Hindawi Publishing Corporation
Journal of Biomedicine and Biotechnology
Volume 2010, Article ID 871379, 8 pages
doi:10.1155/2010/871379
Research Article
Antioxidant Capacities of Peel, Pulp, and Seed Fractions of
Canarium odontophyllum Miq. Fruit
K. Nagendra Prasad,1 Lye Yee Chew,1 Hock Eng Khoo,1 Kin Weng Kong,1
Azrina Azlan,1 and Amin Ismail1, 2
1 Department
of Nutrition and Dietetics, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia,
Serdang 43400, Selangor, Malaysia
2 Laboratory of Analysis and Authentication, Halal Products Research Institute, Universiti Putra Malaysia,
Serdang 43400, Selangor, Malaysia
Correspondence should be addressed to Amin Ismail, amin@medic.upm.edu.my
Received 3 February 2010; Accepted 25 August 2010
Academic Editor: Silvia R. Cianzio
Copyright © 2010 K. Nagendra Prasad et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
Antioxidant capacities of ethylacetate, butanol, and water fractions of peel, pulp, and seeds of Canarium odontophyllum Miq.
(CO) were determined using various in vitro antioxidant models. Ethylacetate fraction of peel (EAFPE) exhibited the highest total
phenolic (TPC), total flavonoid content (TFC), and antioxidant activities compared to pulp, seeds, and other solvent fractions.
Antioxidant capacities were assayed by total antioxidant capability, 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical activity, ferric
reducing antioxidant power (FRAP), and hemoglobin oxidation assay. Total phenolic content of ethylacetate fractions was
positively correlated with the antioxidant activity. This is the first report on the antioxidant activities from CO fruit fractions. Thus,
EAFPE can be used potentially as a readily accessible source of natural antioxidants and as a possible pharmaceutical supplement.
1. Introduction
Antioxidants are the compounds that when added to lipids
and lipid-containing foods can prolong the shelf-life by
retarding the process of lipid peroxidation during processing and storage. Synthetic antioxidants such as butylated
hydroxy toluene (BHT) have restricted usage in foods,
because it is reported to be carcinogenic [1]. Hence, the
importance for utilizing antioxidants from plant origin has
received much attention recently. Various extracts from fruits
have been recognized to possess beneficial effects against
free radicals in biological systems as natural antioxidants
[2]. Many studies have shown positive correlation of the
increased dietary intake of natural phenolic antioxidants
with the reduced coronary heart disease and cancer mortality, as well as with longer life expectancy [3].
Canarium odontophyllum Miq. belongs to the family
Burseraceae and is classified as a underutilized fruit due to
lack of promotion and as an economic potential which has
not been fully explored [4]. The fruit is found in the tropical
rain forest of Sarawak, Malaysia, and is commonly called
“dabai” and consumed by the local communities. The fruits
are oblong in shape (Figure 1(a)) measuring 3-4 cm and
weighing 10–13 g. The fruit peel is purple in color with
yellow pulp (Figure 1(b)) and a single three-angled seed
(Figure 1(c)). Pulp and seed contribute to bulk of the fruit
weight comprising 46% and 44% while peel constitutes 10%.
The fruits are highly seasonal (November-January) and hard
to be consumed as such. Hence, fresh fruits are usually
soaked in warm water for five to ten minutes to soften them
for consumption. The fruit is highly nutritious and rich in
minerals, proteins, carbohydrates, and fat [5].
For the first time, this study investigated the antioxidant
activities of C. odontophyllum fruit fractions, and demonstrated the potent bioactivities of the extracts suitable to be
used as natural antioxidants. Different fruit parts, namely
peel, pulp, and seeds were chosen in an attempt to make
systematic comparisons among their antioxidant capacities
and to identify the fraction with high antioxidant activity
for further studies. In addition, correlations between total
2
Journal of Biomedicine and Biotechnology
(a)
(b)
(c)
Figure 1: Fruits of Canarium odontophyllum (a), pulp (b), and seed (c). Unit of measurement is in cm.
phenolics, flavonoid content, and antioxidant capacities were
also determined.
concentrations. The extraction yields of peel, pulp, and seed
were 24.6, 18.4, and 15.1%, respectively.
2. Materials and Methods
2.4. Determination of Total Phenolic Content. Total phenolic
content of each fraction obtained by the above method
was determined according to the method of Singleton and
Rossi [6] and then expressed as milligram/gram gallic acid
equivalents (GAE). In brief, 100 µL-aliquot of the samples
(1 mg/mL) was added to 2 mL of 20 g/L Na2 CO3 solution.
After 2 minutes of incubation, 100 µL of 50% Folin-Ciocalteu
reagent was added and the mixture was then allowed to
stand for 30 min at 25◦ C. The absorbance was measured at
750 nm using a spectrophotometer (UV 1601, Shimadzu Co.,
Ltd., Kyoto, Japan). The blank consisted of all reagents and
solvents without the sample. The total phenolic content was
determined using the standard gallic acid calibration curve.
2.1. Plant Material. Fresh fruits of Canarium odontophyllum
Miq. (20 kg) at the mature stage were provided by Agriculture Research Centre, Department of Agriculture, Sarawak,
Malaysia. The fruits were transported in ice box by airmail
on the same day to Universiti Putra Malaysia. Fruits were
chosen for uniformity in shape and color, washed carefully
with tap water, and air dried. The fruit peel, pulp, and seeds
were manually separated, then dried in oven at 60◦ C for 24 h,
and finally they were grounded into powder using a blender.
The moisture content of the fresh peel, pulp, and seeds was
determined to be 65.5 ± 2.1, 53.5 ± 4.2, and 23.8 ± 1%,
respectively.
2.2. Chemicals and Reagents. 1,1-diphenyl-2-picrylhydrazyl
(DPPH), 2, 4, 6-tri (2-pyridyl)-l, 3, 5-triazine (TPTZ), aluminium chloride, quercetin, gallic acid, BHT, trichloroacetic
acid, thiobarbituric acid, sodium azide, Tris-HCl buffer,
phosphate buffer, and Hepes were obtained from SigmaAldrich Co. (MO, USA). Folin-Ciocalteu reagent and hydrogen peroxide were obtained from Merck (Darmstadt, Germany). All other chemicals and solvents used were of
analytical grade.
2.3. Extraction. Dried powder (10 g) of CO peel, pulp, and
seeds was extracted separately using a rotary shaker (Unimax
1010, Heidolph, Germany) at 4000 rpm with 100 mL of
50% ethanol at 30◦ C for 5 h. The extract was then filtered,
and concentrated using a rotary evaporator (Buchi, Flawil,
Switzerland). The concentrated extract was then partitioned
sequentially with 100 mL of ethyl acetate, butanol, and
water. The fractions obtained from peel, pulp, and seeds
were collected separately, concentrated, freeze dried, and
stored at –20◦ C until further use. All the freeze-dried
extracts were dissolved in 50% ethanol to get the appropriate
2.5. Determination of Total Flavonoid Content. Total flavonoid content of the fractions was measured following the
aluminum chloride colorimetric assay described by Liu et al.
[7]. An aliquot (2 mL) of the sample was mixed with 0.2 mL
of 5% sodium nitrite. After 5 minutes, 0.2 mL of 10%
aluminum chloride was added to the mixture. Following
6 minutes, 2 mL of 1 M sodium hydroxide were added
to the mixture. The final volume of the reaction mixture
was made up to 5 mL with 50% ethanol. Absorbance was
measured at 510 nm against a blank. The total flavonoid
content was determined using a standard curve of quercetin
(0–50 mg/mL) and the results were expressed as quercetin
equivalents.
2.6. Analyses of Antioxidant Activities
2.6.1. DPPH Radical Scavenging Activity. DPPH radical scavenging activities of the fractions were determined following
the method of Blois [8] with some modifications. Different
concentrations (5, 10, 20, and 40 µg/mL) of the fractions and
BHT were placed in different test tubes and were mixed with
1 mL of 0.2 mM DPPH (dissolved in methanol). The reaction
mixture was shaken vigorously and incubated at 28◦ C in
Journal of Biomedicine and Biotechnology
3
100
DPPH scavenging activity of
pulp fractions (%)
DPPH scavenging activity of
peel fractions (%)
100
75
50
25
0
0
5
10
20
Concentration (µg/mL)
40
75
50
25
0
0
5
10
20
Concentration (µg/mL)
40
(b)
(a)
DPPH scavenging activity of
seed fractions (%)
100
75
50
25
0
0
5
10
20
Concentration (µg/mL)
Ethylacetate
Butanol
40
Water
BHT
(c)
Figure 2: DPPH radical scavenging activity of Canarium odontophyllum peel fractions (a), pulp fractions (b), and seed fractions (c).
a dark room for 40 min. The control was prepared as above
without any extract, and methanol was used for the baseline
correction. The changes in absorbance were measured at
517 nm using a spectrophotometer. The inhibition of DPPH·
radicals was calculated as scavenging activity (%) = (Control
OD − sample OD / control OD) × 100.
2.6.2. Total Antioxidant Capacity by Phosphomolybdenum
Method. Total antioxidant capacities of the CO fractions
and BHT were determined by the method of Prieto et al.
[9]. An aliquot (0.1 mL) of the sample fractions at different
concentrations (5, 10, 20, and 40 µg/mL) was mixed with
1 mL of reagent solution (0.6 M sulphuric acid, 28 mM
sodium phosphate, and 4 mM ammonium molybdate). The
mixture was covered and incubated at 95◦ C for 90 min. After
the mixture was cooled, the absorbance was measured at
695 nm against blank. A typical blank solution contained
1 mL of reagent solution and the appropriate volume of
the same solvent used for dissolving the sample, and it was
incubated under the same conditions. The total antioxidant
activity was expressed as the absorbance value at 695 nm.
A higher absorbance value indicates a higher antioxidant
activity.
2.6.3. Ferric Reducing Antioxidant Power (FRAP) Assay.
Ferric reducing antioxidant power assay of sample extract
was performed according to method of Benzie and Strain
[10] with slight modifications. Working FRAP reagent was
prepared by mixing acetate buffer (300 mM, pH 3.6) : 10 mM
TPTZ solution in 40 mM HCL : 20 mM ferric chloride solution, in proportion of 10 : 1 : 1 (v/v/v). An aliquot (50 µL) of
appropriately diluted sample extract was mixed with 3 mL
of freshly prepared FRAP reagent and mixed thoroughly.
The reaction mixture was then incubated at 37◦ C for 30
minutes. Absorbance of the reaction mixture was read at
593 nm against a blank. A higher absorbance value indicates
higher antioxidant activity.
2.6.4. Hemoglobin Oxidation Assay. Fasting venous blood
(10 mL) from healthy volunteers (aged 20–30 years) were
collected in EDTA tubes (0.4 g/L). As described by Chu and
Liu [11], the plasma was centrifuged at 1600 x g for 20 min
4
Journal of Biomedicine and Biotechnology
a
1
Absorbance (695 nm)
Absorbance (695 nm)
1.2
a
0.8
0.6
0.4
0.2
a
a
b
c c
b
b
d c
b
c c
c c
0
1.2
a
1
a
0.8
0.6
0.4
0.2
a
a
b b c
b bc c
c b c
c
b
d
0
5
10
15
20
Concentration of peel fractions (µg/mL)
5
10
15
20
Concentration of pulp fractions (µg/mL)
(b)
Absorbance (695 nm)
(a)
1.2
a
1
a
0.8
0.6
0.4
0.2
b b c
a
a
c b c
c b
d
c
b
d
0
5
10
15
20
Concentration of seed fractions (µg/mL)
Ethylacetate
Butanol
Water
BHT
(c)
Figure 3: Total antioxidant capacity of Canarium odontophyllum peel fractions (a), pulp fractions (b), and seed fractions (c). Higher
absorbance value indicates higher antioxidant activity. Different letters above the bars for the same concentration indicate statistically
significant differences at P < .05.
at 4◦ C for separation of red blood cells (RBC). Red blood
cells were washed three times with phosphate buffer saline
(PBS).
Hemoglobin oxidation was performed as previously
described by Rodrı́guez et al. [12] with slight modifications.
The experiment was carried out within a day of blood withdrawal. The red blood cells (RBCs) were gently resuspended
with PBS to obtain 5% of RBC and preincubated at 37◦ C for
10 min in the presence of 1 mM sodium azide. Subsequently,
1.6 mL of RBC was transferred to test tube for experimental
analysis. All test tubes except control were added with
10 mM of H2 O2 and with or without the addition of sample
extracts (5, 10, and 15 µg/mL, 0.2 mL), while control test
tube received only 0.2 mL of 50% ethanol. Following 60 min
incubation at 37◦ C, the mixture was kept for 60 sec in an
ice bath and then centrifuged at 1853 x g for 10 min at 4◦ C.
Malondialdehyde (MDA) levels were measured using TBA
assay as described by Buege and Aust [13]. The percentage
inhibition of the fractions against hemoglobin oxidation was
also calculated using the following equation: (%) = (OD
of H2 O2 induced haemoglobin—sample OD/OD of H2 O2
induced haemoglobin) × 100.
2.7. Statistical Analysis. Data were expressed as means ±
standard deviations (SDs) of three replicate determinations
and then analyzed by SPSS V.13 (SPSS Inc., Chicago, USA).
One way analysis of variance (ANOVA) and Duncan’s New
Multiple-range test were used to determine the differences
among the means. P-values <.05 were considered to be
significantly different.
3. Results and Discussion
3.1. Total Phenolic and Flavonoid Contents. Table 1 shows
the total phenolic and flavonoid contents of each fraction of
CO fruit. Great variation in phenolic content was observed
in peel, pulp, and seed fractions of CO ranging from 68
± 1.2 – 10 ± 1.5 mg GAE/g in ethyl acetate fractions, 35 ±
1.6 – 4 ± 0.4 mg GAE/g in butanol fractions, 18 ± 4.8 – 3
± 0.2 mg GAE/g in water fractions. Ethyl acetate fraction
of peel (EAFPE) had the highest (68 ± 1.2 mg GAE/g)
phenolic content, while the lowest (3 ± 0.2 mg GAE/g) was
observed in water fraction of seed. Phenolics present in
fruits and vegetables have received considerable attention
because of their potential antioxidant activity [14]. Phenolic
compounds undergo a complex redox reaction with the
phosphotungstic and phosphomolybdic acids present in the
Folin-Ciocalteu (FC) reagent [6]. However, it should be also
noted that some chemical groups of proteins, organic acids,
and sugars present in the extracts can also react with FC
reagent and therefore can interfere with the results [15].
Ethyl acetate was used to extract medium polar
flavonoids and glycosides while butanol and water were
used for extracting polar compounds like phenolic acids,
aglycones, glucosides, and sugars [16, 17]. In our previous
work, higher phenolic content was obtained in ethyl acetate
Journal of Biomedicine and Biotechnology
5
Absorbance of pulp fractions (nm)
Absorbance of peel fractions (nm)
2
1.5
1
0.5
0
2
1.5
1
0.5
0
0
5
10
20
Concentration (µg/mL)
40
0
10
20
Concentration (µg/mL)
40
(b)
Absorbance of seed fractions (nm)
(a)
5
2
1.5
1
0.5
0
0
5
10
20
Concentration (µg/mL)
25
Water
BHT
Ethylacetate
Butanol
(c)
Figure 4: Reducing power of Canarium odontophyllum peel fractions (a), pulp fractions (b), and seed fractions (c). Higher absorbance value
indicates higher antioxidant activity.
Table 1: Total phenolic and flavonoid content of Canarium odontophyllum fractions.
Sample
Peel
Pulp
Seed
Solvent
Ethyl acetate
n-Butanol
Water
Ethyl acetate
n-Butanol
Water
Ethyl acetate
n-Butanol
Water
TPC∗
68 ± 1.2a
35 ± 1.6b
18 ± 4.8c
14 ± 0.5d
14 ± 0.2d
5 ± 0.4f
10 ± 1.5e
4 ± 0.4f
3 ± 0.2g
TFC∗
173 ± 9.9a
28 ± 0.5d
20 ± 0.4e
134 ± 1.5b
29 ± 2.7d
18 ± 0.5f
115 ± 3.8c
22 ± 1.6e
18 ± 0.1f
∗
Values are mean ± standard deviation of three replicate analyses. TPC:
total phenolics content expressed as mg gallic acid equivalent/g; TFC:
total flavonoids content expressed as mg quercetin equivalent/g. For each
treatment (TPC and TFC), the means in a column followed by different
letters were significantly different at P < .05.
fraction compared to butanol and water [18, 19]. Thus, it
is necessary to extract phenolic compounds effectively from
CO prior to the further evaluation of antioxidant activity.
Flavonoids are one of the most diverse and widespread
group of natural compounds and are probably the most
important natural phenolics. These compounds possess
a broad spectrum of chemical and biological activities
including radical scavenging properties [3, 14]. The total
flavonoid content was found to be the highest in EAFPE (173
± 9.9 mg/g QE) and the lowest (18 ± 0.1 mg/g QE) in water
fraction of seeds.
3.2. DPPH Radical Scavenging Activity. DPPH is a stable
free radical and accepts an electron or hydrogen radical
to become a stable diamagnetic molecule which is widely
used to investigate radical scavenging activity. In DPPH
radical scavenging assay, antioxidants react with DPPH (deep
violet color), and convert it to yellow coloured α,α-diphenylβ-picryl hydrazine. The degree of discoloration indicates
the radical-scavenging potential of the antioxidant [8, 15].
The DPPH radical scavenging activity of all the fractions
from CO increased as concentration increased (Figures 2(a)–
2(c)). Ethyl acetate fraction of peel exhibited the highest
scavenging activity (95.5 ± 1%) compared to other fractions
at a concentration of 40 µg/mL, and was equal to scavenging
6
activity of BHT (Figure 2(a)). Ethyl acetate fractions of
pulp (Figure 2(b)) and seed (Figure 2(c)) also exhibited
high scavenging activity of 87 ± 0.7% and 85.8 ± 3.2% at
40 µg/mL concentration. All the butanol fractions exhibited
moderate scavenging activity of 79.9 ± 1.7% in the pulp
being the highest, while the lowest (17.3 ± 0.3%) was
observed in the seed. Low scavenging activity was noticed
in all the water fractions. It has been found that phenolics,
flavonoids, and tocopherols scavenge DPPH radicals by their
hydrogen donating ability [15, 18]. The results obtained in
this investigation reveals that all the fractions of CO could
act as free radical scavengers, which might be attributed to
their electron donating ability.
3.3. Total Antioxidant Capacity. The total antioxidant capacities of CO fractions was measured spectrophotometrically
through phosphomolybdenum method, which is based on
the reduction of Mo (IV) to Mo (V) by the sample analyte
and the subsequent formation of green phosphate/Mo (V)
compounds with a maximum absorption at 695 nm [9]. A
high absorbance value of the sample indicates its strong
antioxidant activity. Figures 3(a)–3(c) show the total antioxidant capacities of CO fractions and BHT. All the fractions
showed a good total antioxidant capacity, which was concentration dependent. The total antioxidant activity of EAFPE at
20 µg/mL was 0.17 ± 0.03 (Figure 3(a)), significantly higher
(P < .05) than butanol and water fractions. Interestingly,
butanol fraction of pulp (Figure 3(b)) and seed (Figure 3(c))
showed higher value than other fractions. However, the total
antioxidant activity of BHT at all concentrations tested was
highest than CO fractions. Previously, Jayaprakasha et al.
[17] indicated that the total antioxidant activity of citrus
was due to the presence of phenolics and flavonoids. The
total antioxidant capacity in the present investigation may be
attributed to total phenolic and flavonoid contents.
3.4. Ferric Reducing Antioxidant Power (FRAP). Ferric reducing antioxidant power is widely used in evaluating antioxidant activity of plant polyphenols. Principally, FRAP assay
treats the antioxidants in the sample as reductant in a redoxlinked colorimetric reaction [15]. This assay is relatively simple and easy to conduct. FRAP assay measures the reducing
potential of antioxidant to react on ferric tripyridyltriazine
(Fe3+ -TPTZ) complex and produce blue color of ferrous
form which can be detected at absorbance 593 nm [10].
Antioxidant compounds which act as reducing agent exert
their effect by donating hydrogen atom to ferric complex
and thus break the radical chain reaction [20]. In the present
study, CO peel exhibited the highest reducing power followed
by seed and pulp. Among CO peel, the ethyl acetate fraction
exhibited a strong reducing power and was higher than BHT,
as shown in Figure 4(a). At 40 µg/mL, the reducing power
ability of EAFPE and BHT was 1 ± 96.05 and 1.2 ± 0.03. All
the fractions of pulp and seeds showed higher FRAP values
compared with BHT. The reducing power of pulp fractions
(Figure 4(b)) was lower than seed fractions (Figure 4(c)).
Similar observations have been reported by other authors,
where in the FRAP values of peel was higher, followed by
Journal of Biomedicine and Biotechnology
seed and pulp fractions [2]. The reducing power of CO fruit
fractions are probably due to the action of hydroxyl group
of the phenolic compounds which might act as electron
donors.
3.5. Hemoglobin Oxidation Assay. In this study, hemoglobin
oxidation assays was chosen as they mimic human biological
system [21]. Many in vitro models have been tested to
determine the effectiveness of antioxidants against free
radicals; among them, hemoglobin in the erythrocytes has
become a very useful assay to evaluate the effects of free
radicals and antioxidants on cellular system [12]. Oxidative
damage to hemoglobin by exposure to hydrogen peroxide is
a primary mechanism to induce specific structural changes
and might contribute to hemoglobin-mediated toxicity in
diseases linked to oxidative stress [22]. The result showed
that all the fractions had a good protective effect against
hydrogen peroxide induced hemoglobin oxidation (Table 2).
The percentage inhibition of hemoglobin oxidation varied
significantly in all the tested fractions with the highest
activity (50 ± 4.3%) observed in ethyl acetate seed fraction,
while the lowest (33 ± 1.6) was in water pulp fraction.
Malondialdehyde (MDA) is the by-product of peroxidation of phospholipids and generally regarded as a
marker for oxidative stresses, rendering its determination
in biological samples particularly interesting [12]. The
MDA produced from hemoglobin oxidation treated with
ethyl acetate fraction from seed was lower than pulp and
peel fractions at a concentration of 5 µg/mL. The MDA
levels of H2 O2 -induced hemoglobin oxidation treated with
different concentrations (5, 10, and 15 µg/mL) of the fraction
decreased compared to H2 O2 -induced hemoglobin. However, many of the fractions had protective effect against
H2 O2 -induced oxidation only at lower concentration. A
similar finding reported by Li [23] showed that lotus germ
oil had pro-oxidation effect at higher concentrations.
Ethyl acetate fractions of the peel contain higher amount
of phenolic compounds and it is not surprising that peel
extract displays higher antioxidant activity than pulp and
seed. Besides, synergistic action among different antioxidants
in the fraction can also be considered. As given in Table 1,
the total phenolic content of EAFPE was nearly five and
seven times higher than pulp and seeds. Additionally, the
flavonoid contents were also higher compared to pulp and
seeds. All these results clearly indicated that peel fraction
contains more antioxidants than pulp and seed. Our data
was in agreement with Li et al. [24] and Guo et al. [2]
who found that fruit peel of mango, kiwifruit, guava,
and orange among others contains high concentration of
phenolics, flavonols, and antioxidant activities than pulp
and seed extracts. Additionally, the total phenolic content of
ethyl acetate fraction in the present study was much higher
than total phenolic contents of common fruits like apple,
grapes, and mandarine (20.5, 15.1, and 15.9 mg/g DW, resp.)
[25].
Several studies exhibited a close relationship between
antioxidant activities and total phenolic content [7, 17, 20].
A positive correlation (R2 = 0.775) was found between total
Journal of Biomedicine and Biotechnology
7
Table 2: Hemoglobin oxidation inhibitory activity of Canarium odontophyllum fractions.
Samples
Non-induced haemoglobin
(control)
H2 O2 -induced haemoglobin
Fractions
Concentration (µg/mL)
MDA (µM)
Inhibition (%)
—
0.313
—
—
5
10
15
5
10
15
5
10
15
5
10
15
5
10
15
5
10
15
5
10
15
5
10
15
5
10
15
5
10
15
1.42
0.822
0.849
0.924
0.750
0.717
0.844
0.752
0.745
0.916
0.725
0.776
0.813
0.731
0.742
0.979
0.937
0.830
0.802
0.698
0.778
0.793
0.748
0.753
0.773
0.792
0.816
0.808
0.851
1.032
0.901
—
42 ± 7
40 ± 5.9
35 ± 0.2
47 ± 2.2
49.4
47 ± 0.1
46 ± 3.4
47 ± 1.7
48.5
48 ± 1.1
45.2
42 ± 1.1
48 ± 0.4
47 ± 6.2
44 ± 1.1
33 ± 1.6
41 ± 0.7
43 ± 4.8
50 ± 4.3
45.1
44 ± 0.5
49 ± 0.3
46 ± 4.5
45 ± 2.9
44 ± 4.1
42.4
43 ± 0.6
40 ± 0.3
27.2
36.4
Ethyl acetate
Peel
Butanol
Water
Ethyl acetate
Pulp
Butanol
Water
Ethyl acetate
Seed
Butanol
Water
BHT
phenolic contents and DPPH radical scavenging activity.
Similar observations (R2 = 0.804) was also observed for
FRAP and total phenolic content. Fang et al. [26] reported
a similar correlation of R2 = 0.741 between total phenolic
content and FRAP. However, a low correlation between
DPPH (R2 = 0.249), FRAP (R2 = 0.293), hemoglobin
oxidation (R2 = 0.313), and total flavonoids was determined.
Liu et al. [7] reported a negative correlation between
flavonoid content and antioxidant activity. This clearly
indicated that total phenolics are major contributors for
antioxidant activity since, they have a high correlation, while
flavonoids are not the major contributors for antioxidant
activities, since they have a lower correlation in the current study. Further investigations into the identification of
phenolic compounds present in the ethyl acetate fraction
of CO are needed to better elucidate their antioxidant
activities.
4. Conclusion
In the present study, application of different solvents to
extract antioxidant compounds from Canarium odontophyllum peel, pulp, and seeds were investigated. This study
indicated that the ethyl acetate fraction of peel possessed
the highest phenolic and flavonoid contents than other
fractions. Also, it exhibited strong antioxidant capacities in
all the assays, which were comparable to the commercial
BHT antioxidant. This suggests that the peel extract of C.
odontophyllum can be potentially used as a source of natural
antioxidant agent.
8
Acknowledgments
The financial support of Research University Grant Scheme
(RUGS) 91926 from Universiti Putra Malaysia is gratefully
acknowledged. The authors would also like to thank Agricultural Research Centre, Sarawak, for providing the fruits.
The authors are grateful to the Department of Nutrition and
Dietetics, Faculty of Medicine and Health Sciences, Universiti
Putra Malaysia, for laboratory facilities provided to carry out
this study.
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