Diarylheptanoids from Rhizomes of Alpinia officinarum Inhibit Aggregation of α-Synuclein

Article abstract of DOI:10.1021/acs.jafc.7b02021

Two new diarylheptanoids, alpinin A (1) and alpinin B (2), together with 18 known diarylheptanoids (3-20), were isolated from the rhizomes of Alpinia officinarum. Their structures were elucidated by comprehensive spectroscopic analysis, including high-resolution mass spectrometry, infrared spectroscopy, and one- and two-dimensional nuclear magnetic resonance spectroscopy. Structurally, alpinin A is a new member of the small family of oxa-bridged diarylheptanoids and contains the characteristic 2,6-cis-configured tetrahydropyran motif (C₁-C₅ oxa bridge). The absolute configuration of alpinin A was confirmed by asymmetric total synthesis of the enantiomer (ent-1), corroborating the assignment of the molecular structure. The absolute configuration of alpinin B was determined on the basis of the analysis of the circular dichroism exciton chirality spectrum. We evaluated the inhibitory activity of all isolated diarylheptanoids against α-synuclein aggregation at 10 μM. Alpinins A and B significantly inhibited α-synuclein aggregation by 66 and 67%, respectively.

Full text of DOI:10.1021/acs.jafc.7b02021

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Article
Diarylheptanoids from Rhizomes of Alpinia
officinarum Inhibit Aggregation of Alpha-synuclein
Guangmiao Fu, Wei Zhang, Dongsheng Du, Yu Pong Ng, Fanny C. F. Ip, Rongbiao Tong, and Nancy Y. Ip
J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.7b02021 • Publication Date (Web): 14 Jul 2017
Downloaded from http://pubs.acs.org on July 14, 2017
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Diarylheptanoids from Rhizomes of Alpinia officinarum Inhibit Aggregation of Alphaꢀ
synuclein
Guangmiao Fu,†, ¶ Wei Zhang,‡, ¶ Dongsheng Du,† Yu Pong Ng,† Fanny C. F. Ip,†,§,ǁ Rongbiao
Tong,*,‡ Nancy Y. Ip*,†, §,ǁ
‡
§
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†Division of Life Science, Department of Chemistry, and State Key Laboratory of Molecular
Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Hong
Kong, China
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ǁGuangdong Provincial Key Laboratory of Brain Science, Disease and Drug Development,
HKUST Shenzhen Research Institute, Shenzhen, Guangdong, China
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¶These authors contributed equally to this work.
*Corresponding authors:
Prof. Nancy Y. Ip, Division of Life Science
The Hong Kong University of Science and Technology
Clear Water Bay, Hong Kong SAR, China
Phone: 852ꢀ2358ꢀ7304
Fax: 852ꢀ2358ꢀ1552
Eꢀmail: boip@ust.hk
Prof. R. Tong, Department of Chemistry
The Hong Kong University of Science and Technology
Clear Water Bay, Hong Kong SAR, China
Phone: 852ꢀ2358ꢀ7357
Fax: 852ꢀ2358ꢀ1594
Eꢀmail: rtong@ust.hk
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ABSTRACT
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Two new diarylheptanoids, alpinins A (1) and B (2), together with eighteen known
diarylheptanoids (3–20), were isolated from the rhizomes of Alpinia officinarum. Their structures
were elucidated by comprehensive spectroscopic analysis including HRMS, IR, and 1Dꢀ and 2Dꢀ
NMR. Structurally, alpinin A is a new member of the small family of oxaꢀbridged
diarylheptanoids and contains the characteristic 2,6ꢀcisꢀconfigured tetrahydropyran motif (C1ꢀC5
oxaꢀbridge). The absolute configuration of alpinin A was confirmed by asymmetric total
synthesis of the enantiomer (entꢀ1), corroborating the assignment of the molecular structure. The
absolute configuration of alpinin B was determined on the basis of the analysis of the CD exciton
chirality spectrum. We evaluated the inhibitory activity of all isolated diarylheptanoids against
alphaꢀsynuclein aggregation at 10 µM. Alpinins A and B significantly inhibited alphaꢀsynuclein
aggregation by 66% and 67%, respectively.
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KEYWORDS: Alpinia officinarum, diarylheptanoids, alpinin A, alpinin B, inhibit alphaꢀ
synuclein aggregation
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INTRODUCTION
Parkinson’s disease is the second most common progressive neurodegenerative disorder. The
characteristic phenotypes of the disease are majorly the resting tremor and postural instability
with cognitive and emotional disorders. Although the etiology and pathogenesis of Parkinson’s
disease are not fully understood, recent evidence suggests that environmental and genetic factors
might account for the progression of disease.1 Alphaꢀsynuclein (αꢀsynuclein), a protein expressed
predominantly in neurons, especially at synaptic terminals, is the major component of Lewy
bodies in Parkinson’s disease patients, 2, 3 and is therefore implicated in the pathogenesis of the
disease. Alphaꢀsynuclein protein readily adopts various conformations2, 3 it has a strong tendency
to selfꢀaggregate into oligomers, followed by fibrils that are deposited as Lewy bodies and other
similar pathologies. Therefore, small organic molecules that can inhibit αꢀsynuclein aggregation
might provide a potentially effective treatment of Parkinson’s disease. Herein, we report the
isolation and/or synthesis of new natural diarylheptanoid products and the preliminary evaluation
of their inhibition activity against the αꢀsynuclein aggregation.
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Alpinia officinarum (Hance) is a perennial herb from Zingiberaceae family that is ubiquitous in
tropical and subtropical Asian regions, especially Southern China. The rhizome of Alpinia
officinarum is used as a traditional Chinese medicine for strengthening the circulatory system,
treating stomach ache, cold and swelling symptoms.4 Besides its medicinal use, A. officinarum is
also a valuable dietary material. Phytochemical studies have revealed that diarylheptanoids,5ꢀ7
flavonoids,8 and volatile oils are the major characteristic compounds of A. officinarum. It is
noteworthy that many diarylheptanoid natural products present in Alpinia species possess
cytotoxic, antioxidant, antiꢀinflammatory, antiplatelet and antiproliferative activities.9ꢀ12 We were
intrigued by the finding that the total extract of A. officinarum inhibited the aggregation of αꢀ
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synuclein and exhibits a neuroprotective effect. In this article, we describe the isolation and
structural elucidation of two new diarylheptanoids and 18 known ones (Figure 1). We also
investigated their inhibitory effects on αꢀsynuclein aggregation and accomplished the first
asymmetric total synthesis of the enantiomer of compound 1.
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MATERIALS AND METHODS
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General Experimental Procedures. Solvents (Merck; A.R.) for isolation were used as received
unless stated otherwise. Silica gel (Qingdao Marine Chemical Incorporation; 200–300 mesh),
MCI Gel CHP20P (Supelco; 63–150 ꢁm) and Sephadex LHꢀ20 gel (Amersham Biosciences)
were used for column chromatography. Fractions were monitored by thinꢀlayer chromatography
(TLC) on precoated silica gel 60 GF254 aluminum plates (Merck), and the signals were observed
on heated silica gel plates after spraying 10% H2SO4 in EtOH. Preparative HPLC was performed
using a Waters 2996 photodiode array detector (220 nm) equipped with a preparative OBD
column (150 × 19 mm, 5.0 ꢁm, flow rate 15.0 mL/min; Waters Xbridge). Optical rotation was
obtained by a Jasco Pꢀ2000 polarimeter. Spectral data on UV, CD, IR, and NMR were gained
from a PerkinꢀElmer Lambda 900 UV/VIS/NIR spectrophotometer, a Chirascan Applied
Photophysics spectropolarimeter, a PerkinꢀElmer 577 spectrometer (KBr discs), and a Bruker
AMꢀ400 spectrometer, respectively. Highꢀresolution mass spectrometry (HRMS) was recorded
using a Waters Xevo G2ꢀXS QTOF in an electrosprayꢀionization mode (ESI).
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Plant Material. The dried rhizomes of Alpinia officinarum Hance were procured in August 2009
from Zhanjiang, Guangdong, China, authenticated by one of the authors (Guangꢀmiao Fu), and
preserved as a voucher specimen (TCMꢀ40) in the room CYT5014 at HKUST, Hong Kong SAR,
China.
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Extraction and Isolation. A schematic flowchart of the details of extraction and isolation is
provided in the Supporting Information. The dried grounded rhizomes (8.0 kg) of A. officinarum
were extracted with 70% EtOH (40.0 L × 3, 2 h each), and the pooled extract was then
concentrated in vacuo to give a brown paste (700.0 g), which was successively partitioned
between chloroform (1.0 L × 3), and nꢀBuOH (1.0 L × 3) with water (1.0 L) to yield fractions of
chloroform (120.0 g), nꢀBuOH (150.0 g), and water (420.0 g), respectively.
The nꢀBuOH fraction (80.0 g) was fractionated by silica gel column chromatography using a
stepwise gradient elution of CH2Cl2:MeOH (v/v, 100:0, 50:1, 20:1, 15:1, 10:1, 5:1 and 1:1) to
yield seven fractions designated Fr. 1−7. Purification of Fr. 2 (9.7 g) was performed with an MCI
Gel CHP20P column elution with a gradient of MeOH:H2O (v/v, 2:8, 4;6, 5:5, 6:4, 8:2 and 9:1),
Sephadex LHꢀ20 column elution with a mixture of CHCl3:MeOH (v/v, 1:1), and finally
preparative HPLC using ACN:H2O:TFA (v/v/v, 20:80:0.025, in 20 min). This provided the new,
analytically pure compounds 1 (39 mg, alpinin A) and 2 (28 mg, alpinin B), as well as the
previously known diarylheptanoid 3 (28 mg). The separation of Fr. 3 (6.8 g) with Sephadex LHꢀ
20 elution with CHCl3/CH3OH (v/v, 1:1), and preparative HPLC elution with ACN:H2O:TFA
(v/v/v, 10:90:0.025, in 40 min) yielded three known diarylheptanoid compounds: 6 (15 mg), 7
(13 mg), and 8 (20 mg). Fr. 4 (10.6 g) was chromatographed over silica gel with gradient eluting
solvents CHCl3:MeOH (v/v, 10:0, 9:1, 8:2, 7:3, 6:4 and 1:1) to give three subfractions designated
Fr.4ꢀ1−Fr.4ꢀ3, which were categorized according to their polarity estimated by TLC. Compound
11 (17 mg) was obtained from Fr. 4ꢀ1 by Sephadex LHꢀ20 column chromatography elution with
CHCl3:MeOH (v/v, 1:1), and compound 9 (8 mg) was found in Fr. 4ꢀ2 through silica gel column
chromatography elution with a gradient of CHCl3:MeOH (v/v, 20:1, 10:1, 5:1).
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The chloroform fraction (68.0 g) was separated by a silica gel column chromatography using
gradient elution with petroleum ether (60ꢀ80°C):EtOAc (v/v, 10:0, 9:1, 8:2; 7:3, 6:4, 5:5 and
0:10) afforded six subfractions designated Fr. A−Fr. F, which were categorized according to their
polarity estimated by TLC. Separation of Fr.B (9.6 g) on a silica gel column chromatography
elution with a gradient of petroleum ether (60ꢀ80°C):EtOAc (v/v, 30:1, 20:1, 10:1, 5:1, and 1:1)
yielded two pure compounds 17 (35 mg), and 19 (28 mg), as well as a mixture of 18 and 20,
which was efficiently separated by Sephadex LHꢀ20 column chromatography elution with
CHCl3:MeOH (v/v, 1:1) (18, 38 mg; 20, 25 mg). Fr. C (7.5 g) was further fractionated on a silica
gel column eluted with petroleum ether (60ꢀ80°C):EtOAc (v/v, 15:1) to give 12 (20 mg) and
three subfractions designated Fr.Cꢀ1−Fr.Cꢀ3. Compound 13 (22 mg) and 14 (8 mg) from Fr. Cꢀ2,
15 (16 mg) from Fr. Cꢀ3 were then obtained through Sephadex LHꢀ20 column chromatography
elution with CHCl3:MeOH (v/v, 1:1). Similarly, compounds 10 (11 mg) and 16 (25 mg) were
isolated through sequential separation of Fr. D (5.5 g) by Sephadex LHꢀ20 (eluted with
CHCl3:MeOH, v/v, 1:1) and silica gel column chromatography (eluted with petroleum ether (60ꢀ
80°C):EtOAc, v/v, 20:1−10:1). Fr. E (8.8 g) was further fractionated by Sephadex LHꢀ20 (eluted
with CHCl3:MeOH, v/v, 1:1), and preparative HPLC (eluted with ACN:H2O:TFA, v/v/v,
10:90:0.025, in 40 min) to give compounds 4 (17 mg) and 5 (9 mg).
Methylation of 1. K2CO3 (41.0 mg) was added to an acetone solution of compound 1 (13.1 mg
in 2 mL) at room temperature, and stirred under a nitrogen atmosphere for 10 min. Iodomethane
(0.6 mL) was then added and mixed for 1.5 h at room temperature, followed by heating under
reflux at 60°C overnight (~16 h). Upon cooling to room temperature, the reaction mix was
worked up and organic residue was purified by column chromatography on silica gel
(CH2Cl2:MeOH, v/v, 40:1) to give methylated analogue of alpinin A (1a, 12.0 mg).
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Methylation of 2. Following the same procedure as described for synthesis of 1a from alpinin A,
the methylated analogue (2a, 11.8 mg) of alpinin B was obtained from 12.8 mg alpinin B (2).
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Bisꢀpꢀbromobenzoate (2b) of 2a. Et3N (32 ꢁL), 4ꢀdimethylaminopyridine (DMAP, 15 mg), and
pꢀbromobenzoyl chloride (40 mg) were added sequentially to a solution of 2a (10 mg) in
anhydrous CH2Cl2 (0.6 mL). The reaction mixture was heated to 60°C and stirred for 9 h. Upon
cooling to room temperature, the reaction was quenched by H2O (20 mL). The mixture was then
extracted with EtOAc (10 mL× 3), and the combined organic fractions were concentrated in
vacuo to give a residue, which was purified by silica gel column chromatography
(CH2Cl2:MeOH, v/v, 9.5:0.5) to afford 2b (6 mg).
Alpinin A (1): yellowish oil. [α]D25 +51.1° (c 0.42, MeOH). UV (MeOH, nm): λmax (log ε), 281
(1.05). IR (KBr, cm−1): νmax 3358, 2941, 2856, 2361, 2032, 1674, 1607, 1527, 1455, 1340, 1284,
1
1203, 1090, 990, 958, 800. See Table 1 for the Hꢀ and 13CꢀNMR data. HRMS(ESI): m/z
399.1447 [M+Na]+ (calcd. for C20H24O7Na, 399.1420), m/z 377.1607 [M+H]+ (calcd. for
C20H25O7, 377.1600).
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(1R,3S,5R)ꢀ1,5ꢀepoxyꢀ3ꢀhydroxyꢀ1ꢀ(3,4,5ꢀtrimethoxyꢀphenyl)ꢀ7ꢀ(3,4ꢀdimethoxyꢀphenyl)heptane
(1a): amorphous powder. [α]2D5 −3.2° (c 0.10, MeOH). UV (MeOH, nm): λmax (log ε) 230 (2.54),
280 (2.02). IR (KBr, cm−1): νmax 3418, 3073, 2999, 2933, 2853, 2837, 1591, 1516, 1464, 1453,
1
1418, 1260, 1235, 1154, 1139, 1070, 1027, 807. HꢀNMR (CD3OD, 400 MHz) δ: 4.31 (1H, brd,
J = 11.1 Hz, Hꢀ1), 1.95, 1.15 (each 1H, m, Hꢀ2), 3.77 (1H, m, Hꢀ3), 2.01, 1.33 (each 1H, m, Hꢀ4),
3.35 (1H, m, Hꢀ5), 1.90, 1.80 (each 1H, m, Hꢀ6), 2.70 (2H, m, Hꢀ7), 6.70 (2H, s, Hꢀ2′ and Hꢀ6′),
6.84 (1H, d, J = 2.0 Hz, Hꢀ2′′), 6.79 (1H, d, J = 2.0, 8.0 Hz, Hꢀ5′′), 6.70 (1H, d, J = 8.0 Hz, Hꢀ6′′),
3.84 (6H, s, Hꢀ3′ and Hꢀ5′), 3.78 (3H, s, Hꢀ4′), 3.75 (6H, s, Hꢀ3′′ and Hꢀ4′′). See Table 1 for the
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13CꢀNMR data (CD3OD, 100 MHz). HRMS(ESI): m/z 455.2047 [M+Na]+ (calcd. for
C24H32O7Na, 455.2046).
Alpinin B (2): yellowish oil. [α]D25 +14.6° (c 0.22, MeOH); UV (MeOH, nm): λmax (log ε) 281
(2.11). IR (KBr, cm−1): νmax 3375, 2942, 2856, 2361, 2034, 1609, 1528, 1455, 1342, 1285, 1203,
1
13
1090, 991, 960, 800. See Table 1 for the HꢀNMR (CD3OD, 400 MHz) and CꢀNMR (CD3OD,
100 MHz) data. HRMS(ESI): m/z 401.1584 [M+Na]+ (calcd for C20H26O7Na, 401.1576), m/z
379.1752 [M+H]+ (calcd. for C20H27O7, 379.1757).
(3R,5R)ꢀ3,5ꢀdihydroxyꢀ1ꢀ(3,4,5ꢀtrimethoxyꢀphenyl)ꢀ7ꢀ(3,4ꢀdimethoxyꢀphenyl)ꢀheptane
(2a):
amorphous powder. [α]2D5 +6.5° (c 0.10, MeOH). UV (MeOH, nm): λmax (log ε) 230 (2.66), 280
(2.25). IR (KBr, cm−1): νmax 3418, 3000, 2934, 2853, 1591, 1516, 1465, 1453, 1419, 1261, 1235,
1155, 1140, 1070, 1028, 807, 764. 1H NMR (CD3OD, 400 MHz): δ 2.69 (2H, m, Hꢀ1), 1.75 (2H,
m, Hꢀ2), 3.70 (1H, m, Hꢀ3), 1.55 (2H, m, Hꢀ4), 3.70 (1H, m, Hꢀ5), 1.75 (2H, m, Hꢀ6), 2.63 (2H,
m, Hꢀ7), 6.50 (2H, s, Hꢀ2′, Hꢀ6′), 6.82 (1H, d, J = 2.0 Hz, Hꢀ2′′), 6.79 (1H, d, J = 2.0, 8.0 Hz, Hꢀ
5′′), 6.70 (1H, d, J = 8.0 Hz, Hꢀ6′′), 3.80 (6H, s, Hꢀ3′, Hꢀ5′), 3.78 (3H, s, Hꢀ4′), 3.74 (6H, s, Hꢀ3′′,
Hꢀ4′′). See Table 1 for the 13CꢀNMR (CD3OD, 100 MHz) data. HRMS(ESI): m/z 457.2198
[M+Na]+ (calcd. for C24H34O7Na, 457.2202).
Total synthesis of entꢀ1.
(S)ꢀ1ꢀ(3',4'ꢀDibenzyloxyphenyl)hexꢀ5ꢀeneꢀ3ꢀol (23) 13
Compound 22 (336 mg, 1.7 mmol) was added to a solution of (1R)ꢀ(−)ꢀ10ꢀcamphorsulfonic acid
(CSA, 13 mg, 0.06 mmol) and aldehyde 21 (200 mg, 0.6 mmol) in CH2Cl2 (0.096 mL) under a
nitrogen atmosphere. After stirring at room temperature for 5 days, the reaction mixture was
diluted with 20 mL CH2Cl2, quenched with 10 mL of saturated NaHCO3 solution, and extracted
with CH2Cl2 (3 × 5 mL). The combined organic phase was washed with brine, dried over Na2SO4,
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filtered, and concentrated under reduced pressure. The resultant residue was purified by silica gel
chromatography (hexane:EtOAc = 5:1) to give compound 23 as a white solid (130 mg, 58%). [α]
25
D
−13.5° (c 1.0, MeOH) ee = 92.5 %, tR (R) = 20.8 min, tR (S) = 18.7 min, hexane:iꢀPrOH =
90:10. 1HꢀNMR (CDCl3, 400 MHz) δ: 1.63 (s, 1H,OH), 1.68–1.74 (m, 2H), 2.15 (dt, J = 14.8 Hz,
J = 8.0 Hz, 1H), 2.28 (dt, J = 14.0 Hz, J = 5.6 Hz, 1H), 2.60 (dt, J = 16.4 Hz, J = 8.4 Hz, 1H),
2.70 (dt, J = 14.0 Hz, J = 7.6 Hz, 1H), 3.55–3.63 (m, 1H), 5.10–5.20 (m, 6H), 5.73–5.90 (m, 1H),
6.72 (dd, J = 8.4 Hz, J = 2.0 Hz, 1H), 6.81 (d, J = 1.6 Hz, 1H), 6.87 (d, J = 8.0 Hz, 1H), 7.27–
13
7.49 (m, 10H). CꢀNMR (CDCl3, 100 MHz,) δ: 31.5, 38.4, 42.1, 69.7, 71.3, 71.6, 115.4, 115.7,
118.3, 121.2, 127.36, 127.39, 127.74, 127.77, 128.5, 134.7, 135.5, 137.5, 137.6, 147.2, 148.9.
(1S, 3R, 5S)ꢀ1,5ꢀepoxyꢀ3ꢀacetoxyꢀ1ꢀ(3,4ꢀdiacetoxyꢀ5ꢀmethoxyꢀphenyl)ꢀ7ꢀ(3,4ꢀdibenzyloxyꢀphenyl)
heptane (25)
BF3ꢀOEt2 (0.077 mL, 0.62 mmol) was added to a stirred solution of aldehyde 24 (78 mg, 0.31
mmol), homoallylic alcohol 23 (120 mg, 0.31 mmol), TMSOAc (204 mg, 1.55 mmol), and
AcOH (0.12 mL, 2.17 mmol) in dry CH2Cl2 (5 mL) at 0°C under a nitrogen atmosphere. The
reaction mixture was warmed to room temperature and was subsequently stirred for 2 h. When
the reaction was completed, the mixture was diluted with CH2Cl2 and quenched by saturated
aqueous NaHCO3 solution (3 mL). While the separated aqueous phase was extracted with
CH2Cl2 (3 × 5 mL), the combined organic extracts were washed with water (10 mL) and brine
(10 mL), dried over MgSO4 and concentrated under reduced pressure. The crude residue was
purified by silica gel column chromatography (hexane:EtOAc = 5:1) to afford two colorless oils,
25 (80 mg, 38%) and its 3ꢀfluoro derivative (62 mg, 31%).
[α]2D5 −15.8° (c 1.0, CHCl3). IR (KBr, cm−1): νmax 2954, 2919, 2849, 1769, 1728, 1604, 1505,
1
1455, 1424, 1367, 1324, 1240, 1240, 1207, 1180, 1136, 1087, 1012, 891, 850, 750, 696. Hꢀ
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NMR (CDCl3, 400 MHz) δ: 1.38 (q, J = 11.6 Hz, 1H), 1.50 (q, J = 11.6 Hz, 1H), 1.66−1.79 (m,
1H), 1.85−1.95 (m, 1H), 1.95−2.02 (m, 1H), 2.04 (s, 3H), 2.20−2.27 (m, 1H), 2.28 (s, 3H), 2.30
(s, 3H), 2.56−2.76 (m, 2H), 3.37−3.49 (m, 1H), 3.83 (s, 3H), 4.32 (d, J = 11.2 Hz, 1H),
4.91−5.03 (m, 1H), 5.13 (d, J = 3.6 Hz, H), 6.65−6.75 (m, 1H), 6.75−6.85 (m, 2H), 6.85−6.90 (m,
13
2H), 7.22−7.39 (m, 6H), 7.39−7.50 (m, 4H). CꢀNMR (CDCl3, 100 MHz) δ: 20.3, 20.6, 21.3,
31.1, 37.0, 37.5, 39.1, 56.3, 70.4, 71.3, 71.6, 74.5, 76.3, 107.3, 112.4, 115.4, 115.7, 121.2, 127.3,
127.4, 127.7, 128.4, 131.0, 135.3, 137.4, 137.6, 140.6, 143.2, 147.2, 148.9, 152.2, 167.9, 168.3,
170.5. HRMS(ESI): m/z 682.2781 [M]+ (calcd. for C40H42O10, 682.2778).
(1S, 3R, 5S)ꢀ1,5ꢀepoxyꢀ3ꢀhydroxyꢀ1ꢀ(3,4ꢀdihydroxyꢀ5ꢀmethoxyꢀphenyl)ꢀ7ꢀ(3,4ꢀdihydroxyꢀphenyl)
heptane (entꢀ1)
Concentrated HCl (0.2 mL) was added to a solution of 25 (80 mg, 0.12 mmol) in MeOH (2 mL)
at room temperature, followed by stir mixing at room temperature for 12 h. The solvent was
removed under vacuum, the crude product was then reꢀdissolved in MeOH (2 mL), and 10%
Pd/C (10 mg) was carefully added. The mixture was then degassed and filled with nitrogen,
degassed again, and refilled with hydrogen (1 atm). The reaction was stirred at room temperature
for another 12 h. When the starting material was completely consumed, the reaction mixture was
filtered through celite and the filtrate was concentrated under vacuum. The resultant residue was
purified by silica column chromatography (hexane:EtOAc = 1:1) to afford entꢀalpinin A (entꢀ1)
as a white solid (32 mg, 73%). [α]D25 −40.5° (c 1.0, MeOH). IR (KBr, cm−1): νmax 3364, 2922,
2852, 1632, 1526, 1462, 1365, 1288, 1237, 1203, 1077, 785, 651. 1HꢀNMR (CDCl3, 400 MHz) δ:
1.23 (q, J = 11.6 Hz, 1H), 1.43 (q, J = 11.6 Hz, 1H), 1.65–1.80 (m, 1H), 1.80–1.92 (m, 1H),
1.93–2.02 (m, 1H), 2.04–2.14 (m, 1H), 2.48–2.70 (m, 2H), 3.40–3.50 (m, 1H), 3.77–3.85 (m,
1H), 3.86 (s, 3H), 4.22 (d, J = 11.2 Hz, 1H), 4.63 (br, 1H), 6.50–6.60 (m, 3H), 6.60–6.75 (m, 2H).
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13CꢀNMR (CDCl3, 100 MHz) δ: 30.6, 37.7, 40.4, 42.2, 55.3, 67.6, 74.9, 77.6, 101.5, 106.6, 114.9,
115.2, 119.3, 133.1, 133.2, 133.6, 142.8, 144.7, 144.9, 148.1.
Activity Bioassay. A filter trap assay was performed and aggregated αꢀsynuclein was detected
using western blot analysis as described previously with slight modification.14 Recombinant
human αꢀsynuclein (GenWay Biotech., CA, USA) was diluted in 1× Trisꢀbuffered saline (20 mM
Tris, 500 mM NaCl, pH 7.5) and incubated with extracts or compounds at room temperature for
7 days. After incubation, the mixtures were loaded onto a BioꢀDot SF Microfiltration Apparatus
(BioꢀRad, CA, USA) sandwiched with a 0.45 ꢁm nitrocellulose membrane (BioꢀRad). After
filtration and washing twice with Trisꢀbuffered saline, the amount of trapped αꢀsynuclein was
determined by western blot analysis using an antiꢀαꢀsynuclein antibody (1:2000, BD Bioscience,
CA, USA), and an antiꢀmouse secondary antibody (1:1000, Cell Signaling Technology, MA,
USA) and visualized by an ECL detection kit (GE Healthcare, Buckinghamshire, UK). The band
intensity was quantified using ImageJ software (https://imagej.nih.gov/ij/features.html). DMSO
and Congo red served as the solvent and positive control, respectively. We diluted the DMSO
stock solution (0.02%) with Trisꢀbuffered saline to obtain the working concentrations for the
assay. Data are expressed as the mean ± SEM of three individual experiments (n = 3 per
treatment group).
RESULTS AND DISCUSSION
The molecular formula of Alpinin A (1, yellowish oil) is determined as C20H24O7 based on
positiveꢀion HRMS(ESI) spectrum, the pseudomolecular ion peaks at m/z 399.1447 for [M+Na]+
and m/z 377.1607 for [M+H]+. The IR spectrum of 1 displayed absorptions for hydroxyl (broad,
1
3359 cmꢀ1) and substituted benzene groups (1674, 1608 and 1527 cmꢀ1). In the HꢀNMR
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spectrum (Table 1), five lowꢀfield resonances (δH: 6.48−6.62 ppm) demonstrated the presence
1,3,4,5ꢀtetrasubstituted benzene [δH: 6.51 (1H, s, Hꢀ2') and 6.52 (1H, s, Hꢀ6')] and 1,3,4ꢀ
trisubstituted benzene [δH: 6.62 (1H, d, J = 8.1 Hz, Hꢀ5"), 6.64 (1H, d, J = 1.8 Hz, Hꢀ2"), and
6.48 (1H, dd, J = 8.1, 1.8 Hz, Hꢀ6")], and four signals (δH: 4.18, 3.78, 3.43, 3.81 ppm) suggested
that there were four hydrogens on the carbons with oxygen substitution. The 13CꢀNMR and
DEPT spectra (Table 1) revealed that this molecule consisted of 20 carbons, 12 of which were
aromatic (sp2 hybridized; δC 103−150 ppm) and 8 of which were aliphatic (sp3 hybridized; δC
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32−79 ppm). This is concordant with two aromatic rings [1,3,4,5ꢀtetrasubstituted benzene; δC
134.5 (Cꢀ1'), 102.8 (Cꢀ2'), 149.4 (Cꢀ3'), 134.5 (Cꢀ4'), 146.3 (Cꢀ5'), 108.0 (Cꢀ6') ppm, as well as a
1,3,4ꢀtrisubstituted benzene: δC 135.0 (Cꢀ1"), 116.3 (Cꢀ2"), 146.1 (Cꢀ3"), 144.2 (Cꢀ4"), 116.6 (Cꢀ
5"), 120.7 (Cꢀ6") ppm] and heptane moiety with three oxygenated carbons [δC 78.9 (Cꢀ1), 76.3
(Cꢀ3 with a hydroxyl group), and 69.0 (Cꢀ5) ppm] plus methoxy group (δC 56.7 ppm). Analysis
13
of the DEPT and CꢀNMR spectra suggested one methoxy, four methylenes, eight methines
including three oxymethines, and seven quaternary carbons, which are consistent with cyclic
ether substituted with two aromatic rings as represented in compound 1. The cyclic ether ring
1
was proposed to be a tetrahydropyran (THP) on the basis of comprehensive analysis of Hꢀ1Hꢀ
COSY, HSQC, HMBC, and NOESY (NOE correlation between Hꢀ5 and Hꢀ1), which also
allowed us to confirm one methoxy group at the aromatic ring (see Supporting Information). The
spectral analysis results consistently indicated that alpinin A (1) is a THPꢀcontaining
diarylheptanoid. A literature search also indicated that our proposed structure of 1 is similar to
two known THPꢀcontaining diarylheptanoids 5ꢀ[4ꢀhydroxyꢀ6ꢀ(4ꢀhydroxyphenethyl)ꢀtetrahydroꢀ
2Hꢀpyranꢀ2ꢀyl]ꢀ3ꢀmethoxybenzeneꢀ1,2ꢀdiol isolated from the rhizomes of Zingiber officinale15
and
1,5ꢀepoxyꢀ3ꢀhydroxyꢀ1ꢀ(3,4ꢀdihydroxyꢀ5ꢀmethoxyꢀphenyl)ꢀ7ꢀ(3,4ꢀdihydroxyꢀ
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phenyl)heptane.16 Comparison of the NMR data of these three diarylheptanoids revealed obvious
differences at either the aromatic or THP region, which indicate that 1 is a new member of THPꢀ
containing diarylheptanoids; its relative structure of 1 was assigned as shown in Figure 1.
However, its absolute configuration could not be established unambiguously with Mosher’s ester
method, because contrary shielding effects were observed for the protons on the same side.
Therefore, in order to fully establish the relative and absolute configurations of alpinin A and
provide sustainable expedited access to the THPꢀcontaining diarylheptanoids, we initiated the
asymmetric total synthesis of alpinin A (Scheme 1).
The synthesis of entꢀ1 commenced with asymmetric allylation of aldehyde 2113 by using Loh’s
allyl transfer method,17 which provided the homoallylic alcohol 23 with a yield of 58% and 92.5%
ee. The Prins cyclization of homoallylic alcohol 23 and the known aldehyde 2418 afforded
tetrahydropyran 25 with a yield of 38%, along with a 3ꢀfluoro derivative (31%).18 The 2ꢀstep
global deprotection (deacetylation with HCl/MeOH and Pd/Cꢀcatalyzed benzylation) was carried
out to furnish alpinin A with a 73% overall yield for two steps. The NMR and MS spectroscopic
data of our synthetic material were identical to those derived from natural alpinin A isolated
from A. officinarum, which confirmed the molecular structure of our proposed compound 1.
However, the opposite sign of the specific rotation of the synthetic and natural materials
[synthetic: [α]2D5 −40.0° (c 1.0, MeOH), natural: [α]2D5 +51.1° (c 0.42, MeOH)] indicated that the
synthetic alpinin A (entꢀ1) was the enantiomer of 1, which in turn confirmed the absolute
configuration of the natural (+)ꢀalpinin A. The total synthesis was not only a conclusive and
powerful way to confirm the relative and absolute configurations of alpinin A, but also provided
efficient (only 4 steps) and expedited access to the alpinin A and related THPꢀcontaining
diarylheptanoids.
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The molecular formula of Alpinin B (2, yellowish oil) is determined as C20H26O7 based on
HRMS(ESI) spectrum, pseudomolecular ion peaks m/z at 379.1751 for [M+H]+ and m/z at
401.1558 for [M+Na]+. The carbon number of this formula was verified by the 13CꢀNMR
spectrum. Similar to the IR spectrum of 1, the IR spectrum of 2 also indicated the presence of
hydroxyl (3376 cm−1) and substituted benzene (1609 and 1527 cm−1) groups, which was
consistent with a maximum absorption in the UV spectrum (281.4 nm). Careful analysis of its
13
1Hꢀ and CꢀNMR data indicated that the compound has the same 1,3,4,5ꢀtetrasubstituted and
1,3,4ꢀtrisubstituted aromatic rings as compound 1. Additionally, seven carbons of the heptaneꢀ
3,5ꢀdiol moiety were also observed at δC 32.9 (Cꢀ1), 41.4 (Cꢀ2), 68.7 (Cꢀ3), 45.6 (Cꢀ4), 68.7 (Cꢀ
5), 41.3 (Cꢀ6) and 32.4 (Cꢀ7) in the 13CꢀNMR spectrum, and was further confirmed by the HSQC
1
and Hꢀ1H COSY spectral data. Furthermore, the sp3ꢀhybridized aliphatic hydrogen and carbon
resonances in the NMR spectra were nearly identical to those of the previously reported linear
diarylheptanoid derived from the rhizomes of Tacca chantrieri.19 However, these two
compounds differ mainly with respect to the chemical shifts derived from their aromatic rings.
Compound 2 resonates at δC 104.8 (Cꢀ2'), 149.5 (Cꢀ3'), 132.9 (Cꢀ4'), 146.3 (Cꢀ5'), 109.8 (Cꢀ6'),
and δH 6.32. 6.33 (each 1H, s, Hꢀ2', 6'), while the known diarylheptanoid has the corresponding
signals at δC 116.5 (Cꢀ2'), 146.0 (Cꢀ3'), 144.1 (Cꢀ4'), 116.2 (Cꢀ5'), 120.6 (Cꢀ6'), and δH 6.65 (1H,
d, J = 8.1 Hz, Hꢀ5'), 6.62 (1H, d, J = 2.0 Hz, Hꢀ2'), 6.50 (1H, dd, J = 8.1, 2.0 Hz, Hꢀ6').19 This
indicates that Cꢀ3' was substituted by a methoxy group, whose assignment was unequivocally
substantiated by longꢀrange correlation (HMBC) analysis: protons of the methoxy group at δH
3.81 were correlated with carbon Cꢀ3' at δC 149.5. The HMBC correlations between δH 6.32 (Hꢀ
2') to δC 32.9 (Cꢀ1) as well as between δH 6.63 (Hꢀ2") and δH 6.51 (Hꢀ6") to δC 32.4 (Cꢀ7),
indicated that the two benzene rings were located at two ends of the heptane chain. Based on the
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above evidence, the planar structure of 2 was proposed to be a linear diarylheptanoid (Figure 1)
and named alpinin B.
In order to determine the absolute configuration of alpinin B (2), the two hydroxyl groups were
derivatized to pꢀbromobenzoate for the CD spectrum (using the CD exciton chirality method).16
First, the phenolic hydroxyl groups of 4'ꢀOH, 5'ꢀOH, 3"ꢀOH and 4"ꢀOH were alkylated by
iodomethane to provide the corresponding tetramethyl ether (2a); then, the compound was
reacted with pꢀbromobenzoyl chloride to give the dibenzoate 2b. The CD spectrum of 2b
exhibited positive (238.5 nm, △ε +15.1) and negative (253.0 nm, △ε ꢀ13.4) Cotton effects, which
confirmed the absolute configuration as 3R and 5R.19,20 Therefore, the absolute configuration of
2 was proposed to be (3R,5R)ꢀalpinin B.
The structures of compounds 3–20 were elucidated on the basis of careful comparison of the
NMR data with those in the literature, and their molecular structures are shown as 3–5,19 6,21 7–
8,19 9,22 10,23 11,24 12,5 13,25 14,26 15,27 16,28 17–18,24 19,29 and 2026 in Figure 1.
The inhibitory effects of compounds 1–10, 12–18 and 20 on αꢀsynuclein aggregation were
evaluated (Table 2). A filter trap assay was performed, and aggregated αꢀsynuclein was detected
by western blot analysis. Compounds 1–3 and 5–7, which featured the presence of 3,4ꢀdihydroxy
substitution on the benzene ring, exhibited the most potent inhibitory activity against αꢀsynuclein
aggregation, which suggests that the presence of the 3,4ꢀdihydroxy group on the benzene ring is
crucial to their inhibitory activity. In addition, when comparing the inhibitory activity of
compounds 3ꢀ4, with that of 6ꢀ8, the more phenolic hydroxyl groups on the benzene exhibited a
greater activity, which suggests that the inhibition of αꢀsynuclein aggregation is strongly
correlated with the number of hydroxyl groups on the aromatic ring. Furthermore, 1a, a
tetramethylated analogue of compound 1, showed no inhibitory activity, further supporting the
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importance of hydroxyl groups in the observed inhibition. Finally, the results show that the
methoxy substitution on Cꢀ3 of the benzene ring is not essential for inhibitory activity, because
no significant activity difference was observed for compounds 4 and 8 as well as compounds 2
and 5.
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Funding
This study was supported in part by the National Basic Research Program of China
(2013CB530900), the Hong Kong Research Grants Council Themeꢀbased Research Scheme
(T13ꢀ607/12R), General Research Fund (16305314), the Innovation and Technology Fund for
State Key Laboratory (ITCPT/17ꢀ9), the Shenzhen Peacock Plan, the Shenzhen Knowledge
Innovation
Program
(JCYJ20151030140325152,
JCYJ20151030154629774,
GJHS20140425165746765), and the SH Ho Foundation.
Notes
The authors declare no competing financial interests.
REFERENCES
(1) Ascherio, A.; Schwarzschild, M. A. The epidemiology of Parkinson's disease: risk factors
and prevention. Lancet Neurol. 2106, 15, 1257ꢀ1272.
(2) Ghosh, D.; Mehra, S.; Sahay, S.; Singh, P. K.; Maji, S. K. αꢀsynuclein aggregation and its
modulation. Int. J. Biol. Macromol. 2016, pii: S0141ꢀ8130, 31939ꢀ31940.
16
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Journal of Agricultural and Food Chemistry
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377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
(3) Benskey, M. J.; Perez, R. G.; Manfredsson, F. P. The contribution of alpha synuclein to
neuronal survival and function ꢀ Implications for Parkinson's disease. J. Neurochem. 2016, 137,
331ꢀ359.
(4) The State Pharmacopoeia Commission of the People's Republic of China. Pharmacopoeia of
the People's Republic of China; China Medical Science and Technology Press: Beijing, China,
2010, Vol. 1, pp 270ꢀ271.
(5) Shin, D.; Kinoshita, K.; Koyama, K.; Takahashi, K. Antiemetic principles of Alpinia
officinarum. J. Nat. Prod. 2002, 65, 1315ꢀ1318.
(6) Sun, Y.; Matsubara, H.; Kitanaka, S.; Yasukawa, K. Diarylheptanoids from the rhizomes of
Alpinia officinarum. Helv. Chim. Acta. 2008, 91, 118ꢀ123.
(7) Zhao, L.; Liang, J. Y.; Zhang, J. Y.; Chen, Y. A novel diarylheptanoid bearing flavonol
moiety from the rhizomes of Alpinia officinarum Hance. Chin. Chem. Lett. 2010, 21, 194–196.
(8) An, N., Yang, S. L.; Zou, Z. M.; Xu, L. Z. Flavonoids of Alpinia officinarum. Chin. Tradit.
Herb. Drugs. 2006, 37, 663ꢀ664.
(9) Lv, H. N.; She, G. M. Naturally occurring diarylheptanoids. Nat. Prod. Commun. 2010,5,
1687ꢀ708.
(10) Lv, H. N.; She, G. M. Naturally occurring diarylheptanoids ꢀ a supplementary version. Rec.
Nat. Prod. 2012, 6, 321ꢀ333.
(11) Zhu, J. P.; IslasꢀGonzalez, G.; BoisꢀChoussy, M. Recent progress in isolation, bioactivity
evaluation and total synthesis of diarylheptanoids. Org. Prep. Proced. Int. 2000, 32, 505ꢀ546.
(12) Ruedi, P.; Juch, M. Chemistry and biological activities of longꢀchain alkyloxyꢀcatechols of
the [n]ꢀgingerolꢀtype. Curr. Org. Chem. 1999, 3, 623ꢀ646.
17
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Page 18 of 25
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
(13) Voigt, T.; GerdingꢀReimers, C.; Tran, T., Bergmann, S.; Lachance, H.; Schçlermann, B.;
Brockmeyer, A.; Janning, P.; Ziegler, S.; Waldmann, H. A natural product inspired
tetrahydropyran collection yields mitosis modulators that synergistically target CSE1L and
tubulin. Angew. Chem. Int. Ed. 2013, 52, 410ꢀ414.
(14) Wan, O. W.; Chung, K. K. The role of alphaꢀsynuclein oligomerization and aggregation in
cellular and animal models of Parkinson's disease. PLoS One. 2012, 7, e38545.
(15) Tao, Q. F.; Xu, Y.; Lam, R. Y.Y.; Schneider, B.; Dou, H.; Leung, P. S.; Shi, S.Y.; Zhou, C.
X.; Yang, L. X.; Zhang, R. P.; Xiao, Y. C.; Wu, X. M.; Stöckigt, J.; Zeng, S.; Cheng, C. H. K.;
Zhao, Y. Diarylheptanoids and a monoterpenoid from the rhizomes of Zingiber officinale:
antioxidant and cytoprotective properties. J. Nat. Prod. 2008, 71, 12–17.
(16) He, W. S.; Wei, X. Y.; Li, L.; Li, Y.; Guo S. Y.; Guo B. J. A new antioxidant cyclic
diarylheptanoid from the rhizomes of Zingiber officinale. J. Integr. Plant Biol. 2001, 43, 757ꢀ759.
(17) Lee, C.; Loh, T. A highly enantioselective allylꢀtransfer through suppression of
epimerization. Tetrahedron Lett. 2004, 45, 5819ꢀ5822.
(18) Parker, G. D.; Seden, P. T.; Willis, C. L. Synthesis of a novel diarylheptanoid isolated from
Zingiber officinale. Tetrahedron Lett. 2009, 50, 3686–3689.
(19) Yokosuka, A.; Mimaki, Y.; Sakagami, H.; Sashida, Y. New diarylheptanoids and
diarylheptanoid glucosides from the rhizomes of Tacca chantrieri and their cytotoxic activity. J.
Nat. Prod. 2002, 65, 283ꢀ289.
(20) Harada, N.; Saito, A.; Ono, H.; Gawronski, J.; Gawronska, K.; Sugioka, T.; Uda, H.; Kuriki,
T. A CD method for determination of the absolute stereochemistry of acyclic glycols. 1.
Application of the CD exciton chirality method to acyclic 1,3ꢀdibenzoate systems. J. Am. Chem.
Soc. 1991, 113, 3842ꢀ3850.
18
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Journal of Agricultural and Food Chemistry
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422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
(21) Qiu, F.; Li, J.; Kang, N.; Chen, L. X. Diarylheptanoid compounds in Curcuma zedoary and
medicinal application thereof . Faming Zhuanli Shenqing. 2011, CN101979366A.
(22) Ma, J. P.; Jin, X. L.; Yang, L.; Liu, Z. L. Diarylheptanoids from the rhizomes of Zingiber
officinale. Phytochemistry. 2004, 65, 1137ꢀ1143.
(23) Ohta, S.; Koyama, M.; Aoki, T.; Suga, T. Absolute configuration of platyphylloside and [ꢀ)ꢀ
centrolobol. Bull. Chem. Soc. Jpn. 1985, 58, 2423–2424.
(24) Liu, Z. H.; Sang, S. M.; Hartman, T. G.; Ho, C. T.; Rosen, R. T. Determination of
diarylheptanoids from Alpinia officinarum (Lesser Galangal) by HPLC with photodiode array
and electrochemical detection Phytochem. Anal. 2005, 16, 252ꢀ256.
(25) Kiuchi, F.; Shibuya, M.; Sankawa, U. Inhibitors of prostaglandin biosynthesis from Alpinia
officinarum. Chem. Pharm. Bull. 1982, 30, 2279ꢀ2282.
(26) Pulkkinen, J. T.; Honkakoski, P.; Perakyla, M.; Berczi, I.; Laatikainen, R. Synthesis and
evaluation of estrogen agonism of diaryl 4,5ꢀdihydroisoxazoles, 3ꢀhydroxyketones, 3ꢀ
methoxyketones, and 1,3ꢀdiketones: a compound set forming a 4D molecular library. J. Med.
Chem. 2008, 51, 3562ꢀ3571.
(27) Kikuzaki, H.; Kobayashi, M.; Nakatani, N. Diarylheptanoids from rhizomes of Zingiber
officinale. Phytochemistry. 1991, 30, 3647ꢀ3651.
(28) Nguyen, H. T.; Kim, S. K.; Ra, J. C.; Zhao, Y. Z.; Sohn, D .H.; Kim, Y. H. Antioxidative
and hepatoprotective diarylheptanoids from the bark of Alnus japonica. Planta Med. 2010, 76,
626ꢀ629.
(29) Jurgens, T. M.; Frazier, E. G.; Schaeffer, J. M.; Jones, T. E.; Zink, D. L.; Borris, R. P.;
Beck, H. T.; Wanakorn, W. Novel nematocidal agents from Curcuma comosa. J. Nat. Prod. 1994,
57, 230ꢀ235.
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R1O
R2O
OCH3
3'
OR4
3"
OR5
1'
1
O
1"
R3O
5"
3
7
5
449
450
No.
1
1a
R1
H
R2
H
R3
H
R4
H
R5
H
CH3
CH3
H
CH3
CH3
451
No.
R1
R2
R3
R4
R5
R6
R7
OCH3
OCH3
OCH3
OCH3
OCH3
OH
OCH3
OH
H
OH
OH
OCH3
OCH3
H
H
H
OH
H
H
H
H
H
H
OH
OH
2
OCH3
OCH3
OH
OH
OH
OH
OH
OH
OCH3
OCH3
OH
H
OH
H
OCH3
OCH3
OH
OH
OH
OH
OH
OH
2a
2b
3
4
5
6
7
8
pꢀBrꢀBz
pꢀBrꢀBz
H
H
H
H
H
H
H
H
H
H
H
H
H
H
452
453
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Journal of Agricultural and Food Chemistry
No.
9
10
12
13
14
R1
OCH3
H
H
H
R2
OH
OH
H
H
H
R3
R4
OH
H
H
H
R5
OH
OH
OH
OH
OCH3
OH
OH
OH
H
H
H
H
454
455
456
No.
R1
R2
OH
OH
H
H
H
R3
H
H
H
H
R4
OH
H
H
H
R5
OCH3
OH
H
H
H
OH
OH
OH
H
15
16
17
18
20
OH
H
H
457
458
459
11
19
460
461
Figure 1 Chemical structure of natural diarylheptanoids 1–20 and their derivatives 1a, 2a, 2b.
462
463
464
465
466
467
468
469
470
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471
472
473
474
475
476
Scheme 1 The enantioselective synthesis of proposed structure of compound 1
477
478
479
480
481
482
483
484
485
486
487
488
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Journal of Agricultural and Food Chemistry
489
490
491
492
493
494
495
Table 1. NMR Data for Compounds 1–2, 1a and 2a [400 MHz (1H NMR) and 100 MHz (13C NMR) in
CD3OD]
1
1a
2
2a
Position
δH (J in Hz)
δC type
δC
δH (J in Hz)
δC type
δC
1
2
4.18, brd (11.1)
2.08, m
78.9 CH
39.1 CH2
79.0 2.59, m
39.0 1.68, m
32.9 CH2
41.4 CH2
33.4
41.2
1.41, dd (5.80, 11.7)
3.78, m
3
4
76.3 CH
43.6 CH2
76.3 3.84, m
44.0 1.54, m
68.7 CH
45.6 CH2
68.6
45.7
1.95, m
1.21, m
3.43, m
5
6
69.0 CH
41.8 CH2
68.9 3.84, m
41.9 1.68, m
68.7 CH
41.3 CH2
68.5
41.1
1.84, m
1.75, m
7
2.60, m
32.0 CH2
134.5 C
32.4 2.52, m
136.4
32.4 CH2
134.5 C
32.6
136.6
106.7
154.3
139.9
154.3
106.7
136.7
113.5
150.3
148.5
113.1
121.6
56.6
1′
2′
6.51, s
102.8 CH 104.4 6.32, s
104.8 CH
149.5 C
3′
149.4 C
134.5 C
146.3 C
154.4
140.1
154.4
4′
132.9 C
5′
146.3 C
6′
6.52, s
108.0 CH 104.4 6.33, s
135.0 C 138.2
116.3 CH 113.6 6.63, d (2.0)
109.8 CH
135.3 C
1′′
2′′
6.64, d (2.0)
116.5 CH
146.0 C
3′′
146.1 C
144.2 C
150.3
148.6
4′′
144.1 C
5′′
6.62, d (8.0)
6.48, dd (2.0, 8.0)
3.81, s
116.6 CH 113.2 6.66, d (8.0)
116.2 CH
120.6 CH
56.5 CH3
6′′
120.8 CH 121.6 6.51 dd (2.0, 8.0)
3′ꢀOCH3
4′ꢀOCH3
5′ꢀOCH3
3′'ꢀOCH3
56.6 CH3
56.6 3.81, s
61.2
61.1
56.6
56.6
56.5
56.5
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Journal of Agricultural and Food Chemistry
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4′'ꢀOCH3
56.4
56.4
496
497
498
499
500
501
502
503
504
505
Table 2. Effects of the isolated compounds in inhibiting alphaꢀsynuclein aggregation
Compound Inhibition (%) Compound Inhibition (%) Compound Inhibition (%)
66.1±4.4
67.3±6.2
72.4±4.4
16.6±10.6
65.9±9.8
76.0±3.5
61.3±6.3
32.2±11.7
0.0
10.6±3.8
40.3±14.9
20.1±14.6
0.0
0.0
0.0
40.4±17.2
30.3±5.5
0.0
1
2
3
4
5
6
7
8
9
16
17
18
10
12
13
14
15
20
DMSO
Congo reda
64.5±7.6
59.1±11.2
506
507
508
aCongo red and the isolated compounds at the concentration of 10 µM (Inhibition percentage compared to
the control DMSO)
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Journal of Agricultural and Food Chemistry
509
TOC Graphic
510
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