alpha-tocopherol affects the urinary and biliary excretion of 2,7,8-trimethyl-2(2 '-carboxyethyl)-6-hydroxychroman, gamma-tocopherol metabolite, in rats

In this study, we investigated a change in the excretory content of 2,7,8-t rimethyl-2(2'-carboxyethyl)-6-hydroxychroman (gamma -CEHC), a gamma -tocoph erol (gamma -Toc) metabolite, in rat urine and bile by using a new high-per formance liquid chromatography-electrochemical detection (HPLC-ECD) method. In this determination, CEHC [alpha- and gamma -CEHC, where alpha -CEHC = 2 ,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman] in the biological s pecimens were treated with 3 N methanolic HCl to hydrolyze conjugates and t o promote esterification. The methylated samples were extracted by n-hexane /water (1:2). The analyses of the methyl esters of alpha -CEHC and gamma -C EHC were performed by an HPLC-ECD using an ODS-3 column at 35 degreesC. The mobile phase was acetonitrile/water (45:55, vol/vol) containing 50 mM sodi um perchlorate. After rat urine and bile samples, respectively, were methyl ated as described above, methylated biliary metabolites were identified by liquid chromatography-mass spectrometry as methyl esters of gamma -CEHC. Fu rthermore, we examined the differences in the excretion of gamma -CEHC betw een rat urine and bile after an oral administration of gamma -Toc or alpha- + gamma -Toc by the above HPLC method. In the gamma -Toc group, each vitam in E-deficient rat was given 0.5 mt of a stripped corn oil preparation cont aining 10 mg of gamma -Toc, In the alpha- + gamma -Toc group, the rat was g iven 10 mg of alpha -Toe and 10 mg of gamma -Toc. The content of gamma -CEH C in rat urine from the alpha- + gamma -Toc group was increased more in com parison to the gamma -Toc group at 18-36 h after oral administration. Moreo ver, the content of gamma -CEHC in rat bile in the alpha- + gamma -Toc grou p was increased more in comparison to the gamma -Toc group at 6-18 h after oral administration. Therefore, we have suggested that gamma -CEHC was shif ted mainly to urinary excretion after gamma -CEHC had been excreted into th e bile. Furthermore, we assume that alpha -Toe may affect the metabolism of gamma -Toc to gamma -CEHC in the body.