Edible Oils from Selected Unconventional Sources—A Comprehensive Review of Fatty Acid Composition and Phytochemicals Content

: In recent years, there was an increase in the commercial offer of vegetable oils from un-conventional sources, such as fruit, vegetable, and herb seeds. The paper presents a synthesis of available scientific information on 27 oils obtained from the seeds of 14 fruit species (apple, apricot, chokeberry, black berry, blackcurrant, blue berry, cherry, Japanese quince, pear, plum, quince, rasp-berry, rosehip, and strawberry), 8 vegetable species (broccoli, cabbage, carrot, cucumber, onion, parsley, radish, and tomato), and 5 herb species (basil, coriander, fennel, fenugreek, and perilla). A review of the literature showed that oil content in these seeds ranges from ca. 5% for fenugreek to over 55% for apricot kernels. A recommended n-6/n-3 fatty acid ratio below 4-5/1 was noted in 11 species. Japanese quince, blackcurrant, and fenugreek seed oils seem to be good sources of phy-tosterols. Radish seed oil was mostly abundant in tocols, Japanese quince seed oil in squalene, and blackcurrant seed oil in carotenoids. Unfortunately, actual data on the composition of these seed oils are highly variable, making it difficult to precisely identify the most nutritionally valuable oils.


Introduction
The majority of edible commercial plant oils are produced from oilseeds such as palm, soybean, rapeseed (canola), sunflower, peanut, and olive fruits [1].However, more and more companies offer a wide range of unique oils derived from the seeds of fruits, vegetables, and herbs [2,3].This is the manufacturers' response to growing consumer demand for novel oils with unique health-promoting properties or functional characteristics [4].
The main components of plant oils are fatty acids esterified into a glycerol molecule.This is a very diverse group, including subgroups such as saturated, monounsaturated, and polyunsaturated acids.They also differ in chain length, stereoisomerisation of double bonds (cis/trans), and location of the first double bond (e.g., n-3, n-6, n-7, and n-9).From a nutritional point of view, they can be divided into essential and non-essential fatty acids.The latter group is not required in diet since the human organism is able to synthesize them, while n-6 and n-3 fatty acids are categorized as essential fatty acids [5].Higher plants are able to produce the essential n-6 and n-3 PUFAs such as linoleic acid (LA; C18:2 n-6) and α-linolenic acid (ALA; C18:3 n-3).In contrast, animals and humans have no capacity to synthesize LA and ALA from oleic acid (C18:1 n-9) as a precursor due to the lack of required desaturases.LA and ALA are substrates for endogenous elongation and desaturation processes and share the same enzyme systems to produce long-chain PUFAs (LC-PUFAs) such as arachidonic acid (C20:4 n-6) and eicosapentaenoic acid (C20:5 n-3), respectively.It is also commonly known that n-3 and n-6 PUFAs are important in the prevention and counteraction of several diseases, such as coronary heart disease, arthritis, and inflammatory diseases [6].Although desaturases prefer n-3 to n-6 fatty acids, a high LA intake interferes with the desaturation and elongation of ALA [7].The prevalence of n-6 PUFAs is highly prothrombotic and pro-inflammatory, contributing to the prevalence of atherosclerosis, obesity, and diabetes [8].It is worth emphasizing that the typical modern-day diet is extremely deficient in n-3 fatty acids.Currently, the highly recommended n-6/n-3 ratio is estimated at 4-5/1 [9].Among traditional oils, the best value of this ratio is stated for rapeseed oil [10].
On the other hand, many reports and recommendations suggest reducing the intake of saturated fatty acids.They are credited with an increased risk of cardiovascular disease due to their LDL-cholesterol-raising properties.These fatty acids are also related to adverse effects including lower insulin sensitivity, inflammation, and weaker lipid metabolism [11].According to the WHO recommendation, consuming 10% or less of daily calories (i.e., total energy intake) as saturated fatty acids reduces LDL cholesterol (high-certainty evidence), is associated with a reduced risk of all-cause mortality, and may be associated with reduced risk of coronary heart disease [12].Summarizing, the best oils are composed of the lowest share of saturated fatty acids and the highest share of ALA, or the lowest n-6/n-3 ratio.
The main unsaponifiable compounds of plant oils are phytosterols, tocols, squalene, and carotenoids.Among these compounds, in the majority of commercial oils, phytosterols are predominant in mass [13,14].Phytosterols are plant analogues of cholesterol building plant cell membranes and are divided into unsaturated sterols and saturated stanols [15].They have the structure of the four-ring steroid nucleus with a methyl or an ethyl group at the C-24 position or an additional double bond at the C-22 position on a side chain [16].Vegetable oils, nuts, and seeds are prominent sources of phytosterols in the human diet [17], but the highest concentration was found in crude corn fiber and wheat germ oils (8709 mg and 4240 mg/100 g, respectively) [16] and amaranth seed oil (2616 mg/100 g) [18].More than 200 different phytosterols were reported [16], but β-sitosterol, campesterol, and stigmasterol are prevalent in the majority of oils and account for about 65%, 30%, and 3% of diet contents, respectively [17].Various sterols have different bioaccessibilities [19].Although the bioavailability of phytosterols is only 0.5-2%, they can still promote cholesterol balance in the human body [20].
The EFSA scientific panel provided the following health advisory: "Plant sterols have been shown to lower/reduce blood cholesterol.Blood cholesterol lowering may reduce the risk of coronary heart disease" [21].Similarly, the FDA concluded that a dietary intake of 1.3 g or more per day of plant sterol esters or 3.4 g or more per day of plant stanol esters is required to demonstrate a relationship between phytosterol consumption and reduced cardiovascular disease risk [22].Unfortunately, the average intake of phytosterol from the diet on the example of the Chinese population is about 392.3 mg/day, and the main sources are vegetable oils and cereals [23].Similarly, in a typical Western diet, daily intake is ca.300 mg, while in the diet of vegetarians it is ca.600 mg (more data in work from Barkas et al. [24]).That shows that even in vegetarian diets, these values are still below the recommended range.
The second main unsaponifiable compounds are tocopherols and tocotrienols, collectively known as tocols.These compounds belong to the vitamin E family and the difference between them is due to the presence of three double bonds in the side chain of tocotrienols.Both tocopherols and tocotrienols exist as four homologues (α, β, γ, and δ), which differ in the number and location of methyl groups in their chemical structures [25].Vitamin E is only synthesized by photosynthetic organisms (mainly plants and algae), so it is a very important nutrient for humans and animals [26].It is worth noting that individual tocols differ in biological activity (vitamin E activity).Studies showed that α-tocopherol is the most biologically active (100%), followed by β-tocopherol (50%), γ-tocopherol (10%), and δ-tocopherol (3%).The biological activities of α-, β-, and γ-tocotrienol are 30%, 8%, and 5% of that of α-tocopherol, respectively, while the activity of δ-tocotrienol was not defined [27].Furthermore, the synthetic forms of tocopherols are not as bioavailable as their natural counterparts [28].According to the different scientific institutions, 8-15 mg of α-tocopherol or an α-tocopherol equivalent per day for women and men are recommended [29].Vitamin E deficiency can cause anemia, retinopathy, impaired immune response, and neuromuscular and neurological problems.However, the phenomenon is rare in humans and occurs as a result of abnormalities in the absorption or metabolism of dietary fats [30].Nevertheless, the potential health benefits of natural tocols intake are numerous.Literature data show that tocols can exhibit anti-atherosclerotic, anticancer, anti-allergic, immune function-enhancing, anti-cardiovascular, anti-lipidemic, anti-diabetic, anti-hypertensive, anti-inflammatory, anti-obesity, and anti-non-alcoholic steatohepatitis effects (more in work from Szewczyk et al. [29]).Recent studies demonstrated that tocotrienols have even higher chemo-preventive potencies against various degenerative diseases compared to tocopherols [31].Moreover, the antioxidant properties of tocols make them also interesting for food producers [32].Although tocols are common in plants, leaves and seeds of the same species vary in the amount and profile of these compounds.For example, α-tocopherol is typically the main tocopherol homologue in the leaves of plants, whereas seeds can be richer in any of the other three forms of tocopherol.Tocotrienols, on the other hand, are found in the seed endosperm of monocots (e.g., cereal grains) and in the seeds of some dicots, including species of the Apiaceae family (e.g., coriander, celery) [33].The richest sources of natural tocopherols are plant oils, especially those from pomegranate seeds, wheat germ, fig seed, sea buckthorn seeds, and corn germs (74.2-348.3mg/100 g).The highest α-tocopherol concentration (51.2-220.2mg/100 g) was found in wheat germ, fig seed, and safflower, and sunflower oils [34].In turn, palm oil and rice bran oil contain particularly high amounts of tocotrienols (94.0 mg and 46.5 mg/100 g, respectively) [35].
A minor component of selected plant oils is squalene.It is a linear triterpene synthesized in animals, plants, bacteria, and fungi as a precursor for the synthesis of secondary metabolites such as sterols, selected hormones, and vitamins [36].Squalene accumulates in the liver and decreases hepatic cholesterol and triglycerides, with these actions being exerted via a complex network of changes in gene expression at both transcriptional and post-transcriptional levels [37].Due to its increasing roles in the cosmetic, nutraceutical, and pharmaceutical industries, the demand for this compound is high [38].Among the plant sources, squalene content is the highest in amaranth oil (5942 mg/100 g), olive oil (564 mg/100 g), and peanut oil (27.4 mg/100 g) [36].Unfortunately, the majority of commercial oils do not contain this valuable molecule.
Carotenoids, similar to tocols, are an important group of lipid-soluble antioxidants synthetized mainly in plants [39].The compounds are 40 carbon tetraterpenoids with 3-13 conjugated double bonds in their skeleton.Carotenoids are classified as carotenes containing only carbon and hydrogen atoms, and xanthophylls (oxocarotenoids), which also have one or more oxygen atoms [40].Although carotenoids constitute a much larger group of over 1200 structures [41], typical diets can provide approximately 50 carotenoids [42].The main bioavailable dietary carotenoids are lutein, zeaxanthin, β-cryptoxanthin, α-carotene, β-carotene, lycopene, phytoene, and phytofluene, which are the principal carotenoids in human fluids and tissues [42].Some of them (β-carotene, β-cryptoxanthin, and α-carotene) are essential components of mammalian diets, providing precursors for vitamin A biosynthesis [43].In turn, lutein and zeaxanthin absorb blue visible light (400-500 nm), which could help protect the eyes and may also reduce cognitive decline [44].Other health benefits of carotenoids can be explained by their antioxidant activity.Numerous studies proved that these compounds can reduce the risk of a variety of chronic illnesses, including cardiovascular diseases and neurological disorders, type 2 diabetes, and different types of cancer [45,46].The main sources of carotenoids in the human diet are fruits and vegetables [46].Common vegetable oils are generally low in carotenoids, with the exception of sea buckthorn oil and crude palm oil, which contain 67-142 mg and 50-70 mg/100 g, respectively [47].However, the absorption of carotenoids by the human organism occurs more effectively when they are dispersed in a lipid matrix [48].Although no dietary reference intake values are proposed for carotenoids at the present time, dietary recommendations for β-carotene, lutein, and zeaxanthin are being discussed since vitamin A deficiency is a major public health problem in many countries [49,50].
Considering the health-promoting properties of some components of plant oils, the aim of the current study is to characterize specific unconventional oils that are abundant in valuable fatty acids and/or selected low molecular lipophilic phytochemicals.Therefore, available scientific information on the composition of 27 plant sources (Table 1) of uncommon edible oils (listed in the article abstract) is synthetized and compared to currently known sources of phytosterols, tocols, squalene, and carotenoids, and to these with valuable fatty acid composition.In the next paragraphs, the compositions of these oils are presented based on information that is up to date presented by scientists.

Variation in the Oil Content among Unconventional Sources and Fatty Acid Composition of Their Oils
The value of each plant oil source depends on the content of bioactive ingredients and composition of fatty acids.Nevertheless, seeds with low oil content, despite their possible positive chemical composition, are not particularly desirable sources of edible oil.In this respect, the unconventional plants selected in this study differed significantly in oil content (Table 2), from about 5% for fenugreek seeds [80] to over 55% for apricot seeds [52].In the oil industry, seeds with oil content of at least 15% are considered good raw materials.This does not present seeds of carrot, fenugreek, rosehip, Japanese quince, aronia, blueberry, or raspberry [59,80,142,149,216,217].However, considering the content of bioactive ingredients, these raw materials attracted the attention of consumers and the oils obtained from them are now available on the market [3,[218][219][220]].Among the seeds discussed, apricot and perilla seeds were particularly rich in oil, with the oil content reaching 56.4% (cultivar Kabaaşı) [52] and 47.8% (cultivar Yaebsil) [176], respectively.Seeds of some cultivars of parsley, radish, plum, cucumber, and broccoli were also characterized by high oil content with a value over 30% [85,103,152,166,183].The fatty acid compositions of the studied raw materials are presented in Table 3.In the majority of the studied oils, LA and oleic acids prevailed.The shares of LA varied from values below 16% in carrot (three studies), broccoli (one study), cabbage (two studies), coriander (two studies), fennel (three studies), parsley (two studies), perilla (two studies), radish (three studies), rosehip (one study), and basil seed oils (two studies), to values up to ca. 73% in chokeberry seed oil.High shares of LA were also found in apple (36.1-67.9%),blackberry (59.1-66.3%),cucumber (54.5-63.2%),onion (57.0-62.3%),tomato (48.7-64.6%),and pear seed oils (50.7-64.9%).There were also raw materials with a high variation between cited studies in the case of the LA share-e.g., cherry (23.3-47.4%),fenugreek (28.8-43.6%),parsley (9.4-54.2%),and rosehip seed oils (2.1-55.7%)(Table 3).Table 3. Percentages of main fatty acids and n-6/n-3 ratio of oils from unconventional plant sources.

Species Palmitic Stearic Vaccenic Oleic
Petroselinic Linoleic α-Linolenic γ-Linolenic Stearidonic Arachidic Eicosenoic Arachidonic Behenic Erucic n-   An empty cell means that the compound was not detected or not determined in the cited work.tr-traces.* Probably miss-identification for this species because literature data show that petroselinic acid should be predominant.** The n-6/n-3 ratio cannot be calculated due to the lack of n-3 fatty acids.*** Probably missidentification for this species in cited reference.Broccoli belongs to the cruciferous plant family and literature data show that erucic acid should be predominant (not C20:4 n-6).We moved the value 40.9% to the column for erucic acid.**** Probably miss-identification of these fatty acids in cited reference No 205, we proposed names for three main fatty acids.
The vast majority of studied materials contained more than 10% oleic acid.The most abundant were apricot seed oil (57.8-68.3%)and plum seed oil (45.5-76.3%).Unfortunately, in the case of tomato C18:1 acid, it seems that all cited sources miss-identified this acid as oleic, while the real compound would be petroselinic acid (C18:1, n-12).Previous study [221] and the PlantFA data base [222] clearly present that petroselinic acid is a prominent component of oil from such species as tomato, fennel, coriander, and parsley.For example, according to Ngo-Duy [151], the main compound in fatty acids in parsley oil is petroselinic acid.Proper identification of oleic/petroselinic acid is a significant challenge for scientists since these fatty acids differ in biological activities.For example, a recent clinical study confirmed that coriander seed oil (abundant in petroselinic acid) regulates human body inflammation and nociception and thus reduces reactivity in sensitive skin [223].
Other important fatty acids in some of the studied materials were C18:3 isomers-ALA (n-3) and γ-linolenic (n-6).The first of them is more common in plant raw materials, and among the analyzed oils, its share was the highest in: perilla (59.9-62.5%),basil (42.4-71.1%),blueberry (22.0-48.8%),raspberry (35.8-38.1%),blackberry (14.6-31.1%),and strawberry (19.9-31.7%)(all referenced in Table 3).γ-linolenic acid is rarely found in plants.It is worth noting that significant shares of this compound were present in blackcurrant seed oil (up to 18.5%) [163,164].It is reported that this fatty acid may be a potentially effective bioactive phytochemical substance for the treatment of gastric cancer [224] or in the prevention of lipid metabolism disorders [225].
Additionally, saturated fatty acids were found in significant amounts in the majority of oils.The highest shares of palmitic acid were determined in tomato (12.4-16.8%)and cucumber seed oils (14.0-15.5%),while the oils with the highest shares of stearic acid were cucumber and fenugreek seed oils (up to 12.0% and 11.6%, respectively) (Table 3).
Arachidic (C20:0), eicosenoic (C20:1), arachidonic (C20:4), behenic (C22:0), and erucic (C22:1) acids were generally present in smaller amounts in the oils.The exceptions were radish, cabbage, and broccoli seed oils, in which C20:1 accounted for 9.6-11.6%,2.0-9.9%, and 4.6-7.4%,respectively (Table 3).It is worth noting that López-Cervantes [123] found an extremely high content of C20:4 in broccoli seed oil (40.9%).However, the cited authors did not comment on such an extreme result, and it was not possible to find any supporting reports on such a high share of this fatty acid in broccoli seed oil.In general, broccoli seed oil is very poorly tested in terms of its composition.In the work of López-Cervantes [123], the high content of arachidonic acid can be caused by miss-identification because the Crucifereae are known as a good source of erucic acid [88,209], but not arachidonic.
Table 3 shows the highest share of erucic acid in broccoli (up to 51.1%), cabbage (up to 50.8%), and radish seed oils (up to 35.9%).Some of the cited references showed very small shares of this fatty acid, but these results are probably misleading (selected results in Table 3 are marked and comments are added under Table 3).In previous sources, erucic acid (C22:1) was related to harmful health effects [226].Interestingly, a recent study challenges this thesis and encourages further research on this fatty acid [227].
Some of the cited studies present very limited information about the samples analyzed, but it seems as though the different genotypes determine different fatty acid compositions [50,69,97].Additionally, cultivation area may determine differences in fatty acid composition [78].
The oil extraction techniques used in the cited references were different, but some studies showed that there is a limited relationship between extraction technique or solvent and fatty acid composition [145,228,229].On the other hand, there are also studies indicating a high influence of oil extraction technique on fatty acid composition [116,147].

Variation in the Phytosterols Content of Oils from Unconventional Plant Sources
Phytosterol content varied from ca. 70-80 mg/100 g of oil (Brassica pekinensis cabbage and parsley seed oils) to 14,166 mg/100 g of Japanese quince seed oil, which indicates an approx.200-fold difference between these oils (Table 4).The high contents of these compounds were also noted in the majority of the presented samples of blackcurrant seed oil (up to 6894.4 mg/100 g), oil from Ocinum basilicum seeds grown in India (2862.4mg/100 g), all fenugreek seed oils (1409.0-5444.2mg/100 g), some plum seed oils (up to 1569.6 mg/100 g), and tomato seed oils (up to 1230.0 mg/100 g) from plants cultivated in the United States.Interestingly, blackberry seed oils differed in phytosterols in relation to cultivation region, from 403.7, through 616.0-624.3 to 1146.1-1582.6 mg/100 g of seed oils from plants grown in the United States, Serbia, and Poland, respectively (see Tables 1 and  4).Other oils contained from ca. 100 to 1000 mg of phytosterols in 100 g of oils, with the highest variability among apple, apricot, cabbage, coriander, pear, and raspberry seed oils.
Table 4. Phytosterols content of oils from unconventional plant sources (mg/100 g of oil).fenugreek It is worth noting that Japanese quince and blackcurrant seed oils seem to be the best sources of phytosterols in nature, even better than those mentioned in the first paragraph: crude corn fiber, wheat germ, and amaranth seed oils [16,18].However, further studies should be focused on examining and explaining the sources of the stated variation between various plant materials (climate, cultivars, etc.).

Campesterol
The β-sitosterol share, among confirmed phytosterols, varied from 22% (coriander seed oil from plants grown in India) [74] to 95% (cucumber seed oil from plants grown in Thailand) [209].In contrast, campesterol was the predominant compound in coriander seed oil from plants grown in India (78%) [74].Stigmasterol was a significant compound of phytosterols only in purple carrot [131] (34% of the total fraction).Bearing in mind these three main phytosterols in total share, the most variable were oils from blackcurrant, blueberry, fenugreek, onion, and tomato seeds.For these oils, the sum of β-sitosterol, campesterol, and stigmasterol was often above 80% of the total fraction (specific and more detailed data in the cited references).The problem when comparing sterol content was giving different names for the same compound (for example, ∆5-avenasterol = isofucosterol).To facilitate results comparison, both commonly used names for most phytosterols are used in Table 4.
Considering the EFSA recommendation on phytosterol use in doses of 1.3 g of sterols or 3.5 g of stanols, approximately 2-3 tablespoons of Japanese quince oil may meet this recommendation.

Variation in the Tocols Content of Oils from Unconventional Plant Sources
The tocol contents of the seed oils considered are presented in Table 5.As can be seen, the levels of total tocols varied over a wide range, from 3.4 mg/100 g for commercial coldpressed parsley oil produced in the USA [159] to 581.3 mg/100 g in oil from radish seeds originated from China obtained with the use of super-critical carbon dioxide extraction [213].The noticeably low contents (<20 mg/100 g) of these compounds were also determined in some oils from the apple [58,145], apricot [132], blueberry [59,160], cherry [77], raspberry [112], strawberry [72,130,140], broccoli [131], and carrot seeds [131].However, some researchers reported that the content of total tocols in oils from apple and raspberry seeds can reach up to 379.1 and 315.2 mg/100 g, respectively [90,128].It is noteworthy that a higher content of tocols in oils was generally achieved by ultrasound-assisted extraction compared to solid-liquid extractions (maceration or extraction in Soxhlet/Twisselman apparatus).This phenomenon was observed for apple, apricot, cherry, Japanese quince, pear, and plum seed oils (Table 5).In addition, a high variability in the total tocol content of the oils from unconventional sources was assigned to the cultivar.Significant differences were observed for oils extracted from the seeds of apple [90], apricot [91,132], pear [95], and plum cultivars [94].T or T3 presents tocopherol or tocotrienol content; an empty cell means that compound was not detected or not determined.Results centered between third and fourth column present sum of β-tocopherol + γ-tocopherol.
As presented in Table 5, tocopherols (mainly α and γ homologues) are the major tocols in almost all seed oils.α-tocopherol was generally prevalent in oils from the seeds of chokeberry, fenugreek, Japanese quince, onion, parsley, and quince, while γ-tocopherol was typical for apricot, basil, blackcurrant, blackberry, broccoli, cherry, pear, perilla, plum, radish, raspberry, rosehip, and strawberry seed oils.Among the oils that were studied, the most important α-tocopherol sources were Japanese quince (90.5-128.6 mg/100 g) and onion seed oils (49.8-227.3mg/100 g).In turn, the γ-tocopherol content was significantly differentiated and dependent on cultivar and extraction method.The highest concentration (538.9 mg/100 g) was reported in radish seed oil obtained with the use of supercritical carbon dioxide extraction [213].The high amount of this homologue (237.2 mg/100 g) was also determined in apricot (Veselka cultivar) seed oil obtained with the use of ultrasound-assisted extraction [91].Apple seed oils were characterized by varied proportions of all tocopherol homologues.However, most authors showed similar content of α and β homologues or a slight prevalence of one of them [58,90,133,163,168].In cabbage seed oil, comparable shares of α and γ homologues were proved [131,135], and in cucumber seed oil, δ-tocopherol was predominant, accounting for 84% of total tocol content [135].Only a few studies confirmed the occurrence of γ-tocotrienol as a main tocol.Its content in coriander seed oils was 23.1-65.2mg/100 g [135,191], in carrot seed oils was 13.3-14.3mg/100 g [131,190], in one sample of blueberry seed oil was 33.0 mg/100 g [197], in one sample of fennel seed oil was 18.2 mg/100 g [126], and in one sample of tomato seed was 107.9 mg/100 g [107], which constituted over 51% of all tocols.It is worth emphasizing that the data presented in the literature on the profile of tocols in fennel and tomato seed oils is scarce, making it difficult to identify these oils as a source of specific homologs.
The total tocol contents of the selected oil species represented the ranges cited in the literature for common oils [25,230].In addition to the factors mentioned (cultivar, extraction process), the climate during growth and ripening, the time and conditions of harvest, storage, and raw material pre-treatment affect the content and profile of tocols [231].

Variation in Squalene Content of Oil from Unconventional Plant Sources
Among the studied oil sources squalene was determined only in 14 kinds of seed oils (Table 6).The lowest content (only traces) was found in strawberry oil, and the highest in Japanese quince (up to 1497.3 mg/100 g).In one study [180] squalene content was even higher and was 22.72% of total oil, but this result is highly uncertain and should be confirmed in other studies.Relatively high squalene contents were also noted in basil, cherry, pear, and plum seed oils.Unfortunately, these results are often variable.For example, in oils from Japanese quince seeds, the presented results are in the range from 0.07 or 67 mg/100 g (various units in Table and text) to 1497.3 mg/100 g (interestingly, extreme results are obtained by the same analytical method).None of the tested oils (except the questionable one from cucumber seeds) were as rich in squalene as amaranth oil.* Based on chromatograms included in the cited work, the results may be uncertain because of peak shape and detection technique (HPLC-DAD).** The relative percentage of the oil constituents was expressed as percentage by peak area normalization, without using correction factors, so presented results may be uncertain.*** There are two different units in the table and text of cited publication.

Variation in Carotenoids Content of Oil from Unconventional Plant Sources
Carotenoids are present in most seed oils in small amounts (ca.<10 µg/100 g, Table 7).So far, scientific sources present data for only 23 plant sources out of 27 analyzed in this study.The higher content of these bioactive compounds was found in oils from the seeds of chokeberry (11,760 µg/100 g), blackcurrant (10,070-38,000 µg/100 g), fenugreek (15,370 µg/100 g), and rosehip (up to 21,880 µg/100 g) (Table 7).A high cultivar diversity of apple [84], pear [95], and plum seed oils [94] was found for concentration of carotenoids (4.3-16.6 times difference between minimum and maximum values).Furthermore, the variation caused by the extraction method or parameters was confirmed in the case of blackcurrant [105].An empty cell means that compound was not detected or not determined.

Conclusions
For comparison of oil content, fatty acid composition, and pro-healthy lipophilic low molecular compounds in seeds of 27 selected plant species, approximately 180 scientific sources were used (additional references were used to underline current knowledge on chemistry and recommendations for these compounds intake in the Introduction part).This study showed the proper ratio of n-6/n-3 fatty acids (below 4-5/1) in 11 of 27 selected plant sources.The main sources of minor lipophilic compounds were Japanese quince (up to 14,166 mg/100 g oil), blackcurrant (6894.4mg/100 g oil), and fenugreek (up to 5444.2 mg/100 g oil) seed oils abundant in phytosterols; radish seed oil abundant in tocols (up to 581.3 mg/100 g oil); Japanese quince seed oil abundant in squalene (up to 1497.3 mg/100 g oil); and blackcurrant seed oil mostly abundant in carotenoids (up to 38,000 µg/100 g oil).For many species, the reported composition was very divergent.Further studies are needed to discover the real causes of this variability.

Table 1 .
Characteristics of material.

Table 2 .
Oil content of seeds from unconventional plant sources (g/100 g dry matter).

Table 5 .
Tocopherols content of oils from unconventional plant sources (mg/100 g of oil).

Table 6 .
Squalene content of oils from unconventional plant sources (mg/100 g of oil).

Table 7 .
Carotenoids content of oils from unconventional plant sources (µg/100 g of oil).