Chemistry of Natural Compounds, Vol. 42, No. 5, 2006
STEROIDAL GLYCOSIDE-PROTODIOSCIN FROM Digitalis ciliata
L. N. Gvazava1 and V. S. Kukoladze2
UDC 547.918
Trautv. is endemic to the Caucuses and widelydistributed in the flora ofGeorgia. It has been proposed
Digitalis ciliata
asrawmaterial for producing an effectivecardiotonicpreparation ofacetyldigitoxin [1]. Triterpeneglycosides[2, 3], carotinoids
[4], and steroidal glycosides were detected in the remaining extracts, the mother liquors.
After exhaustive extraction of cardenolide glycosides, the remaining solution was condensed to a resinous condition
and subjected (5 g) to total acid hydrolysis with HCl (2 N). Chromatography of the hydrolysate over a column of Al O using
2
3
ether, ether:benzene, and benzene:chloroform isolated three genins that were identified as tigogenin, diosgenin, and gitogenin
by their physical constants and TLC in the presence of authentic samples.
The glycoside composition of
was studied by dissolving the resinous extract in water with vigorous stirring.
D. ciliata
The insoluble solid that contained mainly spirostane glycosides was separated. The aqueous phase was extracted several times
with -butanol. The extracts were combined and evaporated to dryness. The solid was dissolved in ethanol. The glycosides
n
were precipitated with acetone to afford an amorphous cream-colored powder (12.5 g), a portion (3.5 g) of which was
chromatographed successively over columns of silica gel (KSK, 40-100 µm) and Sephadex G-75 using CHCl :CH OH:H O
3
3
2
(65:35:8) to afford a mixture of glycosides 1 and 2, which gave two spots on TLC with a small difference (∆ 0.1) in mobility.
R
f
Rechromatography over the columns isolated the pure compounds 1 (0.185 g) and 2 (0.076 g). Both glycosides gave a positive
reaction with Ehrlich's reagent [5]. Their IR spectra lacked signals characteristic of the spiroketal group. These data indicated
that the compounds were furostanes.
25
Glycoside 1, white amorphous powder (ethanol), mp 189-192°C, [α]
-80.5° (CHCl :CH OH, 1:1, 0.5), lit. [6]
c
3 3
D
25
-1
mp 190-196°C, [α]
-79.8° (pyridine, 0.1). IR spectrum (KBr, ν, cm ): 3400 (OH), 1045, 930 (weak broad band), 915,
c
D
+
+
+
840. FAB MS ( / , %): 1071 [M + Na] , 925 [M + Na - deoxyhexose] , 891 [M + Na - hexose - H O] .
m z
2
The acid hydrolysate of 1 contained diosgenin. GC of the aldonitriles of the sugars identified glucose and rhamnose
in a 1:1 ratio. Hakomori [7] methylation of 1 and subsequent methanolysis produced in the hydrolysate 2,3,4-tri- -methyl-L-
O
rhamnose, 2,3,4,6-tetra- -methyl-D-glucose, and 3,6-di- -methyl-D-glucose.
O
O
Enzymatichydrolysisof1byβ-glucosidasegavetheprosapogenin that wasidentifiedusingphysical constantsandmass
and NMR spectra as dioscin [8]. The hydrolysate contained D-glucose. Considering these data, 1 was assigned the structure
3-O-{[α-L-rhamnopyranosyl-(1→4)]-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranosyl}-(25R)-furost-5-en-3β,22α,26-triol-
26-β-D-glucopyranoside or protodioscin [9].
This glycoside was isolated from plants of the genus Digitalis for the first time.
+
Glycoside 2 had molecular weight m/z 1085 [M + Na] according toFAB MS, 14 amu greater than that of 1. The PMR
spectrum had a 3H singlet at δ 3.26 (OMe). Thus, it was assumed that 2 was the 22-O-methyl ether of 1, which was consistent
13
with its PMR and C NMR spectra and agreed well with the literature [10] (Table 1).
1) I. Kutateladze Institute of Pharmaceutical Chemistry, 0159, Tbilisi, e-mail: liligvazava@yahoo.com;
2) P. Melikishvili Institute of Physical and Organic Chemistry, 0186, Tbilisi, ul. Dzhikia, 5. Translated from Khimiya
Prirodnykh Soedinenii, No. 5, pp. 495-496, September-October, 2006. Original article submitted August 18, 2006.
0009-3130/06/4205-0614 ©2006 Springer Science+Business Media, Inc.
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