Extraction of essential oil, phytochemical screening, and antimicrobial activity study of Eucalyptus globulus

ABSTRACT Eucalyptus globulus also referred to as Blue Gum is a native plant to Australia where they are cultivated extensively for the extraction of its oil. This oil is of great value in medicinal, therapeutic, and industrial applications. The present study is primarily aimed to the identification of phenolic composition and antimicrobial activity of Eucalyptus globulus leaves collected from the Terai region of Nepal. The leaves were partially air-dried, crushed, and subsequently subjected to extraction processes for the preparation of plant extract and essential oil. The GC-MS analysis of essential oil, phytochemical screening, and antimicrobial activity of plant extract were performed. The GC-MS analysis identified a diverse range of compounds, including the major compounds like Eucalyptol(2.52%), Valerianol(5.57%), 10-epi- γ -eudesmol(6.93%), Bulnesol(19.97%) and epi- γ -eudesmol (17.51%) The antimicrobial efficacy of ethyl acetate (EtOAC), methanol (MeOH), and hexane extracts was evaluated against Escherichia coli (ATCC 8739), Staphylococcus aureus (ATCC 6538P), and Candida albicans (ATCC 2091) using the Mueller-Hinton agar well diffusion method. The hexane extract exhibited significant antibacterial activity, particularly against E. coli and C. albicans , with inhibition zones of 2.0 cm and 2.1 cm, respectively. In contrast, the MeOH extract showed the least antibacterial activity across all tested strains. The phenolic profiling revealed Bulnesol as the most abundant compound with a concentration of 19.97 units at a retention time of 40.128 minutes, followed by epi - γ -Eudesmol with 17.51 units. The study underscores the rich phenolic diversity and potent antimicrobial properties of E. globulus leaves, highlighting its potential applications in pharmaceuticals and natural product industries.