Oleanane-type saponins and prosapogenins from Albizia julibrissin and their cytotoxic activities

Article abstract of DOI:10.1016/j.phytochem.2021.112674

Two undescribed oleanane-type saponins, julibrosides K–L, along with three undescribed oleanane-type prosapogenins, julibrosides M–O, were isolated from the stem bark of Albizia julibrissin Durazz. and the mild alkaline hydrolysate of the total saponin, r

Full text of DOI:10.1016/j.phytochem.2021.112674

Phytochemistry 185 (2021) 112674
Contents lists available at ScienceDirect
Phytochemistry
journal homepage: www.elsevier.com/locate/phytochem
Oleanane-type saponins and prosapogenins from Albizia julibrissin and their
cytotoxic activities
,
Qinghua Hana b, Yi Qiana, Xuda Wanga, Qingying Zhanga, Jingrong Cuia, Pengfei Tua,
,
*
Hong Lianga
a State Key Laboratory of Natural and Biomimetic Drugs and Department of Natural Medicines, School of Pharmaceutical Sciences, Peking University Health Science
Center, Beijing, 100191, China
b East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai, 200090, China
A R T I C L E I N F O
A B S T R A C T
Keywords:
Two undescribed oleanane-type saponins, julibrosides K–L, along with three undescribed oleanane-type prosa-
pogenins, julibrosides M–O, were isolated from the stem bark of Albizia julibrissin Durazz. and the mild alkaline
hydrolysate of the total saponin, respectively. Their structures were established by extensive analysis of 1D and
2D NMR experiments (COSY, TOCSY, HSQC, HMBC, and HSQC-TOCSY) and mass spectrometry. Furthermore,
the cytotoxic activities of the isolated compounds against BGC-823, A549, HCT-116, and HepG2 cell lines were
evaluated, and julibroside L showed significant cytotoxic activities against the four cancer cell lines with IC50
Albizia julibrissin Durazz.
Leguminosae
Oleanane-type saponins
Oleanane-type prosapogenins
Cytotoxic activities
values of 5.77, 4.80, 4.26, and 4.93 μM, respectively.
1. Introduction
of A. julibrissin. Furthermore, three undescribed oleanane-type prosa-
pogenins, julibrosides M–O (3–5), were obtained from the mild alkaline
hydrolysate of the total saponin. Herein, we report the isolation, struc-
ture elucidation, and cytotoxic activities of the isolated compounds.
The stem bark of Albizia julibrissin Durazz. (Leguminosae) has been
recorded in Chinese Pharmacopoeia for treating swelling and pain of the
lungs, skin ulcers, and wounds (Pharmacopoeia Committee of China,
2020). Previous chemical studies on A. julibrissin have revealed that
oleanane-type saponins were the principle constituents (Ikeda et al.,
1997; Zou et al., 2000), with a common aglycone unit (acacic acid or
machaerinic acid) and vary in oligosaccharide moieties at C-3, C-28 and
monoterpenoid glycosyl units at C-21. Some of these triterpenoid sa-
ponins exhibited cytotoxic activities against different cancer cell lines in
vitro (Ikeda et al., 1997; Zou et al., 2000; Krief et al., 2005; Zheng et al.,
2006; Cao et al., 2007; Lacaille-Dubois et al., 2011). The total saponin
from A. julibrissin has been reported to inhibit vascular endothelial
growth factor-mediated angiogenesis in vitro and in vivo (Cai et al., 2015)
and improve immune responses by inducing cytokine and chemokine
(Sun et al., 2014). Our previous work showed that the total saponin from
the stem bark of A. julibrissin could inhibit proliferation and promote
apoptosis in human hepatoma carcinoma cells both in vitro and in vivo,
and it exhibited a significant apoptosis-inducing effect via mitochon-
drial apoptotic pathway (Qian et al., 2018). As an ongoing research for
anti-proliferation active constituents, two undescribed oleanane-type
saponins, julibrosides K–L (1–2), were isolated from the total saponin
2. Results and discussion
The EtOH extract of the stem bark of A. julibrissin was suspended in
H2O and partitioned with EtOAc and n-BuOH, respectively. The n-BuOH
soluble fraction, which showed potential cytotoxic activities against
eight cancer cell lines, was subsequently subjected to various column
chromatographies to afford compounds 1–2 (Fig. 1). And the mild
alkaline hydrolysate of total saponin was separated by various column
chromatographies to yield compounds 3–5 (Fig. 1).
Julibroside K (1) was obtained as a white amorphous powder. Its
molecular formula was determined as C102H162O49 by the positive
MALDI-TOF-MS ion at m/z 2193.7686 [M
+
Na]+(calcd. for
C102H162O49Na, 2194.0082) and 2209.7573 [M + K]+(calcd. for
C102H162O49K, 2209.9822), corresponding to 22 indices of hydrogen
deficiency. The IR spectrum showed absorption bands for hydroxy
(3385 cm-1) and carbonyl (1703, 1654 cmꢀ 1) functionalities. The 1H and
13C NMR data of 1 displayed characteristic signals of an oleanane-type
saponin (Table 1), containing nine sugar moieties (Table 2) and two
* Corresponding author.
E-mail address: lianghong@bjmu.edu.cn (H. Liang).
https://doi.org/10.1016/j.phytochem.2021.112674
Received 30 September 2020; Received in revised form 11 January 2021; Accepted 13 January 2021
Available online 23 March 2021
0031-9422/© 2021 Elsevier Ltd. All rights reserved.

Q. Han et al.
Phytochemistry 185 (2021) 112674
(1H, d, J = 7.8 Hz), 4.92 (1H, d, J = 7.8 Hz), 5.01 (1H, d, J = 7.8 Hz),
5.09 (1H, d, J = 7.2 Hz), 5.34 (1H, d, J = 7.8 Hz), 5.89 (1H, br s), 6.05
(1H, d, J = 7.8 Hz), and 6.27 (1H, br s); 99.7, 99.6, 107.0, 103.7, 107.3,
106.2, 102.2, 96.1, and 111.4], and two sets of menthiafolic acid signals
for two monoterpenoid units [δC 167.9, 168.5 (two α, β-unsaturated
ester); 144.1, 115.5, 144.5, 115.2 (two pairs of mono-substituted
olefinic carbons); 80.2, 79.8 (two oxygenated quaternary carbons)].
The aglycone was further recognized to be acacic acid (3β, 16α, 21β-
trihydroxy-olean-12-ene-28-oic acid) by comparison of its 1H and 13C
NMR data with those reported in the literature (Han et al., 2017).
The sugar moieties of 1 were identified as L-arabinose, L-rhamnose,
D-xylose, D-fucose, D-quinovose, and D-glucose by acid hydrolysis fol-
lowed by HPLC analysis of their arylthiocarbamate derivatives with
authentic samples (Tanaka et al., 2007). Moreover, the absolute con-
figurations of the two monoterpenoid units were determined by alkaline
hydrolysis of 1. As shown in Fig. 3, mild alkaline hydrolysis with
NaHCO3 gave prosapogenin-10 (6) and the outer monoterpene glycoside
(7). Compound 7 was further hydrolyzed with snailase to give
(6S)-menthiafolic acid (8). The absolute configuration of C-6′ in 8 was
20
deduced to be S by comparison its optical rotation data [
α
]
+17 (c
D
14
0.11, CHCl3) with those reported in the literature [
α
]
D +18.2 (c 0.22,
Fig. 1. Structures of compounds 1–5.
CHCl3) (Liu et al., 2009). Thus, 7 was identified as (2E, 6S)-2, 6-dime-
thyl-6-hydroxy-2, 7-octadienoic acid methyl ester-6-O-β-D-quinovopyr-
anoside (Kiuchi et al., 1997). Strong alkaline hydrolysis of 6 with NaOH
produced prosapogenin-1 (9) and the inner monoterpene glycoside (10).
10 was identified as (2E, 6S)-6-hydroxy-2-hydroxymethyl-6-methyl-2,
7-octadienoic acid 6-O-β-D-quinovopyranoside by comparison of its
monoterpenoid units (MT and MT’) (Table 3). This was evidenced by the
presence of seven singlet methyl signals and seven carbon signals for the
oleanane core [δH 0.98, 1.04, 1.05, 1.08, 1.18, 1.32, and 1.91 (each 3H,
s); δC 16.3, 29.6, 17.5, 19.5, 17.7, 28.6, and 27.7], nine anomeric pro-
tons and carbons for the sugar moieties [δH 4.85 (1H, d, J = 7.8 Hz), 4.89
Table 1
1H NMR (600 MHz) and13C NMR (150 MHz) data of the aglycone moieties of compounds 1–5 in pyridine-d5.
position
1
2
3
4
5
δC
δH (J in Hz)
δC
δH (J in Hz)
δC
δH (J in Hz)
δC
δH (J in Hz)
δC
δH (J in Hz)
1
2
39.3
1.63a
39.3
1.61, m
39.3
1.61, m
39.2
1.60, m
39.2
1.58a
1.23, m
2.31, m
1.23a
1.19a
1.20a
1.22, m
2.24, m
1.92, m
3.58, m
27.2
27.3
2.28, m
27.2
2.27, m
27.1
2.28, m
27.1
1.95, m
3
4
5
6
88.8
40.0
56.4
18.8
3.61, m
88.6
40.2
56.5
19.1
3.60, m
88.9
40.0
56.4
19.0
3.58, dd (11.1, 3.9)
88.6
39.9
56.3
18.9
3.59, brd, 10.8
88.5
40.2
56.2
19.1
0.98a
0.98a
0.92, br d (12.0)
1.67, m
0.98a
1.50a
0.95a
1.58a
1.35, m
1.61, m
1.49a
7
34.0
40.5
47.5
37.5
24.3
1.74, m
1.94, m
33.9
40.4
48.5
37.5
24.4
1.74, m
1.83a
34.0
40.5
47.5
37.4
24.3
1.69, m
33.8
40.4
47.4
37.4
24.1
1.72, m
1.90a
33.6
40.2
48.3
37.3
24.2
1.72, m
1.80, m
2.01, m
5.44, brs
8
9
1.90a
10
11
2.09, m
1.46, m
5.63, brs
2.04, m
5.48, brs
2.09, m
1.59, m
5.61, brs
2.09, m
5.60, brs
12
13
14
15
123.5
143.7
42.4
123.5
143.4
42.7
123.5
143.8
42.4
123.5
143.6
42.3
123.5
143.3
42.5
36.3
2.27, m
2.05, m
5.23, brs
29.0
2.07a
36.3
2.26, m
2.02, m
5.22, br s
36.1
2.25, m
2.04, m
5.21, br s
28.8
1.98, m
1.50, m
2.24, m
2.14, m
1.51, m
2.30, m
2.21, m
16
74.3
25.2
74.3
74.1
25.0
17
18
19
52.0
41.3
48.2
49.1
41.7
46.9
52.0
41.3
48.2
51.9
41.2
48.1
48.9
41.5
46.8
3.44, dd (14.4, 3.6)
2.96, t (13.7)
3.21, dd (13.5, 3.9)
1.96, t (14.4)
1.34, m
3.43, dd (13.8, 3.6)
2.95, t (13.5)
1.40, m
3.42, dd (13.8, 3.6)
2.93, t (13.8)
1.38, m
3.17, dd (13.8, 3.6)
1.93, m
1.41, dd (12.6, 4.2)
1.30, m
20
21
22
35.8
77.4
36.8
35.9
75.9
36.9
35.8
77.5
36.8
35.7
77.3
36.7
35.9
75.7
36.7
6.31, dd (11.7, 6.0)
2.74, dd (13.2, 4.8)
2.20, t (12.0)
1.32, s
5.19, brs
2.32, m
2.03, t (12.0)
1.36, s
6.30, dd (11.1, 5.7)
2.73, m
6.28, dd (11.1, 5.7)
2.71, m
5.24, dd (11.4, 4.8)
2.25, t (11.4)
2.03, m
2.20, t (12.3)
1.28, s
2.18, t (12.0)
1.30, s
23
24
25
26
27
28
29
30
28.6
17.5
16.3
17.7
27.7
174.8
29.6
19.5
28.4
17.4
16.3
17.8
26.4
175.3
29.3
19.0
28.5
17.6
16.2
17.6
27.6
174.8
29.5
19.5
28.5
17.4
16.1
17.6
27.5
174.7
29.4
19.4
28.2
17.2
16.1
17.6
26.1
175.1
29.1
18.8
1.28, s
1.05, s
1.22, s
1.17, s
1.03, s
1.18, s
0.98, s
0.99, s
0.98, s
0.96, s
0.96, s
1.18, s
1.18, s
1.16, s
1.17, s
1.14, s
1.91, s
1.38, s
1.89, s
1.89, s
1.35, s
1.04, s
1.08, s
0.93, s
0.98, s
1.03, s
1.09, s
1.02, s
1.07, s
0.94, s
0.97, s
a
Overlapped signals are reported without designated multiplicities.
2

Q. Han et al.
Phytochemistry 185 (2021) 112674
Table 2
1H NMR (600 MHz) and13C NMR (150 MHz) data of the sugar moieties of compounds 1–5 in pyridine-d5.
position
1
2
3
4
5
δC
δH (J in Hz)
δC
δH (J in Hz)
δC
δH (J in Hz)
δC
δH (J in Hz)
δC
δH (J in Hz)
sugar (C-3)
Glc1 1
107.0
76.2
78.6
72.1
77.1
70.4
4.92, d (7.8)
4.04, t (7.5)
4.18, m
105.3
83.7
78.4
72.3
77.1
70.2
4.90, d (8.4)
4.26a
105.2
83.3
79.0
72.2
77.3
70.2
4.89, d (7.8)
4.29, t (8.1)
4.13, t (8.7)
4.11, t (8.1)
4.02, t (8.1)
4.73, m
106.9
76.0
78.6
71.9
77.0
70.2
4.90, d (7.8)
4.02, t (7.8)
4.17, t (6.9)
4.08a
105.1
83.2
78.7
72.0
76.9
70.0
4.87, d (7.2)
4.24, t (9.6)
4.10a
2
3
4
5
6
4.25a
4.20a
4.12a
4.08a
4.12, m
4.04, m
4.09a
4.03a
4.77, m
4.75, m
4.75, m
4.72, m
4.39, m
4.34, m
4.34, m
4.37, m
4.30, m
Fuc 1
103.7
82.5
75.6
72.6
71.7
17.6
107.3
76.2
77.9
71.1
67.6
5.01, d (7.8)
103.9
83.0
75.6
72.6
71.7
17.8
107.6
76.5
78.0
71.2
67.6
5.01, d (7.2)
103.8
82.7
75.6
72.5
71.8
17.7
107.4
76.3
77.9
71.1
67.6
4.98, d (7.8)
4.44, t (8.7)
4.14, dd (9.6, 3.0)
4.03, d (3.0)
3.77a
103.6
82.4
75.5
72.4
71.6
17.5
107.2
76.1
77.8
71.0
67.5
4.99, d (7.2)
4.43, t (8.7)
4.13, dd (9.6, 3.0)
4.01, d (3.0)
3.74, m
103.7
82.7
75.4
72.4
71.5
17.5
107.4
76.3
77.8
71.0
67.4
4.98, d (7.2)
4.40, t (8.4)
4.12, dd (9.6, 3.6)
4.01, d (3.0)
3.75, m
2
4.46a
4.44a
3
4.15, m
4.15, m
4
4.03, m
4.03, m
5
3.77, m
3.78, m
6
1.49, d (6.6)
5.09, d (7.2)
4.09, t (7.5)
4.04, t (8.4)
4.11, m
1.51, d (6.0)
5.05, d (7.2)
4.05a
1.50, d (7.2)
5.06, d (6.6)
4.07, t (9.3)
4.05, t (8.7)
4.11, m
1.47, d (6.6)
5.07, d (7.2)
4.09, m
1.48, d (6.0)
5.01, d (6.6)
4.05, t (7.8)
4.01, t (8.4)
4.10, m
Xyl1 1
2
3
4
5
4.05a
4.02, t (8.4)
4.05, t (8.7)
4.46, dd (11.4, 4.8)
3.56, t (10.5)
4.11, m
4.49, m
4.45, m
4.46, dd (11.4, 4.8)
3.61, m
4.40, dd (11.4, 4.8)
3.54, t (10.8)
5.38, d (7.8)
4.11, t (8.4)
4.23, t (9.0)
4.27, t (8.7)
3.91, m
3.59, m
3.58, m
Glc2 1
106.4
75.6
78.5
72.2
78.5
63.2
5.39, d (8.0)
4.13, t (8.1)
4.24, t (9.0)
4.29, t (9.0)
3.93, m
106.2
75.6
78.4
72.2
78.7
63.1
5.42, d (7.8)
4.12, t (8.1)
4.25, t (9.0)
4.29, t (8.7)
3.92, m
106.0
75.6
78.2
72.0
78.4
63.1
2
3
4
5
6
4.47, m
4.43, m
4.41, m
4.25, m
4.21, m
4.20, m
sugar (C-28)
Glc’ 1
96.1
77.2
78.5
71.6
79.5
62.3
6.05, d (7.8)
4.00, t (8.4)
4.18, t (6.0)
4.19a
96.0
77.1
78.7
71.7
79.5
62.5
6.11, d (7.8)
4.04a
96.1
77.4
78.5
71.6
79.5
62.3
6.06, d (7.8)
4.00a
95.9
77.1
78.6
71.4
79.3
62.2
6.04, d (7.8)
4.01, t (8.1)
4.16a
95.8
77.1
78.4
71.4
79.3
62.2
6.06, d (7.8)
4.09, t (8.4)
4.17, t (8.4)
4.19, t (8.4)
3.92a
2
3
4
5
6
4.12, t (8.4)
4.21, br d (8.4)
3.95, m
4.18a
4.18a
4.18a
3.95a
3.96, t (8.1)
4.35, m
4.23, m
5.87, brs
5.19a
3.94, brs
4.33, m
4.34, m
4.36, m
4.33, m
4.22, m
4.22, m
4.20, m
4.20, m
Rha 1
102.2
70.9
82.4
79.4
69.6
19.3
111.4
84.9
78.8
85.8
62.9
5.89, brs
102.2
71.2
82.5
79.6
69.4
19.3
111.4
85.3
78.8
85.1
62.9
6.05, brs
102.2
70.8
82.4
79.4
69.6
19.3
111.4
84.9
78.8
85.7
62.9
102.1
70.8
82.3
79.2
69.4
19.1
111.3
84.7
78.6
85.6
62.8
5.88, brs
102.0
71.0
82.4
79.3
69.3
19.1
111.1
85.0
78.6
85.0
62.7
5.98, brs
2
5.18a
5.19a
5.17a
5.18a
3
4.95a
4.94a
4.96a
4.93a
4.92, m
4
4.49a
4.50a
4.50, m
4.54, m
1.78, d (5.4)
6.28, brs
5.00a
4.48, m
4.48, m
5
4.55a
4.57a
4.53, m
4.52, m
6
1.77, d (6.0)
6.27, brs
1.82, d (6.0)
6.24, brs
4.97a
1.76, d (6.0)
6.26, brs
4.97a
1.79, d (6.0)
6.21, brs
Ara 1
2
3
4
5
4.99, d (3.0)
4.81, dd (6.6, 4.2)
4.74, m
4.93, d (2.4)
4.75, t (7.5)
4.72, m
4.79, m
4.81, m
4.76, m
4.27, m
4.16, m
5.34, d (7.8)
3.99a
4.78a
4.74, m
4.73a
4.27, dd (12.0, 3.0)
4.16, dd (11.7, 4.5)
5.34, d (7.8)
3.99, t (8.7)
4.15, t (9.0)
4.08, t (8.7)
3.97, m
4.31, m
4.24, m
4.27, m
4.17, m
4.15, m
4.15, m
Glc’′ 1
106.2
75.9
78.7
72.2
78.5
63.2
106.2
75.9
78.8
72.2
78.6
63.2
5.36, d (7.8)
4.00, t (8.4)
4.19, m
106.1
75.8
78.5
72.2
78.6
63.1
106.0
75.6
78.6
72.0
78.4
63.0
5.32, d (7.8)
3.99, t (8.4)
4.14, t (9.0)
4.07, t (8.7)
3.96, br d (3.6)
4.49, m
106.0
75.6
78.5
72.0
78.4
63.0
5.32, d (7.8)
3.99, t (8.4)
4.18, t (9.0)
4.09, t (9.0)
3.90a
2
3
4
5
6
4.13, m
4.08, t (8.1)
3.95a
4.12, m
4.01, m
4.51, m
4.51, m
4.51, m
4.21, m
4.49, m
4.21, m
4.24, m
4.19, m
4.20, m
Qui 1
99.6
73.8
79.8
75.3
72.9
19.1
4.89, d (7.8)
4.05, t (8.4)
5.83, t (9.0)
3.77, t (9.6)
3.73, t (6.9)
1.61, d (5.4)
99.8
75.8
76.1
77.6
70.6
18.9
4.89, d (7.8)
4.05, t (8.4)
4.21, m
99.6
75.7
78.6
77.1
72.8
19.1
4.84, d (7.8)
3.97, t (8.4)
4.09a
2
3
4
5.38, t (8.4)
3.69, t (6.9)
1.37, d (6.0)
3.68, t (8.7)
3.68, t (8.7)
1.58, d (5.4)
5
6
Xyl 1
100.6
75.5
79.0
71.5
67.3
4.84, d (7.8)
3.96, t (8.1)
4.11, t (9.0)
4.20, m
100.5
75.4
78.8
71.3
67.1
4.82, d (7.8)
3.94, t (8.4)
4.10, t (8.7)
4.17, m
2
3
4
5
4.29, dd (10.8, 4.8)
3.62, t (10.8)
4.26, m
3.61, m
Qui’ 1
99.7
75.9
78.8
77.2
73.0
19.3
4.85, d (7.8)
3.99, t (8.4)
4.11, t (7.8)
3.70a
2
3
4
5
3.70a
6
1.58, d (5.4)
Xyl’ 1
100.7
4.87, d (7.8)
(continued on next page)
3

Q. Han et al.
Phytochemistry 185 (2021) 112674
Table 2 (continued)
position
1
2
3
4
5
δC
δH (J in Hz)
δC
δH (J in Hz)
δC
δH (J in Hz)
δC
δH (J in Hz)
δC
δH (J in Hz)
2
3
4
5
75.6
79.1
71.6
67.4
3.98, m
4.14, t (8.7)
4.21, m
4.29, m
3.65a
a
Overlapped signals are reported without designated multiplicities.
Table 3
1H NMR (600 MHz) and13C NMR (150 MHz) data of the MT and MT’ moieties of compounds 1–5 in pyridine-d5.
position
1
2
3
4
5
δC
δH (J in Hz)
δC
δH (J in Hz)
δC
δH (J in Hz)
δC
δH (J in Hz)
δC
δH (J in Hz)
MT (C-21)
1
2
3
4
167.9
134.2
145.6
24.0
168.0
128.6
143.3
24.0
167.9
134.2
145.6
24.1
167.8
134.0
145.6
24.0
167.6
133.6
146.4
24.0
7.04, t (7.5)
2.43, m
6.92, t (7.2)
2.44, m
7.06, t (7.8)
2.69, m
7.03, t (7.8)
2.68, m
7.07, t (7.5)
2.71, m
2.32, m
2.12a
5
6
7
8
41.2
1.80a
40.8
1.74, t (8.1)
41.2
1.82, t (7.5)
41.2
1.80, t (6.9)
41.1
1.84, t (8.1)
80.2
80.1
80.0
79.9
80.0
144.1
115.5
6.13, dd (17.7, 11.4)
5.37, d (17.7)
5.17, d (11.4)
4.72, br s
144.4
115.5
6.22, dd (17.7, 10.8)
5.48, d (17.7)
5.29, d (10.8)
1.87, s
144.3
115.4
6.20, dd (17.7, 11.1)
5.37, d (17.7)
5.18, d (11.1)
4.73, br s
144.2
115.3
6.18, dd (17.4, 10.8)
5.35, d (17.4)
5.16, d (10.8)
4.71, br s
144.2
115.2
6.21, dd (17.7, 11.1)
5.39, d (17.7)
5.18, d (11.1)
4.72, br s
9
56.7
24.1
13.0
24.1
56.6
24.1
56.5
24.0
56.4
24.1
10
MT’
1′
1.50, s
1.57, s
1.51, s
1.50, s
1.52, s
168.5
128.6
143.1
23.9
168.2
128.4
143.7
24.1
2′
3′
6.98, t (6.9)
2.68, m
7.05, t (7.2)
2.12a
4′
2.33, m
5′
40.8
1.74, m
40.8
1.77a
1.62, m
6′
7′
8′
79.8
79.9
144.5
115.2
6.18, dd (17.7, 11.1)
5.41, d (17.7)
5.21, d (11.1)
1.80, s
144.4
115.4
6.26, dd (18.3, 11.4)
5.42, d (18.3)
5.23, d (11.4)
1.90, s
9′
13.1
24.1
13.0
24.2
10′
1.51, s
1.55, s
a
Overlapped signals are reported without designated multiplicities.
1)/70.4 (Glc1 C-6), 4.92 (Glc1 H-1)/88.8 (aglycone C-3), suggested a
sugar chain of β-D-xylopyranosyl-(l→2)-β-D-fucopyranosyl-(1 → 6)-β-D-
glucopyranosyl was attached to C-3 of the aglycone. The HMBC corre-
lations of 5.34 (Glc′′ H-1)/82.4 (Rha C-3), 6.27 (Ara H-1)/79.4 (Rha C-
4), 5.89 (Rha H-1)/77.2 (Glc’ C-2), 6.05 (Glc’ H-1)/174.8 (aglycone C-
28), revealed the sugar chain of β-D-glucopyranosyl-(l→3)-[
α-L-arabi-
nofuranosyl-(l→4)]- -L-rhamnopyranosyl-(l→2)-β-D-glucopyranosyl
α
was attached to C-28 of the aglycone. The remaining HMBC correlations
of 4.89 (Qui H-1)/80.2 (MT C-6), 5.83 (Qui H-3)/168.5 (MT’ C-1), 4.85
(Qui’ H-1)/79.8 (MT’ C-6), 6.31 (aglycone H-21)/167.9 (MT C-1),
generated the MT-sugar “hybrid” chain and was attached to C-21 of the
aglycone.
Thus, the structure of 1 was assigned as 21-O-{(2E,6S)-2-hydrox-
ymethyl-6-methyl-6-O-[3-O-(2′E, 6′S)-2′,6′-dimethyl-6′-O-β-D-quinovo-
pyranosyl-2′,7′-octadienoyl-β-D-quinovopyranosyl]-2,7-octadienoyl]}-
3-O-[β-D-xylopyranosyl-(l→2)-β-D-fucopyranosyl-(1 → 6)-β-D-gluco-
pyranosyl] acacic acid 28-O-β-D-glucopyranosyl-(l→3)-[
furanosyl-(l→4)]-
ester, and was named julibroside K.
α-L-arabino-
α
-L-rhamnopyranosyl-(l→2)-β-D-glucopyranosyl
Fig. 2. Key HMBC correlations of 1.
Julibroside L (2) was obtained as an amorphous powder, and its
molecular formula was determined as C107H170O52 on the basis of
MALDI-TOF-MS peaks at m/z 2310.0022 [M + Na]+ and 2325.9697 [M
+ K] +. Acid hydrolysis of 2 yielded a sugar mixture of L-rhamnose, L-
arabinose, D-fucose, D-xylose, D-glucose, and D-quinovose. The 1H and
13C NMR data of 2 bore a resemblance to those of julibroside J44 except
NMR data and optical rotation value with those of reported authentic
sample (Kiuchi et al., 1997) (see Fig. 3).
The connections among the aglycone, the sugar moieties, and the
monoterpenoid units were achieved by detailed HMBC analysis (Fig. 2).
The HMBC correlations of 5.09 (Xyl1 H-1)/82.5 (Fuc C-2), 5.01 (Fuc H-
4

Q. Han et al.
Phytochemistry 185 (2021) 112674
Fig. 3. Mild and strong alkaline hydrolysis of 1.
for the presence of xylopyranosyl signals in 2 instead of the outer qui-
novopyranosyl residues in julibroside J44 (Han et al., 2017), which was
further confirmed by HMBC correlations of 4.87 (Xyl’-H-1)/79.9
(MT’-C-6), 4.89 (Qui-H-1)/80.1 (MT-C-6), and 5.38 (Qui-H-4)/168.2
(MT’-C-1). Consequently, the structure of 2 was identified as 21-O- {(2E,
6S)-2, 6-dimethyl-6-O- [4-O-(2′E, 6′S)-2′, 6′-dimethyl-6′-O-β-D
-xylopyranosyl-2′,7′-octadienoyl-β-D-quinovopyranosyl]-2,7-octadie-
noyl]}-3-O-{β-D-xylopyranosyl-(l→2)-β-D-fucopyranosyl-(1 → 6)-[β-D
6S)-2-hydroxymethyl-6-methyl-6-O-β-D-xylopyranosyl-2,7-octadienoy-
l]-3-O-{β-D-xylopyranosy-(l→2)-β-D-fucopyranosyl-(1 → 6)-[β-D-gluco-
py
-ranosyl-(1 → 2)]-β-D-glucopyranosyl}
acacic
acid
28-O-β-D-glucopyranosyl-(l→3)-[
α
-L-arabinofuranosyl-(l→4)]-α-L-rha-
mnopyranosyl-(l→2)-β-D-glucopyranosyl ester, and was named julibro-
side M.
Julibroside N (4), an amorphous powder, was found to possess a
molecular formula of C85H136O43 on the basis of positive MALDI-TOF-
MS at m/z 1867.7755 [M + Na]+ and 1883.7560 [M + K] +. The 1H
and 13C NMR data of 4 showed high similarity to those of 3 with the
absence of a glucopyranosyl unit. When compared with 3, a downfield
-glucopyranosyl-(1 → 2)]-β-D-glucopyranosyl}
machaerinic acid
28-O-β-D-glucopyranosyl-(l→3)-[
α
-L-arabinofuranosyl-(l→4)]-α-L-rha-
mnopyranosyl-(l→2)-β-D-glucopyranosyl ester, and was named juli-
broside L.
shift of Glc1-C-1 (δ 106.9, +1.7 ppm) and an upfield shift of Glc1-C-2 (δ
C
Julibroside M (3) was obtained as an amorphous powder, and its
molecular formula of C91H146O48 was suggested by the positive MALDI-
76.0, ꢀ 7.3 ppm) were observed, which supported the lack of a sugaCr
moiety linked at Glc1-C-2. Further assignments of the signals of the
glucopyranosyl moiety suggested there was no extended sugar unit
linked with it, and the 13C NMR chemical shifts of the sugar chain
connected to 3-position of the aglycone was superimposable with those
in 1. Consequently, the structure of 4 was identified as 21-O-[(2E, 6S)-2-
hydroxymethyl-6-methyl-6-O-β-D-xylopyranosyl-2,7-octadienoyl]-3-O-
[β-D-xylopyranosyl-(l→2)-β-D-fucopyranosyl-(1 → 6)-β-D-glucopyr-
TOF-MS peaks at m/z 2029.8301 [M + Na]+ and 2045.8099 [M + K] +
.
The 1H and 13C NMR data of 3 (Tables 1ꢀ 3) showed similar resonances
to those of julibroside J31 (Zheng et al., 2006), apart from the absence of
a methyl group and the downfield-shifted anomeric carbon (δ 100.6 in
C
3, δC 99.6 in julibroside J31), indicated the quinovopyranosyl unit at the
6-position of the inner monoterpenoid moiety in julibroside J31 was
replaced by a xylopyranosyl residue in 3, which was further confirmed
by HMBC correlation between δH 4.84 (Xyl-H-1) and δC 80.0 (MT-C-6).
anosyl] acacic acid 28-O-β-D-glucopyranosyl-(l→3)-[
anosyl-(l→4)]- -L-rhamnopyranosyl-(l→2)-β-D-glucopyranosyl ester,
and was named julibroside N.
α-L-arabinofur-
α
Therefore, the structure of
3
was elucidated as 21-O-[(2E,
5

Q. Han et al.
Phytochemistry 185 (2021) 112674
Grace Alltime C18 column (250 × 22 mm, 5
μm). Semipreparative HPLC
Table 4
Cytotoxic activities of compounds 1–5 against four human cancer cell lines.
was performed on a Phenomenex Gemini C18 column (250 × 10 mm,
5 μm) using an Agilent 1260 LC system (Agilent, USA). Column chro-
Compound
IC50 (μM)
matography (CC) was performed on Diaion HP20 (200–300 mesh, Mit-
subishi Chemical Co., Japan), silica gel (200–300 mesh, Qingdao Marine
BGC-823
A549
HCT-116
HepG2
1
21.68 ± 1.38
5.77 ± 0.55
50.68 ± 3.01
68.75 ± 5.13
77.51 ± 2.32
0.052 ± 0.01
22.40 ± 3.47
4.80 ± 0.15
26.00 ± 2.05
4.26 ± 0.16
61.24 ± 1.52
80.21 ± 2.47
59.68 ± 6.35
0.03 ± 0.008
16.52 ± 4.40
4.93 ± 0.21
54.83 ± 3.57
66.43 ± 1.41
74.31 ± 2.19
0.045 ± 0.01
Chemical Inc., Qingdao, China), and ODS-A (50 μm, YMC Co. Ltd.,
2
Japan). Thin layer chromatography (TLC) analysis were carried out
using precoated silica gel GF254 plates (Qingdao Marine Chemical Inc.,
Qingdao, China), and spots were observed under UV254 light and
sprayed by 10% H2SO4–EtOH reagent. HPLC grade solvents used for
HPLC analysis and preparation were purchased from Fisher Scientific
International (Fair Lawn, New Jersey, USA), and deionized water was
purified by Milli-Q Synthesis A10 (Merck Millipore, Massachusetts,
USA). Other solvents used for extraction and isolation were of analytical
grade and purchased from Beijing Tongguang Chemicals (Beijing,
China). All chemicals were purchased from J & K Co. Ltd. (Beijing,
China).
3
57.73 ± 2.38
78.83 ± 3.56
70.35 ± 1.89
0.026 ± 0.006
4
5
taxol
Julibroside O (5) was isolated as an amorphous powder with the
molecular formula of C92H148O47, as determined based on the positive
MALDI-TOF-MSdata(m/z2027.8531[M+ Na]+ and2043.8329[M+ K]
+). The NMR data of 5 were similar to those of julibroside J31 (Zheng
et al., 2006) except for the replacement of an oxymethine (δ 74.2) in
julibroside J31 by a methylene (δC 25.0) in 5. The location of Cthe meth-
ylenewasdesignatedatC-16bytheupfield-shifted carbonsignalsofC-15
and C-17 of the aglycone moiety. The NMR data for aglycone moiety of 5
were in good agreement with those of julibroside J26 (Zou et al., 2006),
which have the same aglycone of machaerinic acid (Kinjo et al., 1992).
Acid hydrolysis of 5 gave a sugar mixture of L-rhamnose, L-arabinose,
D-fucose, D-xylose, D-glucose, and D-quinovose, determined by HPLC
analysis (Tanaka et al., 2007). Accordingly, 5 was assigned as 21-O-[(2E,
6S)-2-hydroxymethyl-6-methyl-6-O-β-D-quinovopyranosyl-2,7-octadie-
noyl]-3-O-{β-D-xylopyranosyl-(l→2)-β-D-fucopyranosyl-(1 → 6)- [β-D
4.2. Plant material
The dried stem bark of Albizia julibrissin Durazz. (Leguminosae) was
collected from Shaanxi Province (Xi’an City, longtitude:125.151421,
latitude: 42.920414), People’s Republic of China, in October 2014,
winter. The plant material was identified by Prof. Mingying Shang,
Department of Natural Medicines, School of Pharmaceutical Sciences,
Peking University Health Science Center. A voucher specimen (HH-
201410) was deposited in the Department of Natural Medicines, School
of Pharmaceutical Sciences, Peking University Health Science Center.
-glucopyranosyl-(1 → 2)]-β-D-glucopyranosyl}
machaerinic acid
28-O-β-D-glucopyranosyl-(l→3)-[
α
-L-arabinofuranosyl-(l→4)]-α-L-rha-
mnopyranosyl-(l→2)-β-D-glucopyranosyl ester, and was named julibro-
4.3. Extraction and isolation
side O.
Compounds 1–5 were screened for cytotoxic activities against four
cancer cell lines (BGC-823, A549, HCT-116, HepG2) by MTT method,
and taxol was selected as the positive control. The results (Table 4)
revealed that compound 2 showed the most potent cytotoxic activity
against the four cancer cell lines, with the IC50 values of 5.77, 4.80, 4.26,
The stem bark of A. julibrissin (18.0 kg) was percolated three times
with 95% EtOH (3 × 20 L), and the residue was percolated with 50%
EtOH (5 × 20 L). After removal of the solvents under reduced pressure,
the residual extract was suspended in H2O and partitioned successively
with EtOAc and n-BuOH. The n-BuOH extract (2.0 kg) was chromato-
graphed on Dianion HP20 macroporous absorbent resin, eluting with
gradient EtOH/H2O to obtain three main fractions represent the poly-
saccharide, lignan glycoside and total saponin, respectively. Cytotoxic
assay indicated that the total saponin was the most active fraction,
exhibited cytotoxic activities against eight human tumor cell lines (Hela,
Panc, HepG2, BGC-823, MCF-7, A549, PC3M1E8, and A375). Then, the
total saponin (1.2 kg) was subjected to silica gel CC eluting with
CH2Cl2–MeOH–H2O (100:10:1 → 60:40:10) to yield 15 fractions (Fr.
1–15). Fr. 9 (160.0 g) was separated over an ODS column eluting with
MeOH: H2O (60:40 → 80:20) to afford two fractions (Fr. 9A and Fr. 9B).
Fr. 9B (total saponin, TSAJ, 100.0 g) was partially passed through an
ODS column, eluted with a gradient solvent system (70%, 72%, 74%,
76%, 78%, 80% MeOH–H2O) to give six corresponding fractions (Fr.
9B1–9B6). Fr. 9B4 (15.0 g) was separated by preparative HPLC using
74% MeOH–H2O, to afford 13 subfractions. Subfraction 5 (900.0 mg)
was purified by preparative HPLC using 32% CH3CN–H2O (2.5 mL/min)
to afford 1 (8.0 mg, tR 22.3 min). Subfraction 10 (66.0 mg) was prepared
on preparative HPLC to give 2 (4.0 mg, tR 47.1 min), with 36%
CH3CN–H2O (2.5 mL/min).
and 4.93 μM, respectively, compound 1 showed moderate inhibitory
activity, while compounds 3–5 were inactive. These results agreed with
previous discussion on preliminary SAR of saponins from this species
(Han et al., 2017).
3. Conclusions
Further phytochemical investigation of A. julibrissin afforded two
previously undescribed oleanane-type saponins (1–2) and three unde-
scribed prosapogenins (3–5). The cytotoxic activities of the isolated
compounds were tested against BGC-823, A549, HCT-116, and HepG2
cell lines, and compound 2 showed significant cytotoxic activities
against the four cancer cell lines.
4. Experimental section
4.1. General experimental procedures
Optical rotations were obtained on a Rudolph Autopol IV automatic
polarimeter (Rudolph Research Analytical, New Jersey, USA). UV
spectra were recorded on a Shimadzu UV-2450 UV–visible spectropho-
tometer (Shimadzu, Kyoto, Japan). IR spectra were recorded with a
Thermo Nicolet Nexus 470 FT-IR spectrometer (Nicolet, Denver, USA).
NMR spectra were recorded on a Bruker AVANCE III-600 instrument
with TMS as reference, and the chemical shifts are indicated as δ values
(ppm). MALDI-TOF-MS data were acquired on an AB SCIEX MALDI TOF-
TOF 5800 Analyzer (AB SCIEX, USA) equipped with a neodymium:
yttrium-aluminum-garnet laser (laser wavelength was 349 nm), in
reflection positive-ion mode. Preparative HPLC separations were per-
formed on an Alltech semi-preparative instrument equipped with a
Fr. 9B (2.0 g) was refluxed for 1 h with saturated NaHCO3 in MeOH
(100 mL). The reaction mixture was evaporated to dryness and the
residue was dissolved in water and partitioned with EtOAc and n-BuOH,
respectively. The n-BuOH extract (700.0 mg) was separated by prepar-
ative HPLC using 31% CH3CN (10.0 mL/min) to afford eight fractions
(Fr. 9B-WJ1–Fr. 9B-WJ8). Fr. 9B-WJ3 (48.4 mg) was further purified by
preparative HPLC using 26% CH3CN–H2O (2.5 mL/min) to yield 3
(4.5 mg, tR 45.8 min). Fr. 9B-WJ4 (31.0 mg) was chromatographed on
preparative HPLC with 27.5% CH3CN–H2O (2.5 mL/min) to give 4
(11.4 mg, tR 33.0 min). Fr. 9B-WJ6 (34.8 mg) was subjected to prepar-
ative HPLC by isocratic solution (2.5 mL/min, 27.5% CH3CN–H2O) to
6

Q. Han et al.
Phytochemistry 185 (2021) 112674
afford 5 (12.1 mg, tR 41.9 min).
4.6. Enzymatic hydrolysis of 7
20
Julibroside K (1): white, amorphous powder; [
α
]
ꢀ 43 (c 0.1,
D
MeOH); UV (MeOH) λmax (log
ε
) 213 (4.6) nm; IR (KBr) νmax 3445, 2929,
Compound 7 (0.7 mg) and snailase (2.0 mg) were dissolved in ace-
tate buffer (0.2 M, pH 5.0, 1.0 mL) and incubated at 55 ◦C for 72 h. The
reaction mixture was extracted with CH2Cl2 to give compound 8
1707, 1648, 1599, 1567, 1515, 1454, 1384, 1133, 1025, 842, 676,
579 cmꢀ 1
;
1H and 13C NMR data, see Tables 1–3; MALDITOFMS m/z
2193.7686 [M
+
Na]+(calcd for
C
102H162O49Na, 2194.0083),
(0.3 mg)
2209.7573 [M + K]+ (calcd for C102H162O49K, 2209.9822).
Compound 8: [
α
]
+ 17 (c 0.11, CHCl3); 1H NMR (400 MHz,
20
CDCl3): δH 6.89 (1H, t, JD= 7.2 Hz, H-3), 5.91 (1H, dd, J = 10.6, 17.4 Hz,
H-7), 5.24 (1H, d, J = 17.2 Hz, H-8a), 5.10 (1H, d, J = 10.8 Hz, H-8b),
2.24 (2H, m, H-4), 1.83 (3H, s, H-9), 1.66 (2H, m, H-5), 1.32 (3H, s, H-
10).
20
Julibroside L (2): white, amorphous powder; [
α
]
ꢀ 20 (c 0.13,
D
MeOH); UV (MeOH) λmax (log ε) 213 (4.6) nm; IR (KBr) νmax 3445, 2929,
1707, 1648, 1599, 1567, 1515, 1454, 1384, 1133, 1025, 842, 676,
579 cmꢀ 1
;
1H and 13C NMR data, see Tables 1–3; MALDITOFMS m/z
2310.0022 [M
+ Na]+(calcd for C107H170O52Na, 2310.0556),
2325.9697 [M + K]+ (calcd for C107H170O52K, 2326.1107).
4.7. Strong alkaline hydrolysis of 6
20
Julibroside M (3): white, amorphous powder; [
α
]
ꢀ 30 (c 0.12,
D
MeOH); UV (MeOH) λmax (log ε) 212 (4.6) nm; IR (KBr) νmax 3372, 2930,
Compound 6 was hydrolyzed with 3% NaOH (1.0 mL) and MeOH
(1.0 mL) for 10 h at room temperature. After adjusting the pH to 5.0 with
2M HCl, the reaction mixture was extracted successively with EtOAc and
n-BuOH. The EtOAc extract of 6 was purified by preparative HPLC using
31% CH3CN (2.5 mL/min) to yield compound 10 (0.2 mg), the n-BuOH
extract was separated by preparative HPLC using 28% CH3CN (2.5 mL/
min) to afford compound 9 (0.3 mg).
1736, 1693, 1386, 1229, 1073, 591 cmꢀ 1
;
1H and 13C NMR data, see
Tables 1–3; MALDITOFMS m/z 2029.8301 [M + Na]+ (calcd for
C
C
91H146O48Na, 2029.8882), 2045.8099 [M
91H146O48K, 2045.9386).
+
K]+ (calcd for
20
Julibroside N (4): white, amorphous powder; [
α
]
ꢀ 30 (c 0.1,
MeOH); UV (MeOH) λmax (log
ε
) 213 (4.6) nm; IR (KBDr), νmax 3416,
2922, 1722, 1676, 1654, 1439, 1384, 1152, 1028, 876, 664, 580 cmꢀ 1
;
1H and 13C NMR data, see Table 1–3; MALDITOFMS m/z 1867.7755 [M
+ Na]+ (calcd for C85H136O43Na, 1867.8353), 1883.7560 [M + K]+
4.8. Cytotoxicity assays
(calcd for C85H136O43K, 1883.9438).
20
Julibroside O (5): white, amorphous powder; [
α
]
ꢀ 30 (c 0.09,
D
Human lung cancer (A549), colorectal cancer (HCT116), gastric
cancer (BGC-823), and liver cancer (HepG2) cell lines were obtained
from the State Key Laboratory of Natural and Biomimetic Drugs, Peking
University Health Science Center (Beijing, People’s Republic of China).
Cell lines were cultured in Dulbecco’s modified Eagle medium (DMEM,
M&C Gene Technology., Ltd, Beijing, China) and supplemented with
10% fetal bovine serum (PAN-Biotech, Aidenbach, Germany), 100 U/mL
MeOH); UV (MeOH) λ
(log ε) 213 (4.6) nm; IR (KBr), νmax 3394,
max
2936, 1751, 1686, 1638, 1459, 1388, 1229, 1073, 648 cmꢀ 1; 1H and 13
C
NMR data, see Tables 1–3; MALDITOFMS m/z 2027.8531 [M + Na]+
(calcd for C92H148O47Na, 2027.9089), 2043.8329 [M + K]+ (calcd for
C
85H136O43K, 2044.0174).
penicillin, and 100 μ
g/mL streptomycin at 37 ◦C with 5% CO2.
4.4. Determination of the absolute configuration of the monosaccharides
Cytotoxic activity was investigated using the MTT colorimetric
method (Alley et al., 1988). Briefly, cells were seeded in a 96-well plate
An HPLC-UV-based method was performed for monosaccharide
determination (Tanaka et al., 2007). Compound 1 (2.0 mg) was dis-
solved in 2M HCl–H2O (2.0 mL) and heated at 95 ◦C for 10 h. The re-
action mixture was extracted with CH2Cl2 3 times, the aqueous layer
contained sugars was evaporated under vacuum to furnish a neutral
residue. L-Cysteine methyl ester hydrochloride (2.0 mg) and anhydrous
pyridine (1.0 ml) were added to the mixture and stirred at 60 ◦C for 1 h.
at a density of 5 × 103 cells per well in 180
μL of medium for 12 h, fol-
lowed by exposure to the test compounds or positive control. After 48 h
exposure, 20
incubated at 37 ◦C for 4 h. Supernatant fractions were aspirated, and
100 L of DMSO was added to each well. The absorbance was measured
μL of MTT (5 mg/mL) was added and the cells were further
μ
at 570 nm using a microplate reader (EnVision, PerkinElmer Life-
sciences, USA). Cytotoxic activity was expressed as IC50 values (con-
centration inhibiting the proliferation rate of tumor cells by 50%,
compared to untreated control cells). All experiments were carried out
in quadruplicate. Taxol was used as the positive control.
The product was mixed with 10 μL o-tolylisothiocyanate and kept at
60 ◦C for another 1 h. The final reaction mixture was analyzed by HPLC
under the following conditions: an Agilent 1260 chromatograph
equipped with a phenomenex column (5 μm, 4.6 × 250 mm); column
temperature: 30 ◦C; mobile phase: isocratic elution of 23% CH3CN–H2O
containing 0.2% formic acid for 50 min and subsequent washing of the
column with 90% CH3CN–H2O for 10 min, flow rate: 0.8 mL/min; in-
Associated content
jection volume: 10 μL; UV detection wavelength: 250 nm. From the acid
Supporting information available.
hydrolysate of 1, L-arabinose, L-rhamnose, D-fucose, D-quinovose,
D-xylose, and D-glucose were confirmed by comparison of the retention
times of their derivatives with those standard sugars derivatized in a
similar way, which showed retention times of 27.16, 40.68, 33.08,
38.08, 28.07, and 24.24 min, respectively. The constituent sugars of
compounds 2–5 were also identified by the same method.
NMR, MS and IR spectra of compounds 1–5 (PDF)
Declaration of competing interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
4.5. Mild alkaline hydrolysis of 1
Solution of compound 1 (5.0 mg) with saturated NaHCO3 in MeOH
(2.0 mL) were refluxed for 1 h, respectively. The reaction mixtures were
concentrated in vacuo to dryness. Then, the residues were dissolved in
water and partitioned successively with EtOAc and n-BuOH respectively.
The EtOAc extract of 1 was purified by preparative HPLC using 31%
CH3CN (2.5 mL/min) respectively to yield compound 7 (0.7 mg, tR
22.2 min), the n-BuOH extract was separated by preparative HPLC using
30% CH3CN (2.5 mL/min) to afford compound 6 (1.0 mg, tR 20 min).
Acknowledgements
This study was financially supported by The Drug Innovation Major
Project (2018ZX09711001-008-003). We are grateful to Prof. Mingying
Shang (Peking University Health Science Center) for identifying the
plant material. We thank the State Key Laboratory of Natural and Bio-
mimetic Drugs, Peking University Health Science Center, for offering
cancer cell lines and certain spectroscopic measurements.
7

Q. Han et al.
Phytochemistry 185 (2021) 112674
the saponin fraction. Chem. Pharm. Bull. 45, 807–812. https://doi.org/10.1248/
Appendix A. Supplementary data
cpb.45.807.
´
Krief, S., Thoison, O., Sevenet, T., Wrangham, R.W., Lavaud, C., 2005. Triterpenoid
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.phytochem.2021.112674.
saponin anthranilates from Albizia grandibracteata leaves ingested by primates in
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acacic acid-type saponins from Leguminosae-Mimosoideae as potent cytotoxic and
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