Dietary sesame seed decreases urinary excretion of alpha- and gamma-tocopherol metabolites in rats.

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