A New Lupane-Type Triterpenoid Saponin from Lonicera macranthoides

Article abstract of DOI:10.1007/s10600-014-0826-y

A new lupane-type triterpenoid saponin, named lonimacranthoside A ₁, was isolated from the flower buds of Lonicera macranthoides. The structure of lonimacranthoside A₁ was elucidated as 3β-O-β-D-glucopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 3)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl-23- hydroxy-lup-20(29)-en-28-oic acid 28-O-β-D-glucopyranosyl-(1 → 6)-β-D-glucopyranosyl ester (1) on the basis of spectral data and chemical evidence. This is the first reported occurrence of a lupane-type saponin in the plant.

Full text of DOI:10.1007/s10600-014-0826-y

Chemistry of Natural Compounds, Vol. 49, No. 6, January, 2014 [Russian original No. 6, November–December, 2013]
A NEW LUPANE-TYPE TRITERPENOID SAPONIN
FROM Lonicera macranthoides
1,2
2
2
2
Yu Chen, Youyi Zhao, Ming Wang, Qizhi Wang,
UDC 547.918
2
2
1,2
Yu Shan, Fuqin Guan, and Xu Feng
*
A new lupane-type triterpenoid saponin, named lonimacranthoside A , was isolated from the flower buds of
1
Lonicera macranthoides. The structure of lonimacranthoside A was elucidated as 3ꢀ-O-ꢀ-D-glucopyranosyl-
1
(1ꢁ4)-ꢀ-D-glucopyranosyl-(1ꢁ3)-ꢂ-L-rhamnopyranosyl-(1ꢁ2)-ꢂ-L-arabinopyranosyl-23-hydroxy-lup-
20(29)-en-28-oic acid 28-O-ꢀ-D-glucopyranosyl-(1ꢁ6)-ꢀ-D-glucopyranosyl ester (1) on the basis of spectral
data and chemical evidence. This is the first reported occurrence of a lupane-type saponin in the plant.
Keywords: Lonicera macranthoides, Caprifoliaceae, lupane-type saponin, lonimacranthoside A .
1
Lupane-type triterpenes and their glycosides (saponins) have attracted increased attention in the past decade since
they exhibit a broad range of biological and medicinal properties such as anticancer, anti-inflammatory, anti-HIV, anti-malarial,
and antifeedant activities [1–6]. In contrast to the widely distributed oleanane-type triterpenoid saponins in nature, lupane-type
saponins are very scarce and occur mainly in plant species of the Acanthopanax, Arenaria, Schefflera, and Pulsatilla genera
[7]. The dried flower buds of Lonicera macranthoides Hand.-Mazz. (Caprifoliaceae) are used in Chinese traditional medicine
as an antipyretic and detoxic agent for treatment of fever, inflammation, and infectious diseases. In the preceding papers
[8–13], we elucidated the structures of 20 oleanane-type triterpenoid saponins isolated from the plant. Further investigation on
this plant has led to the isolation of a new lupane-type saponin named lonimacranthoside A (1). This is the first reported
1
occurrence of a lupane-type saponin in the plant. The present paper describes the isolation and structural elucidation of the
compound.
Lonimacranthoside A (1) was obtained as an amorphous powder. The molecular formula was established to be
1
+
C H
O
from its positive HR-ESI-MS data for the [M + H] at m/z 1399.6713 (calcd 1399.6745) and DEPT NMR spectra.
65 106 32
The spectral features and physicochemical properties revealed 1 to be a triterpenoid saponin. The five methyl groups [ꢃ 0.85,
1
0.94, 1.01, 1.09, and 1.66] and two olefinic protons (ꢃ 4.65 and 4.80) observed in the H NMR spectrum coupled with
13
information from the C NMR spectrum (five tertiary methyl carbons at ꢃ 13.8, 14.9, 16.4, 17.0, and 19.5, and two olefinic
carbons at ꢃ 110.0 and 150.9) suggested that the aglycone possessed a lup-20(29)-ene structure [14–16]. Acid hydrolysis of 1
afforded 23-hydroxybetulinic acid, which was identified by TLC and HPLC comparison with an authentic sample.
The chemical shifts of C-3 (ꢃ 81.3) and C-28 (ꢃ 175.0) revealed that 1 was a bisdesmosidic glycoside [14–16]. The
1
13
H and C NMR spectra of 1 exhibited six sugar anomeric protons at ꢃ 4.91 (1H, d, J = 7.8 Hz), 4.95 (1H, m), 5.06 (1H, d,
J = 7.9 Hz), 5.31 (1H, d, J = 7.8 Hz), 6.15 (1H, br.s), and 6.26 (1H, d, J = 8.2 Hz) and sugar anomeric carbons at ꢃ 95.2, 101.5, 104.6,
104.9, 105.3, and 106.4 (Table 1). The monosaccharides were identified as L-arabinose, L-rhamnose, and D-glucose (ratio 1:1:4) by
GC analysis with authentic monosaccharides and a combination of 2D NMR experiments. The ꢀ-anomeric configurations of the
glucose units were determined by their J
(7.8–8.2 Hz), the ꢂ-anomeric configuration of the arabinose was determined by H-1
H1,H2
(ꢃ 4.95)/H-3 (ꢃ 3.97) and H-1 (ꢃ 4.95)/H-5 (ꢃ 4.16) correlation peaks in the ROESY spectrum [17], and the ꢂ-anomeric configuration
of the rhamnose was determined by H-1 (ꢃ 6.15)/C-3 (ꢃ 83.4) and H-1 (ꢃ 6.15)/C-5 (ꢃ 69.7) correlation peaks in the HMBC spectrum.
1) Jiangsu Key Laboratory for Bioresources of Saline Soils, Jiangsu Institute of Botany, China Academy of Science,
Nanjing Botanical Garden Mem. Sun Yat-Sen, 210014, Nanjing, P. R. China, fax: +86 25 84347084, e-mail: fengxu@mail.cnbg.net;
2) Jiangsu Center for Research & Development of Medicinal Plants, Jiangsu Institute of Botany, China Academy of
Science/Nanjing Botanical Garden Mem. Sun Yat-Sen, 210014, Nanjing, P. R. China. Published in Khimiya Prirodnykh
Soedinenii, No. 6, November–December, 2013, pp. 934–936. Original article submitted September 11, 2012.
0009-3130/14/4906-1087 02014 Springer Science+Business Media New York
1087

1
13
TABLE 1. H (500 MHz) and C NMR (125 MHz) Spectral Data for 1 (pyridine-d , ꢃ, ppm, J/Hz)
5
C atom
HSQC
C atom
HSQC
ꢃC
ꢃC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
39.3
26.5
81.3
43.7
47.8
18.1
34.3
42.8
51.0
36.9
21.2
26.1
38.4
41.2
30.2
32.3
57.0
49.9
47.4
150.9
30.9
37.0
64.0
13.8
17.0
16.4
14.9
175.0
110.0
19.5
1.62 (m), 0.99 (m)
2.18 (m), 1.94 (m)
4.20 (m)
Rha (at Ara C-2)
1
2
3
4
5
6
101.5
71.6
83.4
72.8
69.7
18.4
6.15 (br.s)
4.83 (s)
4.72 (m)
4.38 (m)
4.58 (m)
1.50 (m)
1.60 (m)
1.67 (m), 1.35 (m)
1.45 (m), 1.19 (m)
Glc I (at Rha C-3)
1.40 (m)
1
2
3
4
5
6
106.4
75.4
76.6
81.2
76.6
61.9
5.31 (d, 7.8)
4.02 (m)
4.17 (m)
4.22 (m)
3.84 (m)
1.35 (m), 1.19 (m)
5.39 (br.s)
2.62 (m)
4.40(m), 4.34(m)
1.94(m), 1.07 (m)
2.56 (m), 1.43 (m)
Clc II (at Glc I C-4)
1
2
3
4
5
6
104.9
74.1
78.6
71.6
78.4
62.4
5.06 (d, 7.9)
4.04 (m)
3.81-4.18 ( m)
4.12 (m)
3.81-4.18 ( m)
4.43 (m), 4.19 (m)
1.67 (m)
3.34 (m), 1.60 (m)
2.15 (m), 1.37 (m)
2.18 (m), 1.43 (m)
4.17 (m), 3.80 (m)
1.01 (s)
Glc Iꢄ (at Aglycone C-28)
95.2
73.9
78.2
70.9
78.0
69.5
6.26 (d, 8.2)
4.03 (m)
3.81-4.18 ( m)
4.22 (m)
4.07 (m)
4.65 (m), 4.25 (m)
1
2
3
4
5
6
0.85 (s)
1.09 (s)
0.94 (s)
4.80 (s), 4.65 (s)
1.66 (s)
Glc IIꢄ (at Glc Iꢄ C-6)
105.3
75.1
78.3
71.5
78.4
62.7
4.91 (d, 7.8)
3.94 (m)
3.81-4.18 ( m)
4.07 (m)
3.81-4.18 ( m)
4.40 (m), 4.25 (m)
1
2
3
4
5
6
Ara (at Aglycone C-3)
1
2
3
4
5
104.6
75.5
74.7
69.4
65.9
4.95 (m)
4.43 (m)
3.97 (m)
4.07 (m)
4.16 (m), 3.59 (m)
______
Some HMBC key correlations of the aglycone: H-24/C-3, 4, 5, 23, H-25/C-26, H-26/C-8, 9, 14, H-27/C-8, 14, H-29/C-19, 30,
H-30/C-19, 20, 29.
29
30
3
H C
19
21
22
20
27
12
26
25
O
1
H
Glc II'
O
16
28
H
Glc I'
O
Ara
OH
CH OH
2
OH
15
O
3
O
HO
O
6
HO
OH
O
OH
OH
HO
Rha
CH OH
2
24
O
23
H
H
H C
O
3
HO
Glc II
HO
HO
OH
Glc I
OH
O
O
O
OH
O
HO
1
OH
OH
H
H
Fig. 1. Key HMBC correlations of 1.
1088

The sequence of the sugar linkages connected to C-3 of the aglycone was deduced from the following HMBC correlations:
H-1 (ꢃ 5.06) of Glc II with C-4 (ꢃ 81.2) of Glc I, H-1 (ꢃꢅ5.31) of Glc I with C-3 (ꢃꢅ83.4) of Rha, H-1 (ꢃꢅ6.15) of Rha with C-2
(ꢃꢅ75.5) of Ara, and H-1 (ꢃꢅ4.95) of Ara with C-3 (ꢃꢅ81.3) of aglycone (Fig. 1). The second bisdesmosidic part at C-28 was
established by the following HMBC information: the correlations between H-1 (ꢃ 4.91) of Glc IIꢄ and C-6 (ꢃ 69.5) of Glc Iꢄ,
and H-1 (ꢃ 6.26) of Glc Iꢄ and C-28 (ꢃ 175.0) of the aglycone (Fig. 1).
On the basis of the above evidence, lonimacranthoside A (1) was found to be a new compound and was established
1
as 3ꢀ-O-ꢀ-D-glucopyranosyl-(1ꢁ4)-ꢀ-D-glucopyranosyl-(1ꢁ3)-ꢂ-L-rhamnopyranosyl-(1ꢁ2)-ꢂ-L-arabinopyranosyl-23-
hydroxy-lup-20(29)-en-28-oic acid-28-O-ꢀ-D-glucopyranosyl-(1ꢁ6)-ꢀ-D-glucopyranosyl ester (1).
EXPERIMENTAL
General Methods. UV spectra, Shimadzu UV-2501PC. IR spectra, IMPACT 400 (KBr); NMR spectra, Bruker
AV-500; HR-ESI-MS spectra, Agilent 1100 LC/MSD TOF mass spectrometer. GC was carried out on a Shimadzu GC-2010
gas chromatograph with a DB-1701 capillary column (30 m ꢆ 0.25 mm) and an FID detector operating at 250ꢇC (column
temperature: initial temperature 150ꢇC for 3 min and rising 5ꢇC /min to final 200ꢇC), 30 mL/min N as carrier gas.
2
Plant Material. The flower buds of Lonicera macranthoides Hand.-Mazz., collected from Hunan Province of
P. R. China in 2010, were taxonomically identifided by Prof. Chang-Qi Yuan. A voucher specimen (20100720) was deposited
in Nanjing Botanical Garden Mem. Sun Yat-Sen, Nanjing, Jiangsu, China.
Extraction and Purification. The dried buds (8.0 kg) were extracted with H O (10.0 L) for 3 ꢆ 4 h at 60ꢇC. The
2
combined extract was evaporated to 5.0 L under reduced pressure and then passed through D 101 macroporous adsorbent
resin. The column was eluted with water, 30% EtOH, 70% EtOH, and 95% EtOH. The 30% EtOH fraction (132.0 g) was
chromatographed on a Sephadex LH-20 (1000.0 g) column using 35% EtOH to give nine fractions (A–I). Fraction C (2.0 g)
was repeatedly chromatographed on RP-C (YMC; 12 nm) and Sephadex LH-20 (Amersham Biosciences) columns using an
18
MeOH–H O solvent system to give compound 1 (18 mg).
2
Method for Acid Hydrolysis. Lonimacranthoside A (5 mg) was heated in 1 mL of 1 M HCl (dioxane–H O, 1:1) at
1
2
80ꢇC for 3 h in a water bath. Dioxane was removed and the solution was extracted with EtOAc (1 mL ꢆ 3). The EtOAc portion
was washed with water. Then the aglycone was obtained after removal of EtOAc. The aglycone was tested by TLC with an
authentic sample. The aqueous solution from the acid hydrolysis of saponin was neutralized by passing through an Amberlite
MB-3 resin column eluted with water, then concentrated and dried. The dried sugar mixture was dissolved in pyridine (0.5 mL)
and then treated with hexamethyldisilazane (0.2 mL) and trimethylchlorosilane (0.1 mL) at room temperature for 1 h. After
centrifugalization, the above fraction was analyzed by GC analysis with authentic monosaccharides.
27
Lonimacranthoside A (1). White amorphous powder. C H O . [ꢂ] –24.1ꢇ (c 0.2, MeOH). IR (KBr, ꢈ
,
1
65 106 32
D
max
–1
1
13
cm ): 3410 (OH), 2910 (CH), 1720 (C=O, ester), 1630 (unconjugated C=C), 1050 (C-O-C). H and C NMR, see Table 1.
HR-ESI-MS m/z [M + H] 1399.6713 (calcd 1399.6745), [M – H] at 1397.6544 (calcd 1397.6589).
+
–
ACKNOWLEDGMENT
This study was financially supported by the National Key Technologies R&D Program of China during the
11 Five-Year Plan Period (No. 2009ZX09103-397), Industry-Academy Cooperation Innovation Fund Projects of Jiangsu Province
th
(No. BY2012210), Jiangsu Province Special Foundation for Scientific and Technological Achievement Transformation
(No. BA2011001), and the Open Fund of Jiangsu Key Laboratory for Bioresources of Saline Soils (No. JKLBS2012006).
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