title: Alpha- and gamma-tocotrienols are metabolized to carboxyethyl-hydroxychroman derivatives and excreted in human urine.
abstract: Limited information is available regarding metabolism of vitamin E forms, especially the tocotrienols. Carboxyethyl-hydroxychromans (alpha- and gamma-CEHC) are human urinary metabolites of alpha- and gamma-tocopherols, respectively. To evaluate whether tocotrienols are also metabolized and excreted as urinary CEHC, urine was monitored following tocotrienol supplementation. Complete (24 h) urine collections were obtained for 2 d prior to (baseline), the day of, and 2 d after human subjects (n = 6) ingested tocotrienol supplements. The subjects consumed 125 mg gamma-tocotrienyl acetate the first week, then the next week 500 mg; then 125 mg alpha-tocotrienyl acetate was administered the third week, followed by 500 mg the fourth week. Urinary alpha- and gamma-CEHC were measured by high-performance liquid chromatography with electrochemical detection. Urinary gamma-CEHC levels rose about four- to sixfold in response to the two doses of gamma-tocotrienol and then returned to baseline the following day. Significant (P < 0.0001) increases in urinary alpha-CEHC were observed only following ingestion of 500 mg alpha-tocotrienyl acetate. Typically, 1-2% of alpha-tocotrienyl acetates or 4-6% of gamma-tocotrienyl acetates were recovered as their respective urinary CEHC metabolites. A gamma-CEHC excretion time course showed an increase in urinary gamma-CEHC at 6 h and a peak at 9 h following ingestion of 125 mg gamma-tocotrienyl acetate. In summary, tocotrienols, like tocopherols, are metabolized to CEHC; however, the quantities excreted in human urine are small in relation to dose size.
authors.affiliation: aLinus Pauling Institute, Oregon State University, Corvallis 97331-6512, USA.
authors.forename: J K
authors.initials: JK
authors.lastname: Lodge
authors.forename: J
authors.initials: J
authors.lastname: Ridlington
authors.forename: S
authors.initials: S
authors.lastname: Leonard
authors.forename: H
authors.initials: H
authors.lastname: Vaule
authors.forename: M G
authors.initials: MG
authors.lastname: Traber
mesh_terms: D002839:Chromans / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics* / Q000652:urine*; D002851:Chromatography, High Pressure Liquid; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D007700:Kinetics; D008297:Male; D011422:Propionates / Q000652:urine*; D024508:Tocotrienols; D014810:Vitamin E / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000378:metabolism / Q000493:pharmacokinetics*
chemical_list: D002839:Chromans; D011422:Propionates; D024508:Tocotrienols; D014810:Vitamin E; C084852:2,5,7,8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman; C013649:plastochromanol 8; C082032:tocotrienol, alpha