Two new cucurbitane glycosides from the fruits of siraitia grosvenori

Article abstract of DOI:10.1248/cpb.c19-00210

Two novel cucurbitane glycosides, named as 11-oxomogroside III A₁ and 7β-methoxy-mogroside V, along with sixteen known ones were isolated from the fruits of Siraitia grosvenori SWINGLE. The structures of the new compounds were characterized by chemical and extensive spectral methods.

Full text of DOI:10.1248/cpb.c19-00210

Chemical and Pharmaceutical Bulletin Advance Publication by J-STAGE
DOI:10.1248/cpb.c19-00210
Advance Publication
April 13, 2019
Chem. Phar. Bull.
Note
Two New Cucurbitane Glycosides from the Fruits of Siraitia grosvenori Swingle
#
,a
#,b
b
b
b
*,c
Donghai Chu, Aftab Yaseen, Lun Wang, Bin Chen, Mingkui Wang, Weicheng Hu,
*,b
and Fu Li,
a
School of Biomedical ＆ Chemical Engineering, Liaoning Institute of Science and
b
Technology; Benxi 117004, China; Natural Products Research Center, Chengdu Institute of
c
Biology, Chinese Academy of Sciences; Chengdu 610041, China; and Jiangsu Collaborative
Innovation Center of Regional Modern Agriculture & Environmental protection/Jiangsu Key
Laboratory for Eco-Agricultural Biotechnology around Hongze Lake, Huaiyin Normal
University; Huaian 223300, China.
#
These authors contributed equally to this work. To whom correspondance should be
addressed. e-mail: hu_weicheng@163.com; andy197971@163.com
Ⓒ
2019 The Pharmaceutical Society of Japan

Two novel cucurbitane glycosides, named as 11-oxomogroside III A1 and
7
β-methoxy-mogroside V, along with sixteen known ones were isolated from the fruits of
Siraitia grosvenori Swingle. The structures of the new compounds were characterized by
chemical and extensive spectral methods.
Key words cucurbitane glucoside; Siraitia grosvenori Swingle; structural elucidation
Chemical and Pharmaceutical Bulletin Advance Publication

Introduction
Siraitia grosvenori Swingle, belonging to the famiy Cucurbitaceae, is chiefly distributed
in the south of China and the north of Thailand. The fruits of Siraitia grosvenori are rich in
1
-5)
cucurbitane glycosides,
which showed broad biological activities including
6
-9)
anticarcinogenic, anti-virus, antioxidative and anti-diabetic properties. We had previously
obtained a series of cucurbitane glycosides with anti-diabetic activities from 20 kg of the
10)
fruits of Siraitia grosvenori. The present paper is a continuation of our previous work and
describes the isolation and structural elucidation of two new cucurbitane glycosides (1 and 2)
(Fig. 1), together with sixteen known ones (3-18) from 100 kg of the fruits of this plant.
Results and discussion
Compound 1 was obtained as a white amorphous powder. The molecular formula
+
C H O for compound 1 was determined by HR-ESI-MS at m/z 983.5220 [M+Na] in
48
80 19
positive ion mode. Acid hydrolysis result suggested that the sugar residues in compound 1
1
0)
were composed of only D-glucose according to the method previously described. The
1
H-NMR spectrum (Table 1) displayed three anomeric proton signals at δ 4.86 (1H, d, J = 7.6
Hz, glcIII H-1), 4.91 (1H, d, J = 7.4 Hz, glcI H-1) and 5.49 (1H, d, J = 7.7 Hz, glcII H-1),
1
3
while the C-NMR spectrum (Table 2) showed three anomeric carbon signals at δ 103.7,
04.9 and 105.6, demonstrating the presence of three glucose residues in 1. The coupling
1
constants of the anomeric protons suggested a β configuration for all the glucose moieties.
1
The H-NMR data of 1 suggested the presence of eight methyl hydrogen signals at δ 0.77 (3H,
s, H-18), 1.02 (3H, d, J = 6.2 Hz, H-21), 1.08 (3H, s, H-30), 1.13 (3H, s, H-28), 1.28 (3H, s,
H-19), 1.36 (3H, s, H-27), 1.43 (3H, s, H-29) and 1.47 (3H, s, H-26), two isolated
oxymethine hydrogen signals at δ 3.71 (1H, br s, H-3) and 3.76 (1H, d, J = 8.5 Hz, H-24),
13
and an olefinic methine hydrogen signal at δ 5.68 (1H, br s, H-6), while the C-NMR data
indicated the existance of an obvious oxymethine carbon signal at δ 92.1 (C-24), two double
bond carbon signals at δ 141.5 (C-5) and 119.1 (C-6), and a carbonyl carbon signal at δ 214.2.
1
13
The H-NMR and C-NMR spectra of the aglycone of 1 resembled those of 11-oxomogrol
besides the glycosylation shifts of the C-24, suggesting the aglycone of 1 was 11-oxomogrol
5
)
and the sugar residues might be connected to C-24 of the aglycone. A trisaccharide unit
Chemical and Pharmaceutical Bulletin Advance Publication

composed of β-D-glucopyranosyl-(1→2)-[β-D-glucopyranosyl-(1→6)]-β-D-glucopyranosyl
was attached to C-24 of the aglycone based on the following important HMBC correlations
between the H-1 (d, J = 7.4 Hz, δ 4.91) of GlcI and C-24 (δ 92.1) of the aglycone, between
the H-1 (d, J = 7.7 Hz, δ 5.49) of GlcII and C-2 (δ 82.2) of GlcI, and between H-1 (d, J =
7
.6 Hz, δ 4.86) of GlcIII and C-6 (δ 70.2) of GlcI (Fig. 2). Accordingly, 1 was characterized
and named as 11-oxomogroside III A1.
Compound 2 was isolated as a white amorphous powder. The molecular formula
+
C H O for compound 2 was determined by HR-ESI-MS at m/z 1339.6501 [M+Na] in
61
104 30
positive ion mode. The monosaccharides obtained by acid hydrolysis also revealed the
1
0)
1
presence of only glucose in 2. The H-NMR spectrum (Table 1) displayed five anomeric
proton signals at δ 4.82 (1H, d, J = 7.7 Hz, glcIV H-1), 4.86 (1H, d, J = 7.7 Hz, glcIII H-1),
4
7
.94 (1H, d, J = 7.7 Hz, glcI H-1), 5.14 (1H, d, J = 7.7 Hz, glcV H-1) and 5.45 (1H, d, J =
1
3
.7 Hz, glcII H-1), while the C-NMR spectrum (Table 2) showed five anomeric carbon
signals at δ 103.7, 104.9, 105.5, 105.7 and 107.1, demonstrating the presence of five glucose
1
residues in 2. The H-NMR data of 2 suggested the presence of eight methyl hydrogen signals
at δ 0.84 (3H, s, H-18), 1.01 (3H, s, H-30), 1.11 (3H, d, J = 6.3 Hz, H-21), 1.14 (3H, s, H-28),
1
.35 (3H, s, H-27), 1.47 (3H, s, H-26), 1.59 (3H, s, H-29) and 1.60 (3H, s, H-19), three
isolated oxymethine hydrogen signals at δ 3.45 (1H, d, J = 5.4 Hz, H-7), 3.76 (1H, br s, H-3)
and 3.78 (1H, d, J = 9.8 Hz, H-24), and an olefinic methine hydrogen signal at δ 5.93 (1H, d,
1
3
J = 5.4 Hz, H-6), while the C-NMR data indicated the existance of two obvious oxymethine
carbon signal at δ 87.4 (C-3) and 92.1 (C-24), two double bond carbon signals at δ 149.9 (C-5)
1
and 118.7 (C-6). The proton signal at δ 3.29 (3H, s, -OCH ) in H-NMR spectrum and the
3
1
3
carbon signal at δ 56.2 in C-NMR spectrum indicated the presence of a methoxy group in 2.
1
3
The C-NMR data of 2 were similar to those of mogroside V except those of C-5, C-7 and
C-8 downfielding from δ 144.7, 25.0 and 44.0 in mogroside V to 149.9, 77.9 and 47.8 in 2,
11)
indicating the methoxy group was located at C-7. This was further verified by the HMBC
correlations between -OCH (s, δ 3.29) and C-7 (δ 77.9), and between H-6 (d, J = 5.4 Hz, δ
3
5
.93) and C-7 (δ 77.9). The other part of 2 was the same as that of mogroside V according the
HMBC correlations (Fig. 2). NOE correlations between -OCH (s, δ 3.29) and H-8 (br s, δ
3
Chemical and Pharmaceutical Bulletin Advance Publication

2
.14), H-19 (s, δ 1.60) clearly confirmed the -OCH group was in β orientation (Fig. 2). Thus,
3
2
was elucidated and named as 7β-methoxy-mogroside V.
1
2)
The sixteen known cucurbitane glycosides were elucidated as mogroside II A (3),
1
1
3)
14)
14)
15)
15)
mogroside II A (4), mogroside III (5), mogroside III E (6), mogroside III A (7),
2
1
1
5)
15)
15)
siamenoside I (8),
mogroside IVa (9),
mogroside IVe (10),
mogroside V (11),
4
)
15)
10)
isomogroside V (12), 11-O-mogroside V (13), 11-epi-mogroside V (14), mogroside VI
11)
10)
1)
1)
(
15), 11-O-mogroside VI (16), mogroside VI A (17) and mogroside VI B (18)
according to their spectroscopic data compared with those reported in the literatures.
Experimental
General Procedures Optical rotations were measured with a Perkin-Elmer 341
polarimeter. The HRESIMS spectra were acquired on a Vion IMS QT of (Waters Corp.,
Milford, Massachusetts, USA) in positive ion mode. 1D and 2D NMR data were obtained on
a Bruker Avance-600 spectrometer in C D N. Macroporous resin (HPD-100A, 26-60 mesh)
5
5
was used to enrich total saponins (Cangzhou Bon Adsorber Technology Co. Ltd., Cangzhou,
China). Normal phase column chromatography was carried out with silica gel (100-200 mesh,
Qingdao Haiyang Chemical Factory, Qingdao, China). Preparative-scale HPLC was
implemented on a CXTH system, equipped with a C column (50 × 250 mm i.d., 10 μm,
1
8
Daiso SP-100-10-ODS-P) from Daiso Co., Ltd. (Osaka, Japan) at a flowrate of 90 mL/min.
Plant Material The fruits of Siraitia grosvenori Swingle were purchased in February
2
017 from Lotus Pond Chinese Herbal Medicine Market, Sichuan province, China.
Extraction and Isolation The fruits of Siraitia grosvenori Swingle (100 kg) were
extracted with distilled water (3 × 300 L, each 4 h) at 80 °C. The extracted water solution was
passed through an HPD-100A macroporous resin column eluted with H O, 20% EtOH, 70%
2
EtOH and 95% EtOH (100 L for each gradient elution), respectively. The 70% EtOH eluant
solution was concentrated under reduced pressure to give a crude saponin (1220 g), which
was further separated by silica gel column chromatography with a gradient solvent system of
H O saturated MeOH/CHCl (1:5→1:4→1:3→1:2→1:1), affording nine fractions. Fraction 2
2
3
was isolated by preparative HPLC (26% CH CN) to afford compounds 3 (0.12 g) and 4
3
(
1.21 g). Fraction 3 was further separated by preparative HPLC (25% CH CN) to yield
3
Chemical and Pharmaceutical Bulletin Advance Publication

compounds 1 (620.6 mg), 5 (0.30 g), 6 (1.27 g) and 7 (2.24 g). Part of fraction 5 was isolated
by preparative HPLC (24% CH CN) to afford compounds 8 (3.38 g), 9 (1.56 g) and 10
3
(
3.61 g). Part of fraction 7 was further purified by preparative HPLC (23% CH CN) to give
3
compounds 2 (133.2 mg), 11 (20.2 g), 12 (0.46 g), 13 (4.88 g) and 14 (0.23 g). Fraction 9 was
separated by preparative HPLC (22% CH CN) to yield compounds 15 (0.15 g), 16 (0.32 g),
3
1
7 (1.24 g) and 18 (0.55 g).
20
Compound 1 A white amorphous powder. [α] +20.3° (c 0.20, MeOH). HR-ESI-MS
D
+
m/z 983.5220 (Calcd. for C H O Na : 983.5186).
48
80 19
1
H-NMR (pyridine-d ) δ: Table 1.
5
1
3
C-NMR: Table 2.
20
Compound 2 A white amorphous powder. [α] +7.9° (c 0.15, MeOH). HR-ESI-MS m/z
D
+
1
339.6501 (Calcd. for C H O Na : 1339.6505).
6
1
104 30
1
H-NMR (pyridine-d ) δ: Table 1.
5
1
3
C-NMR: Table 2.
Identification of sugars for 1 and 2 Compounds 1 and 2 (each 5.0 mg) were mixed
and heated with 5% H SO (5 mL) under reflux for 8 h. The reaction mixture was extracted
2
4
with EtOAc. The H O layer was neutralized with Ba(OH) , filtered and subjected to TLC
2
2
analysis with authentic glucose sample (Rf
=
0.35, mobile phase: ethyl
acetate:pyridine:ethanol:water = 8:1:1:2). The optical rotation of the acid hydrolysis solution
2
D
0
was measured as [α] +48.7° (c 0.05, H O). Therefore, the configuration of the glucose in the
2
new compounds should be in D-form.
Confilct of interest The authors declare no conflict of interest.
Chemical and Pharmaceutical Bulletin Advance Publication

References
1
2
3
) Niu B., Ke C.-Q., Li B.-H., Li, Y.-Y., Yi Y.-J., Luo Y.-W., Shuai L., Yao S., Lin L.-G., Li
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Chem. Pharm. Bull., 54, 1425-1428 (2006).
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Pharm. Bull., 55, 1082-1086 (2007).
4
5
) Jia Z.-H., Yang X.-G., Nat. Prod. Commun., 4, 769-772 (2009).
) Kasai R., Nie R.-L., Nashi K.-J., Ohtani K., Zhou J., Tao G.-D., Tanaka O., Agric. Biol.
Chem., 53, 3347-3349 (1989).
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7
8
9
1
) Takasaki M., Konoshima T., Murata Y., Sugiura M., Nishino H., Tokuda H., Matsumoto
K., Kasai R., Yamasaki, K., Cancer Lett., 198, 37-42 (2003).
) Akihisa T., Hayakawa Y., Tokuda H., Banno N., Shimizu N., Suzuki T., Kimura Y., J. Nat.
Prod., 70, 783−788 (2007).
) Xiang-Yang Q.-I., Chen W.-J., Zhang L.-Q., Shan X.-F., Song Y.-F., Sci. Agric. Sin., 39,
3
82−388 (2006).
) Suzuki Y.-A., Murata Y., Inui H., Sugiura M., Nakano, Y., J. Agric. Food Chem., 53,
941-2946 (2005).
0) Li F., Yang F.-M., Liu X., Wang L., Chen B., Li L.-H., Wang M.-K., Food Chem., 228,
67-573 (2017).
2
5
11) Prakash Chaturvedula V.-S., Prakash I., J. Carbohydr. Chem., 30, 16-26 (2011).
12) Yang X.-W., Zhang J.-Y., Qian Z.-M., Chin. Tradit. Herb. Drugs, 39, 810-814 (2008).
13) Takemoto T., Arihara S., Nakajima T., Okuhira M., Yakugaku Zasshi, 103, 1167-1173
(
1983).
4) Matsumoto K., Kasai R., Ohtani K., Tanaka O., Chem. Pharm. Bull., 38, 2030-2032
1990).
5) Li C., Lin L.-M., Luo M., Ma C.-F., Wang Z.-M., China J. Chin. Mater. Med., 36,
21-724 (2011).
1
1
(
7
Chemical and Pharmaceutical Bulletin Advance Publication

OH
GlcIII
HO
HO
OH
GlcIII
HO
HO
O
O
O
OH
HO
HO
O
OH
HO
HO
GlcI
O
OH
GlcI
OH
O
O
HO
HO
O
O
O
HO
HO
O
O
GlcII
OH
GlcII OH
HO
OH
OH
GlcV
O
OH
HO
O
O
HO
OH
HO
GlcIV
O
OCH3
O
HO
HO
OH
2
1
Fig. 1 Chemical Structures of Compounds 1 and 2
Chemical and Pharmaceutical Bulletin Advance Publication

OH
HO
HO
OH
HO
HO
O
O
O
O
OH
HO
OH
O
O
OH
HO
HO
O
HO
OH
O
O
HO
HO
O
O
HO
HO
O
OH
OH
HO
OH
H
OH
O
OH
HO
H
O
H
O
HO
OH
O
O
OCH3
HO
HO
HO
OH
2
1
Fig. 2 Key HMBC and NOE correlations of Compounds 1 and 2
Chemical and Pharmaceutical Bulletin Advance Publication

1
Table 1. H-NMR data for compounds 1 and 2
1
2
1
2
1
2
3
4
5
6
7
8
9
1.62 (o), 2.07 (o)
1.84 (o), 1.92 (o)
3.71 (br s)
2.07 (m), 3.04 (m)
1.91 (m), 2.46 (m)
3.76 (br s)
GlcI 1 4.91 (d, 7.4)
4.94 (d, 7.7)
4.18 (o)
2
3
4
5
6
4.19 (o)
4.23 (o)
4.24 (o)
3.94 (o)
3.94 (o)
4.08 (o)
4.08 (o)
5.68 (br s)
5.93 (d, 5.4)
3.45 (d, 5.4)
2.14 (br s)
3.94(o), 4.90 (o)
3.96 (o), 4.90 (o)
5.45 (d, 7.7)
4.04 (o)
1.83 (o), 2.30 (o)
1.84 (o)
GlcII 1 5.49 (d, 7.7)
2
3
4
5
6
4.05 (o)
4.22 (o)
4.22 (o)
1
0
1
2
2.55 (o)
2.87 (br d, 11.6)
4.21 (o)
4.23 (o)
4.23 (o)
1
1
3.92 (o)
3.91 (o)
2.58 (d, 14.2),
2.17 (o)
4.34 (o), 4.51(o)
4.34 (o), 4.51(o)
3
.07 (d, 14.2)
2.18 (o)
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
GlcIII 1 4.86 (d, 7.6)
4.86 (d, 7.7)
4.06 (o)
2
4.06 (o)
1.19 (m), 1.31 (m)
1.50 (m), 2.25 (m)
1.89 (m)
1.20 (m), 1.25 (m)
1.50 (m), 2.16 (o)
1.81 (m)
3
4.22 (o)
4.22 (o)
4
4.23 (o)
4.23 (o)
5
3.96 (o)
3.96 (o)
0.77 (s)
0.84 (s)
6
4.34 (o), 4.51(o)
4.37 (o), 4.52 (o)
4.82 (d, 7.7)
3.85 (t, 8.3)
4.14 (o)
1.28 (s)
1.60 (s)
GlcIV 1
1.46 (o)
1.57 (o)
2
1.02 (d, 6.2)
1.78 (o), 1.93 (o)
1.60 (m), 1.90 (m)
3.76 (d, 8.5)
1.11 (d, 6.3)
1.70 (o), 1.90 (o)
1.64 (o), 1.90 (o)
3.78 (d, 9.8)
3
4
4.03 (o)
5
4.09 (o)
6
4.31 (o), 4.75 (o)
5.14 (d, 7.7)
4.00 (o)
Glc V 1
1.47 (s)
1.36 (s)
1.13 (s)
1.43 (s)
1.08 (s)
1.47 (s)
1.35 (s)
1.14 (s)
1.59 (s)
1.01 (s)
3.29 (s)
2
3
4
5
6
4.22 (o)
4.25 (o)
3.95 (o)
4.30 (o), 4.49 (o)
-
OCH3
Chemical and Pharmaceutical Bulletin Advance Publication

1
3
Table 2. C-NMR data for compounds 1 and 2
1
2
1
2
1
2
3
4
5
6
7
8
9
21.3
29.8
75.7
41.9
141.5
119.1
24.3
44.2
49.2
36.3
214.2
48.9
49.2
49.8
34.7
28.4
50.0
17.1
20.3
36.0
18.8
33.1
29.3
92.1
72.8
24.7
27.1
28.0
26.4
18.5
26.9
29.5
87.4
42.7
149.9
118.7
77.9
47.8
40.0
37.9
78.2
41.0
47.2
48.5
34.6
28.6
51.1
17.1
26.3
36.7
19.1
33.3
29.6
92.1
72.9
24.7
27.1
28.2
27.3
19.4
56.2
GlcI 1 103.7
103.7
82.6
78.7
71.6
76.5
70.2
105.7
76.0
78.1
72.6
78.5
62.7
104.9
75.5
78.4
71.6
78.1
63.6
107.1
75.1
78.6
71.7
77.4
70.3
105.5
75.3
78.5
71.8
78.4
62.8
2
3
4
5
6
82.2
78.8
71.6
76.5
70.2
GlcII 1 105.6
2
3
4
5
6
76.0
78.1
72.5
78.5
62.7
1
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
GlcIII 1 104.9
2
75.5
78.4
71.6
78.1
63.6
3
4
5
6
GlcIV 1
2
3
4
5
6
Glc V 1
2
3
4
5
6
-
OCH3
Chemical and Pharmaceutical Bulletin Advance Publication