Essential oil Chemical Composition, Antioxidant and Antibacterial Activities of Eucalyptus largiflorens F. Muell

In this study, we investigated the chemical composition, the antibacterial activity, and the antioxidant properties of extracts obtained from the leaves, flowers, and fruits of Eucalyptus largiflorens F. Muell. The antioxidant effects of the methanolic extract of aerial parts of the plant, obtained by Soxhlet apparatus, were estimated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and β-carotene/linoleic acid methods. The essential oils were chemically characterized by gas chromatography (GC) coupled with mass spectrometry (MS) and flame ionization detector (FID). Thirty compounds were identified, with 1,8-cineol, α-pinene, aromadendrene, globulol and α-phellandrene being the major components. The antibacterial activities of the essential oils were tested against several bacterial isolates, including Staphylococcus aureus, Staphylococcus epidermidis and Escherichia Coli, using the disc diffusion method. All the essential oils exhibited antibacterial activity. The maximum zone of inhibition was observed for Escherichia coli, with the fruit essential oil in the concentration (100 μL). There was no significant antioxidant activity in the essential oils, while the extracts exhibited considerable antioxidant effects in comparison to butylated hydroxytoluene (BHT). In this regard, the flower extract showed the highest antioxidant activity in both DPPH (IC50 = 21.5±0.2 μg/mL) and β-carotene/linoleic acid tests (Inhibition (%) = 84.3±0.7). Finally, the fruit essential oil exerts a significant antibacterial activity against several bacterial strains and exhibits a significant antioxidant effect in the β-carotene/linoleic acid tests, thus it may represent an innovative nutraceutical tool able to act on bacteria and host oxidative stress related to infections.