Tocol-derived minor constituents in selected plant seed oils

Various crude and processed seed oils were analyzed for tocopherols (T) and tocotrienols (T-3) by reversed-phase HPLC with fluorescence detection (FL). The oils included processed canola oil, crude corn oil, crude milkweed oil, crude palm oil, crude/processed rice bran oils, crude/processed soybean oil, crude/processed sunflower oil, and related modified oil varieties. The HPLC system consisted of a pentafluorophenylsilica (PFPS) column and a mobile phase of methanol and water. The results of comparative methodological studies with rice bran oils and milkweed oils indicated that the reversed-phase PFPS-HPLC method in conjunction with the use of less hazardous solvents proved to be superior and a viable alternative to the conventional normal-phase HPLC method. Unlike the traditional nonpolar octadecylsilica phase, which fails to resolve beta-gamma pairs of T and T-3, HPLC with the unique polar PFPS column enables separations of all compounds of interest. Except for palm oil, betaT and gammaT were detected in all other crude oils. Although most milkweed oils contained moderate levels of betaT and gammaT, the betaT species was present in relatively low abundance in edible oils despite the observation of fairly high concentrations of gammaT in the latter oils. betaT(3) and gammaT(3) were detected along with alphaT(3) and deltaT(3) only in palm and rice bran oils. Tocol-derived antioxidant distribution data for zero-time processed oils provided potential utility in correlation studies of frying quality and stability. The variable distribution data for crude oils shed some light on market profitability of oilseeds with rich sources of vitamin E-related minor constituents.