Biokinetics in humans of RRR-alpha-tocopherol: the free phenol, acetate ester, and succinate ester forms of vitamin E.
The bioavailability of RRR-alpha-tocopherol from the oral administration of RRR-alpha-tocopherol itself and its acetate and succinate esters was determined in healthy human subjects. Venous blood samples were withdrawn periodically over a 51-h period following oral administration of a gelatin capsule containing an equimolar mixture of RRR-alpha-tocopherol and RRR-alpha-tocopheryl acetate. In a second study, subjects received a capsule containing an equimolar mixture of RRR-alpha-tocopheryl acetate and RRR-alpha-tocopheryl succinate. In Study 1, RRR-alpha-tocopherol was absorbed at similar rates from both the free phenol, and the acetate ester and maximum plasma levels occurred at 12 h in most subjects. The extent of absorption of RRR-alpha-tocopherol varied considerably between subjects in absolute terms, but the relative absorption from the two forms was remarkably consistent, and a ratio of 1.0 was found for parameters of relative bioavailability in plasma. The concentration of RRR-alpha-tocopherol from each form was maximal at approximately 27 h in red blood cells and, as seen with the plasma data, there was a large interindividual variability. In Study 2, there was no significant difference in the extent of absorption of RRR-alpha-tocopherol from the acetate ester and the succinate ester, although there was an apparently higher initial rate of absorption from the acetate ester.
Department of Biology & Biochemistry, Brunel University, Uxbridge, UK.
K H
KH
Cheeseman
A E
AE
Holley
F J
FJ
Kelly
M
M
Wasil
L
L
Hughes
G
G
Burton
D000284:Administration, Oral; D000975:Antioxidants / Q000008:administration & dosage / Q000493:pharmacokinetics*; D001682:Biological Availability; D016001:Confidence Intervals; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007408:Intestinal Absorption; D007700:Kinetics; D008657:Metabolic Clearance Rate; D012016:Reference Values; D013237:Stereoisomerism; D013997:Time Factors; D024505:Tocopherols; D014810:Vitamin E / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000097:blood / Q000493:pharmacokinetics*; D024502:alpha-Tocopherol / Q000031:analogs & derivatives*
D000975:Antioxidants; D014810:Vitamin E; D024502:alpha-Tocopherol; D024505:Tocopherols