Antioxidant C-glycosyl flavones from the leaves of Sasa kurilensis var. gigantea

Article abstract of DOI:10.1016/j.phytochem.2007.12.003

C-glycosyl flavones, kurilensin A (1) and B (2), together with two known compounds, tricin-4′-O-β-d-glucopyranoside (3) and tricin-5-O-β-d-glucopyranoside (4), were isolated from hot-water extracts of the leaves of Sasa kurilensis. The structure of the compounds was determined by spectroscopic analyses including 1D, 2D NMR and MS. The absolute configuration of sugar moieties in 1 and 2 was determined by chiral HPLC analyses of the benzoyl derivatives of acid hydrolysis. Compounds 1 and 2 exhibited higher radical scavenging activity than ascorbic acid in the 1,1-diphenyl-2-pycrylhydrazyl (DPPH) assay system.

Full text of DOI:10.1016/j.phytochem.2007.12.003

Available online at www.sciencedirect.com
PHYTOCHEMISTRY
Phytochemistry 69 (2008) 1419–1424
www.elsevier.com/locate/phytochem
Antioxidant C-glycosyl flavones from the leaves of
Sasa kurilensis var. gigantea
Tatsuya Hasegawa, Ayumi Tanaka, Akiko Hosoda, Fumihide Takano, Tomihisa Ohta *
Department of Pharmacognosy and Chemistry of Natural Products, Graduate School of Natural Science and Technology, Kanazawa University,
Kakuma-machi, Kanazawa 920-1192, Japan
Received 13 June 2007; received in revised form 26 October 2007
Available online 11 February 2008
Abstract
C-glycosyl flavones, kurilensin A (1) and B (2), together with two known compounds, tricin-40-O-b-D-glucopyranoside (3) and tricin-
5-O-b-D-glucopyranoside (4), were isolated from hot-water extracts of the leaves of Sasa kurilensis. The structure of the compounds was
determined by spectroscopic analyses including 1D, 2D NMR and MS. The absolute configuration of sugar moieties in 1 and 2 was
determined by chiral HPLC analyses of the benzoyl derivatives of acid hydrolysis. Compounds 1 and 2 exhibited higher radical scaveng-
ing activity than ascorbic acid in the 1,1-diphenyl-2-pycrylhydrazyl (DPPH) assay system.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Sasa kurilensis; Gramineae; Flavone glycoside; Kurilensin; Benzoyl derivative; Chiral HPLC analysis; Antioxidant activity
1. Introduction
in the northern part of the Japanese archipelago, Saghalien
and Korean peninsula, and is a major source of Sasa leaves
in traditional medicine in Japan. However, the bioactive
compounds contained in the plant have not yet been
clarified.
In this paper, we report the isolation and structural elu-
cidation of four flavonoid glycosides, including two new C-
glycosyl flavones kurilensin A (1) and B (2), as well as their
radical scavenging activities against 1,1-diphenyl-2-pycryl-
hydrazyl (DPPH) radical formation.
The genus Sasa belongs to the bamboo grasses and is
widely distributed in Asian countries including Japan,
Korea, China and Russia (Okabe et al., 1975). Sasa leaves
are known traditionally to have antimicrobial activity in
Japan, and have been used clinically for treating hyperten-
sion, arteriosclerosis, cardiovascular disease and cancer
(Shibata et al., 1975). It is well known that plants of the
genus Sasa biosynthesize triterpenoids, flavone glycosides
and flavonolignans (Ohmoto and Ikuse, 1970; Yoon
et al., 2000; Nakajima et al., 2003). Several studies have
been carried out to identify some active constituents,
including anti-inflammatory and lipid peroxidation factors,
from bamboo leaves belonging to the genus Sasa (Okabe
et al., 1975). Sasa kurilensis (Rupr.) Makino et Shibata
var. gigantea Tatewaki (Gramineae) is also one of the bam-
boo grasses. It is a native Japanese plant that grows mainly
2. Results and discussion
Since Sasa leaves have been used as decoction in some
herbal prescriptions for diseases in Japan, Korea and China
(Shibata et al., 1975). In this study, we therefore attempted
to establish the identity of biologically active constituent(s)
from the hot-water extract of this plant. The lyophilized
powder of the hot-water extract of the leaves of S. kurilensis
was absorbed on a Diaion HP-20 resin, and fractions were
successively eluted with aqueous MeOH. A fraction was
eluted with 50% and 80% aqueous MeOH, which exhibited
*
Corresponding author. Tel.: +81 76 234 4468; fax: +81 76 264 6241.
E-mail address: ohta@p.kanazawa-u.ac.jp (T. Ohta).
0031-9422/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.phytochem.2007.12.003

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T. Hasegawa et al. / Phytochemistry 69 (2008) 1419–1424
strong radical scavenging activities in the DPPH assay. This
fraction was subjected to bioassay-guided fractionation
with several column chromatographic steps, repeated, and
further purified by reversed-phase HPLC to yield four
compounds (1–4) (see Fig. 1).
(J = 1.5 Hz) and four other 1 H signals (d 3.89, 3.44,
3.13, 2.53). Six additional H resonances were observed
at d 4.81, 4.00, 3.95, 3.90, 3.76, 3.70, indicating the presence
1
of a second sugar moiety, which was identified as arabinof-
1
uranose from analysis of the H NMR spectroscopic data
Compound 1 was obtained as an amorphous yellow
powder, and its molecular formula C26H28O14 was estab-
lished from high-resolution fast atom bombardment MS
(HRFABMS), which gave a pseudomolecular ion peak at
m/z 563.1424 [MꢀH]ꢀ. UV maxima occurred at 350 nm
(band I) and 292 nm (band II), characteristic of a flavonoid
and NOE correlation between H-300 (3.96 ppm) and H-500
(3.70, 4.00 ppm). The HMBC spectrum of 1 showed the
anomeric proton signal H-100 (d 4.81) of an arabinofura-
nose moiety coupled to C-6 (d 109.9) of a luteolin moiety,
and another anomeric proton signal H-1000 (d 5.12) of a
rhamnopyranose moiety coupled to C-200 (d 76.3) of an
arabinofuranose moiety (Fig. 2). The absolute configura-
tion of the rhamnopyranose moiety was determined as
the L-form on the basis of chiral HPLC analysis of a ben-
zoyl derivative of acid hydrolysis of 1 (Kasai et al., 2005)
(see Scheme 1). The optical rotation was also identical
between the synthetic model of L-rhamnopyranose tetra-
benzoate (5) [a]D + 75.0 (c 1.6, CHCl3) and a benzoyl
derivative of acid hydrolysis of 1 [a]D + 76.0 (c 0.005,
CHCl3). Thus, compound 1 was determined to be luteolin
6-C-a-arabinofuranosyl-(1 ? 2)-a-L-rhamnopyranoside, a
new flavone glycoside named ‘‘kurilensin A”.
1
system. The H NMR spectrum (in CD3OD) showed the
presence of a luteolin skeleton, which was suggested by
the aromatic protons at d 7.40 (1H, dd, J = 2.0, 8.8 Hz),
d 7.39 (1H, d, J = 2.0 Hz), d6.94 (1H, d, J = 8.8 Hz),
d 6.59 (1H, s), d 6.58 (1H, s) (Markham and Chari, 1982).
The complete assignments of all proton and carbon reso-
nances of the sugar moieties were based on the TOCSY,
COSY, HMQC and HMBC experiments. In the TOCSY
and COSY data, the presence of a rhamnopyranose moiety
was suggested by a characteristic methyl doublet at d 0.68
(J = 6.4 Hz), anomeric proton a doublet at d 5.12
Fig. 1. Chemical structures of compounds 1–4.

T. Hasegawa et al. / Phytochemistry 69 (2008) 1419–1424
1421
Some flavonoid C-glycosides including orientin, isoori-
entin, vitexin and isovitexin have been isolated from the
genus Sasa (Fu et al., 2005). Furthermore, Park et al.
(2007) recently reported that the antioxidative flavonoid
C-glycoside derivatives, isoorientin and isoorientin 200-O-
a-L-rhamnoside, were isolated from the 80% aqueous
MeOH extracts of the leaves of Sasa borealis. Their struc-
tures were similar to that of compounds 1 and 2 from S.
kurilensis. It is therefore suggested that flavone C-glyco-
sides with a luteolin 6-C-arabinose moiety are unusual
for this plant.
Flavonoids are a major class of secondary polyphenolic
metabolites of wide occurrence in the natural plants. There
is a beneficial health effect because of their antioxidant
properties and their inhibitory role in various stages of
tumor development in animal studies (Hollman and Katan,
1999).
Fig. 2. HMBC and NOE correlations of compound 1.
Compound 2 was obtained as an amorphous yellow
powder, and its molecular formula C25H26O14 was estab-
lished from HRFABMS, which gave a pseudomolecular
ion peak at m/z 549.1200 [MꢀH]ꢀ. UV maxima occurred
at 349 nm (band I) and 292 nm (band II), characteristic
of a flavonoid system. The 1H NMR spectrum (in CD3OD)
showed the presence of a luteolin skeleton, which was sug-
gested by the aromatic protons at d 7.39 (1H, dd, J = 2.0,
8.8 Hz), d 7.38 (1H, d, J = 2.0 Hz), d 6.91 (1H, d,
J = 8.8 Hz), d 6.55 (1H, s), d 6.47 (1H, s). In the 1H
NMR spectrum of 2, two anomeric protons appeared at
d 4.26 (1H, d, J = 7.3 Hz) and 4.82 (1H, s), which indicated
the presence of two sugar moieties identified as arabino-
For these reasons, the antioxidant activity of the four
compounds isolated from S. kurilensis was evaluated by
DPPH radical scavenging (Table 2). Since ascorbic acid
has been reported to have radical scavenging activity
(McCune and Johns, 2002), this compound was used as a
positive control in this experiment. In the DPPH assay,
the two new compounds 1 and 2 exhibited free radical scav-
enging activity, with IC50 values of 6.0 and 5.1 lM, this
activity was stronger than that of the positive control
ascorbic acid (12 lM) (Table 2). However, the known com-
pounds 3 and 4 did not scavenge DPPH radical at any con-
centration (Table 2). It is therefore possible that the
presence of the two methoxyl group at C-30 and C-50
instead of free hydroxyl group is detrimental for the radical
scavenging activity (Rice-Evans et al., 1996; Burda and
Oleszek, 2001).
furanose and xylopyranose from analysis of their H–1H
1
1
coupling constants (Aquino et al., 2001). The H and 13C
NMR spectroscopic data of the two sugar moieties were
assigned by the TOCSY, COSY and HMQC experiments,
respectively. The HMBC spectrum of 2 showed the ano-
meric proton signal H-100 (d 4.82) of an arabinofuranose
moiety coupled to C-6 (d 109.2) of a luteolin moiety.
Another anomeric proton signal H-1000 (d 4.26) of a xylopy-
ranose moiety was inferred to be linked at C-200 (d 80.2).
This substitution pattern agreed with the deshielding effect
observed for the C-200 signal. The absolute configuration of
the xylopyranose moiety was determined as the D-form, on
the basis of chiral HPLC analysis of a benzoyl derivative of
acid hydrolysis of 2 (Kasai et al., 2005). Thus, compound 2
was determined to be luteolin 6-C-a-arabinofuranosyl-
2.1. Concluding remarks
In summary, this is believed to be the first report identi-
fying two new antioxidant constituents, kurilensin A (1)
and B (2), of the leaves of S. kurilensis, which have poten-
tial to scavenge the DPPH free radical.
(1 ? 2)-b-D-xylopyranoside,
named ‘‘kurilensin B”.
a new flavone glycoside
3. Experimental
The known compounds tricin-40-O-b-D-glucopyranoside
(3) and tricin-5-O-b-D-glucopyranoside (4) have also been
isolated from S. kurilensis. These were identified by com-
paring their spectroscopic data with those reported in the
literature (Wilson, 1985; Hong et al., 2004).
3.1. General
Optical rotations were determined with a Horiba SEPA-
3000 high-sensitivity polarimeter. UV spectra were mea-
Scheme 1. Acid hydrolysis of 1 and benzoylation of the sugar unit.

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T. Hasegawa et al. / Phytochemistry 69 (2008) 1419–1424
Table 1
13C and 1H NMR spectroscopic data for 1 and 2a
Position
Kurilensin A (1)
Kurilensin B (2)
dC
dH
dC
dH
2
3
4
5
6
7
8
166.3
103.9
184.1
164.1
109.9
164.9
95.1
166.2
103.7
183.8
nd
109.2
nd
6.59 (1H, s)
6.55 (1H, s)
6.58 (1H, s)
95.4
6.47 (1H, s)
9
158.8
105.3
123.5
114.2
146.9
151.1
116.9
120.5
74.2
76.3
71.3
77.7
71.7
158.8
104.7
123.4
114.0
147.2
150.0
116.8
120.3
74.6
80.2
70.7
75.9
71.8
10
1’
2’
3’
4’
5’
6’
1’’
2’’
3’’
4’’
5’’
7.39 (1H, d, 2.0)
7.38 (1H, d, 2.0)
6.94 (1H, d, 8.8)
7.40 (1H, dd, 2.0, 8.8)
4.81 (1H)b
3.76 (1H, brs)
3.96 (1H, brs)
3.76 (1H, m)b
3.70 (1H, d, 12.2)
4.00 (1H, dd, 1.5, 12.2)
5.12 (1H, d, 1.5)
3.89 (1H, dd, 1.5, 3.4)
3.44 (1H, dd, 3.4, 9.3)
3.13 (1H, t, 9.3)
2.53 (1H, dd, 6.4, 9.3)
6.91 (1H, d, 8.8)
7.39 (1H, dd, 2.0, 8.8)
4.82 (1H)b
3.98 (1H, brs)
3.98 (1H, brs)
3.80 (1H, dd, 2.9, 8.8)
3.71 (1H, d, 12.7)
4.00 (1H, m)b
4.26 (1H, d, 7.3)
3.08 (1H, t, 7.3)
3.19 (1H, t, 7.3, 8.8)
3.23 (1H, m)b
1’’’
2’’’
3’’’
4’’’
5’’’
102.4
71.9
72.2
73.3
69.9
106.8
75.6
71.0
77.5
66.8
2.75 (1H, t, 9.8)
3.29 (1H, m)b
6’’’
17.9
0.68 (3H, d, 6.4)
nd, not determined.
a
Values in parentheses indicate coupling constants in Hz.
Coupling constants not clearly defined or obscured by overlap.
b
Table 2
(cc). Further purification was performed by HPLC
equipped with a reversed-phase column (column: Sun-
FireTM Prep C18 5 lm; 10 ꢁ 250 mm; Waters). TLC uti-
lized silica gel 60 F254 (Merck) and RP-18 F254S
(Merck).
DPPH radical scavenging activity of compounds isolated from hot-water
extracts of S. kurilensis
Compounds
IC50 (lM)a
1
6.0
5.1
nab
nab
12
2
3
4
3.2. Plant material
Ascorbic acid
a
IC50 values were determined by regression analysis and expressed as
the mean of three replicates.
Fresh leaves of S. kurilensis were collected on Mt. Hak-
koda in Aomori Prefecture in 2005, kindly provided and
taxonomically identified by HABA laboratory (Tokyo,
Japan) and Nippon Haruma (Aomori, Japan), and depos-
ited in a database at the Graduate School of Natural Sci-
ence and Technology, Kanazawa University, under
Registration No. S-2005-02.
b
na, no activity.
sured on a Shimadzu UV-1600 UV–Vis spectrometer,
whether the IR spectra were recorded on a Shimadzu IR-
460 IR spectrophotometer. NMR spectra were obtained
using a JEOL GSX-500 spectrometer and a JEOL EX-
270 spectrometer in CD3OD and CDCl3, respectively.
Chemical shifts were referenced to the residual solvent
peaks CD3OD (dH 3.30 and dC 49.8) and CDCl3 (dH 7.26
and dC 77.0). Mass spectra were measured on a JEOL
SX-102 mass spectrometer. Diaion HP-20 (Mitsubishi
Chemical), Sephadex LH-20 (25–100 lm, Sigma), silica
gel (63–210 lm, Kanto Chemical) and ODS (63–212 lm,
Wako) and were used for open column chromatography
3.3. Extraction and isolation
The fresh leaves (8.5 kg) of S. kurilensis were extracted
with hot H2O (18 l) at 90 °C for 30 min. After filtration
and removal of the solvent by freeze drying, a residue pow-
der (550 g) was obtained, which was passed through a Dia-
ion HP-20 column with a step-wise gradient of aqueous
MeOH. Fractions (33 g) eluted with 30% and 50% aqueous

T. Hasegawa et al. / Phytochemistry 69 (2008) 1419–1424
1423
MeOH were subjected to ODS cc with a step-wise gradient
of aqueous MeOH (10, 30, 50, 70 and 100%), to give nine
fractions. A biologically active fraction 4 (3.5 g) was fur-
ther separated by silica gel cc with a step-wise gradient of
CHCl3 and MeOH (7:1, 5:1, 3:1, 2:1 and 0:1), to give four
fractions. Fraction 1 (440 mg) was applied to a Sephadex
LH-20 column with MeOH, and H2O (1:1, v/v) as eluent,
then further purified by ODS HPLC with CH3CN H2O
(1:4, v/v) to give kurilensin A (1) (20.0 mg) and kurilensin
B (2) (3.6 mg). Fraction 3 (168 mg) was purified by Sepha-
dex LH-20 cc with MeOH H2O (1:1, v/v) and further puri-
fied by ODS HPLC with CH3CN in H2O (1:3, v/v) to give
tricin-40-O-b-D-glucopyranoside (3) (0.4 mg) and tricin-5-
O-b-D-glucopyranoside (4) (5.8 mg).
Chemical Industries, 4.6 ꢁ 250 mm; MeOH, 1.0 ml/min;
UV detection at 254 nm). The retention time of each of
the benzoyl derivatives of the hydrolysis products of 1 or
2 was found to be 8.2 and 9.1 min, respectively. Further-
more, the retention times of synthetic benzoyl derivatives
of L-rhamnopyranose (5), D-xylopyranose (6) and L-xylopy-
ranose were found to be 8.2 and 9.1 and 8.6 min,
respectively.
3.7. L-rhamnopyranose tetrabenzoate (5) and
D-xylopyranose tetrabenzoate (6)
Benzoyl chloride (0.5 ml) was added to each ice-cooled
solution of ether L-rhamonopyranose (18.0 mg) or D-xylo-
pyranose (15.0 mg) in dry pyridine (1.0 ml), and each mix-
ture was stirred at room temperature for 15 h. MeOH
(1.0 ml) was added dropwise to the reaction mixture, stir-
red for 30 min, and then diluted with EtOAc and aqueous
Na2CO3, and the layers were separated. Each organic layer
was washed with brine, and the combined aqueous layers
for each were extracted with EtOAc. Each combined
organic extracts were dried over MgSO4, and concentrated,
was the corresponding residual dark brown oil were indi-
vidually purified by silica gel cc (eluting with hexane/
EtOAc 5:1) to give either 5 (53 mg, 91%) or 6 (52 mg,
92%) as a colorless oil, respectively. 5: [a]D + 75.0 (CHCl3;
c 1.6); 1H NMR (270 MHz, CDCl3) d 1.44 (3H, d,
J = 6.4 Hz), 4.37 (1H, dd, J = 6.4, 9.8 Hz), 5.81 (1H, t,
J = 9.8 Hz), 5.88 (1H, dd, J = 1.9, 3.4 Hz), 6.00 (1H, dd,
J = 3.4, 10.3 Hz), 6.57 (1H, d, J = 1.5 Hz), 7.27–8.21
(20H, m); 13C NMR (67.5 MHz, CDCl3) d 17.7, 69.3,
69.7, 69.8, 71.1, 91.3, 128.3, 128.4, 128.6, 128.7, 128.8,
128.8, 129.0, 129.7, 129.7, 130.0, 130.1, 130.1, 133.3,
133.4, 133.6, 133.9, 164.0, 165.3, 165.6, 165.7; EIMS m/z
580 [M]+.
3.4. Kurilensin A (1)
Amorphous yellow powder; [a]D–34.0 (MeOH, c 0.13);
UV (MeOH) kmax (loge) 350 (3.9), 292 (3.5) nm; IR mmax
(KBr) 2988, 2862, 2783, 2517, 1506, 1474, 1458, 1398,
1339, 1115, 1051, 1005 cm–1; for 1H NMR (500 MHz,
CD3OD) and 13C NMR (125 MHz, CD3OD) spectroscopic
data, see Table 1; HRFABMS m/z 563.1424 [MꢀH]ꢀ (cal-
culated for C26H27O14, 563.1422).
3.5. Kurilensin B (2)
Amorphous yellow powder; [a]D–28.1 (MeOH, c 0.11);
UV (MeOH) kmax (loge) 349 (3.8), 292 (3.5) nm; IR mmax
(KBr) 3734, 2824, 2519, 2235, 2046, 1717, 1420, 1115,
1009 cm–1; for 1HNMR (500 MHz, CD3OD) and 13CNMR
(125 MHz, CD3OD) spectroscopic data, see Table 1;
HRFABMS m/z 549.1200 [MꢀH]ꢀ (calculated for
C25H25O14, 549.1204).
3.6. Determination of stereochemistry of the secondary sugar
unit in 1 and 2 by chiral HPLC
6: 1H NMR (270 MHz, CDCl3) d 3.97 (1H, t,
J = 10.7 Hz), 4.23 (1H, dd, J = 5.4, 10.7 Hz), 5.48 (1H,
m), 5.57 (1 H, dd, J = 3.4, 10.3 Hz), 6.21 (1H, t,
J = 10.3 Hz), 6.70 (1H, d, J = 3.9 Hz), 7.15–7.57 (12H,
m), 7.79–8.08 (8H, m); 13C NMR (67.5 MHz, CDCl3) d
61.2, 69.4, 69.9, 70.2, 90.2, 128.4, 128.4, 128.6, 128.7,
128.8, 128.9, 129.0, 129.7, 129.8, 129.8, 129.9, 133.3,
133.4, 133.5, 133.8, 164.5, 165.3, 165.4, 165.8; EIMS m/z
566 [M]+.
Compound 1 or 2 (2.0 mg) in MeOH (0.5 ml) was trea-
ted with 6 N HCl (3.0 ml) for 24 h at 80 °C, and evapo-
rated. Each residue was purified by Sephadex LH-20 cc
(eluting with H2O (1:9, v/v) MeOH ? MeOH) to give agly-
cones and sugar moieties, respectively. Benzoyl chloride
(0.1 ml) was added to the ice-cooled solution of each sugar
moiety in dry pyridine (0.5 ml), and each mixture was stir-
red at room temperature for 40 h. MeOH (0.1 ml) was
added dropwise to each of the reaction mixtures, stirred
for 30 min, and then diluted with EtOAc and aqueous
Na2CO3, and the layers were separated. Each organic layer
was washed with brine, and the combined aqueous layers
were extracted with EtOAc. Each of the combined organic
extracts were dried over MgSO4, and concentrated. Each
residual dark brown oil was purified by silica gel cc (eluting
with hexane/EtOAc 5:1) to give the corresponding benzoyl
derivatives of the sugar moieties. The benzoyl derivatives
of each hydrolysis products of 1 or 2 were subjected to
chiral HPLC analyses using CHIRALPAK IB (Daisel
3.8. DPPH radical scavenging activity
The DPPH assay was performed by a method previously
reported by Marsden (1958) and Zhang et al. (2007). In
brief, 100 ll test samples at different concentrations in
MeOH and 8.0 ꢁ 10ꢀ5 M DPPH (Wako) in MeOH
(300 ll) were added to a 96-well microtiter plate. The plate
was shaken for 1 min on a plate shaker, and incubated for
30 min at room temperature in the dark. After incubation,
the absorbance was recorded at 517 nm. The tested samples
at different concentrations without DPPH solution were
used as a blank control to eliminate the influence of sample

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T. Hasegawa et al. / Phytochemistry 69 (2008) 1419–1424
Markham, K.R., Chari, V.M., 1982. 13C NMR spectroscopy of
flavonoids. In: Harborne, J.B., Mabry, T.J. (Eds.), The
Flavonoids: Advances in Research. Chapman & Hall, London, pp.
19–132.
Marsden, S.B., 1958. Antioxidant determinations by the use of a stable
free radical. Nature 181, 1199–1200.
McCune, L.M., Johns, T., 2002. Antioxidant activity in medicinal plants
associated with the symptoms of diabetes mellitus used by the
Indigenous Peoples of the North American boreal forest. J. Ethno-
pharmacol. 82, 197–205.
Nakajima, Y., Yun, Y.S., Kunugi, A., 2003. Six new flavonolignans from
Sasa veitchii (Carr.) Rehder. Tetrahedron 59, 8011–8015.
Ohmoto, T., Ikuse, M., 1970. Triterpenoids of the Gramineae. Phyto-
chemistry 9, 2137–2148.
color. Ascorbic acid was used as a positive control, and
DPPH solution in MeOH served as a negative control. All
tests were independently performed in triplicate and the def-
inition of IC50 values in the tested compounds is concentra-
tion required to scavenge 50% DPPH free radicals. The
DPPH radical scavenging activity was calculated according
to the following equation: DPPH radical scavenging activ-
ity (%) = [{AbsC ꢀ (AbsS ꢀ AbsB)/AbsC}] ꢁ 100.
AbsB is the absorbance of the blank control, AbsC is the
absorbance of the negative control and ABSS is the absor-
bance of the presence of the sample in DPPH solution.
Okabe, S., Takeuchi, M., Takagi, K., Shibata, M., 1975. Stimulatory
effects of the water extract of bamboo grass (folin solution) on gastric
acid secretion in pylorus ligated rats. Jpn. J. Pharmacol. 25,
608–609.
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