A new flavonoidal constituent from taraxacum officinale (L.) weber

Article abstract of DOI:10.14233/ajchem.2013.14046

A new flavone glycoside (A) m.p. 265-268 °C, m.f. C₃₃H ₄₀O₂₁, [M]⁺ 742 (FABMS), has been isolated from stem of Taraxacum oficinale (L.) Weber. It was characterized as 3,5,7,3',4'-pentahydroxy 8-C methyl flavone 7-O-β-D-xylopyranosyl (14)O-β-D glucopyranosyl 3'- O-α-L-rhamnopyranoside alongwith known compound ladanein B by various chemical degradations and spectral analysis.

Full text of DOI:10.14233/ajchem.2013.14046

Asian Journal of Chemistry; Vol. 25, No. 7 (2013), 4117-4118
http://dx.doi.org/10.14233/ajchem.2013.14046
NOTE
A New Flavonoidal Constituent from Taraxacum officinale (L.) Weber
*
RAJ NATH YADAVA and SHIRIN KHAN
Natural Products Laboratory, Department of Chemistry, Dr. H.S. Gour Central University, Sagar-470 003, India
*Corresponding author: E-mail: rnyadava@rediffmail.com
(Received: 10 May 2012;
Accepted: 30 January 2013)
AJC-12773
A new flavone glycoside (A) m.p. 265-268 ºC, m.f. C33H40O21, [M]+ 742 (FABMS), has been isolated from stem of Taraxacum oficinale
(L.) Weber. It was characterized as 3,5,7,3',4'-pentahydroxy 8-C methyl flavone 7-O-β-D-xylopyranosyl (1→4)O-β-D glucopyranosyl 3'-
O-α-L-rhamnopyranoside alongwith known compound ladanein B by various chemical degradations and spectral analysis.
Key Words: Taraxacum officinale (L.) Weber, Compositae, Stem, Flavone glycoside.
Taraxacum oficinale (L.) Weber1-3 belongs to family
Compositae. It is commonly known as 'Kanphool or
Kukraundha' in Hindi. It is found in Himalayas and the Khasi
Hills of Meghalaya, Mishmi Hills of Arunachal Pradesh and
hills of South India at 3000-5000 m and Gujarat. It used in the
treatment of kidney and liver problems. It is also useful in
chromic diseases of the digestive organs especially hepatic
affections and jaundice. It is used to make dandelion wine and
the greens are used in salad. Earlier workers4,5 have reported
various constituents from this plant. In the present paper, we
report the isolation and structural elucidation of a new flavone
glycoside 3,5,7,3',4'-pentahydroxy 8-C methyl flavone 7-O-
β-D-xylopyranosyl (1→4) O-β-D glucopyranosyl 3'-O-α-L-
rhamnopyranoside (A) along with one known compound
ladanein (B) from methanolic extract of the stems of this plant.
All the m.p. were determined on a thermoelectrical melting
point apparatus and are uncorrected. The IR spectra were
recorded in KBr disc. 1H NMR spectra were recorded at 300
MHz in CDCl3 using TMS as internal standard. 13C NMR
spectra were recorded at 90 MHz using CDCl3 as solvent and
mass spectra on a Jeol D 300 mass spectrometer.
by column chromatography over silica gel and studied
separately.
Study of compound A: It has m.p. 265-268 ºC, m.f.
C33H40O21, [M+] m/z 742. Found: C, 51.70; H, 5.17 calcd. for
C33H40O21 C, 51.75; H, 5.12 %. UV-VIS (MeOH): λmax nm
262, 268, 276, 284, 364; IR (KBR, νmax, cm-1): 3438, 2891,
2855, 1731, 1657, 1620, 1568, 1446, 1388, 1347, 2865, 1083,
1
1024; H NMR (300 MHz CDCl3): δ 12.13 (1H, s, 5-OH),
3.87 (3H, s, 8-Me), 6.73 (1H, d, J 2.4 Hz, H-6), 8. 64 (1H, s,
3'-OH), 8.72 (1H, s, 4'-OH), 7.18 (1H, d, J 2.1 Hz, H-2'), 6.80
(1H, d, J 8.4 Hz, H-5'), 7.14 (1H, d, J 8.2, Hz, H-6'), 5.20 (1H,
d, J 1.7 Hz, H-1''), 3.21-3.80 (4H, m, H-2", 3", 4", 5"), 3.82
(1H, dd, J, 12.0, 2.2 Hz, H-6"), 4.96 (1H, d, J 7.4 Hz, H-1'''),
3.33 (1H, m, H-2"'), 3.35 (1H, m, H-3"'), 3.35 (1H, m, H-4'''),
3.24 (2H, m, H-5'''), 5.28 (1H, d, J 7.8 Hz, H-1''"), 4.12 (1H,
dd, J 1.6, 3.6, Hz H-2'"'), 3.85 (1H, dd, J, 3.6,9.0 Hz, H-3''"),
3.72 ( 1H, d, J 9.0 Hz, H-4''"), 3.56 (1H, m, 5''") 1.88 (3H, d,
J 5.8 Hz, H-6'"'); 13C NMR (300 MHz, CDCl3): δ 162.0 (C-2),
102.6 (C-3), 184.8 (C-4), 162.5 (C-5), 101.5 (C-6), 163.9 (C-
7), 96.4 (C-8), 158.1 (C-9), 105.6 (C-10), 130.3 (C-1'), 117.3
(C-2'), 129.2 (C-3'), 132.7 (C-4'), 116.6 (C-5'), 123.9 (C-6'),
104.9 (C-1''), 78.6 (C-3''), 76.5 (C-5''), 76.0 (C-2''), 74.7 (C-
4''), 68.0 (C-6''), 103.8 (C-1'''), 73.5 (C-2'''), 75.8 (C-3'''), 72.0
(C-4'''), 78.2 (C-5'''), 105 (C-1"''), 78.4 (C-3'"'), 77.6 (C-5''"),
75.6 (C-2''"), 73.1 (C-4''"), 62.9 (C-6'"').
The stem of Taraxacum oficinale (L.) Weber were collected
from Patharia hills of Sagar district and authenticated by
Department of Botany, Dr. H.S. Gour University, Sagar, India.
Isolation of compounds: Air dried and powdered stems
(3 kg) of the plant were extracted with methanol. The methanol
soluble fraction was concentrated under reduced pressure to
give brown viscous mass (1.95 g). It gave two spots on TLC
examination indicating it to be mixture of two compounds A
and B. These compounds were separated by TLC and purified
Acid hydrolysis of compoundA: CompoundA (100 mg)
was dissolved in ethanol (20 mL) and refluxed with 10 mL of
10 % H2SO4 on water bath for 4 h. The reaction mixture was
concentrated and allowed to cool and give compound A-1 as
aglycone which was identified as 3,5,7,3',4'-pentahydroxy 8

4118 Yadava et al.
Asian J. Chem.
C-methyl flavone by comparison of its spectral data with
reported literature values. The aqueous hydrolysate was neutra-
lized with BaCO3 and the BaSO4 was filtered off. The filtrate
was concentrated and subjected to paper chromatography
examination using nBAW (4:1:5) solvent system and sugar
were identified as L-rhamnose (Rf 0.37), D-xylose (Rf 0.25)
and D-glucose (Rf 0.19), (Co-PC and Co-TLC).
Hz, H-2'), 7.12 (2H, d, J 8.9 Hz, H-3'), 7.10 (2H, d, J 8.7 Hz,
H-5'), 8 (1H, d, J 8.8 Hz, H-6'), 3.91 (3H, s, OMe), 13C NMR
(300 MHz CDCl3) δ (ppm): 162.90 (C-2), 103.45 (C-3), 183.02
(C-4), 152.09 (C-5), 130.92 (C-6), 61.27 (6-OMe), 157.70 (C-
7), 93.04 (C-8), 151.89 (C-9), 103.99 (C-10), 123.64 (C-1'),
128.65 (C-2'), 11.20 (C-3'), 161.82 (C-4'), 11.10 (C-5'), 128.60
(C-6'), 54.78 (4'- OMe).
Study of Compound Aglycone (A-1): It has m.f.
C15H12O7, m.p 245-247 ºC, [M]+ 304, found (%) C 59.28, H
3.88, calcd. for m.f. C15H12O7, C 59.20, H 3.94; UV λmax (nm)
275, 288, 340; IR (KBr, νmax, cm-1); 3297, 1646, 1600, 1520,
CH3
CH3
OH
CH2OH
O
O
O
O
O
O
OH
O
O
HO
OH
OH
OH
OH
OH
OH
OH
1
1461; H NMR (300 MHz,CDCl3): δ 11.7 (1H, s, C-5-OH),
HO
5.00 (1H, d, J 11.5 Hz, H-2), 4.60 (1H, d, J 11.5 Hz, H-3),
5.98 (1H, d, J 2.0 Hz, H-6), 5.93 (1H, d, J 2.0 Hz, H-8), 7.05
(1H, d, J 1.9 Hz, H-2'), 6.85 (1H, d, J 8.1 Hz, H-5') 6.90 (1H,
dd, J 8.1, 1.9 Hz, H-6'); 13C NMR (300 MHz, CDCl3) δ 85.09
(C-2); 73.64 (C-3); 198.37 (C-4); 164.27 (C-5); 97.29 (C-6);
168.72 (C-7); 96.27 (C-8); 164.47 (C-9); 101.79 (C-10);
129.82 (C-1'); 115.85 (C-2'); 146.28 (C-3'); 147.11 (C-4');
116.05 (C-5'); 120.88 (C-6');
(A)
OH
CH3
OH
HO
O
O
OH
HO
Permethylation of compound A: Compound A (40 mg)
was refluxed with CH3I (5 mL) and Ag2O (20 mg) in DMF
(25 mL) for 2 h and then filtered. The filtrate was hydrolyzed
with 10 % ethanolic H2SO4 for 5 h. to give methylated aglycone
identified 3,5,4'-trimethoxy 8C-methyl flavone and methylated
sugars which were identified as 2,3,4-tri-O-methyl-L-
rhamnose (Rf 0.37), 2,3,6-tri-O-methyl-D-glucose (Rf 1.0) and
2,3,4-tri-O-methyl-D-xylose (Rf 0.94).
(A-1)
OMe
OMe
O
HO
HO
O
(B)
Structures of A, A-1, B
Enzymatic hydrolysis of compound A: Compound A
(25 mg) was dissolved in MeOH (10 mL) and hydrolyzed with
equal volume of takadiastase enzyme. The reaction mixture
was allowed to stay at room temperature for 2 days and filtered
off. The proaglycone and hydrolysate were studied separately.
The hydrolyzate was concentrated and subjected to paper
chromatography examination using nBAW (4:1:5) as solvent
system and aniline hydrogen phthalate as a spraying reagent
which showed the presence of L-rhamnose (Rf 0.37). The
proaglycone was dissolved in MeOH (20 mL) further hydro-
lyzed with equal volume of almond emulsin at room temperature
as usual procedure yielded aglycone identified 3,5,7,3',4'-
pentahydroxy 8C-methyl flavone and sugars were identified
as D-xylose (Rf 0.26) and D-glucose (Rf 0.19) (Co-PC and
Co-TLC).
ACKNOWLEDGEMENTS
The authors are thankful to Head, SAIF, Central Drug
Research Institute, Lucknow for providing various spectra,
elemental analysis and antiviral activity. Thanks are also due
to The Head, Department of Chemistry, Dr. Hari Singh Gour
Central University, Sagar, India for providing the laboratory
facilities.
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C17H14O6, [M+] m/z 314. Found: C 64.96; H 4.45 calcd. for
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