Recherche et détermination structurale des métabolites secondaires de Centaurea niccaeensis All.Var walliana M. (Asteraceae)

Abstract

This work belongs to our research program on the phytochemical study of Centaurea genus (Compositae). The species of this genus, showed their wealth of bioactive secondary metabolites. Our study, which concerns the isolation and the structural determination of sesquiterpene lactones and flavonoids from the ethyl acetate soluble part of the aqueous-EtOH extract of the aerial parts of Centaurea nicaeensis var. walliana M, constitute a contribution in this field and supplement the results obtained in our laboratory from the chloroform soluble part which led to the isolation and the structural establishment of two flavonoids. After maceration of flowers and leaves of this plant, filtration, concentration and successive extractions with chloroform, ethyl acetate and n-butanol, the ethyl acetate extract was submitted to separation and purification by column and thin layer chromatography on silica gel 60. This work led to the isolation in the native state of 5 compounds which were: • A flavone : apigenin • Two flavone glycosides : apigenin 7-(6’’-methylglucuronide) and apigenin 4’-(6’’-methylglucuronide) • A sesquiterpene lactone of elemanolide type-skeleton : melitensin • A cyanogenic compound : prunasin The structures were established by the combination of 1 H NMR, 13 C NMR, 2D NMR experiments, mass spectrometry and UV-Vis spectroscopy data. It is important to note, that apigenin 4’-(6’’-methylglucuronide) is new and then, was not described elsewhere.