Description
Molecules having vitamin E antioxidant activity include four tocopherols (α, β, δ, and γ) and four tocotrienols (α, β, δ, and γ).1 α-Tocopherol is the major lipid soluble antioxidant in vivo and protects against lipid peroxidation.2 α-CEHC is the major urinary metabolite of α-tocopherol following vitamin E supplementation.3 The concentration of α-CEHC in human serum is in the range of 5-10 pmol/ml but increases significantly up to 200 pmol/ml upon supplementation with RRR-α-tocopherol. About one-third of the α-CEHC circulating in the blood is present as a glucuronide conjugate.4 α-CEHC was only excreted when a threshold concentration of 7-9 μmol α-tocopherol/g total lipid in plasma was exceeded. Therefore, excretion of α-CEHC may be considered to be a marker of optimum vitamin E intake.5
References
1. Kamal-Eldin, A., and Appelqvist, L.-?. The chemistry and antioxidant properties of tocopherols and tocotrienols Lipids 31(7),671-701(1996).
2. Burton, G.W., Joyce, A., and Ingold, K.U. Is vitamin E the only lipid-soluble, chain-breaking antioxidant in human blood plasma and erythrocyte membranes? Arch. Biochem. Biophys. 221(1),281-290(1983).
3. Traber, M.G., Elsner, A., and Brigelius-Flohé, R. Synthetic as compared with natural vitamin E is preferentially excreted as α-CEHC in human urine: Studies using deuterated α-tocopheryl acetates FEBS Lett. 437,145-148(1998).
4. Stahl, W.S., Graf, P., Brigelius-Flohé, R., et al. Quantification of the α- and γ-tocopherol metabolites 2,5,7,8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman and 2,7,8-trimethyl-2-(2'-carboxyethyl)-6-hydroxychroman in human serum Anal. Biochem. 275,254-259(1999).
5. Schultz, M., Leist, M., Petrzika, M., et al. Novel urinary metabolite of α-tocopherol, 2,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman, as an indicator of an adequate vitamin E supply Am. J. Clin. Nutr. 62(6),1527S-1534S(1995).
