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-trimethyl-2(2'-carboxyethyl)-6-hydroxychroman (gamma-CEHC), a gamma-tocopherol (gamma-Toc) metabolite, in rat urine and bile by using a new high-performance 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 specimens were treated with 3 N methanolic HCl to hydrolyze conjugates and to promote esterification. The methylated samples were extracted by n-hexane/water (1:2). The analyses of the methyl esters of alpha-CEHC and gamma-CEHC were performed by an HPLC-ECD using an ODS-3 column at 35 degrees C. The mobile phase was acetonitrile/water (45:55, vol/vol) containing 50 mM sodium perchlorate. After rat urine and bile samples, respectively, were methylated as described above, methylated biliary metabolites were identified by liquid chromatography-mass spectrometry as methyl esters of gamma-CEHC. Furthermore, we examined the differences in the excretion of gamma-CEHC between 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 vitamin E-deficient rat was given 0.5 mL of a stripped corn oil preparation containing 10 mg of gamma-Toc. In the alpha- + gamma-Toc group, the rat was given 10 mg of alpha-Toc and 10 mg of gamma-Toc. The content of gamma-CEHC in rat urine from the alpha- + gamma-Toc group was increased more in comparison to the gamma-Toc group at 18-36 h after oral administration. Moreover, the content of gamma-CEHC in rat bile in the alpha- + gamma-Toc group 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 shifted mainly to urinary excretion after gamma-CEHC had been excreted into the bile. Furthermore, we assume that alpha-Toc may affect the metabolism of gamma-Toc to gamma-CEHC in the body.
Kiyose
C
C
Institute of Environmental Science for Human Life, Ochanomizu University, Tokyo, Japan. ckiyose@cc.ocha.ac.jp
Saito
H
H
Kaneko
K
K
Hamamura
K
K
Tomioka
M
M
Ueda
T
T
Igarashi
O
O
D000818:Animals; D001646:Bile / Q000187:drug effects* / Q000378:metabolism*; D002138:Calibration; D002839:Chromans / Q000378:metabolism* / Q000652:urine*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D006868:Hydrolysis; D008297:Male; D013058:Mass Spectrometry; D008745:Methylation / Q000187:drug effects; D011422:Propionates / Q000378:metabolism* / Q000652:urine*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014811:Vitamin E Deficiency; D024502:alpha-Tocopherol / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology*
D002839:Chromans; D011422:Propionates; C107690:2,7,8-trimethyl-2-(beta-carboxyethyl)-6-hydroxychroman; D024502:alpha-Tocopherol