Investigation phytochimique et biologique de Centaurea sempervirens L. (Asteraceae).

Abstract

This work concerns the phytochemical study of Centaurea sempervirens synonym: Cheirolophus sempervirens L. from Asteraceae family. This species was collected from Constantine area. After extraction by maceration followed by chromatographic separations and purifications on columns of grafted silica gel (diol), TLC and semi-preparative reverse phase HPLC, 16 compounds were isolated from the chloroform and ethyl acetate extracts. Among these compounds, 15 were identified. The structure elucidations of these compounds were carried out by the combination of the results obtained from the analyses the high resolution positive electrospray ionization mass spectra, 1D NMR (1H, 13C) and 2D NMR (COSY, HSQC et HMBC) spectra as well as by comparing the results with the data of the literature. The chemical composition of the essential oil of aerial parts of C. sempervirens studied by GC-FID and GC-MS, showed the presence of several chemical groups from which 6,10,14- trimethylpentadeca-2-one (12,4%) and epi-torilenol (5,1%) were the major components. This study was carried out for the first time. The total phenolic and total flavonoid contents of the three extracts were determined, EtOAc extract had the highest phenolic and flavonoid contents followed by n-butanol extract. This step was followed by the evaluation of the in vitro antioxidant activity using two methods: 1, 1- diphenyl-2-picrylhydrazyl radical scavenging (DPPH) and cupric ion reducing antioxidant capacity (CUPRAC). The best result was obtained for the AcOEt with CUPRAC method, where its effect is very closer to quercetin used as standard. The result of the in vitro antibacterial activity of the three extracts by the disk-diffusion method in an agar medium showed no significant activity.