Investigation phytochimique et évaluation des activités biologique d'espèces sahariennes.

Abstract

The aim of this work is the isolation and biological evaluation of new bioactive compounds isolated from two endemics species: Reseda alphonsii (Coss) Müll Arg and Crotalaria saharae Coss, belonging to the family Resedaceae and Fabaceae respectively. These two families are known for their richness in various secondary metabolites with interesting biological activity. Our work on the extraction of the aerial parts of these species followed by the chromatographic separations, permitted the isolation and identification of twenty secondary metabolites from Reseda alphonsii (Coss) Müll Arg, among which, nineteen were identified and fully described. Including two flavonoids aglycons, seven O-glycosylflavonoids, one O-glycosylisoflavonoid ,two phytosterols, two phenolic acids, three amine rhamnoside Including a new phenolic rhamnoside compound and a new spermidine alkaloid. From the chloroforme and ethylacetate extracts of the aerial parts of Crotalaria saharae Coss, fifteen pure compounds have been isolated. The structures of twelve were identified and fully described .They were constituted by : three O-glycosylflavonoids, one C-glycosylflavonoid, five flavonoids aglycons, one O-glycosylpterocarpan and two phytosterols. The molecular structures of the isolated compounds were elucidated by the use of different Spectroscopic methods: UV-visible absorption spectroscopy, 1H and 13C NMR and twodimensional experiments (COSY, NOESY, HSQC, and HMBC), high resolution mass spectrometry (HR-ESI-MS), and by comparison with literature data. The n-butanolic extracts of the two species exhibited a good antibacterial activity against some bacteria strains by the diffusion method on agar medium. These extracts showed a moderate antioxydant activity by using DPPH test. The antiproliferative activity of compounds 6, 9, 10, 15, 17, 18, 21 was evaluated against human cancer PC-3 cells. The results indicated that compound 15 presented the higher inhibitor effect of proliferation of these cell lines. The study of the chemical composition of the essential oil of salvia verbenaca(L.) Briq. ssp. pseudo-jaminiana (Chev.) , species growing in Algeria was characterized by a high level of sesquiterpenic components and a moderate yield of the monoterpenic fraction. Among the major compounds contained in this essential oil: 1,10-di-epicubenol (20,9 %), epi-α-cadinol (11,6%), and bicyclogermacrene (10,9%), are described for the first time in the genus Salvia. The isolated secondary metabolites from the two species indicating that phenolic compounds, in particular flavonoids, remain the dominant constituents. These compounds which are widespread within the genus Reseda and Crotalaria are considered as chemotaxonomic markers.