Lignans from the root of Rhodiola crenulata

Article abstract of DOI:10.1021/jf204660c

Rhodiola crenulata L. is an important species in genus Rhodiola widely used as a health food to reinforce immunity, improve memory and learning, scavenge active-oxygen species, and relieve altitude sickness. Eleven new lignans and a new benzonitrile compound, crenulatanoside A, were isolated from the roots of R. crenulata L. along with 25 known compounds, including 12 lignans. The structures of these compounds were elucidated by spectroscopic data and chemical evidence. Among them, compounds 1-4 and 5-7 were determined to be optical isomers of two 8-O-4′ neolignan glycosides. Compounds 8-11 were aryl tetralin type lignans, and compounds 12 and 13 were dihydrobenzofuran neolignans. All of the isolated compounds were evaluated for their inhibitory activity against α-glucosidase. From the data obtained, compound 37 showed strong inhibitory activity against α-glucosidase with an IC₅₀ value of 96.8 μM.

Full text of DOI:10.1021/jf204660c

Article
pubs.acs.org/JAFC
Lignans from the Root of Rhodiola crenulata
Ya-nan Yang, Zhao-zhen Liu, Zi-ming Feng, Jian-shuang Jiang, and Pei-cheng Zhang*
State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of
Medical Sciences and Peking Union Medical College, Beijing 100050, People's Republic of China
*
S Supporting Information
ABSTRACT: Rhodiola crenulata L. is an important species in genus Rhodiola widely used as a health food to reinforce immunity,
improve memory and learning, scavenge active-oxygen species, and relieve altitude sickness. Eleven new lignans and a new
benzonitrile compound, crenulatanoside A, were isolated from the roots of R. crenulata L. along with 25 known compounds,
including 12 lignans. The structures of these compounds were elucidated by spectroscopic data and chemical evidence. Among
them, compounds 1−4 and 5−7 were determined to be optical isomers of two 8-O-4′ neolignan glycosides. Compounds 8−11
were aryl tetralin type lignans, and compounds 12 and 13 were dihydrobenzofuran neolignans. All of the isolated compounds
were evaluated for their inhibitory activity against α-glucosidase. From the data obtained, compound 37 showed strong inhibitory
activity against α-glucosidase with an IC50 value of 96.8 μM.
KEYWORDS: Rhodiola crenulata, lignan, isolation, health food, α-glucosidase
INTRODUCTION
MATERIALS AND METHODS
Plant Material. The roots of R. crenulata were purchased in July
007 from Pushenglin Corp. The plant material was identified as R.
crenulata growth in Tibet by Professor Lin Ma. A voucher specimen
was deposited in the Herbarium of the Department of Medicinal
plants, Institute of Materia Media, Chinese Academy of Medical
Sciences and Peking Union Medical College, Beijing, People's
Republic of China.
■
■
The plants of the genus Rhodiola are widely distributed in the
Himalayan, western, and northern regions of Asia. There are
approximately 90 species recorded in the world, and more than
2
7
0 species are found in China, mainly in plateau areas, such as
Yunnan, Sichuan, and Tibet. Among them, Rhodiola crenulata
L. is an important species found mostly in the northwest region
of China. For a long time, its roots (Golden Root) have been
used as a health food, antidepressive, and antifatigue and to
reinforce immunity, improve memory and learning, scavenge
General Apparatus and Chemicals. The optical rotations were
measured on a Jasco P-2000 polarimeter. UV spectra were recorded on
a Jasco V650 spectrophotometer. IR spectra were recorded on an
1
−8
1
13
active-oxygen species, and relieve altitude sickness. Recently,
some pharmacological studies have demonstrated that the
genus Rhodiola might have the function of lowering blood
IMPACT 400 (KBr) spectrometer. H NMR (500 MHz), C NMR
125 MHz), and 2D NMR spectra were run on INOVA 500 MHz
(
spectrometer with tetramethylsilane (TMS) as an internal standard,
and values were given in ppm (δ). HRESIMS was performed on
Finnigan LTQ FTMS. Column chromatography was performed with
Macroporous resin (Diaion HP-20, Mitsubishi Chemical Corp. Tokyo,
Japan), Rp-18 (50 μm, YMC, Kyoto, Japan), Sephadex LH-20
9
,10
glucose.
Previous phytochemical studies have reported the isolation of
almost 100 compounds from this genus, including phenols and
their corresponding glycosides, cyanophoric glycosides, terpe-
(
Pharmacia Fine Chemicals, Uppsala, Sweden). Preparative HPLC was
1
1−15
noids, and flavonoids.
Among them, phenols and their
carried out on a Shimadzu LC-6AD instrument with a SPD-20A
detector, using a YMC-Pack ODS-A column (250 mm × 20 mm, 5
μm). HPLC-DAD analysis was performed using an Agilent 1200 series
system (Agilent Technologies, Waldbronn, Germany) with an Apollo
C18 column (250 mm × 4.6 mm, 5 μm; Grace Davison).
Extraction and Isolation. Air-dried roots (20 kg) of R. crenulata
were extracted with 80% EtOH. After the solvent was evaporated
under reduced pressure, the residue was resuspended in H O (5000
corresponding glycosides, monoterpenoid glycosides, and
cyanophoric glycosides were considered as characteristic
constituents of Rhodiola. To date, only three lignans have
been isolated from this genus, one of which was isolated from
1
6
R. crenulata. In our search for constituents from R. crenulata,
1
1 new lignans, 1, 2, and 5−13, and a new benzonitrile
2
compound, crenulatanoside A 36, were isolated from the roots
of R. crenulata. These new compounds along with the 25
already known constituents, which include 12 lignans, were
identified by comparing the spectroscopic data obtained with
those previously reported in the literature. Compounds 1−4
and 5−7 were identified as optical isomers of two 8-O-4′
neolignan glycosides. Compounds 8−11 were identified as aryl
tetralin type lignans, and compounds 12 and 13 were identified
as dihydrobenzofuran neolignans. Compound 36 was identified
as a rare benzonitrile natural product. All of these compounds
were evaluated for their inhibitory activity against α-
glucosidase, and compound 37 was observed to exhibit strong
inhibitory activity against α-glucosidase.
mL) and extracted with EtOAc (3 × 5000 mL). The aqueous layer
(
(
3600 g) was applied to a HDP100 macroporous adsorbent resin
4000 g, dried weight) column. Successive elution from the column
with H O, 15% EtOH, 30% EtOH, 50% EtOH, 70% EtOH, and finally
2
95% EtOH (15 L each) yielded five corresponding fractions after
removing solvents. The fraction eluted with 30% EtOH (240 g) was
separated on a Sephadex LH-20 column with 0−100% MeOH (using a
1
0% stepwise increase in MeOH concentration) to yield fractions 1−9
Received: November 14, 2011
Revised: January 5, 2012
Accepted: January 6, 2012
Published: January 6, 2012
©
2012 American Chemical Society
964
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Journal of Agricultural and Food Chemistry
Article
Figure 1. Structures of compounds 1−37.
using HPLC-DAD analysis. Fraction 1 (3 g) was further separated via
MeOH:H O ratio of 1:9, to yield 24 (60 mg) and 34 (22 mg).
2
reversed-phase preparative HPLC, using a MeOH:H O ratio of 1:4, to
yield 1 (21 mg), 3 (17 mg), 4 (22 mg), 6 (18 mg), and 23 (19 mg).
Fraction 2 (14 g) was separated on a Sephadex LH-20 column and
Fraction 5 (18 g) was separated over a Sephadex LH-20 column and
2
eluted with a gradient of increasing MeOH (0−30%) in H O to yield
2
1
2 subfractions (Fr5-1−Fr5-12). Subfraction Fr5-6 was further
eluted with a gradient of increasing MeOH (0−20%) in H O to yield
2
separated by reverse-phase preparative HPLC, using a MeOH:H O
2
six subfractions (Fr2-1−Fr2-6). Subfraction Fr2-2 was further
ratio of 1:8, to afford 26 (19 mg), 29 (26 mg), and 35 (28 mg). Using
separated by reverse-phase preparative HPLC, using a MeOH:H O
2
a MeOH:H O ratio of 1:9, subfraction Fr5-9 was further separated by
ratio of 1:5, to afford 2 (18 mg), 5 (16 mg), 7 (26 mg), 8 (14 mg), and
2
1
0 (8 mg). Subfraction Fr2-3 was further separated by reverse-phase
reverse-phase preparative HPLC to afford 31 (18 mg), 32 (29 mg), 33
(31 mg), and 36 (24 mg). Using reverse-phase preparative HPLC,
preparative HPLC, using a MeOH:H O ratio of 3:7, to afford 11 (17
mg), 15 (11 mg), 20 (17 mg), and 21 (19 mg). Subfraction Fr2-5 was
separated on a Sephadex LH-20 column and eluted with a gradient of
2
fraction 9 (4 g) was further separated with a MeOH:H O ratio of 1:8
2
to afford 25 (17 mg), 27 (19 mg), 28 (21 mg), and 30 (27 mg).
Figure 1 shows the structure of compounds 1−37.
increasing MeOH (0−30%) in H O to yield four subfractions (Fr2-5-
2
1
−Fr2-5-4). Subfraction Fr2-5-2 was subjected to reverse-phase
(
7S,8R)-4,7,9,3′,9′-Pentahydroxy-3-methoxyl-8-4′-oxyneoli-
preparative HPLC, using a MeOH:H O ratio of 1:4 as the mobile
2
gnan-3′-O-β-D-glucopyranoside (1). White amorphous powder,
phase, to yield 9 (10 mg), 12 (12 mg), 13 (23 mg), and 17 (19 mg).
Subfraction Fr2-5-3 was further separated by reverse-phase preparative
HPLC, using a MeOH:H O ratio of 3:7, to afford 14 (16 mg), 18 (11
mg), 19 (23 mg), and 22 (17 mg). Fraction 6 was further purified by
reverse-phase preparative HPLC, using a MeOH:H O ratio of 2:3, to
yield 16 (25 mg) and 37 (37 mg). The fraction eluted with 15% EtOH
20
D
[
α] +19.3 (c 0.027, MeOH). CD (MeOH) nm: 233 (−15.0), 278
(
−1.7). UV (MeOH) λ nm: 278, 233. IR (KBr) ν : 3365, 2925,
max
max
2
1605, 1506, 1453, 1427, 1261, 1217, 1121, 1060, 1020. HRESIMS m/z
+
1
5
49.1943 [M + Na] (calcd for C H O Na, 549.1948). For H and
25 34 12
13
2
C NMR spectroscopic data, see Tables 1 and 2.
7S,8S)-4,7,9,3′,9′-Pentahydroxy-3-methoxyl-8-4′-oxyneoli-
(
(
130 g) was separated on a Sephadex LH-20 column with 0−100%
gnan-3′-O-β-D-glucopyranoside (2). White amorphous powder,
20
D
MeOH (5% stepwise increase in MeOH concentration) to yield
fractions 1−12 using HPLC-DAD analysis. Fraction 3 (3 g) was
further separated via reversed-phase preparative HPLC, using a
[α] +12.3 (c 0.031, MeOH). CD (MeOH) nm: 238 (+5.9), 290
(+0.5). UV (MeOH) λmax nm: 275, 225. IR (KBr) νmax: 3361, 2928,
1600, 1508, 1448, 1426, 1267, 1217, 1119, 1067. HRESIMS m/z
9
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Journal of Agricultural and Food Chemistry
Article
1
a
Table 1. H NMR Spectroscopic Data (δ) of Compounds 1, 2, and 5−7
position
1
2
5
6
7
2
5
6
7
8
9
7.06 s
6.99 d (1.5)
6.87 d (8.0)
6.99 d (8.0)
4.89 d (7.5)
4.71 m
7.11 s
7.05 s
7.04 s
6.91 d (8.0)
6.97 d (8.0)
4.99 d (5.5)
4.62 m
7.13 d (8.5)
7.02 d (8.5)
5.05 d (4.0)
4.57 m
7.09 d (8.0)
7.01 d (8.0)
4.87 d (7.0)
4.53 m
7.09 d (8.5)
7.02 d (8.5)
4.87 d (7.5)
4.58 m
3.65 m
3.58 m
3.72 m
3.97 m
4.04 m
3
.91 m
2
5
6
7
8
9
1
2
3
4
5
6
3
′
7.06 s
6.98 d (1.5)
6.91 d (8.0)
6.87 dd (8.0, 1.5)
2.59 m
6.77 s
6.65 s
6.66 s
′
6.92 d (8.0)
6.87 d (8.0)
2.63 m
6.78 d (8.5)
6.63 d (8.5)
2.54 m
6.76 d (8.0)
6.62 d (8.0)
2.52 m
6.81 d (8.5)
6.65 d (8.5)
2.53 m
′
′
′
1.83 m
1.80 m
1.78 m
1.78 m
1.78 m
′
3.60 m
3.47 m
3.61 m
3.58 m
3.58 m
″
″
″
″
″
″
5.15 d (7.5)
3.67 m
4.76 d (7.5)
3.58 m
5.05 d (7.5)
3.61 m
5.03 d (7.5)
3.61 m
5.04 d (6.5)
3.64 m
3.60 m
3.37 m
3.55 m
3.57 m
3.57 m
3.54 m
3.49 m
3.53 m
3.53 m
3.52 m
3.65 m
3.55 m
3.58 m
3.60 m
3.62 m
3.94 m
4.03 m
3.91 m
3.91 m
3.81 m
-CH O
3.83 s
3.75 s
3.82 s
3.79 s
3.79 s
3
a
1
H NMR data (δ) were measured in D O at 500 MHz. Coupling constants (J) in Hz are given in parentheses.
2
Table 2. 13C NMR Spectroscopic Data (δ) of Compounds 1, 2, 5−13, and 36
a
a
a
a
a
b
a
b
a
a
a
a
position
1
2
5
6
7
8
9
10
11
12
13
36
1
135.2
113.9
150.2
147.7
118.2
122.8
75.6
135.6
114.2
150.1
147.7
118.2
123.9
74.8
138.5
113.9
151.4
147.9
118.9
122.3
75.2
138.3
114.5
151.1
148.0
118.7
123.1
75.0
138.2
114.2
151.2
148.1
118.6
123.4
75.1
138.6
112.9
144.1
147.0
115.0
120.0
40.0
142.4
115.8
150.1
145.9
118.1
124.3
43.5
135.7
106.6
147.8
133.7
147.8
106.6
46.6
140.4
116.4
150.4
146.4
118.2
125.4
46.5
136.0
122.1
150.5
148.1
119.1
121.9
91.0
139.7
122.0
152.9
147.2
121.4
121.7
90.6
141.0
102.6
162.0
130.2
138.5
124.0
72.2
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
1
2
3
4
5
6
3
5
3
5
87.2
85.4
86.6
86.5
86.4
47.1
51.4
45.3
48.6
55.3
55.5
119.9
18.4
63.5
63.4
63.7
64.0
64.0
61.4
62.3
60.1
71.1
65.7
65.8
′
139.7
120.1
149.3
148.8
120.3
126.3
33.5
139.6
120.4
148.8
148.5
121.4
126.6
33.5
139.7
118.8
148.5
146.9
118.8
123.0
33.4
139.9
118.8
149.1
146.6
119.9
122.7
33.4
139.8
118.5
148.7
146.5
119.8
122.9
33.4
134.0
108.2
151.1
136.7
151.2
125.8
32.6
134.9
112.3
154.6
139.1
153.8
128.5
41.6
130.0
112.1
146.6
144.4
116.2
132.6
32.1
128.6
115.6
148.9
145.9
118.9
134.7
40.9
139.5
118.5
143.1
148.4
132.2
113.2
33.9
139.6
119.2
143.1
148.5
132.1
113.5
33.9
104.3
75.9
′
′
78.7
″
72.4
′
78.6
′
63.5
′
′
36.0
36.1
36.0
36.0
36.0
38.8
76.7
38.0
76.2
36.3
36.3
′
63.8
63.9
63.9
63.9
63.9
64.2
70.2
63.5
70.1
63.9
63.9
″
103.6
76.0
103.6
76.0
103.4
75.7
103.4
75.7
103.5
75.7
102.4
74.0
105.1
76.3
100.7
73.0
106.7
76.3
103.4
75.8
103.5
75.8
″
″
79.0
79.0
78.9
78.9
78.9
76.9
79.0
77.0
78.3
79.0
79.0
″
72.4
72.4
72.2
72.2
72.2
70.0
72.1
69.1
72.0
72.3
72.3
″
78.5
78.5
78.4
78.4
78.4
76.4
78.5
76.9
67.8
78.4
78.4
″
63.5
63.7
63.3
63.4
63.3
59.8
63.1
60.1
63.4
63.4
‴
‴
‴
‴
‴
‴
102.4
72.8
73.0
74.8
72.6
19.4
′-CH O
55.7
61.0
56.2
59.1
63.2
58.9
55.6
58.8
58.8
3
′-CH O
3
-CH O
58.8
58.8
58.6
58.6
58.6
56.0
56.0
58.8
58.8
3
-CH O
3
a
13
C NMR data (δ) were measured in D O at 125 MHz. b13C NMR data (δ) were measured in DMSO at 125 MHz.
2
9
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Journal of Agricultural and Food Chemistry
Article
1
Table 3. H NMR Spectroscopic Data (δ) of Compounds 8−13 and 36
b
a
b
a
a
a
a
position
8
9
10
11
6.86 s
12
7.04 s
13
7.12 s
36
2
6.66 s
6.84 s
6.36 s
6.36 s
5
6
7
6.61 d (8.0)
6.35 d (8.0)
4.19 d (5.5)
6.87 d (8.5)
6.73 d (8.5)
4.06 d (8.5)
6.90 d (7.5)
6.78 d (7.5)
3.98 m
6.92 d (7.0)
7.21 d (7.5)
6.99 d (7.5)
5.67 d (5.0)
7.45 d (7.5)
c
6.91
7.05 d (7.5)
3.78 d (5.5)
5.61 d (6.0)
4.84 dd (12.0,3.5)
4
.96 dd (12.0,3.5)
8
9
1.76 m
3.32 m
2.07 m
3.82 m
1.70 m
3.46 m
2.27 m
3.61 m
3.77 m
3.93 m
3.61 m
3.74 m
4.02 m
3.75 d (11.5)
2.27 s
3
.96 d (11.5)
1
2
3
4
5
6
′
′
′
′
′
′
4.54 d (8.0)
3.35 m
6.62 s
6.83 s
6.69 s
6.38 s
2.72 m
6.86 s
6.33 s
6.98 s
6.99 s
3.46 m
3.48 m
3.49 m
6.93 s
6.94 s
3.78 dd (5.5,12.0)
3
.93 dd (5.5,12.0)
7′
2.45 d (14.0)
2.81 d (16.5)
3.21 d (16.5)
2.81 d (17.0)
3.18 d (17.0)
2.64 m
2.65 m
2.65 dd (15.5,4.0)
8
′
′
1.49 m
3.39 m
1.89 m
1.84 m
3.63 m
1.84 m
3.62 m
9
3.74 m
3.57 dd (10.5, 1.5)
3.74 m
3.62 m
4.15 d (7.5)
3.28 m
3.42 m
3.60 m
3.82 m
3
.43 m
1
2
3
4
5
6
1
2
3
4
5
6
3
5
3
5
″
4.83 d (7.5)
4.94 d (7.5)
3.37 m
4.33 d (7.5)
3.13 m
5.17 d (7.0)
3.58 m
5.19 d (6.5)
3.56 m
c
″
3.17
″
3.03 m
3.11
3.37 m
2.80 m
3.54 m
3.54 m
″
3.66 m
3.18 m
3.59 m
3.61 m
c
″
3.17
3.53 m
3.11 m
3.61 m
3.58 m
c
″
3.56 m
3.89
3.46 m
3.63 m
3.63 m
‴
‴
‴
‴
‴
‴
5.48 brs
3.63 m
3.91 m
3.54 m
3.89 m
1.24 d (5.5)
3.73 s
-CH O
3.75 s
3.82 s
3.69 s
3.69 s
3.72 s
3.86 s
3.82 s
3.84 s
3
-CH O
3
′-CH O
3.68 s
3.17 s
3.89 s
3.27 s
3
′-CH O
3
a
1
b
1
H NMR data (δ) were measured in D O at 500 MHz. H NMR data (δ) were measured in DMSO-d at 500 MHz. Coupling constants (J) in Hz
2
6
c
are given in parentheses. Overlapping signals.
+
1
5
49.1950 [M + Na] (calcd for C H O Na, 549.1948). For H and
5′-Methoxy-(+)-isolariciresinol-4′-O-β-D-glucopyranoside
25
34 12
20
1
3
(
(
8). White amorphous powder, [α]D −21.0 (c 0.021, MeOH). CD
C NMR spectroscopic data, see Tables 1 and 2.
7S,8R)-4,7,9,3′,9′-Pentahydroxy-3-methoxyl-8-4′-oxyneoli-
gnan-4-O-β-D-glucopyranoside (5). White amorphous powder,
MeOH) nm: 238 (+5.9), 273 (+1.2), 287 (−0.3). UV (MeOH) λ
(
max
nm: 282, 238. IR (KBr) ν : 3341, 2938, 1601, 1511, 1489, 1453,
max
+
α]D20 +9.2 (c 0.026, MeOH). CD (MeOH) nm: 233 (−15.9), 277
1411, 1265, 1223, 1117, 1071. HRESIMS m/z 575.2106 [M + Na]
[
(
1
1
13
(
calcd for C H O Na, 575.2099). For H and C NMR
−2.4). UV (MeOH) λ nm: 277, 235. IR (KBr) ν : 3347, 2930,
27 36 12
max
max
spectroscopic data, see Tables 2 and 3.
594, 1509, 1453, 1377, 1268, 1222, 1128, 1073, 1041. HRESIMS m/z
+
1
5′-Methoxy-8′-hydroxyl-(+)-isolariciresinol-4′-O-β-D-gluco-
5
49.1949 [M + Na] (calcd for C H O Na, 549.1948). For H and
25
34 12
20
1
3
pyranoside (9). White amorphous powder, [α]
D
−5.4 (c 0.026,
C NMR spectroscopic data, see Tables 1 and 2.
7R,8R)-4,7,9,3′,9′-Pentahydroxy-3-methoxyl-8-4′-oxyneoli-
gnan-4-O-β-D-glucopyranoside (6). White amorphous powder,
MeOH). CD (MeOH) nm: 239 (+10.1), 273 (+3.6), 288 (−0.9). UV
MeOH) λ nm: 282, 237. IR (KBr) ν : 3351, 2930, 1600, 1512,
(
(
1
max max
492, 1453, 1412, 1270, 1227, 1111, 1072, 1031. HRESIMS m/z
[
(
1
α]D20 −35.3 (c 0.015, MeOH). CD (MeOH) nm: 237 (−4.1), 276
+
1
5
91.2056 [M + Na] (calcd for C H O Na, 591.2048). For H and
27
36 13
−1.4). UV (MeOH) λ nm: 276, 237. IR (KBr) ν : 3316, 2932,
13
max
max
C NMR spectroscopic data, see Tables 2 and 3.
592, 1505, 1454, 1419, 1265, 1221, 1124, 1072, 1024. HRESIMS m/z
5
-Methoxy-(+)-isolariciresinol-4′-O-β-D-glucopyranoside
+
1
5
49.1935 [M + Na] (calcd for C H O Na, 549.1948). For H and
20
D
25
34 12
(10). White amorphous powder, [α] −49.5 (c 0.012, MeOH). CD
1
3
C NMR spectroscopic data, see Tables 1 and 2.
7S,8S)-4,7,9,3′,9′-Pentahydroxy-3-methoxyl-8-4′-oxyneoli-
gnan-4-O-β-D-glucopyranoside (7). White amorphous powder,
(
MeOH) nm: 236 (+1.7), 270 (+0.9), 287 (−2.3). UV (MeOH) λ
nm: 282, 234. IR (KBr) ν : 3368, 2914, 1610, 1511, 1458, 1425,
263, 1221, 1115, 1060. HRESIMS m/z 575.2095 [M + Na] (calcd
for C H O Na, 575.2099). For H and C NMR spectroscopic
max
(
max
+
1
20
1
13
[
(
1
α]D −26.5 (c 0.023, MeOH). CD (MeOH) nm: 235 (+4.6), 272
27
36 12
−0.8). UV (MeOH) λ nm: 277, 220. IR (KBr) ν : 3363, 2933,
data, see Tables 2 and 3.
max
max
598, 1511, 1453, 1413, 1268, 1221, 1105, 1053. HRESIMS m/z
8′-Hydroxy-(+)-isolariciresinol-9-O-β-D-xylopyranoside (11).
+
1
20
5
49.1939 [M + Na] (calcd for C H O Na, 549.1948). For H and
White amorphous powder, [α]D +43.5 (c 0.023, MeOH). CD
25
34 12
1
3
C NMR spectroscopic data, see Tables 1 and 2.
(MeOH) nm: 238 (+8.6), 274 (+7.1), 292 (−9.4). UV (MeOH) λmax
9
67
dx.doi.org/10.1021/jf204660c | J. Agric.Food Chem. 2012, 60, 964−972

Journal of Agricultural and Food Chemistry
Article
nm: 285, 233. IR (KBr) νmax: 3382, 2935, 1600, 1512, 1462, 1430,
the aromatic ring at δ 3.83 (s, 3, OCH ) and a glucopyranosyl
3
1
368, 1255, 1218, 1124, 1072, 1035. HRESIMS at m/z 531.1837 [M +
anomeric proton at δ 5.15 (d, 1, J=7.5 Hz, H-1″) were observed
+
1
13
Na] (calcd for C H O Na, 531.1842). For H and C NMR
1
13
25
32 11
in the H NMR spectrum. The C NMR spectrum of 1 (see
Table 2) showed 25 carbon signals. Aside from the six carbon
signals from the O-glucose unit and a methoxy group, the
remaining 18 carbon signals, including 12 aromatic and six
aliphatic carbons, and the HMBC correlations (see Figure 2) of
spectroscopic data, see Tables 2 and 3.
(
7R,8S)-Dihydrodehydrodiconiferyl Alcohol-3′-O-β-D-gluco-
20
pyranoside (12). White amorphous powder, [α] +46.9 (c 0.029,
D
MeOH). CD (MeOH) nm: 239 (−11.4), 281 (−1.7). UV (MeOH)
λ
nm: 282, 232. IR (KBr) ν : 3347, 2927, 1604, 1517, 1493, 1434,
max
max
1
275, 1209, 1157, 1126, 1074, 1031. HRESIMS at m/z 531.1852 [M +
+
1
13
Na] (calcd for C H O Na, 531.1842). For H and C NMR
25
32 11
spectroscopic data, see Tables 2 and 3.
(
7R,8S)-Dihydrodehydrodiconiferyl Alcohol-3′-O-α-L-rham-
nopyranosyl-4-O-β-D-glucopyranoside (13). White amorphous
powder, [α]D20 −31.5 (c 0.014, MeOH). CD (MeOH) nm: 238
(
−3.2), 279 (−1.0). UV (MeOH) λ nm: 280, 238. IR (KBr) ν
:
max
max
3
6
262, 2930, 1598, 1495, 1404, 1262, 1210, 1062, 1018. HRESIMS m/z
+
1
77.2407 [M + Na] (calcd for C H O Na, 677.2421). For H and
C NMR spectroscopic data, see Tables 2 and 3.
31
42 15
1
3
Crenulatanoside A (36). Colorless oil. UV (MeOH) λmax nm:
02, 238. IR (KBr) νmax: 3370, 2929, 2224, 1585, 1508, 1492, 1424,
3
1
(
+
275, 1235, 1160, 1076, 1044. HRESIMS at m/z 348.1048 [M + Na]
1
13
calcd for C H NO Na, 348.1059). For H and C NMR
15 19 7
spectroscopic data, see Tables 2 and 3.
Inhibitory Activity of α-Glucosidase. The inhibitory activity of
compounds 1−37 on α-glucosidase was determined spectrophoto-
metrically on 96-well microplate reader. Twenty microliters of 0.2 U/
mL α-glucosidase was premixed with 10 μL of compounds at various
concentrations in 50 μL of 100 mM phosphate buffer (pH 7.0) at 37
°
C for 5 min. Then, 20 μL of 2.5 mM substrate p-nitrophenyl-α-D-
glucopyranoside was added to the mixture to initiate the reaction. The
reaction was incubated at 37 °C for 15 min and stopped by the
addition of 50 μL of 0.4 M Na CO . α-Glucosidase activity was
Figure 2. Selected HMBC correlations of 1, 8, 12, and 36.
2
3
determined by measuring the release of p-nitrophenol from p-
nitrophenyl-α-D-glucopyranoside at 400 nm. The control was the
mixture of the test sample with solvent instead. The sample and
control blanks were the mixtures of sample and control except α-
glucosidase was instead with phosphate buffer, respectively. The
inhibition (%) of sample on α-glucosidase could be calculated by the
following formula:
H-7 at δ 4.99 with C-1, C-2, C-6, C-8, and C-9 and of H-7′ at δ
2.63 with C-1′, C-2′, C-6′, C-8′, and C-9′ confirmed the
presence of two phenyl propanoid units. In the HMBC
spectrum, the correlation of H-8 at δ 4.62 with C-4′ at δ 148.8
suggested that 1 was an 8-O-4′ system neolignan. The methoxy
group was determined to be at C-3 based on the HMBC
correlation of methoxy group at δ 3.83 with C-3 at δ 150.2,
while the HMBC correlation of the anomeric proton H-1″ of
sugar moiety at δ 5.15 correlated with C-3′ at 149.3, indicating
that the glucose unit tethered to C-3′. Acid hydrolysis of 1
yielded D-glucose, which was identified by the positive optical
inhibition (%) = [(Asample − Asample blank
)
/
(A − Acontrol blank)] × 100
control
Acid Hydrolysis of 1, 2, 5−13, and 36. A solution of each
20
rotation ([α]D + 39.4), and the β form was determined by the
presence of an anomeric proton at δ 5.15 (d, 1, J = 7.5 Hz, H-
compound in H O (3 mL) was individually hydrolyzed with 1 N HCl
2
(
0.5 mL) at 80 °C for 4 h. Each reaction mixture was extracted with
1
″). The erythro configuration between two chiral centers at C-7
EtOAc (3 × 3 mL) to yield an EtOAc extract and H O phase after
2
and C-8 positions was determined by its small coupling
constant (J7,8 = 5.5 Hz). The 8R absolute configuration was
determined by its CD spectrum, which displays a negative
removing the solvents. The aqueous phases of the hydrolysates were
purified by chromatograph column over silica gel and eluted with a
mixture of MeCN−H O (8:1) to yield glucose with positive optical
2
17
rotations.
Cotton effect at 233 nm. Thus, the structure of 1 was
determined to be (7S,8R)-4,7,9,3′,9′-pentahydroxy-3-methoxyl-
8−4′-oxyneolignan-3′-O-β-D-glucopyranoside (1).
RESULTS AND DISCUSSION
■
Compound 2 was obtained as a white amorphous powder.
Phytochemical Investigation. Compound 1 was obtained
as a white amorphous powder. The molecular formula of 1 was
determined as C H O from an HRESIMS ion at m/z
Positive HRESIMS data of 2 indicated an ion at m/z 549.1943
+
[
(
M + Na] , corresponding to a molecular formula of C H O
25 34 12
2
5
34 12
1
+
calcd for C H O Na, 549.1948). The H NMR spectrum of
5
49.1950 [M + Na] (calcd for C H O Na, 549.1948). The
25 34 12
2
5
34 12
1
2
(
=
(see Table 1) exhibited six aromatic proton signals at δ 6.99
d, 1, J = 1.5 Hz, H-2), 6.87 (d, 1, J = 8.0 Hz, H-5), 6.99 (d, 1, J
8.0 Hz, H-6), 6.98 (d, 1, J = 1.5 Hz, H-2′), 6.91 (d, 1, J = 8.0
H NMR spectrum of 1 (see Table 1) showed six aromatic
proton signals at δ 7.06 (s, 2, H-2, 2′), 6.91 (d, 1, J = 8.0 Hz, H-
5), 6.97 (d, 1, J = 8.0 Hz, H-6), 6.92 (d, 1, J = 8.0 Hz, H-5′),
Hz, H-5′), and 6.87 (dd, 1, J = 8.0, 1.5 Hz, H-6′), revealing the
presence of two ABX system aromatic rings. A methoxy group
and 6.87 (d, 1, J = 8.0 Hz, H-6′), revealing the presence of two
ABX system aromatic rings. Two methylene protons at δ 1.83
(
m, 2, H-8′) and 2.63 (m, 2, H-7′), two oxymethine protons at
at δ 3.75 (s, 3, OCH ) and a glucopyranosyl anomeric proton at
3
1
δ 4.99 (d, 1, J = 5.5 Hz, H-7) and 4.62 (m, 1, H-8), and two
oxymethylene protons at δ 3.65 (m, 2, H-9) and 3.60 (m, 2, H-
δ 4.76 (d, 1, J = 7.5 Hz, H-1″) were also observed in the H
NMR spectrum. The 13C NMR spectrum of 2 (see Table 2)
showed 25 carbon signals, including two C6−C3 units, six
carbons in an O-glucose unit, and a methoxy carbon at δ 58.8.
9
′) established the presence of a 1,2,3-propanetriol moiety and
a 1-propanol moiety. Additionally, a methoxy group attached to
9
68
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Journal of Agricultural and Food Chemistry
Article
The key correlation of H-8 at δ 4.71 with C-4′ at δ 148.5 in the
HMBC spectrum indicated that 2 was also an 8-O-4′ neolignan.
The HMBC correlations of the methoxy proton at δ 3.75 with
C-3 at δ 150.1 and the anomeric proton H-1″ at δ 4.76 with C-
4,7,9,3′,9′-pentahydroxy-3-methoxyl-8-4′-oxyneolignan-4-O-β-D-
glucopyranoside (6).
Compound 7 was obtained as a white amorphous powder.
The molecular formula of 7 was determined as C H O from
2
5
34 12
+
4′ at δ 148.5 showed that 2 was an optical isomer of 1. The
the HRESIMS at m/z 549.1939 [M + Na] (calcd for
sugar unit was determined to be β-D-glucose by acid hydrolysis
and the anomeric proton doublet at δ4.76 (d, 1, J = 7.5 Hz, H-
C H O Na, 549.1948). The UV, IR, and NMR spectroscopic
25
34 12
data of 7 indicated that this compound was also an 8-O-4′
system neolignan and an optical isomer of 5 and 6. The threo
configuration of 6 was confirmed by its coupling constant (J7,8
= 7.5 Hz). However, the CD spectrum of 7 showed a positive
Cotton effect at 235 nm, which differed from that of 6,
indicating that 7 had an 8S absolute configuration. The
structure of 7 was determined to be (7S, 8S)-4,7,9,3′,9′-
pentahydroxy-3-methoxyl-8-4′-oxyneolignan-4-O-β-D-glucopyr-
anoside (7).
1
1
1″) in the H NMR spectrum. Comparison of the H NMR
data (see Table 1) of 2 and 1 showed that the 5.5 Hz coupling
constant between H-7 and H-8 in 1 was 7.5 Hz in 2. This
difference suggested that the configuration between C-7 and C-
8
was threo instead of the erythro form in 1. The 8S absolute
configuration in 2 was determined by the positive Cotton effect
at 238 nm in the CD spectrum of 2. On the basis of these
results, the structure of 2 was determined to be (7S, 8S)-
4
,7,9,3′,9′-pentahydroxy-3-methoxyl-8-4′-oxyneolignan-3′-O-β-
Compound 8 was obtained as a white amorphous powder. Its
molecular formula was determined as C H O from the
D-glucopyranoside (2).
Compound 5 was obtained as a white amorphous powder. Its
molecular formula was determined to be C H O by the
27
36 12
+
positive HRESIMS ion at m/z 575.2106 [M + Na] (calcd for
1
C H O Na, 575.2099). The H NMR spectrum of 8 (see
2
5
34 12
27 36 12
positive HRESIMS ion observed at m/z observed 549.1949
Table 3) showed four aromatic proton signals at δ 6.66 (s, 1, H-
2), 6.61 (d, 1, J = 8.0 Hz, H-5), 6.35 (d, 1, J = 8.0 Hz, H-6), and
6.62 (s, 1, H-2′), revealing the presence of an ABX system of an
aromatic ring and a 1,3,4,5,6-pentasubstituted benzene ring.
+
1
(
[M + Na] . The H NMR spectrum of 5 also showed six
aromatic proton signals at δ7.11 (s, 1, H-2), 7.13 (d, 1, J = 8.5
Hz, H-5), 7.02 (d, 1, J = 8.5 Hz, H-6), 6.77 (s, 1, H-2′), 6.78 (d,
1
1
, J = 8.5 Hz, H-5′), and 6.63 (d, 1, J = 8.5 Hz, H-6′) (see Table
). Furthermore, the C NMR spectrum of 5 (see Table 2)
Additionally, three methoxy groups at δ 3.75 (s, 3, OCH ), 3.68
3
1
3
(s, 3, OCH ), and 3.17 (s, 3, OCH ) and a glucopyranosyl
3
3
showed 25 carbon signals, including six carbons of an O-glucose
unit and a methoxy carbon at δ 58.6. All of these spectroscopic
data were similar to those of 1, suggesting that 5 was also an 8-
O-4′ system neolignan. Careful analysis of the HMBC spectrum
of 5 revealed that the anomeric proton H-1″ at δ 5.05 was
correlated with C-4 at δ 147.9, indicating the linkage position of
glucose unit was at C-4 instead of C-3′ in 1 and 2. The sugar
unit was determined to be in the β-D-glucose form by the same
methods used to characterize the sugar units of 1 and 2. The
erythro configuration of C-7 and C-8 was confirmed by the
coupling constant (J7,8 = 4.0 Hz). The 8R absolute
configuration of 5 was determined by the negative Cotton
effect at 233 nm displayed in the CD spectrum. All of these
data indicated that the structure of 5 was (7S, 8R)-4,7,9,3′,9′-
pentahydroxy-3-methoxyl-8-4′-oxyneolignan-4-O-β-D-glucopyr-
anoside (5).
anomeric proton at δ 4.83 (d, 1, J = 7.5 Hz, H-1″) were also
1
13
observed in the H NMR spectrum. In the C NMR spectrum
of 8 (see Table 2), the 18 skeleton carbon signals suggested
that the aglycone of 8 was also a lignan with the exception of
three methoxyl carbons and six carbons of an O-glucose unit. In
the HMBC spectrum (see Figure 2), the following correlation
peaks confirmed that 8 was an aryl tetralin type lignan: H-7 at δ
4.19 with C-1, C-2, C-6, C-8, and C-9; H-7′ at δ 2.45 with C-1′,
C-2′, C-6′, C-8′, and C-9′; and H-8 at δ 1.76 with C-6′, C-7′, and
C-9′. The positions of three methoxy groups were determined
by the HMBC correlations of the methoxy protons at δ 3.75 (s,
3, OCH ), 3.68 (s, 3, OCH ), and 3.17 (s, 3, OCH ) with C-3,
3
3
3
C-3′, and C-5′, respectively. Additionally, the HMBC
correlation of the anomeric proton H-1″ at δ 4.83 with C-4′
at δ 136.7 indicated that the linkage position of the glucose unit
was at C-4′. The anomeric proton at δ 4.83 (d, 1, J = 7.5 Hz, H-
1″) confirmed that the glucose unit was in the β-form. Acid
hydrolysis of 8 afforded D-glucose, which was identified by the
Compound 6 was obtained as a white amorphous powder.
The same molecular formula as 5, C H O , was determined
2
5
34 12
+
20
from the positive HRESIMS ion at m/z 549.1935 [M + Na]
calcd for C H O Na, 549.1948). The H NMR spectrum
see Table 1) of 6 also showed six aromatic proton signals at
positive optical rotation, [α]D +29.6. The absolute config-
1
(
(
uration of C-7 could be determined from the CD spectrum of
25
34 12
8. The negative Cotton effect at 287 nm indicated that the
18
δ7.05 (s, 1, H-2), 7.09 (d, 1, J = 8.0 Hz, H-5), 7.01 (d, 1, J = 8.0
Hz, H-6), 6.65 (s, 1, H-2′), 6.76 (d, 1, J = 8.0 Hz, H-5′), and
absolute configuration of C-7 in 8 was S. Consequently, 8 was
identified as 5′-methoxy-(+)-isolariciresinol-4′-O-β-D-glucopyr-
anoside (8).
6
.62 (d, 1, J = 8.0 Hz, H-6′), revealing the presence of two ABX
1
3
system aromatic rings. The C NMR spectrum of 6 (see Table
) showed 25 carbon signals, including six carbons of an O-
Compound 9 was obtained as a white amorphous powder.
The molecular formula of 9 was determined as C H O from
2
27
36 13
+
glucose unit and a methoxy carbon at δ 58.6. The HMBC
correlations of the methoxy proton at δ 3.79 with C-3 at δ
an HRESIMS ion at m/z 591.2056 [M + Na] (calcd for
1
C H O Na, 591.2048). The H NMR spectrum of 9 (see
27
36 13
1
1
51.1 and the anomeric proton H-1″ at δ 5.03 with C-4 at δ
48.0 indicated that the methoxy group and the sugar unit were
Table 3) also revealed the presence of four aromatic proton
signals at δ 6.84 (s, 1, H-2), 6.87 (d, 1, J = 8.5 Hz, H-5), 6.73
(d, 1, J = 8.5 Hz, H-6), and 6.83 (s, 1, H-2′); three methoxy
proton signals at δ 3.89 (s, 3, OCH ), 3.82 (s, 3, OCH ), and
located at C-3 and C-4, respectively. The anomeric proton at δ
.03 (J = 7.5 Hz) revealed that the glucose moiety was in the β-
5
3
3
form. The NMR data of 6 were similar to those of 5 with the
exception of the coupling constant between H-7 and H-8. A
bigger coupling constant (J7,8 = 7.0 Hz) confirmed the threo
configuration of 6, and its 8R absolute configuration was
determined by the CD spectrum with a negative Cotton effect
at 237 nm. Thus, the structure of 6 was identified as (7R,8R)-
3.27 (s, 3, OCH ); and a glucopyranosyl anomeric proton
3
1
3
signal at δ 4.94 (d, 1, J = 7.5 Hz, H-1″). The C NMR
spectrum of 9 (see Table 2) displayed 27 carbon signals
corresponding to three methoxy carbons, 18 carbons of two
phenyl propanoid units, and six carbons of an O-glucose unit.
1
13
The similar H and C NMR data to those of 8 suggested that
9
69
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Journal of Agricultural and Food Chemistry
was also an aryl tetralin type lignan. Considering the 36 ppm
downfield shift of C-8′ in the C NMR spectrum and the
difference in the mass spectrum, a hydroxy group was proposed
to be attached to C-8′ in 9. The presence of this hydroxy group
was further confirmed by the HMBC correlation of H-7 and H-
Article
9
H-6′)]. Additionally, a methoxy proton [δ 3.84 (s, 3, OCH )],
3
1
3
two methylene protons [δ2.64 (m, 2, H-7′), 1.84 (m, 2, H-8′)],
two oxymethylene protons [δ 3.77 (m, 1, H-9a), 3.93 (m, 1, H-
9b), and 3.63 (m, 2, H-9′)], and two methine protons [δ 5.61
(d, 1, J = 6.0 Hz, H-7), 3.61 (m, 1, H-8)] were also observed.
13
9
7
with C-8′. The anomeric proton doublet at δ 4.94 (d, 1, J =
.5 Hz, H-1″) indicated that the sugar moiety was in the β-
The C NMR spectra of 12 displayed six carbon signals in the
high-field region attributed to a methine carbon at δ 55.3 (C-8),
an oxymethine carbon at δ 91.0 (C-7), two oxymethylene
carbons at δ 65.7 (C-9) and 63.9 (C-9′), two aliphatic
methylene carbons at δ 33.9 (C-7′) and 36.3 (C-8′), and 12
aromatic carbons in the downfield region. These spectroscopic
data suggested that 12 was a dihydrobenzofuran neolignan
glycoside. In the HMBC experiment of 12 (see Figure 2), the
correlation peaks of H-7 with C-2, C-6, C-8, C-4′, and H-1″
with C-3′ determined that the planar structure of 12 was the
same as the known compound 20. The anomeric proton at δ
configuration. The absolute configuration of C-7 in 9 was
determined by its CD spectrum. A negative Cotton effect at
288 nm indicated that the absolute configuration of C-7 in 9
was S. Thus, 9 was identified as 5′-methoxy-8′-hydroxyl-
(
+)-isolariciresinol-4′-O-β-D-glucopyranoside (9).
Compound 10 was obtained as a white amorphous powder
+
and its positive HRESIMS data ([M + Na] , m/z found
5
75.2095) indicated the molecular formula of 10 to be
1
13
C H O . The similar H and C NMR data to those of 8
27
36 12
1
(
see Table 3) confirmed that 10 was an aryl tetralin type lignan.
5.17 (d, 1, J = 7.0 Hz, H-1″) in the H NMR spectrum of 12
Additionally, four aromatic proton signals at δ 6.36 (s, 2, H-2,
indicated that the glucose unit is in the β-form. CD data of 20
showed a positive Cotton effect at 282 nm, indicating that the
absolute configuration of C-7 is S. Consequently, the 7R
configuration of 12 was determined by the negative Cotton
effect at 281 nm in the CD spectrum of this compound. On the
basis of these results, the structure of 12 was concluded to be
(7R, 8S)-dihydrodehydrodiconiferyl alcohol-3′-O-β-D-glucopyr-
anoside (12).
1
6), 6.69 (s, 1, H-2′), and 6.38 (s, 1, H-5′), found in the H
NMR spectrum, indicated that the lignan skeleton has the
structures of 1,3,4,6-tetrasubstituted and 1,3,4,5-tetrasubstituted
aromatic rings. This finding was further confirmed by an
HMBC experiment, which showed the following correlation
peaks: H-7 at δ 3.78 with C-1, C-2, C-6, C-8, and C-9; H-7′ at δ
2
.72 with C-1′, C-2′, C-6′, C-8′, and C-9′; and H-8 at δ 1.70 with
C-6′, C-7′, and C-9′. The positions of three methoxy groups at δ
.72 (s, 3, OCH ), 3.69 (s, 3, OCH ), and 3.69 (s, 3, OCH )
Compound 13 was obtained as a white amorphous powder.
3
The molecular formula of compound 13 was determined as
3
3
3
+
were determined to be at C-3′, C-3, and C-5 by HMBC
correlations. The β-configuration of the sugar moiety was
determined based on the coupling constant (J = 7.5 Hz). A
negative Cotton effect at 287 nm in the CD spectrum of 10
indicated that the absolute configuration of C-7 was S. These
spectroscopic data identified 10 as 5-methoxy-(+)-isolaricir-
esinol-4′-O-β-D-glucopyranoside (10).
C H O from the HRESIMS ion at m/z 677.2407 [M + Na]
31
42 15
(calcd for C H O Na, 677.2421). Five aromatic proton
31
42 15
signals at δ7.12 (s, 1, H-2), 7.21 (d, 1, J = 7.5 Hz, H-5), 6.99 (d,
1, J = 7.5 Hz, H-6), 6.99 (s, 1, H-2′), and 6.94 (s, 1, H-6′) were
1
detected in the H NMR spectrum of 13 (see Table 3). The
13
C NMR spectrum (see Table 2) showed 31 carbon signals, 25
of which were similar to the 13C NMR data of 12 with the
exception of a set of additional signals assigned to the α-L-
rhamnose moiety. In the HMBC spectrum, the correlation of
H-1″ (δ 5.19) with C-3′ (δ 143.1) indicated that the linkage
point of the glucose unit was at C-3′. Additionally, another
correlation of H-1‴ (δ 5.48) with C-4 (δ 147.2) established
that the rhamnose unit was attached to C-4. The absolute
configuration of C-7 in 13 was determined by investigating its
CD spectrum. The negative Cotton effects at 238 and 279 nm
in the CD spectrum of 13 indicated that the absolute
Compound 11 was obtained as a white amorphous powder.
The molecular formula of 11 was determined as C H O
32 11
25
+
from an HRESIMS ion at m/z 531.1851 [M + Na] (calcd for
C H O Na, 531.1842). Five aromatic proton signals at δ6.86
25
32 11
(
s, 2, H-2, 2′), 6.90 (d, 1, J = 7.5 Hz, H-5), 6.78 (d, 1, J = 7.5
Hz, H-6), and 6.33 (s, 1, H-5′); two methoxyl proton signals at
δ 3.86 (s, 3, OCH ) and 3.82 (s, 3, OCH ); and an anomeric
3
3
proton signal at δ 4.03 (d, 1, J = 7.5 Hz, H-1″) were detected by
1
13
H NMR (See Table 3). In the C NMR spectrum (see Table
19
2), 25 carbon signals were detected and assigned as two
configuration of C-7 is R. Thus, the structure of 13 was
determined to be (7R, 8S)- dihydrodehydrodiconiferyl alcohol-
3′-O-α-L-rhamnopyranosyl-4-O-β-D-glucopyranoside (13).
Compound 36 was obtained as colorless oil. The molecular
formula of 36 was determined as C H NO from the
methoxy carbons, 18 carbons of two C6−C3 units, and five
carbons of an O-xylose unit. The NMR spectroscopic data of 11
were very similar to those of the known compound 15, with the
exception of a set of signals assigned to a xylose moiety in 11.
In the HMBC spectrum, the correlation of the anomeric proton
H-1″ at δ 4.15 with C-9 at δ 71.1 confirmed that the linkage
position with the xylose unit is at C-9. The xylose unit was
determined to be in a β-form by the anomeric proton at δ 4.15
15
19
7
+
HRESIMS ion at m/z 348.1048 [M + Na] (calcd for
1
C H NO Na, 348.1059). The H NMR spectra of 36 revealed
15
19
7
an AB system, which was attributed to a 1,2,3,4-tetrasubstituted
aromatic ring at δ 7.45 (d, 1, J = 7.5 Hz, H-5) and 7.05 (d, 1, J =
7.5 Hz, H-6). In addition, a methyl proton signal at δ 2.27 (s, 3,
(
J = 7.5 Hz). In addition, the absolute configuration of C-7 of
1 is S based on the negative Cotton effect at 292 nm in the
CD spectrum. Hence, 11 was identified as 8′-hydroxy-
1
CH ), methylene proton signals at δ 4.96 (dd, 1, J = 12.0, 3.5
3
Hz, H-7a) and 4.84 (dd, 1, J=12.0, 3.5 Hz, H-7b), and an
(
+)-isolariciresinol-9-O-β-D-xylopyranoside (11).
Compound 12 was obtained as a white amorphous powder.
anomeric proton signal at δ 4.54 (d, 1, J = 8.0 Hz, H-1′) were
1
13
also detected by H NMR (see Table 3). The C NMR
spectrum of 36 displayed 15 carbon signals attributed to six
carbons from an O-glucose unit and six carbons assigned to an
aromatic ring, and the other three carbon signals were
determined to be a methyl carbon, a methylene carbon, and
a quaternary carbon. The quaternary carbon signal was
identified as the carbon signal of a cyano group. From the
The molecular formula of 12 was determined as C H O
from the HRESIMS ion at m/z 531.1852 [M + Na] (calcd for
C H O Na, 531.1842). The H NMR spectra of 12 exhibited
25
32 11
+
1
25
32 11
a 1,3,4-trisubstituted aromatic ring [δ 7.04 (s, 1, H-2), 6.92 (d,
, J = 7.0 Hz, H-5), and 6.91 (overlap, 1, H-6)] and a 1′,3′,4′,5′-
tetrasubstituted aromatic ring [δ 6.98 (s, 1, H-2′) and 6.93 (s, 1,
1
9
70
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Journal of Agricultural and Food Chemistry
Article
above data, the skeleton of 36 was determined as
benzenemethanol, and the positions of the other substituents
were confirmed by the HMBC spectrum (see Figure 2). The
correlation peaks of H-1′ (δ 4.54) with C-7 (δ 72.2) were used
to determine that the linkage position of glucose was at C-7.
The position of the methyl group was confirmed at C-4 based
on the correlation peaks of H-6 (δ 7.05) with C-7 (δ 72.2) and
and a new benzonitrile compound isolated from the roots of R.
crenulata L. Additionally, 25 known compounds, including 12
known lignans, were also isolated. To our knowledge, only
three lignans have been isolated previously from the genus
Rhodiola. All of the isolated compounds were evaluated for
their inhibitory activity against α-glucosidase. From the data
obtained, compound 37 showed strong inhibitory activity
H-5 (δ 7.45) with CH (δ 18.4). Upon further analysis of the
against α-glucosidase with an IC value of 96.8 μM and may be
3
50
HMBC spectrum, the correlation peak of H-5 (δ 7.45) with C-
useful in the prevention and treatment of diabetes.
3
(δ 162.0) indicated the linkage position of the hydroxyl group
was at C-3. The anomeric proton at δ4.54 (d, 1, J = 8.0 Hz, H-
ASSOCIATED CONTENT
Supporting Information
NMR spectra of compounds 1, 2, 5−13, and 36. This material
is available free of charge via the Internet at http://pubs.acs.org.
■
1
1
′) in the H NMR spectrum indicated that the glucose unit
was in the β-form. On the basis of these results, the structure of
6 was concluded to be 2-cyano-3-hydroxy-4-methxyl-benze-
*
S
3
nemethanol-7-O-β-D-glucopyranoside and named crenulatano-
side A.
AUTHOR INFORMATION
Corresponding Author
Tel: +86-10-63165231. Fax: +86-10-63017757. E-mail:
pczhang@imm.ac.cn.
■
Known compounds 3, 4, 14−35, and 37 were identified by
NMR and MS analyses, compared with reference data, and
identified as the following: (7R, 8S)-4,7,9,3′,9′-pentahydroxy-3-
*
2
0
methoxyl-8-4′-oxyneolignan-4-O-β-D-glucopyranoside (3),
7R, 8R)-4,7,9,3′,9′-pentahydroxy-3-methoxyl-8-4′-oxyneoli-
(
Funding
2
1
gnan-4 -O-β-D-glucopyranoside (4), (7R, 8R)-threo-4,7,9,9′-
tetrahydroxy-3,3′-dimethoxy-8-O-4′-neolignan-4-O-β-D-gluco-
This research was supported by the National Natural Science
Foundation of China (No. 30973861) and the Nation Science
and Technology Project of China (No. 2009YZH-HXY07).
1
7
pyranoside (14), (+)-cycloolivil-4′-O-β-D-glucopyranoside
2
2
23
(
15), (+)-isolarisiresinol (16), (+)-isolarisiresinol-4′-O-β-D-
24
glucopyranoside (17), (+)-isolarisiresinol-4-O-β-D-glucopyr-
ACKNOWLEDGMENTS
We thank Ying-hong Wang and Hong-yue Liu for NMR
measurements.
■
2
5
anoside (18), (+)-isolarisiresinol-9-O-β-D-xylopyranoside
2
6
(
19), (7S, 8R)-dihydrodehydrodiconiferyl alcohol-3′-O-β-D-
27
glucopyranoside (20), (7R, 8S)-dihydrodehydrodiconiferyl
alcohol-4-O-β-D-glucopyranoside (21), (7S, 8R)-dihydrode-
hydrodiconiferyl alcohol-9-O-α-L-rhamnopyranoside (22),
olivil-4-O-β-D-glucopyranoside (23), gallic acid (24), 3-O-
methyl gallic acid (25), 4-O-β-D-glucopyranosyloxy-3,5-
dimethoxy-benzoic acid (26), protocatechuic acid (27),
28
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