A new angeloylated triterpenoid saponin from the husks of xanthoceras sorbifolia bunge

Article abstract of DOI:10.1007/s11418-009-0359-z

A new angeloylated oleanane-type triterpenoid saponin, sorbifoliaside (1), and a known saponin, xanifolia O54, were isolated from the husks of Xanthoceras sorbifolia Bunge. Their chemical structures were elucidated on the basis of various spectroscopic analyses coupled with chemical degradation. To our knowledge, compound 1 is the first example of a naturally occurring triterpenoid saponin with an angeloyl group at C-2 of the sugar moiety. The Japanese Society of Pharmacognosy and Springer 2009.

Full text of DOI:10.1007/s11418-009-0359-z

J Nat Med (2010) 64:80–84
DOI 10.1007/s11418-009-0359-z
NOTE
A new angeloylated triterpenoid saponin from the husks
of Xanthoceras sorbifolia Bunge
Hongwei Fu Æ Ying Guo Æ Wei Li Æ Deqiang Dou Æ
Tingguo Kang Æ Kazuo Koike
Received: 9 July 2009 / Accepted: 26 August 2009 / Published online: 29 September 2009
Ó The Japanese Society of Pharmacognosy and Springer 2009
Abstract A new angeloylated oleanane-type triterpenoid
saponin, sorbifoliaside (1), and a known saponin, xanifolia
O54, were isolated from the husks of Xanthoceras sorbi-
folia Bunge. Their chemical structures were elucidated on
the basis of various spectroscopic analyses coupled with
chemical degradation. To our knowledge, compound 1 is
the first example of a naturally occurring triterpenoid
saponin with an angeloyl group at C-2 of the sugar moiety.
traditional medicine for the treatment of rheumatism and
childhood enuresis. To date, triterpenoid saponins with
antitumor activity [1, 2], as well as flavonoids [3], cou-
marins [4], and sterols [5], from the fruit, bark, husk, and
carpophore of X. sorbifolia have been reported. In this
paper, we report the isolation and structure elucidation of
one new angeloylated triterpenoid saponin, sorbifoliaside
(1), and one known saponin, xanifolia O54 (2) [6], from the
husks of X. sorbifolia.
Keywords Xanthoceras sorbifolia Á Sapindaceae Á
Triterpenoid saponin Á Sorbifoliaside
Results and discussion
Introduction
The purification of a 70% EtOH extract from X. sorbifolia
husks, using combinations of silica gel column chroma-
tography and preparative HPLC, afforded two saponins 1
and 2 (Fig. 1). The structures of 1 and 2 were completely
established by various spectroscopic analyses and chemical
degradation.
Xanthoceras sorbifolia Bunge. (Sapindaceae) is a shrub
which is widely distributed in the northwestern and
northeastern regions of China. It has been used in
2
2
Compound 1 was obtained as an amorphous solid, [a]D
9.4 (MeOH, c 0.5). The molecular formula C H O
9 96 24
-
5
H. Fu
was determined by positive-ion HR-ESI–MS (m/z
? 13
1211.6201 [M ? Na] ). The C-NMR spectrum of 1
Zhejiang Provincial Key Laboratory of Chinese Medicine
Screening, Exploitation and Medicinal Effectiveness Appraisal
for Cardio-Cerebral Vascular and Nervous System,
The Key Laboratory of Biomedical Engineering of the Ministry
of Education, Department of Biomedical Engineering,
Zhejiang University, Hangzhou 310027,
displayed 59 carbon signals, of which 30 were assigned to
13
the aglycone. In the C-NMR spectrum, seven methyl
carbons at d 15.6, 16.7, 16.7, 19.5, 26.2, 28.0, and 30.3,
C
People’s Republic of China
two olefinic carbons at d 123.5 and 143.0, as well as a
C
hydroxymethyl carbon at d 74.6, coupled with informa-
C
Y. Guo Á D. Dou (&) Á T. Kang
1
tion from the H-NMR spectrum (seven tertiary methyl
College of Pharmacy, Liaoning University of Traditional
Chinese Medicine, 116600 Dalian, People’s Republic of China
e-mail: doudeqiang2003@yahoo.com.cn
groups at dH 0.84, 0.92, 1.09, 1.21, 1.25, 1.05, and 1.24,
one olefin proton at dH 5.41, and one pair of hydroxy-
methyl protons at dH 4.05 and 4.30) (Table 1), indicated
that the aglycone of 1 had a 28-hydroxyolean-12-ene
skeleton [6]. Furthermore, the NMR spectra showed three
oxymethine protons [dH 3.25 (dd, J = 11.7 and 4.6 Hz),
H. Fu Á W. Li (&) Á K. Koike
Faculty of Pharmaceutical Sciences, Toho University,
Miyama 2-2-1, Funabashi, Chiba 274-8510, Japan
e-mail: liwei@phar.toho-u.ac.jp
1
23

J Nat Med (2010) 64:80–84
81
Fig. 1 The structures of
compounds 1 and 2
OH
OH
OH
22
OH
1
2
H
CH
2
O
H
CH
O
HO
HO
HO
H
2
O
O
HO
HO
HO
O
O
O
3
H
H
HO
H
OH
O
O
O
H
HO
OH
OH HO
HO
O
HO
HO
HO
O
HO
HO
HO
O
O
O
O
O
HO
OH
HO
3
C
O
O
HO
HO
OH
H
3
C
O
HO
HO
OH
1
2
3
.74 (d, J = 9.9 Hz), and 4.31 (d, J = 9.9 Hz)] and the
corresponding carbons (d 89.0, 76.8, and 72.5), suggest-
to the sugar sequence was also drawn from the NOESY
experiment. Besides the signals due to the aglycone and
1
component sugars, in the H-NMR spectrum of 1, the
C
ing the orientation of these protons assignable to H-3,
H-21, and H-22 should be 3b, 21b, and 22a, respectively
signals of two methyls and an olefinic proton [dH 2.03
(t, J = 1.4 Hz), 2.11 (dd, J = 7.1 and 1.4 Hz) and 6.01
(qq, J = 7.4 and 1.4 Hz)] indicated the presence of an
[
2]. In the HMBC spectrum, long-range correlations were
observed for two methyl groups at d 1.24 (s, Me-29) and
H
1
3
1
.21 (s, Me-30) with the oxygenated methine carbon signal
angeloyl group, which was also supported by the C-NMR
at d 76.8 (C-21), the hydroxymethyl protons at dH 4.05
data (d 16.0, 20.8, 128.5, 137.8, and 167.0). The location
C
C
and 4.30 (H -28) with the oxygenated methine carbon
2
of the angeloyl group at C-2 of GlcI was deduced by
the HMBC correlation from dH 5.66 (GlcI-H-2) to dC
167.0 (C-1 of the angeloyl group). Therefore, the structure
of sorbifoliaside (1) was elucidated as 3-O-b-D-glucopyr-
anosyl-(1 ? 6)-(2-O-angeloyl)-b-D-glucopyranosyl sani-
signal at d 72.5 (C-22), two methyls at d 1.05 (s, Me-23)
C
H
and 0.92 (s, Me-24) with the oxygenated methine carbon at
dC 89.0 (C-3). Thus, the aglycone was identified to be
saniculagenin C [7]. Acid hydrolysis of 1, in addition to the
aglycone, gave D-glucose and L-rhamnose in the ratio of 3:1
as component sugars, which were confirmed by GC–MS
analysis following conversion to the trimethylsilylthiazo-
culagenin
C
28-O-a-L-rhamnopyranosyl-(1 ? 2)-b-D-
glucopyranoside.
Compound 2 was a known saponin, xanifolia O54,
which was previously isolated from the same plant [6]. The
NMR data of 2 are given in Tables 1 and 2 because the
1
lidine derivatives [8]. The H-NMR spectrum exhibited
four anomeric proton signals at dH 4.95 (d, J = 8.0 Hz,
GlcI-H-1), 5.10 (d, J = 7.8 Hz, GlcII-H-1), 4.74 (d, J =
1
complete H-NMR assignments of this compound were
7
.8 Hz, GlcIII-H-1), and 6.60 (d, J = 1.2 Hz, Rha-H-1),
and the corresponding anomeric carbon signals at d 103.9,
previously lacking.
In conclusion, a new angeloylated oleanane-type triter-
penoid saponin, sorbifoliaside (1), and a known saponin,
xanifolia O54, were isolated from the husks of X. sorbifolia
Bunge. Angeloylated triterpenoid saponins have been
reported to occur in several genera in the plant kingdom,
such as Xanthoceras [10, 11], Aesculus [12], and Eryngium
[13]. In these natural compounds, the angeloyl moieties
were connected to either the aglycone or the sugar parts of
the saponins. In the latter case, the angeloyl moieties were
usually located at C-3 or C-4 position of the sugar moieties,
which were always a glucopyranosyl or rhamnopyranosyl
moiety [10–16]. To our knowledge, sorbifoliaside (1) is the
first example of a triterpenoid saponin with an angeloyl
group at the C-2 position of the sugar moiety. This finding
may provide a hint to establishing similar structures in the
future, and provides the basis for developing a synthetic
approach to forming the angelate ester at C-2 on different
sugars.
C
1
05.3, 103.5, and 100.4 in the C-NMR spectrum,
3
1
respectively. The b anomeric configurations of the three
glucopyranosyl units were determined from their large
3
JH1,H2 coupling constants (7.8–8.0 Hz). The splitting
pattern of Rha-H-1 (d, J = 1.2 Hz) indicated that the
anomeric proton was equatorial, possessing an a configu-
ration in the C form [9]. When the C-NMR data of 1
1
13
4
were compared with those of saniculagenin C, shifts
resulting from glycosylation were observed at both C-3 and
C-28, indicating that 1 was a 3,28-bisdesmoside. The
linkage sequence of the sugar units at C-3 of the aglycone
was established from the HMBC correlations from d 5.10
H
(
GlcII-H-1) to d 70.2 (GlcI-C-6), and d 4.95 (GlcI-H-1)
C
H
to d 89.0 (C-3) (Fig. 1). Similarly, the sugar chain at C-28
C
was deduced from the HMBC correlations from dH 6.60
(
Rha-H-1) to dC 80.2 (GlcIII-C-2), and dH 4.74 (GlcIII-
H-1) to d 74.6 (C-28). The same conclusion with regard
C
123

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J Nat Med (2010) 64:80–84
1
13
Table 1 H- and C-NMR of
spectroscopic data (d) for the
aglycone moieties of 1 and 2
Position
1
2
dH
dC
38.5
dH
dC
1
2
0.99 (t, 13.2)
1.05 (t, 13.3)
38.8
26.6
1
.52 (dt, 13.2, 3.7)
a
1.64 (dt, 13.3, 3.8)
1.94 (ddd, 13.3, 11.3, 3.8)
2.43 (ddd, 13.3, 4.6, 3.8)
3.34 (dd, 11.3, 4.6)
1.85
26.4
2
.34 (ddd, 13.2, 4.6, 3.7)
3
4
5
6
3.25 (dd, 11.7, 4.6)
89.0
39.1
55.5
18.4
89.0
39.4
55.7
18.1
0.71 (d, 11.5)
1.32 (m)
0.74 (d, 11.9)
1.32 (m)
1
.47 (br d, 11.6)
1.31 (m)
.47 (br d, 11.6)
1.44 (m)
7
32.7
1.32 (m)
32.7
1
1.45 (m)
8
9
40.2
47.8
36.7
23.9
40.2
47.8
36.8
23.8
1.60 (dd, 11.2, 6.4)
1.64 (dd, 11.7, 6.5)
1.95 (2H, m)
1
1
0
1
1.99 (m)
a
1
.85
1
1
1
1
2
3
4
5
5.41 (t like, 3.4)
123.5
143.0
41.8
5.37 (t like, 3.6)
123.5
143.0
42.0
a
1.12 (dt, 13.3, 2.5)
25.7
1.25
25.8
1
.74 (td, 13.3, 5.3)
1.98 (td, 13.3, 2.5)
.17 (m)
1.88 (m)
1
6
18.6
1.96 (m)
18.4
2
2.35 (d, 11.7)
1
1
1
7
8
9
43.1
41.2
46.4
43.2
41.7
46.4
2.79 (dd, 13.5, 3.6)
1.31 (dd, 13.5, 4.8)
2.62 (dd, 13.5, 4.6)
1.31 (dd, 13.5, 4.6)
2.14 (t, 13.5)
2
.11 (t, 13.5)
2
2
2
2
2
2
2
2
2
0
1
2
3
4
5
6
7
8
36.3
76.8
72.5
28.0
16.7
15.6
16.7
26.2
74.6
36.1
76.8
75.2
28.1
16.9
15.8
16.8
26.2
75.9
3.74 (d, 9.9)
4.31 (d, 9.9)
1.05 (s)
3.75 (br d, 9.9)
4.31 (d, 9.9)
1.27 (s)
0.92 (s)
1.00 (s)
0.84 (s)
0.97 (s)
1.09 (s)
1.10 (s)
1.25 (s)
1.27 (s)
4.05 (br d, 14.9)
4.10 (br d, 11.4)
4.19 (br d, 11.4)
1.24 (s)
4
.30 (br d, 14.9)
2
3
9
0
1.24 (s)
1.21 (s)
30.3
19.5
30.3
19.5
1.28 (s)
Angeloxyl-1
167.0
128.5
137.8
16.0
2
3
4
5
6.01 (qq, 7.4, 1.4)
2.11 (dd, 7.1, 1.4)
2.03 (t, 1.4)
Coupling constants (in Hz) are
given in parentheses
20.8
a
Overlapped signals
1
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J Nat Med (2010) 64:80–84
83
1
13
Table 2 H- and C-NMR of
spectroscopic data (d) for the
sugar moieties of 1 and 2
Position
1
Position
2
dH
dC
dH
dC
3
-O-sugar
3-O-sugar
Glc-I-1
4.95 (d, 8.0)
103.9
75.0
76.0
71.8
77.0
70.2
Glc-I-1
4.89 (d, 7.8)
106.8
75.1
76.9
71.8
78.5
70.4
2
3
4
5
6
5.66 (dd, 9.4, 8.0)
4.26 (t, 9.4)
2
3
4
5
6
3.99 (t, 9.2)
4.13 (t, 9.2)
4.09 (t, 9.2)
4.15 (t, 9.0)
4.18 (ddd, 9.2, 5.4, 2.3)
a
4.88
4.35 (ddd, 9.0, 4.8, 1.8)
4.90 (dd, 11.7, 1.8)
a
4
.27 (dd, 11.2, 2.3)
4.28
Glc-II-1
5.10 (d, 7.8)
105.3
74.9
78.4
72.1
78.4
62.7
Glc-II-1
5.14 (d, 7.8)
105.3
75.1
78.2
71.7
78.3
62.7
2
3
4
5
6
4.05 (t, 9.2)
2
3
4
5
6
4.05 (t, 9.4)
4.22 (t, 9.0)
4.23 (t, 9.6)
4.21 (t, 9.4)
4.23 (t, 9.4)
3.94 (ddd, 9.4, 5.3, 2.5)
4.52 (dd, 11.7, 2.5)
3.92 (ddd, 9.4, 4.8, 2.5)
4.51 (dd, 11.7, 2.5)
4.38 (dd, 11.7, 5.0)
4
.35 (dd, 11.7, 5.3)
2
8-O-sugar
28-O-sugar
Glc-III-1
4.74 (d, 7.8)
103.5
80.2
75.1
71.6
77.7
62.6
Glc-III-1
4.74 (d, 7.6)
103.5
79.9
75.5
71.6
76.6
70.1
2
3
4
5
6
4.34 (t, 9.0)
2
3
4
5
6
4.23 (t, 9.0)
4.35 (t, 9.2)
4.25 (t, 9.2)
4.20 (t, 9.4)
4.15 (t, 9.0)
3.79 (ddd, 9.4, 5.5, 2.4)
4.39 (dd, 11.9, 2.4)
3.96 (ddd, 9.4, 4.9, 2.5)
4.69 (dd, 11.4, 2.5)
4.34 (dd, 11.4, 4.9)
5.02 (d, 7.8)
4
.26 (dd, 11.9, 5.5)
Rha-1
6.60 (d, 1.2)
100.4
72.4
72.2
74.3
68.9
18.8
Glc-IV-1
105.6
75.5
78.3
71.6
78.3
62.7
2
3
4
5
6
4.71 (dd, 3.2, 1.3)
4.68 (dd, 9.1, 3.4)
4.32 (t, 5.8)
2
3
4
5
6
4.02 (t, 9.4)
4.21 (t, 9.2)
4.21 (t, 9.0)
a
4.89
3.92 (ddd, 9.2, 4.8, 2.5)
4.51 (dd, 11.7, 2.5)
1.85 (d, 6.2)
4
.39 (dd, 11.7, 5.3)
Rha-1
6.52 (d, 1.2)
100.8
72.4
72.4
74.2
69.2
18.8
2
3
4
5
6
4.72 (dd, 3.3, 1.4)
4.62 (dd, 9.4, 3.5)
4.34 (t, 9.4, 5.9, 3.0)
4.81 (dq, 9.4, 6.2)
1.83 (d, 6.2)
Coupling constants (in Hz) are
given in parentheses
a
Overlapped signals
Experimental
Chemical Manufacture) was used for column chromatog-
raphy. Preparative HPLC was performed using ODS col-
umn (YMC-ODS, 20-mm i.d. 9 250 mm).
General experimental procedures
Optical rotations were measured on a Perkin–Elmer digital
polarimeter. IR spectra were determined on a Perkin–Elmer
Plant material
6
83 infrared spectrophotometer in KBr pellets. HR-ESI–
The husks of X. sorbifolia Bunge were collected from
Chifeng, Inner Mongolia Autonomous Region, People’s
Republic of China, in October 2003, and identified by one
MS were measured on a Bruker FTMS Apex III spec-
trometer. Silica gel (silica gel 60, Qingdao Marine
123

8
4
J Nat Med (2010) 64:80–84
of the authors (Q.D.); a voucher specimen (No. 20050801)
has been deposited at the College of Pharmacy, Liaoning
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3
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2
3
3:127–134
and 95% EtOH. The 70% EtOH elution (100 g) was sub-
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8
2
2
Sorbifoliaside (1): amorphous solid, [a]D -9.4 (MeOH,
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methyl 2-(polyhydroxyalkyl)thiazolidine-4(R)-carboxylates.
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-1 1
357, 1259, 1232, 1050, and 1038 cm ; H-NMR (pyri-
1
1
3
dine-d , 500 MHz) and C-NMR (pyridine-d , 125 MHz),
5
5
see Tables 1 and 2; positive-ion HR-ESI–MS m/z
1
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211.6201 (calcd for C H O Na, 1211.6189).
59 96 24
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Acid hydrolysis
1
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2
2 ml) was heated at 100°C for 2 h under an Ar atmosphere.
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(
C (0.5 mg), which was identified by comparison of their
1
H-NMR data with literature. The H O layer was concen-
2
6
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