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.

Abstract: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

Stems, leaves, buds and flowers of Laurus nobilis L. growing wild in Tunisia were analysed for their essential oil composition. The essential oil of Laurus nobilis L. gathered from different stations were isolated by hydrodistillation and analysed by GC/MS. The oil yields on a dry weight basis ranged between 0.4% and 1.1%. The major component identified was 1,8-cineole, other predominant components were alpha-terpinyl acetate, methyl eugenol, eugenol and linalool. Although the same compounds were present in all plant organs, the leaves differed from the stems in the concentration of 1,8-cineole and methyl eugenol, buds and flowers in the concentration of 1,8-cineole and the stem's oil composition differs from the others in content of methyl eugenol. The results obtained from GC/MS analysis of the volatile oils from individual plant organs were submitted to principal component analysis. Chemometric investigations led to differentiation of stems, leaves and buds-flowers with the respect to the content of 1,8-cineole, metyhyl eugenol and alpha-terpynil acetate; flowers and buds were non-differentiated. Finally, the antibacterial activity of the leaves' essential oils has been assayed.

The antimicrobial properties of essential oil from various species have not been investigated enough in the previous studies dealing with the biological activities of medicinal plants. In Tunisia, L. (Asteraceae) is the only species recorded and is used as vermifuge and emmenagogue. The chemical composition, antibacterial and antifungal properties of essential oils from the flowerheads and roots of spontaneous growing in Tunisia and the chemical composition which leads to the Tunisian chemotype are investigated here for the first time. Essential oils isolated by hydro distillation from flowerheads and roots of were analyzed by GC and GC/MS. Two methods served for antimicrobial assays of the essential oils: diffusion in a solid medium and micro-well dilution assay. Antifungal tests were carried out by the agar incorporation method. Sixty-seven constituents were identified from the essential oil of the flowerhead. The major constituents were: 1,8-cineole and-eudesmol. Two non identified compounds were present at the highest concentration in root oil. Flowerhead oil was characterized by high contents in monoterpenes and sesquiterpenes oxygenated compounds. The flowerhead essential oil demonstrated potent of antibacterial properties against ATCC and ATCC, with MIC of 0.625 μg/ml. These findings demonstrate that the flowerhead essential oils of have excellent antibacterial properties and for this reason they could contribute to decrease the problem of microbial resistance to antibiotics.

This study examines the in vitro antimicrobial and antioxidant activities of the methanolic extracts of three Salvia species from Tunisia: Salvia aegyptiaca L., S. argentea L. and S. verbenaca Ssp. clandestina L. Pugsley. The extracts inhibited the growth of dermatophytes and of bacteria responsible for unpleasant odours to varying degrees; the pathogenic yeasts Candida albicans and Cryptococcus neoformans, the filamentous fungi Aspergillus fumigatus and selected dog otitis bacteria were all resistant to each of the extracts. The extracts were screened for their antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl free radical scavenging and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) test systems, and gave positive results in both tests. The extracts of S. aegyptiaca were the most active in both tests, followed by those of S. verbenaca, then S. argentea. These results confirm the antimicrobial and antioxidant activities of the genus Salvia and underline the potential of these plants either as natural preservatives or in pharmaceutical applications.