hydroxy-2-(fluorophenyl)-7-(4-(4-(2-methoxyphenyl)piperazin-1-yl)butoxy)chroma
n-4-one (7c):
Yellow sticky residue, yield: 27%. [α]20 −1.9 (c 0.1, MeOH). UV (MeOH): λmax (log ε )
D
209.5 (4.67), and 285.5 (4.31) nm. IR (KBr): νmax 2938, 1641, 1576, 1501, 1449, 1373,
1304, 1242, 1163, 835, and 743 cm−1. 1H NMR δ ppm (300 MHz, CDCl3): 12.01 (br s, 1H),
7.47–7.43 (m, 2H), 7.16–7.10 (m, 2H, J＝ 7.8 Hz), 7.05–6.87 (m, 4H), 6.10 (d, 1H, J＝ 2.4
Hz), 6.06 (d, 1H, J＝ 2.1 Hz), 5.40 (dd, 1H, J＝ 13.2, 3.0 Hz), 4.03 (t, 2H, J＝ 6.0 Hz), 3.88
(s, 3H), 3.12–3.02 (m, 5H), 2.82 (dd, 1H, J＝ 17.1, 3.3 Hz), 2.68 (m, 4H), 2.49 (t, 2H, J＝
13
7.5 Hz), 2.40 (s, 3H), 1.87–1.80 (m, 2H), and 1.75–1.68 (m, 2H). C NMR δ ppm (75
MHz, CDCl3): 195.3, 167.6, 164.2, 162.6, 152.3, 141.4, 134.4, 134.3, 128.0, 122.9, 121.0,
118.2, 116.0, 115.7, 111.3, 103.0, 95.7, 94.7, 78.5, 68.3, 58.1, 55.4, 53.5, 50.6, 43.4, 27.0,
and 23.2. ESIMS m/z 520.8 [M + H]+; HR-Q-TOFMS: 521.2506 [M + H]+ (calcd for
C30H33FN2O5, 521.2446).
Procedure for the preparation of 7d and 7e
For the preparation of 7d and 7e, 6-fluoro-3-(4-piperidinyl)-1,2-benzisoxazole (2.5 mmol)
and a catalytic amount of KI were added to a suspension of 6a and 6c (2 mmol) and K2CO3
(1.22 mmol) in acetonitrile (15 mL). The resulting mixture was refluxed for 1 h. After
filtration, the resulting filtrate was evaporated to dryness under reduced pressure. The
residue was evaporated under reduced pressure, and the crude product was purified by
means of chromatography (petroleum ether/EtOAc 2:1) to yield 7d and 7e.
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5-hydroxy-2-(4-methoxyphenyl)-7-(4-(4-(6-fluorobenzo[d]isoxazol-3-yl)piperidin-1-yl)
butoxy)chroman-4-one (7d):
Yellow solid, yield 33%. [α]20 −8.6 (c 0.1, MeOH). UV (MeOH): λmax (log ε ) 202.5 (4.73),
D
229 (4.43), and 285.5 (4.46) nm. IR (KBr): νmax 2947, 2806, 1638, 1576, 1506, 1371, 1302,
1267, 1163, and 827 cm−1. 1H NMR δ ppm (300 MHz, CDCl3): 12.05 (br s, 1H), 7.40 (dd,
1H, J＝ 8.7, 5.1 Hz), 7.44 (d, 2H, J＝ 8.7 Hz), 7.25 (dd, 2H, J＝ 8.7, 2.1 Hz), 7.07 (dt, 1H, J
＝ 9.0, 2.1 Hz), 6.97 (d, 2H, J＝ 8.7 Hz), 6.08 (d, 1H, J＝ 2.1 Hz), 6.06 (br s, 1H, J＝ 2.4
Hz), 5.40 (dd, 1H, J＝ 13.2, 3.0 Hz), 4.03 (t, 2H, J＝ 6.0 Hz), 3.85 (s, 3H), 3.17–3.07 (m,
4H), 2.81 (dd, 1H, J＝ 17.1, 3.0 Hz), 2.47 (t, 2H, J＝ 7.2 Hz), 2.21–2.04 (m, 6H), 1.89–1.80
(m, 2H, H-2’’), and 1.76–1.68 (m, 2H). 13C NMR δ ppm (75 MHz, CDCl3): 195.9 , 167.5,
164.1, 162.9, 161.1, 160.1, 130.5, 127.7, 122.7, 122.5, 117.3, 114.4, 112.5, 112.1, 103.1,
97.6, 97.2, 95.5, 94.6, 79.0, 68.3, 58.3, 55.4, 53.5, 43.2, 34.6, 30.5, 27.0, and 23.3. ESIMS
m/z 560.8 [M + H]+; HR-Q-TOFMS: 561.2447 [M + H]+ (calcd for C32H33FN2O6,
561.2395).
5-hydroxy-2-(4-fluorophenyl)-7-(4-(4-(6-fluorobenzo[d]isoxazol-3-yl)piperidin-1-yl)bu
toxy)chroman-4-one (7e):
Yellow solid, yield 33%. [α]20 −5.2 (c 0.1, MeOH). UV (MeOH): λmax (log ε ) 202 (4.71),
D
226 (4.59), and 285 (4.43) nm. IR (KBr): νmax 3078, 2943, 2803, 1641, 1614, 1580, 1510,
1
1452, 1368, 1302, 1246, 1171, and 816 cm−1. H NMR δ ppm (300 MHz, CDCl3): 12.04
(br s, 1H), 7.72 (dd, 2H, J＝ 8.7, 5.1 Hz), 7.47–7.42 (m, 2H), 7.24 (dd, 2H, J＝ 8.7, 2.1 Hz),
7.16–7.02 (m, 4H), 6.08 (d, 1H, J＝ 2.1 Hz), 6.05 (br s, 1H, J＝ 2.4 Hz), 5.40 (dd, 1H, J＝
12.6, 3.0 Hz), 4.03 (t, 2H, J＝ 6.0 Hz), 3.11–3.01 (m, 4H), 2.80 (dd, 1H, J＝ 17.1, 3.0 Hz),
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2.48 (t, 2H, J＝ 7.2 Hz), 2.22–2.03 (m, 6H), 1.87–1.80 (m, 2H), and 1.75–1.68 (m, 2H). 13C
NMR δ ppm (75 MHz, CDCl3): 195.9, 167.5, 164.1, 162.6, 161.0, 134.3, 134.3, 128.0,
122.7, 122.5, 117.3, 115.9, 115.7, 112.5, 112.1, 103.0, 97.2, 95.7, 94.6, 78.5, 68.3, 58.2,
53.4, 30.4, 43.3, 34.5, 26.9, and 23.2. ESIMS m/z 548.7 [M + H]+; HR-Q-TOFMS:
549.2273 [M + H]+ (calcd for C31H30F2N2O5, 549.2196).
7-(4-Bromopropoxy)-5-hydroxy-2-(4-methoxyphenyl)chroman-4-one (6d):
In the same way as preparation of 6 (a–c), 1,3-dibromopropane (10 mmol) was added to a
solution of 5a (5 mmol) and potassium carbonate in acetone (30 mL), and the mixture was
refluxed for 3 h. After cooling to room temperature, the mixture was filtered, the solvent
was evaporated and the residue was purified by column chromatography (petroleum
1
ether/EtOAc 15:1) to yield 6d as yellow oils. Yield: 54%. H NMR δ ppm (300 MHz,
CDCl3): 12.03 (br s, 1H), 7.41 (d, 2H, J＝ 8.7 Hz), 7.04–6.88 (m, 6H), 6.09 (d, 1H, J＝ 2.1
Hz), 6.05 (br s, 1H, J＝ 1.8 Hz), 5.37 (dd, 1H, J＝ 12.9, 2.7 Hz), 4.03 (t, 2H, J＝ 6.0 Hz),
3.85 (s, 3H), 3.51 (t, 2H, J＝ 6.0 Hz), 3.11 (dd, 1H, J＝ 17.1, 12.9 Hz), 2.80 (dd, 1H, J＝
17.1, 3.0 Hz), and 2.04–1.99 (m, 2H). ESIMS m/z 407.2 [M + H]+ .
Procedure for the preparation of 7f and 7g
In the same way as in the preparation of 7 (a–c), arylpiperazine (piperidine) (2.5 mmol)
was added to a suspension of 6d (2 mmol). The resulting mixture was refluxed for 1 h.
After filtration, the resulting filtrate was evaporated to dryness under reduced pressure. The
residue was evaporated under reduced pressure, and the crude product was purified by
means of chromatography (petroleum ether/EtOAc 2:1 ) to yield 7f and 7g.
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5-hydroxy-2-(4-methoxyphenyl)-7-(4-(4-(2-methoxyphenyl)piperazin-1-yl)propoxy)ch
roman-4-one (7f):
Yellow sticky residue, yield 21%. [α]20 −10.2 (c 0.1, MeOH). UV (MeOH): λmax (log ε )
D
209.5 (4.63), and 285.5 (4.31) nm. IR (KBr): νmax 2945, 2818, 1643, 1574, 1516, 1501,
1
1449, 1375, 1304, 1242, 1163, and 829 cm−1. H NMR δ ppm (300 MHz, CDCl3): 12.04
(br s, 1H), 7.40 (d, 2H, J＝ 8.4 Hz), 7.04–6.87 (m, 6H), 6.09 (br s, 1H), 6.08 (br s, 1H),
5.38 (dd, 1H, J＝ 12.9, 2.4 Hz), 4.08 (t, 2H, J＝ 6.0 Hz), 3.88 (s, 3H), 3.85 (s, 3H),
3.17–3.07 (m, 5H), 2.80 (dd, 1H, J＝ 17.1, 3.0 Hz), 2.69 (m, 4H), 2.58 (t, 2H, J＝ 7.2 Hz),
13
and 2.07–1.99 (m, 2H). C NMR δ ppm (75 MHz, CDCl3): 196.0, 167.2, 164.1, 162.9,
160.1, 152.2, 140.8, 130.4, 127.7, 123.3, 121.1, 118.4, 114.2, 111.2, 103.2, 95.6, 94.6, 79.0,
66.4, 55.4, 54.8, 53.2, 49.8, 43.2, and 29.7. ESIMS m/z 519.0 [M + H]+; HR-Q-TOFMS:
519.2548 [M + H]+ (calcd for C30H34N2O6, 519.2490).
5-hydroxy-2-(4-methoxyphenyl)-7-(4-(4-(6-fluorobenzo[d]isoxazol-3-yl)piperidin-1-yl)
propoxy)chroman-4-one (7g):
Yellow sticky residue, yield 27%. [α]20 −4.5 (c 0.1, MeOH). UV (MeOH): λmax (log ε ) 203
D
(4.69), 227 (4.64), and 285.5 (4.45) nm. IR (KBr): νmax 2930, 2845, 1639, 1574, 1512,
1
1450, 1302, 1252, 1165, and 829 cm−1. H NMR δ ppm (300 MHz, CDCl3): 12.04 (br s,
1H), 7.72 (dd, 1H, J＝ 8.4, 5.1 Hz), 7.39 (d, 2H, J＝ 8.4 Hz), 7.25 (m, 1H), 7.06 (dt, 1H, J
＝ 9.0, 2.1 Hz), 6.96 (d, 2H, J＝ 8.4 Hz), 6.10 (d, 1H, J＝ 2.4 Hz), 6.08 (d, 1H, J＝ 2.4 Hz),
5.40 (dd, 1H, J＝ 12.9, 2.1 Hz), 4.08 (t, 2H, J＝ 6.0 Hz), 3.85 (s, 3H), 3.17–3.08 (m, 4H),
2.81 (dd, 1H, J＝ 17.1, 2.7 Hz), 2.60 (t, 2H, J＝ 7.2 Hz), and 2.33–1.98 (m, 8H). 13C NMR
δ ppm (75 MHz, CDCl3): 196.0, 167.4, 164.1, 162.9, 161.0, 160.0, 130.4, 127.7, 122.7,
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122.6, 117.3, 114.2, 112.5, 112.2, 103.1, 97.6 , 95.6, 94.6, 79.0, 66.7, 55.4, 55.0, 53.5, 43.2,
34.5, 30.4, 30.0, and 26.5. ESIMS m/z 546.9 [M + H]+; HR-Q-TOFMS: 547.2309 [M + H]+
(calcd for C31H31FN2O6, 547.2239).
In vitro evaluation of biological activity
Measurement of dopamine D2 receptor activity
The activity of the D2 receptor was detected by the fluorescent method for measuring
cytoplasmic calcium ion concentration after dopamine stimulation (23, 24). D2 receptor/G
protein α16a co-transfected HEK293 cells (from the Shanghai Institute of Materia Medica,
Chinese Academy of Sciences) were seeded in 96-well plates and incubated overnight at
37°C. The media were then removed, and 40 μL of 10 μM Fluo-4/AM (a calcium
fluorescent probe) (Invitrogen Corporation, USA) was added. The plates were then
incubated for 40 min at 37°C. After the supernatant was discarded and the cells were
washed with calcium buffer, 50 μL of calcium buffer containing tested compounds at the
dosage range from 0.01 nM to 10 μM were added, and the plates were incubated for 10
min. The fluorescence values at an emission wavelength of 525 nm and an excitation
wavelength of 485 nm were detected by the FlexStation II microplate reader (Molecular
Devices, USA), starting 15 s after 25 μL of calcium buffer containing 50 nM dopamine
(an agonist of the dopamine D2 receptor) (Sigma-Aldrich, USA) was automatically added
by the instrument. Data were expressed as: % Response = (FSample−FBlank)/(FDopamine−FBlank).
FSample indicated the fluorescence value of tested compounds, FBlank represented the
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fluorescence value completely suppressed by 10-5 M eticlopride (an antagonist of the
dopamine D2 receptor) (Sigma-Aldrich, USA), and FDopamine indicated the fluorescence
value of the 50 nM dopamine-only group.
Determination of LPS/IFN-γ-induced nitric oxide release from BV2 microglial cells
BV2 mouse microglia (5×105 cells/mL) were seeded in 96-well plates and incubated at
37°C in a humidified atmosphere containing 5% CO2 and 95% air for 5-7 d. After the cells
grew to 70-80% confluence, pre-treatment with tested compounds at the dosage range from
0.1 μM to 10 μM, 4 h prior to LPS (1 μg/mL) (Sigma-Aldrich, USA) and IFN-γ (1 ng/mL)
(Bio-RAD, USA) stimulation for 24 h. The nitrite content (an indicator of NO production)
was measured with the Griess reaction (12,13). The supernatant (100 μL) was mixed with
an equal volume of the Griess reagent (Solution A: 222488; Solution B: S438081)
(Beyotime, China), and the absorbance of the mixture at 525 nm was determined using an
ELISA plate reader (Themo, USA).
In order to eliminate the possibility that the decrease of NO content may be due to the cell
death induced by LPS/IFN-γ, cell viability was also determined by a CCK-8 assay before
the measurement of NO release. A dose of 100 μL of CCK-8 (Dojindo Laboratories, Japan)
solution was added to 1 mL of cell suspension (1×105 cells/mL in 96-well plates) and
incubated for 4 h. The optical density was measured at 540 nm using an ELISA plate
reader.
In vivo evaluation of the effects of synthesized compounds
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Animals
Male BALB/c mice weighing 20 2 g (from Vital River Laboratory Animal Technology
Co. Ltd., China) were housed under a 12 h light/12 h dark cycle with free access to food
and water. Animals were randomly assigned to different experimental groups, and each
group was kept in a separate cage. All experiments were performed in accordance with the
requirements of the Provisions and General Recommendations of Chinese Experimental
Animal Administration Legislation, and approved by the Animal Ethics Committee of
Capital Medical University, China.
Open field test in the MK-801-induced mouse model
BALB/c mice were intragastrically administered compounds 7d–7g (50 mg/kg) for 4 d. On
the 4th day, 60 min after drug administration, mice were placed in Plexiglas boxes (41.5 cm
× 41.5 cm × 41.5 cm) equipped with a video-based Ethovision System (Noldus,
Wageningen, The Netherlands) for evaluating locomotor activity. After baseline recording
for 60 min, a dose of 0.6 mg/kg of (+)-MK-801 hydrogen maleate (an NMDA receptor
antagonist) (Sigma-Aldrich, USA) was intraperitoneally injected, and the locomotor
activity of each mouse was recorded for 210 min at intervals of 10 min. The total distance
of mouse movement was calculated (25,26).
Climbing behavior assay in an apomorphine-induced mouse model
BALB/c mice were intragastrically administered compounds 7d–7g (25 mg/kg) for 4 d.
After drug administration on the 4th day, mice were placed in specially designed cages with
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steel sidewalls (35 cm × 35 cm × 55 cm) and a stainless steel floor covered with aspen
chips. Immediately after subcutaneous injection of a dose of 2 mg/kg apomorphine (an
agonist of dopamine receptor) (Tocris bioscience, Britain), mice were put into the test cage.
After a 20-min period of exploratory activity, climbing behaviour (the time of climbing on
the sides of top of cage) was recorded every 5 min by an observer who was blind to the
drug treatment (27, 28).
Statistical analysis
SPSS 17.0 and Microsoft Excel 2007 were used for the statistical analysis. All data were
expressed as the mean standard error of mean (S.E.M.). The differences among the
groups were analyzed by one-way analysis of variance (ANOVA) with a Tukey post hoc
test when comparing multiple groups. P values lower than 0.05 were regarded as
statistically significant.
Results
Synthesized compounds
In the present experiment, seven novel flavanone derivatives (7a–7g) were synthesized,
and the general strategy is summarized in Fig. 1. The chalcones 3a–3c were obtained
through the condensation of 2,4-di-MOM phloracetophenone 2 with substituted
benzaldehyde. The chalcones then underwent cyclisation in the presence of CH3COONa in
methanol to yield the corresponding dihydroflavonoids 4a–4c. After acidification of 4a–4c
to give 5a–5c, the latter were reacted with 1,4-dibromobutane to yield 6a–6c, or with
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1,3-dibromopropane to yield 6d. The corresponding bromine substitutes were reacted with
1-(2-methoxyphenyl)piperazine in acetonitrile, in the presence of K2CO3 and a catalytic
amount of potassium iodide, to give 7a–7c and 7f, or reacted with
6-fluoro-3-(4-piperidinyl)-1,2-benzisoxazole to give 7d, 7e, and 7g.
Effects of compounds 7a–7g on dopamine D2 receptor activity in vitro
The activity of the D2 receptor was detected by the fluorescent method for measuring
cytoplasmic calcium ion concentration after dopamine stimulation. The results showed that
the synthesized compounds 7a−7g decreased D2 receptor activity in a dose-dependent
manner in D2 receptor/G protein α16a co-transfected HEK293 cells (Fig. 2). Their IC50
values were 0.051–0.35 μM (Table 1).
Effects of compounds 7a–7g on LPS/IFN-γ-induced NO production in BV2 microglial
cells
As shown in Fig. 3, LPS/IFN-γ significantly increased NO content in BV2 microglial cells
(P<0.01). Compound 7g (0.1, 1, 10 μM) inhibited the LPS/IFN-γ-induced over-production
of NO in a dose-dependent manner (P<0.05,P<0.01). At a dose of 10 µM, 7a, 7b, 7d, 7e,
and 7f markedly decreased the levels of NO in LPS/IFN-γ-stimulated BV microglia
(P<0.01). The results indicated that these compounds had an anti-neuroinflammatory
effect.
To eliminate the possibility that the decrease in NO content might be due to the cell death
induced by LPS/IFN-γ, cell viability was determined by the CCK-8 assay in the same
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manner as NO measurement. The results showed that 7a–7g (1, 10, 100 μM) alone or in
the presence of LPS/ IFN-γ had no significant influence on the cell viability of BV2
microglia (data not shown).
Effects of compounds 7d–7g on locomotor activity in MK-801-induced mouse model of
schizophrenia
The open field test was used to detect the locomotor activity in the schizophrenia mouse
model induced by MK-801 (an antagonist of NMDA receptors). Fig. 4A displays the total
distance traveled and recorded at 10-min intervals for 270 min. There were no significant
differences among groups in the total distance traveled in the baseline recording for 60 min.
After intraperitoneal injection of MK-801 (0.6 mg/kg), the total distance traveled for 210
min significantly increased in the model mice (P<0.01), indicating the positive symptom of
schizophrenia. Intragastric administration of 7d, 7e, and 7g (50 mg/kg) for 4 d decreased
the total distance traveled for 210 min, in which the effects of 7d were significantly
different from those observed in the MK-801 model mice (P<0.05) (Fig. 4B). These results
indicated that some of the synthesized compounds suppressed the hyperactivity in the
NMDA receptor antagonist-induced mouse model of schizophrenia.
Effects of compounds 7d–7g on climbing behavior in apomorphine-induced mouse
model of schizophrenia
Apomorphine is an agonist of dopamine receptors, and has been classically linked to motor
agitation, one of the positive symptoms of schizophrenia. In the present experiment, the
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results showed that the latency in the climbing test was significantly increased by the
subcutaneous injection of apomorphine (P<0.01). This increase was reversed by
intragastrical administration of 7d, 7e, 7f, and 7g for 4 d, in which the effects of 7g were
significantly different from that observed in the apomorphine model mice (P<0.05) (Fig. 5).
These results demonstrated that some of the synthesized compounds decreased the
dopamine receptor agonist-induced hyperactivity in the schizophrenia mouse model,
suggesting that the compounds may have a potential antipsychotic effect.
Discussion
It has been reported that natural flavanones possess a broad range of pharmacological
properties, including anti-neuroinflammatory and radical-scavenging effects (11−16). In
addition, some first-line antipsychotic drugs containing an arylpiperazine (piperidine)
group have inhibitive effects on dopamine activity (17−22). In an attempt of creating a
multi-targeted antipsychotic drug, we designed and synthesized compounds 7a–7g, which
have the skeletal structure of flavanones combined with the arylpiperazine (piperidine)
group.
In the biological activity evaluation of synthesized flavanone derivatives, we did in
vitro study first, and found that 7 target compounds inhibited dopamine 2 receptor activity
with different IC50, and 6 compounds suppressed NO release from a microglia
inflammatory cell model. According to the results in vitro, we chose 4 compounds with
better biological activities to continue in vivo study. We used two classic animal models of
schizophrenia for drug screening, and found that some compounds by intragastrical
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administration improved the behavioral impairment in apomorphine-induced mouse model
(dopaminergic mechanism) and in MK-801-induced mouse model (glutamatergic
mechanism).
The dopamine hypothesis of schizophrenia has been proposed for several decades.
The first evidence was gathered from the administration of amphetamine and other
compounds, which increase extracellular concentrations of dopamine and can induce
psychotic symptoms similar to those seen in schizophrenia (29). Recently, a study
including 176 post-mortem samples from patients with schizophrenia has shown an
increased expression of the presynaptic D2 autoreceptor (30), and there is a clear
association between the D2 receptor gene and schizophrenia (31). In the present study, we
evaluated dopamine D2 receptor activity by using D2 receptor/G protein α16a
co-transfected HEK293 cells. In this assay, the activation of the dopamine-induced D2
receptor can activate coupled G protein α16, causing the activation of phospholipase C
(PLC) and the generation of inositol 1,4,5-triphosphate (IP3) and diacylglycerol (DAG). IP3
proceeds to combine with its receptor in the endoplasmic reticulum and mitochondria of
cells, causing the release of calcium ions into the cytoplasm. Thus, the changes of the
intracytoplasmic calcium ion concentration can be used to detect the D2 receptor activation
state (23,24). Our present study showed that synthesized compounds 7a−7g containing an
arylpiperazine (piperidine) group decreased D2 receptor activity in a dose-dependent
manner in D2 receptor/Gα16a co-transfected HEK293 cells. Furthermore, mice treated
with apomorphine, a mixed D1/D2 agonist, tend to adopt a vertical position along the walls
of their cage (32,33). This climbing behavior appears to be elicited by stimulation of DA
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receptors in the striatum (34). In addition, apomorphine has been used as a good tool drug
to induce climbing behavior using a relatively high dose acting as a postsynaptic DA
agonist (35,36). Our in vivo study exhibited that oral administration of 7d, 7e, 7f, and 7g
decreased the hyperactivity in the climbing test in an apomorphine-induced schizophrenia
mouse model. These results suggest that some of the synthesized compounds may have
potential antipsychotic effects via the inhibition of dopamine activity.
Glutamatergic neurons represent the primary excitatory afferent and efferent systems
innervating the cortex, limbic regions, and striatum. The postsynaptic actions of glutamate
are mediated by a family of glutamate-gated ion channels (such as NMDA
receptors),which permit the influx of sodium and calcium, thereby depolarizing (exciting)
neurons (37,38). Much evidence suggests that hypofunction of NMDA receptors mediates
neurotransmission disorder, which is a critical deficit in schizophrenia (39,40). Animals
injected with MK 801 (an antagonist of NMDA receptors) exhibit schizophrenia-like
behaviors, suggesting that the glutamatergic hypofunction may produce the symptoms that
are relevant to schizophrenia (41,42). In the present study, , we found that intragastrical
administration of 7d, 7e, and 7g decreased the hyperlocomotor activity in the open field
test in MK-801-induced schizophrenia model mice. This result suggests that some of the
synthesized compounds may enhance glutamatergic function, which may be useful in the
treatment of schizophrenia.
Recently, neuropathological and neuroimaging studies have provided consistent
evidence of an association between schizophrenia and microglial activation and
proliferation (43−45). Numerous studies have found that people with schizophrenia have
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increased blood concentrations of inflammatory cytokines (46−48). The microglia
hypothesis of schizophrenia proposes that activated microglia in the central nervous system
release pro-inflammatory cytokines and free radicals, which cause abnormal neurogenesis,
neuronal degradation, and white matter abnormalities, contributing to the pathogenesis of
schizophrenia (49). In the present study, we used LPS/IFN-γ to activate microglia and
induce a significant increase in the production of the inflammatory mediator NO. We found
that most of the target compounds with the skeletal structure of flavanones inhibited the
LPS/IFN-γ-induced over-production of NO in BV microglia. This result suggests that these
compounds may have an anti-neuroinflammatory effect, which may be advantageous in
treating schizophrenia.
Conclusion
In the current study, a series of novel flavanone derivatives with an arylpiperazine
(piperidine) group was synthesized. The evaluation of the biological activity showed that
compounds 7a−7g decreased dopamine D2 receptor activity and inhibited
neuroinflammation in vitro. Oral administration of 7d, 7e, and 7g reversed the movement
hyperactivity in mice induced by both MK-801 (an antagonist of NMDA receptors) and
apomorphine (an agonist of dopamine receptors). These results suggest that some of novel
flavanone derivatives have the potential antipsychotic effect, and may be useful in the
treatment of schizophrenia.
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Acknowledgements
This work was supported by National Natural Science Foundation of China (Nos.
81273498, 81473373), National Science and Technology Major Project for New Drug
Research and Development of China (No. 2015ZX09101-016), Beijing New Medical
Disciplines Grant (No. XK100270569), and Beijing High-level Health and Technical
Personal Plan (Nos. 2011-1-7, 2014-2-014). We thank Shanghai Institute of Materia
Medica, Chinese Academy of Sciences for technical assistance in dopamine D2 receptor
test.
Conflict of interest
The authors declare that there are no conflicts of interest associated with this manuscript.
Appendix A. Supplementary data
Supplementary data associated with this article can be found in the online version.
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