Senedensiscins A-F: Six new eudesmane sesquiterpenoid glucosides from Senecio densiserratus

Article abstract of DOI:10.1016/j.tet.2013.10.047

Six new highly oxygenated eudesmane sesquiterpenoid glucosides, senedensiscins A-F (1-6), were isolated from the aerial parts of Senecio densiserratus. Their structures with the absolute configurations were established on the basis of spectroscopic analyses and chemical methods. These compounds represent an unprecedented type of sesquiterpenoid glucoside with the angeloyl group directly connected to the glucosyl moiety and their cytotoxicity was evaluated against the selected human cell lines, HL-60, SMMC-7721, and HeLa.

Full text of DOI:10.1016/j.tet.2013.10.047

Tetrahedron 69 (2013) 10598e10603
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Senedensiscins AeF: six new eudesmane sesquiterpenoid glucosides
from Senecio densiserratus
Jian-Jun Chen, Hong-Bo Wei, Yuan-Zhen Xu, Shu-Chen Hu, Kun Gao *
State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, People’s
Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 26 July 2013
Received in revised form 27 September 2013
Accepted 14 October 2013
Available online 21 October 2013
Six new highly oxygenated eudesmane sesquiterpenoid glucosides, senedensiscins AeF (1e6), were
isolated from the aerial parts of Senecio densiserratus. Their structures with the absolute configurations
were established on the basis of spectroscopic analyses and chemical methods. These compounds rep-
resent an unprecedented type of sesquiterpenoid glucoside with the angeloyl group directly connected to
the glucosyl moiety and their cytotoxicity was evaluated against the selected human cell lines, HL-60,
SMMC-7721, and HeLa.
Keywords:
Ó 2013 Elsevier Ltd. All rights reserved.
Senecio densiserratus
Eudesmane sesquiterpenoid glucoside
Spectroscopic analyses
Cytotoxicity
1. Introduction
sesquiterpene glucoside with the angeloyl group directly con-
nected to the glucosyl moiety. We present herein the details of
The genus Senecio (Asteraceae) contains more than 1500 spe-
cies widely distributed throughout the world and over 200 species
of the genus are found mainly distributed in the northwest and
isolation, structure determination, and cytotoxicity evaluation of
these new products.
1
southwest of China. Most of these have long been used in Chinese
2
2
. Results and discussion
.1. Structure elucidation
folk medicine for their improvement of eyesight, detumescence,
2
anti-inflammatory, vermifuge properties. Pharmacological studies
have shown that some Senecio species possess activities, such as
antifatigue, anti-inflammation, anticancer, and immunomodula-
tion effects.3 Previously chemical investigations on this species
have led to the isolation of various compounds belonging to ere-
Compound 1 was obtained as a colorless gum with a specific
e7
20
rotation of [
determined as C28
a
]
D
ꢀ14 (c 0.3, CH
3
OH). Its molecular formula was
10 by HRESIMS (m/z 565.2968 [MþNa] ,
þ
H
46
O
8
e13
mophilane sesquiterpenes and pyrrolizidine alkaloids.
In our
calcd 565.2983) associated with NMR data (Tables 1 and 2), and
continuous efforts to find new anticancer and antimicrobial drugs
ꢁ
indicated 5 of unsaturation. The IR spectrum showed absorption
or leads from Chinese herbal medicine,1
4e17
an MeOH extract of
ꢀ1
bands for hydroxyl groups (3449 cm ) and ester carbonyl groups
the aerial parts of Senecio densiserratus exhibited a positive re-
sponse to human leukemia (HL-60), human hepatoma (SMMC-
ꢀ1
(
1739 cm ). An angeloyloxy group and an acetoxy group were
1
present in 1, as evidenced from the observed H NMR signals [d 6.18
7
721), and human cervical carcinoma (HeLa) cell lines. Bioactivity-
(
1
1
1H, qq, J¼7.2,1.6 Hz), 2.01 (3H, dq, J¼7.2,1.2 Hz),1.92 (3H, dq, J¼1.6,
guided fractionation of the MeOH extract afforded six highly ox-
ygenated eudesmane sesquiterpenoid glucosides (1e6) with
modest cytotoxicity (Fig. 1). Their structures with the absolute
configurations were established on the basis of spectroscopic
analyses and chemical methods. A literature survey indicates that
senedensiscins AeF (1e6) represent an unprecedented type of
13
.2 Hz);
d
2.07 (3H, s)] in combination with the C NMR signals [
d
18,19
69.5, 140.4, 126.9, 20.5, and 16.0;
signals [
4.60 (1H, d, J¼8.0 Hz) and
and 62.7] suggested that a -glucopyranosyl unit was also present
d
171.0 and 20.7].
The NMR
d
H
C
d 98.4, 78.2, 74.1, 72.6, 69.4,
b
20
13
in 1. Besides these carbons of the above units, the C NMR (DEPT)
spectra of 1 also showed 15 carbon resonances due to 4 methyl, 4
methylene, 5 methine (2 oxygenated), and 2 quaternary carbons (1
oxygenated).
On the basis of these observations, 1 was considered to be
a dicyclic sesquiterpene skeleton with an angeloyloxy unit, an
*
Corresponding author. Fax: þ86 931 8912582; e-mail address: npchem@lzu.
edu.cn (K. Gao).
0
040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.10.047

J.-J. Chen et al. / Tetrahedron 69 (2013) 10598e10603
10599
OH14
OH
OH
1
9
2
3
8
10
5
7
13
4
6
11
1
5H
H
H
O
HO
12
HO
OH
HO
OH
O
O
OAc
6'
HO 4
'
O
AngO
AngO
O
HO
O
5'
AngO
AngO
2'
3'
1'
OH
1
OH
2
OH
3
OH
OH
OH
H
H
H
O
O
O
OH
OAc
OH
O
O
AngO
AngO
HO
O
HO
AngO
AngO
OH
OH
OH
6
4
5
4''
O
O
3''
2'''
1''
Ac=
1'''
Ang=
H
2''
5''
Fig. 1. Chemical structures of compounds 1e6.
acetoxy group, a
b
-glucopyranosyl unit, and two hydroxyl groups.
The He H COSY spectrum of 1 showed two main structural se-
quences, eCHeCH eCH and eCHeCHeCHe[CHe(CH ]e
CH eCH e. The HMBC experiment showed correlations of H-1/C-5,
C-9; H-6/C-4, C-10, C-11; H
5; and H
termined as a highly oxygenated eudesmane sesquiterpenoid
glucoside.
3
-12, H
3
-13/C-7, C-11; H
3
-15/C-3, C-4, C-
1
1
3
-14/C-1, C-5, C-9, C-10 (Fig. 2). Consequently, 1 was de-
2
2
e
3
)
2
2
2
Table 1
1
H NMR Data of Compounds 1e6 in CDCl
3
(
d
in ppm, J in Hz)
Position
1
1b
2a
3a
4a
5b
6a
3.34, dd (7.2, 3.6)
1.60, m
1.51, m
1.69, m
1.53, m
1.94, d (11.6)
4.55, dd (11.6, 4.0)
1.87, m
1.79, m
1.59, m
1.51, m
1.35, m
2.16, m
1.08, d (6.8)
0.97, d (6.8)
0.95, s
3.37, dd (7.2, 3.6)
1.58, m
1.50, m
1.70, m
1.53, m
1.98, d (11.6)
4.54, dd (11.6, 4.4)
1.87, m
1.78, m
1.52, m
1.53, m
1.34, m
2.15, m
1.09, d (6.6)
0.98, d (6.6)
0.96, s
3.36, dd (7.2, 3.2)
1.57, m
1.51, m
1.71, m
1.54, m
1.97, d (11.2)
4.51, dd (11.2, 4.0)
1.89, m
1.79, m
1.52, m
1.51, m
1.35, m
2.15, m
1.08, d (6.8)
0.98, d (6.8)
0.96, s
3.46, dd (11.4, 4.8)
1.65, m
1.52, m
1.92, m
1.62, m
2.28, d (10.4)
4.37, dd (10.4, 4.2)
1.92, m
1.78, m
1.55, m
1.62, m
1.42, m
2.11, m
1.04, d (6.6)
0.98, d (6.6)
0.79, s
3.30, dd (11.6, 3.6)
1.71, m
1.49, m
2.25, m
2.09, m
1.69, br s
4.76, br s
0.92, m
1.70, m
1.55, m
3.31, dd (11.6, 3.6)
1.72, m
1.51, m
2.27, m
2.07, m
1.70, br s
4.73, br s
0.91, m
1.72, m
1.55, m
2.02, m
1.19, m
1.81, m
1.01, d (6.4)
0.95, d (6.4)
0.89, s
5.53, br s
4.84, br s
2
2
3
3
5
6
7
8
8
9
9
1
1
1
1
1
a
b
a
b
a
b
a
b
1
2
3
4
5
2.01, m
1.18, m
1.79, m
1.02, d (6.4)
0.95, d (6.4)
0.89, s
5.53, br s
4.82, br s
4.68, d (7.6)
3.52, dd (8.8, 7.6)
4.96, t (8.8)
3.60, m
1.31, s
1.39, s
1.36, s
5.06, br s
4.97, br s
0
0
0
0
0
1
2
3
4
5
6
6
4.60, d (8.0)
3.57, dd (9.2, 8.0)
4.97, t (9.2)
3.60, m
3.55, m
4.70, d (7.8)
3.65, dd (9.6, 7.8)
5.36, t (9.6)
5.16, t (9.6)
3.58, m
4.64, d (8.0)
3.57, dd (9.2, 8.0)
4.98, t (9.2)
3.66, m
3.47, m
4.66, d (7.8)
3.62, dd (9.6, 7.8)
5.39, t (9.6)
5.13, t (9.6)
3.53, m
4.73, d (7.6)
3.54, dd (9.2, 7.6)
4.96, t (9.2)
3.72, m
3.50, m
3.93, dd (12.0, 3.6)
3.86, dd (12.0, 4.2)
3.57, m
4.67, br d (12.0)
4.36, dd (12.0, 4.8)
’a
’b
4.46, dd (12.0, 2.4)
4.34, dd (12.0, 5.2)
3.79, dd (12.0, 2.4)
3.64, dd (12.0, 4.8)
3.96, dd (12.0, 3.6)
3.85, dd (12.0, 4.4)
3.77, br d (12.0)
3.63, dd (12.0, 4.8)
OAng
0
0
0
0
0
0
3
4
5
6.19, qq (7.2, 1.6)
2.01, dq (7.2, 1.2)
1.92, dq (1.6, 1.2)
6.12, qq (7.2, 1.6)
6.20, qq (7.2, 1.6)
2.02, dq (7.2, 1.2)
1.92, dq (1.6, 1.2)
6.11, qq (7.2, 1.6)
6.06, qq (7.2, 1.6)
1.94, dq (7.2, 1.2)
1.93, dq (7.2, 1.2)
1.83, dq (1.6, 1.2)
1.82, dq (1.6, 1.2)
6.17, qq (7.2, 1.6)
2.01, dq (7.2, 1.2)
1.93, dq (1.6, 1.2)
6.19, qq (7.2, 1.6)
2.02, dq (7.2, 1.2)
1.93, dq (1.6, 1.2)
6
.09, qq (7.2, 1.6)
1.95, dq (7.2, 1.2)
.94, dq (7.2, 1.2)
1.82, dq (1.6, 1.2)
.79, dq (1.6, 1.2)
1
1
OAc
000
2
2.07, s
2.07, s
a
Recorded at 600 MHz.
Recorded at 400 MHz.
b

10600
J.-J. Chen et al. / Tetrahedron 69 (2013) 10598e10603
Table 2
ray diffraction analysis (Fig. 3). Thus, the relative configuration of 1
was assigned from that of 7.
1
3C NMR data of compounds 1e6 in CDCl
3
(d
in ppm)
Position
1b
79.5
2a
79.6
3a
4a
5b
80.6
6a
80.5
OH
OBz
1
2
3
4
5
6
7
8
9
79.8
28.0
39.4
72.2
49.9
79.5
41.7
23.1
35.2
41.7
25.4
22.5
23.5
13.9
22.9
99.2
72.8
78.6
69.8
75.8
62.4
79.4
28.0
39.3
72.3
49.7
78.9
41.7
23.2
35.2
41.4
25.3
22.6
23.2
13.7
23.1
98.4
72.6
78.2
69.4
74.1
62.7
28.0
39.4
72.1
49.9
79.5
41.7
23.1
35.2
41.6
25.4
22.6
23.5
13.8
23.0
99.6
73.4
74.1
68.1
74.6
61.5
30.9
35.5
145.4
47.9
74.5
39.7
22.7
31.9
42.1
25.6
22.3
23.2
12.4
110.3
98.6
73.6
75.0
68.5
73.9
61.5
31.1
35.1
145.4
52.0
71.0
53.3
20.5
38.1
40.5
29.5
20.6
22.3
13.9
109.9
100.1
74.2
78.4
69.6
73.2
62.9
31.2
35.1
146.1
52.0
71.5
53.3
20.5
38.1
40.6
29.3
20.7
22.3
13.9
109.5
100.4
75.7
78.4
70.1
73.2
62.6
1. K2CO3-CH3OH (5%) rt
. HCl-CH3OH (9%) rt
3%
BzCl, Et3N, CH2Cl2
1
2
reflux, 5h
86%
H
HO
H
7
HO
OBz
OH
7
8
Scheme 1. Hydroxylation and further benzoylation of compound 1.
1
1
1
1
1
1
1
2
3
4
5
6
0
1
2
3
4
5
0
0
0
0
0
0
OAng
0
0
0
0
0
0
0
0
0
0
1
2
3
4
5
169.5
126.9
140.4
16.0
167.7
169.6
124.8
140.6
16.0
167.2
167.0
127.3
126.7
140.2
138.7
15.8
15.7
20.4
20.4
169.5
127.1
140.1
16.0
169.6
127.0
140.3
16.0
1
67.1
127.1
26.7
140.4
1
139.4
15.8
1
5.8
20.4
0.3
20.5
20.5
20.5
20.5
2
OAc
0
0
00
00
1
2
171.0
20.7
171.1
20.7
Fig. 3. ORTEP drawing of compound 7.
a
Recorded at 150 MHz.
Recorded at 100 MHz.
b
The absolute configuration of 1 was based on that of 8, which
was, in turn, obtained via benzoylation of 7 and application of the
electronic circular dichroism (ECD) exciton chirality method. The
ECD spectrum of 8 showed the first negative Cotton effect at
l
max¼248 nm corresponding to the exciton coupling between the
benzoyl groups at C-1 and C-6. The counterclockwise manner of
the two chromophores in space thus defined the absolute con-
2
3
figuration of 8 as 1S,4S,5R,6R,7S,10S (Fig. 4). Accordingly, the
absolute configuration of 1 was determined. Compound 1 was
apparently
a rare enantio-eudesmane glucoside, which was
named senedensiscin A.
Fig. 2. Selected 2D NMR correlations for senedensiscin A (1) and D (4).
Furthermore, the
b
-glucopyranosyl was placed on C-6 due to the
4.60 to C-6. The
HMBC correlation from the anomeric proton at
d
0
0
cross-peaks of H-3 and H-6 with the ester carbonyl carbons of the
0
angeloyloxy and acetoxy groups indicated their attachment to C-3
0
and C-6 , respectively, (Fig.2). Therefore, the two hydroxyl groups
must be located at C-1 and C-4, permitting the assignment of the
molecular structure of 1.
To confirm the structure of 1, 1 was deacylated and then the
product was hydrolyzed under acidic condition to yield 7 and
glucose (Scheme 1).21 The structure of the former was confirmed by
comparison of its experimental and reported NMR data, while the
sugar was identified as
D
-(þ)-glucose by TLC comparison with an
authentic sample and by its optical rotation value (Supplementary
Fig. 4. CD spectra (in MeOH) of compounds 8. Bold lines denote the electric transition
dipole of the chromophores.
2
0,22
data).
Compound 7 was obtained as prisms and subjected to X-

J.-J. Chen et al. / Tetrahedron 69 (2013) 10598e10603
10601
Compound 2 was obtained as a colorless gum and its HRESIMS
þ
(
m/z 605.3289 [MþNa] , calcd 605.3296) revealed a molecular
50
formula of C31H O10. The NMR data of 2 were similar to those of 1
except for the presence of one more angeloyloxy group and the
absence of one acetoxy group. The HMBC data revealed correlations
0
0
of H-3 and H-4 to the carbonyl carbons of the two angeloyloxy
0
0
groups, indicating their attachment to C-3 and C-4 , respectively.
The configuration of 2 was elucidated by the NOESY spectrum and
coupling constants (Fig. 5). The 3
J
1,2 values (dd, J¼7.2, 3.6 Hz)
-orientation. A NOESY correlation
between H-1 and H-5 indicated that H-5 was in the -orientation.
showed that H-1 was in the
b
b
3
The large coupling constant between H-5 and H-6 ( J5,6¼11.6 Hz)
indicated that H-6 was in the -orientation. Moreover, the NOESY
correlations between H-6 and H-7/CH -14/CH -15 confirmed that
H-7, CH -14, and CH -15 were -orientated (Fig. 5). The sequential
deacylation and acidic hydrolysis of 2 also afforded 7 and
a
3
3
3
3
a
D-
2
0
20,22
(
þ)-glucose with [
a
]
D
þ56 (c 0.06, H
2
O).
Thus, senedensiscin B
was characterized as 2.
Fig. 6. CD spectra (in MeOH) of senedensiscin D (4), E (5), and F (6).
Compound 5 was obtained as a colorless gum and its molecular
Fig. 5. Selected NOESY correlations (arrow) and relative stereochemistry for sen-
edensiscin B (2) and E (5).
formula was determined as C28
H
44
O
9
by HRESIMS at m/z 547.2878
þ
[
(
44 9
MþNa] (calcd for C28H O Na, 547.2878). The NMR spectra of 5
Tables 1 and 2) were similar to those of 4 except for the presence of
one acetoxy group and the absence of one angeloyloxy group,
suggesting that 5 was also a highly oxygenated 6 -glucopyranosyl-
The molecular formula of senedensiscin C (3) was determined to
b
þ
be C26
calcd for C26
H
44
O
9
on the basis of the HRESIMS at m/z 523.2878 [MþNa]
1-hydroxyeudesm-4(15)-ene derivative. Key HMBC correlations of
13
0
(
44
H O
9
Na, 523.2862) and C NMR analyses, which
H-3 /C]O (OAng) and of H-6’a, H-6’b/C]O (OAc) indicated that the
0
0
indicated the absence of an angeloyloxy group compared to 2
angeloyloxy and acetoxy groups were at C-3 and C-6 , respectively.
0
3
(
Tables 1 and 2). The HMBC correlation of H-3 to the ester carbonyl
The J1,2 values (dd, J¼11.6, 3.6 Hz) showed that H-1 was in the
0
carbon of the angeloyoxy group indicated its attachment to C-3 .
Since the chemical conversions of 3 also afforded 7 and
a-orientation. The NOESY correlations of H-1/H-5 and H-5/H-6, H-7
D-
revealed that H-5, H-6, and H-7 were all a-orientated. The coupling
(
þ)-glucose by sequential deacylation and acidic hydrolysis
constants of H-6/H-5 and H-6/H-7 were <1 Hz because their di-
hedral angles were about 90 , further confirming that the three
ꢁ
(Supplementary data), compound 3 should share the same absolute
configuration as 1 and 2.
protons were cofacial. Furthermore, the NOESY correlations of H-5/
HRESIMS and 13C NMR data for senedensiscin D (4) revealed the
H-3
(Fig. 5). Interestingly, the chemical shift of H-7 (
lower than that in 4 ( 1.92), and the difference was attributed to
the different orientations of H -14 and H-5 in the two compounds.
a
and H
3
-14/H-3
b
revealed that H
3
-14 was in the
b-orientation
molecular formula of C31
H
48
O
9
. Based on a comparison of the NMR
d
0.92) in 5 was
data of 4 (Tables 1 and 2) with those of 2, the signals corresponding
to one of the methyl groups in 2 had been replaced in 4 by those of
d
3
an exocyclic olefinic bond [
d
H
4.97, 5.06 (each 1H, br s);
d
C
145.4 (C),
The absolute configuration of 5, i.e., (1R,5S,6R,7S,10R), was de-
termined via the application of the octant rule to the positive
24
1
10.3 (CH
2
)]. On the basis of the HMBC correlations of H-14a, 14b/
C-3, C-4, and C-5, and H-2, H-6/C-4, the two carbons of the exo-
cyclic double bond in 4 were assigned as C-4 and C-15. The HMBC
Cotton effect, which was observed at
quence of the exocyclic double bond, (Fig. 6). Thus, senedensiscin
l
max¼204 nm as a conse-
25
correlations were also used to confirm that the positions of the
b
-
E was characterized as 5.
glucopyranosyl moiety and the two ester groups of 4 were identical
The molecular formula of senedensiscin F (6) was determined as
3
þ
to those of 2 (Fig. 2). The J1,2 values (dd, J¼11.4, 4.8 Hz) showed that
C
C
26
H
H
42
O
O
8
by the HRESIMS at m/z 505.2759 [MþNa] (calcd for
H-1 was in the a-orientation. Furthermore, the NOESY correlations
26
42
8
Na, 505.2772). The NMR spectra of 6 showed similar sig-
of H-1/H
protons were
-orientation because of the large coupling constant between H-5
3
-14, and of H
3
-14/H-6, H-7 revealed that all of these
nals to those of 5 except for the absence of an acetoxy group, and
the upfield-shift of the proton signals of H-6’a and H-6’b ( 3.93 and
a
-orientated. Finally, H-5 was determined to be in the
d
b
3.86). These observations suggested that the key difference be-
3
0
and H-6 ( J5,6¼10.4 Hz). The absolute configuration of 4, i.e.,
1R,5R,6R,7S,10S), was determined via the application of the octant
rule to the negative Cotton effect, which was observed at
max¼206 nm as a consequence of the exocyclic double bond in 4
Fig. 6).25
tween compounds 5 and 6 was that the C-6 O-acetyl moiety of 5
(
had been replaced with a hydroxyl group. Extensive analysis of
1
1
He H COSY, HSQC, and HMBC data further confirmed this as-
l
signment. The specific rotation of 6 was determined to be ꢀ39 (c
(
0.3, MeOH), which was similar to the ꢀ57 (c 0.4, MeOH) rotation

10602
J.-J. Chen et al. / Tetrahedron 69 (2013) 10598e10603
observed for 5. Furthermore, a positive Cotton effect was observed
for 6 at
max¼207 nm, which was similar to that of observed for 5
Fig. 6). Taken together, these results indicated that compounds 5
and 6 had the same configurations.
(400 MHz) spectrometer with TMS as internal standard. HRESIMS
data were measured on a Bruker Micro TOF-Q II spectrometer. The
X-ray crystallographic data were collected on a Bruker Smart CCD
l
(
diffractometer using graphite-monochromated Mo K
Silica gel (200e300 mesh) used for CC and silica gel GF254
(10e40 m) used for TLC were supplied by Qingdao Marine
a radiation.
2
.2. Evaluation of cytotoxicity
m
Chemical Factory, Qingdao, PR China. Sephadex LH-20 used for CC
was purchased from GE Healthcare Bio-Sciences AB, Uppsala,
Sweden. Spots were detected on TLC under UV light or by heating
The cytotoxicity of senedensiscins AeF (1e6) and compound 7
was evaluated against human leukemia (HL-60), human hepatoma
(
SMMC-7721), and human cervical carcinoma (HeLa) cell lines us-
after spraying with 5% H
the study were of analytical grade.
2 4
SO in EtOH (v/v). All chemicals used in
2
6
ing the sulforhodamine B (SRB) method as previously reported.
The results are shown in Table 3. Interestingly, senedensiscins
AeF, with the angeloyl group directly connected to the glucosyl
moiety, showed moderate activity against the three lines
4.2. Plant material
(
IC50z30
which was inactive (IC50>150
control with an IC50 value of 3
m
M) compared with compound 7 without these groups,
M). Mitomycin was used as positive
M. These finding suggests that the
The aerial parts of S. densiserratus were collected from Danchang
m
m
County, Gansu Province, People’s Republic of China, in August 2006,
and authenticated by Prof. Guoliang Zhang from the School of Life
Science, Lanzhou University. A voucher specimen (No. 20060826)
was deposited at the Natural Product Laboratory of College of
Chemistry and Chemical Engineering, Lanzhou University.
angeloyloxy moieties connected with glucosyl units could be im-
portant in mediating the cytotoxicity of eudesmane sesquiterpenes.
In addition, senedensiscins AeF, in which the angeloyloxy groups
were connected to C-3 , or C-3 and C-4 , showed no difference in
their cytotoxicity against the three cell lines. This result suggests
that the number and the location of the angeloyloxy groups might
have no effects on the cytotoxicity of the compounds.
0
0
0
4.3. Extraction and isolation
The air-dried aerial parts of S. densiserratus (7.97 kg) were pul-
verized and extracted with MeOH (3ꢂ5 L, 7 days each) at room
temperature. The solvent was evaporated under reduced pressure
Table 3
IC50 values for cytotoxicity of compounds 1e6
to obtain an extract (230 g), which was suspended in hot H
2
O
Compounds
IC50
(m
M)
ꢁ
(60 C, 0.5 L). This suspension was extracted successively with
HL-60 cell
SMMC-7721 cell
HeLa cell
petroleum ether, EtOAc, and n-BuOH. The EtOAc-soluble fraction
was concentrated under reduced pressure to afford a residue
(96.5 g), which was subjected to silica gel column chromatography
1
2
3
4
5
6
7
33.0ꢃ4.8
24.5ꢃ6.4
38.5ꢃ8.1
33.2ꢃ4.1
35.6ꢃ4.4
34.7ꢃ6.8
>150
32.8ꢃ6.4
30.9ꢃ5.9
35.2ꢃ2.9
34.3ꢃ3.8
35.1ꢃ3.2
32.4ꢃ3.4
>150
52.4ꢃ9.4
37.4ꢃ6.1
40.9ꢃ8.2
41.3ꢃ4.2
39.2ꢃ3.8
41.5ꢃ4.6
>150
(200e300 mesh, 1200 g) with a gradient of petroleum ether-
eacetone (1:0, 30:1, 10:1, 5:1, 2:1, 1:1, 0:1) as eluent, and six frac-
tions AeF were collected according to TLC analysis.
Fraction D (4.2 g) was separated on a silica gel column (200e300
mesh, 80 g) eluting with petroleum ethereEtOAc (8:1, 5:1, 2:1, 1:1)
to give four fractions FrB.1eFrB.4. FrB.3 (1.5 g) was separated on
Mitomycin
1.5ꢃ0.6
5.4ꢃ1.4
3.3ꢃ1.7
a silica gel column (200e300 mesh, 30 g) using CHCl
10:1, 5:1) to give three crude fractions FrB.3.1eFrB.3.3. FrB.3.2
0.7 g) was further separated on a silica gel column (200e300
mesh, 10 g) with CHCl eEtOAc (10:1) as eluent to obtain 4 (2 mg)
and 5 (12 mg). Fraction E (3.9 g) was separated on a silica gel col-
umn (200e300 mesh, 120 g) eluting with CHCl eEtOAc (10:1, 5:1,
2:1) to give four fractions FrC.1eFrC.4. FrC.2 (1.4 g) was separated
on a silica gel column (200e300 mesh, 35 g) using CHCl eEtOAc
3
eEtOAc (15:1,
3
. Conclusion
(
In summary, six new highly oxygenated eudesmane sesqui-
3
terpenoid glucosides, senedensiscins AeF, were isolated from the
aerial parts of S. densiserratus. Their gross structures and relative
stereochemistry were elucidated based on extensive NMR stud-
ies, and the absolute configurations of them were determined by
chemical methods and CD analyses. To the best of our knowledge,
these new ones are the first examples of sesquiterpene glucoside
with the angeloyl group directly connected to the glucosyl moi-
ety. Preliminary cytotoxicity studies against HL-60, SMMC-7721,
and HeLa cell lines suggested that the angeloyloxy group in the
sugar chain of these eudesmane sesquiterpene glycosides is
critical for the cytotoxicity. These results might be the interesting
topics for both natural products chemistry and pharmacology in
the future.
3
3
(5:1, 2:1) to give four fractions FrC.4.1eFrC.4.4. FrC.4.2 (0.23 g) was
further separated on a silica gel column eluting again with
CHCl
MeOHeCHCl
was further separated on a silica gel column eluting again with
CHCl eEtOAc (5:1), followed by Sephadex LH-20 eluted with
MeOHeCHCl (1:1) to afford 1 (12 mg) and 2 (5 mg).
3
eEtOAc (5:1), followed by Sephadex LH-20 eluted with
3
(1:1) to afford 3 (5 mg) and 6 (4 mg). FrC.4.3 (0.25 g)
3
3
2
0
4.3.1. Senedensiscin A (1). Colorless gum; [
a
]
D
ꢀ14 (c 0.3, CH
3
OH);
ꢀ
1 1
IR (KBr) max 3449, 2924, 1739, 1643, 1461 cm ; H NMR (400 Hz)
and C NMR (DEPT) (100 Hz) see Tables 1 and 2; HRESIMS m/z
n
13
þ
4
4
. Experimental section
565.2968 [MþNa] (565.2983 calcd for C28
46
H O10Na).
2
0
.1. General experimental procedures
Optical rotations were measured on a PerkineElmer 341 po-
4.3.2. Senedensiscin B (2). Colorless oil; [
a
]
D
ꢀ80 (c 0.1, CH
3
OH); IR
ꢀ1 1
(
KBr) nmax 3443, 2928,1726, 1646, 1461 cm ; H NMR (600 Hz) and
1
3
C NMR (DEPT) (150 Hz) see Tables 1 and 2; HRESIMS m/z
larimeter. IR spectra were recorded on a Nicolet NEXUS 670 FT-IR
spectrometer. The ECD spectrum was obtained on a JASCO J-720
spectropolarimeter. NMR spectra were recorded on Varian
Mercury-600BB NMR (600 MHz) and Bruker Avance III-400
605.3289 [MþNa]þ (605.3296 calcd for C31
50
H O10Na).
2
0
4.3.3. Senedensiscin C (3). Colorless oil; [
(KBr)
a]
D
ꢀ25 (c 0.3, CH
3
OH); IR
ꢀ
1 1
nmax 3434, 2919, 1714, 1645, 1464 cm ; H NMR (600 Hz) and

J.-J. Chen et al. / Tetrahedron 69 (2013) 10598e10603
10603
1
3
C NMR (DEPT) (150 Hz) see Tables 1 and 2; HRESIMS m/z
washed five times with 0.1% HOAc and left to dry overnight. The
absorbed sulforhodamine B was dissolved in 150 L unbuffered 1%
Tris base [tris-(hydroxymethyl) aminomethane] solution in H
(pH 10.5). The absorbance of extracted sulforhodamine B at 515 nm
was measured on a microplate reader (Bio-Rad). The experiments
were carried out in triplicate. Each run entailed five or six con-
centrations of the compounds being tested. The percentage survival
rates of cells exposed to the compounds were calculated by as-
suming the survival rate of untreated cells to be 100%.
þ
5
23.2878 [MþNa] (523.2862 calcd for C26
H
44
O
9
Na).
m
2
O
2
0
4
.3.4. Senedensiscin D (4). Colorless oil; [
a]
D
ꢀ22 (c 0.1, CH
3
OH); IR
ꢀ1 1
(
KBr)
n
max 3440, 2923,1725, 1648,1462 cm ; H NMR (600 Hz) and
1
3
C NMR (DEPT) (150 Hz) see Tables 1 and 2; HRESIMS m/z 587.3168
þ
[MþNa] (587.3191 calcd for C31
48 9
H O Na).
2
0
4
.3.5. Senedensiscin E (5). Colorless oil; [
a
]
D
ꢀ57 (c 0.4, CH
3
OH); IR
ꢀ1 1
(
KBr)
n
max 3439, 2935, 1716, 1648,1456 cm ; H NMR (400 Hz) and
1
3
C NMR (DEPT) (100 Hz) see Tables 1 and 2; HRESIMS m/z 547.2878
Acknowledgements
þ
[MþNa] (547.2878 calcd for C28
H
44
O
9
Na).
The research work was financially supported by National Nat-
ural Science Foundation of China (No. 20972062, No. 21002046),
Fundamental Research Funds for the Central Universities (lzujbky-
2
0
4
.3.6. Senedensiscin F (6). Colorless oil; [
a
]
D
ꢀ39 (c 0.3, CH
3
OH); IR
ꢀ
1 1
(
KBr)
n
max 3443, 2932,1723, 1648,1456 cm ; H NMR (600 Hz) and
1
3
C NMR (DEPT) (150 Hz) see Tables 1 and 2; HRESIMS m/z
2
013-51), and National Science Foundation for Fostering Talents in
Basic Research of the National Natural Science Foundation of China
J1103307).
þ
5
05.2759 [MþNa] (505.2772 calcd for C26
42 8
H O Na).
(
2
0
1
4
.3.7. Compound 8. Amorphous solid; [
a
]
D
ꢀ45 (c 0.4, CH
3
OH); H
NMR (CDCl
(
4
(
8
(
1
3
, 400 MHz): 8.01 (4H, m, ArH), 7.58 (2H, m, ArH), 7.46
d
Supplementary data
4H, m, ArH), 5.75 (1H, dd, J¼12.0, 4.0 Hz, H-6), 4.94 (1H, dd, J¼7.2,
.0 Hz, H-1), 2.35 (1H, d, J¼12.0 Hz, H-5), 2.16 (1H, m, H-11), 1.92
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2013.10.047.
1H, m, H-7), 1.89 (1H, m, H-2a), 1.84 (1H, m, H-8a), 1.78 (1H, m, H-
b), 1.75 (1H, m, H-3a), 1.74 (1H, m, H-2b), 1.73 (1H, m, H-3b), 1.59
1H, m, H-9a), 1.44 (1H, m, H-9b), 1.30 (1H, s, H-15), 1.22 (1H, s, H-
4), 1.04 (1H, d, J¼6.8 Hz, H-12), 0.92 (1H, d, J¼6.8 Hz, H-13).
References and notes
1
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4
.4. X-ray crystallographic analysis of 7
2
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3
a computer-controlled Bruker Smart CCD diffractometer equipped
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radiation (
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4.4.1. Crystal data for 7. Colorless block crystal, C H O ,
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M¼256.37, orthorhombic, space group P
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1507e1513.
ꢀ
ꢀ
ꢀ
3
3
(
l
10) A, c¼14.436 (10) A, V¼1125.6 (14) A , Z¼3, Dcalcd¼1.135 g/cm ,
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1
1
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1
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4
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1
00
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ꢁ
2
2
2
chloroacetic acid to give a final concentration of 10%. Fixed cells
were rinsed five times with deionized H
2
O and stained for 10 min
with 0.4% sulforhodamine B dissolved in 0.1% HOAc. The wells were