Seasonal variations in the chemical compositions of essential oils of selected aromatic plants growing wild in Turkey.

摘要

The summer leaves of Thymbra spicata var. spicata and Satureja thymbra, 2 aromatic shrubs growing wild in the East Mediterranean region of Turkey, and the leaves of Salvia fruticosa, Mentha pulegium, Laurus nobilis and Inula viscosa were collected at 4-week intervals to follow plant development and essential oil composition. The essential oils extracted from leaves (and flowering tops) were analysed during the growing season by GC-FID; 19 terpenic constituents were identified. The changes in essential oil content (quantity and composition) varied for all 6 species according to corresponding environmental and growth factors and the major adaptive strategy toward summer drought that each plant species has evolved. The concentration of the fungitoxiccomponents in the essential oils of T. spicata and Satureja thymbra, the phenolic constituents carvacrol and thymol, were low in the early phenological stage and increased gradually with development. Maximum contents were observed in June/July, shortlyafter flowering. The main essential oil compounds of Salvia fruticosa, L. nobilis and M. pulegium were the oxygen-containing monoterpenes 1,8-cineole [eucalyptol] and pulegone; periodic increases and decreases in their concentrations were observed. The essential oil of I. viscosa contained small amounts of some of the investigated components. The best harvest time to obtain essential oils with the highest active ingredients is July for T. spicata, Satureja thymbra, Salvia fruticosa and M. pulegium and September for L. nobilis.