C-Glycosyl Flavones from Two Eastern Siberian Species of Silene

Article abstract of DOI:10.1007/s10600-019-02768-7

Flavonoids from Silene aprica Turcz. and S. samojedorum (Sambuk) Oxelman (Caryophyllaceae) growing in Baikal region were studied for the first time. A total of 14 compounds including three new compounds 1–3 were isolated. Their structures were established using UV, IR, and NMR spectroscopy and mass spectrometry. Apigenin-6-C-(2″-O-α-L-arabinopyranosyl-6″-O-acetyl)-β-D-glucopyranoside (sileneside A, 1) and apigenin-6-C-(2″-O-β-D-glucopyranosyl-6″-O-acetyl)-β-D-glucopyranoside (sileneside B, 2) were observed in S. aprica; 1 and luteolin-6-C-(2″-O-α-L-arabinopyranosyl-6″-O-acetyl)-β-D-glucopyranoside (sileneside C, 3), in S. samojedorum.

Full text of DOI:10.1007/s10600-019-02768-7

DOI 10.1007/s10600-019-02768-7
Chemistry of Natural Compounds, Vol. 55, No. 4, July, 2019
C-GLYCOSYL FLAVONES FROM TWO
EASTERN SIBERIAN SPECIES OF Silene
D. N. Olennikov1* and N. K. Chirikova2
Flavonoids from Silene aprica Turcz. and S. samojedorum (Sambuk) Oxelman (Caryophyllaceae) growing
in Baikal region were studied for the first time. A total of 14 compounds including three new compounds
1
–3 were isolated. Their structures were established using UV, IR, and NMR spectroscopy and mass
spectrometry. Apigenin-6-C-(2″-O-α-L-arabinopyranosyl-6″-O-acetyl)-β-D-glucopyranoside (sileneside A, 1)
and apigenin-6-C-(2″-O-β-D-glucopyranosyl-6″-O-acetyl)-β-D-glucopyranoside (sileneside B, 2) were
observed in S. aprica; 1 and luteolin-6-C-(2″-O-α-L-arabinopyranosyl-6″-O-acetyl)-β-D-glucopyranoside
(
sileneside C, 3), in S. samojedorum.
Keywords: Silene aprica, Silene samojedorum, C-glycosyl flavone, sileneside.
The genus Silene is one of the largest in the family Caryophyllaceae and includes >700 species [1]. Systematic
chemical studies of Silene species were directed mainly at the ecdysteroid [1–3] and triterpenoid compositions [4], i.e.,
biologically active constituents of the genus. Information on flavonoids in Silene is scarce and suggestive of C- and
O-glycosides of apigenin and luteolin [1]. Flavonoids from the two Silene species S. aprica Turcz. [Elisanthe aprica (Turcz.
ex Fisch. et Mey.) Peschkova] and S. samojedorum (Sambuk) Oxelman (Lychnis sibirica L.) that are broadly represented in
steppe and forest-steppe communities of Baikal region were studied during continuing research on Siberian Silene species [5, 6].
The chemical composition of S. aprica has not been published. 20-Hydroxyecdysone and polypodine B were found earlier in
S. samojedorum [7]. Herein, flavonoids from the aerial parts of S. aprica and S. samojedorum are reported and the structures
of three new compounds are described.
Chromatographic separation of the EtOAc and BuOH fractions of S. aprica using column chromatography (CC) over
polyamide and normal and reversed-phase silica gel and preparative HPLC isolated two new flavonoids 1 and 2 and the known
compounds carlinoside (4) [8], schaftoside (5) [9], isoorientin (6) [10], isovitexin-2″-O-arabinoside (7) [11], chrysoeriol-6-C-
β-D-glucopyranosyl-8-C-α-L-arabinopyranoside (8) [12], isovitexin (9) [11], and isoscoparin (10) [13].
R
OH
CH3
O
CH
4' OH
3
4'
HO
7
O
O
HO
7
O
O
O
O
O
6''
O
6''
O
3
HO
HO
HO
1''
2
''
O
OH
O
OH
HO
HO
HO
O
O
1'''
2
'''
OH
OH
HO
OH
1
, 3
2
OH
1
: R = H; 3: R = OH
1
) Institute of General and Experimental Biology, Siberian Branch, Russian Academy of Sciences, 6 Sakh′yanovoi
St., Ulan-Ude, 670047, e-mail: olennikovdn@mail.ru; 2) M. K. Ammosov North-Eastern Federal University, 58 Belinskogo
St., Yakutsk, 677000, e-mail: hofnung@mail.ru. Translated from Khimiya Prirodnykh Soedinenii, No. 4, July–August, 2019,
pp. 552–556. Original article submitted January 21, 2019.
642
0009-3130/19/5504-0642 ©2019 Springer Science+Business Media, LLC

TABLE 1. PMR Spectra of 1–3 (500 MHz, MeOH-d , 298 K, δ, ppm, J/Hz)
4
H atom
1
2
3
3
8
6.63 (1H, s)
6.50 (1H, s)
6.61 (1H, s)
6.52 (1H, s)
6.71 (1H, s)
6.42 (1H, s)
7.38 (1H, d, J = 2.1)
–
6.93 (1H, d, J = 8.2)
7.42 (1H, dd, J = 8.2, 2.1)
4.76 (1H, d, J = 10.0)
4.35 (1H, m)
2
3
5
6
′
′
′
′
7.75 (2H, d, J = 8.8)
6.91 (2H, d, J = 8.8)
6.91 (2H, d, J = 8.8)
7.75 (2H, d, J = 8.8)
4.75 (1H, d, J = 10.0)
4.40 (1H, m)
7.73 (2H, d, J = 8.7)
6.87 (2H, d, J = 8.7)
6.87 (2H, d, J = 8.7)
7.73 (2H, d, J = 8.7)
4.79 (1H, d, J = 9.9)
4.32 (1H, m)
1
2
3
4
5
6
′′
′′
′′
′′
′′
′′
3.11–3.82 (6H, m)
3.09–3.51 (7H, m)
3.08–3.75 (6H, m)
4.51 (1H, d J = 11.0)
.92 (1H, dd, J = 11.0, 6.1)
4.21 (1H, d, J = 5.9)
4.50 (1H, d, J = 11.0)
3.90 (1H, dd, J = 11.0, 6.0)
5.10 (1H, d, J = 8.7)
4.54 (1H, d, J = 11.0)
3.95 (1H, dd, J = 11.0, 6.2)
4.18 (1H, d, J = 6.0)
3
1′′′
2′′′
3′′′
4′′′
5′′′
3.11–3.82 (6H, m)
3.08–3.75 (6H, m)
3.09–3.51 (7H, m)
3.07 (1H, dd, J = 12.0, 5.0)
.85 (1H, dd, J = 12.0, 2.7)
3.04 (1H, dd, J = 11.8, 4.8)
2.80 (1H, dd, J = 11.8, 2.6)
–
2
6′′′
–
3.82 (1H, dd, J = 11.3, 3.2)
.68 (1H, dd, J = 11.3, 2.3)
3
6
′′-CH3CO
1.98 (3H, s)
1.95 (3H, s)
2.01 (3H, s)
1
3
C NMR and mass spectra of 1 were consistent with molecular formula C H O . The UV spectrum of 1 had
2
8 30 15
maxima at 271 and 334 nm that were characteristic of apigenin-type flavones [11]. The IR spectrum showed bands resulting
–
1
from acylation (1654, 1720 cm ). The mass spectrum exhibited a peak for the deprotonated molecule with m/z 605 and
3
fragments with m/z 563, 473, and 431 that formed by loss of an O-acetyl and O-bonded pentose [14]. The MS spectrum of the
fragment with m/z 431 showed species with m/z 341 [431 – 90], 311 [431 – 120], 313 [431 – 90 – CO], and 283 [431 – 120 – CO],
which were characteristic of flavone C-glycosides [14]. Acid hydrolysis of 1 by TFA produced apigenin-6-C-glucoside
(
isovitexin, 9) and L-arabinose. Therefore, 1 was monoacetylated isovitexin O-arabinoside.
The positions of the doublets for the anomeric protons of glucose (δ 4.75) and arabinose (δ 4.21) indicated that they
had the β- and α-configuration, respectively [9, 11] (Table 1). The location of the glucose C-1 resonance at strong field
δ 71.5) and a correlation in the HMBC spectrum between resonances for glucose H-1″ (δ 4.75) and aglycon C-6 (δ 107.5)
confirmed that there was a 6-C-glycoside bond (Table 2). The H-2″ (δ 4.40) and H-6″ resonances (δ 4.51, 3.92) of the
-C-glucose in the PMR spectrum were shifted to weak field as compared with those in isovitexin [11]. Weak-field shifts in
(
6
1
3
the C NMR spectra were also found for the C-2″ (δ 80.1) and C-6″ resonances (δ 64.0) of the 6-C-glucose. Correlations
were found in the HMBC spectrum between the arabinose H-1″′ proton (δ 4.21) and the glucose C-2″ resonances (δ 80.1) and
between the glucose H-6″ protons (δ 3.92, 4.51) and the acetyl carbonyl (δ 170.2), which established that the arabinose and
acetyl were bonded at the C-2″ and C-6″ positions, respectively, of the 6-C-bonded glucose. Thus, the structure of 1 was
apigenin-6-C-(2″-O-α-L-arabinopyranosyl-6″-O-acetyl)-β-D-glucopyranoside, which was called sileneside A.
Compound 2 gave a deprotonated fragment with m/z 635 in the ESI-MS spectrum and fragments indicating loss of
hexose (m/z 473) and acetyl (m/z 593) and then a fragment with m/z 431 that was characteristic of 1. Acid hydrolysis of 2
formed isovitexin (9) and D-glucose. NMR spectra of 2 were similar to those of 1. However, the PMR spectrum had two
resonances for anomeric protons at δ 4.79 and 5.10 ppm that were attributed to protons of C- and O-bonded, respectively,
1
3
β-glucopyranoses. The bonding pattern also confirmed resonances in C NMR spectra for glucose C- and O-bonded moieties
at δ 72.0 (C-1″) and 104.1 ppm (C-1″′), respectively. HMBC spectra revealed correlations between H-1″′ of O-bonded
glucose (δ 5.10) and C-2″ of C-bonded glucose (δ 81.9) and between H-6″ of C-bonded glucose (δ 3.90, 4.50) and the
carbonyl C atom (δ 170.5). These data indicated that 2 was apigenin-6-C-(2″-O-β-D-glucopyranosyl-6″-O-actyl)-β-D-
glucopyranoside, which was called sileneside B.
643

TABLE 2. 13C NMR Spectra of 1–3 (125 MHz, MeOH-d , 298 K, δ, ppm)
4
C atom
1
2
3
C atom
1
2
3
2
3
4
5
6
7
8
9
163.7
102.5
181.5
161.3
107.5
163.2
92.7
156.2
103.2
121.7
128.5
116.0
160.7
116.0
128.5
163.6
102.7
181.7
161.2
107.3
163.0
92.9
156.1
103.0
121.6
128.3
116.2
160.9
116.2
128.3
163.5
102.8
181.5
161.0
107.4
162.9
93.0
156.3
103.3
121.1
112.9
145.3
149.5
115.7
118.9
1′′
2′′
3′′
4′′
5′′
6′′
1′′′
2′′′
3′′′
4′′′
5′′′
6′′′
71.5
80.1
76.5
70.2
77.8
64.0
105.1
67.2
72.3
71.1
64.7
–
72.0
81.9
76.3
70.1
77.9
64.2
104.1
73.5
76.0
68.7
75.7
60.2
20.3
170.5
72.1
80.1
78.0
70.4
77.5
63.7
105.2
67.5
72.6
71.3
64.5
–
1
0
1
′
2
′
3
′
4
′
6′′-CH3CO
6′′-CH3CO
20.4
170.2
20.3
170.4
5
′
6′
Chromatographic separation of fractions from S. samojedorum isolated 1, 4–6, 10, isoscoparin-2″-O-glucoside (11)
8], isovitexin-2″-O-rhamnoside (12) [15], sweritisin-2″-O-rhamnoside (13) [16], spinosin (14) [17], and new flavonoid 3.
[
1
3
C NMR spectroscopy and mass spectrometry of 3 were consistent with the formula C H O . The UV spectrum contained
2
8 30 16
maxima (253, 273, 341 nm) typical of luteolin derivatives. The mass spectral fragmentation pattern was similar to those of
acylated flavone C,O-glycosides [14]. The deprotonated parent with m/z 621 gave daughter fragments from loss of pentose
(
m/z 489) or acetate (m/z 579) or both (m/z 447). Acid hydrolysis of 3 released luteolin-6-C-glucoside (isoorientin, 6) and
L-arabinose.
NMR spectra were similar to those of 1, especially for the carbohydrate resonances, and 6, except for additional
resonances due to arabinose and acetyl groups. HMBC correlations were found between the resonances of the arabinose H-1″′
proton (δ 4.18) and glucose C-2″ (δ 80.1) and between glucose H-6″ protons (δ 3.95, 4.54) and acetyl carbonyl (δ 170.4). As
a result, the structure of 3 was established as luteolin-6-C-(2″-O-α-L-arabinopyranosyl-6″-O-acetyl)-β-D-glucopyranoside
and was called sileneside C.
Acetates of 9 are known for 6″-O- and 2″,6″-di-O-acetylisovitexin from Crotalaria thebaica (Delile) DC. (Leguminosae)
[
18] and 6-O-acetylisovitexin-7-O-glucoside from Stellaria media (L.) Vill. (Caryophyllaceae) [19]. Earlier, acetyl derivatives
of 6 included 2″-O- and 2″,6″-di-O-acetylisoorientin in Rumex acetosa L. (Polygonaceae) [10] and 6″-O-acetylisoorientin in
C. thebaica [18]. The acetyl derivatives of 2-O-arabinosides/glucosides of isovitexin and isoorientin were observed by us for
the first time in the genus Silene although the parent compounds were found in Silene species [20, 21].
Transformations of 1–3 under conditions simulating human in vivo media showed that the compounds were stable to
gastric and intestinal juices. Incubation for 36 h with human intestinal microbiota caused more extensive changes, transforming
1
and 2 into naringenin; 3, into eriodictyol. Earlier, studies of C-glycosylflavone metabolic pathways showed that they could
be transformed into naringenin and eriodictyol [22], which were probably common metabolites for O-glycosyl/acetyl isovitexin
and isoorientin derivatives.
EXPERIMENTAL
The aerial part of S. aprica was collected during flowering in the vicinity of Ivolginsk (Ivolginsky District, Republic
of Buryatia, Russia; Jun. 8, 2017; 51°40′18.37″ N, 107°11′1.05″ E; h 770 m above sea level); S. samojedorum, in the vicinity
of Barskoe (Mukhorshibirsky District, Republic of Buryatia, Russia; Jun. 17, 2017; 51°17′58.24″ N, 107°33′55.85″ E;
h 850 m above sea level). Specimens of raw material are preserved in the herbarium of the IGEB, SB, RAS (No. Ca/ae-17/06-
0
7/1224, Ca/ae-17/06-07/1263). The species was determined by Dr. T. A. Aseeva (IGEB, SB, RAS). Raw material was dried
in a convection oven (50°C) to moisture <5%. CC used polyamide and reversed-phase (RP-SiO ) and normal-phase silica gel
2
644

(
SiO , Sigma-Aldrich, St. Louis, MO, USA). Spectrophotometric studies used an SF-2000 spectrophotometer (OKB Spectr,
2
St. Petersburg, Russia). Mass spectrometric studies used an LCMS-8050 TQ mass spectrometer (Shimadzu, Columbia, MD,
USA) with electrospray ionization (ESI, negative ion mode); ESI interface temperature 300°C; desolvation line, 250°C; heater
block, 400°C; spray gas (N ) flow rate, 3 L/min; heating gas (air) flow rate, 10 L/min; collision-induced dissociation (CID) gas
2
(
(
Ar) pressure, 270 kPa; Ar flow rate, 0.3 mL/min; capillary potential, +25 kV; field potential, 3.5 kV; and mass scan range
m/z), 100–1000. NMR spectra were recorded on a VXR 500S NMR spectrometer (Varian, Palo Alto, CA, USA). Preparative
HPLC used a Summit liquid chromatograph (Dionex, Sunnyvale, CA, USA) equipped with a LiChrospher RP-18 column
(
250 × 10 mm, ∅ 10 μm; Supelco, Bellefonte, PA, USA); mobile phase H O (A) and MeCN (B); ν 1 mL/min; column
2
temperature, 30°C; UV detector, λ 330 nm. Analytical HPLC used a Milichrom A-02 microcolumn liquid chromatograph
(
EcoNova, Novosibirsk, Russia) equipped with a ProntoSIL-120-5-C18 AQ column (2 × 75 mm, ∅ 5 μm; Metrohm AG).
Extraction and Separation of Compounds from the Aerial Part of S. aprica. Ground raw material (580 g) was
extracted (2×) with EtOH (70%) at 70°C for 2 h in an ultrasonic bath (100 W, 35 kHz). The EtOH extract was filtered and
concentrated to dryness in vacuo. The dry solid was suspended in H O (2 L) and extracted with hexane, EtOAc, and BuOH.
2
The EtOAc fraction (28 g) was separated over polyamide (500 g) with elution by H O and EtOH (90%). The EtOH eluate was
2
separated further by CC over SiO (10 × 40 cm) using hexane–EtOAc (100:0→70:30). Subfractions eluted by hexane–EtOAc
2
(
85:15 and 80:20) were chromatographed further over RP-SiO (CC, 5 × 30 cm, eluent H O–MeCN, 50:50→0:100) and
2 2
purified by prep. HPLC [gradient mode (%B): 0–60 min, 40–70%; 60–70 min, 70–100%] to afford 1 (26 mg) and 2 (18 mg).
Subfractions eluted by hexane–EtOAc (70:30) were rechromatographed over SiO (CC, 5 × 35 cm) using EtOAc–Me CO
2
2
(
100:0→90:10) to afford isoscoparin (10, 11 mg) [13]. The BuOH fraction (72 g) was separated over polyamide (800 g, H O
2
and 20–90% EtOH eluents). The fraction eluted by EtOH (20%) was chromatographed over polyamide (CC, 20 × 40 cm,
H O–EtOH eluent, 100:0→50:50) to afford carlinoside (4, luteolin-6-C-β-D-glucopyranoside-8-C-α-L-arabinopyranoside,
2
1
7 mg) [8]. Fractions obtained by elution with EtOH (30% and 40%) were rechromatographed over polyamide to afford
schaftoside (5, apigenin-6-C-β-D-glucopyranoside-8-C-α-L-arabinopyranoside, 25 mg) [9] and isoorientin (6, 15 mg) [10].
Compound 7 (125 mg) precipitated while the fraction eluted by EtOH (50%) was being concentrated. It was reprecipitated
from EtOH and identified as isovitexin-2″-O-arabinoside [11]. Fractions obtained from elution by EtOH (70–90%) were
combined and chromatographed over SiO (CC, 7 × 30 cm, hexane–EtOAc eluent, 100:0→70:30) to afford chrysoeriol-6-C-
2
β-D-glucopyranosyl-8-C-α-L-arabinopyranoside (8, 9 mg) [12] and isovitexin (9, 44 mg) [11].
–
1
Sileneside A (1). C H O . UV spectrum (ÌåÎÍ, λ , nm): 271, 334. IR spectrum (ν, cm ): 1654, 1720.
2
8
30 15
max
–
–
–
–
ESI-MS, m/z: 605 [M – H] , 563 [(M – H) – C H O] , 473 [(M – H) – C H O ] , 431 [(M – H) – C H O – C H O ] ,
2
2
5
8
4
2
2
5 8 4
–
–
3
41 [(M – H) – C H O – C H O – C H O ] , 313 [(M – H) – C H O – C H O – C H O – CO] , 311 [(M – H) – C H O –
2 2 5 8 4 3 6 3 2 2 5 8 4 3 6 3 2 2
–
–
C H O – C H O ] , 283 [(M – H) – C H O – C H O – C H O – CO] . Table 1 lists the PMR spectrum (500 MHz,
MeOH-d , δ, ppm); Table 2, the C NMR spectrum (125 MHz, MeOH-d , δ, ppm).
5
8
4
4
8
4
2
2
5
8
4
4 8 4
1
3
4
4
–
1
Sileneside B (2). C H O . UV spectrum (ÌåÎÍ, λ , nm): 270, 333. IR spectrum (ν, cm ): 1650, 1724.
2
9
32 16
max
–
–
–
–
ESI-MS, m/z: 635 [M – H] , 593 [(M – H) – C H O] , 473 [(M – H) – C H O ] , 431 [(M – H) – C H O – C H O ] , 341
2
2
6
10
5
2
2
6 10 5
–
–
[
(M – H) – C H O – C H O – C H O ] , 313 [(M – H) – C H O – C H O – C H O – CO] , 311 [(M – H) – C H O –
2
2
6
10
5
3
6
3
2
2
6
10
–
5
3
6
3
2 2
–
C H O – C H O ] , 283 [(M – H) – C H O – C H O – C H O – CO] . Table 1 lists the PMR spectrum (500 MHz,
MeOH-d , δ, ppm); Table 2, the C NMR spectrum (125 MHz, MeOH-d , δ, ppm).
6
10
5
4
8
4
2
2
6
10
5
4 8 4
1
3
4
4
Acid Hydrolysis of 1 and 2. A weighed portion (5 mg) was heated with TFA (2 M, 3 mL) at 120°C for 2 h.
The hydrolysate was concentrated with MeOH to dryness in vacuo. The dry solid was dissolved in EtOH (50%, 2 mL).
The resulting solution was passed through a cartridge with polyamide (2 g) followed by elution with H O (50 mL, eluate I) and
2
EtOH (70%, 100 mL, eluate II). Monosaccharides were detected by derivatizing a portion of eluate I with 3-methyl-1-phenyl-
2
-pyrazolin-5-one, as described earlier [23], and analyzing by analytical HPLC (conditions 1). Reductive amination by
L-tryptophan [24] followed by analytical HPLC (conditions 2) were used to determine if the monosaccharides in eluate I were
1
3
D- or L-isomers. Eluate II was analyzed by C NMR spectroscopy and mass spectrometry. The hydrolysate of 1 contained
isovitexin (9) and L-arabinose; hydrolysates of 2–9, D-glucose.
–
13
Isovitexin (9). ESI-MS, m/z 431 [M – H] . C NMR spectrum (125 MHz, ÌåÎÍ-d , δ, ppm): 61.3 (C-6′′, Glc), 70.2
4
(
C-4′′, Glc), 70.6 (C-2′′, Glc), 73.4 (Ñ-1′′, Glc), 78.5 (C-3′′, Glc), 81.6 (C-5′′, Glc), 92.6 (C-8), 102.4 (C-3), 103.0 (C-10),
1
1
07.6 (C-6), 116.2 (C-3′, 5′), 121.9 (C-1′), 128.7 (C-2′, 6′), 156.3 (C-9), 160.8 (C-4′), 161.5 (C-5), 163.1 (C-7), 163.5 (C-2),
81.3 (C-4).
Extraction and Separation of Compounds from the Aerial Part of S. samojedorum. Ground raw material (920 g)
was extracted with EtOH (70%) at 70°C for 4 h in an ultrasonic bath (100 W, 35 kHz). The EtOH extract was concentrated to
645

dryness in vacuo. The dry solid was suspended in H O (4 L) and extracted with hexane, EtOAc, and BuOH. The EtOAc
2
fraction (42 g) was separated beforehand over polyamide (500 g) with elution by H O and EtOH (90%). The EtOH eluate was
2
chromatographed over SiO (CC, 20 × 50 cm, hexane–EtOAc eluent, 100:0→60:40). Fractions eluted by hexane–EtOAc
2
(
85:15 and 80:20) were rechromatographed over RP-SiO (CC, 5 × 30 cm, eluent H O–MeCN, 40:60→0:100) to afford
2 2
sileneosides A(1, 12 mg) and C (3, 31 mg). The fraction eluted by hexane–EtOAc (70:30) was separated again over SiO (CC,
2
5
× 30 cm, EtOAc–Me CO eluent, 100:0→90:10) to afford isoscoparin (10, 22 mg) [13]. The BuOH fraction (125 g) was
2
separated over polyamide (1.5 kg) with elution by H O and EtOH (20–90%). Fractions eluted by EtOH (20–40%) were
2
separated as described above to afford carlinoside (4, 39 mg) [8], schaftoside (5, 63 mg) [9], and isoorientin (6, 24 mg) [10].
Fractions eluted by EtOH (70–90%) were separated by CC over SiO (10 × 40 cm, hexane–EtOAc eluent, 100:0→60:40),
2
RP-SiO (CC, 5 × 40 cm, H O–MeCN eluent, 100:0→0:100), and Sephadex LH-20 (CC, 7 × 80 cm, EtOH–H O eluent,
2
2
2
7
0:30→0:100) to afford the four compounds isoscoparin-2″-O-glucoside (11, 14 mg) [8], isovitexin-2″-O-rhamnoside
(
12, 59 mg) [15], swertisin-2″-O-rhamnoside (13, 12 mg) [16], and spinosin (14, swertisin-2″-O-glucoside, 63 mg) [17].
–1
Sileneside C (3). C H O . UV spectrum (ÌåÎÍ, λ , nm): 253, 273, 341. IR spectrum (ν, cm ): 1652, 1722.
2
8
30 16
max
–
–
–
–
ESI-MS, m/z: 621 [M – H] , 579 [(M – H) – C H O] , 489 [(M – H) – C H O ] , 447 [(M – H) – C H O – C H O ] , 357
[
–
2
2
5
8
4
2
2
5 8 4
–
–
(M – H) – C H O – C H O – C H O ] , 329 [(M – H) – C H O – C H O – C H O – CO] , 327 [(M – H) – C H O – C H O
2 2 5 8 4 3 6 3 2 2 5 8 4 3 6 3 2 2 5 8 4
–
–
C H O ] , 299 [(M – H) – C H O – C H O – C H O – CO] . Table 1 lists the PMR spectrum (500 MHz, MeOH-d , δ,
4 8 4 2 2 5 8 4 4 8 4 4
1
3
ppm); Table 2, the C NMR spectrum (125 MHz, MeOH-d , δ, ppm).
4
Acid hydrolysis of 3 was performed as above. The hydrolysate contained isoorientin (6) and L-arabinose.
–
13
Isoorientin (6). ESI-MS, m/z 447 [M – H] . C NMR spectrum (125 MHz, ÌåÎÍ-d , δ, ppm): 61.5 (C-6′′, Glc),
4
7
1
0.6 (C-4′′, Glc), 70.9 (C-2′′, Glc), 73.5 (C-1′′, Glc), 78.9 (C-3′′, Glc), 81.5 (C-5′′, Glc), 92.8 (C-8), 102.7 (C-3), 103.2 (C-10),
07.3 (C-6), 113.2 (C-2′), 115.9 (C-5′), 119.1 (C-6′), 121.0 (C-1′), 145.5 (C-3′), 149.3 (C-4′), 156.1 (C-9), 161.2 (C-5), 162.7
(
C-7), 163.7 (C-2), 181.6 (C-4).
Stability was studied using the model reported by us earlier for simulating the gastrointestinal tract [25]. The product
composition was determined using analytical HPLC (conditions 3). Compounds 1–3 did not change after incubation with
gastric and intestinal juices. Naringenin for 1 and 2 and eriodictyol for 3 were observed after incubation with intestinal
microbiota.
Analytical HPLC. Conditions 1: mobile phase CH COONH (100 mM, pH 4.5) (A) and MeCN (B); gradient mode
3
4
(
%B): 0–20 min, 20–26%, flow rate 150 μL/min; column temperature, 35°C; UV detector, λ 250 nm. Retention times of
monosaccharide derivatives of 3-methyl-1-phenyl-2-pyrazolin-5-one (t , min): glucose, 12.52; galactose, 13.54; arabinose,
R
1
4.51; xylose, 14.86. Conditions 2: mobile phase NaH PO (10 mM) and Na B O (50 mM) (1:1, pH 9.6); isocratic mode;
2 4 2 4 7
flow rate 200 μL/min; column temperature, 35°C; UV detector, λ 220 nm. Retention times of monosaccharide derivatives
with L-tryptophan (t , min): D-glucose, 8.32; L-glucose, 8.67; D-arabinose, 16.31; L-arabinose, 16.92. Conditions 3: mobile
R
phase LiClO (0.2 M) in HClO (0.006 M) (A) and MeCN (B); gradient mode (%B): 0–6 min, 5–25%; 6–11, 25%; 11–17, 30–60%;
4
4
1
7–22, 100%; flow rate 150 μL/min; column temperature, 35°C; UV detector, λ 270, 330 nm. Retention times of flavonoids
(
tR, min): 3, 6.18; 2, 8.40; 1, 8.62; isoorientin, 11.16; isovitexin, 12.34; eriodictyol, 14.16; naringenin, 15.22; luteolin, 15.37;
and apigenin, 16.02.
ACKNOWLEDGMENT
The work was sponsored by the Ministry of Science and Higher Education of the Russian Federation
Project No. AAAA-A17-117011810037-0).
(
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