Abstract
BackgroundIn 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.MethodsThe essential oils of eight Eucalyptus species harvested from the Jbel Abderrahman, Korbous (North East Tunisia) and Souinet arboreta (North of Tunisia) were evaluated for their antimicrobial activities by disc diffusion and microbroth dilution methods against seven bacterial isolates: Haemophilus influenzae, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pneumoniae and Streptococcus pyogenes. In addition, the bactericidal, fungicidal and the antiviral activities of the tested oils were carried out.ResultsTwenty five components were identified by GC/FID and GC/MS. These components were used to correlate with the biological activities of the tested oils. The chemical principal component analysis identified three groups, each of them constituted a chemotype. According to the values of zone diameter and percentage of the inhibition (zdi, % I, respectively), four groups and subgroups of bacterial strains and three groups of fungal strains were characterized by their sensitivity levels to Eucalyptus oils. The cytotoxic effect and the antiviral activity varied significantly within Eucalyptus species oils.ConclusionsE. odorata showed the strongest activity against S. aureus, H. influenzae, S. agalactiae, S. pyogenes, S. pneumoniae and against all the tested fungal strains. In addition, E. odorata oil showed the most cytotoxic effect. However, the best antiviral activity appeared with E. bicostata. Virus pretreatment with E. bicostata essential oil showed better antiviral activity (IC50 = 0.7 mg/ml, SI = 22.8) than cell-pretreatment (IC50 = 4.8 mg/ml, SI = 3.33). The essential oil of E. astringens showed antiviral activity only when incubated with virus prior to cell infection. This activity was dose-dependent and the antiviral activity diminished with the decreasing essential oil concentration.
Highlights
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
As reported previously [13,14], we have studied the antibacterial activity of 35 Eucalyptus essential oils against four reference gastrointestinal strains (Esherichia coli, ATCC 25922; Pseudomonas aeruginosa, ATCC 227853; Enterococcus faecalis, ATCC 292112; Staphylococcus aureus, ATCC 25932) using the disc diffusion method
Plant materials Samples of clean mature leaves of eight species of the genus Eucalyptus L’HÉR., five of which were collected in June 2006 from Souiniat arboreta located in the North west of Tunisia (E. bicostata, E. cinerea, E. maidenii, E. odorata and E. sideroxylon); two species were collected in April 2006 from Korbous arboreta (E. astringens and E. lahmannii); one species was collected from Jbel abderrahaman arboreta (E. leucoxylon)
Summary
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. Eucalyptus essential oil is traditionally used to treat respiratory tract disorders such as pharyngitis, bronchitis, and sinusitis. In Tunisia, our previous works conducted in 2010 and 2011 had been the first reports to study the antibacterial activities against reference strains. Essential oil has traditionally been used to treat respiratory tract disorders such as pharyngitis, bronchitis, and sinusitis [4]. Streptococcus pyogenes, Streptococcus pneumoniae, Streptococcus agalctia, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumonia and Hemophilis influenzae are the most important causes of the respiratory tract infections and the most resistant to antibiotics. The essential oils extracted from Eucalyptus species, mainly from E. urophylla S.T. Blake, E. grandis, E. camaldulensis, E. citriodora and E. globulus were found to be active on phyto-pathogenic fungi [8,9,10]
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