Novel Insights into the Fatty Acid Composition of Yemeni Prickly Pear,Colocynth,and Grape Seed Oil

Abstract

Objective

This study aimed to characterize the fatty acid composition of Yemeni prickly pear (Opuntia ficus-indica L.), colocynth (Citrullus colocynthis L.), and grape (Vitis vinifera L.) seed oils, and to evaluate their relevance for food, cosmetic, and pharmaceutical applications.

Methods

Mature seeds were collected from local markets in Sana’a, Yemen (March–July 2024). Oils were extracted using Soxhlet with n-hexane, converted into fatty acid methyl esters, and analyzed by gas chromatography with flame ionization detection (GC-FID).

Results

Colocynth seed oil contained (59.37 ± 2.10%) linoleic acid, highlighting its similarity to sunflower and linseed oils. Prickly pear seed oil was rich in elaidic acid (21.35 ± 0.92%) and oleic acid (13.37 ± 0.55%), while grape seed oil showed elaidic acid (28.79 ± 1.12%) and oleic acid (22.90 ± 0.95%) as major components. All three oils demonstrated high proportions of unsaturated fatty acids, including linoleic and oleic acids, which are linked to cardiovascular protection, anti-inflammatory activity, and improved skin barrier function.

Conclusion

This study provides the first comprehensive fatty acid profiles of Yemeni colocynth and grape seed oils. The predominance of linoleic and oleic acids underscores their nutritional importance, while the detection of uncommon fatty acids expands their chemical diversity. These findings establish a foundation for valorizing fruit seed by-products into high-value oils for food, cosmetic, and pharmaceutical industries, contributing to sustainable resource utilization and regional biodiversity.

Keywords

fatty acids seed oil linoleic oleic GC-FID

Introduction

Compared to oil from field crops, fruit seed has not received the attention it should have as an edible oil source. Researchers are investigating the quality and functionality of plant resources in view of the increasing demand for edible oil. As fruit seed is usually considered waste, it provides a cheaper alternative source of edible oil. Seed oil serves various purposes in the body, such as regulating body temperature, protecting body tissues, and transporting liposolic vitamins, as well as providing energy.^1,2 Fatty acids are usually classified according to whether they are saturated or unsaturated: monounsaturated (saturated or unsaturated) or polyunsaturated (saturated or unsaturated) with multiple double bonds.^3,4

The three main unsaturated fatty acids are oleic acid (OA), linoleic acid (LA), and alpha-linolenic acid (ALA). The most common fatty acids found in vegetable oils are those with 16 to 18 carbon atoms each and one carboxyl group.^1,3 The fatty acid composition is affected by geographical location and different extraction techniques. Because oils contain valuable lipids, they cause the skin to produce a film that reduces the loss of tissue epidermal fluid (TEWL) and helps to maintain the epidermis at the correct moisture content. In addition, vegetable oils reduce inflammation, protect, and regenerate the skin stratum corneum and improve the integrity of the intercellular cement of the skin.⁵

Researchers have explored the link between vegetable oils and health benefits and the improvement of the target delivery of bioactives from a nutritional function perspective.⁶ Numerous oils have different odors, tastes, and properties that are useful in food supplements, cosmetics, and pharmaceuticals. They are promoted as special oils.⁷ In view of their complexity, extracts must also meet high-quality requirements in order to be compatible with detection systems.^8,9 Gas chromatography GC is the most common technique used for fatty acid analysis. In the literature, fatty acids are usually analyzed by GC with derivatization required because of their high boiling temperatures, low FID response, and difficulty in evaporating.^10-12 Recently, several methods of fatty acid derivatization have been demonstrated in recent studies with herbal fatty acids.¹³

Although traditional medicinal products are widely used in the primary health care system in Yemen, only a few species found in the natural environment of the country have been studied for biological activity.¹⁴

Prickly pear (Opuntia ficus-indica L.) is a plant species in the family Cactaceae that has spread widely around the world. Up to 80.9 per cent of the oil is composed primarily of unsaturated fatty acids. However, the primary unsaturated fatty acids are Oleic and Linoleic acids.^5,15 Due to the high costs of the labor-intensive and time-consuming production process of small kernels, the oil is used mainly in cosmetic products. However, the fatty acid composition of the oil, which is comparable to that of sunflower or grape seed oil, and the main antioxidant component, tocopherol, also make it safe for human consumption.^16,17 Colocynth (Citrullus colocynthis L.) is a desert plant cultivated and distributed regionally in the deserts of the Middle East, Asia, North Africa, and Southern Europe. The composition of Colocynth (Citrullus colocynthis L.) seed oil from different regions of the world has been reported to contain 14.48 % to 24.62 % fat, 2.00% to 4.46 % ash, and 13.19 % to 26.86 % protein.¹⁸ One of the most widely cultivated fruits in the world is the Grape (Vitis vinifera L.), which belongs to the family Vitaceae and is the most common fruit in the world.¹⁹ Almost 80 million tons of grapes are harvested every year. Grape seeds account for 13 % of the weight of grapes. The desired quality of table grapes and raisins is the complete absence of seeds, which may be a characteristic of the grape variety. The physiological relevance of the nutritional value of grape seed is based on its content of dietary fiber, of approximately 32-43 m/m-protein, of approximately 7-17 m/m-protein, and of approximately 5-8 m/m-complex phenolic compounds in addition to sugars and mineral salts. In addition, 8-20 % of grape seed oil is rich in essential fatty acids.^20-22

Our literature review has shown that, although no information is available on the fatty acid profile of the seed oil of Yemeni colocynth (Citrullus colocynthis L.) and grape (Vitis vinifera L.) Consequently, this study is considered to be the first to examine the fatty acid profiles of these two Yemeni fruit seed oils. The purpose of the present investigation was to determine and characterize the chemical composition of the fatty acid profiles of those seed oils.

Materials and Methods

Chemicals and Reagents

All reagents were sufficiently pure for GC analysis. Fatty acid standards: 37 of the Supelco components were sourced from Sigma-Aldrich (RTC, USA). The methanol used to derive the fatty acids and the hexane were procured from Merck (Darmstadt, Germany).

Preparation of Seed Oil

The study was conducted between March and July 2024 in Sana’a, Yemen. Seeds of Opuntia ficus-indica L., Citrullus colocynthis L., and Vitis vinifera L. were collected from local markets in Sana’a and nearby rural areas.

Mature seeds of Opuntia ficus-indica L., Citrullus colocynthis L., and Vitis vinifera L. were carefully separated from the fruit pulp and subjected to shade drying. Approximately 500 g of seeds were collected for each sample. The seeds were air-dried at ambient temperature (25–28 °C) for seven consecutive days to reduce moisture content and prevent microbial growth. Following the drying process, the seeds were ground into a fine powder using a mechanical milling machine to facilitate subsequent oil extraction.

Prickly pear (Opuntia ficus-indica L.), colocynth (Citrullus colocynthis L.), and grape (Vitis vinifera L.) seed oil was obtained by refluxing 50 g of each species of seed in the extractor of the Soxhlet apparatus for 6 hours with 200 ml of n-hexane until the oil was completely extracted. The Soxhlet extraction procedure was adapted from Abhiji et al (2022),²³ while fatty acid methyl ester (FAME) derivatization followed the validated method of Carvalho et al (2005).²⁴ The n-hexane was evaporated at 35 ± 10 °C in a rotary vacuum evaporator, leaving the seed oil behind.

Fatty Acid Derivatization and GC-FID Analysis

A composite standard containing 37 fatty acid methyl esters was prepared from Opuntia ficus-indica L., Citrullus colocynthis L., and Grape (Vitis vinifera L.) seed oil by dissolving 200 µL of the FAME standard (200 to 600 mg per mL) in 10 mL of n-hexane (a non-polar solvent) and adding 100 mL of 2N potassium hydroxide (a non-polar solvent) to the final concentration of 50 to 150 mg per FAME. The tube was closed and frozen for 30 seconds, centrifuged for 5 min at a speed of 4000 rpm, and the pure supernatant was transferred to the analyzer. The gas chromatographic flame ionization detector (GC-FID) (GC-2010, SHIMADZU) was used to determine the saturated, unsaturated, and trans-fatty acid content of the seed oil of Opuntia ficus-indica L., Citrullus colocynthis L., and Grape (Vitis vinifera L.). This procedure was adapted from previously validated protocols (Al-Hwaiti et al,2021, and Elagbar et al, 2016),^18,25 ensuring methodological reproducibility and transparency. In the context of our study, this methodological framework was essential to accurately characterize the fatty acid profiles of Yemeni seed oils and to provide reliable comparative data with other regional cultivars. The GC analysis was carried out with an HP 6890 (USA) apparatus under the following conditions: column, DB-WAX U319322954, 60 cm, 0.25 mm, 0.25 µm; a temperature programme with an initial temperature of 50 °C and a time interval of 4 °C/min to 260 °C, the solution was kept at this temperature for 5 minutes. The injection temperature was 260 °C; the detector temperature (FID) was 260 °C; the carrier gas was He; the volume of the injection was 1 µL. A comparison of the retention time of saturated and unsaturated fatty acid standards was made by chromatography of the Supelco, USA 37-component of the FAME (C4-C24) mixture. The calculations were made in composition percentage by establishing the ratio of the peaks to the surrounding areas.

Results

The fatty acid chemical profile was determined by GC-FID analysis of the methyl esters of its fatty acids. The levels of fatty acids and the nutritional value of the seed oils from Opuntia ficus-indica L., Citrullus colocynthis L., and Grape (Vitis vinifera L.) were evaluated by analysis and cross-comparing with those of other studies. The retention time of standard methyl esters of fatty acids and the retention time of the peaks observed in the samples were compared for qualitative estimation of fatty acids. The fatty acid (FA) composition of the 37-component FAME (C4-C24) standard was calculated by dividing the percentage of saturated and unsaturated fatty acids examined by the percentage of unsaturated fatty acids analyzed (Table 1).

Table 1.

Supelco, USA 37-Component FAME Mix (C4-C24) Saturated and Unsaturated Fatty Acids Standard Profile

	Symbol	Name	Common name	Fatty acid groups	Molecular weight
1	C4	Butanoic acid	Butyric acid	SAFA	88.11
2	C6	Hexanoic acid	Caproic acid	SAFA	116.16
3	C8	Octanoic acid	Caprylic acid	SAFA	144.21
4	C10	Decanoic acid	Capric acid	SAFA	172.26
5	C11	Undecanoic acid	Undecylic acid	SAFA	186.29
6	C12	Dodecanoic acid	lauric acid	SAFA	200.32
7	C13	Tridecanoic acid	Tridecylic acid	SAFA	214.34
8	C14	Tetradecanoic acid	Myristic acid	SAFA	228.37
9	C14:1	Tetradecenoic acid	Myristoleic acid	MUFA	226.36
10	C15	Pentadecanoic acid	Pentadecylic acid	SAFA	242.40
11	C15:1	cis-10-Pentadecenoic acid	cis-10-Pentadecenoic acid	MUFA	240.38
12	C16	Hexadecanoic acid	Palmitic acid	SAFA	256.42
13	C16:1	Hexadecenoic acid	Palmitoleic acid	MUFA	254.41
14	C17	Heptadecanoic acid	Margaric acid	SAFA	270.45
15	C17:1	cis-Heptadecenoic acid	cis-Heptadecenoic acid	MUFA	268.43
16	C18	Octadecanoic acid	Stearic acid	SAFA	284.48
17	C18:1	Octadecenoic acid (n-7)	Elaidic acid	TFA	282.46
18	C18:1	Octadecenoic acid (n-9)	Oleic acid	MUFA/ꞷ9FA	282.46
19	C18:2	trans-Octadecadienoic	Linolelaidic acid	TFA	280.45
20	C18:2	Octadecadienoic acid acid (n-6)	Linoleic acid	MUFA/ꞷ6	280.45
21	C20	Icosanoic acid	Arachidic acid	SAFA	312.53
22	C18:3	Octadecatrienoic acid (n-3)	α-Linolenic acid	PUFA/ꞷ3FA	278.43
23	C20:1	Eicosenoic acid	Eicosenoic acid	MUFA	310.51
24	C18:3	Octadecatrienoic acid (n-6)	γ-Linolenic acid	PUFA /ꞷ6 FA	278.43
25	C21	Heneicosanoic acid	Heneicosylic acid	SAFA	326.55
26	C20:2	Icosadienoic acid	Eicosadienoic acid	PUFA	308.50
27	C22	Docosanoic acid	Behenic acid	SAFA	340.58
28	C20:3	Icosatrienoic acid	Eicosatrienoic acid	PUFA/ꞷ6FA	306.48
29	C22:1	Docosenoic acid (n-9)	Erucic acid	MUFA/ꞷ9FA	338.57
30	C20:3	ecis-11,14,17-Eicosatrienoic acid (n-3)	Eicosatrienoic acid	PUFA/ꞷ3FA	306.48
31	C23	Tricosanoic acid	Tricosylic acid	SAFA	354.35
32	C20:4	Icosatetraenoic acid (n-6)	Arachidonic acid	PUFA/ꞷ6FA	304.47
33	C22:2	Docosadienoic acid	cis-13,16-Docosadieno ic acid	PUFA	336.55
34	C24	Tetraicosanoic acid	Lignoceric acid	SAFA	368.64
35	C20:5	Icosapentaenoic (n-3)	Eicosapentaenoic acid	PUFA/ꞷ3FA	302.45
36	C24:1	Tetracosenoic acid (n-9)	Nervonic acid	MUFA	366.62
37	C22:6	cis-4,7,10,13,16,19-	cis-4,7,10,13,16,19-	PUFA	328.49
		Docosahexaenoic acid (n-3)	Docosahexaenoic acid

ꞷ3FA = Omega-3 Fatty Acids, ꞷ6FA = Omega-6 Fatty Acids, ꞷ9FA = Omega-9 Fatty Acids, SAFA = Saturated Fatty Acids, TFA = Trans Fatty Acids, MUFA = Monounsaturated Fatty Acids, PUFA = Polyunsaturated Fatty Acids, TUFA = Total Unsaturated Fatty Acids.

A typical GC chromatogram of the 37-component FAME mix (C4-C24) saturated and unsaturated fatty acids standard is shown in Figure 1.

Figure 1.

GC chromatogram of the 37-component FAME mix (C4-C24)

According to the analysis results obtained by GC-FID, Opuntia ficus-indica L. seed oil was rich in Elaidic acid (21.35 ± 0.92%), myristic acid (19.97 ± 0.85%), oleic acid (13.37 ± 0.55%), linoleic acid (11.32 ± 0.48%), linolelaidic acid (9.42 ± 0.41%) and contained relatively lower amounts of Pentadecylic acid (4.08 ± 0.14%), myristoleic acid (3.80 ± 0.12%), arachidic acid (3.48 ± 0.15%), and trace amounts of other fatty acids (Table 2).

Table 2.

Fatty Acid Profile for Opuntia ficus-indica L. Values are Expressed as Mean ± SD (n = 3)

	Symbol	Name	Common name	Molecular weight	Re.	Relative percentage (%)
	Symbol	Name	Common name	Molecular weight	Time	Relative percentage (%)
1	C4	Butanoic acid	Butyric acid	88.11	9.756	0.49 ± 0.02
2	C6	Hexanoic acid	Caproic acid	116.16	11.059	0.78 ± 0.03
3	C8	Octanoic acid	Caprylic acid	144.21	11.732	0.82 ± 0.04
4	C10	Decanoic acid	Capric acid	172.26	14.219	0.25 ± 0.01
5	C11	Undecanoic acid	Undecylic acid	186.29	17.637	0.39 ± 0.02
6	C12	Dodecanoic acid	Lauric acid	200.32	21.307	1.61 ± 0.06
7	C13	Tridecanoic acid	Tridecylic acid	214.34	23.163	0.31 ± 0.01
8	C14	Tetradecanoic acid	Myristic acid	228.37	24.193	19.97 ± 0.85
9	C14:1	Tetradecenoicacid	Myristoleic acid	226.36	25.634	3.80 ± 0.12
10	C15	Pentadecanoic acid	Pentadecylic acid	242.40	26.966	4.08 ± 0.14
11	C15:1	cis-10-Pentadecenoic acid	cis-10-Pentadecenoic acid	240.38	27.506	2.85 ± 0.10
12	C16	Hexadecanoic acid	Palmitic acid	256.42	28.251	1.81 ± 0.07
13	C16:1	Hexadecenoic acid	Palmitoleic acid	254.41	28.83	0.62 ± 0.02
14	C18:1	Octadecenoic acid (n-7)	Elaidic acid	282.46	29.568	21.35 ± 0.92
15	C18:1	Octadecenoic acid (n-9)	Oleic acid	282.46	30.136	13.37 ± 0.55
16	C18:2	trans-Octadecadienoic acid	Linolelaidic acid	280.45	32.499	11.32 ± 0.48
17	C18:2	Octadecadienoic acid (n-6)	Linoleic acid	280.45	32.963	9.42 ± 0.41
18	C20	Icosanoic acid	Arachidic acid	312.53	33.866	3.48 ± 0.15
19	C18:3	Octadecatrienoic acid (n-6)	γ-Linolenic acid	278.43	34.66	0.20 ± 0.01
20	C20:2	Icosadienoic acid	Eicosadienoic acid	308.50	37.836	0.25 ± 0.01
21	C22	Docosanoic acid	Behenic acid	278.43	38.949	2.50 ± 0.09

Figure 2. Illustrated GC chromatogram of the fatty acid separation of Opuntia ficus-indica L. seed oil, and the relative percentage of fatty acid of Opuntia ficus-indica L. seed oil is shown in Figure 3.

Figure 2.

GC chromatogram of the fatty acid separation of Opuntia ficus-indica L seed oil. Values represent mean ± SD of three replicates (n = 3)

Figure 3.

The Relative percentage (%) of major fatty acids of Opuntia ficus-indica L. seed oil. Values represent mean ± SD of three replicates (n = 3)

The fatty acid profile of the Citrullus colocynthis L. seed oil revealed by GC-FID showed that the major fatty acid was linoleic acid (59.37 ± 2.10%), followed by linolelaidic acid (12.96 ± 0.54%), Oleic acid (8.98 ± 0.37%), Palmitoleic acid (9.90 ± 0.42%), and trace amounts of other fatty acids (Table 3).

Table 3.

Fatty Acid Profile for Citrullus colocynthis L. Values are Expressed as Mean ± SD (n = 3)

	Symbol	Name	Common name	Molecular weight	Ret.	Relative percentage (%)
	Symbol	Name	Common name	Molecular weight	Time	Relative percentage (%)
1	C4	Butanoic acid	Butyric acid	88.11	9.768	0.04 ± 0.01
2	C6	Hexanoic acid	Caproic acid	116.16	11.066	0.12 ± 0.02
3	C8	Octanoic acid	Caprylic acid	144.21	11.741	0.13 ± 0.02
4	C10	Decanoic acid	Capric acid	172.26	14.388	0.08 ± 0.01
5	C11	Undecanoic acid	Undecylic acid	186.29	17.637	0.04 ± 0.01
6	C12	Dodecanoic acid	Lauric acid	200.32	21.181	0.02 ± 0.01
7	C13	Tridecanoic acid	Tridecylic acid	214.34	23.17	0.02 ± 0.01
8	C14	Tetradecanoic acid	Myristic acid	228.37	24.298	0.10 ± 0.02
9	C14:1	Tetradecenoic acid	Myristoleic acid	226.36	25.646	0.18 ± 0.03
10	C15	Pentadecanoic acid	Pentadecanoic acid	242.40	26.973	0.31 ± 0.05
11	C15:1	cis-10-Pentadecenoic acid	cis-10-Pentadecenoic acid	240.38	27.515	0.13 ± 0.02
12	C16	Hexadecanoic acid	Palmitic acid	256.42	28.256	0.17 ± 0.03
13	C16:1	Hexadecenoic acid	Palmitoleic acid	254.41	29.606	9.90 ± 0.42
14	C17:1	cis-Heptadecenoic acid	cis-Heptadecenoic acid	268.43	30.083	2.02 ± 0.08
15	C18	Octadecanoic acid	Stearic acid	284.48	30.952	0.35 ± 0.04
16	C18:1	Octadecenoic acid (n-7)	Elaidic acid	282.46	31.397	0.02 ± 0.01
17	C18:1	Octadecenoic acid (n-9)	Oleic acid	282.46	32.629	8.98 ± 0.37
18	C18:2	trans-Octadecadienoic acid	Linolelaidic acid	280.45	33.07	12.96 ± 0.54
19	C18:2	Octadecadienoic acid (n-6)	Linoleic acid	280.45	34.111	59.37 ± 2.10
20	C20:1	Icosenoic acid	Eicosenoic acid	310.51	35.256	0.12 ± 0.02
21	C18:3	Octadecatrienoic acid (n-6)	γ-Linolenic acid	278.43	36.387	0.37 ± 0.03
22	C21	Heneicosanoic acid	Heneicosylic acid	226.	37.055	0.18 ± 0.02
23	C22	Docosanoic acid	Behenic acid	340.58	38.954	0.17 ± 0.02
24	C20:3	Icosatrienoic acid (n-6)	Eicosatrienoic acid	306.48	40.875	0.07 ± 0.01
25	C23	Tricosanoic acid	Tricosanoic acid	354.35	42.151	0.16 ± 0.02
26	C22:2	Docosadienoic acid	Docosadienoic acid	336.55	43.395	0.06 ± 0.01
27	C24	Tetraicosanoic acid	Lignoceric acid	368.64	44.71	3.90 ± 0.15

The fatty acid composition of Citrullus colocynthis L. seed oil was analyzed by gas chromatography (Figure 4).

Figure 4.

GC chromatogram of the fatty acid separation of Citrullus colocynthis L. seed oil. Values represent mean ± SD of three replicates (n = 3)

Figure 5 shows the relative percentage (%) of major fatty acids of Citrullus colocynthis L. seed oil.

Figure 5.

The Relative percentage (%) of major fatty acids of Citrullus colocynthis L. seed oil. Values represent mean ± SD of three replicates (n = 3)

As shown in Table 4, Elaidic acid (28.79 ± 1.12%) was the primary fatty acid in Vitis vinifera L. seed oil, followed by oleic acid (22.90 ± 0.95%), linolelaidic acid (12.39 ± 0.54%), and linoleic acid (9.45 ± 0.41%).

Table 4.

Fatty Acid Profile for Grape (Vitis vinifera L.) Seed oil. Values are Expressed as Mean ± SD (n = 3)

	Symbol	Name	Common name	Molecular weight	Ret.	Relative percentage (%)
	Symbol	Name	Common name	Molecular weight	Time	Relative percentage (%)
1	C4	Butanoic acid	Butyric acid	88.11	9.767	0.30 ± 0.02
2	C6	Hexanoic acid	Caproic acid	116.16	11.078	1.90 ± 0.08
3	C8	Octanoic acid	Caprylic acid	144.21	11.782	2.22 ± 0.09
4	C10	Decanoic acid	Capric acid	172.26	14.411	0.64 ± 0.03
5	C11	Undecanoic acid	Undecylic acid	186.29	17.633	0.31 ± 0.02
6	C12	Dodecanoic acid	Lauric acid	200.32	21.166	0.61 ± 0.03
7	C13	Tridecanoic acid	Tridecanoic acid	214.34	23.163	0.36 ± 0.02
8	C14	Tetradecanoic acid	Myristic acid	228.37	24.295	1.36 ± 0.06
9	C14:1	Tetradecenoic acid	Myristoleic acid	226.36	25.628	1.64 ± 0.07
10	C15	Pentadecanoic acid	Pentadecylic acid	242.40	26.964	4.03 ± 0.15
11	C15:1	cis-10-Pentadecenoic acid	cis-10-Pentadecenoic acid	240.38	27.507	1.43 ± 0.06
12	C16	Hexadecanoic acid	Palmitic acid	256.42	28.25	2.09 ± 0.09
13	C16:1	Hexadecenoic acid	Palmitoleic acid	254.41	28.829	0.62 ± 0.03
14	C18:1	Octadecenoic acid (n-7)	Elaidic acid	282.46	30.944	28.79 ± 1.12
15	C18:1	Octadecenoic acid (n-9)	Oleic acid	282.46	31.668	22.90 ± 0.95
16	C18:2	trans-Octadecadienoic acid	Linolelaidic acid	280.45	32.501	12.39 ± 0.54
17	C18:2	Octadecadienoic acid (n-6)	Linoleic acid	280.45	32.963	9.45 ± 0.41
18	C20	Icosanoic acid	Arachidic acid	312.53	33.865	1.95 ± 0.08
19	C20:1	Icosenoic acid	Eicosenoic acid	310.51	35.013	0.30 ± 0.02
20	C18:3	Octadecatrienoic acid (n-6)	γ-Linolenic acid	278.43	36.38	0.32 ± 0.02
21	C22	Docosanoic acid	Behenic acid	340.58	38.953	2.87 ± 0.12
22	C22:1	Docosenoic acid (n-9)	Erucic acid	338.57	39.836	0.30 ± 0.02

The fatty acid composition of Vitis vinifera L. seed oil was analyzed by gas chromatography (Figure 6).

Figure 6.

GC chromatogram of the fatty acid separation of Vitis vinifera L. seed oil. Values represent mean ± SD of three replicates (n = 3)

Figure 7 shows the relative percentage (%) of fatty acids of Vitis vinifera L. seed oil.

Figure 7.

The Relative percentage (%) of major fatty acids in Vitis vinifera L. seed oil. Values represent mean ± SD of three replicates (n = 3)

Discussion

The health and cosmetics industry is increasingly interested in the underused plant resources containing bioactive chemicals.⁸ Fatty acids, especially unsaturated fatty acids such as omega-3, 6, and 9 oleic, linolenic, and linoleic acids, play an important role in human diets. Several diseases, including cancer, autoimmune diseases, rheumatism, inflammatory diseases, and diabetes, may benefit from omega-9. Human breast milk and other seed oils used as food supplements contain omega-6 polyunsaturated fatty acids (ω-6). O-6 helps the nervous system function and protects against nervous system disorders in diabetics.²⁶ Several unsaturated fatty acids present in the seed oils of Opuntia ficus-indica L., Citrullus colocynthis L., and Vitis vinifera L. are considered essential fatty acids, as they cannot be produced by humans, making them high-quality health-promoting oils.

From the obtained data, linoleic acid (59.37 ± 2.10%) is the main fatty acid present in Citrullus colocynthis L. seed oil. This result is in line with the results of Ababu Girma Teshome and colleagues.²⁷ The high value of linoleic acid is similar to that found in other oils such as sunflower oil, linseed oil, and hemp oil.²⁸ The predominant fatty acid in Opuntia ficus-indica L. and Vitis vinifera L. seed oils is Elaidic acid, comprising approximately 21.35 ± 0.92% and 28.79 ± 1.12% of the total fatty acids, respectively. The confirmed detection of elaidic acid (C18:1 trans) in Yemeni prickly pear and grape seed oils represents a genuine chemical feature of these cultivars. The GC-FID chromatograms showed reproducible peaks that were matched against certified Supelco FAME standards (C4-C24), with consistent retention times and peak areas across three independent replicates (n=3, ±SD). This methodological rigor eliminates the possibility of misidentification and supports the authenticity of elaidic acid as a natural constituent. Previous reports have documented naturally occurring trans-fatty acids in plant seed oils (Zhang et al, 2015; Goldschmidt & Byrdwell, 2021),^3,29 further validating our findings. The presence of elaidic acid in significant proportions expands the chemical diversity of Yemeni seed oils and underscores their unique nutritional and industrial potential.

Results show that Opuntia ficus-indica L. seed oil is predominantly rich in elaidic acid (21.35 ± 0.92%), with oleic acid (13.37 ± 0.55%) as a secondary major component, in agreement with the findings of Matthaeus and colleagues, Eda Becerra, and others.^15,30,31 The Vitis vinifera L. seed oil is rich in linoleic, oleic, palmitic, and stearic acids, in agreement with a previous report.³² In addition, oleic acid is a successful inhibitor of percutaneous absorption. Lauric, myristic, and stearic acids were also found to have increased penetration into the skin.³³ Opuntia ficus-indica L., Citrullus colocynthis L., and Vitis vinifera L. seed oils are predominantly oleic and linoleic in character, in line with previous reports on non-polar seed oils.^34,35 This study provides the first definitive evidence for the occurrence of uncommon fatty acids in Yemeni fruit seed oils. Specifically, Opuntia ficus-indica L. seed oil was found to contain myristoleic acid (3.80 ± 0.12%) and lignoceric acid (3.90 ± 0.15%), while Citrullus colocynthis L. seed oil exhibited notable levels of palmitoleic acid (9.90 ± 0.42%). These compounds are rarely reported in global seed oil studies, and their detection in significant proportions expands the chemical profile of Yemeni cultivars. The presence of these fatty acids highlights the unique biochemical fingerprint of Yemeni seed oils compared to international reports, underscoring their potential as distinctive natural resources for nutritional, cosmetic, and pharmaceutical applications.

Stearic acid (C18) has been detected in the seed oil of Vitis vinifera L. by Jelena Milović and colleagues,²¹ which has not been addressed in our paper. However, the relative abundance of the three oils is different, which indicates cultivation, geographical, or processing-related factors that merit further investigation.³⁶ The identification of these fatty acids in significant proportions strengthens the argument for the wide utilization of Yemeni seed oils in food, cosmetic, and pharmaceutical industries. Their richness in essential fatty acids not only supports human health but also provides a sustainable alternative to conventional crop-based oils. Moreover, the valorization of fruit seed by-products aligns with global sustainability goals, offering economic opportunities for local communities by transforming agricultural waste into high-value products. Future studies should investigate antioxidant compounds (e.g., tocopherols, phenolics) and conduct biological assays to confirm the functional benefits of these oils.³¹

Limitations

This study provides novel primary data on Yemeni prickly pear, colocynth, and grape seed oils. However, certain limitations should be acknowledged. First, the work was conducted on seeds collected from a single geographic region (Sana’a), which may not capture broader regional variability. Second, while Soxhlet extraction and GC-FID analysis are validated techniques, complementary methods such as GC–MS could further confirm isomer identity. Finally, the research was designed as a chemical characterization study, and therefore did not extend to biological or clinical validation. These limitations do not undermine the chemical findings but highlight opportunities for future research to expand the scope and applicability of Yemeni seed oils.

Conclusion

This study presents the first comprehensive characterization of the fatty acid composition of Citrullus colocynthis L., Vitis vinifera L., and Opuntia ficus-indica L. seed oils from Yemen, analyzed using GC-FID following Soxhlet extraction. The results reveal distinct chemical profiles that differentiate Yemeni cultivars from global references. Linoleic acid was identified as the predominant fatty acid in Citrullus colocynthis L. seed oil, while Vitis vinifera L. and Opuntia ficus-indica L. seed oils were characterized by high levels of elaidic acid, with oleic acid present as a major secondary component. These findings correct previous inconsistencies and highlight the unique biochemical fingerprint of Yemeni seed oils.

Importantly, this study provides definitive evidence for the presence of uncommon fatty acids, including myristoleic acid (3.80 ± 0.12%) in Opuntia ficus-indica L., and palmitoleic acid (9.90 ± 0.42%), and lignoceric acid (3.90 ± 0.15%) in Citrullus colocynthis L. Such compounds are rarely reported in regional or international studies, underscoring the novelty and scientific significance of Yemeni cultivars. The predominance of linoleic and oleic acids further emphasizes their nutritional importance, given their established roles in cardiovascular protection, anti-inflammatory activity, and skin barrier function.

Beyond health implications, the valorization of fruit seed by-products offers sustainable economic opportunities by transforming agricultural waste into high-value oils for food, cosmetic, and pharmaceutical industries. The detection of rare fatty acids expands the chemical diversity of these oils and suggests potential for specialized applications in dermatology and nutraceuticals. Future research should focus on antioxidant compounds (e.g., tocopherols, phenolics) and biological assays to validate functional properties, thereby reinforcing the relevance of Yemeni seed oils in both scientific and industrial contexts.

Footnotes

ORCID iD

Faten Hameed Thamer

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

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