Abstract
BackgroundThe use of natural preservatives became of great interest; good examples of these natural preservation agents are plant peels. The use of plant peels has dual benefits; first is their antimicrobial activity against food-borne pathogens, while the second is minimizing agro-industrial wastes. ResultsThe evaluation of the antimicrobial potential of both methanolic and ethanolic extracts of three fruit peels (orange, pomegranate, and banana), against 4 Gram-positive (G+), 3 Gram-negative bacteria (G−), and 2 fungal strains revealed that both pomegranate peel extracts exhibited significantly higher inhibitory effect on all tested G+ bacteria. Methanolic extract of pomegranate peel gave higher activity than the ethanolic one against G+ and G− bacteria except for S. typhimurium. Against A. flavus and A. niger, both pomegranate and orange extracts showed activity ranging between 65 and 100% more than the positive control. The ethanolic extracts of all tested peels showed a considerable capacity of antioxidant compounds compared to the methanolic extracts. The highest antioxidant capacity was found for ethanolic and methanolic extracts of pomegranate, 66.870 and 56.262 mg/ml, respectively. Generally, the concentration of total phenolic compounds was higher than that of total flavonoids followed by tannins. The highest readings of all tested constituents were reported for pomegranate extracts followed by orange and then banana. The total phenolic content, total flavonoids, and tannins were proportional to antioxidant values. GC-MS of pomegranate peel extracts identified 23 compounds in the methanolic extract versus 31 compounds in the ethanolic one. These components were identified based on their retention times and mass spectral fragmentation pattern. 5-hydroxymethylfufural (HMF) represented the major component in both methanolic and ethanolic extracts with peak area percentage of 65.78% and 48.43%, respectively. ConclusionsThe results showed negative effect of methanolic and ethanolic extracts of pomegranate on G+ and G− bacteria and two fungal pathogenic strains. The phytochemical analysis regarded these results to the high content of phenols, flavonoids, and tannins. GC-MS chromatogram identified many compounds known to be effective as antioxidants and antibacterial and antifungal agents. These indications show that pomegranate peel may be a superior natural food-preserver, but further studies about the suitable formulation, dosage, and possible side-effects are still needed.
Highlights
The use of natural preservatives became of great interest; good examples of these natural preservation agents are plant peels
Antimicrobial activity The inhibitory effect of ethanolic and methanolic extracts of the citrus and pomegranates as well as banana peels were estimated against four Gram-positive (G+) and three Gram-negative bacteria (G−) pathogenic bacteria along with two pathogenic fungal strains
Gram-positive bacteria The antimicrobial tests of the three used fruit peels against B. cereus, S. aureus Methicillin-resistant Staphylococcus aureus (MRSA), S. aureus, and L. monocytogenes revealed that both pomegranate peel extracts exhibited the most significant inhibitory effect on the tested strains compared to both the treatments and the positive control, except for kanamycin against B. cereus in the case of ethanolic extract (Table 1)
Summary
The use of natural preservatives became of great interest; good examples of these natural preservation agents are plant peels. The use of plant peels has dual benefits; first is their antimicrobial activity against food-borne pathogens, while the second is minimizing agro-industrial wastes. Food-borne illness due to consumption of food contaminated with pathogenic bacteria and/or their toxins is a vital concern to public health. The symptoms of such illness range from vomiting, nausea, and diarrhea to longterm diseases such as liver or kidney failure, cancer, and neural or brain disorders [1]. Addition of synthetic or chemical agents like formaldehyde, sulfites, nitrates, sorbates, and benzoates and synthetic antioxidants are most widely used as preservatives. The food industry has aimed to move toward the ways of clean labeling and eliminate synthetic preservatives from food formulations and alternate them with natural preservatives [3–8]
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