Résumé:
This work is the assessment of two studies which we conductedon two plants belonging to
Asteraceae family, Centaurea solstitialis ssp.schouwii (CD.) Q. et S. and Serratula cichoracea.
The works carried out on Centaurea solstitialis ssp. schouwii (CD.) Q. et S.began with
the maceration in 70% ethanol of the aerial parts collected in the flowering stage from the area of El
Kala. After filtration,concentration and dilution in distilled water,theremaining solution was
successively extracted with petroleum ether, CHCl3, EtOAcand n-BuOH to give the corresponding
extracts.The antioxidant abilities of CHCl3, EtOAc and n-BuOH extracts were assessed using DPPH
radical scavenging, and cupric ion reducing antioxidant capacity (CUPRAC).Butylhydroxyanisole
(BHA), Butylhydroxytoluene (BHT) and α –Tocopherol were used as controls. The total phenolic
and total flavonoid contents of the extracts were also determined. Concerning the antioxidant
activity, the EtOAc extract was the most active followed by the n-BuOH extract in the two methods.
However, none of the extracts exhibited higher activity than those of the antioxidant standards.
The n-BuOH extract had the highest phenolic and flavonoid contents followed by EtOAc extract.
These data allowed guiding the fractionation of EtOAc and n-BuOH extracts which was
carried out by chromatography on silica gel60column. The obtained fractions, purified
bychromatography on preparative normal silica gel plates led to the isolation of twosesquiterpene
lactones with guaianolide skeleton-type one of which was new, we describe it for the first time in
the literature. We also isolated 5 flavonoid glycosides.The structures of all the isolated compounds
were established by the analyses of: the high resolution mass spectra recorded in ESI positive mode
[HRESI-MS(+)], the results of UV-Vis spectral series , the 1D NMR (1H, 13C and DEPT) and 2D
NMR (COSY, NOESY, HSQC and HMBC) spectra, the results of the acidic hydrolysis of the
glycosylated compoundsand finallywith comparison of their spectroscopic data with those reported
in the literature.
Concerning the species Serratula cichoracea, the carried out work represents continuity
of a study that we previously realized on the ethyl acetate extract obtained by a protocol
similarto that indicated higher forCentaurea solstitialis ssp. schouwii (CD.) Q. et S., after
fractionation of this extract on silica gel column, the study of one of the obtained
fractionsallowed the isolation and the structural determination of two ecdysteroid diastereoisomers.
One of these two compounds was new, we reported it for the first time in the literature.
These works were the object of two international publications.
