Determination of RS,E/Z-tocotrienols by HPLC

Synthetic cu-tocotrienol was separated into four geometrical E/Z side chain isomers by preparative HPLC (permethylated beta -cyclodextrin phase). The isolated isomers were resolved in ethylene glycol dimethyl ether, converted into the corresponding methyl ether using dimethyl sulfate, and the tocotr ienol methyl ethers were extracted with n-hexane. A subsequent HPLC separat ion on a chiral phase (adsorbent cellulose derivated with 3,5-dimethyl phen yl carbamate) discriminates between the enantiomers of each E/Z side chain isomer, achieving the complete resolution of the eight occurring synthetic RS,EIZ-alpha -tocotrienols. The method can be shortened by omitting the pre parative separation of the E/Z tocotrienol isomers prior to the chromatogra phy on the chiral dimethyl phenyl carbamate phase. The simplified method ac hieved the following separation: RS,E/Z-alpha -tocotrienol separated into f ive peaks, RS,E/Z-beta -tocotrienol into eight, RS,E/Z-gamma -tocotrienol i nto six and RS,E/Z-delta -tocotrienol into eight peaks. The naturally occur ring R,E-E-tocotrienol isomer could be identified within the synthetic RS,E /Z-isomers by co-chromatography with tocotrienol methyl ethers derived from natural sources, respectively. (C) 2001 Elsevier Science B.V. All rights r eserved.