The major zeaxanthin dipalmitate derivatives from wolfberry

Article abstract of DOI:10.1080/10286020.2019.1621855

Zeaxanthin dipalmitate (3) and two zeaxanthin dipalmitate derivatives, including one new compound (1), were obtained from wolfberry [the fruit of Lycium barbarum L. (Solanaceae)]. Their structures were unambiguously elucidated by spectroscopic analyses. Compound 2 is isolated from the genus Lycium for the first time, and its 1D/2D NMR data are firstly reported. All the compounds belong to carotenoids which are a kind of major bioactive constituents in wolfberry and are also responsible for wolfberry’s red color.

Full text of DOI:10.1080/10286020.2019.1621855

Journal of Asian Natural Products Research
ISSN: 1028-6020 (Print) 1477-2213 (Online) Journal homepage: https://www.tandfonline.com/loi/ganp20
The major zeaxanthin dipalmitate derivatives from
wolfberry
Jia-Tang Long, Hong-Xia Fan, Zheng-Qun Zhou, Wan-Yang Sun, Qing-Wen Li,
Ying Wang, Min Ma, Hao Gao & Hui Zhi
To cite this article: Jia-Tang Long, Hong-Xia Fan, Zheng-Qun Zhou, Wan-Yang Sun, Qing-Wen Li,
Ying Wang, Min Ma, Hao Gao & Hui Zhi (2019): The major zeaxanthin dipalmitate derivatives from
wolfberry, Journal of Asian Natural Products Research, DOI: 10.1080/10286020.2019.1621855
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JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH
https://doi.org/10.1080/10286020.2019.1621855
The major zeaxanthin dipalmitate derivatives
from wolfberry
a
b
c
c
†
†
Jia-Tang Long , Hong-Xia Fan , Zheng-Qun Zhou , Wan-Yang Sun , Qing-Wen
Lic, Ying Wangd, Min Mab, Hao Gaoc and Hui Zhia
aSchool of Chinese Materia Medica, Guangzhou University of Chinese Medicine, Guangzhou 510006,
b
China; College of Traditional Chinese Medicine/Integrated Chinese and Western Medicine
c
Postdoctoral Research Station, Jinan University, Guangzhou 510632, China; Institute of Traditional
Chinese Medicine and Natural Products, College of Pharmacy/Guangdong Province Key Laboratory
of Pharmacodynamic Constituents of TCM and New Drugs Research, Jinan University, Guangzhou
d
510632, China; Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical
Garden, Chinese Academy of Sciences, Guangzhou 510650, China
ABSTRACT
ARTICLE HISTORY
Received 26 March 2019
Accepted 17 May 2019
Zeaxanthin dipalmitate (3) and two zeaxanthin dipalmitate deriva-
tives, including one new compound (1), were obtained from wolf-
berry [the fruit of Lycium barbarum L. (Solanaceae)]. Their
structures were unambiguously elucidated by spectroscopic analy-
ses. Compound 2 is isolated from the genus Lycium for the first
time, and its 1D/2D NMR data are firstly reported. All the com-
pounds belong to carotenoids which are a kind of major bioactive
constituents in wolfberry and are also responsible for wolfberry’s
red color.
KEYWORDS
Lycium barbarum L.;
Solanaceae; wolfberry;
carotenoids; zeaxanthin
dipalmitate
CONTACT H. Gao
of Pharmacy/Guangdong Province Key Laboratory of Pharmacodynamic Constituents of TCM and New Drugs
Research, Jinan University, Guangzhou 510632, China; H. Zhi zhihui@gzucm.edu.cn School of Chinese Materia
tghao@jnu.edu.cn
Institute of Traditional Chinese Medicine and Natural Products, College
Medica, Guangzhou University of Chinese Medicine, Guangzhou 510006, China
†These authors contributed equally to this work.
Supplemental data for this article is available online at https://doi.org/10.1080/10286020.2019.1621855.
ß 2019 Informa UK Limited, trading as Taylor & Francis Group

2
J.-T. LONG ET AL.
1. Introduction
Carotenoids are isoprenoid compounds (mostly C40) with polyene chains that may
contain up to 15 conjugated double bonds [1]. Carotenoids play an important role in
human nutrition and health, providing provitamin A and having antioxidative, anti-
cancer, and hepatoprotective activities [1–3]. However, carotenoids generally cannot
be produced in the human body, which are synthesized by photosynthetic organisms
as well as some non-photosynthetic bacteria and fungi [4, 5]. The fruit of Lycium bar-
barum L. (Solanaceae), named wolfberry, is known to be a rich source of carotenoids,
and the predominant carotenoid is zeaxanthin dipalmitate [5–7]. Some minor carote-
noids, mainly esterified constituents, were also detected from wolfberry by LC-MS,
including b-cryptoxanthin monopalmitate and its two isomers, zeaxanthin monopal-
mitate and its two isomers, and zeaxanthin [7–9]. Due to the low polarity and com-
plex structure of carotenoids, especially asymmetric esterified compounds, the
purification and identification are difficult. The phytochemical study on carotenoids
in wolfberry still remains inadequate [10].
In our previous phytochemical study on water-soluble constituents of wolfberry,
72 compounds were reported [11–14]. Herein, the investigation of lipid-soluble con-
stituents of wolfberry led to the identification of zeaxanthin dipalmitate (3) and its
two geometrical isomers (1 and 2) (Figure 1). 1 is a new compound, and 2 is isolated
from the genus Lycium for the first time. 2 was only detected in Physalis alkekengi L.
belonging to the family of Solanaceae by LC–MS in the past, and its 1D/2D NMR
data are firstly reported herein [15]. Details of isolation and structure identification of
1ꢀ3 are reported in this paper.
2. Results and discussion
Compound 1 was obtained as dark red amorphous powders. UV spectrum of 1 exhib-
ited absorption maxima at 283, 346, 431, 457, and 483 nm, which were similar to those
of the known compound zeaxanthin dipalmitate (3), suggesting the presence of the
Figure 1. Chemical structures of compounds 1ꢀ3.

JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH
3
Figure 2. The product (1a) prepared from 1 and methyl palmitate were compared by GC–MS.
polyene chain. The molecular ion, Mꢁþ at m/z 1044.8852 by HR-APCI-MS showed that
the molecular formula of 1 was C72H116O4 (15 degrees of unsaturation), which was the
same as that of zeaxanthin dipalmitate (3). GC–MS analysis of products obtained from
alkaline hydrolysis and derivatization reaction exhibited that 1 contained palmitic acid
moieties (Figure 2) [16, 17]. The 13C NMR spectrum of 1 showed 72 carbons. Based on
the DEPT-135 data, these carbons could be categorized into two carbonyl, 22 aromatic
or olefinic carbons (including 14 sp2 methine carbons), two sp3 quaternary carbons, two
oxygenated sp3 methine carbons, 32 sp3 methylene carbons, and 12 methyl carbons. The
1H NMR spectrum displayed that 1 had 14 aromatic or olefinic protons, two oxygenated
sp3 methine protons, 32 sets of sp3 methylene protons, and 12 sets of methyl protons.
The proton signals were associated with the directly attached carbon atoms in the
1
HSQC experiment. The analysis of the 1Hꢀ H COSY experiment and the coupling val-
ues of the protons (Figure 3) showed the presence of 11 subunits [H2-2 ꢀ H-3 ꢀ H2-4,
H-7 ꢀ H-8, H-10 ꢀ H-11 ꢀ H-12, H-14 ꢀ H-15 ꢀ H-150ꢀH-140, H2-20ꢀH-30ꢀH2-40, H-
70ꢀH-80, H-100ꢀH-110ꢀH-120, H2-200ꢀH2-300ꢀH2-400, H2-1500ꢀH3-1600, H2-2000ꢀH2-
3000ꢀH2-4000, and H2-15000ꢀH3-16000]. Based on these deduced subunits, molecular for-
mula, degrees of unsaturation, and alkaline hydrolysis [16, 17], the key HMBC correla-
tions shown in Figure 3 deduced the planar structure of 1. The assignments of all proton
and carbon resonances are provided in Table 1.
0
0
0
0
0
The coupling values (J7/7 ,8/8 ¼ 16.0 Hz, J11,12 ¼ 14.9 Hz, J15,15 ¼ 13.8 Hz, J11 ,12
¼
14.9 Hz) and the key ROESY correlations (between H-12 and H-15, between H-19
and H-7/H-11, between H-20 and H-11/H-14, between H-120 and H-140, between H-
190 and H-70/H-110, between H-200 and H-110/H-150) exhibited that the geometrical
configurations of the related double bonds in 1 were (7E, 9E, 11E, 13Z, 15E, 70E, 90E,
110E, 130E). In plant, naturally occurring zeaxanthin possessed only (3R,30R) configur-
ation [18, 19]; Further, native zeaxanthin dipalmitate from wolfberry was proved to
be only present in the (3R,30R) form [20]. Due to the coexistence with zeaxanthin
and zeaxanthin dipalmitate, the absolute configuration of 1 was deduced to be

4
J.-T. LONG ET AL.
Figure 3. Key 2D NMR correlations of compound 1.
(3R,30R). Therefore, the structure of 1 was identified as (3R,30R,13Z)-3,30-O-dipalmi-
toyl-b-carotene, and named 13Z-zeaxanthin dipalmitate.
Similarly to the structural elucidation of 1, compounds 2 and 3 were identified as
9Z-zeaxanthin dipalmitate (CAS: 2125473-36-9; Supporting Information Table S2)
and zeaxanthin dipalmitate (CAS: 144-67-2; Supporting Information Table S3),
respectively. 9Z-zeaxanthin dipalmitate (2) was only tentatively inferred from Physalis
alkekengi by LC–MS [15]. It is the first time for 2 to be reported from the genus
Lycium, and it is also the first time to report its 1D/2D NMR data.
Compared with zeaxanthin dipalmitate (3), the carbon resonances near the Z-dou-
ble bond of 1 and 2 obviously shifted. C-12 in 1 and C-8 in 2 distinctly shifted to
upfield, while C-20 in 1 and C-19 in 2 significantly moved to downfield (Table 1).
Compared to 3, the obvious shifts of C-12 and C-20 in 1 were caused by c-effect of
the large substituent groups at C-14. Similarly, the distinct shifts of C-8 and C-19 in
2 were also caused by c-effect of the large substituent groups at C-10 compared to 3.
3. Experimental
3.1. General experimental procedures
Optical rotations were recorded on an Anton Paar MCP 200 high precision intelligent
polarimeter (Anton Paar Co. Ltd, Graz, Austria). UV data were measured on a
JASCO V-550 UV/Vis spectrometer (Jasco International Co. Ltd, Tokyo, Japan). IR
data were recorded using a NICOLET IS5 FT-IR spectrometer (Thermo Fisher
Scientific Inc., Sunnyvale, USA). The GC-MS data were obtained on an Agilent
Technologies 7890B GC system equipped with an Agilent Technologies 5977A MSD,
and an Agilent Technologies 7693 Autosampler using an Agilent HP-5ms Ultra Inert
column (30 m ꢂ 250 lm ꢂ 0.25 lm) (Agilent Technologies Inc., CA, USA). The HR-
APCI-MS spectra were obtained on a Thermo-fisher LTQ Orbitrap XL hybrid mass

JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH
5
Table 1. 1H (600 MHz) and 13C (150 MHz) NMR spectral data of 1ꢀ3 in CDCl3 (d in ppm, J in Hz).
1
2
3
a
a
a
No.
dC
dH
dC
36.7
44.0/44.1
dH
dC
dH
1/10
36.7
44.1
36.7
44.1
2/20
1.77, br d (12.1),
Ha 1.57/1.58, t
(12.1), Hb
1.78, Ha 1.57/1.59,
t (11.9), Hb
1.78, ddd (12.1,
3.3, 1.6), Ha
1.58, t
(12.1), Hb
5.07
2.44, dd (16.8,
5.6), Ha 2.11, dd
(16.8, 9.4), Hb
3/30
4
68.1
38.5
5.07
68.1
38.5
5.08
68.1
38.5
4
ꢃ
2.43 , dd (16.9,
4.8), Ha 2.10, dd
(16.9, 10.4), Hb
2.46, dd (17.0,
5.5), Ha 2.12, dd
(17.0, 9.9), Hb
5
6
7
8
9
10
11
125.8
137.8
125.2
138.6
135.5
131.4
126.2
125.9
138.2
127.1
130.9
134.1
129.9
125.7
137.9
125.3
138.6
135.5
131.4
1
ꢃ
6.08, d (16.0)
6.13, d (16.0)
6.11
6.66, d (15.9)
6.09, d (16.1)
6.13, d (16.1)
6.21, d (11.6)
6.07, d (11.2)
6.16, d (11.6)
6.64, dd (14.9,
11.6)
6.64, dd (14.9, 11.6) 123.6
6.73, dd (14.9, 11.2) 124.9
12
13
14
15
16
17
18
19
20
40
129.4
134.8
130.9
128.8
28.5
30.0
21.5
12.7
20.7
38.5
6.89, d (14.9)
136.9
136.4
132.5
129.9
28.5
30.0
21.6
20.7
12.7
38.5
6.29, d (14.9)
137.6
136.4
132.6
130.1
28.5
30.0
21.5
12.7
12.8
38.5
6.36, d (14.9)
7
8
6.24 11, br d (9.5)
6.63
6.26, br d (9.8)
6.63, dd (9.8, 2.8)
1.11, s
1.08, s
1.72, s
1.96, s
1.97, s
2.44, dd (16.8,
5.6), Ha 2.11, dd
(16.8, 9.4), Hb
ꢃ
ꢃ
6.11
6.80, t (13.8)
ꢃ
1.11, s
1.12, s
1.08, s
1.76, s
1.97, s
5
ꢃ
1.07 , s
6
ꢃ
1.72 , s
1.96, s
2
12
12
ꢃ
ꢃ
9
ꢃ
ꢃ
1.99, s
1.97, s
4
ꢃ
2.44 , dd (16.9,
2.43, dd (17.2,
5.5), Ha 2.10, dd
(17.2, 10.0), Hb
4.8), Ha 2.10, dd
(16.9, 10.4), Hb
50
125.8
137.8
125.6
138.6
135.5
131.4
124.7
125.7
137.8
125.3
138.6
135.5
131.4
125.7
137.9
125.3
138.6
135.5
131.4
124.9
60
1
ꢃ
70
6.08, d (16.0)
6.13, d (16.0)
6.08, d (15.7)
6.13, d (15.7)
6.09, d (16.1)
6.13, d (16.1)
80
90
100
110
6.16, d (11.3)
6.63, dd (14.9, 11.3) 124.8
6.16, d (11.5)
6.63
6.16, d (11.6)
6.64, dd (14.9,
11.6)
120
137.7
136.3
132.5
129.2
28.5
30.0
21.5
12.8
12.8
173.6
34.7
25.0
29.1
29.7
29.6
29.7
29.3
29.7
29.6
29.5
29.7
29.3
31.9
22.7
14.1
6.36, d (14.9)
137.6
136.4
132.6
130.1
28.5
30.0
21.5
12.8
12.9
173.6
34.7
25.0
29.1
29.7
29.6
29.7
29.3
29.7
29.6
29.5
29.7
29.3
31.9
22.7
14.1
6.36, d (14.9)
137.6
136.4
132.6
130.1
28.5
30.0
21.5
12.7
12.8
173.6
34.7
25.0
29.6
29.6
29.3
29.7
29.7
29.1
29.6
29.4
29.7
29.3
31.9
22.7
14.1
6.36, d (14.9)
130
7
8
140
6.24, d (13.8)
6.56, t (13.8)
6.25 11, br d (9.5)
6.63
6.26, br d (9.8)
6.63, dd (9.8, 2.8)
1.11, s
1.08, s
1.72, s
ꢃ
ꢃ
150
ꢃ
160
1.11, s
1.11, s
1.07, s
1.72, s
1.97, s
1.97, s
5
170
1.08 , s
ꢃ
6
ꢃ
180
1.73 , s
2
2
9
9
12
12
190
1.96, s
1.96, s
1.97, s
ꢃ
ꢃ
ꢃ
20000
1.97, s
ꢃ
ꢃ
ꢃ
100/1000
200/2000000
300/3000
400/4000
5 /5
2.28, t (6.7)
1.62, quint (6.7)
1.26
1.26
1.26
1.26
1.26
1.26
1.26
1.26
1.26
1.26
1.26
1.28
0.88, t (6.7)
2.28/2.29, t (7.4)
1.62
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.25
1.31
0.88, t (6.7)
2.28, t (7.0)
1.62, quint (7.0)
1.26
1.26
1.26
1.26
1.26
1.26
1.26
1.26
1.26
1.26
1.26
1.29
0.88, t (6.9)
3
ꢃ
3
ꢃ
3
ꢃ
3
ꢃ
3
ꢃ
3
ꢃ
3
ꢃ
3
ꢃ
3
ꢃ
3
ꢃ
10
ꢃ
10
ꢃ
10
ꢃ
10
ꢃ
10
ꢃ
10
ꢃ
10
ꢃ
10
ꢃ
10
ꢃ
10
ꢃ
13
ꢃ
13
ꢃ
13
ꢃ
13
ꢃ
13
ꢃ
13
ꢃ
13
ꢃ
13
ꢃ
13
ꢃ
13
ꢃ
600/6000
700/7000
800/8000
900/9000
1000/10000
1100/11000
1200/12000
1300/13000
1400/14000
1500/15000
1600/16000
Assignment may be interchanged. aThe indiscernible signals due to overlap or having the complex multiplicity are
ꢃ
reported without designating multiplicity.

6
J.-T. LONG ET AL.
spectrometer equipped with an atmospheric pressure chemical ionization (APCI)
source (Thermo Fisher Scientific Inc.). The NMR spectra were acquired with Bruker
AV 400 and 600 spectrometers (Bruker BioSpin Group, Faellanden, Switzerland)
using the solvent signals (CDCl3: dH 7.26/dC 77.0) as internal standards. The analyt-
ical HPLC was performed on a Shimadzu HPLC system equipped with a LC-20AT
pump, a SPD-M20A DAD, a CTO-10AS VP column oven, and a SIL-20A autosam-
pler (Shimadzu Inc., Kyoto, Japan) using a Cosmosil Packed Cholester column
(4.6 ꢂ 250 mm2, 5 lm) (Nacalai Tesque Inc., Kyoto, Japan). The preparative HPLC
was performed on a Shimadzu LC-6-AD liquid chromatography (Shimadzu Inc.) with
a SPD-20A detector using a Cosmosil Packed Cholester column (20.0 ꢂ 250 mm2,
5 lm). Column chromatography (CC) was performed on silica gel (200 ꢀ 300 mesh,
Haiyang Chemical Co. Ltd, Qingdao, China).
3.2. Plant material
The fruit of Lycium barbarum L. (Solanaceae) was collected (Zhongning County,
Ningxia Hui Autonomous Region, China) and identified by one of the authors (Ying
Wang) in 2016. A voucher specimen (LYBA-2016-NX-ZN) was deposited in the
Institute of Traditional Chinese Medicine and Natural Products, College of Pharmacy,
Jinan University, Guangzhou, China.
3.3. Extraction and isolation
The dried wolfberry (45.0 kg) was cold-soaked and extracted four times with 100 L of
CHCl3 for 24 h each time to yield an extract (244.3 g). The extract was subjected to
open silica gel CC (15.0 ꢂ 100.0 cm2) using a successive elution of cyclohexane-
CH2Cl2-MeOH (96:4:0, 93:7:0, 90:10:0, 80:20:0, 70:30:0, 60:40:0, 50:50:0, 40:60:0,
0:100:0, 0:50:50, 0:0:100, v/v/v), yielding fractions F1 ꢀ F19. A portion (0.2 g) of frac-
tion 7 (18.0 g) was isolated using preparative HPLC [45% methyl tert-butyl
ether ꢀ MeOH, 10 ml/min] to yield 3 (tR: 31.2 min, 120.0 mg), 2 (tR: 35.6 min,
24.5 mg), and 1 (tR: 39.0 min, 27.3 mg).
3.3.1. Structural characterization of new compound (13Z-zeaxanthin
dipalmitate, 1)
Dark red amorphous powders; [a]2D5 ꢀ 66.0 (c 0.10, CHCl3); UV (CHCl3) kmax (log e)
283 (4.06), 346 (4.24), 431 (4.54), 457 (4.65), 483 (4.57) nm; IR (KBr) vmax 2923, 2853,
1732, 1466, 1364, 1172, 966 cmꢀ1 1H and 13C NMR spectral data see Table 1;
;
HR-APCI-MS (positive): m/z 1044.8852 [M]ꢁþ (calcd. for C72H116O4, 1044.8868).
3.4. Alkaline hydrolysis
Alkaline hydrolysis was performed using the method described by Pintea and Blas
et al. with minor modifications [16, 17]. Compound 1 (5.0 mg) was dissolved in hex-
ane (0.5 ml) and saponified with 2.0 ml of 1.0 mol/L NaOH in MeOH for 30 min at
80 ꢄC. Then, 1.0 ml of 14% BF3 in MeOH was directly added to the reaction mixture

JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH
7
for 40 min at 80 ꢄC and then cooled. 3.0 ml of hexane and 5.0 ml of water saturated
with NaCl were added and then the mixed solution was centrifuged at 1000 rpm for
5 min. Upper organic layer was filtered through a 0.22 lm membrane filter and trans-
ferred into a GC vial for analysis.
The GC oven temperature was programmed as follow: initial temperature 50 ꢄC
for 2 min and an increase rate of 8.0 ꢄC/min up to 310 ꢄC. Helium was used as a car-
rier gas with flow rate at 1.0 ml/min. The inlet temperature was set at 270 ꢄC. The
injection volume was 1.0 ll with split radio of 100:1. The mass spectrometer was
operated in electron impact (EI) mode (70 eV). The transfer line temperature was set
at 280 ꢄC and the ion source temperature at 230 ꢄC. The compounds were identified
by comparison of mass spectra and retention time with those of reference standard
(methyl palmitate) and those available in libraries (NIST database).
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was financially supported by grants from the National Natural Science Foundation
of China (3171101305, 81703372, and 81703696), Chang Jiang Scholars Program (Hao Gao,
2017) from the Ministry of Education of China, Guangdong Special Support Program
(2016TX03R280), Guangdong Province Universities and Colleges Pearl River Scholar Funded
Scheme (Hao Gao, 2014), Local Innovative and Research Teams Project of Guangdong Pearl
River Talents Program (2017BT01Y036), and K. C. Wong Education Foundation (Hao Gao,
2016). We appreciate the measurement of HR-APCI-MS of compounds by Dr. Xiong Li
(Second Affiliated Hospital, Guangzhou University of Chinese Medicine, Guangzhou
510006, China).
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