Activité antioxydante et antibactérienne des différents extraits de Cotula cinerea

Abstract

Medicinal plants are a rich and diversified source of bioactive molecules, endowed with numerous biological activities The present study aims to evaluate the antioxidant activity and the antibacterial activity extracts from the aerial part of Cotula cinerea species of the family Asteraceae that have medicinal properties very commonly recognized in folk medicine in the Ghardaia region .Thus, the extraction of the active ingredients was carried out according to the traditional methods of preparation (decoction, infusion) and hydroethanol maceration (ethanol/water: 80/20: v/v). The qualitative analysis of the various extracts revealed the presence of polyphenols, flavonoids, tannins, saponins, steroids and terpenes. The quantitative analysis based on the determination of total polyphenols, flavonoids, condensed tannins, which are more abundant in the decoction extract with contents of 28.51±2.46 mg EAG/g, 12.94±1.60 mg ER/g, 7.61±0.93 mg EC/g respectively. The hydroethanolic extract is the richest in phenol acid with content of 8741.12±372.96 μg EAC/g. The antioxidant activity is evaluated by three assays such as ABTS assays, the reducing capacity of iron and β-carotene bleaching. The hydroethanolic extract presents the most important antioxidant potency: of trapped radical cation ABTS •+ (IC 50=4.52±0.18 μg/ml), in the iron reducing capacity (IC 50=60.04 ±1.56 μg/ml) and a very high β-carotene bleach inhibition capacity (IC 50=32.56±4.00 μg/ml). The antimicrobial activity was evaluated by the disk diffusion method in agar medium and by micro-dilution in a liquid medium. The obtained results showed that Staphylococcus aureus and Pseudomonas aeruginosa are the sensitive strain to the action of the hydroethanolic extract with zones of inhibition exceeding 14 mm and MIC of the order of 0.93 mg/ml and 1.89 mg/ml respectively. The extracts of the decoction and infusion are active less on the three tested strains.