title: Relative bioavailability of RRR- and all-rac-alpha-tocopheryl acetate in humans: studies using deuterated compounds.
abstract: Vitamin E in nutritional supplements in its most common form is alpha-tocopheryl acetate. Available stereoisomeric forms are RRR- (1 stereoisomer) and all-rac- (8 stereoisomers). We evaluated the relative bioavailability of RRR- and all-rac-alpha-tocopheryl acetate using the deuterium-labeled isotopes [5-CD3] 2R, 4'R and 8'R-alpha-tocopheryl acetate (d3), and [5,7-(CD3)2]-all-rac-alpha-tocopheryl acetate (d6). Six adults (three males, three females), aged 25-59 y, received 150 mg each of d3 and d6 for 11 consecutive days. Blood samples were collected on days -1, 0, 1-11, 13, 14, 20, 25, 30, 60, 74, 88, 102, 122, and 137. Plasma and red blood cell tocopherol were evaluated by using HPLC and gas chromatography/mass spectrometry to distinguish between d3 and d6 tocopherols. Cholesterol, triglycerides, and LDL and HDL cholesterol were measured. Relative bioavailability of d3 when compared with d6 was 2.0 +/- 0.06 when area under the plasma time concentration curve (AUC d3/d6) by trapezoidal rule (P < 0.05) was used. Correcting for lipid yielded the same finding. Unlabeled tocopherol (d0) decreased (P < 0.05) with vitamin E administration. It was concluded that the ratio of bioavailability of RRR-/all-rac-alpha-tocopheryl acetate is significantly greater than the currently accepted ratio of 1.36.
authors.affiliation: Department of Surgery, East Tennessee State University, Johnson City 37614-0575.
authors.forename: R V
authors.initials: RV
authors.lastname: Acuff
authors.forename: S S
authors.initials: SS
authors.lastname: Thedford
authors.forename: N N
authors.initials: NN
authors.lastname: Hidiroglou
authors.forename: A M
authors.initials: AM
authors.lastname: Papas
authors.forename: T A
authors.initials: TA
authors.lastname: Odom
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001682:Biological Availability; D002851:Chromatography, High Pressure Liquid; D003903:Deuterium; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D008297:Male; D008875:Middle Aged; D013237:Stereoisomerism; D014810:Vitamin E / Q000097:blood / Q000737:chemistry / Q000493:pharmacokinetics*
chemical_list: D014810:Vitamin E; D003903:Deuterium