Activités antioxydante et antimicrobienne d’extraits de Rhamnus alaternus L.

Abstract

Rhamnus alaternus L. a shrub which belonging to the Rhamnaceae family. It’s a medicinal plant largely used in Algerian traditional medicine. The aerial parts of the plant (stems and lives) were subjected to maceration in methanol (EMTF), whereas the roots were extracted in methanol (EMR) with Soxhlet. The decoction has been conducted both on the aerial parts (EATF) and roots (EAR) using distilled water. The yields were: 11 %, 10 %, 6 % and 8 % (w/w) for EMTF, EMR, EATF and EAR respectively. Total phenolic contents were determined using Folin-Ciocalteu reagent and found to be: 218 (EATF), 153 (EAR), 74 (EMTF) and 74 (EMR) mg EAC/ g of fresh weight. Flavonoids were evaluated by AlCl3 method and shown to be 108 (EATF), 113 (EAR), 66 (EMTF) and 49 (EMR) mg EQ/ g of fresh weight. The flavones and flavonols were estimated to be: 44 (EATF), 48 (EAR), 18 (EMTF) and 15 (EMR) mg EQ/ g of fresh weight. Antioxidant activity was evaluated using β-carotene/linoleic acid system, it ranged between 76 and 87 % for all extracts and seems to be closed to that of BHT 92 % when used at 2 mg/ml. Free radical scavenging effects were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH.), The 50 percent inhibitory concentration for DPPH. (IC50) were: 37 (BHT), 52 (EMR), 66 (EATF), 66 (EAR) and 71 µg/ml (EMTF). The antimicrobial sensitivity of the extracts towards eleven bacterial strains (Gram+ and Gram-) and three fungus strains was assessed using to the disc diffusion agar test; only one extract (EMR) has developed an inhibitory effect against five bacteria tested namely: E.coli, S.aureus, K. pneumoniae , E. faecalis and P.aeruginosa. The minimal Inhibitory Concentrations (MICs) were respectively 6,25 mg/ml and 0,2 mg/ml.