Compound 2 has molecular formula of C30H48O4
based on the NMR and positive ESI-MS data (m/z
473 [M+H]+). The spectroscopic data suggested that
2 belong to the urs-12-en-28-oic acid series. This
suggestion was confirmed by 1H-NMR signals at H
5.26 (br s, H-12), 2.22 (d, J = 11.5 Hz, H-18), 3.79
br s (H-3) together with 6 methyl groups [ H 0.84,
0.95, 1.05, 1.17 (each 3H, s), 0.92 (d, J = 6.5 Hz),
0.99 (br s)] and 13C-NMR signals at C 71.30 (C-3),
126.91 (C-12), 139.59 (C-13) and 181.63 (C-28).
Besides, its NMR spectra showed a hydroxymethylen group [( H 3.70, 3.41 (each d, J = 11.5
Hz), C 66.32)]. The HMBC correlations between
protons at H 3.70, 3.41 and carbons at C 22.81 (C-
23), 44.0 (C-4), 71.30 (C-3) confirmed the position
of the second hydroxyl group at C-24. The α
configuration of hydroxyl group at C-3 was
identified by the chemical shift and multiplicity peak
of hydroxyl-methine proton (3.79 ppm, brs). Thus,
the structure of 2 was determined as 3 ,24-
dihydroxy-urs-12-en-28-oic acid by comparison
with spectroscopic data in the literature [7].
Compound 3 gave the pseudo-molecular ion
peak at m/z 253 [M-H]- in the negative ESI-MS
spectrum, according to the molecular formula
C15H10O4 for this compound. Its 1H- and 13C-NMR of
3 showed an anthraquinone type, including six
aromatic protons of two aromatic rings. The
substituents in 3 were determined as two carbonyl
groups at C 182.30, 188.98, a hydroxyl group at C
159.7 and a hydroxymethyl group at H 4.87 (s, 2H);
C 59.13. The spectroscopic data of 3 were
indentical to those of 1-hydroxy-2-
hydroxymethylanthraquinone (digiferruginol) [8].
The molecular formula of 4 was deduced as
C10H12O4 from the negative ESI-MS spectrum (m/z
195 [M-H]-) and NMR data. Its 1H- NMR spectrum
revealed a typical pattern of a 1,3,4-trisubstituted
benzene ring at H 6.89 (d, J = 2.0 Hz), 6.88 (d, J =
8.2 Hz) and 6.81(dd, J = 2.0 & 8.2 Hz), one aromatic
methoxy group at H 3.89 (s, 3H) and one phenolic
hydroxyl group at H 5.72. A hydroxy-methylene
group attached to C-2’ was revealed by the signals at
H 3.88 (dd, J = 3.5 & 9.0 Hz), 4.24 (dd, J = 6.5 &
9.0 Hz) and C 71.64. In summary, the structure of 4
was elucidated as epoxyconiferyl alcohol by
comparison with spectroscopic data in the literature
[9].
Compound 5 indicated the pseudo-molecular ion
peak at m/z 383 [M+Na]+ in the positive ESI-MS
spectrum, according to the molecular formula
C20H24O6 of this compound. Analysis of the 1H-, 13CNMR and DEPT spectral data indicated 5 to be a
tetrahydrofuran-type lignan, showing six aromatic
protons in a pair of ABX system at δH 6.85 (d, J =
2.0 Hz), 6.86 (d, J = 8.0 Hz), 6.80 (dd, J = 2.0 & 8.0
Hz) and 6.68 (2H, m), 6.83 (d, J = 8.0 Hz), two oxymethylene groups at H 3.73-3.78 m, 3.92 m/ C
60.88) and 3.74 (dd, J = 6.2 & 8.5 Hz), 4.04 (dd, J =
6.5 & 8.5 Hz)/ C 72.88, two phenolic hydroxyl
groups at H 5.65, 5.56, two methoxy groups (δH
3.87, 3.86/δC 55.92), an oxy-methine group at H
4.78 (d, J = 7.0 Hz)/ C 82.83 and four aliphatic
protons. Finally, 5 was established as (+)
lariciresinol by comparison with spectroscopic data
and [ ]D value in the literatures [10]. Moreover, the
structure of 5 was also confirmed by 2D-NMR
methods
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Vietnam Journal of Chemistry, International Edition, 55(2): 202-206, 2017
DOI: 10.15625/2525-2321.2017-00444
202
Chemical constituents of Chirita drakei Burtt collected in Ha Long bay,
Quang Ninh province, Viet Nam
Part 1. Compounds isolated from the n-hexane and ethyl acetate extracts
Nguyen Thi Hoang Anh
1,2*
, Nguyen Van Tuan
2,3
, Tran Duc Quan
1
, Dao Duc Thien
1
,
Nguyen Thanh Tam
1
, Giang Thi Kim Lien
4
, Trinh Thi Thuy
1
, Tran Van Sung
1
1
Institute of Chemistry, Vietnam Academy of Science and Technology
2
Graduate University of Science and Technology, Vietnam Academy of Science and Technology
3
Asean College, Van Lam, Hung Yen, Vietnam
4
University of Da Nang
Received 14 March 2017; Accepted for publication 11 April 2017
Abstract
Two triterpenes, an anthraquinone, two lignans and a phenolic compound were isolated from the n-hexane and ethyl
acetate extracts of the aerial part of Chirita drakei Burtt collected in islands, on mountain slopes of Ha Long bay,
Quang Ninh province. Their structures have been elucidated by mass, NMR spectroscopy and comparison with
published data. There are no report on the chemical constituents of Chirita drakei before our study.
Keywords. Chirita drakei, triterpene, anthraquinone, lignin.
1. INTRODUCTION
Ha long bay is one of seven new world’s natural
wonders, which contains the full value of geology,
geomorphology and biodiversity. A set of different
plant species were found here, including mangrove
plants or species grow in coastal sand of islands, on
mountain slopes, on mountain peaks or in store.
Until now, 17 endemic plant species have been
detected in Ha long bay, for example Hedyotis
lecomtei, Allophylus leviscens, Chirita gemella, etc.
[1]. Chirita is the oldest genus of the Gesneriaceae
family, distributed in Malaysia, Southeast Asia and
south of China. Some Chirita species are used in
folk medicine as poultice, hemostasis agents or for
treatment of hypertension,... [2]. Until now there are
only few studies on chemical and biological
activities of the Chirita species. However, these
investigations revealed interesting results. For
example, in the folk medicine of China, Chirita
eburnea Hance is known as reagent to heal coughing
up blood, immunodeficiency diseases. Its chemical
composition contains 4 new -dunnion derivatives,
a new anthraquinone together with 7 known
anthraquinones. The ethyl acetate fraction of ethanol
extract together with two new compounds: (R)-7,8-
dihydroxy- -dunnion, (R)-7-methoxy-6,8-
dihydroxy- -dunnione revealed free radical
scavenging activity with IC50 value of 5.2 µg/mL,
8.4 µM, and 3.6 µM, respectively while of
ascorbate 6.8 µM [3]. Chirita fimbrisepala is used in
folk medicine for treatment of inflammatory such as
hepatitis, enteritis. One of four isolated compounds
from the roots of this plant is a new flavone
glycoside, named mahuangchiside [4]. Therefore, in
order to contribute to the understanding, research,
evaluation, protection, maintenance, and exploitation
of the genetic resources of rare plant species
growing in the Ha Long Bay, the chemical
composition Chirita drakei Burtt species were
investigated. This paper deals with the isolation and
structural elucidation of 6 compounds from the n-
hexane and ethyl acetate extracts of C. drakei’s
aerial parts. All isolated compounds, except 3, were
obtained for the first time from Chirita genus.
2. EXPERIMENTAL
2.1. Equipments and methods
IR: Impact 410, Nicolet, Germany; ESI-MS: LC-
MSD-Trap-SL, Varian, USA, NMR: Bruker Avance
500, Germany with TMS as internal reference (for
1
H) and solvent signal (for
13
C). CC used silica gel
VJC, 55(2), 2017 Nguyen Thi Hoang Anh et al.
203
60G, size 0.043-0.063 mm (Merck), TLC: precoated
silica gel G60F254 plates (Merck), spots were
detected by spraying with vanillin 1 % in conc.
H2SO4 and heating at 110
o
C.
2.2. Plant material
The aerial parts of Chirita drakei were collected
in the islands of Ha Long Bay, Quang Ninh
province, Vietnam in October 2013. A voucher
specimen (VHH.HL 10.2013.1) is deposited in
Institute of Chemistry, VAST, Hanoi, Vietnam. The
scientific name was identified by Dr. Tran Thi
Phuong Anh, Viet Nam National Museum of Nature,
VAST, Hanoi, Vietnam.
2.3. Extraction and isolation of the compounds
The aerial parts of C. drakei (1.7 kg) were
extracted with MeOH:H2O (9:1) (four times) at
room temperature. The methanol extract was
concentrated under vacuum and then aqueous
solution was extracted with n-hexane, EtOAc and
n-BuOH, successively. The solvent was evaporated
in vacuum to afford n-hexane (10.0 g), EtOAc (10.8
g) and n-BuOH (55.0 g) extracts.
The n-hexane extract (10.0 g) was separated by
chromatography on silica gel, eluting gradient with
n-hexane: EtOAc to furnish 10 fractions (H1-H10),
which were combined according to TLC monitoring.
The third fraction H3 (250 mg) was further purified
over silica gel column with n-hexane:EtOAc (from
9:1 to 8:2) as eluting solvent to yield 7 mg of
compound 1. The tenth fraction H10 (40 mg) was
chromatographed on silica gel with n-hexane:EtOAc
(7:3) to give 11 mg compound 2.
The EtOAc extract (10.8 g) was given on silica
gel column, eluting gradient with CH2Cl2:MeOH
(from 100:0 to 0:100) to furnish 12 fractions (E1-
E12). The fifth fraction E5 (350 mg) was further
purified over silica gel column with
n-hexane:EtOAc (2:1) as eluent to yield 5 mg of
compound 3 and 15 mg of 4. The seventh fraction
E7 (350 mg) was given over silica gel column,
eluted with n-hexane:EtOAc (6:4) to furnish 11 mg
of compound 5. Compound 6 (15 mg) was obtained
by repeated silica gel column chromatography of
fraction E10 with CH2Cl2:MeOH (10:1). Besides,
-sitosterol and -sitosterol glucoside were isolated
from fraction E3 and E12, respectively, by
crystallization method.
24-methylen-lanost-8-en-3 -ol (1)
Amorphous white powder. ESI-MS: m/z: 441
[M+H]
+
, C31H53O.
1
H-NMR (500 MHz, CD3OD), H (ppm), J (Hz):
4.71, 4.66 (each br s, 2H-24), 3.24 (dd, J = 4.0; 11.5,
H-3), 0.69, 0.81, 0.88, 0.98, 1.00 (each s, 3H, CH3-
18, 19, 28, 29, 30), 0.92 (d, J = 6.5, CH3-21), 1.02,
1.03 (each d, J = 6.5, CH3-26, 27).
13
C-NMR (125 MHz, CD3OD) C (ppm): 35.59
(C-1), 27.86 (C-2), 79.01 (C-3), 38.90 (C-4), 50.39
(C-5), 18.26 (C-6), 28.21 (C-7), 134.41 (C-8, C-9),
37.03 (C-10), 21.01 (C-11), 26.51 (C-12), 44.51 (C-
13), 49.82 (C-14), 31.00 (C-15), 30.85 (C-16), 50.41
(C-17), 15.76 (C-18), 18.72 (C-19), 36.49 (C-20),
19.15 (C-21), 35.59 (C-22), 31.29 (C-23), 156.94
(C-24), 34.99 (C-25), 22.00 (C-26), 21.87 (C-27),
15.43 (C-28), 27.97 (C-29), 24.27 (C-30), 105.93
(C-24
1
).
3 ,24-dihydroxy-urs-12-ene-28-oic acid (2)
Amorphous white powder. ESI-MS: m/z 473
[M+H]
+
, 471 [M-H]
-
(C30H48O4).
1
H-NMR (500 MHz, CD3OD) H: 3.79 (br s, H-
3), 5.26 (br s, H-12), 2.22 (d, J = 11.5 Hz, H-18),
3.70, 3.41 (each d, J = 11.5 Hz, 2H-24).
13
C-NMR (125 MHz, CD3OD) C: 34.38 (C-1),
71.30 (C-3), 126.91 (C-12), 139.59 (C-13), 54.39
(C-18), 66.32 (C-24), 181.63 (C-28), 17.67 (C-29),
21.57 (C-30).
Digiferruginol (3)
Orange-yellow powder. ESI-MS: m/z 253 [M-
H]
-
C15H10O4.
1
H- and
13
C-NMR, see table 1.
Epoxyconiferyl alcohol (4)
Amorphous brown-black powder. ESI-MS: m/z
195 [M-H]
-
(C10H12O4).
1
H- and
13
C-NMR, see table 1.
Lariciresinol (5)
White powder. [ ]D
25
(MeOH, c 0.1) = +32
0
.
ESI-MS: m/z 383 [M+Na]
+
C20H24O6Na.
1
H- and
13
C-NMR, see table 1.
Isolariciresinol (6)
White powder. [ ]D
25
(MeOH, c 0.1) = +41
0
.
ESI-MS: m/z 359 [M-H]
-
C20H23O6.
1
H- and
13
C-
NMR, see table 1.
3. RESULTS AND DISCUSSION
Six compounds were isolated from n-hexane and
ethyl acetate extracts of the aerial parts of C. drakei
by repeated column chromatography with the
appropriate solvent systems. Their structures were
identified as 24-methylen-lanost-8-en-3 -ol (1),
3 ,24-dihydroxy-urs-12-en-28-oic acid (2),
digiferruginol (3), epoxyconiferyl alcohol (4),
VJC, 55(2), 2017 Chemical constituents of Chirita drakei
204
lariciresinol (5), isolariciresinol (6) by the analysis of
their 1D, 2D-NMR, ESI-MS spectra and compared
with published data.
Compound 1 showed the pseudo molecular ion
peak at m/z 441 [M+H]
+
in the positive ESI-MS
spectrum, according to the molecular formula
C31H52O of this compound. Its
1
H-NMR spectrum
revealed signals of 8 methyl groups [ H 0.69, 0.81,
0.88, 0.98, 1.00 (each 3H, s), 0.92 (d, J = 6.5 Hz),
1.02, 1.03 (each d, J = 6.5 Hz)], one hydroxy-methin
group at H 3.24 (dd, J = 4.0 & 11.5 Hz), one
>C=CH2 group at H 4.71, 4.66 (each 1H, br s), and
aliphatic protons resonanced in the range of 1.10-
2.30 ppm. Besides the carbon signals, which are
suitable with
1
H-NMR data, the
13
C-NMR spectrum
indicated the presence of totally substituted double
bond at C 134.41 (x2C). These two carbons are the
characteristic signals of double bond at C8-C9 in
lanosten-type triterpene. Consequently, the structure
of 1 was identified as 24-methylen-lanost-8-en-3 -ol
from the analysis mentioned above and compared
with reported data [5, 6]. It was isolated for the first
time from Neolitsea sericea species, Lauraceae
family.
Compound 2 has molecular formula of C30H48O4
based on the NMR and positive ESI-MS data (m/z
473 [M+H]
+
). The spectroscopic data suggested that
2 belong to the urs-12-en-28-oic acid series. This
suggestion was confirmed by
1
H-NMR signals at H
5.26 (br s, H-12), 2.22 (d, J = 11.5 Hz, H-18), 3.79
br s (H-3) together with 6 methyl groups [ H 0.84,
0.95, 1.05, 1.17 (each 3H, s), 0.92 (d, J = 6.5 Hz),
0.99 (br s)] and
13
C-NMR signals at C 71.30 (C-3),
126.91 (C-12), 139.59 (C-13) and 181.63 (C-28).
Besides, its NMR spectra showed a hydroxy-
methylen group [( H 3.70, 3.41 (each d, J = 11.5
Hz), C 66.32)]. The HMBC correlations between
protons at H 3.70, 3.41 and carbons at C 22.81 (C-
23), 44.0 (C-4), 71.30 (C-3) confirmed the position
of the second hydroxyl group at C-24. The α
configuration of hydroxyl group at C-3 was
identified by the chemical shift and multiplicity peak
of hydroxyl-methine proton (3.79 ppm, brs). Thus,
the structure of 2 was determined as 3 ,24-
dihydroxy-urs-12-en-28-oic acid by comparison
with spectroscopic data in the literature [7].
Compound 3 gave the pseudo-molecular ion
peak at m/z 253 [M-H]
-
in the negative ESI-MS
spectrum, according to the molecular formula
C15H10O4 for this compound. Its
1
H- and
13
C-NMR of
3 showed an anthraquinone type, including six
aromatic protons of two aromatic rings. The
substituents in 3 were determined as two carbonyl
groups at C 182.30, 188.98, a hydroxyl group at C
159.7 and a hydroxymethyl group at H 4.87 (s, 2H);
C 59.13. The spectroscopic data of 3 were
indentical to those of 1-hydroxy-2-
hydroxymethylanthraquinone (digiferruginol) [8].
The molecular formula of 4 was deduced as
C10H12O4 from the negative ESI-MS spectrum (m/z
195 [M-H]
-
) and NMR data. Its
1
H- NMR spectrum
revealed a typical pattern of a 1,3,4-trisubstituted
benzene ring at H 6.89 (d, J = 2.0 Hz), 6.88 (d, J =
8.2 Hz) and 6.81(dd, J = 2.0 & 8.2 Hz), one aromatic
methoxy group at H 3.89 (s, 3H) and one phenolic
hydroxyl group at H 5.72. A hydroxy-methylene
group attached to C-2
’
was revealed by the signals at
H 3.88 (dd, J = 3.5 & 9.0 Hz), 4.24 (dd, J = 6.5 &
9.0 Hz) and C 71.64. In summary, the structure of 4
was elucidated as epoxyconiferyl alcohol by
comparison with spectroscopic data in the literature
[9].
Compound 5 indicated the pseudo-molecular ion
peak at m/z 383 [M+Na]
+
in the positive ESI-MS
spectrum, according to the molecular formula
C20H24O6 of this compound. Analysis of the
1
H-,
13
C-
NMR and DEPT spectral data indicated 5 to be a
tetrahydrofuran-type lignan, showing six aromatic
protons in a pair of ABX system at δH 6.85 (d, J =
2.0 Hz), 6.86 (d, J = 8.0 Hz), 6.80 (dd, J = 2.0 & 8.0
Hz) and 6.68 (2H, m), 6.83 (d, J = 8.0 Hz), two oxy-
methylene groups at H 3.73-3.78 m, 3.92 m/ C
60.88) and 3.74 (dd, J = 6.2 & 8.5 Hz), 4.04 (dd, J =
6.5 & 8.5 Hz)/ C 72.88, two phenolic hydroxyl
groups at H 5.65, 5.56, two methoxy groups (δH
3.87, 3.86/δC 55.92), an oxy-methine group at H
4.78 (d, J = 7.0 Hz)/ C 82.83 and four aliphatic
protons. Finally, 5 was established as (+)
lariciresinol by comparison with spectroscopic data
and [ ]D value in the literatures [10]. Moreover, the
structure of 5 was also confirmed by 2D-NMR
methods.
Compound 6 has the same molecular formula of
C20H24O6 as of 5 based on ESI-MS (m/z 359 [M-H]
-
)
and NMR data. Its NMR spectra were very similar
to those of 5 with two exceptions. The first is the
disappearance of one aromatic proton in
1
H-NMR of
6. The second, an oxy-methine group in 5 was
replaced by methine group at H 3.82 (d, J = 10.0
Hz)/ C 48.06 in NMR spectra of 6. Combination of
the above spectroscopic analysis and comparison
with spectroscopic data and [ ]D value in [11] led to
conclusion that 6 is (+) isolariciresinol. The
reassignment of signals CH-2, CH-3 and CH-5',
CH-6' in the literature based on the corrections
between H-2 (6.67 ppm) and C-7 (33.57 ppm), H-5
(6.21 ppm) and C-7’ (48.06 ppm), H-5’ (6.76 ppm)
and C-1’ (138.62 ppm), H-6’ (6.63 ppm) and C-7’
VJC, 55(2), 2017 Nguyen Thi Hoang Anh et al.
205
Table 1:
1
H- and
13
C-NMR (500 and 125 MHz) data of compounds 3-5 (CDCl3) and 6 (CD3OD)
C
1
H
13
C
3 4 5 6 3 4 5 6
1 - - - - 159.70 C 132.88 C 134.79 C 129.03 C
2
- 6.89 d
(2.0)
6.85 d (2.0) 6.67 s
137.99 C 108.66 CH 108.36 CH 112.41 CH
3
7.77 d
(7.8)
- - -
134.09 CH 146.74 C 146.65 C 147.20 C
4
7.85 d
(7.8)
- - -
119.34 CH 145.26 C 145.04 C 145.27 C
5 8.30 m 6.88 d (8.2) 6.86 d (8.0) 6.21 s 127.30
+
CH 114.31 CH 114.20 CH 117.35 CH
5a - - - - 133.21*C - - -
6
7.82 m 6.81 dd
(2.0 & 8.2)
6.80 dd
(1.5 & 8.0)
-
134.14
#
CH 118.94 CH
118.75 CH
134.17 C
7 7.82 m - 4.78 d (7.0) 2.79 d (7.5) 134.69
#
CH - 82.83 CH 33.57 CH2
8 8.30 m - 2.40 m 2.02 m 126.84
+
CH - 52.58 CH 40.03 CH
8a - - - - 133.73*C - - -
9
- - 3.73-3.78 m
3.92 m
3.71 m (2H)
188.98 C - 60.88 CH2 65.98 CH2
9a - - - - 115.20 C - - -
10 - - - - 182.30 C - - -
10a - - - - 131.85 C - - -
1’
4.87 s
3.88 dd
(3.5 & 9.0)
4.24 dd
(6.5 & 9.0)
- -
59.13 CH2 71.64 CH2
132.28 C
138.62 C
2’ - 3.10 m 6.68 m 6.70 d (1.5) - 54.13 CH 111.24 CH 113.82 CH
3’ - 4.74 d (4.5) - - - 85.86 CH 146.55 C 149.01 C
4’ - - - - - - 144.01 C 145.94 C
5’ - - 6.83 d (8.0) 6.76 d (8.0) - - 114.44 CH 115.99 CH
6’
- - 6.68 m 6.63 dd
(1.5 & 8.0)
- - 121.97 CH 123.20 CH
7’
- - 2.54 dd
(10.5 &
13.0)
2.90 dd
(5.0 &
13.5)
3.82 d
(10.0)
- -
33.30 CH2
48.06 CH
8’ - - 2.72 m 1.79 t (10.0) - - 42.41 CH 48.02 CH
9’
- - 3.74 dd
(6.2 & 8.5)
4.04 dd
(6.5 & 8.5)
3.42 dd
(4.0 & 11.0)
3.67 d (4.0)
- - 72.88 CH2 62.27 CH2
OMe - 3.89 s 3.87 s 3.79 s - 55.94 CH3 55.92 56.36 CH3
OMe - - 3.86 s 3.82 s - - 55.92 56.41 CH3
CH2OH 2.35 brs - - - - - - -
OH-1 13.01 s - - - - - - -
OH-4 - 5.72 s 5.65 s - - - - -
OH-4’ - - 5.56 s - - - - -
(48.06 ppm) in the HMBC spectrum. (+)
lariciresinol and (+) isolariciresinol were isolated
before from medicinal plant Fagraea racemosa [10].
The structure of compounds 1-6.
VJC, 55(2), 2017 Chemical constituents of Chirita drakei
206
1: 24-methylen-lanost-8-en-3 -ol
2: 3 ,24-dihydroxy-urs-12-en-28-oic acid
3: Digiferruginol
4: Epoxyconiferyl alcohol
5: (+)-Lariciresinol
6: (+)-Isolariciresinol
Acknowledgments. We would like to thank the
National Foundation for Science and Technology
Development of Vietnam (NAFOSTED) for financial
support (Reference code 104.01.2013.59).
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Corresponding author: Nguyen Thi Hoang Anh
Institute of Chemistry
Vietnam Academy of Science and Technology
No. 18, Hoang Quoc Viet, Cau Giay District, Hanoi
E-mail: hoanganhvhh@gmail.com.
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