Flavonoids from Cephalaria gigantea flowers

Article abstract of DOI:10.1007/s10600-006-0250-z

Luteolin, quercetin, cinaroside, quercimeritrin, and the new flavonol bioside gigantoside A were isolated from Cephalaria gigantea (Ledeb.) Bobr. (Dipsacaceae) flowers. Spectral properties and chemical transformations established that gigantoside A had the structure quercetin-7-O-[α-L- arabinopyranosyl(1→6)]-β-D-glucopyranoside.

Full text of DOI:10.1007/s10600-006-0250-z

Chemistry of Natural Compounds, Vol. 42, No. 6, 2006
FLAVONOIDS FROM
FLOWERS
Cephalaria gigantea
I. S. Movsumov,1 E. A. Garaev,1 and M. I. Isaev2
UDC 547.944/945
Luteolin, quercetin, cinaroside, quercimeritrin, andthenewflavonolbiosidegigantosideAwere isolatedfrom
Cephalaria gigantea
(Ledeb.)Bobr. (Dipsacaceae)flowers. Spectralpropertiesandchemicaltransformations
O α
→
β
established that gigantoside A had the structure quercetin-7- -[ -L-arabinopyranosyl(1 6)]- -D-
glucopyranoside.
Key words:
(Ledeb.) Bobr., Dipsacaceae, flavonoids, luteolin, quercetin, cinaroside,
Cephalaria gigantea
1
13
quercimeritrin, gigantoside A, H and C NMR spectra, DEPT, 2D NMR (COSY, HMQC, HMBC, NOESY).
In continuation of phytochemical research on plants of the genus
(Schrad.) growing in the Republic of
Cephalaria
Azerbaidzhan [1-5], we studied
(Ledeb.) Bobr. (Dipsacaceae). Luteolin (1), quercetin (2), cinaroside (3),
C. gigantea
quercimeritrin (4), and a new bioside of quercetin, which we named gigantoside A (5), were isolated and identified from flowers
of this plant. Herein we report the structure of the last of these.
OH
OH
OH
12
O
CH
2
9
2
O
7
HO
O
11
RO
O
O
O
O
OH
OH
2, 4
OH
4
15
10
OH
R
5
1
HO
OH
O
OH
OH
OH
1 - 4
5
1: R = R1 = H
3: R = β-D-Glcp, R1 = H
2: R = H, R1 = OH 4: R = β-D- Glcp, R1 = OH
Acid hydrolysis of the new flavonoid glycoside 5 formed the genin, which was identified as quercetin (2). Paper
chromatography (PC) of the carbohydrate part of the hydrolysate detected D-glucose and L-rhamnose.
13
According to the PMR and C NMR spectra of 5 (Table 1), which contained a single set of H and C signals for the
carbohydrate units, the new glycoside was a bioside of quercetin and contained D-glucose and L-arabinose in a 1:1 ratio.
The anomeric protons in the PMR spectrum of 5 in deuteropyridine resonated as doublets at δ 5.63 with SSCC
J = 7.6 Hz (H-1 of D-glucose) and 4.90 with SSCC J = 6.4 Hz (H-1 of L-arabinose). These values indicated that the
4
monosaccharide units had the pyranose form, the C -conformation, and therefore the β- and α-configuration, respectively
1
[6, 7].
The chemical shifts of the anomeric C atoms of δ 101.92 (100.24) (values in DMSO-d in parentheses) for
6
β-D-glucopyranose and δ 104.91 (103.50) for α-L-arabinose indicated that 5 was a monodesmoside and the pentose was the
terminal monosaccharide.
The HMBC spectrum of 5 (Table 1) contained a correlation peak between the signals of the anomeric proton of the
β-D-glucopyranoside and C-7 of the genin. This unambiguously determined the attachment site at this position of quercetin.
As expected, stepwise hydrolysis of 5 formed the progenin 4, which was identical to quercimeritrin.
1) Azerbaidzhan Medical University, Pharmaceutical Department, Baku, ul. A. Bakikhanova, 23, e-mail:
eldargar@mail.ru; 2) S. Yu. Yunusov Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of
Uzbekistan, Tashkent, fax (99871) 120 64 75, e-mail: m_isaev@rambler.ru. Translated from Khimiya Prirodnykh Soedinenii,
No. 6, pp. 552-554, November-December, 2006. Original article submitted June 3, 2006.
0009-3130/06/4206-0677 ©2006 Springer Science+Business Media, Inc.
677

TABLE 1. Chemical Shifts of H and C Atoms of 5, DEPT Data, and Parameters of 2D NMR 1H-1H COSY, HMQC, HMBC,
and NOESY (δ, ppm, J/Hz, C5D5N and DMSO-d6, 0 = TMS)
Data in Py-d5
Data in DMSO-d6
C atom
DEPT
HMBC
(C atoms)
HMBC
(C atoms) (H atoms)
NOESY
δC
δH (J/Hz)
δC
δH (J/Hz)
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
C
C
C
C
CH
C
CH
C
C
C
CH
C
148.50*
137.84
176.98
161.54
99.57
-
-
-
-
148.32
136.49
176.42
160.78
99.27
-
-
-
-
6.77 d (2.1)
5, 7, 8, 10
6, 7, 9, 10
6.44 d (1.9)
5, 7, 8, 10
163.49
94.70
-
163.02
94.73
-
7.00 d (2.1)
6.77 d (1.9)
7, 9, 10, Gl
Gl
156.50
105.83
123.30*
116.43
146.69
148.28
116.34
121.22
-
-
-
156.19
105.17
122.24
116.11
145.44
148.13
115.80
120.70
-
-
-
8.61 d (2.2)
2, 13, 14, 16
7.73 d (2)
2, 13, 14, 16
-
-
-
-
C
CH
CH
7.41 d (8.5)
8.15 dd (8.5, 2.2)
11, 13, 14
2, 12, 15
6.92 d (8.5)
7.59 dd ( 8.5, 2)
11, 13, 14
2, 12, 14
16
15
β-D-Glcp (G)
1
2
3
4
5
6
CH
CH
CH
CH
CH
CH2
101.92
74.37
77.96
70.86
77.18
68.91
5.63 d (7.6)
7
100.24
73.49
76.50
69.78
75.94
67.94
5.08 d (7)
7
8
4.16
4.28
4.21
3.30
3.25
3.20
G5
4.24
3.56
4.77** (9.5), 4.26
3.95 d (10.2), 3.56
α-L-Arap (A)
1
2
3
4
5
CH
CH
CH
CH
CH2
104.91
71.98
73.92
68.63
65.86
4.90 d (6.4)
4.49 dd (8, 6.5)
4.14
4.25
3.67** (11.3),
4.25
G6
A1, A3
103.50
70.94
72.90
67.66
65.16
4.17 d (6)
3.40
3.30
3.40
3.25,
3.62
G6
A1, A3
A1
A1
A3
______
*Position of signals found from HMBC spectrum.
**Broadened doublets. Chemical shifts of protons without multiplicities and SSCC were found from 2D spectra.
13
The attachment site of L-arabinose was also found using the HMBC spectrum and the C NMR spectrum of the new
13
flavonoid glycoside. Atom C-6 of D-glucose underwent a glycosylation effect in the C HMR spectrum and was observed at
δ 68.91 (67.94), indicating attachment of L-arabinose to this atom. We note that unglycosylated C-6 of D-glucose resonates
around δ 62-63. The attachment site of L-arabinose was confirmed by the HMBC spectrum, where a cross-peak was observed
between the signals of the anomeric proton of L-arabinose and C-6 of D-glucose.
Thus, the experimental results lead to the conclusion that gigantoside A has the structure quercetin-7- -[α-L-
O
arabinopyranosyl(1→6)]-β-D-glucopyranoside.
13
An analysis of the C NMR spectra of quercetin [8], quercimeritrin [8], and gigantoside A indicated that C-7 had a
small (up to -1.3 ppm) negative α-effect of glycosylation; C-9, an interesting γ-effect that was significant and also negative (up
to -5 ppm).
678

EXPERIMENTAL
General Comments. Paper chromatographywas performed on Filtrak No. 11 paper using n-butanol:acetic acid:water
(4:1:5) and n-butanol:pyridine:water (6:4:3). Free monosaccharides were detected using anilinium phthalate. UV spectra were
recorded on an SF-46 spectrophotometer. NMR (1D and 2D) spectra were obtained on a Bruker AM-300 spectrometer in
deuteropyridine (Py-d ) and DMSO-d (δ, 0 = TMS). Water of crystallization was determined on a Q-1500D DTA
5
6
(Paulik—Erdey—Paulik System).
Isolation of Flavonoids from C. gigantea Flowers. Air-dried flowers (1 kg) were collected during full flowering on
July 10, 2005, in Rustam Aliev of Kedabek Region in the Republic of Azerbaidzhan and extracted twice with ethanol (80%)
on a water bath for 3 h. The extracts were condensed to the watery residue and treated successively with CHCl and ether.
3
Fractional crystallization of the ether extract from ethanol afforded pure luteolin (1) and quercetin (2).
The mother liquor was evaporated to half the volume and shaken with an equal volume of CHCl . Cinaroside (3)
3
crystallized at the interface after one day.
Then the mother liquor was extracted with ethylacetate and n-butanol. The ethylacetate extract afforded
quercimeritrin (4).
The butanol extract was evaporated to dryness and treated with hot ethanol to isolate gigantoside A (5).
A Bryant cyanidine test indicated that 1 and 2 were genins; 3-5, glycosides.
Luteolin (1), C H O , mp 328-330°C (ethanol). UV spectrum (MeOH, λ , nm): 353, 265; (CH COONa, λ ,
max
15 10
6
max
3
nm): 373, 370.
Quercetin (2), C H O , yellow needles, mp 307-309°C (ethanol). UV spectrum (MeOH, λ , nm): 370, 256;
15 10
7
max
(CH COONa, λ , nm): 380, 258.
3
max
Cinaroside (3), C H O , yellow crystals, mp 256-258°C (ethanol), [α] -52° (c 0.5, pyridine:methanol, 4:2). UV
21 20 11
D
spectrum (MeOH, λ , nm): 352, 257 (264); (CH COONa, λ , nm): 350, 258. Quantitative hydrolysis (H SO , 5%) for
max
3
max
2
4
4 h of 3 formed luteolin (68.2%) and D-glucose.
Quercimeritrin (4), C H O , yellowcrystals, mp 254-255°C (ethanol), [α] -56° (c 0.24, pyridine:methanol, 4:2).
21 20 12
D
UV spectrum (MeOH, λ , nm): 372, 256; (CH COONa, λ , nm): 350, 256. Acid hydrolysis of 4 formed quercetin (68%)
max
3
max
and D-glucose.
Compounds 3 and 4 were isolated previouslyfrom C. Kotschyi Boriss. et Hoh. [3]. These same glycosides were isolated
from C. gigantea (Ledeb.) Bobr. growing in the northern Caucuses [9].
Gigantoside A (5), C H O ·H O, lemon-yellow crystals, soluble in water and ethanol, very soluble in aqueous
26 28 16
2
ethanol, insoluble in ether, mp 220-222°C (ethanol), [α] -45.2° (c 0.52, DMF). UV spectrum (MeOH, λ , nm): 360, 260;
D
max
(CH COONa, λ , nm): 358, 262; (CH COONa + H BO , λ , nm): 384, 266.
3
max
3
3
3
max
13
Table 1 gives the PMR and C NMR spectra.
Thermal analysis established that 5 contained one water of crystallization. The determination of the water of
crystallization was made at the Institute of Chemical Problems, National Academy of Sciences, Republic of Azerbaidzhan, by
Candidate of Chemical Sciences N. S. Osmanov.
Quercetin (2) from 5. Gigantoside A (50 mg) was hydrolyzed by H SO (20 mL, 5%) on a water bath for 4 h. The
2
4
precipitate that formed on cooling was filtered off, washed with water until the washings were neutral, and chromatographed
over a column of cellulose with elution by ethylacetate to isolate the aglycon (24 mg), which was identified as quercetin.
The carbohydrate part of the hydrolysate was neutralized by BaCO and evaporated. PC of the solid using system 2
3
identified D-glucose and L-arabinose.
Stepwise Hydrolysis of 5. Compound 5 (100 mg) was dissolved in HCl (30 mL, 1%), heated on a water bath for about
1 h, cooled, and extracted with ethylacetate. After the usual work up, the ethylacetate extract was chromatographed over a
column of polyamide with elution by water to isolate starting 5.
Continued elution byethanol (30%) afforded progenin 4, mp 248-250°C (ethanol), [α] -50° (c 0.6, pyridine:ethanol,
D
3:2), which was identified as quercimeritrin.
The hydrolysate was neutralized and concentrated. PC using system 2 detected L-arabinose.
679

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2.
3.
4.
5.
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680