Separation and characterization of cis-trans isomers of α-tocotrienol by HPLC using a permethylated β-cyclodextrin phase

The behaviour of alpha-, beta-, gamma- and delta-tocotrienols (structurally related to tocopherols with naturally trans-configurated double bonds in the side-chain) during HPLC on a permethylated beta-cyclodextrin phase was studied. A newly developed isocratic HPLC method is described with an acetonitrile/water (58:42 by vol.) eluent and fluorescence detection at an emission wavelength of 330 nm (excitation wavelength = 295 nm). Each of the separately injected tocotrienols exhibited four peaks. The four separated components of alpha-tocotrienol were identified by spectroscopy (MS, H-1-NMR, FTIR) to be structural side-chain isomers. The order of retention times was determined to be all-cis-alpha-tocotrienol followed by cis-trans-/trans-cis-alpha-tocotrienol (differentiation between the two compounds was not possible) with all-trans-alpha-tocotrienol as the last eluting isomer.