A new iridoid glycoside from Linaria genestifolia
Muhammad Zubair2006, Fitoterapia
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A new iridoid glycoside named genestifolioside (1) was isolated from the ethanol extract of Linaria genestifolia. Its structure was defined by spectral analysis.
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Fitoterapia 77 (2006) 12 – 14
www.elsevier.com/locate/fitote
A new iridoid glycoside from Linaria genestifolia
Viqar Uddin Ahmad a,*, Farzana Kousar a, Muhammad Zubair a,
Afsar Khan a, M. Shaiq Ali a, M. Iqbal Choudhary a, Bilge Sener b
a
International Centre for Chemical Sciences, H.E.J Research Institute of Chemistry, University of Karachi,
Karachi-75270, Pakistan
b
Department of Pharmacognosy, Faculty of Pharmacy, Gazi University, Ankara, Turkey
Received 6 July 2004; accepted 20 June 2005
Available online 28 November 2005
Abstract
A new iridoid glycoside named genestifolioside (1) was isolated from the ethanol extract of
Linaria genestifolia. Its structure was defined by spectral analysis.
D 2005 Elsevier B.V. All rights reserved.
Keywords: Linaria genestifolia; Genestifolioside; Iridoid glycoside
1. Introduction
The genus Linaria (Scrophulariaceae) is known to contain alkaloids, flavonoids,
diterpenoids and iridoides [1–7]. The present paper is concerned with the isolation of a
new iridoid glycoside, named genestifolioside (1) from L. genestifolia.
2. Experimental
2.1. Methods
1
H NMR and 13C NMR, COSY, HMQC and HMBC spectra: Bruker spectrometers
operating at 500 and 400 MHz; EI, CIMS: JMS-HX-110.
* Corresponding author. Tel.: +92 21 4819020; fax: +92 21 4819018, 4819019.
E-mail address: vuahmad@cyber.net.pk (V.U. Ahmad).
0367-326X/$ - see front matter D 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.fitote.2005.06.008
13
V.U. Ahmad et al. / Fitoterapia 77 (2006) 12–14
2.2. Plant material
L. genestifolia was collected from Ankara, Turkey in July, the flowering season of this
plant, and was sent by Prof. Bilge Sener, Department of Pharmacognosy, Gazi University,
Ankara, Turkey.
2.3. Extraction and purification
The ethanolic extract (627 g) was diluted with H2O defatted with hexane and
chloroform, basified with NH4OH and extracted with n-BuOH. The n-BuOH soluble part
was subjected to VLC by using mixture of CHCl3 and MeOH providing 1 as a white
powder (30 mg) (yield: 0.005 %). Allo-inositol was also obtained from the same column
(50 mg).
Genestifolioside (1). White powder; mp 210 8C; [a]25
99.878 (c 0.001, MeOH);
D
UVmax (MeOH): 300(log e 3.9) nm; IR bands (KBr): 3400–3200 cm 1; FAB-HRMS m/z
408.5432. Calc. for C17H28O11 408.4016.
1
H NMR and 13C NMR data : see Table 1.
3. Results and discussion
The FAB-HRMS of 1 showed the [M]+ ion peak at 408.5432, corresponding to the
molecular formula C17H28O11. The 1H NMR spectrum showed signals of two methyls, one
methylene and six methines in addition to a hexose moiety. A methyl signal at y 1.32 (t, J
6.8 Hz) coupled with a methylene at y 4.10 (q, J 6.8 Hz), the downfield shift of which
Table 1
1
H and 13C NMR data (CD3OD) for 1
C
yH
yC
1
3
4
5
6
7
8
9
10
11
12
1V
2V
3V
4V
5V
6V
5.43 (d, J 7.3)
6.43 (d, J 7.6)
4.81 (d, J 7.6)
93.2
142.3
104.3
72.2
83.8
74.9
78.9
49.2
20.1
63.3
14.4
99.2
74.5
77.5
71.4
74.2
62.3
3.70 (d, J 1.3)
5.40 (d, J 1.3)
3.41 (d, J 7.3)
2.13 (s)
4.10 (2H, q, J 6.8)
1.32 (3H, t, J 6.8 )
4.71 (d, J 8.0)
3.90 (dd, J 8.0, 8.7)
3.42 (br t, J 8.7)
3.53 (dd, J 8.7)
2.9 (m)
3.32 (dd, J 8.7, 11.7)
3.84 (dd, J 1.9, 11.7)
14
V.U. Ahmad et al. / Fitoterapia 77 (2006) 12–14
indicated the linkage with an oxygen atom. The second methyl group at 2.13 ppm was
attached to an oxygen-bearing quaternary carbon as determined by HMBC correlations.
Two doublets at y 6.43 and y 4.81 ( J 7.6 Hz each) were assigned to an olefinic double
bond. Two methine protons showed two doublets at y 3.70 and y 5.40 both with J 1.3 Hz.
Another doublet at y 5.43 ( J 7.3 Hz) was due to a proton carrying the sugar moiety,
coupled with a doublet at y 3.41 ( J 7.3 Hz). The anomeric proton signal at y 4.71 was a
doublet ( J 8.0 Hz). The 13C NMR indicated that the sugar moiety was glucose and the
larger coupling constants of the H-1’ of glucose pointed out to the h-configuration of the
sugar [8]. Table 1 summarizes the NMR data, which support the assignment of structure 1
to the compound. The stereochemistry at C-6 and C-7 was assigned on the basis of the
coupling constants values and was confirmed from the NOESY spectrum. In the NOESY
spectrum, H-6 showed interaction with the quaternary methyl (C-10).
The 13C NMR chemical shifts, decoupling experiments and 2D NMR experiments
support the assignment of structure 1 to the new compound named genestifolioside.
12
CH3
H2C 11
O
OH
6
HO
5
7
9
8
HO
4
1
3
2
O
CH3
10
O
1'
6' OH
5'
O
4'
HO
2'
3'
OH
OH
Compound = 1
References
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[2]
[3]
[4]
[5]
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[8]
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Nicoletti M, Serafini M, Tomassini L, Bianco A, Passacantilli P. Planta Med 1987;53:295.
Ilieva E, Khandzeva N, Popov NS. Phytochemistry 1992;31:1040.
Soren D, Soren RJ, Bentjuhl JN. Phytochemistry 1981;42:2717.
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