Steroids and Triterpenoids from Corypha taliera Roxb: A Critically Endangered Palm Species of Bangladesh
Md. Ashraful Alam,
Ridwan Bin Rashid,
Muhammad Abdullah Al-Mansur,
Mohammad S. Rahman
Mohammad A. Rashid
Corypha taliera Roxb. is a critically endangered palm species. The tree grown in the campus of the University of Dhaka, Bangladesh used to be considered as the only living species in the world. This palm tree raised some interests due to several bioactivities observed earlier and later systematic scientific studies have been undertaken to explore for its secondary metabolites. In the present study, a thorough phytochemical investigation was conducted to explore its chemical features. Initially, the unripe fruits of this palm was extracted with methanol. Later on, it was fractioned by the modified Kupchan partitioning method in to n-hexane, carbontetrachloride, chloroform and aqueous soluble fractions. The n-hexane soluble fraction was subjected to Column Chromatography (CC) over Sephadex LH-20 and the column was eluted with n-hexane-dichloromethane-methanol (2:5:1) mixtures. From the collected fractions stigmasterol (1), β-sitosterol (2), β-amyrin (3), lupeol (4) and betulinic acid (5) were isolated by Preparative Thin Layer Chromatography (PTLC). The structures of these purified compounds were established by extensive spectroscopic analysis and by comparison of their spectral data with published values as well as co-TLC with authentic samples. This is the first report of isolation of steroids and terpenoids from this plant.
to cite this article:
Akhtaruzzaman Chowdhury, Md. Ashraful Alam, Ridwan Bin Rashid, Muhammad Abdullah Al-Mansur, Mohammad S. Rahman and Mohammad A. Rashid, 2013. Steroids and Triterpenoids from Corypha taliera Roxb: A Critically Endangered Palm Species of Bangladesh. Research Journal of Medicinal Plants, 7: 125-129.
Received: January 28, 2013;
Accepted: May 09, 2013;
Published: July 02, 2013
Palm trees are renowned for their contribution to the human race. They can
provide food and arrange landscaping for pleasing appearance. Medicinal scientists
also put some light on their chemical and biological aspects for treating various
pathological states (Asase et al., 2010; De
Smet, 2002; Agbabiaka et al., 2009). Many
palm species are now in a very challenging and endangered condition for their
existence. In Bangladesh, C. taliera is considered as a very rare species
and the only one found in the campus of University of Dhaka, Bangladesh. The
tree was first discovered in 1919 in the then Bengal. The only record of C.
taliera was reported in the University of Dhaka, Bangladesh. In the absence
of any other record, the solitary tree was considered the last living species
in the World (Johnson, 1998; Chowdhury
et al., 2010).
C. taliera (Bengali name-tali palm; Family:Palmae) is a giant monocarpic
palm that grows very slowly upto 10 m in height and 70 cm in diameter near the
base. It is thought to be distributed in Bangladesh, India and throughout the
tropical Asia and takes close to a century for flower to blossom, which will
ultimately lead to gradual death. As a part of the continuous studies on medicinal
plants of Bangladesh (Begum et al., 2010; Rahman
et al., 2011), the preliminary antimicrobial, antioxidant and cytotoxic
activities of the unripe fruits of this palm was reported earlier (Chowdhury
et al., 2010). No other biological or chemical work has been conducted
on this plant. In the present manuscript, the isolation stigmasterol (1), β-sitosterol
(2), β-amyrin (3), lupeol (4) and betulinic acid (5) was reported for the
first time from this palm species.
MATERIALS AND METHODS
General experimental procedures: Gel permeation chromatography was performed
on Sephadex LH-20 while column chromatographic separation was achieved over
silica gel (mesh 70-230). The 1H NMR spectra were recorded using
a Bruker AMX-400 (400 MHZ) instrument in CDCl3 and the δ-values
for 1H and 13C data were referenced to the residual non-deuterated
solvent signals. All solvents were of analytical grade.
Collection of plant materials: The fruits of C. taliera were
collected from the campus of the University of Dhaka, Bangladesh in the month
of April, 2009. A voucher specimen (accession No. DACB-34180) for this collection
has been deposited in Bangladesh National Herbarium, Dhaka.
Extraction and isolation of compounds: The unripe sun dried and powdered
fruits (500 g) of C. taliera was soaked in 1.5 L methanol for 10 days
with occasional shaking and stirring and filtered through a cotton plug followed
by Whatman filter paper No. 1. The extract was then concentrated by using a
rotary evaporator at reduced temperature and pressure. A portion (5 g) of the
concentrated methanol extract was fractioned by the modified Kupchan partitioning
method (VanWagenen et al., 1993; Anjum
et al., 2013). Evaporation of solvents yielded n-hexane (1.25 g),
carbon tetrachloride (0.55 g), dichloromethane (0.60 g) and aqueous soluble
(2.00 g) materials. An aliquot (1.10 g) of the n-hexane soluble fraction was
subjected to Column Chromatography (CC) over Sephadex LH-20 and the column was
eluted with n-hexane-dichloromethane-methanol (2:5:1) mixtures to give a total
of 40 fractions, each 5 mL.
Compound 1 was obtained as colorless crystalline mass from fractions 6 and
7. Compound 2 was isolated as white amorphous powder from fraction 9 by preparative
thin layer chromatography (PTLC, stationary phase silica gel F254,
mobile phase-10% ethyl acetate in toluene, thickness of plates-0.5 mm). Similar
PTLC of fractions 10-12 and 17 over silica gel F254 using 15% and
20% ethyl acetate in toluene afforded compound 3 (10 mg) and 4 (8 mg), respectively
as white amorphous mass. On the other hand, compound 5 was isolated as white
gum from fractions 21-22 by PTLC over silica gel (F254) using 30%
ethyl acetate in toluene as the developing solvent.
RESULTS AND DISCUSSION
The 1H NMR spectra of compounds 1 and 2 (Table 1,
Fig. 1a) readily demonstrated the steroidal nature of these
compounds and were superimposable to the 1H NMR spectra previously
recorded for stigmasterol and β-sitosterol (Jahan et
al., 2010) from the same laboratory. The identity of the compounds was
further confirmed by co-TLC with authentic samples.
|| Structure of the isolated compounds (a) 1 and 2 represent
stigmasterol and β-sitosterol, respectively, (b) 3 represents α-amyrin
and (c) 4 and 5 represent lupeol and betulinic acid, respectively
|| 1H NMR (400 MHZ, CDCl3) data of compounds
|δ (ppm): Chemical shift expressed in parts per million,
J in Hz: Coupling constant expressed in Hertz, mult: Multiplet, s: Singlet,
br.s: Broad singlet, d: Doublet, dd: Double doublet, t: Triplet
The 1H NMR spectrum (400 MHZ, CDCl3) of compound 3 (Table
1, Fig. 1b) revealed eight singlets at δ 0.95 (H3-28),
1.00 (H3-29, H3-30), 0.79 (H3-24), 0.87 (H3-23),
0.85 (H3-25), 1.04 (H3-26) and 1.07 (H3-27).
Integration of the singlets demonstrated the intensity for three protons. It
suggested the presence of eight methyl groups in the molecule. It also revealed
a triplet (J = 3.2 Hz) of one proton intensity centered at δ 5.12, which
could be assigned to the olefinic proton (H-12). The double doublet (J = 11.0,
5.0 Hz) centered at δ 3.23 could be ascribed to the oxymethine proton at
C-3. The splitting pattern of this proton suggested the beta orientation of
the hydroxyl group. The above spectral features are in close agreement to those
observed for α-amyrin (Parvin et al., 2009).
Again the identity of this compound was substantiated by co-TLC with authentic
The 1H NMR spectrum (400 MHZ, CDCl3) of compound 4 (Table
1, Fig. 1c) showed a double doublet (J = 11.5, 5.02 Hz)
of one proton intensity at δ 3.20 typical for H-3 of a triterpene type
carbon skeleton. The broad singlets at δ 4.67 and 4.55 (1H each) were assigned
to the vinylic protons at C-29. A multiplet of one proton intensity at δ
2.28 was attributed to H-19. The spectrum also displayed six singlets at δ
0.78, 0.82, 0.84, 0.93, 0.95, 1.02 of three proton intensity. A broad singlet
of three proton was also appeared at δ 1.67. All of these resonances are
assignable to the methyl group protons at C-4 (H3-24), C-17 (H3-28),
C-10 (H3-25), C-14 (H3-27), C-4 (H3-23), C-8
(H3-26) and C-20 (H3-30), respectively. By comparing these
with published 1H NMR data for lupeol as well as by co-TLC with authentic
sample established its identity as lupeol (4) (Sultana
et al., 2010).
The 1H NMR spectrum of compound 5 (Table 1, Fig.
1c) revealed the presence of a lupene type carbon skeleton. It displayed
signals attributable to an exomethylene group at δ 4.60 and 4.73 (1H, each,
br. s), which together with an allylic methyl at δ 1.68 indicated an isopropenyl
functionality. The double doublet centered at δ 3.17 could be assigned
to H-3. The large couplings (11.2 and 5.2 Hz) of this H-3 with the vicinal methylene
protons suggested the β (beta) orientation of the hydroxyl group at C-3.
In addition, the spectrum also showed a multiplet at δ 2.85 for the methine
proton at C-19 and five methyl group resonances as singlets at 0.74 (H3-24),
0.81, 0.93 (H3-23), 0.96 (H3-26) and 0.97 (H3-27).
On this basis, compound 5 (Fig. 1) was characterized as betulinic
acid. The identity of 5 as betulinic acid was confirmed by comparison with published
values (Parvin et al., 2009) as well as by co-TLC
with an authentic sample.
The present study explored the presence of steroids and triterpenes from C.
taliera. Among the isolated compounds, betulinic acid and lupeol have previously
been reported for anticancer activity (Patocka, 2003;
Saleem, 2009). It might have connection with the cytotoxicity
exhibited in brine shrimp lethality bioassay by C. taliera fruits (Chowdhury
et al., 2010). Preliminary TLC screenings revealed that the extractives
of C. taliera fruits might have more bioactive triterpenes. Further bioactivity
guided isolation is required to identify the bioactive principles.
The unripe fruits of C. taliera were subjected to phytochemical investigation,
which yielded steroids and triterpenes stigmasterol (1), β-sitosterol (2),
β-amyrin (3), lupeol (4) and betulinic acid (5) for the first time from
this palm tree. Among these lupeol and betulinic acid are renowned for having
anticancer activities. More extensive phytochemical and biological investigations
are required to isolate the potential bioactive components from this plant species.
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