Flavonoid oligosides from georgian astragalus falcatus

Article abstract of DOI:10.1007/s10600-011-9938-9

New flavonoid oligosides were isolated from leaves and flowers of Astragalus falcatus Lam. It was found on the basis of chemical transformations, UV, IR, PMR, ¹³C NMR, HMBC, HSQC, 1D-TOCSY, and mass spectral properties that falcoside C had the structure quercetin 3-O-[β-D- glucopyranosyl(1→3)-α-Lrhamnopyranosyl( 1→6)]-β-D- galactopyranoside 7-O-β-D-glucopyranoside; falcoside D, isorhamnetin 3-O-[β-D-xylopyranosyl(1→3)-α-L-rhamnopyranosyl(1→6)] -β-D-galactopyranoside 7-O-α-Lrhamnopyranoside.

Full text of DOI:10.1007/s10600-011-9938-9

Chemistry of Natural Compounds, Vol. 47, No. 3, July, 2011 [Russian original No. 3, May-June, 2011]
FLAVONOID OLIGOSIDES FROM GEORGIAN Astragalus falcatus
*
M. D. Alaniya, N. Sh. Kavtaradze,
UDC 547.972
A. V. Skhirtladze, and M. G. Sutiashvili
New flavonoid oligosides were isolated from leaves and flowers of Astragalus falcatus Lam. It was found on
13
the basis of chemical transformations, UV, IR, PMR, C NMR, HMBC, HSQC, 1D-TOCSY, and mass spectral
properties that falcoside C had the structure quercetin 3-O-[ꢀ-D-glucopyranosyl(1ꢁ3)-ꢂ-L-
rhamnopyranosyl(1ꢁ6)]-ꢀ-D-galactopyranoside 7-O-ꢀ-D-glucopyranoside; falcoside D, isorhamnetin
3-O-[ꢀ-D-xylopyranosyl(1ꢁ3)-ꢂ-L-rhamnopyranosyl(1ꢁ6)]-ꢀ-D-galactopyranoside 7-O-ꢂ-L-
rhamnopyranoside.
13
Keywords: Astragalus falcatus, flavonoids, flagalosides, quercetin, isorhamnetin, falcosides; UV, IR, PMR,
C
NMR, 2M (HSQC, HMBC, 1D-TOCSY) spectra.
We reported previously on flavonoids from leaves and flowers of Astragalus falcatus Lam. (Leguminosae L.) inhabiting
Georgia [1]. The plant is the official raw material for producing the substance for the drug flaronin with hypoazotemic and
diuretic activity [2, 3]. The raw material contains robinin trioside (trade name flaronin) and highly polar compounds as
impurities (up to 5%) in flaronin substance [2]. These glycosides are difficult to isolate because they are highly hydrophilic.
The components could be separated (see Experimental) from the total polar flavonoids that were isolated by preparative
paper chromatography (PC) by using reversed-phase HPLC. The obtained compounds were denoted falcosides A-E. The
individual components were analyzed in order to determine their structures after they were accumulated in significant amounts.
It was found that falcosides A, B, and E were oligosides of kaempferol with sugar components such as D-glucose,
D-galactose, L-arabinose, and L-rhamnose in falcoside A; D-glucose, D-galactose, D-xylose, and L-rhamnose in falcoside B;
and D-glucose, D-galactose, L-arabinose, D-xylose, and L-rhamnose in falcoside E.
13
The structures of falcosides C and D were elucidated on the basis of UV, IR, PMR, C NMR, HMBC, HSQC, and
1D-TOCSY spectroscopy and mass spectrometry.
Falcoside C was a yellow powder that gave a positive Shinoda reaction [4] and negative Bryant test [5]. The molecular
weight 934 (mass spectrometry) corresponded to the formula C H O . The IR spectrum showed absorption bands
39 50 26
–1
characteristic of flavonoids at 3600 cm (OH) and 1650 (ꢃ-pyrone C=O). The compound was designated as a flavonol
glycoside based on absorption maxima in the UV spectrum in EtOH at 360 and 255 nm.
OH
2a
1a
OH
OCH
3
O
O
HO
HO
O
O
O
O
OH
OH
H C
HO
3
O
O
HO
OH
HO
O
O
HO
O
OH
HO
OH
O
O
O
H C
3
HO
H C
3
HO
O
O
O
OH
HO
HO
HO
HO
O
O
OH
OH
O
HO
HO
HO
HO
2b
HO
HO
1
2
I. G. Kutateladze Institute of Pharmaceutical Chemistry, 0159, Tbilisi, Georgia, fax: (995) 32 25 00 23, e-mail:
merialania@yahoo.com. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 337–341, May–June, 2011. Original
article submitted November 29, 2010.
©
0009-3130/11/4703-0377 2011 Springer Science+Business Media, Inc.
377

The glycoside was hydrolyzed by H SO solution (2%) to afford the aglycon (32%) with mp 316–319°C. Comparison
2
4
with an authentic sample identified it as quercetin [6]. The carbohydrate part of the hydrolysate contained D-glucose,
D-galactose, and L-rhamnose according to PC. A comparison of UV spectra of the glycoside and the aglycon that were taken
with added diagnostic reagents showed that carbohydrate units were present on C-3 and C-7 of the aglycon (Experimental).
Thus, flavonoid C was a bisdesmoside.
Treatment of compound C with aqueous base (0.5%) [7] gave D-glucose and an intermediate (1a) that formed after
isolation, purification, and acid hydrolysis quercetin, D-galactose, D-glucose, and L-rhamnose. Therefore, glycoside C included
two D-glucoses, one of which was bonded to C-7 of the aglycon; the other, in a triose on C-3 of the same genin.
Resonances belonging to four anomeric protons of carbohydrates were visible in the PMR spectrum taken in CD OD.
3
This indicated unambiguously that the glycoside contained four sugar molecules. The chemical shifts of all carbohydrate
protons were found using 1D-TOCSY and COSY experiments. Then, chemical shifts of the corresponding C atoms were
1
13
found using HSQC ( H– C) correlations.
Protons of sugars resonated in the PMR spectrum of falcoside C as doublets at 4.80 ppm with SSCC J = 7.6 Hz
(D-glucose H-1), 5.21 with SSCC J = 8.3 Hz (D-galactose H-1), 5.60 with SSCC J = 7.6 Hz (D-glucose H-1), and 4.63 with
SSCC J = 2.1 Hz (L-rhamnose H-1). This indicated that the monosaccharide units had the pyranose form. Monosaccharides
4
1
of the D-series had the C -conformation and ꢀ-configuration; of the L-series, C -conformation and L-configuration [8-10].
1
4
The chemical shifts of C atoms of ꢀ-D-glucopyranose units indicated that they were located in terminal positions.
The HMBC spectrum of 1 (Table 1) showed a correlation peak between the resonance of the ꢀ-D-glucopyranoside
anomeric proton and C-7 of the genin. This determined unambiguously the attachment site in the same position of quercetin.
Alkaline hydrolysis of falcoside C, as expected, formed the progenin (1a) and D-glucose.
The sequence of carbohydrate attachment in the triose on C-3 of the aglycon was found using the HMBC correlation
spectrum of falcoside C.
The HMBC spectrum showed a correlation peak between resonances of the D-galactose anomeric proton and C-3 of
the genin. Thus, the D-galactose was bonded directly to the aglycon. The resonance of C-6 of the D-galactose unit in the
13
C NMR spectrum experienced a glycosylation effect and appeared at ꢄ 66.80 ppm. This indicated that it was substituted
with a carbohydrate [9–11].
13
Atom C-3 of L-rhamnose underwent a glycosylation effect in the C NMR spectrum (ꢄ 80.43). This indicated
unambiguously that the L-rhamnose was the unifying unit in the triose. In fact, cross peaks between resonances of L-rhamnose
H-1 with D-galactose C-6 and L-rhamnose C-3 with D-glucose H-1 were observed in the HMBC spectrum of falcoside C.
The chemical shifts of L-rhamnose C-3 and its adjacent C atoms (C-2, 75.78; C-4, 70.12 ppm) also indicated that this
position was substituted [11]. This meant that the second D-glucose was bonded to L-rhamnose C-3.
Thus, glucoside C had the structure quercetin 3-O-[ꢀ-D-glucopyranosyl(1ꢁ3)-ꢂ-L-rhamnopyranosyl(1ꢁ6)]- ꢀ-D-
galactopyranoside 7-O-ꢀ-D-glucopyranoside.
Falcoside D was also a flavonol glycoside according to its UV spectrum with absorption maxima at 375 and 275 nm.
–1
The IR spectrum had absorption bands at 3500–3600 cm (OH) and 1655 (ꢃ-pyrone C=O) and also confirmed that this
glycoside was a flavonoid.
The glycoside was hydrolyzed by acid (2% H SO ) to form the aglycon (~30%) that was identified as isorhamnetin
2
4
according to the alkali fusion products (phloroglucinol and vanillic acid), mp 300–302°C, and comparison with an authentic
sample [3]. D-Galactose, L-rhamnose, and D-xylose were detected in the carbohydrate part of the glycoside. Judging from
the yield of genin from the acid hydrolysate, glycoside 2 contained four carbohydrate molecules. In fact, the PMR spectrum
exhibited resonances for four anomeric protons.
Glycoside D was cleaved by alkaline solution (0.5%) into L-rhamnose and an intermediate (2a) that formed
isorhamnetin, D-galactose, L-rhamnose, and D-xylose after isolation, purification, and acid hydrolysis. Thus, the glycoside
structure included two L-rhamnoses, one of which was bonded to isorhamnetin C-7; the other, to a triose on C-3 of the same
genin. Thus, this glycoside was also a bisdesmoside.
13
The bonding sequence of the carbohydrates in the triose was found by analyzing PMR, C NMR, and HMBC spectra
1
13
and products of chemical transformation of glycoside D. The HMBC spectrum ( H– C) contained a correlation peak between
resonances of the D-galactose anomeric proton and C-3 of the genin. The correlation between resonances of the D-galactose
and L-rhamnose units was analogous to that of the preceding compound, falcoside C. Thus, the D-galactose in the glycoside
was bonded directly to the aglycon. The L-rhamnose was glycosylated also on C-3 because the chemical shift of C-3 was ꢄ
80.39 ppm. The anomeric proton of D-xylose correlated with L-rhamnose C-3.
378

13
TABLE 1. PMR and C NMR Data for Falcosides C (1) and D (2) (CD OD, ꢄ, ppm, J/Hz)
3
1
2
ꢄH
C atom
ÍÌÂÑ
ÍÌÂÑ
ꢄC
ꢄH
ꢄC
2
3
157.05
133.25
177.34
161.17
97.54
162.80
92.84
157.27
105.67
121.07
115.20
144.70
148.60
116.40
121.60
157.75
133.02
177.14
160.97
96.94
161.60
92.84
156.07
105.77
121.05
113.90
149.60
149.50
115.10
122.30
55.60
4
5
6
6.3 (d, J = 2.2)
6.5 (d, J = 2.08)
5, 7, 8, 10
6, 7, 9, 10
6.0 (d, J = 2.2)
5, 7, 8, 10
7, 9, 10
7
8
6.42 (d, J = 2.02)
9
10
1ꢅ
2ꢅ
3ꢅ
4ꢅ
5ꢅ
6ꢅ
OCH3
7.8 (d, J = 2.1)
7.93 (d, J = 2.20)
2, 1ꢅ, 3ꢅ, 4ꢅ, 6ꢅ
1ꢅ, 6ꢅ, 3ꢅ, 4ꢅ
6.8 (d, J = 8.3)
7.8 (dd, J = 2.1; 8.2)
6.90 (d, J = 8.40)
7.64 (dd, J = 2.2; 8.4)
3.81 s
1ꢅ, 3ꢅ, 4ꢅ, 6ꢅ
1ꢅ, 2, 2ꢅ, 5ꢅ
6ꢅ, 4ꢅ, 1ꢅ
2, 1ꢅ, 2ꢅ, 5ꢅ
3ꢅ
7- -ꢀ-D-Glc unit
O
p
1a
2a
3a
4a
5a
6a
100.60
73.00
74.69
66.07
77.80
59.59
5.60 (d, J = 7.6)
3.85 (dd, J = 9.4; 8.0)
3.59 (dd, J = 9.4; 3.8)
3.82 (dd, J = 10.0; 9.0)
3.70 m
3.54 (dd, J = 12,1; 5.2)
3.70 (dd, J = 12.1; 2.2)
7, 2a
1a, 3a
1a, 4a, 5a
3a, 5a
1a, 4a, 6a
5a, 4a
ꢀ- -Gal unit
D
3, 2b,3b
1b, 3b
p
1b
2b
3b
4b
5b
6b
103.49
73.59
74.72
66.86
75.81
66.80
5.21 (d, J = 8.3)
3.87 (dd, J = 9.4; 8.3)
3.55 (dd, J = 9.4; 3.8)
3.82 (dd, J = 2.9; 1.2)
3.70 (m, J = 3.7)
99.49
73.42
74.71
66.85
75.82
66.79
5.15 m
3, 2b, 3b
1b, 3b
3.86 (dd, J = 9.4; 8.3)
3.60 (dd, J = 9.4; 3.8)
3.83 (dd, J = 2.9; 1.2)
3.71 m
2b, 4b
2b, 4b
3b, 5b
3b, 5b, 6b
4b, 6b
4b, 6b
3.55; 3.74 m
1c, 5b
3.75; 3.54 m
1c, 5b
ꢂ-L-Rha unit on C-6 D-Gal
p
p
1c
2c
3c
4c
5c
6c
96.39
75.78
80.43
70.12
68.04
15.34
4.63 (d, J = 2.1)
3.54 (dd, J = 3.4; 1.8)
3.49 (d, J = 9.0)
6b, 2c
1c, 3c
96.41
75.76
80.39
69.95
67.98
15.37
4.54 (d, J = 2.1)
3.78 (dd, J = 3.8; 2.1)
3.57 (dd, J = 9.6; 3.8)
3.47 (t, J = 9.4)
3.52 (dd, J = 9.5; 6.15)
1.92 (d, J = 6.2)
6b, 2c
1c, 3c
1d, 2c, 4c
3c, 5c, 6c
4c, 6c
1e, 2c, 4c
3c, 5c, 6c
4c, 6c
3.26 (t, J = 9.4)
3.50 (dd, J = 9.5; 6.0)
1.26 (d, J = 6.15)
5c, 4c
5c, 4c
ꢀ-D-Glc unit on C-3 L-Rha
p
p
1d
2d
3d
4d
5d
6d
104.50
75.02
76.85
69.71
78.66
61.30
4.80 (d, J = 7.6)
3.82 (dd, J = 9.4; 7.6)
3.56 (dd, J = 9.4; 3.8)
3.80 (dd, J = 10.0; 9.0)
3.70 m
3.56 (dd, J = 12.0; 2.1)
3.75 (dd, J = 12.0; 4.5)
3c, 2d
1d, 3d
1d, 4d, 2d,
3d, 5d, 6d
1d, 4d, 6d
1d,5d
ꢀ
-D-Xyl unit
p
1e
2e
3e
4e
5e
105.68
75.50
77.63
72.56
65.57
4.68 (d, J = 7.0)
3.20 (dd, J = 9.0; 7.3)
3.32 (t, J = 9.0)
3c, 2e
3e, 4e
2e, 4e
3e, 5e
3e, 4e
3.45 m
3.14 (dd, J = 9.0; 9.0)
3.85 (dd, J = 10.5; 5.0)
7- -ꢂ-L-Rha unit
O
p
1f
2f
3f
4f
5f
6f
99.40
71.40
69.92
68.65
67.37
15.85
5.60 (d, J = 2.0)
4.02 (dd, J = 3.5; 1.8)
3.83 (dd, J = 9.4; 3.4)
3.45 (t, J = 9.4)
3.61 (dd, J = 9.4; 6.1)
1.26 (d, J = 6.2)
7, 2f
1f, 3f
2f, 4f,
3f, 5f
4f, 6f
5f
379

Spectral data confirmed that D-xylose and keioside (2b) [12] were formed by stepwise acid hydrolysis of intermediate
2a. Thus, the bonding sequence of the carbohydrate units on C-3 of the aglycon was D-galactose-(6 1)-ꢂ-L-rhamnose-
(3 1)-D-xylose. The SSCCs of the anomeric protons were consistent with the pyranose form of the monosaccharides; the
4
1
C -conformation and ꢀ-configuration of monosaccharides of the D-series; and the C -conformation and ꢂ-configuration of
1
4
L-series monosaccharides. Therefore, falcoside D was characterized as isorhamnetin 3-O-[ꢀ-D-xylopyranosyl(1ꢁ3)-ꢂ-L-
rhamnopyranosyl(1ꢁ6)]- ꢀ-D-galactopyranoside 7-O-ꢂ-L-rhamnopyranoside.
Falcosides C and D were new compounds.
D-Galactose and L-rhamnose are often encountered as robinobioses in flavonoid glycosides isolated by us [1, 3, 11].
Apparently this is a characteristic signature of flavonoids from Astragalus growing in Georgia.
EXPERIMENTAL
General Comments. Mother liquors remaining after crystallization of robinin (flaronin) that were obtained from the
aqueous alcohol extract of leaves and flowers of A. falcatus were used for the analysis. HPLC (Agilent HP 1000, Palo Alto,
CA) with an XTerra column (7.8 ꢆ 300 mm) packed with Silicagel RP-18 sorbent (particle size 5 ꢇm) and mobile phase flow
rate 2 mL/min were used to separate and accumulate the compounds. PC was carried out on FN 11 paper using solvent
systems BuOH:HOAc:H O (4:1:2, 1), Py:benzene:BuOH:H O (3:1:5:3, 2), and HOAC (15%, 3). Monosaccharides were
2
2
detected in chromatograms by anilinium phthalate.
IR spectra were recorded in KBr on a UR-20 instrument; UV spectra, on an SF-16 spectrophotometer (Lomo); NMR
spectra, in CD OD on Bruker AM-400 and DRX-500 instruments.
3
Mass spectra were recorded in a Thermo Finnigan instrument (San Jose, CA, USA). A solution of the compound in
CD OD was injected at 3 ꢇL/min. The potential on the capillary was 40 V; of the solvent stream, 4.8 kV. The capillary
3
temperature was 220°C. Data were calculated based on positive ions.
Isolation of Flavonoids. Robinin mother liquor (2.2 L) was condensed to 100 mL. Portions (0.1 mL each) were
placed on chromatographic paper for preparative separation. Chromatography was performed using solvent system 1. Glycosides
were eluted from the chromatograms by EtOH (30%). The EtOH extracts were evaporated to produce total highly polar
flavonoids (202 mg) with a very low content of robinin. Portions (5 mg each) of these flavonoids were dissolved in MeOH:H O
2
(1:3, 100 ꢇL) and injected into the chromatograph. The mobile phase consisted of binary CH CN:H O mixtures (from 10:90
3
2
to 30:70). The run time was 60 min. The retention time of falcoside A was 11.0 min; falcoside B, 11.4; robinin, 11.83;
falcoside C, 31.9; falcoside D, 33.7; and falcoside E, 36.2.
All together we isolated 8 mg of falcoside A; 11, falcoside B; 42, falcoside C; 38, falcoside D; 5, falcoside E; and 55,
robinin.
Acid Hydrolysis of FalcosidesA, B, and E. Compounds (8, 11, and 5 mg, respectively) were hydrolyzed separately
by aqueous H SO (2%). Algycons were extracted from the resulting reaction mixture by EtOAc. The combined EtOAc
2
4
extracts were dried over anhydrous Na SO , filtered, and evaporated. The solid was dissolved in EtOH and chromatographed
2
4
using PC and system 1. Aglycons of falcosides A, B, and E turned out to be identical with mp 275–278°C and appeared on PC
at the level of authentic kaempferol [3].
The aqueous part of the hydrolysates of falcosides A, B, and E gave qualitative evidence for D-glucose, D-galactose,
L-arabinose, and L-rhamnnose for falcoside A; D-glucose, D-galactose, and D-xylose for falcoside B; and D-glucose,
D-galactose, L-arabinose, and L-rhamnose for falcoside E.
Falcoside C, yellow powder, MW 934, C H O ; soluble in aqueous alcohol (35–40%). UV spectrum (EtOH,
39 50 26
–1
ꢈ
, nm): 360, 255; +CH COONa: 372, 260; +AlCl : 420, 275; +AlCl /HCl: 402, 363sh, 272. IR spectrum (KBr, cm ):
max
3
3
3
+
3600 (OH), 1660–1650 (ꢃ-pyrone C=O), 1550 (>C=C<). Mass spectrum (EI, 40 eV, m/z, I , %): 935 (3.9) [M + H] , 773
rel
+
+
+
(7.9) [M + H – 162] , 611 (21) [M + H – 162 ꢆ 2] , 465 (14.5) [M + H – 162 ꢆ 2 – 146] , 429 (100) [M + H – 162 ꢆ 2 – 146
+
+
– 2 ꢆ H O] , 303 (31.6) [M + H – 162 ꢆ 2 – 146 – 162] .
2
13
Table 1 presents PMR and C NMR data.
Acid Hydrolysis of Falcoside C. The compound (20 mg) was hydrolyzed by H SO solution (2%, 10 mL). The
2
4
hydrolysis was monitored by PC using system 3. The aglycon was extracted from the reaction mixture using EtOAc. The
EtOAc extract was dried and evaporated. The solid (5.8 mg, 32%) was dissolved in alcohol and crystallized to afford the
380

–1
aglycon, mp 302–305°C. A mixed sample with quercetin did not show melting point depression. IR spectrum (KBr, cm ):
3600 (OH), 1665 (ꢃ-pyrone C=O), 1556 (>C=C<). UV spectrum (EtOH, ꢈ , nm): 370, 269, 255; +CH COONa: 380, 273;
max
3
+AlCl : 455, 276; +AlCl /HCl: 430, 273.
3
3
–
The aqueous part of the hydrolysate was neutralized with AV-17 anion-exchanger (OH -form), evaporated, and
chromatographed using system 2. D-Glucose, D-galactose, and L-rhamnose were detected.
Alkaline Hydrolysis of Falcoside C. The compound (15 mg) was dissolved in NaOH solution (12 mL, 0.5%) and
hydrolyzed as before [7]. When the hydrolysis was finished the reaction mixture was neutralized to pH 7 and extracted with
EtOAc:EtOH (4:1). The extracts were dried to afford a solid (10 mg). D-Glucose was detected by PC in the aqueous part of
the hydrolysate.
The solid intermediate 1a was hydrolyzed by acid analogously as above to afford the genin quercetin. The carbohydrate
part contained D-glucose, D-galactose, and L-rhamnose.
Falcoside D, yellow powder, MW 902, C H O , soluble in aqueous alcohol (35-40%). UV spectrum (EtOH,
39 50 24
ꢈ
, nm): 375, 275; +CH COONa: 360, 285sh, 260; +AlCl : 400, 268, 300sh; +AlCl /HCl: 398, 267, 300sh. IR spectrum
max
3 3 3
–1
(KBr, cm ): 3600 (OH), 1660–1655 (ꢃ-pyrone C=O), 1552 (>C=C<). Mass spectrum (EI, 40 eV, m/z, I , %): 903 (23.6)
[M + H] , 757 (21) [M + H – 146] , 625 (21) [M + H – 146 – 132] , 479 (52.6) [M + H – 146 – 132 – 146] , 395 (100)
[M + H – 132 – 162 – 146 – 2 ꢆ H O – OCH ] , 317 (18.4) [M + H – 146 ꢆ 2 – 132 – 162] .
rel
+
+
+
+
+
+
2
3
13
Table 1 presents the PMR and C NMR spectra.
Acid Hydrolysis of Falcoside D. The compound (12 mg) was hydrolyzed by H SO solution (2%, 13 mL). The
2
4
hydrolysis was monitored by PC using systems 1 and 3. The hydrolysis was complete after 48 min. The aglycon was extracted
from the reaction mixture by EtOAc. The extract was dried and evaporated. The solid (3.6 mg, 29%) was crystallized from
alcohol to afford the aglycon, mp 299–302°C. A mixed sample with isorhamnetin did not give melting point depression.
D-Galactose, D-xylose, and L-rhamnose were detected in the aqueous part of the hydrolysate after the appropriate
work up (see above).
Alkaline Hydrolysis of Falcoside D. The compound (15 mg) was hydrolyzed analogously to falcoside C [7]. The
extracts were condensed to afford intermediate 2a (9 mg). L-Rhamnose was detected in the aqueous part of the hydrolysate by
PC.
Acid Hydrolysis of Intermediate 2a. The glycoside (5 mg) was hydrolyzed by acid analogously as described above
to afford the genin isorhamnetin (2.1 mg). D-Galactose, D-xylose, and L-rhamnose were detected in the carbohydrate part by
PC using system 2.
Stepwise Acid Hydrolysis of Intermediate 2a. Intermediate 2a (4 mg) was hydrolyzed by the literature method
[13]. D-Xylose and glycoside 2b, mp 184–187°C, were detected in the aqueous part of the hydrolysate by PC using system 2.
The glycoside appeared at the level of authentic keioside by PC using system 1 [12].
REFERENCES
1.
2.
3.
M. D. Alaniya, N. F. Komissarenko, and E. P. Kemertelidze, Soobshch. Akad. Nauk Gruz. SSR, 68, 357 (1972).
Pharmacopoeial Article 158/96, 42/1544, 1985; 42-9292-98, 09.03-2000, No. 002626, 2007.
M. D. Alaniya, E. P. Kemertelidze, and N. F. Komissarenko, Flavonoids of Several Georgian Astragalus L. Species
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