A new cycloartane triterpene glycoside from Souliea vaginata

Article abstract of DOI:10.1080/14786419.2016.1169415

A new cycloartane-type triterpene glycoside, namely soulieoside M (1), and one known compound, beesioside I (2), were isolated from the ethanolic extract of the rhizomes of Souliea vaginata. Their structures were determined spectroscopically and compared with previously reported spectral data. Compounds 1 and 2 were evaluated for their cytotoxic activities against three human cancer cell lines.

Full text of DOI:10.1080/14786419.2016.1169415

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Natural Product Research
Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: http://www.tandfonline.com/loi/gnpl20
A new cycloartane triterpene glycoside from
Souliea vaginata
Hai-Feng Wu, Gang Zhang, Mei-Chun Wu, Wen-Ting Yang, Guo-Xu Ma, Di-
Zhao Chen, Xu-Dong Xu, Qiong-Yu Zou & Wei-Cheng Hu
To cite this article: Hai-Feng Wu, Gang Zhang, Mei-Chun Wu, Wen-Ting Yang, Guo-
Xu Ma, Di-Zhao Chen, Xu-Dong Xu, Qiong-Yu Zou & Wei-Cheng Hu (2016): A new
cycloartane triterpene glycoside from Souliea vaginata, Natural Product Research, DOI:
10.1080/14786419.2016.1169415
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Date: 29 April 2016, At: 08:53

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Natural Product research, 2016
http://dx.doi.org/10.1080/14786419.2016.1169415
A new cycloartane triterpene glycoside from Souliea vaginata
Hai-Feng Wub,‡, Gang Zhangb,c,‡, Mei-Chun Wua, Wen-Ting Yangb,c, Guo-Xu Mab,
Di-Zhao Chena, Xu-Dong Xub, Qiong-Yu Zoua,b and Wei-Cheng Hud
aKey laboratory of hunan Province for study and utilization of ethnic Medicinal Plant resources, department
b
of chemistry & chemical engineering, huaihua university, huaihua, P.r. china; Key laboratory of Bioactive
substances and resources utilization of chinese herbal Medicine, Ministry of education, Institute of Medicinal
Plant development, chinese academy of Medical sciences and Peking union Medical college, Beijing,
P.r. china; ccollegeof Pharmacy andshaanxi ProvincialKey laboratory forchineseMedicineBasis& New drugs
research, shaanxi university of chinese Medicine, Xi’an, P.r. china; dJiangsu collaborative Innovation center
of regional Modern agriculture & environmental Protection/Jiangsu Key laboratory for eco-agricultural
Biotechnology around hongze lake, huaiyin Normal university, huaian, P.r. china
ABSTRACT
ARTICLE HISTORY
received 28 december 2015
accepted 13 March 2016
A new cycloartane-type triterpene glycoside, namely soulieoside M
(1), and one known compound, beesioside I (2), were isolated from the
ethanolic extract of the rhizomes of Souliea vaginata. Their structures
were determined spectroscopically and compared with previously
reported spectral data. Compounds 1 and 2 were evaluated for their
cytotoxic activities against three human cancer cell lines.
KEYWORDS
ranunculaceae; Souliea
vaginata; cycloartane
triterpene; cytotoxicity
OH
O
O
O
O
OH
OH
O
O
OH
HO
OH
1. Introduction
Souliea vaginata (Maxim.) Franch. (Ranunculaceae) is a perennial herb mainly native to the
mountains of Gansu, Shanxi and Yunnan provinces of China and is traditionally used as
Chinese folk medicine for the treatment of conjunctivitis, stomatitis, pharyngitis and enteritis
(Institute of Botany, Chinese Academy of Sciences & Institute of Materia Medica, Chinese
Academy of Medical Sciences 1979). Previous phytochemical investigations on this plant
CONTACT Qiong-Yu Zou
zouqioyu@gmail.com; Wei-cheng hu
huweicheng@hytc.edu.cn
supplemental data for this article can be accessed at http://dx.doi.org/10.1080/14786419.2016.1169415.
‡these two authors contributed equally to this work.
© 2016 Informa uK limited, trading as taylor & Francis Group

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H.-F. Wu eT Al.
2
have disclosed the presence of cycloartane triterpene glycosides as the characteristic com-
ponents of the genus Souliea (Sakurai et al. 1986; 1990, 1993; Takao et al. 1985; Zhou et al.
2004; Zhou, Yang, Tu 2005, 2006; Zhou, Yang, Wu et al. 2005; Zhou, Yang, Tu et al. 2006).
Cycloartane triterpene glycosides with variable polycyclic skeletons show diverse biological
activities including anti-complement, antitumour and cholinesterase enzymes inhibitory
effects (Mohamed 2014; Jamila et al. 2015; Satiraphan et al. 2015; Zhao et al. 2016). In the
course of our search for novel antitumour agents, a new cycloartane-type triterpene glyco-
side, soulieoside M (1), and one known compound, beesioside I (2), were isolated from the
ethanolic extract of the rhizomes of S. vaginata (Figure 1). Herein, we report their isolation,
structure elucidation and cytotoxic activities.
2. Results and discussion
Compound 1 was obtained as colourless needles with[ꢀ]2D5 −18 (c = 0.13, MeOH) and exhib-
ited a positive libermann–Burchard reaction. Its molecular formula was deduced as C37H58O12
from its pseudo-molecular ion peak of 717.3841 [M + Na]+ (Calcd 717.3826) in an HR-eSI-MS
experiment, consistent with 9° of unsaturation. The IR spectrum absorption revealed the
presence of hydroxyl (3388 cm−1) and carboxyl (1715 cm−1) groups. The 1H NMR spectrum
of 1 exhibited the signals of two characteristic cyclopropane protons at δH 0.24 and 0.69
(1H each, d, J = 4.0 Hz), an acetyl methyl group at δH 2.04, an oxygenated methylene at 4.48
and 4.65 (1H each, d, J = 13.2 Hz), six singlet methyl groups at δH 1.03, 1.24, 1.31, 1.32, 1.55
and 1.67, as well as ABX-type signals of three methine protons ascribable to H-15 (δH 4.43,
d, J = 9.0 Hz), H-16 (δH 6.00, dd, J = 11.4, 9.0 Hz), and H-17 (δH 2.69, d, J = 11.4 Hz). In addition,
the 1H NMR spectrum also showed one anomeric doublet proton signal at δH 4.85 (J = 7.2 Hz)
in the downfield region indicating the presence of a β-linked sugar and other signals for a
pentose at δH 4.02 (t, J = 8.4 Hz), 4.15 (t, J = 9.0 Hz), 4.22 (m), 3.74 (t, J = 10.8 Hz) and 4.34
(dd, J = 11.4, 5.4 Hz). The sugar was identified as xylose by acid hydrolysis followed by com-
parison with an authentic sample byTlC. Xylose was assigned in the -configuration because
d
this is the only naturally occurring isomer of this sugar (Kadota et al. 1995). The 13C APT NMR
spectrum of 1 displayed 37 carbon resonances including methylene carbon of cyclopropane
ring at δC 31.5 (C-19); one oxymethylene carbon at δC 66.9 (C-18); four oxygenated methine
OH
26
25
O
24
O 20
21
18
O
19
11
13
15
O
1
10
OR1
3
7
30
R2
5
O
O
OH
28
1 R1 = H R2 = OH
2 R1 = Ac R2 = H
HO
OH
Figure 1. structures of compounds 1 and 2.

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NATuRAl PRODuCT ReSeARCH
3
carbons at δC 88.4 (C-3), 80.4 (C-15), 77.9 (C-16) and 69.6 (C-7); three quaternary carbons at
δC 87.3 (C-20), 114.6 (C-24) and 73.1 (C-25); and one carbonyl group at δC 171.1. All
1
carbon-bound protons were assigned based on HSQC and H–1H correlation spectra. The
1H and 13C NMR spectroscopic data (Table S1) of 1 confirmed that the compound was a
cycloartane triterpene monoxyloside and was very similar to those of beesioside I (2) (Ju
et al. 2002) with the differences that an acetoxyl group was replaced by a hydroxyl group
and an additional hydroxyl group was attached at C-7 in 1. Compared with compound 2,
H-15 (δH 4.43) was shifted upfield by 1.22 ppm, C-15 (δC 80.4) upfield by 2.0 ppm and C-16
(δH 78.5) downfield by 2.4 ppm, indicating the presence of 15-OH and 16-OAc groups in 1.
The C-7 (δC 69.6), C-6 (δC 30.7) and C-8 (δC 56.1) signals were shifted downfield by 43.2, 9.9,
and 8.5 ppm, respectively, showing the existence of a hydroxyl group at C-7 in 1. The HMBC
experiment (Figure S2) was performed to establish the location of the functional groups and
the full structure of 1. The HMBC spectrum of 1 showed long-range correlations between
H-17 and C-16 (δC 77.9), C-20 (δC 87.3), H-16 and C-20 (δC 87.3), the carbonyl group (δC 171.1),
and H-15 and C-30 (δC 14.7), which confirmed the presence of the OH-15 and OAc-16 groups.
The hydroxyl group was placed at C-7 due to the observation of long-range correlations
between C-7 and H-5, H-6 and H-8 in the HMBC spectrum. The xylose residue was attached
at C-3 due to the long-range correlation between xylopyranosyl anomeric proton at 4.85
(1H, d, J = 7.2 Hz) and C-3 (δC 88.4). The HMBC experiment also showed the presence of key
correlations between H-19 and C-9, C-10; between H-18 and C-12, C-13, C-14, C-17, C-24;
between C-24 and H-26, H-27. The stereochemistry of 1 was resolved by analysis of NOeSY
spectrum and 1H–1H coupling constant value (J). On the Dreiding model of 1, if the config-
uration of C-20 is S, C-24 should be S, and if C-20 is R, C-24 should be R (Sakurai et al. 1993).
The NOe was detected between H-18/CH3-26, H-17/CH3-21, OAc-16/H-22/H-23, H-15/H-
16/H-17, H-12/CH3-30 and H-16/CH3-30. Thus, the configurations at C-20 and C-24 must be
S, and H-15 and H-16 are both ɑ-oriented. The coupling constants between H-16/H-17
(J = 11.4 Hz) suggested a cis-relationship of the acetoxyl group and the side chain (Kitagawa
et al. 1983; Sakurai et al. 1993). Consequently, a 16β-acetoxyl configuration was indicated.
The coupling constants (J15,16 = 9.0 Hz) suggested the 15β-hydroxyl configurations.
Furthermore, the cross-peaks observed between H-7/H3-30 and H-7/H-5 in the NOeSY
spectrum of 1 unambiguously substantiated the 7β-hydroxyl configuration. The d-configu-
ration of the xylose unit was confirmed using GC-MS analysis after acidic hydrolysis of 1
following derivatisation with l-cysteine methyl ester and silylation (Hara et al. 1987; Zhao
et al. 2016). Therefore, the structure of compound 1 was established as (20S,24S)-16β-
acetoxy-18,24;20,24-diepoxy-9,19-cyclolanostane-3β,7β,15β,25-tetrahydroxy-3-O-β-d-
xylopyranoside and named soulieoside M.
Besides, beesioside I (2) was obtained and identified by comparing its spectroscopic data
with those reported in the literature.
The cytotoxicity of compounds 1 and 2 was assayed against three human cancer cell lines
(HT-29, A549 and MDA-MB231) using the MTT method with 5-Fu as the positive control. The
results showed that compounds 1 and 2 exhibited moderate cytotoxic activity against all
the tested cell lines with IC50 values of 17.3−64.7 μM (Table S2).