Comparative Phytochemical Composition and Antimicrobial Activity of Citrus Peel Essential Oils and Phenolic Compounds

Background: Antimicrobial resistance is imposing an alarming public health threat in regard to the irrational use of the currently available antibiotics and the lack of new antimicrobials.Objective: The current study aims to comparatively investigate the antimicrobial potential and phytochemical compositions of citrus peel essential oils (EOs) and phenolic compounds (PCs) as an approach to combat life-threatening bacterial and fungal infections.Methods: Citrus EOs and PCs were extracted from Citrus aurantifolia, Citrus reshni, Citrus latifolia and Citrus paradisi peels and phytochemically characterized by GC-MS and HPLC, respectively. The antimicrobial potential of citrus peel EOs and PCs was tested against Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Escherichia coli O157:H7, Pseudomonas aeruginosa, Salmonella typhimurium and Candida albicans using disc diffusion and broth microdilution assays.Results: The compositional analysis of citrus peel EOs revealed that limonene was the major volatile constituent, comprising 81.38%, 79.39%, 76.40% and 52.35% of grapefruit, mandarin, orange and lemon EOs, respectively. In addition, naringenin was the most abundant PC in grapefruit, orange and mandarin peel methanolic extracts, whereas catechin was the major PC in lemon peel. Lemon EO displayed the highest inhibitory effects against the investigated Gram-positive and Gram-negative bacteria as well as Candida albicans. Moreover, mandarin PCs exhibited the highest antibacterial effects, while orange PCs displayed the highest anticandidal effects. Furthermore, Gram-positive bacteria displayed higher sensitivity to both citrus peel EOs and PCs.Conclusion: Citrus peel extracts possess versatile bioactive compounds that can be utilized as promising antimicrobial candidates.