Proximate composition of seeds and seed oils from melon (Cucumis melo L.) cultivated in Bulgaria

Abstract The seeds of three varieties of melon (Cucumis melo L.) from Bulgaria were analyzed for their chemical composition and a detailed study of their lipids was carried out. Chemical composition values were as follows: fat content ranged from 41.6 to 44.5%, protein 34.4 to 39.8%, crude fiber 4.5 to 8.5%, carbohydrates 8.2 to 12.7%, soluble sugars 3.7 to 4.2%, and minerals 4.6 to 5.1%. The content of sterols, phospholipids, and tocopherols in the oils was 0.6, 0.7–1.7%, and 435–828 mg/kg, respectively. The major fatty acid in lipids was linoleic (51.1–58.5%), followed by oleic acid (24.8–25.6%). The trilinolein (31.3–32.2%), oleo dilinolein (31.0–34.0%), and palmitoyl dilinolein (14.9–22.3%) have represented 80.0% from the total triglyceride composition of the melon seeds oil. β-Sitosterol predominated in both free and esterified sterols, being, respectively, 52.9–70.8 and 50.4–58.4%. Phosphatidylinositol (24.4–33.9%), phosphatidylcholine (23.0–33.1%), and phosphatidylethanolamine (8.4–17.1%) were the main phospholipids. Palmitic acid (34.4–61.7%) was the major fatty acid of the phospholipids, followed by oleic acid (8.9–27.2%). Linoleic acid (32.7–39.1%) was the main component among the fatty acids of the sterol esters, followed by oleic acid (25.1–30.7%). In the tocopherol fraction of melon seed oils, the main component γ-tocopherol varied from 71.4 to 91.5%.


ABOUT THE AUTHORS
The group's main research activities are to lead investigations over the chemical and lipid composition of different animal fats and vegetable oils; determination of their biologically active components and the possibilities of their application in food, medicine, and cosmetic industry.
The research reported in this paper could relates to wider projects as stabilization of melon seed oils with different natural antioxidants; determination of the best antioxidant for these oils following of subjecting the oils of long-term storage and investigating how their chemical and lipid composition change during the storage under different conditions.

PUBLIC INTEREST STATEMENT
The seeds of three melon varieties (Cucumis melo) from Bulgaria were analyzed for their chemical and lipid composition. Chemical composition consisted as follows: fats, proteins, crude fiber, carbohydrates, soluble sugar, and minerals. The lipid composition of melon seeds included fatty acids, sterols, phospholipids, and tocopherols. They take part in the biologically active components, which contribute to the natural preservation of the oils from auto-oxidation. The major fatty acid in lipids was linoleic, followed by oleic acid. The trilinolein, oleo dilinolein, and palmitoyl dilinolein have represented 80.0% from the total triglyceride composition of the oils. β-Sitosterol predominated in sterols. Phosphatidylinositol, phosphatidylcholine, and phosphatidylethanolamine were the main phospholipids. Palmitic and oleic acids were the major fatty acids of the phospholipids. Linoleic and oleic acids were the main components among the fatty acids of the sterol esters. The main component in tocopherol fraction was γ-tocopherol.
Melon seed oil is rich in biologically active substances such as tocopherols, sterols, phospholipids, which determine its beneficial effect on the human organism (Azhari et al., 2014;Imbs & Pham, 1995;Mariod & Matthäus, 2008). The information about the lipid composition of the melon seeds concerns mainly the physicochemical characteristics and the fatty acid composition of the oils, while the data obtained vary depending on the type of the tested seeds and on the region they originate from (Albishri et al., 2013;Azhari et al., 2014;de Mello et al., 2001;Ibeto, Okoye, & Ofoefule, 2012;Jacks et al., 1972;Lazos, 1986;Mian-Hao & Yansong, 2007;Milovanović & Pićurić-Jovanović, 2005;Obasi et al., 2012;Yanty et al., 2008). Regarding the content of the biologically active substances (sterols, tocopherols, and phospholipids) in the glyceride oils from melon seeds, the data are scarce. In Bulgaria, no research has been done with regards to the application of melon seeds (C. melo) as oilseed feedstock for food and industrial purposes. The information on the lipid composition (fatty acid composition of triacylglycerols, content and composition of sterols, tocopherols, and phospholipids) of melon seeds grown in Bulgaria is rather limited. The objective of this work is to study the general chemical composition of the seeds from three varieties of melon (C. melo), as well as to characterize the isolated lipids with regards to the fatty acid composition, structure of the triacylglycerols, content of the biologically active substances (tocopherols, sterols, and phospholipids).

Plant material
The seeds were obtained from melon fruits (C. melo L.), varieties Honeydew, Dessert 5, and Hybrid 1, grown in region of Plovdiv, southern Bulgaria, crop 2012. Prior to use for analysis, the melon seeds were air dried for 72 h at 25°C.

Chemical composition of seeds
Crude protein was calculated from the nitrogen content by Kjeldahl method using factor 6.25 (Association of Official Analytical Chemist [AOAC], 1996). The carbohydrate content was calculated by the following formula: 100 − (weight in grams [crude protein + crude lipids + water + ash] in 100 g of seeds) (FAO, 2003). The soluble carbohydrates were identified by their extraction with water and was determinate by high-performance liquid chromatography (HPLC) on a Agilent® LC 1220 (USA) instrument equipped with Zorbax Carbohydrate column (150-mm × 4.6-mm, 5-μm, Agilent) and Zorbax Reliance Cartridge guard-column (Agilent), and refractive index detector (RID 1260) (Georgiev, Ognyanov, Yanakieva, Kussovski, & Kratchanova, 2012). The mobile phase was acetonitrile/water (AcN/ H 2 O) (80/20) at 1.0 mL/min. All standards (individual pure monosaccharides with purity ≥98%) were purchased from Sigma Chemical Company (USA). Crude fiber was determined by the gravimetric procedure of AOAC (1995). Ash content was evaluated by incinerating at 550°C in a muffle furnace for 6 h (AOAC, 1995). Moisture was determined according to AOAC (1995).

Isolation of glyceride oil and determination of oil content
The seeds (100 g sample) were air dried and the oil was extracted with n-hexane in Soxhlet for 8 h. The solvent was partly removed in rotary vacuum evaporator, the residue was transferred in preweight glass vessels and the rest of the solvent was removed under stream of nitrogen to a constant weight to determine the oil content (ISO 659, 2009).

Physicochemical parameters of glyceride oils
Peroxide and acid values were determinated titrimetrically by procedures of ISO (ISO 660, 2009;ISO 3960, 2007). Oxidative stability was determinated using accelerated "Rancimat" method where the temperature in the heating block was 100°C and the air flow rate was 20 l/h (ISO 6886, 2006).

Analysis of fatty acids
The fatty acid composition of the triacylglycerols as well as the fatty acid composition of sterol esters and the main classes of phospholipids were determined by gas chromatography (GC) after transmethylation of the respective sample with 2% H 2 SO 4 in absolute CH 3 OH at 50°C (ISO 5509, 2000). Fatty acid methyl esters were purified by thin-layer chromatography (TLC) on 20 × 20-cm plates covered with 0.2-mm Silica gel 60 G layer with mobile phase n-hexane diethyl ether 97:3 (v/v). GC was performed on a HP 5890 (Hewlett Packard GmbH, Austria) gas chromatograph equipped with a 60-m × 0.25-mm × 25-μm (I.D.) capillary DB-23 column and a flame ionization detector. The column temperature was programmed from 130°C (hold 1 min), at 6.5°C/min to 170°C, at 3°C/min to 215°C (hold 9 min), at 40°C/min to 230°C (hold 1 min); the injector and detector temperatures were 270 and 280°C, respectively. Hydrogen was the carrier gas at a flow rate 0.8 mL/min; split was 1:50 and software was Data Apex Clarity TM 2.4.1.93/2005. Identification was performed by comparison of retention times with those of a standard mixture of fatty acids subjected to GC under identical experimental conditions (ISO 5508, 2004). Iodine value (g I 2 /100 g fat) was calculated on the basis of fatty acid composition of the oil (American Oil Chemists Society, 1999).

Analysis of sterols
Unsaponifiables were determined after saponification of the glycerides oil and extraction with n-hexane (ISO 18609, 2000). Quantification of sterols was carried out spectrophotometrically (at 597 nm), after isolation of sterols from other unsaponifiable matter by TLC on Silica gel 60 G in the mobile phase diethyl ether : n-hexane (1:1 v/v) (Ivanov, Bitcheva, & Konova, 1972).
Sterol composition was determined on HP 5890 gas chromatograph (Hewlett Packard GmbH) equipped with 25 m × 0.25-mm DB-5 capillary column and flame ionization detector. Temperature gradient from 90°C (hold 2 min) up to 290°C at a rate of change 15°C/min and then up to 310°C a rate of 4°C/min (hold 10 min); detector temperature-320°C; injector temperature-300°C and carrier gas-hydrogen, split-1:50 and software Data Apex Clarity TM 2.4.1.93/2005. Identification was confirmed by comparison of retention times with those of a standard mixture of sterols (ISO 12228, 1999).

Analysis of tocopherols
Tocopherols were determined directly in the oil by HPLC on a "Merck-Hitachi" (Merck, Darmstadt, Germany) instrument equipped with 250-mm × 4-mm Nucleosil Si 50-5 column (Merck, Darmstadt, Germany) and fluorescent detector "Merck-Hitachi" F 1000. The operating conditions were as follows: mobile phase of n-hexane:dioxan 96:4 (v/v), flow rate 1.0 mL/min, excitation 295 nm, emission 330 nm (ISO 9936, 2006). 20 μL of 1% solution (1 g in 100-mL n-hexane) of oil were injected. Tocopherols were identified by comparing the retention times with those of authentic individual tocopherols. The tocopherol content was calculated on the basis of tocopherol peak areas in the sample versus tocopherol peak area of standard α-tocopherol solution.

Analysis of phospholipids
Another part (100 g) of air-dried seeds was subjected to Folch extraction (Folch, Lees & Sloane-Stanley, 1956). The phospholipids classes were isolated by a variety of the two-dimensional TLC on 20 × 20-cm glass plates with 0.2-mm Silica gel 60 G layer impregnated with aqueous (NH 4 ) 2 SO 4 (1 g in 100-mL water). In the first direction, the plate was developed with chloroform:methanol:ammonia, 65:25:5 (v/v/v) and in the second-with chloroform:acetone:methanol:acetic acid:water, 50:20:10:10: The individual phospholipids were detected and identified by spraying with specific reagents: Dragendorff test (detection of choline-containing phospholipids), Ninhydrin spray (for phospholipids with free amino groups), and Shiff's reagent (for inositol containing phospholipids). Additional identification was performed by comparing the respective R f values with those of authentic commercial standards subjected to Silica gel 60 G TLC under identical experimental conditions. The quantification was carried out spectrophotometrically against a standard curve by measuring the phosphorous content at 700 nm after scrapping the respective phospholipid spot and mineralization of the substance with a mixture of perchloric acid and sulfuric acid, 1:1 by volume (ISO 10540-1, 2003).

Statistical analyses
The statistical analysis was performed using the statistical function from Microsoft Office Excel. For each sample, three determinations have done (n = 3, where n is the number of the replications). The data were presented as mean values ± standard deviation (SD). The level of significance was set at p < 0.05. The limit detection in GC and HPLC was 0.05%.

Chemical composition of melon seeds
The data about the content of the main components in the seeds-oil, proteins, carbohydrates (soluble sugars and fibers), the minerals, and the moisture are presented in Table 1.
Differences between the results about proteins, carbohydrates, and mineral content, which were obtained by our study and the data from other investigations, were probably due to the geographical regions and agricultural conditions such as temperature, moisture, and fertilizing.

Studies on lipid composition of the glyceride oil from melon seeds
The data about the biologically active substances (sterols, phospholipids, tocopherols) in the glyceride oils and in the seeds are presented in Table 2.
The quantity of unsaponifiables was within the limits from 0.7% to 1.0%, which coincided with the data from previous studies (0.65-1.2%) (Azhari et al., 2014;Lazos, 1986;Yanty et al., 2008). The sterol quantity in the three studied varieties was similar (0.6%) and it was close to the values obtained by other authors (0.3-0.8%) (Azhari et al., 2014;Imbs & Pham, 1995;Mariod & Matthäus, 2008). The highest quantity of phospholipids was found in the oil from variety Hybrid 1 (1.7%), and it was close to the content of phospholipids in the seed oil from melon grown in northern Vietnam (1.6%) (Imbs & Pham, 1995).
Larger quantity of tocopherols was found in melon seed oils from varieties Honeydew and Hybrid 1-respectively, 828 and 731 mg/kg. The tocopherol content in the oil from variety Dessert 5 (435 mg/ kg) was close to that of the melon seed oil from C. melo, var. tibish with Sudan origin (432 mg/kg) (Azhari et al., 2014). Values are means ± SD (n = 3 and p < 0.05).
The iodine value (IV), which was a measure of the level of unsaturation of the plant oils was with high values (IV > 100 g I 2 /100 g), as a result of the higher content of the essential linoleic acid. In the literature sources, the iodine value of the melon oil varied from 89.5 to 153.4 g I 2 /100 g, (Azhari et al., 2014;de Mello et al., 2000;Lazos, 1986;Mian-Hao & Yansong, 2007;Obasi et al., 2012;Yanty et al., 2008), while the results obtained by us were close to those of melon oils studied by de Mello et al. The iodine value is an indirect indicator also for the oxidative stability of the oils. The similar values of the iodine values of the studied oils correspond to the similar oxidative stability (7.2-14.3 h). The studied melon oils had from two to three times higher oxidative stability compared to seed oils obtained from different varieties originating from Sudan (C. melo), studied by Mariod and Matthäus (2008) (5.7-5.9 h) and Azhari et al. (2014) (4.28 h).

Fatty acid composition
The data about the fatty acid composition of the triacylglycerols in the seed oils from the studied melon varieties are presented in Table 3. Values are means ± SD (n = 3 and p < 0.05).
In the glyceride oils from seeds of various varieties of melon, the unsaturated fatty acid (UFA) predominated, where their quantity was, respectively, from 76.5 to 83.7% (Figure 1). Values are means ± SD (n = 3 and p < 0.05). b C 12:0 is the lauric acid, C 14:0 is the myristic acid, C 14:1 is the myristoleic acid, C 15:0 is the pentadecanoic acid, C 16:0 is the palmitic acid, C 16:1 is the palmitoleic acid, C 17:0 is the margaric acid, C 18:0 is the stearic acid, C 18:1 is the oleic acid, C 18:2 is the linoleic acid, C 18:3 is the linolenic acid, C 20:0 is the arachidic acid, C 20:1 is the eicosenoic acid (gadoleic).  Their content in the oils of the studied seeds was similar to the data announced by other authors according to whom the quantity of the UFA in the melon seed oils had been from 67.5 to 82.76%, where the share of the PUFA had been over 60.0% (Azhari et al., 2014;de Mello et al., 2001;Mian-Hao & Yansong, 2007;Milovanovic & Picuric-Jovanovic, 2005;Yanty et al., 2008). The ratio of saturated fatty acids: UFA was 1.0:3.3 in the seed oil from Hybrid 1, 1.0:4.3 for the variety Dessert 5, and 1.0:5.1 in the oil from Honeydew. Similar ratio of the fatty acid content was noticed in the melon seed oil from variety C. melo var. tibish with origin from Sudan (SFA/UFA = 4.01) (Azhari et al., 2014).

Triacylglycerol structure
The triacylglycerol structure of the melon oils was determined as well (Table 4).
There were identified in the studied oils, 11 types of combinations between fatty acid radicals, and the three tested samples shown similar structure.
The linoleic acid was a major component in the three main types of triacylglycerols (LLL, LLO, and LLP). The quantity of trilinolein (LLL) in the studied melon oils was 31.3-32.2%, the quantity of oleo dilinolein (LLO) was 31.0-34.0%, and the quantity of palmitoyl dilinolein (LLP) was 14.9-22.3%. The contents of the three main types of triacylglycerol (LLL, LLO, and LLP) in the melon seed oils of variety Honeydew, which, respectively, were 31.3, 33.8, and 14.9% were close to the data obtained by Yanty et al. (2008) for the melon variety Honeydew, with origin from Malaysia (LLL-24.9%, LLO-21.5%, and LLP-15.9%). The other three classes of triacylglycerols (LOO, LOP, and LLS) were identified in quantities within 2.8-7.6%, while the remaining triacylglycerols (LPP, OOO, OOP, LOS, and LPS) existed in insignificant quantities (<0.05-1.5%).

Sterol composition
The data of the content of free sterols and esterefied sterols in the seed oils are presented in Figure 2.
The main part of the sterols was the fraction of the free sterols (75.0-81.7%). These values were a bit higher in comparison to other vegetable oils (sunflower, safflower, and lallemantia seed oil) where the content of free sterols was 70.0-75.0% (Angelova & Zlatanov, 2004;Zlatanov et al., 2010Zlatanov et al., , 2012. The qualitative profile of free and esterified sterols was identical in the all investigated varieties, but the quantitative composition is found to be different (Table 5). The main components in both sterol fractions were β-sitosterol (over 50.0%), Δ 5 -avenasterol (19.7-42.7%), and stigmasterol (2.7-4.8%). Notes: L is the linoleic acid (C 18:2 ), O is the oleic acid (C 18:1 ), S is the stearic acid (C 18:0 ), P is the palmitic acid (C 16:0 ). a Values are means ± SD (n = 3 and p < 0.05).
The quantity of β-sitosterol in the fraction of free sterols in melon seed oils from varieties Dessert 5 and Hybrid 1 (70.8 and 64.7%, respectively) was significant higher than in esterified sterols (55.7 and 58.4%, respectively) while the amount of Δ 5 -avenasterol in the fraction of the esterified sterols was higher than in free sterols. In melon seed oil from variety Honeydew, the content of β-sitosterol in the fraction of free sterols (52.9%) was close to that in esterified sterols (50.4%). The amount of β-sitosterol in both fractions sterols of three melon seed oils (50.4-70.8%) was lower than the values reported by Azhari et al. (2014), wherein the amount of β-sitosterol was about 95.0%. The quantity of stigmasterol was the same in free and esterified sterols. A marked difference was established in the cholesterol content between free and esterified sterols. The content of cholesterol in sterol esters (0.5-1.1%) was several times higher than in the fraction of free sterols (0.2-0.3%). These differences could be put down to the different phases of the biosynthesis and accumulation of those compounds. In the first stage, cholesterol was synthesized and then it was used as precursor for  synthesis of sterol esters (Vlahakis & Hazebroek, 2000). These results were similar with the finding of Mariod and Matthäus (2008) and Albishri et al. (2013), according to which β-sitosterol was the major sterol component, followed by campesterol, while cholesterol and stigmasterol were presented in traces in melon seed oil. In comparison with other vegetable oils, higher quantities of unsaturated sterol derivatives as stigmasterol, Δ 5 -avenasterol, Δ 7 -stigmasterol, and Δ 7 -avenasterol were established in all varieties of melon.

Fatty acid composition of sterol esters
The data of fatty acid composition of sterol esters are shown in Table 6.
In comparison with the fatty acid composition of triacylglycerols, the differences in the contents of the main components (linoleic, oleic, palmitic, and stearic acids) were established. A lower content of linoleic acid (32.7-39.1%) was determined in sterol esters than in triacylglycerols (51.1-58.5%). The C 8:0 is the caprylic acid, C 10:0 is the capric acid, C 12:0 is the lauric acid, C 14:0 is the myristic acid, C 14:1 is the myristoleic acid, C 15:0 is the pentadecanoic acid, C 16:0 is the palmitic acid, C 16:1 is the palmitoleic acid, C 17:0 is the margaric acid, C 18:0 is the stearic acid, C 18:1 is the oleic acid, C 18:2 is the linoleic acid, C 18:3 is the linolenic acid, C 20:0 is the arachidic acid, C 20:1 is the eicosenoic acid (gadoleic), C 22:0 is the Behenic acid, SFA is the saturated fatty acids, UFA is the unsaturated fatty acids. b Not detected. c Values are means ± SD (n = 3 and p < 0.05).

Phospholipid composition
The composition of the phospholipid fraction of the melon seed oils is presented in Table 7.
In the phospholipid fraction of the melon seed oils from different varieties, there were identified all major classes of phospholipids. On the grounds of the obtained data, it can be seen that in the phospholipid fraction from varieties Honeydew and Hybrid 1, there predominated phosphatidylinositol (33.9 and 30.9%) as a major component, followed by phosphatidylcholine (23.0 and 27.7%), while in the variety Dessert 5, phosphatidylcholine was with higher content (33.1%), followed by phosphatidylinositol (24.4%). The highest content of phosphatidylethanolamine was found to be in the variety Hybrid 1 (17.1%), while in varieties Dessert 5 and Honeydew, its content was, respectively, 11.6 and 8.4%. A relatively high content was found out of phosphatidic acids (13.5-16.3%), which were decomposition products of hydrolysis processes, or were the result of uncompleted stage of biosynthesis of the other phospholipids. The quantity of sphingomyelin in variety Dessert 5 was higher (4.3%), while in the phospholipids from variety Honeydew and Hybrid 1, it was lower (0.8 and 0.4%) compared to other vegetable oils where its quantity was within 1.0-2.0% (Gunstone, Harwood, & Dijkstra, 2007). Higher quantity was observed of lysophosphatidylcholine and lysophosphatidylethanolamine (1.7-6.6%). The quantities of monophosphatidylglycerol and diphosphatidylglycerol in the phospholipid fraction were from 0.4% to 0.8%. The data show that the phospholipids of the seeds from different melon varieties had similar qualitative and quantitative composition, with the exception of Dessert 5 variety where the content of phosphatidylinositol and phosphatidylcholine was different.

Fatty acid composition of main classes of phospholipids
The data about the fatty acid composition of the main phospholipid classes of the studied Bulgarian varieties of melon are presented in Table 8.
Within one given variety, we could see differences between the main phospholipid classes. In variety Honeydew, the content of palmitic acid increased in direction phosphatidylethanolamine > phosphatidylcholine > phosphatidylinositol, which was at the expense of lessening of the quantity of the other major component-the oleic acid (from 23.2 to 15.2%). In the other two varieties Dessert 5 and Hybrid 1, the quantity of the palmitic acid was higher in phosphatidylinositol (57.9% Dessert 5 and 61.6% Hybrid 1) and in phosphatidylethanolamine (56.4% Dessert 5 and 61.7% Hybrid 1) compared to phosphatidylcholine (48.8 and 46.8%).
The quantity of stearic acid varied within the limits from 9.4% to 16.3%, and in variety Honeydew, its quantity was the same in the separate phospholipid classes (11.2-11.5%), while in the other two varieties, its quantity increased in the following order phosphatidylinositol > phosphatidylcholine > phosphatidylethanolamine.
A tendency was noticed for lessening the content of the oleic acid in direction phosphatidylinositol > phosphatidylcholine > phosphatidylethanolamine in the phospholipids of variety Honeydew, while in variety Dessert 5, its content increased from 8.9% (phosphatidylinositol) to 22.7% (phosphatidylcholine and phosphatidylethanolamine), while in variety Hybrid 1, it increased in the direction phosphatidylcholine > phosphatidylethanolamine > phosphatidylinositol.
The quantity of linoleic acid in the separate phospholipid classes in the three studied melon varieties was within the limits from 6.7 to 19.8%, and it was highest in the three phospholipid classes of Honeydew.
A common tendency was not found out in the change of the content of saturated fatty acids in the separate classes of phospholipids in the three melon varieties; in the variety Honeydew, the quantity of the saturated acids increased in direction phosphatidylethanolamine (61.4%) > phosphatidylcholine (58.2%) > phosphatidylinositol (54.9%), in variety Dessert 5-in direction phosphatidylinositol (76.2%) > phosphatidylcholine (69.0%) > phosphatidylethanolamine (68.7%), and in variety Hybrid 1phosphatidylinositol (80.0%) > phosphatidylethanolamine (79.2%) > phosphatidylcholine (62.2%). In the given rows about the three studied melon varieties, it was noticed a decrease in the content of the UFA, where this of the PUFA was too low.
Compared to the fatty acid composition of the triacylglycerol fraction considerable differences were noticed. While in the triacylglycerols of all studied oils, the polyunsaturated linoleic acid predominated (51.1-58.5%), however, its quantity in the phospholipid fraction was 6.7-19.8% at the expense mainly of the saturated fatty acids (54.9-80.0%), which quantity is 3-4 times higher than that in the triacylglycerols (16.3-23.5%). The content of SFA in phospholipids was significantly higher and in comparison with sterol esters (28.8-38.0%). From the other side, the smallest were the changes in the content of the MUFA in the factions of the triacylglycerols and phospholipids.
These differences can be explained with the various stages of biosynthesis of fatty acids-at one side of the phospholipids and at the other-of the triacylglycerols. At the first stage of biosynthesis, mainly the saturated fatty acids were synthesized, as well as in the phospholipids, and after themin the sterol esters. The phospholipids were synthesized in the following order: phosphatidylinositol, phosphatidylethanolamine, and phosphatidic acids, while finally, the triacylglycerols were synthesized. In this situation, in the molecules of the phospholipids more saturated fatty acids were included, firstly in phosphatidylinositol, afterwards in phosphatidylethanolamine, phosphatidylcholine, and finally, in the triacylglycerols, when the intensity of synthesis of UFA increased. At last stage, PUFA was synthesized which was included in triacylglycerols (Munshi, Sukhija, & Bhatia, 1983).

Tocopherol composition
The data from the tocopherol composition of melon seed oils are presented in Table 9.
The presence of main classes of tocopherols was found out (α-, β-and γ-tocopherols). The main component in the oils was γ-tocopherol, where its quantity varied from 71.4% (Dessert 5) to 91.5% (Honeydew). A higher content of α-tocopherol was found in the oil from variety Dessert 5 (19.7%), compared to the other two varieties, where its content was from 2.9% (Honeydew) to 6.2% (Hybrid 1). β-Tocopherol was found in minimum quantities in the oil extracted from the seeds of melon variety Honeydew (1.7%). The unsaturated tocopherol representatives in the oils were presented by γ-tocotrienol with quantities from 3.9 to 15.3%. The results we have obtained correlated to the data found in the literature sources about the tocopherol content of the seed oils of variety C. melo var. agrestis, cultivated in Sudan, where γ-tocopherol dominated and it was 80.7 and 77.6% of the total tocopherol quantity, followed by α-tocopherol (18.0-21.0%) (Mariod & Matthäus, 2008), but they differed from the data by Azhari et al. (2014), in which in the melon seed oil from variety C. melo var. tibish there predominated δ-tocopherol (63.4%), followed by γ-tocopherol (30.3%) and α-tocopherol (6.3%). Values are means ± SD (n = 3 and p < 0.05).
b Not detected.