Isolation and structure elucidation of a new flavonol glycoside from Sabia Parviflora

Article abstract of DOI:10.1080/14786419.2019.1679130

A new flavonol glycoside named Sabiapside A (1), along with four known compounds, quercetin-3-O-gentiobioside (2), camellianoside (3), isobariclisin-3-O- rutinoside (4), tsubakioside A (5), was isolated from Sabia parviflora. Their structures were elucidated by extensive spectroscopic analysis including MS, UV, IR and NMR data. The antioxidant activities of these glycosides evaluated by ABTS⁺ and DPPH radical scavenging reaction was higher than that of vitamin C used as the reference antioxidant.

Full text of DOI:10.1080/14786419.2019.1679130

Natural Product Research
Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: https://www.tandfonline.com/loi/gnpl20
Isolation and structure elucidation of a new
flavonol glycoside from Sabia Parviflora
Qingwen Sun, Guoji Pan, Wenfen Xu, Xian Lu, Caihong Bai, Mengge Liu &
Yinrui Chen
To cite this article: Qingwen Sun, Guoji Pan, Wenfen Xu, Xian Lu, Caihong Bai, Mengge Liu &
Yinrui Chen (2019): Isolation and structure elucidation of a new flavonol glycoside from Sabia
Parviflora, Natural Product Research, DOI: 10.1080/14786419.2019.1679130
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NATURAL PRODUCT RESEARCH
https://doi.org/10.1080/14786419.2019.1679130
Isolation and structure elucidation of a new flavonol
glycoside from Sabia Parviflora
Qingwen Sun, Guoji Pan, Wenfen Xu, Xian Lu, Caihong Bai, Mengge Liu and
Yinrui Chen
College of Pharmacy, Guizhou University of Traditional Chinese Medicine, Guiyang, China
ABSTRACT
ARTICLE HISTORY
Received 5 March 2019
Accepted 6 October 2019
A new flavonol glycoside named Sabiapside A (1), along with four
known compounds, quercetin-3-O-gentiobioside (2), camelliano-
side (3), isobariclisin-3-O- rutinoside (4), tsubakioside A (5), was
isolated from Sabia parviflora. Their structures were elucidated by
extensive spectroscopic analysis including MS, UV, IR and NMR
data. The antioxidant activities of these glycosides evaluated by
ABTSþ and DPPH radical scavenging reaction was higher than
that of vitamin C used as the reference antioxidant.
KEYWORDS
Sabia parviflora; flavonol
glycoside; antioxidant;
DPPH; ABTSþ
1. Introduction
Sabia parviflora Wall. Ex Roxb. (Sabiaceae) is an evergreen vine widely distributed in
Yunnan, Guizhou and Guangxi in China (ECFC 1988) which has been traditionally used
as folk medicine to treat icteric hepatitis, rheumatism and inflammation (Wen et al.
2016). Previous studies showed structurally diverse compounds had been isolated
from S. parviflora, including alkaloids (Fan, Wang, et al. 2018; Sui et al. 2011), flavo-
noids (Huang et al. 2014) and pentacyclic triterpenes (Chen et al. 2015; Fan, Li, et al.
2018), with flavonoids being the major bioactive phytochemical constitution (Pan et al.
2018). It was reported that S. parviflora showed various pharmacological activities such
as hepatoprotective (Liu et al. 2008; Yang et al. 2013), antiviral (Qu et al. 2015) and
anti-inflammatory (Wang et al. 2018). The investigation on S. parviflora by our group
CONTACT Qingwen Sun
sqw1978_2006@126.com; Wenfen Xu
wenfenxu@126.com
Supplemental data for this article can be accessed at https://doi.org/10.1080/14786419.2019.1679130.
ß 2019 Informa UK Limited, trading as Taylor & Francis Group

2
Q. SUN ET AL.
led to the isolation of a new flavonol glycoside named Sabiapside A (1) and four
known compounds, quercetin-3-O-gentiobioside (2) (Liu et al. 2008), camellianoside (3)
(Onodera et al. 2006), isobariclisin-3-O-rutinoside (4) (Shen et al. 2013) and tsubakio-
side A (5) (Sato et al. 2017). Herein, we report the isolation, structure identification
and antioxidant activities of all isolated compounds.
2. Results and discussion
2.1. Elucidation of the chemical structure of compounds
Compound 1 was obtained as amorphous yellow powder, positive to Molish reagent.
The molecular formula C33H40O20 was established on basis of its HR-ESI-MS at m/z
755.2043 [M-H]－, corresponding to fourteen degrees of unsaturation. The IR spectrum
clearly indicated the presence of hydroxyl groups (3386 cmꢀ1), aromatic rings (1596
and 1499 cmꢀ1) and carbonyl groups (1653 cmꢀ1). The UV spectrum suggested that it
1
was a flavonoid with absorption maxima at 203, 257 and 356 nm. H NMR spectrum
indicated five aromatic protons at dH 7.71 (1H, d, J ¼ 2.2 Hz), 7.64 (1H, dd, J ¼ 8.5,
2.2 Hz), 6.87 (1H, d, J ¼ 8.5 Hz), 6.54 (1H, d, J ¼ 2.2 Hz) and 6.30 (1H, d, J ¼ 2.2 Hz),
together with three anomeric protons of saccharide moieties at dH 5.13 (1H, d,
J ¼ 7.8 Hz), 4.52 (1H, d, J ¼ 1.7 Hz) and 4.33 (1H, d, J ¼ 7.6 Hz), and six methyl protons
at dH 3.86 (3H, s) and 1.10 (3H, d, J ¼ 6.0 Hz). Proton signals of saccharide moieties at
dH 3.09 to 3.84 were overlapped. 13C NMR and DEPT spectra exhibited 33 carbon sig-
nals corresponding to 10 quaternary carbons, 19 methines, two methylenes and two
methyls. Among these carbon resonances, 15 of them were assigned to the quercetin
skeleton (Onodera et al. 2006) and three carbon signals at dC 106.4 (C-1 of the xylose),
104.5 (C-1 of the glucose), 102.3 (C-1 of the rhamnose) were attributed to anomeric
carbons of the sugar moieties. Detailed analysis of the spectral data above revealed
that compound 1 was similar to compound 3, camellianoside (Onodera et al. 2006).
What 1 differed from 3 was that 1 had one more methoxy than 3. HMBC Correlation
from methoxy protons (dH 3.86) to C-7 (dC 167.3) suggested that methoxy was substi-
tuted at C-7. HMBC correlations of H-6/C-5, C-7, C-8, C-10; H-8/C-7, C-9, C-10; H-20/C-2;
H-50/C-10; and H-60/C-2 indicated that hydroxyl groups were located at C-5, C-7, C-30
and C-40, respectively. Acid hydroysis of 1 with 2 HCl yielded an aglycone and sugar
M
components. The sugars of 1 were finally identified as D-glucose, L-rhamnose and
D-xylose based on specific rotations. Interglycosidic linkages were confirmed by HMBC
correlations of H-1-Glc/C-3; H-1-Rha/C-6-Glc and H-1-Xyl/C-3-Rha. The b-glycosidic link-
ages of the glucopyranoside and xylopyranoside units were determined on the basis
of the J1,2 values for the anomeric protons of 7.8 and 7.6 Hz, respectively, and the
1
a-linkage of the rhamnopyranoside unit on the basis of the JCH value for the anome-
ric position of 168 Hz calculated from HMBC spectrum (Podlasek et al. 1995). Thus, the
structure of compound 1 was identified as 7-methoxy-quercetin-3-O-b-D-xylopyranosyl
(1!3)-O-a-L-rhamnopyranosyl-(1!6)-O-b-D-glucopyranoside, to which we gave the
trivial name Sabiapside A.
Additionally, the structures of compounds 2–5 were determined by comparison of
their spectroscopic data with those reported in the literature.

NATURAL PRODUCT RESEARCH
3
2.2. Results of the antioxidant assay
All compounds exhibit highter antioxidant activities for ABTSþ and DPPH with IC50 val-
ues in the range of 2.88 ꢁ 5.78 lg/mL and 2.41 ꢁ 7.95 lg/mL, respectively, in compari-
son with the positive control vitamin C with IC50 values of 7.14 lg/mL for ABTSþ and
15.88 lg/mL for DPPH in vitro.
3. Experimental
3.1. Apparatus and reagents
The 1 D and 2 D NMR spectra were recorded on Bruker AM-600 spectrometer with
TMS as an internal standard (Bruker, Germany). Mass spectra were collected on a
Waters AutoSpec Premier P776 instrument (Waters, USA). IR (KBr) spectra were
acquired on a Thermo Antaris II spectrometer (Thermo, USA). Semi-preparative
HPLC was carried out on an Agilent 1100 HPLC system with Agilent Eclipse XDB-
C18 column (9.4 ꢂ 250 mm, 5 lm) (Agilent, USA). Optical Rotations were tested on
AUTOPOL1-Digital Automatic Polarimeter (Rudolph, USA). Melting points were deter-
mined on a SGW X-4B Microscopic melting point meter (Shanghaijingke, China).
Column chromatography was performed on self-packed column with D-101 macro-
porous (Shanghai, China), polyamide (100-200 mesh, Zhejiang, China), ODS-A-HG
(50 lm, 12 nm, MC, Japan) or silica gel (200-300 mesh, Qingdao, China). Antioxidant
activity was determined by BioTek Synergy two enzyme standard instrument
(BioTek, USA). 2,2’-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt
(ABTS) and 2,2’-dipheny1(l)-1-picrylhydrazyl (DPPH) were purchased from Sigma
(Sigma, USA). Potassium persulfate (K2S2O8) was purchased from Pharmacia Fine
Chemical (Pharmacia, USA). Vitamin C was purchased from National Institutes for
Food and Drug Control (Beijing, China).
3.2. Plant material
The plants of S. parviflora were collected from Zhenning County, Guizhou Province,
China, in June 2017, and identified by Prof. Qing-wen Sun, College of Pharmacy,
Guizhou University of Traditional Chinese Medicine, where a voucher specimen (No.
170620) was deposited.
3.3. Extraction and isolation
The air-dried and powdered stems and leaves of S. parviflora (10.8 kg) were extracted
with MeOH (60 L) three times. MeOH was removed under reduced pressure to give
1.2 kg of crude exract, which was suspended in H2O (2 L), and then subjected to
macroporous column chromatography eluted with H2O/MeOH (100:0!75:25!
30:70!0:100) to yield three fractions (A-C). Fr. B (167 g) was subjected to silica gel col-
umn chromatography eluted with dichloromethane/MeOH (10:1) to afford Fr. B1 and
Fr. B2. Fr. B1 (8.6 g) was chromatographed over silica gel eluting with dichlorome-
thane/MeOH (20:1!20:4) and further purified by Semi-preparative HPLC with H2O/

4
Q. SUN ET AL.
Figure 1. Structures of compounds 1–5.
MeOH (40:60) to afford compound 4 (62 mg). Fr. B2 (1.6 g) was subjected to an ODS-A-HG
column (H2O/MeOH ¼ 3:7) to afford Fr. B2-1 and Fr. B2-2. Fr. B2-1 (310 mg) was further
purified by Semi-preparative HPLC with H2O/MeOH (40:60) to provide compound 5
(89 mg), Fr. B2-2 (790 mg) was further purified by Semi-preparative HPLC with H2O/MeOH
(50:50) to provide compound 1 (210 mg), 2 (59 mg) and 3 (153 mg), (Figure 1).
Sabiapside A, Yellow amorphous powder, [a]14 D -0.02 (c ¼ 4.98, MeOH). Mp.
242 ꢁ 244 ꢃC. HR-ESI-MS m/z 779.1998 [M þ Na]þ (calcd for C33H40O20Na: 779.2005),
755.2043 [M-H]－ (calcd for C33H40O20: 755.2029). UV (MeOH): kmax 203.33, 257.08 and
355.88 nm. IR (KB) mmax cmꢀ1: 3386, 2931, 1750, 1653, 1596, 1499, 1446, 1303, 1209,
1
1165, 1042, 885, 809, 612. H-NMR (600 MHz, CD3OD): d 7.71 (1H, d, J ¼ 2.2 Hz, H-2’),
7.64 (1H, dd, J ¼ 8.5, 2.2 Hz, H-6’), 6.87 (1H, d, J ¼ 8.5 Hz, H-5’), 6.54 (1H, d, J ¼ 2.2 Hz, H-
8), 6.30 (1H, d, J ¼ 2.2 Hz, H-6), 5.13 (1H, d, J ¼ 7.8 Hz, H-1-Glc), 4.52 (1H, d, J ¼ 1.7 Hz,
H-1-Rha), 4.33 (1H, d, J ¼ 7.6 Hz, H-1-Xyl), 3.86 (3H, s, OCH3), 3.82 (1H, overlapped, H-
6a-Glc), 3.79 (1H, overlapped, H-2-Rha), 3.75 (1H, overlapped, H-5a-Xyl), 3.56 (1H, over-
lapped, H-3-Rha), 3.50 (1H, overlapped, H-2-Glc), 3.47 (1H, overlapped, H-5-Rha),
3.47 (1H, overlapped, H-4-Xyl), 3.43 (1H, overlapped, H-3-Glc), 3.42 (1H, overlapped, H-
4-Rha), 3.41 (1H, overlapped, H-6b-Glc), 3.39 (1H, overlapped, H-5-Glc), 3.33 (1H, over-
lapped, H-3-Xyl), 3.24 (1H, overlapped, H-4-Glc), 3.23 (1H, overlapped, H-2-Xyl), 3.12
(1H, overlapped, H-6a-Xyl), 1.10 (3H, d, J ¼ 6.0 Hz, H-6-Rha); 13C-NMR (150 MHz,
CD3OD): d 179.4 (C-4), 167.3 (C-7), 162.6 (C-5), 159.6 (C-2), 158.4 (C-9), 149.9 (C-40),
145.8 (C-30), 135.8 (C-3), 123.6 (C-60), 123.0 (C-10), 117.9 (C-20), 116.0 (C-50), 106.5 (C-10),
106.4 (C-1-Xyl), 104.5 (C-1-Glc), 102.3 (C-1-Rha), 99.2 (C-6), 93.3 (C-8), 82.5 (C-3-Rha),

NATURAL PRODUCT RESEARCH
5
78.2 (C-3-Glc), 77.5 (C-3-Xyl), 77.2 (C-5-Glc), 75.7 (C-2-Glc), 75.3 (C-2-Xyl), 72.7 (C-4-Rha),
71.7 (C-2-Rha), 71.6 (C-4-Glc), 71.1 (C-4-Xyl), 69.4 (C-5-Rha), 68.9 (C-6-Glc), 66.8 (C-5-
Xyl), 56.5 (7-OCH3), 17.9 (C-6-Rha).
3.4. Hydrolysis experiment
Compound 1 (100 mg) was hydrolyzed by 2 HCl solution 5 h under room tempera-
M
ture. The hydrolysate was neutralized by NaOH and then subjected to polyamide col-
umn chromatography eluted with EtOAc/EtOH/acetic acid/H2O (10:5:1:1) to obtain
glucose, rhamnose and xylose confirmed by TLC. Configurations of these sugars were
determined as D-glucose, L-rhamnose and D-xylose based on the specific rotation val-
ues of þ51.5ꢃ, þ8.1ꢃ and þ18.4ꢃ, respectively.
3.5. Antioxidant activity assay
All compounds were evaluated their ability to scavenge the DPPH radical and ABTSþ
radical cation according to previously reported methods (Yang et al. 2014) with some
modifications. Vitamin C was used as a positive control. The ABTSþ radical was pre-
pared by mixing equal volume of 7 mM ABTS water solution and 2.45 mM potassium
persulfate, and the mixture was reacted in dark at room temperature for 12 h before
use. Prior to the assay, the solution was diluted in water to give an absorbance at
734 nm of 0.70 0.02. The DPPH radical solution was diluted with ethanol in dark to
an absorbance of 0.70 0.02 at 516 nm. After reacting with the ABTSþ radical solution
for 10 min (DPPH radical solution for 30 min), the absorbance value (Ai) of ABTSþ at
734 nm (or Ai of DPPH at 516 nm) was measured. The blank absorbance (A0) was
measured using ethanol. The scavenging activity was determined according to the fol-
lowing equation: AA(%) ¼ [A0- Ai]/A0 ꢂ 100%.
4. Conclusion
Five flavonol glycosides, Sabiapside A (1), quercetin-3-O-gentiobioside (2), camelliano-
side (3), isobariclisin-3-O- rutinoside (4) and tsubakioside A (5), were isolated from
Sabia parviflora for the frst time. The antioxidant activities of these glycosides eval-
uated by ABTSþ and DPPH radical scavenging reaction was higher than that of vitamin
C used as the reference antioxidant. The structure-activity relationship of these com-
pounds showed that phenolic hydroxyl could contribute to the antioxidant activity.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by the National Natural Science Foundation of China [grant number
81560707]; the research center of preservation of germplasm resources and Evaluation in
Traditional Chinese Medicine and Ethnomedicine, Guizhou Province [grant number KY (2017)

6
Q. SUN ET AL.
018]; the project of Top-ranking Construction Discipline of Guizhou Province [grant number
GNYL (2017) 008].
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