Pro-apoptotic activity of acylated triterpenoid saponins from the stem bark of Albizia chevalieri harms

Article abstract of DOI:10.1016/j.phytol.2017.09.008

As a continuation of our interest in apoptosis-inducing triterpenoid saponins from Albizia genus, phytochemical investigation of the stem bark of Albizia chevalieri led to the isolation of three new oleanane-type saponins, named chevalierosides A–C (1–3). Their structures were established on the basis of extensive analysis of 1D and 2D NMR (¹H-, ¹³C NMR, DEPT, COSY, TOCSY, ROESY, HSQC and HMBC) experiments, HRESIMS studies, and by chemical evidence. The pro-apoptotic effect of the three saponins was evaluated on two human cell lines (pancreatic carcinoma AsPC-1 and hematopoietic monocytic THP-1). Cytometric analyses showed that saponins 1–3 induced apoptosis of both human cell lines (AsPC-1 and THP-1) in a dose-dependent manner.

Full text of DOI:10.1016/j.phytol.2017.09.008

Phytochemistry Letters 22 (2017) 95–101
Contents lists available at ScienceDirect
Phytochemistry Letters
journal homepage: www.elsevier.com/locate/phytol
Pro-apoptotic activity of acylated triterpenoid saponins from the stem bark
of Albizia chevalieri harms
Olivier Placide Notéa,b,⁎, Lin Marcellin Messi , Joséphine Ngo Mbing , Sarah Ali Azouaou ,
b,c
b
a
d
e
f
Mamadou Sarr , Dominique Guillaume , Christian Dominique Muller ,
Dieudonné Emmanuel Pegnyemb , Annelise Lobstein
b
a
a
Pharmacognosie et Molécules Naturelles Bioactives, Laboratoire d’Innovation Thérapeutique, UMR 7200, CNRS-Université de Strasbourg, Faculté de Pharmacie, 74 route
du Rhin, F-67401 Illkirch Cedex, France
b
Laboratoire de Pharmacochimie des Substances Naturelles, Département de Chimie Organique, Faculté de Sciences, Université de Yaoundé I, BP 812 Yaoundé, Cameroon
Institut de Recherche Agricole pour le Développement (IRAD), BP 2067 Yaoundé, Cameroon
UMI 3189, FMPO, University Anta Diop of Dakar, Senegal
UFR Médecine-Pharmacie, CNRS-UMR7312, 51 rue Cognacq Jay, 51100 Reims, France
c
d
e
f
Institut Pluridisciplinaire Hubert Curien, UMR 7178 CNRS Université de Strasbourg, 74 route du Rhin, F-67401 Illkirch Cedex, France 67401Illkirch, France
A R T I C L E I N F O
A B S T R A C T
Keywords:
Albizia chevalieri
Mimosaceae
Triterpenoid saponins
Proapoptotic activity
Pancreatic carcinoma AsPC-1
As a continuation of our interest in apoptosis-inducing triterpenoid saponins from Albizia genus, phytochemical
investigation of the stem bark of Albizia chevalieri led to the isolation of three new oleanane-type saponins,
named chevalierosides A–C (1–3). Their structures were established on the basis of extensive analysis of 1D and
1
13
2
D NMR ( H-, C NMR, DEPT, COSY, TOCSY, ROESY, HSQC and HMBC) experiments, HRESIMS studies, and by
chemical evidence. The pro-apoptotic effect of the three saponins was evaluated on two human cell lines
pancreatic carcinoma AsPC-1 and hematopoietic monocytic THP-1). Cytometric analyses showed that saponins
(
1
–3 induced apoptosis of both human cell lines (AsPC-1 and THP-1) in a dose-dependent manner.
1. Introduction
Albizia genus with an interesting apoptosis-inducing selectivity degree
effect on AsPC-1 cell line (Noté et al., 2016b), which was earlier de-
The genus Albizia comprises about 150 species widely distributed in
the tropics, with the greatest diversity in Africa and South America
Abdel-Kader et al., 2001). Phytochemical investigations of Albizia
scribed as a model of cancer stem cells (CSCs) (Wei et al., 2011). As a
continuation of our interest in apoptosis-inducing triterpenoid saponins
from Albizia genus (et al., 2016a,b; et al., 2016a,b), we screened the
saponins content of Albizia chevalieri.
(
genus revealed the presence of triterpenoid saponins, consisting mainly
of glycosides of oleanolic acid, echinocystic acid, and acacic acid. These
glycosides have demonstrated inhibitory activity of the growth of many
cancer cells lines in vitro (Abdel-Kader et al., 2001; Haddad et al., 2003;
Liu et al., 2009; Krief et al., 2005; Zheng et al., 2006; Melek et al., 2007;
Cao et al., 2007; Noté et al., 2009, 2015; Miyase et al., 2010a,b). But
few reports revealed the proapoptotic function of triterpenoid saponins
isolated from plants of Albizia genus. In our knowledge, only three
studies carried out on Albizia adianthifolia, Albizia zygia, and Albizia
glaberrima, respectively, have shown the pro-apoptotic effect of adian-
thifoliosides A and D (Haddad et al., 2004), zygiaosides A–B (Noté
et al., 2016a), and of glaberrimosides A–C (Noté et al., 2016b) on
cancer cells lines. One of our recent contribution revealed the first pro-
apoptotic activity of glycosides of oleanolic acid, so far isolated from
A. chevalieri harms (Mimosaceae) is a tree that grows up to 12 m
high or a shrub growing under harsher conditions of the dry savannah
from Senegal, Niger, Nigeria, and Cameroon (Saidu et al., 2007). Its
leaves extract is used for the management of diabetes mellitus in Niger
and in Eastern Nigeria, and its stem bark has been reported as a remedy
for coughs (Saidu et al., 2007). The decoction of its leaves is used in
Northern Nigeria to treat dysentery (Arbonnier, 2004). Its aqueous
roots and leaves extracts have been reported to possess significant hy-
poglycaemic and hypolipidemic effects (Burkill 1995; Saidu et al.,
2010). Previous phytochemical studies of A. chevalieri revealed the
presence of triterpenoids (Mathias et al., 2016) from its stem bark and
of glucosides of flavanol from its roots (Tchoukoua et al., 2016).
In the present paper, we report the isolation and structure
⁎
Corresponding author at: Laboratoire de Pharmacochimie des Substances Naturelles, Département de Chimie Organique, Faculté de Sciences, Université de Yaoundé I, BP 812,
Yaoundé, Cameroun
E-mail address: oliviernote1@yahoo.fr (O.P. Noté).
http://dx.doi.org/10.1016/j.phytol.2017.09.008
Received 7 May 2017; Received in revised form 24 August 2017; Accepted 22 September 2017
1874-3900/ © 2017 Published by Elsevier Ltd on behalf of Phytochemical Society of Europe.

O.P. Noté et al.
Phytochemistry Letters 22 (2017) 95–101
Fig. 1. Structures of isolated compounds 1- 3.
characterization of three new triterpenoid saponins, named cheva-
lierosides A–C (1–3), along with the evaluation for their pro-apoptotic
effect on two human tumor cells, a human pancreatic cancer cell line
AsPC-1 and a hematopoietic monocytic cancer cell line THP-1, results
are reported herein.
triterpenoid saponin. The unambiguous assignment of all 1H and 13
C
NMR signals of the aglycone of 1 (Table 1), identified as echinocystic,
using correlations observed in COSY, ROESY, HSQC, and HMBC
spectra, was in full agreement with literature data (Melek et al., 2014;
Miyase et al., 2010a, 2010b). Substitutions at C-3 and C-28 of echino-
cystic acid were evidenced by the observed glycosylation-induced shifts
of C-3 at δ
C
C
89.6 and of C-28 at δ 176.0 (Table 1) establishing that 1
2
. Results and discussion
was a 3,28-bidesmosidic echinocystic acid derivative with sugar chains
linked to C-3 and C-28 of the aglycone through an ether and ester bond,
respectively (Woldemichael and Wink, 2001; Sahu and Achari, 2001).
The air-dried powdered roots of A. chevalieri (150 g) were extracted
with 70% EtOH in soxhlet and after evaporation of the solvent, the
hydroalcoholic extract was partitioned against n-BuOH saturated with
water. The n-BuOH fraction was then submitted to vacuum-liquid
chromatography (VLC) on reversed phase silica gel yielding a methanol
fraction that was subjected to a VLC on silica gel. Purification of the
eluted fractions by semipreparative high pressure liquid chromato-
graphy (HPLC) afforded three new echinocystic acid glycosides, named
chevalierosides A–C (1–3) (Fig. 1).
1
The H NMR spectrum of the sugar portion of compound 1 showed
eight anomeric signals at δ
glucose (GlcNHAc)], 5.28 [d, J = 6.6 Hz, arabinose (Ara I)], 4.83 [d,
J = 2.2 Hz, xylose (Xyl I)], 5.55 [d, J = 7.6 Hz, glucose (Glc I)], 6.06
H
5.08 [d, J = 7.3 Hz, 2-amino-2-deoxy-
[
d, J = 8.2 Hz, glucose (Glc II)], 5.00 [d, J = 8.0 Hz, arabinose (Ara
II)], 5.40 [d, J = 7.6 Hz, xylose (Xyl II)], and 6.30 [d, J = 2.2 Hz,
apiose (Api)], which correlated with eight anomeric carbon atom re-
sonances at δ
C
104.5, 103.5, 108.0, 104.5, 92.9, 103.1, 105.2, and
Chevalieroside A (1), obtained as a white amorphous powder, was
1
13
111.6, respectively in the HSQC spectrum (Table 2). The H and
C
assigned a C86
+
H
129NO41 molecular formula, as deduced from the [M
+
NMR data (Table 2) of the monosaccharide residues were assigned
starting from the readily identifiable anomeric proton of each hexosyl
or pentosyl unit, by means of COSY, TOCSY, ROESY, and HMBC spectra
4
NH ]
ion at m/z 1849.8384 in the positive ion mode HRESIMS.
Upon acid hydrolysis with 2.0 M HCl, 1 afforded echinocystic acid unit,
which was identified with an authentic sample, and the sugar compo-
nents 2-amino-2-deoxy-glucose (GlcNHAc), glucose (Glc), apiose (Api),
xylose (Xyl) and arabinose (Ara), which were identified by co-TLC with
authentic samples (Section 3). The absolute configuration of these sugar
residues was determined to be D for GlcNHAc, Glc, Api, Xyl, and L for
Ara based on GC analysis of their trimethylsilylated derivatives (Section
(
Table 2). The 13C NMR data indicated that the sugar residues Glc,
GlcNHAc, Xyl, and Ara were in their pyranose form, whereas the Api
residue was in furanose form. The anomeric proton of Xyl I was de-
3
termined to have the α-orientation based on its relatively small JH-1,H-2
value of 2.2 Hz, whereas Xyl II was β-orientated based on its relatively
large 3
JH-1,H-2 value of 7.6 Hz. The anomeric protons of Api was β-or-
3
3
) (Chaabi et al., 2010).
Extensive analysis of 1D and 2D NMR spectra ( H NMR, 13C NMR,
DEPT, COSY, ROESY, HSQC and HMBC) indicated the presence of seven
tertiary methyl groups at δ 0.75, 0.93, 0.95, 0.97, 1.06, 1.22, and 1.83,
an olefinic broad triplet proton at δ 5.55 (brt, J = 3.5 Hz, H-12) at-
122.8 (C-12), a quaternary carbon at δ 144.5
3.26 (brd, J = 7.6 Hz, H-3), and
4.83–6.30, evidencing that 1 was an oleanane type
1
ientated based on its relatively small
J
H-1,H-2
value of 2.2 Hz. The re-
maining anomeric protons of Glc, GlcNHAc, and Ara, were determined
to have β, and α anomeric configuration, respectively, based on their
H
relative large 3
JH-1,H-2 values (6.6–8.2 Hz) in their pyranose form. The
H
anomeric signal at δ
amido)-2-deoxy-β-D-glucopyranosyl moiety (GlcNHAc) based on the
observation its characteristic signals at 9.08 (d, J = 8.0 Hz,
H
5.08 (d, J = 7.3 Hz) was assigned to 2-(acet-
tached to a carbon at δ
C
C
(
C-13), one oxymethine proton at δ
H
δ
H
sugars signals at δ
H
96

O.P. Noté et al.
Phytochemistry Letters 22 (2017) 95–101
Table 1
Table 2
NMR spectroscopic data (500 MHz for 1H and 125 MHz for 13C) for the aglycone moieties
NMR spectroscopic data (500 MHz for 1H and 125 MHz for 13C) for the sugar moieties of
of compounds 1-3 (δ in ppm and J in Hz).
compounds 1-3 (δ in ppm and J in Hz).
No
1
2
3
Position
1
2
3
δ
C
δ
H
(mult.)
δ
C
δ
H
(mult.)
δ
C
δ
H
(mult.)
δ
C
δ
H
δ
C
δ
H
δ
C
δ
H
1
1
2
2
3
4
5
6
6
7
7
8
9
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
3
a
b
a
b
38.7
26.4
0.92
1.45
1.70
2.13
3.26
–
0.78
1.27
1.57
1.52
1.58
–
1.76
–
1.93
2.00
5.55
–
39.4
26.1
0.94
1.54
1.79
2.20
3.25
–
0.78
1.32
1.59
1.51
1.62
–
1.79
–
1.99
2.13
5.64
–
38.8
26.7
0.92
1.48
1.77
2.16
3.25
–
0.82
nd
nd
1.52
1.62
–
1.79
–
1.98
2.16
5.56
–
3-O-Sugars
GlcNHAc
1
2
3
4
5
6
104.5 5.08 (d, 7.3) 104.2 5.10 (d, 7.3) 104.8 5.09 (d, 7.3)
57.7
81.0
73.4
75.0
68.2
23.8
4.47
4.86
4.50
4.00
4.69; 4.78
2.16
56.8
81.3
73.2
74.9
67.8
23.4
4.55
4.88
4.59
4.05
4.67; 4.80
2.16
57.9
81.2
73.4
75.0
68.4
23.9
4.50
4.89
4.51
3.97
4.69; 4.77
2.16
89.6
39.3
56.0
18.6
89.7
39.8
56.8
18.3
89.8
39.4
56.2
18.9
a
b
a
b
NHCOCH
3
Ara-I
1
2
3
4
5
Xyl-I
1
2
3
4
5
Glc-I
1
2
3
33.6
33.9
33.8
103.5 5.28 (d, 6.6) 103.0 5.30 (d, 6.6) 103.8 5.28 (d, 6.6)
40.1
47.2
37.0
23.8
40.9
46.9
36.7
23.9
40.2
47.2
37.1
24.3
73.3
83.5
69.7
66.5
4.51
4.53
4.14
3.65; 4.22
73.2
82.5
69.4
66.3
4.53
4.59
4.15
3.74; 4.29
73.4
83.7
69.7
66.8
4.51
4.54
4.13
3.64; 4.23
0
1a
1b
2
3
4
5a
5b
6
7
8
9a
9b
0
1a
1b
2a
2b
3
4
5
6
7
122.8
144.5
42.0
122.5
144.2
41.7
123.1
144.4
42.1
108.0 4.83 (d, 2.2) 107.1 4.85 (d, 2.2) 108.2 4.84 (d, 2.2)
75.4
78.3
71.1
67.5
4.05
3.97
4.27
3.49; 4.36
74.5
77.6
71.1
66.3
4.07
4.01
4.26
3.53; 4.38
75.3
78.4
71.2
67.7
4.07
3.97
4.25
3.47; 4.35
–
–
–
36.4
1.76
2.36
5.65
–
3.44
1.32
2.79
–
1.20
2.42
2.17
2.29
1.22 (s)
0.93 (s)
0.75 (s)
0.95 (s)
1.83 (s)
–
36.5
1.85
2.39
5.69
–
3.51
1.37
2.83
–
1.28
2.47
2.20
2.37
1.28 (s)
0.98 (s)
0.83 (s)
1.01 (s)
1.85 (s)
–
36.2
1.78
2.40
5.65
–
3.48
1.33
2.80
–
1.22
2.40
2.16
2.29
1.22 (s)
0.92 (s)
0.78 (s)
0.94 (s)
1.83 (s)
–
75.3
49.1
41.2
47.1
75.2
49.5
41.0
47.8
75.0
49.2
41.4
47.4
104.5 5.55 (d, 7.6) 104.0 5.51 (d, 7.6) 104.7 5.56 (d, 7.6)
75.2
78.2
71.1
78.4
62.3
4.05
4.30
4.28
3.95
74.6
77.7
71.1
77.9
62.5
4.06
4.31
4.26
4.01
75.4
78.4
71.2
78.5
62.5
4.05
4.30
4.28
3.98
4
5
6
30.9
35.9
30.6
35.6
31.0
36.2
4.33; 4.49
4.35; 4.54
4.35; 4.52
28-O-Sugars
Glc-II
1
2
3
4
5
6
Ara-II
1
2
3
4
5
32.3
32.7
32.5
92.9
78.7
76.0
80.2
73.9
63.5
6.06 (d, 8.2) 92.7
6.06 (d, 8.2) 93.1
6.06 (d, 8.2)
4.28
4.14
4.05
3.87
28.2
17.1
15.6
17.4
27.2
176.0
33.3
24.6
28.9
17.7
16.8
18.1
27.9
176.0
33.9
24.2
28.4
17.4
15.9
17.7
27.6
176.1
33.6
24.0
4.29
77.8
76.0
80.2
73.3
63.5
4.31
78.3
76.0
80.0
73.3
63.2
4.14
4.15
4.03
4.06
3.89
3.91
4.51; 4.60
4.54; 4.65
4.52; 4.61
8
9
0
0.97 (s)
1.06 (s)
1.02 (s)
1.12 (s)
0.98 (s)
1.07 (s)
103.1 5.00 (d, 8.0) 101.8 5.17 (d, 8.0) 103.1 4.98 (d, 8.0)
75.2
74.0
68.9
67.5
5.65
4.13
4.26
3.76; 4.37
75.0
74.4
71.1
66.3
5.67
4.16
4.26
3.57; 4.39
75.2
74.0
69.1
67.6
5.65
4.14
4.27
3.73; 4.77
Assignments were based on the HMBC, HSQC, COSY and DEPT experiments.
Xyl-II
1
2
3
4
5
Api
1
2
NHCOCH
assignment was supported by the correlation observed in the HMBC
spectrum between the proton signal at δ 4.47 (H-2 of GlcNHAc) and
the carbonyl signal at δ 170.2 (NHCOCH
). In addition, the 1H NMR
spectrum of compound 1 exhibited two proton signals of a trans-olefinic
8.02 (d, J = 16.2 Hz), and five
3
) and δ
H 3
2.16 (s, NHCOCH ) (Abdel-Kader et al., 2001). This
105.2 5.40 (d, 7.6) 104.4 5.39 (d, 7.6) 105.1 5.39 (d, 7.6)
75.3
84.8
71.1
66.6
4.04
4.15
4.27
3.65; 4.26
74.8
84.9
71.0
66.2
4.03
4.16
4.26
3.67; 4.28
75.2
84.9
71.0
66.7
4.04
4.14
4.28
3.65; 4.26
H
C
3
group at δ
H
6.85 (d, J = 16.2 Hz) and δ
H
111.6 6.30 (d, 2.2) 110.9 6.23 (d, 2.2) 111.9 6.30 (d, 2.2)
aromatic proton signals for a monosubstituted benzene group for a
cinnamoyl moiety. It was also observed signals characteristic for acetyl
78.1
80.6
75.3
65.8
4.82
–
4.37; 4.79
4.21; 4.25
77.7
80.3
74.8
64.8
4.85
–
4.41; 4.79
4.23; 4.25
78.1
80.7
75.5
65.8
4.83
–
4.38; 4.79
4.21; 4.26
3
4
5
group (δ
H
C
/δ 1.86/170.8). The sequencing of the glycoside chains was
achieved by analysis of HMBC and ROESY experiments.
For the sugar chain attached at C-3 of the aglycone, the cross peak
Assignments were based on the HMBC, HSQC, COSY and DEPT experiments.
correlations observed in the HMBC spectrum between H-1 (δ
GlcNHAc and C-3 (δ 89.6) of the aglycone, and in the ROESY spectrum
between H-1 (δ 5.08) of GlcNHAc and H-3 (δ 3.26) of echinocystic
acid, suggested that GlcNHAc was directly attached to C-3 of the
aglycone. Moreover, the HMBC correlation observed between H-1 (δ
.55) of Glc I and C-3 (δ 81.0) of GlcNHAc established the connectivity
between the two sugar units, which was confirmed by the ROESY
correlation observed between H-3 (δ 4.86) of GlcNHAc and H-1 (δ
.55) of Glc I. On the other hand, the HMBC correlation observed be-
tween H-1 (δ 5.28) of Ara I and C-6 (δ 68.2) of GlcNHAc allowed us to
locate Ara I at C-6 of GlcNHAc. This was supported by the ROESY
correlation observed between H-1 (δ 5.28) of Ara I and H-6a (δ 4.69)
of GlcNHAc. This Ara I was substituted at its C-3 by Xyl I, as evidenced
H
5.08) of
C
by the direct and reverse correlations observed in the HMBC spectrum
H
H
between H-1 (δ
H-3 (δ 4.53) of Ara I and C-1 (δ
the ROESY correlation observed between H-1 (δ
4.53) of Ara I. The terminal position of Xyl I was evidenced by the
H
4.83) of Xyl I and C-3 (δ
108.0) of Xyl I. This was supported by
4.83) of Xyl I and H-3
C
83.5) of Ara I and between
H
C
H
H
5
C
(
H
δ
13
absence of any C NMR glycosylation shifts for this sugar moiety. Thus,
H
H
the tetrasaccharide α-D-xylopyranosyl-(1 → 3)-α-L-arabinopyranosyl-
5
(
1 → 6)-[β-D-glucopyranosyl-(1 → 3)]-2-(acetamido)-2-deoxy-β-D-glu-
H
C
copyranosyl moiety was established to be linked at C-3 of the aglycone
Fig. 2).
For the sugar chain attached at C-28 of the aglycone, the cross peak
observed in the HSQC spectrum at δ /δ 6.06/δ 92.9 (Glc II H-1/C-1)
(
H
H
H
C
97

O.P. Noté et al.
Phytochemistry Letters 22 (2017) 95–101
Fig. 2. Key HMBC and ROESY correlations for
Compound 1.
suggested that this sugar should be directly attached to C-28 of the
aglycone through an ester bond. The direct and reverse correlations
common in the three saponins. They will not be further discussed in the
structural elucidation of compounds 2 and 3.
observed in the HMBC spectrum between H-1 (δ
78.7) of Glc II and between H-2 (δ 4.29) of Glc II and C-1 (δ
05.2) of Xyl II, and the ROESY correlation observed between H-1 (δ
.40) of Xyl II and H-2 (δ
of Glc II. Moreover, the HMBC correlation observed between H-1 (δ
.30) of Api and C-3 (δ 84.8) of Xyl II permitted us to attach Api at C-3
H
5.40) of Xyl II and C-2
Chevalieroside B (2), obtained as a white amorphous powder, was
(
δ
C
H
C
assigned a C87
H
137NO42 molecular formula, as deduced from the [M
+
1
5
2
6
H
4
+NH ]
ion at m/z 1885.8960 in the positive ion mode HRESIMS.
H
4.29) of Glc II allowed us to locate Xyl II at C-
Detailed comparison of NMR data of 2 (1D and 2D NMR analysis) with
those of 1, indicated identical acyl moiety at C-6 of Glc-II and the
disappearance of the trans-cinnamoyl moiety signals observed for 1. In
addition, the 1H NMR spectrum of compound 2 exhibited one tri-sub-
H
C
of Xyl II. This was supported by the ROESY correlation observed be-
tween H-1 (δ 6.30) of Api and H-3 (δ 4.15) of Xyl II. On the other
hand, the direct and reverse correlations observed in the HMBC spec-
trum between H-1 (δ 5.00) of Ara II and C-4 (δ 80.2) of Glc II and
between H-4 (δ 4.03) of Glc II and C-1 (δ 103.1) of Ara II, and the
ROESY correlation observed between H-1 (δ 5.00) of Ara II and H-4
4.03) of Glc II allowed us to locate Ara II at C-4 of Glc II. In addition,
the location of the acetyl group at C-6 of Glc II was also evidenced by
the observation of the signals of C-6 of Glc II at δ 63.5 (deshielded,
1.2 ppm) and of C-5 of Glc II at δ 73.9 (shielded, −4.9 ppm) in
comparison to Glc I (δ 78.4). Furthermore, the observation of the
signal of H-2 of Ara II at δ 5.65 (deshielded, +1.15 ppm) and of C-2 of
Ara II at δ 75.2 (deshielded, + 1.8 ppm) in comparison to Ara I (δ
.51 and 73.3) indicated that C-2 of Ara II was esterified. Accordingly,
the cinnamoyl moiety was placed at C-2 of Ara II. This was supported
by the HMBC and ROESY correlations, observed between H-2 (δ 5.65)
of Ara II and the carbonyl group (δ 166.2) of the trans-cinnamoyl
moiety, and between H-3 (δ 4.13) of Ara II and the olefinic proton (δ
.02) of the trans-cinnamoyl moiety, respectively (Fig. 2). Thus, the
tetrasaccharide β-D-apiofuranosyl-(1 → 3)-β-D-xylopyranosyl-(1 → 2)-
(2-O-cinnamoyl)-α-D-arabinopyranosyl-(1 → 4)]-(6-O-acetyl)-β-D-glu-
H
H
stituted olefinic proton signal at δ
H
7.24 (d, J = 7.2 Hz) and one group
6.23 (dd, J = 10.9;
of one-substituted olefin proton signals at δ
H
H
C
17.6 Hz), 5.25 (d, J = 10.9 Hz) and 5.47 (d, J = 17.6 Hz), indicating
that compound 1 had one unit of monoterpenoid moiety (MT) (Liu
et al., 2010). All proton and carbon signals of this MT moiety were fully
assigned by extensive analysis of HSQC and further confirmed by HMBC
spectrum. The stereochemistry of the tri-substituted double bond was
determined as E from the chemical shift of H-3 at δ 7.24 since the Z
H
isomer would appear at higher field (Zhang et al., 1999). The config-
uration of C-6 of the MT moiety was determined as S based on the
H
C
H
(
H
δ
C
+
C
C
H
chemical shift values of C-5 (δ
C
41.0), C-7 (δ
C
C
144.1), C-8 (δ 112.7)
C
H
C
and C-10 (δ 23.6) which were very close to the corresponding values in
4
the 13C NMR data of (6S)-menthiafolic acid 6-O-β-D-quinovoside (Liang
et al., 2005). The esterification of the hydroxyl group at C-2 of Ara II by
MT was suggested from the deshielded position of H-2 of Ara II and C-2
H
C
of Ara II resonances at δ
supported by the HMBC correlation observed between H-2 (δ
Ara II and C-1 (δ 167.3) of MT moiety. Accordingly, the structure of
H
5.67 and δ
C
75.0, respectively. This was
H
H
H
5.67) of
8
C
compound 2 was established as 3-O-β-{α-D-xylopyranosyl-(1 → 3)-α-L-
arabinopyranosyl-(1 → 6)-[β-D-glucopyranosyl-(1 → 3)]-2-(acetamido)-
2-deoxy-β-D-glucopyranosyl}-echinocystic acid 28-O-β-D-apiofuranosyl-
(1 → 3)-β-D-xylopyranosyl-(1 → 2)-{2-O-[(6S,2E)-2,6-dimethyl-2,7-oc-
tadienoyl]-2)-{2-O-[(6S,2E)-2,6-dimethyl-2,7-octadienoyl]- α-L-arabi-
nopyranosyl-(1 → 4)}-(6-O-acetyl- β-D-glucopyranosyl) ester.
[
copyranosyl moiety was established to be attached at C-28 of the
aglycone (Fig. 2). Based on the above evidences, the structure of
compound 1 was established as 3-O-β-{α-D-xylopyranosyl-(1 → 3)-α-L-
arabinopyranosyl-(1 → 6)-[β-D-glucopyranosyl-(1 → 3)]-2-(acetamido)-
2
-deoxy-β-D-glucopyranosyl}-echinocystic acid 28-O-β-D-apiofuranosyl-
Chevalieroside C (3), obtained as a white amorphous powder, was
(
1 → 3)-β-D-xylopyranosyl-(1 → 2)-{2-O-cinnamoyl-α-D-arabinopyr-
assigned a C96
H
143NO43 molecular formula, as deduced from the [M
+
anosyl-(1 → 4)}- (6-O-acetyl- β-D-glucopyranosyl) ester.
4
+NH ]
ion at m/z 2016.9416 in the positive ion mode HRESIMS.
The extensive analysis of 1D and 2D NMR experiments showed that
the oligosaccharide chains at C-3 and C-28 of the echinocystic acid were
Detailed comparison of NMR data of 3 (1D and 2D NMR analysis) with
those of 2, indicated also identical acyl moiety at C-6 of Glc-II, and the
98

O.P. Noté et al.
Phytochemistry Letters 22 (2017) 95–101
presence of a cinnamoyl moiety (Cynn) and monoterpenoid moiety
resistant cancer cells. In addition, this study contributes to complete the
knowledge of the chemical composition of Albizia species, which are
natural sources of bioactive triterpenoid saponins.
(
MT), identified in 1 and 2, respectively. In addition, the NMR spectra
4.52, 4.61) and C-6
75.2), and H-3 (δ
74.0) of Ara-II. The observation of the HMBC corre-
5.65) of Ara II and C-1 (δ 166.4) of the Cynn
4.14) of Ara II and C-1 (δ 167.4) of the
of compound 3 showed acylation shifts at H-6 (δ
(
4
lations between H-2 (δ
moiety, and between H-3 (δ
H
δ
C
63.2) of Glc-II and at H-2 (δ
H
5.65) and C-2 (δ
C
H
.14) and C-3 (δ
C
3. Experimental
H
C
H
C
3.1. General
MT moiety, confirmed the positions of the Cynn and the MT moieties at
C-2 and C-3 of Ara II, respectively. Consequently, the structure of 3 was
established as 3-O-β-{α-D-xylopyranosyl-(1 → 3)-α-L-arabinopyranosyl-
1
Optical rotations were measured on a Jasco P-2000 polarimeter. H
NMR (500 MHz) and 13C NMR (125 MHz) spectra were recorded at
room temperature in pyridine-d5 using a Bruker AVANCE III 500
spectrometer. Chemical shifts are given in δ (ppm) value relative to
TMS as internal standard. HRESIMS spectra were recorded on a
microTOF ESI-TOF mass spectrometer (Agilent) operating in positive
mode. Analytical HPLC was performed on Varian 920-LC apparatus
equipped with an autosampler, a pump, a diode array detector (DAD),
and Galaxie software. Semipreparative HPLC was performed on a
(
1 → 6)-[β-D-glucopyranosyl-(1 → 3)]-2-(acetamido)-2-deoxy-β-D-glu-
copyranosyl}-echinocystic acid 28-O-β-D-apiofuranosyl-(1 → 3)-β-D-xy-
lopyranosyl-(1 → 2)-{2-O-[(6S,2E)-2,6-dimethyl-2,7-octadienoyl-3-O-
cinnamoyl]-2)-{2-O-[(6S,2E)-2,6-dimethyl-2,7-octadienoyl-3-O-cinna-
moyl]-α-L-arabinopyranosyl-(1 → 4)}-(6-O-acetyl- β-D-glucopyranosyl)
ester.
The pro-apoptotic activity of compounds 1–3 was evaluated using
Annexin V-FITC binding assay on two human cell lines: the pancreatic
carcinoma AsPC-1 and the cancerous monocytic THP-1 cell lines. In
result, percentage of apoptotic cells following 24 h of treatment was
increased in a concentration-dependent manner for AsPC-1 and THP-1
cells, respectively (Fig. 3). Computed concentrations of each compound
to induced half-maximal effects (EC50) on cell apoptosis were de-
termined as being 17.91 and 8.11 μM, 13.72 and 5.69 μM, and 3.10 and
Gilson apparatus equipped with Trilution LC software using
a
Nucleodur 100-5 C18ec (21 × 250 mm, 5 μm) column purchased from
Machery-Nagel (Germany). Thin layer chromatography (TLC) was
performed on precoated silica gel plates (60 F254, Merck) using the
system solvent n-BuOH-AcOH-H O, 65:15:25 as eluent. The spots were
2
observed after spray with Komarowsky reagent, which is a mixture
(5:1) of phydroxybenzaldehyde (2% in MeOH) and Ethanolic H SO
4
2
8.32 μM on AsPC-1 and THP-1 cells for chevalierosides A–C, respec-
(50%). Vacuum-liquid chromatography (VLC) was carried out using RP-
tively. The strong pro-apoptotic effect of chevalieroside C (3) on the
pancreatic carcinoma AsPC-1 cells observed at lowest concentration
may be probably due to the number and nature of acyl moieties in
compound 3 compared to compounds 1 and 2. Someone can also
wonder if the pro-apoptotic effect of saponins 1–3 on THP-1 cells is not
due to the presence of acyl moieties in their sugar chains, since the
increase of the percentage of apoptotic cells was not observed for the
THP-1 cancerous cells when the non-acylated glaberrimosides A–C re-
cently isolated from A. glaberrima (Noté et al., 2016a) were tested.
Nevertheless, further studies are necessary to support this conclusion.
Furthermore, the next steps will be to further explain the apoptotic
route induced by chevalieroside C (3) specifically to this highly
18 silica gel 60 (25–40 μm) and silica gel 60 (15–40 μm and 40–63 μm).
3.2. Plant material
The stem bark of A. chevalieri were harvested at Nkolbisson,
Yaoundé peripheral quarter, in Cameroon in October 2011 under the
guidance of Mr. Paul Nana, botanist of the National Herbarium of
Cameroon (NHC), where one specimen (47196/HNC) was deposited.
3.3. Extraction and isolation
The air-dried, powdered stem bark of A. chevalieri (150 g) were
Fig. 3. The apoptotic effect of the three purified sa-
ponins was investigated on 2 human cell lines (AsPC-
1
and THP-1) by capillary cytometry using the
Annexin-V FITC/PI staining assay (n = 3).
: p < 0.05; **: p < 0.01; ***: p < 0.001.
*
99

O.P. Noté et al.
Phytochemistry Letters 22 (2017) 95–101
extracted with 70% EtOH in soxhlet apparatus. The resulting hydro-
alcoholic solution was then evaporated to dryness under reduce pres-
sure to yield a brown residue (4.83 g). This residue was suspended in
France), supplemented with 10% (v/v) fetal bovine serum
(BioWhittaker, Verviers, Belgium), 2 mM ultraglutamine, 50 μM non-
essential amino acids, 50 U/ml penicillin and 50 μg/ml streptomycin
(Sigma-Aldrich). THP-1 cells were grown in RPMI 1640 medium with
2 mM L-alanyl-L-glutamine additionally supplemented with 10% (v/v)
fetal bovine serum and 50 U/ml penicillin and 50 μg/ml streptomycin
(Sigma-Aldrich). Cultures were kept at 37 °C in a humidified incubator
2 2
200 ml of H O and partitioned with n-BuOH sat. H O (3 × 300 ml).
The n-BuOH soluble phase was evaporated to dryness affording 6.14 g
of brown gum residue which was taken in a minimum of water (10 ml)
and then submitted to vacuum-liquid chromatography (VLC) using RP-
1
H
8 silica gel 60 (25–40 μm) eluted with a gradient of MeOH-H
O → 100%MeOH). The 70–85% MeOH extract (600.5 mg) was sub-
jected to VLC using silica gel 60 (15–40 μm) eluted with CHCl -MeOH-
O (80:20:2, 70:30:5, 60:33:7, and 60:40:10) to give four main sub-
fractions (ACE1- ACE4). Subfraction ACE4 (126.3 mg) was purified by
semipreparative HPLC using gradient system of CH CN-H O (20 ml/
min) to yield compounds 1 (t , 13.20 min, 7.9 mg), 2 (t , 13.68 min,
.5 mg), and 3 (t , 16.16 min, 7.2 mg).
2
O (100%
2
equilibrated with 5% CO . Before confluency adherent cells were
trypsinized and subcultured twice a week.
2
3
H
2
3.5.2. Pro-apoptotic evaluation
Cells were treated with the three different compounds of cheva-
lieriosides A–C (1–3) in ranging concentrations (1–15 μM) then col-
lected for apoptosis induction estimation. A minimum of 5000 cells was
acquired per sample and analyzed on the InCyte software (Guava/
Millipore/Merck, CA, USA). Apoptosis rates were assessed by capillary
cytometry (Guava EasyCyte Plus, Millipore Merck) using Annexin V-
FITC (ImmunoTools, Germany) and PI (MiltenyiBiotec Inc., USA) ac-
cording to the manufacturer’s recommendations. Gates were drawn
around the appropriate cell populations using a forward scatter (FSC)
versus side scatter (SSC) acquisition dot plot to exclude debris. Final
concentration of DMSO applied to cells during incubation with tested
drugs was always 0.5%. In the tested setup that concentration had no
adverse effects on cell viability, nor cell morphology. To discriminate
between negative and positive events in the analysis, a non-stained
control sample from each culture condition always accompanied ac-
quisition of the stained cells to define their cut off. Negative control, i.e.
sample with cells without compounds but with the same amount of
DMSO as for diluted compounds, as well as positive control with 15 μM
3
2
R
R
8
R
3-O-β-{α-D-xylopyranosyl-(1 → 3)-α-L-arabinopyranosyl-(1 → 6)-[β-
D-glucopyranosyl-(1 → 3)]-2-(acetamido)-2-deoxy-β-D-glucopyrano
syl}-echinocystic acid 28-O-β-D-apiofuranosyl-(1 → 3)-β-D-xylopyr-
anosyl-(1 → 2)-{2-O-cinnamoyl-α-D-arabinopyranosyl-(1 → 4)}-(6-O-
2
5
acetyl-β-D-glucopyranosyl) ester (1), white amorphous powder; [α]
D
1
13
−
28.8 (c 0.01, MeOH); H NMR (C
5 5
D N, 500 MHz) and C NMR
(C D N, 125 MHz) data, see Tables 1 and 2. Positive HRESIMS: m/z
5 5
+
1
849.8384 [M+NH
-O-β-{α-D-xylopyranosyl-(1 → 3)-α-L-arabinopyranosyl-(1 → 6)-[β-
D-glucopyranosyl-(1 → 3)]-2-(acetamido)-2-deoxy-β-D-glucopyranos
yl}-echinocystic acid 28-O-β-D-apiofuranosyl-(1 → 3)-β-D-xylopyr-
anosyl-(1 → 2)-{2-O-[(6S,2E)-2,6-dimethyl-2,7-octadienoyl]-2)-{2-O-
4
] .
3
[
(6S,2E)-2,6-dimethyl-2,7-octadienoyl]-α-L-arabinopyranosyl-(1 → 4)}-
(
[
6-O-acetyl-β-D-glucopyranosyl) ester (2), white amorphous powder;
2
5
1
13
α]
D
−45.7 (c 0.01, MeOH); H NMR (C
5
D
5
N, 500 MHz) and C NMR
Celastrol, a natural pentacyclic triterpenoid (Enzo Life Sciences,
(
C
5
D
5
N, 125 MHz) data, see Tables 1 and 2. Positive HRESIMS: m/z
Farmingdale, US), were included in each experiment. Cytometers per-
formances were checked weekly using the Guava Easy Check Kit 4500-
0025 (Merck/Millipore/Guava Hayward, CA, USA).
+
1
885.8960 [M+NH
-O-β-{α-D-xylopyranosyl-(1 → 3)-α-L-arabinopyranosyl-(1 → 6)-[β-
D-glucopyranosyl-(1 → 3)]-2-(acetamido)-2-deoxy-β-D-glucopyranos
yl}-echinocystic acid
4
] .
3
28-O-β-D-apiofuranosyl-(1 → 3)-β-D-xylopyr-
3.5.3. Statistical analysis
anosyl-(1 → 2)-{2-O-[(6S,2E)-2,6-dimethyl-2,7-octadienoyl-3-O-cinna-
moyl]-2)-{2-O-[(6S,2E)-2,6-dimethyl-2,7-octadienoyl-3-O-cinnamoyl]-
α-L-arabinopyranosyl-(1 → 4)}- (6-O-acetyl- β-D-glucopyranosyl) ester
Data presented as bar graphs, were expressed as means ± S.E.M. of
at least three independent experiments. Statistical evaluation was per-
formed with the one-way ANOVA test followed by the post-hoc
Bonferroni test using GraphPad Prism software (Prism version 5.04 for
Windows, GraphPad Software, CA, USA); a p-value less than 0.05 was
considered as significant (*), less than 0.01 very significant (**) and less
than 0.001 highly significant (***).
2
5
−50.5 (c 0.01, MeOH); 1H NMR
(3), white amorphous powder; [α]
(C D N, 500 MHz) and C NMR (C D N, 125 MHz) data, see Tables 1
5 5 5 5
D
1
3
+
and 2. Positive HRESIMS: m/z 2016.9416 [M+NH
.4. Acidic hydrolysis of isolated saponins
Each saponin (2 mg) was hydrolyzed with 2 ml of 2 M HCl at 85 °C
4
] .
3
Acknowledgements
during 2 h. After cooling, the solvent was removed under reduced
pressure. The sugar mixture was extracted from the aqueous phase
This work was financially supported by the World Academy of sci-
ences (TWAS) (grant no: 3240277733). The authors are also grateful to
Mr. Victor Nana of the National Herbarium of Cameroon (NHC) for the
identification and collection of plant.
(
2 2 2 2
10 ml) and washed with CH Cl (3 × 5 ml). The combined CH Cl
extracts were washed with water to give after evaporation the aglycone
moiety, which was compared with an authentic standard sample by Co-
TLC. The sugars were first analyzed by TLC over silica gel (CHCl
3
-
References
MeOH-H O, 8:5:1) by comparison with standard samples. The absolute
2
configuration of each monosaccharide was determined from GC–MS
analysis of their trimethylsilylated derivatives by comparison with au-
thentic samples using the method previously described (Chaabi et al.,
Abdel-Kader, M., Hoch, J., Berger, J.M., Evans, R., Miller, J.S., Wisse, J.H., Mamber, S.W.,
Dalton, J.M., Kingston, D.G.I., 2001. Two bioactive saponins from Albizia sub-
dimidiata from the Suriname rainforest. J. Nat. Prod. 64, 536–539.
Arbonnier, M., 2004. Trees, Shrubs and Lianas of West African Dry Zones, quæ ed. CIRAD-
MNHN, Paris.
2010). The following sugars were detected: D-glucose, 2-(acetamido)-2-
Burkill, H.M., 1995. The Useful Plants of West Tropical Africa, vol. 3 Families J-L, Royal
deoxy-D-glucose, D-xylose, L-arabinose, and D-apiose.
Botanic Gardens, Kew 857 pp (W).
Cao, S., Norris, A., Miller, J.S., Ratovoson, F., Razfitsalama, J., Andriantsiferana, R.,
Rasamison, V.E., Tendyke, K., Suh, T., Kingston, D.G.I., 2007. Cytotoxic triterpenoid
saponins of Albizia gummifera from Madagscar rain forest. J. Nat. Prod. 70, 361–366.
Chaabi, M., Chabert, P., Vonthron-Sénécheau, C., Weniger, B., Ouattara, M., Corstjens, H.,
Sente, I., Declercq, L., Lobstein, A., 2010. Acylated flavonol pentaglycosides from
Baphia nitida leaves. Phytochem. Lett. 3, 70–74.
3
3
.5. Pro-apoptotic evaluation
.5.1. Cell lines and culture conditions
The human pancreatic carcinoma cell line ASPC-1 was a gift from
Dr. Timo Kehl (Deutsches Krebsforschungszentrum Heidelberg,
Heidelberg, Germany), and THP-1 (TIB-202) cell lines, were purchased
from ATCC (LGC Standards,Molsheim, France). ASPC-1 cells were cul-
tivated in DMEM-based media (Sigma-Aldrich, Saint-Quentin-Fallavier,
Haddad, M., Miyamoto, T., Laurens, V., Lacaille-Dubois, M.A., 2003. Two new biologi-
cally active triterpenoidal saponins acylated with salicylic acid from Albizia adian-
thifolia. J. Nat. Prod. 66, 372–377.
Haddad, M., Laurens, V., Lacaille-Dubois, M.A., 2004. Induction of apoptosis in a leu-
kemia cell line by triterpene saponins from Albizia adianthifolia. Bioorg. Med. Chem.
100

O.P. Noté et al.
Phytochemistry Letters 22 (2017) 95–101
1
2, 4725–4734.
brain tumor cells. Carbohydr. Res. 404, 26–33.
Krief, S., Thoison, O., Sevenet, T., Wrangham, R.W., Lavaud, C., 2005. Triterpenoid sa-
ponins anthranilates from Albizia grandibracteata leaves ingested by primates in
Uganda. J. Nat. Prod. 68, 897–903.
Noté, O.P., Azouaou, S.A., Simo, L., Antheaume, C., Guillaume, D., Pegnyemb, D.E.,
Muller, C.D., Lobstein, A., 2016a. Phenotype-specific apoptosis induced by three new
triterpenoid saponins from Albizia glaberrima (Schumach. & Thonn.) Benth.
Fitoperapia 109, 80–86.
Noté, O.P., Simo, L., Mbing, J.N., Guillaume, D., Aouazou, S.A., Muller, C.D., Pegnyemb,
D.E., Lobstein, A., 2016b. Two new triterpenoid saponins from the roots of Albizia
zygia (DC.) J.F. Macbr. Phytochem. Lett. 18, 128–135.
Liang, H., Tong, W.Y., Zhao, Y.Y., Cui, J.R., Tu, G.U., 2005. An antitumor compound
julibroside J28 from Albizia julibrissin. Bioorg. Med. Chem. Lett. 15, 4493–4495.
Liu, R., Ma, S., Yu, S., Pei, Y., Zhang, S., Chen, X., Zhang, J., 2009. Cytotoxic oleanane
triterpene saponins from Albizia chinensis. J. Nat. Prod. 72, 632–639.
Liu, R., Ma, S., Liu, Y., Yu, S., Chen, X., Zhang, J., 2010. Albizosides D and E, two new
cytotoxic triterpene saponins from Albizia chinensis. Carbohydr. Res. 345, 1877–1881.
Mathias, S.N., Abubakar, M.S., October, N., 2016. Pentacyclic triterpenoids from the
stem-bark of Albizia chevalieri (Mimosaceae) Hams. Int. J. Pharm. Pharm. Sci. 8,
Sahu, N.P., Achari, B., 2001. Advances in structural determination of saponins and ter-
penoid glycosides. Curr. Org. Chem. 5, 315–334.
Saidu, Y., Lawal, M., Isezuo, S.A., Shehu, R.A., Sahabi, D.M., Bilbis, L.S., 2007. Partial
purification and elucidation of mechanism of hypoglycaemic agent of aqueous leaf
extract of Albizzia chevalieri Harms (Leguminosae). J. Pharmacol. Toxicol. 6,
513–523.
Saidu, Y., Nwachukwu, F.C., Bilbis, L.S., Faruk, U.Z., Abbas, A.Y., 2010. Hypoglycaemic
and hypolipidemic effects of root extracts of Albizzia chevalieri in alloxan induced
diabetic rats. Niger J. Basic Appl. Sci. 18, 72–78.
Tchoukoua, A., Tabopda, T.K., Uesugi, S., Kimura, K.-I., Kwon, E., Momma, H., Ngadjui,
B.T., Koseki, T., Shiono, Y., 2016. Two new 5-deoxyflavan-3,4-diol glucosides from
roots of Albizia chevalieri. Magn. Reson. Chem. 54, 893–896.
2
61–265.
Melek, F.R., Miyase, T., Ghaly, N.S., Nabil, M., 2007. Triterpenoid saponins with N-acetyl
sugar from the bark of Albizia procera. Phytochemistry 68, 1261–1266.
Melek, F.R., Kassem, I.A.A., Miyase, T., Fayad, W., 2014. Caspicaosides E-K, triterpenoid
saponins and cytotoxic acylated saponins from fruits of Gleditsia caspica Desf.
Phytochemistry 100, 110–119.
Miyase, T., Melek, F.R., Ghaly, N.S., Warashina, T., El-Kady, M., Nabil, M., 2010a.
Echinocystic acid 3,16-O-bisglycosides from Albizia procera. Phytochemistry 71,
1
375–1380.
Wei, H.J., Yin, T., Zhu, Z., Shi, P.F., Tian, Y., Wang, C.Y., 2011. Expression of CD44, CD24
and ESA in pancreatic adenocarcinoma cell lines varies with local microenvironment.
Hepatobiliary Pancreat. Dis. Int. 10, 428–434.
Woldemichael, G.M., Wink, M., 2001. Identification and biological activities of triterpe-
noid saponins from Chenopodium quinoa. J. Agric. Food Chem. 49, 2327–2332.
Zhang, Z., Koike, K., Jia, Z., Nikaido, T., Guo, D., Zheng, J., 1999. Triterpenoidal saponins
acylated with two monoterpenic acids from Gleditsia sinensis. Chem. Pharm. Bull. 47,
388–393.
Miyase, T., Melek, F.R., Warashina, T., Selim, M.A., El Fiki, N.M., Kassem, I.A.A., 2010b.
Cytotoxic triterpenoid saponins acylated with monoterpenic acids from fruits of
Gleditsia caspica Desf. Phytochemistry 71, 1908–1916.
Noté, O.P., Mitaine-offer, A.C., Miyamoto, T., Paululat, T., Mirjolet, J.F., Duchamp, O.,
Pegnyemb, D.E., Lacaille-Dubois, M.A., 2009. Cytotoxic acacic acid glycosides from
the roots of Albizia coriaria. J. Nat. Prod. 72, 1725–1730.
Noté, O.P., Jihu, D., Antheaume, C., Zeniou, M., Pegnyemb, D.E., Guillaume, D.,
Chneiwess, H., Kilhoffer, M.C., Lobstein, A., 2015. Triterpenoid saponins from Albizia
lebbeck (L.) Benth and their inhibitory effect on the survival of high grade human
Zheng, L., Zheng, J., Zhao, Y., Wang, B., Wu, L., Liang, H., 2006. Three anti-tumor sa-
ponins from Albizia julibrissin. Bioorg. Med. Chem. Lett. 16, 2765–2768.
101