Réponse adaptative de Pergularia tomentosa L de différents écotypes dans la région de Ghardaïa

Abstract

The spontaneous plants of the Sahara are very characteristic by their mode of adaptation peculiar to the desert environment very constraining to their survival. The aim of this study is to show the adaptive response of Pergularia tomentosa under the conditions of different ecotopes in the region of Ghardaïa (Metlili and Noumerat). The different parts of Pergularia tomentosa (Asclepiadaceae) are harvested at two sites: Metlili and Noumerat. The conservation of this plant is carried out by two methods: freezing and drying in the absence of light and at ambient temperature. The extraction of the active ingredients of this species (fresh and dry) is carried out by maceration using an ethanol / water solvent system: 80/20 (v / v) with a solid / liquid ratio of 1/10 (w / v). The evaluation of the adaptive response is carried out by determining the different classes of phenolic compounds (polyphenols, flavonoids, acid phenols and condensed tannins) and determining the antioxidant potential (ABTS and FRAP). The results obtained show that the most important yields are recorded for the dry plant material of the Noumerat region, particularly leaf extract (12.34 ± 0.92%). The results of total polyphenols, flavonoids, phenol acids and condensed tannins have shown that the dry and fresh fruits and leaves of Pergularia tomentosa of the Noumerat region are the richest in these phenolic compounds. Evaluation of the antioxidant power was carried out using two chemical methods (ABTS and FRAP). The ABTS method indicated that the extract of the dried stems and the fresh fruit extract of Pergularia tomentosa harvested in the Noumerat region had the best ABTS •+ inhibitory potency with IC50 = 1.10 mg/ml and IC50 = 0.64 mg/ml respectively. The FRAP method showed that extracts of dry and fresh fruits for the Metlili region exhibited the best iron reducing powers, respectively IC50 = 7.45 mg/ml and 6.31 mg/ml. Compared with Trolox reference (IC50 = 1.65 mg/ml) the antioxidant power of Pergularia tomentosa remains low. These results showed that there are differences between these two ecotypes which may be due to the physicochemical properties of soil, especially its water retention power.