N -[2-(5-Hydroxy-1 H -indol-3-yl)ethyl]- p -coumaramide from Phragmites australis
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N-[2-(5-HYDROXY-1H-INDOL-3-YL)ETHYL]-p-COUMARAMIDE FROM Phragmites australis
UDC 547.926
A. V. Grigorceva, I. V. Galyautdinov, L. M. Khalilov, V. M. Yanybin, and V. N. Odinokov*
Phragmites australis Trin. ex Steud. is a perennial cereal that is indigenous to all of Russia, Western Europe, Asia, North Africa, and America. The cyanidines 3-O-(6s-O-succinyl)-E-glucopyranoside, 3-O-(6s-O-malonyl)-E-glucopyranoside, and 3-O-E-glucopyranoside (in the ratio 1:32:17) were isolated from the aerial part of P. australis [1]. Rhizomes of the plant are a productive source of indole alkaloids such as gramine, N,N-dimethyltryptamine, bufotenine, and N-methyl-5methoxytryptamine [2]. Extraction by MeOH with subsequent separation by column chromatography over silica gel isolated for the first time from the aerial part of P. australis N-[2-(5-hydroxy-1H-indol-3-yl)ethyl]-p-coumaramide (1), the yield of which was 0.1% of the air-dried mass and the purity of which was at least 98% (chromatography-mass spectroscopy). Compound 1 was isolated initially from seeds of Carthamus tinctorius L. [3] and later from Phyllostachys bambusoides [4]. Its pharmacological trials in vitro showed pronounced anti-inflammatory, antibacterial, antifungal, and antioxidant activity [4–7]. 9 8
HO
5
3a
3
O
H
11
13
15
10
N H
H
19
17
OH
1 7
7a
N H
1
The structure of the isolated compound was confirmed unambiguously by 1D (1H, 13C) and 2D homo- (COSY) and heteronuclear (HSQC, HMBC) NMR spectroscopy and mass spectrometry (MS) in electron-impact (EI) and laser-desorption (MALDI) modes with time-of-flight (TOF) detection of positive ions. The MALDI TOF mass spectrum contained ions [M + Na]+ (m/z 345.409) and [M + K]+ (m/z 361.363). The mass spectrum obtained in EI mode had the molecular ion [M]+ (m/z 322) as the base peak. This indicated that 1 had high thermal stability. Resonances in the 13C NMR spectrum of 1 were assigned using heteronuclear correlation 2D HSQC and HMBC NMR experiments. The resonance at G 6.41 ppm appeared as a doublet that belonged to H-12 and correlated with C-12 (G 117.20 ppm) (HSQC spectrum). A doublet at G 7.47 ppm correlated with C-13 (G 140.33 ppm) and belonged to H-13. Assignment of the resonance at G 6.41 ppm to H-12 was confirmed by the presence of cross peaks with C-11 (G 167.89 ppm) and C-14 (G 128.04 ppm). The vicinal spin–spin coupling constant (16.0 Hz) of protons H-13 and H-12 indicated that the double bond in 1 had the E-configuration. The presence of a cross peak between C-13 (140.33 ppm) and aromatic protons H-19 and H-15 (G 7.40 ppm) showed that the hydroxyl was in the para-position of the aromatic ring. N-[2-(5-Hydroxy-1H-indol-3-yl)ethyl]-p-coumaramide or N-p-Coumaroylserotonin (1). Air-dried ground aerial part of P. australis (100 g) was extracted at room temperature for 24 h with MeOH (3 u 700 mL). The extract was filtered off and evaporated in a rotary evaporator. The dry residue (2.6 g) was chromatographed over a column of silica gel (CHCl3:MeOH, 15:1). A yellow fraction with Rf 0.8 was collected. Eva
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