Linus Pauling Institute

Vitamin E, as all-rac α-tocopheryl-acetate (TAc), has a bioavailability of only 5.4% in swine and, therefore, is a poor vitamin E source. Tocopheryl-phosphate (TP) has been used successfully as a vitamin E source around 1940 but it was subsequently replaced by TAc as it was easier to manufacture. Recently, it has been proposed as an in vivo intermediate in vitamin E metabolism with possibly gene-regulatory functions. TP may be more bioavailable than TAc as intestinal hydrolysis and emulsification are not required. The objective of this work was to compare the bioavailability of TAc and TP in swine. Piglets (18.6 ± 0.6 kg) fitted with jugular catheters received a single test meal (350 g) containing either deuterated (trimethyl-d9) TAc or TP (75 IU/kg body weight, n = 8 per treatment). Twelve serial blood samples were obtained starting pre-meal until 78 h post-meal for analysis of deuterated T and TP using LC MS/MS. Results were standardized by dividing them by the dose per kg body weight and were subsequently modeled with a multi-compartment model. T from TAc had a slow appearance rate (0.040 ± 0.014 h-1) and rapid disappearance rate (0.438 ± 0.160 h-1) with a plateau value of 0.414 ± 0.129 µM/(µmol/kg BW). TP appeared faster in plasma (0.119 ± 0.058 h-1, P = 0.01) while the elimination rate was similar (0.396 ± 0.098 h-1, P = 0.51). The plateau value of TP was only numerically higher (0.758 ± 0.778 µM/(µmol/kg BW), P = 0.34). TP was quickly converted to T; its appearance rate was 0.026 ± 0.009 h-1, slower than the appearance rate of T from TAc (P = 0.01), while the elimination rate was 0.220 ± 0.062 h-1, slower than that of T from TAc (P = 0.00). The conversion of TP to T may have been incomplete, as its plateau value was only 0.315 ± 0.109 µM/(µmol/kg BW). The area under the curve, expressed relative to area under the curve for T from TAc, was 34.5% for TP and 107.3% for T from TP. These data confirm that TP is more quickly absorbed than T from TAc. TP is also converted to T and thus a functional precursor of T. Nevertheless, as a source of T TP failed to offer a clear advantage over TAc in bioavailability.