Analysis of fatty acid steryl esters in tetraploid and hexaploids wheats: identification and comparison between chromatographic methods

Steryl esters with fatty acid obtained from 14 genotypes of tetraploid (T. dicoccon and T. durum) and 17 genotypes of hexaploid (T. spelta and T. aestivum) wheats were analysed using different chromatographic strategies. GC-FID and HPLC-ELSD analysis of non-hydrolysed SE indicated major differences between the tetraploid and hexaploid species, the latter being qualitatively and quantitatively rich in this class of compounds. The hydrolysed SE injected into GC confirmed the differences between the classes of tetraploid wheats, where palmitic acid was not detectable, and hexaploid wheats, where traces of oleic acid were found. The distribution of the steryl residues between both classes of wheat did not differ. Lastly, the HPLC method hyphenated to ESI-MS detection enabled SE to be recognised by the characteristic fragmentations and ion-adducts of each molecule. In particular, minor traces of campesteryl and sitosteryl and practically no trace of stigmasteryl palmitates were found in T. durum and its hulled ancestor T. dicoccon, while steryl oleates were not detectable (the minimum amount detectable being 0.02mg/100g d.b.) in T. aestivum and its hulled ancestor T. spelta, which is consistent with the filogenesis of tetraploid and hexaploid wheat species. Steryl linoleates and linolenates were found to be equally distributed in both tetraploid and hexaploid wheats.