Anti-Quorum Sensing, Antibacterial, Antioxidant Activity and Acute Oral Toxicity of Acacia hockii De Wild. (Fabaceae)

Abstract

Multi-drug resistance in microorganisms is a serious problem of public health at international level. Many researchers have suggested alternatives to antibiotics with minimal or no major side effects. The World Health Organization also has confirmed the importance of the use of medicinal plants in the management of primary health care. Thus, this study aimed to evaluate the anti-quorum sensing, antimicrobial, antioxidant activities and to characterize the phytoconstituents of leafy stems of Acacia hockii, a plant used in traditional medicine in Bénin. The ethanolic and aqueous extracts were obtained by maceration and decoction respectively. The fractions were prepared by liquid/liquid partition. Quorum-sensing activity was evaluated by inhibitions of pyocyanin and violacein production using Chromobacterium violaceum CV026 and Pseudomonas aeruginosa PAO1. Antioxidant potentials of extracts and fractions were evaluated using by 2,2-diphenyl-1-picryl-hydrazyl, Ferric reducing and hydrogen peroxide scavenging methods. The minimum inhibitory concentration ranged from 0.625 mg/ml to 5 mg/ml. At a sub-inhibitory concentration of 100 μg/mL, ethyl acetate fraction significantly inhibited violacein and pyocyanin production respectively by 69.35% and 45.55% compared to control, without any effect on bacterial kinetic growth. The total phenolics, flavonoids and condensed tannin of extracts ranged from 30.62 to 24.85 mg GAE/100 mg, 32.52 to 26.04 mg QE/100 mg and 17.9 to 13.26 mg CE/100 mg. Ethanolic extract was highest content of total phenolics and condensed tannin while the high rate of total flavonoids was content in aqueus extract. The ethyl acetate fraction showed the highest antioxidant property in comparison to the other extracts and fractions. Ethyl acetate fraction expressed more antibacterial and antioxidant activities. HPLC analysis of ethyl acetate fraction revealed the presence of five phenolic: acid gallic, chlorogenic, tannic, ferrulic, ellargic acid and two flavonoids: hyperoside and Rutin. In the acute oral toxicity of aqueous extract at 2000 mg/kg body weight, no deaths nor biochemical and hematological alterations were observed. The results suggested that acacia hockii is not toxic and contains antibacterial compunds justifying its traditional use in the treatment of infectious diseases.