Eucalyptus torquata, Eucalyptus woodwardii and Their Hybrid Eucalyptus torwood Essential Oils: GC-MS Profile, In Vitro Evaluation of the Antimicrobial Activities, Molecular Docking Study and in Silico ADME Profiling

Eucalyptus torwood is a spontaneous hybrid of two species: Eucalyptus torquata and Eucalyptus woodwardii. Our work aims to study the essential oils of these three taxa, including yield, chemical composition and antimicrobial activities, with the aim of analyzing the effect of hybridization on these parameters. The essential oil yields were 2.6, 2.52 and 2.12% for E. torquata, E. woodwardii and E. torwood, respectively. All three oils showed the same α-pinene content (around 12%), but E. woodwardii was richer in aromandendrene than the other two eucalypts, which have higher torquatone contents. Also, E. torwood showed a specific richness in β-eudesmol and a lower percentage in 1,8-cineole. The antibacterial and antifungal activity was determined against six bacterial strains, the results obtained highlight that the essential oils tested showed antimicrobial activity against gram-positive bacteria to different degrees, while on gram- negative bacteria they showed resistance. The yeast Candida albicans was most sensitive to the three Eucalyptus essential oils. To clarify the antibacterial effect of the major phytocompounds, we employed computational methods, including ADME and molecular docking. Significant results were obtained, molecular docking simulations highlighted high binding score of four major abundant compounds towards targeted receptors (pdb: 2zcq and pdb: 1kzn).