New flavanonglycoside from Glycyrrhiza glabra

Article abstract of DOI:10.1023/A:1012505721054

A new flavanonglycoside pinocembroside, 2(S)-7-O-β-D-glucopyranosyl-5-hydroxyflavanone, was isolated from the aerial part of Glycyrrhiza glabra L. Its structure was determined using chemical transformations and spectral data.

Full text of DOI:10.1023/A:1012505721054

Chemistry of Natural Compounds, Vol. 37, No. 3, 2001
NEW FLAVANONGLYCOSIDE FROM Glycyrrhiza glabra
M. P. Yuldashev
UDC 547.972
A new flavanonglycoside pinocembroside, 2(S)-7-O- -D-glucopyranosyl-5-hydroxyflavanone, was isolated
from the aerial part of Glycyrrhiza glabra L. Its structure was determined using chemical transformations
and spectral data.
Key words: Glycyrrhiza glabra, 2(S)-7-O- -D-glucopyranosyl-5-hydroxyflavanone.
We isolated 7-O-methylglabranin, 6-C-prenylpinocembrin, glabranin, pinocembrin, galangin, and the new isoflavonoid
glabrisoflavone from the aerial part of Glycyrrhiza glabra L. [1]. In continuation of the research, we obtained a new compound
1
from the CHCl fraction of the alcohol extract. The UV spectrum of 1 ( max, nm, 286, 351) is characteristic of flavanone
3
derivatives [2]. This is confirmed by the PMR spectrum, which contains signals for H-2 as a doublet of doublets with spin—spin
coupling constants (SSCC) 4.0 and 11.5 Hz and for 2H-3 as two binary doublets [2]. Furthermore, the spectrum exhibits signals
for seven aromatic protons, an anomeric proton, and other protons of the carbohydrate in addition to a bonded hydroxyl (see
Experimental). Therefore, the compound is a glycoside.
Acetylation of 1 produced the pentaacetyl derivative 2, the mass spectrum of which has a weak peak for the molecular
ion with m/z 628 and strong peaks for fragments of the tetraacetylhexose with m/z 331, 169, and 109 [3].
Acid hydrolysis of 1 afforded pinocembrine [4] and D-glucose.
RO CH
2
O
O
C
B
O
A
OR
RO
OR
O
OR
1
2
: R = H;
: R = COCH
3
The site of carbohydrate attachment was established by comparing the UV spectra of 1 and its aglycone. The absorption
maxima in the spectrum of 1, in contrast with those of the aglycone, do not experience a bathochromic shift upon addition of
NaOAc. This indicates that the 7-OH of the flavanone was glycosylated [2].
The PMR spectrum of 1 has the resonance of the anomeric proton of D-glucose at 5.63 ppm as a doublet with SSCC
6.5 Hz. This is consistent with a -glycosidic bond of the carbohydrate to the aglycone [2]. Therefore, pinocembroside is 2(S)-
7
-O- -D-glucopyranosyl-5-hydroxyflavanone (1) and is a new natural compound.
EXPERIMENTAL
We used solvent systems CHCl —CH OH (97:3) (1) and n-butanol—pyridine—water (6:4:3) (2).
3
3
Column chromatography used KSK 100/160 µm silica gel. TLC was performed on Silufol UV-254 plates. Compounds
on TLC were visualized using UV light and ammonia vapor. Sugar on paper chromatography (Filtrak No. 12) was developed
o
by spraying with acidic anilinium phthalate with subsequent heating for 3-5 min at 90-100 C.
S. Yu. Yunusov Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan,
Tashkent, fax (99871) 120 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 193-194, May-June, 2001.
Original article submitted June 25, 2001.
©
0
009-3130/01/3703-0224$25.00 2001 Plenum Publishing Corporation
2
24

PMR spectra were recorded on a Tesla BS-567A 100 MHz instrument ( , ppm, 0 = HMDS). Mass spectra were
obtained on an MX-1310 instrument with 50 eV ionization potential. IR spectra were recorded on a Perkin—Elmer System
2
000 FT-IR Fourier spectrometer in KBr pellets; UV spectra, on a Perkin—Elmer Lambda 16 spectrometer.
Isolation of Pinocembroside (1). Further elution of the CHCl fraction [1] on a column using system 1 isolated from
3
o
fractions 179-186 compound 1 (0.25 g), C H O , mp 139-141 C. UV spectrum (EtOH,
, nm): 286, 351; CH CO Na: 285,
3 2
21
22
9
max
-1
353. IR spectrum (KBr,
, cm ): 3570-3340 (OH), 1660 (C O of -pyrone), 1615, 1568, 1517 (aromatic C C), 1100-1005
max
(C–O of glycosides).
PMR spectrum ( , ppm, J/Hz, C D N): 2.74 (1H, dd, J = 4.0, J = 17.5, H-3 eq), 3.07 (1H, dd, J = 11.5, J = 17.5,
5
5
H-3ax), 3.82-4.55 (carbohydrate protons), 5.33 (1H, dd, J = 4.0, J = 11.5, H-2ax), 5.63 (1H, d, J = 6.5, H-1 ), 6.48 (2H, br.s,
H-6,8), 6.95-7.44 (m, 5H-Ar ring B), 11.93 (1H, br.s, 5-OH).
Pinocembroside Pentaacetate (2). Glycoside 1 (20 mg) was dissolved in pyridine (1 mL) and acetic anhydride (3 mL)
o
+
and worked up as usual after 4 h to prepare the pentaacetate of 2 (12 mg), mp 93-95 C, C H O . Mass spectrum, m/z: M 628,
3
1 32 4
5
85 [M - 43], 542, 511, 471, 381, 369, 365, 351, 331, 293, 271, 256, 211, 179, 169, 127, 109.
Acid Hydrolysis of Pinocembroside. Glycoside 1 (25 mg) was hydrolyzed in HCl (15 mL, 5%) for 4 h on a boiling-
water bath. The precipitated aglycone was filtered off and recrystallized from CHCl —hexane. Yield of pinocembrin (5,7-
3
o
+
dihydroxyflavanone) 9 mg, mp 194-196 C, C H O (M 256) [4]. The hydrolysate contained D-glucose according to PC in
1
5 12 4
system 2.
REFERENCES
1
2
.
.
M. P. Yuldashev, E. Kh. Batirov, A. D. Vdovin, and N. D. Abdullaev, Bioorg. Khim., 26, 873 (2000).
T. J. Mabry, K. R. Markham, and M. B. Thomas, The Systematic Identification of Flavonoids, Springer-Verlag,
Berlin (1970), p. 146.
3
.
.
N. K. Kochetkov and O. S. Chizhov, Mass Spectrometry of Carbohydrates [in Russian], in: Methods of
Carbohydrate Research, Mir, Moscow (1975).
N. Sh. Kattaev and G. K. Nikonov, Khim. Prir. Soedin., 93 (1974).
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