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Fatty Acids, Sterols, Polyphenols, andChlorophylls of Olive Oils Obtained fromTunisian Wild Olive Trees (Olea europaeaL. Var. Sylvestris)Hédia Hannachi a , Nizar Nasri a , Walid Elfalleh b , Nizar Tlili a , AliFerchichi b & Monji Msallem ca Département de Biologie, Faculté des Sciences de Tunis , CampusUniversitaire , Tunis , Tunisiab Institut des Régions Arides de Médenine, Laboratoire d'Aridocultureet Culture Oasiennes , Tunisiac Institut de l'Olivier , Tunis , TunisiaAccepted author version posted online: 20 Nov 2012.Publishedonline: 09 May 2013.
To cite this article: Hédia Hannachi , Nizar Nasri , Walid Elfalleh , Nizar Tlili , Ali Ferchichi & MonjiMsallem (2013): Fatty Acids, Sterols, Polyphenols, and Chlorophylls of Olive Oils Obtained fromTunisian Wild Olive Trees (Olea europaea L. Var. Sylvestris), International Journal of Food Properties,16:6, 1271-1283
To link to this article: http://dx.doi.org/10.1080/10942912.2011.584201
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International Journal of Food Properties, 16:1271–1283, 2013Copyright © Taylor & Francis Group, LLCISSN: 1094-2912 print / 1532-2386 onlineDOI: 10.1080/10942912.2011.584201
FATTY ACIDS, STEROLS, POLYPHENOLS, ANDCHLOROPHYLLS OF OLIVE OILS OBTAINED FROMTUNISIAN WILD OLIVE TREES (OLEA EUROPAEA L. VAR.SYLVESTRIS)
Hédia Hannachi1, Nizar Nasri1, Walid Elfalleh2, Nizar Tlili1,Ali Ferchichi2, and Monji Msallem3
1Département de Biologie, Faculté des Sciences de Tunis, Campus Universitaire,Tunis, Tunisia2Institut des Régions Arides de Médenine, Laboratoire d’Aridoculture et CultureOasiennes, Tunisia3Institut de l’Olivier, Tunis, Tunisia
Olive (Olea europaea L.) includes cultivated olive trees (var. europaea) and wild olive trees oroleaster (var. sylvestris) as two botanical varieties. These olive varieties were widely spreadin the Mediterranean Region. The aim of this study was to determine fatty acid composi-tions, sterols, polyphenols, and chlorophylls of oils obtained from 12 wild olive trees fromNorthern Tunisia. Two dominated oil cultivars in Tunisia (Chétoui and Chemlali) were alsoused to compare results. The fatty acid methyl ester and the sterol compositions were ana-lyzed using gas-liquid chromatography and thin layer chromatography methods, respectively.The polyphenols and chlorophylls were determined using the calorimetrical method. Resultsindicated that oils extracted from wild olives displayed good balanced fatty acid compositions,sterols, polyphenols, and chlorophylls. Qualitatively, for wild and cultivated olive oils, the oilhas an identical composition, whereas the quantitative variation showed that some wild treesseem to be interesting oil sources as two Tunisian dominated cultivars. The highest oleic acidand polyphenol contents were 71.55% and 537.6 mg/kg of oil found in wild olives (OIch2,OIch1). The β-sitosterol was the major sterolic fraction and ranged from 84.72 to 75.70%according to the wild olives. Consequently, wild olives would be a new future edible olive oilsource, as well as commonly cultivated ones.
Keywords: Olea europaea L. Var. sylvestris, Olive oil, Fatty acids, Sterols, Polyphenols.
INTRODUCTION
The olive tree (Olea europaea L.) is the most extensive crop in the MediterraneanBasin. It includes the cultivated (var. europaea) and wild (var. sylvestris) olive trees. Olivetree yields two products, table olives and olive oil, both of which are important commodi-ties in world markets. The Olea europaea L. spreads in the Mediterranean Basin whereit is indigenous and in other regions with a Mediterranean climate where it has been
Received 2 March 2011; accepted 23 April 2011.Address correspondence to Hédia Hannachi, Département de Biologie, Faculté des Sciences de Tunis,
Campus Universitaire 2092, Tunis, Tunisia. E-mail: [email protected]
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1272 HANNACHI ET AL.
introduced, such as in South Africa.[1] The olives cover about 8.7 million ha, supportinga total of almost 750 million olive trees in 33 countries of the world. The MediterraneanBasin accounts for 97% of the olive orchards. In Tunisia, it occupies about 1.6 million ha,representing one-third of arable lands of the country.[2] Olive oil is a natural fruit juice,of fine aroma, and pleasant taste, and has a high nutritional value. It is appreciated for itsstability and good characteristics. It is considered as the most useful edible oil in the worlddue to its nutriment contents and beneficial effects.[3] It was reported that olive oil is freeof cholesterol and does not have adverse effects on the human body.
Olive oil is characterized by an oxidative stability enabling long shelf storage, sen-sory quality, and health properties stemming from a prominent and well balanced chemicalcomposition.[4] Olive oil has a preventive role in cardiovascular and inflammatory diseases;its consumption is associated with a lower coronary risk.[5] Epidemiological studies havereported that the consumption of olive oil is inversely associated with pancreas cancer.[6]
In addition, the role of olive oil in the potential prevention of breast cancer has been givenattention.[7] The most important natural antioxidants are polyphenols, tocopherols, and pig-ments, since these compounds delay the oxidation of fatty acids and the production ofunpleasant flavors.[8] Despite the large amount of olive oils produced and their confirmednutritional values, there are no reliable data on the chemical composition of oil from wildolive trees. Little is known about wild olive trees in Tunisia.[9] Several historical reports[10]
have pointed out that the wild olive trees were native in Tunisia. The molecular diversityrevealed that a few cultivars are issued from the Tunisian wild olive trees based on assigna-tion and admixture analyses.[11] Using nuclear and choroplastic SSR markers, it has beenreported that the olive in Tunisia has probably three geographical origins.[12] Therefore,the wild olive trees were important genetic resources deserving to be known, not only itsgenetic characterization but also its technological potentialities, such as the oil composition.Olive tree genetic improvement is promoted by crosses cultivars to create new combina-tions of traits. It is used to improve oil composition (low content of saturated fatty acidsand high oleic acid content), oil yield, disease resistance, and organoleptic characters of thefinal products. The knowledge of the extent and the type of genetic variability available andexploitable is essential to a correct layout of breeding programs. The olive resources wouldbe represented, not only by olive cultivars collections but also by wild olive resources. Thewild olive trees dispread in Tunisia in natural and agro-ecosystems.[13] Olive oil from cul-tivated olive trees provides beneficial effects on human health. But little is known aboutoil extracted from wild olive trees, in particular, oil composition. The present study wasconducted to evaluate oil composition of wild olives and the two dominated cultivars oilsin Tunisia.
MATERIALS AND METHODS
Plant Material and Oil Extraction
In this study, nine wild olive trees were sampled in a natural ecosystem representedby both parks and forests (Ichkeul, Tunis, Téboursouk, and Dougga). In these localities,the wild olive trees were in natural association with pistachio (Pistacia lentiscus), and theywere isolated from all cultural practices. Three wild olive trees were sampled either aroundorchards in agro-ecosystem (Slouguia, Testoure, and Medjez El Bab) and were in associ-ation with prickly pear (Opuntia ficus indica). Two dominated olive cultivars, ‘Chemlali’and ‘Chétoui’, were also chosen to compare results between wild trees and cultivar olive
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OILS OBTAINED FROM TUNISIAN WILD OLIVE TREES 1273
BA
Figure 1 Geographical sites of wild olive trees and ‘Chétoui’, and ‘Chemlali’, two main cultivars of olives. (a)Tunisia map, and (b) locations details.
Table 1 List and locations of the studied wild and the two main cultivar olive trees.
Wild olive trees/Cultivar Location Altitude (m) Latitude Longitude
OSlg Slouguia 112 40◦ 70′ 8◦ 07′OTest Testour 112 40◦ 62′ 7◦ 48′OTeb Teboursouk 440 40◦ 51′ 7◦ 68′ODoug Dougga 365 40◦ 58′ 7◦ 52′OMedj Medjez El Bab 112 40◦ 70′ 8◦ 07′OIch Ichkeul Park 130 37◦ 17′ 9◦ 67′OTun Belvédère Park 66 40◦ 87′ 8◦ 71′Chétoui and Chemlali Slouguia 112 40◦ 70′ 8◦ 07′
oils (Fig. 1, Table 1). These two cultivars contribute by 80% of total oil production inTunisia.
Oil extraction was carried out in similar industrial extraction conditions using anoleodosor system. Olives were crushed and slowly mixed for 30 min at 25◦C. The pasteobtained was centrifuged at 3000 × g. The extracted oils were separated by decantationand stored at 4◦C for polyphenols, chlorophylls, and sterols analysis. Total lipids contentwas determined on dry weight matter following the Soxhlet extraction method. About 40 gof fresh matter was dried at 75◦C. Then, the dried matter was ground and extracted intriplicate with 200 mL hexane at 60◦C for 6 h. The hexane was removed with a rotaryevaporator at 40◦C. All experiments were conducted on triplicate from olives harvested atfull maturity (December).
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1274 HANNACHI ET AL.
Fatty Acid Composition Analysis
Fatty acid methyl ester (FAME) preparation. FAMEs were prepared accord-ing to Metcalfe et al.[14] and modified by Lechevallier.[15] An aliquot (0.2 mL) of total lipidswas evaporated in a tube of methylation. Fatty acids were esterified with 5 mL of a methano-lic sodium hydroxide solution (0.5 N) for 15 min in a boiling water bath at 60◦C. As fortransmethylation, the mixture was homogenized with 3 mL of a methanolic solution ofBF3 (20%, w/v) and the reaction was allowed to proceed for 5 min. FAMEs were extractedtwice with 10 mL of petroleum ether (boiling point 20–75◦C) and 10 mL of distilled water.The solvent was evaporated and the residues were solubilized in chloroform.
Gas-liquid chromatography. FAMEs were analyzed by gas-liquidchromatography in a Hewlett-Packard HP-4890D (Hewlett-Packard, Wilmington,DE, USA) gas chromatography equipped with a Supelcowax capillary column (Supelco,Bellefonte, PA, USA; 0.25 μm film thickness; 30 m–0.53 mm), operated isothermallyat 200◦C with an inlet carrier gas (nitrogen) pressure of 0.4 bar. The injector (split-splitless) and the flame ionization detector (FID) were maintained at 230 and 250◦C,respectively. Nitrogen was used as the carrier gas at 1 mL/min with split injectorsystem (split ratio 1:100). Fatty acids were expressed in percentage of chromatographicareas. FAMEs were identified by using standards, analyzed in the same experimentalconditions.
Total phenol content. Total phenol compounds were quantifiedcalorimetrically.[16] Phenolic compounds were isolated from a solution of oil in hex-ane (10 g of oil in 25 ml of hexane) by triple-extraction with water-methanol (60:40 V/V).A total of 2.5 mL of the combined extract was mixed with 1.25 mL of Folin-Ciocalteureagent. After 3 min, 2.5 ml of saturated Na2CO3 solution was added to the mixturefollowed by the addition of 9 mL of distilled water. The mixture was kept in the dark for60 min, after which the absorbance read at 725 nm. The blank test was made by 9 mL ofdistilled water, 5 mL of methanol 60%, and 1.25 mL of Folin-Ciocalteu reagent.
Total phenols were determined with a UV visible spectrophotometer (JENWAY6505 UV/Vis; JENWAY Ltd., Dunmow, Essex, UK) at 725 nm.
Chlorophylls content. The authors used the Wolf method[17] to measure thechlorophyll content based on absorbance at 630, 670, and 710 nm of olive oil samples.The absorbance was determined using the carbonate tetrachloride (CCl4) as the ‘blank’measured by spectrophotometer (JENWAY 6505 UV/Vis).
Sterols Content
Saponification of the lipids. In order to separate sterols, oils from wild and cul-tivated olives were treated with a potassium hydroxide. In fact, 5 g of oil were treatedwith 50 mL of ethanolic potassium hydroxide solution KOH (2N). The mixture was heatedat 60◦C for 1.30 h. After cooling, 50 mL of water was added. The unsaponifiable frac-tion was extracted four times with 50 mL of ethyl ether. The combined ether extract waswashed with 50 mL of ethanol-water (1:1). The extracted ether was dried over anhy-drous sodium sulphate Na2SO4, filtered and concentrated on a rotary evaporator. Theunsaponifiable fraction was dissolved into chloroform for thin layer chromatography (TLC)analysis.[18]
TLC separation and GC analysis. The unsaponifiable matter was separated intosub-fraction on TLC plates coated with ethanolic potassium hydroxide solution KOH-methanol (2 N) impregnated silica gel, previously activated by heating at 100◦C for
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OILS OBTAINED FROM TUNISIAN WILD OLIVE TREES 1275
1 h. The unsaponifiable fraction (5% solution of the unsaponofiable) and internal stan-dards 5-α-cholestanol (0.2%) were spotted on the plates. Elution was performed usinghexane/diethyl ether 65:35 (v/v) as the mobile phase. After development, the plate wassprayed with a 0.2% solution of 2,7-dichlorofluorescein in ethanol, and the sterol bandsappeared under UV light. Sterol bands were scraped off and dissolved in chloroform(10 mL). The obtained solution was filtered. The chloroform was evaporated by mildheating in a gentle flow of nitrogen. The sterolic fraction was dried in an oven at 105◦Cfor approximately 10 min. The sterolic fraction was treated with a silylation reagent(pyridine/hexamethyldisilazane/trimethylchlorosilane, 9:3:1, v/v/v) at the ratio of 50 μl
Figure 2 Typical chromatograms of sterol composition of (a) standard olive oil and of (b) wild olive oil samples(OSlg). Peaks: (1) Cholesterol; (2) Cholestanol (internal standard); (3) 24-Metilencholesterol; (4) Campesterol;(5) Campestanol; (6) Stigmasterol; (7) Chlerosterol; (8) β-Sitosterol; (9) Sitostanol; (10) �5-Avenasterol; (11)�5,24-Stigmastadienol; (12) �7-Stigmastenol; (13) �7-Avenasterol.
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1276 HANNACHI ET AL.
of reagent for every milligram of sterols for at least 15 min at ambient temperature.Then, this solution was centrifuged for a few minutes. The clear solution is ready for gaschromatography analysis. The trimethylsilyl ethers were analyzed by gas chromatographyin a Hewlett-Packard HP-4890D chromatograph equipped with a FID column (30 m ×0.32 mm, 0.25 μm film thickness) with stationary phase of 5% phenyl methyl siloxane,operated isothermally at 280◦C, with an inlet carrier gas (helium) giving a column flow of1.3 mL/min. The injector with a split ratio of 1:15 was maintained at 280◦C and the flameionization detector (FID) at 290◦C. Sterols was identified on the basis of retention timesand by comparison with mixture of sterol analyzed under the same conditions. Sterols wereexpressed as percentage of total sterols. The identification of individual peaks was madeon the basis of the retention times and by comparison with the mixture of standard sterolsanalysed under the same conditions (Fig. 2a).
Statistical and Chemometric Methods
All analyses were carried out in triplicate and the results were presented as means ±SD (Standard Deviation). Wild and cultivated olive value for each oil compound was com-pared to the mean of all samples by calculating a confidence interval. Analysis of variance(ANOVA) were used on oil composition (fatty acid composition, sterols, polyphenols, andchlorophylls content) of cultivated olive (cultivars) and wild olive trees based on Duncan’smultiple range test using the software Statistica (StaSoft, Johannesburg, ZA).
RESULTS
Total Lipids and Fatty Acid Composition
In wild olive oils, the total lipid ranged from 10.42% (OIch1) to 26.27% (OTest).For the both dominated Tunisian cultivars Chétoui and Chemlali, the total lipids were59.08 and 51.37%, respectively (Table 2). As expected, the oleic acid is the major fatty acidfor studied olive oils (both wild and dominated cultivars), followed by linoleic C18:2 andpalmitic C16:0 acids. Oleic acid contents for wild olive trees varied from 47.03% (OIch1) to71.55% (OIch2). For Chétoui and Chemlali, contents are 57.20 and 64.90%, respectively(Table 2). Except two wild olive trees (OIch1 and OIch3), the oleic acid content obtainedfrom wild olive oils is higher than the standard values (55%) adopted for extra virgin oliveoil.[19] We noticed also that the wild olive trees OIchk2, OTun2, OTun3, OSlg, OTeb, andOMed displayed higher oleic acid contents, compared to Chemlali (64.90%) and Chétoui(57.20%).
Monounsaturated fatty acids (MUFA) in the wild oils ranged from 47.37% (OIch1) to72.06% (OIch2). Chétoui and Chemlali dominated cultivars have 57.80 and 65.22%,respectively. The MUFA average was 63.81% in wild olive tree and 61.30% in cultivarsoils. Palmitoleic acid content ranged from 0.16% (OIchk1) to 2.59% (ODoug) in wildtree oils. The Chétoui and Chemlali cultivars have 0.61 and 0.31%, respectively. ExceptOIch1 and OIch3 (0.27 and 0.16%), all wild olive trees have more palmitoleic acid than thetwo dominated cultivars oils.
The concentration levels of polyunsaturated fatty acids (PUFA) are given (Table 2).Some wild olive oils have higher PUFA levels, such as OTest (21.49%), OIchk1 (37.26%),and OIchk3 (31.75%), than the cultivar Chétoui (20.73%). Five wild olive oils (OTest,OIch1, OIch3, OTun1, and OTun4) have PUFA percentage higher than the Chemlali cultivar(16.80%) (Table 2). The linoleic acid is the major polyunsaturated fatty acids in olive oil.
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Tabl
e2
Fatty
acid
sco
mpo
sitio
n∗(%
ofto
talf
atty
acid
s)of
oils
obta
ined
from
wild
and
two
mai
ncu
ltiva
rsof
oliv
es.
Oil
rate
/D
ried
Mat
ter
C16
:0C
16:1
C18
:0C
18:1
C18
:2C
18:3
C20
:0∑
UFA
∑M
UFA
∑PU
FA∑
SFA
OSl
g19
.25
±0.
75b
12.9
2±
0.90
ab1.
69±
0.18
g2.
58±
0.72
a68
.91
±1.
55fg
12.5
2±
0.49
a0.
86±
0.05
a0.
52±
0.06
cde
83.9
8±
0.45
bcd
70.6
0±
0.36
hi13
.38
±0.
43a
16.0
2±
0.16
abc
OTe
st26
.27
±1.
21e
16.5
1±
0.33
de0.
82±
0.08
cd2.
80±
0.25
ab57
.81
±2.
74c
19.8
3±
0.59
d1.
66±
0.13
ab0.
57±
0.04
cde
80.1
2±
0.56
abc
58.6
3±
1.27
cd21
.69
±0.
1d19
.88
±0.
15de
OTe
b24
.49
±4.
00de
13.6
9±
1.85
abc
0.98
±0.
30de
2.21
±0.
90a
65.7
2±
2.13
def
14.6
9±
0.82
abc
1.29
±0.
30ab
0.41
±0.
11bc
d82
.71
±3.
45bc
d66
.69
±2,
30fg
h16
.03
±1.
15ab
c16
.35
±2.
75ab
c
OIc
h110
.42
±1.
58a
13.0
9±
0.20
ab0.
27±
0.01
a2.
01±
0.20
a47
.03
±1.
14a
33.5
6±
3.12
f3.
70±
0.17
bc0.
32±
0.06
ab84
.56
±0.
45cd
47.3
0±
0.14
a37
.26
±0.
65f
15.4
2±
0.33
abc
OIc
h220
.18
±2.
18bc
12.1
1±
1.00
a0.
62±
0.10
bc1.
70±
0.51
a71
.55
±2.
03g
12.5
2±
1.04
a1.
34±
0.98
ab0.
13±
0.02
a86
.01
±2.
00d
72.0
6±
2.00
i13
.29
±1.
12a
13.3
1±
1.14
a
OIc
h318
.85
±2.
00b
13.9
9±
0.57
abc
0.16
±0.
04a
2.21
±0.
90a
51.5
2±
2.41
b28
.95
±1.
95e
2.80
±0.
40c
0.34
±0.
06bc
83.7
6±
0.30
bcd
52.0
1±
2.47
b31
.75
±2.
35e
16.2
5±
1.37
abc
OT
un1
24.9
0±
1.00
de14
.23
±2.
00ab
cd0.
70±
0.20
cd2.
63±
1.00
a63
.74
±2.
00d
16.7
0±
1.12
c1.
53±
0.20
ab0.
44±
0.22
bcd
82.6
2±
4.40
bcd
64.4
1±
2.20
ef18
.21
±2.
20c
17.2
6±
2.78
bcd
OT
un2
21.7
6±
1.76
bcd
16.2
0±
2.10
cd1.
31±
0.15
f1.
82±
0.35
a66
.96
±1.
97de
f12
.46
±1.
10a
0.90
±0.
30a
0.29
±0.
10ab
81.7
0±
0.52
bcd
68.2
8±
2.12
fghi
13.4
3±
1.60
a18
.13
±1.
56cd
e
OT
un3
18.9
3±
2.93
b15
.14
±1.
67bc
d1.
22±
0.20
ef2.
56±
0.42
a67
.03
±2.
10de
f12
.90
±1.
00ab
0.83
±0.
19a
0.30
±0.
10ab
82.0
2±
2.60
bcd
68.2
3±
1.78
fghi
13.7
9±
0.82
a18
.00
±2.
66cd
e
OT
un4
19.0
7±
1.93
b11
.79
±2.
00a
1.29
±0.
25ef
1.98
±0.
89a
65.0
2±
3.00
de15
.48
±1.
85bc
1.52
±0.
80ab
0.41
±0.
09bc
d83
.30
±0.
40bc
d66
.27
±3.
25fg
17.0
3±
2.85
bc14
.13
±2.
90ab
OM
edj
19.6
8±
2.68
bc14
.32
±2.
05ab
cd1.
32±
0.20
f2.
63±
0.45
a67
.89
±2.
05ef
g12
.22
±1.
90a
1.25
±0.
23a
0.32
±0.
10ab
82.5
6±
4.38
bcd
69.1
8±
2.25
ghi
13.3
7±
2.13
a17
.17
±1.
50bc
d
OD
oug
23.0
9±
0.91
cde
18.6
8±
0.22
e2.
59±
0.18
h4.
36±
0.70
c59
.49
±1.
70c
13.6
6±
0.60
ab0.
64±
0.07
a0.
59±
0.08
de76
.38
±0.
54a
62.0
8±
0.34
de14
.30
±0.
02ab
23.6
2±
0.36
f
Mea
n20
.57
±4.
1314
.34
±1.
991.
08±
0.66
2.41
±0.
7162
.74
±7.
3317
.10
±7.
051.
42±
0.65
0.39
±0.
1382
.48
±2.
4363
.81
±7.
6218
.63
±7.
9317
.13
±2.
71C
héto
ui59
.08
±0.
98g
16.6
6±
0.63
de0.
61±
0.14
bc3.
77±
0.24
bc57
.20
±4.
43c
20.0
8±
0.95
d0.
65±
0.06
a0.
68±
0.10
e78
.98
±3.
66ab
57.9
6±
4.57
c21
.03
±0.
91d
21.1
2±
0.98
ef
Che
mla
li51
.37
±0.
7f12
.83
±0.
20ab
0.34
±0.
05ab
4.60
±0.
40c
64.8
9±
2.06
de15
.96
±2.
70bc
0.85
±0.
20a
0.54
±0.
05cd
e80
.78
±4.
39ab
c64
.64
±2.
11ef
16.1
3±
2.27
abc
18.0
2±
0.65
cde
Mea
n55
.22
±5.
4514
.77
±2.
670.
48±
0.18
4.18
±0.
5960
.82
±4.
9117
.69
±3.
350.
89±
0.11
0.62
±0.
1079
.88
±1.
2761
.30
±4.
7318
.58
±3.
4619
.57
±2.
19
∗ Eac
hva
lue
pres
ente
das
the
mea
n±
stan
dard
devi
atio
n(n
=3)
.Su
pers
crip
tlet
ters
with
diff
eren
tlet
ters
inth
esa
me
colu
mn
ofoi
lsam
ples
(wild
and
culti
vate
dol
ives
)in
dica
tesi
gnifi
cant
diff
eren
ce(P
<0.
05)
anal
yzed
byD
unca
n’s
mul
tiple
rang
ete
st. ∑
UFA
:∑un
satu
rate
dfa
ttyac
ids;
∑M
UFA
:∑m
onou
nsat
urat
edfa
ttyac
ids;
∑PU
FA:∑
poly
unsa
tura
ted
fatty
acid
s;∑
SFA
:∑sa
tura
ted
fatty
acid
s.
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1278 HANNACHI ET AL.
This fatty acid percentage varied from 12.22 (OMedj) to 33.56% (OIchk1) in wild olive treeoils; for Chétoui and Chemlali cultivars, contents are 20.08 and 15.96%, respectively. Thesaturated fatty acids were 21.10% in Chétoui and 17.97% in Chemlali cultivars. However,contents of these saturated fatty acids varied from 13.94% (OIchk2) to 23.62% (OIch1) inwild olive oils. Moreover, we noted 8 out of 12 wild olives have less saturated fatty acidsthan two cultivars oils. The palmitic acid is the major saturated fatty acid in olive oil, vary-ing from 11.79% (OTun4) to 18.681% (ODoug) in wild olive oils. Contents of the stearicacid are similar in cultivated and wild olive oils. This is in agreement with IOOC criteria.
Phenols Content
The phenolic compounds content was expressed as total phenols. For all wildolive trees, contents ranged from 59.58 mg/kg (OTeb) to 537.6 mg/kg (OIch1) averag-ing approximately 196 mg/kg of oil. Chétoui and Chemlali cultivars have 490.06 and214.47 mg/kg, respectively. Consequently, phenols content from wild olive oils are sim-ilar to dominated cultivars. However, for OIch1 (537.6 mg/kg), content of phenols arehigher than both dominated cultivars. The oils from nine wild olive trees were charac-terized by their distinct total phenols content pattern (Table 3), excepting three OTest,OTun1, and OTeb, which contain less than 100 mg/kg phenolic compounds. Quantitatively,polyphenols content was statistically different (p < 0.05) depending on the wild andcultivated olive trees.
Chlorophylls Content
Table 3 clearly shows that the OSlg and OTest wild olive oils contain the highestvalues 12.17 and 13.45 mg/kg of oil, respectively, whereas the mean chlorophyll con-tents are 7.1 mg/kg for Chétoui and Chemlali oils. Quantitatively, the chlorophylls contentwas statistically different according the wild olive trees, whereas this difference was notsignificant according the two olives cultivars.
Table 3 Polyphenols and chlorophylls of oils obtained from wild and the two main cultivarsof olives.
Polyphenols (mg/kg of oil) Chlorophylls (mg/kg of oil)
OSlg 159.9 ± 4.7d 12.2 ± 2.5d
OTest 95.7 ± 3.8b 13.4 ± 3.6d
OTeb 59.6 ± 3.0a 5.2 ± 1.2bc
OIch1 537.6 ± 5.9j 5.1 ± 1.1bc
OIch2 215.5 ± 3.6f 3.2 ± 1.2ab
OIch3 350.1 ± 8.3h 2.3 ± 1.0a
OTun1 94.7 ± 4.7b 1.4 ± 0.9a
OTun2 113 ± 5.8c 4.00 ± 1.5abc
OTun3 108.5 ± 6.6c 2.1 ± 0.5a
OTun4 164.9 ± 8.3d 1.2 ± 0.2a
OMedj 190.9 ± 6.25e 3.9 ± 0.7abc
ODoug 268.32 ± 5.6g 4.45 ± 1.6abc
Chétoui 490.6 ± 4.8i 7.1 ± 2.4c
Chemlali 214.7 ± 2.3f 7.1 ± 2.6c
Superscript letters with different letters in the same column of oil samples (wild and culti-vated olives) indicate significant difference (P < 0.05) analyzed by Duncan’s multiple rangetest.
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OILS OBTAINED FROM TUNISIAN WILD OLIVE TREES 1279
Sterols Content
Sterols are important constituents of olive oils because they are related to the qualityof the oil. The β-Sitosterol is the major sterol, followed by �5-Avenasterol and campesterol(Fig. 2b, Table 4). The β-Sitosterol varied from 75.7% (OTeb) to 84.72% (OTun4). TheChétoui cultivar has 76.03% and Chemlali cultivar has 77.89%. The �5-Avenasterol rangesfrom 4.86% (OSlg) to 14.49% (OTeb) in wild olive oils. The �5-Avenasterol is presentin Chétoui and Chemlali cultivars at 18.40 and 13.53%, respectively. Sterols contents arestatistically different according the wild and cultivated olive trees (p < 0.05), except for24-metilencholesterol and chlerosterol.
DISCUSSION
The main source of vegetable fats in the Mediterranean diet is olive oil. The com-position of this oil differs from other vegetable oils that are currently consumed in manycountries. Total lipids for wild olive trees ranged from 10.42% (OIch1) to 26.27% (OTes),averaging 20.57% on dried matter. These values are lesser than those of dominated culti-vars (59.08 and 51.37%, respectively, for Chétoui and Chemlali) and in general for Tunisiancultivars.[20] These differences are mainly due to location distribution since the chemicalcomposition of crops varies with the crop cultivars, soil and climatic conditions of the areaother than genetic control.[21]
Olive oil contains high amounts of oleic acid and a smaller amount of linoleic acid.Oils extracted from olives having oleic acid higher than 55% are categorized as extra vir-gin olive.[19] Present findings clearly show that eleven out of twelve of our studied wildolive trees have oleic acid content higher than 55% (Table 2). Therefore, they are consid-ered as extra virgin oils in agreement with IOOC norms. As expected, our results showedthat the oleic acid is the major fatty acids in wild olive oils as the cultivated olive oils.Consequently, the wild olive oils could be a good source of essential fatty acids requiredfor human health. The PUFA are now well documented to have protective effects againstlipid peroxidation.[22] Recently, scientist signaled many species rich lipids and fatty acidscomposition as pomegranate seeds.[23]
In the present study, a high concentration level of MUFA and polyphenol con-tent were detected in the wild olive oils (Tables 2 and 3). The high range variation ofpolyphenols content in wild olive oils is in agreement with literature.[24] Polyphenols areimportant antioxidants that protect the oil against oxygen radicals at the cellular level anddue to self oxidation along long shelf storage. Phenols improve olive oil quality due to bothorganoleptic effect and namely for its sharp bitter taste[25] and they are responsible for fra-grance and peculiar flavor of olive oil.[26] Polyphenols content varied according the olivecultivars.[27] It has been reported that the main characteristics of olive oil was the largetotal phenol content.[28] Oxidative stability was mainly correlated with the concentrationof total phenols.[29] The cultivar genotype is the most important factor influencing theantioxidant profile of the olive oil,[29] hence, the wild olive oils subject of this study consti-tute a new edible oil source characterized by an important natural antioxidant substance,which varied according the oil samples. Particularly, OIch1 phenol content was 537.6± 5.9 mg/kg, which was higher than both Chétoui (490.6 ± 4.8 mg/kg) and Chemlali(214.7 ± 2.3 mg/kg). This finding makes Olch1 an attractive candidate as a nutritionalsupplement for commercial olive oil to prevent oil oxidation.
Olive oil color was the principal result of chlorophylls content. The wild olive oilsshow statistically significant variation (from 1.2 to 13.4 mg/kg) which was in agreement
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Tabl
e4
Ster
olco
mpo
sitio
nof
oilo
btai
ned
from
wild
and
the
two
mai
ncu
ltiva
rsof
oliv
es.
Cho
lest
erol
24-
Met
ilenc
hole
ster
olC
ampe
ster
olC
ampe
stan
olSt
igm
aste
rol
Chl
eros
tero
lβ
-Sito
ster
olSi
tost
anol
�5-
Ave
nast
erol
�5,
24-
Stig
mas
tadi
enol
�7-
Stig
mas
teno
l�
7-A
vena
ster
ol
OSl
g0.
19±
0.06
e0.
09±
0.03
b3.
06±
0.16
def
0.21
±0.
02bc
d0.
62±
0.10
abc
0.85
±0.
11ab
84.4
8±
2.14
c4.
53±
0.44
f4.
86±
0.07
ab0.
26±
0.06
a0.
21±
0.03
de0.
24±
0.03
a
OTe
st0.
15±
0.03
cde
0.05
±0.
02b
3.94
±0.
10g
0.11
±0.
02a
0.87
±0.
15ab
cd0.
92±
0.05
b84
.49
±2.
05c
1.51
±0.
39c
6.83
±0.
18bc
0.47
±0.
09bc
d0.
13±
0.02
ab0.
36±
0.07
a
OTe
b0.
12±
0.02
bcd
0.10
±0.
02b
2.77
±0.
29bc
de0.
87±
0.11
f0.
98±
0.07
cde
0.79
±0.
12ab
75.7
0±
2.61
a2.
90±
0.80
d14
.49
±1.
00e
0.35
±0.
07ab
0.28
±0.
04f
0.35
±0.
06a
OIc
h10.
02±
0.01
a0.
09±
0.04
b1.
67±
0.39
a0.
13±
0.02
ab0.
54±
0.13
ab0.
76±
0.05
ab82
.63
±3.
30bc
0.56
±0.
32ab
12.6
4±
0.41
de0.
41±
0.05
bc0.
17±
0.02
abcd
0.31
±0.
04a
OIc
h20.
03±
0.01
a0.
08±
0.01
b2.
81±
0.70
bcde
0.21
±0.
04bc
d0.
53±
0.13
a0.
80±
0.02
ab82
.33
±2.
27bc
0.75
±0.
07ab
11.1
8±
1.30
d0.
45±
0.08
bcd
0.21
±0.
02de
0.29
±0.
02a
OIc
h30.
02±
0.01
a0.
06±
0.02
b2.
10±
0.03
abc
0.13
±0.
03ab
1.22
±0.
29e
0.72
±0.
09ab
81.5
6±
1.26
bc0.
73±
0.03
ab12
.17
±1.
05d
0.49
±0.
11bc
d0.
16±
0.03
abcd
0.30
±0.
04a
OT
un1
0.11
±0.
02bc
0.09
±0.
02b
2.56
±0.
33ab
cde
0.19
±0.
04bc
0.82
±0.
21ab
cd0.
67±
0.11
a81
.36
±1.
26bc
0.96
±0.
06ab
c12
.20
±1.
85d
0.50
±0.
02bc
de0.
20±
0.03
cde
0.32
±0.
03a
OT
un2
0.16
±0.
02de
0.07
±0.
04b
2.18
±0.
95ab
cd0.
78±
0.04
e0.
71±
0.49
abcd
0.78
±0.
17ab
81.5
3±
2.59
bc0.
65±
0.11
ab11
.67
±0.
55d
0.53
±0.
08dc
e0.
18±
0.01
bcd
0.65
±0.
05b
OT
un3
0.11
±0.
01bc
0.09
±0.
01b
2.43
±0.
19ab
cde
0.27
±0.
02cd
0.98
±0.
19cd
e0.
80±
0.19
ab81
.12
±1.
18bc
1.09
±0.
35bc
11.3
2±
3.57
d0.
48±
0.16
bcd
0.19
±0.
03cd
e0.
95±
0.14
c
OT
un4
0.17
±0.
03e
0.79
±0.
08c
3.15
±0.
66ef
g0.
23±
0.03
cd0.
96±
0.25
bcde
0.86
±0.
06ab
84.7
2±
1.69
c3.
68±
0.17
e4.
04±
0.13
a0.
61±
0.03
def
0.19
±0.
02bc
de0.
54±
0.13
b
OM
edj
0.15
±0.
03cd
e0.
10±
0.03
b2.
99±
0.21
cdef
0.28
±0.
02d
1.04
±0.
12de
0.91
±0.
04b
83.3
8±
3.95
c2.
33±
0.42
d7.
60±
0.57
c0.
47±
0.09
bcd
0.12
±0.
02a
0.37
±0.
11a
OD
oug
0.08
±0.
03b
0.11
±0.
02b
4.00
±0.
86g
0.28
±0.
08d
0.84
±0.
25ab
cd0.
82±
0.11
ab82
.79
±2.
11c
2.69
±0.
18d
6.26
±0.
25bc
0.56
±0.
11cd
e0.
44±
0.07
ef0.
97±
0.24
c
Ché
toui
0.24
±0.
04f
0.04
±0.
02a
2.04
±0.
23ab
0.20
±0.
01bc
d0.
62±
0.16
abcd
0.83
±0.
04ab
76.0
3±
4.55
a0.
34±
0.19
a18
.40
±0.
30f
0.66
±0.
10ef
0.24
±0.
03ef
0.34
±0.
11a
Che
mla
li0.
29±
0.02
g0.
09±
0.04
b3.
72±
0.50
fg0.
20±
0.03
bcd
0.57
±0.
11ab
c0.
85±
0.06
ab77
.89
±1.
48ab
0.86
±0.
08ab
13.5
3±
0.92
de0.
75±
0.08
f0.
15±
0.02
abc
1.08
±0.
11c
Supe
rscr
iptl
ette
rsw
ithdi
ffer
entl
ette
rsin
the
sam
eco
lum
nof
oils
ampl
es(w
ildan
dcu
ltiva
ted
oliv
es)
indi
cate
sign
ifica
ntdi
ffer
ence
(P<
0.05
)an
alyz
edby
Dun
can’
sm
ultip
lera
nge
test
.
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3
OILS OBTAINED FROM TUNISIAN WILD OLIVE TREES 1281
with high variation (from 2 to 23 mg/kg) observed in olive oil from Spain.[24] Chlorophyllsfrom oils are an important parameter because they are correlated to oil quality. Pigmentsare involved in autoxidation and photoxidation mechanisms.[30] The research conductedon olive oil chemical composition highlights that the polyphenols are remarkably variableaccording to the variety, the agronomic conditions, the state of ripeness, and the technol-ogy of conservation.[31] Moreover, some authors attribute the variation of polyphenol andchlorophylls contents to the genetic factor.[32,33]
As for sterols, the β-Sitosterol is the major sterol, followed by �5-Avenasterol andcampesterol which was in agreement with oils extracted from cultivars olives[24,33] and inother vegetable oils.[34] Sterols are important constituents of olive oils because they arerelated to the quality of the oil. The �5-avenasterol content ranged from 4.04% (OTun4) to14.49% (OTeb) according wild olive trees. Some wild olive trees have high �5-avenasterolcontent (Table 4). This compound has been associated with antioxidant activity.[35] Thesterols percentages were in agreement with IOOC criteria.[19] Plant sterols are naturaldietary components with serum cholesterol-lowering proprieties.[36] This finding resultedin several studies of the cholesterol-lowering effects of plant sterol in humans.[33] The qual-itative characterization of wild and two cultivars olive oils was in agreement with the resultsreported by Casas et al.[37] However, the quantitative characterization was different, whichcan be explained by the fact of geographical growing area and the olive varieties.[37]
Epidemiological evidence showed a lower incidence of CHD (Coronary HeartDisease) in Mediterranean countries[38] where olive oil is the primary source of fats.[39]
The β-sitosterol, the major sterol component, has some nutritional criteria; it reducescholesterol level of blood and is sometimes used in treating hypercholesterolemia. Theβ-sitosterol inhibits cholesterol absorption in the intestines.[40] Plant sterols were reportedto have antioxidant proprieties.[41] The wild olive oils have β-sitosterol content conformityto IOOC limit permitted.
CONCLUSION
In this study, wild olive trees displayed oil composition in agreement with theInternational Olive Oil Council (IOOC) norms as extra virgin oil. Therefore, they con-stitute important olive resources for nutritional oil quality. The wild olive tree is valuablebecause it provides shelter for diverse birds and wild plants in harsh environments. In thisstudy, we also noticed that the wild olive tree is valued according to its oil compositionas fatty acids composition, polyphenols compounds, chlorophylls, and sterols content. Thewild olives seem to constitute new nutritional oil sources; therefore, these wild olive treeswith valuable oil composition could be experienced for yield, regularity of production, andother agronomic traits and if approved, the wild olive trees constitute new olive cultivarsto increase high olive oil quality in Tunisia. Eight wild olives produced fatty acids that arein agreement with IOOC criteria as extra virgin oil. The other criteria, like polyphenolscompounds, chlorophylls, and sterols, could be some parameters to qualify the wild oliveoil as a valuable nutritional oil source.
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