Abstract
Some of the essential polyunsaturated fatty acids (PUFAs) as ARA (arachidonic acid, n-6), EPA (eicosapentaenoic acid, n-3) and DHA (Docosahexaenoic acid, n-3) cannot be synthesized by mammals and it must be provided as food supplement. ARA and DHA are the major PUFAs that constitute the brain membrane phospholipid. n-3 PUFAs are contained in fish oil and animal sources, while the n-6 PUFAs are mostly provided by vegetable oils. Inappropriate fatty acids consumption from the n-6 and n-3 families is the major cause of chronic diseases as cancer, cardiovascular diseases and diabetes. The n-6: n-3 ratio (lower than 10) recommended by the WHO can be achieved by consuming certain edible sources rich in n-3 and n-6 in daily food meal. Many researches have been screened for alternative sources of n-3 and n-6 PUFAs of plant origin, microbes, algae, lower and higher plants, which biosynthesize these valuable PUFAs needed for our body health. Biosynthesis of C(18) PUFAs, in entire plant kingdom, takes place through certain pathways using elongases and desaturases to synthesize their needs of ARA (C(20)-PUFAs). This review is an attempt to highlight the importance and function of PUFAs mainly ARA, its occurrence throughout the plant kingdom (and others), its biosynthetic pathways and the enzymes involved. The methods used to enhance ARA productions through environmental factors and metabolic engineering are also presented. It also deals with advising people that healthy life is affected by their dietary intake of both n-3 and n-6 FAs. The review also addresses the scientist to carry on their work to enrich organisms with ARA.