The prickly pear (Opuntia spp.) is an important plant in the economies of arid and semiarid areas, considering its low agronomic requirements and high water use efficiency. Characterizing the chemical composition of this plant will open new avenues for food, pharmaceutical, and cosmetic applications. In this context, this study examined the physical and chemical parameters of fruit seed oils of two prickly pear species from Rhamna area located in the center of Morocco: Opuntia ficus-indica (OFI), represented by the varieties “Safra” and “Aakria,” and Opuntia megacantha (OM), represented by the variety “Derbana.” The evaluated parameters included oil content, free acidity, specific extinction coefficients (K232 and K270), pigment content, fatty acid, and triglyceride composition. The seed oil contents of the three varieties “Safra,” “Aakria,” and “Derbana” were 8.09%, 8.74%, and 8.04%, respectively. OM (“Derbana”) seed oil was the most stable. The three studied varieties had higher contents of α-pheophytin and carotenoids than that of chlorophyll. Oil from the “Aakria” variety was distinguished by having the highest contents of α-pheophytin and chlorophyll. Significant differences in some fatty acid and triglyceride contents were noted. The major fatty acids of the three varieties were linoleic acid (60.55%–63.46%), followed by oleic acid (18.88%–21.81%) and palmitic acid (13.03%–13.75%). Furthermore, the chromatographic profiles of the triglycerides have shown the dominance of trilinolein (LLL, 24.33%–26.49%) and oleoyl-dilinoleoyl-glycerol (OLL, 20.92%–21.92%). Some triglycerides could be considered species markers, especially OLL, dipalmitoyl-linoleoyl-glycerol (PPL), oleoyl-linoleoyl-linolenoyl-glycerol and palmitoyl-oleoyl-dilinoleoyl-glycerol fraction (OLLn + PoLL), and stearoyl-dioleoyl-glycerol (SOO). This study provides a basis for qualitatively evaluating the therapeutic and cosmetic potential of prickly pear derivatives and for establishing quality standards of seed oil derived from the two species studied.
The prickly pear (Opuntia spp.) belongs to the Cactaceae family. Native to Mexico, it was introduced into the Mediterranean region around the end of the 15th century and into North Africa around the end of the 16th century . Opuntia ficus-indica (OFI) is a spineless and dominant species. It is found in different varieties that differ in color and that are harvested in varying stages of ripeness. Opuntia megacantha (OM) is a thorny species that is mainly used for farm fencing. The seeds are used for oil extraction . Phenology studies of these species have shown that they produce vegetative and floral buds during the spring and undergo long periods of fruit development in the summer .
Currently, the prickly pear is of great interest not only for its ecological roles but also for its potential in food, industrial, pharmaceutical, and cosmetic applications. The literature reports promising information concerning the biological activities and chemical composition of different parts of this plant (fruit pulp, cladodes, seeds, and flowers). Pulps, peels, and cladodes are rich in bioactive compounds, especially antioxidants, including vitamin C, vitamin E, carotenoids, flavonoids, glutathione, and pigments [4–6].
The seeds constitute 2–3.8% of the fruit weight . The oil is rich in polyunsaturated fatty acids. Linoleic acid was established as a major fatty acid in seed oils, followed by oleic and palmitic acids. Myristic, stearic, and arachidonic acids were detected in OFI seed oil in low amounts [8–10]. Significant levels of vitamins (tocopherol and vitamin K1) and sterols were also found in this oil. Beta-sitosterol was the sterol marker, accounting for 72% of the total. The major tocopherol is gamma-tocopherol, representing an average of 90% of total tocopherols, compared with delta-tocopherol (9%) and alpha-tocopherol (1.8%) . Furthermore, prickly pear seed oil has a rich aroma because of acids, alcohols, aldehydes, esters, hydrocarbons, ketones, and other compounds, such as 2-propenal, acetic acid, pentanal, 1-pentanol, hexanal, 2-hexenal, heptanal, 2-heptenal (Z), octanal, 2-octenal, nonanal, 2,4-decadienal (E,E), and trans-4,5-epoxy-(E)-2-decenal . However, the chemical composition of this oil, particularly its fatty acid and tocopherol composition, changes according to geographic origin .
Previous studies have conducted useful chemical investigations to evaluate the therapeutic and cosmetic potential of prickly pear seed oil. However, for other oils sold worldwide, such as olive oil and argan oil, quality standards have been established; such standards for prickly pear seed oil are lacking. Therefore, extensive studies on the purity and quality of prickly pear seed oil and its shelf life are essential to promote the quality and utility of this product on a commercial scale. A recent study focused on the sanitary and commercial quality related to the oxidative stability under different storage conditions and adulteration detection of prickly pear seed oil, especially in OFI species .
The present study aims to establish a comparative assessment through the physical and chemical characterizations of prickly pear seed oils of three varieties belonging to two species of the prickly pear (Opuntia spp.): OM species locally called “Derbana” and OFI species represented by the varieties “Safra” and “Aakria” from Rhamna, located in the center of Morocco. To the best of our knowledge, this is the first study to compare seed oils of these prickly pear species. The results of this investigation will also provide useful information for future studies evaluating the therapeutic and cosmetic potential of prickly pear seed oil.
2. Materials and Methods
2.1. Plant Material and Oil Extraction
Two prickly pear species (Opuntia spp.) collected from the Rhamna region (central Morocco) were studied.(i)Two varieties of OFI: (i) the variety with yellow orange pulp locally called “Safra” or “Mles” and (ii) the variety with carmine red pulp, locally called “Aakria.”(ii)OM: locally called “Derbana” or “El-Hercha” .
Homrani Bakali et al.  reported that two prickly pear types, spineless and spiny, are represented, respectively, by Opuntia ficus-indica f. ficus-indica (OFI) and Opuntia ficus-indica f. amyclaea, taxonomic synonym (homotypic) of Opuntia megacantha (OM), and nomenclatural synonym (heterotypic) of Opuntia amyclaea.
The plant voucher specimens of the two species used in this study were deposited at the Regional Herbarium “MARK” of the Faculty of Sciences Semlalia, Cadi Ayyad University (Marrakesh, Morocco).
The fruits of both species, OFI and OM, were harvested at the ripe stage in the Skhour Rhamna region, located approximately 100 km north of Marrakesh (Rhamna Province, Morocco). They were hand-peeled, and the pulp was separated from the seeds using a hand crusher and sieve. The seeds were then washed thoroughly with water, dried in an oven at 30°C for 24 h, and crushed using a PULVERISETTE 14 grinder (Fritsch International, Germany).
First, 45 g of seed powder was collected for each variety; then, the oils were extracted with hexane using a Soxhlet extraction system for 6 h at 65°C. At the end of the extraction, the organic phase was evaporated using a rotary evaporator under vacuum with minimal heating (40°C). The obtained oil was placed in dark glass vials for protection from light and bubbled with a stream of nitrogen to remove residual traces of hexane. The vials were stored at 4°C until further analysis. The oil content is expressed in g/100 g of seed powder.
2.2. Determination of Oil Physical Quality Parameters
The oil-specific extinction coefficients K232 and K270, which are used to evaluate conjugated dienes and conjugated trienes, respectively, were determined according to the IOC standard .
For free acidity determination, the method used was described by the standard NF.T 60-204 . Briefly, 1 g of oil was obtained in 20 mL of an equal volume of ether/ethanol (50/50, v/v) and neutralized, and then, free fatty acids were titrated using an ethanolic potassium hydroxide solution in the presence of phenolphthalein. The end product exhibited a slightly pink color.
2.3. Determination of Oil Chemical Parameters
2.3.1. Pigment Content
The pigment content of prickly pear seed oil (expressed in ppm) was determined according to the methods described by Wolff  for chlorophyll, Psomiadou and Tsimidou  for α-pheophytin, and Mosquera-Minguez et al.  for carotenoids. The fractions of α-pheophytin and chlorophyll were quantified at wavelengths of 630, 670, and 710 nm, and those of the carotenoids were determined at 470 nm.
2.3.2. Fatty Acid Composition
Fatty acid composition was determined by the gas chromatography analysis according to the analytical methods described in the IOC standard . Fatty acid methyl esters (FAMEs) were prepared by adding 0.2 mL of a methanolic solution of potassium hydroxide (2 N) to the oil solution prepared with 0.1 g of oil and n-heptane (2 mL). Before injection into the chromatograph, the n-heptane solution was shaken vigorously for 15 s and allowed to stand until the upper part became clear (5 min). The fatty acids separation was carried out using gas chromatograph Varian CP 3380, equipped with a capillary column packed with a stationary phase (CP-Wax 50 CB: length L = 25 m; inner diameter Ф = 0.25 mm; Ft = 0.20 μm), using split/splitless injector (split ratio of 1 : 100) equipped with the autosampler Varian CP-8400 and FID detector. The temperatures of the injector, detector, and oven were 220, 230, and 190°C, respectively. Nitrogen was used as the carrier gas at a flow rate of 154.0 mL/min. The injection volume was 1 µL. Fatty acids were identified by the use of control fatty acids and by the recourse to the methods of imprinting. For fatty acid quantification, the total area (TA) was the sum of all the peaks that appeared in the chromatogram, from C16 : 0 to C20 : 1. The percentage of each peak (FAx (%)) was calculated using the following equation:where Ax is the individual peak area of each FAME and AT is the total area of all FAME peaks.
Based on fatty acid composition, the iodine value (IV), which measures the level of unsaturation in oils and is expressed in grams of iodine absorbed by 100 g of oil, was calculated from the percentages of fatty acids (FA) according to the following equation proposed by Dıraman and Dibeklioğlu :
2.3.3. Triglyceride Composition
The triglyceride composition was analyzed by high-performance liquid chromatography (HPLC) (Jasco PU, 2080) with a refractive index detector (RI-930), a type recorder-integrator (FP, 1520), and a stainless steel column (250 mm × 4.5 mm, LiChrosorb, RP 18, Art 50333) filled with silica particles of 5 µm in diameter. The eluent was a mixture of acetone and acetonitrile (50/50, v/v) at a flow rate of 1.5 ml/min at 40°C. A volume of 20 µL of 5% (w/v) oil and acetone solution was injected into the HPLC system. The triglycerides were identified using the official EEC method .
The chemical parameters of the studied oils were compared to those of other fruit and seed oils, especially those of argan seeds (Argania spinosa), sesame seeds (Sesamum indicum), black cumin or Nigella seeds (Nigella sativa), olive fruit (Olea europaea), and lentisk seeds (Pistacia lentiscus). Selection of these oils was based on their characteristics, which are well defined and are widely used in various applications, especially in nutraceuticals and cosmetics.
2.4. Statistical Analyses
Data are presented in tables and figures as the mean ± standard error of three independent experiments. Statistical analysis was performed using one-way analysis of variance (ANOVA) where the varieties constitute the only factor considered. The comparison between the means was carried out with the Student–Newman–Keuls test. The difference between means was significant at .
3. Results and Discussion
3.1. Oil Content
The respective seed oil contents of OFI (“Safra” and “Aakria”) and OM (“Derbana”) varieties were 8.09%, 8.74%, and 8.04% (Table 1). The “Aakria” variety had the highest oil content (8.74%). These results are in agreement with those obtained for Algerian OFI varieties by Chougui et al.  and Ramadan and Mörsel . However, higher oil content (up to 14.4%) has been reported for a Turkish OFI variety by Matthäus and Özcan , who reported that the difference in the oil content of the seeds can be attributed to varietal and environmental effects. The oil content of prickly pear seeds appears to be very low compared to that of other plant species from which oils are derived, including argan seeds (53%) , sesame seeds (52%) , Nigella seeds (37%) , olive fruits (20%–40.73%) [23, 24], and lentisk seeds (7.67%–21.33%) .
Prickly pear species and varieties
Nutraceutical and cosmetic fruits or seed oils
Olive, Olea europaea [23, 24]
Argan, Argania spinosa 
Sesame, Sesamum indicum 
Black cumin, Nigella sativa 
Lentisk, Pistacia lentiscus 
Oil content (%)
8.09a ± 0.06
8.74b ± 0.03
8.04a ± 0.03
Free acidity (%)
0.71a ± 0.04
0.64a ± 0.04
0.60a ± 0.04
Extinction coefficient K232
2.25b ± 0.03
2.24b ± 0.04
1.82a ± 0.07
Extinction coefficient K270
0.92b ± 0.04
0.95b ± 0.08
0.66a ± 0.04
Means (±standard errors) with the same letter within rows did not differ significantly according to the Student–Newman–Keuls test at .