Guaiane-type sesquiterpenoids from Alisma orientalis

Article abstract of DOI:10.1016/S0031-9422(03)00222-X

Two guaiane-type sesquiterpenoids named orientalol E (1) and orientalol F (3) were isolated from the rhizome of Alisma orientalis (SAM) JUZEP together with two known guaiane-type sesquiterpenoids alismol (2) and alismoxide (4). Their relative stereo-struc

Full text of DOI:10.1016/S0031-9422(03)00222-X

Phytochemistry 63 (2003) 877–881
www.elsevier.com/locate/phytochem
Guaiane-type sesquiterpenoids from Alisma orientalis
a,
a
a
b
Guo-Ping Peng *, Gang Tian , Xian-Feng Huang , Feng-Chang Lou
aNanjing University of Traditional Chinese Medicine, Nanjing, 210029, PR China
bChina Pharmaceutical University, Nanjing, 210029, PR China
Received 19 December 2002; accepted 25 February 2003
Abstract
Two guaiane-type sesquiterpenoids named orientalol E (1) and orientalol F (3) were isolated from the rhizome of Alisma orien-
talis (SAM) JUZEP together with two known guaiane-type sesquiterpenoids alismol (2) and alismoxide (4). Their relative stereo-
structures were elucidated by spectroscopic methods, whereas absolute stereostructures were determined on the basis of chemical
correlation.
#
2003 Elsevier Ltd. All rights reserved.
Keywords: Alisma orientalis; Alismataceae; Sesquiterpenoids; Guaiane; Orientalol E and F; Stereostructure
1
. Introduction
255.1938 [M+H]+ (calc. 255.1955) and NMR spectro-
scopic analysis. The IR spectrum exhibited a broad
absorption at 3400.6 cm due to hydroxyl. The H
MNR showed two tertiary methyls groups [ꢀH 1.33 and
1.21 (each 3H, s)], one isopropyl group [ꢀH 1.95 (1H,
sept, J=6.9Hz), 1.03 (3H, d, J=6.9Hz), 1.01 (3H, d,
ꢀ
1
1
The plant Alisma orientalis (SAM) JUZEP has been
widely cultivated in China and Japan, and its dried rhi-
zomes have been used as folk medicines for diabetes,
diuretics and they are an important crude drug compo-
nent for several Chinese preparations. Our continuing
phytochemical investigation on the sesquiterpenoids of
the plant led to the isolation of two guaiane-type ses-
quiterpenoids named orientalol E (1) and F (3) along
with two known compounds alismol (2) and alismoxide
J=6.9Hz)], and one oxygenated methine at ꢀ 3.80 (1H,
H
1
3
d, J=9.3Hz). The C NMR and INEPT spectra
revealed the presence of four methyl carbons, four
methylene carbons, three methine carbons, one oxyge-
nated methine carbon (ꢀC 72.1), and three oxygenated
quaternary carbons (ꢀC 79.1, 86.4 and 83.0). These
spectral features (Table 1) suggested 1 to be a guaiane-
type sesquiterpenoid, and its 13C NMR spectrum was
similar to that of 4 except for C-5, C-6, C-7, C-10. The
assignment of the protonated carbons was performed by
application of a HMQC experiment. In the HMBC
spectrum, the following correlations were noted: the
(
4). Previously, it was reported to contain a few tri-
terpenoids, sesquiterpenoids e.g. alismol (2), alismoxide
4), germacrene C, orientalols A–C and sulphate of
(
orientalols (Nakajima et al., 1994; Oshima et al., 1983;
Yoshikawa et al., 1992, 1993a, 1993b).
2
. Results and discussion
proton signal at ꢀH 1.33 (H -14) with the carbon reso-
3
nance at ꢀ 79.1 (C-4), 54.5 (C-5), 40.1 (C-3); the proton
C
2
.1. Relative stereostructures of 1 and 3
Orientalol E (1) was isolated as a pale yellow oil,
whose molecular formula was determined to be
resonance at ꢀH 1.03 (H -12) and ꢀH 1.01 (H -13) with
3
3
the carbon signals at ꢀC 31.8 (C-7), 32.4 (C-11); the
proton signal at ꢀH 1.95 (H-11) with the carbon reso-
nance at ꢀ 86.4 (C-7), 72.1 (C-6), 29.0 (C-8), 17.4 (C-
C
C H O by a combination of HR-ESI-MS at m/z
1
12), 18.3 (C-13); the proton resonance at d 1.21 (H-15)
5
26
3
H
with the carbon signal at ꢀ 50.4 (C-1), 31.8 (C-9) and
C
83.0 (C-10); the proton signal at ꢀH 3.80 (H-6) with the
carbon signals at ꢀC 79.1 (C-4), 54.5 (C-5), 86.4 (C-7),
29.0 (C-8), 32.4 (C-11). The correlations of 1 observed
*
Corresponding author. Tel.: +86-025-6798186; fax: +86-025-
522534.
E-mail address: guopingpeng@sohu.com (G.-P. Peng).
6
0
031-9422/03/$ - see front matter # 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0031-9422(03)00222-X

878
G.-P. Peng et al. / Phytochemistry 63 (2003) 877–881
Table 1
13
1
3
C NMR and HNMR spectral data of compounds 1, 1a, 3, 4 (400 or 300 MHz, d, ppm, CDCl as solvent)
Compounds
No.
Orientalol E
Orientalol E 6-acetate
Orientalol F
Alismoxide
ꢀC
ꢀH
ꢀC
50.5
ꢀH
ꢀC
ꢀH
ꢀC
ꢀH
1
2
3
4
5
6
7
8
9
50.4
23.5
40.1
79.1
54.5
72.1
86.4
29.0
31.8
83.0
32.4
17.4
18.3
25.1
23.6
1.72
1.67 m
57.7
24.0
39.1
133.6
133.0
74.0
86.7
28.6
31.7
84.5
31.8
17.3
18.2
14.7
24.1
2.69
1.21, 1.81
2.31, 2.20
50.9
21.6
40.6
80.3
50.0
121.4
149.7
25.2
42.5
76.8
37.3
21.2
21.5
22.7
21.5
22.8
40.1
78.8
52.8
72.1
85.7
30.3
31.4
83.0
32.9
17.4
18.2
24.7
23.6
170.7
1.57
3.80 d, J=9.3
1.76 d
5.04 d
4.44, brs
5.52
1.71, 1.60
1.83, 1.29
10
11
12
13
14
15
1.95
1.78
1.95
1.03 d J=6.9
1.01 d, J=6.9
1.33 3H, s
1.21 3H, s
0.93 d
0.98 d
1.37 s
1.22 s
1.01, d J=6.9
1.03, d, J=6.9
1.89, 3H, s
1.19, 3H, s
0.97
0.96
1.26
1.20
OCOCH
3
2
1.5
2.04 s
1
1
among protons were determined on the basis of H– H
COSY experiments. Treatment of 1 with AC O-pyridine
the acetylation shift. Thus the planar structure of
orientalol E was determined as 1.
2
afforded a monoacetate 1a (Fig. 1). The acetylation
shifts observed were as follows: the resonance due to
C-8 (ꢀ 30.3) appeared at a lower field than that in 1
The relative stereostructure of 1 was characterized by
NOESY experiment. The correlations from H-1,
assumed to be a oriented, to Me-14, from Me-14 to H-6,
from H-6 to Me-14 and Me-12 suggested that these
protons and methyls were all in an a-configuration. The
correlations from H-5 to Me-15 and H-8b suggested
that the protons and methyls were all in b-configur-
(ꢀ 29.0), while those of C-5 and C-7 (ꢀ 52.8, 85.7)
were at a higher field than those in 1 (ꢀ 54.5, 86.7).
In addition, the H-6 signal of 1a (ꢀ 5.04) was
observed at lower field than that of 1 (ꢀ 3.80) due to
3
Fig. 1. (1) R=H, (1a) R=COCH .

G.-P. Peng et al. / Phytochemistry 63 (2003) 877–881
879
ation. These correlations indicated that the A/B ring
2.2. Absolute stereostructures of orientalol E (1) and
alismoxide (4)
junction is trans oriented. Therefore, the structure of 1
was established as 4b, 6b-dihydroxy-7a, 10a-epoxy-1, 5-
trans-guaiane (Fig. 1).
Next, in order to clarify the absolute stereostructure
of orientalol E (1) and alismoxide (4), we carried out the
conversion of 2 into 4 and 1. At first, 2 was naturally
oxidized to a mixture contaning 2 and 4, which was
purified by prep. TLC to give pure 4. Then, 4 was trea-
ted with m-chloroperbenzoic acid (mCPBA) to give pure
1 (Scheme 1). Since the absolute stereostructure of 2 had
been determined by CD spectral analysis, and on the
basis of the transformation from 2 to alismoxide (4) and
orientalol E (1), the absolute stereostructures of orien-
talol E (1) and alismol (3) were determined to be 1R, 4S,
5R, 6S, 7R, 10R and 1R, 4S, 5R, 10R (Yoshikawa et al.,
1993c).
Orientalol F (3) was isolated as pale yellow oil, whose
molecular formula was determined to be C H O by a
1
5
24
2
combination of HR-ESI-MS at m/z 237.1844 [M+H]+
(
an absorption band at 3476.4 cm due to a hydroxyl
calc. 237.1849) and NMR. The IR spectrum exhibited
1
ꢀ
1
group. The H MNR showed the presence of two ter-
tiary methyl groups at ꢀ 1.89 and 1.19 (each 3H, s), one
isopropyl group at ꢀH 1.95 (1H, sept, J=6.9Hz), 1.03
H
(
oxygenated methine at ꢀ 4.44 (1H, d, J=9.3 Hz). The
3H, d, J=6.9Hz), 1.01 (3H, d, J=6.9Hz), and one
H
1
3C NMR and DEPT spectrum revealed the presence of
four tertiary methyl carbons, four methylene carbons,
two methine carbons, one oxygenated methine carbon,
a tetrasubstituted double bond (ꢀC 133.62 and 133.04)
and two oxygenated quaternary carbons (ꢀ 85.75 and
C
3. Experimental
8
4.47). These spectral features (Table 1) suggested 3 to
be a guaiane-type sesquiterpenoid, when 13C NMR
spectra was similar to that of 1 except for a tetra-
substituted double bond (ꢀC 133.62 and 133.04) and a
3.1. General experimental procedures
MPs: PHMK79/1212; uncorr. IR: Nicolet 170sx
spectrometer. NMR: Burker ACF-300 or Burker ASR-
400 spectrometer (400 or 300 MHz for H, 100 or 75
MHz for 13C), both with TMS as int. standard. EI-MS:
Nicolet FTMS-2000; HR-ESI-MS: PE Biosystems
Mariner System 5140 instrument. Optical rotations were
measured with a JASCO DIP-181 spectropolarimeter in
MeOH solution. CC: silica gel H (10–40 m, made in
QingDao Oceanic Chemical Industry). prep. TLC
tertiary methyl (ꢀ 14.7). The assignment of the proto-
C
1
nated carbons was performed by a HMQC experiment.
Based on the above observations and by analyses of
HMBC spectral data as shown in Fig. 2, the structure of
orientalol F was established as 3 (Fig. 1). The relative
stereostructure of 3 was characterized by NOESY
experiment (Fig. 3), and it was established as
6
b-hydroxy-7a, 10a-epoxyguaiane-4, 5-ene (Fig. 1).
(thickness=1 mm): silica gel H (10–40 m), spots were
visualized by spraying with 10% H SO followed by
2
4
heating.
.2. Plant material
Rhizome of Alisma orientalis (SAM) JUZEP was col-
3
lected in the province of the People’s Republic of China.
A voucher specimen (97-0721) was deposited at the
Faculty of Pharmaceutical Sciences, Nanjing University
of Traditional Chinese Medicine.
Fig. 2. HMBC correlations of 3.
3.3. Extraction and isolation
The dried plant material (28 kg) was extracted with
EtOAc (IOL, twice) at room temperature. The EtOAc
solutions were combined and concentrated under reduced
pressure to give an extract which was subjected to silica gel
CC with petroleum ether–EtOAC (8:2–2:8) gradient to
give four fractions (Fr. A-Fr. D). Fr. B was subjected to
silica gel CC, eluted with petroleum ether–EtOAc (95:5,
8
5:15, 75:25, 70:30) to give 300 fractions. Frs. (85–96)
were applied to a silica gel column to give pure alismol
1, 800 mg). Similarly, Frs. (105-122) were purified by
prep. TLC to give pure orientalol F (2, 30 mg). Fr. D
(
Fig. 3. NOESY correlations of 3.

880
G.-P. Peng et al. / Phytochemistry 63 (2003) 877–881
Scheme 1. Reactions performed to elucidate the absolute configuration of alismoxide (4) and orientalol E (1) [Reaction conditions: (a) air, room
temperature, 3 months; (b) m-chloroperbenzoic acid (mCPBA), ClCH CH Cl, room temperature, 30 h].
2
2
was subjected to silica gel CC, eluted with CHCl3–
MeOH (95:5, 85:15, 75:25, 70:30) to give 50 fractions.
Frs (38–45) were applied to a silica gel column to give
pure alismoxide (4, 300 mg) and orientalol E (1, 50 mg).
CDCl as solvent): ꢀ 55.1, 24.8, 40.3, 80.6, 47.3, 121.4,
3
149.6, 30.0, 37.1, 153.9, 37.4, 21.3, 21.5, 24.1, 106.4.
3.8. Alismoxide (4)
ꢁ
25
ꢁ
3
6
.4. Orientalol E ((1R*, 4S*, 5R*, 6S*, 7R*, 10R*)-4,
-dihydroxy-7, 10-epoxy-1, 5-trans-guaiane) (1)
Colorless prisms, mp 140–142 C; [a] =+5.2
D
(MeOH; c 0.5); H-NMR and C NMR data see Table 1.
1
13
2
5
KBr
max
Pale yellow oil; [a] =+3.7 (MeOH; c 0.5); IR (u
cm ): 3400 (–OH), 2961, 2873, 1464, 1379, 1308, 1158,
3.9. Conversion from 3 to 1 and 4
D
ꢀ1
1
13
1067, 1014, 813, 734; H NMR and C NMR spectral
+
data see Table 1; HR-ESI-MS: m/z 255.1983 [M+H] ,
C H O requires 255.1955.
1
The oil 3 (200 mg) was exposed to air at room tempera-
ture for 3 months. The reaction mixture was purified by
prep. TLC to furnish a pure sample of 4 (20 mg), identical
5
27
3
(IR and NMRdata) withthe natural compound. Asolution
of 4 (100 mg) in ClCH CH Cl (5 ml) was treated with m-
3
.5. Acetylation of orientalol E (1)
2
2
chloroperbenzoic acid (mCPBA, 200 mg) and the whole
mixture was stirred at room temperature for 30 h. The
reaction mixture was separated by prep. TLC to give pure
compound 1 (15 mg), identical (IR and NMR data) with
the natural compound. The optical rotation of the semi-
The oil 1 (10 mg) in pyridine (0.5 ml) was added to
acetic anhydride (0.5 ml) and the mixture was stirred at
room temperature for 24 h. After evaporation of excess
reagent, the residue was separated by prep. TLC to give
pure compound 1a. Compound 1a was pale yellow oil;
2
5
synthetic compound 1 ([a] =+3.4 (concentration 0.5
mg/ml (MeOH)) is almost the same as natural compound.
D
KBr
ꢀ1
1
IR (umax cm ): 3437 (–OH), 1736 (>C¼O), 1461, 1377,
13
1243, 948; H NMR and C NMR data see Table 1;
+
HR-EI-MS: m/z 296.3957 [M] , C H O requires
1
7
28
4
+
+
2
H O] , 236 [M–HAc] .
96.3934; EIMS: m/z 296 [M] , 281 [M–Me] , 278 [M–
Acknowledgements
+
+
2
We thank Dr. Qi-Nan Wu (Nanjing University of
Traditional Chinese Medicine, Nanjing, China) for
identification of this plant and Prof. Yi-Hua Yu
3
5
.6. Orientalol F (6ꢁ-hydroxy-7ꢂ, 10ꢂ-epoxyguaiane-4,
-ene) (3)
(
Shanghai Institute of Organic Chemistry, Shanghai,
2
5
KBr
max
Pale yellow oil; [a] =+4.3 (MeOH, c 0.5); IR (u
cm ): 3476, 2965, 2932, 2876, 1488, 1375, 1177, 1073,
Chinese Academy of Sciences, China) for measuring
NMR spectrum. This work was partially supported by
National Key Technologies R & D Program during
Five-Year Plan Period from Ministry of Science and
Technology of the People’s Republic of China (No. 96-
D
ꢀ1
016, 901; for H NMR and 13C NMR spectral data,
1
1
see Table 1; HR-ESI-MS: m/z 237.1844 [M+H] ,
+
C H O , requires 237.1849).
1
5
24
2
903-02-03).
3
.7. Alismol (2)
2
5
ꢁ
KBr
max
References
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D
ꢀ1
1
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