Summary of terpenoids of Sacha inchi seed oil and biological effects.
Sacha inchi oil is a product obtained from oilseed (Plukenetia volubilis L.) and is an excellent source of bioactive compounds, especially in polyunsaturated fatty acids, tocopherols, and sterols. These compounds are causally related to their positive impact on human health. In this study summarizes some monoterpenes, sesquiterpenes, and triterpenes reported in Sacha inchi oil seeds and reviews their sensory properties. The terpenoids that characterize Sacha inchi seed oil are: α-pinene, sabinene, limonene, aristolene, cycloartenol, 24-methylene cycloartenol, lanosterol, β-sitosterol, stigmasterol, campesterol and phytol. The sensory properties of this oil are due to a set of volatile compounds including terpenoids, the odor descriptors of monoterpenes, sesquiterpenes and diterpenes are: flower, pine, turpentine, pepper, wood, lemon, orange, and sweet. These compounds were characterized by gas chromatography with different detectors.
- sacha inchi seed oil
- sensory properties
- chromatographic analysis
The Sacha inchi (
Kodahl  mentioned that Sacha inchi seed has an unusual chemical composition as it contains remarkably high amounts of polyunsaturated fatty acids. According to the NTP  indicates that the requirements for the polyunsaturated fatty acids (PUFAs) profile is as follows: α-linolenic acid (ω-3, greater than 42%), linoleic acid (ω-6, greater than 32%) and polyunsaturated fatty acids (greater than 80%) of the total lipid fraction. Other main representatives of the unsaponifiable fraction are tocopherols, which are distributed in the oil as follows: α-tocopherol (60–70 mg/kg), β-tocopherol (18–29 mg/kg), γ-tocopherol (1108–1367 mg/kg), δ-tocopherol (641–856 mg/kg), and sterols fraction of commercial oils was 1130–3635 mg/kg, and the main sterols were β-sitosterol, stigmasterol, campesterol and ∆5-avenasterol [8, 9]. Other compounds of interest are phenolic compounds (the main classes of phenols found in sacha inchi seed oil (SISO) are phenyl alcohol, isocoumarin, flavonoid, secoiridoid, and lignan) , volatile organic compounds (while the classes of VOCs identified in commercial oil were aldehydes, hydrocarbons, alcohols, ketone, furan, and carboxylic acid), and terpenoids .
Terpenoids are a large family of chemical compounds which can be found in a large number of plants, many of which have characteristic odors, flavors, and colors, and are main components of essential oils (especially monoterpenes and sesquiterpenes) . Terpenoids can be structurally decomposed into two or more isoprene units or 2-methyl-1,3-butadiene and classified as monoterpenes (C10H16), sesquiterpenes (C15H24), diterpenes (C20H32), triterpenes (C30H48), and tetraterpenes or carotenes (C40H64) . In vegetable oils, several terpenoids have been identified, these compounds provide aromatic properties (monoterpenoids: myrcene, citral, linalool, thymol, menthol, carvone, eucalyptol, α- and β-pinene, etc.), and are natural fat-soluble pigments (tetraterpenoids: lycopene, γ-carotene, β-carotene, lutein, zeaxanthin, etc.) , this last group of chemical species are responsible for transmitting the chromatic characteristics in vegetable oils. A list of oils from conventional and non-conventional plant sources where terpenoids have been identified: soybean, olive, rapeseed, sunflowerseed, flaxseed, sesame, pumpkin, pistachio, almond, hazelnut, safflower, hempseed, sacha inchi oils [15, 16, 17, 18, 19, 20].
Traditionally, plant-based terpenoids have been used by humans in the food (terpenoids as natural flavorings compounds, preservatives for dairy products, stability of edibles oils flavored with essential oils) [21, 22, 23], pharmaceutical (production of pharmaceutical terpenoids for the treatment of human diseases) [24, 25], and chemical industries (natural additives for food or fragrances in perfumery) . Various studies have shown the efficacy of terpenoids due to their biological and medical properties [25, 27, 28]. Table 1 summarizes most of the effects, however some of heightened interest are mentioned in this section.
|α-Pinene||Monoterpene||Cytogenetic, gastroprotective, anxiolytic, cytoprotective, anticonvulsant, and neuroprotective|||
|Sabinene||Monoterpene||Antioxidant, antibacterial and antifungal||[29, 30]|
|Limonene||Monoterpene||Gastroprotective, anti-inflammatory, bradycardic, antiarrhythmic, antitumor, antiviral, and antibacterial||[31, 32, 33]|
|Aristolene||Sesquiterpene||Antifungal, antioxidant, and anticancer||[34, 35]|
|Cycloartenol||Triterpene||Anticancer, and antidiabetic||[36, 37]|
|Lanosterol||Triterpene||Cytotoxic and immunomodulatory||[38, 39]|
|β-Sitosterol||Sterol||Anticancer, lipid-lowering, anti-inflammatory, and antioxidant||[40, 41, 42, 43]|
|Stigmasterol||Sterol||Lipid-lowering, antiasthmatic, immunomodulatory, antioxidant, and anti-inflammatory||[41, 44]|
|Campesterol||Sterol||Anti-inflammatory, and cytotoxic|||
|Phytol||Diterpene||Antitumoral, antimutagenic, antimicrobial, anxiolytic, metabolism-modulating, cytotoxic, antioxidant, autophagy- and apoptosis-inducing, antinociceptive, anti-inflammatory, immune-modulating, antidiabetic, anti-atherogenic, lipid-lowering, antispasmodic, antiepileptic, antidepressant and immunoadjuvant||[46, 47]|
This document summarizes some monoterpenes, sesquiterpenes, and triterpenes reported in Sacha inchi oil seeds and reviews their sensory properties.
2. Overview of terpenoids biosynthesis in Sacha inchi seed oil
The biosynthesis of these compounds occurs via the methylerythritol phosphate pathway (MEP) or mevalonate (MVA) pathway involves several reactions to isopentenyl diphosphate production from acetyl CoA. The isopentenyl diphosphate (IPP) combines with dimethyl-allyl diphosphate (DMAPP) to that subsequently converted to geranyl pyrophosphate (GPP) by enzymatic catalysis of isopentenyl diphosphate isomerase. Geranyl pyrophosphate is the substrate to produce monoterpenoids. The enzymatic reaction is mediated by monoterpene synthases . The monoterpenes found in SISO were α-pinene, sabinene and limonene (Figure 1). α-Pinene (C10H16) is the main bicyclic monoterpene found in this oil, it is also widely distributed in nature. The sesquiterpenes are formed by the condensation of IPP with GPP to yield farnesyl pyrophosphate (FPP) . The GPP to FPP reaction is mediated by farnesyl pyrophosphate synthase. The only sesquiterpene found in SISO is the aristolene (C15H24) . On the other hand, this biochemical pathway may be used for triterpene (some triterpenes were found in SISO, namely cycloartenol, 24-methylene cycloartenol and lanosterol isomers) and probably sterols (individual sterols found in SISO, namely β-sitosterol, stigmasterol, campesterol, Δ5-avenasterol, Δ5,24- stigmastadienol, Δ7-stigmastenol, Δ7-avenasterol, etc.) [8, 9, 51], and brassinosteroids biosynthesis, whereas geranylgeranyl pyrophosphate (GGPP) is utilized for the biosynthesis of photosynthetic pigments such as carotenoids, chlorophylls and diterpenes (phytol) (Figure 1) [9, 52, 53].
3. Terpenoids in Sacha inchi seed oil
In the scientific literature there are few reports on the volatile composition of sacha inchi oil [20, 49]. The terpenoid fractions in the Sacha inchi oil is observed in Table 2. The identification of the classes of terpenoids found in Sacha inchi seed oil and commercial Sacha inchi oil were monoterpenes, sesquiterpenes, diterpenes, triterpenes and sterols. The first terpenoids identified in this oil were sterols: β-sitosterol > stigmasterol > campesterol > Δ5-avenasterol . The sterol composition of these main compounds is around ~96%. The sterol content in the Sacha inchi seed oil was reported as 2472 mg/kg. While the sterol contents in commercial oils ranging from 1130 to 3635 mg/kg [8, 9].
|Terpenoids||Sacha inchi seed oil||Commercial Sacha inchi oil|
|α-Pinene (μg/kg)||(3.35–1179.24) μg/kg|
|Sabinene (μg/kg)||(0.87–416.51) μg/kg|
|Limonene (μg/kg)||(0.93–187.83) μg/kg|
|Aristolene (μg/kg)||(3.99–34.82) μg/kg|
|Cycloartenol (%)||(2.59–34.54) %|
|24-Methylene cycloartenol (%)||(0.80–11.79) %|
|Lanosterol (%)||(0.10–47.44) %|
|β-Sitosterol (%)||127.4 mg/100 g||(21.45–68.91) %|
|Stigmasterol (%)||58.7 mg/100 g||(10.4–27.4) %|
|Campesterol (%)||15.3 mg/100 g||(5.1–18.9) %|
|Δ5-Avenasterol (%)||(0.10–7.78) %|
|Phytol (%)||(0.10–43.51) %|
The sterol content in Sacha inchi seed oil is represented by the content of β-sitosterol, stigmasterol and campesterol (Table 2). The β-sitosterol, followed by stigmasterol or campesterol and other minor sterols (triterpenes) such as fucosterol, and Δ5-avenasterol are the most representative in vegetable oils. In addition, 50% to 80% of the plant sterols intake comes from oils, spreads, butters, breads, cereals, grains, pastes, and vegetables . On the other hand, other triterpenoids such as cycloartenol, 24-Methylene cycloartenol, and lanosterol were detected in commercial Sacha inchi oil, the contents ranged from 0.10 to 47.44%, 2.59 to 24.15%, 0.80 to 11.79%, respectively. A sole example of diterpene such as phytol were found in the range of 0.10 to 43.51% . The monoterpenoids and sesquiterpene in the sacha inchi oil were α-pinene, sabinene, limonene and aristolene these compounds were also identified by Monroy-Soto et al. . In addition, it has been reported that this class of terpenoids are considered potentiators. In this context, the minimum inhibitory concentration of some monoterpenoids (α-pinene and limonene) on bacteria such as
The storage food products are subject to changes in the chemical composition and as a result the formation of undesirable volatile compounds. Therefore, terpenoids as natural preservatives can be used to slow down food spoilage. Some monoterpenoids such as limonene can be used as substitutes for synthetic antioxidants (TBHQ, BHA, BHT) and improves oxidative stability in edible oils . Wang et al.  have mentioned that monoterpenoids can be used as a reference for the food manufacturing, lifestyle, and nutrition in the future.
4. Terpenoids and sensory properties in Sacha inchi seed oil
Terpenoids are compounds responsible for the smell of most plants. Phytol, α-pinene, sabinene, limonene, and aristolene have been found in Sacha inchi oil (Table 3). These compounds provide some odor notes such as flower, pine, turpentine, pepper, wood, lemon, orange, and sweet. The content of monoterpenoids and sesquiterpenoids in Sacha inchi oil, fraction constituted about 9.0% of total volatile fraction. Ramos-Escudero et al.  have mentioned that these compounds are responsible for the floral aroma in this oil. However, the sensory characteristics of Sacha inchi oil not only correspond to the sensory notes of the terpenoids, but to a combination of sensory attributes such as herbal, green, nutty, seeds, butter, rancid, fruity, floral, and woody [20, 59]. Different volatile compounds including terpenoids have been identified in vegetable oils and each compound has different characteristics of key odorants. For example, in virgin sunflower oil the most preferred attributes were sweet and wood/vegetable resin, the latter possibly due to the presence of terpenes such as linalool and α- and β-pinene. Furthermore, the sensory profile of Niger seed oil showed positive attributes such as dried fruit, spicy and bitter, which could be related to the presence of some terpenes, specifically limonene and phellandrene. On the other hand, the sensory notes of pine perceived in the pine nut (
5. Comparison of terpenoid contents in other vegetable oils
Information about the volatile composition, including some terpenoids in vegetable oils can be found in published reports. Aguilar-Hernández et al.  reported the profile of terpenoids including monoterpenes and sesquiterpenes in lemon peel oil. In this oil around 23 terpenoids have been found, the most relevant being limonene, γ-terpinene, sabinene, α-pinene, β-pinene, α-thujene, terpinolene, α-terpineol, neral, geranial, and trans- α- bergamotene. Ivanova-Petropulos et al.  reported a higher content of terpenoids in sunflower seed oil and pumpkin seed oil. The most common monoterpenoids and sesquiterpenoids in both oils were: α-thujene, α-pinene, α-fenchene, camphene, verbenene, sabinene, 2-β-pinene, α-phellandrene, α-terpinene, DL-limonene, β-phellandrene, 1,8-cineole,
|Compounds||Flaxseed oil||Rapeseed oil||Sesame seed oil||Sunflower seed oil||Pumpkin oil||Sacha inchi oil||Pistachio oils||Almond oil||Hazelnut oil|
6. Application of chromatographic techniques in Sacha inchi seed oil
There are few reports about the chemical characterization of the terpenoids in the Sacha inchi oil (Table 5). The separation of the different analytes from the sterol fraction was conducted using the following columns: SAC™-5/Merck (Phase: 5% diphenyl/95% dimethyl polysiloxane), HP-5/Agilent J&W (Phase: 5% phenyl-methylpolysiloxane), and SPB-5/Merck (5% diphenyl/95% dimethyl polysiloxane). While the separation of volatile compounds was carried out using columns with high polar (DB-WAX/Agilent J&W, and TRB-WAX/Teknokroma/ 100% polyethylene glycol) and nonpolar (DB-5/Agilent J&W/5% phenyl-methylpolysiloxane) stationary phases.
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Monroy-Soto et al.  evaluated the volatile composition of Colombian commercial Sacha inchi oil using headspace-solid phase microextraction coupled GC–MS-O. Ramos-Escudero et al.  analyzed the Peruvian commercial Sacha inchi by HS-SPME/GC–MS, through which 16 volatile compounds (among them limonene, α-pinene, and sabinene) may have a significant influence upon perceived flavor and odor.
Sacha inchi oil is a product of economic importance that has been characterized according to its chemical composition. At present several classes of chemical compounds have been identified and quantified, and more recently the volatile composition. The volatile organic compounds correspond to notes generated by alcohols, aldehydes, ketones, and terpenoids. The classes of terpenoids found in Sacha inchi oil were monoterpenes, sesquiterpenes, diterpenes, and triterpenes. These compounds provide different sensory properties in the oil. Furthermore, the characterization is conducted mainly by gas chromatography (GC) coupled to flame ionization detector (FID) and mass spectrometry (MS) detection.
Conflict of interest
The authors declare no conflict of interest.