Abstract
BACKGROUND: The significant rise in antibiotic resistance has become an alarming situation urging the search for new antibacterial agents. Nature has always been a limitless source of bioactives with high safety profile. This study evaluates the antibacterial activity of essential oils from the leaves and fruit peels of Minneola tangelo cultivated in Egypt. In vitro cytotoxicity assay was conducted to ensure the safety profile of the active essential oils. METHODS: The antibacterial activity of clinical isolates of Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus was assessed using the Kirby-Bauer disk diffusion method. Chemical profiling of the leaf and peel essential oils was performed using GC-MS. In vitro cytotoxicity assay of the leaf essential oil was conducted using sulforhodamine B assay. In silico docking study was conducted to explore the possible antibacterial mechanisms. RESULTS: The leaf essential oil exhibited antibacterial activity against the tested isolates, whereas the peel oil was inactive. GC-MS analysis showed differences in the chemical composition of the leaf and fruit peel oils, where 60% of the leaf oil is dominated by linalool (31.6%), cis-β-ocimene (16.1%), and γ-terpinene (14.3%), whereas the fruit peel oil is solely dominated by D-limonene (82%). Cytotoxicity assay on Caco-2 cell line showed IC(50) value of 277.36 µg/mL while that on fibroblast HFB4 cell line was > 1000 µg/mL. In silico studies revealed high affinity of linalool to FabI, a crucial enzyme in the fatty acid biosynthesis pathway of MRSA as well as an affinity to Penicillin binding protein PBP2a. Binding of linalool to shikimate kinase of Acinetobacter baumannii was also demonstrated. CONCLUSION: Essential oil of M. tangelo is a promising antibacterial agent against multidrug resistant strains with a high safety profile.