Structure determination of conjugated linoleic and linolenic acids.

• Current chromatography method cannot fully distinguish cis/trans isomers of CLA/CLnA. • Combination of GC and Ag+-HPLC is the most effect method so far. • Ion mobility spectrometry offers potential for fast conjugated lipid characterization. • Chemo-metric methods coupling mass spectrometry are another possible approach. Conjugated linoleic and linolenic acids (CLA and CLnA) can be found in dairy, ruminant meat and oilseeds, these types of unsaturated fatty acids consist of various positional and geometrical isomers, and have demonstrated health-promoting potential for human beings. Extensive reviews have reported the physiological effects of CLA, CLnA, while little is known regarding their isomer-specific effects. However, the isomers are difficult to identify, owing to (i) the similar retention time in common chromatographic methods; and (ii) the isomers are highly sensitive to high temperature, pH changes, and oxidation. The uncertainties in molecular structure have hindered investigations on the physiological effects of CLA and CLnA. Therefore, this review presents a summary of the currently available technologies for the structural determination of CLA and CLnA, including the presence confirmation, double bond position determination, and the potential stereo-isomer determination. Special focus has been projected to the novel techniques for structure determination of CLA and CLnA. Some possible future directions are also proposed. [ABSTRACT FROM AUTHOR]