Simultaneous determination of alpha-, gamma-tocopherol and their quinones in rats plasma and tissues using reversed-phase high-performance liquid chromatography

We established a method to determine simultaneously alpha- and gamma-tocopherol (-Toc) and their quinones (alpha-TQ and rho-gamma-TQ) in biological samples by reverse-phase high-performance liquid chromatography (HPLC). Tocs had a shorter retention time than TQs, and alpha-forms had a shorter retention times than gamma-forms. Four peaks of Tocs and TQs were completely separated by this method. Subsequently, we investigated the distribution of alpha-, gamma-Toc and TQ in rat tissues and the excretion of Tocs and TQs in rat bile by the above HPLC method. Rats deficient in vitamin E were divided into two groups, gamma-Toc group and alpha+gamma-Toc group, and tissues were collected at 6 and 24 h after intravenous administration of Tocs. Also, bile collection was started immediately and performed at 3 h intervals during 24 h after intravenous administration. The concentration of alpha- and gamma-Toc and their quinones in plasma, tissues and bile were determined by this method. gamma-Toc concentration in the liver of alpha+gamma-Toc group was higher than that of gamma-Toc group. However, rho-gamma-TQ in the liver was not significantly different between alpha+gamma-Toc group and gamma-Toc group. Also, both alpha-TQ and rho-gamma-TQ were present in very low concentrations in all tissues. Therefore, we suggested that the distribution of gamma-Toc is affected by alpha-Toc present in vivo, but the oxidative production of rho-gamma-TQ from gamma-Toc is not affected.