Evidence in the formation of conjugated linoleic acids from thermally induced 9t12t linoleic acid: a study by gas chromatography and infrared spectroscopy

Abstract

Thermally induced isomerisation leading to the formation of Conjugated Linoleic Acids (CLA) has been observed for the first time during the thermal treatment of 9t12t fatty acid triacylglycerol, and methyl ester. Fifteen microlitre portions of the triacylglycerol sample containing 9t12t fatty acid (trilinoelaidin) were placed in micro glass ampoules and sealed under nitrogen, then subjected to thermal treatment at 250 o C. The glass ampoules were removed at regular time intervals, cut open, and the contents were analysed by infrared spectroscopy using a single reflectance attenuated total internal reflectance crystal accessory. The samples were then subjected to derivatisation into their methyl esters. The methyl esters of the isomerised fatty acids were analysed by gas chromatography. The same procedure was repeated with methyl ester samples containing 9t12t fatty acid (methyl linoelaidate). Each sample was subjected to infrared measurements and gas chromatographic analysis after appropriate dilution in heptane.The results show that the thermally induced isomerisation of 9t12t fatty acids from both triacylglycerol molecules and methyl esters give identical CLA profiles as those found for the thermally induced isomerisation of 9c12c fatty acids. The infrared spectrometry provides additional evidence confirming the formation of CLA acids during thermal treatment. A mechanism for the formation of the CLAs from 9t12t fatty acid molecules is also formulated for the first time. This mechanism complements the pathways of formation of CLAs from 9c12c fatty acids during thermal treatment.Key words: Linoelaidin, Conjugated Linoleic Acids, Gas Chromatography, infrared spectroscopy, isomerisation. IntroductionConjugated Linoleic Acids (CLA) are natural components found in animal products such as meat and dairy products derived from ruminant animals. Conjugated Linoleic Acids have gained considerable attention in recent times because of their health benefits (Ip et al., 1991 and1994;Nicolosi et al., 1993;Shanta et al., 1992). This interest has been followed by an explosion of research reports on the benefits of CLAs in the areas of cancer, heart disease, diabetes and many other areas (Parodi, 1996; Belury and Van den Heuvel, 1997;Schrezenmeir and Jagia, 2000; Pariza, 2000;Scimeca and Miller, 2000;Kritchevsky, 2000;Thom et al., 2001;Voorrips et al., 2002;Belury, 2002;Larsen et al., 2003;Tricon et al., 2004; Lin Yang et al., 2004;Zulet et al., 2005;Wang et al., 2006;Bhattacharya et al, 2006;Kelley et al, 2007; Fite et al., Amarù and Field, 2009;Coakley et al, 2009). The results in these reports are based on the studies on animals and the beneficial effects on humans are yet to be proven.

Isomerization of 9c11t/10t12c CLA in Triacylglycerols

“…The identity of the relatively large peak in the group was confirmed as methylene interrupted 9t12t (18:2) fatty acid. In an earlier report [23], it was shown that the CLAs can also be formed by thermally inducing a triacylglycerol containing 9t12t fatty acid. Therefore, the formation of 9t12t (18:2) is possible during thermal induction of CLA fatty acids.…”

“…Therefore, the formation of 9t12t (18:2) is possible during thermal induction of CLA fatty acids. The reaction takes place through an intramolecular [1,3], sigmatropic rearrangement or a free radical chain reaction mechanism [16,23]. The identification of 9t12t led to the inclusion of the [1,3] sigmatropic transformation part in the mechanism presented in Fig.…”

“…3 Interactive substraction of the second derivative infrared spectrum of the starting material from the spectra of samples thermally induced at 250°C [1,3] and [1,5] sigmatropic transformations, and positional isomerizations can be found in Destaillats and Angers [11,16] and Christy [23]. The figure is similar to the one formulated by Destaillats and Angers [11,16] and Christy [23], but presented collectively in a manner to explain the appearance of the cis-trans and trans-cis isomers of CLAs that can be expected in a thermal induction experiment of another cis-trans CLA isomer. Thermal induction of 9c11t yields very little or no 11t13c and 12c14t isomers.…”

The impact of technical cashew nut shell liquid on thermally-induced trans isomers in edible oils

“…In addition, other studies have highlighted the formation of conjugated linoleic acids (CLAs) during the heating of edible oils, showing that trans,trans CLA isomers are the predominant products, followed by cis,trans and trans,cis CLA isomers (Christy 2009;Guo et al 2015). Recently, interest in CLAs has increased due to the biological activities associated with their numerous isomers.…”

Thermally Induced Isomerisation Kinetics of the 9c11t and 10t12c Conjugated Linoleic Acids in Triacylglycerols as Studied by FT-IR Spectrometry Aided by Gas Chromatography

“…The chemistry and mechanistic pathways involved in the formation of CLAs were also discussed in the above research reports. Christy [14] has also contributed to supplement the mechanistic aspects by demonstrating that CLA isomers could be produced by thermal induction of 9t12t LA. In a recent report Christy [15] demonstrated that the [1,5] sigmatropic transformations and positional isomerisation could be achieved by subjecting triacylglycerols of CLAs to a suitable high temperature.…”