Bruceadysentoside A, a new pregnane glycoside and others secondary metabolites with cytotoxic activity from brucea antidysenterica J. F. Mill. (simaroubaceae)

Article abstract of DOI:10.1080/14786419.2019.1655024

The chemical investigation of the root barks leaves and stem barks of Brucea antidysenterica J. F. Mill. (Simaroubaceae) led to the isolation of a new pregnane glycoside, named Bruceadysentoside A or 3-O-β-L-arabinopyranosyl-pregn-5-en-20-one (1) together with seventeen known compounds. Their structures were established from spectral data, mainly HRESIMS, 1D and 2D NMR and by comparison with literature data. Compounds 1, 2, 5, 6, 8, 10, 12 and 13 were tested in vitro for their effects on the viability of two different human cancer cell lines, namely prostate PC-3 adenocarcinoma cells and colorectal HT-29 adenocarcinoma cells. No substantial activities were recorded for 2, 10, 12 and 13 (up to 10 μM concentration). 1, 5 and 8 did not show strong anti-proliferative effects up to 100 μM, however, 6 exhibited a stronger anti-proliferative effect with IC50 values of ～ 100 μM against PC-3 and ～ 200 μM against HT-29.

Full text of DOI:10.1080/14786419.2019.1655024

Natural Product Research
Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: https://www.tandfonline.com/loi/gnpl20
Bruceadysentoside A, a new pregnane glycoside
and others secondary metabolites with cytotoxic
activity from brucea antidysenterica J. F. Mill.
(simaroubaceae)
Yves Salomon Makong, Ghislain Wabo Fotso, Gervais Happi Mouthe, Bruno
Lenta, Robert Rennert, Norbert Sewald, Norbert Arnold, Jean Duplex Wansi
&
Bonaventure Tchaleu Ngadjui
To cite this article: Yves Salomon Makong, Ghislain Wabo Fotso, Gervais Happi Mouthe, Bruno
Lenta, Robert Rennert, Norbert Sewald, Norbert Arnold, Jean Duplex Wansi & Bonaventure
Tchaleu Ngadjui (2019): Bruceadysentoside A, a new pregnane glycoside and others secondary
metabolites with cytotoxic activity from bruceaꢀantidysenterica J. F. Mill. (simaroubaceae), Natural
Product Research, DOI: 10.1080/14786419.2019.1655024
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NATURAL PRODUCT RESEARCH
https://doi.org/10.1080/14786419.2019.1655024
Bruceadysentoside A, a new pregnane glycoside and
others secondary metabolites with cytotoxic activity from
brucea antidysenterica J. F. Mill. (simaroubaceae)
a
b
b
Yves Salomon Makong , Ghislain Wabo Fotso , Gervais Happi Mouthe , Bruno
c
d
e
d
a
Lenta , Robert Rennert , Norbert Sewald , Norbert Arnold , Jean Duplex Wansi
b
and Bonaventure Tchaleu Ngadjui
a
b
Department of Chemistry, Faculty of Science, University of Douala, Douala, Cameroon; Department
c
of Organic Chemistry, Faculty of Science, University of Yaound ꢀe 1, Yaounde, Cameroon; Department
of Chemistry, Higher Teacher Training College, University of Yaound ꢀe 1 1, Yaounde, Cameroon;
d
Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, Halle (Saale), Germany;
e
Organic and Bioorganic Chemistry, Department of Chemistry, Bielefeld University,
Bielefeld, Germany
ABSTRACT
ARTICLE HISTORY
Received 5 May 2019
Accepted 30 July 2019
The chemical investigation of the root barks leaves and stem
barks of Brucea antidysenterica J. F. Mill. (Simaroubaceae) led to
the isolation of
a
new pregnane glycoside, named
KEYWORDS
Bruceadysentoside A or 3-O-b-L-arabinopyranosyl-pregn-5-en-20-
one (1) together with seventeen known compounds. Their struc-
tures were established from spectral data, mainly HRESIMS, 1 D
and 2 D NMR and by comparison with literature data. Compounds
Brucea antidysenterica;
Bruceadysentoside A;
cytotoxic activities;
hydnocarpin; pregnane
glycoside; Simaroubaceae
1, 2, 5, 6, 8, 10, 12 and 13 were tested in vitro for their effects on
the viability of two different human cancer cell lines, namely pros-
tate PC-3 adenocarcinoma cells and colorectal HT-29 adenocarcin-
oma cells. No substantial activities were recorded for 2, 10, 12
and 13 (up to 10 lM concentration). 1, 5 and 8 did not show
strong anti-proliferative effects up to 100lM, however, 6 exhib-
ited a stronger anti-proliferative effect with IC50 values of
ꢀ
100lM against PC-3 and ꢀ 200 lM against HT-29.
CONTACT Ghislain Wabo Fotso
ghis152001@gmail.com; Jean Duplex Wansi
jdwansi@yahoo.fr
Supplemental data for this article can be accessed at https://doi.org/10.1080/14786419.2019.1655024.
ß 2019 Informa UK Limited, trading as Taylor & Francis Group

2
Y. SALOMONMAKONG ET AL.
1. Introduction
Brucea antidysenterica J. F. Mill. (Simaroubaceae) is a deciduous, straight cylindrical,
erect tree that grows to an average height of 7 m; exceptionally large trees may reach
a height of 10-15 m. Leaves are alternate, usually crowded at the end of younger
twigs. Fruits are composed of drupes-like ellipsoid mericarps. They are bitter and poi-
sonous to farm animals (Dale and Greenway 1961; Burkill 2000). B. antidysenterica is
native to Upper Guinea, Nigeria, Cameroon, Congo, Angola and to Eastern Africa from
Ethiopia to Tanzania and Zimbabwe (Exell et al. 1963). It is used in folk medicine for
the treatment of numerous affections including malaria, helminthic infections, diarrhea,
dysentery, fever, asthma and other disorders (Watt and Breyer-Brandwijk 1962; Grace
and Fowler 2008). Extracts prepared from the roots have been shown to be active
against Plasmodium gallinaceum in chicks and hence there is the possibility of antimal-
arial activity (Spencer et al. 1947). Previous phytochemical studies on the genus
Brucea have led to the isolation of quassinoids such as bruceins A-H and M with cyto-
toxic activities (Imamura et al. 1995; Bawn et al. 2008; Noorshahida et al. 2009; Su
et al. 2013); 20-hydroxyyadanzigan with anticomplement activity (Zhan et al. 2019).
Canthin-6-one alkaloids (Harris et al. 1985; Kitagawa et al. 1994) and triterpenoids (Liu
et al. 2009) were also isolated from this genus. The present work describes the isola-
tion of a new pregnane glycoside from the leaves of Brucea antidysenterica together
with the evaluation of the cytotoxicity activities of some of the isolated compounds in
two cancer cell lines: HT-29 and PC-3.
2. Results and discussion
Compound 1 was obtained as a white amorphous powder soluble in pyridine. It
showed positive Molish and Liebermann–Burchard reactions demonstrating its saponin
nature (Zheng et al. 2010). Its molecular formula C H O was deduced from its
26 40 6

NATURAL PRODUCT RESEARCH
3
Figure 1. Structures of the isolated compounds 1-18.
þ
HRESIMS in positive-ion mode which exhibited a pseudo-molecular ion peak [M þ Na]
þ
at m/z 471.2827 (calcd 471.2723 for C H O Na ). Its IR spectrum showed characteris-
26 40 6
ꢁ
1
tic bands of hydroxyl, ketone and alkene respectively at 3307, 1690 and 1647 cm
.
Compound 1 was hydrolyzed to give the monosaccharide L-arabinose. This was in
accordance with the molecular formula of 1, C H O corresponding to a pregnane
2
6 40 6
1
13
(
C-21) linked to a pentose (C-5). This was confirmed by the H and C NMR data of 1

4
Y. SALOMONMAKONG ET AL.
coupled with its HSQC and DEPT spectra which displayed characteristic signals of a
pregnane skeleton with two angular methyl groups at d 0.58 (s, 3 H)/13.0 and d 0.88
(s, 3 H)/19.1. However, the signal of the third methyl group C-21 didn’t appear as
doublet but was rather replaced by a characteristic signal of the methyl of an acetyl
group at d 2.07 (s, 3 H)/31.2. This information was confirmed by the presence of the
13
signal of a ketone group at C-20 (d 208.3) on the C spectra. The anomeric proton of
the L-arabinose was observed at d 4.82 (1 H, d, J ¼ 7.1 Hz, H-1’)/102.9 and based on its
high coupling constant, the configuration of the sugar was determined as b. The sig-
nal of one olefinic proton H-6 was observed at d 5.32 (brs, 1 H)/121.4. The cross-ana-
1
3
lysis of the C and DEPT spectra of 1 revealed (3 ꢂ CH , 8 ꢂCH 6 ꢂCH, 3 ꢂC for the
3
2,
aglycone). This information suggested that compound 1 is likely to be a pregn-5-ene-
-ol-20-one bearing the L-arabinose sugar unit at C-3. This was in accordance with the
HMBC spectrum of 1 in which a long-range correlation between H-3 (d 3.85) and C-1’
€a 102.9), together with correlation of H-1’ (d 4.82) and C-3 (d 77.7). On the HRESIMS
3
(
þ
þ
of 1 the base peak [M-ara] at m/z 299.2444 (C H O ) was consistent with the loss
21 31
of the sugar unit. Compound 1 was then univocally characterized as 3-O-b-L-arabino-
pyranosyl-pregn-5-en-20-one, an unreported glycosylated pregnane derivative to
which the trivial name Bruceadysentoside A was given.
The structures of the known compounds were identified as: 1-hydroxy-11-
m eꢀ thoxycanthin-6-one (2) (Harris et al. 1985), b-sitosterol (3) (Chaturvedula and
Prakash 2012), hexadecanoic acid (palmitic acid) (4) (Bulama et al. 2014), 1,11-dime-
thoxycanthin-6-one (5) (Narihiko et al. 1986), hydnocarpin (6) (Pan et al. 2009), (3-(3-
methyl-1-oxo-2-butenyl))-1H-indole (7) (Vijaya et al. 1993), (20 R)-O-(3)-a-L-arabinopyra-
nosylpregn-5-ene-3b,20-diol (8) (Liu et al. 2009) and (20 R)-O-(3)-b-D-glucopyranosyl-
(
1!2)-a-L-arabinopyranosyl-pregn-5-ene-3b,20-diol (9) (Liu et al. 2011). canthin-6-one
(10) (Narihiko et al. 1986), 1-methoxycanthin-6-one (11) (Ohmoto et al. 1976), cleomis-
cosin C (12) (Ray et al. 1985), bruceolline F (13) (Yishan et al. 1994), 2-hydroxy-1, 11-
dimethoxycanthin-6-one (14) (Harris et al. 1985), bruceolline D (15) (Yishan et al.
1
2
994), mixture of stigmasterol and b-sitosterol (16) (Chaturvedula and Prakash 2012),
-methoxycanthin-6-one (17) (Njar et al. 1993) and 3,3-dimethylindole (18) (National
Center for Biotechnology Information) (Figure 1).
Bruceadysentoside A (1), 1-hydroxy-11-methoxycanthin-6-one (2), 1,11-dimethoxy-
canthin-6-one (5), hydnocarpin (6), (20 R)-O-(3)-a-L-arabinopyranosylpregn-5-en-3b,20-
diol (8) canthin-6-one (10), cleomiscosin C (12) and bruceolline F (13) were tested for
their effects on the viability of two different human cancer cell lines, namely prostate
PC-3 adenocarcinoma cells and colorectal HT-29 adenocarcinoma cells. The cell viabil-
ity and cytotoxicity assay was conducted by using the tetrazolium salt MTT and colori-
metric read-out after 48 h cell treatment. The saponin digitonin (100 mM), a very
potent permeabilizer of cell membranes, was used as positive control compromising
the cells to yield 0% cell viability after 48 h. Initially, all compounds were fast screened
with 10 lM, whereby the compounds 2, 10, 12 and 13 were detected to be inactive,
whereas the other compounds showed some conflicting signs of activity (data not
shown). Hence, the compounds 1, 5, 6 and 8 were subsequently tested with concen-
trations up to 100 mM (1, 8) and 200 mM (5, 6), respectively to determine IC50 values.
Whereas the compounds 1, 8 (data not shown) as well as compound 5 did not show

NATURAL PRODUCT RESEARCH
5
substantial anti-proliferative effects (IC s > 100 mM for 1 and 8; IC > 200 mM for 5),
50
50
hydnocarpin (6) exhibited a stronger antiproliferative effect with IC50 values of ꢀ
00 mM against PC-3 prostate cancer cells and ꢀ 200 mM against HT-29 colon cancer
cells (Figure 2).
1
3. Experimental (supplementary data)
3.1. Bruceadysentoside a or 3-b-L-arabinopyranosyl-pregn-5-ene-3-ol-20-one (1)
þ
C H O , white amorphous powder; HRESI-MS m/z: 471.2827 [M þ Na] (cald for
2
6 40 6
þ
þ
1
4
71.2723); m/z 299.2444 [M-ara] (C H O ). H NMR (600 MHz, pyridine-d5) d: 0.58
21 31
(3H, s, 18-CH3), 0.88 (3H, s, 19-CH3), 0.89 (1H, m, H-9), 0.97 (1H, m, H-14), 1.01 (1H, m,
H-1a), 1.07 (1H, m, H-15a), 1.23 (1H, m, H-8), 1.26 (1H, m, H-11a), 1.27 (1H, m, H-12a),
1
1
.28 (1H, m, H-7a), 1.46 (1H, m, H-11b), 1.52 (1H, m, H-7b, 15b), 1.55 (1H, m, H-16a),
.72 (1H, m, H-1b), 1.73 (2H, m, H-2), 1.92 (1H, m, H-12b), 2.07 (3H, s, 21-CH3), 2.29
(
(
1H, m, H-16b), 2.39 (1H, m, H-4a), 2.44 (1H, t, J ¼ 9.1 Hz, H-17), 2.65 (1H, m, H-4b), 3.77
1H, t, J ¼ 10.7 Hz, H-5’a), 3.85 (1H, m, H-3), 4.18 (1H, t, J ¼ 8.8 Hz, H-3’), 4.29 (1H, d, m,
H-4’), 4.31 (1H, m, H-5’b), 4.42 (1H, t, J ¼ 7.9 Hz, H-2’), 4.82 (1H, d, J ¼ 7.1 Hz, H-1’), 5.32
1
3
(
2
(
6
1H, brs, H-6); C NMR (150 MHz, pyridine-d5) d: 13.0 (C-18), 19.1 (C-19), 21.1(C-11),
2.9 (C-16), 24.4 (C-15), 30.1 (C-2), 31.2 (C-21), 31.7 (C-8), 31.8 (C-7), 36.7 (C-10), 37.4
C-1), 38.5 (C-12), 39.0 (C-4), 43.7 (C-13), 50.0 (C-9), 56.5 (C-14), 63.4 (C-17), 66.7 (C-5’),
9.3 (C-4’), 72.3 (C-2’), 74.4 (C-3’), 77.7 (C-3), 102.9 (C-1’), 121.4 (C-6), 140.8 (C-5), 208.3
C-20).
(
4. Conclusion
The chemical investigation of the leaves, root and stem barks of Brucea antidysenterica
J. F. Mill. (Simaroubaceae) afforded an unreported pregnane glycoside derivative
together with seventeen known compounds including ten alkaloids, four steroids
among which two glycosylated pregnane derivatives, a fatty acid, a coumarinolignan
and a flavolignan. It is worth noting that quassinoids which are known to be present
in several Brucea species were not isolated neither in leaves, nor stem and root barks
of Brucea antidysenterica. However indole alkaloids were identified as principal constit-
uents of this specie and can be considered as chemotaxonomic markers of the Brucea
genus. One of them, identified as 3,3-dimethylindole is reported here for the first time
from natural source. In addition the evaluation of the cytotoxic activities of some of
the isolated compounds revealed that hypnocarpin, the only flavolignan isolated in
this study, was the most active compound especially on prostate PC-3 adenocarcin-
oma cells and moderately on colorectal HT-29 adenocarcinoma cells compared to the
coumarinolignan, cleomiscosin C which did not show any activity at the same
concentration.
Acknowledgements
YM, JDW and BTN are particularly grateful to the YABINAPA Graduate School for providing
research facilities in Cameroon. GWF is thankful to DAAD for a 3 months fellowship in Prof

6
Y. SALOMONMAKONG ET AL.
Ludger Wessjohann and Dr. Norbert Arnold laboratory in the Leibniz-Institut f u€ r
Pflanzenbiochemie (IPB). They are acknowledged for providing facilities for spectroscopic ana-
lysis and cytotoxicity screening of some of the isolated compounds. We wish to thank the
Alexander von Humboldt Foundation, Germany for Research Group Linkage funding 2015-2018
of the Norbert Sewald-Jean Duplex Wansi research group cooperation and generous support
with laboratory equipment.
Disclosure statement
No potential conflict of interest was reported by the authors.
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