Antibacterial effects of Iranian native sour and sweet pomegranate (Punica granatum) peel extracts against various pathogenic bacteria

Nowadays, uncontrolled and frequent use of antibiotics may cause emergence of microbial resistanceamong pathogenic agents. Therefore, the use of new synthetic and natural antimicrobial compounds isinevitable. One source of natural compounds in this respect comes from plants. The purpose of this study was to examine the antibacterial effects of peel extracts from sour and sweet pomegranate. Methanolic extracts of sour and sweet pomegranate peels and aqueous solutions of tetracycline and chloramphenicol were prepared. Antibiogram tests using disk diffusion technique and serial dilution method were performed against ten pathogenic bacteria isolated from animals, and relative minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were also determined for the above compounds. Thegreatest zone of inhibition induced by the action of pomegranate peel extracts was obtained forStaphylococcus aureus (about 25 mm) and the smallest zone of inhibition was obtained for Pasteurellamultocida (about 9 mm). In addition, the lowest MIC and MBC values of pomegranate peel extract wereobtained for Staphylococcus aureus (7.8 and 62.5 mg/ml, respectively). Results of serial dilution testsindicate that bactericidal effect of sour pomegranate peel extract was more than that for sweet pomegranatepeel extract; and sweet pomegranate peel extract exerts a bacteriostatic action against bacteria. Theantibacterial effect was greater against Gram-positive bacteria compared to that for the Gram-negativebacteria. Effects of these extracts were considerably lower than those for tetracycline and chloramphenicol.In conclusion, methanolic extracts of pomegranate peels exhibit relatively good bacteriostatic andbactericidal effects.