Chapter 1 – During the past decade, a number of foodstuff have been the focus of scientific research since epidemiological and clinical studies showed their effect against chronic diseases such as cancer, cardiovascular disease and leukoplakia, skin damage and aging –related eye disease. Tocopherols and Tocotrienols, which are grouped as Tocols, are constituted Vitamin E. They are composed of a polar chromanol ring linked to an isoprenoid-derived hydrocarbon side chain with different saturation. There are four isomers in both Tocopherols (α-, β-, γ-, δ-) and Tocotrienols (α-, β-, γ-, δ-) based on the methyl groups of the chromanol ring. Tocols are very important phytochemical compounds and the level and relative composition of the eight isomers are considerably varied between different plant matrices. Regarding the analysis and determination of tocols, an interesting field of research is the application of Liquid Chromatography to separate the eight isomers. The two main techniques are Normal Phase (NP-) and Reversed Phase (RP-) High Performance Liquid Chromatography (HPLC). The eight isomers could be separated easily with NP-HPLC in contrast with RP-HPLC where in most cases the β- and γ- isomers of both Tocopherols and Tocotrienols are co-eluted. Relative research is targeting in isomers’ separation with simple RP-HPLC techniques, which have the advantages of reproducible chromatographic peak characteristics, stability, easy equilibration and low volatile mobile phases. Another research field regarding tocols separation and analysis are the different extraction methods used to isolate them from the different edible plant matrices with the highest possible yields. Chapter 2 – All-trans retinoic acid (ATRA) and 1, 25-dihydroxyvitamin D3 (1,25(OH)2D3) are involved in a variety of important physiological processes, among which their role in the induction of differentiation of leukemia cells has attracted particular attention in recent years.