Secoiridoid glycosides from the fruits of Cornus officinalis

Article abstract of DOI:10.1080/14786419.2020.1834547

Five new secoiridoid glycosides, cornusphenosides E-I (1–5), were isolated and characterized from an active fraction of ethanol extract of the fruits of Cornus officinalis. Their structures were determined by extensive spectroscopic data analysis, includi

Full text of DOI:10.1080/14786419.2020.1834547

Natural Product Research
Formerly Natural Product Letters
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/gnpl20
Secoiridoid glycosides from the fruits of Cornus
officinalis
Xin Wang , Xiang-Jian Zhong , Na Zhou , Lin-Lin Ji , Jin-Jie Li , Ning Cai , Qing-
Bo Wang , Peng-Cheng Lin & Xiao-Ya Shang
To cite this article: Xin Wang , Xiang-Jian Zhong , Na Zhou , Lin-Lin Ji , Jin-Jie Li , Ning Cai ,
Qing-Bo Wang , Peng-Cheng Lin & Xiao-Ya Shang (2020): Secoiridoid glycosides from the fruits of
Cornusꢀofficinalis , Natural Product Research, DOI: 10.1080/14786419.2020.1834547
To link to this article: https://doi.org/10.1080/14786419.2020.1834547
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NATURAL PRODUCT RESEARCH
https://doi.org/10.1080/14786419.2020.1834547
Secoiridoid glycosides from the fruits of Cornus officinalis
a
a
a
a
a
a
ꢀ
ꢀ
Xin Wang , Xiang-Jian Zhong , Na Zhou , Lin-Lin Ji , Jin-Jie Li , Ning Cai ,
Qing-Bo Wanga, Peng-Cheng Linb and Xiao-Ya Shanga
aBeijing Key Laboratory of Bioactive Substances and Functional Foods, Beijing Union University,
b
Beijing, China; Qinghai Provincial Key Laboratory of Phytochemistry for Tibetan Plateau,
Qinghai University for Nationalities, Xining, China
ABSTRACT
ARTICLE HISTORY
Received 24 June 2020
Accepted 22 September 2020
Five new secoiridoid glycosides, cornusphenosides E-I (1–5), were
isolated and characterized from an active fraction of ethanol
extract of the fruits of Cornus officinalis. Their structures were
determined by extensive spectroscopic data analysis, including
2 D NMR and HRESIMS experiments. In the preliminary assay,
compound 5 (when evaluated at 10 lM) showed the neuroprotec-
tive effect against H2O2-induced SH-SY5Y cell damage.
KEYWORDS
Cornus officinalis; secoiridoid
glycosides; neuroprotective
activity
1. Introduction
The fruits of Cornus officinalis, named “Shan Zhu Yu” in Chinese, are important trad-
itional Chinese medicines used for dementia, lumbar debility, and diabetes (Chinese
Pharmacopoeia Commission 2015; Williams et al. 2011). They are among the most
common ingredients of formulations used for nourishing the liver and kidneys
(Chinese Pharmacopoeia Commission 2015). Considerable chemical and pharmaco-
logical studies have been reported, along with the isolation of more than a hundred
compounds from various extracts of C. officinalis (He et al. 2012; Xie et al. 2012; Jang
et al. 2014; Ma et al. 2014; Park et al. 2016; Kang et al. 2018; Ye et al. 2020). Among
the reported chemical constituents, iridoids were recognized as main active
CONTACT Xiao-Ya Shang
These authors contributed equally to this work.
shangxiaoya@buu.edu.cn
ꢀ
Supplemental data for this article can be accessed at https://doi.org/10.1080/14786419.2020.1834547.
ß 2020 Informa UK Limited, trading as Taylor & Francis Group

2
X. WANG ET AL.
Figure 1. Structures of compounds 1–5.
components, especially the iridoid glycosides which had significant effects on the neu-
rodegenerative diseases (Yao et al. 2009; Ye et al. 2017; Huang et al. 2018). As a part
of our program to systematically study the chemical diversity of medicinal/edible hom-
ologous resources and their biological effects, an ethanol extract of the fruits of C. offi-
cinalis was investigated. In the previous study, we found that the 40% ethanol elution
fraction of the ethanol extract of C. officinalis, obtained over a microporous resin,
showed potential neuroprotective activities. In order to investigate minor iridoids with
novel structures and neuroprotective activities, a series of chromatography methods
were used to firstly remove morroniside and loganin which were the main iridoid gly-
cosides with neuroprotective activity, and then the four sub-fractions (F1-F4) were
obtained. Through the neuroprotective activity screening in vitro, the sub-fractions
F2ꢁF4 still exhibited the strong neuroprotective activity. Seven novel iridoids were iso-
lated from sub-fraction F2, one of which had a moderate neuroprotective activity
(Wang et al. 2018; Ji et al. 2019). To further clarify the neuroprotective active com-
pounds of C. officinalis, a continuation on another active sub-fraction F3 has resulted
in the structure characterization of five new secoiridoid glycosides (1–5) (Figure 1).
Herein, we report the isolation, structure elucidation, and neuroprotective activities of
these compounds.
2. Results and discussion
Compound 1 was obtained as an amorphous powder with a specific rotation of
[a] ꢂ 35.5 (0.03, MeOH). Its molecular formula, C26H36O12, was deduced by the
HRESIMS (m/z: 539.21326 [M-H]-). The IR spectrum showed absorption bands for
hydroxy (3392 cmꢂ1) and carbonyl (1706 cmꢂ1) groups. The 1H and 13C NMR data
(Table S1) of 1 displayed the signal characteristic of an iridoid glycoside, which were
similar to those reported for 7b-morroniside (Ma et al. 2014). The only evident differ-
ence was that 1 showed the resonances due to an additional p-hydroxyphenyl pro-
panol group. The 1 D NMR data exhibited an AA0BB0 signal pattern [(dH 6.69 (2H, d,
J ¼ 8.5 Hz, H-60, 80) and dH 7.02 (2H, d, J ¼ 8.5 Hz, H-50, 90)], two methylene signals at dH
1.89 (2H, m, H-20) and dH 2.63 (2H, t, J ¼ 7.5 Hz, H-30), and one oxygen carbon signal at

NATURAL PRODUCT RESEARCH
3
1
dC 67.6. H-1H COSY correlations of H-10a and H-10b/H-20/H-30 together with the HMBC
correlations of H-30 with C-40/C-50/C-90 revealed the presence of a p-hydroxyphenyl pro-
panol group (Figure S1). The C-6 upfield shift (dC 33.9 from dC 34.2) and the C-7 downfield
shift (dC 98.4 from dC 92.3) suggested the attachment of the p-hydroxyphenyl propanol
group to the C-7 carbon. The assumption was confirmed by the HMBC correlation of H-7
(dH 4.81) with C-10 (dC 95.6) of the p-hydroxyphenyl propanol group.
The relative configuration of 1 was established by the analysis of the NOESY
spectrum (Figure S2). In the NOESY spectrum, correlations between CH3-10 and H-1/H-
7a indicated that H-1, H-7 and CH3-10 were both a-oriented. Moreover, NOESY
correlations between H-8b and H-5/H-9 confirmed that H-5, H-8 and H-9 were all
b-oriented. The acid hydrolysis of 1 afforded D-glucose, which was identified using GC
analysis after the chiral derivatization. The b-anomeric configuration for the glucosyl
3
00
00
unit was judged from its large JH1 , H2 coupling constant (J ¼ 7.9 Hz). Analysis of the
1H-1H COSY, HSQC and HMBC spectra led to the complete assignments of the proton
and carbon signals in compound 1 (Table S1). For convenience purposes, compound 1
was named as cornusphenoside E.
Compound 2 gave a molecular formula of C25H34O12 according to its HRESIMS (m/z:
525.19775 [M-H]-). Comparison of the spectroscopic data of 2 with those of 1 showed
they were almost superimposable on those of the iridoid skeleton, but the p-hydroxy-
phenyl propanol group at C-7 in 1 was replaced by a p-hydroxyphenyl ethanol group
in 2. In the HMBC spectrum (Figure S1), the correlation from H-7 (dH 4.82) to C-10 (dC
69.5) suggested the p-hydroxyphenyl propanol group attaching to C-7 of the
7b-morroniside moiety. Thus, compound 2 was named as cornusphenoside F.
Compound 3 was assigned a molecular formula of C25H34O12 from its HRESIMS (m/z:
525.19775 [M-H]-). It showed similar UV, IR, and NMR data to 2, suggesting their structural
resemblance. Comparing the NMR data between 2 and 3, the downfield shifts of C-5, C-6,
C-7, and C-8 (dC 31.8 from dC 28.0, dC 35.7 from dC 33.9, dC 103.5 from dC 98.1, dC 74.1
from dC 66.3;) revealed that 7b-morroniside moiety in 2 was replaced by 7a-morroniside
moiety in 3. This discrepancy was confirmed by NOESY correlations of H-7 and H-5/H-8b
(Figure S2). Hence, cornusphenoside G was characterized as 3.
Compound 4 was isolated as an amorphous powder, and its molecular formula was
established as C24H33O15 on the basis of HRESIMS (m/z: 561.18207 [M þ HCOO]-). The
1H NMR and 13C NMR spectra of 4 (Table 1) resembled of those of 1; however, the p-
hydroxyphenyl propanol group was replaced by a 2, 5-dihydroxymethyl furan moiety
in 4. The 1 D NMR data showed an olefinic signal coupling pattern at dH 6.27 (1H, d,
J ¼ 3.1 Hz, H-30) and 6.33 (1H, d, J ¼ 3.1 Hz, H-40), two methylene signals at dH 4.47 (1H,
d, J ¼ 12.9 Hz), (1H, d, J ¼ 12.9 Hz) and 4.50 (2H, s, H-60); and an furan group (dC 109.2,
111.3, 156.4, 152.7). The HMBC correlation of H-10 with C-30 and H-60 with C-40 revealed
the presence of a 2, 5-dihydroxymethyl furan moiety (Figure S1). Furthermore, the
HMBC correlation from H-7 to C-10 verified the location of the furan group at C-7 of
the 7b-morroniside moiety. From these data, the structure of compound 4, named as
cornusphenoside H, was characterized as shown in Figure 1.
Compound 5 gave a molecular formula of C24H31O15 as established by HRESIMS (m/
z: 559.16595 [M þ HCOO]-). The NMR spectroscopic data of 5 were very similar to those
of 4 except that an aldehyde group [dH 9.57 (1H, s, H-60); dC 179.5] was attached at C-

4
X. WANG ET AL.
50 instead of a hydroxymethyl group, which indicated the presence of the 5-hydroxy-
methyl furfural moiety in 5. Furthermore, a HMBC correlation of H-7 with C-10 sug-
gested the 5-hydroxymethyl furfural moiety attaching to C-7 of the 7b-morroniside
moiety (Figure S1). Accordingly, cornusphenoside I was characterized as 5.
The effect of compounds 1-5 on H2O2-induced SH-SY5Y cells damage was deter-
mined by MTT assay. The results showed that only compound 5 exhibited the signifi-
cant neuroprotective effect (Table S2).
According to the literature, iridoid glycosides were recognized as the main neuro-
protective active components, and the main compound morroniside has the most sig-
nificant neuroprotective activity (Wang et al. 2009; Jeong et al. 2012; Ji et al. 2019).
Compounds 1-5 were the analogues of morronisides, which had different substituents
at C-7 position. However, the neuroprotective activities of compound 1-5 were differ-
ent from morronisides, only compound 5 showed neuroprotective activity, which indi-
cated that the substitution of C-7 might reduce or eliminate their neuroprotective
activity. Compound 5 has the same 5-hydroxymethylfural substitution as known com-
pounds cornusphenosides A and B, isolated and identified in our previous research,
but cornusphenosides A and B showed inactive on H2O2-induced SH-SY5Y cells dam-
age, which indicated that the substitution of glucoside also had effects on the neuro-
protective activities (Wang et al. 2018).
3. Experimental
3.1. General experimental procedures
The 1 D and 2 D NMR spectra were acquired in CD3OD with TMS internal standard on
Varian 500 MHz and Bruker AV500-III spectrometers (Bruker Corporation, Billerica,
Massachusetts, USA). HR-ESIMS was performed using a Thermo QE Plus orbitrap mass
spectrometer (Thermo, Waltham, MA, USA). IR spectra were recorded on a Nicolet IS5
spectrometer by FT-IR microscope transmission method (Nicolet Instrument, Inc.,
Madison, Wisconsin, USA). CD spectra were recorded on a JASCO J-810 circular dichro-
ism spectrometer (JASCO Corporation, Tokyo, Japan). Column chromatography was
performed with silica gel (160-200 mesh, Qingdao Marin Chemical, Inc., Qingdao,
China) and Sephadex LH-20 (Pharmacia Biotech AB, Uppsala, Sweden). Medium pres-
sure liquid chromatography experiments were performed using a Buchi Pump Mooute
C-650 pump (Buchi Corporation, Flawil, Switzerland). HPLC experiments were per-
formed using an instrument consisting of a Waters e2695 pump, and a Waters 2998
dual-wave-length absorbance detector (Waters Corporation, Milford, Massachusetts,
USA) with a Sunfire C18 preparative column (Waters, 5 lm, 250 ꢃ 19 mm, i.d.).
3.2. Plant material
The fruits of C. officinalis were purchased from Tong-Ren-Tang Company in Beijing,
and authenticated by Professor Wen Wang (Xuanwu Hospital of the Capital Medical
University, China). A voucher specimen (20090305) has been deposited at the Beijing
Union University, Beijing Key Laboratory of Bioactive Substances and Functional Foods,
Beijing Union University, Beijing, China.

NATURAL PRODUCT RESEARCH
5
3.3. Extraction and isolation
The dried fruits (10 kg) of C. officinalis were extracted with 50% EtOH (100 L ꢃ 3) at
room temperature and the combined extracts were concentrated under reduced pres-
sure to dryness. The residue was suspended in H2O and applied to a Diaion HP-20 col-
umn that was eluted using a stepwise gradient of EtOH-H2O (0:100, 20:80, 40:60,
70:30, and 95:5, v/v), to afford five fractions. After removing the solvent, the EtOH-H2O
(40:60, v/v) eluate (500 g) was separated subsequently by silica gel chromatography
eluting with CHCl3-MeOH (15:1 to 8:1, v/v) to afford four major fractions (F1ꢁF4) based
on TLC analysis. F3 was chromatographed on a reversed-phase C18 silica column,
eluted with an EtOH-H2O (5:95-100:0, v/v) gradient, to give seven fractions (F3-1ꢁF3-
7). Fraction F3-6 was separated subsequently by a reversed-phase C18 silica flash
column eluting with MeOH-H2O (20:80-100:0, v/v) gradient, to give six fractions (F3-6-
1-F3-6-6). Fraction F3-6-2 was chromatographed over Sephadex LH-20 and eluted with
CHCl3-MeOH (2:1, v/v) as the mobile phase to give two subfractions F3-6-2-1 and F3-6-
2-2. Fraction F3-6-2-2 was purified by preparative reversed-phase HPLC, eluting with
acetonitrile-H2O (35:65, 18 ml/min), to afford 1 (60 mg, tR ¼ 45.0 min). Fraction F3-6-2-1
was purified by preparative reversed-phase HPLC, eluting with actonitrile-H2O (30:70,
18 ml/min) to afford 2 (30 mg, tR ¼ 39.0 min) and 3 (25 mg, tR ¼ 43.4 min). Further sep-
aration of fraction F3-5 by reversed-phase C18 silica flash column, eluting with MeOH-
H2O (15:85-100:0, v/v) gradient, which was purified by Sephadex LH-20, eluting with
CHCl3-MeOH (2:1, v/v) to afford subfractions F3-5-1ꢁF3-5-4. Subfraction F3-5-2 and F3-
5-3 were purified by preparative reversed-phase HPLC, eluting with MeOH-H2O (36:64,
18 ml/min) to afford 4 (20 mg, tR ¼ 33.2 min) and with acetonitrile-H2O (20:80, 18 ml/
min) to afford 5 (50 mg, tR ¼ 38.5 min).
3.4. Physical and spectroscopic data of compounds 1–5
Compound 1: White amorphous powder, [a]2D5ꢂ 35.5 (0.03, MeOH); UV (c 0.08, C2H3N)
kmax (log e) 242 (3.41) nm; CD (MeOH) 206 (De ꢂ5.98), 240 (De ꢂ33.5) nm; IR
vmax3,392, 1,706 cmꢂ1
;
1H NMR (methanol-d4, 500 MHz) and 13C (methanol-d4,
125 MHz) spectral data, see Table S1; (-)-HRESIMS m/z 539.21326 [M-H]- (calcd for
C26H35O12, 539.21326).
Compound 2: White amorphous powder, [a]2D5ꢂ 45.3 (0.03, MeOH); UV (c, 0.06,
C2H3N) kmax (log e) 240 (3.40) nm; CD (MeOH) 222 (De ꢂ19.58), 254 (De ꢂ3.05) nm; IR
vmax 3,394, 2,939, 1,705 cmꢂ1; H NMR (methanol-d4, 500 MHz) and 13C (methanol-d4,
1
125 MHz) spectral data, see Table S1; (-)-HRESIMS m/z 525.19775 [M-H]- (calcd for
C25H34O12, 525.19775).
Compound 3: White amorphous powder, [a]2D5ꢂ 66.6 (0.02, MeOH); UV (c
0.06 C2H3N) kmax (log e) 240 (3.41) nm; CD (MeOH) 206 (De ꢂ5.98), 240 (De ꢂ33.5) nm;
IR vmax 3,394, 2,942, 1,701 cmꢂ1; H NMR (methanol-d4, 500 MHz) and 13C (methanol-
1
d4, 125 MHz) spectral data, see Table S1; (-)-HRESIMS m/z 525.19775 [M-H]- (cacld for
C25H34O12, 525.19775).
Compound 4: White amorphous powder, [a]2D5ꢂ 29.2 (0.03, MeOH); UV (c 0.03
MeOH) kmax (log e) 252 (3.60) nm; CD (MeOH) 229 (De ꢂ21.02) nm; IR vmax3,400,
2,917, 1,704 cmꢂ1 1H NMR (methanol-d4, 500 MHz) and 13C (methanol-d4, 125 MHz)
;

6
X. WANG ET AL.
spectral data, see Table S1; (-)-HRESIMS m/z 561.18207 [M þ HCOO]- (cacld for
C24H33O15, 561.18229).
Compound 5: White amorphous powder, [a]2D5ꢂ 33.5 (0.02, MeOH); UV (c
0.04 C2H3N) kmax (log e) 240 (3.80) nm, 280 (4.04) nm; CD (MeOH) 232 (De ꢂ6.33), 286
1
(De þ 1.64) nm; IR vmax 3,408, 2,912, 1,678, 1,640 cmꢂ1; H NMR (methanol-d4, 500 MHz)
and 13C (methanol-d4, 125 MHz) spectral data, see Table S1; (-)-HRESIMS m/z 559.16595
[M þ HCOO]- (cacld for C24H31O15, 559.16580).
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
The authors gratefully acknowledge financial supports from the Scientific Research Common
Program of Beijing Municipal Commission of Education (Grant No. KM201911417014), Premium
Funding Project for Academic Human Resources Development in Beijing Union University
(BPHR2019DZ02), Key projects of the Beijing Natural Sciences Foundation and Beijing Municipal
Education Committee (No. KZ201811417049), and the Innovation Platform for the Development
and Construction of Special Project of Key Laboratory for Tibet Plateau Phytochemistry of
Qinghai Province (2019-ZJ-Y19).
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