Abstract

Microbial infections remain public health problems because of the upsurge of bacterial resistance. The present study aimed to evaluate the anti-quorum sensing, antimicrobial activities and chemical compositions of Acacia macrostachya. Total phenolic, flavonoid and condensed tannin content were determined according to Folin-Ciocalteu, aluminium chloride and Broadhurst methods respectively. Microdilution method using p-iodonitrothétrazolium was used to evaluate the antibacterial activity. Inhibition of pyocyanin and violacein production by extract and fraction was used to evaluate anti-quorum sensing activity. The antioxidant activity was evaluated using 2,2-diphenyl-1-picryl-hydrazyl, Ferric reducing and hydrogen peroxide scavenging methods. The minimum inhibitory concentration of the extracts and fractions ranged from 0.312 mg/ml to 5 mg/ml. At 100 µg/mL, ethyl acetate fraction significantly inhibited production of violacein (56.45 %,) and pyocyanin (48.88 %). The total phenolic, flavonoids and condensed tannin contents ranged respectively from 31.85±0.31 to 21.26±0.67 mg GAE/100 mg, 26.35±0.71 to 25.42±0.36 mg QE/100 mg and 18.24±0.12 to 15.9±0.17 mg CE/100 mg. The antioxidant activity correlates with phenolic, flavonoids and tannin contents. HPLC analysis of the ethyl acetate fraction allowed to identify three phenolic acids and five flavonoids. The results described here could justify the use of A. macrostachya by tradiditional healers to treat infections and particularly gastrointestinal disorders.

Key words: Acacia macrostachya, antioxidant, antibacterial, quorum sensing