Investigating the antifungal, antioxidant, and antibacterial activities of Ocimum basilicum L. and Mentha piperita L. essential oils and their synergistic potentials with antibiotics
Simay Türk, Şükriye Gülnur Aşçı, Tuba Sevimoğlu, Sibel DöşlerBackground and Aims: This research focuses on assessing the antioxidant, antifungal and antibacterial properties of Mentha piperita Lamiaceae and Ocimum basilicum Lamiaceae essential oils and their potential synergistic effects with various antibiotics.
Methods: The study identifies the chemical composition of M. piperita and O. basilicum essential oils by employing gas chromatography-mass spectrometry (GC-MS), cupric reducing antioxidant capacity (CUPRAC), and 2,2-Diphenyl-1- picrylhydrazyl (DPPH) methods to identify antioxidant activity. The study also uses the minimal inhibitory concentration (MIC) method for the antibacterial and antifungal activity tests.
Results: The main constituents of M. piperita are menthol (51.89%), L-menthone (17.81%), L-menthol (10.17%), and menthyl acetate 6.29%. The main constituents of O. basilicum are 65.51% estragole, 18.51% L-linalool, 2.69% bisabolene, and 2.66% trans-4-methoxycinnamaldehyde. With regard to the DPPH method, IC50 values of 0.028 and 0.019 were found for M. piperita and O. basilicum, respectively, based on the inhibition values. The results for the CUPRAC method indicate O. basilicum to show more antioxidant activity than M. piperita. According to the MICs, the essential oils are effective against bacteria at 1:4-1:16 dilutions, while the MIC values for the oil mixture (1:1) are significantly lower at a dilution of up to 1:2048. When combining the oils combined with the antibiotics (i.e., tobramycin and ceftazidime), they provide a synergistic activity against Staphylococcus epidermidis, Escherichia coli, and Klebsiella pneumoniae. The antifungal activity tests reveal no sufficient activity against the mold Aspergillus niger, while a limited effect was observed against the yeast Candida albicans.
Conclusion: The results show that the studied essential oils, especially their mixture at a 1:1 ratio, could be a good treatment option either alone or as a drug adjuvant due to their antibacterial and antioxidant properties.