This work is a collection of my teaching activities and postdoctoral researches carried out within the laboratory "Chimie des Produits Naturels" (CPN) and the 'Natural resources' research project supported by the UMR CNRS 6134 "Environmental Sciences" of the University of Corsica Pasquale Paoli. The works concern the characterization of aromatic and medicinal plants (AMP) and products of agriculture through the volatile complex mixtures that are derived. These complex mixtures are essential oils, hydrosols, solvent extracts and volatile fractions. The different steps of the analytical sequence were discussed, the choice of plants and their sampling, the sample preparation, analysis, interpretation of the results using the statistical tool and their enhancement through the research of active molecules. The first part deals with the characterization of the essential oils, hydrosols, solvent extracts and volatile fractions from AMP and the aromas of olive-oils and citrus juices. To do this, we examined the potential of alternative methods to hydrodistillation, such as microwave-assisted extraction and Solid Phase MicroExtraction. The analysis is performed in the laboratory CPN using chromatographic techniques as Gas Chromatography (GC) for quantification and GC coupled with Mass Spectrometry (GC/MS) for the identification of the constituents. We have optimized the analytical sequence using complementary techniques such as column chromatography, SM using chemical ionization mode and the Nuclear Magnetic Resonance for the identification of missing references libraries molecules. The second part concerns the development of a new research axis which aims to highlight the active compounds through the study of antibacterial and antifungal activities of essential oils and plant extracts. We have highlighted the biological properties of essential oils and extracts against bacteria involved in food borne illness and nosocomial infections. The last part is developing the prospects aimed at strengthening the work on the AMP and agricultural products of Corsica by exploring new matrices (polar fraction) and new extraction techniques. The valorization of plant complex mixtures by the search for new antibiotics surpassing the mechanisms of resistance of bacteria and of new antioxidants remains scientific challenge for the future.