Chemistry of Natural Compounds, Vol. 43, No. 6, 2007
VERBASCOSIDE FROM
Verbascum phlomoides
L. N. Gvazava1 and V. S. Kikoladze2
UDC 547.918:547.192
Plants of the genus
L. (Scrophulariaceae) are rich in biologically active compounds [1-3], are widely used
Verbascum
in folk medicine [4, 5] and homeopathic practice [6] of many countries, and are interesting as pharmacological materials. In
particular, wild in Georgia is used for manydiseases [7] so that its chemical composition was thoroughlystudied.
V. phlomoides
The aerial parts of
together with the flower heads (500 g of air-dried raw material) were extracted with
V. phlomoides
methanol (50%) on a water bath at 60°C. The extracts were combined, filtered, and distilled in vacuo. The aqueous residue
was evaporated and treated with petroleum ether to remove ballast materials. The resulting aqueous concentrate was filtered
over columns (5 × 10 cm) of nylon and Al O . The total phenolic compounds were separated and fractionated repeatedly over
2
3
a column (1.2 m × 2.5 cm) of polyamide with elution by H O:MeOH with an increasing gradient of alcohol from 0 to 100%.
2
This isolated phenolic compound 1, which was not a flavonoid and was identified using chemical transformations and mass and
NMR spectroscopy.
OH
OH
O
1
O CH CH
OH
2
2
RO
1''
O
OH
1'''
Me
HO
O
HO
OH
1, 1a
OH
OH
1'
1: R =
OC CH CH
1a: R = H
Alkaline hydrolysis of 1 in NaOHsolution (0.05 N) produced caffeic acid and glycoside1a, the mass spectrum ofwhich
displayed a weak peak for a molecular ion with / 462, corresponding to the formula C H O . Therefore, 1 was an ester
m z
20 30 12
+
of caffeic acid and glycoside 1a. Acetylation of 1a by acetic anhydride in pyridine produced its octaacetate ( / 798 [M] ),
m z
which was hydrolyzed by H SO (5%). GC of the carbohydrate part of the hydrolysate detected the acetates of sorbitol and
2
4
rhamnol in a 1:1 ratio.
The aglycon was prepared by hydrolyzing 1 (50 mg) with H SO (5%). After the carbohydrate part was removed, the
2
4
mixture was chromatographed over a column of silica gel (1.2 m × 3.0 cm) with elution successively by H O→MeOH→BuOH
2
13
to afford the aglycon (18.7 mg) that was identified using mass, PMR, and C NMR spectroscopy as (3,4-dihydroxy-
phenyl)ethanol.
The configuration ofthe glycosidic bonds of the sugars and the attachment site of the components in 1 were established
13
using PMR spectra (double homo- and heteronuclear resonance) and C NMR spectra (Table 1) in addition to nuclear
Overhauser effect experiments. The results agreed with those in the literature [8] and enabled 1 to be assigned the structure
β-(3,4-dihydroxyphenyl)ethyl-O-α-L-rhamnopyranosyl-(1→3)-β-D-(4-O-caffeoyl)glucopyranoside or verbascoside.
The isolation from V. phlomoides of the separate components of 1 has been reported [9]. However, verbascoside itself
has not been isolated from the studied species until now. We are inclined to explain this by the climatic and geographical
peculiarities of the habitat of this plant.
1) I. Kutateladze InstituteofPharmacochemistry, 0159, Tbilisi, ul. P. Sarajishvili, 36, e-mail: liligvazava@yahoo.com;
2) P. Melikishvili Institute of Physical and Organic Chemistry, 0186, Tbilisi, ul. Jikia, 5. Translated from Khimiya Prirodnykh
Soedinenii, No. 6, pp. 589-590, November-December, 2007. Original article submitted May 23, 2007.
0009-3130/07/4306-0710 ©2007 Springer Science+Business Media, Inc.
710
Gvazava
