Etude Phytochimique et Evaluation de l'Activité Antioxydante de Quelques Plantes de la Région de Ghardaïa au Sud Algérien

Abstract

This zork aims to promote three plant species Asphodelus tenuifolius (Tazia), Peganum harmala (Harmel) and Pergularia tomentosa (Kalga) which grow spontaneously in the Ghardaïa region in the north of the Algerian northern Sahara, through a contribution to the phytochemical study and evaluation of the antioxidant power of crude aqueous extracts of their aerial parts. These plant species, which are widely used for their countless traditional therapeutic virtues among the population of the Ghardaïa region, belong to three different families Asphodelaceae, Zygophyllaceae and Asclepiadaceae respectively and are all xerophytic species. To do this, phytochemical screening tests are carried out to highlight the presence or absence of the main secondary metabolites of these plants. Extractions by aqueous maceration are carried out. The contents of total polyphenols in the crude extracts obtained are then determined. The antioxidant power of the extracts obtained against the free radical DPPH and ABTS radicals is subsequently evaluated. From all the results obtained, the phytochemical screening tests revealed the presence of some major compounds of secondary metabolism in the three species, more particularly the phenolic compounds, and the absence of certain others which are also important. The Asphodelus tenuifolius species showed itself to be the best with a maximum content of around 76 ± 1.35 mg EAG/g MVS in total polyphenols and a yield equal to 14% in aqueous crude extract. The antioxidant power tests made it possible to evaluate the power of the aqueous crude extracts in the reduction and trapping of DPPH and ABTS free radicals. The results obtained on the inhibitory power of DPPH reveal that the isolated extracts are very active and have strong antioxidant powers with priority for the extract of the species Asphodelus tenuifolius (IC50 = 65.44 ± 0.113 µg/ mL). As for ABTS free radicals, the crude aqueous extracts of the same species presented the best antioxidant power (IC50 = 64.13 ± 0.013 µg/ mL). Compared to the synthetic antioxidants trolox and ascorbic acid, the crude aqueous extracts of all the plant species studied turned out to be better with more or less low IC50 values. On the other hand, the inhibitory properties of the crude extract isolated from the species Pergularia tomentosa are still less effective than those of ascorbic acid, which has been shown to be effective in trapping and reducing ABTS radicals. Finally, the species Asphodelus tenuifolius stands out from other species in terms of biochemistry and antioxidant activity.