The study of biophenolic compounds is supported by the current interest in natural products and the on-going replacement of synthetic antioxidants by natural antioxidants from plant sources. The importance of phenolic compounds is related to the quality profile of olive and flaxseed products and the use of them in the production of potential functional foods. Scientific research papers are presented. First part includes biotransformations and antioxidant function of phenolics in olive oil extraction, considering variables such as the influence of irrigation treatments, ripening index of olive fruit and technological aspects. Hydroxytyrosol (3,4-DHPEA) and the new secoiridoid derivative, methylated form of 3,4-DHPEA-EDA (dialdehydic form of elenolic acid linked to hydroxytyrosol) were found to be important antioxidants. Flaxseed, used as a food ingredient, was matter of investigation as well. A solvent extraction followed by hydrolysis treatments results in the identification of secoisolariciresinol diglycoside (SDG). It appears that SDG and phenolic acids (ferulic and p-coumaric glycoside might not be responsible of the main flaxseed antioxidant function.