INTRODUCTION:

Olive cultivation is widespread throughout the Mediterranean region and is important for the rural economy, local heritage and the environment⁽¹⁾. Mediterranean areas have a significantly lower incidence of cardiovascular heart disease when compared with other countries according to some studies, This phenomenon has been associated with dietary habits that depend mainly on virgin Olive oil^(2,3),

which is the most important food product that has a great effect due to its sensory properties and unique composition including antioxidants compounds such as phenols, tocopherols, and volatile compounds, in addition to the high level of unsaturated fatty acids especially Oleic acid and Linoleic acid, that have specific roles in the prevention of infection and degenerative diseases, neurological disorders, and breast and colon cancers.^(4-7) Oleic acid is the main monounsaturated fatty acid in olive oil which it constitutes a large percentage of the total fatty acids in it⁽⁸⁾, It has benefits health effects where it plays important role in decreasing blood level of low density lipoproteins (LDL) and increasing blood level of high density lipoproteins (HDL)⁽⁹⁾, regulating the activity of signaling pathway of adrenergic receptors (α- and β-adrenoceptors) which are key elements in the central and peripheral control of blood pressure⁽⁸⁾ thus, causing a reduction in blood pressure and prevention of heart disease.^(8,10)Depending on studies, On November 2004, the Federal Drug Administration (FDA) of the U.S.A permitted a claim on olive oil labels concerning: “the benefits on the risk of coronary heart disease of eating about two tablespoons (23g) of olive oil daily, due to the monounsaturated fatty acid in olive oil”⁽¹¹⁾in general, olive oil contents low level of saturated fatty acids (SFA): mainly Palmitic acid, Stearic acid, and trace of Myristic acid. It contents also High level of MUFA especially Oleic acid, and small amount of Palmitoleic acid, Low level of PUFA mainly Linoleic acid (Omega 6), very low Linolenic acid (Omega3) and Arachidonic acid⁽¹²⁾. Fatty acids compositional limits adopted in the most recent editions of Codex Alimentarius and International Olive Oil Council (IOC) are given in table (1)⁽¹³⁾

Table (1) fatty acids composition in olive oil according Codex Alimentarius and IOC

Fatty acid		Codex Alimentarius	IOC
Myristic acid	C14:0	< 0.1	< 0.05
Palmitic acid	C16:0	7.5- 20	7.5- 20
Palmitoleic acid	C16:1	0.3-3.5	0.3-3.5
Heptadecanoic acid	C17:0	< 0.5	< 0.3
Heptadecenoic acid	C17:1	< 0.6	< 0.3
Stearic acid	C18:0	0.5- 5	0.5- 5
Oleic acid	C18:1 cis	55- 83	55- 83
Linoleic acid	C18:2	3.5-21	3.5-21
Linolenic acid	C18:3	--	< 1
Arachidonic acid	C20:4	< 0.8	< 0.6

The content of fatty acids as well as the ratio between unsaturated and saturated fatty acids is important parameter for determination of nutritional value of certain oil. Also, the determination of minor fatty acids in olive oil is very important for the acute knowledge of lipid profile during the authentication of the varietal origin of oils⁽¹⁴⁾. therefore the newest trend in food processing industry in notifying the composition of olive oils and other food commodities for the content of each individual fatty acid.⁽¹⁵⁾.

Fatty acids composition may differ from sample to sample, depending on the zone of production and the climate (temperature and rainfall) which may influence the physiological behavior of the olive tree and consequently the fruit ripening process modifying both the amount and the qualitative characteristics of oil in olives.⁽¹⁶⁾ Some studies showed a relationship between thermal conditions and fatty acids composition of oil, where they found that locations with the high temperature and low altitude could be associated with an increased polyunsaturation and the lowest Oleic percentage. This could be attributed to a modification of lipid biosynthesis coinciding with a wet summer.⁽⁶⁾ So many studies have been carried out to categorize virgin olive oils from different geographical regions^(4,17). This research aims to evaluate the Syrian olive oil available in local market, produced in various Syrian agricultural areas by determining its content of fatty acids and some parameters (total saturated fatty acids SFA, total unsaturated fatty acids TUFA, monounsaturated fatty acids MUFA, polyunsaturated fatty acids PUFA, and MUFA/PUFA) that indicate its quality which compliance with Codex Alimentarius and IOC, and distinguish characteristics of the cultivar or the geographical origin of olive oil^(18,19). and compare the results with fatty acid composition of olive oils produced in other Mediterranean regions (Lebanon, Spain, Greece).

MATERIAL AND METHOD:

Chemicals, reagents and Instruments:

A 37- component Fatty acids methyl esters mix was purchased from Larodan Sweden, and was used to confirm the retention times and mass spectra for peak identification. (2mol/l) Methanolic potassium hydroxide solution, (1mol/l) hydrochloric acid solution, and n-Hexane were obtained from FLUKA. Gas chromatography (GC) Agilent A7890 equipped with a Mass spectroscopy (MS) was used for the specific analysis of Oleic acid in the oil extract.

Samples:

For the present study, Twelve olive oil samples produced in four agricultural areas included (coastal region, northern region, interior region, and southern region) were obtained from different local Syrian market, In addition to six olive oil samples (exterior regions) from other Mediterranean countries (Lebanon, Spain, and Greece.) were purchased for comparison.

The samples were labeled as indicated in table(2):

Table(2) olive oil samples obtained from Syrian local market and some Mediterranean areas:

Agricultural area	Sample 1	Sample2	Sample3
Syrian olive oil samples:
Coastal region	C1	C2	C3
Northern region	N1	N2	N3
Interior region	I1	I2	I3
Southern region	S1	S2	S3
Exterior olive oil samples
Spain	SP1	SP2	--
Greece	GR1	GR2	--
Lebanon	LE1	LE2	--

Identification and quantification of fatty acids methyl esters (FAMEs):

Esterification method:^(20,21)

0.2g of olive oil was put into test tube and dissolved in 2.4ml of n-hexane, an aliquot 0.6 ml of (2mol/l) methanolic potassium hydroxide solution was added. The tube was capped and shaken for 20 s and allowed to boil for one minute in water bath at 70°C . Then, 1.2ml of (1mol/l) hydrochloric acid was added and gently stirred . Next , 3 ml of n-hexane was added and the upper phase containing the fatty acids methyl esters was decanted and dissolved in n-hexane to 10ml and 0.5 ϻl of the obtained solution was injected into the GC-MS.

Gas chromatography mass spectrometry analysis:⁽²²⁾

GC–MS analysis was carried out using an Agilent A7890 gas chromatograph with a 5975C inert XL EL/CI MS detector equipped with HP-5MS 5% Phenyl Methyl Silox(30 m x 250 µm x 0.25 µm) capillary column . Helium was used as the carrier gas at a flow rate of 184.2 ml/ min with a split ratio of 30:1, and the sample size was1.0 μL. The following temperature program was used: injector temperature 230°C, initial column temperature 100°C (held 5 min), temperature ramp 10°C/min to 240°C and held at this temperature for 10min. The total run time was 30 min. the injection was performed manually. Data acquisition was realized in the scan mode (range 40-400 m/z). The fatty acids were identified by comparing their retention times and mass spectral data to the mass spectral data obtained by analysis of standard fatty acids methyl esters solution under the same conditions.

RESULTS AND DISCUSSION:

Fatty acids profile for olive oil samples:

the olive oil samples were determined by GC-MS, and the corresponding chromatograms were presented as: Coastal oil sample C1 figure(1), Northern oil sample N1 figure(2), Interior oil sample I1figure (3), Southern oil sample S1 figure (4), Lebanese oil sample LE1 figure(5), Spanish oil sample SP1 figure(6), Greek oil sample GR1 figure(7).

Determination of Saturated fatty acids:

the results showed that total SFA vary between (14-18.32%) where it was found in the highest value in Spanish oil samples whish contents Palmitic acid C16:0 in high value up to (16.98%), and low value of Stearic acid C18:0 (1.34%). While all Syrian samples contained lower amount of Palmitic acid and higher amount of Stearic acid ranged between (11.88- 15.16%) and (2.19-2.96%) respectively. the other exterior samples content between (13.4-14.07%) Palmitic acid, and (1.63- 2.44%) Stearic acid. There was no trace of Myristic acid C14:0 in any of the sample tested which consistent with Codex Alimentarius, as shown in the table (3). all these SFA percentages were consistent with those obtained in most studies on Mediterranean olive oil samples^(6,23).

Determination of unsaturated fatty acids:

the results showed that total unsaturated fatty acids vary between (80.51-85.28%), the Greek oil samples contained the highest percentage of MUFA (82.04%) while all other samples were contained MUFA ranging between (67.73- 77.05%), Oleic acid forms the majority of them in all oil samples, Palmitioleic acid forms small amount of them in all oil samples except the coast and northern oil samples that were free of it due to the lower temperatures in these areas (between 25-35°C) than the rest of Syria, while the highest percentage of PUFA was found in southern oil sample where it reached (13.95%) which contains Linoleic acid only, and no Linolenic acid which consistent with Codex Alimentarius. the high MUFA/PUFA ratio was in the Greek oil sample (29.09) which makes it the most stable oil, followed by Spanish oil sample (17.9),⁾ while the Syrian oil samples ranged between(4.85-8.60) similary to studies have shown the MUFA/PUFA ratio in Syrian olive oil is up to (48)⁽⁶⁾. the unsaturated fatty acids profile are listed in table (4)

The differences observed between olive oil samples for the fatty acid composition may be explained by the different agricultural areas. This agree with the results described by other authors for oils from olives growing in different regions^(17-24-25). Notes that the fatty acids composition of all olive oil samples was in the range of Codex Alimentarius and IOC standard. These results contradict some studies in Egypt, which have worked to compare commercial olive oils exported from some Mediterranean areas (Syria, Spain, and Greece). and available in Egyptian markets, which showed that Spanish oil contained the highest percentage of Oleic acid up to 78%, while Syrian olive oils did not contain more than 65% and no trans acids was found in all samples⁽⁶⁾ . And also these results agree with the results of a study carried out by the general commission for agricultural research in Syria GCSAR 2006 which showed the high quality of olive oil in various cultivated Syrian areas.⁽²⁶⁾.

Table (3): saturated fatty acids composition of different types of virgin olive oil

Olive oil brand		SFA	C16:0	C18:0	C14:0
Coastal region	C1	14.07	11.88	2.19	---
	C2	13.92	11.52	2.4	---
	C3	14.01	11.26	2.75	---
Northern region	N1	16.7	14.19	2.51	---
	N2	16.25	14.05	2.2	---
	N3	16.64	14.14	2.5	---
Interior region	I1	16.46	13.5	2.96	---
	I2	16.55	13.9	2.65	---
	I3	16.49	13.8	2.69	---
Southern region	S1	18	15.16	2.84	---
	S2	18.2	15.2	3	---
	S3	17.98	15.01	2.97	---
Spain	SP1	18.32	16.98	1.34	---
Spain	SP2	18.21	16.81	1.4	---
Greece	GR1	15.11	13.48	1.63	---
Greece	GR2	15.01	13.4	1.61	---
Lebanon	LE1	16.51	14.01	2.44	---
Lebanon	LE2	16.8	14.2	2.6	---

Table (4): unsaturated fatty acids composition of different types of virgin olive oil

Olive oil brand		C16:1	C18:1	C18:2	C18:3	TUFA	MUFA	PUFA	MUFA/PUFA
Coastal region	C1	---	75.28	9.71	---	85.28	75.57	9.71	7.78
	C2	---	74.45	10.2	---	84.9	74.7	10.2	7.32
	C3	---	74.3	9.95	---	84.53	74.58	9.95	7.49
Northern region	N1	---	71.53	10.15	---	83.28	72.35	10.15	7.12
	N2	---	70.11	10.2	---	81.06	70.86	10.2	6.94
	N3	---	70.1	10.24	---	81.14	70.9	10.24	6.92
Interior region	I1	0.41	73.65	8.82	---	84.08	75.26	8.82	8.53
	I2	0.39	73.51	8.7	---	83.6	74.9	8.7	8.60
	I3	0.34	73.71	8.79	---	84.05	75.26	8.79	8.56
Southern region	S1	0.28	66.73	13.8	---	81.95	68.15	13.8	4.93
	S2	0.31	66.22	13.95	---	81.68	67.73	13.95	4.85
	S3	0.3	67.95	13.85	---	83.2	69.35	13.85	5
Spain	SP1	0.78	74.63	4.6	---	81.65	77.05	4.6	16.75
Spain	SP2	0.75	73.99	4.25	---	80.51	76.26	4.25	17.9
Greece	GR1	0.29	80.8	2.82	---	84.86	82.04	2.82	29.09
Greece	GR2	0.29	80.0	2.9	---	83.29	80.39	2.9	27.72
Lebanon	LE1	0.26	70.96	8.35	---	81.27	72.92	8.35	8.7
Lebanon	LE2	0.28	70.66	8.21	---	80.9	72.69	8.21	8.85

CONCLUSIONS:

The fatty acids profile, which is influenced by cultivar and environment, is an important part of the oil quality, it has previously been used by a number of authors as a parameter for oil classification^(28-27), where the proportion of the different fatty acids can determine the nutritional value of the oil. the fatty acids profiles of all olive oil samples were in the range of Codex Alimentarius and IOC standard.

ACKNOWLEDGEMENTS:

The authors acknowledge the financial support received from Damascus University. Scientific assistance provided by Prof. Mounir Ataei (Faculty of Pharmacy, Arab international university) , D. Ghassan Abochama (Faculty of science, University of Damascus) and D. Wissam Zam ( Al Andalus university) is greatly appreciated.

Figure (1) Chromatogram of C1 olive oil sample

Figure (2) Chromatogram of N1 olive oil sample

Figure (3) Chromatogram of I1 olive oil sample

Figure (4) Chromatogram of S1 olive oil sample

Figure (5) Chromatogram of L1 olive oil sample

Figure (6) Chromatogram of SP1 olive oil sample

Figure (7) Chromatogram of GC1 olive oil sample

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Received on 22.10.2019 Modified on 02.12.2019

Research J. Pharm. and Tech 2020; 13(5): 2345-2349.

DOI: 10.5958/0974-360X.2020.00422.9