Enhanced Resolution of Conjugated Linoleic Acid Isomers by Tandem-Column Silver-Ion High Performance Liquid Chromatography

Abstract

A commercial mixture of conjugated linoleic acid (CLA) isomers, reportedly consisting of six components, was recently resolved into 12 peaks attributed to CLA isomers using silver-ion high performance liquid chromatography (Ag + -HPLC). In this study, the coupling of two analytical silver-ion high performance liquid chromatography columns (tandem-column Ag + -HPLC) in series led to the enhanced resolution of CLA isomers. Many CLA isomers were baseline resolved and the pair 18 : 2 8,10 c/t and 18 : 2 7,9 c/t found in cheese products, was resolved for the first time. In this work, a similar commercial CLA mixture was separated into 16 peaks, while CLA isomers from cheese also gave rise to 16 peaks. As expected, the CLA isomers were separated into three geometric groups in the order trans,trans, cis/trans, and cis,cis. Semi-preparative Ag + -HPLC, followed by gas chromatography -mass spectroscopy of the dimethyloxazoline derivatives, was used to confirm the identity of the newly resolved positional CLA isomers. The double bond configuration of CLA isomers was established by gas chromatography -Fourier transform infrared spectroscopy. Two minor t,t CLA isomers found in cheese, presumably 18 : 2 t6t8 and 18 : 2 t13t15, were also separated. The CLA isomeric composition of 16 commercial cheese products was determined.

Conjugated linoleic acid evokes de‐lipidation through the regulation of genes controlling lipid metabolism in adipose and liver tissue

“…The conjugated linoleic acid (CLA) family consists of several conjugated and stereoisomeric variations of linoleic acid ( cis, cis -D 9,12 -octadecadienic acid), of which 16 have currently been identified (1)(2)(3). Natural forms of CLA can be found predominantly in ruminant products, such as milk, cheese and beef (3)(4)(5)(6)(7), and exist primarily (80-90%) as the cis -9, trans -11 isomer (c9t11), also known as rumenic acid (7)(8)(9)(10).…”

9‐trans,11‐trans‐CLA: Antiproliferative and proapoptotic effects on bovine endothelial cells

“…The present study compares the effects of all five CLA isomers that are commercially available in pure form at this time on the proliferation of both normal, adherent cells (BAEC) and a leukemic cell line grown in suspension (THP-1). Cis, trans isomers constitute the major (86-93% of total isomers) CLA isomer class found in dairy and beef products (27)(28)(29). The 9c,11t-CLA represented more than 70% of this class whereas the next most abundant isomer in this group, 7t,9c-CLA, amounted to only 10%.…”

Separation of conjugated linoleic acid-containing mono-, di- and triacylglycerols by silver-ion high-performance liquid chromatography

“…While improved resolution has been obtained by linking up to 6 Ag + -HPLC columns in series [32], this author and others [12] believe two to four columns should be consid- ** Initial fractionation method only. ** Before/after; i.e.…”