Evaluation of the antioxidant activity of Thymbra capitata, Thymus mastichina and Thymus camphoratus essential oils.

摘要

The antioxidant properties of the essential oils of Thymbra capitata, Thymus mastichina and T. camphoratus collected during the vegetative phase (January 2002) at Algarve, Portugal, were evaluated and compared to synthetic antioxidants (butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT)). In addition, the chemical composition of the essential oils was determined using gas chromatography and gas chromatography-mass spectrometry. Antioxidant activity was measured by determination of the free radical scavenging activity of the essential oils in groundnut and sunflower oils. Results revealed that the essential oils were predominantly composed of oxygen-containing monoterpenes (61-76%). Carvacrol was the dominant component in Thymbra capitata oil (72%), 1,8-cineole (49%) in Thymus mastichina oil, and linalool (17%), linalyl acetate (15%) and 1,8-cineole (11%) in T. camphoratus oil. The essential oils and BHA showed weak free radical scavenging ability in groundnut oil when compared to BHT. In sunflower oil, the essential oils and the synthetic antioxidants exhibited relatively low free radical scavenging ability. Significant differences in acid value were detected after several days of storage. From day 55 of storage until the end of the experiment, the acid value for both groundnut and sunflower oils with added essential oils was similar and significantly lower than that of the control, but significantly higher than those with added BHA and BHT. It is suggested that further studies are needed to accurately evaluate the potentials and limitations of essential oils of aromatic plants in Portugal as natural antioxidants..