Abstract
In vitro antimicrobial activity of different pomegranate (Punica granatum L.) peel extracts was evaluated against four food born pathogenic bacteria, extraction was done using methanol and chloroform. Agar well diffusion assay indicated pronounced activity for the methanol extracts, while chloroform was found to be less effective against all tested bacterial strains. The strongest antimicrobial activity was obtained by methanolic extract of sour peel against Salmonella typhi. Therefore, it was chosen for further assays against the most affected species. The MIC value of the extract recorded 312.5 μg/ ml for Salmonella. The efficiency of 9 commercial antibiotics on Salmonella treated by the sub MIC was reassessed and illustrated increasing efficiency of the antibiotics on the treated cells which also demonstrated decreased resistance to β–lactam antibiotics. The effect of sub MIC on Salmonella virulence factors (biofilm formation, motility, hemolysin and protease enzymes) was investigated. No hemolytic ability was detected for non treated cells, while capacity to produce protease enzyme was greatly reduced. Reduction of up to 80% of biofilm formation was attended with remarkable reduction in motility. Evaluation of antioxidant activity by DPPH radical scavenging assay showed considerable antioxidant capacity. Following, the cytotoxicity of pomegranate extract was assessed against breast (MCF-7), lung (A-549) and normal lung (WI-38) cell lines. The selected extract reduced cell viability for the studied cell lines, A-549 was found to be the most responsive. Accordingly, the extract was characterized by GC/MS which identified the presence of 28 phytoconstituents. TEM of the treated Salmonella showed severe destruction.

Key words: Punica granatum, Peel extract, Salmonella typhi, Agro-industrial wastes.