Selected antimicrobial essential oils to eradicate multi-drug resistant bacterial biofilms involved in human nosocomial infections.

Biofilms are the primary source of contamination linked to nosocomial infections by promoting bacterial resistance to antimicrobial agents, including disinfectants. Using essential oils, this study aims to inhibit and eradicate the biofilm of enterobacteria and staphylococci responsible for nosocomial infections at Guelma Hospital, northeastern Algeria. Thymbra capitata, Thymus pallescens and Artemesia herba-alba essential oils were evaluated against clinical strains of Klebsiella pneumoniae, Escherichia coli, and Staphylococcus aureus. The antimicrobial activity of the essential oils under consideration was assessed using an agar disc diffusion assay and the determination of minimum inhibitory concentrations (MICs). In addition, the crystal violet method and scanning electron microscopy (SEM) evaluated biofilm inhibition and eradication by those antimicrobial agents. The results indicate that T. pallescens essential oil was the most effective antimicrobial agent against pathogenic bacteria, with large zones of inhibition (up to 50 mm against S. aureus), low MICs (0.16 to 0.63 mg/mL), and powerful biofilm eradication up to 0.16 mg/mL in both 24 h and 60-min exposure times. Thus, Algerian thyme and oregano could be used in various ways to combat the biofilm that causes nosocomial infection in local hospitals.

First Phytochemical Profiling and In-Vitro Antiprotozoal Activity of Essential Oil and Extract of Plagiochila porelloides.

Volatiles metabolites from the liverwort Plagiochila porelloides harvested in Corsica were investigated by chromatographic and spectroscopic methods. In addition to already reported constituents, three new compounds were isolated by preparative chromatography and their structures were elucidated by mass spectrometry (MS) and NMR experiments. Hence, an atypic aliphatic compound, named 1,2-dihydro-4,5-dehydronerolidol and two isomers, (E) and (Z), possessing an unusual humbertiane skeleton (called p-menth-1-en-3-[2-methylbut-1-enyl]-8-ol) are newly reported and fully characterized in this work. The in vitro antiprotozoal activity of essential oil and extract of P. porelloides against Trypanosoma brucei brucei and Leishmania mexicana mexicana and cytotoxicity were determined. Essential oil and Et2O extract showed a moderate activity against T. brucei with IC50 values: 2.03 and 5.18 µg/mL, respectively. It is noteworthy that only the essential oil showed a high selectivity (SI = 11.7). Diethyl oxide extract exhibited moderate anticancer (cancerous macrophage-like murine cells) activity and also cytotoxicity (human normal fibroblast) with IC50 values: 1.25 and 2.96 µg/mL, respectively.

Smart IM-MS and NMR study of natural diastereomers: the study case of the essential oil from Senecio transiens.

Unambiguous identification of the components of a natural mixture remains a challenging and meticulous issue. Usually, different analytical techniques and laborious separation protocols are employed; nevertheless, in some cases, delicate and equivocal problems are hardly addressed by traditional methods. In this context, an original methodology for the analysis of natural samples consisting of recent mass spectrometry methods based on ion mobility (MS-IM) is proposed. As an example, a polar fraction obtained by the essential oil prepared from Senecio transiens, an endemic plant harvested on the Corsica Island, was selected for this study to show how IM-MS-based methods easily provide very useful insights suggesting the presence of two diastereomers. To unambiguously confirm this hypothesis and verify reliability of the IM-MS results, the purified compounds were further analysed by means of nuclear magnetic resonance (NMR) methodologies, allowing the structural elucidation and the identification of two new natural compounds, diastereomers of 4-acetoxy-5,9-dimethyl-3-(2-methylpropenyl)-2-oxabicyclo[4.4.0] dec-9-ene, reported here for the first time.

Guaianolide Derivatives from the Invasive Xanthium spinosum L.: Evaluation of Their Allelopathic Potential.

Ziniolide, xantholide B (11α-dihydroziniolide), and 11ß-dihydroziniolide, three sesquiterpene lactones with 12,8-guaianolide skeletons, were identified as volatile metabolites from the roots of Xanthium spinosum L., an invasive plant harvested in Corsica. Essential oil, as well as hydrosol and hexane extracts, showed the presence of guaianolide analogues. The study highlights an analytical strategy involving column chromatography, GC-FID, GC-MS, NMR (1D and 2D), and the hemi-synthesis approach, to identify compounds with incomplete or even missing spectral data from the literature. Among them, we reported the 1H- and 13C-NMR data of 11ß-dihydroziniolide, which was observed as a natural product for the first time. As secondary metabolites were frequently involved in the dynamic of the dispersion of weed species, the allelopathic effects of X. spinosum root's volatile metabolites were assessed on seed germination and seedling growth (leek and radish). Essential oil, as well as hydrosol- and microwave-assisted extracts inhibited germination and seedling growth; root metabolite phytotoxicity was demonstrated. Nevertheless, the phytotoxicity of root metabolites was demonstrated with a more marked selectivity to the benefit of the monocotyledonous species compared to the dicotyledonous species. Ziniolide derivatives seem to be strongly involved in allelopathic interactions and could be the key to understanding the invasive mechanisms of weed.

Direct Identification of α-Bisabolol Enantiomers in an Essential Oil Using a Combined Ion Mobility-Mass Spectrometry/Quantum Chemistry Approach.

Enantiomer-specific identification of chiral molecules in natural extracts is a challenging task, as many routine analytical techniques fail to provide selectivity in multicomponent mixtures. Here we describe an alternative approach, based on the combination of ion mobility-mass spectrometry (IM-MS) and quantum chemistry (QM), for the direct enantiomers differentiation in crude essential oils. The identification of α-bisabolol enantiomers contained in the raw essential oil (EO) from the Corsican Xanthium italicum fruits is reported as a proof-of-concept. Accordingly, IM-MS experiments performed in Ag+-doped methanol revealed the presence of both (+)- and (-)-α-bisabolol in the EO, while molecular simulations provided the structures of the two α-bisabolol enantiomer silver(I) adducts.

Caution: Chemical Instability of Natural Biomolecules During Routine Analysis.

Natural products (NPs) constitute a significant source of active biomolecules widely used in medicine, pharmacology and cosmetics. However, NPs structural characterization has the drawback of their chemical instability during the extraction steps and their likely transformation during the analytical protocol. In particular, tamariscol and conocephalenol are two compounds largely used in the cosmetic industry for their odorant properties. Thus, in the present study, we focused on the evolution of these two metabolites (extracted from Frullania tamarisci and Conocephalum conicum, respectively), as followed by NMR. Interestingly, we found that, once dissolved in deuterated chloroform, these two tertiary alcohols are both subjected to transformation processes, leading to degradation compounds with altered structures. Accordingly, these detected degradation compounds have been fully characterized by NMR and the experimental findings were supported by computational chemistry data.

Essential Oil of Algerian Eryngium campestre: Chemical Variability and Evaluation of Biological Activities.

The chemical composition of essential oils extracted from aerial parts of Eryngium campestre collected in 37 localities from Western Algeria was characterized using GC-FID and GC/MS analyses. Altogether, 52 components, which accounted for 70.1 to 86.8% of the total composition oils were identified. The main compounds were Germacrene D (0.4-53.4%), Campestrolide (1.6-35.3%), Germacrene B (0.2-21.5%), Myrcene (0.1-8.4%), α-Cadinol (0.2-7.6%), Spathulenol (0.1-7.6%), Eudesma-4(15)-7-dien-1-ß-ol (0.1-7.6%) and τ-Cadinol (0.3-5.5%). The chemical compositions of essential oils obtained from separate organs and during the complete vegetative cycle of the plant were also studied. With the uncommon 17-membered ring lactone named Campestrolide as the main component, Algerian E. campestre essential oils exhibited a remarkable chemical composition. A study of the chemical variability using statistical analysis allowed the discrimination of two main clusters according to the geographical position of samples. The study contributes to the better understanding of the relationship between the plant and its environment. Moreover, the antimicrobial activity of the essential oil was assessed against twelve strains bacteria and two yeasts involved in foodborne and nosocomial infections using paper disc diffusion and dilution agar assays. The in vitro study demonstrated a strong activity against Gram-positive strains such as S. aureus, B. cereus, and E. faecalis. The cytotoxicity and antiparasitic activities (on Lmm and Tbb) of the collective essential oil and one sample rich in campestrolide, as well as some enriched fractions or fractions containing other terpenic compounds, were also analyzed. Campestrolide seems to be one compound responsible for the cytotoxic and antileishmanial effect, while myrcene or/and trans-ß-farnesene have a more selective antitrypanosomal activity.

Chemical Composition and Biological Investigations of Eryngium triquetrum Essential Oil from Algeria.

The chemical composition, antibacterial and antioxidant activities of the essential oil obtained from Eryngium triquetrum from Algeria were studied. The chemical composition of sample oils from 25 locations was investigated using GC-FID and GC/MS. Twenty-four components representing always more than 87% were identified in essential oils from total aerial parts of plants, stems, flowers and roots. Falcarinol is highly dominant in the essential oil from the roots (95.5%). The relative abundance of falcarinol in the aerial parts correlates with the phenological stages of the plant. Aerial parts of E. triquetrum produce an essential oil dominated by falcarinol during the early flowering stage, and then there is a decrease in falcarinol and rebalancing of octanal during the flowering stage. To our knowledge, the present study is the first report of the chemical composition of E. triquetrum essential oil. Evaluation of the antibacterial activity by means of the paper disc diffusion method and minimum inhibitory concentration assays, showed a moderate efficiency of E. triquetrum essential oil. Using the DPPH method, the interesting antioxidant activity of E. triquetrum essential oil was established. These activities could be attributed to the dominance of falcarinol. The outcome of our literature search on the occurrence of falcarinol in essential oils suggests that E. triquetrum from Algeria could be considered as a possible source of natural falcarinol.

Structural Elucidation and Cytotoxicity of a New 17-Membered Ring Lactone from Algerian Eryngium campestre.

The chemical composition of a hexanic extract of Eryngium campestre, obtained from its aerial parts, was investigated by GC-FID, GC/MS, HRMS, NMR and VCD analyses. The main compounds were germacrene D (23.6%), eudesma-4(15)-7-dien-1-ß-ol (8.2%) and falcarindiol (9.4%), which are associated with a new uncommon and naturally found 17-membered ring lactone. This 17-membered ring features conjugated acetylenic bonds, named campestrolide (23.0%). The crude extract showed moderate antitrypanosomal (Trypanosoma brucei brucei), antileishmanial (Leishmania mexicana mexicana) and anticancer (cancerous macrophage-like murine cells) activities, and also displayed cytotoxicity, (human normal fibroblasts) in similar concentration ranges (IC50 = 3.0, 3.9, 4.0 and 4.4 µg/mL respectively). Likewise, campestrolide displayed low activity on all tested cells (IC50: 12.5⁻19.5 µM) except on Trypanosoma, on which it was very active and moderately selective (IC50 = 2.2 µM. SI= 8.9). In conclusion, the new compound that has been described, displaying a singular structure, possesses interesting antitrypanosomal activity that should be further investigated and improved.

Chemical Composition of Essential Oils of Xanthium spinosum L., an Invasive Species of Corsica.

Xanthium spinosum L. is a highly invasive plant originated from South America throughout the world as well as in Corsica Island. The chemical composition of X. spinosum essential oils from 25 Corsican locations was investigated using GC-FID and GC/MS. Seventy-four components, which accounted for 96.2% of the total amount, were reported for the first time in the essential oil from aerial parts. The main compounds were eudesma-4(14),7-dien-1ß-ol (61; 21.3%), germacrene D (36; 8.8%) and cadalene (60; 8.7%). Comparison with the literature highlighted the originality of the Corsican essential oil and eudesma-4(14),7-dien-1ß-ol could be used as taxonomical marker to the systematics of the Xanthium genus. The essential oils obtained from separate organs and during the plant vegetative cycle were also studied to gain more knowledge about the correlations between the volatile production and the phenological states of this weed. The production of oxygenated sesquiterpenes was predominant during the plant-flowering process. The study focuses on direct correlation between the chemical composition of individual 25 oil samples and the morphological differences of the plant. Our results have gained more knowledge about the secondary metabolite production that occurs during the plant life, they could be interesting in order to manage the dispersal of X. spinosum.

Essential Oils as Biocides for the Control of Fungal Infections and Devastating Pest (Tuta absoluta) of Tomato (Lycopersicon esculentum Mill.).

Thymus capitatus and Tetraclinis articulata essential oils as well their major components (carvacrol and α-pinene) were evaluated for their antifungal and insecticidal activities. Both oils showed good in vitro antifungal activity against Fusarium oxysporum, Aspergillus niger, Penicillium sp., Alternaria alternata, and Botrytis cinerea, the fungi causing tomato rot. In vivo results indicate the efficacies of both essential oils and carvacrol of reduce postharvest fungal pathogens, such as B. cinerea and Al. alternata that are responsible of black and gray rot of tomato fruit. Disease incidence of Al. alternata and B. cinerea decreased on average from 55% to 80% with essential oil of Th. capitatus and pure carcvacrol, while Te. articulata essential oil exhibited inhibition of fungal growth of 55% and 25% against Al. alternata and B. cinerea, respectively, with concentration of 0.4 µl/l air. The insecticidal activity of Th. capitatus and Te. articulata essential oils exhibited also a good insecticidal activity. At the concentration of 0.2 µl/ml air, the oils caused mortality over 80% for all larval stages of Tuta absoluta and 100% mortality for the first-instar after 1.5 h only of exposure. α-Pinene presented lower insecticidal and antifungal activities compared to essential oils of Th. capitatus, Te. articulata and pure carvacrol. Thus, these essential oils can be used as a potential source to develop control agents to manage some of the main pests and fungal diseases of tomato crops.

Chemical Variability, Antioxidant and Antifungal Activities of Essential Oils and Hydrosol Extract of Calendula arvensis L. from Western Algeria.

The chemical composition of the essential oils and hydrosol extract from aerial parts of Calendula arvensis L. was investigated using GC-FID and GC/MS. Intra-species variations of the chemical compositions of essential oils from 18 Algerian sample locations were investigated using statistical analysis. Chemical analysis allowed the identification of 53 compounds amounting to 92.3 - 98.5% with yields varied of 0.09 - 0.36% and the main compounds were zingiberenol 1 (8.7 - 29.8%), eremoligenol (4.2 - 12.5%), ß-curcumene (2.1 - 12.5%), zingiberenol 2 (4.6 - 19.8%) and (E,Z)-farnesol (3.5 - 23.4%). The study of the chemical variability of essential oils allowed the discrimination of two main clusters confirming that there is a relation between the essential oil compositions and the harvest locations. Different concentrations of essential oil and hydrosol extract were prepared and their antioxidant activity were assessed using three methods (2,2-diphenyl-1-picrylhydrazyl, Ferric-Reducing Antioxidant Power Assay and ß-carotene). The results showed that hydrosol extract presented an interesting antioxidant activity. The in vitro antifungal activity of hydrosol extract produced the best antifungal inhibition against Penicillium expansum and Aspergillus niger, while, essential oil was inhibitory at relatively higher concentrations. Results showed that the treatments of pear fruits with essential oil and hydrosol extract presented a very interesting protective activity on disease severity of pears caused by P. expansum.

Essential Oil Composition of Phagnalon sordidum (L.) from Corsica, Chemical Variability and Antimicrobial Activity.

The chemical composition of Phagnalon sordidum (L.) essential oil was investigated for the first time using gas chromatography and chromatography/mass spectrometry. Seventy-six compounds, which accounted for 87.9% of the total amount, were identified in a collective essential oil of P. sordidum from Corsica. The main essential oil components were (E)-ß-caryophyllene (14.4%), ß-pinene (11.0%), thymol (9.0%), and hexadecanoic acid (5.3%). The chemical compositions of essential oils from 19 Corsican locations were investigated. The study of the chemical variability using statistical analysis allowed identifying direct correlation between the three populations of P. sordidum widespread in Corsica and the essential oil compositions they produce. The in vitro antimicrobial activity of P. sordidum essential oil was evaluated and it exhibited a notable activity on a large panel of clinically significant microorganisms.

Chemical Variability and Biological Activities of Essential Oils of Micromeria inodora (Desf.) Benth. from Algeria.

The chemical composition of the essential oils isolated from the aerial parts of Micromeria inodora (Desf.) Benth. collected in 24 Algerian localities was investigated from the first time using GC-FID, GC/MS and 13 C-NMR. Altogether, 83 components which accounted for 94.7% of the total oil composition were identified. The main compounds were trans-sesquisabinene hydrate (1; 20.9%), α-terpinyl acetate (2; 19.8%), globulol (3; 4.9%), caryophyllene oxide (4; 4.3%), ß-bisabolol (5; 2.9%) and trans-7-epi-sesquisabinene hydrate (6; 2.6%). Comparison with the literature highlighted the originality of the Algerian M. inodora oil and indicated that 1 might be used as taxonomical marker. The study of the chemical variability allowed the discrimination of two main clusters confirming that there is a relation between the essential-oil compositions and the soil nature of the harvest locations. Biological activity of M. inodora essential oil was assessed against fourteen species of microorganisms involved in nosocomial infections using paper disc diffusion and dilution agar assays. The in vitro study demonstrated a good activity against Gram-positive strains such as Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, and Enterococcus faecalis, and moderate activity against Candida albicans. These results might be useful for the future commercial valorization of M. inodora essential oil as a promising source of natural products with potential against various nosocomial community and toxinic infections.

Essential-oil composition and chemical variability of Senecio vulgaris L. from Corsica.

The chemical composition of the essential oils isolated from the aerial parts of Senecio vulgaris plants collected in 30 Corsican localities was characterized using GC-FID and GC/MS analyses. Altogether, 54 components, which accounted for 95.2% of the total oil composition, were identified in the 30 essential-oil samples. The main compounds were α-humulene (1; 57.3%), (E)-ß-caryophyllene (2; 5.6%), terpinolene (3; 5.3%), ar-curcumene (4; 4.3%), and geranyl linalool (5; 3.4%). The chemical composition of the essential oils obtained from separate organs and during the complete vegetative cycle of the plants were also studied, to gain more knowledge about the plant ecology. The production of monoterpene hydrocarbons, especially terpinolene, seems to be implicated in the plant-flowering process and, indirectly, in the dispersal of this weed species. Comparison of the present results with the literature highlighted the originality of the Corsican S. vulgaris essential oils and indicated that α-humulene might be used as taxonomical marker for the future classification of the Senecio genus. A study of the chemical variability of the 30 S. vulgaris essential oils using statistical analysis allowed the discrimination of two main clusters according to the soil nature of the sample locations. These results confirmed that there is a relation between the soil nature, the chemical composition of the essential oils, and morphological plant characteristics. Moreover, they are of interest for commercial producers of essential oil in selecting the most appropriate plants.

Chemical variability and antioxidant activity of Limbarda crithmoides L. essential oil from Corsica.

The chemical compositions of 25 Corsican Limbarda crithmoides ssp. longifolia essential oils were investigated for the first time using GC-FID, GC/MS, and NMR analyses. Altogether, 65 compounds were identified, accounting for 90.0-99.3% of the total oil compositions. The main components were p-cymene (1; 15.1-34.6%), 3-methoxy-p-cymenene (4; 11.8-28.5%), 2,5-dimethoxy-p-cymenene (5; 5.9-16.4%), thymol methyl ether (6; 1.3-14.9%), α-phellandrene (2; 0.9-11.9%), and α-pinene (3; 0.2-13.4%). The chemical variability of the Corsican oil samples was studied using multivariate statistical analysis, which allowed the discrimination of two main clusters. A direct correlation between the water salinities of the plant locations and the chemical compositions of the L. crithmoides essential oils was evidenced. Indeed, essential oils rich in 1 (30.4-34.6%) were found in samples growing in the wetlands of the southern oriental coast, which exhibit high salinity levels (24.4±0.2-33.9±0.2 ppt), and essential oils with lower contents of 1 (15.1-27.3%) were isolated form samples growing in the wetlands of northern Corsica, which exhibit lower salinity levels (10.90±0.20-15.47±0.15 ppt). The antioxidant potential of L. crithmoides essential oil was also investigated, by assessing the DPPH(.) - and ABTS(.+) -scavenging activities and the reducing power of ferric ions, and was found to be interesting. Moreover, using bioassay-guided fractionation of the essential oil, a higher antioxidant activity was obtained for the oxygenated fraction and both ester and alcohol subfractions.

A combined in vitro-in silico approach for the discovery of novel endogenous enzymatic and ctDNA sequence of bioactive molecules from aerial and root parts of Centaurea sulphurea as antioxidant's agents.

The excess free radicals not neutralized by the antioxidant defenses damage the essential macromolecules of our cells, causing abnormalities in the expression of genes and membrane receptors, cell proliferation or death, immune disorders, mutagenesis, deposits of proteins or lipofuschin in tissues. The first objective of this study was to elucidate the composition of the essential oil of the aerial and root part of Centaurea sulphurea during beginning of the vegetative cycle (March), beginning of the flowering stage (April) and full bloom (May/June) using GC/FID and GC/MS. The second aim was to describe the antioxidant activity using three methods (2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric-reducing antioxidant power (FRAP), ß-carotene bleaching assay) and bioinformatical study of ctDNA sequence and three endogenous enzymes inhibition. The essential oils obtained from the root during the full bloom period consisted mainly of caryophyllene oxide, aplotaxene and (Z)-phytol. While, the aerial parts were dominated by caryophyllene oxide, verridiflorol and humulene epoxide II. The results showed that essential oil presented an excellent antioxidant activity with IC50 values of 2.06 g/L and 1.29 g/L, for aerial and root parts, compared to butylated hydroxyltoluene (BHT) and Ethylenediaminetetraacetic acid (EDTA) controls and the nicotinamide adenine dinucleotide phosphate (NADPH) co-crystallized inhibitor. The results of the molecular docking revealed that (Z)-phytol (Ligand 39) has an affinity to interact with ctDNA sequence, and three targets Endogenous enzymes. The molecular dynamics study was conducted for the best inhibitors (Z)-phytol. A few key residues were identified at the binding site of receptors. The in-silico assessment of the ADME properties and BOILED-Egg plot reveals that compound (Z)-phytol (L39) is permeable to the blood brain barrier and have high lipophilicity and high coefficient of skin permeability in the intestines with good bioavailability. The ADMET analysis also showed that this oxygenated diterpene is safer to replace the synthetic drugs with side effects. Further testing is needed to assess its effectiveness in reducing oxidative stress for use in the pharmaceutical industry.Communicated by Ramaswamy H. Sarma.

Evaluation of the antioxidant and anti-inflammatory activity of the Anacyclus valentinus L. essential oil and its oxygenated fraction.

AIM AND OBJECTIVE: Synthetic antioxidants and anti-inflammatories are widely used by the food and pharmaceutical industries. Like any synthetic product, these are toxic and represent a significant health risk. The objective of this study was to determine the chemical composition of Anacyclus valentinus essential oil and its oxygenated fraction, as well as their in-vitro antioxidant and anti-inflammatory properties. MATERIALS AND METHODS: The essential oil was hydrodistilled using a Clevenger-type device and the oxygenated fraction was obtained by column chromatography using diethyl ether. The essential oil and its oxygenated fraction were analysed by GC and GC/MS. The antioxidant activities were performed using three different methods Radical scavenging activity (DPPH), ß-carotene bleaching test, and the Ferric-Reducing Antioxidant Power (FRAP), using BHT as a positive control. The activity of anti-inflammatory of essential oil and its oxygenated fraction was assessed by the protein denaturation method using the diclofenac sodium as a positive control. RESULTS: The essential oil of Anacyclus valentinus was represented mainly by oxygenated sesquiterpene compounds (37.7%), hydrocarbon sesquiterpenes (14.7%), oxygenated monoterpenes (18.4%) and non-terpenic compounds (15.6%). The oxygenated fraction was composed mainly of oxygenated sesquiterpenes (40.6%), oxygenated monoterpenes (38.5%), and non-terpene compounds (19.4%). Essential oil and hydrosol extract showed antioxidant activity. The most potent activity was observed by the oxygenated fraction in the DPPH (IC50 = 8.2 mL/L) and ß-carotene bleaching (IC50 = 5.6 mL/L) tests. While the essential oil of A. valentinus showed very good anti-inflammatory activity with an IC50 of 0.3 g/L higher than that of diclofenac (IC50= 0.53 g/L). CONCLUSION: The results showed that the essential oil and the oxygenated fraction of A. valentinus are rich in sesquiterpene compounds and possess interesting antioxidant and anti-inflammatory properties. However, other studies are necessary to be able to offer these extracts to the pharmaceutical and food industries.

Efficacy of endemic Algerian essential oils against single and mixed biofilms of Candida albicans and Candida glabrata.

OBJECTIVES: This study investigated the in vitro effect of Origanum glandulosum, Ammoides verticillata, and Saccocalyx satureioides essential oils against planktonic cells and biofilms formed by single and mixed species of Candida albicans and Candida glabrata oral isolates. The effect of the essential oils in combination with amphotericin B on planktonic cells was also studied. DESIGN: The antifungal susceptibility of planktonic cells was evaluated by disc diffusion and broth microdilution methods. Resazurin assay and scanning electron microscopy (SEM) were employed to determine the antibiofilm activity. The combinatory effect was evaluated by the checkerboard method. Essential oils were characterized by gas chromatography-mass spectrometry (GC-MS). RESULTS: The minimal inhibitory concentrations (MICs) and the minimum fungicidal concentrations (MFCs) of the studied essential oils were ranged between 250 and 2000 µg/mL. Biofilms were inhibited and eradicated by the essential oils at sub-inhibitory concentrations of 500 and 1000 µg/mL, respectively. SEM studies revealed a reduction in the preformed biofilm as a result of Origanum glandulosum essential oil treatment for single and mixed biofilms. Synergistic activity was found when Origanum glandulosum essential oil was combined with amphotericin B against Candida albicans. GC-MS analysis revealed that thymol was the major compound in Origanum glandulosum (38.36 %) and Ammoides verticillata (48.99 %) essential oils, while Saccocalyx satureioides essential oil was dominated by borneol (27.36 %). CONCLUSIONS: The studied essential oils showed significant antifungal and antibiofilm activities, which support their effectiveness as promising candidates for the management of oral Candida infections.

Bicyclo[4.4.0]decane oxygenated sesquiterpenes from Eryngium maritimum essential oil.

Investigation of the essential oil of the aerial parts of Eryngium maritimum L. from Corsica led to the isolation of one known sesquiterpene (1) and three new oxygenated sesquiterpenes with a muurolane or cadinane skeleton (2-4). Structure assignments of 4 ßH -muurol-9-en-15-al (1), 4 ßH -cadin-9-en-15-al (2), 4 ßH -muurol-9-en-15-ol (3) and 4 ßH -cadin-9-en-15-ol (4) were carried out by GC/MS (EI and CI) and comprehensive 1D and 2D NMR spectroscopy. Antibacterial activity of Eryngium maritimum L. oil and column chromatography fractions have been investigated for the first time. The oxygenated fraction, which contains the four sesquiterpenes, was efficient against Listeria monocytogenes and Echerichia coli.