Etude phytochimique et évaluation des activités biologiques des espèces

Abstract

This present work concerns the phytochemical and biological study of three Algerian plants belonging to the Lamiaceae family : Mentha aquatica L., Stachys guyoniana de Noé and Thymus dreatensis Batt. Chromatographic separations and purifications of extracts from the aerial parts and roots of Mentha aquatica led to the isolation and identification of 1 6 compounds, including one new triterpene and 5 triterpene acids which are new for the genus. The structures of isolated compounds were particularly established by the use of NMR 1D and 2D (1H, 13C, COSY H-H, HMQC and HMBC), high resolution mass spectrometry (ESI-MS and HR-ESI-MS) and by comparison with literature data. GC and GC/MS analyses of T. dreatensis essential oil showed that it was mainly represented by thymol (28.1%) followed by γ-terpinene (18.7%), thymyl methyl ether (10.9%) and linalool (5.0%). This oil showed a good antioxidant activity by the bleaching of β-carotene. 5 methods were used to evaluate the antioxidant activity of Mentha aquatica and Stachys guyoniana. The latter showed a good activity with 4 methods: β-carotene, DPPH, ABTS and metal chelating whereas Mentha aquatica exhibited a moderate activity with CUPRAC and ABTS tests. Compared with the other tested extracts, the n-butanol extract of Stachys guyoniana showed the highest anticholinesterase activity. The two plants showed an antibacterial potential against some bacterial strains, by the use of agar diffusion method and MIC's determination.