Variation in the main components of the essential oils from the leaves and flowers of Portuguese Thymus albicans over a single season

Miguel, Maria Graça; Duarte, F.; Venancio, F.; Tavares, R.

http://hdl.handle.net/10400.1/6251

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Abstract(s)

The comparison of the chemical composition of the leaf and the flower oils isolated from Thymus albicans Hoffm. et Link belonging to the 1,8-cineole chemotype, collected at Gambelas, Algarve, during the flowering phase (June to September) %vas carried out. The oils isolated f'roin both the f'resh leaves and the f'resh flowers by hydrodistillation were analyzed and compared by GC and GUMS. The oil yields from the fresh leaves ranged from 3.1% in June, to 6.7% in July (full bloom), while the oil Yields from the fresh flowers ranged from 4.8% in July, to 7.0% in September. Independent of the harvesting period, the oils isolated were characterized by their richness in 1.8-cineole either from the leaves (59.7-66.0%) or from the flowers (57.0-66.7%). The flower oils contained the highest concentration of alpha-pinene, beta-pinene and linalool, while the leaf oils were richest in camphor, citronellol, bornyl acetate and geranyl propionate. Quantitative differences were also found in some oxygenated sesquiterpe-nes according to the developmental flowering stage being one of the most interesting those registered viridiflorol, ledol and intermedeol. The highest amounts of these components in both the leaf and the flower oils were observed in July, starting then to decrease until September just as the behavior already found for 1-8-cineole in the flower oils.