Antibacterial activity and toxicity of Psophocarpus tetragronolobus

A methanol extract of the Psophocarpus tetragonolobus (L.) DC (Leguminosae) leaves was screened for antimicrobial activity against Pseudomonas aeruginosa. Antimicrobial tests were carried out using the disk diffusion assay and broth dilution method against Pseudomonas aeruginosa. The extract showed favorable antimicrobial activity against Pseudomonas aeruginosa with a minimum inhibitory concentration (MIC) value of 2.55 mg/mL. Apart from the antibacterial effects, imaging using scanning electron microscopy (SEM) was done to determine the major alterations in the microstructure of the Pseudomonas aeruginosa. The main abnormalities noted via SEM studies were alterations in morphology and complete collapse of the bacterial cells after 36 h of exposure to the extract. The effect of the extract on the growth profile of the bacteria was also examined. The extract changed the normal growth profile of Pseudomonas aeruginosa, thus confirming the bactericidal effect of the extract on Pseudomonas aeruginosa. Furthermore, the extract was also tested against brine shrimp for toxicity. The extract exhibited no significant toxicity (LC50 = 1.30 mg/mL) against Artemia salina L. (Artemiidae).