Two new phenylpropanoids and a new dihydrostilbenoid from the flower buds of Magnolia biondii pamp and their acetylcholinesterase inhibitory activities

Article abstract of DOI:10.1080/14786419.2019.1693567

Two new phenylpropanoids, named (2'R*,3'R*)-2',3'-dihydroxy-4'-methoxy-caffeoyl butyrate (1), 9-acetoxy syringin (2), and a new dihydrostilbene, named (8'R)-4',5-dihydroxy-4,8'-dimethoxy-2-hydroxyethyl diphenylethane (3), together with five analogues (4–8), were isolated from the flower buds of Magnolia biondii Pamp. Their structures were elucidated by extensive spectroscopic analyses and comparison with literature data. The absolute configurations were deduced by comparison of experimental and calculated gauge-independent atomic orbital (GIAO) 1 D NMR data. Moreover, the isolated compounds (1–8) were evaluated in?vitro for their acetylcholinesterase (AChE) inhibitory activities.

Full text of DOI:10.1080/14786419.2019.1693567

Natural Product Research
Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: https://www.tandfonline.com/loi/gnpl20
Two new phenylpropanoids and a new
dihydrostilbenoid from the flower buds
of Magnolia biondii pamp and their
acetylcholinesterase inhibitory activities
Yan-Gang Cao, Hong-Wei Li, Bing Cao, Jian-Chao Wang, Yan-Li Zhang, Xuan
Zhao, Xiao-Ke Zheng & Wei-Sheng Feng
To cite this article: Yan-Gang Cao, Hong-Wei Li, Bing Cao, Jian-Chao Wang, Yan-Li Zhang,
Xuan Zhao, Xiao-Ke Zheng & Wei-Sheng Feng (2019): Two new phenylpropanoids and a new
dihydrostilbenoid from the flower buds of Magnoliaꢀbiondii pamp and their acetylcholinesterase
inhibitory activities, Natural Product Research, DOI: 10.1080/14786419.2019.1693567
To link to this article: https://doi.org/10.1080/14786419.2019.1693567
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NATURAL PRODUCT RESEARCH
https://doi.org/10.1080/14786419.2019.1693567
Two new phenylpropanoids and a new dihydrostilbenoid
from the flower buds of Magnolia biondii pamp and
their acetylcholinesterase inhibitory activities
a,b
a,b
a,b
a
a,b
Yan-Gang Cao , Hong-Wei Li , Bing Cao , Jian-Chao Wang , Yan-Li Zhang
,
a
a,b
a,b
Xuan Zhao , Xiao-Ke Zheng and Wei-Sheng Feng
a
School of Pharmacy, Henan University of Chinese Medicine, Zhengzhou, P.R. China;
b
Co-construction Collaborative Innovation Center for Chinese Medicine and Respiratory Diseases by
Henan & Education Ministry of P.R. China, Zhengzhou, P.R. China
ABSTRACT
ARTICLE HISTORY
Received 11 September 2019
Accepted 10 November 2019
ꢀ
ꢀ
Two new phenylpropanoids, named (2’R ,3’R )-2’,3’-dihydroxy-4’-
methoxy-caffeoyl butyrate (1), 9-acetoxy syringin (2), and a new
dihydrostilbene, named (8’R)-4’,5-dihydroxy-4,8’-dimethoxy-2-
hydroxyethyl diphenylethane (3), together with five analogues
KEYWORDS
Magnolia biondii Pamp;
Magnoliaceae; phenylpropa-
noids; dihydrostilbenoids;
acetylcholinesterase inhibi-
tory activity
(4–8), were isolated from the flower buds of Magnolia biondii
Pamp. Their structures were elucidated by extensive spectroscopic
analyses and comparison with literature data. The absolute config-
urations were deduced by comparison of experimental and calcu-
lated gauge-independent atomic orbital (GIAO) 1 D NMR data.
Moreover, the isolated compounds (1–8) were evaluated in vitro
for their acetylcholinesterase (AChE) inhibitory activities.
1. Introduction
Magnolia biondii Pamp from the Magnoliaceae family is widely distributed in Korea,
China, and Japan (Nguyen et al. 2017). The dried flower buds of M. biondii, commonly
known as Xin-yi in China, have been used in Chinese medicine to treat allergic rhinitis,
CONTACT Xiao-Ke Zheng
zhengxk.2006@163.com; Wei-Sheng Feng
fwsh@hactcm.edu.cn
School of
Pharmacy, Henan University of Chinese Medicine, Zhengzhou 450046, P.R. China.
Supplemental data for this article can be accessed at https://doi.org/10.1080/14786419.2019.1693567.
ß 2019 Informa UK Limited, trading as Taylor & Francis Group

2
Y.-G. CAO ET AL.
sinusitis, and headache (Park et al. 2012). Phytochemical studies of this plant have
resulted in the identification of various metabolites such as esstenial oils (Hu et al.
2018), lignans (Ma et al. 1996; (Zhang et al. 2017)), neolignans (Ma et al. 1996; Chung
et al. 2012), monoterpends (Feng et al. 2016), sesquiterpends (Nguyen et al. 2017), and
alkaloids (Talapatra et al. 1982). Extracts of M. biondii have been reported to possess
anti-inflammatory (Qi et al. 2011; Nguyen et al. 2017), anti-allergenic (Tsuruga et al.
1991; Zhang et al. 2017), and anti-platelet-activating factor (anti-PAF) (Jung et al. 1998).
Alzheimer’s disease (AD), a neurodegenerative disorder, is the leading cause of
dementia among the elderly. Therapeutic approach to enhance cholinergic neurotrans-
mission by the use of cholinesterase (AChE) inhibitors is the most successful treatment
for AD according to the cholinergic hypothesis and evidences from the clinical trials
(
(
Bhadra et al. 2012). Natural products were the important sources of new drugs
(Newman and Cragg 2016)) and many natural phenolic compounds were evaluated
as AChE inhibitors for potential application in the treatment of AD (Lu et al. 2017;
Posri et al. 2019). In our effort to discover diverse constituents with AChE inhibitory
ꢀ
ꢀ
activities, two new phenylpropanoids, named (2’R ,3’R )-2’,3’-dihydroxy-4’-methoxy-caf-
feoyl butyrate (1), 9-acetoxy syringin (2), and a new dihydrostilbene, named (8’R)-4’,5-
dihydroxy-4,8’-dimethoxy-2-hydroxyethyl diphenylethane (3), together with five known
compounds (4–8), were isolated from the flower buds of M. biondii and their AChE
inhibitory effects were evaluated.
2. Results and discussion
Compound 1 was isolated as a white amorphous powder with a molecular formula of
1
C H O determined by the HRESIMS and NMR data. In the H NMR spectrum of 1,
1
4 16 8
the signals suggested the presence of an 1,3,4-trisubstituted benzene ring [dH 7.04
(
1H, d, J ¼ 2.0 Hz, H-2), 6.95 (1H, dd, J ¼ 8.2, 2.0 Hz, H-6), and 6.78 (1H, d, J ¼ 8.2 Hz,
H-5)], a conjugated olefinic group [d 7.58 (1H, d, J ¼ 16.0 Hz, H-7) and 6.26 (1H, d,
H
J ¼ 16.0, H-8)], two oxymethines [d 4.23 (1H, d, J ¼ 3.8 Hz, H-3’) and 4.11 (1H, m,
H
H-2’)], an oxygenated methylene [d 4.30 (1H, dd, J ¼ 11.3, 5.2 Hz, H-1’a) and 4.25 (1H,
H
dd, J ¼ 11.3, 6.2 Hz, H-1’b)], and a methoxy group [d 3.75 (3H, s, 4’-OCH )]. In its
H
3
1
3
C NMR spectrum, fourteen carbon signals, including two carboxylic carbons [d
74.3 (C-4’) and 168.9 (C-9)], three sp quaternary carbons [d 149.7 (C-4), 146.9 (C-3)
C
C
2
1
2
and 127.7 (C-1)], five sp methine carbons [d 147.3 (C-7), 123.0 (C-6), 116.5 (C-5),
1
7
C
3
15.1 (C-2), and 114.8 (C-8)], two sp oxygenated methine carbons [d 73.5 (C-3’), and
C
3
2.0 (C-2’)], a sp oxymethlene carbon [d 65.4 (C-1’)], and a methoxy group [d 52.5
C
C
(
4’-OCH )] were observed. The 1 D NMR data of 1 were similar to those of caffeoyl
3
ester of apionic acid (Braca et al. 2001) with the mian difference being the absence of
a hydroxymethyl moiety and the presence of a methoxy group attached to the C-4’,
which was determined by the HMBC correlation of methoxy group protons with C-4’.
Thus, the planar structure of 1 was elucidated.
The gauge-independent atomic orbital (GIAO) 1 D NMR calculations for four isomers
[
3
(2’R,3’R)-1, (2’R,3’S)-1, (2’S,3’R)-1, and (2’S,3’S)-1] were conducted at the mPW1PW91/6-
1G(d,p) level in MeOH and the calculated NMR and experimental data were analysed
by the DP4þ probability method. As a result, (2’R,3’R)-1 (50.24% probability) and

NATURAL PRODUCT RESEARCH
3
(
2’S,3’S)-1 (49.76% probability) were probably the right structure (See supplementary
ꢀ
ꢀ
information, Figure S39). Therefore, the structure of 1 was elucidated as (2’R ,3’R )-
2
’,3’-dihydroxy-4’-methoxy-caffeoyl butyrate.
Compound 2 was isolated as a white amorphous powder. The molecular formula
1
of 2 was determined to be C H O by the HRESIMS and NMR data. The H NMR
1
9 26 10
spectrum displayed resonances for an 1,3,4,5,-tetrasubsituted aromatic ring [d 6.77 (2H,
H
s, H-2, 6)], a conjugated olefinic group [d 6.59 (1H, d, J ¼ 16.0 Hz, H-7) and 6.35 (1H, dt,
H
J ¼ 16.0, 6.2Hz, H-8)], an oxygenated methylene [d 4.67 (2H, t, J ¼ 6.2 Hz, H-9)], two
H
methoxy groups [d 3.76 (6H, s, 3, 5-OCH )], and a methyl group [d 2.05 (3H, s, H-2’)].
H
3
H
Furthermore, an anomeric proton resonance was observed at d 4.94 (1H, d, J ¼ 6.6 Hz,
H
H-1’’), together with additional sugar signals appeared at d 3.01–3.59 (6H, m). Nineteen
H
13
carbon signals in the C NMR and DEPT135 spectra were attributed to a carboxylic car-
bon [d 170.2 (C-1’)], four sp quaternary carbons [d 152.7 (C-3, 5), 134.4 (C-4), and
31.6 (C-1)], four sp methine carbons [d 133.1 (C-7), 123.2 (C-8), and 104.8 (C-2, 6)], an
2
C
C
2
1
C
oxygenated methylene carbon [dC 64.3 (C-9)], two methoxy carbons [dC 56.4 (3, 5-
OCH )], and a methyl group [d 20.8 (C-2’)], as well as six monosaccharide carbon atoms
3
C
[dC 102.4 (C-1’’), 77.2 (C-5’’), 76.6 (C-3’’), 74.2 (C-2’’), 69.9 (C-4’’), and 60.9 (C-6’’)]. The
above NMR data resembled to those of syringin (Li et al. 2015) with the exception of an
extra acetyl group, which attached to the C-9 based on the HMBC correlation of H-9
with C-1’. Acid hydrolysis of 2 yielded D-glucose, which was detected in the hydrolysate
by chiral HPLC analysis (See supplementary information, Figure S41). The b-configuration
of D-glucose was determined based on the coupling constant (J ¼ 6.6Hz) of the
anomeric proton. Thus, the structure of 2 was assigned as 9-acetoxy syringin.
Compound 3 was isolated as a white amorphous powder with a molecular formula
1
of C H O determined by the HRESIMS and NMR data. The H NMR data of 3
1
8 22 5
revealed signals for an 1,2,4,5-tretasubstituted aromatic ring [d 6.76 (1H, s, H-3) and
H
5
.73 (1H, s, H-6)], an 1,4-bisubstituted aromatic ring [d 6.87 (2H, d, J ¼ 8.5 Hz, H-2’, 6’)
H
and 6.70 (2H, d, J ¼ 8.5 Hz, H-3’, 5’)], an oxygenated methine [d 4.10 (1H, d,
H
J ¼ 11.8 Hz, H-8’)], an oxymethylene [d 3.75 (1H, dd, J ¼ 12.5, 9.0 Hz, H-8a) and 3.43
H
(
1H, dd, J ¼ 12.5, 6.5 Hz, H-8b)], and two methylenes [d 4.05 (1H, dd, J ¼ 12.2, 2.4 Hz,
H
13
H-7’a), 3.15 (2H, m, H-7), and 2.59 (1H, dd, J ¼ 12.2, 10.0 Hz, H-7’b)]. Its C NMR data
2
indicated the presence of six sp quaternary carbons [d 157.4 (C-4’), 149.4 (C-4), 145.7
C
2
(C-5), 129.0 (C-1’), 127.1 (C-1), and 120.7 (C-2)], six sp methine carbons [d 132.2 (C-2’,
C
3
6
8
2
’), 116.3 (C-3’, 5’), 115.8 (C-6), and 112.5 (C-3)], a sp oxymethine carbon [d 79.9 (C-
C
’)], an oxymethlene carbon [d 60.7 (C-8)], two methylene carbons [d 38.6 (C-7’) and
C
C
7.1 (C-7)], and two methoxy groups [d 56.5 (8’-OCH ) and 56.4 (4-OCH )]. The above
C
3
3
NMR data resembled those of 1-(2-(2-hydroxyethyl)-4,5-dimethoxyphenyl)-2-(4-methox-
yphenyl) ethanol (Ivanov et al. 2007), but for the absence of a methoxy group.
The methoxy groups were located at C-4 and C-8’, respectively, based on the HMBC
correlations from protons of 4-OCH to C-4 and from protons of 8’-OCH to C-8’.
3
3
The GIAO NMR data of (8’R)-3 and (8’S)-3 were calculated and the simulated and
experimental data were used for DP4þ probability analysis. The results indicated
that (8’R)-3 with 100% probability was the better suitable for 3 (See supplementary
information, Figure S40). Therefore, the structure of 3 was elucidated as (8’R)-4’,
5-dihydroxy-4,8’-dimethoxy-2-hydroxyethyl diphenylethane.

4
Y.-G. CAO ET AL.
Figure 1. Structures of compounds 1–8 from Magnolia biondii Pamp.
By comparison of the NMR data with those reported in the literatures, five known
compounds were identified as dihydroconiferylalcohol (4) (Huang et al. 2014), dihydro-
syringenin (5) (Rustaiyan et al. 1991), 3-(4-hydroxy-3-methoxyphenyl) propane-1,2-diol
(6) (Kikuzaki et al. 1999), b-hydroxypropiovanillone (7) (Karonen et al. 2004),
3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl) propan-1-one (8) (Jones et al. 2000).
The isolated compounds (1–8) were evaluated in vitro for their AChE inhibitory
activities. As a result, compounds 3–6, and 8 exhibited slightly inhibitory
effects with the values from 25.7–43.1 lM (See supplementary information,
Table S1) (Figure 1).
3. Experimental
3.1. General experimental procedures
Optical rotations were record by a Rudolph AP-IV polarimeter (Rudolph, Hackettstown,
NJ, USA). ECD spectra were obtained using an Applied Photophysics Chirascan qCD
spectropolarimeter (AppliedPhotophysics, Leatherhead, Surrey, UK). UV spectra were
measured by a Thermo EVO 300 spectrometer (Thermo, Waltham, MA, USA). IR spectra
were recorded on a Thermo Nicolet IS 10 spectrometer (Thermo, Waltham, MA, USA).
NMR spectra were measured by a Bruker Avance III 500 spectrometer (Bruker,
Germany). MS spectra were acquired using a Bruker maXis HD mass spectrometer
(Bruker, Germany). Semipreparative HPLC separations were conducted on a Saipuruisi
LC 50 HPLC system, equipped with an UV/VIS 50 detector (Saipuruisi, Beijing, China).
Monosaccharide elucidation was performed on a Waters 2695 separation module equi-
ped with an evaporative light scattering detector (ELSD) (Waters, Milford, MA, USA)
using a CHIRALPAK AD-H column (250 ꢁ 4.6 mm) (Daicel Chiral Technologies Co., Ltd.,
China). Column chromatographies were performed using MCI gel CHP-20 (TOSOH
Corp., Tokyo, Japan), ODS gel (50 lm) (YMC Group, Kyoto, Japan), Sephadex LH-20
(
(
40–70 lm) (Amersham Pharmacia Biotech AB, Uppsala, Sweden), Toyopearl HW-40C
TOSOH Corp., Tokyo, Japan), and silica gel (160–200 mesh) (Marine Chemical Industry,
Qingdao, China).

NATURAL PRODUCT RESEARCH
5
3.2. Plant material
The flower buds of M. biondii gathered in Nanzhao, Henan province, China, were iden-
tified by Professor Chengming Dong, School of Pharmacy, Henan University of Chinese
Medicine, Zhengzhou, China. A voucher specimen (20140609) was deposited at the
Department of Pharmaceutical Chemistry, Henan University of Chinese Medicine.
3.3. Extraction and isolation
The flower buds of M. biondii (5.0 kg) were extracted with 50% aqueous acetone
(
20 L ꢁ 3, smashed tissue extraction) at room temperature. The combined solutions
were evaporated under vacuum to give a crude extract (463 g), which was suspended
in H O (2 L) and then successively extracted with petroleum ether, EtOAc and n-BuOH
2
(
2 L ꢁ 5), respectively. The n-BuOH fraction (60.0 g) was subjected to Diaion HP-20 col-
umn chromatography (CC) and eluted with EtOH-H O (0:100, 20:80, 40:60, 80:20, 95:5,
2
v/v) to give five subfractions (Fr. I–Fr. V). Fr. II (14.0 g) was then applied to ODS CC
eluted with a MeOH-H O (0:100, 5:95, 10:90, 15:85, 20:80, 25:75, 35:65,45:55, 100:0, v/v)
2
gradient to give nine fractions (Fr. 1–Fr. 9). Fr. 3 (20.5 mg) was purified by preparative
HPLC eluted by MeOH-H O (25:75) to give 1 (1.4 mg, t ¼ 72.9 min) and 3 (3.5 mg,
2
R
t ¼ 96.6 min). Fr. IV (50.2 g) was subjected to silica gel eluted with a CH Cl -MeOH
R
2
2
(100:0, 80:20, 60:40, 40:60, 20:80, 0:100) gradient to yield nine subfractions (Fr. A–Fr. I).
Fr. B (55.8 mg) was purified by preparative HPLC eluted by MeOH-H O (15:85) to give
2
6
(6.3 mg, t ¼ 27.8 min) and 5 (4.3 mg, t ¼ 35.7 min). Fr. C (221.8 mg) was purified by
R
R
preparative HPLC eluted by MeOH-H O (35:65) to give 2 (30.4 mg, t ¼ 39.5 min). Fr. D
2
R
(82.4 mg) was chromatographied by preparative HPLC eluted by MeOH-H O (30:70) to
2
give 7 (4.9 mg, t ¼ 49.8 min) and 8 (8.3 mg, t ¼ 67.2 min). Fr. F (34.6 mg) was purified
R
R
by preparative HPLC eluted by MeOH-H O (25:75) to give 4 (4.6 mg, t ¼ 24.3 min).
2
R
Compound 1: white amorphous powder; [a] þ 42.8 (c 0.03, MeOH); UV (MeOH) k
max
ꢂ1
2
04,301,330 nm; IR (iTR) ꢀ : 335,323,602,341,173,000,000,000,000,000,000,000 cm
;
max
þ
1
HRESIMS m/z 335.0731 [M þ Na] (calcd for 335.0737, C H O Na); H NMR (500 MHz,
14 16 8
CD OD): d 7.58 (1H, d, J ¼ 16.0 Hz, H-7), 7.04 (1H, d, J ¼ 2.0 Hz, H-2), 6.95 (1H, dd,
3
H
J ¼ 8.2, 2.0 Hz, H-6), 6.78 (1H, d, J ¼ 8.2 Hz, H-5), 6.26 (1H, d, J ¼ 16.0 Hz, H-8), 4.30 (1H,
dd, J ¼ 11.3, 5.2 Hz, H-1’a), 4.25 (1H, dd, J ¼ 11.3, 6.2 Hz, H-1’b), 4.23 (1H, d, J ¼ 3.8 Hz,
13
H-3’), 4.11 (1H, m, H-2’), 3.75 (3H, s, 4’-OCH ); C NMR (125 MHz, CD OD): d 174.3 (C-
3
3
C
4
1
’), 168.9 (C-9), 149.7 (C-4), 147.3 (C-7), 146.9 (C-3), 127.7 (C-1), 123.0 (C-6), 116.5 (C-5),
15.1 (C-2), 114.8 (C-8), 73.5 (C-3’), 72.0 (C-2’), 52.5 (4’-OCH3).
Compound 2: white amorphous powder; [a] –43.5 (c 0.24, MeOH); UV (MeOH) k
max
ꢂ1
2
4
6
01,223,268 nm; IR (iTR) ꢀ : 341,917,331,653,105,000,000,000 cm ; HRESIMS m/z
max
–
1
49.1215 [M þ Cl] (calcd for 449.1209, C H O Cl); H NMR (500 MHz, DMSO-d ): d
19
26 10
6
H
.77 (2H, s, H-2, 6), 6.59 (1H, d, J ¼ 15.9 Hz, H-7), 6.35 (1H, dt, J ¼ 15.9, 6.2 Hz, H-8), 4.94
(
1H, d, J ¼ 6.6 Hz, H-1’’), 4.67 (2H, t, J ¼ 6.2 Hz, H-9), 3.76 (6H, s, 3, 5-OCH ), 3.59 (1H, d,
3
J ¼ 11.3 Hz, H-6’’a), 3.41 (1H, dd, J ¼ 11.3, 4.6 Hz, H-6’’b), 3.20 (1H, m, H-2’’), 3.18 (1H, m,
13
H-3’’), 3.17 (1H, m, H-4’’), 3.04 (1H, m, H-5’’), 2.05 (3H, s, H-2’); C NMR (125 MHz,
DMSO-d ): d 170.2 (C-1’), 152.7 (C-3, 5), 134.4 (C-4), 133.1 (C-7), 131.6 (C-1),123.2 (C-8),
6
C
104.8 (C-2, 6) 102.4 (C-1’’), 77.2 (C-5’’), 76.6 (C-3’’), 74.2 (C-2’’), 69.9 (C-4’’), 64.3 (C-9),
6
0.9 (C-6’’), 56.4 (3, 5-OCH ), 20.8 (C-2’).
3

6
Y.-G. CAO ET AL.
Compound 3: white amorphous powder; [a] –36.5 (c 0.07, MeOH); UV (MeOH) kmax
2
0
11,228,286,319 nm; IR (iTR) ꢀmax
:
3,466,295,629,242,850,000,000,000,000,000,000,
ꢂ1
þ
1
00,000 cm ; HR-ESI-MS m/z 341.1357 [M þ Na] (calcd for 341.1359, C H O Na); H
18 22 5
NMR (500 MHz, CD OD): d 6.87 (2H, d, J ¼ 8.5 Hz, H-2’, 6’), 6.76 (1H, s, H-3), 6.70 (2H,
3
H
d, J ¼ 8.5 Hz, H-3’, 5’), 5.73 (1H, s, H-6), 4.10 (1H, d, J ¼ 11.8 Hz, H-8’), 4.05 (1H, dd,
J ¼ 12.2, 2.4 Hz, H-7’a), 3.81 (3H, s, 4-OCH ), 3.75 (1H, dd, J ¼ 12.5, 9.0 Hz, H-8a), 3.43
3
(
1H, dd, J ¼ 12.5, 6.5 Hz, H-8b), 3.15 (2H, m, H-7), 3.14 (3H, s, 8’-OCH ), 2.59 (1H, dd,
3
13
J ¼ 12.2, 10.0 Hz, H-7’b); C NMR (125 MHz, CD OD): d 157.4 (C-4’), 149.4 (C-4), 145.7
3
C
(
C-5), 132.2 (C-2’, 6’), 129.0 (C-1’), 127.1 (C-1), 120.7 (C-2), 116.3 (C-3’, 5’), 115.8 (C-6),
1
12.5 (C-3), 79.9 (C-8’), 60.7 (C-8), 56.5 (8’-OCH ), 56.4 (4-OCH ), 38.6 (C-7’), 27.1 (C-7).
3 3
3.4. Acid hydrolysis of compound 2
ꢃ
Compound 2 (1.0 mg) was hydrolyzed with 2 M HCl (2.5 mL) (80 C, 3 h). The mixture
was dried and the residue was dissolved in H O (2 mL) and extraction with ethyl acet-
2
ate (3 ꢁ 2 mL) (Kang et al. 2017). The dry aqueous was subjected to chiral HPLC
equipped with a Chiralpack AD-H column (250 ꢁ 4.6 mm) and an evaporative light
scattering detection (ELSD), using hexane:alcohol:trifluoroacetic acid mixture
ꢂ1
(
750:250:0.25) as the mobile phase (0.5 mLꢄmin ) (Lopes and Gaspar, 2008).
Retention time of the sugar derivative obtained from compound 2 was similar to
that of D-glucose (t ¼ 17.0 min), so the sugar was identified as D-glucose.
R
3.5. Acetylcholinesterase inhibition assays
AChE inhibition was determined using a modified Ellman’s method (Rhee et al. 2001;
Zhang et al. 2015).
4. Conclusion
ꢀ
ꢀ
In this study, two new phenylpropanoids, (2’R ,3’R )-2’,3’-dihydroxy-4’-methoxy-caffeoyl
butyrate, 9-acetoxy syringin, and a new dihydrostilbenoid, (8’R)-4’,5-dihydroxy-4,8’-dime-
thoxy-2-hydroxyethyl diphenylethane, together with five known compounds, were isolated
from flower buds of M. biondii. The AChE inhibitory bioassay indicated that compounds
4–6, and 8 exhibited slightly AChE inhibitory activities with IC50 values 25.7–43.1 lM.
Disclosure statement
The authors declare no conflicts of interest.
Funding
This work was supported by the Central Leading Local Science and Technology Development
Special Foundation ([2016]149) and Science and Technology Key Project of Henan Province
(182102410080).

NATURAL PRODUCT RESEARCH
7
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