Separation of vitamin E (tocopherol, tocotrienol, and tocomonoenol) in palm oil

Previous reports showed that vitamin E in palm oil consists of various isomers of tocopherols and tocotrienols (alpha-tocopherol (alpha-T), alpha-tocotrienol, gamma-tocopherol, gamma-tocotrienol, and delta-tocotrienol), and this is normally analyzed using silica column HPLC with fluorescence detection. In this study, an HPLC-fluorescence method using a C(30) silica stationary phase was developed to separate and analyze the vitamin E isomers present in palm oil. In addition, an alpha-tocomonoenol (alpha-T(1)) isomer was quantified and characterized by MS and NMR. alpha-T(1) constitutes about 3-4% (40 +/- 5 ppm) of vitamin E in crude palm oil (CPO) and is found in the phytonutrient concentrate (350 +/- 10 ppm) from palm oil, whereas its concentration in palm fiber oil (PFO) is about 11% (430 +/- 6 ppm). The relative content of each individual vitamin E isomer before and after interesterification/transesterification of CPO to CPO methyl esters, followed by vacuum distillation of CPO methyl esters to yield the residue, remained the same except for alpha-T and gamma-T(3). Whereas alpha-T constitutes about 36% of the total vitamin E in CPO, it is present at a level of 10% in the phytonutrient concentrate. On the other hand, the composition of gamma-T(3) increases from 31% in CPO to 60% in the phytonutrient concentrate. Vitamin is present at 1160 +/- 43 ppm, and its concentrations in PFO and the phytonutrient concentrate are 4,040 +/- 41 and 13,780 +/- 65 ppm, respectively. The separation and quantification of alpha-T(1) in palm oil will lead to more in-depth knowledge of the occurrence of vitamin E in palm oil.