Quality, chemical composition, and antimicrobial potential of Citrus peel essential oils against urinary tract infection pathogens

Urinary tract infection (UTI) is one of the most common microbial infections worldwide, and the growing resistance to conventional antibiotics highlights the need for alternative therapies. This study evaluated the quality, chemical composition, and antimicrobial activity of Citrus peel essential oils (CPEOs) against six UTI-causing pathogens: Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC 2537, Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 6538, Candida albicans ATCC 10231, and Aspergillus niger ATCC 6275. Essential oils were extracted from the peels of C. aurantiifolia, C. limon, C. nobilis, C. amblycarpa, and C. sinensis, and their quality parameters were assessed in comparison with ISO standards. The chemical composition determined using gas chromatography-mass spectrometry (GC-MS), revealed limonene, β-pinene, γ-terpinene, and linalool as the predominant constituents, which were further validated by Fourier-transform infrared spectroscopy (FTIR) analysis. Antimicrobial activity was examined using inhibition zone and minimum inhibitory concentration (MIC) assays. The results showed that C. limon essential oil (CLEO) exhibited the strongest antimicrobial activity, with inhibition zones reaching up to 81.17 ± 0.827 mm against K. pneumoniae and MIC values as low as 2 µg/mL against C. albicans. In contrast, C. sinensis and C. nobilis essential oils displayed weaker activity, and no significant inhibition was observed against P. aeruginosa. The strong antimicrobial activity of CLEO is likely associated with its higher γ-terpinene content, which is known to disrupt microbial membranes and induce cell death. Overall, these findings highlight CPEOs, particularly CLEO, as promising natural antimicrobial agents for the prevention and management of UTI.