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Title: ANALYSIS OF CLA-ENRICHED TRIACYLGLYCEROL MIXTURES BY ISOCRATIC SILVER-ION HPLC

Author
item Adlof, Richard
item MOHEDE, I - LODERS CROKLAAN, NE
item DUCHATEAU, G - UNILEVER, THE NETHERLANDS

Submitted to: Journal of Chromatography A
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Conjugated linoleic acid (CLA; 9c,11t-18:2), present in dairy products and beef, has been reported in animals to have anti-cancer, growth-promoting, anti heart disease, anti-diabetic and fat-reducing properties. The "CLA" found in human diet supplements is usually a mixture of isomers, with each isomer having a different effect. "CLA" mixtures have recently become commercially available in the glyceride form, the same form as the fats in our usual diet. Since fat structure can be related to how well our bodies use fats, a rapid method to analyze these new CLA-containing mixtures was required. Silver ion high performance liquid chromatography was found to be a useful method to separate these different structures, with potential future applications in the analysis of seed oil glycerides and less-complex CLA-containing glyceride mixtures for patent applications or in CLA-containing diet supplements.

Technical Abstract: Silver ion HPLC (Ag-HPLC) was applied to the fractionation of a triacylglycerol (TAG) sample enriched (>80%) with conjugated linoleic acid (CLA). After conversion of the TAGs to fatty acid methyl esters using sodium methoxide in methanol, Ag-HPLC (dual-column; isocratic solvent system of 0.1% acetonitrile in hexane; UV detection at 233 nanometers) was used to determine the CLA isomer distribution (50/50 mixture of 9c,11t- and 10t,12c-18:2). Three or four Ag-HPLC columns connected in series (0.6-1.0% acetonitrile in hexane as solvent; UV detection at 206 nanometers) were used to analyze the sample in TAG form. Elution times for CLA- enriched TAGs averaged 30 minutes or less. Isocratic solvent conditions were used to eliminate the solvent equilibration times of 30 minutes or more required between sample injections when solvent programming is used. The ratio of TAGs containing three vs. only two CLA molecules was found to be approximately 3 to 1. Ag-HPLC has thus been shown to be a useful method for rapidly analyzing not only CLA isomers as esters, but also in the TAG form. DEFINITIONS: Ag-HPLC (silver-ion high performance liquid chromatography; CLA (conjugated linoleic acid); TAG (triacylglycerol); GC (gas chromatography); ACN (acetonitrile).