Studies on the Antibacterial Potential and Time-kill Assays of Methanol Leaf Extract of Lawsonia inermis (Linn)

Lawsonia inermis is used for the treatment of several ailments such as rheumatoid arthritis, diarrhoea and skin diseases. The design of this study focused on the determination of the antibacterial potential and rate of killing of some bacterial isolates by methanol leaf extract of Lawsonia inermis. Agar-well diffusion method was used to determine the antibacterial activity of the extract obtained against a panel of bacteria. The minimum inhibitory concentrations (MIC), minimum bactericidal concentrations (MBC), phytochemical and rate of killing of some bacterial isolates by the leaf extract were also studied. The presence of saponins, phytosterol, phenol, flavonoids, glycosides and alkaloids was revealed by phytochemical analysis. Appreciable antibacterial activity by the extract at a final concentration of 35 mg/mL was observed against all the bacterial strains used for this study. The mean diameter of zones of inhibition exhibited by the extract ranged between 9.0±1.0 mm - 17.3±0.6 mm while conventional ampicillin and streptomycin diameter of zones of inhibition ranged from 16.0±0.0 mm - 28.3±0.7 mm and 13.0±0.0 mm - 26.3±0.6 mm respectively. The MIC exhibited by the extract against susceptible test organisms ranged between 0.27 mg/mL - 4.375 mg/mL while MBC ranged between 0.55 mg/mL and 8.75 mg/mL. The time kill assay showed that the percentage of the cells killed increased with increasing concentrations of the extract, as well as, contact time intervals. In conclusion, the methanol leaf extract of L. inermis contains various phytochemicals which accounted for the appreciable antibacterial activity exhibited against some of the bacterial strains used in this study and thus supports its usefulness as a potential source of antibacterial agents.