Two novel secoiridoid glucosides from Tripterospermum chinense

Article abstract of DOI:10.1080/10286020.2012.723201

Two novel secoiridoid glucosides, tripterospermumcins C (1) and D (2), were isolated from the aerial parts of Tripterospermum chinense, along with four known compounds, tripterospermumcin B (3), sweroside (4), loganic acid (5), and 8-epi-kingiside (6). Their structures were determined by analysis of 1D and 2D NMR data, as well as by comparison with model compounds. Compound 1 was a rare iridoid tetramer with four glucosides.

Full text of DOI:10.1080/10286020.2012.723201

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Two novel secoiridoid glucosides from
Tripterospermum chinense
Tao Zhang a , Jian Li b , Bin Li b , Li Chen b , Hai-Long Yin a , Shi-
Jun Liu b , Ying Tian b & Jun-Xing Dong b
a Beijing University of Technology , Beijing , 100124 , China
b Beijing Institute of Radiation Medicine , Beijing , 100850 , China
Published online: 23 Oct 2012.
To cite this article: Tao Zhang , Jian Li , Bin Li , Li Chen , Hai-Long Yin , Shi-Jun Liu , Ying Tian &
Jun-Xing Dong (2012) Two novel secoiridoid glucosides from Tripterospermum chinense , Journal of
Asian Natural Products Research, 14:12, 1097-1102, DOI: 10.1080/10286020.2012.723201
To link to this article: http://dx.doi.org/10.1080/10286020.2012.723201
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Journal of Asian Natural Products Research
Vol. 14, No. 12, December 2012, 1097–1102
Two novel secoiridoid glucosides from Tripterospermum chinense
Tao Zhanga, Jian Lib, Bin Lib, Li Chenb, Hai-Long Yina, Shi-Jun Liub, Ying Tianb and
Jun-Xing Dongb*
aBeijing University of Technology, Beijing 100124, China; bBeijing Institute of Radiation Medicine,
Beijing 100850, China
(Received 27 April 2012; final version received 17 August 2012)
Two novel secoiridoid glucosides, tripterospermumcins C (1) and D (2), were isolated
from the aerial parts of Tripterospermum chinense, along with four known compounds,
tripterospermumcin B (3), sweroside (4), loganic acid (5), and 8-epi-kingiside (6).
Their structures were determined by analysis of 1D and 2D NMR data, as well as by
comparison with model compounds. Compound 1 was a rare iridoid tetramer with four
glucosides.
Keywords: tripterospermumcin C; tripterospermumcin D; Tripterospermum chinense
1. Introduction
2. Results and discussion
Tripterospermum chinense (Migo)
H. Smith is widely distributed in South
China, traditionally used for the treat-
ment of cough, hemoptysis, and pulmon-
ary disease by local inhabitants [1]. The
constituents of this plant have been
previously investigated and shown to
contain iridoid glucosides and xanthones
[2,3]. As a part of our continuing study
of the constituents of the genus Tripter-
ospermum (Gentianaceae), we have con-
ducted a phytochemical screening of the
aerial parts of T. chinense and isolated
two new secoiridoid glycosides, tripter-
ospermumcins C and D (Figure 1),
together with four known iridoid gluco-
sides. In this paper, we report the
structural determination of these com-
pounds on the basis of extensive spectro-
scopic analysis, including 2D NMR data,
as well as by comparison with model
compounds. To the best of our knowl-
edge, 1 was a rare iridoid tetramer with
four glucosides.
Compound 1, a white amorphous powder,
showed IR absorption bands at 3425 cm21
for the hydroxyl groups and at 1698 and
1634 cm21 for the a,b-unsaturated ester
carbonyl groups. The positive ESI-MS
exhibited a pseudo molecular ion peak
at m/z 1497 [M þ Na]þ, and the high-
resolution HR-ESI-MS gave the peak at
m/z 1497.5057 [M þ Na]þ, corresponding
to the formula C66H90O37. Acid hydrolysis
of 1 gave D-glucose. The 1H NMR
spectrum of 1 indicated the presence of
olefinic proton signals of the enol at d 7.50
(1H, s), 7.46 (2H, s), and 7.41 (1H, s). The
13C NMR spectrum of 1 showed signals
due to four a,b-unsaturated ester carbonyl
groups at d 166.6 £ 2, 165.9 and 165.7,
and 152.5, 152.0 £ 2, 150.8, 109.6 £ 2,
108.7, and 107.1 for double bonds. In the
13C NMR spectrum, four anomeric carbon
signals at d 98.7 £ 3 and 98.3 were
assigned readily. Four sets of terminal
carbon–carbon double bond signals at d
134.6, 134.5, 134.2, 133.9, and 119.0 £ 2,
*Corresponding author. Email: dongjx@vip.sina.com
ISSN 1028-6020 print/ISSN 1477-2213 online
q 2012 Taylor & Francis
http://dx.doi.org/10.1080/10286020.2012.723201
http://www.tandfonline.com

1098
T. Zhang et al.
Figure 1. The structures of compounds 1–3.
118.6, 119.8 were characteristic for four
secoiridoid glucoside units. These data
indicated clearly that 1 is an iridoid
tetramer consisting of four secoiridoid
glucoside units (units A and B) [4].
indicating that units A and B were linked,
as shown in Figure 1 [4,5]. The linkage
was also ascertained by long-range corre-
lations between H-7a2 at dH 6.64 and C-
7b2 at dC 195.0, H-7b2 at dH 9.18, and C-
7a2 at dC 155.8 in the HMBC spectrum
(Figure 2). The stereochemistry of the
double bond conjugated to the aldehyde
was assigned with NOESY experiment. In
the NOESY spectrum, the correlations
between H-7a2 and H-7b2 gave evidence
for Z-configuration. Almost identical
The NMR spectroscopic data of units
A and B were closely related to those of
the known compound 3, respectively.
The NMR spectra exhibited signals of
an aldehyde [dH 9.18 (s), dC 195.0] and
a trisubstituted carbon–carbon double
bond [dH 6.64 (br. s), dC 140.7, 155.8],

Journal of Asian Natural Products Research
1099
Figure 2. Key HMBC correlations for compound 1.
NMR spectroscopic data indicated that
units A and B, and 3 should be of the same
configuration. NOESY supported the
correctness of the above configuration. In
the NOESY spectrum, the correlations
between H-5a1 and H-9a1, between
H-6a1b, H-8a1, and H-1a1, suggested that
H-5a1 should be cis to H-9a1, and H-6a1b
and H-1a1 should be trans to H-9a1. The
same relative configuration was also
determined for unit A2, unit B1, and unit
B2. Thus, the structure of 1 was deter-
mined as shown in Figure 1, named
tripterospermumcin C.
data were almost identical to those of
7-ketologanin [6], except for the methoxy
group. Consequently, units A and B are
linked by an ester bond, which was also
confirmed by HMBC analysis. In the
HMBC spectrum, long-range correlations
were observed between H-7a of unit A at d
4.06 and 4.01 and C-11b of unit B at d
165.9. The stereochemistry of unit B
portion in 2 was determined by NOESY
analysis. NOESY cross-peaks between H-
5b, H-9b, and CH3-10b revealed that H-9b
should be cis to H-5b and CH3-10b. Thus,
compound 2, named tripterospermumcin
D, was elucidated as shown in Figure 1.
The four known compounds were
identified as tripterospermumcin B, swero-
side, loganic acid, and 8-epi-kingiside by
comparing their spectroscopic data with
those reported in the literature [2,7–9].
Compound 2 was obtained as a white
amorphous powder. It showed IR absorp-
tion bands due to the hydroxyl groups
(3423 cm21) and a,b-unsaturated ester
carbonyl groups (1700, 1634 cm21). The
molecular formula was determined to be
C33H46O19 by the positive-ion HR-ESI-
MS at m/z 769.2543 [M þ Na]þ. Acid
1
3. Experimental
hydrolysis of 2 gave D-glucose. The H
and 13C NMR spectroscopic data for 2
showed characteristic peaks of bis-iridoid
glucosides. Unit A, a secoiridoid moiety,
had proton and carbon signals almost
identical to those of unit A of 3. For
unit B, the 1H and 13C NMR spectroscopic
3.1 General experimental procedures
Optical rotations were measured with a
PerkinElmer 343 polarimeter (PerkinEl-
mer, Waltham, MA, USA). IR spectra
were recorded on the Bio-Rad FTS-65A
spectrometer (Bio-Rad, Richmond, VA,

1100
T. Zhang et al.
USA). UV spectra were recorded on
Shimadzu UV-2501 PC (Shimadzu,
Kyoto, Japan). The NMR spectra were
recorded with a Varian UNITYINOVA 600
(Varian, Palo Alto, CA, USA) and JNM-
ECA-400 (JEOL, Tokyo, Japan), and the
chemical shifts were given on d (ppm)
scale with tetramethylsilane as an internal
standard. The HR-ESI-MS was recorded
on a 9.4-T Q-FT-MS Apex Qe (Bruker
Co., Billerica, MA, USA). ESI-MS was
recorded on Thermo Finnigan Advantage
MAX HPLC-MS (Thermo Electron, Pitts-
burgh, PA, USA). Macroporous resin AB-
8 (Nan Kai College Chemical Inc., Tianjin,
China), silica gel (Qingdao Marine Chem-
istry Factory, Qingdao, China), Sephadex
LH-20 (Pharmacia, Uppsala, Sweden), and
3.3 Extraction and isolation
The aerial parts of T. chinense (60 kg)
were refluxed three times with EtOH–H2O
(3:2). The combined extract was concen-
trated under reduced pressure to furnish a
dark brown residue (1800 g), which was
suspended in H2O and partitioned in turn
with CHCl3 and n-BuOH. The n-BuOH
extract was evaporated under reduced
pressure to yield a residue (386 g). The
latter was separated chromatographically
on macroporous resin AB-8 (15 £ 100 cm)
and eluted with a gradient mixture of
EtOH–H2O (1:5, 1:1, and 9:1; 60,000 ml
each) to give five fractions (A–E).
Fraction C (134 g) was separated chro-
matographically on silica gel column
(12 £ 50 cm) with a gradient mixture of
CHCl3–MeOH (20:1, 10:1, 5:1, 5:2, and
1:1) as eluent, and a total of 160 tubes
(1000 ml each) were collected. Tubes
70–75 (11 g) and 118–127 (4 g) were
individually subjected to a series of
purification steps using Sephadex LH-20
column chromatography (MeOH), ODS
silica gel column chromatography
(3 £ 50 cm; MeOH–H2O, 40:60 and
70:30), and finally purified by preparative
HPLC (MeOH–H2O, 55:45, flow rate:
8.0 ml/min) to afford 1 (46 mg, tR:
21.63 min), 2 (26 mg, tR: 9.03 min), and 3
(100 mg, tR: 18.48 min). Fraction B (86 g)
was subjected to a series of purification
steps using silica gel column chromatog-
raphy (CHCl3–MeOH, 100:1, 60:1, 30:1,
15:1, 7:1, 3:1, and 1:1), Sephadex LH-20
column chromatography (MeOH) and
preparative HPLC (MeOH–H2O, 35:65,
flow rate: 8.0 ml/min) were carried out to
afford 4 (450 mg), 5 (100 mg), and 6
(40 mg, tR: 10.23 min).
˚
ODS silica gel (120 A, 50 mm, YMC,
Kyoto, Japan) were used for column
chromatography. HPLC was carried out
using Waters 600E system (Waters,
Milford, MA, USA): an analytical column,
ODS (5 mm, 4.6 £ 250 mm, Hanbon
Science & Technology Co., Ltd, Huaian,
China); preparative column, a YMC C18
(5 mm, 20.0 £ 250 mm, YMC, Kyoto,
Japan); detector, Knauer RID (refractive
index detector, Knauer, Berlin, Germany)
and Alltech ELSD (evaporative light-
scattering detector, Alltech, Los Angeles,
CA, USA) 2000ES. Gas chromatographic
analysis was carried out with an Aglient
6890 Series gas chromatograph equipped
with an H2 flameionization detector. The
column was a HP-5 capillary column
(30 m £ 0.25 mm £ 0.25 mm) (Agilent,
Santa Clara, CA, USA).
3.2 Plant material
The aerial parts of T. chinense were
collected from Yongshun region of
Hunan Province, China, in April 2010.
The plant was identified by Prof. Bin Li
(Beijing Institute of Radiation Medicine),
and a voucher specimen (No. 100403) is
deposited in the herbarium of Beijing
Institute of Radiation Medicine, Beijing.
3.3.1 Tripterospermumcin C (1)
White amorphous powder from MeOH–
20
H2O (55:45), 46 mg. ½aꢀD 2116.4
(c 0.084, MeOH). UV (MeOH) lmax
234 nm. IR (KBr) nmax: 3425, 2923, 1698,
:
1634, 1293, and 1075 cm21. For H and
1

Journal of Asian Natural Products Research
1101
13C
Table 1. 1H and 13C NMR spectral data of compound 1a (d in DMSO-d6).
1H
1H
13C
1a1
3a1
4a1
5a1
6a1
7a1
8a1
9a1
10a1
11a1
12a1
Glc1
1
5.46–5.50 ob
7.46 s
1a2
3a2
4a2
5a2
6a2
7a2
8a2
9a2
10a2
11a2
5.46–5.50 o
7.50 s
1a1
3a1
4a1
5a1
6a1
7a1
8a1
9a1
10a1
11a1
12a1
Glc1
1
95.6
1a2
3a2
4a2
5a2
6a2
7a2
8a2
9a2
10a2
11a2
95.6
152.5
108.7
30.0
152.0
109.6
30.3
28.9
62.2
134.6
43.1
119.0
166.6
51.1
2.77 m
2.73 m
1.67 m, 1.77 m
6.64 br. s
5.62–5.72 o
2.43 m
5.25 m, 5.30 m
1.77 m, 1.83 m
3.95–4.00 o, 4.09 m
5.62–5.72 o
2.55–2.58 o
5.25 m, 5.30 m
28.9
155.8
133.9
44.0
119.8
165.9
3.59 s
Glc2
1
2
3
4
Glc2
1
2
3
4
4.50–4.55 o
2.95–3.00 o
3.15–3.16 o
3.03 o
4.50–4.55 o
2.95–3.00 o
3.15–3.16 o
3.03 o
98.7
73.0
77.2
70.0
98.7
73.0
77.2
70.0
2
3
4
2
3
4
5
6
3.15–3.16 o
3.65–3.69 o, 3.43 o
5.46–5.50 o
7.46 s
5
6
3.15–3.16 o
3.65–3.69 o, 3.43 o
5.46–5.50 o
7.41 s
5
6
76.6
61.1
95.6
152.0
109.6
30.3
28.9
61.8
134.5
43.1
119.0
166.6
51.1
5
6
76.6
61.1
95.4
150.8
107.1
29.7
140.7
195.0
134.2
43.2
1b1
3b1
4b1
5b1
6b1
7b1
8b1
9b1
10b1
11b1
12b1
Glc3
1
1b2
3b2
4b2
5b2
6b2
7b2
8b2
9b2
10b2
11b2
1b1
3b1
4b1
5b1
6b1
7b1
8b1
9b1
10b1
11b1
12b1
Glc3
1
1b2
3b2
4b2
5b2
6b2
7b2
8b2
9b2
10b2
11b2
2.73 m
3.78 m
1.67 m, 1.77 m
3.95–4.00 o, 3.84 m
5.62–5.72 o
2.55–2.58 o
5.25 m, 5.30 m
9.18 s
5.62–5.72 o
2.73 m
5.00–5.09 o
118.6
165.7
3.59 s
Glc4
Glc4
4.50–4.55 o
2.95–3.00 o
3.15–3.16 o
3.03 o
3.15–3.16 o
3.65–3.69 o 3.43 o
1
2
3
4
5
6
4.50–4.55 o
2.95–3.00 o
3.15–3.16 o
3.03 o
3.15–3.16 o
3.65–3.69 o, 3.43 o
98.7
73.0
77.2
70.0
76.6
61.1
1
2
3
4
5
6
98.3
73.0
77.1
70.0
76.6
61.1
2
3
4
5
2
3
4
5
6
6
a Recorded at 600 MHz.
b Overlapped with other signals.
13C NMR spectral data, see Table 1. HR-
ESI-MS (pos.): m/z 1497.5057 [M þ Na]þ
(calcd for C66H90O37Na, 1497.5053).
(pos.): m/z 769.2543 [M þ Na]þ (calcd for
C33H46O19Na, 769.2526).
3.4 Acid hydrolysis and sugar analysis
3.3.2 Tripterospermumcin D (2)
Compounds 1 and 2 (2.0 mg each) were
individually hydrolyzed in 2 M CF3COOH
(2 ml) at 958C for 3 h. The reaction mixture
was extracted with CH2Cl2 (5 ml) three
times. The aqueous layer was repeatedly
evaporated to dryness with EtOH until
neutral. In the monosaccharide mixture,
White amorphous powder from MeOH–
H2O (55:45), 26 mg. ½aꢀ2D0 296.2 (c 0.110,
MeOH). UV (MeOH) lmax: 234 nm. IR
(KBr) nmax: 3423, 2927, 1700, 1634, 1290,
and 1075 cm21. For 1H and 13C NMR
spectral data, see Table 2. HR-ESI-MS

1102
T. Zhang et al.
Table 2. 1H and 13C NMR spectral data of compound 2a (d in DMSO-d6).
1H
13C
1H
5.55 d (3.0)
7.41 s
13C
1a
3a
4a
5a
6a
7a
8a
9a
10a
11a
12a
Glc1
1
5.47 d (4.8)
7.46 s
95.6
152.0
109.6
30.2
28.9
62.1
134.6
43.1
118.9
166.6
51.0
1b
3b
4b
5b
6b
7b
8b
9b
93.2
151.5
109.1
26.4
2.77 m
3.10 m
2.60 d (10.8), 2.44 br s
1.75 m, 1.85 m
4.01 m, 4.06 m
5.70 m
2.57 m
5.30 d (17.4), 5.22 br d (10.2)
42.0
217.7
42.7
44.2
13.1
165.9
1.94 m
2.30 m
1.05 d (16.2)
10b
11b
3.58 s
Glc2
4.52 d (8.4)
2.97 m
98.7
73.0
77.3
70.0
76.6
61.1
1
2
3
4
5
6
4.51 d (8.4)
2.97 m
3.10 o
2.99 m
3.10 o
3.74 m, 3.40 m
98.6
73.0
77.3
70.0
76.6
61.1
2
3
4
5
3.10 ob
2.99 m
3.10 o
3.74 m, 3.40 m
6
a Recorded at 600 MHz.
b Overlapped with other signals.
glucose was detected by TLC on a silica
gel [using n-BuOH–EtOAc–C5H5N–
H2O (6:1:5:4) as development] by com-
parison with authentic sample: glucose (Rf
0.46). The residue of the sugars was
dissolved in anhydrous pyridine (2 ml),
12 mg of L-cysteine methyl ester hydro-
chloride was added, and the mixture was
stirred at 608C for 1 h. Then, the mixture
hexamethyldisilazane–trimethylchlorosi-
lane (2:1; 0.6 ml) was added, and the
mixture was kept at 608C for 0.5 h [10].
The supernatant was analyzed by GC
under the following conditions: column
temperature: 1808C/2508C; programmed
increase, 158C/min; carrier gas: N2
(1 ml/min); injection and detector tem-
perature: 2508C; injection volume: 4.0 ml,
and split ratio: 1/50. The derivative of
D-glucose was detected with tR values of
17.91 min.
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We are grateful to Mrs Yan Xue and Mrs
Mei-Feng Xu of the National Center of
Biomedical Analysis for the measurements
of the MS and NMR spectra.