Albidosides H and I, two new triterpene saponins from the barks of Acacia albida Del. (Mimosaceae)

Article abstract of DOI:10.1080/14786419.2017.1371156

Two new triterpene saponins, albidosides H (1) and I (2), along with the three known saponins were isolated from the barks of Acacia albida. Their structures were elucidated on the basis of extensive 1D- and 2D-NMR studies and mass spectrometry. Albidosid

Full text of DOI:10.1080/14786419.2017.1371156

Natural Product Research
Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: http://www.tandfonline.com/loi/gnpl20
Albidosides H and I, two new triterpene saponins
from the barks of Acacia albida Del. (Mimosaceae)
Abdou Tchoukoua, Turibio Kuiate Tabopda, Ingrid Konga Simo, Shota Uesugi,
Misa Ohno, Ken-ichi Kimura, Eunsang Kwon, Hiroyuki Momma, Yoshihito
Shiono & Bonaventure Tchaleu Ngadjui
To cite this article: Abdou Tchoukoua, Turibio Kuiate Tabopda, Ingrid Konga Simo, Shota
Uesugi, Misa Ohno, Ken-ichi Kimura, Eunsang Kwon, Hiroyuki Momma, Yoshihito Shiono &
Bonaventure Tchaleu Ngadjui (2018) Albidosides H and I, two new triterpene saponins from
the barks of Acacia albida Del. (Mimosaceae), Natural Product Research, 32:8, 924-932, DOI:
10.1080/14786419.2017.1371156
To link to this article: https://doi.org/10.1080/14786419.2017.1371156
Published online: 04 Sep 2017.
Article views: 36
View supplementary material
Submit your article to this journal
View related articles
View Crossmark data
Citing articles: 1 View citing articles
Full Terms & Conditions of access and use can be found at
http://www.tandfonline.com/action/journalInformation?journalCode=gnpl20

Natural Product research, 2018
Vol. 32, No. 8, 924–932
https://doi.org/10.1080/14786419.2017.1371156
Albidosides H and I, two new triterpene saponins from the
barks of Acacia albida Del. (Mimosaceae)
Abdou Tchoukouaa,b, Turibio Kuiate Tabopdaa, Ingrid Konga Simoc, Shota Uesugid,
Misa Ohnod, Ken-ichi Kimurad,e, Eunsang Kwonf, Hiroyuki Mommaf, Yoshihito Shionob
and Bonaventure Tchaleu Ngadjuia,g
adepartment of organic chemistry, university of Yaounde 1, Yaounde, cameroon; bFaculty of agriculture,
Yamagata university, tsuruoka, Japan; cdepartment of chemistry, university of dschang, dschang, cameroon;
dlaboratory of chemical Biology, the united Graduate school of agricultural sciences, Iwate university,
e
f
Morioka, Japan; Graduate school of agriculture, Iwate university, Morioka, Japan; research and analytical
center for Giant Molecules, Graduate school of science, tohoku university, sendai, Japan; gFaculty of Medicine
and Biomedical sciences, department of Medicine and traditional Pharmacopoeia, university of Yaounde 1,
Yaounde, cameroon
ABSTRACT
ARTICLE HISTORY
received 15 May 2017
accepted 10 august 2017
Two new triterpene saponins, albidosides H (1) and I (2), along with the
three known saponins were isolated from the barks of Acacia albida.Their
structures were elucidated on the basis of extensive 1D- and 2D-NMR
studies and mass spectrometry. Albidosides H (1) and I (2) were assayed
for their cytotoxicity against HeLa and HL60 cells using MTT method.
KEYWORDS
NMr; 1h; 13c; Mimosaceae;
Acacia albida; triterpene
saponins; cytotoxicity
Acacia albida barks
1. Introduction
Acacia albida (Mimosaceae) is a tree up to 24 m in height, with large straight bole, up to 3 m
in girth, and rounded crown. In folk medicine, the decoction of the bark of A. albida is used
for diarrhoea, colds, haemorrhage, leprosy, ophthalmic and in cleansing fresh wounds (Irvine
CONTACT turibio Kuiate tabopda
ttabopda@yahoo.fr; Yoshihito shiono
yshiono@tds1.tr.yamagata-u.ac.jp;
Bonaventure tchaleu Ngadjui ngadjuibt@yahoo.fr
supplemental data for this article can be accessed at https://doi.org/10.1080/14786419.2017.1371156.
© 2017 Informa uK limited, trading as taylor & Francis Group

NATURAL PRODUCT RESEARCH
925
1961). A. albida possesses anti-pyretic, anti-inflammatory, anti-diarrhoea (Tijani et al. 2008),
anti-trypanosomiasis (Tijani et al. 2009; Ndidi et al. 2015), antibacterial (Salawu et al. 2010),
antioxidant (Karoune et al. 2015), and anti-malarial activities (Wurochekke et al. 2013).
Our previous phytochemical study on the MeOH extract of the roots of Acacia albida Del.
(Mimosaceae) has led to the isolation of seven new triterpene saponins, named albidosides A-G
(Tchoukoua et al. 2017). A further detailed investigation of the barks of this plant resulted in the
isolation of the two additional triterpene saponins. Herein, we report the isolation and structure
elucidation of these two new triterpene saponins named albidosides H (1) and I (2).These com-
pounds were evaluated for their cytotoxicity against two human cancer cells, HeLa and HL60.
2. Results and discussion
The air-dried and powdered barks of Acacia albida were extracted with MeOH. After filtration
and evaporation procedures, the MeOH extract was dissolved in H2O and successively par-
titioned with n-hexane, EtOAc, and n-BuOH saturated with H2O. The n-BuOH extract, enriched
in saponins, was subjected to open column chromatography using Sephadex LH-20 and
further separated by Flash chromatography over a prepack silica gel and repeated open ODS
column chromatography to afford two new saponins, albidosides H (1) and I (2) (Figure 1)
together with three known saponins.
Albidoside H (1) was obtained as colourless powder. The IR spectrum showed absorptions
bands for C = O (1735 cm−1), OH (3614 cm−1), and C = C stretching (1650 cm−1). Its HRESIMS
(positive-ion mode) exhibited an accurate pseudo-molecular ion peak at m/z 1446.6879
[M + Na]+, consistent with the molecular formula C67H109NO31Na. Acid hydrolysis of 1 with
2 N HCl gave echinocystic acid (16α-hydroxyoleanolic acid), 2-acetamido-2-deoxyglucose
(GlcNHAc), glucose (Glc), rhamnose (Rha), xylose (Xyl), and fucose (Fuc), which were identified
by comparison in HPLC of their retention time and optical rotation with standard sugars. Its
1H NMR spectrum showed seven angular methyl signals as singlet at δH 0.74, 0.76, 0.85, 0.92,
0.93, 0.94 and 1.34 (each 3H), one olefinic proton signal at δH 5.27 (1H, m), and six anomeric
protons at δH 4.41 (1H, d, J = 7.8 Hz), 4.43 (1H, d, J = 8.2 Hz), 4.52 (1H, d, J = 6.9 Hz), 4.68 (1H,
d, J = 7.8 Hz), 5.22 (1H, d, J = 1.7 Hz), and 5.28 (1H, d, J = 7.3 Hz). The 13C NMR spectrum showed
characteristic signals of an olean-12-ene skeleton with seven methyl singlet signals at δC
14.7, 15.4, 16.6, 23.5, 25.8, 27.1 and 31.9, two ethylenic carbons at δC 122.1 and 143.2, and
six anomeric carbons at δC 93.4, 100.0, 103.3, 103.5, 103.6, and 103.9. The HMBC correlations
between two angular methyl groups at δH 0.74 (3H, s, H3-24) and δH 0.94 (3H, s, H3-23 ) with
δC 89.8 (C-3) confirmed the location of the alcoholic function at C-3. The absolute configu-
ration of C-3 and C-16 was determined by a NOESY experiment between H-3 (δH 3.07) and
H-5 (δH 0.73), and between H-16 (δH 4.43) and H-26 (δH 0.76), Based on these findings, the
aglycone was identified as 3β,16α-hydroxyoleanolic acid (echinocystic). Based on the 1H, 13
C
NMR spectral data and literature, the anomeric configurations of the sugar moieties were
determined as β for glucose, 2-deoxy-2-acetamidoglucose, fucose, and xylose, and α-configu-
1
ration for rhamnose and arabinose (Zheng et al. 2006; Miyase et al. 2010). The H and 13C
NMR signals due to the aglycone of 1 were almost superimposable with those of albidosides
E – G, indicating that the aglycone of 1 was echinocystic acid. Glycosylation of the alcoholic
function at C-3 and acidic function at C-28 was indicated by the downfield position of C-3
resonance (δC 89.8) and upfield position of C-28 (δC 175.8) with reference to the correspond
-
ing signal in echinocystic acid (Mimaki et al. 2004; Melek et al. 2007). Detailed comparison

926
A. TCHOUKOUA ET AL.
Figure 1. chemical structures of compounds 1 and 2.

NATURAL PRODUCT RESEARCH
927
1
of the H, 13C, TOCSY, HSQC, HMBC, and NOESY data of 1 with those of similar saponins
showed that the signals for the sugar chain at C-3 were similar to those of albidosides D and
F, and the sugar chain at C-28 identical to that of albidosides B and E. In the HMBC spectrum,
the anomeric proton at δH 4.43 (1H, d, J = 8.2 Hz, GlcNHAc H-1) showed correlation with Agly
C-3 (δC 89.8), hence, GlcNHAc was linked to Agly C-3 through ether linkage. The signal of
GlcNHAc C-4 (δC 79.7) was shifted downfield by 9 ppm as compared to that of albidoside A,
due to the glycosylation shift. The long-range correlations between H-1 (δH 4.41) of the
terminal Glc and GlcNHAc C-4 (δC 79.7) and H-1 of GlcNHAc and Agly C-3 (δC 89.8) and the
reverse correlation between Agly H-3 (δH 3.07) and GlcNHAc C-1 (δC 103.6) further confirmed
the glycosidic chain at C-3 of the aglycone. The attachment of the glycosidic chain to C-28
of the aglycone was based on a correlation between H-1 (δH 5.28) of glucose and C-28 (δC
175.8) of the aglycone. The HMBC spectrum showed interglycosidic correlations for the tet-
rasaccharidic chain between H-1 (δH 4.68) of the xylose and C-4 (δC 77.1) of the rhamnose,
H-1 (δH 4.52) of the fucose and C-3 (δC 81.6) of the rhamnose, H-1 (δH 5.22) of the rhamnose
and C-2 (δC 76.8) of the glucose. NOESY observed across the glycosidic bonds confirmed the
previous assignments of the HMBC spectrum. Therefore, albidoside H (1) was elucidated as
3-O-β-D-glucopyranosyl-(1→4)-β-D-2-deoxy-2-acetamidoglucopyranosylechinocystic acid-
28-O-β-D-fucopyranosyl-(1→3)-[β-D-xylopyranosyl-(1→4)]-α-L-rhamnopyranosyl-(1→2)-β-D-
glucopyranosyl ester.
Albidoside I (2) was obtained as colourless powder. The IR spectrum showed absorption
bands for C = O, OH, and C = C stretching at νmax 1735, 3583, and 1650 cm−1, respectively. Its
HRESIMS (positive-ion mode) exhibited an accurate pseudo-molecular ion peak at m/z
1518.7088 [M + Na]+, consistent with the molecular formula C70H113NO33Na. Upon acidic
hydrolysis with 2 N HCl, 2 gave oleanolic acid which was identified with authentic sample
and also afforded xylose, glucose, rhamnose, arabinose, and 2-acetamido-2-deoxyglucose
which were identified by comparison in HPLC of their retention time and optical rotation
with standard sugars. The anomeric configurations of the sugar moieties were determined
as β for glucose, 2-deoxy-2-acetamido glucose, and xylose, and α for rhamnose and arab-
inose. The 1H NMR spectrum of 2 showed signals of seven anomeric protons at δH 4.40 (1H,
d, J = 8.4 Hz), 4.47 (1H, d, J = 6.9 Hz), 4.51 (1H, d, J = 5.9 Hz), 4.55 (1H, d, J = 7.7 Hz), 4.64 (1H,
d, J = 7.9 Hz), 5.10 (1H, d, J = 1.7 Hz), and 5.45 (1H, d, J = 6.1 Hz) which correlated in HMQC
with carbons at δC 103.4, 104.5, 102.1, 103.9, 103.9, 100.0, and 94.3, respectively. Detailed
1
comparison of the H and 13C NMR data of 2 with those of albidoside G showed that the
signals for the sugar residues at C-3 and C-28 of the two compounds were similar, except
for the data due to the GlcNAc linked at C-3 of the aglycone. In 2, GlcNAc C-4 was downfield
shifted by 8 ppm compared to reference sugars while in albidoside G, it is GlcNAc C-6 that
was downfield shifted by 8 ppm. The sequence of the trisaccharide chain at C-3 of aglycone
was unambiguously defined by the HMBC experiment in which long-range correlations were
observed between H-1 (δH 4.40) of GlcNAc and Agly C-3 (δC 89.1), H-1 (δH 4.47) of Ara I and
GlcNAc C-4 (δC 79.4) and between H-1 (δH 4.51) of Ara II and C-4 (δC 67.6) of Ara I. The sequence
of the four other sugars linked at C-28 of aglycone was confirmed by HMBC correlations of
Xyl I H-1 (δH 5.45) to Agly C-28 (δC 176.4), Rha H-1 (δH 5.10) to Xyl I C-2 (δC 75.3), Glc H-1 (δH
4.55) to Rha C-3 (δC 81.4), Xyl II H-1 (δH 4.64) to Rha C-4 (δC 77.6). Consequently, the structure
of 2 was concluded to be 3-O-α-L-arabinopyranosyl-(1→4)-α-L-arabinopyranosyl-(1→4)-β-D-
2-deoxy-2-acetamidoglucopyranosyloleanolic acid-28-O-β-D-glucopyranosyl-(1→3)-[β-D-
xylopyranosyl-(1→4)]-α-L-rhamnopyranosyl-(1→2)-β-D-xylopyranosyl ester.

928
A. TCHOUKOUA ET AL.
Compounds 1 and 2 were evaluated for cytotoxicity on two human cancer cells lines
(HeLa and HL60) using the MTT method. Compound 1 exhibited strong cytotoxic effect (IC50
12.7 μM on HL60 and 20.8 μM on HeLa) while 2 exhibited weak cytotoxicity. These results
are in accordance with the previous findings which speculate that in albidosides A – G, the
cytotoxicity is greater when the aglycone is echinocystic acid and the sugar linked to agly-
cone C-3 is GlcNAc unsubstituted at C-6.
3. Experimental
3.1. General experimental procedure
The ESI-MS was measured on a Varian AAT 311A mass spectrometer, and HR-ESI-MS were
taken on a JEOL HX110 mass spectrometer. 1D and 2D NMR spectra were run on JEOL JNM-
ECZ600R/S1 600 MHz NMR spectrometer. The 1H (600 MHz) and 13C (150 MHz) chemical shifts
were referenced to the residual solvent peak of methanol-d4 at δH 3.30 for proton and δC
49.0 ppm for carbon. All sample concentrations ranged from 6 to 10 mg/mL with a total
volume of 0.5 mL for each sample. The 1H sweep width was set at 11,282 Hz for all experi-
ments with a 45° pulse for 1H and a 30° pulse for 13C. The pulse programs of the COSY, HSQC
and HMBC experiments were taken from the Varian Software Library and a standard pulse
sequences were used for 2D spectra. Homonuclear 2D spectra and inverse proton-detected
heteronuclear 2D spectra were acquired in the phase-sensitive mode, and HMBC spectra
were acquired in the absolute value mode. The COSY was acquired with 200 F1 increments
with 32 scans per increment. Sinebell weighting was applied to the F2 dimension before
zero filled to 32 K points, and a sinebell was applied to the F1 and zero filled to 2 K points
before Fourier transformation. The NMR notebook software was using for 1D and 2D spectra
processing. Proton-detected heteronuclear correlations were measured using HSQC (opti-
1
mised for JCH=145 Hz) and HMBC (optimised for JCH=8 Hz). TOCSY spectra were acquired
using the standard MLEV17 spin-locking sequence and 90 ms mixing time. The mixing time
in the ROESY experiment was set to 500 ms. Sinebell weighting was applied to both 1H and
13C dimensions and zero filled to 4 K and 1 K, respectively. The chemical shifts are given in
ppm (δ), relative to TMS as internal standard, and coupling constants are in Hz. Column
chromatography (CC) was carried out on silica gel (70–230 mesh, Merck) and vacuum liquid
chromatography (VLC) on reversed-phase materials (Lichroprep RP-18, 25–40 μm). Optical
rotations were taken with a Horiba SEPA-300 polarimeter. IR spectra were obtained with a
Jasco J-20A spectrophotometer. Semi-preparative HPLC was carried out with Shimadzu
pump and UV LC-10A detector (set at 206 nm) on Mightysil RP-18 column (250 × 6.0 mm i.
d.) at the flow rate of 1.5 mL/min. TLC was performed on Merck precoated aluminium silica
gel 60 F254 sheets, and compounds were detected using sulphuric acid spray reagent.
3.2. Plant material
Acacia albida Del. var. microfoliata De Wild. (Mimosaceae) was collected at 40 km in the south
of Maroua (10°35’N, 14°19’E, Alt 406 m), Far North Region of Cameroon and identified by
Mr. Tapsou, botanist at the Institute of Agricultural Research for Development in December
2013 and a voucher specimen N° 49880 HNC has been deposited at the National Herbarium
Cameroon.

NATURAL PRODUCT RESEARCH
929
3.3. Extraction and isolation
The air-dried and powdered barks of Acacia albida (800 g) were extracted with MeOH at
room temperature. After filtration and evaporation procedures, 32.02 g of MeOH extract was
obtained. The crude extract was dissolved in H2O (400 mL), and successively partitioned with
n-Hexane (3 × 200 mL), EtOAc (3 × 200 mL), and n-BuOH (3 × 200 mL) saturated with H2O.
The n-BuOH extract (7.0 g), enriched in saponins, was subjected to open column chro-
matography using Sephadex LH-20 as stationary phase and developed with MeOH to give
3 main fractions (Fr. A-1 ~ A-3). Fr. A-2 was subjected to Flash chromatography using a
prepack silica gel cartridge, 80 g. Elution was performed with CHCl3-MeOH-H2O mixtures
(80:20:2 and 70:30:3) to yield 270 fractions (Fr. B-1 ~ B-270). Fr. B-185 ~ B-195 (60 mg) were
chromatographed on ODS employing MeOH-H2O (7:3) yielding albidoside F (14 mg), 1
(12 mg) and 2 (9 mg). Fr. B-215 ~ B-224 (23 mg) were applied to an open ODS column with
solvent system MeOH-H2O (7:3) to give albidoside G (10.8 mg). Fr. B-162 ~ B-168 (20 mg)
were submitted to open ODS column chromatography with the solvent system MeOH-H2O
(7:3) yielding albidoside B (8.9 mg).
3.4. Acid hydrolysis and HPLC analysis
According to the reported method (Tchoukoua et al. 2017), compounds 1 and 2 were hydro-
lysed to give the aglycones (oleanolic or echinocystic acids) and the sugars fraction. After
the sugar fraction was passed through a Sep-Pak-C18 cartridge (Waters, Milford, MA, USA;
with 40% MeOH) and Toyopak-IC-SP-M-cartridge (Tosoh; with 40% MeOH), it was analysed
by HPLC (MeCN-H2O 17: 3, flow rate, 0.9 mL.min−1; detection, refractive index (RI) and optical
rotation (OR): 7.79 (L-rhamnose, negative OR); 8.26 (D-fucose, positive OR); 9.35 (L-arabinose,
positive OR), 9.73 (D-xylose, positive OR). 15.37 (D-glucose, positive OR); 14.81
(2-deoxy-2-acetamidoglucopyranose, positive OR).
3.5. MTT cytotoxicity assay
HL60 cells (RCB0041, RIKEN BioResource Center, Tsukuba, Japan) and Hela cells (RCB0007)
were grown in RPMI 1640 medium or DMEM medium (Wako Pure Chemical Industries, Osaka,
Japan) supplemented with 10% heat-inactivated FBS (Sigma Aldrich Corp. St. Louis, USA)
and penicillin (50 units/mL)-streptomycin (50 μg/mL) (Gibco Corp., Carlsbad, USA) in a humid-
ified atmosphere at 37 °C under 5% CO2. The cytotoxicity of the compounds was examined
by MTT assay, as described previously (Tchoukoua et al. 2017).
3.6. Albidoside H (1)
[ꢀ]25
1650, 1542, 1373, 1245, 1033 cm−1; HR-ESI-MS (positive-ion mode) m/z 1446.6879 ([M + Na]+
White amorphous powder;
D -3.50 (c 0.4, MeOH); IR νmax (KBr) 3614, 3421, 2927, 1735,
1
calcd for C67H109NO31Na 1446.6881); H NMR (CD3OD, 600 MHz): δ (Aglycone) 0.93 (1H, m,
H-1α), 1.61 (1H, m, H-1β), 1.66 (1H, m, H-2α), 1.92 (1H, m, H-2β), 3.07 (1H, m, H-3), 0.73 (1H,
m, H-5), 1.35 (1H, m, H-6α), 1.54 (1H, m, H-6β), 1.35 (1H, m, H-7α), 1.52 (1H, m, H-7β), 1.59
(1H, m, H-9), 1.87 (1H, m, H-11), 5.27 (1H, br s, H-12), 1.38 (1H, m, H-15α), 1.71 (1H, m, H-15β),
4.43 (1H, br s, H-16), 2.89 (1H, dd, J = 14.4, 3.6 Hz, H-18), 1.01 (1H, m, H-19α), 2.26 (1H, t,

930
A. TCHOUKOUA ET AL.
J = 13.8 Hz, H-19β), 1.14 (1H, m, H-21α), 1.37 (1H, m, H-21β), 1.79 (1H, m, H-22α), 1.85 (1H, m,
H-22β), 0.94 (3H, s, H-23), 0.74 (3H, s, H-24), 0.92 (3H, s, H-25), 0.76 (3H, s, H-26), 1.34 (3H, s,
H-27), 0.85 (3H, s, H-29), 0.93 (3H, s, H-30), (3-O-sugars) 4.43 (1H, d, J = 8.2 Hz, GlcNAc-H1),
3.70 (GlcNAc-H2), 3.35 (GlcNAc-H3), 3.57 (GlcNAc-H4), 3.29 (GlcNAc-H5), 3.59 (GlcNAc-H6α),
3.85(GlcNAc-H6β), 1.91 (3H, s, NHCOCH3), 4.41 (1H, d, J = 7.8 Hz, Glc-H1), 3.18 (1H, m, Glc-H2),
3.33 (1H, m, Glc-H3), 3.23 (1H, m, Glc-H4), 3.59 (1H, m, Glc-H6α), 3.85 (1H, m, Glc-H6β),
(28-O-sugars) 5.28 (1H, d, J = 7.3 Hz, Glc-H1), 3.42 (1H, m, Glc-H2), 3.22 (1H, m, Glc-H3), 3.44
(1H, m, Glc-H4), 3.65 (1H, m, Glc-H5), 3.66 (1H, m, Glc-H6α), 3.83 (1H, m, Glc-H6β), 5.22 (1H,
d, J = 1.7 Hz, Rha-H-1), 4.23 (1H, m, Rha-H-2), 3.94 (1H, m, Rha-H-3), 3.66 (1H, m, Rha-H-4),
3.82 (1H, m, Rha-H-5), 1.25 (3H, d, J = 6.1 Hz, Rha-H-6), 4.68 (1H, d, J = 7.8 Hz, Xyl-H1), 3.08
(1H, m, Xyl-H2), 3.42 (1H, m, Xyl-H3), 3.44 (1H, m, Xyl-H4), 3.13 (1H, t, J = 10.8 Hz, Xyl-H5α),
3.81 (1H, m, Xyl-H5β), 4.52 (1H, d, J = 6.9 Hz, Fuc-H1), 3.28 (1H, m, Fuc-H2), 3.29 (1H, m, Fuc-
H3), 2.98 (1H, t, J = 8.7 Hz, Fuc-H4), 3.58 (1H, m, Fuc-H5), 1.20 (1H, d, J = 6.1 Hz, Fuc-H6). 13
C
NMR (CD3OD, 150 MHz): δ (Aglycone) 38.4 (C-1), 25.4 (C-2), 89.8 (C-3), 38.4 (C-4), 55.6 (C-5),
17.8 (C-6), 33.0 (C-7), 39.2 (C-8), 46.6 (C-9), 36.2 (C-10), 23.0 (C-11), 122.1 (C-12), 143.2 (C-13),
41.3 (C-14), 34.9 (C-15), 73.3 (C-16), 48.5 (C-17), 40.9 (C-18), 46.5 (C-19), 29.8 (C-20), 35.0 (C-21),
30.4 (C-22), 27.1 (C-23), 15.4 (C-24), 14.7 (C-25), 16.6 (C-26), 25.8 (C-27), 175.8 (C-28), 31.9
(C-29), 23.5 (C-30), (3-O-sugars) 103.6 (C-1 GlcNAc), 56.3 (C-2 GlcNAc), 75.0 (C-3 GlcNAc), 79.7
(C-4 GlcNAc), 76.8 (C-5 GlcNAc), 61.1 (C-6 GlcNAc), 21.7 (NHCOCH3), 172.1 (NHCOCH3), 103.3
(C-1 Glc), 73.7 (C-2 Glc), 76.4 (C-3 Glc), 70.1 (C-4 Glc), 60.6 (C-6 Glc), (28-O-sugars) 93.4 (C-1
Glc), 76.8 (C-2 Glc), 77.1 (C-3 Glc), 70.0 (C-4 Glc), 77.3 (C-5 Glc), 61.0 (C-6 Glc), 100.0 (C-1 Rha),
69.8 (C-2 Rha), 81.6 (C-3 Rha), 77.1 (C-4 Rha), 67.8 (C-5 Rha), 17.3 (C-6 Rha), 103.5 (C-1 Xyl),
74.3 (C-2 Xyl), 76.9 (C-3 Xyl), 70.0 (C-4 Xyl), 65.7 (C-5 Xyl), 103.9 (C-1 Fuc), 73.7 (C-2 Fuc), 76.6
(C-3 Fuc), 75.7 (C-4 Fuc), 72.6 (C-5 Fuc), 16.7 (C-6 Fuc).
3.7. Albidoside I (2)
[ꢀ]25
White amorphous powder;
D -0.44 (c 0.4, MeOH); IR νmax (KBr) 3737, 3583, 3436, 2325,
1735, 1650, 1523, 1018 cm−1; HR-ESI-MS (positive-ion mode) m/z 1518.7088 ([M + Na]+ calcd
for C70H113NO33Na 1518.7093); 1H NMR (CD3OD, 600 MHz): δ (Aglycone) 0.99 (1H, m, H-1α),
1.60 (1H, m, H-1β), 1.62 (1H, m, H-2α), 1.86 (1H, m, H-2β), 3.06 (1H, m, H-3), 0.76 (1H, m, H-5),
1.35 (1H, m, H-6α), 1.53 (1H, m, H-6β), 1.35 (1H, m, H-7), 1.56 (1H, m, H-9), 1.87 (1H, m, H-11),
5.23 (1H, br s, H-12), 1.15 (1H, m, H-15α), 1.61 (1H, m, H-15β), 1.61 (1H, m, H-16α), 2.02 (1H,
m, H-16β), 2.81 (1H, dd, J = 14.4, 4.2 Hz, H-18), 1.11 (1H, m, H-19α), 1.69 (1H, m, H-19β), 1.15
(1H, m, H-21α), 1.36 (1H, m, H-21β), 1.59 (1H, m, H-22α), 1.72 (1H, m, H-22β), 0.95 (3H, s, H-23),
0.74 (3H, s, H-24), 0.92 (3H, s, H-25), 0.76 (3H, s, H-26), 1.14 (3H, s, H-27), 0.88 (3H, s, H-29),
0.90 (3H, s, H-30), (3-O-sugars) 4.40 (1H, d, J = 8.4 Hz, GlcNAc-H1), 3.64 (GlcNAc-H2), 3.35
(GlcNAc-H3), 3.58 (GlcNAc-H4), 3.27 (GlcNAc-H5), 3.59 (GlcNAc-H6α), 3.85 (GlcNAc-H6β), 1.92
(3H, s, NHCOCH3), 4.47 (1H, d, J = 6.9 Hz, Ara-H1), 3.63 (1H, m, Ara-H2), 3.54 (1H, m, Ara-H3),
3.83 (1H, m, Ara-H4), 3.55 (1H, m, Ara-H5α), 3.79 (1H, m, Ara-H5β), 4.51 (1H, d, J = 5.9 Hz,
Ara-H1), 3.66 (1H, m, Ara-H2), 3.56 (1H, m, Ara-H3), 3.71 (1H, m, Ara-H4), 3.84 (1H, m, Ara-H5α),
3.80 (1H, m, Ara-H5β), (28-O-sugars) 5.45 (1H, d, J = 6.1 Hz, Xyl-H1), 3.48 (1H, m, Xyl-H2), 3.51
(1H, m, Xyl-H3), 3.28 (1H, m, Xyl-H4), 3.30 (1H, m, Xyl-H5α), 3.87 (1H, m, Xyl-H5β), 5.10 (1H, d,
J = 1.7 Hz, Rha-H-1), 4.24 (1H, m, Rha-H-2), 3.98 (1H, m, Rha-H-3), 3.63 (1H, m, Rha-H-4), 3.78
(1H, m, Rha-H-5), 1.23 (3H, d, J = 6.4 Hz, Rha-H-6), 4.64 (1H, d, J = 7.9 Hz, Xyl-H1), 3.07 (1H, m,
Xyl-H2), 3.30 (1H, m, Xyl-H3), 3.33 (1H, m, Xyl-H4), 3.12 (1H, m, Xyl-H5α), 3.81 (1H, m, Xyl-H5β),

NATURAL PRODUCT RESEARCH
931
4.55 (1H, d, J = 7.7 Hz, Glc-H1), 3.28 (1H, m, Glc-H2), 3.29 (1H, m, Glc-H3), 3.42 (1H, m, Glc-H4),
3.23 (1H, m, Glc-H5), 3.66 (1H, m, Glc-H6α), 3.84 (1H, m, Glc-H6β). 13C NMR (CD3OD, 150 MHz)
δ (Aglycone) 38.3 (C-1), 25.6 (C-2), 89.1 (C-3), 38.4 (C-4), 55.4 (C-5), 17.9 (C-6), 32.5 (C-7), 39.2
(C-8), 47.5 (C-9), 36.3 (C-10), 23.1 (C-11), 122.6 (C-12), 143.5 (C-13), 41.5 (C-14), 27.4 (C-15),
22.6 (C-16), 46.7 (C-17), 41.5 (C-18), 45.7 (C-19), 30.0 (C-20), 33.4 (C-21), 32.0 (C-22), 27.1 (C-23),
15.6 (C-24), 14.6 (C-25), 16.3 (C-26), 24.8 (C-27), 176.4 (C-28), 32.0 (C-29), 22.6 (C-30),
(3-O-sugars) 103.4 (C-1 GlcNAc), 56.4 (C-2 GlcNAc), 74.8 (C-3 GlcNAc), 79.4 (C-4 GlcNAc), 76.8
(C-5 GlcNAc), 61.0 (C-6 GlcNAc), 21.8 (NHCOCH3), 172.1 (NHCOCH3), 104.5 (C-1 Ara), 71.7 (C-2
Ara), 72.8 (C-3 Ara), 67.6 (C-4 Ara), 65.7 (C-5 Ara), 102.1 (C-1 Ara), 72.2 (C-2 Ara), 72.7 (C-3 Ara),
79.1 (C-4 Ara), 64.4 (C-5 Ara), (28-O-sugars) 94.3 (C-1 Xyl), 75.3 (C-2 Xyl), 74.4 (C-3 Xyl), 69.8
(C-4 Xyl), 65.1 (C-5 Xyl), 100.0 (C-1 Rha), 69.8 (C-2 Rha), 81.4 (C-3 Rha), 77.6 (C-4 Rha), 67.9
(C-5 Rha), 17.2 (C-6 Rha), 103.9 (C-1 Xyl), 74.4 (C-2 Xyl), 76.4 (C-3 Xyl), 70.0 (C-4 Xyl), 65.8 (C-5
Xyl), 103.9 (C-1 Glc), 74.0 (C-2 Glc), 77.1 (C-3 Glc), 70.4 (C-4 Glc), 77.2 (C-5 Glc), 61.2 (C-6 Glc)
4. Conclusion
The present study carried out on barks of Acacia albida lead to the isolation and identification
of two new triterpene saponins named albidosides H (1) and I (2), together with albidosides
B, F, and G, previously isolated from the roots of the same plant (Tchoukoua et al. 2017).
Albidoside H (1) exhibited strong cytotoxic effect (IC50 12.7 μM on HL60 and 20.8 μM on
HeLa) while albidoside I (2) exhibited weak cytotoxicity.
Disclosure statement
No conflict of interest was reported by the authors.
Funding
This works was financially supported by the JSPS RONPAKU [grant number R11516].
References
Irvine FR. 1961. Woody plants of Ghana, with Special reference to their uses. London: Oxford University
Press; p. 984.
Karoune S, Falleh H, Kechebar MS, Halis Y, Mkadmini K, Belhamra M, Rahmoune C, Ksouri R. 2015.
Evaluation of antioxidant activities of the edible and medicinal Acacia albida organs related to
phenolic compounds. Natural Product Research. 29:452–454.
Melek FR, Miyase T, Ghaly NS, Nabil M. 2007. Triterpenoid saponins with N-acetyl sugar from the bark
of Albizia procera. Phytochem. 68:1261–1266.
MimakiY, Yokosuka A, Hamanaka M, Sakuma C, Yamori T, ShibataY. 2004. Triterpene saponins from the
roots of Clematis chinensis. J Nat Prod. 67:1511–1516.
MiyaseT, MelekFR, GhalyNS,WarashinaT, El-KadyM, NabilM.2010. Echinocysticacid3,16-O-bisglycosides
from Albizia procera. Phytochemistry. 71:1375–1380.
Ndidi US, Umar IA, Mohammed A, Samuel C, Oladeru AO, Yakubu RN. 2015. Effects of aqueous extracts
of Acacia albida stem bark on Wistar albino rats infected with Trypanosoma evansi. Natural Product
Research. 29:1153–1156.
Salawu OA, Tijani AY, Babayi H, Nwaeze AC, Anagbogu RA, Agbakwuru VA. 2010. Anti-malarial activity
of ethanolic stem bark extract of Faidherbia Albida (Del) a. Chev (Mimosoideae) in mice. Arch Appl
Sci Res. 2:261–268.

932
A. TCHOUKOUA ET AL.
Tchoukoua A, Tabopda TK, Uesugi S, Ohno M, Kimura KI, Kwon E, Momma H, Horo I, Çalişkan ÖA,
Shiono Y, Ngadjui BT. 2017. Triterpene saponins from the roots of Acacia albida Del. (Mimosaceae).
Phytochem. 136:31–38.
Tijani AY, Uguru MO, Salawu OA. 2008. Antipyretic, anti-inflammatory, and anti-diarrheal properties of
Faidherbia albida in rats. Afr J Biotech. 7:696–700.
Tijani AY, Uguru MO, Salawu OA, Abubakar A, Onyekwelu NO, Akingbasote JA. 2009. Effect of Faidherbia
albida on some biochemical parameters of rats infected with Trypanosoma brucei brucei. Afr J Pharm
Pharmacol. 3:26–30.
Wurochekke AU, Mahmoud SJ, Zailani HA. 2013. Antimicrobial Activity of stem bark of Faidherbia
albida. Br J Pharm Res. 3:786–794.
Zheng L, Zheng J, ZhaoY, Wang B, Wu L, Liang H. 2006. Three anti-tumor saponins from Albizia julibrissin.
Bioorg Med Chem Lett. 16:2765–2768.