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Studies on the chemical constituents of <i>Phyllanthus emblica</i>
Habib-ur-Rehman
a
; Khawaja Ansar Yasin
a
; Muhammad Aziz Choudhary
a
; Naeem Khaliq
a
; Atta-ur-
Rahman
b
; Muhammad Iqbal Choudhary
b
; Shahid Malik
b
a
Department of Chemistry, University of Azad Jammu and Kashmir, Muzaffarabad, Pakistan
b
H. E. J.
Research Institute of Chemistry, University of Karachi, Karachi, Pakistan
To cite this Article Habib-ur-Rehman, Yasin, Khawaja Ansar , Choudhary, Muhammad Aziz , Khaliq, Naeem , Atta-ur-
Rahman, Choudhary, Muhammad Iqbal and Malik, Shahid(2007) 'Studies on the chemical constituents of <i>Phyllanthus
emblica</i>', Natural Product Research, 21: 9, 775 — 781
To link to this Article: DOI: 10.1080/14786410601124664
URL: http://dx.doi.org/10.1080/14786410601124664
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Natural Product Research, Vol. 21, No. 9, 20 July 2007, 775–781
Studies on the chemical constituents of Phyllanthus emblica
HABIB-UR-REHMAN*y, KHAWAJA ANSAR YASINy, MUHAMMAD
AZIZ CHOUDHARYy, NAEEM KHALIQy, ATTA-UR-RAHMANz,
MUHAMMAD IQBAL CHOUDHARYz and SHAHID MALIKz
yDepartment of Chemistry, University of Azad Jammu and Kashmir,
Muzaffarabad-13100, Pakistan
zH. E. J. Research Institute of Chemistry, University of Karachi,
Karachi-75270, Pakistan
(Received 17 November 2006; in final form 15 February 2007)
Phytochemical investigations on Phyllanthus emblica have resulted in the isolation of the
two new flavonoids, kaempferol-3-O--
L-(6
00
-methyl)-rhamnopyranoside (1) and kaempferol-
3-O--
L-(6
00
-ethyl)-rhamnopyranoside (2). Their structures were determined on the basis of
extensive spectroscopic studies including 2D-NMR experiments.
Keywords: Phyllanthus emblica; HMQC interactions; Euphorbiaceae; Amla
1. Introduction
Phyllanthus emblica Linn. a monoecious glabrous or pubescent deciduous tree belongs
to the family Euphorbiaceae. The plant is commonly known as Amla and found
throughout plains of Pakistan at an elevation of 610–1390 m above the sea level.
Various species of the genus including P. emblica possess pharmaceutical properties and
are commonly used to cure various ailments [1–7]. Every part of the plant is useful in
antidotal treatment of snakebite and scorpion-sting. The fruits of the plant are known
to be a rich source of vitamin C and are frequently used in making pickles, preserves
and jellies. The formulation of the ripe fruits find therapeutic use in the ‘sidha’ system of
indian medicine [8]. The leaves are used in aphrodisiac, antipyretic, useful in biliousness,
asthma, bronchitis, leucorrhoea and vomiting. The leaves are also used in cases of
chronic dysentery and are also considered as a bitter tonic. Antithermic lotions have
also been prepared from leaves of the plant. The roots, the bark and the ripe fruit are
astringent. The flowers are refrigerant and aperient. The unripe fruit is cooling, diuretic
and laxative. The exudation from the incisions on the fruit is used as an external
application in inflammation of eye. The juice of the fresh bark with honey and turmeric
is given in gonorrhoea. The decoction of the roots given in myalgia following upon
some febrile condition. The extract of the plant also showed antioxidant and
*Corresponding author. Email: drhabib56@yahoo.com
Natural Product Research
ISSN 1478-6419 print/ISSN 1029-2349 online ß 2007 Taylor & Francis
http://www.tandf.co.uk/journals
DOI: 10.1080/14786410601124664
Downloaded By: [PERI Pakistan] At: 09:50 28 June 2010
antiatheroscleotic activities [9]. The plant contains a variety of structures [10–12], some
of which proved to be physiologically active [13–17].
Our investigations on ethanolic extract of the plant have resulted in the isolation of
kaempferol-3-O--
L-(6
00
-methyl)-rhamnopyranoside (1) and kaempferol-3-O--L-
(6
00
-ethyl)-rhamnopyranoside (2). The structures of the compounds were determined
on the basis of spectroscopic data including the 2D-NMR experiments.
2. Results and discussion
Kaempferol-3-O-a-
L-(6
00
-methyl)-rhamnopyranoside (1): The mass spectrum of com-
pound (1) showed the molecular ion at m/z 432.1034, corresponding to the molecular
formula C
21
H
20
O
10
, indicating 12
of unsaturation in the molecule. The other major
fragmentation peaks were found to be at m/z 431, 415, 391, 367, 340, 339, 325, 286, 285,
269, 255, 227, 211, 183 and 163. The peak at m/z 415 showed the loss of hydroxyl group
from the molecule. The characteristic fragment of flavonoid glycosides appears at m/z
286 showed the loss of 146 m.u. indicating the cleavage of the O-sugar bond. Similarly,
the peak at m/z 339 showed the loss of 93 m.u. (C
6
H
3
O), indicating the cleavage of a
phenol moiety from the molecule. The molecular ion was confirmed by the FAB
positive and FAB negative mass spectrometry.
The UV (MeOH) spectrum of compound 1 showed absorptions at
max
345, 266, 224,
215 and 210 nm, indicating the presence of kaempferol chromophore in the molecule.
The IR (CHCl
3
) showed major absorptions at 1090, 1590, 1655, 2890 and 3540 cm
1
,
indicating the presence of the C–O, C¼C, C¼O(, -unsaturated), C–H and O–H
functionalities in the molecule.
The
1
H-NMR (CDCl
3
300 MHz) spectrum showed the presence of 20 proton
resonances. The 2H singlet at 6.71 showed the presence of two symmetrical aromatic
protons, 6H and 8H at meta disposition to each other. The 2H doublet at 7.23
(J ¼ 8.0 Hz) was assigned to the 2
0
-H and 6
0
-H, indicating a pair of symmetrical protons.
Another 2H doublet at 8.03 (J ¼ 8.0 Hz) was assigned to the other pair of symmetrical
protons, 3
0
-H and 5
0
-H. The assignments of 3
0
-H/5
0
-H and 2
0
-H/6
0
-H were made on the
basis of HMBC interactions of the protons with 1
0
-C and 4
0
-C, respectively. A 1H
singlet at 6.26 was assigned to the 1
00
-H. The absence of splitting showed that the
dihedral angle between the 1
00
-H and 2
00
-H would be 90
. A singlet at 5.07 and a
doublet at 4.57 (J ¼ 7.0 Hz) were assigned to the 2
00
-H and 3
00
-H. The double doublet at
4.05 (J
1
¼ 7.0 Hz, J
2
¼ 6.5 Hz) was assigned to the 4
00
-H, while another double doublet
at 4.24 (J
1
¼ 6.5 Hz, J
2
¼ 6.1 Hz) was assigned to the 5
00
-H. A 3H doublet at 1.28
(J ¼ 6.1 Hz) was assigned to the 6
00
-H. The
1
H-NMR chemical shift assignments are
presented in table 1.
The
13
C-NMR (CHCl
3
, 75 MHz) spectrum showed the presence of 21 carbon
resonances in the molecule. The multiplicities of the carbon signals were determined by
the DEPT experiments. The signals at 94.39 and 99.70 were assigned to the 6C/8C
aromatic carbons adjacent to the hydroxyl functions while the hydroxyl bearing
carbons resonated at 165.84 (C-5) and 162.50 (C-7). The symmetrical carbons of the
phenol moiety were appeared as a 2C signal each at 131.23 (C-2
0
/C-6
0
) and 116.20
(C-3
0
/C-5
0
). The signal at 161.44 was assigned to the phenol carbon (4
0
-C) bearing OH
function. The anomeric carbon appeared at 103.61 indicating the presence of an
-glucosidic unit [13–15]. The other methine carbons of the glycosidic moiety appeared
776 Habib-ur-Rehman et al.
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at 73.18 (2
00
-C), 72.54 (4
00
-C), 71.80 (3
00
-C) and 69.21 (5
00
-C). The absence of a
signal around 65.00 showed the absence of –CH
2
OH function and the presence of a
methyl signal at 18.10 indicated the presence of 6
00
-methyl group. The downfield
quaternary carbon signal at 178.80 was assigned to the carbonyl carbon (4C). The
13
C-NMR chemical shifts are presented in table 2.Inlinegraphic is hidden
The signal at 8.03 assigned to the 3
0
-H/5
0
-H symmetrical protons showed COSY
interactions with the signal at 7.23 assigned to the 2
0
-H/6
0
-H, another pair of
symmetrical protons. The absence of COSY interactions of the signal at 6.71 (6H and
8H) indicated that the two aromatic protons are placed at meta disposition. The signal
at 6.26 assigned to 1
00
-H showed no detectable COSY interaction with the signal at
5.07 (2
00
-H). The latter also did not show COSY interaction with the signal at 4.57
assigned to the 3
00
-H, indicating besides the 1
00
-H and 2
00
-H, 90
dihedral angle between
the 2
00
-H and 3
00
-H. The signal at 4.57 (3
00
-H) showed COSY interactions with the
signal at 4.05 (4
00
-H) which in turn showed interactions with the signal at 4.24 (5
00
-H).
The signal at 4.24 showed strong COSY interaction with the signal at 1.28 assigned
to the 6
00
-methyl protons.
The 3H signal at 1.28 (6
00
-CH
3
) showed HMQC interaction with carbon resonance
at 18.10 (6
00
-C). The 1H signal at 4.24 showed interaction with the C-signal at 69.21.
The 1H signal at 4.57 showed interaction with the C-signal at 71.80 (3
00
-C) while the
signal at 4.05 (4
00
-H) showed interaction with the C-signal at 72.54 (4
00
-C). The
H-signal at 4.57 (3
00
-H) showed HMQC interaction with the C-signal at 71.80 (3
00
-C).
The 1H signal at 5.07 (2
00
-H) showed interaction with the C-signal at 73.18 (2
00
-C).
The 2H signal at 8.03 (3
0
-H/5
0
-H) showed interaction with the C-signal at 116.20
(3-C/5
0
-C) while the 2H signal at 7.23 (2
0
-H/6
0
-H) showed interaction with C-signals at
131.45 (2
0
-C/6
0
-C). The signal at 6.71 assigned to the 6H and 8H showed HMQC
interactions with the C-signals at 99.70 and 94.39, assigned to the 6C and 8C,
respectively. The H-signal at 6.26 (1
0
-H) showed HMQC interactions with the C-signal
at 103.61 (1
00
-C).
The 3H signal 1.28 (6
00
-CH
3
) showed HMBC interactions with the C-signals at
69.21 (5
00
-C) and 72.54 (4
00
-C). The H-signal at 4.24 (6
00
-H) showed interactions
with the C-signals at 18.10 (6
00
-C) and 71.80 (3
00
-C) while the H-signal at 5.07
(2
00
-H) showed interactions with the C-signal at 72.54 (4
00
-C). The H-signal at 8.03
Table 1.
1
H-NMR chemical shift assignments of compounds 1 and 2.
Proton no. 12
6H 6.71 (1H, s) 6.60 (1H, s)
8H 6.71 (1H, s) 6.60 (1H, s)
2
0
-H 7.23 (1H, d, J ¼ 8.0 Hz) 7.13 (1H, d, J ¼ 8.0 Hz)
3
0
-H 8.03 (1H, d, J ¼ 8.0 Hz) 8.15 (1H, d, J ¼ 8.0 Hz)
5
0
-H 8.03 (1H, d, J ¼ 8.0 Hz) 8.15 (1H, d, J ¼ 8.0 Hz)
6
0
-H 7.23 (1H, d, J ¼ 8.0 Hz) 7.13 (1H, d, J ¼ 8.0 Hz)
O-Hs 5.31 (6H, bs) 5.30 (6H, bs)
1
00
-H 6.26 (1H, s) 6.29 (1H, m)
2
00
-H 5.07 (1H, s) 4.73 (1H, m)
3
00
-H 4.57 (1H, d, J ¼ 7.0 Hz) 4.31 (1H, d, J ¼ 7.0 Hz)
4
00
-H 4.05 (1H, dd, J
1
¼ 7.0 Hz, J
2
¼ 6.5 Hz) 4.12 (1H, dd
0
J
1
¼ 7.0 Hz, J
2
¼ 6.7 Hz)
5
00
-H 4.24 (1H, dd, J
1
¼ 6.5 Hz, J
2
¼ 6.1 Hz) 4.20 (1H, dd, J
1
¼ 6.7 Hz, J
2
¼ 6.5 Hz)
6
00
-H 1.28 (3H, d, J ¼ 6.1 Hz) 1.41 (2H, m)
7
00
-H – 0.88 (3H, m)
Phytochemical investigations of P. emblica 777
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(3
0
-H/5
0
-H) showed HMBC interactions with the C-signals at 131.23, 131.45 and
161.44. The H-signal at 7.23 (2
0
-H/6
0
-H) showed interactions with the C-signals at
116.20 (3
0
-C and 5
0
-C), 121.80 (1
0
-C) and 131.23 (2C) while the H-signal at 6.71
(6H and 8H) showed HMBC interactions with the C-signals at 157.57, 157.65,
162.50 and 165.84. The H-signal at 6.26 showed HMBC interactions with the
C-signals at 73.18 (2
00
-C). Similar
1
H–
13
C interactions were also observed for other
glycosidic protons. Based on the above spectroscopic data, structure 1 was assigned to
the compound, kaempferol-3-O--
L-(6
00
-ethyl)-rhamnopyranoside.
Kaempferol-3-O-a-
L-(5
00
-ethyl)-rhamnopyranoside (2): The mass spectrum of compound
2 showed the molecular ions peak at m/z 446.1235, corresponding to the molecular
formula C
22
H
22
O
10
, indicating 12
of unsaturation in the molecule. The other major
fragmented ion peaks were found to be at m/z 445, 431, 429, 352, 286, 269, 255, 227,
210, 183, and 163. The peak at m/z 431 showed the loss of methyl group from the
molecule. A fragment characteristic to flavonoid glycosides appear at m/z 286. The peak
at m/z 269 showed the loss of 177 m.u., indicating the cleavage of the O-sugar bond.
Similarly, the peak at m/z 353 showed the loss of 93 m.u. (C
6
H
5
O), indicating the
cleavage of phenol moiety from the molecule. The molecular ion was confirmed by the
FAB positive mass spectrometry.
The UV (MeOH) spectrum of the compound 1 showed max at 210, 230, 285 nm,
indicating the presence of kaempferol chromophore in the molecule. The IR (CHCl
3
)
showed major absorptions at 1090, 1590, 1655, 2890 and 3540 cm
1
indicating the
presence of the C–O, C¼C, C¼O(, -unsaturated), C–H and O–H functionalities in
the molecule.
Table 2.
13
C-NMR chemical shift assignments of compounds 1 and 2.
Carbon no. 12
2C 131.23 (C) 131.40 (C)
3C 121.70 (C) 121.93 (C)
4C 178.75 (C) 178.70 (C)
4a-C 157.65 (C) 157.60 (C)
5C 165.84 (C) 165.80 (C)
6C 94.39 (CH) 99.50 (CH)
7C 162.50 (C) 162.55 (C)
8C 99.70 (CH 94.20 (CH)
8a-C 157.57 (C) 157.30 (C)
1
0
-C 121.80 (C) 122.10 (C)
2
0
-C 131.23 (CH) 131.69 (CH)
3
0
-C 116.20 (CH) 116.28 (CH)
4
0
-C 161.44 (C) 161.30 (C)
5
0
-C 116.20 (CH) 116.28 (CH)
6
0
-C 131.23 (CH) 131.69 (CH)
1
00
-C 103.61 (CH) 103.60 (CH)
2
00
-C 73.18 (CH) 73.38 (CH)
3
00
-C 71.80 (CH) 71.60 (CH)
4
00
-C 72.54 (CH) 72.00 (CH)
5
00
-C 69.21 (CH) 69.20 (CH)
6
00
-C 18.10 (CH
3
) 29.76 (CH
2
)
7
00
-C – 9.18 (CH
3
)
778 Habib-ur-Rehman et al.
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The
1
H-NMR (CDCl
3
, 300 MHz) spectrum showed the presence of 22 proton
resonances in the molecule. The 2H singlet at 6.60 showed the presence of two
symmetrical aromatic protons (6H/8H) at meta disposition to each other. The doublets
at 7.13 (J ¼ 8.0 Hz) and 8.15 (J ¼ 8.0 Hz) of 2H each indicating the two pairs of
symmetrical protons, 2
0
-H/6
0
-H and 3
0
-H/5
0
-H, respectively. The signal at 6.29 was
assigned to the 1
00
-H. The multiplet at 4.73 and a doublet at 4.31 (J ¼ 7.0 Hz) were
assigned to the 2
00
-H and 3
00
-H, respectively. The double doublet at 4.12 (J
1
¼ 7.0 Hz,
J
2
¼ 6.7 Hz) was assigned to the 4
00
-H while another double doublet at 4.20
(J
1
¼ 6.7 Hz, J
2
¼ 6.5 Hz) was assigned to the 5
00
-H. A 2H multiplet at 1.41 was
assigned to the 6
00
-CH
2
protons. A 3H multiplet at 0.88 was assigned to the methyl
protons. The
1
H-NMR assignments and coupling interactions were confirmed by the
2D-COSY and also by the HMQC and HMBC experiments. The
1
H-NMR chemical
shift assignments are presented in table 1.
The
13
C-NMR (CHCl
3
, 75 MHz) spectrum showed the presence of 22 carbon
resonances in the molecule. The multiplicities of the carbon signals were determined by
the DEPT experiments. The peaks at 99.50 and 94.20 were assigned to the aromatic
carbons 6C and 8C, adjacent to the hydroxyl functions, respectively while the OH
bearing carbons, (5C and 7C) resonated at 165.80 and 162.55, respectively. The
symmetrical carbons of the phenol moiety (2
0
-C/6
0
-C and 3
0
-C/5
0
-C) were appeared as a
2C signal each at 131.69 and 116.28. The signal at 161.30 was assigned to the
phenol carbon (4
0
-C) bearing OH function. The anomeric carbon (1
00
-C) appeared at
103.60, indicating the presence of -glucosidic unit [13–15]. The other methine carbon
signals appeared at 73.38, 71.60, 72.00 and 69.20, were assigned to the 2
00
-C, 3
00
-C,
4
00
-C and 5
00
-C. The absence of the signal around 65.00 showed the absence of CH
2
OH
function and the presence of methylene and methyl signals at 29.76 and 9.18,
respectively, indicated the presence of –CH
2
CH
3
at 5
00
-C. The downfield quaternary
carbon signal at 178.70 was assigned to the carbonyl carbon (4C). The
13
C-NMR
chemical shifts are presented in table 2. Based on the above spectral data, structure 2
was assigned to the compound, kaempferol-3-O--
L-(6
00
-ethyl)-rhamnopyranoside.
3. Experimental
3.1. Instrumental
UV spectra were recorded on a Shimadzu 1601 Japan made double beam spectro-
photometer, IR spectra were recorded on FTIR Shimadzu Japan made, mass spectra
were recorded on Varian MAT 312 mass spectrometer connected to DDP 11/34 DEC
computer system. The
1
H-NMR spectra were recorded at 300 MHz on Bruker AM 300
NMR Spectrometer while the
13
C-NMR spectra were recorded at 75 MHz on the same
instrument. The optical rotation was recorded on polartromic universal Australian
Standard K-157 digital Polarimeter. TLC experiment were performed on silica gel
(GF-254, 0.2 mm) E.Merk.
3.2. Plant material
The shoots and leaves (5 kg) of P. emblica Linn. (Euphorbeaceae) were collected in June
2002 from the Village Jatlan, District Mirpur, Azad Kashmir, Pakistan. The plant was
Phytochemical investigations of P. emblica 779
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identified by a taxonomist at the Department of Botany, University of Azad Jammu
and Kashmir, Muzaffarabad where a voucher specimen is deposited in the herbarium of
the department.
3.3. Isolation of (1) and (2)
The shoots and leaves of P. emblica were dried and cut into small pieces. The dried plant
material was crushed to powder. The powdered material (1.3 kg) was extracted with
methanol (4.2 L) and filtered. The filtrate was evaporated on a rotary evaporator under
reduced pressure to dryness, which resulted to a blackish green material.
The methanol extract was subjected to the silica-gel column chromatography and
eluted with a mixture of chloroform and methanol (7.0 : 3.0). This resulted seven frac-
tions of 15 mL each. The fraction 3 was subjected to the PTLC experiments to identify
the isolation pattern. The system of CHCl
3
/CH
3
OH (5.0:5.0) indicated two bands
having distinct Rf values. Therefore, the fraction was subjected to the PTLC with
CHCl
3
/CH
3
OH (5.0 : 5.0) as the solvent system. This afforded semi-pure compounds
1 and 2 which were further purified by rechromatography on PTLC with
CHCl
3
/CH
3
OH (5.5 : 4.5) as the solvent system. This resulted in the isolation of the
pure compounds 1 (Rf ¼ 0.7; 23 mg; m.p. 78
C; 1.77 10
3
% yield; []
D
45
) and
2 (Rf ¼ 0.6; 15 mg; m.p. 83
C; 1.16 10
3
% yield; []
D
70
).
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