Abstract

*Bako B., Danladi A. H., Bulus G. G. and Ushie O. A.

ABSTRACT

In recent years, there has been growing interest in exploring the potential of natural products for the development of new antimicrobial agents due to the emergence of antibiotic resistance. Justicia secunda, a medicinal plant widely distributed in tropical regions, has been traditionally used for its therapeutic properties. This study focused on quantitatively analyzing the phytochemical composition of crude extracts obtained from Justicia secunda leaves and assessing their potential antimicrobial properties against bacteria and fungi. The results indicated significant levels of bioactive compounds, including tannins (3.974 mg/g), phenols (2.430 mg/g), flavonoids (2.210 mg/g), alkaloids (0.588 mg/g), and saponins (0.434 mg/g), present in the extracts. In the antimicrobial testing, all the Justicia secunda leaf extracts demonstrated activity against both bacteria and fungi. Notably, the methanol extracts displayed the highest antimicrobial activity, with a zone of inhibition diameter of 15.5 mm against Staphylococcus aureus. The ethyl acetate extracts exhibited activity against Staphylococcus aureus (10 mm) while the acetone extracts showed activity against Staphylococcus aureus (12 mm) and Escherichia coli (8.5 mm). Moreover, the methanol extracts exhibited activity against Staphylococcus aureus (15.5 mm), Streptococcus pneumoniae (12 mm), Escherichia coli (8.5 mm), Salmonella typhi (8.0 mm), and Candida albican (9.5 mm). The determination of minimum inhibitory concentration (MIC) values revealed that the methanol extracts had the lowest MIC values (100 mg/mL) against Staphylococcus aureus and Streptococcus pneumoniae, while the ethyl acetate extracts showed the lowest MIC value (100 mg/mL) against Escherichia coli. The acetone extracts demonstrated the lowest MIC values (200 mg/mL) against Staphylococcus aureus, and the methanol extracts displayed the lowest MIC value (200 mg/mL) against Salmonella typhi. These low MIC values suggest the potential high efficacy of the extracts against the tested microorganisms. The study reveals Justicia secunda leaf extracts' abundant bioactive compounds and potential as a valuable source for broad-spectrum natural antimicrobial agents, urging further research for pharmaceutical development and therapeutic applications against infectious diseases.