Background and purpose: Intestinal bacterial infections are treated with antibiotics; but there are some reports on the effects of medicinal plants in digestive disorders. Today, medicinal herbs are more suggested due to increasing resistance of bacteria to antibiotics, people are more relying on the medicinal herbs. This study aimed to evaluate the antibacterial effect of orange peel extract.

Materials and methods: After collecting orange peel samples, the methanol extract was provided using maceration method and the effect of this extract against the standard strains of bacteria (Staphylococcus aureus, Bacillus cereus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Salmonella enterica) was assessed using microdilution (well plates) in brain-heart infusion medium.

Results: In this study, all the standard strains of bacteria in wells were sensitive to the extract. Meanwhile, different minimum inhibitory concentrations (MIC) were observed in various genera. The first group (Bacillus cereus) was the most sensitive due to receiving MIC=3.12 μl/ml of the extract. In the second group, Staphylococcus and Salmonella were expressed as they were administered administered MIC 6.25 μl/ml of the extract. The third group (Klebsiella and Pseudomonas) was listed as the most resistant group, which received MIC=12.5 μl/ml of the extract.

Conclusion: Research on the use of natural products, which are used in traditional medicine for gastrointestinal disorders, can be valuable in terms of antibacterial activity and adjustment of microbial flora. In this study, it was demonstrated that orange peel can inhibit the growth of many bacteria in-vitro.