Flavonoids from tartary buckwheat seeds

Article abstract of DOI:10.14233/ajchem.2013.13277

Nine flavonoids were isolated from the seeds of tartary buckwheat. Their structures were eulcidated as quercetin (1), rutin (2), vitexin (3), orientin (4), hyperin (5), tricin-7-O-b-D-glucopyranoside (6), chrysoeriol (7), tectochrysin (8) and luteolin-7-O

Full text of DOI:10.14233/ajchem.2013.13277

Asian Journal of Chemistry; Vol. 25, No. 4 (2013), 2012-2014
http://dx.doi.org/10.14233/ajchem.2013.13277
Flavonoids from Tartary Buckwheat Seeds
1
2,*
BAIXING WANG and HAOBIN HU
1College of Agriculture and Forestry, Longdong University, Qingyang 745000, P.R. China
2College of Chemistry and Chemical Engineering, Longdong University, Qingyang 745000, P.R. China
*Corresponding author: Fax: +86 934 8632822; Tel: +86 934 8522487, E-mail: hhb-88@126.com
(Received: 17 December 2011;
Accepted: 10 October 2012)
AJC-12268
Nine flavonoids were isolated from the seeds of tartary buckwheat. Their structures were eulcidated as quercetin (1), rutin (2), vitexin (3),
orientin (4), hyperin (5), tricin-7-O-β-D-glucopyranoside (6), chrysoeriol (7), tectochrysin (8) and luteolin-7-O-β-D-glucopyranoside
(9), by means of spectroscopic methods, especially by 1H and 13C NMR, FAB-MS and GC, as well as by chemical methods and comparison
with literature data.
Key Words: Tartary buckwheat seed, Flavonoid.
disilazane-trimethylchlorosilane (HMDS-TMCS) (0.1 mL) at
60 ºC for 1 h. After being partitioned between n-hexane (0.5
mL) and H2O (0.5 mL), the n-hexane extract was concentrated
and analyzed by GC under the following conditions: HP-5
MS fused silica capillary column (30 m × 0.25 mm, film
thinkness 0.25 µm), column temperature at 230 ºC, injection
temperature at 250 ºC, N2 as carrier gas. The sugars were
confirmed by comparison of the retention times of their
derivatives with standard samples [retention time, D-glucose
(21.7 min), D-galactose (25.4 min) and L-rhamnose (19.1
min)]. The presence of L-rhamnose in 2, D-galactose in 5,
D-glucose in 2, 3, 4, 6 and 9 were detected.
INTRODUCTION
Flavonoids are a group of naturally occurring plant
compounds that serve many functions e.g., antioxidant, anti-
tumor, antiinflammatory, antituberculosis, antimalarial,
antimicrobial and antiviral, etc.1,2. The seeds of tartary buck-
wheat (Fagopyrum tataricum Gaertn.) serve as a rich source
of flavonoids and have been popularly recognized as an
excellent selective antioxidant and hypolipidaemic nutrient
food in China and many other countries of the world3. In
order to make full use of tartary buckwheat, our recent
research led to the isolation of 9 flavonoids from the seeds
of tartary buckwheat.
RESULTS AND DISCUSSION
EXPERIMENTAL
The seeds of tartary buckwheat were collected in September
2010 from Ring County of China and extracted three times
with 95 % aqueous EtOH at room temperature. The extract
was dissoved in 50 % aqueous EtOH and extracted with petro-
leum ether and EtOAc. The EtOAc extract was separated by
repeated column chromatography (Silica-gel, Diaion HP-20
and Sephadex LH-20) and recrystallization to give nine flavonoid
compounds. On the basis of chemical (acid hydrolysis) and
spectral analyses (UV, IR, MS and NMR) and comparison with
the literature data, their structures were elucidated as quercetin
Acid hydrolysis of compounds and determination of
the absolute configuration of the monosaccharide: A
solution of compound (5.0 mg, 2-6 and 9) in 2 mol/L HCl-
dioxane (1:1, 1 mL) was refluxed in a water bath at 90 ºC for
2 h. After removal of dioxane, the solution was extracted with
EtOAc (1 mL × 3). The aqueous layer was neutralized by
passing through an Amberlite MB-3 resin column eluted with
H2O, then concentrated and dried to furnish a monosaccharide
residue. Then, the sugars were detected by TLC analysis
[CHCl3-CH3OH-H2O-HOAc (15:6:2:3), detection solution:
aniline-phthalic acid] against the standard samples. The residue
was dissolved in pyridine (0.2 mL) and then a pyridine solution
(0.3 mL) of L-cysteine methyl ester hydrochloride (5 mg) was
added to the solution. The mixture was kept at 60 ºC for 1.5 h,
dried in vacuo and trimethylsilylated with hexamethyl-
(1)4,5, rutin (2)6,7, vitexin (3)8, orientin (4)9, hyperin (5)10,11
tricin-7-O-β-D-glucopyranoside (6)12, chrysoeriol (7)13,14
,
,
tectochrysin (8)15 and luteolin-7-O-β-D-glucopyranoside
(9)16,17.Although quercetin, rutin, vitexin, orientin and hyperin
have been previously isolated from tartary buckwheat18, this
is first report on the occurrence of tricin-7-O-glucopyranoside,

Vol. 25, No. 4 (2013)
Flavonoids from Tartary Buckwheat Seeds 2013
TABLE-1
1H-NMR DATA OF COMPOUNDS 1-9 (δH in DMSO-d6, 400 MHz, J: Hz)
Proton
1
2
3
4
5
6
7
8
9
3
6
6.76 (s)
6.28 (s)
6.64 (s)
6.25 (s)
7.01 (s)
6.88 (s)
6.68 (s)
6.74 (s)
6.18 (d, 2.0) 6.21 (d, 2.0)
6.38 (d, 2.0) 6.40 (d, 2.0)
6.19 (d, 2.4) 6.92 (d, 1.9) 6.22 (d, 2.0) 6.39 (d, 2.1) 6.43 (d, 1.9)
6.41 (d, 2.4) 6.43 (d, 1.9) 6.49 (d, 2.0) 6.51 (d, 2.1) 6.79 (d, 1.9)
8
2’
3’
4’
5’
6’
7.62 (d, 2.0) 7.51 (d, 2.1) 7.99 (d, 8.1) 7.48 (d, 2.0) 7.51 (d, 1.7)
6.88 (d, 8.1)
7.32 (s)
7.54 (m)
7.85 (m)
7.48 (m)
7.54 (m)
7.48 (m)
7.85 (m)
7.41 (d, 2.1)
6.88 (d, 8.1) 6.82 (d, 8.2) 6.88 (d, 8.1) 6.85 (d, 8.4) 6.81 (d, 8.4)
6.98 (d, 8.4)
7.54 (dd,
8.4, 2.0)
6.88 (d, 8.0)
7.46 (dd,
8.0, 2.1)
7.56 (dd,
8.1, 2.0)
12.48 (s)
7.60 (dd, 7.99 (d, 8.1) 7.52 (dd,
8.2, 2.1)
12.58 (s)
7.66 (dd,
8.4, 1.7)
12.62 (s)
7.32 (s)
8.4, 2.0)
13.16 (s)
C5-OH
OCH3
13.21 (s)
12.95 (s)
3.90 (s)
12.71 (s)
3.89 (s)
12.98 (s)
3.85 (s)
Anomeric H
Glu
5.41 (d, 7.9) 4.68 (d, 7.6) 4.67 (d, 7.8)
4.38 (br s)
5.02 (d, 7.4)
5.08 (d, 7.5)
Rha
Gal
5.36 (d, 7.8)
TABLE-2
13C-NMR (DEPT) DATA OF COMPOUNDS 1-9 (δC in DMSO-d6, 100 MHz)
Carbon
1
2
3
4
5
6
7
8
9
2
146.8 (C)
135.6 (C)
175.6 (C)
160.1 (C)
99.0 (CH)
163.7 (C)
93.2 (CH)
156.0 (C)
102.5 (C)
121.8 (C)
114.9 (CH)
144.8 (C)
147.7 (C)
115.4 (CH)
119.6 (CH)
156.6 (C)
133.4 (C)
177.2 (C)
161.2 (C)
98.7 (CH)
164.1 (C)
93.6 (CH)
156.5 (C)
104.1 (C)
121.3 (C)
115.7 (CH)
144.8 (C)
148.4 (C)
121.7 (CH)
116.5 (CH)
163.9 (C)
164.1 (C)
156.2 (C)
164.5 (C)
163.8 (C)
163.8 (C)
164.3 (C)
3
4
102.4 (CH) 102.3 (CH) 133.8 (C) 103.9 (CH) 103.8 (CH) 104.3 (CH) 103.4 (CH)
182.1 (C)
161.1 (C)
182.0 (C)
160.5 (C)
177.6 (C)
161.0 (C)
182.1 (C)
157.3 (C)
181.9 (C)
157.4 (C)
182.2 (C)
162.0 (C)
181.9 (C)
159.8 (C)
5
6
98.2 (CH) 98.1 (CH) 98.9 (CH) 95.4 (CH) 98.8 (CH) 98.1 (CH) 99.5 (CH)
7
162.6 (C)
104.6 (C)
156.2 (C)
104.2 (C)
121.6 (C)
162.6 (C)
104.6 (C)
156.0 (C)
104.1 (C)
122.0 (C)
164.3 (C)
163.2 (C)
164.2 (C)
165.2 (C)
164.3 (C)
8
93.7 (CH) 99.5 (CH) 94.6 (CH) 92.6 (CH) 94.5 (CH)
9
156.9 (C)
104.0 (C)
121.3 (C)
161.2 (C)
105.4 (C)
120.5 (C)
161.7 (C)
103.3 (C)
120.4 (C)
157.4 (C)
105.6 (C)
131.5 (C)
157.3 (C)
105.2 (C)
121.0 (C)
10
1’
2’
3’
4’
5’
6’
CH3O
Sugar
1
129.1 (CH) 114.0 (CH) 115.4 (CH) 104.6 (CH) 110.2 (CH) 126.2 (CH) 113.7 (CH)
115.9 (CH) 145.8 (C)
160.4 (C) 149.7 (C)
145.0 (C)
148.6 (C)
148.3 (C)
140.1 (C)
150.8 (C) 129.0 (CH) 145.6 (C)
147.9 (C) 131.4 (CH) 149.9 (C)
115.9 (CH) 115.7 (CH) 116.1 (CH) 148.3 (C) 115.8 (CH) 129.0 (CH) 115.8 (CH)
129.1 (CH) 119.4 (CH) 122.4 (CH) 104.6 (CH) 121.8 (CH) 126.2 (CH) 119.3 (CH)
55.6 (CH3) 56.1 (CH3) 55.7 (CH3)
Glu
Rha
Glu
Glu
Gal
Glu
Glu
101.2 (CH) 100.8 (CH) 73.8 (CH) 73.4 (CH) 101.9 (CH) 100.8 (CH)
74.3 (CH) 70.1 (CH) 70.8 (CH) 70.8 (CH) 71.3 (CH) 73.3 (CH)
76.3 (CH) 70.6 (CH) 78.6 (CH) 78.8 (CH) 73.4 (CH) 77.4 (CH)
70.1 (CH) 71.9 (CH) 70.5 (CH) 70.7 (CH) 68.1 (CH) 69.8 (CH)
75.8 (CH) 68.2 (CH) 81.7 (CH) 82.0 (CH) 75.8 (CH) 76.6 (CH)
67.0 (CH2) 17.5 (CH3) 61.3 (CH2) 61.7 (CH2) 60.3 (CH2) 60.8 (CH2)
100.1 (CH)
73.1 (CH)
77.5 (CH)
69.7 (CH)
76.4 (CH)
60.6 (CH2)
2
3
4
5
6
R4
chrysoeriol, tectochrysin and luteolin-7-O-glucopyranoside in
this genus.
R5
R6
R2
Quercetin (1), yellow needles (CHCl3-MeOH), m.p. 312-
314 ºC. UV spectrum (MeOH, λmax, nm): 208 sh, 255, 284,
379 sh; IR spectrum (KBr, νmax, cm-1): 3406 (OH), 1665 (C=O),
1611, 1562, 1522, 1452 (Ar); negative FAB-MS m/z: 301 [M-
H]–. 1H and 13C NMR (Tables 1 and 2).
R3
O
O
R1
Rutin (2), yellow powder (CHCl3-MeOH), m.p. 191-192
ºC. UV spectrum (MeOH, λmax, nm): 207, 259 sh, 261, 356 sh;
IR spectrum (KBr, νmax, cm-1): 3422 (OH), 1656 (C=O), 1604,
1567, 1506, 1456 (Ar), 1363 (CH3), 1064, 1025 (glycosidic
bond); negative FAB-MS m/z: 609 [M-H]–. 1H and 13C NMR
(Tables 1 and 2).
OH
Flavonoid R1
R2
R3
R4
R5
R6
H
H
H
H
H
OH
H
H
OH
OH
OH OH
OH OH
1
2
3
4
5
6
7
8
9
OGlc-(6→1)-Rha
H
Glc OH
Glc OH
H
OH
H
OH OH
OH OH
Vitexin (3), yellow crystal (MeOH), m.p. 269-271 ºC. UV
(MeOH, λmax, nm): 250, 267 sh, 337 sh; IR spectrum (KBr, νmax,
OGal
H
H
H
H
H
H
OH
OGlc OCH3 OH OCH3
cm-1): 3278 (OH), 1660 (C=O), 1608, 1500 (Ar); negative FAB-
H
H
OH
OCH3
OCH3 OH
H
H
H
H
OGlc OH OH
H
MS m/z: 431 [M-H]–. 1H and 13C NMR (Tables 1 and 2).
H

2014 Wang et al.
Asian J. Chem.
Orientin (4), yellow crystal (MeOH), m.p. 261-263 ºC.
UV (MeOH, λmax, nm): 248 sh, 258 sh, 324; IR spectrum (KBr,
max, cm-1): 3312 (OH), 1658 (C=O), 1612, 1500 (Ar); negative
FAB-MS m/z: 447 [M-H]–. 1H and 13C NMR (Tables 1 and 2).
Hyperin (5), pale yellow needles (MeOH), m.p. 235-237
ºC. UV spectrum (MeOH, λmax, nm): 206 sh, 257, 299, 362 sh;
IR spectrum (KBr, νmax, cm-1): 3423 (OH), 1661 (C=O), 1604,
1562, 1501, 1463 (Ar); negative FAB-MS m/z: 463 [M-H]–.
1H and 13C NMR (Tables 1 and 2).
ACKNOWLEDGEMENTS
This work was financially supported by the Scientific and
Technological project of Qingyang City (GK061-25) of China.
ν
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13
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