Biflavones and Furanone Glucosides from Zabelia tyaihyonii

Article abstract of DOI:10.1002/hlca.201500054

Two new biflavones, (aR)-3′-methoxycupressuflavone (1) and (aR)-3′,3′′′-dimethoxycupressuflavone (2), and two new furanone glucosides, zabeliosides A and B (3 and 4, resp.), along with two known biflavones, cupressuflavone (5) and amentoflavone (6), were isolated from the leaves of Zabelia tyaihyonii. The structures of the new compounds were elucidated by 1D- and 2D-NMR, HR-ESI-MS, and circular dichroism.

Full text of DOI:10.1002/hlca.201500054

Helvetica Chimica Acta – Vol. 98 (2015)
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Biflavones and Furanone Glucosides from Zabelia tyaihyonii
by Hari Janga), Jin Woo Leea), Qinghao Jina), Soo-Young Kimb), Dongho Leec), Jin Tae Honga),
Youngsoo Kima), Mi Kyeong Leea), and Bang Yeon Hwang*a)
a) College of Pharmacy, Chungbuk National University, Cheongju 28644, Republic of Korea
(phone: þ 82-43-2612814; fax: þ 82-43-2682732; e-mail: byhwang@chungbuk.ac.kr)
b) National Institute of Biological Resources, Incheon 22689, Republic of Korea
c) College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea
Two new biflavones, (aR)-3’-methoxycupressuflavone (1) and (aR)-3’,3’’’-dimethoxycupressuflavone
(2), and two new furanone glucosides, zabeliosides A and B (3 and 4, resp.), along with two known
biflavones, cupressuflavone (5) and amentoflavone (6), were isolated from the leaves of Zabelia
tyaihyonii. The structures of the new compounds were elucidated by 1D- and 2D-NMR, HR-ESI-MS, and
circular dichroism.
Introduction. – Zabelia tyaihyonii (T.H.Chung ex Nakai) Hisauti & H.Hara
(formerly known as synonym of Abelia tyaihyonii T.H.Chung ex Nakai (Caprifolia-
ceae)), a species endemic of Korea, is a deciduous shrub belonging to the family
Linnaeaceae. It is distributed mainly in the central and northern parts of the Korean
peninsula [1 – 3]. Previous phytochemical studies on the genus Zabelia resulted in the
isolation of bisiridoid and secoiridoid glucosides [4][5]. However, to the best of our
knowledge, no phytochemical investigation of Z. tyaihyonii has been reported. In this
study, two new biflavones, (aR)-3’-methoxycupressuflavone (1) and (aR)-3’,3’’’-
dimethoxycupressuflavone (2), and two new furanone glucopyranosides, zabeliosides
A and B (3 and 4, resp.), along with two known biflavones, cupressuflavone (5) and
amentoflavone (6; Fig. 1), were isolated from the MeOH extract of the leaves of
Z. tyaihyonii. Herein, we report the isolation and structure elucidation of the new
compounds 1 – 4.
Results and Discussion. – Compound 1 was obtained as yellow amorphous powder.
The molecular formula, C31H20O11, was deduced from HR-ESI-MS (m/z 591.0899
([M þ Na]þ; calc. 591.0898)). The IR spectrum showed the presence of OH
1
(3291 cmÀ1) and C¼O (1647 cmÀ1) groups. The H- and 13C-NMR spectra (Table 1)
exhibited signals of two chelated OH groups (d(H) 13.15 (s, HOÀC(5)) and 13.12 (s,
HOÀC(5’’))), two C¼O groups (d(C) 182.5 (C(4,4’’))), one 1,4-disubstituted benzene
ring (d(H) 7.44 (d, J ¼ 9.0, HÀC(2’’’,6’’’)), 6.73 (d, J ¼ 9.0, HÀC(3’’’,5’’’)); d(C) 161.5
(C(4’’’)), 128.4 (C(2’’’,6’’’)), 121.7 (C(1’’’)), 116.3 (C(3’’’,5’’’))), two 1,2,3,4,5-pentasub-
stituted benzene rings (d(H) 6.33 (s, HÀC(6)), 6.34 (s, HÀC(6’’)); d(C) 164.2 (C(7,7’’)),
161.3 (C(5,5’’)), 155.2 (C(9,9’’), 104.0 (C(10’’)), 103.9 (C(10)), 99.5 (C(8,8’’)), 99.4
(C(6,6’’))), one 1,3,4-trisubstituted benzene ring (d(H) 6.96 (d, J ¼ 2.0, HÀC(2’)), 6.74
(d, J ¼ 8.5, HÀC(5’)), 7.22 (dd, J ¼ 8.5, 2.0, HÀC(6’)); d(C) 150.9 (C(4’)), 148.2 (C(3’)),
ꢀ 2015 Verlag Helvetica Chimica Acta AG, Zürich

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Helvetica Chimica Acta – Vol. 98 (2015)
Fig. 1. Structures of 1 – 6 isolated from Z. tyaihyonii
121.9 (C(1’)), 120.6 (C(6’)), 116.2 (C(5’)), 109.3 (C(2’)), and one MeO group (d(H) 3.62
(s); d(C) 55.7)). The remaining two olefinic signals (d(H) 6.83 (s, HÀC(3)) and 6.74 (s,
HÀC(3’’))) are characteristic of HÀC(3,3’’) of the flavone skeleton. The aforemen-
tioned data suggested that 1 could be a cupressuflavone derivative, a biflavonoid
consisting of two flavone units linked through a C(8)ÀC(8’’) bond, with a MeO group
[6][7]. In the HMBC spectrum of 1 (Fig. 2), the correlations HÀC(6)/C(5), HÀC(6)/
C(7), HÀC(6)/C(8), HOÀC(5)/C(5), HÀC(6’’)/C(5’’), HÀC(6’’)/C(7’’), HÀC(6’’)/
C(8’’), and HOÀC(5’’)/C(5’’) further confirmed the formation of the CÀC linkage of
the two flavone units between C(8) and C(8’’). The location of the MeO group at C(3’)
was determined by the HMBCs between the MeO H-atoms at d(H) 3.62 and C(3’) at
d(C) 148.2 (Fig. 2). The absolute configuration of 1 was elucidated on the basis of its
optical rotation and circular dichroism (CD) data [7 – 10]. Compound 1 showed a
negative optical rotation ([a]2D5 ¼ À38.0 (c ¼ 0.1, MeOH)), a positive Cotton effect at
362 nm, and a negative Cotton effect at 326 nm, indicating that 1 has an axially chiral
(aR)-8,8’-biflavone unit ((M)-configuration). Therefore, 1 was identified as (aR)-3’-
methoxycupressuflavone.
Compound 2 was obtained as yellow amorphous powder and had the molecular
formula C32H22O12, as determined by HR-ESI-MS (m/z 621.0999 ([M þ Na]þ; calc.
1
621.1003)). The H- and 13C-NMR spectra of 2 (Table 2) were similar to those of 1,

Helvetica Chimica Acta – Vol. 98 (2015)
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Table 1. 1H- and 13C-NMR Data (500 and 125 MHz, resp.; in (D6)DMSO) of 1. d in ppm, J in Hz.
Position
d(H)
d(C)
Position
d(H)
d(C)
2
3
4
5
–
163.7
103.0
182.5
161.3
99.4
2’’
3’’
4’’
5’’
6’’
–
163.9
103.1
182.5
161.3
99.4
6.83 (s)
–
–
6.74 (s)
–
–
6
6.33 (s)
6.34 (s)
7
8
–
–
164.2
99.5
7’’
8’’
–
–
164.2
99.5
9
10
1’
2’
3’
4’
5’
6’
–
–
–
155.2
103.9
121.9
109.3
148.2
150.9
116.2
120.6
55.7
9’’
–
–
–
155.2
104.0
121.7
128.4
116.3
161.5
116.3
128.4
–
10’’
1’’’
2’’’
3’’’
4’’’
5’’’
6’’’
5’’-OH
6.96 (d, J ¼ 2.0)
7.44 (d, J ¼ 9.0)
6.73 (d, J ¼ 9.0)
–
6.73 (d, J ¼ 9.0)
7.44 (d, J ¼ 9.0)
13.12 (s)
–
–
6.74 (d, J ¼ 8.5)
7.22 (dd, J ¼ 8.5, 2.0)
3.62 (s)
3-MeO
5-OH
13.15 (s)
–
Fig. 2. Key HMBCs of 1 and 3
except for the presence of an additional MeO group. However, the 1H- and 13C-NMR
data of 2 revealed a symmetrical structure with each half of the molecule, C16H11O6,
consisting of a 1,3,4-trisubstituted benzene ring, a 1,2,3,4,5-pentasubstituted benzene
ring, an olefinic group, and a MeO group. The location of the MeO groups at C(3’,3’’’)
was confirmed by the HMB correlation of the H-atoms of the MeO groups with
C(3’,3’’’). The C(8)ÀC(8’’) linkage of two flavones was further confirmed by the
HMBC cross-peaks HÀC(6,6’’)/C(5,5’’), HÀC(6,6’’)/C(7,7’’), HÀC(6,6’’)/C(8,8’’), and
HOÀC(5,5’’)/C(5,5’’). The absolute configuration of 2 was determined to be same as
that of 1 on the basis of similar optical rotation ([a]2D5 ¼ À37.8 (c ¼ 0.1, MeOH)) and
CD data, i.e., a positive Cotton effect at 362 nm and a negative Cotton effect at 326 nm.
Therefore, 2 was identified as (aR)-3’,3’’’-dimethoxycupressuflavone.

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Table 2. 1H- and 13C-NMR Data (500 and 125 MHz, resp.; in (D6)DMSO) of 2. d in ppm, J in Hz.
Position
d(H)
d(C)
2,2’’
3,3’’
4,4’’
5,5’’
6,6’’
–
163.7
103.1
182.5
161.3
99.4
6.88 (s)
–
–
6.42 (s)
7,7’’
8,8’’
–
–
164.0
99.3
9,9’’
–
–
–
155.2
104.0
121.9
109.3
148.2
151.0
116.2
120.6
55.7
10,10’’
1’,1’’’
2’,2’’’
3’,3’’’
4’,4’’’
5’,5’’’
6’,6’’’
3’,3’’’-MeO
7.01 (d, J ¼ 2.0)
–
–
6.77 (d, J ¼ 8.5)
7.28 (dd, J ¼ 8.5, 2.0)
3.63 (s)
Compound 3 was obtained as brown syrup with the molecular formula C20H22O10
from HR-ESI-MS data (m/z 445.1105 ([M þ Na]þ; calc. 445.1105)). The IR spectrum
1
showed the presence of OH (3336 cmÀ1) and C¼O (1647 cmÀ1) groups. The H- and
13C-NMR data of 3 (Table 3) exhibited resonances for a (2E)-p-coumaroyl group
(d(H) 7.59 (d, J ¼ 16.0, HÀC(8)), 7.56 (d, J ¼ 8.5, HÀC(2,6)), 6.80 (d, J ¼ 8.5,
HÀC(3,5)), 6.40 (d, J ¼ 16.0, HÀC(7)); d(C) 166.2 (C(9)), 160.4 (C(4)), 145.6
(C(7)), 130.8 (C(2,6)), 125.5 (C(1)), 116.3 (C(3,5)), 114.5 (C(8))), a (2,5-dihydro-5-
oxofuran-3-yl)methoxy group (d(H) 5.90 (s, HÀC(3’’)), 4.83 (br. s, CH2(5’’)), 4.68 – 4.69
(m, 1 H of CH2(1’’’)), 4.54 – 4.55 (m, 1 H of CH2(1’’’)); d(C) 173.5 (C(2’’)), 169.2
(C(4’’)), 114.5 (C(3’’)), 71.7 (C(5’’)), 64.6 (C(1’’’))) [11], and a glucose moiety (d(H)
4.56 (d, J ¼ 8.0, HÀC(1’)); d(C) 100.5 (C(1’)), 77.6 (C(4’)), 74.4 (C(3’)), 73.9 (C(2’)),
70.5 (C(5’)), 61.2 (C(6’))). Acid hydrolysis of 3 yielded b-d-glucose by GC/MS analysis.
The coupling constant J ¼ 8.0 of the anomeric H-atom indicated the b-configuration of
the glucose moiety. In the HMBC spectrum of 3 (Fig. 2), the anomeric H-atom (d(H)
4.56) correlated with C(1’’’) (d(C) 64.6), indicating the attachment of the (2,5-dihydro-
5-oxofuran-3-yl)methoxy moiety at C(1’). Moreover, the HMB correlation of HÀC(2’)
(d(H) 4.70) and C(9) (d(C) 166.2) corroborated that the (2E)-p-coumaroyloxy group
was located at C(2’) (Fig. 2). Therefore, 3 was determined to be (2,5-dihydro-5-
oxofuran-3-yl)methyl 2-O-[(2E)-p-coumaroyl]-b-d-glucopyranoside, and it was named
zabelioside A.
Compound 4 was obtained as brown syrup. The molecular formula, C20H22O10, was
1
deduced from HR-ESI-MS data (m/z 445.1103 ([M þ Na]þ; calc. 445.1105)). The H-
and 13C-NMR data of 4 (Table 3) were quite similar to those of 3, except for the
presence of a (2Z)-p-coumaroyl moiety instead of a (2E)-p-coumaroyl moiety. This was
supported by the coupling constant (J ¼ 12.5) and characteristic chemical shifts for
HÀC(7) and HÀC(8) (d(H) 5.78 and 6.89, resp.) of 4. Acid hydrolysis of 4 gave b-d-
glucose and the coupling constant (J ¼ 8.0) of the anomeric H-atom indicated the

Helvetica Chimica Acta – Vol. 98 (2015)
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Table 3. 1H- and 13C-NMR Data (500 and 125 MHz, resp.; in (D6)DMSO) of 3 and 4. d in ppm,
J in Hz.
Position
3
4
d(H)
d(C)
d(H)
d(C)
1
–
125.5
130.8
116.3
160.4
145.6
114.5
166.2
100.5
73.9
74.4
77.6
70.5
61.2
–
125.8
133.1
115.4
159.4
144.1
115.6
165.5
100.3
73.8
74.3
77.6
70.6
61.2
2,6
3,5
4
7
8
7.56 (d, J ¼ 8.5)
6.80 (d, J ¼ 8.5)
–
6.40 (d, J ¼ 16.0)
7.59 (d, J ¼ 16.0)
–
4.56 (d, J ¼ 8.0)
4.70 (dd, J ¼ 9.0, 8.0)
3.49 – 3.50 (m)
3.24 – 3.25 (m)
3.27 – 3.28 (m)
3.70 (dd, J ¼ 12.0, 2.0, Ha),
3.50 (dd, J ¼ 12.0, 6.0, Hb)
–
7.66 (d, J ¼ 9.0)
6.75 (d, J ¼ 9.0)
–
5.78 (d, J ¼ 12.5)
6.89 (d, J ¼ 12.5)
–
4.55 (d, J ¼ 8.0)
4.68 (dd, J ¼ 9.0, 8.0)
3.45 – 3.46 (m)
3.20 – 3.21 (m)
3.21 – 3.22 (m)
3.70 (dd, J ¼ 12.0, 2.0, Ha),
3.50 (dd, J ¼ 12.0, 6.0, Hb)
–
9
1’
2’
3’
4’
5’
6’
2’’
3’’
4’’
5’’
1’’’
173.5
114.5
169.2
71.7
173.5
114.5
169.1
71.6
5.90 (s)
–
5.91 (s)
–
4.83 (br. s)
4.68 – 4.69 (m), 4.54 – 4.55 (m)
4.83 (br. s)
4.66 – 4.67 (m), 4.55 – 4.56 (m)
64.6
64.5
b-configuration of the glucose moiety. The locations of the (2,5-dihydro-5-oxofuran-
3-yl)methoxy and (2Z)-p-coumaroyloxy groups were assigned at C(1’) and C(2’),
respectively, by the observed HMB correlations. Therefore, 4 was determined
to be (2,5-dihydro-5-oxofuran-3-yl)methyl 2-O-[(2Z)-p-coumaroyl]-b-d-glucopyrano-
side, and it was named zabelioside B.
The two known compounds were identified as cupressuflavone (5) [12 – 14] and
amentoflavone (6) [15][16] by comparison of their physicochemical and spectroscopic
data with those reported in the literature.
This study was supported by the Medical Research Center Program (2010 – 0029480) of the National
Research Foundation of Korea.
Experimental Part
General. Thin layer chromatography (TLC): silica gel 60 F254 aluminum plates (SiO2; Merck);
visualized by UV light at 254 nm and by spraying with 10% aq. H2SO4, followed by heating. Column
chromatograpy (CC): SiO2 (70 – 230 mesh; Merck). Prep. HPLC: Waters HPLC system; YMC Jꢀsphere
ODS-H80 column (150 Â 20 mm i.d., 4 mm); Waters 525 pump; Waters 2996 detector. Optical rotations:
Jasco DIP-1000 polarimeter. CD Spectra: Jasco J-715 spectropolarimeter; lmax (De) in nm. IR Spectra:
1
Jasco 4100 FT-IR spectrophotometer; KBr pellets; n˜ in cmÀ1. H- and 13C-NMR spectra: Bruker AMX-
500 spectrometer (500 and 125 MHz, resp.); in (D6)DMSO; d in ppm rel. to Me4Si as internal standard, J
in Hz. GC/MS: Agilent 6890/5973i apparatus; in m/z. HR-ESI-MS: Waters QTOF Micromass
spectrometer; in m/z.
Plant Material. Leaves of Z. tyaihyonii were collected from Yeongwol, Gangwon-do, Korea, in June
2012. A voucher specimen (NIBRVP0000366697) was authenticated by S.-Y. K. and deposited with the
Herbarium of the National Institute of Biological Resources, Korea.

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Helvetica Chimica Acta – Vol. 98 (2015)
Extraction and Isolation. Dried and powdered leaves of Z. tyaihyonii (150 g) were extracted with
MeOH (3 Â 3 l, overnight) at r.t., and the soln. was evaporated in vacuo. The residue was suspended in
H2O (1 l) and partitioned successively with hexane, CH2Cl2, and AcOEt (each 3 Â 1 l). The AcOEt-
soluble fraction (1.2 g) was subjected to CC (SiO2; hexane/CH2Cl2, CH2Cl2, and CH2Cl2/MeOH, gradient
system) to afford six fractions, Frs. 1 – 6. Fr. 3 (206 mg) was purified by prep. HPLC (MeCN/H2O 30 :70
to 80 :20; flow rate, 6 ml minÀ1) to give 1 (7.1 mg) and 2 (6.4 mg). Fr. 4 (240 mg) was further purified by
prep. HPLC (MeCN/H2O 40 :60 to 100 :0; flow rate, 6 ml minÀ1) to give 3 (13.7 mg), 4 (7.3 mg), 5
(5.4 mg), and 6 (2.3 mg).
Acid Hydrolysis of 3 and 4 and Determination of Sugar Components. Compounds 3 and 4 (3.0 mg)
were dissolved in 1n HCl (1 ml) and heated at 808 for 3 h. The solvent was removed under reduced
pressure, and each mixture was suspended in H2O and partitioned with AcOEt (3 Â 3 ml). The aq. layer
was evaporated in vacuo, and the residue (sugar portion) was dissolved in anh. pyridine (0.1 ml), and l-
cysteine methyl ester hydrochloride (0.06m, 0.1 ml) was added. After heating the mixture at 608 for 2 h,
NaBH4 (2.0 mg) was added, and the mixture was stirred for 1 h at r.t. Trimethylsilylimidazole soln.
(0.1 ml) was added, and the mixture was then heated at 608 for 2 h. The dried product was partitioned
with hexane and H2O, and the hexane layer was then analyzed by GC/MS on a DB 5 MS column
(0.25 mm  30 m, 0.25 mm; detector, FID; column temp., 2508; injector temp., 2808; detector temp., 2808;
carrier gas, He (1 ml minÀ1)). The hydrolysates of 3 and 4 showed peaks at tR 17.77 min, identical to that
of authentic b-d-glucose.
(aR)-3’-Methoxycupressuflavone (¼ 5,5’,7,7’-Tetrahydroxy-2-(4-hydroxy-3-methoxyphenyl)-2’-(4-hy-
droxyphenyl)-[8,8’-bi-4H-1-benzopyran]-4,4’-dione; 1). Yellow amorphous powder. [a]2D5 ¼ À38.0 (c ¼
0.1, MeOH). CD (MeOH): 267 (þ2.87), 326 (À 7.73), 362 (þ 3.02). UV (MeOH): 337 (3.89), 287
(3.98), 229 (4.17). IR: 3291, 2939, 1647, 1581, 1508, 1488, 1397, 1244, 1186. 1H- and 13C-NMR: see Table 1.
HR-ESI-MS: 591.0899 ([M þ Na]þ, C31H20NaO1þ1 ; calc. 591.0898).
(aR)-3’,3’’’-Dimethoxycupressuflavone (¼ 5,5’,7,7’-Tetrahydroxy-2,2’-bis(4-hydroxy-3-methoxyphen-
yl)-[8,8’-bi-4H-1-benzopyran]-4,4’-dione; 2). Yellow amorphous powder. [a]2D5 ¼ À37.8 (c ¼ 0.1, MeOH).
CD (MeOH): 267 (þ1.62), 326 (À4.94), 362 (þ1.40). UV (MeOH): 347 (3.87), 285 (3.97), 237 (4.18).
IR: 3305, 2939, 1679, 1542, 1508, 1417, 1022. 1H- and 13C-NMR: see Table 2. HR-ESI-MS: 621.0999
([M þ Na]þ, C32H22NaO1þ2 ; calc. 621.1003).
Zabelioside A (¼(2,5-Dihydro-5-oxofuran-3-yl)methyl 2-O-((2E)-p-Coumaroyl)-b-d-glucopyrano-
side; 3). Brown syrup. [a]2D5 ¼ À56.0 (c ¼ 0.1, MeOH). UV (MeOH): 314 (3.75). IR: 3336, 1647, 1397,
1019. 1H- and 13C-NMR: see Table 3. HR-ESI-MS: 445.1105 ([M þ Na]þ, C20H22NaO1þ0 ; calc. 445.1105).
Zabelioside B (¼(2,5-Dihydro-5-oxofuran-3-yl)methyl 2-O-((2Z)-p-Coumaroyl)-b-d-glucopyrano-
side; 4). Brown syrup. [a]2D5 ¼ À48.0 (c ¼ 0.1, MeOH). UV (MeOH): 309 (3.74). IR: 3292, 1711, 1629,
1362, 1024. 1H- and 13C-NMR: see Table 3. HR-ESI-MS: 445.1103 ([M þ Na]þ, C20H22NaO1þ0 ; calc.
445.1105).
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Received March 4, 2015