Dietary Sesame Seed Decreases Urinary Excretion of α- and γ-Tocopherol Metabolites in Rats

Abstract

We previously showed that dietary sesame seed and its lignan inhibited γ-tocopherol metabolism to 2,7,8-trimethyl-2(2'-carboxyethyl)-6-hydroxychroman (γ-CEHC), a γ-tocopherol metabolite, and markedly elevated tissue γ-tocopherol concentration in rats. The aim of this study was to clarify the effect of dietary sesame seed on α-tocopherol metabolism. Vitamin E-deficient rats fed a vitamin E-free diet for 4 wk were fed a diet containing α-tocopherol, α- and γ-tocopherol, or α-tocopherol with sesame seed for 7 d. Urinary excretion of 2,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman (α-CEHC), a α-tocopherol metabolite, in rats fed α-tocopherol with sesame seed was inhibited (p<0.05) as compared with that in rats fed α-tocopherol alone, or α- and γ-tocopherol. The γ-CEHC excretion was also less (p<0.05) in rats fed α-tocopherol with sesame seed than that in rats fed α- and γ-tocopherol. The inhibition of α- and γ-CEHC excretion by sesame seed was accompanied by elevation (p<0.05) of the α- and γ-tocopherol concentration in the liver. These results suggest that dietary sesame seed inhibits not only γ-tocopherol metabolism to γ-CEHC but also α-tocopherol metabolism to α-CEHC in rats.