Recherche et détermination structurale des métabolites secondaires et évaluation de l’activité biologique d’une espèce de la famille Scrophulariaceae

Abstract

A bibliographic search on the genus Linaria (Scrophulariaceae) shows that this genus is reputed to accumulate a diversity of secondary metabolites, in particular iridoids and flavonoids, molecules known for their various biological activities. In this work, our interest focused on the phytochemical and biological study of an Algerian species, Linaria scariosa (Scrophulariaceae). The endemism of this specie for Algeria and Tunisia has encouraged us to start this work, especially since this plant has never been studied. The study began with the evaluation of the chemical composition by GC / MS which showed a richness in iridoids, which is in good agreement with the chemotaxonomy of the family Scrophulariaceae. The various chromatographic separation methods used in our experiment made it possible to isolate, from the ethyl acetate and n-butanol extracts, 10 compounds : four iridoids, five flavonoids and one sterol. Among the isolated compounds, one new iridoid named 6-O-transcinnamoylantirrinoside, and two new flavonoids named desmethoxycentauriedin-7-O-β-neohesperidoside and desmethoxycentauriedin-7-O-α-rhamnopyranosyl(1’’’’→2’’)-β-rutinoside. The structural elucidation of the isolated compounds was carried out by analyzing the UVVisible, NMR1D (1H, 13C and DEPT) and 2D (HSQC, HMBC, COSY and NOESY) spectra and comparing with the data of the literature. The biological activity tests: antioxidant (in vitro), anticholinesterase (in vitro), and antibacterial (in vitro) performed on the extracts, show that the species exhibit remarkable antioxidant and anticholinesterase activity. The inhibitory activity of α-glucosidase performed on the three new products indicates that the new iridoids has a remarkable inhibitory effect on α-glucosidase.