In 1957, Tunisia introduced 117 species of Eucalyptus; they have been used as fire wood, for the production of mine wood and to fight erosion. Actually, Eucalyptus essential oil is traditionally used to treat respiratory tract disorders such as pharyngitis, bronchitis, and sinusitis. A few investigations were reported on the biological activities of Eucalyptus oils worldwide. In Tunisia, our previous works conducted in 2010 and 2011 had been the first reports to study the antibacterial activities against reference strains. At that time it was not possible to evaluate their antimicrobial activities against clinical bacterial strains and other pathogens such as virus and fungi.

The essential oils of fifteen Eucalyptus species harvested from the Jbel Abderrahman and Korbous arboreta (North East Tunisia) were screened for their antibacterial activities by the agar disc diffusion method. Eighteen major components as identified by GC/FID and GC/MS were selected for a study of the chemical and biological activity variability. The main one was 1,8-cineole, followed by spathulenol, trans-pinocarveol, α-pinene, p-cymene, globulol, cryptone, β-phellandrene, viridiflorol, borneol, limonene and isospathulenol. The chemical principal component analysis identified five species groups and subgroups, where each group constituted a chemotype, however that of the values of zone diameter of the inhibition (zdi) identified six groups of Eucalyptus oils, characterized by their antibacterial inhibition ability. The strongest activity was shown by E. platypus oil against Enterococcus faecalis and by E. lamannii oil against Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. A correlation between the levels of some major components and the antibacterial activities was observed.

A number of bio-active secondary metabolites have been identified and reported for several Hypericum species. Many studies have reported the potential use of the plant extracts against several pathogens. However, Hypericum triquetrifolium is one of the least studied species for its antimicrobial activity. The aim of the present study was to evaluate the cytotoxic effect of the essential oils of Hypericum triquetrifolium as well as their antimicrobial potential against coxsakievirus B3 and a range of bacterial and fungal strains.

Background: The chemical composition and biological activity of Eucalyptus essential oils have been studied extensively (EOs). A few of them were tested for antibacterial effectiveness against otitis strains. The chemical composition and antibacterial activity of the EOs of eight TunisianEucalyptusspecies were assessed in the present study.Methods: Hydrodistillation was used to extract EOs from the dried leaves of eightEucalyptusspecies:Eucalyptus accedens, Eucalyptus punctata, Eucalyptus robusta,Eucalyptus bosistoana, Eucalyptus cladocalyx, Eucalyptus lesouefii, Eucalyptus melliodoraandEucalyptus wandoo.They are assessed by GC/MS and GC/FID and evaluated for antibacterial activity using agar diffusion and broth microdilution techniques against three bacterial isolates (Haemophilus influenzae,Haemophilus parainfluenzae,Klebsiella pneumoniae) and three reference bacteria strains (Pseudomonas aeruginosa,ATTC 9027;Staphylococcus aureus,ATCC 6538; andEscherichia coli,ATCC 8739). Furthermore, the selected twenty-one major compounds and all values of the inhibition zone diameters were subjected to further statistical analysis using PCA and HCA.Results: The EO yields of the studiedEucalyptusspecies range from 1.4 ± 0.4% to 5.2 ± 0.3%. Among all the species studied,E. lesouefiihad the greatest mean percentage of EOs. The identification of 128 components by GC (RI) and GC/MS allowed for 93.6% – 97.7% of the total oil to be identified.1,8-cineole was the most abundant component found, followed byα-pinene,p-cymene, and globulol. The chemical components of the eight EOs, extracted from the leaves ofEucalyptusspecies, were clustered into seven groups using PCA and HCA analyses, with each group forming a chemotype. The PCA and HCA analyses of antibacterial activity, on the other hand, identified five groups.Conclusion: The oils ofE. melliodora,E. bosistoana,andE. robustashow promise as antibiotic alternatives in the treatment of otitis media.

The dried leaves hydrodistillation of seven species of the genus Eucalyptus Herit. (E. eremophila (Diels) Maiden, E. oleosa F. Muell, E. patellaris F. Muell, E. astringens (Maiden) Maiden, E. striaticalyx W.V. Fitz, E. salubris F. Muell and E. transcontinentalis Maiden) harvested of Hajeb Layoun arboreta (region of Kairouan, Tunisia) in two periods (June 2004 and January 2005), shows that essential oil yields, related to the dry material, vary from 0.1 to 5.3 % according to the species and to the date of harvest. The best yields were recorded in January harvest. 74 components were identified by GC-MS. Contents of the different samples vary according to the species and to the harvest. Main compounds are 1,8-cineole (8.6 – 58.5 %), α-pinene (2.8 – 29.4 %), viridiflorol (1.7 % –23.6 %), limonene (0.4 – 19.7 %) and pinocarvone (0.1 – 8.2 %). E. eremophila presents the most raised yield in essential oil and the best rate in 1,8-Cineole.