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DOI: 10.1055/s-2007-986863
Thermal stability of the essential oils isolated from Tunisian Thymus capitatus Hoff. et Link.: evaluation of chemical composition, antioxidant and antibacterial activities
Plant volatile oils have been recognized since antiquity to possess biological activities. Chief amongst these are their antibacterial, antifungal and antioxidant properties. Thyme essential oils have been previously reported to have antioxidant activity mainly mediated by the phenolic fraction of the oils (1, 2). Tunisian thyme (Thymus capitatus Hoff. et Link.) is a perennial, herbaceous shrub belonging to the Lamiaceae family commonly used in Tunisia for culinary purposes.
The chemical composition, antioxidant and antibacterial activities of essential oils isolated from the aerial parts of Tunisian T. capitatus during the flowering phase were stored under dark conditions at 60° during 37 days were evaluated. Samples taken periodically were used to evaluate the chemical composition and the antioxidant and the antibacterial activities. The chemical composition was analysed by GC and GC/MS. The antioxidant activity of the oils (100, 500 and 1000mg.l-1) was assessed by free radical scavenging (DPPH) and by TBARS assays. Antibacterial ability of T. capitatus essential oils was tested by the disc agar diffusion against three different strains of Staphylococus aureus (C15, ATCC6538 and ATCC25923).
With some fluctuations, carvacrol (48–74%) remained as the major component of the oil independent of the storage period. Terpinen-4-ol was the only oil component whose relative amount increased whereas that of carvacrol decreased. α-Terpinene and γ-terpinene decreased over time whereas p-cymene increased in the same period. Despite the thirty-seven days of storage at 60°C, T. capitatus essential oil still showed a high antioxidant activity and a stable antimicrobial activity.
References: [1] Miguel, G., Simões, M., Figueiredo, A.C., Barroso, J.C., Pedro, L.G. and Carvalho L. 2004. Composition and antioxidant activities of the essential oils of Thymus caespititus, Thymus camphoratus and Thymus mastichina. Food Chem. 86: 183–188. [2] Bounatirou, S., Smiti, S., Miguel, M.G., Faleiro, L., Rejeb, M.N., Neffati, M., Costa, M.M., Figueiredo, A.C., Barroso, J.G., Pedro, L.G. 2007. Chemical composition, antioxidant and antibacterial activities of the essential oils isolated from Tunisian Thymus capitatus Hoff. et Link.. Food Chem. (in press).