Resin glycosides from Porana duclouxii

Article abstract of DOI:10.1080/10286020.2013.864281

A new intact resin glycoside (3) and two glycosidic acids (1 and 2), all having a common trisaccharide moiety and (11S)-hydroxytetradecanoic acid or (3S,11S)-dihydroxytetradecanoic acid as the aglycone, were obtained from the roots of Porana duclouxii. Their structures were elucidated by spectroscopic analyses and chemical correlations. These compounds represent the first examples of resin glycosides from the genus Porana.

Full text of DOI:10.1080/10286020.2013.864281

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Resin glycosides from Porana duclouxii
Wen-Bing Dingab, Dai-Gui Zhangc, Chun-Jie Liua, Guan-Hua Lia &
You-Zhi Liab
a Hunan Provincial Key Laboratory for Biology and Control of Plant
Diseases and Insect Pests, College of Plant Protection, Hunan
Agricultural University, Changsha, 410128, China
b National Research Center of Engineering & Technology for
Utilization of Botanical Functional Ingredients, Hunan Agricultural
University, Changsha, 410128, China
c Key Laboratory of Plant Resources Conservation and Utilization,
Jishou University, Jishou, 416000, China
Published online: 10 Dec 2013.
To cite this article: Wen-Bing Ding, Dai-Gui Zhang, Chun-Jie Liu, Guan-Hua Li & You-Zhi Li (2014)
Resin glycosides from Porana duclouxii, Journal of Asian Natural Products Research, 16:2, 135-140,
DOI: 10.1080/10286020.2013.864281
To link to this article: http://dx.doi.org/10.1080/10286020.2013.864281
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Journal of Asian Natural Products Research, 2014
Vol. 16, No. 2, 135–140, http://dx.doi.org/10.1080/10286020.2013.864281
Resin glycosides from Porana duclouxii
Wen-Bing Dingab, Dai-Gui Zhangc, Chun-Jie Liua, Guan-Hua Lia and You-Zhi Liab*
aHunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests,
College of Plant Protection, Hunan Agricultural University, Changsha 410128, China; National
b
Research Center of Engineering & Technology for Utilization of Botanical Functional Ingredients,
Hunan Agricultural University, Changsha 410128, China; Key Laboratory of Plant Resources
Conservation and Utilization, Jishou University, Jishou 416000, China
c
(Received 16 May 2013; final version received 6 November 2013)
A new intact resin glycoside (3) and two glycosidic acids (1 and 2), all having a
common trisaccharide moiety and (11S)-hydroxytetradecanoic acid or (3S,11S)-
dihydroxytetradecanoic acid as the aglycone, were obtained from the roots of Porana
duclouxii. Their structures were elucidated by spectroscopic analyses and chemical
correlations. These compounds represent the first examples of resin glycosides from the
genus Porana.
Keywords: Porana duclouxii; resin glycoside; triglycoside
1. Introduction
fraction was obtained. This paper
describes the isolation and characteriz-
ation of an intact resin glycoside and two
glycosidic acids from the fraction, which
were trivially named poranaside A (3),
poranic acid A (1), and poranic acid B (2),
respectively.
The genus Porana (Fam. Convolvulaceae)
consists of about 20 species occurring in
subtropical and tropical areas worldwide
[1]. Some plants of this genus, such as
Porana racemosa and Porana mairei, are
recorded in Chinese folk medicine for the
treatment of cough, nameless swelling,
overworked pain, and severe fever [2].
Previous phytochemical studies on this
genus led to the isolation of ecdysteroids,
coumarins, sterols, and flavanoids [3–6].
Resin glycosides are known to be charac-
teristic of constituents in Convolvulaceae,
which have been obtained from more than
34 species belonging to six genera
(Ipomoea, Merremia, Convolvulus, Oper-
culina, Cuscuta, and Calystegia) of this
family [7]. However, they have not been
reported from any Porana species so far.
Porana duclouxii, a Chinese endemic
species, is distributed in Hubei, Yunnan
and Sichuan provinces of Chinese main-
land [1]. In our phytochemical study on
P. duclouxii, a crude resin glycoside
2. Results and discussion
Poranic acid A (1) was obtained as a white
powder, with m.p. 175–1788C. Its molecular
formula, C32H58O16, was determined from
NMR (1H and 13C) and ESI-MS data and
confirmed by HR-ESI-MS. The negative ion
ESI-MS of 1 exhibited an [M–H]2 ion peak
at m/z 697 as well as a series of fragment ions
at m/z 551 [697–146 (C6H10O4)]2, 389
[551–162 (C6H10O5)]2, and 243 [389–146
1
(C6H10O4)]2. The H NMR signals of 1
displayed recognizable signals for three
anomeric protons [dH 6.33 (br s); 5.87 (d,
J ¼ 7.0 Hz); 4.87 (d, J ¼ 7.5 Hz)]. The 13C
NMR spectrum gave 32 signals, of which 18
carbons were assignable to a trisaccharide
moiety and 14 carbons to the aglycone
*Corresponding author. Email: liyouzhi2008@sina.com
q 2013 Taylor & Francis

136
W.-B. Ding et al.
moiety. All the above evidence indicated that
1 was a triglycoside with a hydroxytetrade-
[8,9], this compound was very similar to
cuscutic acid A2 [8], except the inner D-
fucose in cuscutic acid A2 was substituted by
a D-quinovose in 1. By complete acidic
hydrolysis, 1 furnished 11-hydroxytetrade-
canoic acid, D-quinovose, D-glucose, and
L-rhamnose. The absolute configuration
of 11-hydroxytetradecanoic acid was
canoic acid as the aglycone. The 1H and 13
C
NMR signals of 1 were carefully assigned
with the aid of H–H COSY, HSQC, and
HMBC experiments (Table 1). Comparing
the 1H and 13C NMR chemical shifts of 1 and
the related triglycosides in the literatures
Table 1. 1H and 13C NMR spectral data of compounds 1, 2, and 3.
1
2
3
Position
dH
dC
dH
dC
dH
dC
Qui-1
2
3
4
5
4.87 (d, 7.5)
102.1 4.87 (d, 7.5)
102.1 4.81 (d, 7.4)
102.3
78.8
4.34 (dd, 7.5, 8.8)
4.42 (dd, 9.0, 8.8)
3.59 (dd, 9.0, 9.0)
3.70 (m)
1.55 (d, 6.0)
5.87 (d, 7.0)
4.27 (dd, 7.2, 8.9)
4.25a
4.10 (t, 8.9)
3.86 (m)
4.46 (dd, 11.4, 2.6) 62.9
4.26 (11.4, 6.7)
79.6
79.0
76.7
72.2
18.4
4.34 (dd, 7.5, 8.5) 79.5
4.41 (dd, 9.0, 8.5) 79.0
3.59 (dd, 9.0, 9.0) 76.7
3.70 (m)
1.55 (d, 6.1)
4.40a
4.32 (dd, 9.0, 8.5) 79.3
3.59 (dd, 9.0, 9.0) 76.6
72.2
18.4
3.72 (m)
1.61 (d, 6.0)
72.3
18.4
101.2
77.8
79.2
72.2
77.7
62.8
6
Glc-1
101.7 5.87 (d, 7.2)
101.7 5.97 (d, 7.2)
4.24a
2
3
4
5
6
78.6
78.9
72.2
77.5
4.27 (dd, 7.2, 8.9) 78.6
4.25a
78.9
72.2
77.5
4.23a
4.07 (t, 9.0)
3.85a
4.10 (t, 8.9)
3.86 (m)
4.43 (dd, 9.2, 2.3) 62.9
4.26a
4.43 (dd, 9.2, 2.3
4.27a
Rha-1
2
3
4
5
6
Ag-1
2
3
4
5–9
6.33 (br s)
4.76 (br s)
4.69 (dd, 9.2, 3.2)
4.32 (dd, 8.9, 3.3)
5.00 (m)
101.8 6.34 (br s)
101.9 6.41 (br s)
72.1 4.70 (br s)
101.4
72.2
4.71 (dd, 9.2, 3.3) 70.0
72.1
72.4
74.1
69.4
18.6
177.1
35.2
25.6
29.6
25.1
29.5
29.8
29.9
30.1
34.6
80.2
37.3
4.74 (br s)
4.66 (dd, 9.2, 3.3) 72.4
4.32 (dd, 8.9, 3.3) 74.1
5.00 (m)
1.80 (d, 6.2)
5.94 (t, 9.4)
5.10 (m)
1.63 (d, 6.3)
75.6
66.9
18.3
172.7
69.4
18.6
175.3
43.8
68.4
37.9
25.2
26.1
30.0
30.0
30.3
34.6
80.1
37.3
1.80 (d, 6.1)
2.48 (t, 7.4)
1.73 (m)
2.87 (br d, 6.0)
4.53 (m)
1.70 (m)
1.68 (m)
1.54 (m)
2.70 (dd, 6.4, 3.1) 43.2
4.53 (m)
1.64–1.70 (m)
1.69 (m)
68.0
37.9
25.2
26.0
29.9
30.0
30.3
34.6
80.6
37.3
1.34a
1.69 (m)
1.20–1.40a
1.20–1.40a
1.20–1.40a
1.20–1.40a
1.65–1.80 (m)
3.88 (m)
1.63 (m)
1.26–1.47a
1.26–1.47a
1.26–1.47a
1.63–1.77 (m)
3.88 (m)
1.26–1.44a
1.26–1.44a
1.26–1.44a
1.65–1.74 (m)
3.88 (m)
10
11
12
1.77 (m)
1.60 (m)
1.75 (m)
1.58 (m)
1.78 (m)
1.60 (m)
13
14
OMe
ang-1
2
1.57 (m)
0.90 (t, 7.1)
18.6
14.2
1.65 (m)
0.90 (t, 7.1)
18.8
14.2
1.53 (m)
0.91 (t, 6.1)
3.61 (s)
18.5
14.2
51.1
167.7
128.4
137.3
3
5.88 (m)
4
2-Me
2.07 (dd, 7.2, 1.4) 16.0
2.00 (d, 1.4) 20.9
a
Signals are overlapping, S in ppm, J in Hz.

Journal of Asian Natural Products Research
137
determined as 11S by comparison of specific
rotation of methyl ester with those obtained
from Mexican jalap roots [10]. The absolute
configurations of sugars were determined by
direct comparison of specific optical rotation
with authentic samples and confirmed by
GC–MS with their TMSi-derivatives,
respectively. The connectivities between
the hydroxyl fatty acid aglycone and
oligosaccharide, and among monosacchar-
ides in 1 were supported by its HMBC
spectrum. The long-range correlations were
observed as follows: H-1 (dH 4.87) of Qui
with C-11 (dC 80.2) of the aglycone (11S-
convolvulinolic acid), H-1 (dH 5.87) of Glc
with C-2 (dC 79.6) of Qui, H-1 (dH 6.33) of
Rha with C-2 (dC 78.6) of Glc. These data
confirmed that the linkage of 1 was Rha-
(1 ! 2)-Glc-(1 ! 2)-Qui-(1 ! 11)-agly-
cone. Furthermore, the component sugar
moieties were determined to be b-quinopyr-
anosyl, b-glucopyranosyl, and a-rhamno-
13C NMR spectra of 2 were superimposable
on those of 1 except for signals due to the
aglycone moiety. Moreover, the HMBC and
13C NMR spectra demonstrated that the
oligosaccharide moieties of 1 and 2 were
identical. On mild acid hydrolysis, com-
pound 2 afforded D-quinovose, D-glucose,
L-rhamnose, and (3S, 11S)-dihydroxytetra-
decanoic acid (ipurolic acid) [11,12]. Thus,
2 was characterized as (3S,11S)-dihydrox-
ytetradecanoic acid 11-O-a-L-rhamnopyra-
nosyl-(1 ! 2)-O-b-D-glucopyranosyl-
(1 ! 2)-b-D-quinovopyranoside (Figure 1).
Poranaside A (3) had a molecular
formula of C38H66O18, as determined from
a quasi-molecular ion at m/z 811.4316
[M þ H]þ in the positive ion HR-ESI-MS.
Its 1H and 13C NMR spectra (Table 1)
displayed characteristic signals for a glyco-
sidic acid core closely similar to poranic acid
B (2), as well as additional resonances
indicating the presence of a methoxyl group
[dH 3.61 (3H, s)/dC 51.1] and a short organic
acid moiety (angeloyl moiety). The signals
readily distinguished for an olefinic methine
at dH 5.88 (m), an olefinic tertiary methyl
group at dH 2.00 (d, J ¼ 1.4 Hz), and an
olefinic secondary methyl group at dH 2.07
(dd, J ¼ 7.2, 1.4 Hz) in the 1H NMR
spectrum, and five correspounding carbon
resonances at dC 167.7, 137.3, 128.4, 20.9,
and 16.0 in the 13C NMR spectrum (Table 1)
which were due to the angeloyl moiety [13].
Compound 3 was then subjected to saponi-
fication with 5% KOH and the products
fractionated into organic and glycosidic acid
1
pyranosyl, respectively, by vicinal H–1H
coupling constants (Table 1). Accordingly, 1
was characterized as (11S)-hydroxytetrade-
canoic acid 11-O-a-L-rhamnopyranosyl-
(1 ! 2)-O-b-D-glucopyranosyl-(1 ! 2)-b-
D-quinovopyranoside (Figure 1).
The molecular formula of poranic acid
B (2), with m.p. 180–1838C, was deter-
mined as C32H58O17, by the negative ESI-
MS, showing the pseudo-molecular ion
peak at m/z 713 [M–H]2, along with
fragment peaks at m/z 567 and 405, all of
which were 16 mass units (OH) more than
those corresponding ions of 1. The 1H and
Figure 1. Structures of 1, 2, and 3.

138
W.-B. Ding et al.
fractions. The former examined by GC–MS
gave a peak corresponding to angelic acid,
with EI-MS ions at m/z 100 [M]þ(100), 85
(29), 72 (0.8), 55 (86), 53 (16), and 39 (25).
The glycosidic acid fraction furnished
poranic acid B (2), which was confirmed by
1H and 13C NMR and HPLC. The long-range
correlations were observed from OCH3 (dH
3.61) to the aglycone carbon (dC 172.7), and
from H-4 (dH 5.94) of Rha to the angeloyl
carbon (dC 167.7) in the HMBC spectrum.
The HMBC information indicated that the
aglycone was a methyl ester, while the
angeloyl moiety was located at C-4 of Rha.
Comparing the NMR spectral data of 3 with
its glycosidic acid core (2), the signal at 4-H
of Rha was shifted toward downfield by
1.62 ppm, and the C-1 of aglycone was
shifted toward upfield by 2.6ppm (Table 1),
which further confirmed the linkage of 3.
Therefore, the structure of poranaside A (3)
was characterized as (3S,11S)-dihydroxyte-
tradecanoic acid 11-O-(4-O-angeloyl)-a-L-
rhamnopyranosyl-(1 ! 2)-O-b-D-glucopyr-
anosyl-(1 ! 2)-b-D-quinovopyranoside,
methyl ester (Figure 1).
gel 60 (200–300 mesh, Qingdao Marine
Chemical Ltd, Qingdao, China), Develosil
ODS (50 mm, Nomura Chemical Co. Ltd.,
Osaka, Japan), and Sephadex LH-20 (GE
Healthcare, Uppsala, Sweden) were used.
Analytical GC was carried out on a
Shimadzu GCMS-QP2000 Plus apparatus
(Shimadzu Corporation, Tokyo, Japan)
with an ionization energy of 70 eV.
3.2 Plant material
The roots of P. duclouxii were collected in
Shennongjia, Hubei, China, in February
2012, and identified by Prof. Zhang Dai-
gui (Key Laboratory of Plant Resources
Conservation and Utilization, Jishou Uni-
versity). A voucher specimen (zdg3431)
has been deposited at Jishou University.
3.3 Extraction and isolation
The powdered air-dried roots of P. duclouxii
(150g) were extracted with methanol thrice
in an ultrasonic bath, each for 48h at room
temperature, and the extract was concen-
trated under reduced pressure to give 80g of
residue. The residue was suspended in water
and then extracted with EtOAc. A lot of
emulsion layer occurred between water and
EtOAc. The emulsion layer was concen-
trated under reduced pressure and subjected
to Sephadex LH-20 column chromatog-
raphytogiveacruderesinglycosidefraction
(R, 5.0 g). A part of R (2.0g) was further
subjected to ODS column chromatography,
using MeOH/H2O mixtures of decreasing
polarities (80:20 to 95:5) to give four
subfractions (R1–R4). R1 (150mg) was
separated by preparative HPLC using
MeOH/H2O (8:2, v/v) with a flow rate of
5 ml/min. Each peak was collected by
manual recycling, to afford poranaside A
(3) (30 mg, tR 45min). However, other
efforts to isolate individual components
from these sub-fractions were unsuccessful.
The resin glycoside fraction (2.0 g) was
treated with 5% KOH at 858C for 4 h.
The reaction mixture was acidified to pH 4.0
3. Experimental
3.1 General experimental procedures
Optical rotations were obtained on WZZ-
2B automatic polarimeter (Precision Instru-
ment Co., Shanghai, China); melting point
was measured using a X-4 micromelting
point apparatus (Cany Precision Instru-
ments Co., Shanghai, China). The 1H, 13C,
and 2D NMR spectra were recorded on a
Bruker DRX-400 instrument (Bruker BioS-
pin GmbH Company, Rheinstetten,
Germany) using TMS as an internal
standard. EI-MS and HR-ESI-MS data
were obtained on an API QSTAR mass
spectrometer (Applied Biosystem/MSD
Sciex, Concord, ON, Canada). Preparative
HPLC was performed with a Waters 1525
Binary HPLC pump and a Waters 2414
refractiveindexdetectorusingaYMC-Pack
ODS-A column (5 mm, 250 mm £ 20 mm).
For column chromatography (CC), silica

Journal of Asian Natural Products Research
and extracted with Et2O (50 ml £ 3). The 3.4 Acid hydrolysis of 1 and 2
139
aqueous layer was further extracted with n-
BuOH (3 £ 100 ml), and then the n-BuOH
layer was concentrated in vacuo to yield a
residue (540mg), which was subjected to
Sephadex LH-20 CC using MeOH to afford
a glycosidic acid fraction (300 mg). A
portion (100 mg) of this fraction was
subjected to preparative HPLC using
MeOH/H2O (7:3) with a flow rate of 5 ml/
min to obtain poranic acids A (1) (28 mg, tR
35min), B (2) (36 mg, tR 60min).
Compounds 1 and 2 (13 and 15 mg,
respectively) were separately dissolved in
5% H2SO4 (2 ml) and heated at 958C for
1 h. The reaction mixture was diluted with
H2O (2 ml) and then extracted with
Et2O. The Et2O layer was dried (anhydr.
Na2SO4) and concentrated to afford a
hydroxy fatty acid fraction. The hydroxy
fatty acid fraction was treated with CH2N2
to yield corresponding methyl ester 1a
(4.0 mg, 11S-hydroxytetradecanoate) and
2a (4.5 mg, 3S,11S-dihydroxytetradecano-
ate), respectively.
3.3.1 Poranic acid A (1)
20
Compound 1a: m.p. 26–288C; ½aꢀD þ 1.3
20
(c 0.3, CHCl3); 13C NMR (in CDCl3,
100 MHz) d: 14.1 (C-14), 18.8, 25.4, 24.7,
25.6, 29.1, 29.2, 29.4, 29.5, 29.6, 34.1,
37.5, 39.7, 51.6 (OCH3), 71.7 (C-11), and
174.3 (C-1). Its physical and spectral
properties were identical to that of (11S)-
hydroxytetradecanoate (convolvulinic
acid methyl ester) [10].
White powder, m.p. 175–1788C, ½aꢀD
224.0 (c 0.3, MeOH); For 1H NMR
(400 MHz, C5D5N) and 13C NMR
(100MHz, C5D5N) spectroscopic data, see
Table 1; positive ion ESI-MS m/z: 721
[M þ Na]þ; negative ESI-MS m/z: 697
[M–H]2, 551, 389, 243; HR-ESI-MS m/z:
697.3646 [M–H]2 (calcd for C32H57O16,
697.3652).
Compound
2a:
m.p.
67–708C;
½aꢀD þ 11.5 (c 0.5, CHCl3); 13C NMR
(in CDCl3, 100 MHz) d: 14.1 (C-14), 18.8,
25.4, 25.6, 29.4, 29.5, 29.6, 36.5, 37.5,
39.7, 41.1, 51.8 (OCH3), 68.0 (C-3), 71.7
(C-11), and 173.4 (C-1). Its physical
and spectral properties were identical to
that of (3S,11S)-dihydroxytetradecanoate
(ipurolic acid methyl ester) [11].
20
3.3.2 Poranic acid B (2)
20
White powder, m.p. 180–1838C, ½aꢀD
220.0 (c 0.3, MeOH); For 1H NMR
(400 MHz, C5D5N) and 13C NMR
(100MHz, C5D5N) spectroscopic data, see
Table 1; positive ion ESI-MS m/z: 737
[M þ Na]þ; negative ESI-MS m/z: 713
[M–H]2, 567, 405; HR-ESI-MS m/z:
713.3592 [M–H]2 (calcd for C32H57O17,
713.3601).
The aqueous layer was neutralized with
5% NaOH and desalted by passage through
a Sephadex LH-20 column using MeOH to
afford a mixture of sugars (6mg), from
which D-glucose (Rf 0.3), D-quinovose (Rf
0.51), and L-rhamnose (Rf 0.52) were
detected by TLC (CHCl3:MeOH:H2O,
6:4:1) [11]. An aliquot of the mixture was
separated by HPLC, using the Thermo
Hypersil GOLD Amino column 250 mm
£ 4.6 mm column, condition: 78% CH3CN:
H2O, flow rate 0.5 ml/min] to give
3.3.3 Poranaside A (3)
20
Colorless syrup, ½aꢀD 214.0 (c 0.1,
1
MeOH); For H NMR (400MHz, C5D5N)
and 13C NMR (100MHz, C5D5N) spectro-
scopic data, see Table 1; positive ion ESI-
MS m/z: 811 [M þ H]þ, 833 [M þ Na]þ;
negative ESI-MS m/z: 845 [M þ Cl]2, 809
[M–H]2; HR-ESI-MS m/z: 811.4316
[M þ H]þ (calcd for C38H67O18, 811.4322).
20
L-rhamnose [tR 14.0 min, ½aꢀD þ 6.8
(c 0.5, water)], D-quinovose [tR 14.2min,
20
½aꢀD þ 40.0 (c 0.3, water)], and D-glucose

140
W.-B. Ding et al.
20
[tR 20.1min, ½aꢀD þ 90.7 (c 0.4, water)].
Another aliquot of the mixture (1.0mg) was
derivatized with Sigma Sil-A for 35min at
708C and analyzed by GC–MS [HP-5MS
column (30 m £ 0.25mm, 0.25mm); injec-
tion temperature: 250.08C; column flow:
1.33 ml/min; ion source temperature:
200.08C; interface temperature: 220.08C],
showing tR of 9.11, 10.56, and 12.17 min,
identical to those of authentic L-rha, D-qui,
and D-glc (J&K Chemicalw, J&K Scientific
Ltd, Beijing, China) derivatives prepared in
a similar way, respectively.
[M]þ(100), 85 (29), 72 (0.8), 55 (86), 53
(16), and 39 (25).
Acknowledgements
This work was supported by the National
Nature Science Foundation of China (No.
31071715) and the Youth Innovation Foun-
dation of Hunan Agricultural University, China
(No. 12YJ07).
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KOH (3 ml) at 858C for 4 h. The reaction
mixture was acidified to pH 4.0 and
extracted with Et2O (3 £ 10ml). The Et2O
layer was dried (anhydr. MgSO4) and
concentrated to a small volume (about
0.2 ml) to afford a short chain organic acid
fraction. The aqueous layer was further
extracted with n-BuOH (3 £ 20ml). The n-
BuOHsolutionwasconcentratedinvacuoto
yield a residue which was subjected to
Sephadex LH-20 CC using MeOH to afford
a glycosidic acid 2 (15 mg). The short chain
organic acid fraction obtained from 3
(1.0mg) was examined by GC–MS using
a Shimadzu GCMS-QP2000 Plus apparatus,
equipped with Rxiw-5 ms fused silica
capillary column (30 m £ 0.25 mm,
0.25 mm). The carrier gas was helium.
Column temperature was initially 508C and
increased to 1608C at 208C/min and to
2208C at 58C/min, to give one predominant
peak which was identified to be angelic
acid (tR 3.7 min): EI-MS: m/z 100
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