Flavonoid constituents from spiraea brahuica

Article abstract of DOI:10.1002/hlca.201100214

Sparins A-C (1-3, resp.), three new flavonoids, were isolated from the CHCl₃ subfraction of the EtOH extract of the whole plant of Spiraea brahuica, along with 3′,7-di-O-methylquercetin (4) and luteolin 7-β-D-glucopyranoside (5), reported for the first time from this species. The structures of the new compounds were elucidated by spectroscopic techniques including MS and 2D-NMR spectroscopy. Copyright

Full text of DOI:10.1002/hlca.201100214

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Helvetica Chimica Acta – Vol. 95 (2012)
Flavonoid Constituents from Spiraea brahuica
by Uzma Rasheed Mughala), Rashad Mehmooda), Abdul Malik*a), Bakhat Alia), and
Rasool Bakhsh Tareenb)
a) International Center for Chemical and Biological Sciences, H. E. J. Research Institute of Chemistry,
University of Karachi, Karachi-75270, Pakistan (phone: þ 92-21-4824926; fax: þ 92-21-4819018-9;
e-mail: abdul.malik@iccs.edu)
b) Department of Botany, University of Balochistan, Sariab Road, Quetta, Pakistan
Sparins A – C (1 – 3, resp.), three new flavonoids, were isolated from the CHCl3 subfraction of the
EtOH extract of the whole plant of Spiraea brahuica, along with 3’,7-di-O-methylquercetin (4) and
luteolin 7-b-d-glucopyranoside (5), reported for the first time from this species. The structures of the new
compounds were elucidated by spectroscopic techniques including MS and 2D-NMR spectroscopy.
Introduction. – The genus Spiraea belongs to the family Rosaceae and comprises
well over 90 species growing as shrubs in the temperate region of the Northern
hemisphere and in Eastern Asia [1]. Various species of Spiraea are used as effective
medicines for the treatment of inflammation and malaria [2]. In China, the fruits and
roots of various Spiraea species are used as diuretic and detoxicant agents, and also for
the treatment of cough, headache, and toothache [2][3]. One of the species of the
genus Spiraea is Spiraea brahuica which is distributed in Asia and abundantly grows in
the Ziarat Valley of the Balochistan Province of Pakistan. No phytochemical or
pharmacological work has so far been carried out on this species. The chemotaxonomic
and ethnopharmacological significance of the genus Spiraea prompted us to undertake
phytochemical studies on S. brahuica. As a result, we isolated three new flavonoids
named sparin A (1), sparin B (2), and sparin C (3), along with 3’,7-di-O-methyl
quercetin (¼ rhamnazin; 4), and luteolin 7-b-d-glucopyranoside (5), reported for the
first time from this species (Fig.).
Figure. Compounds 1 – 5 isolated from Spiraea brahuica
1
)
Trivial atom numbering; for systematic names, see Exper. Part.
ꢀ 2012 Verlag Helvetica Chimica Acta AG, Zꢁrich

Helvetica Chimica Acta – Vol. 95 (2012)
101
Results and Discussion. – The EtOH extract of the whole plant of S. brahuica Boiss.
was suspended in H2O and successively extracted with hexane, CHCl3, AcOEt, and
BuOH. The CHCl3-soluble subfraction was subjected to a series of chromato-
graphic separations to yield compounds 1 – 5. All of these gave a blue-green color
with ethanolic FeCl3 solution for phenols and also a positive Shinoda test for flavonoids.
Sparin A (1) was obtained as yellow needles. The HR-FAB-MS of 1 showed a
quasimolecular-ion peak [M þ H]þ at m/z 615.1130 consistent with the molecular
formula C32H23O13. The IR spectrum showed the presence of OH (3429 cmꢀ1), a
conjugated CO (1668 cmꢀ1), a conjugated olefinic bond (1623 cmꢀ1), and aromatic
moieties (1540, 1500 cmꢀ1). The UV spectrum exhibited the characteristic absorption
maxima for a flavonoid at 214, 265, and 344 nm [4]. A bathochromic shift of 32 nm of
band-II on addition of AlCl3 indicated that position 5 of the flavonoid had a free
ionizable phenolic OH group [5]. The 13C-NMR and distortionless enhancement by
polarization transfer (DEPT) spectra showed 32 well resolved signals comprising two
Me and ten CH groups, and 20 quaternary C-atoms (Table 1). The signals at d(C) 177.4
and 177.3, 149.5 and 147.5, 138.2 and 137.9 and 105.3 and 104.4 were typical of C(4),
C(2), C(3), and C(10) of two 3-O-bearing flavonoid moieties. The signals of ten O-
bearing aromatic C-atoms were observed at d(C) 137.9 – 165.6 (Table 1). The two MeO
groups resonated at d(C) 55.9 and 55.8. The 1H-NMR spectrum showed two signals at
d(H) 13.6 and 14.1 revealing the presence of free OH groups at C(5) and C(5’’),
respectively. It further showed separate signals for two units of a monomethyl ether of
quercetin including meta-coupled H-atoms at d(H) 6.60 and 6.57 (each d, J ¼ 2.1 Hz,
1 H) as well as d(H) 6.86 and 6.75 (each d, J ¼ 1.8 Hz, 1 H). The signals of a
trisubstituted ring B were observed at d(H) 8.62 (d, J ¼ 2.1 Hz, 1 H), 8.12 (dd, J ¼ 8.4,
2.1 Hz, 1 H,), and 7.43 (d, J ¼ 8.4 Hz, 1 H). Another set of signals of a trisubstituted
aromatic ring was observed at 8.28 (d, J ¼ 2.1 Hz, HꢀC(2’’’)), 8.18 (dd, J ¼ 8.4, 2.1 Hz,
HꢀC(6’’’), and 7.35 (d, J ¼ 8.4 Hz, HꢀC(5’’’). Comparison of the 13C-NMR spectra of 1
with those reported for quercetin (¼2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-
benzopyran-4-one) showed downfield shifts of C(4’) (d(C) 150.2) and C(4’’’) (d(C)
150.3), providing evidence for the combination of two quercetin units through
dehydration of the phenolic groups at C(4’) and C(4’’’). Both the MeO groups at d(H)
3
3.86 and 3.75 (2s) showed J correlations, with C(7) (d(C) 165.4) and C(3’’’) (d(C)
148.1) confirming their presence at C(7) and C(3’’’), respectively. The dimeric structure
of sparin (1) was fully supported by its HMBC features (Table 1).
Sparin B (2) was obtained as yellow needles. The HR-FAB-MS of 2 showed a
quasimolecular-ion peak [M þ H]þ at m/z 643.1446 consistent with the molecular
formula C34H27O13. The UV and IR spectra were similar to those of 1. The 13C-NMR
spectra (broad band and DEPT; Table 1) showed 34 signals comprising four Me and ten
CH groups, and 20 quaternary C-atoms. The spectrum was similar to that of 1, except
1
for the presence of four MeO groups at d(C) 61.3, 55.9, 55.8, and 55.7. The H-NMR
spectrum also showed close resemblance to that of 1, except for the presence of signals
of four MeO groups at d(H) 4.18 (s, 3 H), 3.86 (s, 3 H), and 3.75 (s, 6 H). Sparin B (2) is
therefore the di-O-methyl ether of 1. The presence of MeO groups at C(3) (d(C)
141.3), C(7) (d(C) 165.5), C(7’’) (d(C) 165.6), and C(3’’’) (d(C) 148.1) was confirmed
by HMBC cross-peaks (Table 1). Further HMBC features were in complete agreement
with the assigned structure of sparin B (2).

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Helvetica Chimica Acta – Vol. 95 (2012)
Table 1. 13C- and 1H-NMR Data (125 and 500 MHz, resp.; C5D5N), and Important HMBC Features of
Compounds 1 and 21). d in ppm, J in Hz.
1
2
d(C)
d(H)
HMBC
d(C)
d(H)
HMBC
Rhamnetin
149.5
3,7-Di-O-methylquercetin
C(2)
C(3)
C(4)
C(5)
–
–
–
–
148.8
141.3
177.4
161.8
–
–
–
–
–
–
–
–
137.9
177.4
161.8
–
–
–
HꢀC(6)
97.9 6.57 (d,
J ¼ 2.1)
C(5), C(7),
C(8), C(10)
–
97.9 6.57 (d,
J ¼ 2.1)
C(5), C(7),
C(8), C(10)
–
C(7)
165.4
–
165.5
–
HꢀC(8)
91.9 6.60 (d,
J ¼ 2.1)
C(6), C(7),
C(9), C(10)
–
–
91.9 6.60 (d,
J ¼ 2.1)
C(6), C(7),
C(9), C(10)
–
–
C(9)
C(10)
C(1’)
156.9
105.3
123.3
–
–
–
156.9
105.3
123.4
–
–
–
–
–
HꢀC(2’)
116.6 8.62 (d,
J ¼ 2.4)
C(1’), C(2), C(3’),
C(4’), C(6’)
–
116.6 8.61 (d,
J ¼ 2.1)
C(1’), C(2), C(3’),
C(4’), C(6’)
–
C(3’)
C(4’)
148.4
150.2
–
–
147.1
149.5
–
–
–
–
HꢀC(5’)
116.6 7.43 (d,
J ¼ 8.4)
C(1’), C(3’),
C(4’), C(6’)
C(1’), C(2), C(2’),
116.6 7.43 (d,
J ¼ 8.4)
C(1’), C(3’),
C(4’), C(6’)
C(1’), C(2), C(2’),
HꢀC(6’)
121.1 8.12 (dd,
121.1 8.12 (dd,
J ¼ 8.4, 2.4) C(4’), C(5’)
J ¼ 8.4, 2.1) C(4’), C(5’)
MeOꢀC(3)
MeOꢀC(7)
–
–
–
61.3 4.18 (s)
55.8 3.75 (s)
Rhamnazin
C(3)
C(7)
55.8 3.75 (s)
Isorhamnetin
C(7)
C(2’’)
C(3’’)
C(4’’)
C(5’’)
147.5
138.2
177.3
162.4
–
–
–
–
–
–
–
–
147.5
138.1
177.3
162.4
–
–
–
–
–
–
–
–
HꢀC(6’’)
99.2 6.75 (d,
J ¼ 1.8)
C(5’’), C(7’’),
C(8’’), C(10’’)
–
99.2 6.74 (d,
J ¼ 1.8)
C(5’’), C(7’’),
C(8’’), C(10’’)
–
C(7’’)
165.6
–
165.6
–
HꢀC(8’’)
94.4 6.86 (d,
J ¼ 1.8)
C(6’’), C(7’’),
C(9’’), C(10’’)
–
–
–
94.4 6.86 (d,
J ¼ 1.8)
C(6’’), C(7’’),
C(9’’), C(10’’)
–
–
C(9’’)
C(10’’)
C(1’’’)
157.4
104.4
123.8
–
–
–
157.4
104.4
123.3
–
–
–
–
HꢀC(2’’’)
112.5 8.28 (d,
J ¼ 2.1)
C(1’’’), C(2’’), C(3’’’), 112.5 8.28 (d,
C(1’’’), C(2’’), C(3’’’),
C(4’’’), C(6’’’)
–
C(4’’’), C(6’’’)
–
J ¼ 2.1)
C(3’’’)
C(4’’’)
148.1
150.3
–
–
148.1
150.2
–
–
–
–
HꢀC(5’’’)
116.6 7.35 (d,
J ¼ 8.4)
C(1’’’), C(3’’’),
C(4’’’), C(6’’’)
C(1’’’), C(2’’), C(2’’’), 122.8 8.17 (dd,
116.6 7.36 (d,
J ¼ 8.4)
C(1’’’), C(3’’’),
C(4’’’), C(6’’’)
C(1’’’), C(2’’), C(2’’’),
HꢀC(6’’’)
122.8 8.18 (dd,
J ¼ 8.4, 2.1) C(4’’’), C(5’’’)
J ¼ 8.4, 2.1) C(4’’’), C(5’’’)
MeOꢀC(7’’)
MeOꢀC(3’’’)
–
–
–
55.7 3.75 (s)
55.9 3.86 (s)
C(7’’)
C(3’’’)
55.9 3.86 (s)
(3’’’)

Helvetica Chimica Acta – Vol. 95 (2012)
103
Sparin C (3) was obtained as yellow needles and gave a positive Molish test for a
flavonoid glycoside. The HR-FAB-MS showed a quasimolecular-ion peak [M þ H]þ at
m/z 447.1285 consistent with the molecular formula C22H23O10. The IR spectrum was
similar to that of 1. The UV spectrum showed absorption maxima at 215, 263, and
342 nm. A bathochromic shift of 15 nm of band-II indicated the presence of a free
ionizable phenolic OH group at position 5. The 13C-NMR sprectra (broad band and
DEPT; Table 2) showed 22 signals comprising one Me, one CH2, and eleven CH
groups, and nine quaternary C-atoms. The signals at d(C) 162.5, 104.3, 182.9, and 105.3
were typical for a flavonoid moiety. The O-substituted aromatic C-atoms resonated at
d(C) 166.2, 165.1, 158.7, and 155.3, while an aromatic C-methyl was observed at d(C)
16.8. The signal at d(C) 98.8 could be assigned to the anomeric C-atom of a hexose
moiety, while its other O-bearing C-atoms appeared in the range d(C) 78.9 – 61.7. The
1H-NMR spectrum (Table 2) showed meta-coupled H-atoms of ring A at d(H) 6.98 and
6.83 (each d, J ¼ 2.1 Hz, 1 H). The signals of a disubstituted ring B were observed at
d(H) 7.88 (d, J ¼ 2.1 Hz, 1 H), 7.49 (dd, J ¼ 8.4, 2.1 Hz 1 H), and 7.26 (d, J ¼ 8.4 Hz,
1 H). The Me group resonated at d(H) 2.48 (s). The signal of HꢀC(3) was observed at
d(H) 6.92 (s) and the anomeric H-atom at d(H) 5.80 (d, J ¼ 7.5 Hz). The larger
coupling constant allowed us to assign b-configuration to the hexose moiety. The
CHꢀO H-atoms were observed at d(H) 4.41 – 4.19, while the CH2ꢀO H-atoms
appeared at d(H) 4.55 and 4.42 – 4.45. Acid hydrolysis of sparin C (3) gave 3’-
Table 2. 13C- and 1H-NMR Data (125 and 500 MHz, resp.; C5D5N), and HMBC Features of Compound 3.
d in ppm, J in Hz.
d(C)
d(H)
HMBC
C(2)
165.1
104.3
182.9
105.3
158.7
99.1
–
–
HꢀC(3)
6.92 (s)
–
–
–
C(2), C(4), C(5), C(1’)
–
–
–
C(4a), C(5), C(7), C(8)
–
C(4a), C(6), C(7), C(8a)
–
C(4)
C(4a)
C(5)
HꢀC(6)
6.83 (d, J ¼ 2.1)
C(7)
166.2
94.6
–
HꢀC(8)
C(8a)
C(1’)
6.98 (d, J ¼ 2.1)
–
–
162.5
122.3
125.4
124.2
155.3
115.4
128.1
98.8
78.1
74.5
70.1
78.9
–
HꢀC(2’)
7.88 (d, J ¼ 2.1)
C(1’), C(2), C(3’), C(4’), C(6’)
–
–
C(1’), C(3’), C(4’), C(6’)
C(1’), C(2), C(2’), C(4’), C(5’)
C(7), C(2’’), C(3’’), C(5’’)
–
–
–
–
–
C(3’)
–
–
C(4’)
HꢀC(5’)
HꢀC(6’)
HꢀC(1’’)
HꢀC(2’’)
HꢀC(3’’)
HꢀC(4’’)
HꢀC(5’’)
CH2(6’’)
7.26 (d, J ¼ 8.4)
7.49 (dd, J ¼ 8.4, 2.1)
5.80 (d, J ¼ 7.5)
4.34 – 4.35 (m)
4.36 – 4.38 (m)
4.19 – 4.22 (m)
4.39 – 4.41 (m)
4.42 – 4.45 (m),
4.55 (dd, J ¼ 10.2, 1.8)
2.48 (s)
61.7
C(5’), C(4’)
C(3’)
MeꢀC(3’)
16.8

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Helvetica Chimica Acta – Vol. 95 (2012)
methylapigenin and a glycone which could be identified as d-glucose by the sign of the
optical rotation and comparison of the retention time of its Me3Si ether with a standard
in gas chromatography (GC). The anomeric H-atom at d(H) 5.80 showed 3J correlation
with C(7) (d(C) 166.2) allowing us to position the glucose moiety at C(7). The Me
2
3
location could be assigned to C(3’) (d(C) 124.2) based on J and J correlations
(Table 2). Further HMBC features were in complete agreement with the assigned
structure of sparin C (3) as 3’-methylapigenin 7-b-d-glucopyranoside.
The known compounds were identified as 3’,7-di-O-methylquercetin (4) [6] and
luteolin 7-b-d-glucopyranoside (5) [7] by comparison of physical and spectral data with
those reported in the literature.
Experimental Part
General. Column chromatography (CC): silica gel (SiO2; 230 – 400 mesh; E. Merck, Darmstadt,
Germany). Vacuum liquid chromatography (VLC): SiO2 (230 – 400 mesh; E. Merck). TLC: SiO2 60 F254
plates (E. Merck). GC: Schimadzu gas chromatograph (GC-9A); 3% OV-1-silanized Chromosorb W
column; column temp. 1808; injection port and detector temp. 275 – 3008; flow rate 35 ml/min; flame-
ionization detector. M.p.: Gallenkamp apparatus; uncorrected. Optical rotation: Jasco-P-2000 polar-
imeter. UV Spectra: Hitachi-UV-3200 spectrophotometer; lmax (log e) in nm. IR Spectra: Jasco-302-A
spectrometer; in KBr; ˜n in cmꢀ1. NMR Spectra: Bruker-AMX-500 instrument; d in ppm rel. to Me4Si as
internal standard, J in Hz. EI-MS: Finnigan-MAT-312 mass spectrometer. HR-FAB-MS: Jeol-JMS-HX-
110 mass spectrometer; glycerol as matrix.
Plant Material. The whole plant Spiraea brahuica Boiss. (Rosaceae; 40 kg) was collected from the
Ziarat Valley of Balochistan Province of Pakistan and identified by Prof. Dr. Rasool Bakhsh Tareen, plant
taxonomist, Department of Botany, University of Balochistan, Quetta, where a voucher specimen has
been deposited with the herbarium (Voucher specimen No. SB.RBT.08.BUH).
Extraction and Isolation. The shade-dried whole-plant material (40 kg) was extracted with EtOH
(3 ꢁ 50 l, 10 d each) at r.t. The combined extract was concentrated at r.t. to yield a residue (700 g), which
was suspended in H2O (1.5 l) and successively extracted with hexane (80 g), CHCl3 (100 g), AcOEt
(55 g), and BuOH (40 g). The CHCl3-soluble subfraction (50 g) was subjected to VLC (hexane, hexane/
CHCl3, CHCl3, and CHCl3/MeOH of increasing polarity); Fractions A – J. Fr. E (3 g; obtained with
CHCl3/MeOH 9 :1) was subjected to CC (SiO2, CHCl3 and CHCl3/MeOH of increasing polarity):
Frs. E.1 – E.5. Fr. E.3 (40 mg; obtained with CHCl3/MeOH 93 :7) was a semi-pure compound which was
resubjected to CC (SiO2, CHCl3/MeOH 93 :7): 4 (35 mg). Fr. E.4 (44 mg; obtained with CHCl3/MeOH
88 :12) was resubjected to CC (SiO2, CHCl3/MeOH 9 :1) binary mixture of compounds (32 mg); final
purification was achieved by prep. TLC (CHCl3/MeOH 88 :12) to furnish 1 (13 mg) and 2 (15 mg). Fr. F
(35 mg, obtained with CHCl3/MeOH 8.6 :1.4) was a binary mixture CC (SiO2, CHCl3/MeOH 88 :12 and
86 :14) afforded 3 (13 mg) and 5 (17 mg), resp.
Sparin A (¼ 3,5-Dihydroxy-2-{3-hydroxy-4-[2-methoxy-4-(3,5,7-trihydroxy-4-oxo-4H-1-benzopyran-
2-yl)phenoxy]phenyl}-7-methoxy-4H-1-benzopyran-4-one; 1): Yellow needles. M.p. 324 – 3258. IR (KBr):
3429, 1668, 1623, 1540, 1500. UV (MeOH): 344 (4.1), 265 (4.0), 214 (1.8). 1H- and 13C-NMR: Table 1. EI-
MS: 316 (75, [M ꢀ 3’’’-methoxy-5’’,7’’-dihydroxyflavonol]þ), 301 (6), 287 (16), 273 (18), 245 (15), 217
(9), 167 (9), 153 (20), 151 (19), 135 (100), 121 (19), 107 (21), 92 (25), 77 (35), 69 (33), 55 (25). HR-FAB-
MS (pos.): 615.1130 ([M þ H]þ, C32H23O1þ3 ; calc. 615.1138).
Sparin B (¼2-{4-[4-(3,5-Dihydroxy-7-methoxy-4-oxo-4H-1-benzopyran-2-yl)-2-methoxyphenoxy]-
3-hydroxyphenyl}-5-hydroxy-3,7-dimethoxy-4H-1-benzopyran-4-one; 2): Yellow needles. M.p. 290 – 2918.
IR (KBr): 3435, 1670, 1626, 1543, 1500. UV (MeOH): 345 (4.2), 264 (3.9), 214 (1.4). 1H- and 13C-NMR:
Table 1. EI-MS: 330 (13, [M ꢀ 3’’’,7’’-dimethoxy-5’’-hydroxyflavonol]þ), 316 (100), 301 (10), 287 (15),
273 (16), 245 (11), 217 (9), 167 (10), 153 (18), 151 (19), 135 (30), 121 (14), 109 (16), 95 (14), 77 (20), 69
(38), 55 (32). HR-FAB-MS (pos.): 643.1446 ([M þ H]þ, C34H27O1þ3 ; calc. 643.1451).

Helvetica Chimica Acta – Vol. 95 (2012)
105
Sparin C (¼ 3’-Methylapigenin 7-b-d-Glucopyranoside ¼ 7-b-d-Glucopyranosyloxy)-5-hydroxy-2-(4-
hydroxy-3-methylphenyl)-4H-1-benzopyran-4-one; 3): Yellow needles. M.p. 254 – 2558. IR (KBr): 3425,
1667, 1629, 1538, 1500. UV (MeOH): 342 (4.1), 263 (3.9), 215 (1.3). 1H- and 13C-NMR: Table 2. EI-MS:
284 (100, [M ꢀ glucose]þ), 269 (11), 256 (10), 230 (9), 153 (33), 152 (24), 134 (13), 111 (15), 96 (8), 78
(12), 69 (10), 55 (7). HR-FAB-MS (pos.): 447.1285 ([M þ H]þ, C22H23O1þ0 ; calc. 447.1291).
Acid Hydrolysis of 3. Sparin C (3; 8 mg) in 10% HCl soln. was refluxed for 40 min. The cooled
mixture was extracted with AcOEt. The residue recovered from the org. phase crystallized from MeOH
(m.p. 136 – 1388) and was identified as 3’-methylapigenin by comparison of physical and spectral data
with those reported in [8]. The aq. phase was concentrated, and the sugar was identified as d-glucose by
the sign of its optical rotation ([a]D ¼ þ52.8) and co-TLC (BuOH/AcOEt/AcOH/H2O 6 :1:1:1,
visualization with aniline phthalate reagent) with an authentic sample of d-glucose. The sugar was
further confirmed by comparing the retention time of its Me3Si ether with that of a standard sample in
GC [9][10].
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Received May 23, 2011