Recherche et détermination structurale de métabolites secondaires de trois espèces algériennes.

Abstract

This work is devoted to the phytochemical and biological study of three species endemic to Algeria. It concerning Astragalus gombo and Genista cinerea ssp. ramosissima, both belong to the Fabaceae family and the third species is Cistanche violacea from the Orobanchaceae family. The phytochemical investigation of n-butanol extracts from the aerial parts of A. gombo and Genista cinerea ssp. ramosissima allowed the isolation of 8 products and the structural identification of 5 of them. All the identified products present a kaempferol or quercetin skeleton which is glucosided in 3. While, the phytochemical investigation of ethyl acetate and n-butanol extracts of C. violacea allowed the isolation of 15 products and identification of 7 from the EtOAc among which two are new (one iridoid and one phenylethanoid glycoside) and five others reported for the first time in the Cistanche genus. The structural elucidation of the isolated compounds was carried out by combining the various spectroscopic methods (UV, 1D & 2D NMR) as well as by comparing the results with the literature data. Quantification of the total polyphenols and total flavonoids of the EtOAc and n-BuOH extracts of G. cinerea ssp. ramosissima was performed by colorimetric methods. This step showed a content of polyphenols and flavonoids more important in the n-BuOH extract. The antioxidant activity of the EtOAc and n-BuOH extracts was evaluated by the free radical scavenging method (DPPH). The n-BuOH extract exhibited the strongest effect with respect to the DPPH free radical comparing to BHT used as standard. The EtOAc extract of C. violacea was estimated for its anti-inflammatory activity by using two methods (HRBC membrane stabilization method and Albumin denaturation inhibition). The results showed that this extract can be used as source of new anti-inflammatory agents.