Essential oil extracted from peach (Prunus persica) kernel and its physicochemical and antioxidant properties Hao Wu a,c , John Shi a,*, Sophia Xue a , Yukio Kakuda b , Dongfeng Wang a,c , Yueming Jiang d , Xingqian Ye e , Yanjun Li f , Jayasankar Subramanian g
Trang 1Essential oil extracted from peach (Prunus persica) kernel and its physicochemical and antioxidant properties
Hao Wua,c, John Shia,*, Sophia Xuea, Yukio Kakudab, Dongfeng Wanga,c, Yueming Jiangd, Xingqian Yee,
a Guelph Food Research Center, Agriculture and Agri-Food Canada, Ontario N1G 5C9, Canada
b Department of Food Science, University of Guelph, Ontario N1G 2W0, Canada
c College of Food Science and Technology, Ocean University of China, Qingdao, Shandong 266003, China
d South China Botanical Garden, The Chinese Academy of Sciences, Guangzhou 510650, China
e Department of Food Science and Nutrition, School of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310029, China
f Hangzhou Wahaha Group Co., Hangzhou 310018, China
g Department of Plant Agriculture, University of Guelph, Vineland Station, Ontario L0R 2E0, Canada
a r t i c l e i n f o
Article history:
Received 9 December 2010
Received in revised form
19 May 2011
Accepted 19 May 2011
Keywords:
Antioxidant
Fatty acids
Functional food
Phenolic compounds
a b s t r a c t
Peach kernel oil was extracted using Soxhlet extraction with different solvents (petroleum ether, ethyl ether, chloroform and hexane) The physicochemical properties (acid value, iodine value, peroxide value and saponification value), the fatty acid composition, phenolic constituents and contents, and antioxi-dant activities of peach kernel oil were examined As per our results, oil extracted with hexane has better overall quality Its acid, peroxide, iodine and saponification values were 0.895 mg KOH/g oil, 0.916 mg/g oil, 36.328 mg/100 g oil and 101.836 mg KOH/g oil, respectively Large proportions of unsaturated fatty acid (91.27%) and high content of phenolic compounds (4.1593 mg GAE/g), which contribute to considerably strong antioxidant activity, were found in oil The main fatty acids found in the peach kernel oil were oleic acid (61.87 g/100 g oil) and linoleic acid (29.07 g/100 g oil) The HPLC analysis of phenolic compounds showed that rutin, (-)-epicatechin gallate, hydrocinnamic acid, sinopinic acid, dithiothreitol and caffeic acid were major constituents The results suggested that peach kernel oil is a good source of the unsaturated fatty acid, phenolic compounds with strong antioxidant activity, and has the potential to
be used as nutrient rich food oil The results also verified that peach kernel meals contained higher amounts of total phenolic and stronger antioxidant activities than oils, enabling their application as ingredients for functional or enriched foods
Crown CopyrightÓ 2011 Published by Elsevier Ltd All rights reserved
1 Introduction
Peach is the third most important deciduous tree fruits
world-wide, ranking after apples and pears A significant part of the
har-vested peaches is processed resulting in a substantial amount of
waste stones Peach kernel contain almost 50 wt% of oils (Yolanda,
Albertina, Juan & Pando, 2009) The peach kernel has slightly toxic
effects when used excessively due to its content of hydrogen
cyanide (prussic acid) Hydrogen cyanide is a chemical compound
with extremely poisonous, because it binds irreversibly to the iron
atom in hemoglobin, making it unavailable to transport the vital O2
to the body’s cells and tissues The dose should not be excessive and
any excessive dose may cause headache, blurred vision, palpita-tions, or even death from respiratory failure However, since the concentration of hydrogen cyanide in peach kernel is small
products (Barceloux, 2008, chap 5)
Peach kernel oil has been widely used in the cosmetics industry
as an ingredient in soaps, shampoos, lotions, creams, and shampoos because it is a light, penetrating oil, and absorbs easily and does not leave a greasy feeling Peach kernel oil is nutritionally attractive and has an opportunity of producing high value products from the bio-waste in peach industry due to their unsaturated fatty acid and antioxidant constituents (Saadany, Kalaf, & Soliman, 2004) There-fore, peach kernel can be considered as an important source of essential oil for the food and nutraceutical supplement industries Fatty acids, especially, unsaturated fatty acids, are important as nutritional substances and metabolites in living organisms Many
* Corresponding author Tel.: þ1 519 780 8035; fax: þ1 519 829 2602.
E-mail address: john.shi@agr.gc.ca (J Shi).
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Trang 2kinds of fatty acids play an important role in the regulation of
a variety of physiological and biological functions (Zhao, Wang, You,
& Suo, 2007) The main fatty acids found in peach kernel oil are
about 58% oleic acid and 32% linoleic acid (Kamel & Kakuda, 1992)
Oleic acid is an 18-carbon monounsaturated fatty acid, essential in
human nutrition and helps reducing triglycerides, LDL-cholesterol,
total cholesterol and glycemic index (Eduardo, 2010) Also, the
increase in stability over oxidation of vegetable oil is attributed to
oleic acid (Abdulkarim, Long, Lai, Muhammad, & Ghazali, 2007)
The linoleic acid is an essential fatty acid from omega-6 group
(18:2(n-6).) and very important for development and maintenance
of the nervous system and the physiological functions in humans,
since it reduces total and LDL-cholesterol levels Phenolic
tannins have been the scope of many studies lately due to their
antioxidant effects
Phenolic compounds make important contributions to the
nutritional properties, sensory characteristics and the shelf life of
peach kernel oil However, the fate of individual phenolic
compounds in the course of peach kernel oil extraction as well as
their contribution to the overall antioxidant properties of oils has
not yet been investigated
The extraction technique used to obtain high aggregate value
compounds from natural products is crucial for product quality
Soxhlet extraction is a standard technique and is the main reference
to which other extraction methods are compared The advantage of
conventional Soxhlet is that the sample is repeatedly brought into
contact with the fresh portions of the solvent, thereby helping to
displace the transfer equilibrium There is a wide variety of official
methods involving a sample preparation step based on Soxhlet
extraction (US EPA Method 3540, 1995; AOAC Method 963.15, 1990;
British Standard, BS 4267, 1994, 8 p.) In short, Soxhlet extraction is
a general, well-established technique which clearly surpasses in
performance other conventional extraction techniques
However, there are only few studies on the extraction of peach
kernel oil (Yolanda, Albertina, Juan & Pando, 2009), and the fatty
acid profile, polyphenolic compound, physicochemical properties
and antioxidative properties of peach kernel oil were not well
established yet Therefore, the objectives of this study were to
compare the efficiency of the extraction solvents; evaluate the
quality of peach kernel oil through the physicochemical properties,
fatty acid composition, profile of phenolic compounds and
anti-oxidant activity; and at last define the most effective solvent that
can be used in the extraction of peach kernel oil with Soxhlet
2 Materials and methods
2.1 Materials
Peaches (Prunus persica) were harvested from orchard of
Vine-land Research Centre (Ontario, Canada) Peach pits were collected
and cracked to obtain the kernel The kernel were then ground in
a food grinder (Waring commercial Co Ltd., USA) to reduce the
a sieve (The W.S Tyler Company of Canada Ltd., Canada), sealed in
a plastic container and stored in a refrigerator until extraction The
storage conditions assured eliminating effects of oxygen and
humidity and to avoid oxidation of the dried peach pit powder
during storage time
FolineCiocalteu reagent and 2, 20-Diphenyl-b-picrylhydrazyl
(DPPH) were supplied by Sigma (St Louis, MO, USA) Standards of
fatty acid methyl esters (FAME) (mixture 463) were obtained from
Nu-Chek-Prep, Inc (Elysian, MN, USA) Polyphenol standards for
HPLC analysis were supplied as follows: keracyanin chloride,
(þ)-catechin, (-)-epicatechin gallate, 3,4-dihydroxybenzoic acid,
rutin hydrate, procyanidin B2, ellagic acid, caffeic acid, DL-dithiothreitol, protocatechinic acid, procatechol, gentisics acid, kuromanin chloride, vanillic acid, myricetin, hydrocinnamic acid, sinopinic acid, and obtained from Sigma (St Louis, MO, USA) KI,
Na2S2O3,KOH, phenolphthalein, HCl, starch indicator, I2, Br2were from Fisher Chemicals (Fair Lawn, NJ, U.S.A) The solvents employed for extraction and HPLC performance were all obtained from Caledon Laboratories LTD (Georgetown, ON, Canada)
2.2 Methods 2.2.1 Oil extraction
Leimann, Pedrosa, and Ferreira (2008) The extractions were per-formed at least in duplicate, with different solvents: petroleum ether, hexane, ethyl ether and chloroform, with polarities of 0.01, 0.06, 2.9 and 4.4, respectively The solvents chosen for present study are normally used to extract oil from plant kernel Thirty grams of ground peach kernel was extracted in a soxhlet-extractor
temperature of 50C was chosen to avoid thermal degradation on bioactive compounds in the extracts Also the temperate is in the range of boiling temperature of these solvent The resulting extracts, obtained by the different methods were separated by evaporating the solvents used in a rotary evaporator under reduced pressure and at temperature of 50C The obtaining the fractions
oil physicochemical properties were determined The meals were also collected after extracting oils, and weighted after evaporating excess solvent under nitrogen The total yield of extracted oil for each method was obtained by the mean value of extracted oil mass divided by mass of raw material used (30 g), on dry weight base (d.b)
The Oils and their meals were evaluated to compare their total phenolic content, phenolic profiles and antioxidant capacity 2.2.2 Physicochemical properties of peach kernel oils Acid value, iodine value, peroxide value and saponification value
(1990)methods The hydrocyanic acid content of the extracted oil was determined by the method ofBlinn and Boyd (1964) 2.2.3 Fatty acid (FA) analyses
The fatty acid profile was determined as fatty acid methyl esters (FAME) by gas chromatography The methyl esters were prepared
by following produces Oils (50 mg) were dissolved in sodium dried
solution immediately becomes cloudy as sodium-glycerol deriva-tives were precipitated After set for 5 min at room temperature, the reaction was stopped by adding a saturated solution of oxalic acid in diethyl ether (30mL) with brief agitation The mixture was centrifuged at about 1500 g for 4 min to precipitate sodium oxalate, and the solvent was removed in a gentle stream of nitrogen at room temperature Fresh diethyl ether (1 mL) or hexane was added, and
an aliquot of this was taken directly for GC analysis
Palo Alto, CA, USA) equipped with aflame ionisation detector and
USA), a 100 m CP-Sil 88 fused capillary column (Varian Inc., Mis-sissauga, ON, Canada), and ChemStation software system (version A.09, HewlettePackard, Palo Alto, CA, USA) were used for analysing
Trang 34 min, increase by 13C/min to 175C, hold again at 175C for
27 min, increase at 4C/min to 215C, and then hold at 125C for
35 min A FAME Standard (mixture 463) was used to identify the
FAME and quantitative analysis The FA amount was expressed as
percent of total FAs
2.2.4 Determination of total phenolic content
Peach kernel oils (3 g) were extracted with 25 mL methanol,
vortexed for 5 min, and then centrifuged at 4000 g for 10 min Peach
kernel meals (5 g) were extracted with 15 mL Meth/H2O (90:10, v/v)
by continuous agitation for 30 min, and then centrifuged at 4000 g
for 10 min The supernatant in each case was collected for phenolic
content and antioxidant activity measurements
Total phenolic content was determined by the FolineCiocalteu
method A combination solution consisting of 0.2 mL sample
extract, 1.0 mL 0.25 N FolineCiocalteu reagent, 0.8 mL of Na2CO3
solution (7.5: 92.5, w/v,) and 2 mL distilled water were mixed
well in a 20 mL vial using a Vortex and incubated at room
determined at 765 nm against the blank (methanol replaced
content was expressed as gallic acid equivalent (GAE) in mg/g
fresh weight (FW) Additional dilutions were made if the
absor-bance value measured was beyond the linear range of the
stan-dard curve
2.2.5 Profile of phenolic compounds in peach kernel oil analysed by
HPLC
method An HP 1100 HPLC system equipped with an alphaBond
C18 125A column (4.6 250 mm, particle size 5mm) and coupled
with Agilent 1100 series ChemStation software was used for
quantifying the individual phenolic compounds The mobile
pha-ses consisted of 2.0% acetic acid in distilled water (A) and
aceto-nitrile (B) The column was eluted at 1.0 mL/min under a linear
gradient from 5% mobile phase B to 75% over 20 min, to 100% over
5 min, isocratic for 5 min, to 25% over 5 min and to 5% over 5 min
at 280 nm with an HP 1100 series ultraviolet (UV) Diode Array
Detector Standards were injected for identification and
quantita-tive analysis
2.2.6 Radical-scavenging activity (DPPH)
The antioxidant activity was determined by DPPH method
which was based on the evaluation of the free-radical scavenging
capacity In this method, the 2,2 diphenyl-1-picrylhydrazyl (DPPH)
radical was used to measure the antioxidant activity A 100mL of
sample diluted in the ratio of 1:100 with methanol:water (6:4) was
mixed with 2 mL of 0.1 mol/L DPPH in methanol After incubating at
room temperature for 30 min in the dark, the absorbance of the
mixture was measured at 517 nm Radical scavenging activity was
expressed as the inhibition percentage
2.2.7 Trolox equivalent antioxidant capacity (TEAC) assay
A distilled water solution of 5 mmol/L aqueous solution ABTS
filtered through a 0.2mm Acrodisc PVDF syringefilter to eliminate traces of MnO2 This solution was then diluted in PBS (pH 7.40) to an absorbance of 0.700 at 734 nm Trolox standards were prepared
extract (0.2 mL) above and the Trolox standard were mixed with each of 2 mL of the ABTS radical cation solution and then stirred vigorously The absorbance was monitored at 734 nm over a 30 min period using a spectrophotometer The activities of antioxidants were estimated at least at three different concentrations within the range of the Trolox dose-absorbance response curve Antioxidant activity was expressed asmM Trolox Equivalent (TE)/100 g 2.3 Statistical analysis
The extractions and all analyses were carried out at least in triplicate and data were expressed as means standard deviation
A one-way analysis of variance (ANOVA) was performed to
difference) test A probability value of p< 0.05 was considered significant and only significant differences were considered unless stated otherwise
3 Results and discussion 3.1 Physicochemical properties of oils
extraction, the solvent of ethyl ether provided significantly highest total oil yield (0.38 0.07 g/g d.b), follow by chloroform extraction (0.35 0.06 g/g d.b) There no significant difference was observed
on the total oil yields that extracted by petroleamether (0.25 0.04 g/g d.b) and hexane (0.26 0.04 g/g d.b) The results indicated that peach oil has many intermediate to high polarity compounds result in the obtained high oil yields Moreover, the interaction between solvent and solutes, both solvent polarity and their boiling temperature may contribute mean factors on the
kernel oil
The acidity, iodine, peroxide and saponification values are the major characterization parameters for oil quality The peach kernel oils were very light yellow in colour and had an acceptable odour The hydrocyanic acid contents in all samples were not detected that indicated the peach kernel oils were completely free from the toxic hydrocyanic acid The statistical analysis showed that different
properties and fatty acid profile of the oils The acid value was
a measure of total acidity of the lipid, involving contributions from all the constituent fatty acids that make up the glyceride molecule (Ekpa & Ekpe, 1995) As shown in Table 1, the total acidity,
Table 1
Physicochemical property of peach kernel oils extracted with different solvents (means S.D.).
Saponification value (mg KOH/g oil) 165.701 3.872 a 156.599 4.205 b 154.275 2.876 b 101.836 0.702 c a-b Means within the same row not followed by the same letter differ significantly (p < 0.05) Each experiment was performed in triplicates.
Trang 4expressed as the acid value, was highest in ethyl ether extract
(1.099 mg KOH/g oil), followed by hexane extract (0.895 mg KOH/g
oil) and the lowest value was found in the chloroform extract
(0.608 mg KOH/g oil)
Peroxide value is one of the most widely used testings for
oxidative rancidity in oils and fats It is a measure of the
concen-tration of peroxides and hydroperoxides formed in the initial stages
of lipid oxidation Generally, the peroxide value should be less than
10 mg/g oil in the fresh oils as any increase in this value (usually
20 mg/g or above) results in rancidity of the oils (Pearson, 1976, pp
widely in the extracts, ranging from 0.256 mg/g oil for the
petro-leum ether extract to 2.366 mg/g oil for the ethyl ether extract A
significant difference (p < 0.01) in the peroxide values was
observed between the ethyl ether extract and others The peroxide
chloroform extract (0.259 0.014 mg/g) were significantly lower
than all others.Ojeh (1981)reported that oils with high peroxide
values are unstable and easily become rancid (having a
disagree-able odour) The results suggested that the peach kernel oils
extracted with petroleum ether, chloroform and hexane could be
stored with less deterioration than the oil extracted with ethyl
ether The acid and peroxide values were good indices for the
stability of the oil These two parameters of the peach kernel oil
Hosahalli, & Kyu, 2009).Farhoosh, Einafshar, and Sharayei (2009)
reported that the acid value of crude soybean oil and canola oil
were 1.89 mg KOH/g oil and 1.94 mg KOH/g oil, respectively They
were both higher than the acid value of peach kernel oils in this
study.Hafidi, Pilch and Ajanan (2005)showed the peroxide value of
peach kernel oils, as seen in our results It clearly indicated that the
peach kernel oil may have low levels of oxidation
The iodine value is used to determine the unsaturation of oils
and in assessing the stability of oil in industrial applications (Xu,
Hanna, & Josiah, 2007) The range of iodine numbers were
36.328e75.726 mg/100 g oil, thus, the peach kernel oil could be
classified as non-drying oil The oil extracted with hexane had the
lowest iodine value, which reflected its characteristics such as
higher resistance to oxidation, longer shelf life and higher quality
The differences in iodine values between oil samples maybe were
due to the different fatty acid compositions The oil extracted with petroleum ether has high monounsaturated fatty acids, whereas the oil extracted with hexane contains more polyunsaturated fatty acids
Saponification index was highest in the petroleum ether extract (165.701 mg KOH/g oil), followed by the chloroform extract (156.599 mg KOH/g oil) while the lowest value was in hexane extract (101.836 mg KOH/g oil) The saponification index is a useful tool for the evaluation of the chain length (molecular weight) of fatty acids occurring in the triacylglycerols in oil The lower saponification value indicates a very high content of low molecular weight triacylglycerols The results suggested that the oils extracted with hexane had the higher fatty acid contents It is important to point out that, a strong correlation wasn’t observed between the physicochemical properties and polarity of the solvents The solvent polarity can be defined as the molecule ability to participate
on interaction with other similar polarity molecules This lack of any useful correlation suggests that apart from solvent polarity, oil solubility in the solvents may play important roles
3.2 Profile of fatty acid (FA) composition in peach kernel oil extract The total FA composition of the extracts obtained in this study was determined by GC and was shown inTable 2 The FA profile is
a main determinant of the oil quality The extracted oil contained major fatty acid compounds were oleic acid (61.87e65.74 g/100 g oil), linoleic acid (25.89e29.07 g/100 g oil) and palmitic acid (5.632e6.355 g/100 g oil) These amounts of oleic acid were lower than those reported by Sánchez-Vicente, Albertina, Juan & Pando (2009) However, the amounts of linoleic acid and palmitic acid were similar to the report of Sánchez-Vicente, Albertina, Juan & Pando (2009) The differences in genotypes, growing conditions and perhaps the time of harvest and storage practices after
Renuncil, and Pando (2009) and those used in this study may contribute to the observed differences
All oil samples had high amounts of the unsaturated fatty acid (UFA) that primarily were oleic and linoleic acids In the peach oils extracted with various solvents in this study the UFA content was well over 90% and was not significantly different from each other The total polyunsaturated fatty acids (PUFA) content (29.11 g/100 g
Table 2
Fatty acid composition (%w/w) of oils extracted with different solvents (means S.D.).
SFA: Total saturated fatty acids; MUFA: Total monounsaturated fatty acids; PUFA: Total polyunsaturated fatty acids; UFA: Total unsaturated fatty acids; S/U: values of ratio saturated/unsaturated fatty acids.
a-b Means within the same row not followed by the same letter differ significantly (p < 0.05) Each experiment was performed in triplicates.
Trang 5oil) of the peach kernel oil extracted with hexane was significantly
higher than others (25.92e26.06 g/100 g oil), but the total
mono-unsaturated fatty acid (MUFA) contents in the hexane extracted oil
differences on PUFA and MUFA contents in the extracted oil by the
other three solvents.Natália, Bruna, Maria, Julian and Sandra (2010)
reported the use of solvents presenting polarity indexes (PI) lower
than 4.4 enhanced the extraction of oleic acid and linoleic acid
among the UFA But in present study, no relation was founded
research, peach/almond samples were submitted to Soxhlet for 6 h
at the solvent boiling point temperature, while our results are
based on peach kernel oil, extracted in Soxhlet for 24 h at 50C The
difference may be attributed to the different extract temperature
and time
Amounts of fatty acids in the peach kernel oils were in the order
of MUFA> PUFA > SFA (total saturated fatty acids) irrespective of
the solvent used Peach kernel oil presented relatively low contents
of saturated fatty acid, high contents of unsaturated fatty acids
compared with other common vegetable/fruit seed oils, such as
canola, corn, grape seed, olive, peanut, sesame, soybean and walnut
(Fasina, Craig-Schmidt, Colley, & Hallman, 2008; USDA, 2006)
Based on the contents of SFA, USFA, MUFA and PUFA the fatty acid
composition of peach kernel oil is similar to almond oil (SFA 8.84 g/
100 g, USFA 91.16 g/100 g, MUFA 65.64 g/100 g and PUFA 25.52 g/
100 g, respectively) (Fasina et al., 2008)
The unsaturated fatty acids are very important for the stability
of oils because of the chemical reactions occurring at the double
bonds The rates of those oxidation reactions depend on the
number of double bonds in the carbon chain Therefore oils with
a high proportion of oleic acid are more stable than others Oleic
acid is less susceptible to the oxidation than polyunsaturated fatty
acid from the n-6 series (linoleic acid)
The linoleic acid as an essential fatty acid contributes health
benefits for human body and it is preferred by industries when oil
hydrogenation is required (Kamel, Karim, Mouna, Mohamed, &
Brahim, 2009) Based on the results of physicochemical properties
and fatty acid profile of the peach kernel oil, it can be concluded
that the peach kernels can become valuable resource to produce
high value essential oil products The high quality and nutritional
value of peach kernel oil has potential application in human foods
3.3 Total phenolic content
The phenolic compounds are the main component responsible
for antioxidant activity, is mainly due to their redox properties,
which can play an important role in absorbing and neutralising free
radicals, quenching singlet and triplet oxygen, or decomposing
content through the method of Folin-Ciocalteau represents a good
estimative of antioxidant potential of food samples
The total phenolic contents of kernel meal and oil by different
significantly higher amount of total phenolic contents compared to
the oils (6.992e7.951 mg GAE/g) The oils extracted with solvents
resulted in low phenolic contents (3.829e4.1593 mg GAE/g),
indi-cating that only parts of the phenolic content were transferred to
oils The loss of phenolic compounds in extracted oils is likely due
to the thermal impact and its insolubility in oil The results
sug-gested that after oil extraction, the meals still can be used for
antioxidant extraction or functional ingredients Although the
polarities of chloroform and ethyl ether were stronger, hexane
Moreover, the values of the total phenolic contents were not
significantly different This indicates that not only the solvent
characteristics such as polarity affected the total phenolic content, but also the solubility of phenolic compounds, the localization of these compounds in the tissue matrix, and characteristics of matrix must also be involved The results suggested that the best method
to produce high extraction yield and total phenolic content for peach kernel oil is Soxhlet extraction with hexane as solvent 3.4 Phenolic profiles
In the oils and meals, a total of 15 phenolic compounds was
spectra with standards, and are shown inTable 3 There are yet some other unidentified compounds due to the lack of standards The meals extracted with petroleum ether and ethyl ether showed the most complex phenolic profile with eight phenolic acids and six flavonoids
HPLC analysis revealed the presence of dithiothreitol, rutin and caffeic acid as the major phenolic compounds in the oils extracted with petroleum ether, chloroform and ethyl ether Rutin is considered to be one of the most important phenolics compounds that effectively boosts vitamin C’s efficacy, improve eye health, strengthen fragile capillaries, reduce cholesterol, improve blood circulation, and act as antioxidants Dithiothreitol and caffeic acid can repress the activation of pro-carcinogens and can activate enzymatic systems (Phase II) as well as prevent oxidative damage
to the DNA which has been shown to be important in the in the age-related development of some cancers (Vattem, Ghaedian, & Shetty,
2005)
Rutin was the predominant phenolic compound in the oil extracted with hexane accounting for 76.65 g/100 g of the total amount In contrast, the major phenolics compounds in the meals were different compared to their corresponding oil extracts The procyanidin B2 and the hydrocinnamic acid were the predominant phenolic compounds in the meals extracted with petroleum ether and ethyl ether, and the hydrocinnamic acid, the rutin were the predominant phenolic compounds in the meals extracted with chloroform and hexane
Because of the different number and arrangement of the hydroxyl groups as well as the presence of electron-donating substituents in the ring structure of phenolic compounds, the polarity of phenolic compounds were different So, the oils and meals extracted with solvents with different polarities might contain different types of phenolic compounds Our studies on the oils and the meals showed differences on the phenolic composi-tions and contents compared with peach puree and concentrate
Fig 1 Total phenolics content of peach kernel oils and meals extracted with different solvents The mean value obtained from three replications ( oils, meals).
Trang 6(Bengoechea, Sancho, & Bartolome, 1997), which pointed out that
chlorogenic acid, was the main phenolic compound in both peach
puree and concentrate This indicates that the phenolic compounds
are different in the peach kernel oil and meal
antioxi-dant activities compared to the phenolic acid fraction (Thorsten,
Andreas, Dietmar, & Reinhold, 2009) Rutin is one of the most
importantflavonoids Oil extracted with hexane was characterised
by high rutin content, which may account for the high total
phenolic content However, we could not determine which
phenolic compounds actually contributed to the total antioxidant
activity of oils and meals The phenolic acids andflavonoid
poly-phenolics present in extracts may contribute individually or
synergistically to the antioxidant activities
Interestingly, the phenolic contents determined by the
FolineCiocalteu method exceeded the total amount of individual
phenolics as quantified by HPLC This is probably due to the fact
that all monomeric, oligomeric and polymeric polyphenols were
molecular compounds were covered by HPLC A similar
phenom-enon has been described for the determination of the total phenolic
content of residues of grape seed oil (Thorsten et al., 2009)
3.5 Antioxidant activities of meals and oils
The DPPH radical scavenging is a common method to evaluate
the ability of antioxidant components to scavenge free radicals
generated Only the oil extracted with hexane exhibited stronger
DPPH radical-scavenging activity, compared with the meals (Fig 2)
In addition, the oil extracted with hexane is more active, compared
to the meal It has been reported that free radical-scavenging
activity is greatly influenced by the phenolic composition of the
sample (Cheung, Cheung, & Ooi, 2003) Thus, the antioxidant
activity of the oils and meals extracted from peach kernels may be
attributed to their phenolic contents in the samples Although the
oil extracted with hexane contained lower amount of total
phenolics than that of meal, it showed a higher DPPH
radical-scavenging efficiency than their meal, which could be attributed
to their high rutin content
The TEAC assay is widely applied to assess the total amount of
radicals that can be scavenged by an antioxidant, i.e the
antioxi-dant capacity The results of the TEAC analysis for peach kernel oils
and meals are shown inFig 3 All the oils and meals inhibited the
oxidation of ABTS-þradical to varying degrees In the present study,
the oil with the highest antioxidant activity was extracted with
chloroform and ethyl ether, which had TEAC values of 65.22 and 63.95mm TAE/100 g, respectively Highest antioxidant capacity in the meals was found in the extracts with petroleum ether
(Fig 3) and this trend was similar to the changes in total phenolic content
Polyphenols have been reported to be responsible for the anti-oxidant activities of botanical extracts The DPPH assay and TEAC assay have been used to measure antioxidant activity and the results generally correlate with total phenolic content A direct correlation between radical-scavenging activity and phenolic content of the oils and the meals was observed The TEAC and DPPH antioxidant activity values were increased with increasing phenolic content of the oils and the meals analysed, in agreement with previous works in different foodstuffs (Ismail, Chan, Mariod, & Ismail, 2010)
Regression equation was used to determine the correlation coefficient (R2) on the plot of total phenolic content against TEAC or DPPH The correlations between the total phenolic content and the antioxidant activity based on TEAC was high (R2¼ 0.9566), while the correlation between total phenolic content and DPPH was low (R2 ¼ 0.5913) It is due to a different mechanism and reaction
Fig 2 Antioxidant activity of peach kernel oils and meals extracted with different solvents on DPPH reduction The mean value obtained from four replications ( oils,
Table 3
Phenolic compounds (mg/g) of peach kernel oils and meals extracted with different solvents (means S.D.).
Phenolic compounds
(mg/g)
Dithiothreitol 1.203 0.098 0.652 0.034 0.755 0.036 nd 0.835 0.036 0.327 0.056 0.107 0.008 nd
(þ)-catechin 0.186 0.043 0.207 0.065 0.376 0.017 nd 0.037 0.003 0.291 0.068 0.008 0.004 0.434 0.080
Caffeic acid 0.969 0.098 0.563 0.080 1.084 0.068 0.596 0.098 0.888 0.352 0.591 0.087 0.091 0.002 0.518 0.102 (-)-epicatechin gallate 0.115 0.006 0.463 0.002 0.222 0.014 0.700 0.020 0.171 0.011 0.440 0.024 0.254 0.048 0.468 0.054 Hydrocinnamic acid 0.342 0.010 0.788 0.080 0.089 0.036 1.140 0.088 0.179 0.023 0.826 0.122 0.186 0.056 0.880 0.089 Sinopinic acid nd 0.169 0.008 0.365 0.120 0.319 0.015 0.183 0.001 0.127 0.017 0.115 0.001 0.465 0.067 Rutin 0.263 0.015 0.575 0.021 0.552 0.028 1.005 0.120 0.436 0.028 0.499 0.101 2.737 0.187 0.859 0.144 Ellagic acid 0.105 0.007 0.572 0.017 nd 0.276 0.026 0.043 0.006 0.470 0.023 0.036 0.006 0.434 0.042 nd: not detected The mean values obtained from four replicates for each determination.
Trang 7between individual polyphenol compounds with DPPH or TEAC.
DPPH is measure as free radical scavenging activity based on the
reduction of 1,1-diphenyl-2-picrylhydrazyl TEAC is a measurement
of antioxidant strength based on Trolox Equivalency Most phenolic
compounds have deoxidization properties (TEAC), but not all
polyphenols compounds can react with free radical (DPPH), so the
correlation between total phenols and TEAC is positively higher
than DPPH Several studies had reported a good correlation
between the phenol content of plant extracts and antioxidant
activity (Bahorun, Luximon-Ramma, Crozier, & Aruoma, 2004;
Djeridane et al., 2006), but other studies report a poor correlation
(Sellappan & Akoh, 2002) As indicated above, not only phenolic
non-phenolic, such as fatty acid profile, could contribute to the overall
antioxidant potential
4 Conclusions
Peach kernel oils were extracted by organic solvents
(petro-leum ether, ethyl ether, chloroform and hexane) and evaluated for
their characterization and quality analysis According to the
anal-ysis of physicochemical properties, fatty acid profile, total phenols
and antioxidant capacity based on DPPH radical-scavenging and
TEAC, the results showed that these oils are rich in oleic acid and
linoleic acid, indicating that they are stable and tolerant to
rancidity The effects of different extraction solvents significantly
influenced the physicochemical properties of oil, and the phenolic
composition and antioxidant properties of the meals and extracted
oils The results suggested that the oil extracted with hexane has
better quality Hexane has been widely used for extraction in food
industry due to it is easily be evaporated from extracts This oil
may be considered as an important source of unsaturated fatty
acid and has the potential to be used as nutrient rich food oil
contained higher amounts of total phenolic and stronger
antioxi-dant activities than oils, enabling their application as ingredients
of functional or enriched foods The results of present study
provide useful information for essential oil and food industry As
a bio-waste in peach processing industry, the peach kernel has
potential applications in the food industry Due to its special
composition, rich in polyunsaturated fatty acids, including linoleic
and oleic acids, and in antioxidant compounds In food
applica-tions, it can be substituted for olive oil and grape seed oil in salad
products such as salad oil, salad dressing, dips, and sauces, and it
can also be used as cooking oil
Acknowledgements Authors gratefully acknowledge the contribution of the MOE/ AAFC Program and Guelph Food Research Center, Agriculture and Agri-Food Canada
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