Biogenesis of Conjugated Linoleic Acids

Biogenesis of Conjugated Linoleic Acids

Sailas Benjamin (University of Calicut, India), Kizhakepowathil Nair Unni (University of Calicut, India), Prakasan Priji (University of Calicut, India) and Andre-Denis Girard Wright (University of Arizona, USA)
DOI: 10.4018/978-1-5225-0607-2.ch001
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Abstract

One of the key areas in animal husbandry is to improve the quality (nutritional value) of dairy and meat products by enriching them with Conjugated Linoleic Acids (CLAs) like (cis-9, trans-11)- and (trans-10, cis-12)-octadecadienicacids; the former (rumenic acid) predominates all the CLAs. Though Vaccenic Acid (VA) is the immediate precursor of rumenic acid, dietary unsaturated fatty acids like Oleic Acid (OA), Linoleic Acid (LA) and a-Linolenic Acid (ALA) are the distant precursors of CLAs; and that CLA and VA are formed as intermediates during the biohydrogenation of the dietary OA, LA and ALA into fully saturated stearic acid. The mutual inter-relationship of rumen microbiota encompassing bacteria, protozoa and fungi facilitates the biohydrogenation process. Thus, this chapter critically evaluates the knowledge accumulated during the past four decades on the precursor of CLAs, micro-organisms involved in the production of CLA, the mechanism of biohydrogenation, and chemical synthesis of CLA, coupled with the rationale for biohydrogenation and factors affecting the production of CLA.
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Chemistry Of Cla, The Omega Paradigm

Very often, CLAs are erroneously classified as omega-6 (abbreviated as ω-6) FAs. In fact, CLA is a class of FAs comprising as many as 56 isomers with conjugated (neighboring) double bond pairs (i.e., at positions 6,8-; 7,9-; 8,10-; 9,11-; 10,12-; 11,13-; 12,14-; and 13,15- with cis-cis, cis-trans, trans-cis or trans-trans geometric configurations) varying along the acyl chain of LA (Dobson, 2003). From this, it is evident that only the isomers with the conjugated double bonds on carbon positions starting at 10 (from –COOH terminus) have indeed their first C-C double bond at the ω-6 position, while counting from the methyl (CH3-) terminus (i.e. from the last or omega-C on the acyl chain) (Figure 1). Thus, trans-10, cis-12-CLA (designated as 10-CLA) is a typical ω-6 CLA; while the biologically active and predominantly (natural) occurring cis-9, trans-11-CLA (designated as 9-CLA, the rumenic acid) is a typical ω-7 FA (Benjamin & Spener, 2009; Benjamin et al., 2015). Though, LA is devoid of conjugated double bonds, it is also an ω-6 FA, while counting the double bond position from the methyl terminus of the FA chain (Figure 1).

Figure 1.

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