Abstract Perilla frutescens seeds are a good source of polyunsaturated omega 3 6 9 fatty acids (PUFAs). The seeds of perilla are small end globular weight about 4 g/1000, contained approximately 35–45% oil. However the leaves are a very poor source of oil, since they contain only 0.2%. In addition, only the seed oil contains the omega 3 fatty acids alpha-linolenic acid (ALA). In comparing to other plant oils, perilla seed oil consistently contains the one of the highest proportion of omega 3 (ALA) fatty acids, at 54–64%. The omega 6 (linoleic acid) component is usually around 14% and omega 9 (Oleic acid) is also present in perilla oil. These polyunsaturated fatty acids are most beneficial to human health and in prevention of different diseases like cardiovascular disorders, cancer, inflammatory, rheumatoid arthritis etc.
General description of Perilla frutescencs
Perilla frutescens, is a member of the Lamiaceae/Labiatae family and commonly called perilla. The crop is annual and is native to India and China. Major producing countries of perilla are China, India, Japan, Korea, Thailand, other East Asian countries. The herb is about 1 m high with small flowers, a gray-brown fruit, and glossy, downy-haired leaves. Cultivation of the crop is grown from seed and sown in May. Harvesting is usually between the end of September and beginning of October. The applicable parts of perilla plants are the leaves and seeds.
There are two main types: red and green perilla. Perilla seeds, also called EBARA seed. This oil is a kind of light yellow clear and transparent liquid, with aromatic odor and slight soluble in ethanol. Major fatty acids of the oil are unsaturated fatty acids like Oleic acid 14–23%, linoleic acid 11–16%, linolenic acid 54–64% (Graph 1). This oil also contains saturated fatty acids 6.7–7.6%. Perilla seeds contain different polyphenols or flavones (rosemarinic acid, luteolin, chrysoeriol, quercetin, catcehin, apegenin and shishonin). Perilla seed oil is used as cooking oil, fuel. It is dry oil used as in paint, varnish and ink manufacturing or as a substitute for linseed oil. The seed cakes are used as animals and birds feed (Gediminas et al. 2008; Talbott and Hughes 2006; Longvah et al. 2000; Borchers et al. 1997; Narisawa et al. 1994).
Source and uses of omega fatty acids
Perilla is used for oil production as a rich source of omega-3 polyunsaturated fatty acids (PUFAs), specifically alpha-linolenic acid (ALA). It also contains omega 6 and omega 9 fatty acids. Omega fatty acids are the essential for our health, so the omega-3s and 6s must be obtained through our diet or by supplementation. It is the best resources for additional human omega-3 polyunsaturated fatty acids (PUFAs). ALA (omega 3 fatty acid), is found in some other plant oils sources such as flaxseed (linseed), with lower amounts in walnut, canola, soy and animal sources like fish oil (cold water fish as salmon, cod and mackerel).
Perilla oil suppresses the production of chemical mediator in the allergy and inflammatory responses. These essential fatty acids have been associated with benefits in a wide range of inflammatory conditions, heart diseases, colitis/Crohn’s disease, asthma, allergies, antimicrobial, anticancer etc. Perilla is also used for nausea, sunstroke, to induce sweating and as an antispasmodic. In vivo metabolism of polyunsaturated omega-3 fatty acids, it mainly exists in the form of DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid). These two specific omega-3 fatty acids metabolites are inserted in cell membranes throughout the body, where cellular machinery converts them into substances which prevent abnormal clotting, reduce inflammation, and relax blood vessels and improved ventilatory parameters (Lewis 2008; Talbott and Hughes 2006; Calder 2004; James et al. 2000; Chin et al. 1992; Mattson and Grundy 1985).
Other dietary sources of omega-3 fatty acids
Flax seeds produce linseed oil, which has a very high omega−3 fatty acid content Six times richer than most fish oils in n−3, flax (or linseed) (Linum usitatissimum) and its oil are perhaps the most widely available botanical source of n−3. Flaxseed oil consists of approximately 55% ALA (alpha-linolenic acid). Flax, like chia, contains approximately three times as much n−3 as n−6. 15 g of flaxseed oil provides 8 g of ALA, which is converted in the body to EPA and then DHA at efficiency of 5–10% and 2–5%, respectively (Azcona et al. 2008; Lewis 2008; Albert et al. 2002; Schacky and Dyerberg 2001; James et al. 2000; Mattson and Grundy 1985) (Tables 1 and 2).
The most widely available source of EPA and DHA is cold water oily fish such as salmon, herring, mackerel, anchovies and sardines. Oils from these fish have a profile of around seven times as much omega 3 fish oil as omega 6. Other oily fish such as tuna also contain omega 3 fish oil in somewhat lesser amounts. Consumers of oily fish should be aware of the potential presence of heavy metals and fat-soluble pollutants like PCBs and dioxin which may accumulate up the food chain. Although fish is a dietary source of n−3 fatty acids, fish do not synthesize them; they obtain them from the algae or plankton in their diet (James et al. 2000; Renaud 2002; Chin et al. 1992).
Eggs produced by chickens fed a diet of greens and insects produce higher levels of n−3 fatty acids (mostly ALA) than chickens fed corn or soybeans. In addition to feeding chickens insects and greens, fish oils may be added to their diet to increase the amount of fatty acid concentrations in eggs. The addition of flax and canola seeds to the diet of chickens, both good sources of alpha-linolenic acid, increases the omega-3 content of the eggs (Azcona et al. 2008; Trebunová et al. 2007).
The n−6 to n−3 ratio of grass-fed beef is about 2:1, making it a more useful source of n−3 than grain-fed beef, which usually has a ratio of 4:1. In most countries, commercially available lamb is typically grass-fed, and thus higher in n−3 than other grain-fed or grain-finished meat sources. The omega 3 content of chicken meat may be enhanced by increasing the animals’ dietary intake of grains that are high in n−3, such as flax, chia, and canola (Azcona et al. 2008; Trebunová et al. 2007).
Seal oil is a source of EPA, DPH, and DPA. According to Health Canada, it helps to support the development of the brain, eyes and nerves in children up to 12 years of age (Azcona et al. 2008; Trebunová et al. 2007).
Milk and cheese from grass-fed cows may also be good sources of n−3. The microalgae Crypthecodinium cohnii and Schizochytrium are rich sources of DHA (22:6 n−3) and can be produced commercially in bioreactors. This is the only source of DHA acceptable to vegans. Oil from brown algae (kelp) is a source of EPA. Walnuts are one of few nuts that contain appreciable n−3 fat, with approximately a 1:4 ratio of n−3 to n−6. Acai palm fruit also contains n−3 fatty acids. Omega-3 is also found in soft gels in pharmacies and nowadays it is also found in combination with omega 6, omega 9 and shark liver oil(Azcona et al. 2008; Trebunová et al. 2007).
Chemistry of fatty acids
Perilla is an alternative source of fatty acids that contains both saturated and unsaturated (monosaturated and polyunsaturated) fatty acids. Fatty acids having more than one double bonds are termed as PUFAs. It contains saturated fatty acids mainly palmitic acid 5–7%, stearic acid 1–3%, monosaturated oleic acid 12–22%, and poly saturated fatty acids linoleic acid 13–20%, γ-linolenic acid 0–1%, α-linolenic acid 52–64%, icosanoic acid 0–1%. Increase in the number of double bonds progressively decreases the melting point. Unsaturated fatty acids are lower melting point than saturated fatty acids. Plant triglycerides have a large portion of unsaturated fatty acids such as oleic, lenoleic and linolenic acids. Animal triglycerides have high proportion of saturated fatty acids such as palmitic and stearic acids (Tables 3 and 4).
Nomenclature of fatty acids
The systemic nomenclature of fatty acids is derived from the name of its parent hydrocarbon by replacing its final e by oleic acid. Thus the names of saturated fatty acids end with the suffix anoic acid and those of unsaturated fatty acids with the suffix enoic acid. The numbering of carbon atoms in fatty acids is started at the carboxyl terminus and end methyl carbon is known as omega carbon atom (Figs. 4 and 5).
Various conventions are adopted for indicating the position of the double bonds. The most widely used are involve the use of the symbol Δ fallowed by superscript number. For example Δ9 means that there is a double bound between carbon 9 and carbon 10. Alternatively the position of the double bond is indicated by the numerals as in case simple alkenes. Lastly note that total number of carbon atoms and number of position(s) of double bond(s) is again indicated by convention. Examples, the symbol 18;0 denote a C18 fatty acid with no double bonds, the symbol 18: 1; 9 denote a C 18 fatty acid with a double bond between carbon 9 and carbon 10 and the symbol 18: 2; 9,12 denote a C 18 fatty acid with two double bonds between C9 and C10 and between C12 and 13 (Renaud 2002; Mattson and Grundy 1985) (Table 5).
Definition of omega fatty acids
The names “omega 3” or “omega 6” or “omega 9” fatty acids refer to where a double bond occurs in the fatty acid molecule. The terms “omega” or “n minus” refer to the position of the double bond of the fatty acid closest to the methyl end of the molecule. Thus, oleic acid, which has its double bond 9 carbons from the methyl end, is considered an omega 9 (or an n–9) fatty acid. Similarly, linoleic acid, common in vegetable oils, is an omega-6 (n–6) fatty acid because its second double bond is 6 carbons from the methyl end of the molecule (i.e., between carbons 12 and 13 from the carboxyl end). Omega 3 and omega 6 fatty acids are “essential fatty acids”, meaning that these fatty acids cannot synthesized by body itself. Instead, we must include them in our diet or through supplements to meet our body demands. Omega 9 fatty acids are “conditionally essential”, which means that if we have the other fatty acids in our diet, then our body can manufacture omega 9 fatty acids. Otherwise, omega 9 fatty acids must be consumed or supplemented as well. DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) are the two specific omega 3 fatty acids found in fish oil such as cold water fish as salmon, cod and mackerel (Green et al. 2007; Calder 2004; Renaud 2002; Chin et al. 1992; Ip et al. 1996; Mattson and Grundy 1985).
Importance of omega fatty acids
Among plant oils, the balance between omega 3 omega 6 omega 9 fatty acids must dictate which oil is chosen. Oils which predominate in omega 3 component would be most likely to promote health, only perilla and flax seed (vegetable) oil predominate in omega 3 fatty acid. Most would actually contribute to the imbalance of omega-6 fatty acids because they contain more omega-6 than omega-3. Any amount of omega 9 is beneficial, but in balancing these fatty acids, the omega-3 component is the most important.