Polyphénols are plant secondary metabolites which are abundant in the diet. Their extraction using efficient processes and a better understanding of their physico-chemical properties that modulate their possible activities in the gastric tract are important scientific goals which underline this work. The first part deals with the direct enrichment of olive oil in polyphénols of olive leaves under ultrasonic irradiation in comparison with conventional maceration. After optimization of extraction parameters, the ultrasound-assisted process came up as more efficient than the conventional method at laboratory (reactor 3 L) to industrial pilot scale (reactor 30L). In the second part, the reactivity of some polyphenols, both common an representative ot the main classes (rutin, quercetin, catechin, chlorogenic acid and olive phenols) with DPPH radical and transition metal ions of biological interest (FeII, FeIII, CuI, CUII) was studied by UV-visible spectroscopy (kinetic studies), UPLC-MS (analysis of oxidation products) and via colorimetric tests for the determination of the redox state of the metal ions.The study of the antiradial activity (DPPH test) in aqueous micellar medium confirmed the antioxidant capacity of selected polyphenols in the presence and absence of bovine serum albumin (BSA) protein and a starch model (b-cyclodextrin). The study of the ability of phenolic compounds to bind metal ions in weakly acidic solution(pH=5-6), suggested that flavonols and hydroxycinnamic acids are able to complex FeIII from the gastric compartment when pH is slightly acid (1-2 h after the meal). However, interaction with FeII and copper ions is probably negligible. Interaction FeIII-polyphenol leads to stable complexes (without significant oxidation ot he polyphenol), but can be inhibited by the polyphenol-protein interactions
