Chemical composition, antifungal and antiproliferative activities of essential oils from Thymus numidicus L.

In this study, Thymus numidicus Poir. plant material was collected from two different locations in north-western Tunisia and the aerial parts essential oils (EOs) were extracted via hydro-distillation. Gas chromatography coupled to mass spectrometry (GC-MS) and flame ionisation detection (GC-FID) were used for the qualitative analysis and quantification of the volatile constituents. Thymol (50.1-52.8%) was identified as the main compound of both EOs. To evaluate the potential application of the EOs as antifungal agents, the in vitro inhibitory effects were tested against six fungal strains; a strong antifungal activity of one sample was observed (MIC = 40-400 µg/mL). The in vitro antiproliferative activity was investigated on two human cancer cell lines, i.e. the colonic (HCT116) and breast adenocarcinoma (MCF7) using the colourimetric MTT assay. Again, the same sample demonstrated to possess good antiproliferative activity against both cancer cell lines, with IC50 values of 26.9 and 11.7 µg/mL, respectively.

Correlation between chemical composition and antibacterial activity of some Lamiaceae species essential oils from Tunisia.

BACKGROUND: Lamiaceae family is one of the most diverse and common plant families in terms of ethnomedicine due to their potential therapeutic effects. The aim of this study is to investigate the correlation between the chemical composition and the antibacterial effect of five essential oils from this family against five reference bacterial strains responsible of nosocomial diseases and foodborne illnesses. METHODS: The commercial essential oils of Tunisian Rosmarinus officinalis, Thymus capitatus, Origanum majorana and Salvia officinalis were analyzed by GC/FID and GC-MS. Essential oils were evaluated for their antibacterial activities by disc diffusion and microbroth dilution methods against five reference bacterial strains: Pseudomonas aeruginosa, Escherichia coli, Salmonella enterica, Bacillus subtilis and Staphylococcus aureus. The inhibition zone diameter values and the twenty major compounds of the selected essential oils were subjected to PCA and HCA analysis. RESULTS: Analysis by GC/FID and GC/MS allowed the identification of ninety-one components representing 96.0 to 98.2% of the total oils. The different component contents varied according to the species. The main components were carvacrol, 1,8-cineole, α-thujone, α-terpineol and α-pinene. The PCA and the HCA of the selected essential oil components and the inhibition zone diameter (IZD) values identified four species groups and subgroups. Each essential oils group constituted a chemotype responsible for their bacterial inhibition ability. Thymus capitatus essential oil showed the strongest antibacterial activity with MBC ranging from 0.73 to 2.94 mg mL- 1. CONCLUSION: Rosmarinus officinalis, Thymus capitatus, Origanum majorana and Salvia officinalis essential oils have shown promising antibacterial activities against reference bacterial strains responsible for nosocomial diseases and foodborne illnesses.

Chemical Characterization of Five Tunisian Eucalyptus Essential Oils Species.

Hydrodistillation of the dried leaves of five Eucalyptus species, E. alba Reinw. ex Blume, E. citriodora Hook., E. paniculata Sm., harvested from Choucha arboreta (region of Sejnane, northwest of Tunisia), E. pimpiniana Maiden from Mjez Elbab arboreta (north east of Tunisia) and E. bicolor A.Cunn ex Hook from Sidi Smail arboreta (center of Tunisia), in March 2017, afforded essential oils in yields varying from 1.3±0.2 to 6.0±0.9 % according to the species. E. citriodora provided the highest mean percentage of essential oil amongst all the species. Analysis by GC (RI) and GC/MS allowed the identification of 138 components representing 84.6-98.7 % of the total oil. The content of the different samples varied according to the species. The main components were citronellol, followed by 1,8-cineole, α-pinene, τ-cadinol, 7-epi-α-eudesmol, trans-pinocarveol, spathulenol, aromadendrene, γ-cadinene and δ-cadinene. The principal components and the hierarchical cluster analyses separated the five leaf essential oils into three groups, each group constituted a chemotype.

Chemical composition and antimicrobial and allelopathic activity of Tunisian Conyza sumatrensis (Retz.) E.WALKER essential oils.

Conyza sumatrensis (Retz.) E.WALKER (Asteraceae) is a spontaneous annual herb, fairly widespread throughout Tunisia, which has rarely been studied or valued in any sector. Essential oils were obtained by hydrodistillation of different parts (flower heads, leaves, stems, and roots) of C. sumatrensis plants, which were collected in autumn (November 2007) at the flowering stage in the area of Monastir, Tunisia. In total, 98 compounds, representing 88.1-99.3% of the oil composition, were identified by GC-FID and GC/MS analyses. The root essential oil was distinguished by its high content in acetylenes (matricaria ester, 4; 74.3%), while those from flower heads and leaves were dominated by oxygenated sesquiterpenes (61.1 and 50.3%, resp.). The oils of C. sumatrensis from Tunisia belonged to a matricaria ester/caryophyllene oxide chemotype. All the oils were evaluated for antibacterial, antifungal, and allelopathic activities. The results indicate that the leaf oil exhibited significant in vitro antibacterial activity against Enterococcus faecalis, Staphylococcus aureus, and Proteus mirabilis and that the C. sumatrensis oils isolated from the aerial parts presented high mycelia-growth inhibition of Candida albicans and the filamentous fungi tested. Moreover, the essential oils of the different plant parts inhibited the shoot and root growth of Raphanus sativus (radish) seedlings. Indeed, the inhibition of the hypocotyl growth varied from 28.6 to 90.1% and that of the radicle from 42.3 to 96.2%.

Evaluation of the cytotoxic effect and antibacterial, antifungal, and antiviral activities of Hypericum triquetrifolium Turra essential oils from Tunisia.

BACKGROUND: 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. METHODS: The essential oils of Hypericum triquetrifolium harvested from five different Tunisian localities (Fondouk DJedid, Bou Arada, Bahra, Fernana and Dhrea Ben Jouder) were evaluated for their antimicrobial activities by micro-broth dilution methods against bacterial and fungal strains. In addition, the cytotoxic effect and the antiviral activity of these oils were carried out using Vero cell lines and coxsakievirus B3. RESULTS: The results showed a good antibacterial activities against a wide range of bacterial strains, MIC values ranging between 0.39-12.50 mg/ml and MBC values between 1.56-25.0 mg/ml. In addition, the essential oils showed promising antifungal activity with MIC values ranging between 0.39 µg/mL and 12.50 µg/mL; MFC values ranged between 3.12 µg/mL and 25.00 µg/mL; a significant anticandidal activity was noted (MIC values comprised between 0.39 µg/mL and 12.50 µg/mL). Although their low cytotoxic effect (CC50 ranged between 0.58 mg/mL and 12.00 mg/mL), the essential oils did not show antiviral activity against coxsakievirus B3. CONCLUSION: The essential oils obtained from Hypericum triquetrifolium can be used as antimicrobial agents and could be safe at non cytotoxic doses. As shown for the tested essential oils, comparative analysis need to be undertaken to better characterize also the antimicrobial activities of Hypericum triquetrifolium extracts with different solvents as well as their purified fractions and their pure secondary metabolites.

Chemical composition and larvicidal activity of several essential oils from Hypericum species from Tunisia.

The chemical composition of the essential oils extracted from some Tunisian Hypericum species and their larvicidal activity against Culex pipiens larvae were evaluated. The chemical compositions of the essential oils from the aerial plant parts were analyzed using gas chromatography-mass spectrometry. One hundred and thirty-four compounds were identified, ranging between 85.1 and 95.4 % of the oil's composition. The components were monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpene hydrocarbons, oxygenated sesquiterpenes, non-terpenic hydrocarbons, and others. The larvicidal activity of the essential oils was evaluated using a method recommended by WHO. Larvicidal tests revealed that essential oils from the Hypericum species have a significant larvicidal activity against C. pipiens, with LC(50) ranging between 102.82 and 194.70 ppm. The most powerful essential oils against these larvae were Hypericum tomentosum and Hypericum humifusum samples, followed by the essential oil of Hypericum perforatum.

Chemical composition of 8 eucalyptus species' essential oils and the evaluation of their antibacterial, antifungal and antiviral activities.

BACKGROUND: 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. METHODS: The 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. RESULTS: Twenty 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. CONCLUSIONS: E. 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 (IC(50) = 0.7 mg/ml, SI = 22.8) than cell-pretreatment (IC(50) = 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.

Chemical composition and intraspecific variability of the essential oils of five populations of Hypericum triquetrifolium Turra growing in North Tunisia.

The chemical composition of the essential oils of five populations of Hypericum triquetrifolium Turra from Tunisia and their intraspecific variability were analyzed in detail by GC/MS. One hundred seventy-four compounds were identified, representing averages of 87.9 to 98.7% of the oil composition. The components are represented here by homologous series of monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpenes hydrocarbons, oxygenated sesquiterpenes, non-terpenic hydrocarbons, and others. Sesquiterpene hydrocarbons were the most abundant chemical compounds. Multivariate chemometric techniques, such as cluster analysis (CA) and principal-component analysis (PCA), were used to characterize the samples according to the geographical origin. By statistical analysis, the analyzed populations were classified into four chemotype groups.

Correlation between chemical composition and antibacterial activity of essential oils from fifteen Eucalyptus species growing in the Korbous and Jbel Abderrahman arboreta (North East Tunisia).

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, ß-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.

Chemical composition and antioxidant activity of the essential oil of Juniperus phoenicea L. berries.

This study is designed to examine the chemical composition and antioxidant activity of the essential oil of Juniperus phoenicea L. ripe and unripe berries. GC and GC/MS analyses resulted in the detection of 42 components representing approximately 96.50-99.57% of the oils. Major components of the oils were α-pinene (58.61-77.39%), camphene (0.67-9.31%), δ-3-carene (0-10.01%) and trans-verbenol (0-5.24%). Antioxidant activities were determined by two different test systems, DPPH and ABTS radical scavenging activities. In both systems ripe berries exhibited better activity potential than the unripe ones.

Variation in volatile leaf oils of five Eucalyptus species harvested from Jbel Abderrahman arboreta (Tunisia).

Hydrodistillation of the dried leaves of five species of the genus Eucalyptus L' Hér., viz., E. dundasii Maiden, E. globulus Labill., E. kitsoniana Maiden, E. leucoxylon F. Muell., and E. populifolia Hook., harvested from Jbel Abderrahman arboreta (region of Nabeul, northeast of Tunisia) in April 2006, afforded essential oils in yields varying from 0.9±0.3 to 3.8±0.6%, dependent on the species. E. globulus and E. Kitsoniana provided the highest and the lowest percentage of essential oil amongst the species examined, respectively. Analysis by GC (RI) and GC/MS allowed the identification of 127 compounds, representing 93.8 to 98.7% of the total oil composition. The contents of the different samples varied according to the species. The main components were 1,8-cineole (2; 4.7-59.2%), followed by α-pinene (1; 1.9-23.6%), trans-pinocarveol (6; 3.5-21.6%), globulol (8; 4.3-12.8%), p-cymene (3; 0.5-6.7%), α-terpineol (1.5-4.5%), borneol (0.2-4.4%), pinocarvone (1.1-3.8%), aromadendrene (1.4-3.4%), isospathulenol (0.0-1.9%), fenchol (4; 0.1-2.5%), limonene (1.0-2.4%), epiglobulol (0.6-2.1%), viridiflorol (9; 0.8-1.8%), and spathulenol (0.1-1.6%). E. leucoxylon was the richest species in 2. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) separated the five Eucalyptus leaf essential oils into four groups, each constituting a chemotype.

Variation in volatile leaf oils of seven eucalyptus species harvested from Zerniza arboreta (Tunisia).

Leaves of seven species of the genus Eucalyptus L'Hér., viz., E. cladocalyx F. Muell., E. citriodora Hook., E. diversicolor F. Muell., E. fasciculosa F. Muell., E. grandis W. Hill, E. ovata Labill., and E. botryoides Sm., were harvested from Zerniza arboreta (region of Sejnene, northwest of Tunisia) in June 2007. Of the latter species, leaves were collected from trees having two origins, Morocco and Italy. Hydrodistillation of the dried leaves provided essential oils in yields varying from 0.4±0.0 to 3.3±0.1%, according to the species. E. citriodora had the highest mean percentage of essential oil amongst the species examined, whereas the lowest one was obtained for E. botryoides originating from Morocco. Analysis by GC (RI) and GC/MS allowed the identification of 140 compounds, representing 92.5 to 99.4% of the total oil composition. The contents of the different samples varied according to the species. The main components were 1,8-cineole (2), followed by α-pinene (1), p-cymene, borneol, α-terpineol, cryptone, spathulenol, trans-pinocarveol (4), bicyclogermacrene (5), caryophyllene oxide, and ß-phellandrene. Principal components analysis and hierarchical cluster analysis separated the eight Eucalyptus leaf essential oils into five groups, each constituting a chemotype.

Variation in volatile leaf oils of eleven eucalyptus species harvested from korbous arboreta (Tunisia).

Hydrodistillation of the dried leaves of eleven species of the genus Eucalyptus L'Hér., i.e., E. astringens Maiden, E. camaldulensis Dehnh., E. diversifolia Bonpl., E. falcata Turcz., E. ficifolia F. Muell., E. gomphocephala DC., E. lehmannii (Schauer) Benth., E. maculata Hook., E. platypus Hook., E. polyanthemos Schauer, and E. rudis Endl., harvested from Korbous arboreta (region of Nabeul, northeast of Tunisia) in April 2006, afforded essential oils in yields varying from 0.1+/-0.1 to 3.8+/-0.1%, dependent on the species. E. astringens and E. ficifolia showed the highest and the lowest mean percentage of essential oil amongst all the species examined, respectively. Analysis by GC (RI) and GC/MS allowed the identification of 138 components, representing 74.0 to 99.1% of the total oil. The contents of the different samples varied according to the species. The main components were 1,8-cineole, followed by trans-pinocarveol (1), spathulenol (2), alpha-pinene, p-cymene, (E,E)-farnesol, cryptone, globulol (3), beta-phellandrene, alpha-terpineol, viridiflorol, and alpha-eudesmol. The principal-component and the hierarchical-cluster analyses separated the eleven Eucalyptus leaf essential oils into seven groups, each constituting a chemotype.

Leaf essential oil of Juniperus oxycedrus L. (Cupressaceae) harvested in northern Tunisia: composition and intra-specific variability.

The essential oil composition of leaves of 60 individual trees of Juniperus oxycedrus L. growing in four locations in Tunisia harvested in three different seasons were investigated by GC and GC/MS. Seventy compounds were identified in the oils, and a relatively high variation in their contents were found. All the oils were dominated by terpenic hydrocarbons, with alpha-pinene (27.35-58.03%) as the main component, followed by geranyl acetone (13; 1.96-7.14%), 13-epimanoyl oxide (16; 1.35-6.95%), and eudesma-4(15),7-dien-1-ol (11; 1.39-4.18%). The 18 major oil components were processed by hierarchical clustering and principal component analysis (PCA) allowing to establish four groups, one divided into two subgroups, of populations according to the location and season of harvest. Their oils were differentiated by one compound or more, showing a clear seasonal and geographical polymorphism in their chemical composition allowing the identification of specific chemotypes. The pattern of geographic variation in the essential oil composition indicated that the oils of the populations from the continental site (Makthar) were clearly distinguished from those of the littoral localities (Tabarka, Hawaria, and Rimel).

Variation in volatile leaf oils of 13 Eucalyptus species harvested from Souinet arboreta (Tunisia).

Hydrodistillation of the dried leaves of 13 species of the genus Eucalyptus L' Hér., viz., E. bicostata Maiden, Blakely & Simmonds, E. cinerea F. Muell. ex Benth., E. exerta F. Muell., E. gigantea Hook. f., E. gunnii Hook. f., E. macarthurii Deane & Maiden., E. macrorrhyncha F. Muell., E. maidenii F. Muell., E. odorata Behr., E. pauciflora Sieber ex Sprengel, E. sideroxylon A. Cunn. ex Woolls, E. tereticornis Sm., and E. viminalis Labill., harvested from Souinet arboreta (region of Ain Draaham, north of Tunisia) in June 2006, afforded essential oils in yields varying from 0.5+/-0.2 to 3.9+/-0.4%, dependent on the species. E. cinerea and E. exerta provided the highest and the lowest percentage of essential oil amongst all the species examined, respectively. Analysis by GC (RI) and GC/MS allowed the identification of 142 components, representing 81.5 to 98.9% of the total oil. The contents of the different samples varied according to the species. The main components were 1,8-cineole (1), followed by cryptone, spathulenol (4), p-cymene (2), viridiflorol (6), globulol (7), beta-eudesmol, alpha-terpineol (5), limonene (8), D-piperitone, alpha-pinene (3), cuminal, and gamma-eudesmol. The principal component and the hierarchical cluster analyses separated the 13 Eucalyptus leaf essential oils into three groups, each constituting a chemotype.

Variation in volatile leaf oils of twelve eucalyptus species harvested from Hajeb Layoun arboreta (Tunisia).

Hydrodistillation of the dried leaves of twelve species of the genus Eucalyptus L' Hér., i.e., E. brockwayi C. A. Gardn., E. gracilis F. Muell., E. gillii Maiden, E. largiflorens F. Muell., E. loxophleba Benth., E. occidentalis Endl., E. oldfieldii F. Muell., E. salmonophloia F. Muell., E. sargentii Maiden, E. stricklandii Maiden, E. torquata Luehm., and E. woodwardii Maiden, harvested from Hajeb Layoun arboreta (region of Kairouan, central Tunisia) in January 2005, afforded essential oils in yields varying from 0.5+/-0.1 to 5.7+/-0.5%, dependent on the species. E. sargentii and E. brockwayi provided the highest and the lowest percentage of essential oil amongst all the species examined, respectively. Analysis by GC (RI) and GC/MS allowed the identification of 133 components, representing 92.9-98.8% of the total oil. The contents of the different samples varied according to the species. The main components were 1,8-cineole, terpinen-4-ol, alpha-pinene (2), p-cymene, aromadendrene (1), globulol (5), trans-pinocarveol (6), spathulenol (7), beta-eudesmol, torquatone (3), and 4-methylpentan-2-yl acetate (8). The principal component analysis and the hierarchical clustering indicated that the volatile leaf oil composition of the twelve Eucalyptus species could be clearly differentiated.

Seasonal and geographical influences on the chemical composition of Juniperus phoenicea L. essential oil leaves from the Northern Tunisia.

The essential-oil composition of 60 individual trees of Juniperus phoenicea L. from four Tunisian populations in three different periods were investigated by GC and GC/MS analyses. 59 Compounds were identified in the oils, and a relatively high variation in their contents was found. All the oils were dominated by the terpenic hydrocarbon fraction, and the main component was alpha-pinene (20.28-40.86%). The results of the oil compositions were processed by hierarchical clustering and principal component analysis (PCA) allowing establishing four groups of essential-oils differentiated by one compound or more. Pattern of geographic variation in essential-oil composition indicated that individuals from the continental site (Makthar) were clearly distinguished from those from littoral localities (Tabarka, Hawaria, and Rimel).