Phenolic compounds from the rhizomes of Smilax China L. & their anti-inflammatory activity

Article abstract of DOI:10.3390/molecules22040515

A new triflavanoid, kandelin B-5 (1), was isolated from the rhizomes of Smilax China L., together with six known phenylpropanoid substituted flavan-3-ols (2-7), nine flavonoids (8-16), two stilbenoids (17, 18), and two other compounds (19, 20). The structure of compound 1 was determined on the basis of 1D, 2D NMR and HR-ESI-MS data, as well as chemical method. Compounds 2-5, 8-12, 15, 17, and 19 were evaluated for anti-inflammatory activity. Only compounds 10, 15 and 17 showed slightly IL-1expression inhibitory activities on LPS induced THP-1 cells, with inhibition rate of 15.8%, 37.3%, and 35.8%, respectively, at concentration of 50 μg/mL.

Full text of DOI:10.3390/molecules22040515

molecules
Article
Phenolic Compounds from the Rhizomes of
Smilax china L. and Their Anti-Inflammatory Activity
Cheng Zhong 1, Deng Hu 1, Lian-Bing Hou 2, Lu-Yao Song 2, Ying-Jun Zhang 3, Yang Xie 1,* and
Li-Wen Tian 1,
*
1
School of Pharmaceutical Sciences, Southern Medical University, Guangzhou 510515, China;
vanbenchat@126.com (C.Z.); hudeng19900922@126.com (D.H.)
Department of Pharmacy, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China;
lianbingh@hotmail.com (L.-B.H.); songluyao.nice@163.com (L.-Y.S.)
State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany,
Chinese Academy of Sciences, Kunming 650201, China; zhangyj@mail.kib.ac.cn
Correspondence: yxie201203@126.com (Y.X.); lwtian@smu.edu.cn (L.-W.T.);
2
3
*
Tel.: +86-20-6164-8593 (Y.X.); +86-20-6164-8549 (L.-W.T.); Fax: +86-20-6164-8533 (Y.X. & L.-W.T.)
Academic Editor: Isabel C. F. R. Ferreira
Received: 20 February 2017; Accepted: 18 March 2017; Published: 3 April 2017
Abstract: A new triflavanoid, kandelin B-5 (
together with six known phenylpropanoid substituted flavan-3-ols (
two stilbenoids (17 18), and two other compounds (19 20). The structure of compound
determined on the basis of 1D, 2D NMR and HR-ESI-MS data, as well as chemical method.
Compounds 12 15 17, and 19 were evaluated for anti-inflammatory activity. Only compounds
10 15 and 17 showed slightly IL-1 expression inhibitory activities on LPS induced THP-1 cells,
1
), was isolated from the rhizomes of Smilax china L.,
), nine flavonoids ( 16),
was
2
–7
8–
1
,
,
2–
5,
8–
,
,
,
β
with inhibition rate of 15.8%, 37.3%, and 35.8%, respectively, at concentration of 50 µg/mL.
Keywords: Smilax china; phenolic compounds; anti-inflammatory activity
1. Introduction
Smilax china L. (Liliaceae), a perennial climbing deciduous shrub, is widely distributed in
Southern China, and Southeast Asian countries. The leaves of S. china are used as detoxication
agent in folk China [
Chinese Pharmacopoeia with the efficacy of carminative, diaphoretic, and circulative [
studies on the title species have disclosed the presence of steroidal saponins [ ], flavonoids [
phenylpropanoids [ ], and stilbenoids [ ]. These isolated compounds showed a wide spectrum of
1
]; while the rhizomes of S. china, called “Jin Gang Teng”, are collected by
]. Previous
],
2
3
4,5
6
7,8
activities, such as immunosuppressive activity [9], anti-oxidative activities [10], anti-inflammatory
activities [3,11].
The pharmaceutical preparations of S. china are widely used in clinic for the treatment of chronic
pelvic inflammatory disease, a kind of chronic inflammation in the female genital organs, connective
tissues and pelvic peritoneum. Recently, we reported five known flavonoids from the anti-chronic
pelvic inflammation fraction of S. china using high speed counter current chromatography [12
Further detail chemical investigation on the title species led to the isolation of a new triflavanoid ( ) and
12 15 17, and 19 were evaluated
,13].
1
19 known phenolic compounds (2−20) (Figure 1). Compounds
2
–
5
,
8
–
,
,
for their anti-inflammatory activity. Herein we describe the isolation and structure elucidation of these
compounds as well as their anti-inflammatory activities.
Molecules 2017, 22, 515; doi:10.3390/molecules22040515
www.mdpi.com/journal/molecules

Molecules 2017, 22, 515
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OH
OH
O
OH
OH
B
OH
O
2
O
O
C
4
9
OH
7
A
3 OH
10
7'''
O
OH
OH
5
OH
OH
OH
O
HO
O
2'
3'
7'
COOH
OH
O
OH
OH
OH
5'
OH
OH
4'
OH
HO
OH
HO
O
2''
3''
7''
OH
OH
OH
OH
5''
4''
OH
OH
2 7''
3 7''
20
1
OH
R
OH
O
OH
HO
O
O
OH
OH
2
O
OH
OH
7''
O
OH
OH
3
O
OH
O
O
O
O
OH
OH
OH
OH
HO
OH
OH
8
R = H 2R, 3R
9 R = OH 2R, 3R
10
4 7''
6 7''
5
7
7''
7''
R = OH 2S, 3S
11 R = OH 2R, 3S
12 R = OH 2S, 3R
OH
OH
OH
OH
HO
O
O
R
HO
O
HO
O
O
OH
OH
O
OH
O
OH
OH
OH
HO
16
15
13 R = OH
14
R = H
OH
HO
COOH
O
OH
OH
O
HO
HO
OH
OH
HO
HO
HO
O
OH
HO
OH
19
17
18
Figure 1. Chemical structures of 1–20.

Molecules 2017, 22, 515
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2. Results and Discussion
The ethanol extract of the rhizomes of S. china was partitioned with Ethyl Acetate (EtOAc),
and then subjected to column chromatography (CC) over MCI gel CHP 20P, Sephadex LH-20,
Toyopearl HW 40F, silica gel, and preparative HPLC to yield a new triflavanoid (
known compounds. The known compounds were identified as cinchonain IIa (
IIb ( ) [14], cinchonain Ia ( ) [15], cinchonain Ib ( ) [15], catechin-[8,7-e]-4 -(3,4-dihydroxyphenyl)-
dihyro-2(3H)-pyranone ( ) [15], catechin-[8,7-e]-4 -(3,4-dihydroxyphenyl)-dihyro-2(3H)-pyranone
) [16], astilbin ( ) [17], neoastilbin (10) [17], isoastilbin (11) [17], isoneoastilbin
-L-rhamnopyranoside (13) [12], luteolin-3-O- -L-rhamnopyranoside (14) [18],
], resveratrol (18) [ ], chlorogenic
1), together with 19
2
) [14], cinchonain
3
4
5
β
6
α
(7
) [15], engeletin (
8
9
(
12) [17], quercetin-3-O-
α
0
α
(-)-epicatechin (15), 5,7,4 -trihydroxyflavonone (16), scirpusin A (17) [
4
4
acid (19) [19], and protocatechuic acid (20) [19], by comparison of their physicochemical data with
those reported in the literature. Of them, compounds 2–3, 14, 16, and 20 were isolated from the genus
Smilax for the first time.
Compound
1
was isolated as white amorphous powder. The molecular formula, C54H44O21,
was determined on the basis of the HRESIMS data (m/z 1027.2285 [M
−
H]−; calcd. 1027.2297).
The 1H-NMR data of
1 showed three singlets at δH 6.10, 5.90, 5.90, arising from the A-rings, three
pairs of signals due to the flavan C2-H and C3-H at δH 5.17 (br.s, H-2), 4.48 (d, J = 7.4 Hz, H-20), 3.83
(m, H-30), 3.73 (d, J = 9.2 Hz, H-200), 3.71 (br.s, H-3), and 3.41 (m, H-300), two singlet methine signals
at δ α), 2.05 (dd,
4.51 (s, H-40), 4.34 (s, H-4), and a methylene signal at δH 2.40 (br.d, J = 15.6 Hz, H-400
J = 7.0, 15.6 Hz, H-400β). The connectivities of these protons on C-rings were identified by 1H-1H COSY
experiment (Figure 2). The above evidence indicated the presence of a triflavanoid moiety, which
was consistent with 13C-NMR data. The 13C-NMR showed three aromatic methine carbons at δC 95.7,
95.5, 94.3, nine aliphatic carbons δC 82.1, 81.4, 75.6, 70.8, 68.2, 66.7, 36.3, 35.9, 30.7, and overlapped
carbon signals arising from four 3,4-dihydroxybenzyl rings. The chemical shifts of the C-2 carbons,
as well as the coupling patterns of the C2 proton signals suggested that the triflavanoid contains
an epicatechin and two catechin moieties [20]. The 13C-NMR coupled with HSQC data showed the
presence of an ester (δC 169.0), a methine (δC 33.6; δH 3.81, m), and a methylene [δC 37.0; δH 2.84 (dd,
J = 6.0, 16.0 Hz), 2.25(dd, J = 10.0, 16.0 Hz)], suggesting the existence of a phenylpropanoid moiety.
The phenylpropanoid moiety was connected with A-ring of the upper flavan-3-ol unit since all the
protons on A rings showed singlets in the 1H-NMR spectrum [20]. Additionally, the phenylpropanoid
moiety was presumed to be connected with C-8 position of upper flavan-3-ol unit as indicated by
the carbon chemical shift of C-6 and C-8 [δC: 96.0 (C-6), 105.2 (C-8) for C-8 substituted isomer; δ0C
:
106.2 (C-6), 99.4 (C-8) for C-6 substituted isomer] [21]. The two singlet methine signals at
δ
4.51 (H-4 ),
was
3
), suggesting the C(4), C(80)-linkages of flavan-3-ol
4.34 (H-4) indicated two
β
linkages of three flavan-3-ol units [14]. The 1D NMR of compound
) or IIb (
1
very similar to that of cinchonain IIa (
2
moieties. The obviously up-field shifted of H-200 in the terminal catechin unit as comparing with
catechin, attribute to the deshielding effect of phenyl group on the middle flavan-3-ol unit, suggested
the C(40), C(800)-linkages of middle and terminal flavan-3-ol units.
The constitution and points of the interflavanoid linkages in
acid-catalyzed degradation with cysteamine (Figure 3). Complete degradation of
-(2-aminoethylthio)-cinchonain Ib (1a), 4 -(2-aminoethylthio)-catechin (1b) [22], and catechin (1c),
1
were confirmed by hydrochloric
1
afforded
4
β
β
establishing that it consists of cinchonain Ib and catechin units. 1a showed strong positive cotton effects
at 230 nm and negative cotton effect at 250 nm, indicating that the phenyl group of phenylpropanoid
unit was α-oriented. Thus, the structure of 1 was elucidated as showed in Figure 1.

Molecules 2017, 22, 515
4 of 8
Figure 2. Key 1H-1H COSY and HMBC correlations of 1.
Figure 3. Acid-catalyzed thiolysis of 1.
Interleukin-1β (IL-1β), an important mediator of the inflammatory response, is involved in a
variety of cellular activities, including cell proliferation, differentiation, and apoptosis. Compounds
12 15 17, and 19 were evaluated for their IL-1 expression inhibitory activities on lipopolysaccharide
(LPS) induced THP-1 cells. Compounds 10 15, and 17 showed slightly inhibitory activities, with
inhibition rate of 15.8%, 37.3%, and 35.8%, respectively, at concentration of 50 g/mL. The other
2–5,
8
–
,
,
β
,
µ
compounds showed no obvious activity at the same concentration. CCK-8 results revealed that these
tested compounds showed no obvious cytotoxicities towards THP-1 cells at same concentration,
indicating that the anti-inflammatory activities of compounds 10
from cytotoxic effects. Previous studies revealed the unique immunosuppressive activity of astilbin
) [23]; While our results suggested that astilbin ( ) and its isomers (10 12) didn’t directly inhibit the
production of proinflammatory cytokines IL-1 . (-)-Epicatechin and stilbene are reported to show
, 15, and 17 were not resulted
(9
9
–
β
anti-inflammatory activities [24]. Consistently, our results showed that (-)-Epicatechin (15) and stilbene
dimer, scirpusin A (17), inhibited IL-1β expression on the LPS induced THP-1 cells.
3. Materials and Methods
3.1. General Experimental Procedures
Optical rotation was measured with an MCP-500 polarimeter (Anton Paar). The UV spectrum
was recorded with a TU-1810DSPC UV-Vis spectrometer (Puxi Tongyong). IR spectrum was measured
on a IR Affinity-1 spectrophotometer (Shimadzu); CD was measuredon a ChirascanTM (Applied
Photophysics Ltd., Leatherhead, UK). NMR was acquired on an AV-400 spectrometer (Bruker) with

Molecules 2017, 22, 515
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TMS as internal standard, J in Hz; HRESIMS spectra were measured on the Orbitrap Fusion high
resolution mass spectrometer (Thermo) equipped with ESI source. Preparative or semi-preparative
HPLC were performed on a HPLC system equipped with a Waters 1525 pump and a Waters 2487 Dual
Wavelength Detector using a Thermo hypersil C18 column (5
hypersil C18 column (5 m, 250 10 mm, i.d.). Open column chromatography was performed using
silica gel (200–300 mesh, Qingdao Marine Chemical, Qingdao, China), Sephadex LH-20 (25–100 m,
m,
µm, 150
×
25.0 mm, i.d.) or Thermo
µ
×
µ
Fiji), MCI gel CHP 20P (75–150
Merck, Kenilworth, NJ, USA).
µm, Fiji), Toyopearl HW 40F (TOSOH, Tokyo, Japan) or ODS (40–63 µ
3.2. Plant Materials
The rhizomes of S. china were purchased from Shenzhen Hongen Pharmaceutical Company,
and were identified by one of the authors (L.B. Hou). The voucher specimen of this material
(NO. SMU-NPC-201301) was deposited in Natural Product Chemistry Lab, School of Pharmaceutical
Sciences, Southern Medical University, Guangzhou, China.
3.3. Extraction and Isolation
The rhizomes of S. china (6.0 kg) were refluxed with 95% ethanol at 75 ◦C for three hours, three
times and filtered. The combined filtrate was concentrated to yield crude extracts (1.2 kg). The crude
extracts were suspended in H2O, and then partitioned with EtOAc and n-BuOH consecutively.
A portion (8.5 g) of the EtOAc-solution fraction (150 g) was subjected to MCI gel CHP 20P (MeOH/H2O,
1:9–10:0) CC to give seven fractions A-G. Fraction A (0.21 g) was chromatographed over MCI gel CHP
20P (MeOH/H2O, 1:9–4:6), and ODS (MeOH/H2O, 2:8–5:5) to afford 20 (4.0 mg). Fraction B (0.25 g)
was chromatographed over Toyopearl HW 40F (MeOH/H2O, 3:7–8:2) to yield four sub-fractions,
B1–B4. Sub-fraction B1 was subjected to MCI gel CHP 20P (MeOH/H2O, 2:8–6:4) to yield 19
(4.0 mg). Sub-fraction B2 was chromatographed over ODS (MeOH/H2O, 2:8–6:4), Toyopearl HW
40F (MeOH/H2O, 3:7–7:3), and Sephadex LH-20 (100% MeOH) to yield 15 (9.0 mg). Sub-fraction
B4 was purified by preparative HPLC (gradient model, MeOH/H2O, 20–80% over 30 min, MeOH
and H2O contained 0.1% TFA) to yield
1 (16 mg). Fraction C (4.08 g) was chromatographed over
MCI gel CHP 20P (MeOH/H2O, 3:7–9:1) to yield three sub-fractions, C1-C3. Sub-fraction C2 was
purified by Toyopearl HW 40F (MeOH/H2O, 4:6–1:0) CC, and preparative HPLC (gradient model,
MeOH/H2O, 20–80% over 30 min, MeOH and H2O contained 0.1% TFA) to afford
(26 mg). Sub-fraction C3 was subjected to CC over Toyopearl HW 40F (MeOH/H2O, 4:6–1:0) to
yield three sub-fractions, C3-1, C3-2, C3-3. Sub-fraction C3-2 was purified by semi-preparative HPLC
(35% MeOH, isocratic model) to afford (8 mg), 10 (40 mg), 11 (6 mg), and 12 (5 mg). Sub-fractions
C3-3 was purified by semi-preparative HPLC (gradient model, MeOH/H2O, 20–80% over 30 min,
MeOH and H2O contained 0.1% TFA) to yield (21 mg), (15 mg), (4 mg), and (6 mg). Fraction
2 (21 mg), and
3
9
4
5
6
7
D (1.0 g) was chromatographed over MCI gel CHP 20P (MeOH/H2O, 4:6–1:0), Toyopearl HW 40F
(MeOH/H2O, 4:6–1:0), and Sephadex LH-20 (100% MeOH) to afford 13 (42 mg). Fraction E (1.0 g) was
chromatographed over MCI gel CHP 20P (MeOH/H2O, 4:6–8:2), Toyopearl HW 40F (MeOH/H2O,
4:6–8:2) to yield 8 (30 mg), and 16 (9.0 mg). Fraction F (0.4 g) was subjected to CC over MCI gel CHP20P
(MeOH/H2O, 6:4–1:0), Sephadex LH-20 (100% MeOH), and silica gel (DCM/MeOH, 9:1–8:2) to afford
14 (12 mg), 17 (5 mg), and 18 (9 mg).
Kandelin B-5 (
(4.55), 282 (4.03) nm; IR(KBr)
1 λmax (logε): 227
): Amorphous powder, [α]2D5 = 86.5 (c = 0.18, MeOH); UV (MeOH),
ν
max 3350, 1743, 1616, 1521, 1448, 1284, 1109 cm−1; 1H-NMR (4−00 MHz,
DMSO-d6) and 13C-NMR (100 MHz, DMSO-d6): see Table 1; (-)-HRESIMS: 1027.2285 [M
−
H] (Calcd
for C54H43O21, 1027.2297).

Molecules 2017, 22, 515
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1
Table 1. H- (400 MHz) and 13C-NMR (100 MHz) data of 1 (in DMSO-d6, J in Hz, δ in ppm).
Position
δ
δC
H
2
3
4
6
8
5.17 br.s
3.71 br.s
4.34 br.s
5.90 s
75.6
70.8
36.3
94.0
108.0
99.5
81.4
66.7
35.9
95.1
108.0
103.6
82.1
68.2
30.7
95.7
107.7
100.4
38.1
33.9
169.0
10
0
2
3
4
6
4.48 d (7.4)
3.38 m
4.51 br.s
5.90 s
0
0
0
0
8
0
10
00
2
3
4
6
3.73 d (9.2)
3.41 m
2.84 dd (6.0, 16.0)
2.25 dd (10.0, 16.0)
00
00
00
00
8
00
10
α
2.40 br.d (15.6)
2.05 dd (7.0, 15.6)
β
-COO-
3.4. Thiolysis of Compound 1
A mixture of compound
1 (8 mg), cysteamine (20 mg), and 1 M aqueous hydrochloric acid (3 mL)
was refluxed for 2 h with stirring. After removal of the solvent by evaporation under reduced pressure,
the oily residue was applied to a Sephadex LH-20 column (DCM/MeOH, 1:1), and was further purified
by semi-preparative HPLC (gradient model, MeOH/H2O, 10–90% over 30 min) to afford: 1a (0.9 mg),
1b (0.6 mg), and 1c (0.4 mg).
4β
-(2-aminoethylthio)-cinchonain Ib (1a): Amorphous powder, [α]2D5 = 41.8 (c = 0.09, MeOH); 1H-NMR
(400 MHz, Acetone-d6):
δ
6.91 (1H, d, J = 1.9 Hz, H-20), 6.74 (2H, s, H-50, 60), 6.71 (2H, m, H-200, 500),
6.53 (1H, dd, J = 2.0, 8.1 Hz, H-600), 6.23 (1H, s, H-6), 5.27 (1H, br.s, H-2), 4.45 (1H, m, H-700), 4.17 (1H,
br.s, H-4), 4.12 (1H, br.s, H-3), 3.07 (1H, dd, J = 6.9, 15.9 Hz, H-800a), 2.90 (1H, br.d, J = 15.9 Hz, H-800b),
3.80-2.80 (4H, m, S-CH2-CH2-N); (-)-ESIMS: m/z 526 [M − H]−.
4β
-(2-aminoethylthio)-catechin (1b): Amorphous powder, [α]2D5 = 33.2 (c = 0.06, MeOH); 1H-NMR
(400 MHz, Acetone-d6):
δ
6.91 (1H, d, J = 1.9 Hz, H-20), 6.75 (1H, d, J = 8.1 Hz, H-50), 6.70 (1H, dd,
J = 1.9, 8.1 Hz, H-60), 5.91 (2H, s, H-6, 8), 5.31 (1H, d, J = 9.3 Hz, H-2), 4.00 (1H, m, H-3), 3.88 (1H, d,
J = 6.6 Hz, H-4), 3.60–2.40 (4H, m, S-CH2-CH2-N).
catechin (1c): Amorphous powder; 1H-NMR (400 MHz, Acetone-d6):
δ
6.91 (1H, d, J = 1.9 Hz, H-20),
6.81 (1H, d, J = 8.1 Hz, H-50), 6.77 (1H, dd, J = 1.9, 8.1 Hz, H-60), 6.04 (1H, d, J = 1.9 Hz, H-8), 5.89 (1H,
d, J = 1.9 Hz, H-6), 4.57 (1H, d, J = 7.8 Hz, H-2), 4.00 (1H, m, H-3), 2.93 (1H, dd, J = 5.5, 16.0 Hz, H-4a),
2.90 (1H, dd, J = 8.4, 16.0 Hz, H-4b).
3.5. Quantitation of Cytokine IL-1β
The human acute monocytic leukemia (THP-1) cells (Shanghai Cell Bank, C.A.S., Shanghai, China)
were cultured in Dulbecco’s Modefied Eagles Medium (DMEM) containing 10% Fetal Bovine Serum
(FBS) at 37 ◦C in a humidified atmosphere with 5% CO2. The cells were seeded into 96-well plates
with density of 1
with cell sustainable medium. After incubation for 1 h, the cells were treated with 1
for another 24 h. The cells were treated with LPS alone or LPS plus dexamethasone as blank control
×
105 cells per milliliter. Thereafter, cells were treated with sample solutions diluted
g/mL of LPS
µ

Molecules 2017, 22, 515
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and positive control, respectively. The supernatant was collected by centrifugation (14,000 rpm, 4 ◦C).
The quantity of IL-1 in culture supernatant was determined by using Enzyme Linked Immunosorbent
Assay (ELISA) kit specific for IL-1 25]. The inhibition rates were calculated according to the formula:
β
β
[
Inhibition rate = [(C − T)/C] × 100%
(1)
of
where C is the average quantity of IL-1
the group with the test compound.
β of the blank control and T is the average quantity of IL-1β
3.6. Cytotoxicity Assay
The effect of compounds 2–5, 8–12, 15, 17, and 19, on the viability of THP-1 cells were evaluated
using the Cell Counting Kit-8 (CCK-8) according to the manufacturer’s instructions. Briefly, THP-1
cells were seeded into 96-well plates at a density of 2.5
×
104 cells/well in the presence of sample
solutions (50, 100, 200
µM, respectively) or absence of compounds for 48 h. Thereafter, 10
µL CCK-8
◦
solutions were added to each well for further incubation at 37 C in 4 h. The optical density was
measured at a wavelength of 450 nm using a microplate reader [26]. Cell viability was expressed as
a percentage of the control.
4. Conclusions
In this study, a new triflavanoid, kandelin B-5 (
china L., together with six known phenylpropanoid substituted flavan-3-ols (
16), two stilbenoids (17 18), and two other compounds (19 20). The structure of compound
was determined on the basis of 1D, 2D NMR and HR-ESI-MS data, as well as chemical method.
Compounds 12 15 17, and 19 were evaluated for anti-inflammatory activities. Only neoastilbin
10), (-)-epicatechin (15), and scirpusin A (17) showed slight IL-1 expression inhibitory activities on
LPS induced THP-1 cells.
1), was isolated from the rhizomes of Smilax
2–7), nine flavonoids
(8
–
,
,
1
2
–5
,
8–
,
,
(
β
Supplementary Materials: Supplementary materials are available online. The NMR spectra of
ESIMS, and CD spectra of hydrolysis products of 1.
1
; the 1H-NMR,
Acknowledgments: This work was financially supported by the State Key Laboratory of Phytochemistry and
Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences (NO. P2015-KF07),
Science and Technology Program of Guangzhou, China (NO. 201607010147), and Guangdong Medical Science
Foundation (NO. A2015225).
Author Contributions: C.Z. and L.-W.T. performed the isolation and structure elucidation of the chemicals, and
the preparation of the manuscript. D.H. participated in the isolation process. L.-B.H. and L.-Y.S. carried out
the bioassay experiments. L.-W.T., Y.X. and Y.-J.Z. planned, and organized the whole research of this study.
All authors approved the final version manuscript.
Conflicts of Interest: The authors declare no conflicts of interest.
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Sample Availability: Samples of the compounds are available from the authors.
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