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- Portuguese thymbra and thymus Species volatiles: Chemical composition and biological activitiesPublication . Figueiredo, A. C.; Barroso, J. G.; Pedro, L. G.; Salgueiro, L. R.; Miguel, Maria Graça; Faleiro, LeonorThymbra 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 biological activities of Algerian Thymus oilsPublication . Hazzit, M.; Baaliouamer, A.; Verissimo, A. R.; Faleiro, Leonor; Miguel, Maria GraçaThe compositions of essential oils isolated from nine samples of three Thymus species (Thymus algeriensis, Thymus pallescens and Thymus dreatensis) were analysed by GC and GC-MS, and a total of 114 components were identified. T. pallescens collected from various regions showed a great similarity in their compositions and were characterised by carvacrol (44.4-57.7%), p-cymene (10.3-17.3%) and gamma-terpinene (10.8-14.2%) as the major components for four samples; only one sample was thymol-rich (49.3t) with a small amount of carvacrol (9.0%). On the other hand, T. algeriensis showed a chemical polymorphism, even for samples from the same location, and two new chemotypes for this species were proposed. Oxygen-containing monoterpenes were the predominant class (76.3%) in T. dreatensis oil, with linalool (30.4%), thymol (20.2%) and geraniol (19.6%) as the principal constituents. The oils were screened for their possible antioxidant activities by four complementary assays, namely DPPH free radical scavenging, hydroxyl radical scavenging, inhibition of lipid peroxidation and reducing power. The two new chemotypes of T algeriensis exhibited strong hydroxyl radical scavenging (IC(50) = 2.2-3.3 mu g/ml), but were not or only slightly active against the other radicals and exhibited a weak reducing power. Despite their chemical similarity, T. pallescens oils sometimes produced significant differences in their antioxidant activities. The essential oils were also screened for their antimicrobial activity against five bacteria (three Gram-positive and two Gram-negative) and one yeast (Candida albicans). The tested essential oils showed antimicrobial activity against the microorganisms used, in particular against two important pathogens, C. albicans and Helicobacter pylori. (C) 2009 Elsevier Ltd. All rights reserved.
- Antimicrobial activity of the essential oils of Dittrichia viscosa subsp viscosa on Helicobacter pyloriPublication . Silva, D.; Denham, E.; Faleiro, Leonor; Miguel, Maria Graça; Cavaleiro, C.; Salgueiro, L. R.Dittrichia viscosa subsp. viscosa (Compositae) is found on edges, wood clearings and in waste places of the Iberian Peninsula. Aerial parts of D. viscosa were collected at flowering phase in September-October 2001 around Lisbon, Portugal and the essential oils isolated by hydro-distillation for 4 h using a Clevenger-type apparatus. The oils were analyzed by gas chromatography and gas chromatography-mass spectrometry. Preliminary examination of the essential oils allowed the identification of 32 components. Only four components reached percentages over 5%: fokienol (11.8%), T-muurorol (7.9%), (E)-nerolidol (5.5%) and delta-cadinene (5.0%). The essential oils were tested against Helicobacterpylori and Listeria monocytogenes. Essential oils did not have antimicrobial activity against L. monocytogenes. The essential oil at 0.88 to 22.22 mu g.ml(-1) did not inhibit the growth of H. pylori, affected the growth slightly at 44.40 mu g.ml(-1), and completely inhibited the growth at 88.80 to 133.20 mu g.ml(-1) Results show that use of D. viscosa essential oil in the treatment of gastric disorders caused by H. pylori can be effective.
- Listeria monocytogenes biofilm-associated protein (BapL) may contribute to surface attachment of L-monocytogenes but is absent from many field isolatesPublication . Jordan, Suzanne J.; Perni, Stefano; Glenn, Sarah; Fernandes, Isabel; Barbosa, Manuela; Sol, Manuela; Tenreiro, Rogerio P.; Chambel, Lelia; Barata, Belarmino; Zilhao, Isabel; Aldsworth, Timothy G.; Adrião, Andreia Lúcia Gonçalves; Faleiro, L; Shama, Gilbert; Andrew, Peter W.Listeria monocytogenes is a food-borne pathogen capable of adhering to a range of surfaces utilized within the food industry, including stainless steel. The factors required for the attachment of this ubiquitous organism to abiotic surfaces are still relatively unknown. In silico analysis of the L. monocytogenes EGD genome identified a putative cell wall-anchored protein (Lmo0435 [BapL]), which had similarity to proteins involved in biofilm formation by staphylococci. An insertion mutation was constructed in L. monocytogenes to determine the influence of this protein on attachment to abiotic surfaces. The results show that the protein may contribute to the surface adherence of strains that possess BapL, but it is not an essential requirement for all L. monocytogenes strains. Several BapL-negative field isolates demonstrated an ability to adhere to abiotic surfaces equivalent to that of BapL-positive strains. BapL is not required for the virulence of L. monocytogenes in mice.
- Composition of the essential oils of Thymus and Origanum species from Algeria and their antioxidant and antimicrobial activitiesPublication . Hazzit, M.; Baaliouamer, A.; Faleiro, Leonor; Miguel, Maria GraçaThe composition of the essential oils of Origanum and Thymus species restricted to Algeria and the North Africa region was determined. Antioxidant and antibacterial activities of the isolated essential oils were also determined. The oils of oregano plants were strongly characterized by p-cymene (16.8-24.9%), gamma-terpinene (16.8-24.9%), thymol (8.4-36.0%), and carvacrol (1.1-29.7%), a thymol chemotype for Origanum floribundum and a R-terpineol chemotype for Thymus numidicus being described for the first time. The strains of Listeria monocytogenes tested were relatively resistant to the action of essential oils of either Origanum or Thymus species. All essential oils possessed antioxidant activity, but this was dependent on the specific chemical composition and the method employed to determine such activity.
- Stress response and autolytic behaviour of Listeria monocytogenes isolated from portuguese cheesePublication . Faleiro, Maria Leonor; Andrew, Peter WilltamLislería momcytogenes has become a serious pathogen associated with food borne disease. The major outbreaks of Usteriosis are associated with the consumption of dairy products, including cheese. The ability of L. momcytogenes to tolerate and grow m acidic conditions is one of lhe principal characteristics which allow it to grow in actdic foods such as cheese.
- Susceptibility of Helicobacter pylori to essential oil of Dittrichia viscosa subsp revolutaPublication . Miguel, Maria Graça; Faleiro, Leonor; Cavaleiro, C.; Salgueiro, L. R.; Casanova, J.The essential oil of Dittrichia viscosa subsp. revoluta and its fractions were assessed for anti-Helicobacter activity. The essential oil was isolated by hydrodistillation, submitted to flash column chromatography and analysed by gas chromatography, gas-chromatography coupled to mass spectrometry and C-13-nuclear magnetic resonance. The anti-Helicobacter activity was determined by incorporation of the crude essential oil and oxygenated fractions of the oil into the culture medium. At a concentration of 0.025 mu L/mL no recovery was registered when one of the oxygenated fractions of the oil, mainly constituted by 3-methoxy cuminyl isobutyrate (about 40%), was used. This fraction revealed a higher activity against the six H. pylori strains tested when compared with the other oxygenated fractions. The crude essential oil at a concentration of 0.33 mu L/mL reduced the initial population of H. pylori CCUG 15818 of 8.52 +/- 0.30 log(10) cfu/mL to 7.67 +/- 0.22 log(10) cfu/mL. The susceptibility of several Helicobacter pylori strains to the oxygenated fraction of Dittrichia viscosa subsp. revoluta essential oil suggests the possible use of these natural products in combating this widespread infection. Copyright (C) 2007 John Wiley & Sons, Ltd.
- Stress response of Listeria monocytogenes isolated from cheese and other foodsPublication . Faleiro, Maria Leonor; Andrew, Peter; Power, DeborahThe responses to pH and sodium chloride of four strains of Listeria monocytogenes isolated from Portuguese cheese, with a sodium chloride concentration of about 2% (w/v) and a pH value from 5.1 to 6.2, were studied. Two isolates from meat and two clinical isolates related to food-borne listeriosis, in which the implicated food product had about 2–3.5% (w/v) sodium chloride, also were studied. The effect of temperature on pH and sodium chloride sensitivity was also determined. The results show that natural isolates vary in response to these stresses and the data were often at variance with previously published data. Strains varied in sensitivity to low pH and to high sodium chloride concentration but the cheese isolates tended to be more resistant. A lower temperature was associated with a decrease in resistance to low pH and to sodium chloride. All strains showed an acid tolerance response induction when grown at pH 5.5 and although the time required for maximum induction of the response varied between strains, 2 h of acid adaptation, at least, was necessary which is longer than previously reported. Some strains showed an osmotolerance response after incubation in 3.5% (w/v) sodium chloride. Osmoadaptation, in addition to inducing an osmotolerance response, also induced cross-protection against acid shock conditions (pH 3.5). The acid tolerance response also induced a cross-protection against osmotic shock conditions (20% (w/v) sodium chloride). In some cases there was a relationship between the degree of resistance and adaptation, but usually the behaviour of a particular strain was independent of the conditions from which it was isolated.
- Chemical composition, antioxidant and antibacterial activities of the essential oils isolated from Tunisian Thymus capitatus Hoff. et Link.Publication . Bounatirou, S.; Smiti, S.; Miguel, Maria Graça; Faleiro, Leonor; Rejeb, M. N.; Neffati, M.; Costa, M. M.; Figueiredo, A. C.; Barroso, J. G.; Pedro, L. G.The chemical composition, antioxidant and antibacterial activities of essential oils isolated by hydrodistillation from the aerial parts of Tunisian Thymus capitatus Hoff. et Link. during the different phases of the plant development, and from different locations, were evaluated. The chemical composition was analyzed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The main components of the essential oils were carvacrol (62-83%), p-cymene (5-17%), gamma-terpinene (2-14%) and P-caryophyllene (1-4%). The antioxidant activity of the oils (100-1000 mg l(-1)) was assessed by measurement of metal chelating activity, the reductive potential, the free radical scavenging (DPPH) and by the TBARS assay. The antioxidant activity was compared with that of synthetic antioxidants: butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). Both the essential oils and BHA and BHT showed no metal chelating activity. Although with the other methodologies, there was a general increase in the antioxidant activity, with increasing oil concentration, maxima being obtained in the range of 500 and 1000 mg l(-1) for flowering and post-flowering phase oils. Major differences were obtained according to the methodology of antioxidant capacity evaluation. Antibacterial ability of Th. capitatus essential oils was tested by disc agar diffusion against Bacillus cereus, Salmonella sp., Listeria innocua, four different strains of Staphylococus aureus (Cl 5, ATCC25923, CFSA-2) and a multi-resistant form of S. aureus (MRSA-2). Antibacterial properties were compared to synthetic antibiotics. Higher antibacterial activity was observed with the flowering and the post-flowering phase essential oils. (c) 2007 Elsevier Ltd. All rights reserved.
- Antimicrobial activity of essential oils isolated from Portuguese endemic species of ThymusPublication . Faleiro, Leonor; Miguel, Maria Graça; Ladeiro, F.; Venancio, F.; Tavares, R.; Brito, J. C.; Figueiredo, A. C.; Barroso, J. G.; Pedro, L. G.Aims: Thymus species are wild species mostly found in the arid lands of Portugal. Possible antimicrobial properties of Thymus essential oils have been investigated. The chemical composition of the essential oils and the antimicrobial activity of Thymus mastichina (L) L. subsp. mastichina , T. camphoratus and T. lotocephalus from different regions of Portugal were analysed. Methods and Results: Hydrodistillation was used to isolate the essential oils and the chemical analyses were performed by gas chromatography (GC) and GC coupled to mass spectrometry. The antimicrobial activity was tested by the disc agar diffusion technique against Candida albicans , Escherichia coli , Listeria monocytogenes , Proteus mirabilis , Salmonella spp. and Staphylococcus aureus . Pure linalool, 1,8-cineole and a mixture (1:1) of these compounds were included. Linalool, 1,8-cineole or linalool/1,8-cineole and linalool/1,8-cineole/linalyl acetate were the major components of the essential oils, depending on the species or sampling place. The essential oils isolated from the Thymus species studied demonstrated antimicrobial activity but the micro-organisms tested had significantly different sensitivities. Conclusions: The antimicrobial activity of essential oils may be related to more than one component. Significance and Impact of the Study: Portuguese endemic species of Thymus can be used for essential oil production for food spoilage control, cosmetics and pharmaceutical use. Further studies will be required to elucidate the cell targets of the essential oil components.