Two new C-glycosylflavones from Boea hygrometrica

Article abstract of DOI:10.1080/10286020.2011.579903

Two new C-glycosylflavones, named 5,7,3′,4′-tetrahydroxy-6- methoxy-8-C-β-Dgluco-pyranosyl flavonoside (1), 5,3′,4′- trihydroxy-6,7-dimethoxy-8-C-[β-D-apiofuranosyl-(1 → 2)]-β-D-glucopyranosyl flavonoside (2), together with nine known compounds (3-11), were isolated from 50% acetone extract of Boea hygrometrica (Bunge.) R.Br. Their structures were established by spectroscopic techniques including MS, IR, UV, and 2D NMR.

Full text of DOI:10.1080/10286020.2011.579903

Journal of Asian Natural Products Research
Vol. 13, No. 7, July 2011, 618–623
Two new C-glycosylflavones from Boea hygrometrica
Wei-Sheng Feng*, Yuan-Jing Li, Xiao-Ke Zheng, Yan-Zhi Wang, Fang-Yi Su and
Yuan-Yuan Pei
School of Pharmaceutical Science, Henan University of Traditional Chinese Medicine, Zhengzhou
4
50008, China
(Received 25 November 2010; final version received 7 April 2011)
0
0
Two new C-glycosylflavones, named 5,7,3 ,4 -tetrahydroxy-6-methoxy-8-C-b-D-
0
0
gluco-pyranosyl flavonoside (1), 5,3 ,4 -trihydroxy-6,7-dimethoxy-8-C-[b-D-apiofur-
anosyl-(1 ! 2)]-b-D-glucopyranosyl flavonoside (2), together with nine known
compounds (3–11), were isolated from 50% acetone extract of Boea hygrometrica
(Bunge.) R.Br. Their structures were established by spectroscopic techniques including
MS, IR, UV, and 2D NMR.
Keywords: Gesneriaceae; Boea hygrometrica; C-glycosylflavones
1
.
Introduction
along with nine known flavonoid glyco-
0
sides 5,4 -dihydroxy-6,7-dimethoxy-8-C-
Boea hygrometrica (Bunge.) R.Br.
belongs to Gesneriaceae, Boea Comm.ex
Lam. Boea Comm.ex Lam consists of
about 20 species in the world, and about 3
species of this genus is distributed in
China. B. hygrometrica, a traditional
Chinese herb, is widely distributed in
China. It has been used in traditional
Chinese medicine to activate blood
circulation, dissipate stasis, and stop
bleeding [1]. Studies on modern pharma-
cology demonstrated that it had functions
such as antibiosis and anti-inflammatory
[
b-D-xylopyranosyl-(1 ! 2)]-b-D-gluco-
0
0
pyranosyl flavonoside (3) [3], 5,3 ,4 -
trihydroxy-6,7-dimethoxy-8-C-[b-D-xylo-
pyranosyl-(1 ! 2)]-b-D-glucopyranosyl
0
0
flavonoside (4) [3], 5,3 ,4 -trihydroxy-
7
,8-dimethoxy-6-C-[b-D-xylopyranosyl-
1 ! 2)]-b-D-glucopyranosyl flavonoside
(
(
0
5) [4], 5,7,4 -trihydroxy-6-methoxy-8-C-
[b-D-xylopyranosyl-(1 ! 2)]-b-D-gluco-
0
pyranosyl flavonoside (6) [4], 5,7,4 -
trihydroxy-8-methoxy-6-C-[b-D-xylopyr-
anosyl-(1 ! 2)]-b-D-glucopyranosyl fla-
0
[2]. However, few of the phytochemical
vonoside (7) [4], 5,7,4 -trihydroxy-6-
methoxy-8-C-b-D-glucopyranosyl flavo-
studies of the plant have been reported
previously. To obtain the active constitu-
ents, the plant was investigated. In this
paper, two new C-glycosylflavones,
0
noside (8) [5], 5,4 -dihydroxy-6,7-
dimethoxy-8-C-b-D-glucopyranosyl fla-
0
vonoside (9) [3], 5,4 -dihydroxy-7-meth-
oxy-6-C-[b-D-apiofuranosyl-(1 ! 2)]-b-
0
0
named 5,7,3 ,4 -tetrahydroxy-6-methoxy-
-C-b-D-glucopyra-nosyl flavonoside (1)
8
D-glucopyranosyl flavonoside (10) [6],
0
0
0
and 5,3 ,4 -trihydroxy-6,7-dimethoxy-8-
C-[b-D-apiofuranosyl-(1 ! 2)]-b-D-glu-
copyranosyl flavonoside (2) (Figure 1),
and 5,4 -dihydroxy-7-methoxy-6-C-b-D-
glucopyranosyl flavonoside (11) [7],
among which, compounds 3–11 were
*Corresponding author. Email: fwsh@hactcm.edu.cn
ISSN 1028-6020 print/ISSN 1477-2213 online
q 2011 Taylor & Francis
DOI: 10.1080/10286020.2011.579903
http://www.informaworld.com

Journal of Asian Natural Products Research
619
OH
O
5
H CO
10
3
3
4
OH
O
4
6
7
6'
5
9
H CO
10
8
3
3
5'
H CO
6'' OH
O
2
6
7
3
1'
2'
6'
9
8
5''
''
OH
O
2''
4' OH
2
5
'
HO
O
1
'
OH
3''
3'
OH
4
6
'' OH
1''
5
''
O
2''
2
'
4'
OH
OH
3'
OH
O
4
''
OH
1
''
OH
5'''
3
''
O
OH
4'''
1
'''
3
''' 2'''
OH OH
1
2
Figure 1. The chemical structures and selected HMBC correlations of compounds 1 and 2.
þ
obtained from this plant for the first time
Figure 2).
ESI-MS at m/z 501.1006 [M þ Na] . Its
(
IR (KBr) spectrum showed absorption
2
bands for hydroxyl (3393 cm ) and
1
2
1
carbonyl (1653 cm ) groups, as well as
aromatic rings (1593, 1561, 1496,
2
.
Results and discussion
2
1
1
Compound 1 was isolated as a yellow
amorphous powder with mp 118–1218C
1460 cm ). The H NMR spectrum
showed the presence of three aromatic
2
0
and [a ] þ9.20 (c 0.4, MeOH). The UV
proton signals, resonated at d 7.51 (d, 1H,
H
D
(MeOH) spectrum showed the absorption
maxima at 274 and 350 nm. The molecular
J ¼ 2.1 Hz), 7.46 (dd, 1H, J ¼ 8.1,
2.1 Hz), 6.89 (d, 1H, J ¼ 8.1 Hz) as one
ABX system of B-ring, and a proton at
dH 6.50 (s, 1H), a characteristic signal for
formula of 1 was determined as C H O
2 22 12
2
by the pseudo-molecular ion in the HR-
R1
R2
R3
O
OH
R4
OH
O
R1
H
R2
R3
R4
2
3
4
5
6
7
8
9
glc -xyl
OCH3
OCH3
OCH3
OH
OCH3
2
OH
glc -xyl
OCH
3
2
OH
H
OCH
glc -xyl
3
2
glc -xyl
OCH
3
2
H
OCH3
glc
OH
glc -xyl
H
OH
OCH3
OCH3
glc -apiose
H
glc
H
OCH3
OCH3
OCH3
2
1
0
H
1
1
H
H
glc
Figure 2. The structures of compounds 3–11.

6
20
W.-S. Feng et al.
1
13
Table 1. H NMR (400 MHz) and C NMR (100 MHz) spectral data of compounds 1 and 2
CD OD, d ppm).
(
3
1
2
No.
d
H
(J, Hz)
dc
d
H
(J, Hz)
dc
Aglycone
2
3
4
5
6
7
8
9
166.7
103.3
184.4
153.3
132.3
153.7
105.3
158.3
105.6
124.0
114.9
147.1
151.0
116.8
120.9
60.9
168.8
101.4
184.2
154.6
137.3
159.1
111.8
153.0
108.7
118.2
112.5
149.9
151.2
117.7
121.9
61.2
6.50 (s, 1H)
6.50 (s, 1H)
1
1
2
3
4
5
6
6
7
0
0
0
0
0
0
0
7.51 (d, 1H, J ¼ 2.1 Hz)
7.46 (d, 1H, J ¼ 2.0 Hz)
6.89 (d, 1H, J ¼ 8.1 Hz)
7.46 (dd, 1H, J ¼ 8.1, 2.1 Hz)
3.88 (s, 3H)
6.73 (d, 1H, J ¼ 8.0 Hz)
7.44 (dd, 1H, J ¼ 8.0, 2.0 Hz)
3.90 (s, 3H)
-OCH
-OCH
3
3
4.00 (s, 3H)
62.8
Glc
0
0
0
0
0
0
0
0
0
0
0
0
1
2
3
4
5
6
5.01(d, 1H, J ¼ 9.6 Hz)
4.11 (m, 1H)
3.53 (m, 1H)
3.68 (m, 1H)
3.48 (m, 1H)
75.7
72.9
80.3
72.3
82.9
63.3
4.86 (d, 1H, J ¼ 10.0 Hz)
4.28 (m, 1H)
3.62 (m, 1H)
3.70 (m, 1H)
3.47 (m, 1H)
74.9
77.5
80.9
72.5
83.3
63.6
3.97 (d, 1H, J ¼ 9.6 Hz)
3.84 (d, 1H, J ¼ 10.0 Hz)
3.85 (m, 1H)
3.67 (m, 1H)
Api
0
0
0
0
00
00
00
00
1
2
3
4
5.11 (d, 1H, J ¼ 1.8 Hz)
3.77 (d, 1H, J ¼ 1.8 Hz)
111.3
78.5
80.6
74.2
3.11 (d, 1H, J ¼ 9.7 Hz)
2
3.26 (s, 2H)
.71 (d, 1H, J ¼ 9.7 Hz)
0
00
5
64.7
1
3
C-ring of the flavone skeleton, as well as
six protons linked to the oxygenated
carbons at dH 3.30–4.11 and a methoxyl
group at dH 3.88 (s, 3H). One anomeric
signal at dH 5.01 (d, 1H, J ¼ 9.6 Hz)
suggested the existence of one sugar in
configurated. The C NMR spectrum
(Table 1) clearly showed 22 carbon
signals, 15 assigned to the aglycone, 6 to
the glucose moiety, and 1 to the methoxyl.
1
13
The H NMR and C NMR spectral data
of compound 1 were very similar to those
1
3
0
compound 1. The C NMR signals at d
0
of 5,7,4 -trihydroxy-6-methoxy-8-C-b-D-
glucopyranosyl flavonoside (8) [5], except
0
00
00
7
5.7 (C-1 ), 72.9 (C-2 ), 80.3 (C-3 ), 72.3
0
0
00
00
(
C-4 ), 82.9 (C-5 ), and 63.3 (C-6 )
for the presence of a hydroxyl group
0
indicated that the sugar was glucose and
the CZC linkage between the aglycone
and the sugar [3,5]. The coupling constant
of the anomeric proton (J ¼ 9.6 Hz)
suggested that glucose should be b-
instead of H-3 in compound 1, i.e. the B-
0
0
ring of compound 1 was 3 ,4 -dihydrox-
0
yphenyl, different from 4 -hydroxyphenyl
of compound 8. In addition, the HMBC
correlations of methoxyl group at d 3.88
H

Journal of Asian Natural Products Research
621
0
0
with C-6 at d 132.3 indicated its linkage signals of glucose are at d 74.9 (C-1 ), 77.5
C
0
0
00 00 00
site. H-1 at dH 5.01 correlated with
the carbon signals at d 153.7 (C-7), 105.3
(C-2 ), 80.9 (C-3 ), 72.4 (C-4 ), 83.3 (C-
00 00
5 ), and 63.6 (C-6 ) and those of apiose are
C
000 000
(
C-8), and 158.3 (C-9), which revealed
at d 111.3 (C-1 ), 78.5 (C-2 ), 80.6 (C-
0
0
000
000
000
that C-1 of glucose was linked to C-8 of
the aglycone. All the hydrogen and carbon
signals were assigned by HSQC and
HMBC experiments. On the basis of
the above evidence, the structure of 1
3 ), 74.2 (C-4 ), and 64.7 (C-5 ). More-
over, the b-configurations of glucose and
apiose were determined by the coupling
constants of the anomeric protons at
dH 4.86 (d, 1H, J ¼ 10.0 Hz) and 5.11
0
0
1
was determined to be 5,7,3 ,4 -tetrahy-
droxy-6-methoxy-8-C-b-D-glucopyrano-
syl flavonoside.
(d, 1H, J ¼ 1.8 Hz). The H NMR and
1
3
C NMR spectral data of compound 2
0
0
were very similar to those of 5,3 ,4 -
trihydroxy-6,7-dimethoxy-8-C-[b-D-xylo-
pyranosyl-(1 ! 2)]-b-D-glucopyranosyl
flavonoside (4) [3], except for the presence
of apiose instead of xylose in compound 2.
In the HMBC spectrum (Figure 1), the
following correlative signals were
observed: the methoxyl at dH 3.90 with
Compound 2 was isolated as a yellow
amorphous powder with mp 151–1538C
2
0
and [a] 285.33 (c 0.24, MeOH). The
D
UV (MeOH) spectrum showed the absorp-
tion maxima at 268 and 348 nm. The
molecular formula of 2 was determined as
C H O by the pseudo-molecular ion in
2
8 32 16
þ
HR-ESI-MS at m/z 647.1583 [M þ Na] .
C-6 at d 137.3 and the other methoxyl at
C
Its IR (KBr) spectrum indicated the
dH 4.00 with C-7 at dC 159.1 indicated
00
2
presence of hydroxyl (3377 cm ) and
1
their linkage sites. H-1 at dH 4.86
correlated with the carbon signals at dC
2
1
carbonyl (1652 cm ) groups, as well as
aromatic rings (1602, 1570, 1523,
159.1 (C-7), 111.8 (C-8), and 153.0 (C-9),
00
2
457 cm ). The H NMR spectrum
1
1
1
showed the presence of three aromatic
which revealed that C-1 of glucose was
linked to C-8 of the aglycone. The signal at
000
d 5.11 (H-1 ) correlated with the carbon
H
proton signals, resonated at d 7.46 (d, 1H,
H
00
signal at d 77.5 (C-2 ), indicating that
C
J ¼ 2.0 Hz), 7.44 (dd, 1H, J ¼ 8.0,
0
00
00
2
one ABX system, and a characteristic
.0 Hz), and 6.73 (d, 1H, J ¼ 8.0 Hz) as
the C-1 of the apiose was linked to C-2
of the glucose. All the hydrogen and
carbon signals were assigned by HSQC
and HMBC experiments. On the basis
of the above evidence, the structure of 2
was determined to be 5,3 ,4 -trihydroxy-
6,7-dimethoxy-8-C-[b-D-apiofuranosyl-
(1 ! 2)]-b-D-glucopyranosyl flavonoside.
signal at d 6.50 (s, 1H) for C-ring of the
H
flavone skeleton. Two methoxyl groups at
dH 3.90 (s, 3H) and 4.00 (s, 3H) were
observed, as well as 11 protons linked to
0
0
the oxygenated carbons at d 2.71–4.28,
H
suggested the existence of two sugars in
compound 2. Two signals at dH 4.86 (d,
1
H, J ¼ 10.0 Hz) and 5.11 (d, 1H,
3
.
Experimental
J ¼ 1.8 Hz) were the anomeric protons of
1
3
3.1 General experimental procedures
two sugars, respectively. The C NMR
spectrum (Table 1) clearly showed 28
carbon signals. Besides 15 carbon signals
of aglycone and 2 methoxy1 groups, the
rest 11 should be carbon signals of two
Optical rotations were obtained using a
Perkin–Elmer 341 polarimeter. UV spec-
tra were measured with a Shimadzu UV-
VIS 2201 spectrophotometer. IR spectra
were measured with a Shimadzu FTIR-
1
3
sugars. According to the
C NMR
1
13
analysis and acid hydrolysis, the sugars
were identified as glucose and apiose.
By comparison of its NMR spectral data
8201 PC spectrometer. The H and
NMR spectra were obtained on a Bruker
C
1
DPX-400 spectrometer (400 MHz for H
1
3
13
NMR and 100 MHz for C NMR) with
with those reported in [6], the C NMR

6
22
W.-S. Feng et al.
TMS as an internal reference. HR-ESI-MS
were recorded on an APEX II spec-
trometer. Column chromatography was
performed on Diaion HP-20 (Mitsubishi
Chemical Corp., Tokyo, Japan), silica gel
MeOH–H O, 6:1:0.1) to yield compounds
2
4 (85.2 mg), 5 (85.2 mg), 6 (12.3 mg), and
7 (12.3 mg). Fraction B was chromato-
graphed on Toyopearl HW-40 (coarse
grade) developing with 10% MeOH–
50% MeOH. The 10% MeOH eluate
(7.1 g) of B was rechromatographed on
Toyopearl HW-40 (70% MeOH) and on
(160–200 mesh, Qingdao Marine Chemi-
cal Industry, Qingdao, China), Toyopearl
HW-40 and Sephadex LH-20 (TOSOH
Corp., Tokyo, Japan). TLC was conducted
on self-made silica gel G (Qingdao Marine
Chemical Industry) plates. The chemical
reagents were purchased from Beijing
Chemical Plant (Beijing, China) and
Tianjin No. 3 Reagent Plant (Tianjin,
China).
silica gel (CHCl –MeOH, 10:1) to yield
3
compounds 1 (11 mg) and 8 (15 mg). The
20% MeOH eluate (5.4 g) of B was
rechromatographed on Toyopearl HW-40
(MeOH) and on silica gel (CHCl –MeOH,
3
8:1:0.05) to yield compounds 9 (35 mg)
and 10 (21 mg). Fraction C was chromato-
graphed on Toyopearl HW-40 (coarse
grade), developing with 10% MeOH–
3
.2 Plant material
5
0% MeOH. The 10% MeOH eluate
The fresh plants of B. hygrometrica were
collected from Xixia County, Henan
Province of China, in July 2009, and
identified by Prof. Cheng-Ming Dong of
Henan University of Traditional Chinese
Medicine. Its voucher specimen
(6.8 g) of C was rechromatographed on
Toyopearl HW-40 (MeOH) and on silica
gel (EtOAc–EtOH–H O, 12:2:1) to yield
2
compounds 2 (12 mg) and 11 (15 mg).
(MED20090725) has been deposited in
our laboratory.
0
0
3
8
.3.1 5,7,3 ,4 -Tetrahydroxy-6-methoxy-
-C-b-D-glucopyranosyl flavonoside (1)
3
.3.1.1 A yellow amorphous powder.
2
D
0
3
.3 Extraction and isolation
Air-dried whole plants of B. hygrometrica
5.0 kg) were extracted with 50% aq.
[
nmax: 3393, 2925, 1653, 1593, 1561, 1496,
a] þ9.20 (c 0.4, MeOH); IR (KBr)
2
1460 cm ; UV (MeOH) lmax: 274,
1
(
1 13
350 nm. H and C NMR spectral data
Me CO two times at room temperature,
2
and concentrated under reduced pressure
below 458C. The water-soluble part was
chromatographed over Diaion HP-20 with
are shown in Table 1. HR-ESI-MS: m/z
þ
501.1006 [M þ Na]
(calcd for
C H O Na, 501.1009).
22 22 12
H O containing increasing amounts of
2
MeOH to afford H O eluate 42.1 g (A),
2
2
0% MeOH eluate 35.6 g (B), and 30%
0
0
3
.3.2 5,3 ,4 -Trihydroxy-6,7-dimethoxy-
MeOH eluate 28.5 g (C). Fraction A was
chromatographed on Toyopearl HW-40
8
-C-[b-D-apiofuranosyl-(1 ! 2)]-b-D-
glucopyranosyl flavonoside (2)
(
coarse grade) developing with 10%
MeOH–50% MeOH. The 10% MeOH
eluate (6.4 g) of A was rechromatographed
on Toyopearl HW-40 (50% MeOH) and on
silica gel (CHCl –MeOH–H O, 6:1:0.1)
3.3.2.1 A yellow amorphous powder.
2
0
[a] 285.33 (c 0.24, MeOH); IR (KBr)
nmax: 3377, 2933, 1652, 1602, 1570, 1523,
D
21
1457cm ; UV(MeOH) lmax: 268, 348 nm.
1
3
2
13
H and C NMR spectral data are shown in
to yield compound 3 (30.1 mg). The 20%
MeOH eluate (4.3 g) of A was rechroma-
tographed on Toyopearl HW-40 (70%
MeOH) and on silica gel (CHCl3 –
Table 1. HR-ESI-MS: m/z 647.1583
þ
[M þ Na] (calcd for C H O Na,
2
8
32 16
647.1588).

Journal of Asian Natural Products Research
623
3
.4 Acid hydrolysis of compound 2
of Henan Province and for the plant
identification.
Compound 2 (3 mg) was heated in 3 ml of
HCl/H O/EtOH (2:1:2) at 808C for 4 h.
2
The hydrolysate was partitioned between
EtOAc and H O, and the aqueous layer
References
2
was compared with authentic samples on
TLC with silica gel [CHCl /MeOH/H O
[1] B.Z. Ding and S.Y. Wang, Flora of Henan
(Henan Science & Technology Press,
Zhengzhou, 1990), p. 466.
3
2
(5:1:0.1)], which showed that the sugar
was apiose and the glucose was linked to
the aglycone with CZC bond.
[
2] Z.W. Xie, C.S. Fan, and Z.Y. Zhu, National
Herbal Compendium (People’s Medical
Publishing House, Beijing, 2000), p. 151.
3] W.S. Feng, X.K. Zheng, Y.B. Liu, and
J. Li, Acta Pharmacol. Sin. 39, 110 (2004).
4] W.S. Feng, X.K. Zheng, Y.B. Liu, and H.X.
Kuang, J. Asian Nat. Prod. Res. 9, 85
(2007).
[
[
Acknowledgements
This work was financially supported by the
Ministry of Education of China (2003078) and
program for Science & Technology Innovation
Talents in Universities of Henan Province
[5] S. Canigueral, M.J. Salvia, R. Vila, and
J. Iglesias, J. Nat. Prod. 59, 419 (1996).
[6] C.M. Ma, N. Nakamura, and M. Hattori,
Chem. Pharm. Bull. 46, 982 (1998).
[7] W.S. Feng, Q. Li, X.K. Zheng, and H.X.
Kuang, Nat. Prod. Res. Dev. 18, 617
(2006).
(
2010HASTIT014). We thank Prof. Cheng-
Ming Dong (Henan University of Traditional
Chinese Medicine, China) for making the
original plant collections from Xixia County