Résumé:
The work presented in this thesis contributes to the valorization of both Algerian medicinal plants (Crataegus oxyacantha L. (Rosaceae) and Cytisus triflorus L'Her. (Fabaceae) by characterizing them by a phytochemical study, an evaluation of the antioxidant and antimicrobial activities, and a structural identification of certain phenolic compounds. Thus, in order to obtain an extract enriched in metabolites of interest, flavonoids, we opted for two extraction methods, a liquid solid extraction using different solvents of increasing polarity (CHCl3, EtOAc and n-Butanol) and a second extraction using the Matrix solid phase dispersion (MSPD) method, using different solvents of increasing polarity (100% H2O, 1:1 H2O / EtOH and 100% EtOH).
This study allowed the isolation 21 compounds and structural elucidation of 16 compounds.
Of these 16 compounds, 3 acids and 7 flavonoids: (3 flavonols including 1 glucosyl, 1 glucosyl flavanone, 1 Flavanol and 2 flavones) were isolated from C. oxyacantha L. From the EtOAc extract the aerial parts (Flowers + Leaves) of the species Cytisus triflorus L'Her., 6 secondary metabolites were identified (flavonoids). Among these compounds, 3 flavones: (Chrysin, Prunetin) and 3 glucosyl flavonoids (2 Chrysine and Isoquercitrin). Of these isolated compounds, 3 new in the species. These major active ingredients possess various biological activities and play an important and acknowledged role in maintaining good health. The structures of the isolated compounds were established by HPLC-DAD chromatogram analysis, UV-vis spectra and high resolution electrospray mass spectra (HRESI-MS), by extensive use and interpretation of NMR experiments spectra : 1D NMR (1H, 13C and DEPT) and 2D NMR (COSY, HSQC and HMBC) and by comparison with the literature data. The in vitro evaluation antioxidant activity of the various extracts and of three isolated products of C. oxyacantha, and the AcOEt extract and three products isolated from C. triflorus was performed by the radical scavenging method (DPPH *). The extracts of two plants have interesting antioxidant activities, dependent on the content of total polyphenols and flavonoids. The various extracts studied were also revealed a high antibacterial activity towards S. aureus. Similarly, a tendency shown indicating that the richest extracts of flavonoids and polyphenols exhibit the higher antibacterial activities.
