A liquid chromatographic (LC) method was developed for determination of tocopherols and tocotrienols in foods. Tocopherols and tocotrienols were released after saponification of test portions for 40 min at 80 degrees C, followed by extraction with hexane-ethyl acetate. After evaporation of the organic solvents, the extract was injected in the LC system. Separation of individual tocopherols and tocotrienols was satisfactory. Some interferences were encountered from tocomoneols, tocodienols, 2-tert-butyl-4-hydroxyanisole (BHA), 2,6-di-tert-butyl-4-methylphenol, (BHT), and plastochromanol-8. The response of the LC system was linear over a range of 0-10 micrograms/mL for tocopherols and tocotrienols. The detection limit for these compounds was 0.1 micrograms/mL. Repeatabilty relative standard deviation values for tocopherols and tocotrienols in margarine, infant formula, and broccoli (concentration range, 0.11-22 mg/100 g) varied from 1.3 to 6.4%. Recoveries ranged from 91 to 105%.
This article is a review of the fundamental chemistry of the tocopherols and tocotrienols relevant to their antioxidant action. Despite the general agreement that alpha-tocopherol is the most efficient antioxidant and vitamin E homologue in vivo, there was always a considerable discrepancy in its “absolute” and “relative” antioxidant effectiveness in vitro, especially when compared to gamma-tocopherol. Many chemical, physical, biochemical, physicochemical, and other factors seem responsible for the observed discrepancy between the relative antioxidant potencies of the tocopherols in vivo and in vitro. This paper aims at highlighting some possible reasons for the observed differences between the tocopherols (alpha-, beta-, gamma-, and delta-) in relation to their interactions with the important chemical species involved in lipid peroxidation, specifically trace metal ions, singlet oxygen, nitrogen oxides, and antioxidant synergists. Although literature reports related to the chemistry of the tocotrienols are quite meager, they also were included in the discussion in virtue of their structural and functional resemblance to the tocopherols.