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TitleAo-The Antioxidant, Angiotensin Converting Enzyme Inhibition Activit
TagsPolyphenol High Performance Liquid Chromatography Antioxidant Phenols Reactive Oxygen Species
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Table of Contents
                            The antioxidant, angiotensin converting enzyme inhibition activity, and phenolic compounds of bamboo shoot extracts
	Introduction
	Materials and methods
		Bamboo shoots
		Extraction
		HPLC analysis of ascorbic acid and phenolic compound
		DPPH radical scavenging activity
		ACE inhibition activity
		Antimicrobial activity
		Statistical analysis
	Results and discussion
		Extraction yield
		Analysis of ascorbic acid and phenolic compounds
		Scavenging activity on DPPH radicals
		Effect of extracts on the activity of ACE
		Antimicrobial activity tests
	Conclusion
	References
                        
Document Text Contents
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lable at ScienceDirect

LWT - Food Science and Technology 43 (2010) 655–659
Contents lists avai
LWT - Food Science and Technology

journal homepage: www.elsevier .com/locate/ lwt
The antioxidant, angiotensin converting enzyme inhibition activity, and phenolic
compounds of bamboo shoot extracts

Eun-Jin Park 1, Deok-Young Jhon*

Department of Food Science and Human Nutrition, Chonnam National University, Gwangju, 500-757 Republic of Korea
a r t i c l e i n f o

Article history:
Received 10 June 2008
Received in revised form
14 September 2009
Accepted 6 November 2009

Keywords:
Bamboo shoots
Antioxidant
Antimicrobial
ACE inhibition
Phenolic compound
* Corresponding author. Department of Food N
University, 300 YongBong-Dong, Gwangju, 500-757 R
530 1335; fax: þ82 62 530 1339.

E-mail address: [email protected] (D.-Y. Jhon
1 Present address: Department of Biology, Kyung H

DongDaeMun-Gu, Seoul 130-701, Republic of Korea.

0023-6438/$ – see front matter � 2009 Elsevier Ltd.
doi:10.1016/j.lwt.2009.11.005
a b s t r a c t

This study was undertaken to evaluate the functional properties of two of the most popular species of
edible bamboo shoots in Korea (Phyllostachys pubescens and Phyllostachys nigra). Powdered bamboo
shoots were extracted with methanol and an aqueous suspension of the obtained methanol extract was
partitioned successively with chloroform, ethyl acetate, and butanol, leaving a residual water extract. All
obtained extracts were evaluated for their antioxidant capacity and antimicrobial activity, angiotensin
converting enzyme (ACE) inhibition activity, and ascorbic acid and phenolic compound content. Meth-
anol and water fractions showed a particularly high ascorbic acid contents. The ethyl acetate fraction
contained a high concentration of phenolic compounds. Among all extracts, the ethyl acetate and butanol
fractions showed particularly high antioxidant activity. Methanol extract had a significantly higher ACE
inhibitory activity than other extracts. None of the extracts inhibited the tested bacteria.

� 2009 Elsevier Ltd. All rights reserved.
1. Introduction

Bamboo is a group of genera of evergreen plants belonging to the
Poaceae or grass family. Bamboo shoots are the immature and edible
culms arising from the rhizomes. Shoots emerge in early spring, can
grow quickly at over 1 m per day, and usually become lignified
(woody) in 2–3 days (Luo, Xi, Fu, & Lu, 2002; Wang, 2002; Zhang,
Yang, Han, & Dong, 2000). For these reasons, bamboo shoots have
limitations for consumption and storage. Among the edible 60–90
genera of bamboo shoots, Phyllostachys pubescens and Phyllostachys
nigra are the major species cultivated in Korea (statistical data of
Korea Forest Research Institute, 2005). Bamboo leaves (Phyllostachys
Sieb. et Zucc.) have antioxidant capacity due to high polyphenol
content (Lu, Wu, Shi, Dong, & Zhang, 2006). Park, Lim, Kim, Choi, and
Lee (2007) reported that a butanol extract of bamboo leaves (Sasa
borealis) exhibited significant antioxidant capacity against the
1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. Ethanol extracts of
bamboo (Phyllostachys bambusoides) have a nitrite scavenging
ability (Lim, Na, & Baik, 2004). Kim, Cho, Lee, Ryu, and Shim (2001)
reported that extracts of bamboo leaves and stems (Phyllostachys
spp.) showed strong antibacterial activities. Most research studies
utrition, Chonnam National
epublic of Korea. Tel.: þ82 62

).
ee University HoeGi-Dong 1,

All rights reserved.
have investigated the functional activities of bamboo leaves and
stems. However, only a few studies have reported on the functional
properties of bamboo shoots. Wang and Ng (2003) reported on the
antifungal protein (dendrocin) isolated from bamboo shoots (Den-
drocalamus latiflora Munro). Thus, further studies of the functional
and bioactive properties of bamboo shoots are needed.

Solvent extraction is frequently used for isolation of antioxidant,
of which extraction yield is dependent on the solvent and method
of extraction. Several extraction techniques have been reported for
extraction using solvents with different polarities, such as meth-
anol, ethanol, chloroform, ethyl acetate, acetone, petroleum ether,
butanol, and water (Cheung, Cheung, & Ooi, 2003; Singh, Murthy, &
Jayaprakasha, 2002). Extracted fractions have been assayed for
their functional properties, such as antioxidant capacity, angio-
tensin converting enzyme inhibition activity, antimicrobial activity,
nitrite scavenging ability, and the presence of phenolic compounds.
Plant phenols are bioactive compounds of interest because they are
an important group of strong natural antioxidants, and some of
them are potent antimicrobial compounds.

Free radicals produced by radiation, chemical reactions and
several reactions with various compounds may contribute to
oxidative damage of lipids, protein, and nucleic acids in living cells
(Morrissey & O’Brien, 1998). The mechanism of antioxidant capacity
may involve the scavenging of free radicals (Dini, Tenore, & Dini,
2006). Plant foods are potential sources of natural antioxidants, such
as vitamin C, tocopherol, carotenoids, flavonoid, and phenolic
compounds which prevent free radical damage (Diplock et al.,1998;
Paganga, Miller, & Rice-Evan, 1999; Vinson, Hao, Su, & Subik, 1998).

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E.-J. Park, D.-Y. Jhon / LWT - Food Science and Technology 43 (2010) 655–659656
Angiotensin converting enzyme (ACE; peptidyldipeptide
hydrolase EC 3,4,15,1) plays an important physiological role in the
control of blood pressure. Since ACE activity raises blood pressure,
it is recommended to inhibit ACE activity in patients suffering from
hypertension (Hernaandex-Ledesma, Martian-Aalvarez, & Pueyo,
2003). Therefore, inhibition of ACE results in an overall anti-
hypertensive effect. Several studies have been conducted using
synthetic drugs, which can cause undesirable side effects. Edible
plants are natural and abundant resources of bioactive chemicals.
Since it is recommended to use several natural foods to inhibit ACE
activity, many studies have been investigated ACE inhibitory
compounds from foods. Up until now, many different protein
hydrolysates, such as soy sauce, tuna, bonito, and soybean, have
been reported up to now show ACE inhibition activity (Kinoshita,
Yamakoshi, & Ikeuchi, 1993; Kohama et al., 1988; Matsumura, Fujii,
Takeda, Sugita, & Shimuzu, 1993; Okamoto, Hanagata, Kawamura, &
Yanagida, 1995).

The objective of the present study was to analyze the functional
properties, such as antioxidant capacity, antimicrobial potential,
ACE inhibitory activity, ascorbic acid contents, and phenolic
compounds, of solvent extracts of bamboo shoots, and to compare
the effect of solvent extraction (methanol, chloroform, ethyl
acetate, butanol, and water) on those functional properties.

2. Materials and methods

2.1. Bamboo shoots

Two kinds of bamboo shoots (P. pubescens, PP and P. nigra, PN)
were used in this experiment. Bamboo shoots were grown and
harvested in the spring of 2006 in Dam-Yang, Korea. Harvested
bamboo shoots were trimmed immediately, lyophilized, and
pulverized using 0.254 mm sieves (FM-681C, Hanil Co., Korea).

2.2. Extraction

Each sample of bamboo shoots powder (10 g) was extracted by
mixing with a magnetic stirrer with 1500 mL of 99.9 mL/mL
methanol at room temperature (20–25�C) for 24 h in 3–5 replicates.
The total extract was filtered through Whatman No. 6 filter paper
and evaporated in a rotary vacuum evaporator (Vacuum rotary
evaporator, Dai-Han Inc., Korea) at 35�C. Methanol (MeOH) extract
was partitioned successively with chloroform (CHCl3), ethyl acetate
(EtOAc), and butanol (BuOH), leaving residual water fractions
(H2O). All obtained extracts, including the residual water fractions,
were evaporated in a rotary vacuum evaporator at 35�C in water
bath. Each extract was dissolved in 99.9 mL/mL methanol, in
concentrations of 1–10 mg/mL, centrifuged at 14,000 � g for 20
min, and the supernatant was stored at refrigerator temperature
(4�C) before subsequent experiments.

2.3. HPLC analysis of ascorbic acid and phenolic compound

For analysis of ascorbic acid and phenolic compounds, each extract
was mixed with 99.9 mL/mL methanol and vortexed for 30 min at the
highest setting. Mixed samples were centrifuged at 14,000� g for 20
min and the supernatant was filtered through a 0.45 mm syringe filter.
Final samples were analyzed by HPLC (LC-900, Jasco International Co.,
Ltd, Japan). The operating conditions of HPLC for analysis of ascorbic
acid and phenolic compounds in bamboo shoots were as follows:
Instrument, LC-900 (Jasco International, Co., Ltd, Japan); Column, m-
BondapakTM C18 (i.d. 3.9 � 300 mm); Detector, UV-975 (Jasco Inter-
national, Japan); Detectionwavelength, 254 nm; Mobile phase,13 mL/
mL MeOH and 1 mL/mL HAc (gradient elution); Flow rate,1.0 mL/min;
Chart speed, 2 mm/min.
2.4. DPPH radical scavenging activity

Radical scavenging activity was determined using a 2,2-
diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay with
modification (Joyeux, Mortier, & Fleurentin, 1995; Robards, San-
chez-Moreno, Larrauri, & Sauracalixto, 1998). Eight hundred ml of
each extracts was mixed with 400 mL of 0.4 mmol/L methanolic
DPPH. Mixtures were vortexed for 30 sec at the highest setting and
left for 30 min in the dark. After that, absorbance was measured at
517 nm using MeOH as blank. The scavenging activity of the DPPH
radical was calculated using the following equation: Scavenging
activity (%) ¼ 100 � (A0 � A1)/A0, where A0 is the absorbance of the
methanol control, and A1 is the absorbance in the presence of
bamboo shoots extracts. The inhibition concentration (IC50) was
defined as the amount of extract required for 50% reduction of free
scavenging activity. The IC50 values were obtained from the
resulting inhibition curves. Results were compared with the
activity of butylated hydroxytoluene (BHT), butylated hydrox-
yanisole (BHA), ascorbic acid, and catechin (Sigma, St. Louis, MO,
USA) as control antioxidants.

2.5. ACE inhibition activity

The ACE (angiotensin-converting enzyme) inhibition activity
was measured spectrophotometrically using Hip-His-Leu (N-hip-
puryl-1-histidyl-leucine tetrahydrate, Sigma, USA) as a substrate.
Ten mL of bamboo shoot extracts were mixed with 100 mL of
substrate and 40 mL of angiotensin converting enzyme (peptidyl-
dipeptidase A, dissolved in 0.01 mol/L potassium phosphatase
monobasic and 0.5 mol/L sodium chloride, amended to pH 7.0,
Sigma, USA). Mixtures were incubated at 37�C for 60 min and 125
mL of 1 mol/L HCl was added to stop the reaction. After that, samples
were mixed with 850 mL of ethyl acetate, vortexed for 1 min at the
highest setting, and centrifuged at 14,000 � g for 20 min. Five
hundred mL of the supernatant was dried at 100�C. Dried samples
were mixed with 1 mL of deionized water, vortexed for 1 min at the
highest setting, and absorbance was measured at 230 nm using
deionized water as a blank. ACE inhibition activity was calculated
using the following equation: ACE inhibition activity (%)¼ [(C0 – Cb)
– (S0 – Sb)/(C0 – Cb)] � 100, where C0 is the absorbance of the
deionized water control, Cb is the absorbance of the deionized
water sample, S0 is the absorbance of the tested sample, and Sb is
the absorbance without sample.

2.6. Antimicrobial activity

In order to determine the antimicrobial activity of extracts, the
paper disc method was used. The following microorganisms were
tested: Escherichia coli (ATCC 35210), Enterococcus faecium (ATCC
19434), Ent. faecalis (ATCC 29212), and Streptococcus mutans (ATCC
27352). Each strains of E. coli, Enterococcus spp., and Strep. mutans
was enumerated on LB agar (0.1 g/100 mL tryptone; 0.5 g/100 mL
yeast extract; 1 g/100 mL sodium chloride; and 1.5 g/100 mL agar),
MRS agar (Difco, Detroit, MI, USA), and m-BHI agar [modified Brain
Heart Infusion agar: BHI broth (Difco) supplemented with 0.5 g/100
mL yeast extract; 2 g/100 mL glucose; and 1.5 g/100 mL agar],
respectively. Three strains, including E. coli, Ent. faecium, and Ent.
faecalis, were incubated at 37�C for 24 h, and Strep. mutans was
incubated at 37�C for 72 h in an anaerobic jar (BBL, USA). Each
microorganism culture (107–8 cfu/mL) at 2 mg/100 mL (v/v) total
weight was mixed with cooled agar medium, poured onto the
surface of agar, and cooled to be solidified. Five hundred mL of
extracts, which were filtered using 0.45 mm syringe filter, were
loaded on 8 mm sterilized paper discs (Toyo Roshi Kaisha Ltd., Japan)
and allowed to dry. The loaded discs were placed on the agar surface,

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Table 1
The extraction yields of powdered bamboo shoots by various solvents.

Solvent Yield (g/100 g, w/w)a

P. pubescens (PP) P. nigra (PN)

Methanol extract 30.3 � 2.1b 24.3 � 1.8
Chloroform fraction 4.2 � 0.3 5.6 � 0.2
Ethyl acetate fraction 0.7 � 0.0 1.0 � 0.1
Butanol fraction 8.4 � 1.1 5.5 � 0.8
Water fraction 15.4 � 1.0 12.1 � 0.9
a Yield ratios (g/100 g, w/w)¼ [solid in extract or fraction (g)/raw material (100 g,

dry weight)].
b All experiments were replicated three times and results are presented as mean� SE.

E.-J. Park, D.-Y. Jhon / LWT - Food Science and Technology 43 (2010) 655–659 657
rehydrated with 0.1 mL of deionized water, and the compounds
allowed to diffuse in the hood for 1 h. The plates were incubated at
37�C for 24–72 h. After incubation, inhibition zones formed around
the disc were measured with a transparent ruler in millimeters.
2.7. Statistical analysis

Three replicate trials for each experiment were performed.
Analysis of variance was performed and means separated using the
ANOVA procedure of SAS (SAS Institute, Cary, NC, USA). Mean
values were reported for all analyses and separated using Duncan’s
multiple range tests. Significant differences between values were
presented at a significance level of P ¼ 0.05.
3. Results and discussion

3.1. Extraction yield

Efficiency of extraction is an important factor for the compar-
ison of functional activities. Several researchers reported that
relatively higher antioxidant capacity and phenolic acid contents
were observed from methanolic extracts (Sosulski, Krygier, &
Hogge, 1982; Zielinski & Kozlowska, 2000) compared to other
solvents. Therefore, crude methanolic extracts was selected as
a basis for further partitioning by several solvents, such as chloro-
form, ethyl acetate, butanol, and water. The extraction yields
(expressed as w/w percentages) of the bamboo shoots extracts is
shown in Table 1. The extraction yield of methanol extracts were
30.3 g/100 mL (PP) and 24.3 g/100 mL (PN), respectively. The
relative extraction yield of other solvents decreased in the
following order (PP and PN): water fractions (15.4 and 12.1 g/100
mL) > butanol fractions (8.4 and 5.5 g/100 mL) > chloroform
fractions (4.2 and 5.6 g/100 mL) > ethyl acetate fractions (0.7 and
1.0 g/100 mL). This implies that most of the soluble components in
bamboo shoots were high polarity.
Table 2
Ascorbic acid and phenolic compounds in bamboo shoot (Phyllostachys pubescens, PP) ex

Compound Contents (mg/100 g, dry weight basis)

MeOH CHCl3

Ascorbic acid 154.7 � 8.5a 1.0 � 0.0
Protocatechuic acid 2.8 � 0.2 0.1 � 0.0
p-Hydroxybenzoic acid 1.7 � 0.0 0.4 � 0.0
Catechin 0 0
Caffeic acid 0 0
Chlorogenic acid 0 0
Syringic acid 0 0
p-Coumaric acid 0 0
Ferulic acid 0 0

a All experiments were replicated three times and results are presented as mean � SE
3.2. Analysis of ascorbic acid and phenolic compounds

Oxidative stress is defined in general as an excessive amount of
free radicals, such as superoxide (O2

�) and hydroxyl radical (OH�), as
well as hydrogen peroxide (H2O2) (Cerutti, 1991). ROS are strongly
associated with aging, carcinogenesis, and cardiovascular disease
(Moskovitz, Yim, & Choke, 2002). Cells have several antioxidant
mechanisms to prevent the effects of ROS. Antioxidative enzymes,
such as superoxide dismutase and calatase, ascorbic acid (vitamin
A), and tocopherol (vitamin E) have effective ROS scavenging
properties (Fridovich, 1999). Phenolic compounds, also, are anti-
oxidants and have been isolated from fruits, vegetables, grains,
medicinal plants, nuts, herbs and edible oils (Goli, Barzegar, &
Sahari, 2005; Hayouni, Abedrabba, Bouix, & Hamdi, 2007; Kuti
& Konuru, 2004; Li, Wong, Cheng, & Chen, 2008; Liyana-Pathirana &
Shahidi, 2006; Yanishlieva & Marinova, 2001). Therefore, the
determination of phenolic acid content is necessary before
measuring antioxidant capacity. In this investigation, the five
bamboo shoots extracts were evaluated for content of ascorbic acid
and phenolic compounds using HPLC analysis.

Table 2 and 3 shows ascorbic acid content and phenolic
compound compositions of individual extracts. The ascorbic acid
content, on a dry weight basis, were as follows (PP and PN):
methanol, 154.7 and 195.3 mg; chloroform, 1.0 and 9.3 mg; ethyl
acetate, 51.0 and 162.5 mg; butanol, 50.9 and 114.3 mg; and water,
136.3 and 231.8 mg per 100 g of bamboo shoots. Methanol extracts
and water fractions showed particularly high ascorbic acid content.
In bamboo shoots, eight phenolic acids (protocatechuic acid,
p-hydroxybenzoic acid, catechin, caffeic acid, chlorogenic acid,
syringic acid, p-coumaric acid, and ferulic acid) were identified and
quantified by HPLC. The most abundant compounds were proto-
catechuic acid, p-hydroxybenzoic acid, and syringic acid. Syringic
acid was a most abundant acid of the butanol fraction of PP. In ethyl
acetate fractions, six and eight compounds were detected in PP and
PN, respectively. Ethyl acetate fractions of PP contained proto-
catechuic acid, 0.5 mg; p-hydroxybenzoic acid, 2.9 mg; caffeic acid,
0.3 mg; syringic acid, 1.3 mg; p-coumaric acid, 1.3 mg; and ferulic
acid, 0.5 mg per 100 g of bamboo shoots. Catechin and chlorogenic
acid were detected only in the PN extracts. The PN extracts con-
tained protocatechuid acid, 1.5 mg; p-hydroxybenzoic acid, 8.1 mg;
catechin, 10.6 mg; caffeic acid, 1.5 mg; chlorogenic acid, 4.1 mg;
syringic acid, 2.5 mg; p-coumaric acid, 3.5 mg; and ferulic acid, 1.85
mg per 100 g of bamboo shoots. There were no phenolic acids in
water fractions of the tested extracts. However, ethyl acetate frac-
tions contained a high phenolic acid concentration, followed by
butanol fractions. It has been reported that the correlation between
antioxidant capacity of plant materials and their phenolic
compound content is statistically significant (Velioglu, Mazza, Gao,
& Oomah, 1998). Although the concentrations and varieties of
phenolic compounds were highest in the ethyl acetate fractions, the
tracts by various solvents.

EtOAc BuOH H2O

51.0 � 3.2 50.9 � 1.7 136.3 � 4.2
0.5 � 0.0 1.3 � 0.0 0
2.9 � 0.0 0.6 � 0.0 0
0 0 0
0.3 � 0.0 0 0
0 0 0
1.3 � 0.0 6.7 � 0.2 0
1.3 � 0.0 0 0
0.5 � 0.0 0 0

.

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Table 3
Ascorbic acid and phenolic compounds in bamboo shoot (Phyllostachys nigra, PN) extracts by various solvents.

Compound Contents (mg/100 g, dry weight basis)

MeOH CHCl3 EtOAc BuOH H2O

Ascorbic acid 195.3 � 3.4a 9.3 � 0.8 162.5 � 5.7 114.3 � 3.2 231.8 � 10.1
Protocatechuic acid 0 0 1.5 � 0.0 0 0
p-Hydroxybenzoic acid 5.4 � 0.2 0.6 � 0.0 8.1 � 1.2 1.4 � 0.0 0
Catechin 0 0 10.6 � 1.9 0 0
Caffeic acid 0 0 1.5 � 0.0 0 0
Chlorogenic acid 0 0 4.1 � 0.3 3.5 � 0.5 0
Syringic acid 0 1.8 � 0.0 2.5 � 0.0 2.1 � 0.1 0
p-Coumaric acid 0 0 3.5 � 0.1 0 0
Ferulic acid 0 0 1.8 � 0.0 0 0
a All experiments were replicated three times and results are presented as mean � SE.

70

80

)

E.-J. Park, D.-Y. Jhon / LWT - Food Science and Technology 43 (2010) 655–659658
extraction yields of those were extremely low and hence their
contribution was insignificant.

3.3. Scavenging activity on DPPH radicals

DPPH radical scavenging activity, which is a mechanism of
measuring the decrease in DPPH radical absorption after exposure to
radical scavengers, frequently can be used to rapidly determine
antioxidant capacity. Comparison of antioxidant capacities between
extracts of bamboo shoots is shown in Table 4 and radical scavenging
activity expressed as IC50. A wide range of antioxidant capacity among
the tested fractions was observed. The IC50 of each fraction increased
in the following order (PP and PN): ethyl acetate fractions (0.8 and 0.4
mg/mL) z butanol fractions (0.7 and 0.8 mg/mL) > chloroform frac-
tions (4.0 and 2.3 mg/mL) z methanol extracts (3.6 and 3.4 mg/mL)>
water fractions (4.7 and 5.3 mg/mL). Strong DPPH radical scavenging
activity was also found in the ethyl acetate and butanol fractions
possessing high phenolic contents (Tables 2 and 3). However, those
activities were significantly lower than those of the control antioxi-
dants, such as BHT, BHA, ascorbic acid, and catechin. From the earlier
result, it was found that the water and chloroform fractions had
relatively lower antioxidant capacities due to their lower phenolic
compounds contents. Overall, the antioxidant capacities of the frac-
tions were highly correlated with their total phenolic contents and
these results are also similar to those of previous findings (Beta, Nam,
Dexter, & Sapirstein, 2005; Bouaziz, Chamkha, & Sayadi, 2004; Kuti &
Konuru, 2004; Liyana-Pathirana & Shahidi, 2006).

3.4. Effect of extracts on the activity of ACE

In the ACE inhibition tests, ACE catalyses the degradation of the
substrate, Hip-His-Leu, so that ACE activity might be derived from the
decrease in absorbance after reaction. Therefore, inhibition of ACE is
Table 4
Antioxidant capacity of solvent fractions from the powdered bamboo shoots and
control antioxidant by DPPH radical scavenging method.

Fraction Antioxidant capacitya (IC50: mg/mL)

P. pubescens (PP) P. nigra (PN)

Methanol extract 3.6 � 0.2b 3.4 � 0.3
Chloroform fraction 4.0 � 0.0 2.3 � 0.0
Ethyl acetate fraction 0.8 � 0.0 0.4 � 0.0
Butanol fraction 0.7 � 0.0 0.8 � 0.0
Water fraction 4.7 � 0.3 5.3 � 0.8

BHT 0.006 � 0.0 0.006 � 0.0
BHA 0.008 � 0.0 0.008 � 0.0
Ascorbic acid 0.009 � 0.0 0.009 � 0.0
Catechin 0.023 � 0.0 0.023 � 0.0
a Amount of bamboo shoots extract required for 50% reduction of free radical

scavenging activity.
b All experiments were replicated three times and results are presented as

mean � SE.
indicative of an overall anti-hypertensive effect. Figs.1 and 2 show the
dose-response curve for the ACE inhibition activities of bamboo
shoots extracts at 1, 5, and 10 mg/mL concentrations. The inhibitory
activities increased proportional to extract concentration. The results
showed that methanol extracts had significantly higher ACE inhibi-
tory activity than other extracts with increasing concentrations.
Butanol and ethyl acetate fractions showed higher ACE inhibition
activities than did chloroform and water fractions. Synthetic drugs,
such as captopril and benazepril, were used for comparison of ACE
inhibitory activity with the tested compounds (Vermeirssen, Camp, &
Verstraete, 2002). To obtain approximately 50% ACE inhibitory
activity, 3.6 ng/mL of captopril were needed (Chen, Chang, Chung, &
Chou, 2007). In our study, 3.5 (PP) and 6.0 (PN) mg/ml of methanol
extracts, the ones showing a highest ACE activity, were needed to
produce activity similar to captopril. Although the ACE inhibition
activities of bamboo shoots extracts were significantly less than those
of synthetic drugs, it is useful to know that bamboo shoot extracts did
have potent ACE inhibitory compounds.
3.5. Antimicrobial activity tests

None of the fractions extracted from either species bamboo
shoots inhibited any of the tested bacteria, such as E. coli, Ent. fae-
cium, Ent. faecalis, and Strep. mutans, at 1, 5, and 10 mg/mL
concentrations (data not shown). Zhu, Zhang, Lo, and Lu (2005)
reported that the minimum inhibitory concentrations (MICs) used
for fungi were at or below 2.5 mg/mL and for bacteria were at or
above 2.5 mg/mL. The concentrations tested in our experiment did
0

10

20

30

40

50

60

0 2 4 6 8 10 12
Concentration (mg/ml)

A
C

E
In

hi
bi

tio
n

ac
tiv

ity
(%

Fig. 1. Angiotensin converting enzyme (ACE) inhibition activity by solvent fractions
from powdered bamboo shoots (Phyllostachys pubescens, PP). C, methanol fraction; B
chloroform fraction; : ethyl acetate fraction; 6 butanol fraction; - water fraction.

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