Four new glycosides from the seeds of Cassia obtusifolia

Article abstract of DOI:10.1016/j.phytol.2015.05.005

Four new glycosides, including one anthraquinone glycoside (1), one naphthalene glycoside (2), and two naphthopyrone glycosides (3-4), with 10 known compounds (5-14) were isolated from the seeds of Cassia obtusifolia L. The new structures were determined by spectroscopic analysis and chemical transformations.

Full text of DOI:10.1016/j.phytol.2015.05.005

Phytochemistry Letters 13 (2015) 81–84
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Short communication
Four new glycosides from the seeds of Cassia obtusifolia
Liying Tang, Hongwei Wu, Huijuan Su, Xidan Zhou, Guohong Zhou, Ting Wang,
*
Zhenzhen Kou, Zhuju Wang
Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing 100700, China
A R T I C L E I N F O
A B S T R A C T
Article history:
Four new glycosides, including one anthraquinone glycoside (1), one naphthalene glycoside (2), and two
naphthopyrone glycosides (3–4), with 10 known compounds (5–14) were isolated from the seeds of
Cassia obtusifolia L. The new structures were determined by spectroscopic analysis and chemical
transformations.
Received 9 March 2015
Received in revised form 5 May 2015
Accepted 7 May 2015
Available online 23 May 2015
ã2015 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.
Keywords:
Cassia obtusifolia L
Anthraquinone glycosides
Naphthalene glycoside
Naphthopyrone glycosides
1. Introduction
2. Results and discussion
Cassia obtusifolia L. belongs to the Cassia genus in the
leguminous family, the seeds of which have been widely used as
traditional herbal medicine or health tea in many Asian countries
for a long time. In traditional Chinese medicine, it has the efficiency
to remove “heat”, improve eyesight, and relax bowels (Pharmaco-
poeia of the People’s Republic of China, 2005). Modern pharmaco-
logical research has revealed that the seed has multiple functions,
such as liver protection, bacteriostasis, catharsis, diuresis, neuro-
protection, antitumor and anti-oxidation, and it is highly valued for
the treatment of hypercholesterolaemia, hypertension and hyper-
lipidaemia (Patil et al., 2004; Ju et al., 2010; Xu et al., 2014).
Previously, we reported the structural determination of six new
anthraquinones and one naphthalene (Wang et al., 2007; Tang
Compound 1 was obtained as a yellow powder (MeOH), showing
positive reaction with Molish and Bornträger reagents. Its
methanolic solution had
(½a 2D0
ꢁ57.958). Its UV spectrum displayed absorption bands at
221, 257, and 287 nm. Its molecular formula was determined as
39H50O24 based on the HRESIMS data at m/z 901.2574 [M-H]+
a
negative optical rotation
ꢀ
C
(calcd for 901.2614, C39H49O24). The general appearance of its 1H
and 13C NMR spectra (Tables 1 and 2), in addition to the
information obtained from its mass spectrum, suggested an
anthraquinone skeleton for 1. By the analysis of the HMBC and
HMQC spectrum, the aglycone part was determined to be
chrysophanol. The 13C NMR spectrum of 1 showed thirty-nine
carbon signals, including one methyl (
signals ascribed to the aglycone part of anthraquinone, and
twenty-four sugar carbon signals (four anomeric carbons at
103.9, 102.8, 102.7, and 100.5 and other carbons at 88.6–60.5).
d 21.7), fourteen carbon
et al., 2008 Xu et al., 2014). As
a continuation of these
investigations, a phytochemical screening was conducted with
the seeds of Cassia obtusifolia L., resulting in the isolation of four
new glycosides, assigned as one anthraquinone glycoside (1), one
naphthalene glycoside (2), two naphthopyrone glycosides (3–4),
and ten known compounds (5–14). The structures of (1–4) were
determined by spectroscopic analysis, including 2D NMR, and
chemical transformations.
d
d
From the above information, compound 1 was identified as an
anthraquinone glycoside with four monosaccharides. After hydro-
lysis with 5% hydrochloric acid methanol solution and trimethyl
silylation, the GC analysis and the NMR data showed that the sugar
chain only consisted of D-glucose residues by comparison with the
authentic simple. Therefore, the sugar chain was composed of four
glucose residues. The four anomeric proton signals were deter-
mined at
(2H, d, J = 6.8 Hz). The conformation of
as -type by the J value. The DEPT spectrum showed four
secondary carbon signals at 60.5, 60.9, 68.7, and 68.9, which
belonged to the 6 position carbon signals of the four glucose
d
5.17 (1H, d, J = 7.2 Hz), 4.16 (1H, d, J = 7.6 Hz), and 4.31
D-glucose was determined
b
d
* Corresponding author. Tel.: +86 10 6403 3301; fax: +86 10 6403 3301.
E-mail address: wangzhuju@sina.com (Z. Wang).
http://dx.doi.org/10.1016/j.phytol.2015.05.005
1874-3900/ã 2015 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.

82
L. Tang et al. / Phytochemistry Letters 13 (2015) 81–84
Table 1
1H and 13C NMR data of the aglycone for compounds 1–4 (500 and 125 MHz, DMSO, J in Hz,
d
in ppm).
1
2
3
4
Positon
H
C
H
C
H
C
H
C
1
2
3
4
5
6
7
8
9
10
4a
5a
8a
9a
10a
3-CH3
2-CH3
8-OH
2-COCH3
2-COCH3
6-OCH3
8- OCH3
158.3
122.9
147.5
121.4
118.3
136.0
124.1
161.3
187.6
182.0
134.3
151.5
123.2
133.7
118.6
101.6
158.4
103.3
155.3
165.7
7.58 (d, 1.5)
169.0
106.8
183.9
161.9
157.6
101.5
161.2
99.9
6.20 (s)
152.3
104.0
110.5
100.7
160.9
102.3
157.7
163.0
132.4
141.7
7. 71 (d, 1.5)
7.66 (d, 8.0)
7.74 (dd, 7.2, 8.0)
7.34 (d, 7.2)
7.06 (s)
6.89 (d, 2.0)
6.15 (s)
7.15 (s)
6.76 (d, 2.0)
7.05 (d, 2.0)
6.80 (d, 2.0)
6.33 (d, 2.0)
6.94 (d, 2.0)
7.21 (s)
101.1
103.8
107.8
136.9
108.8
116.7
118.1
132.4
21.7
140.4
152.5
109.3
98.5
18.8
2.48 (s)
2.22 (s)
19.5
2.22 (s)
3.86 (s)
2.39 (s)
3.88 (s)
20.3
55.6
12.91 (s)
204.4
32.2
55.4
2.48 (s)
3.82 (s)
55.6
residues, and
d
68.7 and 68.9 were at the lower field displacement.
C-6' (d 68.8) and H-1” [4.16 (1H, d, J = 7.6 Hz)] were ascertained by
This showed that three monosaccharides were connected through
the 1H-1H COSY, HSQC and HMBC experiments, which revealed the
presence of a 1 !6 linkage between the first two glucoses units.
The anomeric proton signals of the other two glucoses in the sugar
two 1 !6 linkages. Comparing the 13CNMR data of 1 and standard
glucose, it can be found that the signal at d 88.6 was the C-3, which
moved to lower field displacement. Therefore, the sugar chain
should also have one 1 !3 linkage. The HMBC spectrum showed an
chain were both at
relationship with
68.9 and 88.6. Based on the 1H-1H COSY and
HSQC spectrum, H-1”, H-2” (
were confirmed. This result indicated that
could only be the signal of C-3”'. Therefore, the connection of the
second and third glucose was a 1 !6 linkage, and the last two
glucoses were connected by a 1 !3 linkage. The connections of the
d 4.31 (1H, d, J = 6.8 Hz), with an HMBC
d
anomeric proton signal at d 5.17 (1H, d, J = 7.2 Hz) with both the C-1
d
2.96), H-3”(
d
3.15) and C-3”(d 76.0)
(
d
158.3) of the aglycone part and the sugar carbon signal at
and 3.19 with 74.9 have cross-peaks. Therefore, the proton
signals at 5.17 (1H, d, J = 7.2 Hz) and 3.19 and the carbon signal at
74.9 were assigned to H-1', H-5'and C-3'. Then, H-6' ( 4.12, 3.41),
d 74.9,
d
88.6 was not C-3” and
d
d
d
d
d
d
Table 2
1H and 13C NMR data of the sugar for compound 1–4 (500 and 125 MHz, DMSO, J in Hz,
d
in ppm).
1
2
3
4
Positon
H
C
H
C
H
C
H
C
'1
'2
'3
'4
'5*
'6 a
b
"1
"2
"3
"4
"5
"6 a
b
"'1
"'2
"'3
"4
"'5
"'6 a
b
""1
""2
""3
""4
""5*
""6 a
b
5.17 (d, 7.2)
3.44 (m)a
3.46 (m)a
3.06 (m)b
3.19 (m)c
4.12 (m)
100.5
73.3
74.9
70.3
75.9
68.8
5.09 (d, 6.0)
3.35 (m)a
3.47 (m)
102.4
73.3
75.0
70.4
75.9
68.8
5.06 (d, 7.5)
3.43 (m)a
3.46 (m)a
3.08 (m)b
3.20 (m)c
4.13 (m)
100.9
73.6
75.1
70.4
75.9
68.8
5.06 (d, 7.5)
3.40 (m)a
3.45 (m)a
3.06 (m)b
3.22 (m)c
4.14 (m)
100.8
73.4
75.0
70.3
76.0
68.8
3.07 (m)b
3.22 (m)c
4.15 (m)
3.41 (m)a
4.16 (d, 7.6)
2.96 (m)
3.43 (m)d
4.18 (d, 7.5)
2.98 (m)
3.16 (m)e
3.21 (m)c
3.33 (m)a
4.03 (m)
3.71 (m)
4.36 (d, 7.0)
3.26 (m)
3.36 (m)a
3.21 (m)c
3.74 (m)
3.46 (m)a
4.18 (d, 7.5)
3.00 (m)
3.18 (m)c
3.24 (m)c
3.35 (m)d
4.00 (m)
3.71 (m)
4.33 (d, 7.5)
3.22 (m)c
3.34 (m)d
3.20 (m)c
3.70 (m)
3.41 (m)a
4.18 (d, 7.5)
3.01 (m)
102.7
73.7
76.0
69.9
76.3
68.9
102.8
73.8
76.0
70.0
76.1
68.8
102.9
73.9
76.1
70.0
76.4
68.8
102.8
73.8
76.0
69.9
76.2
68.8
3.15 (m)d
3.21 (m)c
3.31 (m)
3.17 (m)c
3.22 (m)c
3.36 (m)
4.01 (m)
3.98 (m)
3.64 (m)e
4.31 (d, 6.8)
3.17 (m)d
3.28 (m)
3.72 (m)e
4.33 (d, 7.5)
3.24 (m)c
3.40 (m)a
3.24 (m)c
3.76 (m)
102.8
71.9
88.6
68.6
75.8
60.5
102.6
71.9
88.8
68.6
75.8
60.6
102.5
72.0
88.8
68.7
75.8
60.6
102.4
71.9
88.6
68.6
75.8
60.5
3.17 (m)d
3.74 (m)
3.64 (m)e
3.39 (m)
3.63 (m)
3.40 (m)
4.35(d, 7.0)
3.11 (m)
3.64 (m)
3.40 (m)
3.66 (m)e
3.42 (m)a
4.33 (d, 7.5)
3.12 (m)
4.31 (d, 6.8)
3.10 (m)
103.9
73.4
76.7
69.7
75.8
60.9
104.0
73.5
76.8
69.9
75.8
60.9
4.33 (d, 7.5)
3.11 (m)e
3.12 (m)e
3.06 (m)b
3.24 (m)c
3.67 (m)
104.1
73.6
76.9
69.8
75.9
61.0
103.9
73.5
76.8
69.8
75.8
60.9
3.06 (m)b
3.03 (m)b
3.19 (m)c
3.66 (m)e
3.45 (m)a
3.09 (m)b
3.06 (m)b
3.17 (m)e
3.66 (m)
3.43 (m)d
3.08 (m)b
3.05 (m)b
3.26 (m)c
3.67 (m)e
3.41 (m)a
3.42 (m)a
*1H and 13C NMR signals of this position could be interchanged a, b, c, d, e were overlapped, respectively.

L. Tang et al. / Phytochemistry Letters 13 (2015) 81–84
83
four monosaccharides were also identified by 2D NMR and
hydrolysis. Thus, the structure of was characterized as
chrysophanol-1-O- -glucopyra-
-glucopyranosyl -(1 !3)-O-
-glucopyranosyl-(1 !6)- O- - glucopyrano-
1-O-
b
-
D
-glucopyranosyl-(1 !3) -O-
b
-
D
-glucopyranosyl-(1!6)-O-
1
b-D-glucopyranoside (5) (Wong and Wong, 1989), aurantio-
obtusin (6), obtusinfolin (9) (Tang et al., 2009a), chryso-obtusin
(7), emodin (8), obtusifolin-2-glucoside (10), chrysophanol (12),
physicon (13) (Choi et al., 1996), rubrofusarin gentiobioside (11)
b
D
-D
b-D
b-D
nosyl-(1 !6)-O-
b
-
side.
(Susumu k. Michio, 1988), and aurantio-obtusin-6-O-
pyranoside (14) (Tang et al., 2009b).
b-D-gluco-
Compound 2 was purified as a pale yellow crystal with a
negative optical rotation (½a D20
ꢀ ꢁ49.964) in methanolic solution.
The Molish and Bornträger reagent test showed a positive reaction.
The UV spectrum displayed absorption bands at 236, 265 and
320 nm, and the compound was assigned the molecular formula
3. Experimental
3.1. General experimental procedure
C
38H54O24 from its negative-ion HRESIMS at m/z 893.2927 [M-H]ꢁ
(calcd for C38H53O24, 893.2927). The NMR spectroscopic data of the
aglycone portion revealed that it was torachrysone (El-Halawany
et al., 2007). Comparing the 1H and 13C NMR spectra of 1 and 2
(Tables 1 and 2), the data of the sugar chain were similar, and the
Optical rotations were measured on an Autopol V polarimeter
with MeOH as solvent at 20 ꢂC. Melting points were measured on a
Sgwx-4 melting point apparatus (China). UV spectra were recorded
on an Agilent UV-8453 spectrophotometer (USA). 1D and 2D NMR
data were obtained on a BrukerAV-500 instrument (Germany) in
DMSO, using TMS as the internal standard. The chemical shifts are
four anomeric carbon signals were at
102.4, with the other sugar carbon signals at
corresponding anomeric proton signals at 5.09 (1H, d, J = 6.0 Hz),
4.18 (1H, d, J = 7.5 Hz), and 4.36 (2H, d, J = 7.0 Hz). The key HMBC
correlations from 5.09 (H-1') to 155.3 (C-8 of the aglycone)
d
104.0, 102.8, 102.6, and
d
88.6-60.5, and the
d
given in d (ppm), and the coupling constants (J) are reported in Hz.
HRESIMS were recorded on an Agilent G-6540 Q-TOF MS (USA).
Silica gel GF254 prepared for TLC and silica gel (100–200 mesh) for
column chromatography were obtained from Qingdao Marine
Chemical Company, Qingdao, China. Macroporous adsorption resin
AB-8 was produced by the Chemical Plant of Nankai University,
Tianjin, China. The compounds were purified by preparative HPLC
on a Gilson 306 pump, 800C dynamic mixer, 506C system interface,
and 118UV detector instrument (USA) equipped with a YMC-Pack
ODS-A column (250 ꢃ 20 mm, Japan). The GC data were recorded
on an Agilent GC 7890A GC system using an HP-5 (30 m ꢃ 0.32
d
d
indicated that the sugar chain was linked to the C-8 of the aglycone,
and the connections of the other three monosaccharides were also
identified by 2D NMR and hydrolysis. Thus, the structure of 2 was
characterized as torachrysone 8-O-
b-
D
-glucopyranosyl-(1 !3)-O-
b
b
-
D
-glucopyranosyl-(1 !6)-O-
b-D
-glucopyranosyl-(1 !6)-O-
-D
-glucopyranoside.
Compound 3 was isolated as a pale yellow crystal, showing a
positive reaction with Molish and Bornträger reagents. Its
UV spectrum displayed absorption bands at 224, 253 and
mm ꢃ 0.25
m
m) column, FID detection, N2 carrier gas, 250 ꢂC
injection temperature, 280 ꢂC detection temperature, and 280 ꢂC
column temperature.
276 nm, and it had a negative optical rotation (½a D20
ꢀ ꢁ649.537) in
methanolic solution. The molecular formula of 3 was C39H52O25, as
deduced from the data of its HR-negative-ESI-MS at m/z 919.2710
[M-H]ꢁ (calcd for C39H51O25 919.2719). The evidence above and the
1H and 13C NMR spectra (Tables 1 and 2) suggested rubrofusarin
3.2. Plant material
The seeds of Cassia obtusifolia L. were collected in Anguo, Hebei
province, China and were identified by Professor Chen Sui Qing
(Henan University of Traditional Chinese Medicine). A voucher
specimen was deposited in our laboratory (voucher No. COL-2009-
05).
(Lee et al., 2006) for 3. The four anomeric protons at
4.33, and 4.33 (each 1H, d, J = 7.5 Hz) and the corresponding
carbons at 100.9, 102.9, 102.5 and 104.1 revealed the presence of
d 5.06, 4.18,
d
four sugar moieties. Similar to compound 2, the analysis of the
comparison of the 1H and 13C NMR spectra of 3 with 1 (Tables 1 and
2) showed that the data of the sugar chain were similar. The site of
attachment of the four glucose units to the aglycone was assigned
to C-6, as indicated from the HMBC correlation between the proton
3.3. Extraction and isolation
The dried and powdered seeds of Cassia obtusifolia L. (15 kg)
were extracted with hot 70% EtOH (45 L ꢃ 2). After the solvent was
concentrated under reduced pressure, the extracted EtOH (1500 g)
was suspended in water (10 L) and extracted with petroleum ether
(5 L ꢃ 4) and chloroform (5 L ꢃ 4) to afford a petroleum ether
soluble fraction (200 g) and a chloroform soluble fraction (150 g).
The remaining water extracts were passed through a macroporous
adsorption resin AB-8 column eluted with H2O–EtOH (9:1) (5 L),
H2O–EtOH (7:3) (5 L), H2O–EtOH (1:1) (5 L), H2O–EtOH (3:7) (5 L),
and EtOH (5 L). The 30% EtOH eluate portion (320 g) was subjected
to silica gel column chromatography eluted with CHCl3–MeOH
(9:1, 4:1, 2:1, 1:1) and MeOH alone to give 8 fractions (A–H).
Fraction A was applied to a silica gel column eluted with petroleum
ether–acetone (5:1) to give 12 (15.3 mg) and 13 (20.9 mg).
Fractions B and C were separated by silica gel column chromatog-
raphy eluted with petroleum ether–EtOAC (4:1) and (3:1) to give 7
(25.3 mg), 8 (18.0 mg) and 9 (12.3 mg). Fractions D and G were
purified by silica gel column chromatography eluted with
petroleum ether–EtOAC (3:1) and sephadex LH-20 eluted with
MeOH–H2O (8:2) to give 6 (30.0 mg) and 10 (16.8 mg). Fraction F
was separated by polyamide column chromatography eluted with
MeOH–H2O (8:2) and purified by sephadex LH-20 eluted with
MeOH–H2O (1:1) to give 11 (200.0 mg) and 14 (21.3 mg). Fraction H
at
d 5.17 (H-1') and the carbon at d 157.6 (C-6) of the aglycone. The
connections of the other three glucoses were also confirmed by 2D
NMR and hydrolysis. Therefore, the structure of 3 was rubrofu-
sarin-6-O-
(1 !6)–O-
b
b
-
-
D
-glucopyranosyl-(1 !3)-O-
b
-
D
-glucopyranosy1-
D
-glucopyranosyl-(1 !6)-O-b-D- glucopyranoside.
Compound 4 was obtained as a pale yellow crystal, and its UV
spectrum displayed absorption bands at 207, 225, 269, and 278 nm.
Its methanolic solution had
a
negative optical rotation
(½a 2D0
ꢀ ꢁ19.985). The molecular formula of 4 was determined as
C39H52O25 from the [M-H]ꢁ ion peak at m/z 919.2692 in the HRESI
mass spectrum (calcd for C39H51O25 919.2719). Comparing the 1H
and 13C NMR data (Table 1 and 2), with the exception of the
carbonyl signal, compound 4 was similar to 3, suggesting that it
could be a naphtha-a-pyrone glycoside (Hatano et al., 1999).
Furthermore, the aglycone part was identified to be toralactone,
and the sugar part was assigned as the same as that of 3 by the 2D
NMR and hydrolysis analysis. Thus, the structure of 4 was deduced
as toralactone-9-O-
b
b-D-
-D
–glucopyranosyl-(1 !3)-O-
b
-
D
D
-glucopyra-
-glucopyra-
nosy1-(1 !6)-O-
glucopyranosyl-(1 !6)-O-
b-
noside.
By extensive analysis of their 1H and 13C NMR data, ten known
compounds (5–14) were isolated and identified as chrysophanol-

84
L. Tang et al. / Phytochemistry Letters 13 (2015) 81–84
Fig. 1. Structures of compounds 1-4.
was applied to an ODS silica gel column eluted with MeOH–H2O
(1:1) to yield 1 (20.2 mg) and 5 (10.5 mg), and the other portionwas
separated by preparative HPLC, eluting with CH3OH-H2O (45:55) to
give compounds 2 (14.7 mg), 3 (12.0 mg) and 4 (11.5 mg) Fig. 1.
(25.040 min), 2 (25.041 min), 3 (25.039 min), and 4 (25.045 min)
with those of a standard sample of D-glucose (25.047 min).
Conflict of interest
3.3.1. Compound 1
The authors declare no conflicts of interest.
Yellow powder, mp 205–206 ꢂC; ½a D20
ꢁ57.958 (c = 0.10, MeOH);
ꢀ
UV lmax (MeOH) nm (log e
): 221, 257, 287; 1H NMR and 13C NMR
Acknowledgements
data, see Table 1 and 2; HRESI-MS m/z 901.2574 [M-H]ꢁ (calcd for
39H49O24, 901.2614).
This work was financially supported by the National Natural
Science Foundation of China [No. 81173552] and the Beijing
Natural Science Foundation (No. 7154228).
C
3.3.2. Compound 2
Pale yellow crystal, mp 187–188 ꢂC; ½a D20
ꢁ49.964 (c = 0.10,
ꢀ
References
MeOH); UV lmax (MeOH) nm (log e
): 236, 265, 320; 1H NMR and
13C NMR data, see Table 1 and 2; HRESI-MS m/z 893.2927[M-H]ꢁ
Choi, J.S., Jung, J.H., Lee, H.J., Kang, S.S., 1996. The NMR Assignments of
anthraquinones from Cassia tora. Arch. Pharm. Res. 19, 302–306.
El-Halawany, A.M., Chung, M.H., Nakamura, N., Ma, C.M., Nishihara, T., Hattori, M.,
2007. Estrogenic and anti-estrogenic activities of Cassia tora phenolic
constituents. Chem. Pharm. Bull. 55, 1476–1482.
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and antibacterial effect of some naphthalenes and anthraquinones on
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(calcd for C38H53O24, 893.2927).
3.3.3. Compound 3
Pale yellow crystal, mp 210–211 ꢂC; ½a D20
ꢁ649.537 (c = 0.10,
ꢀ
MeOH); UV lmax (MeOH) nm (log e
): 224, 253, 276; 1H NMR and
13C NMR data, see Table 1 and 2; HRESIMS m/z 919.2710 [M-H]ꢁ
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(calcd for C39H51O25 919.2719).
3.3.4. Compound 4
Pale yellow crystal, mp 216–217 ꢂC; ½a D20
ꢁ19.985 (c = 0.10,
ꢀ
MeOH); UV lmax (MeOH) nm (log e
): 207, 225, 269, 278; 1H NMR
and 13C NMR data, see Table 1 and 2; HRESIMS m/z 919.2692 [M-
H]ꢁ (calcd for C39H51O25 919.2719).
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3.4. Acid hydrolysis of the glycosides
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Compounds 1,2, 3 and 4 (each 2 mg) were heated in 2 M HCl
(5 ml) at 90 ꢂC for 4 h. (Xu et al., 2014) The reaction mixture was
extracted with CHCl3 (5 ml ꢃ 3). Each remaining aqueous layer was
concentrated to dryness to give a residue and was dissolved in
pyridine (0.3 ml), and then L-cysteine methyl ester hydrochloride
(3.0 mg) was added to the solution. The mixture was heated at
60 ꢂC for 1 h, and trimethyl chlorosilane (0.5 ml) was added,
followed by heating at 60 ꢂC for 30 min. Then, the solution was
concentrated to dryness and dissolved in water (1 ml ꢃ 3), followed
by extraction with n-hexane (1 ml ꢃ 3). The hexane extract was
subjected to GC analysis. The absolute configurations of the
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from the seed of Cassia obtusifolia. Arch. Pharm. Res. doi:http://dx.doi.org/
10.1007/s12272-014-0462-x.
monosaccharide were confirmed to be
D-glucose by comparison of
the retention times of the monosaccharide derivatives of 1