This article is a review of the fundamental chemistry of the tocopherols and tocotrienols relevant to their antioxidant action. Despite the general agreement that α-tocopherol is the most efficient antioxidant and vitamin E homologuein vivo, there was always a considerable discrepancy in its “absolute” and “relative” antioxidant effectivenessin vitro, especially when compared to γ-tocopherol. Many chemical, physical, biochemical, physicochemical, and other factors seem responsible for the observed discrepancy between the relative antioxidant potencies of the tocopherolsin vivo andin vitro. This paper aims at highlighting some possible reasons for the observed differences between the tocopherols (α-, β-, γ-, and δ-) 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.

The chemistry and antioxidant properties of tocopherols and tocotrienols

Bioavilability and Analysis of Vitamins in Foods , Bioavilability and Analysis of Vitamins in Foods , کتابخانه دیجیتال جندی شاپور اهواز

Bioavailability and analysis of vitamins in foods

In this paper, I shall discuss the important trends of the past seven years in applications of antioxidants in foods. The nature and course of lipid autoxidation and antioxidant action have been treated in a previous paper of this Symposium (Symposium, 1979), as has the effect of water activity. Other papers will deal with the biological effects of antioxidant use, including antimicrobial action. Natural antioxidants will also be treated elsewhere. Therefore, I shall discuss primarily the use of the commonly added synthetic antioxidants (Fig. 1) and four naturally occurring ones — α-tocopherol and ascorbic (Fig. 2), citric and phosphoric acids, which common usage seems to segregate from the “natural” antioxidants. In addition, I shall handle many secondary antioxygenic compounds and treatments, such as oxygen exclusion or scavenging, browning antioxidants, and products produced by fermentation, smoking, nitrite curing, and hydrolysis of vegetable protein.

Recent Trends in Food Applications of Antioxidants

2 – carotenoids as food colors

Vitamins in Pharmaceutical Formulations

Both alpha- and gamma-tocopherol are degraded by Fe2+ and Cu2+. Ascorbic acid and EDTA completely inhibit the Cu2+ oxidation but only ascorbic acid completely prevented the Fe3+ oxidation although EDTA and citric acid gave some protection. On the other hand pure tocopherols, undiluted, were stable to air and light over a period of years.

W.M. Cort

Papers

STABILITY OF ALPHA‐ AND GAMMA‐TOCOPHEROL: Fe3+ AND Cu2+ INTERACTIONS