Botanical Studies (2006) 47: 37-43.
*
Corresponding author: E-mail: wchou@tmu.edu.tw; Fax:
886(2) 2378-0134.
Structure-activity relationships of five myricetin
galloylglycosides from leaves of
Acacia confusa
Tzong-Huei LEE
1
, Der-Zen LIU
2
, Feng-Lin HSU
1
, Wen-Chung WU
1
, and Wen-Chi HoU
1*
1
Graduate Institute of Pharmacognosy, Taipei Medical University, Taipei, Taiwan
2
Graduate Institute of Biomedical Materials, Taipei Medical University, Taipei, Taiwan
(Received June 30, 2005; Accepted September 7, 2005)
ABSTRACT.
Five structure-related myricetin galloylglycosides isolated from leaves of Acacia confusa
were previously reported (Lee et al., 2000, J. Nat. Prod., 63, 710-712). However, the structure-activity
relationships were not reported. In this research, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging
activity, and inhibitory activities against semicarbazide-sensitive amine oxidase (SSAo) and angiotensin
converting enzyme (ACE) were compared among five compounds, namely, myricetin 3-O-(3"-O-galloyl)-α-
rhamnopyranoside 7-methyl ether (compound 1, 630 Da), myricetin 3-O-(2"-O-galloyl)-α-rhamnopyranoside
7-methyl ether (compound 2, 630 Da), myricetin 3-O-(2"-O-galloyl)-α-rhamnopyranoside (compound 3,
616 Da), myricetin 3-O-(3"-O-galloyl)-α-rhamnopyranoside (compound 4, 616 Da), myricetin 3-O-(2", 3"
-di-O-galloyl)-α-rhamnopyranoside (compound 5, 768 Da). For DPPH scavenging activity, the IC
50
for five
compounds was 591, 1522, 3210, 1389, and 867 μM, respectively. For SSAo inhibitory activity, the IC
50
for
five compounds was 36.16, 93.20, 119.50, 88.20, and 39.35 μM, respectively. The IC
5 0
of positive control
of semicarbazide was 34.21 μM. The five compounds have the same orders of compound 1> compound 5>
compound 4> compound 2> compound 3 for DPPH scavenging activity and SSAO inhibitiony. It was found
that gallic acid in the R
3
position was the key role for both biological activities. For ACE inhibitory activity,
compound 1, compound 2, and compound 5 showed dose-dependent inhibitory modes and the IC
50
was 60.32,
151.90, and 19.82 μM, respectively.
Keywords: Acacia confusa; Angiotensin converting enzyme (ACE); 1, 1-diphenyl-2-picrylhydrazyl (DPPH);
Myricetin galloylglycoside; Semicarbazide-sensitive amine oxidase (SSAo); Structure-activity relationships
(SAR).
INTRODUCTION
Free radical-mediated reactions are involved in
degenerative or pathological processes such as aging
(Harman, 1995), cancer, coronary heart disease, and
Alzheimer ’s disease (Ames, 1983; Smith et al., 1996; Diaz
et al., 1997). Meanwhile, there are many epidemiological
results revealing an association between a diet rich in
fresh fruit and vegetable and a decrease in the risk of
cardiovascular diseases and certain forms of cancer in
humans (Salah et al., 1995). Several reports concern
natural compounds in fruits and vegetables for their
antioxidant activities, such as phenolic compounds (Rice-
Evans et al., 1997), anthocyanin (Espin et al., 2000),
echinacoside in Echinaceae root (Hu and Kitts, 2000),
methanolic and hot-water extracts of Liriope spicata L.
(Hou et al., 2004), the storage proteins of sweet potato
root (Hou et al., 2001a), yam tuber (Hou et al., 2001b),
potato tuber (Liu et al., 2003b), and yam mucilages (Hou
et al., 2002; Lin et al., 2005).
The semicarbazide-sensitive amine oxidase (SSAo,
EC 1.4.3.6), which contains a cofactor of one or
more topaquinone, is a common name for a group of
heterogenous enzymes widely distributed in nature, in
plants, microorganisms, and the organs of mammals
(vasculature, dental pulp, eye and plasma) (Boomsma
et al., 2000). SSAo converts primary amines into the
corresponding aldehydes, generating hydrogen peroxide
and ammonia. It was found that the endogenous
compounds aminoacetone and methylamine are good
substrates for most SSAos (Precious et al., 1988). In
recent research, plasma SSAo was found raised in
diabetes mellitus and heart failure and implicated in
roles in atherosclerosis, endothelial damage, and glucose
transport into adipocytes (Yu and Zuo, 1993, 1996;
Boomsma et al., 1997, 2003).
Several classes of pharmacological agents have been
used in the treatment of hypertension (Mark and Davis,
2000). one class of anti-hypertensive drugs known as
angiotensin I converting enzyme (ACE) inhibitors (i.e.
peptidase inhibitors) has a low incidence of adverse side-
effects and is the preferred class of anti-hypertensive
agents when treating patients with concurrent secondary
BIOCHEMISTRY
pg_0002
38
Botanical Studies, Vol. 47, 2006
diseases (Fotherby and Panayiotou, 1999). ACE (EC
3.4.15.1) is a dipeptide-liberating exopeptidase which
has been classically associated with the renin-angiotensin
system regulating peripheral blood pressure (Mullally
et al., 1996). The potent ACE inhibitors were frequently
derived from food proteins (Ariyoshi, 1993; Hsu et
al., 2002). However, pomegranate juice (Aviram and
Dornfeld, 2001), flavan-3-ols and procyanidins (Actis-
Goretta et al., 2003), and tannins (Liu et al., 2003a) were
also reported to have ACE inhibitory activity.
Acacia confusa (Leguminosae) is widely distributed on
the hills and lowlands of Taiwan. Five structure-related
myricetin galloylglycosides (Figure 1)—namely, myricetin
3-O-(3"-O-galloyl)-α-rhamnopyranoside 7-methyl ether
(compound 1, 630 Da), myricetin 3-O-(2"-O-galloyl)-
α-rhamnopyranoside 7-methyl ether (compound 2, 630
Da), myricetin 3-O-(2"-O -galloyl)-α-rhamnopyranoside
(compound 3, 616 Da), myricetin 3-O-(3"-O-galloyl)-
α -rhamnopyranoside (compound 4, 616 Da), and
myricetin 3-O-(2", 3"-di-O-galloyl)-α-rhamnopyranoside
(compound 5, 768 Da)—isolated from leaves of Acacia
confusa were previously reported (Lee et al., 2000).
However, the structure-activity relationships (SAR)
were not reported. In this research, the 1,1-diphenyl-
2-picrylhydrazyl (DPPH) radical scavenging activity,
and inhibitory activities against SSAo and ACE were
compared among five compounds.
MATERIALS AND METHODS
Materials
ACE (I unit, rabbit lung) was purchased from Fluka
Chemie GmbH (Switzerland); DPPH, benzylamine,
2’, 2-azinodi(3-ethylbenzthiazoline-6-sulfonic acid,
ABTS), bovine plasma (P-4639, reconstituted with 10 ml
deionized water), horseradish peroxidase (148 units/mg
solid), N-(3-[2-furyl] acryloyl)-Phe-Gly-Gly (FAPGG),
semicarbazide, and other chemicals and reagents were
from Sigma Chemical Co. (St. Louis, Mo, USA).
Extraction and purificaction of five structure-
related myricetin galloylglycosides from
Acacia
confusa
Five structure-related flavonol galloylglycosides
isolated from leaves of Acacia confusa were previously
reported (Lee et al., 2000). The methanolic extracts were
isolated in series by Sephadex LH-20 column, Si-flash
column, and reverse-phase HPLC. Each structure was
identified by
13
C and
1
H NMR, CoSY, HMQC and HMBC
spectra. The purity of each compound was higher than
99%, determined by reverse-phase HPLC.
Scavenging activity against DPPH radical
analyzed by spectrophotometry
The scavenging activity of five structure-related
flavonol galloylglycosides against DPPH radical was
measured according to the method of Hou et al. (2001a,
b). Each sample was dissolved in DMSo to a final
concentration of 2 mg/ml as stock solutions. Each 0.3 ml
sample solution (compound 1, 158.73, 317.46, 476.19,
634.92 μM; compound 2, 317.46, 555.56, 793.65, 1587.3
μM; compound 3, 811.69, 1623.38, 2435.06, 3246.75
μM; compound 4, 487.01, 811.69, 1217.53, 1623.38 μM;
compound 5, 390.63, 520.83, 651.04, 976.56 μM) was
added to 0.1 ml of 1 M Tris-HCl buffer (pH 7.9) and
then mixed with 0.6 ml of 100 μM DPPH in methanol
for 20 min under light protection at room temperature.
The decrease of absorbance at 517 nm was measured and
expressed as .A517. Means of triplicates were measured.
DMSo was used as a blank experiment. The scavenging
activity of DPPH radicals (%) was calculated with the
equation: (.A517
blank
. .A517
sample
) ÷ .A517
blank
× 100%.
The IC
50
stands for the concentration of 50% scavenging
activity.
SSAO inhibitory activities of five structure-
related myricetin galloylglycosides
SSAo inhibitory activity was determined by
spectrophotometric method according to Szutowicz et al.
(1984) with some modifications. The total 200 μl reaction
solution [containing 50 μl of 200 mM phosphate buffer,
pH 7.4, 50 μl of 8 mM benzylamine, bovine plasma
(containing SSAo, 2.53 units) and different amounts
of sample solution (compound 1, 15.87, 31.75, 47.62,
63.49 μM; compound 2, 47.62, 63.49, 95.24, 111.11
μM; compound 3, 81.17, 113.64, 129.87, 194.81 μM;
compound 4, 64.94, 97.40, 129.87, 162.34 μM; compound
5, 26.04, 39.06, 52.08, 65.10 μM) and semicarbazide
(6.25, 12.5, 25, and 50 μM)] was placed at 37°C for
one h and then heated at 100°C to stop reaction. After
cooling and a brief centrifugation, the 90 μl reaction
solution was isolated and added to the 710 μl solution
containing 200 μl of 200 mM phosphate buffer (pH 7.4),
100 μl of 2 mM ABTS solution, and 25 μl of horseradish
peroxidase (10 μg/ml). The changes of absorbance at 420
nm were recorded during 1 min and expressed as .A420
nm/min. Means of triplicates were measured. DMSo was
used as a blank experiment. The SSAo inhibition (%)
was calculated with the equation: (.A420 nm/min
blank
-
.A420 nm/min
sample
) ÷ .A420 nm/min
blank
× 100%. The
IC
50
stands for the concentration of 50% inhibitions.
Determination of ACE inhibitory activity of
structure-related myricetin galloylglycosides by
spectrophotometry.
The ACE inhibitory activity was measured according
to the method of Holmquist et al. (1979) and Lee et al.
(2003) with some modifications. The 15 μl (15 mU)
commercial ACE (1 U/mL, rabbit lung) were mixed with
50 μl of sample solution (compound 1, 14.76, 44.60,
79.21, 148.90 μM; compound 2, 44.60, 74.44, 148.90,
178.73 μM; compound 5, 12.11, 24.35, 36.59, 48.83 μM)
and then 1 mL of 0.5 mM FAPGG [dissolved in 50 mM
pg_0003
Lee et al. — SAR of five myricetin galloylglycosides
39
Tris-HCl buffer (pH 7.5) containing 0.3 M NaCl] was
added. The decreased absorbance at 345 nm (.A
inhibitor
)
was recorded during 5 min at room temperature. DMSo
was used instead of sample solution for blank experiments
(.A
blank
). The ACE activity was expressed as .A345 nm,
and the ACE inhibition (%) was calculated as follows: [1-
(.A
inhibitor
÷ .A
control
)
] × 100%. Means of triplicates were
determined.
RESULTS AND DISCUSSION
Flavonoids are one type of polyphenol—a group which
includes isoflavones, flavones, and flavanones—and
have been reported to exhibit many biological activities
(Hodnick et al., 1994; Hoult et al., 1994; Siess et al., 1995;
Naasani et al., 1998; Lee et al., 2001). Lee et al. (2000)
isolated five structure-related myricetin galloylglycosides
(Figure 1), and the IC
50
of anti-hatch activity against brine
shrimp from four of them was 50 μg/ml (79.37 μM), 89
μg/ml (141.27 μM), 75 μg/ml (121.75 μM), and 64 μg/ml
(83.33 μM), respectively, for compound 1, compound
2, compound 4, and compound 5. Compound 3 was not
measured. The four compounds ranked for their anti-hatch
activity against brine shrimp take the order: compound
1> compound 5> compound 4> compound 2. Chang et al.
(2001) reported the antioxidant activity of 70% ethanolic
extracts from Acacia confusa bark and heartwood. In
this research, the DPPH radical scavenging activity
and inhibitory activities against SSAo and ACE were
compared among five myricetin galloylglycosides.
Scavenging activitiy against DPPH radical
analyzed by spectrophotometry
DPPH radicals were widely used in the model system
to investigate the scavenging activities of several natural
compounds. When DPPH radical was scavenged, the
color of the reaction mixture changed from purple to
yellow with decreasing of absorbance at wavelength
517 nm. Figure 2 shows the scavenging activity against
DPPH radicals from five structure-related myricetin
galloylglycosides. The dose-dependent DPPH radical
scavenging activities from five pure compounds were
found. For compound 1, the scavenging activities against
DPPH were 13.86, 24.71, 43.74, and 52.59%, respectively,
for 158.73, 317.46, 476.19, 634.92 μM; for compound 2,
the scavenging activities against DPPH were 15.36, 23.71,
33.39, and 51.86%, respectively, for 317.46, 555.56,
793.65, 1587.3 μM; for compound 3, the scavenging
activities against DPPH were 20.87, 39.40, 47.58, and
50.25%, respectively, for 811.69, 1623.38, 2435.06,
3246.75 μM; for compound 4, the scavenging activities
against DPPH were 23.21, 38.06, 48.25, and 52.42%,
respectively, for 487.01, 811.69, 1217.53, 1623.38 μM; for
compound 5, the scavenging activities against DPPH were
24.37, 36.56, 42.57, and 53.42%, respectively, for 390.63,
520.83, 651.04, 976.56 μM. The IC
50
of each compound
against DPPH radial was shown at Table 1. The IC
50
for
five compounds were 591, 1522, 3210, 1389, and 867
μM, respectively. The five compounds had the order of
compound 1> compound 5> compound 4> compound 2>
compound 3 for DPPH scavenging activity, which was the
same order as for anti-hatch activity against brine shrimp
(Lee et al., 2000). For anti-DPPH activity, with the same
methyl group in the R
1
position, the gallic acid in the R
3
position (compound 1) was more effective (2.5 fold) than
in the R
2
position (compound 2), and this efficiency was
Figure 1. Structures of five myricetin galloyoglycosides
isolated from leaves of Acacia confusa.
Figure 2. The scavenging activity of five myricetin
galloylglycosides against DPPH radicals. Means of triplicates
were measured. The scavenging activity of DPPH radical (%)
was calculated according to the following equation: (A517
blank
.
A517
sample
) ÷ A517
blank
× 100%.
pg_0004
40
Botanical Studies, Vol. 47, 2006
also found in compound 3 and compound 4. With the
same hydrogen atom in the R
1
position, the gallic acid
in the R
3
position (compound 4) was more effective (2.3
fold) than in the R
2
position (compound 3). With the same
gallic acid in the R
3
position and hydrogen atom in the R
2
position, the methyl group in the R
1
position (compound
1) was more effective (2.35 fold) than the hydrogen atom
in the same position (compound 4), and this efficiency
was also found in compound 2 and compound 3. With the
same gallic acid in the R
2
position and the hydrogen atom
in the R
3
position, the methyl group in the R
1
position
(compound 2) was more effective (2.11 fold) than the
hydrogen atom in the same position (compound 3). While,
with two gallic acid groups in the R
2
and R
3
positions
(compound 5) were more effective than one in the R
2
position (compound 3) or in the R
3
position (compound
4). It was concluded that the gallic acid in the R
3
position
was the key for anti-DPPH activity among five structure-
related compounds.
SSAO inhibitory activities of five structure-
related myricetin galloylglycosides
Figure 3 shows the SSAo inhibitory activity from
five structure-related myricetin galloylglycosides. The
dose-dependent SSAo inhibitory activities from five
pure compounds were found. For compound 1, the
SSAo inhibitory activities were 12.17, 41.44, 67.05, and
81.44%, respectively, for 15.87, 31.75, 47.62, 63.49 μM;
for compound 2, the SSAo inhibitory activities were
20.83, 33.47, 50.65, and 74.43 %, respectively, for 47.62,
63.49, 95.24, 111.11 μM; for compound 3, the SSAO
inhibitory activities were 25.36, 44.55, 60.85, and 72.58
%, respectively, for 81.17, 113.64, 129.87, 194.81 μM;
for compound 4, the SSAo inhibitory activities were
33.45, 56.72, 71.64, and 88.44%, respectively, for 64.94,
97.40, 129.87, 162.34 μM; for compound 5, the SSAO
inhibitory activities were 31.99, 48.93, 76.48, and 88.44
%, respectively, for 26.04, 39.06, 52.08, 65.10 μM. The
IC
50
of SSAo inhibitory activity of each compound was
shown at Table 1. For SSAo inhibitory activity, the IC
50
for five compounds was 36.16, 93.20, 119.50, 88.20,
and 39.35 μM, respectively. The IC
50
of semicarbazide
(positive control) was 34.21 μM which was close to that
of compound 1. The five compounds had the order of
compound 1> compound 5> compound 4> compound
2> compound 3, which was the same as for DPPH
scavenging activities (above-mentioned) and anti-hatch
activity against brine shrimp (Lee et al., 2000). For SSAo
inhibitory activity, with the same methyl group in the R
1
position, the gallic acid in the R
3
position (compound
1) was more effective (2.6 fold) than in the R
2
position
(compound 2), and this efficiency was also found in
compound 3 and compound 4. With the same hydrogen
atom in the R
1
position, the gallic acid in the R
3
position
(compound 4) was more effective (1.35 fold) than in the
R
2
position (compound 3). With the same gallic acid in the
R
3
position and the hydrogen atom in the R
2
position, the
methyl group in the R
1
position (compound 1) was more
effective (2.44 fold) than the hydrogen atom in the same
position (compound 4), and this efficiency was also found
in compound 2 and compound 3. With the same gallic acid
Table 1. Comparisons of the DPPH scavenging activity and inhibitory activities against SSAO and ACE among five myricetin
galloyoglycosides isolated from leaves of Acacia confusa.
Myricetin galloylglycoside Scavenging activity of DPPH radical
(μM)
a
SSAo inhibitory activity
(μM)
a
ACE inhibitory activity
(μM)
a
Compound 1
591
36.16
60.32
Compound 2
1522
93.20
151.90
Compound 3
3210
119.50
ND
b
Compound 4
1389
88.20
ND
Compound 5
867
39.35
19.82
a
Expressed as the IC
50
value.
b
Not detectable.
Figure 3. The effects of five myricetin galloylglycosides on the
activities of semicarbazide-sensitive amine oxidase (SSAo, 2.53
units) from bovine plasma. The semicarbazide (6.25, 12.5, 25,
and 50 μM) was used as a positive control. Deionized water was
used as a blank experiment. The changes of absorbance at 420
nm were recorded during 1 min and expressed as .A420 nm/
min. The SSAo inhibition (%) was calculated with the equation:
(.A420 nm/min
blank
. .A420 nm/min
sample
) ÷ .A420 nm/min
blank
× 100%.
pg_0005
Lee et al. — SAR of five myricetin galloylglycosides
41
in the R
2
position and hydrogen atom in the R
3
position,
the methyl group in the R
1
position (compound 2) was
more effective (1.28 fold) than the hydrogen atom in the
same position (compound 3). Two gallic acid groups in the
R
2
and R
3
positions (compound 5) were more effective than
one in the R
2
position (compound 3) or in the R
3
position
(compound 4). It was concluded that the gallic acid in the
R
3
position was the key role for SSAo inhibitory activity
among five structure-related compounds.
ACE inhibitory activity of myricetin
galloylglycosides by spectrophotometry
Figure 4 shows the ACE inhibitory activity from
five structure-related myricetin galloylglycosides. It
was found that three out of five compounds had dose-
dependent ACE inhibitory activities. For compound 1, the
ACE inhibitory activities were 34.33, 46.27, 54.48, and
64.90 %, respectively, for 14.76, 44.60, 79.21, 148.90
μM; for compound 2, the ACE inhibitory activities were
35.80, 47.02, 49.25, and 56.71 %, respectively, for 44.60,
74.44, 148.90, 178.73 μM; for compound 5, the ACE
inhibitory activities were 37.31, 57.46, 67.91, and 71.64
%, respectively, for 12.11, 24.35, 36.59, 48.83 μM. The
IC
50
of ACE inhibitory activity of each compound was
shown at Table 1. The IC
50
of compound 1, compound
2, and compound 5 was 60.32, 151.90, and 19.82 μM,
respectively. For ACE inhibitory activity, with the same
methyl group in the R
1
position, the gallic acid in the R
3
position (compound 1) was more effective (2.52 folds)
than in the R
2
position (compound 2). Two gallic acid
groups in the R
2
and R
3
positions (compound 5) were more
effective than one in the R
2
position (7.66 folds, compound
2) or in the R
3
position (3.04 folds, compound 1). Liu et
al. (2003) reported that gallotannins of five gallic acid
groups of 1,2,3,4,6-penta-O-galloyl-β-D-glucose (IC
50
,
73.1 μM) was more effective in ACE inhibitory activity
than four gallic acid groups of 1,2,3,6-tetra-O-galloyl-β-
D-glucose (IC
50
, 101.4 μM). The IC
50
of two or three gallic
acid groups in gallotannin were higher than 200 μM.
In conclusion, the SAR of DPPH radical scavenging
activity and inhibitory activities of SSAo and ACE in
five structure-related myricetin galloylglycosides were
reported. The five compounds have the same orders of
compound 1> compound 5> compound 4> compound 2>
compound 3 for DPPH scavenging activity and SSAo
inhibition. It was postulated that gallic acid in the R
3
position was the key role for anti-DPPH radicals and
SSAo inhibitory activity. For ACE inhibitory activity, the
orders were compound 5> compound 1> compound 2. It
was postulated that more gallic acid groups were the key
to ACE inhibitory activity.
Acknowledgments. The authors want to thank the
financial support (NSC93-2313-B038-001) from the
National Science Council, Republic of China.
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Lee et al. — SAR of five myricetin galloylglycosides
43
相思樹葉子五種楊梅樹皮素配糖體之結構-活性關係
李宗徽
1
 劉得任
2
 徐鳳麟
1
 吳紋君
1
 侯文琪
1
1
臺北醫學大學生藥學研究所
2
臺北醫學大學生物醫學材料研究所
  從相思樹葉子分離五種楊梅樹皮素配糖體在之前就已經有報告 (Lee et al., 2000, J. Nat. Prod., 63,
710-712),但是結構-活性之間的關係並沒有報告。本½研究將比較五種分離的化合物,包括 myricetin
3-O-(3"-O-galloyl)-α-rhamnopyranoside 7-methyl ether (化合物 1,分子量 630 Da), myricetin 3-O-(2"
-O-galloyl)-α-rhamnopyranoside 7-methyl ether (化合物 2,分子量 630 Da), myricetin 3-O-(2"-O-galloyl)-
α-rhamnopyranoside (化合物 3,分子量 616 Da), myricetin 3-O-(3"-O-galloyl)-α-rhamnopyranoside (化
合物 4,分子量 616 Da), 及myricetin 3-O-(2", 3"-di-O-galloyl)-α-rhamnopyranoside (化合物 5,分子量
768 Da),對於清除 DPPH 自由基與抑制 Semicarbazide-sensitive 胺.(SSAo)及血管收縮素轉化.
(ACE)活性的關係。就清除 DPPH 自由基方面,五種化合物 50% 抑制所需濃度分別為 591, 1522,
3210, 1389, 及 867 μM。就抑制 Semicarbazide-sensitive 胺.方面,五種化合物 50% 抑制所需濃度分別
為 36.16, 93.20, 119.50, 88.20, 及 39.35 μM。就上面清除 DPPH 自由基與抑制 Semicarbazide-sensitive 胺
.的結果可以發現,五種結構相關化合物顯現出以下相同次序:化合物 1> 化合物 5> 化合物 4> 化合物
2> 化合物 3,而 gallic acid 位在 R3 的位置,與上述兩種活性有密切的關係。就抑制血管收縮素轉化.
(ACE)方面,只有化合物 1,化合物 2,及化合物 5 具有濃度相關抑制活性, 三種化合物 50% 抑制所
需濃度分別為 60.32, 151.90, 及 19.82 μM。
關鍵詞:相思樹;DPPH 自由基;Semicarbazide-sensitive 胺.;血管收縮素轉化.;楊梅樹皮素配糖
體;結構-活性關係。
pg_0008