Valorisation de plantes sahariennes endémiques du genre Helianthemum-Activité antioxydante.

Abstract

This work is the assessment of a study that we conducted on two endemic plants of the septentrional Sahara from the Cistaceae family: Helianthemum ruficomum and Helianthemum confertum. To our best knowledge, no studies are reported so far for these species. The purpose of this work was to investigate the chemical composition and the radical scavenging capacity of these species and their isolated components. The ethyl acetate and «-butanol soluble parts of the aqueous-ethanol extracts of the aerial parts of these species were evaluated for their free radical scavenging capacity by ABTS'+ assay. The obtained data which showed important antioxidant powers were confirmed by TEAC and ORAC assays. On-line HPLC- ABTS'+ assays were then applied to screen the extracts. The results which revealed remarcable wealth in antioxidants allowed guiding the fractionation of the extracts by column chromatography on silica gel 60. The obtained fractions were purified by chromatography on preparative plates ofsilica gel 60 and/or by semi-preparative reverse phase HPLC leading to the isolation and the identification of14 compounds from H. ruficomum and 6 compounds from H confertum. The compounds were identified by spectral analyses, mainly ESI-HRMS (+), UV, ID NMR (*H,13C, DEPT) and 2D NMR (DOSY, COSY, NOESY, HSQC and HMBC) and comparison of their spectroscopic data with those reported in the literature. The antioxidant power of the isolated compounds was also evaluated by on-line HPLC-ABTS'+, TEAC and ORAC. The results clearly indicate high antioxidant potential of the extracts and tested compounds isolated from these two species. This work was the object of a published paper and two other in progress.