Chalconoid and stilbenoid glycosides from Guibourtia tessmanii.

Article abstract of DOI:10.1016/S0031-9422(02)00108-5

Phytochemical studies on the stem bark of Guibourtia tessmanii yielded a dihydrochalcone glucoside, 2',4-dihydroxy-4'-methoxy-6'-O-beta-glucopyranoside dihydrochalcone and a new stilbene glycoside, 3,5-dimethoxy-4'-O-(beta-rhamnopyranosyl-(1-->6)-beta- glucopyranoside) stilbene besides the known pterostilbene. Their structures were established on the basis of one and two dimensional NMR spectroscopic techniques, FABMS and chemical evidence.

Full text of DOI:10.1016/S0031-9422(02)00108-5

Phytochemistry 60 (2002) 803–806
www.elsevier.com/locate/phytochem
Chalconoid and stilbenoid glycosides from Guibourtia tessmanii
V. Fuendjiepa, J. Wandjib,*, F. Tillequinc, D.A. Mulhollandd, H. Budzikiewicze,
Z.T. Fomumb, A.M. Nyembab, M. Kochc
a
´
´
´
Centre de Recherche en Plantes Medicinales et Medecine Traditionnelle, IMPM, BP 193 Yaounde, Cameroon
´
b
´
Department ofOrganic Chemistry, University ofYaounde I, Faculty ofScience, PO Box 812 Yaounde , Cameroon
c
´ ´
Laboratoire de Pharmacognosie- UMR/CNRS 8638, Universite Rene-Descartes, Faculte de Pharmacie,
´
4-Avenue de l’Observatoire, F-75006 Paris, France
dDepartment ofChemistry, University ofNatal, Durban 4041, South Africa
eInstitut fuer Organische Chemie, Greinstr. 4, 50939 Koeln, Germany
Received 18 January 2002; received in revised form 15 March 2002
Abstract
Phytochemical studies on the stem bark of Guibourtia tessmanii yielded a dihydrochalcone glucoside, 20,4-dihydroxy-40-methoxy-
60-O-b-glucopyranoside dihydrochalcone and a new stilbene glycoside, 3,5-dimethoxy-40-O-(b-rhamnopyranosyl-(1!6)-b- gluco-
pyranoside) stilbene besides the known pterostilbene. Their structures were established on the basis of one and two dimensional
NMR spectroscopic techniques, FABMS and chemical evidence. # 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Guibourtia tessmanii; Leguminosae (Caesalpiniaceae); Stem bark; Stilbenoids; Chalconoids; Glycosides
1. Introduction
extracts were repeatedly subjected to column chroma-
tography on silica gel using n-hexane, ethylacetate and
methanol in increasing polarity. Compounds 1–3 were
isolated.
The plant Guibourtia tessmanii Leguminosae (sub-
family Caesalpiniaceae) was identified in Cameroon at
the Centre Province (Aubreville, 1970). It is well known
in folk medicine in the Central Africa (Adjanohoun,
1984). Previous chemical studies on this species yielded
stilbenoid compounds (Nyemba et al., 1995). Interest in
this class of compounds have been stimulated by their
biological activity and strong antimicrobial, antifungic
and helmintic effects (Rimando et al., 1994). As a con-
tinuation of the chemical studies of the same species, we
now report in this paper the isolation and structural
determination of a new dihydrochalcone glucoside 1
and a new stilbene glycoside 2 along with the known
pterostilbene 3.
The elemental composition of compound 1 was
shown to be C22H26O10 by HR–EIMS (m/z 450.1524
[M+]) and CI/NH3 MS (m/z 451 [M+H]+, 468
[M+NH4]+), and its fast atom bombardment mass
spectrum (FABMS) 451 [M+H]+. The peaks in the
EIMS at m/z 107 (C7H7O) and 342 resulting from a
benzylic cleavage (Lien et al., 2000; Greenaway et al.,
1989) revealed the existence of a dihydrochalcone ske-
leton with an hydroxyl substituting ring B and the ring
Asubstituted with one hydroxyl, one methoxyl and one
O-glucosyl groups. The 1H NMR spectrum of 1 showed
two methylene triplets at ꢀ 3.12 and 2.80 with a coupling
constant of 7.5 Hz in agreement with H2-a and H2-b
respectively. The two doublets at ꢀ 7.05 and 6.60 with a
coupling constant of 8.7 Hz were assigned to the four
aromatic protons of ring B, H-2/H-6 and H-3/H-5
respectively, thus the hydroxyl group was located at the
C-4 position. On the other hand the presence of the
glucosyl unit in 1 was confirmed by its MS which
showed two dominant peaks at m/z 306 and 288. In
addition, its 1H NMR spectrum exhibited resonance for
2. Results and discussion
The stem bark of G. tessmanii was extracted with
chloroform and ethylacetate successively. The combined
* Corresponding author. Tel.: +237-2310-957; fax: +237-231-75-
88.
0031-9422/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0031-9422(02)00108-5

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V. Fuendjiep et al. / Phytochemistry 60 (2002) 803–806
Fig. 1. COLOC correlations in compound 1.
Table 1
1H and 13C NMR chemical shifts for compound 1
Attribution
13C (DMSO)
1H (DMSO) J (Hz)
a
b
1
46.3
30.0
132.5
130.3
116.0
156.3
116.0
130.3
107.3
166.1
96.3
166.3
94.6
161.3
205.4
56.7
–
3.12, t, J=7.5
2.80, t, J=7.5
–
7.05, d, J=8.7
6.60, d, J=8.7
2
3
4
–
6.60, d, J=8.7
5
6
7.05, d, J=8.7
–
10
20
–
6.15, d, J=2.0
30
the anomeric proton of the b-glucose moiety at ꢀ 5.05
(d, J=7.0 Hz). Furthermore, the hydroxyl signal at ꢀ
13.36 indicated a chelat bonding; thus this group was
linked to C-20 of ring A. Finally, the two doublets at ꢀ
6.15 and 6.30 with a coupling constant of 2.0 Hz were
consistent with the two protons H-30and H-50 in ring A
of the reported phlorizin (Proksa et al., 1988). Thus the
methoxyl and O-glucopyranosyl groups were located at
C-40 and C-60 with the respective positions to be deter-
mined. Assignments for all proton and carbon reso-
nances (see Table 1) were achieved by COSY, HETCOR
and COLOC experiments. The COLOC spectrum
exhibited correlations (Fig. 1) particularly between the
carbon at ꢀ 166.3 and the protons at ꢀ 3.80 (OCH3), 6.15
(H-30) and 6.30 (H-50) on one hand and the carbon at ꢀ
161.3 and the protons at ꢀ 5.05 (anomeric proton H-100)
and 6.30 (H-50) on the other hand. The carbon C-20 at ꢀ
166.1 correlated with the proton at ꢀ 6.15 (H-30). All
these results clearly confirmed that, on ring A, the
methoxyl group was linked to the C-40 and the O-b-
glucopyranosyl unit was linked to the C-60 position.
Thus the structure of compound 1 was established as
20,4-dihydroxy-40 -methoxy-60-O-b-glucopyranoside di-
hydrochalcone. It was shown to be the new 40-O-
methylderivative of the known phlorizin (Proksa et al.,
1988).
40
–
6.30, d, J=2.0
50
60
–
CO
OCH3
OH-4
OH-20
100
–
3.80, s
9.10, s
13.36, s
5.02, d, J=7.0
–
101.8
74.3
78.4
70.7
77.8
61.8
200
300
3.00–3.24, m
400
500
600
Compound 2 was obtained as colourless crystals. Its
elemental composition was shown to be C28H36O12 by
HR–EIMS (m/z 564.2205 [M]+). The 13C NMR spec-
trum showed 14 aryl/vinyl signals and no C=O reso-
nances. Detailed analysis of the spectrum suggested that
1
this compound was a stilbeneglycoside. The H NMR
spectrum of 2 showed the presence of nine aryl/vinyl
proton resonances. Two of them formed an AB system
at ꢀ 6.82 and 7.15 (d, J=16.0 Hz), the large coupling
constant indicating a trans geometry. The 13C reso-
nances at ꢀ 125.9 and 128.7 assigned to the carbons C-a
and C-b respectively confirmed that compound 2 had a

V. Fuendjiep et al. / Phytochemistry 60 (2002) 803–806
805
Table 2
1H and 13C assignments for compounds 2 and 3
of the two sugars were established from the 13C NMR/
DEPT, HETCOR and COLOC spectral measurements.
The COLOC spectrum of 2 showed an important
correlation between the glucosyl anomeric proton H-100
at ꢀ 4.84 and the aglycone carbon signal at ꢀ 160.5
(C-40). The interconnectivity between the two sugars
was deduced from the important correlation observed
between the rhamnosyl anomeric proton H-1000 at ꢀ 4.43
and the glucosyl methylene carbon signal at ꢀ 66.3
(C-600). Thus, the structure of compound 2 was estab-
lished as 3,5-dimethoxy-40-O-(b-rhamnopyranosyl-(1!6)-
b-glucopyranoside) stilbene.
Attribution
2 (DMSO)
3 (DMSO)
13C
1H, J (Hz)
13C
1H, J (Hz)
a
b
1
125.9
128.7
139.3
107.1
159.0
100.5
158.8
107.1
129.5
127.9
114.2
160.5
114.2
127.9
55.2
7.14, d, J=16.0
6.95, d, J=16.0
–
125.2
128.8
139.6
104.0
159.0
100.4
159.7
107.0
128.3
127.8
115.5
158.0
115.5
127.9
55.3
55.2
–
6.82, d, J=16.0
7.15, d, J=16.0
–
6.77, d, J=2.1
2
6.77, d, J=2.2
–
3
–
6.46, d, J=2.1
4
6.47, d, J=2.2
–
5
–
6.77, d, J=2.1
6
6.77, d, J=2.2
–
10
–
7.46, d, J=8.8
6.75, d, J=8.8
The 1H NMR spectrum of compound 3 was char-
acterized by the presence of two vinyl proton signals
with a trans-geometry. The 13C NMR spectra showed
12 aryl signals, two vinyl signals and no C=O reso-
20
7.50, d, J=8.8
6.91, d, J=8.8
–
30
40
–
6.75, d, J=8.8
50
6.91, d, J=8.8
7.50, d, J=8.8
3.76, s
1
60
7.46, d, J=8.8
3.76, s
3.76, s
nances. The H NMR of 3 showed the presence of two
OCH3
OCH3
100
200
300
400
500
600
1000
2000
3000
4000
5000
6000
methoxyl proton resonances. Furthermore, all NMR
data of 3 (Table 2) were found to be in full agreement
with the structure of the reported pterostilbene
(Rimando et al., 1994).
55.1
105.1
73.2
3.76, s
4.84, d, J=7.3
–
–
–
–
–
–
–
–
–
–
–
–
–
76.5a
–
69.8
3.00–3.85, m
–
75.4a
66.3
–
–
3. Experimental
101.5
70.8
70.3
4.43, d, J=6.2
–
–
3.1. General
–
72.1
68.3
3.00–3.85, m
–
–
MPs were determined using a Kofler microhot stage
apparatus. IR spectroscopy was performed on a Perkin-
Elmer 257 spectrometer. [ꢁ]D Were read on a Perkin-
Elmer 241 polarimeter. UV spectra were recorded on a
Beckman 25 spectrometer. FABMS were recorded using
ZAB Spec MS instrument. CIMS and EIMS were
recorded on Nermag R10–10C spectrometer. NMR
experiments were performed on a Varian Gemini 400
MHz instrument and a Bruker AC 300 spectrometer. Si
gel 60H (5–40 mm), 60C (20–40 mm) and 60 (240–400
mesh) were used for CC under compressed air (300
mbar) while precoated Si gel 60F254 plates were used for
TLC. The solvent used for spectra determination was
DMSO-d6.
17.9
1.18, d, J=6.2
–
a
Values could be interchanged.
(E)-stilbene skeleton. Aset of three proton resonances
at ꢀ 6.47 (1H) and 6.77 (2H) as doublets (J=2.2 Hz)
were assigned to a 1,3,5-trisubstituted phenyl group.
The 3,5-substituents were established to be two meth-
oxyl groups with the six proton signals shown as a
singlet at ꢀ 3.76 and the 13C signals at ꢀ 55.2 and 55.1.
Another set of four proton resonances at ꢀ 6.90 (2H,
H-20/H-60) and 7.42 (2H, H-30/H-50) with the coupling
constant J=8.8 Hz were consistent with an AA0BB0
system of a para-substituted second phenyl group.
Compound 2 gave a positive Molish test (a-naphtol
1%/H2SO4 cc) suggesting the presence of a glycosyl
moiety. Acid hydrolysis of 2 yielded an aglycone that
was identified to pterostilbene 3 (Rimando et al., 1994)
and two sugars identified as glucose (Banks and
Cameron, 1971) and rhamnose (Uniyal et al., 1990).
3.2. Plant material
Stem bark of G. tessmanii was collected in Eseka
locality (Centre Province of Cameroon) in June 1998.
The plant was identified and collected by Mr Nole Tsa-
bang, IMPM Yaounde, in Cameroon. The herbarium
specimen documenting the collection has been deposited
in the National Herbarium, Yaounde (HNC No. 5670).
1
Furthermore the H NMR spectrum of 2 showed two
doublets at ꢀ 4.84 (J=7.3 Hz) and 4.43 (J=6.2 Hz)
assigned to the anomeric protons of the glucosyl and
rhamnosyl patterns respectively. The 13C NMR spec-
trum indicated the respective anomeric carbons at ꢀ
105.1 and 101.5. The EIMS of 2 showed ion fragments
at m/z 418 [Mꢀ146]+ and 256 [Mꢀ308]ꢀ suggesting the
successive eliminations of the terminal rhamnosyl and
the inner glucosyl fragments respectively. The linkages
3.3. Extraction and isolation
The plant material (1.5 kg) was air-dried, ground and
extracted successively with CHCl3 and EtOAc at room
temperature. The solvents were evaporated using

806
V. Fuendjiep et al. / Phytochemistry 60 (2002) 803–806
vacumm pump and both crude extracts were combined
under TLC control to yield a viscous material (100 g).
Part of the crude extract (60 g) was chromatographed
over Si gel with n-hexane, EtOAc and MeOH in
increasing polarity to result three main series: A (800
mg) [n-hexane/EtOAc (7:3)], B (900 mg) [EtOAc/MeOH
(9:1)] and C (350 mg) [EtOAc/MeOH (17:5)]. Further
CC of three series yielded compounds 1–3.
nose while the aglycone was identical to pterostilbene 3
also isolated from the same plant.
3.3.3. 3,5-Dimethoxy-40-hydroxystilbene (pterostilbene) 3
Compound 3 (60 mg) was purified by CC of the series
A [Si gel, n-hexane/EtOAc (3:1)]; oil; Rf 0.32 [Si gel,
CHCl3
max
CHCl3/MeOH (19:1)]. IR v
cmꢀ1: 3390 (OH), 1620
(C=C), 1600, 1590. 1H and 13C NMR data (Table 2) were
identical to the authentic compound (Rimando et al., 1994).
3.3.1. 20,4-Dihydroxy-40-methoxy-60-O-(ꢂ-glucopyrano-
side) dihydrochalcone 1
Compound 1 (75 mg) was purified by CC of the series
B [Si gel, EtOAc/MeOH (9:1); colourless crystals from
Acknowledgements
CH2Cl2]. Mp 135–136 ꢁC; Rf 0.27 [Si gel, CHCl3/MeOH
This research was partially financed by the IMPM
funds. W.J. is grateful for IFS grant No. F/2624–2
(Sweden), for the sponsorship of the Universite Rene
Descartes Paris-V during his research visit in Paris,
France and for the financial support from the OPCW
(The Netherlands), through the Internship at the Uni-
versity of Natal, Durban, South Africa. Thanks are due
to Mr. Dilip Jagjivan for the measurements of some
NMR spectra and to Mr. Nole Tsabang for the identi-
fication and the collection of this plant.
KBr
max
(9:1)]. IR v
cmꢀ: 1 3530 (br. OH), 2930, 2850, 1650
EtOH
max
(conj. C=O), 1600, 1570, 1470, 800. UV l
nm
(logE): 290 (4.19), 236 (sh), 204 (sh). Positive FABMS m/z
451 [M+H]+. CI/NH3 MS m/z (rel. int.): 468
[M+NH4]+ (20), 451 [M+H]+ (18), 433 [M+
HꢀH2O]+ (15), 419 [M-OCH3]+ (5), 342(10), 306
[M+NH4-Glc] (100), 289 [M+HꢀGlc]+(90), 272 [M-
OGlc]+ (10), 107 (5). EIMS (70 eV) m/z 450 [M]+ (10),
342 (8), 288 (MꢀGlc)+(80), 272 (MꢀOGlc)+ (20), 328
(100), 107 (6). HR–EIMS (m/z 450.1524 [M]+),
C22H26O10 required 450.1526. 1H NMR (300 MHz,
DMSO) and 13C NMR (75 MHz, DMSO), see Table 1.
References
Adjanohoun, E.J., 1984. Contribution aux Usages Ethnobotaniques et
Floristiques du Gabon. ACCT 39.
3.3.2. 3,5-Dimethoxy-40-O-(ꢂ-rhamnopyranosyl-(1!6)-
ꢂ-glucopyranoside)stilbene 2
Compound 2 (86 mg) was purified by CC of the series
C [Si gel, EtOAc/MeOH (17:5); colourless crystals from
CH2Cl2]. Mp 242–243 ꢁC; Rf 0.25 [Si gel, CHCl3/MeOH
Aubreville, A., 1970. Flore du Cameroun. Legumineuse (Cesalpi-
noides). Museum d’Histoire Naturelle, Paris.
Banks, H.J., Cameron, D.W., 1971. Anew natural stilbene glycoside
from Rheum rhaponticum (Polyganaceae). Aust. J. Chem. 24, 2427–
2430.
(4:1)]. [a]2D2 ꢀ50ꢂ2ꢁ (c 0.2, aq acetone). IR vmax
KBr
Greenaway, W., May, J., Whathey, R., 1989. Flavonoid aglycones
identified by gas chromatography–mass spectrometry in bud exudate
of Populus balsamifera. Journal of Chromatography 472, 393–400.
Lien, T.P., Porzel, A., Schmidt, J., Sung, T.V., Adam, G., 2000. Chal-
conoids from Fissistigna bracteolatum. Phytochemistry 53, 991–995.
Nyemba, A.M., Ngando Mpondo, T., Kimbu, S.F., Connolly, J.D.,
1995. Stilbenes glycosides from Guibourtia tessmanii. Phytochem-
istry 39, 895–898.
cmꢀ1: 3350 (br. OH), 2950, 1615, 1592, 1300, 1260,
1253, 965. HR–EIMS (m/z 564.2205 [M]+), C28H36O12
required 564.2207. EIMS (70 eV) m/z (rel. int.): 564,
[M]+(10), 418 [Mꢀ146]+ (10), 403 [MꢀGlcꢀCH3] (15),
385 [MꢀOGlc] (45), 369 [MꢀOGlcꢀCH3] (70), 256
[Mꢀrutinosyl]+(100). 1H NMR (300 MHz, DMSO)
and 13C NMR (75 MHz, DMSO) see Table 2.
Proksa, B., Uhrin, D., Odonmazhig, P., Badga, D., 1988. Isolation of
phlorizin from leaves of Armeniaca sibirica. Pharmazie 43, 658–659.
Rimando, A.M., Pezzulo, J.M., Farnsworth, N.R., Santisuk, T., Reu-
trakul, V., 1994. Revision of the NMR assignments of pterostilbene
and of dihydrodehydrodiconiferyl alcohol: cytotocic constituents
from Anogeissus acuminata. Natural Product Letters 4, 267–272.
Uniyal, G.C., Agrawal, P.K., Thakur, R.S., Sati, O.P., 1990. Steroidal
glycosides from Agave cantala. Phytochemistry 29, 937–940.
Acid hydrolysis of compound 2: 30 mg of 2 were dis-
solved in 0.6 M HCl (4 ml)/MeOH (100 ml) and
refluxed at room temperature for 10 h. The solvent was
evaporated in vacuo and work up of the crude yielded
two different sugars and one aglycone. The sugars were
identified by TLC comparaison to glucose and rham-