Sweritranslactone D, a hepatoprotective novel secoiridoid dimer with tetracyclic lactone skeleton from heat-transformed swertiamarin

Article abstract of DOI:10.1016/j.fitote.2021.104879

Swertia mileensis, known as Qing-Ye-Dan (QYD), has been documented in Chinese Pharmacopoeia to cure hepatitis. Interestingly, its announced main active component, swertiamarin, could not be detected in the decoction, which indicated that the efficacy of QYD might be attributed to heat-transformed products of swertiamarin (HTPS). Further investigation on HTPS led to the isolation of sweritranslactone D (1), a novel secoiridoid dimer possessing a tetracyclic lactone skeleton, with better hepatoprotective activity than N-acetyl-L-cysteine in vitro.

Full text of DOI:10.1016/j.fitote.2021.104879

Fitoterapia 151 (2021) 104879
Contents lists available at ScienceDirect
Fitoterapia
journal homepage: www.elsevier.com/locate/fitote
Sweritranslactone D, a hepatoprotective novel secoiridoid dimer with
tetracyclic lactone skeleton from heat-transformed swertiamarin
,
,
Ya-Dan Zoua 1, Xiao-Xia Maa 1, Sheng-Nan Dua, Ping-Xing Qia, Fang-Yan Hea, Zhu-Ya Yanga,
Wen-Hong Tana, Afsar Khanb, Zhi-Hong Zhoua *, Lu Liua
,
,*
a Yunnan Key Laboratory of Southern Medicinal Resource, Yunnan University of Chinese Medicine, Kunming 650500, People’s Republic of China
b Department of Chemistry, COMSATS University Islamabad, Abbottabad Campus, Abbottabad 22060, Pakistan
A R T I C L E I N F O
A B S T R A C T
Keywords:
Swertia mileensis, known as Qing-Ye-Dan (QYD), has been documented in Chinese Pharmacopoeia to cure hep-
atitis. Interestingly, its announced main active component, swertiamarin, could not be detected in the decoction,
which indicated that the efficacy of QYD might be attributed to heat-transformed products of swertiamarin
(HTPS). Further investigation on HTPS led to the isolation of sweritranslactone D (1), a novel secoiridoid dimer
possessing a tetracyclic lactone skeleton, with better hepatoprotective activity than N-acetyl-L-cysteine in vitro.
Swertiamarin
Sweritranslactone D
Secoiridoid dimer
Hepatoprotective
1. Introduction
established on the basis of extensive spectroscopic methods and X-ray
crystallographic diffraction analysis. The plausible transformation
Swertia mileensis, well-known in China under the name “Qing-Ye-
Dan” and documented in Chinese Pharmacopoeia (1977–2020 editions)
for curing viral hepatitis, belongs to the genus Swertia of family Gen-
tianaceae [1]. Clinical reports revealed that Qing-Ye-Dan tablets, pre-
pared from the boiling water extract of S. mileensis, showed curing rate
up to 95.3% for 422 patients and 96.8% for 93 patients, respectively, to
cure acute hepatitis with high alanine transaminase (ALT) and aspartate
transaminase (AST) levels [2]. Swertiamarin, an iridoid glycoside, is
generally considered to be the main active component of S. mileensis to
treat hepatitis [3]; its content in the whole plant of S. mileensis is up to
12%, and beyond 50% in its cold-water extract [4–9]. Owing to struc-
tural instability of iridoid glycosides, swertiamarin was not detected 6 h
later, in both Qing-Ye-Dan (QYD) decoction and heat-transformed
products from swertiamarin (HTPS), by TLC method after heat treat-
ment in water. Hence, the actual active components of QYD might be
HTPS. Based on this hypothesis, we evaluated the hepatoprotective ac-
tivity of swertiamarin, QYD tablets, and HTPS via serum ALT and AST
analyses in mice model of acute liver injury by carbon tetrachloride
(CCl4). Results showed that both the low- and high-dose groups of HTPS
significantly alleviated liver injury by decreasing the levels of serum ALT
and AST. Further investigations on HTPS led to the isolation of a novel
tetracyclic lactone iridoid dimer, sweritranslactone D (1) (Fig. 1), along
with a new analogue (2) and 7 known compounds. Their structures were
pathways of these products are also proposed. Furthermore, these
compounds were evaluated for hepatoprotective activity in vitro in L-O2
cell model induced by 4-acetamidophenol (AP), with N-Acetyl-L-
cysteine (NAC) as positive control. All the isolates exhibited hep-
atoprotective activity, and interestingly, compound 1 showed a potent
activity compared to the positive control.
2. Experimental
2.1. General experimental procedures
Optical rotations were measured on a JASCO P-1020 polarimeter. All
the 1D and 2D NMR spectra were recorded on Bruker DRX-600 spec-
trometer. Unless otherwise specified, chemical shifts (δ) were expressed
in ppm with reference to the solvent signals. ESI-MS and HR-ESI-MS
analyses were carried out on Waters Xevo TQS and Waters AutoSpec
Premier P776 mass spectrometers, respectively. Silica gel (100–200 and
200–300 mesh, Qingdao Marine Chemical Co., Ltd., China), and MCI gel
(75–150 μm, Mitsubishi Chemical Corporation, Tokyo, Japan) were used
for column chromatography. Fractions were monitored by TLC (GF 254,
Qingdao Marine Chemical Co., Ltd.), and the spots were visualized by
10% H2SO4/EtOH reagent.
* Corresponding author.
E-mail addresses: kmzhouzh@163.com (Z.-H. Zhou), todayliulu@163.com (L. Liu).
1
These authors contributed equally to this work.
https://doi.org/10.1016/j.fitote.2021.104879
Received 24 January 2021; Received in revised form 28 February 2021; Accepted 1 March 2021
Available online 6 March 2021
0367-326X/© 2021 Elsevier B.V. All rights reserved.

Y.-D. Zou et al.
Fitoterapia 151 (2021) 104879
2.2. Preparation and isolation
Table 1
13C (150 MHz) and 1H (600 MHz) NMR spectroscopic data of 1 (Chloroform‑d1)
and 2 (DMSO‑d6).
The mixture of swertiamarin (5.8 kg) in water (17.5 kg) was heated
under reflux conditions for 6 h to obtain an aqueous mixture (15 kg). A
portion of the mixture (5 kg) was subjected to medium pressure liquid
chromatography (MPLC) column (5.6 × 48.0 cm) with gradient elution
(MeOH/H2O, v/v, from 5 to 100%) to get 5 fractions A-E on the basis of
TLC detection. Fr. B (250 g) was chromatographed on macroreticular
resin column (5.0 × 100.0 cm), eluted with gradient solvent system of
MeOH/H2O (0–100%, v/v) to yield 9 subfractions (Fr. B1–B9). Fr. B4
(206 g) was chromatographed on silica gel column (5.0 × 65.0 cm) with
gradient elution (petroleum ether/ethyl acetate, 8:1–2:1, v/v) to get 12
fractions (Fr. B4-1–B4-12). Compound 4 (17.8 g) was obtained by
recrystallization from Fr. B4-2. Compounds 5 (3.1 g) and 3 (700 mg)
were isolated through MCI column, eluted with MeOH/H2O (30–100%,
v/v) and MeOH/H2O (20–100%, v/v), from Fr. B-4 and Fr. B-5,
respectively. Compounds 2 (100 mg) and 6 (1.5 g) were obtained by
recrystallization from Fr. B4-5 and Fr. C (65 g), respectively. The rest of
Fr. C was subjected to macroreticular resin column (5.0 × 76.0 cm),
eluted with gradient solvent system of MeOH/H2O (0–100%, v/v) to
yield 8 subfractions (Fr. C1–C8). Fr. C6 was chromatographed over MCI
column (MeOH/H2O, 0–100%, v/v) and silica gel column (4.8 × 26.0
cm, petroleum ether/ethyl acetate, 8:1–2:1, v/v) to get compound 8
(105 mg) and 9 (45 mg). Fr. D (48.3 g) was separated into 15 sub-
fractions by using silica gel column (10.0 × 60.0 cm). Compounds 1 (10
mg) and 7 (2.7 g) were obtained from Fr. D13 and Fr. D3 through MPLC
(MeOH/H2O, 75:25, v/v) and silica gel column chromatography (pe-
troleum ether/acetone, 95:5, v/v).
Position
1
2
δC
δH (mult., J in Hz)
δC
δH (mult., J in Hz)
3
94.2, CH
5.28, s
69.3,
CH
3.84, overlap
4
5
6
125.5, C
154.4, C
31.4,
52.1, C
141.0, C
124.4,
CH
2.83, m; 2.20, m
4.32, m
6.10, dd (6.1, 2.9)
CH2
7
65.6,
66.8,
CH2
4.73, dd (15.6, 6.0);
5.08, d (15.6)
CH2
8
31.3, CH
2.39, m
71.1,
CH
3.97, dd (6.0, 6.2)
9
40.6, CH
2.03, dd (2.9, 11.4)
1.03, d (7.1)
47.3,
CH
2.32, br s
10
17.3,
20.3,
CH3
0.86, d (6.0)
CH3
11
12
162.5, C
56.2,
171.2, C
3.59, s
CH3
3′
60.6, CH
5.00, d (3.0)
72.8,
CH
3.84, overlap
4′
123.7,
CH
44.7, C
5′
157.1,
CH
127.5, C
6′
28.3,
CH2
2.64, m; 2.23, m
4.39, m
36.6,
3.21, br s; 3.16, br s
CH2
7′
65.3,
CH2
171.6, C
8′
120.9,
CH2
5.34, dd (1.1, 10.2);
5.16, dd (1.1, 17.0)
2.88, dd (4.9, 8.7)
36.5,
CH
2.65, br s
2.2.1. Sweritranslactone D (1)
9′
52.0, CH
126.5,
CH
5.33, br s
23
Colorless cubic crystals (MeOH); [
α]
ꢀ 5.2 (c 0.10, CHCl3/MeOH,
D
v/v = 1:1); 1H and 13C NMR data: see Table 1; HR-ESI-MS m/z 369.1308
[M + Na]+ (Calcd for C19H22O6Na, 369.1309).
10′
11′
132.3,
CH
5.63, ddd (8.7, 10.1,
17.0)
21.6,
CH3
0.97, d (7.2)
163.5, C
72.6,
CH2
4.36, d (11.0); 4.26,
d (11.0)
2.2.2. Sweritranslactone E (2)
23
Colorless cubic crystals (MeOH); [
α]
ꢀ 4.3 (c 0.10, CHCl3/MeOH,
D
v/v = 1:1); 1H and 13C NMR data: see Table 1; HR-ESI-MS m/z 333.1349
Fig. 1. Chemical structures of compounds 1–9.
2

Y.-D. Zou et al.
Fitoterapia 151 (2021) 104879
[M + H]+ (Calcd for C18H21O6, 333.1333).
2.4. Detailed description of hepatoprotective studies in AP-induced L-O2
cell model
2.2.3. Crystal data
Crystal data for sweritranslactone D (1): C19H22O6, M = 346.37,
2.4.1. Model of AP-induced L-O2 cells
monoclinic, a = 16.603(3) Å, b = 7.2973(11) Å, c = 14.317(2) Å,
α
=
The L-O2 cells were cultured in the exponential growth phase; the
model was established successfully under the conditions of AP at a
concentration of 5 mmol/mL for 48 h, and then the cells were treated
90.00◦, β = 104.624(2)◦, γ = 90.00◦, V = 1678.3(4) Å3, T = 100(2) K,
space group P21/c, Z = 4,
μ
(Mo K
α
) = 0.102 mmꢀ 1, 15,656 reflections
measured, 4038 independent reflections (Rint = 0.0351). The final R1
with different concentrations of the isolates from HTPS (0.8
μ
g/mL, 1.6
g/mL, 100
g/mL) at a density of 5 × 104 cells/100
μL per well and incubated for
values were 0.0372 (I > 2
σ
(I)). The final wR(F2) values were 0.0920 (I >
μ
g/mL, 3.1 μg/mL, 6.3 μg/mL, 12.5 μg/mL, 25 μg/mL, 50 μ
2
σ
(I)). The final R1 values were 0.0512 (all data). The final wR(F2)
μ
values were 0.1062 (all data). The goodness of fit on F2 was 1.087.
(CCDC 1500816).
24 h at 37 ◦C in 5% CO2 incubator [12].
Crystal data for sweritranslactone E (2): C18H20O6, M = 332.34,
2.4.2. Detection of the survival rate of AP-induced L-O2 cells
monoclinic, a = 12.076(3) Å, b = 15.221(3) Å, c = 8.4687(17) Å,
α
=
The L-O2 cell survival rate was measured by an assay based on the
cleavage of yellow tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2,5-
diphenyltetrazolium bromide (MTT) to form purple formazan crystals in
viable cells. The compounds were dissolved in dimethyl sulfoxide
(DMSO) and diluted with culture medium. The cells were then treated
with 10% (v/v) MTT dye solution (5 mg/mL) for 4 h. The medium of
90.00◦, β = 106.346(3)◦, γ = 90.00◦, V = 1493.6(5) Å3, T = 100(2) K,
space group P21/c, Z = 4,
μ
(Mo K
α
) = 0.111 mmꢀ 1, 13,632 reflections
measured, 3577 independent reflections (Rint = 0.0472). The final R1
values were 0.0449 (I > 2
σ
(I)). The final wR(F2) values were 0.1234 (I >
2
σ
(I)). The final R1 values were 0.0639 (all data). The final wR(F2)
values were 0.1369 (all data). The goodness of fit on F2 was 1.043.
(CCDC 978382).
MTT solution was replaced with DMSO (100 μL). The 96-well culture
plates were then gently shaken in the dark for 30 min, and the absor-
bance at 570 and 630 nm (background) was measured with a microtiter
plate reader. The positive (cells treated with different concentrations of
NAC at 0.25–4 mg/mL) controls were run in parallel. All the assays were
carried out in triplicate.
Crystal data for Swerimilegenin E (4): C10H14O4, M = 198.21,
triclinic, a = 7.5840(11) Å, b = 8.2096(11) Å, c = 8.3996(12) Å,
α =
82.695(2)◦, β = 73.440(2)◦, γ = 72.745(2)◦, V = 478.20(12) Å3, T = 100
(2) K, space group P-1, Z = 2,
μ
(Mo K
α
) = 0.106 mmꢀ 1, 5038 reflections
measured, 2608 independent reflections (Rint = 0.0234). The final R1
values were 0.0389 (I > 2
σ
(I)). The final wR(F2) values were 0.1077 (I >
3. Results and discussion
2
σ
(I)). The final R1 values were 0.0405 (all data). The final wR(F2)
values were 0.1093 (all data). The goodness of fit on F2 was 1.110.
(CCDC 978476).
Sweritranslactone D (1) was obtained as colorless cubic crystals
(MeOH). Its molecular formula C19H22O6 was established by 13C NMR
and HR-ESI-MS data (m/z 369.1308, [M + Na]+, calcd 369.1309) with
nine double-bond equivalents. The 13C NMR spectroscopic data
(Table 1) exhibited 19 carbon resonance signals due to two methyls
(including one methoxy), five methylenes (one with terminal double
bond), six tertiary carbons (one with an olefinic carbon), and six qua-
ternary carbons (two ester carbonyls and four olefinic carbons). Thus, a
tetracyclic ring structure was proposed for compound 1 to satisfy nine
degrees of unsaturation.
Crystal data for Swerimilegenin G (5): C18H22O7, M = 350.36,
monoclinic, a = 9.4346(6) Å, b = 8.3218(5) Å, c = 21.8117(14) Å,
α =
90.00◦, β = 101.3520(10)◦, γ = 90.00◦, V = 1679.00(18) Å3, T = 100(2)
K, space group P21/c, Z = 4,
μ
(Mo K
α
) = 0.107 mmꢀ 1, 17,390 reflections
measured, 4761 independent reflections (Rint = 0.0224). The final R1
values were 0.0363 (I > 2
σ
(I)). The final wR(F2) values were 0.0937 (I >
2
σ
(I)). The final R1 values were 0.0414 (all data). The final wR(F2)
values were 0.0973 (all data). The goodness of fit on F2 was 1.044.
(CCDC 950258).
Comprehensive interpretation of 2D NMR spectroscopic data,
1
1
–
including H H COSY, HSQC, and HMBC, allowed the establishment
1
1
–
2.3. Detailed description of hepatoprotective studies in CCl4-induced liver
injury mice model
of planar structure of 1. In H H COSY spectrum, cross peaks of H2-6
(δ 2.20, 2.83)/H2-7 (δ 4.32), H-3ʹ (δ 5.00)/H-9 (δ 2.03)/H-8 (δ
2.H39) (H3-10, δH 1.03)/HH-9ʹ (δH 2.88)/H-10ʹ (δH 5.63)H/H2-8ʹ (δH 5.16,
5.34), and H2-6ʹ (δH 2.23, 2.64)/H2-7ʹ (δH 4.39) suggested the presence
of three key fragments (C-6/C-7), (C-3ʹ/C-9/C-8(C-10)/C-9ʹ/C-10ʹ/C-8),
and (C-6ʹ/C-7ʹ) (Fig. 2). In the HMBC spectrum of 1, correlations of H2-7
with C-11 (δC 162.5) and C-5 (δC 154.4), of H2-6 with C-4 (δC 125.5), of
H
H
2.3.1. Model of CCl4-induced acute liver injury in mice
After 5 days of adaptive feeding with food and water ad libitum, 96
mice were randomly divided into eight groups (n = 12): Normal group
(Normal, olive oil, 0.1 mL/kg/day by intragastrical route); CCl4 group
(Model, olive oil, 0.1 mL/kg/day by intragastrical route); the positive
group (DBB, dimethyl diphenyl bicarboxylate, 150 mg/kg/day); Qing-
Ye-Dan tablet group (QYD, 10.5 g/kg/day); low dose of swertiamarin
group (L-SW, 0.52 g/kg/day); high dose of swertiamarin (H-SW, 1.05 g/
kg/day); low dose of HTPS (L-HTPS, 0.42 g/kg/day); high dose of HTPS
(H-HTPS, 0.84 g/kg/day). Animal treatment was continued for 7
consecutive days. After 1 h of the last administration, all mice were
intraperitoneally injected with CCl4 (0.1 mL of 0.12% CCl4 in olive oil/
10 g body weight) except normal group. Mice were executed after 24 h
of injection and the blood was collected from the orbit in sodium heparin
tubes [10].
H2-7ʹ with C-11ʹ (δ 163.5) and C-5ʹ (δ 157.1), and of H2-6ʹ with C-4ʹ (δ
123.7) indicated tCwo separately constructed
α
,β-unsaturated δ-lactone
C
C
rings (A and D) (Fig. 2). The HMBC correlations of H-3 (δ 5.28)/C-5 and
H
C-3ʹ (δC 60.6), and of H-9/C-4 led to B ring. The presence of ring C was
identified with cross peaks of H-3ʹ/C-5ʹ and H-9ʹ/C-4ʹ in the HMBC
spectrum of 1. Rings A, B, C, and D were fused successively on the basis
of HMBC correlations from H-3 to C-11, from H-6 to C-9, from H-3ʹ to C-
11ʹ, from H-9ʹ to C-6ʹ and from H-10ʹ to C-5ʹ. Owing to the HMBC cor-
relation of H3-12 (δH 3.59)/C-3, the methoxy group (C-12, δ 56.2) was
placed at C-3. Thus, the planar structure of compound 1 wasCestablished
as an iridoid dimer derivative having 6/6/6/6 tetracyclic architecture
together with two
unprecedented.
α,β-unsaturated δ-lactone rings, which is
2.3.2. Detection of serum transaminases ALT and AST
As described previously [11], the serum transaminases ALT and AST
levels were determined by using assay kit (Nanjing Jiancheng Bio-
engineering Institute, Nanjing, China) according to the manufacturer’s
protocol.
The relative configuration of 1 was deduced from its ROESY spec-
trum. As depicted in 3D molecular model (Fig. 2), the correlations of H-
9/H3-10 and H-10ʹ, and of H-3ʹ/H3-12 implied that the orientations of H-
9, H3-10 and H-10ʹ, and of H-3ʹ and H3-12, were at the same side,
respectively. Furthermore, a small coupling constant (3.0 Hz) between
H-3ʹ and H-9 demonstrated a cofacial orientation of H-3ʹ and H-9.
3

Y.-D. Zou et al.
Fitoterapia 151 (2021) 104879
Fig. 2. Key 2D NMR correlations and X-ray ORTEP drawing of 1.
Colorless cubic crystals of 1 were obtained in MeOH, which allowed a
successful performance of X-ray crystallographic analysis (Fig. 2).
The X-ray crystallographic data (CCDC 1500816) corroborated the
planar structure and the relative configuration of 1 elucidated via NMR
data. Thus, the relative configuration of 1 was determined as
3S*,3ʹS*,8R*,9R*,9ʹS*.
The plausible transformation pathways of 1 from swertiamarin in
boiling water are proposed in Scheme 1. Under the boiling conditions,
swertiamarin might undergo a series of chemical reactions, from dehy-
dration to intramolecular nucleophilic substitution (Route I), to form 6
[13]. Then, via decarboxylation and reduction, 6 could produce 3
[14–15]. The key intermediate (X1) could be obtained by selective ring
opening and dehydration of 3. Finally, a [4 + 2] cyclization reaction
[16–17] of two X1 moieties, followed by intermolecular nucleophilic
addition and methylation reaction may lead to sweritranslactone D.
Sweritranslactone E (2), colorless cubic crystals (MeOH), was
assigned a molecular formula C18H20O6, based on HR-ESI-MS quasi-
molecular ion peak at m/z 333.1349 ([M + H]+, calcd 333.1333). The
1H and 13C NMR spectroscopic data (Table 1) of 2 were similar to those
of swerilactone A [18], except for the location of a double bond in 2. The
assignment was supported by detailed analysis of 2D NMR data of 2
(Fig. 3). The correlations in the ROESY spectrum could not provide
1
1
–
Fig. 3. Key
of 2.
H
H COSY and HMBC correlations, and X-ray ORTEP drawing
sufficient information to establish the stereochemistry of compound 2.
The crystallographic data (CCDC 978382) of 2 was obtained, which
verified the planar structure, and also clarified the stereochemistry of 2
(Fig. 3) as 3R*,3ʹS*,4S*,4ʹR*,8R*,8ʹR*,9R*.
Thus, the differences between 2 and swerilactone A were the
epimeric C-8ʹ and double bond migration from C-5ʹ/C-6ʹ to C-5ʹ/C-9ʹ in
2. Sweritranslactone E, iridoid dimer derivative, is another example of
HTPS. Its conversion process is also proposed in Scheme 1. Intermediate
Scheme 1. Putative transformation pathways of compounds 1–8 from swertiamarin in boiling water.
4

Y.-D. Zou et al.
Fitoterapia 151 (2021) 104879
X1 via hydrolysis, reduction, and intramolecular nucleophilic substitu-
tion, might produce intermediate (X2). Then, a [4 + 2] cyclization re-
action might occur between X2 and X1 via enolization. Finally,
intramolecular nucleophilic addition reaction may produce sweri-
translactone E. Transformation pathways of other known compounds
4–8 [14,19], isolated from HPTS, are proposed in Scheme 1.
Table 2
Effect of the isolates from HTPS on the survival rate of L-O2 AP-induced liver
injury cells.
Compounds
b
Dose/
μ
g/mL
Survival rate/%
emaxa/%
cmax
/μ
g/mL
NAC
1
0.25–4 mg/mL
0.8–100
0.8–100
0.8–100
0.8–100
0.8–100
0.8–100
0.8–100
0.8–100
0.8–100
ꢀ 2.16–15.84
ꢀ 4.38–20.28
ꢀ 9.78–10.55
0.72–13.10
ꢀ 3.26–4.19
ꢀ 6.85–5.56
ꢀ 4.01–0.61
ꢀ 13.79–3.89
ꢀ 4.11–4.75
ꢀ 0.55-4.43
15.84
20.28
10.55
13.10
4.19
1000
25
The hepatoprotective activity of swertiamarin, QYD tablets and
HTPS was determined, using a mouse model of CCl4-induced liver
injury, based on the analyses of serum ALT and AST activities. The re-
sults (Fig. 4) revealed that the serum levels of liver injury markers ALT
and AST increased in the mice treated with CCl4 and significantly
inhibited the CCl4-treated over-expressing mice in experimental groups.
Furthermore, both the low- and high-dose groups of HTPS showed equal
activity, compared with positive control (DBB), indicating that HTPS
were mainly responsible for hepatoprotective effect, rather than
swertiamarin.
2
1.6
25
3
4
50
5
5.56
6.3
1.6
6.3
0.8
25
6
0.61
7
3.89
8
4.75
9
4.43
a
emax: Maximal Effect.
b
cmax: Concentration at Maximal Effect.
For further elucidation of the hepatoprotective activity of HTPS, all
the isolates were tested in vitro in L-O2 AP-induced cell model, with
NAC as positive control. The results (Table 2) displayed that all the
isolates exhibited hepatoprotective activity, while the novel compound
1 showed a more potent activity than the positive control.
sweritranslactone D (1), a novel secoiridoid dimer possessing a tetra-
cyclic lactone skeleton with better hepatoprotective activity than N-
acetyl-L-cysteine in vitro.
Iridoids are famous for their unstable structures with many reaction
points. Hence, traditional phytochemical research methods may result
in the generation of artifacts during the process of extraction, isolation,
and storage of plants. Our study uncovered that the isolates from HTPS
contained some compounds previously considered to be natural prod-
ucts. This phenomenon will cause the thinking for the process of tradi-
tional Chinese medicine, especially for those containing unstable active
components. The work might spark controversy on the current experi-
mental results. Meanwhile, this study also provides an effective method
4. Conclusion
Swertiamarin is the main active component in QYD tablets recorded
in Chinese Pharmacopoeia, but after the decoction (one step for QYD in
the manufacturing process) for 6 h, swertiamarin could not be detected.
Further research on the material base on HTPS led to the isolation of
Fig. 4. Effect of QYD, SW and HTPS on the serum levels of ALT, AST after CCl4- induced acute liver injury in mice. Bar graphs with error bars represent mean ± SEM
(n = 12). ▴▴▴P < 0.001 versus Normal; ***P < 0.001, *P < 0.05 versus Model; ★★★p < 0.001, ★p < 0.05 versus DBB.
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Y.-D. Zou et al.
Fitoterapia 151 (2021) 104879
to obtain novel compounds from natural products.
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