Acetylated anthraquinone glycosides from Cassia obtusifolia

Article abstract of DOI:10.1080/10286020.2011.570264

Three new acetylated anthraquinone glycosides (1-3) were isolated from the seed of Cassia obtusifolia, together with one parent anthraquinone glycoside (1a). Their structures were determined on the basis of spectroscopic methods and physicochemical properties as obtusifoline-2-O-β-d-2, 6-di-O- acetylglucopyranoside (1), obtusifoline-2-O-β-d-glucopyranoside (1a), obtusifoline-2-O-β-d-3, 6-di-O-acetylglucopyranoside (2), and obtusifoline-2-O-β-d-4, 6-di-O-acetylglucopyranoside (3).

Full text of DOI:10.1080/10286020.2011.570264

Journal of Asian Natural Products Research
Vol. 13, No. 6, June 2011, 486–491
Acetylated anthraquinone glycosides from Cassia obtusifolia
abc
Xiao-Hui Wu , Jin-Jin Cai , Jin-Lan Ruan , Jian-Shi Lou , Hong-Quan Duan ,
d
b
a
a
a
c
c
c
Jun Zhang , Chun-Ru Cheng , De-An Guo , Zhi-Yuan Wu and Yan-Wen Zhang *
a
a
b
College of Pharmacy, Tianjin Medical University, Tianjin 300070, China; Key Laboratory of
Natural Medicinal Chemistry and Resources Evaluation of Hubei Province, College of Pharmacy,
Tongji Medical Center, Huazhong University of Science, Wuhan 430030, China; Shanghai Institute
c
of Materia Medica, Shanghai Research Center for Modernization of Traditional Chinese Medicine,
Chinese Academy of Sciences, Shanghai 201230, China; The Teaching Hospital of Chengdu
University of Traditional Chinese Medicine, Chengdu 610072, China
d
(
Received 11 November 2010; final version received 6 March 2011)
Three new acetylated anthraquinone glycosides (1–3) were isolated from the seed of
Cassia obtusifolia, together with one parent anthraquinone glycoside (1a). Their
structures were determined on the basis of spectroscopic methods and physicochemical
properties as obtusifoline-2-O-b-D-2, 6-di-O-acetylglucopyranoside (1), obtusifoline-
2-O-b-D-glucopyranoside (1a), obtusifoline-2-O-b-D-3, 6-di-O-acetylglucopyranoside
(2), and obtusifoline-2-O-b-D-4, 6-di-O-acetylglucopyranoside (3).
Keywords: Leguminosae; Cassia obtusifolia; acetylated anthraquinone glycosides;
spectroscopic methods
1
.
Introduction
part of the continuous chemical constitu-
ents investigation of this plant, three new
acetylated anthraquinone glycosides (1–3)
were isolated and determined on the basis
of spectroscopic methods and physico-
chemical properties, along with the parent
anthraquinone glycoside 1a (Figure 1). In
this paper, the isolation and the structural
elucidation of the three new compounds
Cassia obtusifolia Linn, a member of the
genus Cassia (Leguminosae), is a widely
used traditional Chinese medicinal plant
and widely distributed in China, Japan, the
Philippines, and South Korea. It belongs to
the economically and medically important
family Leguminosae (Syn. Cesalpinia-
ceae), subfamily Ceasalpinioideae [1,2].
The seeds of the plant have been widely
used for the treatment of purgation, red
and tearing eyes, dizziness, headache, etc.
(
1–3) are described.
2. Results and discussion
[
3]. In previous investigations of this plant,
Compound 1 was obtained as yellow
needles with the molecular formula
C H O , determined on the basis of
a number of compounds were isolated,
including flavonoids, triterpenoids, anthro-
nes, and anthraquinones [4–8]. Anthra-
quinones were confirmed to exert the main
effect on purgation [9]. We have pre-
viously reported three new compounds A–
C from the seeds of C. obtusifolia [8]. As
2
6 26 12
NMR and HR-ESI-MS data (m/z 553.1328
þ
13
[M þ Na] ). The C NMR spectrum
exhibited 12 aromatic carbons (d 152.0,
155.9, 140.1, 125.1, 118.4, 136.4, 124.0,
161.0, 124.5, 116.8, 129.7, 132.4) and two
*Corresponding author. Email: zhangyanwen@tijmu.edu.cn
ISSN 1028-6020 print/ISSN 1477-2213 online
q 2011 Taylor & Francis
DOI: 10.1080/10286020.2011.570264
http://www.informaworld.com

Journal of Asian Natural Products Research
487
CH3
OH
O
O
R O
2
8
1
O
8
a
9a
4a
9
OR3
7
6
2
OR4
O
10
1
0a
3
CH3
5
4
R O
1
O
R1 R2 R3 R4
1
1
2
3
A c
H
Ac
Ac
Ac
H
H
H
H
Ac
H
H
H
H
a
H
Ac
Figure 1. Structure of compound 1–3 and 1a.
carbonyl carbons (d 187.8, 181.3) sugges-
tive of a typical anthraquinone structure.
In the above 12 aromatic carbons, two
aromatic carbons at d 155.9 (C-2) and
161.0 (C-8) were substituted by hydroxy,
one aromatic carbon at d 152.0 (C-1) by a
methoxyl (d 61.4), and one aromatic
carbon at d 140.1 (C-3) by a methyl
1
Table 1. H NMR (400 MHz) data of 1–3 and 1a (d values, J in Hz, in DMSO-d6).
Position
Compound 1
Compound 2
Compound 3
Compound 1a
1
2
3
4
7.86 (s)
7.92 (s)
7.90 (s)
7.89 (s)
4
5
6
7
8
8
9
9
1
1
1
3
a
7.65 (dd, 1.2, 8.4)
7.74 (dd, 8.0, 8.4)
7.33 (dd, 1.2, 8.0)
7.68 (dd, 1.2, 8.2)
7.73 (dd, 8.0, 8.2)
7.35 (dd, 1.2, 8.0)
7.68 (dd, 1.2, 8.3)
7.79 (dd, 7.8, 8.3)
7.30 (dd, 1.2, 7.8)
7.60 (dd, 1.3, 8.2)
7.69 (dd, 7.8, 8.2)
7.27 (dd, 1.3, 7.8)
a
a
0
0a
-OCH
-CH
3
3.91 (s)
2.41 (s)
3.88 (s)
2.40 (s)
3.80 (s)
2.38 (s)
3.94 (s)
2.45 (s)
3
0
Glc:1
0
4.96 (d, 8.0)
4.67 (m)
3.45 (m)
3.29 (m)
3.26 (m)
5.00 (d, 8.0)
3.30 (m)
4.88 (m)
3.39 (m)
3.37 (m)
5.00 (d, 7.8)
3.20 (m)
3.47 (m)
4.66 (m)
3.98 (m)
5.02 (d, 8.0)
3.22 (m)
3.33 (m)
3.30 (m)
3.07 (m)
2
0
3
0
4
0
5
0
6
4.22 (dd, 12.0, 2.0) 4.20 (dd, 12.0, 2.0) 3.82 (dd, 12.0, 5.0) 3.62 (m)
.94 (dd, 12.0, 5.7) 3.99 (dd, 12.0, 5.0) 3.77 (dd, 12.0, 2.0) 3.55 (m)
2.10 (s)
3
0
2
3
4
6
-OCOCH
-OCOCH
-OCOCH
3
3
3
0
0
0
2.08 (s)
2.11 (s)
1.88 (s)
-OCOCH3 1.93 (s)
1.91 (s)

4
88
X.-H. Wu et al.
1
d 17.3). Examination of the H and
13
(
C
(J ¼ 8.0 Hz). So the sugar moiety was
determined as b-D-glucose, and it con-
nected to the C-2 position of the
anthraquinone aglycone by the HMBC
NMR spectroscopic data of 1 (Tables 1
and 2) indicated that the molecule
consisted of an anthraquinone, one methyl,
one methoxyl, one sugar, and two acetyl
moieties.
0
1
13
correlation of H-1 /C-2. The H and
C
NMR spectra of 1 were similar to those of
1a [11], except for the two additional
acetyl groups in 1. Alkaline hydrolysis of 1
with 1% KOH gave the same deacetylated
glycoside 1a, which was identified by TLC.
In the HMBC spectrum, the correlations
1
13
The H and C NMR spectra of 1 were
similar to those of obtusifoline [10], apart
from glycosidation chemical shifts signals
of C-1 (d 152.0), C-2 (d 155.9), and C-3
(
two acetyl groups. The sugar moiety was
d 140.1) and the presence of additional
0
0
0
0
between H-2 /2 -OCOCH and H-6 /6 -
3
2
0
identificated as D-glucose (½aꢀ þ 39.6, c
OCOCH indicated that the acetyl moi-
3
D
0 0
0.1, H O) by acid hydrolysis and by
comparison with an authentic sample. The
eties were connected to C-2 and C-6
2
(Figure 2). On the basis of the above
observations, the structure of compound 1
was established as obtusifoline-2-O-b-D-2,
6-di-O-acetylglucopyranoside.
b-configuration of the glycosidic bond
1
13
was deduced from the H and C NMR
spectral data of the sugar moiety
1
3
Table 2.
Position
C NMR (100 MHz) data of 1–3 and 1a (d values, in DMSO-d6).
Compound 1
Compound 2
Compound 3
Compound 1a
1
2
3
4
152.0
155.9
140.1
125.1
124.5
118.4
136.4
124.0
161.0
116.8
187.8
129.7
181.3
132.4
61.4
152.2
155.7
139.9
124.8
124.5
118.2
136.3
124.1
161.2
116.9
187.9
129.6
181.4
132.3
61.2
152.0
156.0
140.3
125.0
124.3
117.9
136.4
124.0
161.0
116.6
188.0
129.5
181.1
132.2
61.3
154.3
153.5
142.4
125.1
124.4
118.0
136.5
123.9
160.8
116.6
187.8
129.7
181.4
132.2
61.0
4
5
6
7
8
8
9
9
1
1
1
3
a
a
a
0
0a
-OCH3
-CH
17.3
17.5
17.6
17.6
3
0
Glc:1
0
104.5
75.4
76.2
71.7
75.4
106.8
74.0
78.7
71.2
75.5
107.0
75.6
75.7
72.4
73.5
106.7
75.9
78.1
71.2
77.9
2
0
3
0
4
0
5
0
6
0
64.7
173.1
64.3
64.0
62.3
2
3
4
6
-OCOCH3
2
1.7
0
0
0
-OCOCH
-OCOCH3
-OCOCH
3
173.1
2
1.3
172.6
2
1.4
173.1
21.1
3
173.5
1.1
173.9
21.0
2

Journal of Asian Natural Products Research
489
CH3
OH
O
O
R O
2
O
OR3
OR4
O
CH3
R O
1
O
Figure 2. Selected HMBC correlations (H ! C) for compounds 1–3 and 1a.
Compounds 2 and 3 were obtained as
yellow needles having the same molecular
formula C H O as 1 on the basis of
Marine instrument. Silica gel (200–300
mesh), C18 reversed-phase silica gel
(150–200 mesh, Merck, Mumbai, India)
etc. were used for column chromato-
graphy, and pre-coated silica gel GF254
plate (QingDao Marine Chemical Plant,
QingDao, China) was used for TLC.
2
6 26 12
HR-ESI-MS and NMR analysis. And the
1
13
H and C NMR spectra of 2 and 3 were
similar to those of 1 apart from the
0
0
0
chemical shifts of C-2 , C-3 , and C-4 in
compound 2 and the chemical shifts of
0
0
0
C-3 , C-4 , and C-5 in compound 3, due to
the different link site of the acetyl groups
to b-D-glucose among 1, 2, and 3. The
3.2 Plant material
The seeds of C. obtusifolia were purchased
from Shanghai Derentang Pharmaceutical
Co. Ltd. The plants were authenticated
by Prof. De-An Guo, Shanghai Institute
of Materia Medica, Chinese Academy of
Sciences, China. A voucher specimen (SC
0
acetyl groups of 2 were linked to C-3 and
0
0
0
C-6 by the HMBC correlations of H-3 /3 -
0
0
OCOCH3 and H-6 /6 -OCOCH . The
3
0
0
HMBC correlations between H-4 /4 -
0
0
OCOCH and H-6 /6 -OCOCH indicated
3
3
0
222009) has been deposited in the Shang-
that the acetyl moieties were connected to
0
0
hai Research Center for Modernization of
TCM, ShanghaiInstitute of Materia Medica.
C-4 and C-6 of 3. Thus, 2 and 3 were
characterized as obtusifoline-2-O-b-D-3,
6-di-O-acetylglucopyranoside and obtusi-
foline-2-O-b-D-4, 6-di-O-acetylglucopyr-
anoside, respectively.
3
.3 Extraction and isolation
The seeds of C. obtusifolia (4.0 kg) were
ground and extracted with 95% ethanol
(
10 £ 4 l) at room temperature. The
3
.
Experimental
ethanol extract was concentrated under
vacuum to leave a residue that was
suspended in H O (4 l) and extracted
3
.1 General experimental procedures
IR spectra were recorded with a Perkin-
Elmer 577 spectrometer as KBr pellet.
NMR spectra were recorded with a Bruker
AM-400 spectrometer with TMS as an
internal standard. Diaion HP-20 (Mitsu-
bishi Chemical Industries, Tokyo, Japan).
All solvents used were of analytical grade
2
with petroleum ether (3 £ 4 l), CHCl
3
(3 £ 4 l), EtOAc (3 £ 4 l), and n-BuOH
(3 £ 4 l), sequentially. The EtOAc extract
(26.0 g) was separated by column chroma-
tography on silica gel (200–300 mesh,
300 g) eluting with a CHCl :MeOH
3
(Shanghai Chemical Plant, Shanghai,
China). HRESIMS were obtained on a
gradient (30:1, 20:1, 10:1, 5:1, 2:1, 1:1)
to yield fractions I–III. Fraction II (0.9 g)

4
90
X.-H. Wu et al.
was then repeatedly chromatographed on a
silica gel (200–300 mesh) column using
CHCl :MeOH (5:1). The final purification
in the same manner as 1 to afford 1a,
which was determined by co-TLC
(CHCl :MeOH:H O, 3:1:0.1, R ¼ 0.30).
3
3
2
f
was carried out by ODS, with eluting
solvent MeOH:H O (1:1). This yielded
2
new compounds 1 (28 mg, t 10.8 min), 2
R
3.5 Acid hydrolysis of 1–3
(
31 mg, tR 9.2 min), and 3 (25 mg, tR
1.6 min).
Compounds 1, 2, and 3 (3 mg each) were
refluxed in 10% HCl and stirred at 908C
for 3 h, respectively. The aglycone was
extracted with EtOAc. The aqueous layers
of the acid hydrolysis of 1, 2, and 3 were
1
3.3.1 Obtusifoline-2-O-b-D-2, 6-di-O-
acetylglucopyranoside (1)
neutralized with NaHCO and then concen-
3
Yellow needles; IR (KBr) nmax: 3869, 3215,
2
and C NMR spectral data, see Tables 1
21 1
trated. D-glucose was determined in each
aqueous layer by TLC on a silica gel plate
and by comparing with authentic sample,
900, 1751, 1666, 1641, and 1550cm . H
3
1
and 2; HRESIMS (positive-ion mode):
þ
respectively. The R
and 0.16 with CHCl :MeOH:H O (3:1:0.1)
3
values were 0.15, 0.15,
f
m/z 553.1328 [M þ Na]
(calcd for
2
C H O Na, 553.1322).
26 26 12
and n-BuOH:HOAc:H O abbreviated to
2
BAW (4:1:5, upper layer) as developing
system, respectively. The optical rotation
3.3.2. Obtusifoline-2-O-b-D-3, 6-di-O-
acetylglucopyranoside (2)
2
0
20
D
was ½aꢀ þ 39.6 (1), ½aꢀ þ 35.9 (2),
D
2
0
½
aꢀ þ 38.2 (3). Thus, D-glucose was
Yellow needles; IR (KBr) nmax: 3880, 3236,
D
21 1
identified.
2
and C NMR spectraldata, see Tables 1 and
911, 1760, 1682, 1600, and 1541cm . H
1
3
2
;
HRESIMS (positive-ion mode):
þ
m/z 553.1325 [M þ Na] (calcd for
Acknowledgements
C H O Na, 553.1322).
26 12
2
6
Special thanks are due to the Analytical Center,
Shanghai Institute of Materia Medica, Shanghai
Institutes for Biological Sciences, Chinese
Academy of Sciences, for measurements of
the mass and NMR spectra.
3.3.3. Obtusifoline-2-O-b-D-4, 6-di-O-
acetylglucopyranoside (3)
Yellow needles; IR (KBr) nmax: 3852,
3
1
220, 2934, 1738, 1652, 1644, and
2
558 cm
1
1
. H and C NMR spectral
13
References
[
1] S.A.I. Rizvi, S.C. Varshney, S.L. Abbas,
and N. Jahan, Phytochemistry 11, 1823
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(
positive-ion mode): m/z 553.1326
þ
(
1972).
[
M þ Na] (calcd for C H O Na,
[2] H. Joshi and V.P. Kapoor, Carbohydr.
Res. 338, 1907 (2003).
2
6
26 12
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3
.4 Alkaline hydrolysis of 1–3
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4] S. Kitanaka, F. Kimura, and M. Takido,
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[
[
(
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2
Compounds 2 and 3 (5 mg) were treated

Journal of Asian Natural Products Research
491
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