title: A novel 5'-carboxychroman metabolite of gamma-tocopherol secreted by HepG2 cells and excreted in human urine.
abstract: HepG2 cells were incubated with a medium containing fetal bovine serum enriched with RRR-gamma-tocopherol (gamma-TOH). After 48 h the medium was extracted and analyzed for gamma-TOH metabolites by gas chromatography-mass spectrometry. In addition to gamma-CEHC, the 3'-carboxychroman metabolite of gamma-TOH previously reported in human urine, these cells secreted a second substance whose extraction and mass spectral characteristics were consistent with those of the 5'-carboxychroman analog of gamma-CEHC, 2,7, 8-trimethyl-2-(delta-carboxymethylbutyl)-6-hydroxychroman. This is the first report of metabolism of gamma-TOH to carboxychroman metabolites in cell culture. Analysis of human urine samples revealed the consistent presence of the novel 5'-carboxychroman metabolite, along with that of gamma-CEHC. Oral supplementation with purified RRR-gamma-TOH resulted in elevated urinary concentrations of both metabolites, although the concentration of the 5'-gamma-carboxychroman metabolite was consistently and substantially less than that of gamma-CEHC. The presence of both metabolites is consistent with the involvement of an omega-oxidation-like process in the phytyl tail shortening of gamma-TOH to water soluble metabolites excreted in urine.
authors.affiliation: Division of Nutritional Sciences, Cornell University, Ithaca, New York 14853, USA. rsp3@cornell.edu
authors.forename: R S
authors.initials: RS
authors.lastname: Parker
authors.forename: J E
authors.initials: JE
authors.lastname: Swanson
mesh_terms: D002460:Cell Line; D002839:Chromans / Q000378:metabolism*; D006801:Humans; D014810:Vitamin E / Q000378:metabolism* / Q000652:urine
chemical_list: D002839:Chromans; D014810:Vitamin E