S.C. Popwo Tameye et al.
Phytochemistry Letters 43 (2021) 150–153
Ukweni, 2007; Kofie et al., 2015; Uzama et al., 2018). Previous phyto-
chemical investigation of the stem bark of F. exasperata reported the
isolation of a new sphingolipid and furanocoumarins and also fatty
acids, glycerol esters, glycerol derivatives, pheophorbide/pheophytin
derivatives, flavonoid and pyrimidine derivatives (Jiofack et al., 2012;
Bafor et al., 2013; Amponsah et al., 2013). A recent work on the
methanol extract of the roots of F. exasperata permitted the isolation of a
new cinnamic acid derivative (Popwo et al., 2020). In the continuity of
this work, we report the isolation and structural elucidation of two new
cinnamic acid derivatives along with twelve known compounds from the
stem barks of Ficus exasperata.
ether bond between C-2/C-9 was further confirm with the absence of 3J
heteronuclear correlation between oxymethylene protons H-4′ and the
quaternary aromatic carbon C-9. Taking into account of biosynthesis
consideration of chromene which derive from C-alkylation of phenol
derivative by dimethylallyl pyrophosphate to form a C-alkylated inter-
mediate, followed by an oxidative cyclization of the alkyl group to form
chromene. The structure of compound 1 was thus determined as
3′-[(2-hydroxymethyl)-7-methox-
y-2-methyl-2H-6-chromenyl]-(E)-acrylamid and the trivial name of
ficusanolide A was given.
NMR spectra data of both compound 1 and 2 were quite superpos-
able with a slight difference observed on the coupling constant of the
olefinic protons H-2′ (5.87, d, J =12.3 Hz) and H-3′ (6.89, d, J =12.3 Hz)
indicating that both compounds were stereoisomers. Indeed, compound
2 exhibited a coupling constant of 12.3 Hz suggestive of a cis configu-
ration of the double bond while it was trans (J =16.0 Hz) in compound 1.
The structure of compound 2 was thus determined as 3′-[(2-hydrox-
ymethyl)-7-methoxy-2-methyl-2H-6-chromenyl]-(Z)-acrylamid with the
trivial name of ficusanolide B (Figs. 1 and 2)
2. Results and discussion
2.1. Phytochemical study
The methanol extract of the air-dried stem barks of Ficus exasperata
was chromatographed on a column of silica gel and thin layer chroma-
tography (TLC) eluted with ether petroleum, the mixture of ether pe-
troleum and EtOAc and mixture of EtOAc and MeOH in increasing
polarity to afford two new cinnamic acid derivatives stereoisomers
together with twelve known compounds (see Fig. S20 Supplementary
informations). By comparison to the reported data, the known com-
pounds were identified as ficusanol (3) (Popwo et al., 2020),
umbelliferone-6-carboxylic acid (4) (Hyun et al., 2013), oxypeucedanin
hydrate (5) (Jiofack et al., 2012), marmesin (6) (Monteiro et al., 2002),
decursinol (7) (Mo et al., 2017), β-amyrin acetate (8), lupeol (9),
betulinic acid (10) (Chandramu et al., 2003), ursolic acid (11) (Martins
et al., 2013), a mixture of stigmasterol (12) and β-sitosterol (13), and
sitosteryl-3-O-β-D-glucopyranoside (14) (Habib et al., 2007).
2.2. Biological test
2.2.1. Cytotoxicity
The cytotoxicity of ursolic acid (11), lupeol (9), betulinic acid (10),
the per acetylated derivative of betulinic acid (15), oxypeucedanin hy-
drate (5), decursinol (7), marmesin (6), ficusanol (3), ficusanolide A (1)
and ficusanolide B (2) was evaluated on two cancers cell lines: The
human cervix carcinoma cell line KB-3ꢀ 1 and the human colon cancer
cell line HT-29 at the concentration of 0.00025 mol/L. The results
revealed that only ursolic acid exhibited a moderated activity on both
tested cancer cells with IC50 = 50.9
cell line KB-3ꢀ 1 and IC50 = 34.4 M for the human colon cancer cell line
HT-29 while the IC50 of griseofulvin used as reference was 17 M and 21
M respectively (see Table S2 supplementary datas) (Table 1)
μM for the human cervix carcinoma
The acetylation of betulinic acid was carried out by using acetic
anhydride and pyridine at room temperature for 12 h to afford 3-O-
acetyl-betulinic acid (15) (Fadipe et al., 2017).
μ
μ
μ
Compound 1 and compound 2 were obtained as a pale-yellow
amorphous powder and gave the same molecular formula of
3. Experimental
C
15H17O4N. The Fourier Transform (FT)-IR spectrum of compound 1
displayed prominent absorptions at 3411 (OH), 1647 (amide carbonyl),
ꢀ 1
–
–
–
3.1. General experimental procedures
1584 (C C) and 1538 (CN) cm
. Their UV spectrum in methanol
displayed two absorption maxima at λmax 235.0 and 263.0 nm consistent
with n→л* and л→л* electronic transitions typical of chromophore
having double bonds and heteroatoms. The 1H-NMR spectrum shows in
the olefinic region the signals of two trans coupled protons deshielded by
conjugation to a carbonyl at δH 6.40 (d, J =16.0 Hz) and 7.79 (d, J =16.0
Hz). In addition, it also displayed the signals of two olefinic proton of a
six-member ring which were correlated on the COSY spectrum, typical
of a chromene ring at δH 5.54 (d, J =10.0 Hz) and 6.45 (d, J =10.0 Hz)
(Cheng-Hsiung et al., 1989) alongside two aromatic protons appearing
The 1H and 13C NMR spectra were recorded at room temperature
using a Bruker DRX-500, 600 MHz spectrometer (Bruker, Rheinstetten,
Germany) with TMS as the internal standard (δ 0.00 ppm). The chemical
shift values were expressed in ppm units relative to TMS and coupling
constants J were measured in Hz. ESI-Mass spectra were obtained with
Agilent 6220 TOF LCMS mass spectrometer (Agilent Technologies, Santa
Clara, CA, USA). Silica gel 70–230 mesh (Merck) was used for column
chromatography, while aluminum sheets precoated with silica gel 60
F
254 (Merck) were used for TLC with a mixture of ether petroleum-ethyl
as singlet at δ 7.21 and 6.50 suggestive of the presence of a 2,3,5,6-tet-
H
1
acetate and ethyl acetate-methanol as eluents. The compounds were
visualized under ultraviolet light (254 nm) or by iodine vapor and by
spraying with H2O-H2SO4 (1:1) reagents followed by heating.
rasubstituted benzene ring. This H-NMR spectrum indicates the pres-
ence of one methoxy group at
δ
3.86 (s) in addition of a
hydroxymethylene group at δH 3.64 (d,HJ =11.8 Hz) and 3.60 (d, J =11.8
Hz). Its 13C NMR spectrum shows the signal of 15 carbon atoms
including one α
,β-unsaturated amid carbonyl at δC 172.0 (C-1′) attached
3.2. Plant material
on the benzene ring as evidenced by 3J HMBC correlations with the
olefinic proton H-3′ (δH 7.79) and between proton H-3′ with aromatic
The stem barks of F. exasperata were collected on February 2017 near
the campus of the Faculty of Science of the University Douala, Littoral
region of Cameroon, with the localisation 4◦02′53′′N, 9◦42′15′′E. The
plant was identified by Mr. Nana Victor from the National Herbarium of
Cameroon by comparison with a deposited specimen registered under
the reference number 45,226 HNC.
carbon C-7(δ 161.1). The observed 13C chemical shift of C-4′ (68.7) and
C
C-7 (161.1) are consistent with the deshielding effect of oxygen substi-
tution more electro-attractive than nitrogen atom to confirm that the
amino group is at C-1′. Indeed, the amino group at position 4′ would
have caused the decrease of the chemical shift of C-4′ under 60 ppm and
at position 7, it would have caused the decrease of the chemical shift of
C-7 under 150 ppm. In addition, HMBC correlation of the methoxy group
with aromatic carbon C-7 indicates its position at C-7 on the aromatic
ring. HMBC spectrum also shows strong correlations between the
angular olefinic carbon of the chromene ring at δC 126.1 (C-3) indicating
the presence of a 2-methyl-2-hydroxymethylenechromene moiety. The
3.3. Extraction and purification
The stem barks of F. exasperata were harvested, chopped into small
pieces, air-dried and ground into powder. The obtained powder (4.5 kg)
was macerated twice at room temperature using methanol (15 L) for
151
Popwo Tameye, Stevine Claudiale
