全 文 ：DOI：10.3969/j：issn.2095-1191.2012.05.641
南方农业学报 JOURNAL OF SOUTHERN AGRICULTURE 2012，43（5）：641-648
ISSN 2095-1191；CODEN NNXAAB http：//www.nfnyxb.com
Received date：2012-03-15
Foundation item：Guangxi Scientific and Techonological Plan Research Foundation （No. 1010006-5）； Scientific and Technological
Development Research Foundation from Guangxi Academy of Agricultural Sciences（Grant No.201036）
Biography：* for corresponding author: LUO Rui-hong（1970-）， Ph.D， professor， research interest：Cultivation and breeding of horti-
cultural crops， E-mail：luoruihong@gxaas.net. LI Yi-wei（1983-）， research interest： Cultivation and breeding of horticultural
crops, E-mail：lywei@gxaas.net
苹婆（Sterculia nobilis Smith）种胚营养
及保健性评价
李一伟，陆玉英，陈香玲，任 惠，苏伟强，刘业强，罗瑞鸿*
（广西农业科学院园艺研究所，南宁 530007）
摘要：【目的】研究华南原产的一种木本粮用果树苹婆可食部分——种胚的营养和人体保健性，为推广应用苹婆
提供科学依据。【方法】以广西不同产地来源苹婆GXPN01和GXDX01为材料，对其种胚营养成分进行测定，并通过测定
其多酚提取物的还原力和金属螯合力以及对DPPH自由基、羟自由基和超氧阴离子自由基清除能力，了解其抗氧化活
性。【结果】苹婆种胚营养成分以淀粉和蛋白质为主，含有丰富的脂肪、维生素、多酚、氨基酸和微量元素（Ca，Fe，
Zn），维生素C和维生素E含量明显高于其他维生素。此外，苹婆种胚多酚物质（尤其是类黄酮）含量高，并表现较强的
DPPH自由基清除能力、还原力、金属螯合力以及羟自由基和超氧阴离子自由基清除能力。【结论】苹婆种胚具有较高
的营养价值和包括较强的抗氧化能力在内的保健作用，苹婆是一种具有较高开发价值的木本粮用果树。
关键词：苹婆；营养成分；多酚提取物；抗氧化
Nutritional and health care valuation of seed embryo
Sterculia nobilis Smith
LI Yi- wei，LUYu- ying，CHENXiang- ling，RENHui，SUWei- qiang，LIUYie- qiang，
LUORui- hong*
（Horticultural Research Institute，Guangxi Academy of Agricultural Sciences，Nanning 530007，China）
Abstract： 【Objective】To provide scientific basis for extention of a South China origin woody grain potential
plant， Steculia nobilis Smith （SNS）， its seed embryo， the edible part of the plant was investigated on the characteris-
tics of nutrition and health care. 【Method】A comprehensive research was performed to determine nutritional compositions
and antioxidant activities of polyphenols in seed embryo of two kinds of SNS （GXPN01 and GXDX01）. 【Result】The
results indicated that the nutrient compositions of SNS seed embryo mainly consisted of starch and protein， and exhibited
rich fat， starch， vitamin， polyphenol， amino acid and trace elements（Ca， Fe， Zn）， and vitamin C and vitamin E
contents were considerably higher than other vitamins. Additionally， SNS seed embryo contained considerable polyphenols
（especially flavonoids）， which possessed stronger antioxidant potential by evaluating reducing power， metal chelating
capacity and radical-scavenging activity of 1，1-diphenyl-2-picrylhydrazyl （DPPH）， and hydroxyl radical- and superoxide
anion-scavenging activity. 【Conclusion】Sterculia nobilis Smith is strongly recommended woody food plant for its nutritional
seed embryo with health care results including antioxidant activities.
Key words： Sterculia nobilis Smith； seed embryo； nutritional compositions； content； antioxidant activities
CLC number：S759.3 Document code：A Article：2095-1191（2012）05-0641-08
Sterculia nobilis Smith （SNS ） ， a woody plant
indigenous to southern China， belongs to the family
Sterculiaceae. It is often planted as a garden tree in
Taiwan， southeastern Fujian， southern Guangdong，
Guangxi and Yunnan in China. It also sporadically
distributes in India， Vietnam， Indonesia， Malaysia，
Sri Lanka and Japan， etc. Although SNS has strong
adaptation and high commercial value， a large scale
cultivation is absent presently. Sterculia is a genus
colloquially termed the tropical chestnuts. Some of
Sterculia species， such as Sterculia foetida and
Sterculia nobilis， are rich in polyphenols in their
南 方 农 业 学 报
leaves or nuts （Ramachandran Nair et al.， 1977； Xia
et al.， 2009）， and therefore serve as the good natu-
ral medicines. SNS nut and follicle are often used as
the traditional Chinese medicines for treating gas-
troenteric disorder and bloody flux.
The ripe SNS nut has a vermeil shell enwrapping
1-5 brown seeds. The shell will automatically split
when SNS nut matures. After removing the vermeil
shell and the brown seed capsule from the seed， a
pale yellow or creamy white seed embryo appears.
The seed embryo is often used for dish in local diet.
Additionally， the SNS lumber and bark can be uti-
lized as the raw materials for furniture and paper.
Owing to above benefits， SNS deserves attention and
exploitation. The previous researches on this plant fo-
cused largely on its landscape gardening function. Up
to now， little information is available on evaluation of
nutritional quality and antioxidant activity of SNS
nut， and the more investigation is required prior to
further development of this nut. Actually， SNS nut
contains a great quantity of protein， fiber， vitamins，
amino acids and trace elements. It is rich in polyphe-
nols with antioxidant activities， which play the im-
portant roles to human health.
In biological system， the oxidative stress has
been associated with the pathogenesis of many human
diseases such as cancer， heart disease， hypertension
and kidney disease （Karp and Koch， 2006； Mariani
et al.， 2005）. The application of natural antioxidants
from food sources can improve current treatments for
these diseases. Polyphenols in some nuts， such as
walnut （Anderson et al.， 2001）， Chinese water chestnut
（You et al.， 2007）， cacao beans （Padilla et al.， 2008），
cashew nut （Kamath and Rajini， 2007）， hazelnuts and
pistachios （Arcan and Yemenicio lu， 2009）， exhibit
the strong antioxidant activity and possess the ability
to scavenge both active oxygen species and elec-
trophiles （Robards et al.， 1999）. Just like other nuts，
SNS nut is also a good resource of natural antioxidant
because of its significant amount of polyphenols， and
thus it is worthwhile to investigate this nut detailedly
and throughly. The objective of the present study was
to evaluate nutritional quality and antioxidant activity
of polyphenol extracts from SNS nut. The study is
helpful to elucidate health benefit of SNS nut so as to
further exploit and introduce it into more areas.
1 Materials and methods
1. 1 Plant materials
Two kinds of SNS seed embryo （100 mature
samples every kind of nut）， GXPN01 and GXDX01，
were respectively harvested from orchards in Pingnan
and Daxin towns of Guangxi in August， 2010. The
nuts without any defects and diseases were selected，
the shells were removed， while the seed embryos
were collected， weighed and then stored at -20℃
until further extraction and analysis.
The used chemicals and reagents included com-
mercial standards 1 ， 1 - diphenyl - 2 - picrylhydrazyl
（DPPH） and 2，4，6-tripyridyl-s-triazine （TPTZ），
gallic acid， rutin， which were purchased from Sig -
ma-Aldrich （St. Louis， MO， USA）. Commercial an-
tioxidant ascorbic acid was purchased from Aladdin
Reagent Inc. （Shanghai， China）. Other chemicals and
reagents were of analytical grade.
1. 2 Analysis of nutr itional compositions
SNS seed embryos （20 g） were homogenized in
distilled water. The homogenate was filtered through
double layers of muslin. The filtrate was centrifuged
at 3500 × g for 15 min and then the supernatant was
collected as sample to analyze the contents of total
soluble solids， total protein， total fat， ash， starch，
vitamin and amino acid. Total soluble solids content
was determined at 20℃ with a hand -refractometer
（CANY Co.， Shanghai， China）. Total protein content
was estimated by Kjeldahl method and total fat con-
tent was assayed by Soxhlet method described by
AOAC （1990）. The ash content was determined by
the ignition method using the crucible and muffle fur-
nace. The starch was assayed by enzyme hydrolysis
method. Trace elements were evaluated by atomic ab-
sorption spectrometry （Thermo， N.Y.， USA）. Vitamin
contents were assayed by the methods described by
Kenneth and AOAC （1990）. Amino acid contents were
determined using an automatic acid analyzer （Hitachi，
Tokyo， Japan）. All data was expressed on a fresh weight
（FW） basis.
1. 3 Extraction of polyphenols
Polyphenols were extracted according to the
modified method of Zhang et al. （2000）. At 20℃， 50
g of SNS seed embryos was chopped into pieces and
then extracted for 30 min using 100 mL of methanol/
acetone/water （3.5 ∶3.5 ∶3.0， v/v/v） containing 1%
JOURNAL OF SOUTHERN AGRICULTURE642· ·
formic acid. The extraction was performed twice in a
shaking incubator （ZHWY-200B， Zhicheng Analyti-
cal Co.， Shanghai， China）. All extracts were com-
bined and filtered through two layers of cheesecloth.
The collected filtrate was centrifuged for 15 min at
7000 × g. The supernatant was collected and evapo-
rated under vacuum at 40℃ to remove methanol and
acetone. Lipophilic pigments were then eliminated
from the aqueous phase by two successive extractions
in a separatory funnel with two - fold volume of
petroleum ether. The aqueous phase was collected，
evaporated and dried under vacuum at 35℃ . The
residue was re-dissolved in 10 mL of ethanol and
used as polyphenol sample.
Total phenolic content was determined using the
Folin-Ciocalteau method described by Singleton and
Rossi （1965） with some modifications. At the room
temperature， 1 mL of 10 -fold diluted extracts by
methanol/acetone/water （3.5∶3.5∶3.0 v/v/v） containing
1% formic acid was thoroughly mixed with 1 mL of
Folin-Ciocalteau reagent and set for 3 min. Then， 3
mL of sodium carbonate （75 g/L） was added into the
mixture and allowed to stand for 2 h. Sample aliquots
were filtered through the 0.45 μm filter prior to the
determination of total phenolics using a UV-Visible
Spectrophotometer （UV-1700，Shimadzu，Kyoto，Japan）
monitoring at 760 nm. Total phenolic content was
standardized against gallic acid and expressed as mi-
crogram per milliliter of gallic acid equivalents （GAE）.
Total flavonoid content was determined accor-
ding to the modified method of Lin and Tang （2007）.
At the room temperature， 1 mL of polyphenol -
ethanol solutions was thoroughly mixed with 0.3 mL
of 5% sodium nitrite and set for 6 min. Then， 0.3
mL of 10% aluminum nitrate was added into the mix-
ture. After 6 min， 4 mL of 4% sodium hydroxide was
blended into the mixture. Sample aliquots were al-
lowed to stand for 2 h before the determination of to-
tal flavonoid content using the spectrophotometer
monitoring at 510 nm. Total flavonoid content was
standardized against rutin and expressed as microgram
per milliliter of rutin equivalents.
1. 4 Antioxidant activity assays
1. 4. 1 DPPH radical -scavenging activity The
DPPH-scavenging activity was estimated by the mod-
ified method of Sun etal. （2007）. Aliquots （0.5 mL）
of 0 （control）， 25， 50， 100， 250， 500 and 1000 μg/mL
of polyphenol extracts dissolved in ethanol were
added into 2.5 mL of 0.2 mM DPPH solution in
ethanol. The absorbance at 517 nm of samples was
measured after 30 min of incubation at 26℃ in the
dark . DPPH- scavenging activity （% ）=1-［（A-B）/
A0］ ×100， where A =absorbance of sam ple， B =ab-
sorbance of 0.5 mL of polyphenol extracts+2.5 mL of
ethanol， and A0=absorbance of control. The calcula-
tion of 50% inhibition concentration （IC50） to sca-
venge 50% of radical was obtained according to the
method of Senevirathne et al. （2006）. Ascorbic acid
was used as positive control.
1. 4. 2 Ferric reducing/antioxidant power （FRAP）
FRAP assay was conducted by the modified method of
Benzie and Strain（1996）. The working FRAP reagent
was produced by mixing 300 mM acetate buffer （pH
3.6）， 10 mM TPTZ solution and 20 mM FeCl3·6H2O
in a 10/1/1 ratio prior to use and then heated to 37℃
in a water bath. A total of 3 mL of FRAP reagent was
added to a testtube and a blank reading was then
taken at 593 nm using the spectrophotometer. A total
of 100 μL of 0~1000 μg/mL polyphenol extracts dis-
solved in ethanol and 300 μL of distilled water were
added to the cuvette. After the addition of the FRAP
reagent， a second reading at 593 nm was performed
after 40 min of incubation at 37℃ in a water bath.
The changes in absorbance after 40 min from the ini-
tial blank reading were compared with the standard
curve . Standards of known Fe （ II ） concentrations
were used at 0-1000 μM and then a standard curve
was prepared by plotting the FRAP value of each
standard versus its concentration. The result was ex-
pressed as the concentration of antioxidant exhibiting
a ferric reducing ability per gram of sample（μM/g）.
1. 4. 3 Metal chelating capacity The metal chelating
capacity （MCC） was determined by the modified method
of Dinis et al. （1994）. Aliquots （1 mL） of 0 （control），
25， 50， 100， 250， 500 and 1000 μg/mL polyphenol
extracts dissolved in ethanol were added in 2.8 -mL
distilled water and then mixed with 50 μL of 2 mM
FeCl2·4H2O and 150 μL of 5 mM ferrozine. The mix-
ture was shaken at 120 × g. After 20 min， the Fe
（II） was monitored by measuring the formation of
ferrous ion-ferrozine complex at 562 nm. The metal
chelating capacity was calculated as follows： chelating
capacity （% ）=（1- absorbance of sample/absorbance
of control） × 100.
Li et al.：Nutritional and health care valuation of seed embryo Sterculia nobilis Smith 643· ·
南 方 农 业 学 报
1. 4. 4 Hydroxyl radical -scavenging activity The
hydroxyl radical -scavenging activity was measured
according to the modified method of Lee et al. （2002）.
A 0.4-mL aliquot of 0 （control）, 50, 100, 250, 500
and 1000 μg/mL polyphenol -ethanol solutions was
mixed with 1 mL of reaction buffer （containing 100.0
μM FeCl3, 104.0 μM EDTA, 2.5 mM H2O2, 2.5 mM
deoxyribose, 100.0 μM ascorbic acid）. The reaction
solutions were incubated for 1 h at 37℃ and then 1
mL of 0.5% thiobarbituric acid （dissolved in 0.025 M
NaOH） and 1 mL of 2.8% trichloroacetic acid were
added into the mixtures. The mixtures were incubated
for 30 min at 80℃ and cooled in ice bath. The ab-
sorbances of samples were measured at 532 nm. Hy-
droxyl radical-scavenging activity（%）=（1-absorbance
of sample/absorbance of control）×100.
1. 4. 5 Superoxide anion-scavenging activity The
superoxide anion -scavenging activity was measured
according to the modified method of Siddhurajua et
al. （2002）. A 0.4-mL aliquot of 0 （control）, 50, 100,
250, 500 and 1000 μg/mL polyphenol-ethanol solu-
tions was mixed with 3 mL of reaction solution （con-
taining 1.3 μM riboflavin， 13.0 mM methionine，
63.0 μM NBT， 100.0 μM EDTA， 0.05 M pH 7.8
sodium phosphate buffer） and then incubated for 15
min under the 4000 lux illumination at 25℃. The ab-
sorbances of samples were measured at 560 nm. Su-
peroxide anion-scavenging activity（%） =（1- absorbance
of sample/absorbance of control） ×100.
1. 5 Data analysis
All experiments were performed in triplicate （n=
3）， and an ANOVA test （using SPSS 13.0 statistical
software, SPSS Inc.， Chicago， USA） was used to
compare the mean values of each treatment. Signifi-
cant differences between the means of parameters
were determined by using the LSD test（P<0.05）. The
results represented mean±standard error（SE） of three
replicated determinations.
2 Results and discussion
2. 1 Nutritional compositions
In the present study, total soluble solids, starch,
total protein and total fat contents were no significant
difference in both SNS seed embryos （Tab.1）. Un-
der the same conditions, the contents of above nutri-
tional compositions in both SNS seed embryos were
obviously higher than those in some nut kernels with
similar taste from China， such as Chinese chestnut
（cv. Hubei; Total soluble solid, starch and total pro-
tein contents were 18.036±1.769°Brix， 45.908±4.18
g/100 gFW and 8.608 ± 1.16 g/100 gFW） （Chen
et al.， 2000） and Carya hunanesis Cheng （Total solu-
ble solid, total protein and total fat contents were
3.51°Brix， 8.18 g/100 gFW and 56.57 g/100 gFW）
（Fan et al.， 2007）. Trace elemental levels in SNS
seed embryos were also listed in Tab.1 on a FW basis.
Generally speaking, the contents of calcium （Ca）， fer
rum （Fe） and zinc （Zn） were very high in both SNS
seed embryos. The contents of Ca and Fe in GXPN01
were obviously higher than those in GXDX01, while
the manganese （Mn） content in GXPN01 was signifi
cantly lower than that in GXDX01. Additionally， the
total amino acid contents was determined accounting
for an average of 2.31 g/100 gFW for GXPN01 and
2.41 g/100 gFW for GXDX01 （Tab.2）. There was no
obvious difference in individual amino acid content
in both SNS seed embryos. From Tab.2， vitamin C
and vitamin E contents were considerably high in
comparison with other vitamins in both SNS seed em-
bryos. These two vitamins in GXDX01 were remar-
kably superior to those in GXPN01.
2. 2 Determination of total phenolic and total
flavonoid contents
Total phenolic and total flavonoid contents in
SNS seed embryos were calculated as 332.69 ± 3.97
μg/g GAE and 1.97±0.01 mg/g Rutin for GXDX01,
while 471.69±40.12 μg/g GAE and 2.03±0.48 mg/g
Rutin for GXPN01. The total phenolic contents in two
SNS seed embryo were lower than that in Chinese
chestnut （1620±10 μg/g GAE）， but the total flavonoid
contents in both were higher than that in Chinese
chestnut （0.059±0.002 mg/g Rutin）（Qi et al.， 2009）.
Tab.1 Contents of nutritional compositions in nut kernels
of Sterculia nobilis
Nutritional compositions
Total soluble solids（°Brix）
Ash (g/100 gFW)
Starch (g/100 gFW)
Total protein (g/100 gFW)
Total fat (g/100 gFW)
Total phenolic (μg/gGAE)
Total flavonoids (mg/g Rutin)
Cu (mg/gFW)
Fe (mg/gFW)
Zn (mg/gFW)
Mn (mg/gFW)
Mg (mg/gFW)
Ca (μg/gFW)
GXDX01
36.82±0.02
3.8±0
62.85±0.05
18.36±0.02
2.0±0
332.69±3.97
1.97±0.01
12.34±0.07
72.32±0.02
33.73±0.50
14.97± 0.05
0.1545±0.0005
420±14.14
GXPN01
25.75±0.03
4.8±0
58.0±0.3
22.29±0.03
2.35±0.05
471.69±40.12
2.03±0.48
13.94±0.06
201.39±1.84
34.97±0.03
6.93±0.01
0.0985±0.0025
575±21.21
JOURNAL OF SOUTHERN AGRICULTURE644· ·
Fig.1 Scavenging activity（%）of polyphenol extracts from SNS
nuts on DPPH radical
Tab.2 Contents of vitamin and amino acid in nut kernels
of Sterculia nobilis a
Amino acids
（g/100 g FW）
Total amino acid
Aspartic acid
Threonine
Serine
Glutamic acid
Proline
Arginine
Glycine
Alanine
Cysteine
Valine
Methionine
Isoleucine
Leucine
Tyrosine
Phenylalanine
Lysine
Histidine
Tryptophan
GXDX01
2.41
0.28
0.10
0.09
0.33
0.14
0.35
0.12
0.14
0.02
0.13
0.01
0.09
0.15
0.12
0.08
0.21
0.05
0.02
GXPN01
2.31
0.29
0.09
0.08
0.31
0.08
0.34
0.11
0.11
0.02
0.13
0.01
0.09
0.15
0.11
0.08
0.19
0.05
0.02
Vitamins
（μg/100 g FW）
Vitamin A
Vitamin B2
Vitamin C
Vitamin D
Vitamin E
GXDX01
0.82
61.6
8360
3.50
580
GXPN01
0.98
75.2
6090
2.96
480
a The contents of amino acids and vitamins were assayed by Center for
Analysis and Test Research, Guangxi Zhuang Autonomous Region, and the
results represented mean of three replicated determinations
Li et al.：Nutritional and health care valuation of seed embryo Sterculia nobilis Smith
Polyphenols， especially flavonoids， were closely related
to antioxidant activities of SNS seed embryo. Many
researches have reported that polyphenols such as
flavonoids exhibit strong free radical scavenging ac
tivities and antioxidant capabilities in vivo and in vitro，
suggesting that they play an important role in impro-
ving immunity， inhibiting mutagenesis or preventing
cancer， inflammatory and cardiovascular diseases
（Lin et al.，1999；Yilmaz and Toledo，2004）. Through
the present study， SNS seed embryos contained con-
siderable polyphenols， especially flavonoids， and there-
fore the nuts probably possessed strong antioxidant
potential， which would exhibit biologic effects in terms
of health promotion.
2. 3 Antioxidant activity
2. 3. 1 DPPH radical -scavenging activity Free
radical - scavenging activity is one of the known
mechanisms by which antioxidants inhibit lipid pero-
xidation （Duan et al.， 2007）. The DPPH radical-sca-
venging activity has been extensively used for screen-
ing antioxidants from fruits， vegetables and nuts. From
Fig.1， the polyphenol extracts from SNS kernels ex-
hibited strong DPPH radical -scavenging activity. In
the low concentration range from 0 to 250 μg/mL， no
significant difference （P>0 .05 ） in the scavenging
activity was observed and polyphenol of GXPN01 and
GXDX01 showed similar DPPH radical -scavenging
capabilities to the strong commercial antioxidant
ascorbic acid. However， in the high concentration
range from 500 to 1000 μg/mL， ascorbic acid pre-
sented more intense scavenging activity than polyphe-
nol of GXPN01 and GXDX01. In comparison with two
SNS polyphenol extracts， the scavenging activity of
GXDX01 polyphenol was somewhat higher than that
of GXPN01 at high concentration（e.g. at 1000 μg/mL，
the DPPH radical -scavenging activity of GXDX01
and GXPN01 polyphenol were around 75.06 and
67.29%， respectively）. The calculation of IC50 further
confirmed that GXDX01 polyphenol （ IC50 =207 .183
μg/mL） possessed higher DPPH radical -scavenging
activity than GXPN01 （IC50=246.206 μg/mL）. In ad-
dition， in the present study， the DPPH radical-sca-
venging activity was linearly correlated with the con-
centrations of SNS polyphenol extracts and ascorbic
acid in the low concentration range from 0 to 100 μg/
mL. The corresponding correlation coefficients were
0.9794 for GXPN01 polyphenol （y=0.3717x+2.0749），
0.9638 for GXDX01 polyphenol （y=0.415x+1.2182）
and 0.9881 for ascorbic acid（y=0.4557x+1.8338）.
2. 3. 2 FRAP assay Reducing power is widely used
in evaluating the antioxidant activity of polyphenols
The reducing property is generally associated with the
presence of reductones which exert antioxidant action
by breaking the free radical chains via hydrogen atom
donation （Duh， 1998）. Reductones are also reported
to prevent peroxide formation by reacting with certain
precursors of peroxide （Rathee et al.， 2007）. As shown
in Fig.2， the concentration-dependent scavenging ef-
fected by SNS polyphenol extracts and the positive
control （ascorbic acid） was evident. The reducing pow-
Concentration（μg/mL）
DP
PH
sc
av
en
gi
ng
ac
tiv
ity
645· ·
南 方 农 业 学 报
Fig.3 Metal chelating capacity of polyphenol extracts from SNS
nuts
Fig.4 Hydroxyl radical scavenging capacity of polyphenol extracts
from SNS nuts
JOURNAL OF SOUTHERN AGRICULTURE
Fig.2 Reducing power（FRAP values）of polyphenol extracts from
SNS nuts
er of ascorbic acid and GXDX01 polyphenol had no
significant difference （P>0.05）， while was significantly
higher （P<0.05） than that of GXPN01 polyphenol from
100 μg/mL. Furthermore， the FRAP value was posi-
tively correlated with the concentrations of SNS
polyphenol extracts and ascorbic acid in the ranges
from 0 to 1000 μg/mL. The corresponding correlation
coefficients were deter mined to be 0 . 9885 for
GXPN01 polyphenol （y=1.3765x+55.796）， 0.9441
for GXDX01 polyphenol （y=1.6541x+128.53） and
0.9396 for ascorbic acid （y=1.6621x+134.97）.
2. 3. 3 Metal chelating capacity The metal chela-
ting capacity （MCC） depends on the ability of sam-
ples to chelate transition metals， which possess the
ability to catalyze hydrogen peroxide decomposition
and Fenton -type reactions. As shown in Fig.3， the
MCC of GXPN01 polyphenol was slightly lower than
that of EDTA （positive control）， but significantly
higher （P<0.05） than that of GXDX01 polyphenol
from 100 μg/mL. In addition， the MCC was linearly
correlated with the concentrations of SNS polyphenol
extracts and EDTA in the low concentration range
from 0 to 100 μg/mL. The corresponding correlation
coefficients were 0.9132 for GXPN01 polyphenol （y=
0.60564x +5.0783）， 0.8709 for GXDX01 polyphenol
（y=0.33023x+4.4841） and 0.9855 for EDTA （y=
0.7462x-1.6314）.
2. 3. 4 Hydroxyl radical -scavenging activity Hy-
droxyl radical is one of the most effective free radi-
cals amongst all the oxygen free radicals， so it has
been a very important research field in order to find
some natural antioxidants or scavengers which having
strong scavenging effects on oxygen free radicals es-
pecially on hydroxyl radical （Adom and Liu， 2002）.
To determine the hydroxyl radical scavenging capaci-
ty， the effect of polyphenol extracts on hydroxyl radi-
cal generated by Fe3+ ions was analyzed by evaluating
the degree of deoxyribose degradation. From Fig.4，
there was no significant difference （P>0.05） on hy-
droxyl radical -scavenging activity between GXPN01
polyphenol and GXDX01 polyphenol in the whole
concentration range. By the calculation， the IC50 of
GXDX01 polyphenol （IC50 = 237.234 μg/mL） was
slightly lower than that of GXPN01 polyphenol （IC50
=257.335 μg/mL）， suggesting that the hydroxyl radical-
scavenging activity of GXDX01 polyphenol was
slightly higher than that of GXPN01 polyphenol.
Ascorbic acid showed the highest scavenging activity
（ IC50 =130.784 μg/mL） comparing with both SNS
polyphenol extracts. Additionally， the hydroxyl radi-
cal-scavenging capacity was linearly correlated with
the concentrations of SNS polyphenol extracts and
ascorbic acid in the low concentration range from 0 to
100 μg/mL. The corresponding correlation coefficients
were 0.9005 for GXPN01 polyphenol （y=0.40097x+
3 . 20071 ） ， 0 . 9544 for GXDX01 polyphenol （ y =
0.43119x + 2.5635） and 0.8478 for ascorbic acid （y=
0.48375x + 4.06756）.
Re
du
ci
n
po
we
r（
μm
ol
/g）
Concentration（μg/mL）
Concentration（μg/mL）
M
et
al
ch
el
at
in
gc
ap
ac
ity（
%）
Concentration（μg/mL）
H
yd
ro
xy
lr
ad
ic
al
sc
av
en
gi
ng
ac
tiv
ity
646· ·
Li et al.：Nutritional and health care valuation of seed embryo Sterculia nobilis Smith
Fig.5 Superoxide anion- scavenging activity of polyphenol ex-
tracts from SNS nuts
2. 3. 5 Superoxide anion-scavenging activity Su-
peroxide anion radical plays an important role in
plant tissues， which involves in the formation of other
cell-damaging free radicals. Superoxide anion radical
is the intermediary metabolite （Blokhina et al.， 2003）.
The relative scavenging activity of polyphenol extracts
on superoxide radical is shown in Fig.5. Generally，
no significant difference （P>0.05） on the scavenging
activity was observed between GXPN01 polyphenol
(IC50 =888.373 μg/mL） and GXDX01 polyphenol
(IC50 =935.246 μg/mL） in the whole concentration
range. Ascorbic acid （IC50=600.451 μg/mL） showed
the highest superoxide anion -scavenging activity ，
comparing with both SNS polyphenol extracts. In ad-
dition， the superoxide anion-scavenging activity was
linearly correlated with the concentrations of SNS
polyphenol extracts and ascorbic acid in the low con-
centration range from 0 to 100 μg/mL. The corre-
sponding correlation coefficients were 0.9767 for GX-
PN01 polyphenol （y=0.28541x-0.06879）， 0.8887
for GXDX01 polyphenol （y=0.25599x+1.15501） and
0.9504 for ascorbic acid （y=0.32366x+2.74328）.
3 Conclusions
By the present study， the nutritional compositions
in two kinds of SNS seed embryo （GXPN01 and
GXDX01） were determined. The results indicated that
both SNS seed embryos exhibited significantly higher
contents of total soluble solids， starch， total proteins
and total fat comparing with several nuts with similar
taste from China. The trace elements Ca， Fe and Zn
contents were very high and the individual amino acid
content was no obvious difference in GXPN01 and
GXDX01 kernels. Vitamin C and vitamin E contents
were considerably high comparing with other vitamins
in both kernels. Additionally， SNS seed embryos con-
tained considerable polyphenols （especially flavonoids），
which possessed strong antioxidant potential. The an-
tioxidant activity analysis on polyphenol extracts from
both SNS seed embryos showed that， in certain con-
centration range， GXDX01 polyphenol possessed
higher DPPH radical-scavenging activity and reducing
power than GXPN01 polyphenol， while GXPN01
polyphenol had higher metal chelating capacity than
GXDX01 polyphenol. There was no significant diffe-
rence on hydroxyl radical-scavenging activity and su-
peroxide anion -scavenging activity between GXPN01
polyphenol and GXDX01 polyphenol in the whole
concentration range from 0 to 1000 μg/mL. The fur-
ther research is needed to investigate chemical struc-
ture and other bioactivity of SNS polyphenol. By
through investigation， the health benefit of SNS nut
can be elucidated so that it can be spread into more
areas.
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（责任编辑 韦莉萍；审校 李杨瑞）
648· ·