Composition and antioxidant activities of the essential oils of Thymus caespititius, Thymus camphoratus and Thymus mastichina

Abstract

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. α-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 α-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 α-tocopherol, the antioxidant capacity significantly increased in the presence of ABAP.