This study aims to investigate the physicochemical characteristics, phenolics content, and oil composition of pomegranate oil seeds (PSO). Quality indices, pigments, phenolics content, and antioxidant activity were determined. PSO was fractioned into polar lipids: glycolipids (GL) and phospholipids (PL). Sterols profile and fatty acids composition of total lipids (TL), GL, and PL were determined by GC/FID. The free acidity, the peroxide value, and the specific extinction coefficients were, respectively, 1.69%, 3.42 in milliequivalents of active oxygen per kilogram of oil, 4.15, and 3.95. PSO is rich in phenols (93.42 mg/Kg) but poor in pigments. The sterols markers were
Several studies have reported that consumed oils have enormous effects on human physiology, including lipid metabolism, development of chronic disease, and well-being [
Fruits sample were collected at full maturity from pomegranate trees of
Oil was extracted by the method of Soxhlet as described previously by Nasri and Triki (2004) [
Free acidity, peroxide value, and
Free acidity was determined by titration of a solution of oil dissolved in ethanol/ether (1 : 1, vol/vol) with ethanolic solution of potassium hydroxide (0.1 M). The result was expressed as % of oleic acid.
Peroxide value was determined by incubating a mixture of oil and chloroform/acetic acid (10 : 15, vol/vol) with a solution of potassium iodide in the dark for 5 min. Then, 25 ml of water and 500
The total chlorophyll content was calculated according to method of Kiritsakis (1998) [
Beta-carotene was measured according to the method described by Dhibi et al. (2014) [
Phenolic fraction was extracted following the procedure of Mraicha et al. (2010) [
Total phenols and O-diphenols were measured following method of Montedoro et al. (1992) [
For O-diphenols content, 100
Total flavonoid content were determined used method of Bouaziz et al. (2010) [
The capacity of PSO to scavenge the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) was measured according to the method described by Bouaziz et al. (2005) [
The unsaponifiable fraction was extracted from PSO with diethyl ether, dried, and dissolved in chloroform as described by Lukić et al. (2013) [
Total lipids, glycolipids, and phospholipids from grounded seeds were extracted according to Bligh and Dyer (1959) [
Assays were carried out in triplicate. The results are shown as the mean values with standard deviation.
The physicochemical properties of pomegranate oil are presented in Table
Quality, antiradical activity and phenols, flavonoids, and pigments contents in pomegranate seeds oil of Tounsi variety.
Concentrations | |
---|---|
Total phenols (mg/kg) | 93.42 ± 1.57 |
Flavonoids (mg/kg) | 59.46 ± 2.68 |
O-Diphenols (mg/kg) | 30.1 ± 5.89 |
Β-Carotene (mg/kg) | 3.17 ± 0.21 |
Chlorophylls (mg/kg) | 0.02 ± 0.0003 |
Free acidity (%) | 1.69 ± 0.00 |
Peroxide value (meqO2/kg) | 3.42 ± 0.68 |
|
4.15 ± 0.05 |
|
3.95 ± 0.08 |
DPPH activity (IC50 (mg/ml)) | 0.37 ± 0.09 |
Each value represents the mean of three determinations (
The oxidative state of oils is determined using the peroxide value and specific extinction at 232 and 270 nm, respectively. The peroxide value PV of oil is a valuable index to determine oil quality. If the peroxide value becomes higher than 9 meqO2/kg oil, it indicates oxidative corruption in oil [
The specific extinction coefficients at 232 nm and 270 nm are related, respectively, to the degree of primary and secondary oxidation of the oils and thus directly correlate to the amount of peroxide [
The values of
As shown in Table
The level of pigments, however, depends on the stage of fruit ripeness, the extraction process, and storage conditions. Thus, oils extracted from older fruits may contain more carotene pigment or oils from younger fruits contain more chlorophyll pigment [
Phenolic content is primary parameter for vegetables quality evaluation and directly involved in the prevention of oxidation and oil preservation. Seeds oils generally contain polyphenols preventing their oxidation [
The antioxidant activity of the PSO was measured by DPPH test. Table
Sterols are an important nonacylglycerol constituents of vegetable oil because they relate to the quality of the oil and are widely used to check genuineness while it can be used to determine adulteration of an olive oil, and it has recently been suggested that it may be used to classify virgin olive oils according to their fruit variety.
Table
Sterols and triterpenic dialcohols composition (%) of pomegranate oil seeds of Tounsi variety.
Percent | |
---|---|
Cholesterol | 0,23 ± 0.02 |
24-Methylene-cholesterol | 0,01 ± 0.00 |
Campesterol | 6,35 ± 0.11 |
Campestanol | 0,08 ± 0.01 |
Stigmasterol | 3,21 ± 0.03 |
Δ5,23-Stigmastadienol | 0,05 ± 0.01 |
Clerosterol | 1,23 ± 0.04 |
|
77,94 ± 0.12 |
Sitostanol | 0,44 ± 0.03 |
Δ5-Avenasterol | 7,45 ± 0.07 |
Δ5,24-Stigmastadienol | 0,93 ± 0.02 |
Δ7-Stigmastenol | 0,27 ± 0.02 |
Δ7-Avenasterol | 0,76 ± 0.01 |
Erythrodiol | 0,34 ± 0.020 |
Uvaol | 0,77 ± 0.05 |
Each value represents the mean of three determinations (
The fatty acid profile of TL and its lipids class were presented in Table
Fatty acid composition of individual lipid classes of pomegranate seeds.
Total lipids (%) | Phospholipids (%) | Glycolipids (%) | |
---|---|---|---|
|
0,51 ± 0,05 | 0,97 ± 0,48 | 1,19 ± 0,09 |
|
0,36 ± 0,07 | 0,25 ± 0,06 | 0,42 ± 0,15 |
|
0,14 ± 0,03 | 0,05 ± 0,01 | 0,32 ± 0,02 |
|
22,08 ± 2,71 | 43,00 ± 1,12 | 38,25 ± 3,63 |
|
1,88 ± 0,28 | 0,25 ± 0,09 | 0,30 ± 0,02 |
|
0,40 ± 0,01 | 0,31 ± 0,03 | 0,37 ± 0,06 |
|
0,27 ± 0,07 | 0,30 ± 0,08 | 0,45 ± 0,05 |
|
0,54 ± 0,08 | 0,69 ± 0,02 | 0,96 ± 0,08 |
|
0,83 ± 0,07 | 0,53 ± 0,01 | 0,28 ± 0,02 |
|
8,94 ± 1,41 | 24,24 ± 1,20 | 22,40 ± 1,64 |
|
10,47 ± 0,76 | 8,88 ± 0,92 | 7,74 ± 1,13 |
|
2,12 ± 0,23 | 1,36 ± 0,38 | 1,13 ± 0,08 |
|
0,04 ± 0,02 | 0,03 ± 0,02 | 0,13 ± 0,06 |
|
0,03 ± 0,00 | 0,01 ± 0,00 | 0,13 ± 0,01 |
|
0,01 ± 0,00 | 0,01 ± 0,00 | 0,14 ± 0,01 |
|
28,86 ± 0,26 | 9,98 ± 0,60 | 9,60 ± 0,55 |
|
2,82 ± 0,04 | 3,76 ± 0,88 | 3,64 ± 1,05 |
|
1,02 ± 0,26 | 0,35 ± 0,08 | 0,46 ± 0,05 |
|
0,10 ± 0,02 | 0,21 ± 0,08 | 0,15 ± 0,01 |
|
0,10 ± 0,00 | 0,02 ± 0,01 | 0,05 ± 0,03 |
|
0,16 ± 0,10 | 0,01 ± 0,01 | 0,12 ± 0,02 |
|
0,91 ± 0,24 | 1,41 ± 0,09 | 1,28 ± 0,12 |
|
0,43 ± 0,01 | 0,22 ± 0,20 | 0,06 ± 0,03 |
|
0,08 ± 0,00 | 0,01 ± 0,00 | 0,08 ± 0,02 |
|
0,14 ± 0,03 | 0,01 ± 0,00 | 0,05 ± 0,00 |
|
0,11 ± 0,05 | 0,01 ± 0,01 | 0,13 ± 0,01 |
|
1,25 ± 0,24 | 0,90 ± 0,08 | 1,35 ± 0,26 |
|
5,12 ± 0,25 | 0,68 ± 0,06 | 1,42 ± 0,10 |
|
1,41 ± 0,86 | 0,03 ± 0,01 | 0,91 ± 0,24 |
|
2,97 ± 2,10 | 0,03 ± 0,00 | 0,43 ± 0,07 |
|
3,04 ± 1,49 | 1,20 ± 0,11 | 1,47 ± 0,37 |
|
0,45 ± 0,22 | 0,05 ± 0,03 | 0,25 ± 0,04 |
|
0,58 ± 0,19 | 0,51 ± 0,09 | 0,44 ± 0,03 |
|
0,15 ± 0,00 | 0,03 ± 0,04 | 0,14 ± 0,10 |
|
35,17 ± 3,74 | 71,97 ± 2,46 | 66,29 ± 5,22 |
|
16,73 ± 0,20 | 11,97 ± 1,32 | 10,91 ± 1,22 |
|
46,44 ± 4,57 | 16,36 ± 1,41 | 19,02 ± 0,98 |
|
49,33 ± 0,34 | 25,75 ± 2,64 | 24,38 ± 2,63 |
|
0,99 ± 0,22 | 0,60 ± 0,09 | 0,89 ± 0,16 |
|
13,30 ± 4,46 | 2,03 ± 0,12 | 4,91 ± 0,73 |
Each value represents the mean of three determinations (
Total SFA fraction was represented as 35.17% of total lipids. This result is not consistent with those suggested by Mekni et al. (2014) who they found that Gabsi variety seed oil contains 8.51% of total SFA. Among the different components of this fraction, palmitic acid was the main SFA (22.08%) followed by stearic acid (C18:0) with a percentage of 8.94%. Other SFAs such as arachidic acid (C20:0) and behenic acid (C22:0) were presented but in lesser amount within 0.9–1.25%. However, lauric acid and myristic acid were found in insignificant levels. Our results, concerning the dominance of different SFAs, were in good agreement with previous reports [
The mean content of UFA is almost 63.17%, in which 16.73% are monounsaturated fatty acids (MUFA), 29.33% di-UFA, and 12.59% of tri-UFA. Major MUFA was oleic acid (C18:1 w9 cis) which accounted for 10.47%, followed by vaccenic acid (C18:1 w7 cis) and palmitoleic acid (C16:1 cis) with amounts of 2.12% and 1.88%, respectively. trans-form is present in trace and the trans/cis ratio of MUFA was 0.026. Our results do not correspond with those found by Mekni et al. (2014) [
Polyunsaturated fatty acids (PUFAs) fraction represented 46.44% of total lipids in which there were 32.87% cis-form content, 0.35% trans-form content, and 8.92% conjugated form. PSO is characterized by the presence of different types of omega families. In fact, Omega 6 was found to be the major PUFA and it is characterized by the predominance of linoleic acid (C18:2 w6 (c9, c11)) with a content of 28.86% followed by
The predominance of linoleic acid was confirmed in almost PSO studies but its amount was lower than that found in our study. For example, Mekni et al. (2014) [
Omega 3 PUFAs were represented by the
Conjugated fatty acids consisted about 13.30% and they represented by three conjugated linoleic acids (CLA) and five conjugated linolenic acids (CLnA) identified by chromatographic mass-spectrometry analysis as different geometric isomers of conjugated linolenic acid and, namely, punicic acid (C18:3 (c9, t11, c13)) is the major isomer (ca. 5.12%), followed by catalpic acid (C18:3 (t9, t11, c13)) (ca. 3.04%), a-eleostearic acid (C18:3 (c9, t11, t13)) (ca. 2.97%), jacaric acid (C18:3 (c8, t10, c12)) (ca. 1.41%), and b-eleostearic (C18:3 (t9, t11, t13)) (ca. 0.45%). Kaufman and Wiesman (2007) [
In our study, the MUFA/PUFA ratio was 0.36% which indicates the PUFA richness of PSO so the health-benefiting potential.
The total lipids isolated from PSO were fractioned into neutral lipids and polar lipids (namely, also bound lipids) which represented by glycolipids GL and phospholipids PL. Then PL and GL fractions were taken for fatty acid composition study. The results were illustrated in Table
Typical chromatogram of fatty acids analyzed by GC in pomegranate seeds oil.
USFA amounts in GL and PL did not differ significantly from each other. In fact, GL resemble PL in their contents of MUFA in which oleic acid (C18:1 w9 (cis)) was the major MUFA accounting for 8.88% and 7.74%, respectively, in PL and GL fractions.
Concerning PUFA, the amount is slightly higher in GL than in PL. Linoleic acid, the main PUFA, was found to be in similar amount in the two lipid classes, similar to linolenic acid, the next major PUFA. Compared to TL, the ratio of MUFA to PUFA was much higher in polar lipids. The corresponding values for this ratio in PL and GL were, respectively, 0.73% and 0.57%. This indicates that MUFA were more bound in PL than in GL. Conjugated PUFA amount in GL were found to be twofold of that in PL and they were represented mainly by punicic acid and
In conclusion of this investigation, it is clear that pomegranate seeds give a considerable yield of oil and the oil seems to be a good source of essential fatty acids, phenolics compounds, and phytosterols. Furthermore, the high percentage of PUFA, sterols, and the considerable amount of phenols make it desirable in terms of nutrition and new nonconventional supply for edible purposes and pharmaceutical industries. This work could also serve for developing quality characteristics of PSO.
This work was presented in “5ème Congrès de l’Association Tunisienne de Physiologie & de Bio-Surveillance de l’Environnement.”
The authors declare that there are no conflicts of interest regarding the publication of this article.
This work was supported by the Ministry of High Education, Scientific Research and Technology of Tunisia. The authors gratefully thank the laboratory personnel. They are also grateful to the National Office of Oil (Sousse).