Phytochemical screening and in-vitro antibacterial activity of leaf extracts of Justicia secunda Vahl on selected clinical pathogens

The phytochemical constituents and antibacterial activity of leaf extracts of Justicia secunda against five selected clinical pathogens were investigated. Leaves of Justicia secunda were obtained and authenticated, and subjected to drying at room temperature for thirty days. The dried leaves were blended into powder for solvent extraction. Aqueous, ethanol and methanol, extracts of the leaves were prepared and concentrated using a rotary evaporator. The phytochemical analysis was carried out using standard methods while the antibacterial activity of the extracts against the clinical isolates was determined using the agar well diffusion method. Saponins, tannins, flavonoids, cardiac glycosides, terpenoids, steroids, anthraquinones and alkaloids were all present in the methanol, ethanol and aqueous extracts, while cardiac glycosides and alkaloids were absent in the aqueous extract. All the extracts had antibacterial activity against the test bacteria at 150 mg/mL, with the exception of the aqueous and methanol extracts that had no activity against E. coli. The MIC of the aqueous extract for both B. cereus and L. monocytogenes was 37.5 mg/mL, 150 mg/mL for S. aureus, 18.75 mg/mL for P. aeruginosa, with no activity against E. coli. The methanol extract of had a minimum inhibitory concentration (MIC) of 18.75 mg/mL on all the tested bacteria, with the exception of E. coli with no activity, while the MIC of the ethanol extract on P. aeruginosa was 75 mg/mL, and 18.75 mg/mL for the other bacteria. J. secunda could be promising in the future design of antibacterial drugs due to its antibacterial properties as observed in this study