Three new muurolane-type sesquiterpene glycosides from the whole plants of Balanophora fungosa subsp. indica

Article abstract of DOI:10.1080/14786419.2019.1602831

Three new muurolane type sesquiterpene glycosides, named balanoindicosides A ? C (1 ? 3), were isolated from the whole plant of Balanophora fungosa subsp. indica using various chromatographic methods. Their structures were determined by extensive analysis of HR-ESI-MS and NMR spectroscopy. The stereochemistry of muurolane sesquiterpene backbone was demonstrated by NOESY analysis. Configuration of C-12 in compounds 2 and 3 could be distinguished by chemical shift value of C-14. Compounds 1-3 exhibited weak cytotoxic activity towards HepG-2, HL-60, LU-1, and MCF-7 cell lines.

Full text of DOI:10.1080/14786419.2019.1602831

Natural Product Research
Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: https://www.tandfonline.com/loi/gnpl20
Three new muurolane-type sesquiterpene
glycosides from the whole plants of Balanophora
fungosa subsp. indica
Bui Huu Tai, Nguyen Xuan Nhiem, Pham Hai Yen, Tran Hong Quang, Nguyen
Thi Cuc, Do Thi Trang, Vu Van Doan, Dan Thi Thuy Hang, Chau Van Minh &
Phan Van Kiem
To cite this article: Bui Huu Tai, Nguyen Xuan Nhiem, Pham Hai Yen, Tran Hong Quang, Nguyen
Thi Cuc, Do Thi Trang, Vu Van Doan, Dan Thi Thuy Hang, Chau Van Minh & Phan Van Kiem
(2019): Three new muurolane-type sesquiterpene glycosides from the whole plants of Balanophora
fungosa subsp. indica, Natural Product Research, DOI: 10.1080/14786419.2019.1602831
To link to this article: https://doi.org/10.1080/14786419.2019.1602831
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NATURAL PRODUCT RESEARCH
https://doi.org/10.1080/14786419.2019.1602831
Three new muurolane-type sesquiterpene glycosides from
the whole plants of Balanophora fungosa subsp. indica
a,b
a,b
a,b
a
Bui Huu Tai , Nguyen Xuan Nhiem , Pham Hai Yen , Tran Hong Quang ,
a
a
a
a
Nguyen Thi Cuc , Do Thi Trang , Vu Van Doan , Dan Thi Thuy Hang ,
Chau Van Minh and Phan Van Kiem
a
a,b
a
Institute of Marine Biochemistry, Vietnam Academy of Science and Technology (VAST), Hanoi,
b
Vietnam; Graduate University of Science and Technology, VAST, Hanoi, Vietnam
ABSTRACT
ARTICLE HISTORY
Three new muurolane type sesquiterpene glycosides, named
balanoindicosides A ꢀ C (1 ꢀ 3), were isolated from the whole
plant of Balanophora fungosa subsp. indica using various
chromatographic methods. Their structures were determined by
extensive analysis of HR-ESI-MS and NMR spectroscopy. The
stereochemistry of muurolane sesquiterpene backbone was dem-
onstrated by NOESY analysis. Configuration of C-12 in compounds
Received 26 December 2018
Accepted 24 March 2019
KEYWORDS
Balanophora fungosa;
balanoindicoside A;
balanoindicoside B;
balanoindicoside C;
muurolane sesquiterpene
glycoside
2
and 3 could be distinguished by chemical shift value of C-14.
Compounds 1-3 exhibited weak cytotoxic activity towards HepG-
, HL-60, LU-1, and MCF-7 cell lines.
2
CONTACT Phan Van Kiem
phankiem@yahoo.com
Institute of Marine Biochemistry, Vietnam Academy of
Science and Technology, 18-Hoang Quoc Viet, Caugiay, Hanoi, Vietnam.
Supplemental data for this article can be accessed at https://doi.org/10.1080/14786419.2019.1602831.
ß 2019 Informa UK Limited, trading as Taylor & Francis Group

2
B. HUU TAI ET AL.
Figure 1. Chemical structures of compounds 1–3 isolated from B. fungosa subsp. indica.
1. Introduction
Balanophora genus comprises parasitic plants and mainly distributed in the sub-tropic
and tropic regions. Balanophora species are normally parasitized on the roots of ever-
green trees. They do not have green leaves and their aerial parts look like a mush-
room rather a flowering plant. In traditional medicines, various Balanophora species
such as B. abbreviata, B. fungosa, B. japonica, B. laxiflora have been used for antidote,
antipyretic, antiseptic, and tonic properties (Hosokawa et al. 2004; Jiang et al. 2008;
Panthama et al. 2009; She et al. 2009; Quang et al. 2018). Previous studies remarked
that Balanophora genus contains triterpenes, flavonoids, lignans, phenolic acid deriva-
tives, and hydrolysable tannins (Hosoya et al. 2010; She et al. 2013; Wei et al. 2017). In
our study program on chemical constituents of Balanophora parasitic plants, the whole
plants of B. fungosa subsp. indica were macerated in methanol. Crude extract was suc-
cessively partitioned in dichloromethane and ethyl acetate. Obtained water-soluble
fraction was further purified by chromatographic methods to yield three compounds
1
–3. Their structures (Figure 1) were determined to be new muurolane sesquiterpene
glycosides using HR-ESI-MS and NMR spectroscopy.
2. Results and discussion
Compound 1 was obtained as a white amorphous powder. In the negative mode HR-
ꢀ
ESI-MS of 1, quasi-molecular ion peaks at m/z 451.2107 [M þ Cl] (calcd. for
-
C H O Cl, 451.2099) and m/z 461.2398 [M þ HCOO] (calcd. for C H O , 461.2387)
2
1
36
8
22 37 10
indicated that compound 1 had molecular formula of C H O , showing four degrees
of unsaturation. The H-NMR spectrum of 1 contained signals of 3 methyl groups (a
singlet at d 1.03 and two doublet at d 0.95 and 0.82), an olefinic proton at d 5.86
21 36 8
1
H
H
H
13
(
br s), and an anomeric proton at d 4.24 (d, J ¼ 7.6 Hz). The C-NMR contained sig-
H
nals of 21 carbons which were classified by HSQC into 3 methyl groups, 5 methylenes,
1 methines, and 2 non-protonated carbons. In addition, the HSQC spectrum of 1
1
revealed signals for a glucopyranosyl group at d 102.8/d 4.24 (d, J ¼ 7.6 Hz), d 78.2/
C
H
C
d 3.35 (t, J ¼ 9.2 Hz), d 78.0/d 3.23 (m), d 75.1/d 3.19 (dd, J ¼ 7.6, 9.2 Hz), d 71.7/
H
C
H
C
H
C
d
3.27 (t, J ¼ 9.2 Hz), d 62.8/d 3.87 (br d, 11.6 Hz) and 3.66 (dd, J ¼ 5.6, 11.6 Hz).
H
C
H
Fifteen remaining carbon signals suggested 1 to be a structure of sesquiterpene. Two
sp carbon signals (d 136.8 and 127.2) indicated the presence of a C-C double bond.
2
C
Therefore, the four degrees of unsaturation indicated that compound 1 was a bicyclic
sesquiterpene glycoside. Except for sugar moiety, NMR data of aglycone of 1 was

NATURAL PRODUCT RESEARCH
3
recognized in close similarity with that of dendronobilin G, a muurolane-type sesqui-
terpene (Zhang et al. 2007). An O-glucopyranosyl group binding at C-11 was con-
firmed by downfield shifted of C-11 (d 74.1) in comparison with that of free hydroxy
C
group in dendronobilin G (dC-11 67.3) (Zhang et al. 2007) and further confirmed by
0
HMBC correlation between anomeric H-1 (d 4.24) and C-11 (d 74.1). The presence of
H
C
D-glucose moiety in 1 was further confirmed by acid hydrolysis, converted to thiocar-
bamoylthiazolidine derivative, and followed by HPLC analysis (Tanaka et al. 2007) in
comparison with authentic D/L-glucose (Supporting information). Configurations of
muurolane-type backbone (beta orientation of H-1, H-6, and isopropyl group at C-7)
were supported by NOESY correlations between H-1 (d 1.21) and H-6 (d 1.81), H-6
H
H
and H -13 (d 0.82). The NOESY correlations between H -15 (d 1.03) and H-1/H-6 indi-
3
H
3
H
cated beta orientation of C-15 meanwhile NOESY correlations between H-9 (dH 3.42)
and H-7 (dH 1.22) suggested both alpha-axial orientations of H-7 and H-9.
Consequently, structure of compound 1 was determined to be 9b,10a,11-trihydroxy-
muurol-4-ene 11-O-b-D-glucopyranoside and named as balanoindicoside A
Compound 2 was obtained as a white amorphous powder. In the HR-ESI-MS of
ꢀ
compound 2, quasi-molecular ion peaks at m/z 451.2109 [M þ Cl] (calcd. for
-
C H O Cl, 451.2099) and m/z 461.2395 [M þ HCOO] (calcd. for C H O , 461.2387)
2
1
36
8
22 37 10
indicated that compound 2 was an isomer of 1, sharing the same molecular formula
C H O . The NMR data 2 (Table S1) suggested that it differed from compound 1 in
2
2 36 8
1
the structure of aglycone moiety. Specifically, the H-NMR of 2 contained two methyl
groups at d 1.18 (s) and d 0.97 (d, J ¼ 7.2 Hz), indicating the presence of substituted
H
H
group at C-12, C-13, or C-14 of muurolane backbone. The singlet methyl signal at dH
1
.18 was assigned to H -15 from its HMBC correlation with methine C-1 (d 47.2). The
3 C
HMBC correlations between H -15 and methylene C-9 (d 35.5)/non-protonated C-10
3
C
(
d 73.1) indicated a hydroxy group at C-10. The HMBC correlations between H -14 (d
C
3
H
0
.97) and methine C-7 (d 44.0)/methine C-12 (d 34.0)/methylene C-13 (d 72.9) con-
C C C
firmed an oxygenated group at C-13. A free hydroxy group at C-11 was deduced from
upfield shifted d value (d 67.5) in comparison with compound 1 (dC-11 74.1) and in
C
C-11
consistence with the literature (dendronobilin G, dC-11 67.3) (Zhang et al. 2007).
Location of double bond was also determined at C-4/C-5 by HMBC correlations
between H -11 (d 3.93) and C-4 (d 138.4)/C-5 (d 127.5), H-5 (d 5.97) and C-6 (d
C
2
H
C
C
H
3
1
5.1). An O-glycosidic linkage at C-13 was confirmed by HMBC correlation between H-
0
(dH 4.25) and C-13 (d 72.9). Acid hydrolysis of 2 gave D-glucose which was con-
C
firmed by HPLC analysis its thiocarbamoylthiazolidine derivative in comparison with
authentic samples (Supporting information). Similar to compound 1, the NOESY corre-
lations between H-1 (d 1.58) and H-6 (d 2.60), H-6 and H-13 (d 3.67, 3.75) supported
H
H
H
for the beta orientations of H-1, H-6, and isopropyl fragment in the muurolane back-
bone. The appearance of NOESY correlations between H -15 and H -9 (d 1.50, 1.45)
3
2
H
suggested for axial location (beta-orientation) of hydroxy group at C-10. This deduc-
tion was agreed by the slight downfield shifted of C-10 (dC 73.1) as compared to
alpha-oriented hydroxy group (dC-10 71.7) (Kim et al. 2014). Because of glycosylation at
C-13, an additional chiral carbon is formed at C-12. Its relative R-configuration was pro-
posed by chemical shift value of adjusted methyl C-14 (dC-14 16.8) in comparison with
that reported in the literature (rel-R: dC-14 15.1 and rel-S: dC-14 10.2) (Collins et al. 2002).

4
B. HUU TAI ET AL.
ꢁ
Finally, structure of compound 2 was established to be (12R )-10b,11,13-trihydroxy-
muurol-4-ene 13-O-b-D-glucopyranoside and named as balanoindicoside B.
Compound 3 was obtained as a white amorphous powder. Its molecular formula
ꢀ
was determined as C H O by quasi-molecular ion peaks at m/z 449.1951 [M þ Cl]
21 34 8
-
(
calcd. for C H O Cl, 449.1942) and m/z 459.2241 [M þ HCOO] (calcd. for C H O ,
2
1
34
8
22 35 10
4
59.2230) in the HR-ESI-MS, showing five degrees of unsaturation. Like compounds 1
and 2, compound 3 was expected to be a muurolane-type bicyclic sesquiterpene
13
glycoside by its spectral data and the biosynthesis. The C-NMR spectrum of com-
2
pound 3 contained signals of three quaternary sp carbons (d 138.9, 135.8, 129.8)
C
2
and one sp methine (d 125.7), indicating the presence of one tri- and one tetra-sub-
C
stituted C-C double bond. A hydroxy group at C-11, and trisubstituted C-C double
bond at C-4/C-5 and were confirmed by hydroxymethylene signals (dH 3.90/d 67.0),
C
and HMBC correlations between H -11 (d 3.90) and C-4 (d 138.9)/C-5 (d 125.7), H-5
2
H
C
C
(
d 5.72) and C-6 (d 40.3). Another hydroxymethylene group (C-15) was deduced by
H C
resonant signals at d (4.16, 3.94) and d (62.2). The HMBC correlations between H -15
H
C
2
(
d 4.16, 3.94) and C-1 (d 135.8)/C-10 (d 129.8)/C-9 (d 29.0) confirmed tetra-substi-
H C C C
tuted C-C double bond forming between C-10 and C-1. The O-glucopyranosyl group
at C-13 was demonstrated by HMBC correlations between H -14 (d 0.85) and C-12 (d
C
3
H
0
3.8)/C-13 (d 74.9), anomeric proton H-1 (d 4.25) and C-13. A large spin coupling
C H
3
constant between H-6 and H-7 (JH-6/H-7 ¼ 9.2 Hz) was supported for trans-axial
coupling of those protons in the muurolane-type sesquiterpene. Difference from
compound 2, the upfield chemical shift value of C-14 (d 11.2) suggested the relative
C
S-configuration of C-12 in compound 3 (Collins et al. 2002). The presence of D-glucose
moiety in 3 was also confirmed by acid hydrolysis and followed by HPLC analysis
of the thiocarbamoylthiazolidine derivative in comparison with authentic samples
(
(
Supporting information). Therefore, structure of compound 3 was determined to be
12S )-11,13,15-trihydroxymuurola-1(10),4-diene 13-O-b-D-glucopyranoside and named
ꢁ
as balanoindicoside C.
Cytotoxic effects of compounds 1-3 (100 and 20 lM) were screened against four
human cancer cell lines including hepatocellular carcinoma (HepG-2), promyelocytic
leukemia (HL-60), lung carcinoma (LU-1), and breast carcinoma (MCF-7). At diluted
concentration of 20 lM, all compounds displayed weak cytotoxic activity. The
percentage of cells death was obtained in the range from 11.84 ± 0.87 to 26.55 ± 1.83
for all tested cell lines (Table S2).
3. Experimental
3.1. General
Optical rotation was measured on a Jasco P2000 polarimeter. NMR spectra were
recorded on a Varian 400 MHz spectrometer using TMS as an internal standard.
HR-ESI-MS were acquired on an Agilent 6530 Accurate Mass Q-TOF LC/MS system.
Flash column chromatography was performed using silica gel, reverse phase C-18, and
diaion HP-20 resins. Thin layer chromatography was carried out using pre-coated
silica gel 60 F254 and RP-18 F254S plates.

NATURAL PRODUCT RESEARCH
5
3.2. Plant material
Balanophora parasitic samples were collected at Dak Lak, Vietnam in July 2016. Its sci-
entific name, Balanophora fungosa subsp. indica (Arn.) B. Hansen, was identified by
botanist Nguyen The Cuong, Institute of Ecology and Biological Resources, VAST. A
voucher specimen (number NCCT-P02) was deposited at the Institute of Marine
Biochemistry, VAST. Reference samples were well consisted with those described in
the literature (Kanis et al. 1973).
3.3. Extraction and isolation
The dried powdered plant sample (3.5 kg) was ultrasonically extracted with MeOH for
three times (each 5 L, 30 minutes in room temperature). The crude extract (300 g) was
suspended in water (2 L) and successively partitioned with dichloromethane (three
times, each 2 L) and then ethyl acetate (three times, each 2 L). Resulted water layer
was poured on a diaion HP-20 resin column chromatography (CC), washed with water
(
1.5 L), and eluted stepwise with methanol/water (25, 50, 75, and 100% volume of
methanol, each 2 L) to give four fractions BFW1-BFW4, respectively. Fraction BFW2
34.0 g) was roughly separated on a silica gel CC, eluting with dichloromethane/metha-
(
nol (stepwise: 40/1, 20/1, 10/1, 5/1/, 3/1, 1/1, v/v) to give six fractions BFW2A-BFW2F.
Fraction BFW2C (7.6 g) was repeatedly chromatographed on a silica gel CC eluting
with dichloromethane/acetone/water (4/1/0.5, v/v/v) to give four fractions BFW2C1-
BFW2C4. Fraction BFW2C2 was purified on a reverse phase silica gel C-18 (RP-18) CC,
eluting with methanol/water (1/2, v/v) to give compound 2 (6 mg). Fraction BFW2C4
was loaded on a silica gel CC and eluted with dichloromethane/methanol/water (5/1/
0.1, v/v/v) to give two smaller fractions BFW2C4A and BFW2C4B. Compound 3 (5 mg)
was isolated from fraction BFW2C4A using a RP-18 column and methanol/water (1/1,
v/v) as an eluent. The BFW2C4B fraction was also purified on a RP-18 CC, eluting with
acetone/water (1/2, v/v) to give compound 1 (8 mg).
3
.3.1. Balanoindicoside A (1)2
5
-
White amorphous powder, ½aꢂ : -27.5 (c 0.1, MeOH); HR-ESI-MS m/z 451.2107 [M þ Cl]
D
-
(
calcd. for C H O Cl, 451.2099); m/z 461.2398 [M þ HCOO] (calcd. for C H O ,
2
1
36
8
22 37 10
1
0
61.2387); H NMR (CD OD, 400 MHz) d : 5.86 (br s, H-5), 4.24 (d, 7.6, H-1 ), 4.21 (d,
3 H
4
1
3
9
1
1
1
0
0
2.0, H -11), 4.07 (d, 12.0, H -11), 3.87 (br d, 11.6, H -6 ), 3.66 (dd, 5.6, 11.6, H -6 ),
.42 (dd, 4.0, 11.2, H-9), 3.35 (t, 9.2, H-3 ), 3.27 (t, 9.2, H-4 ), 3.23 (m, H-5 ), 3.19 (dd, 7.6,
.2, H-2 ), 2.29 (m, H -3), 2.23 (m, H-12), 2.10 (m, H -2), 2.07 (m, H -3), 1.81 (m, H-6),
.74 (m, H -8), 1.24 (m, H -2), 1.22 (m, H-7), 1.21 (m, H-1), 1.16 (m, H -8), 1.03 (s, H -
5), 0.95 (d, 6.8, H -14), 0.82 (d, 6.8, H -13); C NMR (CD OD, 100 MHz) d : 136.8 (C-4),
27.2 (C-5), 102.8 (C-1 ), 79.0 (C-9), 78.2 (C-3 ), 78.0 (C-5 ), 76.3 (C-10), 75.1 (C-2 ), 74.1
a
b
a
b
0
0
0
0
a
a
b
a
b
b
3
1
3
3
3
3
C
0
0
0
0
0
0
(
(
C-11), 71.7 (C-4 ), 62.8 (C-6 ), 49.9 (C-1), 46.1 (C-7), 40.5 (C-6), 30.8 (C-8), 28.0 (C-3), 26.9
C-12), 22.9 (C-2), 21.9 (C-14), 15.5 (C-13), 14.1 (C-15).
3
.3.2. Balanoindicoside B (2)
2
D
5
White amorphous powder, ½aꢂ : -38.1 (c 0.1, MeOH); HR-ESI-MS: m/z 451.2109
-
-
[M þ Cl] (calcd. for C H O Cl, 451.2099); m/z 461.2395 [M þ HCOO] (calcd. for
21 36 8

6
B. HUU TAI ET AL.
1
0
C H O , 461.2387); H-NMR (CD OD, 400 MHz) d : 5.98 (br s, H-5), 4.25 (d, 8.0, H-1 ),
2
2
37 10
3
H
0
.93 (br s, H -11), 3.87 (br d, 11.2, H -6 ), 3.75 (dd, 8.4, 9.2, H -13), 3.67 (dd, 5.2, 9.2, H -
2 a a b
3), 3.65 (dd, 5.2, 11.2, H -6 ), 3.34 (t, 8.4, H-3 ), 3.26 (t, 8.4, H-4 ), 3.24 (m, H-5 ), 3.17
3
1
0
0
0
0
b
0
(
dd, 8.0, 8.4, H-2 ), 2.60 (m, H-6), 2.21 (m, H-12), 2.11 (m, H -3), 2.05 (m, H -3), 1.62 (m,
a
b
H -2), 1.58 (m, H-1), 1.55 (m, H -2), 1.50 (m, H -9), 1.47 (m, H -8), 1.45 (m, H -9), 1.43
a
b
a
a
b
1
3
(
m, H -8), 1.40 (m, H-7), 1.18 (s, H -15), 0.97 (d, 7.2, H -14); C-NMR (CD OD, 100 MHz)
b
3
3
3
0
0
0
0
d : 138.4 (C-4), 127.5 (C-5), 104.3 (C-1 ), 78.2 (C-3 ), 77.9 (C-5 ), 75.2 (C-2 ), 73.1 (C-10),
C
0
0
7
6
2.9 (C-13), 71.7 (C-4 ), 67.5 (C-11), 62.8 (C-6 ), 47.2 (C-1), 44.0 (C-7), 35.5 (C-9), 35.1 (C-
), 34.0 (C-12), 29.3 (C-15), 27.8 (C-3), 22.7 (C-8), 21.2 (C-2), 16.8 (C-14).
3
.3.3. Balanoindicoside C (3)
2
D
5
White amorphous powder; ½aꢂ : þ24.9 (c 0.1, MeOH); HR-ESI-MS: m/z 449.1951
-
-
[
M þ Cl] (calcd. for C H O Cl, 449.1942); m/z 459.2241 [M þ HCOO] (calcd. for
21 34 8
1
0
C H O , 459.2230); H NMR (CD OD, 400 MHz) d : 5.72 (br s, H-5), 4.25 (d, 7.6, H-1 ),
2
2
35 10
3
H
0
.16 (d, 11.6, H -15), 3.94 (d, 11.6, H -15), 3.90 (br s, H -11), 3.84 (br d, 12.0, H -6 ), 3.83
a b 2 a
4
(
0
dd, 6.4, 9.6, H -13), 3.64 (dd, 5.6, 12.0, H -6 ), 3.44 (dd, 7.2, 9.6, H -13), 3.32 (t, 9.2, H-
a b b
0
0 0 0
), 3.25 (t, 9.2, H-4 ), 3.24 (m, H-5 ), 3.15 (dd, 7.6, 9.2, H-2 ), 2.89 (m, H -2), 2.66 (br d,
a
3
9
1
.2, H-6), 2.24 (m, H-12), 2.22 (m, H -3), 2.19 (m, H -9), 1.99 (m, H -3), 1.98 (m, H -9),
.97 (m, H -2), 1.42 (m, H-7), 1.66 (m, H -8), 1.64 (m, H -8), 0.85 (d, 6.8, H -14); C-
b
a
a
b
1
3
b
a
b
3
NMR (CD OD, 100 MHz) d : 138.9 (C-4), 135.8 (C-1), 129.8 (C-10), 125.7 (C-5), 104.6 (C-
3
C
0
0 0 0 0 0
1
6
8
), 78.2 (C-3 ), 75.2 (C-2 ), 74.9 (C-13), 77.9 (C-5 ), 71.7 (C-4 ), 67.0 (C-11), 62.8 (C-6 ),
2.2 (C-15), 41.2 (C-7), 40.3 (C-6), 33.8 (C-12), 29.1 (C-3), 29.0 (C-9), 27.4 (C-2), 22.8 (C-
), 11.2 (C-14).
3.4. Cytotoxic assay
The HepG-2, HL-60, LU-1, and MCF-7 cell lines were obtained from Milan University,
Italy and Hawaii University, USA. The cells were maintained and cultured in RPMI 1640
ꢃ
medium containing 10% fetal bovine serum, 100 U/ml penicillin/streptomycin at 37 C
in a humidified atmosphere (5% CO and 95% air). Cytotoxic effects of compounds
2
were determined using sulforhodamine B assay (Monks et al. 1991). The cells were
seeded in 96-well culture plate and treated with or without compounds (final concen-
trations of 20 and 100 lM) for three days. After that, cells were stained with sulforhod-
amine B and measured optical density (OD) at wavelength of 515 nm. Difference of
OD values between sample and vehicle wells reflected cells viability during treated
with compounds. Experiments were performed in triplicate. Results are described as
percentage of cells death (Mean ± SD) in the presence of compounds. Ellipticine (final
concentration 2 lM) was used as a positive control in our experiments
4. Conclusion
Three new muurolane-type sesquiterpene glycosides (1–3) were isolated from the
whole plants of Balanophora fungosa subsp. indica. Stereochemistry of compounds
1
–3 were demonstrated by analysis of NOESY spectra. Configuration at C-12 of com-
pounds 2 and 3 were established by chemical shift value of C-14. At concentration of

NATURAL PRODUCT RESEARCH
7
2
0 lM, compounds 1–3 displayed weak cytotoxic activity (11.84%–26.55%) towards
HepG-2, HL-60, LU-1, and MCF-7 human cancer cell lines. Up to concentration of
00 mM, cytotoxic effects of compounds 1–3 showed in the range from 20.87%
1
to 54.47%.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This research was supported by Vietnam National Foundation for Science and Technology
Development (NAFOSTED) under grant number 104.01-2015.75.
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