Candida rugosa lipase selectivity toward trans,cis- and cis,trans-conjugated linoleic acid isomers

It is known that conjugated linoleic acid (CLA) isomers have different beneficial health effects, and it has been demonstrated that the effects of CLA may be isomer dependent. For this reason, CLA isomer fractionation is a very important topic, and recently, various enzymatic methods for the fractionation of CLA isomers have been studied. In this paper, a commercial CLA standard including four isomers (c11,t13-, t10,c12-, c9,t11- and t8,c10-CLA) were subjected to enzymatic esterification with L-menthol in order to examine the ability of Candida rugosa lipase to discriminate among the isomers. The lipase was incubated at 30 C for different reaction times, and subsequently, the degree of enzymatic esterification was established by ligh-performance liquid chromatography (HPLC) with light scattering detection. Moreover, in this study, a silver–ion HPLC analysis was developed to determine the isomer profile of L-menthyl-CLA. Since the t8,c10- and c11,t13-CLA isomers are not commercially available, they were obtained by sigmatropic rearrangement of c9,t11- and t10,c12-CLA, respectively. The highest selectivity for the c9,t11-CLA isomer was obtained when enzymatic esterification was carried out for 8 h. This study demonstrated that C. rugosa lipase has a higher selectivity for cis,trans isomers, than for trans,cis isomers; in particular, it has a higher selectivity for c9,t11- than for c11,t13-CLA.