New polyacetylenes glycoside from Eclipta prostrate with DGAT inhibitory activity

Article abstract of DOI:10.1080/10286020.2018.1452914

One new polyacetylene glycoside eprostrata Ⅰ (1), together with seven known compounds (2–8), were isolated from Eclipta prostrata. Their structures were elucidated on the basis of spectroscopic and physico-chemical analyses. All the isolates were evaluated inhibitory activity on DGAT in an in vitro assay. Compounds 1–8 were found to exhibit inhibitory activity of DGAT1 with IC₅₀ values ranging from 74.4?±?1.3 to 101.1?±?1.1?μM.

Full text of DOI:10.1080/10286020.2018.1452914

Journal of Asian Natural Products Research
ISSN: 1028-6020 (Print) 1477-2213 (Online) Journal homepage: http://www.tandfonline.com/loi/ganp20
New polyacetylenes glycoside from Eclipta
prostrate with DGAT inhibitory activity
Xiao Meng, Ban-Ban Li, Xin Lin, Yi-Yu Jiang, Le Zhang, Hao-Ze Li & Long Cui
To cite this article: Xiao Meng, Ban-Ban Li, Xin Lin, Yi-Yu Jiang, Le Zhang, Hao-Ze Li & Long Cui
(2018): New polyacetylenes glycoside from Eclipta prostrate with DGAT inhibitory activity, Journal
of Asian Natural Products Research, DOI: 10.1080/10286020.2018.1452914
To link to this article: https://doi.org/10.1080/10286020.2018.1452914
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Journal of asian natural Products research, 2018
ꢁꢁpꢂ://ꢃꢄꢅ.ꢄꢆg/10.1080/10286020.2018.1452914
ꢀ
New polyacetylenes glycoside from Eclipta prostrate with
DGAT inhibitory activity
Xiao Meng, Ban-Ban Li, Xin Lin, Yi-Yu Jiang, Le Zhang, Hao-Ze Li and Long Cui
cꢄꢇꢇꢈgꢈ ꢄꢉ Pꢀꢊꢆmꢊꢋy, Bꢈꢅꢀꢌꢊ uꢍꢅvꢈꢆꢂꢅꢁy, Jꢅꢇꢅꢍ 132013, cꢀꢅꢍꢊ
ABSTRACT
ARTICLE HISTORY
One new polyacetylene glycoside eprostrata Ⅰ (1), together with seven
known compounds (2–8), were isolated from Eclipta prostrata. Their
structures were elucidated on the basis of spectroscopic and physico-
chemical analyses. All the isolates were evaluated inhibitory activity
on DGAT in an in vitro assay. Compounds 1–8 were found to exhibit
inhibitory activity of DGAT1 with IC values ranging from 74.4 ± 1.3
rꢈꢋꢈꢅvꢈꢃ 20 sꢈpꢁꢈmbꢈꢆ 2017
aꢋꢋꢈpꢁꢈꢃ 11 Mꢊꢆꢋꢀ 2018
KEYWORDS
aꢂꢁꢈꢆꢊꢋꢈꢊꢈ; Eclipta prostrata;
dGat; pꢄꢇyꢊꢋꢈꢁyꢇꢈꢍꢅꢋ
gꢇꢌꢋꢄꢂꢅꢃꢈꢂ
5
0
to 101.1 ± 1.1 ꢀM.
1
. Introduction
Eclipta prostrata belongs to therophyte herb of the family Asteraceae. It is growing widely
in the tropical and subtropical areas of the world, and known as “Mohanlian” in China,
principally in the provinces of Jiangsu, Jiangxi and Zhejiang [1]. e aerial parts of E.
prostrata is one significant traditional folk medicine and used as a health food or tonic to
treat infectious hepatitis, jaundice, liver cirrhosis, aching and weakness of the knees and
loins, spitting of blood, epistaxis, hematuria and diarrhea with bloody stools, and abnormal
uterine bleeding [2]. Previous phytochemical investigation of the plant have uncovered a
number of bioactive compounds such as thiophenes, steroids, triterpenes [3], flavonoids,
polyacetylenes, polypeptides, and coumestons. [4].
Trigycerides (TG) are one of the main forms of energy storage. e excess supply of
TG in certain tissues leads to serious diseases such as obesity, type 2 diabetes mellitus and
CONTACT lꢄꢍg cꢌꢅ
ꢋꢌꢅꢇꢄꢍg71@bꢈꢅꢀꢌꢊ.ꢈꢃꢌ.ꢋꢍ
tꢀꢈ ꢂꢌppꢇꢈmꢈꢍꢁꢊꢇ ꢃꢊꢁꢊ ꢉꢄꢆ ꢁꢀꢅꢂ ꢊꢆꢁꢅꢋꢇꢈ ꢋꢊꢍ bꢈ ꢊꢋꢋꢈꢂꢂꢈꢃ ꢊꢁ ꢀꢁꢁpꢂ://ꢃꢄꢅ.ꢄꢆg/10.1080/10286020.2018.1452914.
©
2018 iꢍꢉꢄꢆmꢊ uK lꢅmꢅꢁꢈꢃ, ꢁꢆꢊꢃꢅꢍg ꢊꢂ tꢊyꢇꢄꢆ & fꢆꢊꢍꢋꢅꢂ Gꢆꢄꢌp

2
X. MENG ET AL.
hypertriglyceridemia [5]. TG synthesis has been assumed to occur primarily by diacylglyc-
erol acyltransferase (DGAT), a key enzyme in TG biosynthesis that catalyzes the final step
in glycerol phosphate pathway [6]. As a part of our exploration on the traditional medicine,
E. prostrata was studied, which resulted in the isolation of a new polyacetylenic glucoside
(
1), along with seven known compounds (2–8) (Figure 1). Herein we report the isolation
and structural elucidation of a new eprostrata Ⅰ (1) and evaluation of DGAT inhibitory
activity about these isolates.
2
. Results and discussion
Compound 1 was isolated as a brownish amorphous powder. e molecular formula was
+
1
established as C H O based on HRESIMS at m/z 361.1260 for [M + Na] . In H NMR
17
22
7
spectrum the proton signals at δ 5.27 (1H, dt, J = 10.5, 1.5), 5.61 (1H, dt, J = 17.5, 1.5) and
H
6
.33 (1H, ddd, J = 16.5, 10.5, 5.5) implied the presence of a terminal double bond. e signal
1
3
at δ 1.82 (3H, s) suggested one methyl was attached to acetylene bond. e C NMR spec-
H
trum exhibited 17 carbon resonances, classified into four quaternary carbons, ten methines
including six oxygen-substituted carbons, two methylenes including one oxygen-substituted
methylene, and one methyl group. e signals at δc 116.4, 138.9, 148.7, 110.3 were ascribed
to two double bonds. By analysis of degrees of unsaturation, four quaternary carbon signals
at δc 60.3, 76.0, 65.8, 80.2 were ascribed to two actylene bonds. And the signals at δc 105.1,
1
13
7
6.1, 79.2, 72.0, 79.0, 63.0 were assigned to a glucopyranosyl unit. e H and C NMR
spectra of 1 were quite similar to that of (5E)-trideca-1,5-dien-7,9,11-triyne-3,4-diol-4-O-
1
1
β-D-glucopyranoside (2) [7]. e H- H COSY correlations from H-1 (δ 5.27, 5.61) to
H
H-2 (δ 6.33), H-2 to H-3 (δ 4.73), H-3 to H-4 (δ 4.80), H-4 to H-5 (δ 6.85), H-5 to H-6
H
H
H
H
(
δ 6.30) were observed. HMBC correlations from H-1 to C-2 (δ 138.9), C-3 (δ 74.7),
H
C
C
from H-4 to C-5 (δ 148.7), C-6 (δ 110.3), from H-6 to C-7 (δ 60.3), C-8 (δ 76.0), from
C
C
C
C
H-11 to C-5 (δ 148.7), C-6 (δ 110.3), C-7 (δ 60.3), C-8 (δ 76.0), C-9 (δ 65.8), C-10 (δ
C
C
C
C
C
C
8
0.2), established the connectivity of C-1-C-2-C-3-C-4-C-5-C-6-C-7, and demonstrated
that C-7 to C-11 were connected to diacetylene chain of C-8-C-9-C-10-C-11. e HMBC
correction from H-1′ (δ 5.17, 1H, d, J = 7.5) to C-4 suggested the glucopyranosyl unit was
H
linked at C-4 (Figure 2). Accordingly, compound 1 was elucidated as (5E)-hendeca-1,5-
dien-7,9-diyne-diol-4-O-β-D-glucopyranoside, named eprostrata Ⅰ.
Along with one new eprostrata Ⅰ (1), seven known compounds (2–8) were obtained
from E. prostrata. Seven known compounds were identified as (5E)-trideca-1,5-dien-
7,9,11-triyne-3,4-diol-4-O-β-D-glucopyranoside (2) [7], 3-O-β-D-glucopyranosyl-
1-hydroxy-4E,6E-tetradecene,8,10,12-triyne (3) [7], 2-O-β-D-glucosyltrideca-3E,11E-dien-
5,7,9-triyne-1,2,13-triol (4) [8], 2-O-β-D-glucosyltrideca-3E,11E-dien-5,7,9-triyne-1,2-diol
Figure 1. sꢁꢆꢌꢋꢁꢌꢆꢈ ꢄꢉ ꢋꢄmpꢄꢌꢍꢃ 1.

JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH
3
1
1
Figure 2. Kꢈy hMBc ꢊꢍꢃ h- h cosY ꢋꢄꢆꢆꢈꢇꢊꢁꢅꢄꢍꢂ ꢄꢉ ꢋꢄmpꢄꢌꢍꢃ 1.
1
13
1
13
Table 1. h ꢊꢍꢃ c nMr ꢂpꢈꢋꢁꢆꢊꢇ ꢃꢊꢁꢊ ꢄꢉ ꢋꢄmpꢄꢌꢍꢃ 1 ꢅꢍ pyꢆꢅꢃꢅꢍꢈ-d ( h: 500 Mhz, c: 125 Mhz).
5
1a
Position
δC
δH, mult. (J in Hz)
1
116.4, ch2
5.27 (1h, ꢃꢁ, 10.5, 1.5)
5.61 (1h. ꢃꢁ, 17.5, 1.5)
2
3
4
5
6
7
8
9
138.9, ch
74.7, ch
83.8, ch
148.7, ch
110.3, ch
60.3, c
76.0, c
65.8, c
80.2, c
4.6, ch3
105.1, ch
76.1, ch
79.2, ch
72.0, ch
79.0, ch
63.0, ch2
6.33 (1h, ꢃꢃꢃ, 16.5, 10.5, 5.5)
4.72-4.74 (1h, m)
4.79-4.82 (1h. m)
6.85 (1h, ꢃꢃ, 16.0, 5.0)
6.30 (1h, ꢃꢃ, 16.0, 1.5)
1
1
0
1
1.82 (3h, ꢂ)
5.17 (1h, ꢃ, 7.5)
4.10 (1h, ꢁ, 8.0)
1
2
3
4
5
6
'
'
'
'
'
'
3.91-3.93 (1h, m)
4.25-4.26 (1h, m)
4.23-4.25 (1h, m)
4.37 (1h, ꢃꢃ, 11.5, 3.5)
4.50 (1h, ꢃꢃ, 11.0, 3.0)
ꢊcꢀꢈmꢅꢋꢊꢇ ꢂꢀꢅꢉꢁꢂ ꢅꢍ ppm ꢆꢈꢇꢊꢁꢅvꢈ ꢁꢄ tMs; ꢋꢄꢌpꢇꢅꢍg ꢋꢄꢍꢂꢁꢊꢍꢁꢂ (J) ꢅꢍ hz.
(
5) [8], 2-O-β-D-glucosyltrideca-3E,11Z-dien-5,7,9-triyne3–1,2-diol (6) [8], α-terthienyl-
methanol (7) [9], α-formylterthienyl (8) [9] based on the NMR data.
All the isolates were assayed their inhibitory activity against DGAT1 and DGAT2. Results
were summarized in Table 2. e known DGAT inhibitor, kuraridine, was used as positive
control in this assay [10]. Among the isolates, compounds 1–8 exhibited the most potent
inhibitory activity on DGAT1, with IC values ranging from 74.4 ± 1.3 to 101.1 ± 1.1 μM.
5
0
As shown in Table 2, compounds 5 and 8 showed moderate inhibitory abilities on DGAT1,
the other compounds exhibited weak effect. All compounds were inactive when tested
against DGAT2.

4
X. MENG ET AL.
Table 2. iꢍꢀꢅbꢅꢁꢄꢆy ꢊꢋꢁꢅvꢅꢁy ꢄꢉ ꢋꢄmpꢄꢌꢍꢃꢂ 1–8 ꢊgꢊꢅꢍꢂꢁ dGat1 ꢊꢍꢃ dGat2.
IC50 (ꢀM)a
Compounds
DGAT1
DGAT2
1
2
3
4
5
6
7
8
93.1 ± 1.2
92.4 ± 1.3
87.1 ± 1.1
81.3 ± 1.3
74.4 ± 1.3
101.1 ± 1.1
89.8 ± 1.4
78.4 ± 1.5
10.4 ± 1.4
＞200
＞200
＞200
＞200
＞200
＞200
＞200
＞200
18.7 ± 1.2
b
Kꢌꢆꢊꢆꢅꢃꢅꢍꢈ
ꢊ
ic50 vꢊꢇꢌꢈꢂ wꢈꢆꢈ ꢃꢈꢁꢈꢆmꢅꢍꢈꢃ by ꢆꢈgꢆꢈꢂꢂꢅꢄꢍ ꢊꢍꢊꢇyꢂꢈꢂ ꢊꢍꢃ ꢈxpꢆꢈꢂꢂꢈꢃ ꢊꢂ mꢈꢊꢍꢂ ± sd ꢄꢉ ꢁꢀꢆꢈꢈ ꢆꢈpꢇꢅꢋꢊꢁꢈꢂ.
Pꢄꢂꢅꢁꢅvꢈ ꢋꢄꢍꢁꢆꢄꢇ.
b
3
. Experimental
3
.1. General experimental procedure
Optical rotations were measured using a JASCO-P-2000 digital polarimeter (Tokyo,
Japan). UV spectra were taken in MeOH using a Shimadzu spectrophotometer (Shimadzu,
Tokyo, Japan). IR spectra were recorded on a Schimadzu FTIR-8900 spectrophotometer
(
Tokyo, Japan). Nuclear magnetic resonance (NMR) spectra were obtained from a Varian
Unity Inova 500 MHz spectrometer (Varian Unity Inova, Phoenix, USA) using TMS as
the internal standard. All accurate mass experiments were performed on a Micromass
QTOF (Micromass, Wythenshawe, UK) mass spectrometer. ESIMS were recorded on a
JEOL JMSAX × 505-WA (Tokyo, Japan). Column chromatography was conducted using
silica gel 60 (40–63 and 63–200 μm particle size, Yantai Xinde Chemical Co., Ltd, Yantai,
China) and RP-18 (150–63 μm particle size, Merck, Darmstadt, Germany). Silica gel 60 F254
plates from Merck were used for thin-layer chromatography (TLC). HPLC were carried out
using a Shimadzu System LC-10AD pump equipped with a model SPD-10Avp UV detector
(
Shimadzu, Tokyo, Japan), and an Optima Pak® C18 column (10 × 250 mm, 10 μm particle
size, Shiseido Fine Chemicals, Tokyo, Japan).
HEK293 Tet-on cells were obtained from Clontech (PaloAlto, CA, USA). Fatty acid-free
BSA and sn-1,2-dioleoylglycerol was obtained from Sigma-Aldrich (St. Louis, MO, USA).
1
4
[
C]-oleoyl CoA was purchased from PerkinElmer, Inc (WoodBridge, ON, Canada).
3
.2. Plant material
e stem of Eclipta prostrata was collected in Jilin city, Jilin province, China, and authenti-

cated by Professor Gao Li (College of Pharmacy, Yanbian University). A voucher specimen
of the plant (No. 20130221) was deposited at the College of Pharmacy, Beihua University,
Jilin, China.
3
.3. Extraction and isolation
e stem (1.0 kg) of E. prostrata was extracted with MeOH at room temperature for 2 weeks
and the solution was concentrated to obtain a crude extract (83.0 g). is extract was


JOURNAL OF ASIAN NATURAL PRODUCTS RESEARCH
5
suspended in H O, partitioned successively with n-hexane, EtOAc and BuOH, and then
2
the organic solvents were removed. A portion of the EtOAc-soluble fraction (31.0 g) was
chromatographed over a silica gel column using a gradient of CH Cl -MeOH (from 10:1,
2
2
5
:1, 0:1), and was separated into 11 fractions (Fr.1-Fr.11). Fr.9 (3.1 g) was chromatographed
over silica gel, eluted with a stepwise gradient of CH Cl -MeOH (from 10: 1, 5: 1, 2:1, 0:1)
2
2
to afford 7 subfractions (Fr.91-Fr.97) Fr.92 (1.1 g) was subjected to a Rp-18 column and was
eluted with MeOH-H O (40% to 100% MeOH in H O) to yield 8 fractions (Fr.921 - Fr.928).
2
2
Fr.922 (35.0 mg) was separated by HPLC, using an isocratic solvent system of 20% MeOH
in H O as the mobile phase at a flow rate of 4 ml/min over 60 min yielded compounds 1
2
(
15.1 mg, t = 41.2 min) and 2 (8.3 mg, t = 37.4 min). Fr.925 (24.2 mg) was purified by
R
R
semipreparative HPLC using an isocratic solvent system of 35% MeOH in H O at a flow
2
rate of 4 ml/min for 90 min to yield compound 3 (8.4 mg, t = 59.1 min). Fr.926 (78.0 mg)
R
was purified by semipreparative HPLC using an isocratic solvent system of 55% MeOH in
H O at a flow rate of 4 ml/min for 70 min to yield compounds 4 (11.4 mg, t = 22.3 min), 5
2
R
(
5.4 mg, t = 42.5 min) and 6 (7.7 mg, t = 43.2 min). Fr.94 (0.9 g) was subjected to a Rp-18
R
R
column and eluted with MeOH-H O (50% to 100% MeOH in H O) to yield 6 Fractions
2
2
(
Fr.941 - Fr.946). Fr.944 (61.5 mg) was separated by HPLC, using an isocratic solvent system
of 62% MeOH in H O as the mobile phase at a flow rate of 4 ml/min for 60 min to produce
2
compounds 7 (11.7 mg, t = 38.6 min) and 8 (7.4 mg, t 43.9 min).
R
R=
3
.3.1. Eprostrata I (1)
2
5
Brownish amorphous powder; ꢀ + 42.5 (c, 0.1, MeOH); UV (MeOH) λmax (log ε) 346,
D
3
27, 307, 288, 269, 256, 242, 230 nm; IR (KBr) ν 3371, 3012, 2882, 2235, 1709, 1628,
max
−1
1
13
1
613, 1527, 1436, 1366, 1081, 1042, 934 cm ; H (500 MHz) and C (125 MHz) NMR
+
spectral data in pyridine-d , see Table 1; HRESIMS m/z: 361.1260 [M + Na] (calcd for
C H O Na, 361.1263).
5
1
7
22
7
3
.3.2. DGAT assays
Preparation of microsomes from rat liver and measurement of the in vitro DGAT1 activity
were performed as reported previously [10].
3
.4. Acidic hydrolysis
Compound 1 (5.0 mg) in a mixture of MeOH (1.0 ml) and 10% HCl (1.0 ml) was stirred at
reflux for 4 h. e hydrolysate was allowed to cool, diluted 2-fold with H O, and extracted
2
with EtOAc (3 × 2 ml). e aqueous layer was neutralized with 2 M ammonium hydroxide
and concentrated in vacuo to give a residue in which D-glucose was identified by comparison
with authentic sugar samples (n-BuOH/AcOH/H O 4:1:5, upper layer; PhOH/H O, 4: 1)
2
2
on TLC (sprayed with aniline phthalate reagent from Sigma-Aldrich, followed by heating).
3
.5. Determination of sugar configuration
Compound 1 (2.0 mg) was hydrolyzed by 3.5% HCl (0.4 ml) at 110 °C for 2.5 h. e reaction
mixture was neutralized with 0.5 M NaOH. Af er drying under vacuum, the residue was
dissolved in pyridine (0.4 ml) containing L-cysteine methyl ester hydrochloride (2.0 mg)
and heated at 60 °C for 1 h. O-Toylisothio-cyanate (2.0 ml) was then added and the mixture

6
X. MENG ET AL.
was heated at 60 °C for 1 h. Each reaction mixture was directly analyzed by reversed phase
HPLC. A C HPLC column (4.6 × 250 mm, 10 mm particle size) was used (temperature
1
8
3
5 °C, flow rate 0.8 ml/min; eluate, CH CN-H O (25: 75) containing 50 mM H PO ). e
3 2 3 4
reaction conditions for DL-glucose were same as described above. Retention times for
authentic sugar derivatives, D-glucose (18.7), L-glucose (17.1) were used for comparison
with retention times from reaction mixtures for each glycoside. Peaks at 18.9 min of the
sugar derivatives from 1 coincided with derivatives of D-glucose (18.7 min).
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding

is work was supported by the Scientific and Technological Developing Scheme of Jilin Province
of China [grant number 20150101225JC].
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