Infectious diseases continue to pose a significant threat to global health, particularly in developing countries, where they rank among the leading causes of mortality. The escalating costs of antibiotic treatments, combined with the growing resistance of pathogens, highlight the urgent need for alternative therapies, such as those derived from plant sources like Eucalyptus, which has shown diverse antimicrobial properties. This study aims to analyze the chemical composition and antimicrobial properties of essential oils extracted from various Eucalyptus species collected in Jiroft city, Iran. By exploring these plant-based compounds, the research seeks to contribute to the development of alternative treatments for infectious diseases, especially in the context of increasing antibiotic resistance and the growing global interest in herbal medicines. Leaves of Eucalyptus globulus Labill., Eucalyptus camaldulensis Dehnh., and Eucalyptus microtheca F. Muell. were used for essential oil extraction, followed by chemical composition analysis using gas chromatography-mass spectrometry (GC/MS). The antibacterial effects of various concentrations of the essential oils on Streptococcus pyogenes , Escherichia coli , and Staphylococcus aureus were evaluated using the agar disk-diffusion method. Additionally, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the essential oils were determined for each bacterium using the tube dilution method. Twenty-one components were identified in the essential oils. The total percentages of identified compounds in the essential oils were 98.54% for E. globulus , 89.46% for E. microtheca , and 96.02% for E. camaldulensis . The predominant compound in all Eucalyptus varieties was eucalyptol ( E. globulus : 83.5%, E. microtheca : 29.5%, E. camaldulensis : 64.1%). Essential oils from E. camaldulensis and E. globulus exhibited significant antibacterial activity against S. aureus and S. pyogenes , whereas E. microtheca essential oil showed antibacterial activity only against S. aureus and no activity against S. pyogenes . The MIC of E. camaldulensis for S. aureus and S. pyogenes was less than 8.7 µg/ml, while the MIC of E. globulus for S. aureus was 31.25 µg/ml and for S. pyogenes was 62.5 µg/ml. For E. microtheca , the MIC was 15.6 µg/ml for S. aureus , but no activity was observed against S. pyogenes (MIC > 1000 µg/ml). The essential oils from Eucalyptus cultivars demonstrated inhibitory effects against S . pyogenes and S. aureus and may have potential applications as natural preservatives.
Sataie-Mokhtari et al. (Sat,) studied this question.