Additional new minor cucurbitane glycosides from siraitia grosvenorii

Article abstract of DOI:10.3390/molecules19033669

Continuous phytochemical studies of the crude extract of Luo Han Guo (Siraitia grosvenorii) furnished three additional new cucurbitane triterpene glycosides, namely 11-deoxymogroside V, 11-deoxyisomogroside V, and 11-deoxymogroside VI. The structures of a

Full text of DOI:10.3390/molecules19033669

Molecules 2014, 19, 3669-3680; doi:10.3390/molecules19033669
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Additional New Minor Cucurbitane Glycosides from
Siraitia grosvenorii
Indra Prakash 1,* and Venkata Sai Prakash Chaturvedula 2
1
The Coca-Cola Company, Organic Chemistry Department, Global Research and Development,
One Coca-Cola Plaza, Atlanta, GA 30313, USA
2
Natural Ingredient Development, Blue California, 30111 Tomas, Rancho Santa Margarita,
CA 92688, USA; E-Mail: saipc@bluecal-ingredients.com
* Author to whom correspondence should be addressed; E-Mail: iprakash@coca-cola.com;
Tel.: +1-404-676-3007; Fax: +1-404-598-3007.
Received: 25 February 2014; in revised form: 14 March 2014 / Accepted: 17 March 2014 /
Published: 24 March 2014
Abstract: Continuous phytochemical studies of the crude extract of Luo Han Guo
(Siraitia grosvenorii) furnished three additional new cucurbitane triterpene glycosides,
namely 11-deoxymogroside V, 11-deoxyisomogroside V, and 11-deoxymogroside VI. The
structures of all the isolated compounds were characterized on the basis of extensive NMR
1
and mass spectral data as well as hydrolysis studies. The complete H- and 13C-NMR
spectral assignments of the three unknown compounds are reported for the first time based
on COSY, TOCSY, HSQC, and HMBC spectroscopic data.
Keywords: Siraitia grosvenorii; curcubitaceae; Luo Han Guo; curcubitane glycosides;
structure elucidation; NMR; MS
1. Introduction
The fruit of Siraitia grosvenorii (Momordica grosvenorii; Cucurbitaceae), known as Luo Han Guo,
has been used for centuries in Traditional Chinese medicine for the treatment of dry cough, sore throat,
and minor stomach and intestinal troubles [1–4]. An intriguing characteristic of Luo Han Guo that is
well known now throughout the world is its intense sweet taste and it has been used as a non-caloric
natural sweetener in some countries [5]. The extract from this fruit has been reported to be about
150 times sweeter than sucrose. The non-caloric sweet taste of S. grosvenorii fruit results primarily

Molecules 2014, 19
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from the content of a group of cucurbitane-type triterpene glycosides also known as mogrosides that
are present at about 1% in the flesh of the fruit. Early chemical investigation of Luo Han Guo resulted
in the isolation of various triterpenoid glycosides and polyphenols [1–5].
In continuation of our study on the isolation of natural sweeteners from S. grosvenorii [6–9], we
have investigated a commercial aqueous alcoholic extract of Luo Han Guo, which resulted in the
isolation of three new curcubitane glycosides, 11-deoxymogroside V (1), 11-deoxyisomogroside V (2),
and 11-deoxymogroside VI (3) (Figure 1). This paper describes the isolation, purification, and
structure elucidation of these three new mogrosides 1–3 based on the extensive NMR and mass
spectroscopic as well as hydrolysis studies. The complete assignments of the 1H- and 13C-NMR values
of the isolated compounds were made on the basis of COSY, TOCSY, HSQC, and HMBC spectral
data as well as comparison with the spectral data of known compounds 4–6.
Figure 1. Structures of 11-deoxymogroside V (1), 11-deoxyisomogroside V (2),
11-deoxymogroside VI (3), mogroside V (4), isomogroside V (5), and mogroside VI (6).
2. Results and Discussion
Compound 1 was isolated as a white powder and its molecular formula was deduced as C60H102O28
from the positive ESI Time of Flight (TOF) mass spectrum (MS) studies which showed an [M+H]+ ion
at m/z 1,271.6649. The 1H-NMR spectrum of 1 showed the presence of seven methyl singlets at δ 0.84,
0.85, 0.91, 1.09, 1.39, 1.51, and 1.52; a secondary methyl signal as a doublet at 1.11 (J = 6.0 Hz); nine
1
sp3 methylene and five sp3 methine groups between δ 1.09–2.54. The H-NMR spectrum of 1 also
showed the presence of two oxymethine protons at δ 3.73 and 3.80; an olefinic proton corresponding to
13
a trisubstituted double bond at δ 5.49. The C-NMR spectrum of 1 showed a tertiary hydroxy group

Molecules 2014, 19
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resonating at δC 72.9. The above spectral data is characteristic to the aglycone moiety of the
triterpenoid mogrol, isolated earlier from S. grosvenorii [5,6]. The 1H-NMR spectrum of 1 also showed
the presence of five anomeric protons at δ 4.84, 4.85, 4.93, 5.18, and 5.56, indicating the presence of
five hexose moieties. This was confirmed by the MS/MS spectrum of 1, selecting the [MH]− ion at
m/z 1,269 for fragmentation, indicated the loss of five sugar moieties at m/z 1,107.5968, 945.5433,
783.4903, 621.4369, and 459.3816 having a difference of 162 atomic mass units, indicative of the
presence of these five hexose moieties. Acid hydrolysis of 1 with 5% H2SO4 afforded glucose, which
was identified by direct comparison with an authentic sample by TLC [10–12], suggested the presence
of five glucosyl moieties in its structure. The configuration of the sugars present in 1 was identified by
preparing the corresponding thiocarbamoyl-thiazolidine carboxylate derivatives and comparison of
their retention times with the standard sugars as described in the literature [13]. The placement of the
five sugar units in 1 was confirmed as 1→6 linked β-D-glucobiosyl substituent at C-3 and 2,6-
branched β-D-glucotriosyl moiety at C-24 were identified on the basis of the key COSY, and HMBC
correlations as shown in Figure 2.
Figure 2. Key COSY and HMBC correlations of 11-deoxymogroside V (1).
The large coupling constants observed for the five D-glucose anomeric protons suggested the
β-orientation, as reported for mogrol glycosides. A series of 1D TOCSY experiments selecting each
anomeric proton resonating at δ 4.84, 4.85, 4.93, 5.18, and 5.56 together with their HMBC correlations
1
1
13
helped in assigning the H-NMR spectral data for the sugar units in 1. The H- and C-NMR values
for all the protons and carbons were assigned on the basis of COSY, TOCSY, HSQC and HMBC
correlations and are given in Table 1. A close comparison of the NMR and MS spectral data of 1 with
mogroside V (4) [6] suggested that the structure of 1 is identical to 4 except for the absence of the
11-hydroxyl group. The stereochemistry of various chiral centers in 1 was considered similar to 4 based on
1
13
identical H- and C-NMR values and multiplicities at the corresponding positions [6,14–16]. Thus, the
structure of 1 was deduced as 11-deoxymogroside V.

Molecules 2014, 19
3672
1
Table 1. H- and 13C-NMR chemical shift values (δ, ppm) for the compounds 1–3 in
pyridine-d5/D2O (10:1) a–c
.
1
2
3
Position
1H
13C
1H
13C
1H
13C
1.62 m
1.85 m
1.97 m
2.54 br d
(12.0)
3.73 br s
(W1/2 = 7.5)
---
1.51 m
1.80 m
1.91 m
2.38 br d
(12.0)
3.65 br s
(W1/2 = 6.8)
---
1.61 m
1.92 m
1
22.6
22.6
22.5
1.97 m
2.43 br d (11.0)
2
3
28.9
87.5
28.9
87.7
28.8
86.6
3.72 br s (W1/2
7.1)
=
4
5
6
41.9
143.4
118.8
42.4
143.3
118.9
---
---
41.5
142.9
119.2
---
---
5.49 d (4.2)
1.64 m
2.24 m
1.62 m
---
5.50 m
1.65 m
2.24 m
1.62 m
---
2.28 m
1.37 m
1.58 m
1.46 m
1.65 m
---
5.70 br s
1.67 m
2.43 m
1.59 m
---
2.28 m
1.35 m
1.62 m
1.44 m
1.63 m
---
7
24.4
24.5
24.7
8
9
10
43.6
35.1
38.3
43.8
36.6
38.4
43.8
34.4
38.2
2.27 m
1.36 m
1.59 m
1.45 m
1.62 m
---
11
12
32.4
30.6
32.6
30.8
32.5
30.9
13
14
46.7
49.4
46.5
49.7
46.1
49.3
---
---
---
1.09 m
1.19 m
1.49 m
2.16 m
1.69 m
0.85 s
0.91 s
1.57 m
1.11 d (6.0)
1.76 m
2.00 m
1.66 m
1.97 m
3.80 d (9.0)
---
1.09 m
1.19 m
1.48 m
2.15 m
1.68 m
0.85 s
0.88 s
1.56 m
1.10 d (6.3)
1.76 m
1.99 m
1.65 m
1.93 m
3.80 d (8.9)
---
1.08 m
1.20 m
1.50 m
2.16 m
1.69 m
0.84 s
0.99 s
1.57 m
1.10 d (6.1)
1.75 m
2.00 m
1.67 m
1.94 m
3.80 d (9.4)
---
15
16
34.9
28.2
35.0
28.4
35.1
28.5
17
18
19
20
21
50.8
15.5
28.1
36.2
19.1
50.9
15.7
28.2
36.3
19.2
50.8
15.8
28.3
36.2
19.3
22
23
33.3
29.0
33.4
29.1
33.3
29.0
24
25
26
27
28
29
30
Glc-1
1
92.4
72.9
26.7
24.4
28.2
25.6
18.0
92.6
73.2
26.9
24.5
28.3
25.8
18.2
92.6
72.8
26.9
24.6
28.2
25.9
18.2
1.39 s
1.52 s
1.09 s
1.51 s
0.84 s
1.39 s
1.51 s
1.11 s
1.52 s
0.83 s
1.39 s
1.52 s
1.06 s
1.50 s
0.85 s
4.93 d (6.8)
4.29 m
103.7
81.1
78.3
71.0
4.92 d (6.8)
4.27 m
103.8
81.2
78.4
71.1
4.93 d (7.1)
4.29 m
103.8
81.1
78.2
71.2
2
3
4
4.30 m
3.98 m
4.29 m
3.97 m
4.29 m
3.98 m

Molecules 2014, 19
3673
Table 1. Cont.
1
2
3
Position
1H
13C
1H
13C
1H
13C
5
6
4.10 m
3.98 m
4.89 d (9.7)
76.1
4.09 m
3.97 m
4.88 d (9.4)
76.2
4.09 m
3.98 m
4.89 d (9.5)
76.3
69.9
70.0
70.0
Glc-2
1
2
3
4
5
4.850 d (7.3)
4.06 m
104.5
74.9
77.6
71.3
78.0
4.85 d (7.7)
4.06 m
4.28 m
4.18 m
3.94 m
4.30 m
4.50 m
104.6
75.0
77.6
71.4
78.2
4.850 d (7.7)
4.06 m
104.5
75.0
78.2
71.5
78.2
4.27 m
4.18 m
3.95 m
4.30 m
4.29 m
4.18 m
3.93 m
4.30 m
6
62.2
62.2
62.4
4.50 d (11.0)
4.50 dd (1.9, 12.0)
Glc-3
1
2
3
4
5
5.56 d (7.9)
4.11 m
104.6
75.6
77.9
71.9
78.1
5.18 d (7.7)
4.08 m
4.27 m
4.16 m
4.02 m
4.23 m
4.53 m
104.8
74.7
77.8
71.4
78.3
5.56 m
4.11 m
4.23 m
4.07 m
4.01 m
104.7
75.8
78.0
72.2
78.2
4.23 m
4.07 m
4.00 m
4.32 m
4.32 m
6
63.1
62.2
63.3
4.60 d (12.0)
4.60 dd (2.3, 12.0)
Glc-4
1
2
3
4
5
4.845 d (7.3)
3.95 m
106.6
75.1
77.9
77.0
74.9
4.84 d (7.7)
3.98 m
4.27 m
4.27 m
3.92 m
4.30 m
4.50 m
106.7
74.8
76.5
81.4
76.2
4.86 d (7.7)
4.28 m
4.29 m
3.98 m
4.07 m
4.32 m
4.78 m
104.5
81.3
78.2
71.2
76.8
4.23 m
4.13 m
4.06 m
4.35 m
6
69.9
62.1
69.8
4.83 m
Glc-5
1
2
3
4
5
5.18 d (7.9)
4.06 m
104.9
74.9
78.0
71.3
78.1
5.57 d (8.1)
4.10 m
4.23 m
4.07 m
4.00 m
4.31 m
4.59 m
104.8
75.8
77.8
72.2
78.3
5.34 d (7.7)
4.09 m
4.24 m
4.30 m
3.92 m
4.46 m
4.55 m
104.7
76.8
77.7
71.3
78.2
4.31 m
4.19 m
4.00 m
4.35 m
6
62.5
63.2
62.5
4.54 d (12.0)
Glc-6
1
2
3
4
5
5.16 d (7.8)
4.07 m
4.29 m
4.19 m
4.01 m
4.35 m
4.57 m
105.0
74.9
78.2
71.5
78.3
6
62.6
a
b
Assignments were made on the basis of COSY, TOCSY, HSQC and HMBC spectral data; Coupling
constants are in Hz; c Chemical shift values are in δ (ppm); Glc: β-D-glucosyl.

Molecules 2014, 19
3674
Compound 2, was also isolated as a white amorphous powder and its molecular formula was
inferred as C60H102O28 from the ESI TOF MS data, suggesting its molecular weight as 1,270; identical
1
to 1. The H-NMR spectrum of 2 showed the presence of seven methyl singlets at δ 0.83, 0.85, 0.88,
1.11, 1.39, 1.51, and 1.52; a secondary methyl signal as doublet at δ 1.10 (J = 6.3 Hz); nine methylene
and four methine groups between δ 1.09–2.38; two oxymethine protons at δ 3.65 and 3.80; an olefinic
proton corresponding to a trisubstituted double bond at δ 5.50; five anomeric protons at 4.84, 4.85,
4.92, 5.18, and 5.57; a tertiary hydroxy group resonating at δC 73.2. Acid hydrolysis of 2 with 5%
H2SO4 also afforded glucose, which was identified by direct comparison with an authentic sample by
co-TLC [10–12] and its configuration was identified as D, similar to 1. The large coupling constants
observed for the five D-glucose anomeric protons suggested the β-orientation as in 1 and other
mogrosides [5,6]. From the above spectral and chemical studies, compound 2 was found to be similar
to compound 1 in its structure by having identical chemical shifts for the aglycone moiety in its
1H-NMR spectral data and five glucosyl moieties. Based on the key COSY and HMBC correlations of
2 as shown in Figure 3, it was found that three glucosyl units are present at C-24 as 2,6-branched
β-D-glucotriosyl moiety similar to 1, whereas the additional two glucosyl units at C-3 were attached as
1→4 linked β-D-glucobiosyl substituent suggesting a structure identical to that of isomogroside V (5) [17],
except for the absence of the 11-hydroxyl group. This was supported by the MS data of 2 which
showed 16 atomic mass units less for 5. The 1H- and 13C-NMR values for all the protons and carbons
were assigned on the basis of COSY, TOCSY, HSQC and HMBC correlations and are given in Table 1.
Considering the stereochemistry at all chiral centers similar to isomogroside V (5) [17] by the identical
1H- and 13C-NMR values as well as in comparison with reported values for various cucurbitane
glycosides [6,14–16], the structure of 2 was assigned as 11-deoxyisomogroside V.
Figure 3. Key COSY and HMBC correlations of 11-deoxyisomogroside V (2).
Compound 3, was also obtained as a white amorphous powder. The positive ESI TOF mass
spectrum of 3 showed an [M+H]+ ion at m/z 1,433.7169 which was in good agreement with the
1
13
molecular formula C66H112O33. The H- and C-NMR spectrum of 3 showed seven methyl singlets; a
secondary methyl signal as doublet; nine methylene and five methine groups; two oxymethine protons;

Molecules 2014, 19
3675
an olefinic proton corresponding to a trisubstituted double bond; a tertiary hydroxy group similar to the
aglycone moiety peaks observed in 1 and 2. The MS/MS spectrum of 3, selecting the [M–H]− ion at
m/z 1431 for fragmentation, indicated the loss of six sugar moieties at m/z 1269.6481, 1107.5962,
945.5418, 783.4893, 621.4377, and 459.3869, and further the difference of 162 mass units suggests the
presence of six hexose moieties. This was also supported by the presence of anomeric protons
resonating at δ 4.85, 4.86, 4.93, 5.16, 5.34, and 5.56 in its 1H-NMR spectral data. Acid hydrolysis of 3
that was performed as in 1 and 2 confirmed the sugars as D-glucose and the large coupling constants
observed for the six D-glucose anomeric protons suggested their β-orientation. The above spectral and
hydrolysis studies indicated that the structure of 3 has six β-D-glucotriosyl units on the aglycone
moiety presented in compounds 1 and 2. The presence of a 2,6-branched β-D-glucotriosyl moieties at
the C-24 and C-3 positions in 3 was supported on the basis of the key COSY and HMBC correlations
shown in Figure 4 and in comparison of its NMR values with 1 and mogroside VI (6) [6]. The 1H- and
13C-NMR values for all the protons and carbons were assigned on the basis of COSY, TOCSY,
HSQC and HMBC correlations and are given in Table 1, suggesting the stereochemistry at all
chiral centers identical to compounds 1 and 2 [6,14–16]. Thus, the structure of 3 was confirmed as
11-deoxy- mogroside VI.
Figure 4. Key COSY and HMBC correlations of 11-deoxymogroside VI (3).
HO
O
O
HO
HO
OH
HO
HO
Glc-II
O
O
Glc-I
O
HO
HO
O
Glc-III
HO
COSY
OH
HMBC
H
OH
O
HO
HO
O
O
O
Glc-VI
HO
OH
Glc-IV
O
HO
HO
HO
O
HO
OH
HO
Glc-V
3. Experimental
3.1. General
NMR spectra were acquired on a Bruker Avance DRX 500 MHz instrument with a 5 mm inverse
detection probe using standard pulse sequences. The spectrum was referenced to the residual solvent
signal (δH 8.71, δC 149.9 for pyridine-d5), chemical shifts are given in δ (ppm), and coupling constants

Molecules 2014, 19
3676
are reported in Hz, MS and MS/MS data were generated with a Waters Premier Quadrupole Time-of-
Flight (Q-Tof) mass spectrometer equipped with an electrospray ionization source operated in the
positive-ion mode and ThermoFisher Discovery OrbiTrap in the positive Positive Mode Electrospray.
Samples were diluted with water: acetonitrile (1:1) containing 0.1% formic acid and introduced via
infusion using the onboard syringe pump. The details of various columns and other parameters used
for HPLC purification for methods 1–6 are given below:
Method 1; Column: Phenomenex Gemini NX C18, 250 × 21.2 mm, 5 μm (p/n 00G-4097-P0) with a
Phenomenex guard column; UV Detection: 210 nm; Mobile Phase A: water; Mobile Phase B:
Acetonitrile; Flow Rate: 20 mL/min.
Methods 2 and 5: Column: Phenomenex Synergi Hydro RP, 250 × 10 mm, 4 μm (p/n 00G-4375-N0)
with a Phenomenex guard column; UV Detection: 210 nm; Mobile Phase A: water; Mobile Phase B:
Acetonitrile; Flow Rate: 5 mL/min.
Methods 3 and 6: Column: ZIC-HILIC, 250 × 10 mm, 5 μm (p/n HX 129616) with a Phenomenex
guard column; UV Detection: 210 nm; Mobile Phase A: water; Mobile Phase B: Acetonitrile; Flow
Rate: 5 mL/min.
Method 4: Column: Waters Atlantis Prep T3, 250 × 10 mm, 5 μm (p/n 186003694) with a
Phenomenex guard column; UV Detection: 210 nm; Mobile Phase A: water; Mobile Phase B:
Acetonitrile; Flow Rate: 5 mL/min.
3.2. Plant Material
The Luo Han Guo commercial extract was purchased from Chengdu Biopurify Phytochemicals,
Chengdu, Sichuan, China. A voucher specimen is deposited at The Coca Cola Company,
No. VSPC-3166-99.
3.3. Isolation
An aliquot of commercial crude extract of mogrosides (15 g, 90% mogrosides) was taken in a
round-bottomed flask and MeOH (60 mL) was added. The mixture was stirred for 15 min and heated to
reflux. After refluxing the mixture for 1 h, it was cooled to RT and stirring was continued for an additional
24 h after the addition of acetone (300 mL). The solid formed was filtered out and concentrated the
filtrate concentrated to obtain a residue (2.3 g). A series of HPLC purifications were performed on this
residue (Table 2) to obtain the three new mogrosides. A first round of HPLC purification was
performed using method 1 and fractions eluted between 19 and 21 min were collected, which on
evaporation under vacuum furnished Fraction 1. A second round of purification of Fraction 1 was
performed using method 2 and fractions collected between 6.5 and 8.5 min, as well as 19 and 23 min
were collected, which on concentration yielded Fractions 2 and 3, respectively. Purification of Fraction
2 using HPLC method 3, collection of the elute at 16.4 min and concentration, followed by a final
round of purification using HPLC method 4 over multiple runs furnished 3 (tR 16.4 min, 4.2 mg).
Similarly, purification of Fraction 3 using HPLC method 5, collection of the elute between 15 and
17 min, and a final round of purification using HPLC 6 method over multiple runs furnished 1
(4.2 mg), and 2 (3.6 mg).

Molecules 2014, 19
Table 2. RP-HPLC methods for the isolation and purification of cucurbitane glycosides 1–3.
3677
HPLC Method Time (min) % of Mobile Phase A % of Mobile Phase B
Method 1
0.0
90
75
54
10
10
90
90
75
75
70
70
10
10
75
75
18
18
50
95
95
18
18
75
75
65
30
30
75
75
75
75
71
70
66
66
48
48
30
30
75
75
15
15
95
95
15
15
10
25
46
90
90
10
10
25
25
30
30
90
90
25
25
82
82
50
5
15.0
20.0
21.0
26.0
26.5
31.0
0.0
15.0
16.0
30.0
31.0
36.0
37.0
45.0
0.0
15.0
20.0
21.0
25.0
26.0
31.0
0.0
15.0
30.0
31.0
35.0
36.0
40.0
0.0
Method 2
Method 3
Method 4
Method 5
5
82
82
25
25
35
70
70
25
25
25
25
29
30
34
34
52
52
70
70
25
25
85
85
5
8.5
10.0
16.5
18.5
24.5
26.5
29.0
31.0
37.0
37.1
45.0
0.0
20.0
30.0
31.0
36.0
37.0
Method 5
Method 6
5
85
85

Molecules 2014, 19
3678
1
11-deoxymogroside V (1). White powder, H-NMR [500 MHz, pyridine-d5/D2O (10:1), δ ppm] and
13C-NMR [125 MHz, pyridine-d5/D2O (10:1), δ ppm] data see Table 1; HRMS (M+H)+ m/z 1271.6649
(calcd. for C60H103O28: 1271.6636).
11-deoxyisomogroside V (2). White powder; 1H-NMR [500 MHz, pyridine-d5/D2O (10:1),
13
δ ppm] and C-NMR [125 MHz, pyridine-d5/D2O (10:1), δ ppm] data see Table 1; HRMS (M+Na)+
m/z 1293.6447 (calcd. for C60H102O28Na: 1293.6455).
1
11-deoxymogroside VI (3). White powder; H-NMR [500 MHz, pyridine-d5/D2O (10:1), δ ppm]
and 13C-NMR [125 MHz, pyridine-d5/D2O (10:1), δ ppm] data see Table 1; HRMS (M+H)+ m/z
1433.7169 (calcd. for C66H113O33: 1433.7164).
Acid Hydrolysis of Compounds 1–3. To a solution of each compound (2 mg) in MeOH (3 mL) was
added 5% H2SO4 (3 mL) and the mixture was refluxed for 8 h. The reaction mixture was then
neutralized with saturated sodium carbonate and extracted with ethyl acetate (EtOAc, 2 × 25 mL) to
give an aqueous fraction containing sugars and an EtOAc fraction containing the aglycone part. The
aqueous phase was concentrated and compared with standard sugars using the TLC systems
EtOAc/n-butanol/water (2:7:1) and CH2Cl2/MeOH/water (10:6:1) [10–12]. The sugar was identified as
glucose for all three compounds 1–3.
General Procedure for Acid Hydrolysis and Determination of Sugar Configuration in 1–3
Each compound 1–3 (1 mg) was hydrolyzed with 0.5 M HCl (0.5 mL) for 1.5 h. After cooling, the
mixture was passed through an Amberlite IRA400 column and the eluate was lyophilized. The residue
was dissolved in pyridine (0.25 mL) and heated with L-cysteine methyl ester HCl (2.5 mg) at 60 °C for
1.5 h. Then, O-tolyl isothiocyanate (12.5 µL) was added to the mixture and heated at 60 °C for an
additional 1.5 h. The reaction mixture was analyzed by HPLC: column Phenomenex Luna C18,
150 × 4.6 mm (5 μm); 25% acetonitrile-0.2% TFA water, 1 mL/min; UV detection at 250 nm. The
sugar was identified as D-glucose (tR, 12.42, 12.57 and 12.51 min) in all compounds 1–3 [authentic
samples, D-glucose (tR, 12.44) and L-glucose (tR, 11.24 min)] [13].
4. Conclusions
Three new triterpenoid glycosides 1–3 were isolated from a commercial extract of
S. grosvenorii. The structures of the new compounds were identified as 11-deoxymogroside V,
11-deoxyisomogroside V and 11-deoxymogroside VI, respectively, on the basis of extensive NMR and
mass spectroscopic data and chemical studies. To the best of our knowledge this is the first report of
the isolation of these three triterpene glycosides from S. grosvenorii in Nature. The discovery of these
compounds is an important addition in expanding our understanding of the diversity of the triterpenoid
glycosides present in the S. grosvenorii.
Supplementary Materials
Supplementary materials can be accessed at: http://www.mdpi.com/1420-3049/19/3/3669/s1.

Molecules 2014, 19
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Acknowledgments
We wish to thank Chengdu Biopurify Phytochemicals, China for providing the crude mogroside
extract of S. grosvenorii.
Conflicts of Interest
The authors declare no conflict of interest.
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Sample Availability: Samples of the new triterpene glycosides 1–3, and the known mogrosides 4–6, are
available from the authors.
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