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Radical‐scavenging properties of extracts from the white button mushroom, Agaricus bisporus

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BACKGROUND:Agaricus bisporus is the premier cultivated edible mushroom but is usually considered to be of lesser value nutritionally and medicinally compared with other cultivated mushrooms. The objective of this study was to investigate the radical-scavenging properties of methanolic extracts and the free radical-processing enzyme activities of water extracts from A. bisporus fruit bodies. Analyses were performed on total fruit bodies from three strains and on separated stipe, cap and gills from one strain, all cultivated experimentally under the same conditions. RESULTS: EC50 values of scavenging ability on 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH•), scavenging ability on 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cations (ABTS•+) and reducing power of methanolic extracts from total fruit bodies ranged between 1.7 and 5.0 and were 1.1–1.9 times higher in a white hybrid than in two wild strains, cream and brown. The gills exhibited higher antioxidant activities relative to the stipe and cap. In water extracts, glutathione peroxidase activities were up to eight times higher than glutathione reductase activities and no difference was observed between strains. Catalase activity was highest in the brown wild strain. The only significant differences in free radical-processing enzymes between the three parts of the mushroom were higher catalase activity in the gills and lower glutathione reductase activity in the stipe. CONCLUSION: The radical-scavenging properties of the button mushroom are comparable to those of other edible mushrooms and dependent on the strain and on the section of the fruit body. Copyright
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Journal of the Science of Food and Agriculture J Sci Food Agric 88:970975 (2008)
Radical-scavenging properties
of extracts from the white button
mushroom, Agaricus bisporus
Jean-Michel Savoie,Nathalie Minvielle and Mich `
ele L Largeteau
INRA, UR1264, Mycologie et S ´
ecurit ´
e des Aliments, BP 81, F-33883 Villenave d’Ornon, France
Abstract
BACKGROUND: Agaricus bisporus is the premier cultivated edible mushroom but is usually considered to be
of lesser value nutritionally and medicinally compared with other cultivated mushrooms. The objective of this
study was to investigate the radical-scavenging properties of methanolic extracts and the free radical-processing
enzyme activities of water extracts from A. bisporus fruit bodies. Analyses were performed on total fruit bodies
from three strains and on separated stipe, cap and gills from one strain, all cultivated experimentally under the
same conditions.
RESULTS: EC50 values of scavenging ability on 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH), scavenging
ability on 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cations (ABTS•+ ) and reducing power of
methanolic extracts from total fruit bodies ranged between 1.7 and 5.0 and were 1.1 1.9 times higher in a white
hybrid than in two wild strains, cream and brown. The gills exhibited higher antioxidant activities relative to the
stipe and cap. In water extracts, glutathione peroxidase activities were up to eight times higher than glutathione
reductase activities and no difference was observed between strains. Catalase activity was highest in the brown
wild strain. The only significant differences in free radical-processing enzymes between the three parts of the
mushroom were higher catalase activity in the gills and lower glutathione reductase activity in the stipe.
CONCLUSION: The radical-scavenging properties of the button mushroom are comparable to those of other
edible mushrooms and dependent on the strain and on the section of the fruit body.
2008 Society of Chemical Industry
Keywords: Agaricus bisporus; antioxidant activity; mushrooms; free radical-processing enzymes
INTRODUCTION
The button mushroom, Agaricus bisporus (J.E. Lange)
Imbach, is the premier cultivated edible mushroom
and is consumed throughout the world. However, A.
bisporus is usually considered to be of lesser value
nutritionally and medicinally compared with other
cultivated mushrooms that are predominantly grown
in Asia.1Recent evidence suggests that A. bisporus
also contains high levels of substances of possible
medicinal importance, such as tyrosinase, aromatase
inhibitors and immunomodulating and antitumour
polysaccharides.1Cold water extracts of A. bisporus
have the ability to neutralise genotoxic effects of reac-
tive oxygen species.2This genoprotective effect was
associated with tyrosinase. Recent studies illustrate
the anticancer activity in vitro and in vivo of A. bis-
porus extract, and its major fatty acid constituents
that suppress aromatase activity and oestrogen biosyn-
thesis are responsible for the potential breast can-
cer chemopreventive effect.3Ergosterol, vitamin D2
content and antioxidant activity are also proposed
as interesting components for the development of
A. bisporus as a nutraceutical for tomorrow.4Owing
to its nutritional value, with a low calorie, purine,
carbohydrate and sodium content as well as a high
content of several vitamins, potassium, phosphorus
and some trace elements, A. bisporus, like other mush-
rooms, is considered to be a valuable component
of the human diet, especially by health-conscious
people.5This suggests that the value of A. bis-
porus as a functional food warrants more detailed
study.
It is well known that antioxidant and free radical-
scavenging activities of natural products can coun-
teract injurious and carcinogenic changes induced
by free radicals. These properties are the result of
chemical reactions associated with the presence of
various compounds and enzymes. The primary func-
tion of antioxidant properties is to prevent cell damage
induced by reactive oxygen species (ROS). The reduc-
ing power present might contribute to the elimination
of H2O2and other ROS in mushroom cells. Activities
of free radical-processing enzymes, including enzymes
Correspondence to: Jean-Michel Savoie, INRA, UR1264, Mycologie et S ´
ecurit ´
e des Aliments, BP 81, F-33883 Villenave d’Ornon, France
E-mail: savoie@bordeaux.inra.fr
(Received 7 May 2007; revised version received 5 October 2007; accepted 24 October 2007)
Published online 5 February 2008;DOI: 10.1002/jsfa.3175
2008 Society of Chemical Industry. J Sci Food Agric 0022 5142/2008/$30.00
Radical-scavenging activity of Agaricus bisporus
of the ascorbate/glutathione cycle, may contribute to
the antioxidant activity.
Although research has been focused on the antioxi-
dant properties of various speciality mushrooms, little
information is available about A. bisporus antioxidant
properties. Our objective was to investigate the radical-
scavenging properties of methanolic extracts and the
free radical-processing enzyme (other than tyrosinase)
activities of water extracts from A. bisporus fruit bod-
ies. The composition of mushrooms may vary within
a species because of differences in strain, cultivation
technique and maturity at harvest.6Thus analyses
were performed on total fruit bodies from three strains
and on separated stipe, cap and gills from one strain,
cultivated experimentally under the same conditions.
MATERIALS AND METHODS
Samples
Two wild strains of A. bisporus from the CGAB
collection (INRA/CTC, Villenave d’Ornon, France)
and a cultivar were studied. Bs0118H is a cream
wild strain (lightness measured with a Minolta
Chromameter(Minolta, Osaka, Japan) varying from
0 (black) to 100 (white), L=87) isolated in eastern
France in 1992. Bs0633 is a brown wild strain (L=62)
isolated to the east of Budapest, Hungary by Jozsef
Geml in 1999. X25 is a white commercial hybrid
(L>90) from Euromycel (Saint Benoit la Forˆ
et,
France). To obtain fruit bodies, the A. bisporus strains
were grown on commercial compost supplied by a
local mushroom grower (Renaud SA, Pons, France),
spawned with mycelium grown on rye grain, at the
rate of 8 g kg1compost in 0.9m
2trays. Five trays
were spawned with each A. bisporus strain. Incubation
was performed at 24 C and 92% relative humidity
for 13 days, after which a conventional casing layer
was added on top of the compost. Nine days after
casing, the temperature in the cultivation room was
decreased to 16 C. Mushrooms of the first flush were
harvested at commercial stage, i.e. buttons with a
pileus diameter of 35 cm, and transported to the
laboratory within 15 min. Twenty fruit bodies of each
strain were randomly selected, placed on plates on
ice, immediately sliced and then freeze-dried (CS 2H
lyophilisator, Serail CVRP, Argenteuil, France).
The lyophilised slices from each strain were mixed
and ground into a fine powder (Culatti mill, IKA-
Labortechnik, Staufen, Germany). For the strain
Bs0118H, ten fruit bodies were treated as above, but,
before being sliced, the stipe, cap and gills of each
were separated.
Extractions
For methanolic extraction a 3 g subsample of
lyophilised powder was extracted with 30 mL of
methanol in a shaking incubator (125 rpm) for 24 h at
22 C and then by stirring energetically for 20 min. The
extract was filtered using Whatman No. 1 filter paper.
The residue was then extracted with two additional
30 mL portions of methanol as described above.
The three extracts were combined and the volume
was adjusted to 100 mL with methanol. For radical-
scavenging ability and reducing power measurements
the crude extract was diluted 10 100 times to yield
extracts equivalent to 0.3 –3 mg mushroom powder
mL1.
Water extraction for free radical-processing enzyme
activity measurements was performed with a 250 mg
subsample of lyophilised powder and 10 mL of
extraction buffer. The mixture was placed on an ice
bed in a shaking incubator for 15 min and centrifuged
at 12 000 ×gfor 15 min at 4 C (CR3I centrifuge,
Jouan, Saint-Herblain, France).
Antioxidant properties of methanolic extracts
The scavenging ability on 1,1-diphenyl-2-picrylhydra-
zyl radicals (DPPH) was measured as in Mau
et al.7or Choi et al.8according to Shimada et al.9
A 1 mL aliquot of each extract (0.3 3 mg mL1)was
mixed with 1 mL of methanolic solution containing
0.4 mmol L1DPPHand incubated in the dark
for 30 min at room temperature, after which the
absorbance at 517 nm was measured (UVIKON-XS
spectrophotometer, Bio-teck Instruments, Colmar,
France). The effective concentration at which DPPH
radicals were scavenged by 50% (EC50 value expressed
as mg mushroom powder mL1) was obtained by
interpolation from linear regression analysis. Butylated
hydroxyanisole (BHA) was used as a standard
antioxidant for comparison.
The scavenging ability on 2,2-azino-bis(3-ethyl-
benzothiazoline-6-sulfonic acid) radical cations
(ABTS•+) was measured according to the method of
Re et al.10 as modified by Choi et al .8ABTS (7 mmol
L1) and potassium persulfate (2.4 mmol L1)were
mixed and left to stand in the dark overnight to gen-
erate ABTS•+. This solution was diluted to 1/10 and
1 mL was added to 0.5 mL of extract. After 90 min
at 30 C the absorbance at 436 nm was measured.
The effective concentration at which ABTS+radicals
were scavenged by 50% (EC50 value expressed as mg
mushroom powder mL1) was obtained by interpola-
tion from linear regression analysis. BHA was used as
a standard antioxidant for comparison.
The reducing power was determined as in Mau
et al.7according to the method of Oyaizu.11 A0.5mL
aliquot of each diluted extract was mixed with 0.5 mL
of 0.02 mol L1phosphate buffer (pH 6.5) and 0.5 mL
of 10 g L1potassium ferricyanide. The mixture was
incubated at 50 C for 20 min and 0.5 mL of 100 g L1
trichloroacetic acid was added. Precipitates were
eliminated by centrifugation at 200 ×gfor 10 min.
A 1 mL aliquot of supernatant was added to 1 mL
of water and 0.2 mL of 1 g L1ferric chloride and
the absorbance at 700 nm was measured after 5 min.
The EC50 value of reducing power, calculated as
the effective concentration (mg mL1)atwhichthe
absorbance was 0.5, was obtained by interpolation
J Sci Food Agric 88:970 975 (2008) 971
DOI: 10.1002/jsfa
J-M Savoie, N Minvielle, ML Largeteau
from linear regression analysis. BHA was used as a
standard antioxidant for comparison.
DPPH, ABTS, BHA, potassium ferricyanide and
trichloroacetic acid were purchased from Sigma
(Sigma-Aldrich, Saint-Quentin Fallavier, France).
Ferric chloride was obtained from Merck (Darmstadt,
Germany).
Total phenolic content in methanolic extracts
The total phenolic content in the methanolic extracts
of mushrooms was determined spectrophotometri-
cally according to the Folin Ciocalteu colorimetric
method12 with ferrulic acid as standard. To 0.1 mL
of extract were added 2.4 mL of distilled water,
0.375 mL of 200 g L1Na2CO3and 0.125 mL of
FolinCiocalteu reagent (Merck). The absorbance at
750 nm was measured after incubation at 20 C for 1 h.
Activities of free radical-processing enzymes in
water extracts
All enzyme activities were determined at 30 C.
Catalase (EC 1.11.1.6.) activity was determined
by monitoring the disappearance of hydrogen per-
oxide (H2O2) in a reaction mixture composed
of 2.9 mL of 50 µmol L1H2O2(Sigma, 30% sta-
bilised) in 0.1 mmol L1phosphate buffer (pH 7)
and 0.1 mL of water extract. After incubation for
5min the H
2O2concentration was determined via
the horseradish peroxidase-catalysed oxidation of 3-
methyl-2-benzothiazolinone hydrazone (MBTH) and
3-dimethylaminobenzoic acid (DMAB). Assays con-
tained 0.25 mL of sample solution, 0.25 mL of a 20
UmL
1solution of horseradish peroxidase (Sigma)
and 0.625 mL of a chromophore solution comprising
0.6 mmol L1MBTH and 7.5 mmol L1DMAB in
0.05 mol L1phosphate buffer (pH 6). During incu-
bation of this mixture for 3 min at room temperature,
all the H2O2present was consumed by the peroxi-
dase for the oxidation of DMAB and MBTH, and the
absorbance at 590 nm was measured. Blanks without
peroxidase were used as reference, and controls with
2800 U bovine liver catalase (Sigma) mL1sample
solution were used to check that H2O2was responsible
for the chromophore oxidation in the assays. Standard
curves were obtained with dilutions of H2O2from 3 to
64 µmol L1in 0.05 mol L1phosphate buffer (pH 6).
Catalase activity was calculated from the difference in
H2O2concentration between a control without extract
and the assay with extract. One unit of catalase activity
reduced 1 nmol H2O2min1at pH 7 and 30 C.
Glutathione reductase (EC 1.6.4.2) and glutathione
peroxidase (EC 1.11.1.9) activities were determined
as in Sigma-Aldrich’s procedures according to Foster
and Hess13 and Wendel14 respectively.
The assays are based on reduction and oxidation of
glutathione by the enzymes coupled with oxidation
of nicotinamide adenine dinucleotide phosphate,
reduced form, (NADPH) to nicotinamide adenine
dinucleotide phosphate, oxidized form (NADP) and
a UV assay of the decrease in NADPH absorbance
at 340 nm. One unit of glutathione reductase reduced
1µmol oxidised glutathione min1at pH 7.6 and
30 C. One unit of glutathione reductase activity
catalysed the oxidation by H2O2of 1 µmol reduced
glutathione to oxidised glutathione min1at pH 7 and
30 C.
Superoxide dismutase (SOD) activity was mea-
sured using a procedure based on the inhibition of
nitroblue tetrazolium (NBT) reduction under light
by the enzyme.15 The reaction mixture contained
1 mL of NBT solution (1 g L1in 0.01 mol L1
phosphate buffer, pH 7), 1 mL of riboflavin solu-
tion (1 mg riboflavin +0.4 mL tetramethylethylenedi-
amine in 100 mL of 0.01 mol L1phosphate buffer,
pH 7) and either 10 µL of water extract or 10 µL
of water as control. Changes in absorbance at 560 nm
were read to measure NBT reduction. The SOD activ-
ity was estimated by the level of decrease in NBT
reduction due to the conversion of O•−
2to H2O2by
the enzyme.
Statistical analysis
For each methanolic extract and each water extract,
three samples were prepared for assays of antioxidant
properties and free radical-processing enzyme activi-
ties respectively. Absorbance readings were repeated
three times. Means were analysed by one-way analysis
of variance (ANOVA) and Fisher’s least significant dif-
ference (LSD) test using the Systatpackage (SPSS,
Inc., Chicago, USA). Pvalues <0.05 were regarded
as significant.
RESULTS AND DISCUSSION
Antioxidant properties of methanolic extracts
from Agaricus bisporus strains
The methods of scavenging DPPH and ABTS+
radicals and determination of the reducing power
are widely used to evaluate the antioxidant activity
of specific compounds or extracts. The scavenging
effect on DPPHwas more efficient than the
scavenging effect on ABTS•+ and the reducing power
to discriminate the strains of A. bisporus (Table 1).
Variations in antioxidant properties with strain, period
of mushroom harvest and shelf life have to be taken
into account. Antioxidant activities (EC50 values) of
50% methanolic extracts from mushrooms of four
strains of A. bisporus, determined by scavenging
of stable DPPH radicals, varied from 1.0 to 3.6
times.16 In the work of Pinheiro et al.17 the protective
influence of Agaricus blazei meal against the potential
of diethylnitrosamine for rat liver carcinogenicity
also depended on both the strain and the period
of mushroom harvest. In the present study, all
mushrooms were collected during the first flush at
the same development stage and treated within 15 min
after harvest. For both radicals the methanolic extract
of the white hybrid X25 was the least active, with
EC50 values significantly higher than those of the
other two strains (Table 1). The methanolic extract
972 J Sci Food Agric 88:970975 (2008)
DOI: 10.1002/jsfa
Radical-scavenging activity of Agaricus bisporus
Table 1. EC50 values of antioxidant properties of methanolic extracts from Agaricus bisporus strains X25, Bs0633 and Bs0118H
EC50 (mg mL1)
Antioxidant property X25 Bs0633 Bs0118H
Scavenging effect on DPPH2.79 ±0.09a 2.60 ±0.10b 1.69 ±0.04c
Scavenging effect on ABTS•+ 4.97 ±0.05a 3.47 ±0.24b 3.33 ±0.07b
Reducing power 3.37 ±0.03a 3.11 ±0.08a 1.76 ±0.27b
EC50 value: the effective concentration at which 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH) or 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic
acid cation radicals (ABTS•+) were scavenged by 50%; the absorbance was 0.5 for reducing power. EC50 values were obtained by interpolation from
linear regression analysis. Each value is expressed as mean ±standard deviation (n=3). Means with different letters within a row are significantly
different (P<0.05).
of the cream wild strain Bs0118H had the strongest
scavenging effect on DPPH radicals and the highest
reducing power. By comparison, EC50 values for BHA
were 8.8, 29.0 and 21.7 mg L1for scavenging of
DPPH, scavenging of ABTS•+ and reducing power
respectively. Our data are in agreement with a variation
in antioxidant properties of A. bisporus due to genetic
differences and strengthen the possibility of cultivar
improvement for this trait by breeding programmes.
Another factor of variation that was suspected was
the part of the mushroom considered. It is currently
observed that the biomass repartition between stipe,
cap and gills varies with the development of
the mushroom. Significant differences in radical-
scavenging activity between the parts could explain
some of the variation dependent on the period of
mushroom harvest. The scavenging effect on DPPH
and the reducing power were more efficient than
the scavenging effect on ABTS•+ to discriminate
the sections of the fruit bodies (Table 2). With the
lowest EC50 values, the antioxidant power of the
gills was always higher than that of the stipe and
the cap (Table 2). Higher concentrations of H2O2
have been measured in the gills than in other tissues
in some strains of A. bisporus.18 This mushroom
is characterised by pigmented lamellae in which
redox reactions are important. The scavenging effect
on DPPH radicals and the reducing power were
significantly stronger in the cap than in the stipe, but
the differences are small. The proportion of lamellae
and their discolouration are changing throughout the
development of the fruit bodies, and the relative
proportion of stipe and cap tissues depends on both
the strain and the cultivation conditions. Variations
in antioxidant activity dependent on the part and
the development stage of the mushroom have to be
investigated in order to improve the development of
A. bisporus as a nutraceutical.
Several studies have reported a positive relation-
ship between the phenolic content and antioxidant
activity in mushrooms.7,8,19,20 Total phenolic con-
tents measured in the present study varied from 62 to
95 µmol ferulic acid equivalents g1mushroom pow-
der (Table 3). In order to be compared with some
other studies, it was calculated that these values cor-
respond to 31 and 49 mg gallic acid equivalents g1
extract respectively. This is higher than the value of
23.5 mg g1obtained for Agrocybe cylindricea.21 In the
Table 2. EC50 values of antioxidant properties of methanolic extracts from stipe, cap and gills of Agaricus bisporus strain Bs0118H
EC50 (mg mL1)
Antioxidant property Stipe Cap Gills
Scavenging effect on DPPH1.93 ±0.03a 1.77 ±0.03b 0.82 ±0.02c
Scavenging effect on ABTS•+ 2.95 ±0.08a 2.90 ±0.11a 1.16 ±0.02b
Reducing power 1.39 ±0.06a 1.26 ±0.03b 0.58 ±0.01c
EC50 value: the effective concentration at which 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH) or 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic
acid cation radicals (ABTS•+) were scavenged by 50%; the absorbance was 0.5 for reducing power. EC50 values were obtained by interpolation from
linear regression analysis. Each value is expressed as mean ±standard deviation (n=3). Means with different letters within a row are significantly
different (P<0.05).
Table 3. Phenolic contents in methanolic extracts of Agaricus bisporus strains X25, Bs0633 and Bs0118H
Phenolic content (µmol ferulic acid equivalents g1)
Bs0118H
X25 Bs0633 Total Stipe Cap Gills
61.93 ±11.33d 95.01 ±10.86b 80.16 ±12.89c 68.31 ±8.95d 61.93 ±11.33d 224.39 ±15.90a
Each value is expressed as mean ±standard deviation (n=9). Means with different letters are significantly different (P<0.05).
J Sci Food Agric 88:970 975 (2008) 973
DOI: 10.1002/jsfa
J-M Savoie, N Minvielle, ML Largeteau
present study the brown wild strain Bs0633 had the
highest phenolic concentration in the extract and the
lowest antioxidant properties. Phenolic compounds
coming from the brown pileipellis apparently had no
effect on the development of antioxidant properties.
This is in agreement with the negative correlation
between the free phenolic content and antiradical effi-
ciency of fresh A. bisporus from four strains collected
at two dates observed by Czapski.16 This seems to be a
characteristic of A. bipsorus, but it does not signify that
some specific phenolic compounds do not contribute
to antioxidant activity. In contrast, by comparing dif-
ferent mushroom species, Lee and Jang22 proposed
that the total soluble phenolics contribute greatly to
the scavenging effects of a 75% ethanolic extract of A.
bisporus. Here the high antioxidant power of the gills
(Table 2) was associated with a threefold higher phe-
nolic content (Table 3). Our data suggest that some
phenolic compounds present in the gills could be the
main factors of the antioxidant activity of methano-
lic extracts from A. bisporus, even if this tissue is not
abundant.
Comparison of the present results with published
data on antioxidant activities in mushroom methanolic
extracts is difficult, because the extraction procedures,
the quantities of extracts used in the reaction
mixtures and the data expression are diverse. In
the present study, no concentration of the extracts
was performed and we used EC50 values, i.e. the
effective concentration (mg dried mushroom mL1)
at which DPPH radicals were scavenged by 50%. This
method appeared to be more efficient if we want
to compare a large number of strains or species.
In other studies with other mushrooms, methanolic
extracts had been concentrated and EC50 values used
were mg dry matter in methanolic extract mL1,
with extraction yields around 30%. Consequently, a
concentration of 10 mg mushroom mL1is equivalent
to a concentration of 3 mg dry matter extracted
by methanol mL1in the other studies. With
converted EC50 values ranging between 0.51 and 0.84,
methanolic extracts of A. bisporus had antioxidant
properties lower than A. blazei with an EC50 value
of 0.2621 but higher than Dictyophora indusiata (basket
stinkhorn) with an EC50 value of 2 and higher than
Grifola frondosa (maitake), Hericium erinaceus (lion’s
mane) and Tricholoma giganteum (white matsutake)
with EC50 values of 4.5.23 Huang et al.21 calculated
an EC50 value based on dried samples of Agrocybe
cylindricea fruit bodies and obtained 1.64, which is
close to the value obtained for the cream wild strain
of A. bisporus. For the reducing power, their converted
EC50 value was double that obtained here. Thus,
considering this comparison of mushroom methanolic
extracts, A. bisporus could be classified with the group
of mushrooms with excellent potential antioxidant
activities proposed by Mau et al.23 By comparing
the antioxidant activities in 75% ethanolic extracts of
A. bisporus, Volvariella volvacea, Flammulina velutipes,
Pleurotus ostreatus and Lentinula edodes, Lee and Jang22
observed that A. bisporus had the highest scavenging
activities of DPPH,ABTS
•+ and H2O2.
Activities of free radical-processing enzymes in
water extracts
The primary function of antioxidant properties is
to prevent cell damage induced by ROS. Under
normal conditions, ROS are cleared from the cell by
the action of SOD, which catalyses the conversion
of O•−
2to H2O2;H
2O2is then decomposed in
the presence of catalase. In addition, glutathione
peroxidase catalyses the peroxidation of reduced
glutathione. Reduced glutathione is generated by
glutathione reductase.
In water extracts of A. bisporus, glutathione per-
oxidase activities were up to eight times higher than
glutathione reductase activities and no difference was
observed between strains (Table 4). Glutathione per-
oxidase activity was apparently not limiting for free
radical processing, but it was dependent on the gener-
ation of reduced glutathione by glutathione reductase.
Glutathione reductase and catalase activities were at
their highest levels in the water extract of the brown
wild strain Bs0633 (Table 4), whereas this strain had
the middle position for antioxidant activity in its
methanolic extract (Table 1). The only significant dif-
ferences in free radical-processing enzymes between
the three parts of the mushroom were higher catalase
activity in the gills and lower gluthatione reductase in
the stipe (Table 5). In an attempt to quantify SOD
activity by the inhibition of NBT reduction by O•−
2
generated by light oxidation of riboflavin, we obtained
inversely a 40 50% increase in NBT reduction. This
was probably due to the high NBT reduction activ-
ity of the gills, which gave an increase of 185%,
whereas no significant variation in NBT reduction
was observed in the stipe and the cap. The absence
of SOD could be due both to problems during the
extraction and to the interference of the reducing
power present in the water extracts during the assay.
This reducing power, which was predominant in the
gills (Table 2), was associated with the total phenolic
content.
Table 4. Activities of free radical-processing enzymes in water extracts from Agaricus bisporus strains X25, Bs0633 and Bs0118H
Antioxidant enzyme activity X25 Bs0633 Bs0118H
Catalase (nmol H2O2min1mg1)0.49 ±0.01b 0.59 ±0.02a 0.56 ±0.08ab
Glutathione reductase (µmol min1mg1)1.57 ±0.13ab 1.76 ±0.09a 1.41 ±0.17b
Glutathione peroxidase (µmol min1mg1)12.97 ±1.30a 13.65 ±1.52a 13.13 ±1.36a
Each value is expressed as mean ±standard deviation (n=3). Means with different letters within a row are significantly different (P<0.05).
974 J Sci Food Agric 88:970975 (2008)
DOI: 10.1002/jsfa
Radical-scavenging activity of Agaricus bisporus
Table 5. Activities of free radical-processing enzymes in water extracts from stipe, cap and gills of Agaricus bisporus strain Bs0118H
Antioxidant enzyme activity Stipe Cap Gills
Catalase (nmol H2O2min1mg1)0.42 ±0.02b 0.56 ±0.06b 0.72 ±0.02a
Glutathione reductase (µmol min1mg1)0.98 ±0.15c 3.81 ±0.13a 3.29 ±0.23b
Glutathione peroxidase (µmol min1mg1)12.03 ±1.66a 12.08 ±1.13a 13.23 ±0.02a
Each value is expressed as mean ±standard deviation (n=3). Means with different letters within a row are significantly different (P<0.05).
CONCLUSION
Activities of free radical-processing enzymes, including
enzymes of the ascorbate/glutathione cycle, are mea-
surable in A. bisporus fruit bodies and may contribute
to the antioxidant activity, but no significant variation
between strains was observed. The radical-scavenging
properties of compounds soluble in methanol are sig-
nificant and vary with the strain and with the part of
the fruit body studied. The results presented here indi-
cate that the premier cultivated mushroom, the white
button mushroom, might be beneficial for antioxidant
protection of the human body. Potentialities exist for
improving this property by improving cultivated strains
in breeding programmes using the variability present
in wild strains. On the other hand, the definition of the
optimal stage of harvest with the choice of the tissue
for application in the food industry would improve the
efficiency of A. bisporus as a functional food.
ACKNOWLEDGEMENT
We are grateful to Axelle Bouder for excellent technical
assistance.
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DOI: 10.1002/jsfa
... respectively. The higher brow the stipes may be owing to higher phenolic content and higher PPO activity in th compared with the cap, as widely reported in the literature [7,37,38]. L* values were above 80 during all storage periods, except L* values of EOs125 that were s lower than 80 on day 12. These L* values may be regarded as acceptable in acco with published criteria [9,39], which considered L* values above 80 in mushroom be acceptable. ...
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