Two new biflavonones from Coreopsis tinctoria

Article abstract of DOI:10.1080/10286020.2017.1307833

Two new biflavonone compounds, sikokianin D (1) and sikokianin E (2), were isolated from the capitulum of Coreopsis tinctoria. The structures of these compounds were elucidated by spectroscopic techniques including NMR, HRESIMS and circular dichroism (CD)

Full text of DOI:10.1080/10286020.2017.1307833

Journal of Asian Natural Products Research
ISSN: 1028-6020 (Print) 1477-2213 (Online) Journal homepage: http://www.tandfonline.com/loi/ganp20
Two new biflavonones from Coreopsis tinctoria
Ren-Jie Yan, Mo-Ying Li, Hai-Feng Zhou, De-Yun Kong & Tong Wu
To cite this article: Ren-Jie Yan, Mo-Ying Li, Hai-Feng Zhou, De-Yun Kong & Tong Wu (2017):
Two new biflavonones from Coreopsis tinctoria, Journal of Asian Natural Products Research, DOI:
10.1080/10286020.2017.1307833
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Date: 06 April 2017, At: 01:42

Journal of asian natural Products research, 2017
http://dx.doi.org/10.1080/10286020.2017.1307833
Two new biflavonones from Coreopsis tinctoria
Ren-Jie Yan, Mo-Ying Li, Hai-Feng Zhou, De-Yun Kong and Tong Wu
state Key laboratory of new drug & Pharmaceutical Process, shanghai institute of Pharmaceutical industry,
shanghai 200040, china
ABSTRACT
ARTICLE HISTORY
received 31 March 2016
accepted 14 March 2017
Two new biflavonone compounds, sikokianin D (1) and sikokianin
E (2), were isolated from the capitulum of Coreopsis tinctoria. The
structures of these compounds were elucidated by spectroscopic
techniques including NMR, HRESIMS and circular dichroism (CD).
KEYWORDS
compositae; Coreopsis
tinctoria; biflavonones;
chemical constituents
1. Introduction
Coreopsis tinctoria is an annual plant that belongs to Chrysanthemum family. It grows in
the Karakorum Mountains at an altitude of above 3000 m in southern Xinjiang of China
[1]. Its capitulum has been consumed as tea, and generally used as folk medicine in treating
diabetes, hyperlipaemia, and hypertension because of its effects in reducing blood pressure
and vasorelaxant [2–5], as well as antioxidant [6] and anti-coagulating activities [7]. Several
flavonoids, phenolic acids [8], bisabolane-type sesquiterpenoids [9], and C14-polyacetylene
glycosides [10] were reported from this plant previously. Considering its notable pharma-
cological properties, we made a phytochemical research on the capitulum and obtained two
novel biflavonones, sikokianin D (1) and sikokianin E (2) (Figure 1). Herein, we report the
isolation and structure elucidation of 1 and 2.
CONTACT tong Wu
wu.tong@sipi.com.cn
© 2017 informa uK limited, trading as taylor & francis Group

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R.-J. YAN ET AL.
Figure 1. structures of compounds 1 and 2.
Table 1. 1h nMr (400 hz) and 13c nMr (100 hz) spectral data of compounds 1 and 2 in dMso-d6 (δ in
ppm).
1
2
Position
δH
δC
δH
δC
2,2′′′
3,3′′′
5.72 d (12.0)
2.66 d (12.0)
84.3
51.0
5.72 d (12.0)
2.66 d (12.0)
84.3
50.9
4,4′′′
5,5′′′
6,6′′′
7,7′′′
8,8′′′
9,9′′′
10,10′′′
1′,1′′′′
2′,2′′′′
3′,3′′′′
4′,4′′′′
5′,5′′′′
6′,6′′′′
1′′,1′′′′′
2′′,2′′′′′
3′′,3′′′′′
4′′,4′′′′′
5′′,5′′′′′
6′′,6′′′′′
–
191.7
117.1
109.5
151.1
135.2
150.4
116.4
127.5
115.8
145.4
146.3
115.8
118.6
101.7
73.3
–
7.21 d (8.8)
6.88 d (8.8)
–
191.7
117.0
109.7
151.1
135.2
150.5
116.5
127.5
115.8
145.4
146.3
115.7
118.6
101.6
73.3
7.22 d (8.8)
6.88 d (8.8)
–
–
–
–
–
–
–
–
–
6.59 s
–
–
6.58 d (2)
–
–
6.75 d (8.0)
6.34 d (8.0)
4.82 d (6.8)
3.28–3.30, m
3.28–3.30, m
3.20–3.22, m
3.38–3.40, m
3.49, dd (11,5.5)
3.73,brd (11)
6.75 d (8.8)
6.34 d (8.8, 2.0)
4.83 d (6.8)
3.28–3.30, m
3.28–3.30, m
3.20–3.22, m
3.38–3.40, m
3.49, dd (11,5.5)
3.72,brd (11)
75.9
69.9
77.4
60.8
76.0
69.9
77.4
60.9
2. Results and discussion
Compounds 1 and 2 were obtained as brown amorphous powder. e molecular formula,
C42H42O22, was deduced from HR-ESI-MS (m/z 897.2064 [M–H]−; calcd. 897.2089). e
chemical reaction with HCl–Mg reagent indicated that 1 is a flavonoid. e IR spectrum
showed the presence of OH groups (3409 cm−1), conjugated C=O groups (1670 cm−1), and
aromatic rings (1619 and 1522 cm−1). e UV spectrum showed a maximum absorption at
290 nm, which is characteristic of a flavonone. By analysis of 13C-NMR data, the presence
of two C=O at δC 191.7 was established. e C (2 and 2′′′) at δC 84.3, and C (3 and 3′′′) at δC
51.0 signals in the 13C-NMR spectrum suggested that 1 consisted of two flavonone units [11].
e 1H-NMR spectrum (Table 1) showed two methine groups (δH 5.72, 2H, d, J = 12.0 Hz;
δH 2.66, 2H, d, J = 12.0 Hz) in the rings C and C′′′ of biflavanone. e ten aromatic H-atom

JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH
3
Figure 2. Key hBMc correlations for compound 1.
signals (δH 6.34–7.22) indicated the presence of two sets of typical 7, 8-dioxygenated A
and A′′′ rings at δH 7.22 (2H, d, J = 8.8 Hz) and δH 6.88 (2H, d, J = 8.8 Hz), and two sets
of ABX spin system attributed to 1,3,4-trisubstituted aromatic B and B′′′ rings at δH 6.59
(2H, brs), 6.75 (2H, d, J = 8.0 Hz) and δH 6.34 (2H, d, J = 8.0 Hz). Linkage of the B ring
to the C ring was established at C (2 and 2′′′) by HMBC experiment (Figure 2), in which
H–C (2′ and 2′′′′) at δH 6.59 (2H, s) and H–C (6′and 6′′′′) at δH 6.34 (2H, d, J = 8.0 Hz)
correlated with C (2 and 2′′′) at δC 84.3. e presence of signals of H–C (3 and 3′′′) at δH
2.66 (2H, d, J = 12.0 Hz) showed that 1 has a structure dimerized at the C-3 position of the
two flavonone units [12,13]. Additionally, a series of typical signals of sugar residues were
recognized, including the anomeric H-atom at δH 4.82 (2H, d, J = 6.8 Hz), which revealed
a β-configuration present in the sugar residue on the basis of the coupling constant [14].
e sugar residues of 1 and 2 were determined as D-glucose by acid hydrolysis and further
GC analysis of its corresponding acetylated derivative [15]. Appearance of two peaks in
HPLC spectrum suggested that 1 and 2 are possible to have different absolute configura-
tions (Figure 3). e comparison of the NMR data between 1 and 2 revealed they had the
same planar structure, indicating they should be stereoisomers. e J-values of H–C (2
and 2′′′) at δH 5.72 (2H, d, J = 12.0 Hz) and H–C (3 and 3′′′) at δH 2.66 (2H, d, J = 12.0 Hz)
suggested 1 and 2 both have the trans-trans configurations [11]. In order to establish the
absolute configurations at C-2 and C-3 in 1 and 2, the circular dichroism curves of 1 and
2 were measured. e CD data of 1 exhibited two strong Cotton effects at 329 nm (Δε =
+ 13.889) corresponding to n→π* transition and at 290 nm (Δε = −25.359) corresponding to
π→π* transition for the carbonyl groups. e positive sign of the former predicted the con-
figuration 2S, 3R for 2, 3-diequatorial substituents (J = 12.0 Hz) on basis of the octant rule,
modified for aryl ketones [16,17]. e structure of 1 was elucidated to be (2S*, 2′′′S*, 3R*,
3′′′R*)-[3, 3′′′-bi-4H-1-benzopyran]-4, 4′′′- dione, 7, 7′′′-bis (β-D-glucopyranosyloxy)- 2,
2′′′, 3, 3′′′-tetrahydro-8, 8′′′-dihydroxy-2, 2′′′-bis (3′,4′-hydroxyphenyl), and named sikoki-
anin D. Differently, the CD of 2 showed mesomeric effects, at 329 nm (Δε = + 0.184) and
at 290 nm (Δε = + 0.010), indicating that the aglycone of 2 was meso-form [18]. us, e
structure of 2 was identified as (2S*, 2′′′R*, 3R*, 3′′′S*)-[3, 3′′′-bi-4H-1-benzopyran]-4,
4′′′-dione, 7, 7′′′-bis (β-D-glucopyranosyloxy)-2, 2′′′, 3, 3′′′-tetrahydro-8, 8′′′-dihydroxy-2,
2′′′-bis (3′, 4′-hydroxyphenyl), and named sikokianin E.

4
R.-J. YAN ET AL.
Figure 3. the hPlc analysis of 1 and 2.
3. Experimental
3.1. General experimental procedures
Optical rotations were determined with a Perkin-Elmer-341 polarmeter (Perkin-Elmer,
San Jose, CA, U.S.A). UV-vis spectra were recorded using a Techcomp 8500 spectrometer
(Techcomp, Shanghai, China). IR spectra were recorded in KBr pellets on a Nicolet-NEXUS-
670-FTIR spectrophotometer (Nicolet, Madison, WI, U.S.A). NMR spectra were obtained
with a Varian INOVA-400/500 instrument (Varian, Palo alto, CA, U.S.A). e 1H and 13
C
NMR chemical shifs were relative to solvent signals at δH/C 2.49/39.5 (DMSO-d6), using
tetramethylsilane as internal standard. MS was measured on a Waters Q-Tof micro Ya019
mass spectrometer (Waters, Lee-derville, WA, U.S.A). CD spectra were measured by MOS
450 detector (Bio-Logic Co., Claix, France). Preparative HPLC was obtained on a Shimadzu
HPLC system consisting of two LC-8A pumps and an SPD-M10A detector. For preparative
purposes, a Shimadzu PRC-ODS (15 μm, i.d. 20 mm × 250 mm, Shimadzu, Kyoto, Japan)
was used. Analytical HPLC was carried out on Agilent Technologies 1260 Infinity Series LC
system (U.S.A) equipped with a binary pump, DAD detector and chromatographic column
(4.6 × 250 mm; 5 μm; Xridge C-18 column; Waters; Milford, U.S.A). Analytical GC was
carried out on Agilent 6890N system (H2 flame ionization detector; Agilent Minneapolis,
MN, U.S.A) and a capillary column (30 m × 0.32 mm × 0.25 μm; Abel AB-5; Appleton, WI,
U.S.A). Column chromatography (CC) was carried out on silica gel (100–200 or 200–300
mesh; Shanghai Sanpont Co., Ltd, Shanghai, China), D101 macroporous resin (Cangzhou

JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH
5
Bon Adsorber Technology Co., Ltd, Cangzhou, China), C18 reversed-phase silica gel (50
mesh, YMC Co., Ltd, Kyoto, Japan). Silica gel HSGF254 (Yantai Jiangyou Guijiao Kaifa Co.,
Ltd, Yantai, China) was used for thin layer chromatography (TLC). Fractions were moni-
tored by TLC on silica-gel plates sprayed with 10% H2SO4 in EtOH, followed by heating.
3.2. Plant material
e capitula of Coreopsis tinctoria were collected in August 2012 in Xinjiang Uygur Autonomous
Region of China. e plant was identified by Prof. Deyun Kong, Shanghsai Institute of
Pharmaceutical Industry, China, and the voucher specimen (NO. 20121201) was deposited at
the Herbarium of the Shanghsai Institute of Pharmaceutical Industry, China. e search for
chemical constituents from C. tinctoria has been an ongoing project in our laboratory.
3.3. Extraction and isloation
e powder of dried capitula (2 kg) was extracted with water under reflux for 3 h (1–20 L).
e water extract was subjected to macroporous adsorption resin (D101) chromatography
column and eluted with H2O, 30, 50, 70, and 95% EtOH to obtain five fractions (Fr.1~5).
Fr.2 (30% EtOH, 132 g) was subjected to polyamide column chromatography (CC) and
eluted with H2O/EtOH (100:0–5:95, v/v) to obtain five fractions (Fr.2-1~Fr.2-5). Fr.2-2 (30%
EtOH, 56 g) was subjected to silica gel CC with elution of a gradient of petroleum ether-ethyl
acetate, followed by EtOAc–MeOH gradient, to afford ten fractions (Fr.2-2-1~Fr.2-2-10).
Fr.2-2-6 (1.3 g) was subjected to C18 reversed-phase silica gel with elution of a gradient
of H2O/MeOH (95:5–30:70) to afford nine fractions (Fr.2-2-6-1~Fr.2-2-6-9). Fr.2-2-6-2
(90 mg) was separated by semipreparative reversed-phase (RP) HPLC (acetonitrile/H2O,
18:82, v/v; 3 ml/min) to afford 1 (7 mg, tR: 12 min) and 2 (8 mg, tR: 18 min).
3.3.1. Compound 1
A brown amorphous powder; [ꢀ]D20 + 20.3 (c 0.08, H2O). UV (H2O) λmax (log ε) nm: 290
(4.35); IR (KBr) νmax cm−1: 3409, 3344, 1670, 1619, 1522, 1461, 1367, 1322, 1265, 1211,
1
1190, 1083, 1063, 989, 892, 781, 634, 576 cm−1; for H and 13C NMR spectral data, see
Table 1; HR-ESI-MS: m/z 897.2064 [M–H]− (calcd for C42H41O22, 897.2089). CD (H2O)
Δε329 nm +13.889, Δε290 nm −25.359, Δε224 nm +46.178.
3.3.2. Compound 2
A brown amorphous powder; [ꢀ]D20 + 68.5 (c 0.08, H2O). UV (H2O) λmax (log ε) nm: 290
(4.29); IR (KBr) νmax cm−1: 3408, 3344, 1670, 1619, 1522, 1461, 1367, 1322, 1265, 1223,
1
1190, 1083, 1063, 989, 892, 781, 634, 576; for H and 13C NMR spectral data, see Table
1; HR-ESI-MS: m/z 897.2072 [M–H]− (calcd for C42H41O22−, 897.2089). CD (H2O)
Δε329 nm +0.184, Δε290 nm +0.010, Δε224 nm +0.008.
3.4. Acid hydrolysis of 1 and 2
Compounds 1 and 2 (5 mg each) were refluxed in 2 mol/L HCl (2 ml) for 3 h. e mixture
was neutralized with NaHCO3 and then partitioned with ethyl acetate. To the dried aque-
ous layer, pyridine and acetic anhydride (1 ml each) were added, and the mixture was kept

6
R.-J. YAN ET AL.
overnight. e acetylated derivatives were subjected to GC analysis to identify the sugars.
Conditions for GC: AB-5 (30 m × 0.32 mm × 0.25 μm) column; column temp.: from 100
to 250 °C, programmed increase 10 °C/min and keeping 250 °C for 5 min; injector and
detector temp., 250 °C; injection volume, 2.0 ml; split ratio, 1:20; carrier gas, N2 at 1 ml/
min [15]. D-glucose (tR: min) was detected from 1 and 2 (identical to authentic materials).
3.5. HPLC analysis of 1 and 2
Around 2 mg of compound 1, 2 and two compounds mixture were dissolved in 1.0 ml
of mobile phase and filtered through a Millipore (0.45 μm) filter prior to injection.
Chromatographic analysis was conducted at 30 °C and a flow rate of 1 ml/min. e mobile
phase consisted of acetonitrile (A) and 0.1% phosphoric acid in water (B); the eluting gra-
dient was used as follows: 0–30 min, 14.0% (A).
Disclosure statement
No potential conflict of interest was reported by the authors.
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