Thymus algeriensis Boiss. et Reut., a north African endemic plant species: genetic diversity and population structure as assessed by molecular markers, a pioneer step for conservation implications.

BACKGROUND: Thymus algeriensis Boiss. et Reut. is one of the most widespread North African species of the genus Thymus L. The species is subshrub growing primarily in subtropical biome of Morocco, Algeria, Tunisia and Libya. In Tunisia, the plant species is under high pressure of anthropogenic activities including over-collecting. The assessment of genetic diversity and population structure of T. algeriensis is a pioneer step to retrace its evolutionary history and to perform appropriate conservation strategies of the plant species. METHODS AND RESULTS: Seven wild populations growing, widely, in different bioclimatic zones were selected and analysed using two molecular markers systems. Fifteen Simple Sequence Repeats (SSRs) and fifteen Inter-Simple Sequence Repeats (ISSRs) were used to characterize genetically 140 different genotypes. The results showed a high molecular variation within populations and among the studied genotypes. The intra-populations genetic diversity revealed by SSRs was higher (P = 80.95%, Na = 2.143 and He = 0.364) than that based on ISSRs (P = 78.12%, Na = 1.632, He = 0.265 and I = 0.398). As demonstrated by inbreeding coefficients, a significant level of differentiation and a low level of gene flow were detected among studied populations (FST = 0.161 for SSRs and ΦST = 0.197 for ISSRs). Furthermore, the results of ISSRs marker suggest land strips as barriers in population genetic structure. While SSRs marker reflects a relatively structured bioclimatic patterns of studied populations. The Bayesian analysis showed a specific adaptation of populations to local environments. CONCLUSIONS: The used molecular markers (ISSRs and SSRs) seem to be effective in deciphering genetic polymorphism of Tunisian genotypes of T. algeriensis. Therefore, the genetic structure of the studied genotypes could constitute a starting point for further conservation, characterization and breeding programs.

Variation in Phenolic Content, Antioxidant Activity and Alpha-amylase and Acetylcholinesterase Inhibitory Capacities of Different Extracts from Tunisian Satureja barceloi (Willk) L.

The antioxidant activity and the anti-α-amylase and anti-acetylcholinesterase capacities of secondary metabolites from different organs (roots, stems, leaves and flowers) of Tunisian Satureja barceloi were determined. The variation in the distribution of phenolic metabolites among roots, stems, leaves and flowers extracts of S. barceloi with various solvent systems (methanol, ethyl acetate, hexane and distilled water) has not been characterized before. Significant variation of phenolic compounds was observed according to organs rather than to extracting solvents. The analyzed organs show a high level of phenolic compounds although the stems contains the highest total polyphenols (132.53±0.48 mg AGE/g Ex), flavonoids (48.99±0.65 mg RE/g Ex) and flavonols (34.93±0.29 mg QE/g Ex) contents. The phenolic fraction was dominated by sagerinic acid, caffeic acid glucoside and epigallocatechin, detected using HPLC-PDA/ESI-MS. The antioxidant activity of all extracts, evaluated by four in vitro tests, was high and varied significantly according to the type of solvent used and the plant organ. The aqueous extracts of leaves exhibited the greatest inhibitory effect on alpha-amylase while the methanolic extract of leaves and stems revealed the most important acetylcholinesterase inhibitory effect. Hence, S. barceloi extracts could be used as a source of various bioactive molecules in pharmaceutical industry.

A comparative study of secondary metabolites profiling and biological activity of Smyrnium olusatrum L. leaf, flower and fruit.

Essential oil (EO) composition of Smyrnium olusatrum was characterised by high proportion of furanosesquiterpenes (51.66-69.35%). The leaf methanolic extract composition was found to be rich with Quercetin-O-hexoside (39.78%). Apigenin 6,8-di-Chexoside represent the major component of flower (18.2%) and fruits (18.82%). Flower extract exhibited the highest contents of total phenolic (48.97 mg GAE/g) and flavonoid (52.63 mg RE/g). The ß-carotene and lycopene contents were in the order of 4.55-26.14 mg/100g, and 8.00-49.45 mg/100g, respectively. Methanolic extracts and EOs of different organs were found to possess antioxidant activities, as determined by scavenging effect, chelating activity and ß-carotene-linoleic acid model system. Furthermore, Fruit S. olusatrum EO exhibited a potent inhibitory activity against Acetylcholinesterase, while the methanolic extract showed a weaker activity. The methanolic extract displayed inhibitory effects on α-amylase, whereas the EOs was not as efficient in inhibiting this enzyme. The observed level of biological activities varied depending on the specific extracts and organs studied.

Phytoprostanes and phytofurans: Bioactive compounds in aerial parts of Acacia cyanophylla Lindl.

The relevance of oxylipins as biomarkers of oxidative stress has been established in recent years. Phytoprostanes and phytofurans are plant metabolites derived from peroxidation of α-linolenic acid (ALA) induced by ROS. Previous findings have suggested new valuable biological properties for these new active compounds in the frame of diverse pathophysiological situations and health constraints. Lipidomic profiling of different aerial parts of the same Acacia cyanophylla Lindl. specimen, was evaluated for the first time here, using LC-MS/MS technology. Analysis revealed the existence of six PhytoPs and three PhytoFs. Stems have the highest amount of these metabolites with 179.35 ng/g and 320.79 ng/g respectively. This first complete profile paves the way to explore Acacia cyanophylla Lindl. as a source of plant oxylipins for therapeutic or pharmaceutical uses.

Influence of droplet size on the antibacterial efficacy of citral and citronella oil nanoemulsions in polysaccharide coated fresh-cut apples.

Fresh-cut fruits are highly perishable and susceptible to bacterial contamination. Polysaccharides edible coating loaded with essential oils nanoemulsions have the potential to extend shelf life and improve quality of fruits. The effectiveness of this approach is dependent on the properties of the nanoemulsions, such as droplet size (DS) and stability. This study aimed to optimize the production of citral (CT) and citronella oil (CTO) nanoemulsions (CT-CTO-NEs) incorporated in edible coating film to be used as natural antimicrobial agent in fresh-cut apples. After testing different combinations of surfactant (tween 80) and cosurfactant (propylene glycol) to obtain stable oil-in-water (o/w) nanoemulsions, the results demonstrated that optimized CT-CTO-NEs with DS less than 500 nm have been successfully achieved with high stability for 3 weeks at 4 °C. In addition, CT-CTO-NEs were obtained by In situ formation under magnetic stirring without applying complex high shear homogenization processes. Desired stability of CT-CTO-NEs also has been achieved within semi-solid matrix (sodium alginate cross-linked film). The relationship between DS and antibacterial activity was observed, with the smallest DS (< 100 nm) showing the highest antibacterial efficacy against Listeria monocytogenes and Escherichia coli. These results emphasize the importance of DS in the effectiveness of CT-CTO-NEs as an antibacterial coating for fresh-cut fruits.

Insights for the control of dried-fruit beetle Carpophilus hemipterus (Nitidulidae) using rosemary essential oil loaded in chitosan nanoparticles.

Natural insecticidal products, essentially essential oils and their bioactive compounds are available as an excellent alternative method to control insect pests as well as they are less toxic to human health. However, due to their volatile constituents, encapsulation could be considered as the most suitable solution for their practical application. Therefore, this study aims to explore the insecticidal toxicity of chitosan nanoparticles loaded with Rosmarinus officinalis essential oil against adults of Carpophilus hemipterus. Chitosan nanoparticles were prepared by ionic gelation method with an encapsulation efficiency 41.543.1% and loading capacity 5.24G0.28%. Results revealed that chitosan nanoparticles loaded rosemary oil exhibited interesting insecticidal toxicity towards C. hemipterus adults in stored dates with 50.73% mortality. Overall, this work pointed out that the innovative design method based on chitosan-nanoparticles loaded rosemary oil can be promoted in integrated pest management program for stored date pests.

Laurel essential oil: biological activities and application for semolina preservation against the red flour beetle Tribolium castaneum (Tenebrionidae).

The phytochemical composition of Laurus nobilis essential oil and their anticholinesterase, antioxidant, and insecticidal potential were studied. Also, the oil volatile fraction was compared in semolina at the beginning and after storage periods. For that, a headspace solid-phase-microextraction analysis (HS-SPME) coupled with gas chromatography and mass spectrometry was undertaken. Significant quantitative and qualitative differences of the oil volatile fraction were detected according to storage periods and occupation space ratios. Additionally, anti-acetylcholinesterase activity of L. nobilis oil against T. castaneum adults was evaluated. Results revealed that insecticide activity varied according to storage duration and occupation space. Besides, the oil acts on acetylcholine hydrolysis by inhibiting the activity of acetylcholinesterase. These results highlighted that L. nobilis essential oil may be recommended as an eco-friendly alternative for preserving semolina during storage.

Lipid Profile Quantification and Species Discrimination of Pine Seeds through NIR Spectroscopy: A Feasibility Study.

Pine seeds are known for their richness in lipid compounds and other healthy substances. However, the reference procedures that are commonly applied for their analysis are quite laborious, time-consuming, and expensive. Therefore, it is important to develop rapid, accurate, multi-parametric, cost-effective and, essentially, environmentally friendly analytical techniques that are easily implemented at an industrial scale. The viability of using near-infrared (NIR) spectroscopy to analyse the seed lipid content and profile of three different pine species (Pinus halepensis, Pinus brutia and Pinus pinaster) was investigated. Moreover, species discrimination using NIR was also attempted. Different chemometric models, namely partial least squares (PLS) regression, for lipid analysis, and partial least square-discriminant analysis (PLS-DA), for pine species discrimination, were applied. In relation to the discrimination of pine seed species, a total of 90.5% of correct classification rates were obtained. Regarding the quantification models, most of the compounds assessed yielded determination coefficients (R2P) higher than 0.80. The best PLS models were obtained for total fat, vitamin E, saturated and monounsaturated fatty acids, C20:2, C20:1n9, C20, C18:2n6c, C18:1n9c, C18 and C16:1. Globally, the obtained results demonstrated that NIR spectroscopy is a suitable analytical technique for lipid analysis and species discrimination of pine seeds.

Genetic diversity and population structure of Tunisian wild Kermes oak (Quercus coccifera L.): Assessment by ISSR molecular markers and implication for conservation.

BACKGROUND: In Tunisia, Kermes oak (Quercus coccifera L.) populations are severely destroyed due to deforestation. Nowadays, no preservation programs are attempted, yet, to conserve and promote the potential value of this resource. In this work, we assessed the genetic diversity of seven natural Tunisian populations of Q. coccifera from different bioclimates using Inter-Simple Sequence Repeats molecular markers. The distribution of the genetic diversity of Q. coccifera constitutes the pioneer step in the process of the conservation of the species. METHODS AND RESULTS: Nine selected ISSR markers were analyzed to characterize the genetic profiles of 70 different genotypes. The ISSR primers produced 64 loci ranging from 6 (UBC809 and UBC810) to 9 (UBC873) with an average of 7.11 at the species level. The average percentage of the polymorphic loci varied from 64.06% (Tabarka) to 76.56% (El Haouaria). The analyzed genotypes (70 individuals) revealed a high level of genetic diversity at species level (Na = 1.697; Ne = 1.517; He = 0.289; I = 0.418). The major proportion of the variation was attributable to individual differences within populations (76.07%). Analysis of molecular variance revealed also significant differentiation among all populations (ΦST = 0.245) and among populations within bioclimates (ΦSC = 0.233), even at a low scale space. The UPGMA and the PCoA analyses showed that most populations clustered independently to bioclimate or geographical distance indicating that genetic differentiation mainly occurs at local space scale due to genetic drift. CONCLUSIONS: The in-situ conservation of the species should be maintained on natural populations as a forest genetic resources. Moreover, ex-situ conservation should involve the selection of genotypes with extensive collection of seeds and cuttings from different populations of the target area.

Morphological and Chemical Differentiation between Tunisian Populations of Pinus halepensis, Pinus brutia, and Pinus pinaster.

The lipid fraction of seeds from different pine species and populations was studied regarding total lipid content, fatty acid profile and vitamin E composition. The investigated seeds contained a high percentage of lipid (13.6 to 31.5 %). Lipid fractions were found to be rich in vitamin E, which varied significantly among species and populations. P. halepensis (Ph-Hn) showed the highest content of vitamin E (256.3 mg/kg of seeds) and the uppermost content of α-tocopherol (44 mg/kg). However, P. halepensis (Ph-Kas) was the richest in γ-tocopherol (204.9 mg/kg). Lipid fractions had a low content of δ-tocopherol (1.2 to 3.6 mg/kg. The highest content of γ-tocotrienol (∼18 %) was determined for P. halepensis (Ph-Dc and Ph-Hn). Thirteen fatty acids were identified by GC-FID with significant variation between the investigated species. The linoleic acid was the major fatty acid followed by oleic acid and palmitic acid. The chemical differentiation among species for the composition of fatty acids and vitamin E was confirmed by PCA. Significant correlations were observed between the content of vitamin E and fatty acids and ecological parameters of P. halepensis populations.

Arginase inhibitory properties of flavonoid compounds from the leaves of Mulberry (Morus alba, Moraceae).

OBJECTIVES: We aimed to isolate and identify bioactive molecules from Morus alba (Moraceae) leaves having arginase inhibitory activity towards the combat of clinical outcomes related to endothelial dysfunction. METHOD: Extraction and isolation were carried out by successive macerations, prepurification by using a Solid Phase Extraction (SPE) and separation using preparative PLC. The structures of the isolated components were established and confirmed by spectroscopic analyses, including the ESI-HRMS and NMR spectroscopic investigations. Biological evaluation was performed by using an in vitro assay with liver bovine purified arginase and by an ex vivo aortic ring study. KEY FINDINGS: We demonstrated that a phenolic extract from the leaves of M. alba possesses mammalian arginase inhibitory capacities. Investigation of the chemical constituents of its leaves results in the isolation and identification of ten compounds investigated in vitro for their arginase inhibitory capacities. Four compounds showed significant inhibition of arginase, with percentage inhibition ranging from 54% to 83% at 100 µm. In isolated rat aortic rings incubated with NO synthase inhibitor, Luteolin-7-diglucoside compound (2) was able to increase acetylcholine-induced relaxation. CONCLUSIONS: These results demonstrated the attractive ability of M. alba to be a potential source for the discovery of new active products on vascular system.

Thin-layer chromatography-bioautographic method for the detection of arginase inhibitors.

Arginase represents a promising therapeutic target for various pathologies including inflammatory, cardiovascular, and parasitic diseases or cancers. In the current work, we report, for the first time, about the development of a thin-layer chromatography-based bioautography which can be used to rapidly detect arginase inhibitors in complex matrices such as plant extracts. The assay is based on the detection of urea produced by arginase using the coloring reagent α-isonitrosopropiophenone, resulting in the formation of a pink background on thin-layer chromatography plates. The assay conditions were optimized in order to provide sufficient contrast between the pink colored thin-layer chromatography plate and the clearer zones generated by the presence of arginase inhibitors. Different parameters were tested, such as incubation time and temperature, atmospheric conditions, as well as substrate and enzyme concentrations. This technique makes it possible to detect 0.1 µg of a known arginase inhibitor, Nω -hydroxy-nor-Arginine, after it has been spotted, either pure or mixed with a Myrtus communis methanolic fruit extract, and the plate has been developed in an appropriate solvent. The newly developed method was used to reveal the presence of an inhibitor in hempseed cakes (Cannabis sativa L.).

Interspecific variability of 1,8-cineole content, phenolics and bioactivity among nine Eucalyptus taxa growing under the sub-humid bioclimate stage.

Background Eucalyptus essential oils and extracts are used since the ancient times in alternative medicine. The 1,8-cineole is the most significant constituent of Eucalyptus essential oil, while phenolic contents define the value of eucalyptus extracts. Based on the last considerations, interspecific variability of 1,8-cineole content, phenolics and antioxidant potentials among nine Eucalyptus taxa growing under the sub-humid bioclimate stage of Tunisia was investigated. Methods Essential oil profiling was assessed based on gas chromatography-mass spectrometry analysis. Total phenolic and flavonoid contents were assessed using Folin-Ciocalteau and aluminium chloride colorimetric methods, respectively. The antioxidant ability of Eucalyptus volatile metabolites and extracts was achieved based on two test systems namely DPPH and FRAP assays. Results Qualitative and quantitative variations in the composition of essential oils according to the studied taxon were shown. The total phenolic and flavonoid contents varied also significantly among the investigated samples. Based on the obtained results, the species Eucalyptus sideroxylon exhibits the highest 1,8-cineole content (76.24 ± 0.86), total phenolics and flavonoids contents (38.5 ± 1.4 mg GAE /g DW and 18.6 ± 0.3 mg RE /g DW, respectively). Moreover this species highlighted the highest free radical-scavenging ability and ferric reducing power for both essential oil and methanolic extracts. Chemometric multivariate analysis showed the classification of the nine studied taxa to three clusters. Conclusions The pattern of 1,8-cineole concentration, phenolic and flavonoid contents for the studied nine Eucalyptus species and hybrid showed E. sideroxylon species as the potential candidate for further improvement strategies regarding the production of eucalyptus essential oils and phenolics with high quality for pharmaceutical industry.

Phytochemicals, antioxidant, anti-acetyl-cholinesterase, and antimicrobial activities of decoction and infusion of Pelargonium graveolens.

In Tunisia, Pelargonium graveolens is widely consumed as a food aromatizing hydrosol. Recent studies have shown the potential of plant solvent-free extracts as food and pharmaceutical natural additives. Accordingly, in this study, we investigate the phenolic content, the volatile fractions of green P. graveolens extracts such as infusion and decoction, and we evaluate their biological activities. The total phenolic content of the infusion (27.05 mg GAE/gDM) is significantly different from that of decoction (31.2 mg GAE/gDM). The GC-MS analysis identified about twenty volatile components in both extracts. The DPPH inhibition and the ß-carotene bleaching tests of the infusion and the decoction had considerable results. Besides, infusion and decoction exhibited a relatively high anti-acetyl-cholinesterase activity and a considerable antimicrobial activity against S. aureus, among three tested pathogenic bacteria.

Phytochemical profile and insecticidal activity of Agave americana leaf extract towards Sitophilus oryzae (L.) (Coleoptera: Curculionidae).

The main objective of the present study is to introduce a new and ecologically safe method for managing the rice weevil, Sitophilus oryzae. Therefore, the Agave americana leaf extract's phytochemical profile, and its insecticidal activity against the adults of S. oryzae were evaluated. The A. americana leaf extract was screened for the following phytochemicals: total phenolics (14.70 ± 0.31 mg GAE/g FW), total flavonoids (5.15 ± 0.18 mg RE/g FW) and saponins (10.32 ± 0.20 mg OAE/g FW). The HPLC-ESI/TOF-MS analysis results revealed that flavonoid glycosides (kaempferol, quercetin, and isorhamnetin derivates) were the major phenolic compounds of the A. americana leaf extract. In addition, the GC-MS analysis identified n-alkanes (77.77%) as significant compounds of the lipophilic fraction from the leaf extract. Moreover, the insecticidal potential was assessed through contact and repellent bioassays towards the rice weevil adults. The LD50, LC50, and RC50 values were 10.55 µg/insect, 8.99 µg/cm2, and 0.055 µg/cm2 for topical application method, treated filter-paper method, and repellent bioassay, respectively. Furthermore, the A. americana leaf extract inhibited digestive enzyme activities, and median inhibition concentrations IC50 were evaluated to be 146.06 ± 1.74 and 86.18 ± 1.08 µg/mL for α-amylase and protease, respectively. Overall, our results highlighted the promising potential of the leaf extract against S. oryzae adults, allowing us to recommend the extract under investigation as an ecofriendly alternative to synthetic insecticides.

Post-harvest management control of Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae): new insights through essential oil encapsulation in cyclodextrin.

BACKGROUND: Essential oils are reported to be bio-insecticides. However, problems related to their volatility, oxidation and poor water solubility need to be solved before they can be considered as replacement pest control methods. Thus, an appropriate formulation is needed for commercial use. In this work, a new control method based on the use of a powdered cyclodextrin (CD)/1,8-cineole inclusion complex was assessed against larvae and adults of Ectomyelois ceratoniae (Zeller) in comparison with two Rosmarinus officinalis (L.) essential oils, free 1,8-cineole (oils major compound) and a mixture of 50% CD/1,8-cineole inclusion complex and 50% free 1,8-cineole. RESULTS: Solid CD/1,8-cineole complex was more toxic against E. ceratoniae larvae than the two crude essential oils. At a concentration of 15 µL liter-1 air, the respective mortalities were 94.12%, 35.29% and 19.61% for solid CD/1,8-cineole complex, Thala and Cap Zbib oils after 37 days of exposure. Moreover, the solid CD/1,8-cineole complex achieved 5% adult emergence versus 68.33% for Cap Zbib and 55% for Thala oils. The half-life of solid CD/1,8-cineole inclusion complex (10.98 days) was considerably longer than that of the mixture (7.53 days) or free 1,8-cineole (3.43 days). CONCLUSION: This work highlights the utility of essential oil encapsulation in CD to overcome restrictions when used to control the date moth E. ceratoniae during storage. © 2019 Society of Chemical Industry.

Relationship between chemotypic and genetic diversity of natural populations of Artemisia herba-alba Asso growing wild in Tunisia.

A total of 80 individuals collected from eight populations growing wild in different geographic zones were considered to assess the intraspecific variability of essential oil composition, genetic diversity and population structure of Artemisia herba-alba. The essential oil composition varied significantly between populations. Essential oil profiles were classified into four chemotypes (trans-sabinyl acetate, α-thujone/trans-sabinyl acetate, camphor and α-thujone/camphor/ß-thujone). Despite significant correlation between the amount of some essential oil compounds and a set of climatic data, the global chemical divergence among populations was not related to their bioclimatic and geographic appurtenances. A high level of genetic diversity within populations was revealed either with RAPD and ISSR markers (Na = 1.67, PPL = 66.5%, H = 0.26, I = 0.38 and Na = 1.7, PPL = 69.8%, H = 0.26, I = 0.38, respectively). The level of genetic diversity varied across populations and chemotypes. Populations from the α-thujone/trans-sabinyl acetate chemotype exhibited the highest genetic diversity as revealed by the RAPD markers. However, populations from α-thujone/camphor/ß-thujone chemotype showed the important genetic variation determined by ISSR markers. A significant genetic differentiation among populations and among chemotypes was detected. The combined analysis showed a significant correlation (r = 0.484, p = .032) between the chemical and molecular markers. The PCA, performed on percentages of major oil compounds and the frequencies of polymorphic RAPD and ISSR bands, divided populations according to their chemotypic classification. Taking into consideration the current situation of A. herba-alba populations and their endangered habitats, these results are of value in order to ensure the in-situ and ex-situ conservation of this medicinal species.

Essential Oil Variability in Natural Populations of Artemisia campestris (L.) and Artemisia herba-alba (Asso) and Incidence on Antiacetylcholinesterase and Antioxidant Activities.

The intraspecific variability of Artemisia herba-alba and A. campestris essential oils and the evaluation of their antioxidant and antiacetylcholinesterase activities were determined. Artemisia herba-alba essential oil was found rich in camphor (19.61%), α-thujone (19.40%), ß-thujone (9.44%), chrysanthenone (9.26%), and trans-sabinyl acetate (8.43%). The major compounds of A. campestris essential oil were germacrene D (16.38%), ß-pinene (16.33%), and limonene (9.17%). Significant variation in the essential oil composition was observed among populations of each species. The divergence between populations was attributed to the variation of some climatic factors such as altitude, annual rainfall, winter cold stress, summer precipitation, summer drought stress, evapotranspiration, and humidity. Artemisia herba-alba and A. campestris essential oils exhibited promising antioxidant and antiacetylcholinesterase activities. The level of activity varied significantly according to the species and the essential oil. The highest scavenging activity (IC50 = 0.14 mg/ml) and the uppermost capacity to prevent ß-carotene bleaching (IC50 = 0.10 mg/ml) characterized A. campestris from population 6. A. campestris population 3 possessed the uppermost ability to reduce ferric ions (450.7 µmol Fe2+ /g EO). The population 2 of A. campestris showed the strongest antiacetylcholinesterase activity (IC50 = 0.02 mg/ml). The variation of these activities between the essential oils was explained by their composition differences.

Essential Oils of Myrtaceae Species Growing Wild in Tunisia: Chemical Variability and Antifungal Activity Against Biscogniauxia mediterranea, the Causative Agent of Charcoal Canker.

The chemical composition of five Eucalyptus species and five Myrtus communis L. populations was investigated using GC/MS and GC-FID. For Eucalyptus essential oils, 32 compounds, representing 88.56 - 96.83% of the total oil according to species, were identified. The main compounds were 1,8-cineole, α-pinene, p-cymene, γ-gurjunene, α-aromadendrene, and ß-phellandrene. For Myrtle essential oils, 26 compounds, representing 93.13 - 98.91% of the total oil were identified. α-Pinene, 1,8-cineole, linalool, and myrtenyl acetate were found to be the major compounds. Principal component analysis (PCA) showed chemical differentiation between Eucalyptus species and between Myrtle populations. Biscogniauxia mediterranea, the causative agent of charcoal canker, was identified according to its morphological and molecular characteristics. Essential oils of the investigated Eucalyptus species and Myrtle populations were tested for their antifungal capacity against this fungus. The antifungal activity varied according to the essential oil composition. Biscogniauxia mediterranea exhibited powerful resistance to some essential oils including them of Eucalyptus lehmannii and Eucalyptus sideroxylon but it was very sensitive to Eucalyptus camaldulensis oil (IC50  = 3.83 mg/ml) and M. communis oil from Zaghouan (IC50  = 1 mg/ml). This sensitivity was found to be correlated to some essential oil compounds such as p-cymene, carvacrol, cuminaldehyde, and linalool.