New Glycosides of Eriodictyol from Dracocephalum palmatum

Article abstract of DOI:10.1007/s10600-018-2499-4

Two new glycosides of eriodictyol were isolated from the aerial part of Dracocephalum palmatum and identified using UV, NMR, and CD spectroscopy and mass spectrometry as (S)-eriodictyol-7-O-(6′′-O-malonyl)-β-Dglucopyranoside (pyracanthoside-6′′ -O-malonat

Full text of DOI:10.1007/s10600-018-2499-4

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DOI 10.1007/s10600-018-2499-4
Chemistry of Natural Compounds, Vol. 54, No. 5, September, 2018
NEW GLYCOSIDES OF ERIODICTYOL FROM Dracocephalum palmatum
1*
2
3
D. N. Olennikov, N. K. Chirikova, Eungyoung Kim,
3
2,3,4
Sang Woo Kim, and I. S. Zul′fugarov
Two new glycosides of eriodictyol were isolated from the aerial part of Dracocephalum palmatum and identified
using UV, NMR, and CD spectroscopy and mass spectrometry as (S)-eriodictyol-7-O-(6′′-O-malonyl)-β-D-
glucopyranoside (pyracanthoside-6′′-O-malonate, 1) and (S)-eryodictyol-7-O-(4′′-O-malonyl)-β-D-
glucopyranoside (pyracanthoside-4′′-O-malonate, 2). The stabilities of 1 and 2 were studied under simulated
stomach and intestinal conditions.
Keywords: Dracocephalum palmatum, Lamiaceae, (S)-eriodictyol-7-O-(6′′-O-malonyl)-β-D-glucopyranoside,
(S)-eriodictyol-7-O-(4′′-O-malonyl)-β-D-glucopyranoside, pyracanthoside-6′′-O-malonate, pyracanthoside-4′′-O-malonate.
Dracocephalum palmatum Steph. ex Willd. (Lamiaceae) is indigenous to northern Yakutia and is used by nomads as
a medicinal and food plant [1]. Previous chemical investigations of D. palmatum identified phenylpropanoids, coumarins,
flavonoids, triterpenoids [1, 2], lipids, essential oil, simple phenols, and carbohydrates [3]. Herein, two new flavonoids
isolated from D. palmatum are reported.
Chromatographic separation of fraction F3-2 (prep. HPLC, CC) isolated eight compounds (1–8) including the known
flavonoids acacetin-7-O-(6′′-O-acetyl)-β-D-glucopyranoside (agastachoside, 3) [4], apigenin-7-O-(6′′-O-acetyl)-β-D-
glucopyranoside (4) [5], luteolin-7-O-(6′′-O-acetyl)-β-D-glucopyranoside (5) [6], acacetin-7-O-(6′′-O-malonyl)-β-D-
glucopyranoside (6) [7], apigenin-7-O-(6′′-O-malonyl)-β-D-glucopyranoside (7) [7], luteolin-7-O-(6′′-O-malonyl)-β-D-
glucopyranoside (8) [7], and two new compounds 1 and 2.
O
O
OH
OH
3'''
3'
3'
OH
OH
OH
6''
1'''
HO
O
4'
6''
O
O
9
7
O
O
O
7
1''
O
O
O
HO
O
OH 1''
1'''
HO
HO
OH
O
3
5
OH
OH
O
OH
1
2
13
Compound 1 had molecular formula C H O based on C NMR spectroscopic and mass spectrometric data
24 24 14
–
(m/z 535, [M – H] ). Acid hydrolysis of 1 gave eriodictyol and D-glucose. The ESI-MS contained fragment ions with m/z 449
and 287 that were consistent with loss of species with m/z 86 (malonyl) and 162 (glucosyl) [8]. PMR and C NMR spectra
13
were similar to that of eriodictyol-7-O-β-D-glucopyranoside (pyracanthoside, miscanthoside; 1a) [9] with the exception of
additional resonances [δ 3.26 (2H, s); δ 41.2, 167.1, 167.8] due to the malonyl group (Table 1) [10].
H
C
1) Institute of General and Experimental Biology, Siberian Branch, Russian Academy of Sciences, 6 Sakh′yanovoi
St., Ulan-Ude, 670047, fax: +73012 434743, e-mail: olennikovdn@mail.ru; 2) M. K. Ammosov North-Eastern Federal
University, 58 Belinskogo St., Yakutsk, 677000, e-mail: hofnung@mail.ru; 3) Department of Biological Sciences,
Pusan National University, 46241, Busan, Republic of Korea, e-mail: kimsw@pusan.ac.kr; 4) Institute of Molecular
Biology and Biotechnology, National Academy of Sciences of Azerbaijan, 2a Metbuat Prosp., Baku, AZ 1073,
e-mail: iszulfugarov@pusan.ac.kr. Translated from Khimiya Prirodnykh Soedinenii, No. 5, September–October, 2018,
pp. 731–734. Original article submitted March 28, 2018.
©
860
0009-3130/18/5405-0860 2018 Springer Science+Business Media, LLC

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13
TABLE 1. PMR (500 MHz) and C NMR Spectra (125 MHz) of 1 and 2 (MeOH-d , δ, ppm, J/Hz)
4
1
2
C atom
δH
δC
δH
δC
Eriodictyol
2
3
5.46 (1Í, dd, J = 12.0, 3.0)
3.15 (1Í, dd, J = 17.1, 12.0)
2.70 (1Í, dd, J = 17.1, 3.0)
78.5
42.0
5.33 (1Í, dd, J = 12.1, 3.0)
3.12 (1Í, dd, J = 17.0, 12.1)
2.71 (1Í, dd, J = 17.0, 3.0)
78.6
42.2
4
5
6
–
–
197.0
163.0
96.4
–
–
196.8
163.2
96.2
6.03 (1Í, m)
6.00 (1Í, m)
7
8
–
165.5
95.2
–
165.0
95.5
6.08 (1Í, m)
6.12 (1Í, m)
9
10
–
–
–
162.6
102.5
129.4
115.6
145.7
145.1
114.8
117.6
–
–
–
162.3
102.4
129.8
115.3
145.4
145.0
114.3
117.5
′
1
6.95 (1Í, m)
7.01 (1Í, m)
2′
–
–
–
–
′
3
4′
5′
6′
6.75 (2Í, m)
6.72 (2Í, m)
7- -β-D-Glucopyranosyl
O
5.06 (1Í, d, J = 7.1)
3.36–3.39 (2Í, m)
99.7
73.1
76.3
69.9
74.1
64.1
5.02 (1Í, d, J = 7.0)
3.31–3.40 (2Í, m)
99.8
72.7
75.2
71.2
73.4
60.0
1′′
2′′
3′′
4′′
3.30 (1Í, m)
3.72 (1Í, m)
4.46 (1Í, dd, J = 1.7, 12.1)
4.40 (1Í, m)
3.75 (1Í, m)
3.61 (1Í, d J = 12.0)
′′
5
6′′
4.12 (1Í, dd, J = 7.0, 12.1)
3.51 (1Í, dd, J = 5.4, 12.0)
6′′- -Malonyl
4′′- -Malonyl
O
O
–
167.1
41.2
–
166.9
41.0
′′′
1
3.26 (2Í, s)
3.24 (2Í, s)
2′′′
′′′
–
167.8
–
167.9
3
The acyl group was positioned on C-6′′ according to weak-field shifts of glucose resonances for C-6′′ (δ 64.1) and
H-6′′ [δ 4.46 (1H, dd, J = 1.7, 12.1 Hz), 4.12 (1H, dd, J = 7.0, 12.1 Hz)] as compared to resonances of 1a (δ 60.4; δ 3.66,
C
H
3.43) [9] and correlations in HMBC spectra between glucose H-6′′ (δ 4.12, 4.46) and malonyl C-1′′′ (δ 167.1) [11].
H
C
The absolute configuration of the eriodictyol C-2 phenyl was determined using circular dichroism. A positive Cotton effect at
327 nm and a negative effect at 298 nm indicated that C-2 had the S-configuration [12]. Thus, the structure of 1 was determined
as (S)-eriodictyol-7-O-(6′′-O-malonyl)- β-D-glucopyranoside or pyracanthoside-6′′-O-malonate.
Compound 2 had molecular formula C H O and mass and UV spectra that were similar to those of 1. This
24 24 14
indicated that 2 was also an eriodictyol-7-O-β-D-glucopyranoside derivative with a malonic-acid substituent. A comparison
13
of PMR and C NMR spectra of 2 and those of 1 and 1a showed that they were similar. However, weak-field shifts were
observed for resonances of glucopyranose C-4′′ (δ 71.2) and H-4′′ [δ 4.40 (1H, m)] relative to those of 1a (δ 69.1; δ 3.18)
C
H
(Table 1). HMBC spectra showed a correlation between glucopyranose H-4′′ (δ 4.40) and δ 166.9, indicating that the
C
malonyl moiety was bonded to glucopyranose C-4′′ [10].
The absolute configuration of C-2 was determined as S from the positive Cotton effect at 325 nm and a negative effect
at 300 nm. The results established the structure of 2 as (S)-eriodictyol-7-O-(4′′-O-malonyl)-β-D-glucopyranoside or
pyracanthoside-4′′-O-malonate.
Esters of malonic acid and eriodictyol glycosides have not previously been isolated from plants. Until now, the only
known flavanone containing a malonic-acid fragment was naringin-6′′-malonate from leaves and fruit of Citrus paradisi
Macfad. [13] and fruit of C. × aurantium L. (Rutaceae) [14].
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1,2
TABLE 2. Products from Reactions of 1 and 2 with Simulated Physiological Media
Simulated medium
1
2
Control (H2O)
Stomach juice
Intestinal juice
1 (100)
2 (100)
1 (80), 2 (15), 1a (5)
1 (62), 2 (31), 1a (7)
2
(21), (25),
(53),
(< 1)
(39), (2),
(58),
(< 1)
1b
1
2
1a
1b
1
1a
Intestinal microflora
1a (2), 1b (98)
1a (1), 1b (99)
______
1
2
Component peak area (% of total peak areas) is shown in parentheses; 1a, eriodictyol-7-O-β-D-glucopyranosyl; 1b, eriodictyol.
The stabilities of 1 and 2 under simulated gastrointestinal-tract (GIT) conditions showed that both compounds in
stomach juice underwent chemical reactions involving acyl migration and deacylation (Table 2). Compound 1 with malonyl
on glucopyranose C-6′′ was more stable than 2 to acyl migration. Incubation in stomach juice converted ~15% of 1 into 2
whereas 2 was >60% converted into 1. Only 5–7% of the total compound mass was deacylated under these same conditions.
However, the content of deacylated 1a increased to 53–58% in juice of later GIT stages. Intestinal microflora caused more
extensive changes of 1 and 2 that led to total hydrolysis of the compounds to eriodictyol (1b). Previously, the same transformation
pathway in physiological fluids was demonstrated for naringenin and hesperetin glycosides [15] and is probably common for
flavanone glycosides.
EXPERIMENTAL
General comments were published [1–3]. Spectrophotometric studies used an SF-2000 spectrophotometer (OKB
Spectr, St. Petersburg, Russia). Circular dichroism spectra were recorded on a J-1500 spectrometer (JASCO, Easton, MD,
USA). Mass spectrometric studies used an LCMS-8050 TQ-mass-spectrometer (Shimadzu, Columbia, MD, USA).
The conditions were electrospray ionization (ESI, negative-ion mode); ESI interface temperature 300°C; desolvation line
temperature 250°C; heating block 400°C, sprayer-gas (N ) flow rate 3 L/min; heating-gas (air) flow rate 10 L/min;
2
collision-induced dissociation (CID) gas (Ar) pressure 270 kPa; Ar flow rate 0.3 mL/min; capillary potential 3 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); LiChrospher RP-18 column
(250 × 10 mm, ∅ 10 μm; Supelco, Bellefonte, PA, USA); mobile phase H O (A) and MeCN (B); flow rate 1 mL/min; column
2
temperature 30°C; and UV detector at 280 and 330 nm.
Isolation of 1–8. The extraction conditions for obtaining fraction F3-2 were described before [1]. Fraction F3-2 was
chromatographed over a polyamide column (CC, 4 × 120 cm) with elution by H O–MeOH mixtures (100:0→0:100) to produce
2
subfractions F3-2-1–F3-2-10. Subfractions F3-2-2 and F3-2-3 were combined and separated over Sephadex LH-20
(CC, 3 × 110 cm, MeOH–H O eluent, 100:0→0:100) and by prep. HPLC [gradient mode (%B): 0–10 min, 10–70%;
2
10–60 min, 70–100%] to isolate acacetin-7-O-(6′′-O-acetyl)-β-D-glucopyranoside (agastachoside, 3, 17 mg) [4]; apigenin-7-
O-(6′′-O-acetyl)-β-D-glucopyranoside (4, 10 mg) [5], and luteolin-7-O-(6′′-O-acetyl)-β-D-glucopyranoside (5, 22 mg) [6].
Subfractions F3-2-7–F3-2-9 were combined and chromatographed over RP-SiO (CC, 3 × 100 cm, H O–MeCN eluent,
2
2
100:0→0:100) and by prep. HPLC [gradient mode (%B): 0–35 min, 5–45%; 35–50 min, 45–60%; 50–70 min, 60–90%;
70–90 min, 90–100%]. This produced 1 (18 mg), 2 (10 mg), acacetin-7-O-(6′′-O-malonyl)-β-D-glucopyranoside (6, 15 mg)
[7], apigenin-7-O-(6′′-O-malonyl)-β-D-glucopyranoside (7, 14 mg) [7], and luteolin-7-O-(6′′-O-malonyl)-β-D-glucopyranoside
(8, 27 mg) [7].
(S)-Eriodictyol-7-O-(6′′-O-malonyl)-β-D-glucopyranoside (6′′-O-malonylpyracanthoside, 1). Ñ Í Î .
24 24 14
–
–
–
(–)ESI-ÌS (m/z): 535 [M – Í] , 449 [(M – Í) – 86] , 287 [(M – Í) – 86–162] . UV spectrum (ÌåÎÍ, λ , nm):
max
13
–4
284. CD spectrum (MeOH, c 4.01·10 M; λ , Δε): 298 (–25.4), 327 (+15.2). Table 1 lists PMR (500 MHz) and C NMR
max
(125 MHz) spectral data.
(S)-Eriodictyol-7-O-(4′′-O-malonyl)-β-D-glucopyranoside (4′′-O-malonylpyracanthoside, 2). Ñ Í Î .
24 24 14
–
–
–
(–)ESI-ÌS (m/z): 535 [M – Í] , 449 [(M – Í) – 86] , 287 [(M – Í) – 86 – 162] . UV spectrum (ÌåÎÍ, λ , nm): 283. CD
spectrum (MeOH, c 3.92·10 M; λ , Δε): 300 (–21.7), 325 (+16.1). Table 1 lists PMR (500 MHz) and C NMR (125 MHz)
max
–4
13
max
spectral data.
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Acid Hydrolysis of 1 and 2. The compound (2 mg) was dissolved in TFA (5%, 3 mL) and heated at 110°C for 2 h.
The hydrolysate was concentrated in vacuo, dissolved in MeOH, and chromatographed over polyamide (CC, 10 g) with
elution by H O (50 mL, eluate I) and EtOH (90%, 50 mL, eluate II). The eluates were concentrated in vacuo and analyzed by
2
HPLC (conditions 1, monosaccharides as 3-methyl-1-phenyl-2-pyrazolin-5-one derivatives [3]; conditions 2, phenolic
compounds). Eluate 1 was also analyzed to determine D- and L-monosaccharides after derivatization with L-tryptophan [16].
Eluate I from hydrolysis of 1 and 2 contained D-glucose (t 12.52 min); eluate II, eriodictyol (t 5.52 min).
R
R
HPLC. Conditions 1: ProntoSIL-120-5-C18AQ column (2 × 75 mm, ∅ 5 μm; MetrohmAG); mobile phase: NH OAc
4
(100 mM, pH 4.5) (A) and MeCN (B); gradient mode (%B): 0–20 min, 20–26%; flow rate 150 μL/min; column temperature
35°C; and UV detector at 250 nm. The retention times of reference standards (t , min) were mannose 6.83; glucose 12.52; and
R
galactose 13.54. Conditions 2: ProntoSIL-120-5-C18 AQ column (2 × 75 mm, ∅ 5 μm; Metrohm AG); mobile phase LiClO
4
(0.2 M) in HClO (0.006 M) (A) and MeCN (B); gradient mode (%B): 0–18 min, 25–100%; 18–20 min, 100%; flow rate
4
150 μL/min; column temperature 35°C; and UV detector at 270 nm. Retention times of reference standards (t , min) were
R
eriodictyol 5.53; naringenin 6.72; sakuranetin 8.82; and isosakuranetin 9.45.
The stabilities of the compounds were studied using simulated GIT media that were described by us before [17].
The composition of the reaction products was determined using analytical HPLC [3].
ACKNOWLEDGMENT
The research was sponsored by FASO Russia (Projects No. 0337-2016-0006, AAAA-AA17-117011810037-0) and
the Ministry of Education and Science of Russia (Project No. 20.7216.2017/6.7).
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