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Browsing by Author "Carvalho, L. M."

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  • Composition and antioxidant activities of the essential oils of Thymus caespititius, Thymus camphoratus and Thymus mastichina
    Publication . Miguel, Maria Graça; Simões, M.; Figueiredo, A. C.; Barroso, J. G.; Pedro, L. G.; Carvalho, L. M.
    The essential oils, isolated by hydrodistillation, from the aerial parts of Thymus caespititius, Thymus camphoratus and Thymus mastichina, collected during the vegetative phase, were analysed by gas chromatography (GC) and gas chromatography coupled to mass spectrometry (GC-MS). The antioxidant property of these oils was tested, with and without peroxidation inducer, by the egg yolk-based thiobarbituric acid-reactive substances assay, in the concentrations of 62.5, 125, 250 and 500 mg l(-1). alpha-Terpineol (32%) dominated Th. caespititius essential oil and 1,8-cineole (58%) that of Th. mastichina. Linalool (17%), linalyl acetate (15%) and 1,8-cineole (11%) were the main components of Th. camphoratus oil. The oils demonstrated antioxidant capacity in the absence of radical inducer 2,2'-azobis-(2-amidinopropane) dihydrochloride (ABAP), mainly that of Th. caespititius at 250 and 500 mg l(-1), comparable in some cases to that of alpha-tocopherol and butylated hydroxytoluene (BHT). The presence of ABAP diminished the antioxidant ability of all essential oils tested, Th. caespititius oil still showing the highest antioxidant capacity at 500 mg l(-1). At 250 and 500 mg l(-1), for BHA, and 500 mg l(-1), for alpha-tocopherol, the antioxidant capacity significantly increased in the presence of ABAP. (C) 2003 Elsevier Ltd. All rights reserved.
    2004Journal article Restricted access Show more
  • Evaluation of the antioxidant activity of Thymbra capitata, Thymus mastichina and Thymus camphoratus essential oils
    Publication . Miguel, Maria Graça; Falcato Simoes, M.; Figueiredo, A. C.; Barroso, J. G.; Pedro, L. G.; Carvalho, L. M.
    The essential oils of Thymbra capitata, Thymus mastichina and Thymus camphoratus, collected during the vegetative phase, were predominantly composed of oxygen-containing monoterpenes (61-76%). Carvacrol was the dominant component of T. capitata oil (72%), 1,8-cineole (49%) dominated that of Th. mastichina, and linalool (17%), linalyl acetate (15%) and 1,8-cineole (11%) dominated Th. camphoratus oil. The essential oils and butylated hydroxyanisole (BHA) showed weakfree radical scavenging ability in peanut oil when compared to butylated hydroxytoluene (BHT). In sunflower oil, both the essential oils and the synthetic antioxidants exhibited relatively low free radical scavenging ability. Significant differences in the acid value were detected after several days' storage. From day 55 of storage until the end of the experiment, the acid value for both peanut and sunflower oil with added essential oils was similar and significantly lower than that of the control, but significantly higher than those with added BHA and BHT.
    2005Journal article Restricted access Show more