Flavonoid galacturonides and glucuronide from the aerial part of Scutellaria schachristanica

Full text of DOI:10.1007/s10600-013-0519-y

Chemistry of Natural Compounds, Vol. 49, No. 1, March, 2013 [Russian original No. 1, January–February, 2013]
FLAVONOID GALACTURONIDES AND GLUCURONIDE
FROM THE AERIAL PART OF Scutellaria schachristanica
1*
1
2
K. A. Eshbakova, Z. O. Toshmatov, A. Yili,
UDC 547.972
2
1
H. A. Aisa, and N. D. Abdullaev
In continuation of our chemistry research on flavonoids from plants of the genus Scutellaria (Lamiaceae) [1–3], we
isolated four compounds 1–4 of flavonoid nature from the EtOAc fraction of the aerial part of the indigenous species
S. schachristanica Juz.
OH
COOH
R
1
O
3'
1
O
O
9
7
1'
HO
R
2
OH
3
5'
10
1: R = H, R = OH
1
2
5
2: R = R = OH
OH
O
1
2
3: R = R = H
1 - 3
1
2
13
The structures of the isolated compounds were elucidated using UV, IR, PMR, C NMR, DEPT, HSQC, HMBC, and
COSY spectroscopy and mass spectrometry.
Compound 1 was a greenish-yellow powder. The UV spectrum of 1 (MeOH, ꢀ , nm: 205.5, 268.5, 333.5) was
max
characteristic of flavone derivatives. The PMR spectrum exhibited resonances characteristic of the spectrum of apigenin,
a resonance for an anomeric proton, and resonances for other carbohydrate protons. Therefore, 1 was a flavonoid glycoside.
Acid hydrolysis of 1 produced apigenin with mp 347.2°C [1] and D-galacturonic acid (PC with an authentic sample).
13
The presence of the latter was confirmed by a resonance for a COOH group at 171.75 ppm in the C NMR spectrum and PMR
spectral data (Table 1).
The sugar anomeric proton in the PMR spectrum of the glycoside of 1 resonated as a doublet at ꢁ 5.05 ppm with
4
SSCC J = 7.8 Hz, indicating that monosaccharide units had the pyranose form, C -conformation, and ꢂ-configuration [3].
1
A correlation peak between resonances of the anomeric proton and C-7 of the genin was observed in the HMBC
spectrum of 1 (Table 1). This determined unambiguously the attachment site at this same position of apigenin.
Thus, 1 was apigenin 7-O-ꢂ-D-galacturonide [4]. A flavonoid with a galacturonide, nepetoside A (norwogonin-7-O-
ꢂ-D-galacturonide), was isolated earlier from S. nepetoides [5].
13
Compound 2 was also a flavonoid glycoside according to PMR and C NMR spectral data (Table 1).
Acid hydrolysis of 2 formed luteolin [6] and D-galacturonic acid.
A correlation peak between resonances of the anomeric proton and C-7 of the genin in the HMBC spectrum indicated
unambiguously that the D-galacturonic acid was bonded to the C-7 position.
Thus, according to the combined analyses, physicochemical properties, and literature data, 2 was identified as luteolin-
7-O-ꢂ-D-galacturonide [4].
13
Compound 3 was a glycoside of chrysin according to the spectral data (Table 1). The C NMR spectrum contained
a resonance for a COOH group at ꢁ 172.00 ppm. However, the R values and solubilities of 3 and chrysin-7-O-ꢂ-D-glucuronide,
f
which was isolated previously by us [2], differed. Compound 3 turned out to be much more polar than chrysin-7-O-ꢂ-D-
glucuronide.
1) S. Yu. Yunusov Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan,
100170, Tashkent, fax: (99871) 120 64 75, e-mail: e_komila@yahoo.com; 2) Xinjiang Key Laboratory of Plant Resources and
Natural Products Chemistry, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi
830011, P. R. China. Translated from Khimiya Prirodnykh Soedinenii, No. 1, January–February, 2013, pp. 92–93. Original
article submitted April 28, 2012.
©
0009-3130/13/4901-0103 2013 Springer Science+Business Media New York
103

13
TABLE 1. PMR and C NMR Spectra of 1–3 (DMSO-d , ꢁ, ppm, J/Hz)
6
1
2
3
C atom
HMBC
10
HMBC
ꢁÑ
ꢁÍ
ꢁÑ
ꢁÍ
ꢁÑ
ꢁÍ
2
3
4
5
6
7
8
164.28
102.68
181.84
160.89
99.56
162.96
94.52
164.81
101.93
181.51
160.96
99.51
162.89
94.46
3, 2ꢄ, 6ꢄ
10
163.87
105.91
182.15
161.10
100.25
162.85
95.33
6.76 s
6.64 s
7.04 s
ÎÍ, 12.95 s
6.40 (d, J = 1.8)
6
6
7, 5
7, 5
6.39 (d, J = 1.2)
6.75 (d, J = 1.2)
6.46 (d, J = 1.8)
6.87 (d, J = 1.8)
1', 6, 8
1', 6, 8
10
6.76 (d, J = 1.8)
9
156.85
105.16
120.39
128.29
115.92
161.77
115.92
128.29
156.83
105.12
125.10
112.11
146.44
149.00
115.73
119.50
157.2
10
1ꢄ
2ꢄ
3ꢄ
4ꢄ
5ꢄ
6ꢄ
105.94
131.10
126.85
129.62
132.59
129.72
126.93
7.85 (d, J = 8.4)
6.88 (d, J = 8.4)
7.36 br.s
8.09 (d, J = 6.6)
7.59 m
7.59 m
7.59 m
8.09 (d, J = 6.6)
2ꢄ, 5ꢄ
2ꢄ, 5ꢄ
2ꢄ
6.88 (d, J = 8.4)
7.85 (d, J = 8.4)
6.76 (d, J = 8.4)
7.39 (dd, J = 1.2; 8.4)
ꢂ-D-Gal unit
p
1ꢄꢄ
2ꢄꢄ
3ꢄꢄ
99.56
72.91
76.51
71.94
73.60
171.75
5.05 (d, J = 7.8)
3.29 m
3.30 m
3.20 m
3.6 (d, J = 11.2)
2ꢄꢄ, 5ꢄꢄ
99.72
72.97
76.51
71.95
73.61
171.68
5.03 (d, J = 7.8)
3.22 m
3.29 m
3.18 m
3.52 (d, J = 9.6)
2ꢄꢄ, 5ꢄꢄ
1ꢄꢄ
2ꢄꢄ, 4ꢄꢄ, 5ꢄꢄ
100.39
73.55
77.20
72.45
74.10
172.00
5.04 (d, J = 7.8)
3.26 m
3.31 m
3.19 m
3.54 (d, J = 10.2)
ꢄꢄ
ꢄꢄ ꢄꢄ
4
3 , 5
5ꢄꢄ
6ꢄꢄ
3ꢄꢄ, 4ꢄꢄ
4ꢄꢄ, 5ꢄꢄ
3ꢄꢄ, 4ꢄꢄ
5ꢄꢄ
Acid hydrolysis of 3, as expected, formed chrysin [1]. Paper chromatography detected D-galacturonic acid in the
carbohydrate part of the hydrolysate.
Based on spectral, chemical, and literature data, 3 had the structure of chrysin-7-O-ꢂ-D-galacturonide [7], which was
isolated earlier from Centaurea pseudoscabiosa subsp. pseudoscabiosa Boiss. et Buhse growing in Turkey.
Compound 4 that was isolated by us was apigenin-7-O-ꢂ-D-glucuronide according to spectral, chemical, and literature
data [8].
Apigenin-7-O-ꢂ-D-galacturonide (1). C H O , mp 236.6°C. UV spectrum (MeOH, ꢀ , nm): 205.5, 268.5,
21 18 11
max
–1
333.5. IR spectrum (ꢃ, cm ): 3383.94 (OH), 2922.64 (CH), 1725 (COOH), 1658.50 (C=O), 1606.38 (C=C), 1496.13, 1413.87,
1344.19 (C=C), 1245.40, 1173.93, 1106.04, 1058.45 (C–O–C), 835.30, 763.84 (C–H), 622.26. HR-ESI-MS m/z 445.6
+
[M – H] , C H O 446.
21 18 11
Apigenin-7-O-ꢂ-D-glucuronide (4) was isolated by elution of the column with MeOH:H O (9:1). C H O ,
2
21 18 11
mp 175.5°C. PMR spectrum (600 MHz, DMSO-d , ꢁ, ppm, J/Hz): 3.14 (1H, m, H-4ꢄꢄ), 3.23 (1H, m, H-2ꢄ), 3.27 (1H, m,
6
H-3ꢄꢄ), 3.51 (1H, d, J = –5.4, H-5ꢄꢄ), 5.02 (1H, d, J = 7.2, H-1ꢄꢄ), 6.42 (1H, br.s, H-6), 6.81 (1H, br.s, H-8), 6.83 (1H, s, H-3),
6.92 (2H, d, J = 9.0, H-3ꢄ, 5ꢄ), 7.93 (2H, d, J = 9.0, H-2ꢄ, 6ꢄ), 12.74 (1H, br.s, 5-OH).
13
C NMR spectrum (150 MHz, DMSO-d , ꢁ, ppm): 163.61 (C-2), 103.15 (C-3), 182.12 (C-4), 161.42 (C-5), 99.86
6
(C-6), 163.21 (C-7), 95.07 (C-8), 157.39 (C-9), 105.69 (C-10), 120.92 (C-1ꢄ), 128.99 (C-2ꢄ), 116.43 (C-3ꢄ), 162.12 (C-4ꢄ),
116.53 (C-5ꢄ), 128.99 (C-6ꢄ), 100.24 (C-1ꢅ), 73.47 (C-2ꢅ), 77.14 (C-3ꢅ), 72.48 (C-4ꢅ), 74.09 (C-5ꢅ), 171.86 (C-6ꢅ).
Thus, compounds 1–3 were isolated for the first time from the genus Scutellaria and compound 4, for the first time
from S. schachristanica.
ACKNOWLEDGMENT
The work was supported by the “National Science and Technology Minister of China Project 2011BAI05B05 and the
CAS/SAFEA International Partnership Program for Creative Research Team”.
104

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