Antibacterial Activity of Red Bell Pepper Ethanolic Extract and Nalidixic Acid on Pathogenic Microorganisms

Nowadays, resistance of pathogenic microbial strains to therapeutic antibiotics has caused concern in human societies, therefore, the use of plant extracts has been considered because of its potential to control and treat bacterial infections. Red bell pepper with scientific name (Capsicum annuum L.) is a genus of Eggplants, native to tropical and subtropical regions. The aim of this study was to evaluate the antimicrobial activity of red bell pepper ethanolic extract on Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Staphylococcus aureus, Listeria innocua and Bacillus cereus in vitro.

In this experimental study, red bell pepper extract was extracted with ethanol solvent. The antimicrobial activity of the extract was determined by 4 methods disk diffusion agar, well diffusion agar, minimum inhibitory concentration (macrodilution broth) and minimum bactericidal concentration on pathogenic strains. The obtained means were used for statistical analysis. Data were analyzed using SPSS software version 26 and Duncan's test at a significance level of 5%.

The results of disk diffusion agar and well diffusion agar showed that the highest growth inhibition zone of red bell pepper extract was related to Pseudomonas aeruginosa and the lowest diameter of growth inhibition zone was related to Escherichia coli and Staphylococcus aureus, respectively. The inhibition zone diameter in Salmonella typhi and Listeria innocua compared to red bell pepper ethanolic extract was larger than the inhibition zone diameter nalidixic acid antibiotic. The minimum inhibitory concentrations of Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Staphylococcus aureus, Listeria innocua and Bacillus cereus were 400, 400, 400, >400, 200 and 400 mg/ml, respectively. The minimum bactericidal concentration of red bell pepper ethanolic extract for all bacteria was higher than the minimum inhibitory concentration.

The results of this study showed that red bell pepper extract has antimicrobial activity and has the potential to be used in the pharmaceutical industry to control bacterial infections. It is suggested that more research be done in this field in order to determine the appropriate dose of the extract.