Chemistry of Natural Compounds, Vol. 49, No. 1, March, 2013 [Russian original No. 1, January–February, 2013]
FLAVONOIDS FROM THE AERIAL PART OF Calamagrostis epigeios
*
V. S. Kislichenko, I. S. Burlaka, and U. V. Karpyuk
UDC 547.972
Calamagrostis Adans. is a genus of grasses (Poaceae Barnh.) that numbers about 200 species. Seven species of these
grow in Ukraine. C. epigeios L. Roth. (bushreed) is a perennial herbaceous wild plant [1] that is not the official species despite
the fact that its raw material base is rather large.
We studied previously the fatty-acid and polysaccharide compositions of bushreed [2]. We studied phenolic compounds
of bushreed grass in order to write a national monograph in the State Pharmacopoeia of Ukraine for this type of raw material.
Ground raw material was extracted with EtOH (70%). The extract was evaporated and chromatographed (PC) using
n-BuOH:AcOH:H O (4:1:2) (direction I) and AcOH (15%) (direction II). Analysis of the chromatograms in visible and
2
UV light using specific reagents enabled up to 20 compounds of phenolic nature to be found in the grass. Several of them were
assigned as hydroxycinnamic acids and coumarin-type compounds (11). The others were flavonoids (9) [3, 4].
Air-dried raw material (1.0 kg, ground to particle size 2.5–3 mm) that was collected during flowering in Kharkov
Oblast (Ukraine) in 2011 was extracted exhaustively with EtOH (70%) (1:10 raw material:extractant ratio) in order to isolate
compounds and establish their structures. The resulting EtOH:H O extract was evaporated in vacuo in a rotary evaporator to
2
an aqueous residue that was worked up successively with CHCl , EtOAc, and n-BuOH. The solvents were distilled off to
3
afford CHCl (16.1 g), EtOAc (12.3), and BuOH (17.4) fractions.
3
The evaporated concentrated EtOAc extract was placed on a polyamide column and eluted by CHCl and its mixtures
3
with EtOH of gradually increasing concentration of the latter by 10% per 1 L. Fractions of 100 mL were collected and
monitored by PC using the indicated solvents. Identical fractions were combined, evaporated to dryness, dissolved in the
minimum amount of EtOH (96%) by adding several drops of H O, and left to crystallize. As a result, nine pure compounds
2
were isolated. These were identified using UV, IR, and PMR spectra; results of chemical transformations; and comparison
with authentic standard samples.
Apigenin (5,7,4ꢀ-trihydroxyflavone) (1). C H O , yellow crystals, soluble in EtOH, EtOAc, Me CO; insoluble
1
5
10
5
2
in CHCl ; mp 343–346°C. UV spectrum (EtOH, ꢁ , nm): 272, 343; +CH COONa: 275, 365; +CH COONa + H BO : 272,
3
max
3
3
3
3
–
1
3
45. IR spectrum (KBr, ꢂmax, cm ): 3520–3100 (OH), 1665–1635 (ꢃ-pyran C=O), 1625–1440 (aromatic C=C) [3].
Luteolin (5,7,3ꢀ,4ꢀ-tetrahydroxyflavone) (2). C H O , yellow needle-like crystals, soluble in Me CO, EtOH;
1
5
10
6
2
insoluble in CHCl , C H ; mp 328–330°C. UV spectrum (EtOH, ꢁ , nm): 260, 272, 356; +CH COONa: 272, 368;
3
6
6
max
3
–
1
+
CH COONa + H BO : 272, 376. IR spectrum (KBr, ꢂ , cm ): 3450–3300 (OH), 1665–1635 (ꢃ-pyran C=O), 1612–1580
3 3 3 max
(
(
aromatic C=C). PMR spectrum (100 MHz, C D N, ꢄ, ppm, J/Hz): 6.61 (1H, d, J = 2.0, H-6), 6.73 (1H, d, J = 2.0, H-8), 6.78
1H, s, H-3), 7.09 (1H, d, J = 8.0, H-5ꢀ), 7.53 (1H, br.s, H-2ꢀ), 7.60 (1H, dd, J = 2.0, 8.0, H-6ꢀ) [4].
5 5
The structure of 2 was confirmed by constants of the acetyl and methoxy derivatives. The compound was acetylated
by acetic anhydride in the presence of Py to form the tetraacetate with mp 226–228°C.
Cinaroside (luteolin-7-O-ꢅ-D-glucopyranoside) (3). C H O . Quantitative acidic and enzymatic hydrolysis
2
1 20 11
was performed in order to confirm the glycosidic nature of the compound. This produced equimolar amounts of the aglycon
and the carbohydrate part. PC using Me CO:n-BuOH:H O (7:2:1) found D-glucose in the acid-hydrolysis products of 3. The
2
2
aglycon was identified as 2 based on physicochemical properties. The position of the carbohydrate unit was established using
chemical and spectral methods. A bathochromic shift of absorption maximum I in the UV spectrum of 3 was not observed
upon adding NaOAc. Therefore, it was assumed that the carbohydrate was located on C-7. The IR spectrum contained
–
1
–1
–1
absorption bands for hydroxyls (3480–3300 cm ), ꢃ-pyran carbonyl (1665 cm ), aromatic C=C (1558, 1510 cm ), and
glycoside C–O (1100, 1020 cm ).
–
1
National Pharmaceutical University, Kharkov, Ukraine, e-mail: cncvc@mail.ru. Translated from Khimiya Prirodnykh
Soedinenii, No. 1, January–February, 2013, pp. 116–117. Original article submitted November 19, 2012.
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009-3130/13/4901-0133 ©2013 Springer Science+Business Media New York
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