Lígia Salgueiro

Antifungal activity of Thymus oils and their major compounds

The increasing recognition and importance of fungal infections, the difficulties encountered in their treatment and the increase in resistance to antifungals have stimulated the search for therapeutic alternatives. Essential oils have been used empirically. The essential oils of Thymus (Thymus vulgaris, T. zygis subspecies zygis and T. mastichina subspecies mastichina) have often been used in folk medicine. The aim of the present study was to evaluate objectively the antifungal activity of Thymus oils according to classical bacteriological methodologies − determination of the minimal inhibitory concentration (MIC) and the minimal lethal concentration (MLC) − as well as flow cytometric evaluation. The effect of essential oils upon germ tube formation, an important virulence factor, was also studied. The mechanism of action was studied by flow cytometry, after staining with propidium iodide. The chemical composition of the essential oils was investigated by gas chromatography (GC) and gas chromatography/mass spectroscopy (GC/MS). The antifungal activity of the major components (carvacrol, thymol, p‐cymene and 1,8‐cineole) and also possible interactions between them were also investigated. The essential oils of T. vulgaris and T. zygis showed similar antifungal activity, which was greater than T. mastichina. MIC and MLC values were similar for all the compounds tested. At MIC values of the essential oils, propidium iodide rapidly penetrated the majority of the yeast cells, indicating that the fungicidal effect resulted primarily from an extensive lesion of the cell membrane. Concentrations below the MIC values significantly inhibited germ tube formation. This study describes the potent antifungal activity of the essential oils of Thymus on Candida spp., warranting future therapeutical trials on mucocutaneous candidosis.

Antifungal activity of the clove essential oil from Syzygium aromaticum on Candida, Aspergillus and dermatophyte species

The composition and antifungal activity of clove essential oil (EO), obtained from Syzygium aromaticum, were studied. Clove oil was obtained commercially and analysed by GC and GC-MS. The EO analysed showed a high content of eugenol (85.3 %). MICs, determined according to Clinical and Laboratory Standards Institute protocols, and minimum fungicidal concentration were used to evaluate the antifungal activity of the clove oil and its main component, eugenol, against Candida, Aspergillus and dermatophyte clinical and American Type Culture Collection strains. The EO and eugenol showed inhibitory activity against all the tested strains. To clarify its mechanism of action on yeasts and filamentous fungi, flow cytometric and inhibition of ergosterol synthesis studies were performed. Propidium iodide rapidly penetrated the majority of the yeast cells when the cells were treated with concentrations just over the MICs, meaning that the fungicidal effect resulted from an extensive lesion of the cell membrane. Clove oil and eugenol also caused a considerable reduction in the quantity of ergosterol, a specific fungal cell membrane component. Germ tube formation by Candida albicans was completely or almost completely inhibited by oil and eugenol concentrations below the MIC values. The present study indicates that clove oil and eugenol have considerable antifungal activity against clinically relevant fungi, including fluconazole-resistant strains, deserving further investigation for clinical application in the treatment of fungal infections.

Antifungal activity of Juniperus essential oils against dermatophyte, Aspergillus and Candida strains

Aims:  The increasing resistance to antifungal compounds and the reduced number of available drugs led us to search therapeutic alternatives among aromatic plants and their essential oils, empirically used by antifungal proprieties. In this work the authors report on the antifungal activity of Juniperus essential oils (Juniperus communis ssp. alpina, J. oxycedrus ssp. oxycedrus and J. turbinata).

Essential oil of Daucus carota subsp. halophilus: Composition, antifungal activity and cytotoxicity

ETHNOPHARMACOLOGICAL RELEVANCE Essential oils are known to possess antimicrobial activity against a wide spectrum of bacteria and fungi. Daucus carota L. is used since olden times in traditional medicine, due to recognized therapeutic properties, namely the antimicrobial activity of their essential oils. AIM OF THE STUDY In the present study the composition and the antifungal activity of the oils of Daucus carota L. subsp. halophilus (Brot.) A. Pujadas (Apiaceae), an endemic plant from Portugal, were evaluated. Moreover, their cytotoxicity in mouse skin dendritic cells at concentration showing significant antifungal activity was also evaluated. MATERIAL AND METHODS The oils were investigated by GC and GC-MS and the antifungal activity (MIC and MLC) were evaluated against yeasts, dermatophyte and Aspergillus strains. Assessment of cell viability was made by the MTT assay. RESULTS The results showed large variations in the compositions during ontogenesis, particularly in the amounts of elemicin that increased significantly in the ripe umbels (5.9% vs. 31.0%). The results also demonstrated that the oil with high amounts of elemicin, which have stronger antifungal activity, showed no cytotoxic effect, at concentrations ranging from 0.16 to 0.64 microl/ml, for as long as 24h. CONCLUSION It is possible to find appropriate doses of Daucus carota oil showing both antifungal activity and very low detrimental effect on mammalian cells.

Portuguese Thymbra and Thymus Species Volatiles: Chemical Composition and Biological Activities

Thymbra capitata and Thymus species are commonly known in Portugal as thyme and they are currently used as culinary herbs, as well as for ornamental, aromatizing and traditional medicinal purposes. The present work reports on the state of the art on the information available on the taxonomy, ethnobotany, cell and molecular biology of the Portuguese representatives of these genera and on the chemotaxonomy and antibacterial, antifungal and antioxidant activities of their essential oils and other volatile-containing extracts.

Chemical composition and antifungal activity of the essential oils of Lavandula viridis L'Her.

In the present work we report for what we believe to be the first time the antifungal activity and mechanism of action of the essential oils of Lavandula viridis from Portugal. The essential oils were isolated by hydrodistillation and analysed by GC and GC/MS. The MIC and the minimal lethal concentration (MLC) of the essential oil and its major compounds were determined against several pathogenic fungi. The influence of subinhibitory concentrations of the essential oil on the dimorphic transition in Candida albicans was also studied, as well as propidium iodide and FUN-1 staining of Candida albicans cells by flow cytometry following short treatments with the essential oil. The oils were characterized by a high content of oxygen-containing monoterpenes, with 1,8-cineole being the main constituent. Monoterpene hydrocarbons were present at lower concentrations. According to the determined MIC and MLC values, the dermatophytes and Cryptococcus neoformans were the most sensitive fungi (MIC and MLC values ranging from 0.32 to 0.64 µl ml⁻¹), followed by Candida species (at 0.64-2.5 µl ml⁻¹). For most of these strains, MICs were equivalent to MLCs, indicating a fungicidal effect of the essential oil. The oil was further shown to completely inhibit filamentation in Candida albicans at concentrations well below the respective MICs (as low as MIC/16). Flow cytometry results suggested a mechanism of action ultimately leading to cytoplasmic membrane disruption and cell death. Our results show that L. viridis essential oils may be useful in the clinical treatment of fungal diseases, particularly dermatophytosis and candidosis, although clinical trials are required to evaluate the practical relevance of our in vitro research.

Chemical characterization and biological activity of essential oils from Daucus carota L. subsp. carota growing wild on the Mediterranean coast and on the Atlantic coast

The essential oils and supercritical CO(2) extracts of wild Daucus carota L. subsp. carota growing spontaneously in Sardinia and in Portugal were investigated. The main components in the Sardinian essential oil of flowering and mature umbels with seeds are beta-bisabolene (17.6-51.0%) and 11-alpha-(H)-himachal-4-en-1-beta-ol (9.0-21.6%); instead, the oils from Portuguese samples are predominantly composed of geranyl acetate (5.2-65.0%) and alpha-pinene (3.5-37.9%). Supercritical extracts contain lower amounts of monoterpenes and higher amounts of sesquiterpene hydrocarbons. Antifungal activities of the Sardinian oils were the highest, particularly for dermatophytes and Cryptococcus neoformans, with MIC values of 0.16-0.64 microL mL(-1).

Essential oils from four piper species

Abstract The essential oils from Piper capense , P. nigrum , P. guineense and P. umbellatum from S. Tome e Principe were investigated for the first time. They were analysed by GC, GC-mass spectrometry and 13 C NMR. Monoterpene hydrocarbons were the main group of constituents in three of the samples ( P. capense, P. nigrum and P. umbellatum ), whereas for the other species ( P. guineense ) phenylpropanoid derivatives were the most important ones. β -Pinene (32.5%) and β -caryophyllene (12.6%) were the major compounds in the volatile oil of P. capense . Dillapiole (44.8%), followed by myristicin (9.8%), were the main constituents of P. guineense . The most important constituents in the essential oil of P. nigrum were limonene (18.8%), β -caryophyllene (15.4%), sabinene (16.5%) and β -pinene (10.7%). The essential oil of P. umbellatum was characterised by its high β -pinene (26.8%), α -pinene (17.6%) and (E)-nerolidol (12.4%) content.

Chemical polymorphism of the essential oil of Thymus carnosus from portugal

Abstract The composition of the essential oils of 11 populations of Thymus carnosus from Portugal and their infraspecific variability were investigated by GC, GC-MS and 13CNMR. The results obtained were submitted to Principal Component and Chemometric Cluster Analyses. Borneol was the main constituent in all the populations except in one, which had a high content of linalool. This compound showed high percentages in samples originating from the region of Estremadura. Multivariate analysis allowed the distinction between three different groups of essential oils, (i) borneol/cis-sabinene hydrate/terpinen-4-ol, (ii) linalool/borneol/trans-sabinene hydrate and (iii) borneol/camphene.

Monoterpenic aldehydes as potential anti-Leishmania agents: Activity of Cymbopogon citratus and citral on L. infantum, L. tropica and L. major

In order to contribute for the search of new drugs for leishmaniasis, we study the susceptibility of Leishmania infantum, Leishmania tropica and Leishmania major to Cymbopogon citratus essential oil and major compounds, mrycene and citral. C. citratus and citral were the most active inhibiting L. infantum, L. tropica and L. major growth at IC(50) concentrations ranging from 25 to 52 μg/ml and from 34 to 42 μg/ml, respectively. L. infantum promastigotes exposed to essential oil and citral underwent considerable ultrastructural alterations, namely mitochondrial and kinetoplast swelling, autophagosomal structures, disruption of nuclear membrane and nuclear chromatin condensation. C. citratus essential oil and citral promoted the leishmanicidal effect by triggering a programmed cell death. In fact, the leishmanicidal activity was mediated via apoptosis as evidenced by externalization of phosphatidylserine, loss of mitochondrial membrane potential, and cell-cycle arrest at the G(0)/G(1) phase. Taken together, ours findings lead us to propose that citral was responsible for anti-Leishmania activity of the C. citratus and both may represent a valuable source for therapeutic control of leishmaniasis.