Stilbene dimer xylosides and flavanols from the roots of Lysidice rhodostegia and their antioxidant activities

Article abstract of DOI:10.1016/j.fitote.2021.104997

Eight new stilbene dimer xylosides (1–8) and one new flavanol (9), along with seven known ones (10–16) were isolated from the roots of Lysidice rhodostegia. Their structures were elucidated by extensive analysis of spectroscopic data (IR, UV, HR-ESI-MS, 1D and 2D NMR), ECD calculations and acid hydrolysis. Compounds 1–16 were evaluated for their antioxidant activities using DPPH radical-scavenging assay. Especially, compounds 9 and 10 exhibited stronger antioxidant effects than the positive control (vitamin E), with IC₅₀ values of 9.57 ± 1.30 and 13.60 ± 1.47 μM, respectively.

Full text of DOI:10.1016/j.fitote.2021.104997

Fitoterapia 153 (2021) 104997
Contents lists available at ScienceDirect
Fitoterapia
journal homepage: www.elsevier.com/locate/fitote
Stilbene dimer xylosides and flavanols from the roots of Lysidice rhodostegia
and their antioxidant activities
,
,c,
Sheng-Yuan Zhanga 1, Zhong-Nan Wub 1, Ying-Ying Lib, Qing Tangb, Zhao-Chun Zhanb,
,
,
b,
,*
Wen-Zhi Wangb, Yao-Lan Lia b, Guo-Cai Wanga *, Yu-Bo Zhangb
a Guangdong Provincial Key Laboratory of Conservation and Precision Utilization of Characteristic Agricultural Resources in Mountainous Areas, Jiaying University,
Meizhou 514015, PR China
b Institute of Traditional Chinese Medicine & Natural Products, Guangdong Province Key Laboratory of Pharmacodynamic Constituents of TCM and New Drugs Research,
College of Pharmacy, Jinan University, Guangzhou 510632, PR China
c The First Affiliated Hospital, Jinan University, Guangzhou 510632, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
Eight new stilbene dimer xylosides (1–8) and one new flavanol (9), along with seven known ones (10–16) were
isolated from the roots of Lysidice rhodostegia. Their structures were elucidated by extensive analysis of spec-
troscopic data (IR, UV, HR-ESI-MS, 1D and 2D NMR), ECD calculations and acid hydrolysis. Compounds 1–16
were evaluated for their antioxidant activities using DPPH radical-scavenging assay. Especially, compounds 9
and 10 exhibited stronger antioxidant effects than the positive control (vitamin E), with IC50 values of 9.57 ±
Lysidice rhodostegia
Stilbene dimer xyloside
Flavanol
Antioxidant activity
1.30 and 13.60 ± 1.47 μM, respectively.
1. Introduction
O-rutinoside (14) [16], lysidiside N (15) [16], lysidiside E (16) [17]. The
isolation and structural elucidation of the new compounds are reported
in this paper. Moreover, compounds 1–16 were evaluated for their
antioxidant activities using the DPPH radical-scavenging assay. All
tested isolates showed various levels of antioxidant activities, with IC50
Lysidice rhodostegia Hance (Fabaceae) is known as “Yihua” in China
[1], and mainly distributes in south and southwest of China, including
Guangdong, Guangxi and Yunnan Provinces [2]. The roots of L. rho-
dostegia are used as a traditional medicine for the treatment of hemor-
rhage (topically), rheumatic arthralgia (orally and topically), fracture
(topically), etc. [1–3]. Modern pharmacological investigations demon-
strated that the plants of the genus Lysidice possessed antioxidant [4–6],
vasodilatatory [7], and antiarrhytmic activities [8]. Previous phyto-
chemical studies on this plant showed that derivatives of phlor-
oglucinols, stilbenes and flavonoids are the main bioactive components
[9–11].
values ranging from 9.57 ± 1.30 to 56.92 ± 1.46 μM. Especially, com-
pounds 9 and 10 exhibited stronger antioxidant effects than the positive
control (vitamin E), with IC50 values of 9.57 ± 1.30 and 13.60 ± 1.47
μM, respectively.
2. Experimental
2.1. General experimental procedures
Previously, acylphloroglucinol glucosides were isolated from L.
rhodostegia by our group, and the antioxidant activity of the compounds
was investigated [4]. Further investigation of L. rhodostegia led to the
isolation of eight new stilbene dimer xylosides (1–8) and one new fla-
vanol (9) (Fig. 1), along with seven known ones, (2R,3S,4R)-2,3-trans-
3,4-trans-4-(2,4,6-trihydroxyphenyl)-3′,4′,5,7-tetrahydroxyflavan-3-ol
(10) [12], trans-resveratrol (11) [13], piceid (12) [14], 3-hydroxy-5-
[(1Z)-2-(4-hydroxyphenyl)ethenyl] phenyl (13) [15], (E)-resveratrol-3-
Optical rotations were measured on a JASCO P-1020 polarimeter.
ECD data were measured by a JASCO J-810 spectrometer. IR spectra
were scanned using a JASCO FT/IR-480 plus FT-IR spectrometer with
KBr pellets. UV spectra were obtained by a JASCO V-550 UV/VIS
spectrophotometer. Thin-layer chromatography (TLC) was used on silica
gel GF254 plates (Yantai Chemical Industry Research Institute, Yantai,
China). Column chromatography (CC) was performed using silica gel
* Corresponding authors at: Institute of Traditional Chinese Medicine and Natural Products, College of Pharmacy, Jinan University, Guangzhou 510632, China.
E-mail addresses: twangguocai@jnu.edu.cn (G.-C. Wang), ybzhang@jnu.edu.cn (Y.-B. Zhang).
1
These authors contributed equally to this work.
https://doi.org/10.1016/j.fitote.2021.104997
Received 29 May 2021; Received in revised form 1 July 2021; Accepted 15 July 2021
Available online 22 July 2021
0367-326X/© 2021 Elsevier B.V. All rights reserved.

S.-Y. Zhang et al.
Fitoterapia 153 (2021) 104997
Fig. 1. Chemical structures of 1–16.
(100–200 and 200–300 mesh, Qingdao Marine Chemical Plant, Qing-
2.3.1. Lysidostegin A (1)
25
dao, P. R. China), ODS (50
μm, YMC, Kyoto, Japan) and Sephadex LH-20
Brown oil; [
α]
+29.3 (c 1.0, MeOH); UV (MeOH) λmax: 198, 285
D
(Pharmacia Biotech, Uppsala, Sweden). HR-ESI-MS analyses were per-
formed using an Agilent 6210 ESI/TOF mass spectrometer. Analytical
HPLC was carried out on a Waters system (600E Multisolvent Delivery
System, 2487 Dual λ Absorbance Detector) with a Cosmosil C18
nm; IR (KBr) νmax: 3403, 2921, 2849, 1610, 1515, 1489, 1285, 1158,
984, 699 cmꢀ 1
;
1H and 13C NMR data, see Table 1; HR-ESI-MS m/z
609.1723 [M + Na]+ (calcd for C33H30NaO10, 609.1731).
analytical column (5
μ
m, 4.6 × 250 mm). Preparative HPLC was applied
2.3.2. Lysidostegin B (2)
25
on an Agilent 1260 Chromatograph equipped with a G1311C pump and
a G1315D photodiode array detector (Agilent Technologies, CA,USA)
Brown oil; [
α]
+14.5 (c 1.0, MeOH); UV (MeOH) λmax: 197, 284
D
nm; IR (KBr) νmax: 3415, 2928, 2842, 1604, 1515, 1489, 1292, 1147,
with a Cosmosil C18 preparative column (5
μm, 20 × 250 mm). NMR
988. 715 cmꢀ 1
;
1H and 13C NMR data, see Table 1; HR-ESI-MS m/z
spectra were recorded on a Bruker AV-500 spectrometer with TMS as
internal standard. The chemical shifts (δ) are expressed in ppm and
coupling constants (J) in Hz. All the reagents were purchased from
Tianjin Damao Chemical Company (Damao,Tianjin, China).
609.1720 [M + Na]+ (calcd for C33H30NaO10, 609.1731).
2.3.3. Lysidostegin C (3)
25
Brown oil; [
α]
+32.7 (c 1.0, MeOH); UV (MeOH) λmax: 198, 206
D
nm; IR (KBr) νmax: 3393, 1675, 1601, 1522, 1486, 1240, 1168, 832
cmꢀ 1; 1H and 13C NMR data, see Table 2; HR-ESI-MS m/z 609.1733 [M
+ Na]+ (calcd for C33H30NaO10, 609.1731).
2.2. Plant materials
The roots of L. rhodostegia were collected from Jiangmen (E113.060,
N22.610), Guangdong Province of China, in March of 2018, which were
authenticated by Zhenqiu Mai, the senior engineer of Guangdong
Province. A voucher specimen (20180322) was stored in the Institute of
Traditional Chinese Medicine & Natural Products, Jinan University,
Guangzhou, China.
2.3.4. Lysidostegin D (4)
25
Brown oil; [
α]
+18.6 (c 1.0, MeOH); UV (MeOH) λmax: 198, 206
D
nm; IR (KBr) νmax: 3390, 1680, 1595, 1528, 1483, 1240, 1045, 847
cmꢀ 1; 1H and 13C NMR data, see Table 2; HR-ESI-MS m/z 609.1722 [M
+ Na]+ (calcd for C33H30NaO10, 609.1731).
2.3.5. Lysidostegin E (5)
25
Brown oil; [
α]
+35.2 (c 1.0, MeOH); UV (MeOH) λmax: 197, 310
D
2.3. Extraction and isolation
nm; IR (KBr) νmax: 3361, 2920, 1678, 1601, 1450, 1207, 1042, 835
cmꢀ 1; 1H and 13C NMR data, see Table 3; HR-ESI-MS m/z 741.2153 [M
+ Na]+ (calcd for C38H38NaO14, 741.2154).
The dried and powdered roots (14.0 kg) of L. rhodostegia were
extracted with 95% EtOH at room temperature. After the concentration
of the combined ethanol extract, the residue (1.5 kg) was suspended in
H2O and then partitioned with PE, EtOAc and n-BuOH, respectively. The
EtOAc extract (400 g) was subjected to a silica gel CC eluted with CHCl3/
CH3OH (1:0 to 0:1, v/v) solvent system to afford five fractions (Fr. A-E).
Fr. B (27.9 g) was separated by ODS CC, using the CH3OH/H2O (4:6 to
1:0, v/v) system to get five subfractions (Fr. B1-B5). Then, Fr. B2 (3.8 g)
was separated by Sephadex LH-20 with CH3OH to afford compounds 1
(4.8 mg), 2 (6.8 mg), 11 (10.5 mg) and 12 (12.3 mg). Compounds 3 (5.5
mg, tR = 12.5 min), 4 (10.5 mg, tR = 21.3 min), 13 (8.3 mg, tR = 27.5
min) and 14 (11.2 mg, tR = 30.1 min) were afforded from Fr. B3 (4.3 g)
by the preparative HPLC using CH3OH/H2O (70:30, v/v, 7 mL/min). Fr.
B4 (7.2 g) was further purified via preparative HPLC (CH3OH/H2O,
75:25, v/v, 7 mL/min) to obtain 5 (7.8 mg, tR = 17.5 min), 6 (14.6 mg, tR
= 25.1 min), 15 (13.2 mg, tR = 28.3 min) and 16 (14.1 mg, tR = 32.1
min). Fr. B5 (5.1 g) was separated using Sephadex LH-20 with CH3OH
and then purified by preparative HPLC (CH3OH/H2O, 70:30, v/v, 7 mL/
min) to obtained 7 (7.2 mg, tR = 28.3 min), 8 (8.5 mg, tR = 34.3 min), 9
(9.5 mg, tR = 37.8 min) and 10 (11.4 mg, tR = 40.2 min).
2.3.6. Lysidostegin F (6)
25
Brown oil; [
α]
+16.4 (c 1.0, MeOH); UV (MeOH) λmax: 199, 310
D
nm; IR (KBr) νmax: 3375, 2927, 1688, 1605, 1487, 1235, 1179, 1043,
836 cmꢀ 1; 1H and 13C NMR data, see Table 3; HR-ESI-MS m/z 741.2141
[M + Na]+ (calcd for C38H38NaO14, 741.2154).
2.3.7. Lysidostegin G (7)
25
Brown oil; [
α
]
+31.9 (c 1.0, MeOH); UV (MeOH) λmax: 197, 308
nm; IR (KBr) νmax:D3334, 1583, 1512, 1447, 1206, 1172, 1015, 962, 837,
678 cmꢀ 1; 1H and 13C NMR data, see Table 4; HR-ESI-MS m/z 771.2272
[M + Na]+ (calcd for C39H40O15Na, 771.2259).
2.3.8. Lysidostegin H (8)
25
Brown oil; [
α]
+22.9 (c 1.0, MeOH); UV (MeOH) λmax: 198, 308
D
nm; IR (KBr) νmax: 3331, 2929, 1598, 1514, 1444, 1314, 1173, 1074,
959, 835, 675 cmꢀ 1; 1H and 13C NMR data, see Table 4; HR-ESI-MS m/z
771.2256 [M + Na]+ (calcd for C39H40O15Na, 771.2259).
2

S.-Y. Zhang et al.
Fitoterapia 153 (2021) 104997
Table 1
Table 2
NMR data of 1 and 2 (in CD3OD, 600 MHz for 1H, δ in ppm, J in Hz).
NMR data of 3 and 4 (in DMSO‑d6, 600 MHz for 1H, δ in ppm, J in Hz).
Position
1
2
1H–1H
HMBC
Position
3
4
1H–1H
HMBC
COSY
COSY
δH
–
δC
δH
–
δC
δH
–
δC
δH
–
δC
1
132.4,
C
132.7,
C
–
–
1
130.3,
C
130.3,
C
–
–
2
7.19 (d,
8.6)
128.7,
CH
7.19 (d,
8.5)
128.7,
CH
H-3
H-2
–
C-4, 6
C-1, 5
–
2
7.18 (d,
8.6)
127.9,
CH
7.19 (d,
8.6)
127.9,
CH
H-3
H-2
–
C-4, 6
C-1, 5
–
3
6.81 (d,
8.6)
116.4,
CH
6.82 (d,
8.5)
116.4,
CH
3
6.75 (d,
8.6)
115.3,
CH
6.75 (d,
8.6)
115.3,
CH
4
–
158.8,
C
–
158.8,
C
4
–
157.6,
C
–
157.6,
C
5
6.81 (d,
8.6)
116.4,
CH
6.82 (d,
8.5)
116.4,
CH
H-6
H-5
H-8
H-7
–
C-1, 3
C-2, 4
5
6.75 (d,
8.6)
115.3,
CH
6.75 (d,
8.6)
115.3,
CH
H-6
H-5
H-8
H-7
–
C-1, 3
C-2, 4
6
7.19 (d,
8.6)
128.7,
CH
7.19 (d,
8.5)
128.7,
CH
6
7.18 (d,
8.6)
127.9,
CH
7.19 (d,
8.6)
127.9,
CH
7
5.39 (d,
9.0)
94.9,
CH
5.37 (d,
9.0)
94.8,
CH
C-2, 6,
9
7
5.38 (d,
9.0)
92.7,
CH
5.37 (d,
9.0)
92.7,
CH
C-2, 6,
9
8
4.50 (d,
9.0)
58.7,
CH
4.47 (d,
9.0)
58.7,
CH
C-1,
10, 14
–
8
4.44 (d,
9.0)
55.7,
CH
4.47 (d,
9.0)
55.7,
CH
C-1,
10, 14
–
9
–
145.4,
C
–
145.3,
C
9
–
143.7,
C
–
143.7,
C
10
11
12
13
14
1′
2′
3′
4′
5′
6′
7′
8′
6.33 (t,
1.8)
–
110.3,
CH
6.33 (t,
1.8)
–
110.3,
CH
–
C-12,
14
10
11
12
13
14
1′
2′
3′
4′
5′
6′
7′
8′
6.03 (t,
1.8)
–
106.0,
CH
6.03 (t,
1.8)
–
106.0,
CH
–
C-12,
14
160.0,
C
160.0,
C
–
–
158.7,
C
158.7,
C
–
–
6.47 (t,
1.8)
–
103.7,
CH
6.46 (t,
1.8)
–
104.0,
CH
–
C-10,
14
6.29 (t,
1.8)
–
102.9,
CH
6.30 (t,
1.8)
–
102.9,
CH
–
C-10,
14
160.2,
C
160.4,
C
–
–
158.7,
C
158.7,
C
–
–
6.38 (t,
1.8)
–
108.9,
CH
6.36 (t,
1.8)
–
109.1,
CH
–
C-10,
12
6.03 (t,
1.8)
–
106.0,
CH
6.03 (t,
1.8)
–
106.0,
CH
–
C-10,
12
141.1,
C
141.1,
C
–
–
139.3,
C
139.3,
C
–
–
7.21 (br s)
124.1,
CH
7.19 (br s)
124.1,
CH
–
C-8, 4′,
6′, 7′
–
7.24 (br s)
123.0,
CH
7.19 (br s)
123.0,
CH
–
C-8, 4′,
6′, 7′
–
–
–
132.1,
C
–
–
132.1,
C
–
–
–
131.3,
C
–
–
131.3,
C
–
161.0,
C
161.0,
C
–
–
159.0,
C
159.0,
C
–
–
6.89 (d,
8.2)
110.4,
CH
6.82 (d,
8.3)
110.4,
CH
H-6′
H-5′
H-8′
H-7′
C-1′, 3′
C-2′, 4′
6.89 (d,
8.3)
109.4,
CH
6.82 (d,
8.4)
109.4,
CH
H-6′
H-5′
H-8′
H-7′
C-1′, 3′
C-2′, 4′
7.41 (d,
8.2)
128.8,
CH
7.39 (d,
8.3)
128.9,
CH
7.41 (d,
8.3)
127.8,
CH
7.44 (d,
8.4)
127.8,
CH
7.01 (d,
16.0)
129.3,
CH
7.00 (d,
16.0)
129.3,
CH
C-2′,
6′, 9′
C-1′,
10′,
14′
7.09 (d,
16.0)
128.1,
CH
7.09 (d,
16.0)
128.1,
CH
C-2′,
6′, 9′
C-1′,
10′,
14′
6.79 (d,
16.0)
127.6,
CH
6.78 (d,
16.0)
127.6,
CH
6.88 (d,
16.0)
125.0,
CH
6.89 (d,
16.0)
125.9,
CH
9′
–
132.4,
C
–
132.4,
C
–
–
–
9′
–
130.3,
C
–
130.3,
C
–
–
–
10′
6.45 (d,
2.0)
105.8,
CH
6.43 (d,
2.0)
105.8,
CH
C-8′,
12′,
14′
–
10′
6.63 (t,
2.0)
105.0,
CH
6.43 (t,
2.0)
105.0,
CH
C-8′,
12′,
14′
–
11′
12′
13′
14′
–
159.7,
C
–
159.6,
C
–
–
–
–
11′
12′
13′
14′
–
158.6,
C
–
158.6,
C
–
–
–
–
6.17 (d,
2.0)
–
102.7,
CH
6.14 (d,
2.0)
–
103.0,
CH
C-10′,
14′
6.09 (t,
2.0)
–
101.4,
CH
6.10 (t,
2.0)
–
101.4,
CH
C-10′,
14′
159.7,
C
159.6,
C
–
158.5,
C
158.5,
C
–
6.45 (d,
2.0)
105.8,
CH
6.43 (d,
2.0)
105.8,
CH
C-8′,
10′,
12′
6.57 (t,
2.0)
107.1,
CH
6. 58 (t,
2.0)
107.1,
CH
C-8′,
10′,
12′
1′′
2′′
3′′
4′′
5′′
4.82 (d,
7.5)
102.4,
CH
4.74 (d,
7.5)
102.8,
CH
H-2′′
C-11,
1′′
2′′
3′′
4′′
5′′
4.82 (d,
7.2)
100.8,
CH
4.81 (d,
7.2)
100.8,
CH
H-2′′
C-11′,
3′′
3′′
3.39–3.43
(m)
74.6,
CH
3.35–3.39
(m)
74.6,
CH
H-1′′,
3′′
C-3′′
3.15–3.19
(m)
73.4,
CH
3.14–3.18
(m)
73.1,
CH
H-1′′,
3′′
C-3′′
3.29–3.31
(m)
77.7,
CH
3.31–3.34
(m)
77.7,
CH
H-2′′,
4′′
C-1′′,
5′′
3.20–3.24
(m)
76.5,
CH
3.19–3.23
(m)
76.5,
CH
H-2′′,
4′′
C-1′′,
5′′
3.54–3.58
(m)
71.0,
CH
3.50–3.55
(m)
71.0,
CH
H-3′′,
5′′
C-2′′
3.31–3.36
(m)
69.3,
CH
3.35–3.39
(m)
69.4,
CH
H-3′′,
5′′
C-2′′
3.85–3.80
(m)
66.9,
CH2
3.85–3.89
(m)
66.9,
CH2
H-4′′
C-3′′
3.69–3.72
(m)
65.7,
CH2
3.69–3.73
(m)
65.7,
CH2
H-4′′
C-3′′
3.26–3.30
(m)
3.21–3.28
(m)
3.24–3.27
(m)
3.25–3.29
(m)
3

S.-Y. Zhang et al.
Fitoterapia 153 (2021) 104997
Table 3
Table 3 (continued)
NMR data of 5 and 6 (in DMSO‑d6, 600 MHz for 1H, δ in ppm, J in Hz).
Position
5
6
1H–1H
HMBC
C-3′′′
1H–1H
HMBC
COSY
Position
5
6
δH
δC
δH
δC
COSY
δH
–
δC
δH
–
δC
2′′′
3′′′
4′′′
5′′′
3.15–3.20
(m)
73.0,
CH
3.14–3.18
(m)
73.0,
CH
H-1′′′
3′′′
,
,
,
1
130.1,
C
130.1,
C
–
–
3.20–3.22
(m)
76.3,
CH
3.19–3.23
(m)
76.4,
CH
H-2′′′
4′′′
C-1′′′
5′′′
,
2
7.19 (d,
8.6)
127.9,
CH
7.18 (d,
8.6)
127.8,
CH
H-3
H-2
–
C-4, 6
C-1, 5
–
3.33–3.37
(m)
69.4,
CH
3.35–3.39
(m)
69.3,
CH
H-3′′′
5′′′
C-2′′′
3
6.76 (d,
8.6)
115.3,
CH
6.76 (d,
8.6)
115.3,
CH
3.70–3.73
(m)
65.7,
CH2
3.69–3.73
(m)
65.6,
CH2
H-4′′′
C-3′′′
4
–
157.7,
C
–
157.7,
C
3.24–3.28
(m)
3.25–3.29
(m)
5
6.76 (d,
8.6)
115.3,
CH
6.76 (d,
8.6)
115.3,
CH
H-6
H-5
H-8
H-7
–
C-1, 3
C-2, 4
6
7.19 (d,
8.6)
127.9,
CH
7.18 (d,
8.6)
127.8,
CH
2.3.9. Lysidostegin I (9)
25
7
5.40 (d,
9.0)
92.5,
CH
5.44 (d,
9.0)
92.4,
CH
C-2, 6,
9
Yellow powder; [
α
]
+15.5 (c 1.0, MeOH); UV (MeOH) λmax: 200,
279 nm; IR (KBr) νmax: D3308, 1625, 1506, 1385, 1290, 1110, 1018, 829
cmꢀ 1; 1H and 13C NMR data, see Table 5; HR-ESI-MS m/z 413.1213 [M
+ H]+ (calcd for C22H21O8, 413.1231).
8
4.50 (d,
9.0)
55.5,
CH
4.52 (d,
9.0)
55.5,
CH
C-1,
10, 14
–
9
–
143.7,
C
–
143.7,
C
10
11
12
13
14
1′
2′
3′
4′
5′
6′
7′
8′
6.24 (t,
1.6)
–
107.4,
CH
6.24 (t,
1.6)
–
107.1,
CH
–
C-12,
14
2.4. Determination of the absolute configurations of sugars
158.6,
C
158.5,
C
–
–
The methods of acid hydrolysis and HPLC analysis were used to
confirm the absolute configurations of sugars in compounds 1–8 [18].
The compound (3 mg) were placed into 10 mL of HCl (2 M), and the
mixture was heated under reflux in a 90 ◦C water bath for 6 h. Then, the
solution was extracted with CH2Cl2 three times. After combination of the
CH2Cl2 extracts, the solvent was evaporated, and the residue was reac-
ted with anhydrous pyridine, L-cysteine methyl ester hydrochloride and
6.36 (t,
1.6)
–
102.1,
CH
6.30 (t,
1.6)
–
102.0,
CH
–
C-10,
14
158.7,
C
158.6,
C
–
–
6.25 (t,
1.6)
–
108.5,
CH
6.25 (t,
1.6)
–
108.5,
CH
–
C-10,
12
139.2,
C
139.2,
C
–
–
◦
2-methylphenyl isothiocyanate at 60 C for 1 h. Finally, the reaction
7.26 (br s)
123.0,
CH
7.24 (br s)
123.0,
CH
–
C-8, 4′,
6′, 7′
–
mixtures were subjected to HPLC analysis using CH3CN-H2O (20:80, 1
mL/min). As shown in Fig. S2, S13, S24, S35, S46 and S57 (Supporting
Information), all of the reaction mixtures of compounds 1–6 displayed
peaks at the same retention times as the D-xylose derivative standard (tR
= 19.4 min, Fig. S1, Supporting Information), determining that the
xylose moieties in compounds 1–6 are D-configured. The retention times
of the sugar derivatives in compound 7/8 were 16.5 and 19.4 min
(Figs. S68 and S79, Supporting Information), demonstrating that the
sugar derivatives in compound 7/8 were D-glucose (tR = 16.5 min,
Fig. S1, Supporting Information) and D-xylose, respectively.
–
–
131.0,
C
–
–
131.1,
C
–
159.0,
C
158.9,
C
–
–
6.91 (d,
8.6)
109.4,
CH
6.90 (d,
8.6)
109.4,
CH
H-6′
H-5′
H-8′
H-7′
C-1′, 3′
C-2′, 4′
7.46 (d,
8.6)
127.8,
CH
7.44 (d,
8.4)
127.8,
CH
7.08 (d,
16.0)
128.4,
CH
7.09 (d,
16.0)
128.4,
CH
C-2′,
6′, 9′
C-1′,
10′,
14′
6.91 (d,
16.0)
125.9,
CH
6.90 (d,
16.0)
125.9,
CH
2.5. Antioxidant activity
9′
–
130.3,
C
–
131.1,
C
–
–
–
10′
6.59 (t,
2.0)
107.1,
CH
6.63 (t,
2.0)
107.0,
CH
C-8′,
12′,
14′
–
Compounds 1–16 were tested for their antioxidant activities using
the DPPH method [18], with the vitamin E as a positive control. The
assay was conducted in a 96-well format using serial dilutions of 100 μL
11′
12′
13′
14′
–
158.4,
C
–
158.4,
C
–
–
–
–
aliquots of tested compounds (ranging from 1000 to 31.25
μM) and
vitamin E (1000–31.25 M), respectively. Then, the absorbance was
μ
6.30 (t,
2.0)
–
102.9,
CH
6.31 (t,
2.0)
–
103.0,
CH
C-10′,
14′
measured at 515 nm after 30 min in the dark. Three replicate wells were
set in parallel for every group. Methanol was used as a negative control.
The DPPH scavenging capacity (SC) was calculated according to the
following formula: SC% = [(A0-A1/A0)] × 100%. A0 is the absorbance
value of the control group; A1 is the absorbance value of the sample
group.
158.5,
C
158.5,
C
–
6.64 (t,
2.0)
104.9,
CH
6. 58 (t,
2.0)
105.0,
CH
C-8′,
10′,
12′
1′′
2′′
3′′
4′′
5′′
4.75 (d,
7.0)
101.1,
CH
4.81 (d,
7.2)
100.9,
CH
H-2′′
C-11,
3′′
3.15–3.20
(m)
73.1,
CH
3.14–3.18
(m)
73.1,
CH
H-1′′,
3′′
C-3′′
3. Results and discussion
3.20–3,23
(m)
76.5,
CH
3.19–3.23
(m)
76.5,
CH
H-2′′,
4′′
C-1′′,
5′′
25
Compound 1 was isolated as brown oil with [
α
]
+29.3 (c 1.0,
MeOH). Its molecular formula was deduced as C33H30OD10 on the basis of
3.33–3.37
(m)
69.3,
CH
3.35–3.39
(m)
69.4,
CH
H-3′′,
5′′
C-2′′
its 13C NMR and HR-ESI-MS (m/z 609.1723 [M + Na]+, calcd for
3.70–3.74
(m)
65.7,
CH2
3.69–3.73
(m)
65.7,
CH2
H-4′′
C-3′′
C
33H30NaO10, 609.1731) data. The IR spectrum suggested the presence
of a hydroxy group (3403 cmꢀ 1) and an aromatic ring (1601 cmꢀ 1). The
3.24–3.38
(m)
3.25–3.29
(m)
1H NMR spectrum (Table 1) showed characteristic signals for an aro-
1′′′
4.81 (d,
7.0)
100.8,
CH
4.79 (d,
7.0)
100.6,
CH
H-2′′′
C-11′,
3′′′
matic ABX spin system [δ 7.41 (1H, d, J = 8.2 Hz), 7.21 (1H, br s), 6.89
H
(1H, d, J = 8.2 Hz)], an aromatic AA'XX′ spin system [δH 7.19 (2H, d, J =
8.6 Hz), 6.81 (2H, d, J = 8.6 Hz)], an aromatic ABC spin system [δ 6.47
H
4

S.-Y. Zhang et al.
Fitoterapia 153 (2021) 104997
Table 4
Table 4 (continued)
NMR data of 7 and 8 (in DMSO‑d6, 600 MHz for 1H, δ in ppm, J in Hz).
Position
7
8
1H–1H
HMBC
C-3′′′
1H–1H
HMBC
COSY
Position
7
8
δH
δC
δH
δC
COSY
δH
–
δC
δH
–
δC
2′′′
3′′′
4′′′
5′′′
3.15–3.20
(m)
73.0,
CH
3.15–3.20
(m)
100.9,
CH
H-1′′′
3′′′
,
,
,
1
130.1,
C
130.1,
C
–
–
3.20–3.23
(m)
76.5,
CH
3.20–3.23
(m)
73.1,
CH
H-2′′′
4′′′
C-1′′′
5′′′
,
2
7.19 (d,
8.6)
127.9,
CH
7.19 (d,
8.6)
127.7,
CH
H-3
H-2
–
C-4, 6
C-1, 5
–
3.31–3.38
(m)
69.4,
CH
3.31–3.38
(m)
76.5,
CH
H-3′′′
5′′′
C-2′′′
3
6.76 (d,
8.6)
115.3,
CH
6.77 (d,
8.6)
115.3,
CH
3.70–3.74
(m)
65.7,
CH2
3.70–3.74
(m)
69.4,
CH
H-4′′′
C-3′′′
4
–
157.7,
C
–
157.7,
C
3.24–3.28
(m)
3.24–3.28
(m)
65.7,
CH2
5
6.77 (d,
8.6)
115.3,
CH
6.77 (d,
8.6)
115.3,
CH
H-6
H-5
H-8
H-7
–
C-1, 3
C-2, 4
6
7.19 (d,
8.6)
127.9,
CH
7.19 (d,
8.6)
127.7,
CH
7
5.46 (d,
9.0)
92.3,
CH
5.46 (d,
9.0)
92.4,
CH
C-2, 6,
9
Table 5
NMR data of 9 (600 MHz for 1H in DMSO‑d6, 13C in CD3OD, δ in ppm, J in Hz).
8
4.52 (d,
9.0)
55.6,
CH
4.52 (d,
9.0)
55.6,
CH
C-1,
10, 14
–
Position
δH
δC
1H–1H COSY
HMBC
9
–
143.6,
C
–
143.8,
C
2
4.49 (d, 9.5)
83.4, CH
81.0, CH
40.5, CH
158.4, C
96.4, CH
159.2, C
95.3, CH
157.8, C
107.8, C
132.6, C
116.0, CH
146.0, C
146.3, C
160.0, CH
120.8, CH
119.3, C
156.7, CH
103.2, CH
156.2, C
109.4, CH
129.7, CH
59.6, CH3
H-3
C-4
3
4.22 (t, 9.5)
H-2, H-4
C-10, 1′
10
11
12
13
14
1′
2′
3′
4′
5′
6′
7′
8′
6.28 (t,
1.6)
–
107.1,
CH
6.28 (t,
1.6)
–
107.1,
CH
–
C-12,
14
4
4.41 (d, 9.5)
H-3
C-2, 5, 9, 2′, 6′
5
–
–
–
158.7,
C
158.6,
C
–
–
6
5.70 (d, 1.6)
–
C-8, 10
7
–
–
–
6.38 (t,
1.6)
–
102.0,
CH
6.38 (t,
1.6)
–
101.9,
CH
–
C-10,
14
8
5.87 (d, 1.6)
–
C-6, 10
9
–
–
–
158.8,
C
158.8,
C
–
–
10
–
–
–
1′
–
–
–
6.23 (t,
1.6)
–
108.3,
CH
6.23 (t,
1.6)
–
108.4,
CH
–
C-10,
12
2′
6.85 (d, 1.2)
–
C-4′, 6′
3′
–
–
–
–
–
139.2,
C
139.2,
C
–
–
4′
–
5′
6.72 (d, 8.4)
6.69 (dd, 8.4, 1.2)
–
H-6′
C-1′, 3′
C-2′, 4′
–
7.25 (br s)
123.0,
CH
7.25 (br s)
123.0,
CH
–
C-8, 4′,
6′, 7′
–
6′
H-5′
1′′
2′′
3′′
4′′
5′′
6′′
3-OCH3
–
–
–
131.2,
C
–
–
131.1,
C
–
4.18 (d, 6.5)
6.10 (d, 2.4)
–
6.15 (dd, 8.2, 2.4)
6.38 (d, 8.2)
2.68 (s)
–
–
–
C-1′′, 5′′
–
158.9,
C
158.9,
C
–
–
–
H-6′′′
H-5′′′
–
C-1′′, 3′′
C-2′′, 4′′
C-3, 4
6.91 (d,
8.6)
109.4,
CH
6.91 (d,
8.6)
109.3,
CH
H-6′
H-5′
H-8′
H-7′
C-1′, 3′
C-2′, 4′
7.45 (d,
8.6)
127.8,
CH
7.45 (d,
8.6)
127.7,
CH
7.08 (d,
16.0)
128.4,
CH
7.08 (d,
16.0)
128.4,
CH
C-2′,
6′, 9′
C-1′,
10′,
14′
(1H, t, J = 1.8 Hz), 6.38 (1H, t, J = 1.8 Hz), 6.33 (1H, t, J = 1.8 Hz)], an
aromatic AB2 spin system [δH 6.45 (2H, d, J = 2.0 Hz), 6.17 (1H, d, J =
2.0 Hz)], a trans olefinic proton system [δH 7.01 (1H, d, J = 16.0 Hz),
6.79 (1H, d, J = 16.0 Hz)], two methines [δH 5.39 (1H, d, J = 9.0 Hz),
4.50 (1H, d, J = 9.0 Hz)], and an anomeric proton [δH 4.82 (1H, d, J =
7.5 Hz)]. The analysis of its 13C NMR data (Table 1) revealed the pres-
ence of 33 carbon resonances, including 12 quaternary carbons (7
oxygenated), 20 methines (4 oxygenated), and 1 methylene. The NMR
data of compound 1 resembled those of resveratrol (E)-dehydrodimer-
11-O-β-D-glucopyranoside [19], except for the absence of a glucose unit
6.91 (d,
16.0)
125.9,
CH
6.91 (d,
16.0)
125.9,
CH
9′
–
130.3,
C
–
130.3,
C
–
–
–
10′
6.58 (t,
2.0)
107.1,
CH
6.58 (t,
2.0)
107.1,
CH
C-8′,
12′,
14′
–
11′
12′
13′
14′
–
158.4,
C
–
158.4,
C
–
–
–
–
6.30 (t,
2.0)
–
102.9,
CH
6.30 (t,
2.0)
–
103.0,
CH
C-10′,
14′
and the presence of a xylose unit (δ 102.4, 77.7, 74.6, 71.0, 66.9) in 1.
C
158.5,
C
–
The differences indicated the glucose unit in resveratrol (E)-dehy-
drodimer-11-O-β-D-glucopyranoside was replaced by a xylose unit in 1.
Moreover, the type of sugar residue was also confirmed by the acid
hydrolysis of 1 (Figs. S1 and S2, Supporting Information). The HMBC
6.64 (t,
2.0)
104.9,
CH
6.64 (t,
2.0)
158.5,
C
C-8′,
10′,
12′
cross-peak from H-1′′ (δH 4.82) to C-11 (δ 160.0) indicated that the D-
1′′
2′′
3′′
4′′
5′′
6′′
1′′′
4.74 (d,
7.4)
100.1,
CH
4.78 (d,
7.4)
105.0,
CH
H-2′′
C-11,
C
3′′
3
xylose moiety was connected to C-11 (Fig. 2). The JH1-H2 coupling
3.15–3.18
(m)
73.2,
CH
3.15–3.18
(m)
99.9,
CH
H-1′′,
3′′
C-3′′
constant demonstrated β-configuration for the xylosyl bond (3JH1 -H2
=
′′
′′
7.5 Hz). Moreover, the NOE correlations between H-7 (δH 5.39) and H-
3.19–3.21
(m)
77.0,
CH
3.19–3.21
(m)
73.1,
CH
H-2′′,
4′′
C-1′′,
5′′
10 (δ 6.33)/H-14 (δ 6.38) and between H-8 (δ 4.50) and H-2 (δ
H
H
7.19)/H-6 (δ 7.19) iHndicated that H-7 and H-8 were on the oppositHe
3.12–3.15
(m)
69.6,
CH
3.12–3.15
(m)
76.8,
CH
H-3′′,
5′′
C-2′′
side (Fig. 3). HThe absolute configuration of 1 was confirmed by quantum
3.21–3.24
(m)
76.6,
CH
3.21–3.24
(m)
69.4,
CH
H-4′′,
6′′
C-3′′
C-4′′
chemical
ECD
calculations.
The
ECD
spectra
for
(7S,8S,1′′S,2′′R,3′′S,4′′R)-1 and its enantiomer were performed using the
TDDFT-ECD method, and were calculated at the B3LYP/6–31 + G(d)
level in the gas phase. The experimental ECD spectrum of 1 exhibited a
3.45–3.48
(m)
60.6,
CH2
100.8,
CH
3.45–3.48
(m)
76.6,
CH
H-5′′
4.81 (d,
7.0)
4.81 (d,
7.0)
60.4,
CH2
H-2′′′
C-11′,
3′′′
negative cotton effect at 213 nm (Δ
ε ꢀ 13.2) and a positive cotton effect
at 235 nm (Δ
ε
+ 4.7), which were similar to those of the calculated ECD
5

S.-Y. Zhang et al.
Fitoterapia 153 (2021) 104997
1
–
Fig. 2. Key 1
H
H COSY and HMBC correlations of 1, 3, 5, 7 and 9.
Fig. 3. Key NOESY correlations of 1 and 9.
Compound 2 was isolated as brown oil with [
25
α
]
+14.5 (c 1.0,
CHCl3). The HR-ESI-MS of compound 2 showed an [MD+ Na]+ ion peak
at m/z 609.1720 (calcd for C33H30NaO10, 609.1731), consistent with the
molecular formula of C33H30O10. The NMR spectroscopic data (Table 1)
of 2 was almost identical to those of 1, which indicated that 2 possessed
the same planar structure as that of 1. The β-configuration of the xylosyl
bond in 2 was determined by the anomeric proton signal at δH 4.74 (1H,
d, J = 7.5 Hz). Analysis of the NOESY spectrum, H-7 and H-8 were also
located on the opposite side, indicating that the relative configuration of
2 was same as that of 1. Interestingly, compounds 1 and 2 had the same
NMR data, but showed different retention times in HPLC analysis. And
the rotation data of 1 (+29.3) and 2 (+14.5) were all positive, indicating
they were not a pair of enantiomers. These informations implied that
compounds 1 and 2 could be a pair of diastereoisomers with the oppo-
sitely absolute configurations of C-7 and C-8. Furthermore, the absolute
configuration of 2 was established by quantum-chemical ECD calcula-
tion. The predicted ECD spectra of 2, (7R,8R,1′′S,2′′R,3′′S,4′′R)-2, and its
enantiomer, were compared with the experimental spectra, indicating
the absolute configuration of 2 was 7R,8R,1′′S,2′′R,3′′S,4′′R (Fig. S100,
Supporting Information). Accordingly, compound 2 was elucidated and
named lysidostegin B.
Fig. 4. Experimental and calculated ECD spectra of compound 1.
Compound 3 had the molecular formula C33H30O10 assigned by HR-
ESI-MS (m/z 609.1733 [M + Na]+, calcd for C33H30NaO10, 609.1731).
According to its 1D and 2D NMR spectra (Table 2), compound 3 has the
spectrum for (7S,8S,1′′S,2′′R,3′′S,4′′R)-1 (Fig. 4). Hence, the absolute
configuration of 1 was elucidated as 7S,8S,1′′S,2′′R,3′′S,4′′R. Based on
the above analysis, the structure was elucidated as shown and named
lysidostegin A.
1
1
–
same stilbene dimer skeleton as that of 1, with the H H COSY cor-
relations between H-2 (δ 7.18) and H-3 (δ 6.75), between H-5 (δ
H
H
H
6

S.-Y. Zhang et al.
Fitoterapia 153 (2021) 104997
6.75) and H-6 (δH 7.18), between H-7 (δH 5.38) and H-8 (δH 4.44), be-
tween H-5′ (δ 6.89) and H-6′ (δ 7.43), between H-7′ (δ 7.09) and H-8′
ESI-MS (m/z 771.2272 [M + Na]+, calcd for C39H40O15Na, 771.2259).
According to 1D and 2D NMR spectra (Table 4), compound 7 has the
same stilbene dimer skeleton as resveratrol (E)-dehydrodimer-11-O-β-D-
glucopyranoside [19], except for the presence of an additional xylose
unit (δC 100.8, 76.5, 73.0, 69.4, 65.7) in 7, and the aromatic AB2 spin
system (D ring) of resveratrol (E)-dehydrodimer-11-O-β-D-glucopyr-
anoside was replaced by an aromatic ABC spin system (D ring) of 7. This
indicated an additional xylose unit connecting to C-11′ in 7, which was
verified by the HMBC cross-peak from H-1′′′(δH 4.81) to C-11′ (δC 158.4)
(Fig. 2). The β-anomeric configurations of xylosyl and glucosyl units
were determined by the anomeric proton signals at δH 4.81 (1H, d, J =
7.0 Hz) and 4.74 (1H, d, J = 7.4 Hz) in 7. The trans-configuration of C-7/
C-8 was consistent with the observed coupling constant (J7–8 = 9.0 Hz).
H
H
(δH 6.88) (Fig. 2). In addition, tHhe HMBC cross-peaks from H-8 to C-10
(δ 106.0)/C-14 (δ 106.0), and from H-8′ to C-10′ (δ 105.0)/C-14′ (δ
C
C
C
C
107.1) indicated that B and D rings were aromatic AB2 and ABC spin
systems, respectively, which were different from those of 1. These dif-
ferences indicated that the D-xylose unit was connected to C-11′ in 3,
which was supported by the HMBC cross-peaks from H-1′′ (δ 4.82) to C-
H
11′ (δC 158.6) (Fig. 2). The xylosyl bond was β-configuration in 3, which
was determined by the anomeric proton signal at δ 4.82 (1H, d, J = 7.2
Hz). The trans-configuration of C-7/C-8 was consistHent with the coupling
constant (J7–8 = 9.0 Hz) observed in 1H NMR spectrum. Thus, the
relative stereochemistry of C-7 and C-8 in 3 was 7S*, 8S* or 7R*,8R*.
The sign of the calculated ECD spectra for (7S,8S,1′′S,2′′R,3′′S,4′′R)-3
correlated well with the overall shape of the experimental ECD spectra
for 3 (Fig. S101, Supporting Information). Thus, the absolute configu-
ration of 3 was established as 7S,8S,1′′S,2′′R,3′′S,4′′R. And it was named
as lysidostegin C.
Furthermore,
the
calculated
ECD
spectrum
for
(7S,8S,1′′S,2′′R,3′′S,4′′R,5′′S,1′′′S,2′′′R,3′′′S,4′′′R)-7 matched well with
that measured for 7 (Fig. S105, Supporting Information). Thus, the ab-
solute
configuration
of
7
was
established
as
7S,8S,1′′S,2′′R,3′′S,4′′R,5′′S,1′′′S,2′′′R,3′′′S,4′′′R. Therefore, the structure
of compound 7 was identified as shown, and it was named lysidostegin
G.
The HR-ESI-MS of compound 4 showed an [M + Na]+ ion peak at m/
z 609.1722 (calcd for C33H30NaO10, 609.1731), consistent with the
molecular formula of C33H30O10. The 1D and 2D NMR spectroscopic
data (Table 2) of 4 was nearly the same as those of 3, however, with
The molecular formula of 8 was established to be C39H40O15 by its
HR-ESI-MS m/z 771.2256 [M + Na]+ (calcd for C39H40O15Na,
771.2259). Its NMR data (Table 4) were similar to those of 7, indicating
that 8 possessed the same skeleton of stilbene dimer. The β-D-xylose and
β-D-glucose moieties were determined by the acid hydrolysis and the
anomeric proton signals at δ 4.81 (1H, d, J = 7.0 Hz) and 4.78 (1H, d, J
= 7.4 Hz). However, the rotHation data of 8 (+22.9) and 7 (+31.9) were
different, which indicated that compounds 8 and 7 might be a pair of
diastereoisomers with the oppositely absolute configurations of C-7 and
different rotation data (3: [
α
]
25 +32.7 and 4: [
α
]
25 +18.6). Similarly to
D
compounds 1 and 2, compounds 3 and 4 mighDt also be a pair of di-
astereoisomers with the opposite absolute configuration of C-7 and C-8.
Furthermore, the calculated ECD spectrum for (7R,8R,1′′S,2′′R,3′′S,4′′R)-
4 was in good agreement with the experimental data for 4 (Fig. S102,
Supporting Information). Thus, the absolute configurations of 4 was
established as 7R,8R,1′′S,2′′R,3′′S,4′′R. Therefore, the structure of 4 was
identified and named lysidostegin D.
C-8.
Furthermore,
the
calculated
ECD
spectrum
for
Compound 5 showed an [M + Na]+ ion peak at m/z 741.2153 (calcd
for C38H38NaO14, 741.2154) in the HR-ESI-MS spectrum, consistent with
the molecular formula of C38H38O14. The 1H and 13C NMR data (Table 3)
of 5 were similar to those of 1. The most notable differences between
them were the presence of an additional xylose unit in 5, and the aro-
matic AB2 spin system (D ring) of 1 was replaced by an aromatic ABC
spin system (D ring) of 5. These suggested that the additional xylose unit
was connected to C-11′ in 5, which was verified by the HMBC cross-peak
(7R,8R,1′′S,2′′R,3′′S,4′′R,5′′S,1′′′S,2′′′R,3′′′S,4′′′R)-8 was in good agree-
ment with the experimental data for 8 (Fig. S106, Supporting Informa-
tion). Thus, the absolute configuration of 8 was established as
7R,8R,1′′S,2′′R,3′′S,4′′R,5′′S,1′′′S,2′′′R,3′′′S,4′′′R. And it was named lysi-
dostegin H.
Compound 9 was isolated as yellow powder with [
α
]
25 +15.5 (c 1.0,
MeOH). Its molecular formula was deduced as C22H20O8Don the basis of
its 13C NMR and HR-ESI-MS (m/z 413.1213 [M + H]+, calcd for
from H-1′′′(δH 4.81) to C-11′ (δ 158.4) (Fig. 2). Moreover, the type of
C22H21O8, 413.1231) data. The IR spectrum suggested the presence of a
C
sugar residue was confirmed by the acid hydrolysis of 5, wherein only
the D-xylose was detected. The β-anomeric configurations of the two
xylosyl units were determined by the anomeric proton signals at δH 4.81
(1H, d, J = 7.0 Hz) and 4.75 (1H, d, J = 7.0 Hz) in 5. The trans-
configuration of C-7/C-8 was consistent with the coupling constant (J7–8
= 9.0 Hz) observed in 1H NMR spectrum. Furthermore, the calculated
ECD spectrum for (7S,8S,1′′S,2′′R,3′′S,4′′R,1′′′S,2′′′R,3′′′S,4′′′R)-5
matched well with that of measured for 5 (Fig. S103, Supporting In-
formation). Thus, the absolute configuration of 5 was established as
7S,8S,1′′S,2′′R,3′′S,4′′R,1′′′S,2′′′R,3′′′S,4′′′R. Thus, the structure of 5 is
determined and named as lysidostegin E.
hydroxy group (3308 cmꢀ 1) and an aromatic ring (1625 and 1506
cmꢀ 1). The 1H NMR spectrum (Table 5) showed characteristic signals for
an aromatic AX spin system [δH 5.87 (1H, d, J = 1.6 Hz), 5.70 (1H, d, J =
1.6 Hz)], an aromatic ABX spin system [δ 6.85 (1H, d, J = 1.2 Hz), 6.72
(1H, d, J = 8.4 Hz), 6.69 (1H, dd, J = 8.4,H1.2 Hz)], an aromatic ABC spin
system [δ 6.38 (1H, d, J = 8.2 Hz), 6.15 (1H, dd, J = 8.2, 2.4 Hz), 6.10
(1H, d, J H= 2.4 Hz)], three methines [δH 4.49 (1H, d, J = 9.5 Hz), 4.41
(1H, d, J = 9.5 Hz), 4.22 (1H, t, J = 9.5 Hz)], and a methoxy group [δ
2.68 (3H, s)]. The analysis of its 13C NMR data (Table 5) revealed thHe
presence of 22 carbon resonances, including 10 quaternary carbons (7
oxygenated), 11 methines (2 oxygenated), and 1 methoxy group. The
NMR data of compound 9 resembled those of the known compound 10
[12], except for the presence of an additional methoxy group (δC 59.6) in
The molecular formula of 6 was determined to be C38H38O14 by HR-
ESI-MS (m/z 741.2141 [M + Na]+, calcd for C38H38NaO14, 741.2154).
Its NMR data (Table 3) were similar to those of 5, indicating that 6
possessed the same skeleton of stilbene dixyloside. The β-D-xylose
moieties were determined by the acid hydrolysis and the anomeric
proton signals at δH 4.81 (1H, d, J = 7.0 Hz) and 4.79 (1H, d, J = 7.0 Hz).
However, the rotation data of 6 (+16.4) and 5 (+35.2) were different,
which indicated that compounds 6 and 5 might be a pair of di-
astereoisomers with the oppositely absolute configurations of C-7 and C-
9 and the chemical shift of C-3 shifted from δ 68.0 in the known one to
C
δC 81.0 in 9. The differences indicated the hydroxy group at C-3 in 9 was
1
1
–
replaced by a methoxy group. This was confirmed by the H H COSY
cross-peaks between H-3 (δH 4.22) and H-2 (δH 4.49)/H-4 (δH 4.41),
together with the HMBC cross-peaks from 3-OCH3 (δH 2.68) to C-3 (δ
81.0)/C-4 (δC 40.5) (Fig. 2). The relative stereochemistry of 9 waCs
similar to the known compound 10, which was determined by the
NOESY correlations between 3-OCH3 and H-2/H-4 (Fig. 3). The absolute
configuration of 9 was confirmed by quantum-chemical ECD calcula-
tions. The experimental ECD spectrum of 9 was similar to that of the
calculated ECD spectrum for (2R,3S,4R)-9 (Fig. S107, Supporting In-
formation). Hence, the absolute configuration of 9 was elucidated as
2R,3S,4R. Based on the above analysis, the structure was elucidated as
shown and named lysidostegin I.
8.
Furthermore,
the
calculated
ECD
spectrum
for
(7R,8R,1′′S,2′′R,3′′S,4′′R,1′′′S,2′′′R,3′′′S,4′′′R)-6 was in good agreement
with the experimental data for 6 (Fig. S104, Supporting Information).
Thus, the absolute configuration of
6
was established as
7R,8R,1′′S,2′′R,3′′S,4′′R,1′′′S,2′′′R,3′′′S,4′′′R. Therefore, the structure of 6
was determined and named as lysidostegin F.
Compound 7 was assigned the molecular formula C39H40O15 by HR-
7

S.-Y. Zhang et al.
Fitoterapia 153 (2021) 104997
Science and Technology Planning Project of Guangdong Province (No.
2020B121201013), and the high performance public computing service
platform of Jinan University.
Table 6
Antioxidant activities of compounds 1–16.
Compounds
IC50
(μ
M)a
Compounds
IC50
(
μ
M)a
1
2
3
4
5
6
7
8
9
26.59 ± 1.78
25.12 ± 2.33
30.71 ± 1.83
28.05 ± 1.69
32.54 ± 1.68
34.17 ± 2.29
22.71 ± 1.19
24.31 ± 1.22
9.57 ± 1.30
10
13.60 ± 1.47
35.51 ± 1.92
31.60 ± 2.45
49.37 ± 1.93
40.38 ± 2.57
45.76 ± 1.12
56.92 ± 1.46
17.39 ± 1.72
Appendix A. Supplementary data
11
12
13
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.fitote.2021.104997.
14
15
16
Vitamin Eb
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The authors declare no competing financial interest.
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This work was supported by grants from the National Natural Science
Foundation of China (Nos. 81973190, 81803376, 81703662), the
Guangdong Basic and Applied Basic Research Foundation (No.
2020B1515020033), the Natural Science Foundation of Guang-dong
Province (No. 2018B030311020), the Guangdong Basic and Applied
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Basic
Research
Foundation-Regional
Joint
Fund
(No.
2020A1515110415), the Local Innovative and Research Teams Project
of Guangdong Pearl River Talents Program (No. 2017BT01Y036),
8