Eucalyptus globulus essential oil as food preservative: Chemical composition, antimicrobial (in vitro and in situ), antibiofilm and insecticidal potential

The use of species within the Eucalyptus genus has been widespread in traditional medicine practices globally. However, concerns regarding safety and toxicity data have been prominent due to the extensive use of its essential oil, which is widely regarded for its medicinal properties and various applications. This research aimed to analyze the chemical makeup of Eucalyptus globulus essential oil (EGEO) and explore its antibacterial and insecticidal properties both in laboratory settings and real-life scenarios. Gas chromatography/mass spectrometry (GC/MS) was employed to identify the chemical constituents of EGEO, revealing 1,8-cineole (86.1 %), ο-Cymene (4.9 %), α-Pinene (3.8 %), γ-Terpinene (2.2 %), and α-Terpinene (1.6 %) as the primary components. The disc diffusion method demonstrated EGEOʼs strongest antimicrobial activity against Micrococcus luteus (p < 0.05), while minimal inhibition concentration tests indicated notable effectiveness against Streptococcus pneumoniae (MIC₅₀ 2.25 mg/mL and MIC₉₀ 2.79 mg/mL). In situ antibacterial assessments using white radish and pear food models showed heightened activity compared to contact application, particularly with the highest concentration (500 µg/L), yielding optimal results against Pseudomonas putida (p < 0.05). Additionally, the study investigated EGEO's antibiofilm properties against Salmonella enterica using mass spectrometry and the crystal violet method. In terms of insecticidal action, EGEO at 100 % concentration resulted in the mortality of 90 % of Harmonia axyridis individuals. This comprehensive investigation contributes to a deeper understanding of both the chemical composition and biological activities of Eucalyptus globulus essential oil, highlighting its potential as a source of natural compounds with promising therapeutic properties.