Cycloartane glycosides from Euphorbia glareosa

Full text of DOI:10.1007/s10600-009-9378-y

Chemistry of Natural Compounds, Vol. 45, No. 4, 2009
CYCLOARTANE GLYCOSIDES FROM Euphorbia glareosa
L. N. Gvazava1* and V. S. Kikoladze2
UDC 547.918
We have previously reported the isolation from various species of Euphorbia growing in Georgia of flavonoids [1]
and polyphenols [2]. We also found that all studied species contained in addition to the aforementioned classes of compounds
triterpene glycosides of the cycloartane series. Herein we communicate results from a study of the structure of cycloartane
glycosides isolated from E. glareosa (Euphorbiaceae).
Triterpene glycosides were obtained by exhaustive extraction (2 × 5 L) of ground air-dried roots (0.8 kg) at room
temperature. The MeOH extract was evaporated and worked up by the literature method [3] to afford triterpenoids (20.5 g
total) that were separated over a column of silica gel (L 40/100, Czech Rep.) using CHCl :CH OH (1, 15:1), CHCl :CH OH:H O
3
3
3
3
2
(
2, 70:23:4), C H :EtOAc (3, 2:1 and 1:1), and CHCl :C H :EtOAc (4, 1:1:1) [3]. We isolated eight compounds designated
6 6 3 6 14
in order of increasing polarity as 1–8. Compounds 1 and 2 were the genins cyclosiversigenin and asgenin; the others, their
glycosides.
Compound 1, cyclosiversigenin, C H O (cycloastragenol, astramembrangenin [4]), yield 0.036% (here and
3
0 50 5
2
0
henceforth of the weight of air-dried raw material), mp 238–240°C, [α] +50.4° (c 2.0, MeOH). IR spectrum (KBr,
νmax, cm ): 3500–3350 (OH), 3040, 1760, 1750, 1260–1250. PMR spectrum (Py-d , δ, ppm, J/Hz, 0 = HMDS): 4.90 (1H, q,
D
−
1
5
J = 7.0, H-16), 3.78 (1H, br.q, H-24), 3.57 (2H, m, H-3, H-6), 0.51 (d, J = 4.0) and 0.23 (br.s, 2H-19); CH groups 1.76, 1.46,
3
1
.35, 1.25, 1.21, 1.18, 0.92 [3].
Compound 2, cycloasgenin, C H O , yield 0.011%, mp 234–235°C, [α] +130.4° (c 0.8, MeHO). IR spectrum
2
0
3
0
48
6
D
−
1
(
KBr, νmax, cm ): 3450–3350 (OH), 3060 (cyclopropane CH ), 1706–1695 (C=O). PMR spectrum (Py-d , δ, ppm, J/Hz,
2
5
0
2
= HMDS): 4.92 (1H, q, J = 7.3, H-16), 4.20 (1H, dd, J = 9.8, 2.5, H-11), 3.72 (1H, m, H-6), 1.64 (d, J = 4.0) and 0.46 (br.s,
H-19), 3.75 (1H, dd, J = 8.8, 5.6, H-24), CH groups 1.70, 1.44, 1.41, 1.39. 1.21, 1.16, 0.84 [3].
3
A study of the acid hydrolysis products of the glycosides [5] showed that they all contained cyclosiversigenin as the
genin. The structures of the carbohydrate parts of the glycosides were established using chemical transformations (Hakomori
methylation [6] with subsequent methanolysis and GC of the sugars) and IR and PMR spectral data.
Compound 3, cyclosiversigenin 3,6-O-β-D-dixylopyranoside, C H O , 0.008%, mp 218–221°C (MeOH),
4
0 66 13
2
0
−1
[
α] +29.0° (c 0.71, MeOH). IR spectrum (KBr, νmax, cm ): 3200-3600 (OH), 3040–3060 (cyclopropane CH ).
D
2
PMR spectrum (Py-d , δ, ppm, J/Hz): 4.56 and 4.42 (d, J = 7.2, H′ and H′′), 1.70, 1.44, 1.25, 0.95 (eath 3H, s, CH ), 1.16 (9H,
5
3
s, CH × 3), 0.46 (1H, br.s, H -19) [7, 8].
3
a
Compound 4, cyclosiversigenin 3-O-[β-D-xylopyranoside-(2′-O-acetyl)]-6-O-β-D-xylopyranoside, C H O , 0.03%,
42 68 14
mp 253–254°C (MeOH), [α]2 +31° (c 0.90, MeOH). IR spectrum (KBr, νmax, cm ): 3360–3500 (OH), 1750, 1260 (ester).
PMR spectrum (Py-d , δ, ppm, J/Hz): 5.32 (1H, br.t, H-2′), 4.68 (1H, d, J = 6.2) and 4.55 (1H, d, J = 7.5); anomeric protons
0
−1
D
5
of two xyloses: 1.90 (3H, s, CH CO), 1.52, 1.41, 1.26, 1.18, 1.15, 1.07, 0.95, (each 3H, s, CH ), 0.45 (1H, d, J = 4.0, H -19)
3
3
a
[
8, 9].
Compound 5, cyclosiversigenin 3-O-β-D-xylopyranoside-6-O-β-D-glucopyranoside, C H O , 0.009%, mp 247–
4
1 68 14
49°C (MeOH), [α]2 +37.0° (c 0.5, MeOH). IR spectrum (KBr, νmax, cm ): 3300–3500 (OH), 3040 (cyclopropane CH ).
0
−1
2
D
2
PMR spectrum (Py-d , δ, ppm, J/Hz): 4.78 (1H, d, J = 7.8, H-1′′), 4.52 (1H, d, J = 7.4, H-1′), 1.82, 1.40, 1.26, 0.80, (each 3H,
5
s, CH ), 1.16 (9H, s, CH ), 0.44 (1H, d, J = 3.9, H -19) [10].
3
3
a
1
) I. Kutateladze Institute of Pharmaceutical Chemistry, 0159, Tbilisi, ul. P. Saradzhishvili, 36, Georgia, e-mail:
liligvazava@yahoo.com; 2) P. Melikishvili Institute of Physical and Organic Chemistry, 0186, Tbilisi, ul. Dzhikiya, 5, Georgia.
Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 498–499, July–August, 2009. Original article submitted February
6
, 2009.
0
009-3130/09/4504-0595 ©2009 Springer Science+Business Media, Inc.
595

Compound 6, cyclosiversigenin 3-O-[β-D-xylopyranoside-(2′-O-acetyl)]-6-O-β-D-glucopyranoside, C H O ,
4
3 70 15
.014%, mp 266–268°C, [α]2 +47.0° (c 0.85, MeOH). IR spectrum (KBr, νmax, cm ): 3300–3500 (OH), 1750, 1250 (ester).
0
−1
0
D
PMR spectrum (Py-d , δ, ppm, J/Hz): 2.04 (3H, s, CH CO), 1.82, 1.58, 1.40, 1.27, 0.95 (each 3H, s, CH ), 1.32 (6H, s, CH ),
5
3
3
3
0
.54 (1H, d, J = 4.2, H -19), 0.22 (1H, d, J = 4.2, H -19) [8, 11].
a b
All studied glycosides were described from E. glareosa for the first time. The study of the structures of the cycloasgenin
glycosides is continuing.
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