A study was conducted to evaluate the bioavailability of alpha-, gamma- and delta-tocotrienols administered via oral, intravenous, intramuscular and intraperitoneal routes in rats. Three separate experiments, each conducted according to a two-way crossover design, were carried out to compare intravenous and oral, intramuscular and oral, and intraperitoneal and oral administration. Oral absorption of all three tocotrienols was found to be incomplete. Of the three tocotrienols, alpha-tocotrienol had the highest oral bioavailability, at about 27.7+/-9.2%, compared with gamma- and delta-tocotrienols, which had values of 9.1+/-2.4% and 8.5+/-3.5%, respectively. Such biodiscrimination was also observed in their total clearance rates (estimated from the intravenous data). alpha-Tocotrienol showed the lowest clearance rate at about 0.16 L kg(-1) h(-1), whereas that of delta- and gamma-tocotrienols was quite similar, with values of 0.24 and 0.23 L kg(-1) h(-1), respectively. Interestingly, all three tocotrienols were found to be negligibly absorbed when administered intraperitoneally and intramuscularly. Thus, these two routes of administration should be avoided when evaluating the biological activities of the tocotrienols in whole animal experiments.

Background: Studies on the cholesterol lowering activity of tocotrienols have yielded mixed results, with some showing cholesterol lowering effect while some showing no activity.Aim: A randomized, double-blind, parallel group study was conducted to investigate the cholesterol lowering activity of tocotrienols. Methods: Thirty-two hypercholesterolemic subjects were randomly assigned to orally receive either 300 mg of mixed tocotrienols capsules daily or placebo capsules containing 300 mg of soya bean oil for a period of 6 months. The subjects were monitored before supplementation and monthly thereafter for their serum cholesterol as well as tocotrienol and tocopherol concentrations.Results: The serum total cholesterol and low density lipoprotein (LDL) cholesterol of the subjects in the tocotrienol supplementation group were decreased significantly by -8.9 ± 0.9% and -12.8 ± 2.6% respectively after 4 months of supplementation and the reduction persisted till the end of the 6-month study, with a reduction of -10.8 ± 1.0% and  -17.3 ± 1.8%, respectively from baseline. Moreover, there was a 22-fold increase in the total tocotrienol concentrations from baseline during supplementation compared to the placebo group, while the concentration of α-tocopherol recorded only a modest increase. On the other hand, the serum cholesterol, total tocotrienol and α-tocopherol concentrations of subjects in the placebo group remained essentially unchanged.Conclusions: Supplementation with mixed tocotrienols at dose of 300 mg per day resulted in the lowering of the serum total and LDL cholesterol levels after 5 months of supplementation.Keywords: tocotrienols, cholesterol-lowering, total cholesterol, LDL cholesterol, tocopherols