Three new sucrose fatty acid esters from Equisetum hiemale L.

Article abstract of DOI:10.1002/hlca.201100515

Three new monosubstituted sucrose fatty acid esters, 1-3, were isolated from Equisetum hiemale L., together with nine known compounds, 4-12. Their structures were elucidated by spectroscopic analyses. Compounds 5, 6, and 10-12 were isolated from the title

Full text of DOI:10.1002/hlca.201100515

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Helvetica Chimica Acta – Vol. 95 (2012)
Three New Sucrose Fatty Acid Esters from Equisetum hiemale L.
a
b
a
a
b
a
b
a b
by Jin-Tang Cheng ) ), Juan He ), Xing-Yao Li ) ), Xing-De Wu ) ), Li-Dong Shao ) ), Liao-Bin
a
b
a
b
a
b
a
a
a
a
Dong ) ), Xu Deng ) ), Xiu Gao ) ), Li-Yan Peng ), Xiao Cheng ), Yan Li ), and Qin-Shi Zhao* )
a) State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of
Botany, Chinese Academy of Sciences, Kunming 650204, P. R. China
(
phone: þ 86-871-5223058; fax: þ 86-871-5215783; e-mail: qinshizhao@mail.kib.ac.cn)
b
)
Graduate University of Chinese Academy of Sciences, Beijing 100039, P. R. China
Three new monosubstituted sucrose fatty acid esters, 1 – 3, were isolated from Equisetum hiemale L.,
together with nine known compounds, 4 – 12. Their structures were elucidated by spectroscopic analyses.
Compounds 5, 6, and 10 – 12 were isolated from the title plant for the first time. All these compounds
were evaluated for their cytotoxic activity. However, none of them was cytotoxic.
Introduction. – The family Equisetaceae, comprised of two genera (Equisetum and
Hippochaete) and about 25 species, is widely distributed in temperate regions [1].
Members of this family are known to contain several types of compounds such as
flavonoids, steroids, megastigmanes, and fatty acids [2 – 7]. Equisetum hiemale L.
(
Equisetaceae) was used as a Traditional Chinese Medicine called as ꢀMuzeiꢁ in
Chinese for the treatment of eye diseases [8]. Previous chemical investigations on this
plant have led to the isolation of a series of flavonoids and phenolic compounds [9]. In
the course of our search for structurally unique and potentially bioactive natural
products, three new monosubstituted sucrose fatty acid esters, 6-O-[(9Z,12Z,15Z)-
octadeca-9,12,15-trienoyl]-b-d-fructofuranosyl a-d-glucopyranoside (1), 6-O-[(7Z,
10Z,13Z)-hexadeca-7,10,13-trienoyl]-b-d-fructofuranosyl a-d-glucopyranoside (2),
and 6-O-[(7Z,10Z)-hexadeca-7,10-dienoyl]-b-d-fructofuranosyl a-d-glucopyranoside
(
(
3), together with nine known compounds, b-sitosterol (4) [10], a-tocopherolquinone
5) [11], 3,3’-[propane-2,2-diylbis(benzene-4,1-diyloxy)]bis(propane-1,2-diol) (6) [12],
trans-feruloyl-4-b-glucoside (7) [13], trans-ferulic acid (8) [14], vanillic acid (9) [14],
6R,7aS)-5,6,7,7a-tetrahydro-6-hydroxy-4,4,7a-trimethylbenzofuran-2(4H)-one (10)
(
[
15], 3b-hydroxy-5a,6a-epoxy-7-megastigmen-9-one (¼(3E)-4-[(1S,4R,6R)-4-hy-
droxy-2,2,6-trimethyl-7-oxabicyclo[4.1.0]hept-1-yl]but-3-en-2-one; 11) [16], 4-hy-
droxy-2,3-dimethylnon-2-en-4-olide (¼ 5-hydroxy-3,4-dimethyl-5-pentylfuran-2(5H)-
one; 12) [17], were isolated from the aerial parts of E. hiemale L. Herein, we describe
the isolation and structure elucidation of the isolates.
Results and Discussion. – The AcOEt extract of the aerial parts of E. hiemale L. was
subjected to various column chromatographic separation columns, as well as
preparative HPLC, to afford three new compounds, 1 – 3.
Compound 1 was isolated as a colorless oil. The molecular formula was established
þ
as C H O by HR-ESI-MS (m/z 625.3186 ([M þ Na] ); calc. 625.3200), correspond-
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ꢂ 2012 Verlag Helvetica Chimica Acta AG, Zꢃrich

Helvetica Chimica Acta – Vol. 95 (2012)
1159
ꢀ
1
ing to six degrees of unsaturation. The IR absorption bands at 3428 and 1726 cm
1
implied the presence of ester and OH groups. The H-NMR data (Table 1) revealed the
occurrence of six olefinic H-atoms (d(H) 5.31 – 5.39), four CH groups (d(H) 1.25 –
2
1
.33), and one terminal Me group (d(H) 0.98, t, J ¼ 7.5, Me(18)). Correspondingly,
the C-NMR spectrum (Table 2) exhibited the signals of six olefinic C-atoms (d(C)
32.7, 131.1, 129.2, 129.1, 128.9, 128.3), ten CH groups (d(C) 21.5 – 34.9), a Me group
13
1
2
(d(C) 14.7 (q, C(18)), and a CO group (d(C) 175.5 (s, C(1))). These data suggested that
1
possessed a linolenic acid residue, which was confirmed by comparison of the
spectroscopic data with those reported in the literature [18]. The other twelve C-atom
resonances were displayed in the region of d(C) 62.5 – 105.5, suggesting the existence of
a disaccharide moiety, which was determined as sucrose and confirmed by alkaline
hydrolysis of compound 1. Alkaline hydrolysis of 1 with 0.5% NaOH yielded linolenic
acid and sucrose (see Exper. Part). The fatty acid residue is attached to HOꢀC(6’’) of
sucrose, as deduced by HMBCs of the signals of CH (6’’) (d(H) 4.39 and 4.33) with the
2
one of C(1) (d(C) 175.5 (s)) of 1. Based on these data, compound 1 was characterized as
6-O-[(9Z,12Z,15Z)-octadeca-9,12,15-trienoyl]-b-d-fructofuranosyl a-d-glucopyrano-
side.

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Helvetica Chimica Acta – Vol. 95 (2012)
Table 1. 1H-NMR Data of Compounds 1 – 3. Recorded in CD OD; d in ppm, J in Hz.
3
H-Atom
1
2
3
CH (2)
2.35 (t, J ¼ 7.4)
1.60 – 1.61 (m)
1.25 – 1.33 (m)
1.25 – 1.33 (m)
1.25 – 1.33 (m)
1.25 – 1.33 (m)
2.05 – 2.10 (m)
5.31 – 5.39 (m)
5.31 – 5.39 (m)
2.80 – 2.83 (m)
5.31 – 5.39 (m)
5.31 – 5.39 (m)
2.05 – 2.10 (m)
5.31 – 5.39 (m)
5.31 – 5.39 (m)
2.05 – 2.10 (m)
0.98 (t, J ¼ 7.5)
5.34 (overlap)
3.42 (dd, J ¼ 9.7, 3.6)
3.72 (overlap)
3.34 (dd, J ¼ 9.5, 9.5)
3.83 (overlap)
3.72 (overlap),
2.35 (t, J ¼ 7.5)
1.61 – 1.65 (m)
1.29 – 1.38 (m)
1.29 – 1.38 (m)
2.07 – 2.11 (m)
5.31 – 5.40 (m)
5.31 – 5.40 (m)
2.80 – 2.83 (m)
5.31 – 5.40 (m)
5.31 – 5.40 (m)
2.80 – 2.83 (m)
5.31 – 5.40 (m)
5.31 – 5.40 (m)
2.07 – 2.11 (m)
0.98 (t, J ¼ 7.5)
–
2.35 (t, J ¼ 7.4)
1.61 – 1.65 (m)
1.30 – 1.40 (m)
1.30 – 1.40 (m)
2.06 – 2.09 (m)
5.31 – 5.38 (m)
5.31 – 5.38 (m)
2.78 (dd, J ¼ 6.2, 6.2)
5.31 – 5.38 (m)
5.31 – 5.38 (m)
2.06 – 2.09 (m)
1.30 – 1.40 (m)
1.30 – 1.40 (m)
1.30 – 1.40 (m)
0.91 (t, J ¼ 6.6)
–
2
CH (3)
2
CH (4)
2
CH (5)
2
CH (6)
2
CH (7) or HꢀC(7)
2
CH (8) or HꢀC(8)
2
HꢀC(9) or CH (9)
2
HꢀC(10)
CH (11) or HꢀC(11)
2
HꢀC(12) or CH (12)
2
HꢀC(13) or CH (13)
2
CH (14) or HꢀC(14)
2
HꢀC(15) or CH (15)
2
HꢀC(16) or Me(16)
CH (17)
2
Me(18)
HꢀC(1’)
HꢀC(2’)
HꢀC(3’)
HꢀC(4’)
HꢀC(5’)
–
–
5.34 (overlap)
3.41 (dd, J ¼ 9.8, 3.8)
3.72 (overlap)
3.32 (dd, J ¼ 9.5, 9.5)
3.83 (overlap)
3.72 (overlap),
3.83 (overlap)
3.62 (br. s)
5.34 (overlap)
3.41 (dd, J ¼ 9.8, 3.8)
3.71 (overlap)
3.33 (dd, J ¼ 9.5, 9.5)
3.83 (overlap)
3.71 (overlap),
3.83 (overlap)
3.62 (br. s)
CH (6’)
2
3.83 (overlap)
CH (1’’)
3.62 (br. s)
2
HꢀC(3’’)
HꢀC(4’’)
HꢀC(5’’)
4.10 (d, J ¼ 8.2)
4.09 (d, J ¼ 8.2)
4.00 (t-like, J ¼ 8.1)
3.92 (td, J ¼ 7.8, 3.3)
4.39 (dd, J ¼11.7, 7.8),
4.32 (dd, J ¼11.7, 3.3)
4.09 (d, J ¼ 8.2)
4.01 (t-like, J ¼ 8.1)
3.92 (td, J ¼ 7.8, 3.1)
4.39 (dd, J ¼ 11.7, 7.8),
4.32 (dd, J ¼ 11.6, 3.1)
4.01 (t-like, J ¼ 8.1)
3.92 (td, J ¼ 7.8, 3.0)
4.39 (dd, J ¼ 11.5, 7.9),
CH (6’’)
2
4.33 (dd, J ¼ 11.6, 3.0)
þ
Compound 2, a colorless oil, showed a molecular-ion peak at m/z 597 ([M þ Na] )
1
in the ESI-MS, corresponding to the molecular formula C H O . The H- and
28
46 12
13
C-NMR spectra (Tables 1 and 2, resp.) revealed that compound 2 was quite similar to
compound 1. The most striking difference was the absence of two non-O-bearing CH
groups. Detailed analysis of the H, H-COSY and HMBC spectra revealed the
2
1
1
occurrence of a partial structure, ꢀCH ꢀ(CH¼CHꢀCH ) ꢀMe with the following
2
2 3
chemical shifts: d(C) 28.0 (t), 128.1 (d), 128.9 (d), 26.3 (t), 129.1 (d), 129.2 (d), 26.5 (t),
1
30.8 (d), 132.7 (d), 21.4 (t), and 14.6 (q). The two CH groups absent in 2 were part of
2
the CH chain between the olefinic and ester groups in compound 1, which suggested
2
13
that compound 2 possessed a hexadeca-7,10,13-trienoic acid residue. In the C-NMR
spectrum, the three allylic CH C-atoms (C(6), C(9), and C(12)) were shifted upfield to
2
d(C) 28.0, 26.3, and 26.5, which indicated that the geometry of C¼C bonds is most
probably (Z) [19 – 21]. The HMBCs of the signals of CH (6’’) (d(H) 4.39 and 4.32) with
2
the one of C(1) (d(C) 175.4 (s)) indicated that the hexadeca-7,10,13-trienoic acid
residue was attached to HOꢀC(6’’) of sucrose. Accordingly, the structure of compound

Helvetica Chimica Acta – Vol. 95 (2012)
1161
Table 2. 13C-NMR Data of Compounds 1 (100 MHz), 2 (100 MHz), and 3 (150 MHz). Recorded in
CD OD; d in ppm.
3
C-Atom
1
2
3
C-Atom
1
2
3
C(1)
175.5 (s)
34.9 (t)
26.0 (t)
175.4 (s)
34.8 (t)
25.8 (t)
29.8 (t)
30.4 (t)
28.0 (t)
175.6 (s)
35.0 (t)
26.0 (t)
30.0 (t)
C(16)
C(17)
C(18)
C(1’)
C(2’)
C(2’)
C(4’)
C(5’)
C(6’)
C(1’’)
C(2’’)
C(3’’)
C(4’’)
C(5’’)
C(6’’)
132.7 (d)
21.5 (t)
14.7 (q)
93.5 (d)
73.3 (d)
74.7 (d)
71.5 (d)
74.2 (d)
62.5 (t)
63.8 (t)
105.5 (s)
78.9 (d)
76.9 (d)
80.6 (d)
67.0 (t)
14.6 (q)
14.6 (q)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
a
30.2 (t) )
93.4 (d)
73.2 (d)
74.6 (d)
71.4 (d)
74.2 (d)
62.4 (t)
63.7 (t)
105.4 (s)
78.8 (d)
76.8 (d)
80.6 (d)
66.9 (t)
93.6 (d)
73.3 (d)
74.7 (d)
71.6 (d)
74.4 (d)
62.6 (t)
63.8 (t)
105.6 (s)
78.9 (d)
77.0 (d)
80.8 (d)
67.1 (t)
a
b
30.2 (t) )
30.6 (t) )
a
c
30.4 (t) )
28.1 (t) )
d
e
30.7 (t)
28.2 (t)
128.3 (d) )
128.1 (d) )
129.2 (d) )
129.4 (d) )
26.7 (t)
130.8 (d) )
d
e
128.9 (d) )
f
g
26.3 (t) )
f
d
e
128.9 (d) )
129.1 (d) )
h
d
e
26.4 (t) )
129.2 (d) )
131.1 (d) )
f
g
c
129.1 (d) )
26.5 (t) )
28.3 (t) )
f
d
b
129.2 (d) )
130.8 (d) )
132.7 (d)
21.4 (t)
30.7 (t) )
h
26.6 (t) )
32.8 (t)
23.8 (t)
f
131.1 (d) )
a) – ) Assignments may be interchanged.
h
2
was determined as 6-O-[(7Z,10Z,13Z)-hexadeca-7,10,13-trienoyl]-b-d-fructofurano-
syl a-d-glucopyranoside.
Compound 3 was obtained as a colorless oil. The molecular formula was established
þ
as C H O by the HR-ESI-MS (m/z 599.3036 ([M þ Na] ); calc. 599.3043),
28
48 12
13
indicating five degrees of unsaturation. The C-NMR spectrum (Table 2) indicated
the presence of two C¼C bonds (d(C) 131.1 (d), 130.8 (d), 129.4 (d), 129.2 (d)), ten
non-O-bearing CH groups, as well as one Me group (d(C) 14.6 (q, C(16)). Comparison
2
of the spectroscopic data with those of 2 revealed an overall similarity, except for the
absence of one C¼C bond. The upfield shift of the signal of CH (15) (d(H) 1.30 – 1.40
2
(
overlap)) suggested that the C¼C bond between C(13) and C(14) of compound 2 was
1 1
saturated in compound 3, which was confirmed by HMBC and H, H-COSY
correlations (Fig.). On the basis of the fact that signals of the allylic C-atoms were
shifted upfield (d(C) 28.1 and d(C) 28.3), the geometry of C¼C bonds in compound 3
was determined as (Z) [19 – 21]. The fatty acid residue was attached to HOꢀC(6’’) of
sucrose, as deduced by HMBCs of the signals of CH (6’’) (d(H) 4.39 and 4.32) with the
2
1
1
Figure. Key H, H-COSY correlations (—) and HMBCs (H ! C) of 3

1
162
Helvetica Chimica Acta – Vol. 95 (2012)
one of C(1) (d(C) 175.6 (s)). Consequently, the chemical structure of compound 3 was
determined to be 6-O-[(7Z,10Z)-hexadeca-7,10-dienoyl]-b-d-fructofuranosyl a-d-glu-
copyranoside.
The structures of the known compounds were identified by comparison of their
spectroscopic data with those reported in the literature.
Compounds 1 – 12 were tested for cytotoxicity against HL-60, A-549, SMMC-7721,
MCF-7, and SW480 cell lines in vitro. However, all of them were inactive.
This work was financially supported by the National Basic Research Program of China (973 Program
Nos. 2009CB522303 and 2011CB915503), the National Natural Science Foundation of China (Nos.
9
2
0813004 and U0932602), the projects from Chinese Academy of Sciences (Nos. 2009311211011 and
009312311024), and the State Key Laboratory of Phytochemistry and Plant Resources in West China
(
No. P2010-ZZ05).
Experimental Part
General. Solvents were distilled before use. Column chromatography (CC): silica gel (SiO ; 200 – 300
2
mesh, 10 – 40 mm; Qingdao Marine Chemical Inc., Qingdao, P. R. China), MCI gel (75 – 150 mm;
Mitsubishi Chemical Corporation, Japan), and Sephadex LHꢀ20 (Amersham Pharmacia Biotech,
Sweden). Fractions were monitored by TLC, and spots were visualized by heating SiO plates sprayed
2
with 10% H SO in EtOH. Semi-prep. HPLC: Zorbax SB-C-18 column (i.d. 9.4 ꢁ 250 mm; Agilent Co.,
2
4
Ltd.). Prep. HPLC: Shimadzu PRC-ODS (K) column, Shimadzu LC-8A prep. liquid chromotography.
Optical rotations: JASCO P-1020. UV Spectra: Shimadzu UV-2401PC. IR Spectra: Tensor 27; KBr
pellets. 1D- and 2D-NMR spectra: Bruker AM-400 and Advance III 600 spectrometers with TMS as
internal standard; unless specified, chemical shifts (d) in ppm with reference to the solvent signals, J in
Hz. MS: API QSTAR Pulsar-1 mass spectrometer.
Plant Material. The aerial parts of E. hiemale were collected from the area of Changbaishan, Jilin
Province, P. R. China, in July 2010. The sample was identified by X. C., and a voucher specimen (KIB
1
00701) has been deposited with the State Key Laboratory of Phytochemistry and Plant Resources in
West China, Kunming Institute of Botany, Chinese Academy of Sciences.
Extraction and Isolation. The air-dried and powdered aerial parts of the plant (5 kg) were extracted
with EtOH 95% (3 ꢁ 15 l, 24 h each) at r.t. and filtered. The filtrate was evaporated to give a residue
(
420 g), which was suspended in H O and then extracted with AcOEt. The AcOEt extract (160 g) was
2
decolorized over MCI gel (eluted with 90% MeOH) and then was subjected to CC (SiO ; petroleum
2
ether (PE)/Me CO, gradient system) to afford Frs. 1 – 5. Repeated crystallization from a mixture of
2
Me CO/MeOH from Fr. 1 gave compound 4 (5 g). Fr. 2 was subjected to CC (SiO ; PE/Me CO 99 :1, and
2
2
2
Sephadex LH-20; CHCl /MeOH, 1:1) to yield compound 5 (46 mg). Fr. 3 was subjected to CC (SiO ; PE/
3
2
Me CO, increasing polarity) to provide Frs. 3.1 – 3.8. Fr. 3.2 was purified by using semi-prep. HPLC (20%
2
MeOH in H O) to yield compounds 10 (88 mg) and 11 (9 mg). After the purification of Fr. 3.7 with
2
Sephadex LH-20 (CHCl /MeOH 1:1) and prep. HPLC (65% MeOH in H O) compound 12 (60 mg) was
3
2
isolated. Fr. 3.8 was subjected to prep. HPLC (35% MeOH in H O), compounds 8 (16 mg) and 9 (23 mg)
2
were obtained. Fr. 5 was subjected to CC (SiO ; CHCl /MeOH 95 :5 ! 1:1) to provide Frs. 5.1 – 5.10.
2
3
Repeated chromatography of Fr. 5.3 with a gradient system of CHCl /MeOH 95 :5 ! 7:3 yielded
3
compound 6 (25 mg). From Fr. 5.7, compound 7 (30 mg) was obtained after prep. HPLC (60% MeOH in
H O). Fr. 5.8 was first subjected to CC (SiO ; CHCl /MeOH 93 :7), then to prep. HPLC (78% MeOH in
2
2
3
H O) to yield compounds 1 (60 mg), 2 (6 mg), and 3 (3 mg).
2
6
-O-[(9Z,12Z,15Z)-Octadeca-9,12,15-trienoyl]-b-d-fructofuranosyl a-d-Glucopyranoside (1). Col-
25:8
orless oil. [a] ¼ þ35.9 (c ¼ 0.50, MeOH). UV (MeOH): 268 (3.35), 232 (3.60), 202 (3.69). IR (KBr):
D
1
13
þ
3
428, 2931, 1726, 1063. H- and C-NMR: see Tables 1 and 2, resp. ESI-MS (pos.): 625 ([M þ Na] ). HR-
þ þ
ESI-MS: 625.3186 ([M þ Na] , C H NaO ; calc. 625.3200).
30
50
12
6-O-[(7Z,10Z,13Z)-Hexadeca-7,10,13-trienoyl]-b-d-fructofuranosyl a-d-Glucopyranoside (2). Col-
2
5:7
orless oil. [a] ¼ þ30.7 (c ¼ 0.30, MeOH). UV (MeOH): 268 (3.33), 231 (3.42), 203 (3.96). IR (KBr):
D

Helvetica Chimica Acta – Vol. 95 (2012)
1163
1
13
þ
3
425, 2930, 1726, 1065. H- and C-NMR: see Tables 1 and 2, resp. ESI-MS (pos.): 597 ([M þ Na] ). HR-
þ
þ
ESI-MS (pos.): 597.2872 ([M þ Na] , C H NaO12 ; calc. 597.2887).
28
46
6
-O-[(7Z,10Z)-Hexadeca-7,10-dienoyl]-b-d-fructofuranosyl a-d-Glucopyranoside (3). Colorless oil.
2
5:8
[
a] ¼ þ44.6 (c ¼ 0.20, MeOH). UV (MeOH): 229 (3.43), 202 (3.97). IR (KBr): 3422, 2928, 1736, 1064.
D
1
13
þ
H- and C-NMR: see Tables 1 and 2, resp. ESI-MS (pos.): 599 ([M þ Na] ). HR-ESI-MS (pos.):
þ
þ
12
5
99.3036 ([M þ Na] , C H NaO ; calc. 599.3043).
28
48
Alkaline Hydrolysis of 1. Compound 1 was treated with 0.5% NaOH (0.5 ml) in MeOH (3 ml) at r.t.
for 18 h. The mixture was neutralized with 1n HCl and extracted with CHCl . The org. layer and the H O
3
2
layer were concentrated under reduced pressure. From the org. layer of compound 1, linolenic acid was
identified with authentic samples and by TLC. Sucrose was obtained from the H O layer, and identified
2
as sucrose by comparison with authentic samples and by TLC behavior, solvent: CHCl /MeOH/H O
3
2
4
5 :30 :1.
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Received December 21, 2011