Preparation of a Large Quantity of cis - 9, trans - 11 and trans - 10, cis - 12 Conjugated Linoleic Acid (CLA) Isomers from Synthetic CLA

Conjugated linoleic acid (CLA) refers to a collective term of positional and geometric isomers of linoleic acid, which are different in their biological activities. The predominant isomer of CLA in animal tissues is cis-9,trans-11; smaller amounts of trans-10,cis-12 also occurs. To develop a method for preparation of a large quantity of the relatively pure cis-9,trans-11 CLA and trans-10,cis-12 CLA isomers, CLA methyl ester (CLA-Me) was chemically synthesized from linoleic acid by the alkaline isomerization method. The synthetic CLA-Me, mainly composed of cis-9,trans-11 CLA and trans-10,cis-12 CLA, was dissolved in acetone, stored at -68oC for 1 day, and the supernatant (cis-9,trans-11 CLA-Me) was separated from the precipitate (trans-10,cis-12 CLA-Me). After the processes were repeated three times at -68oC, the whole processes were repeated three times at -71oC in order to increase the purity of these two isomers. The cis-9,trans-11 CLA and trans-10,cis-12 CLA isomers were further purified by the urea adduct. Purities of the cis-9,trans-11 CLA-Me and trans-10,cis-12 CLA-Me were 90.3 and 99.9%, respectively. This method could be employed for the preparation of a large quantity of highly purified cis-9,trans-11 CLA-Me or trans-10,cis-12 CLA-Me from synthetic CLA-Me.