Studies on Occurence, Essential Oil Data and Habitat Conditions of Hungarian Thymus pannonicus and Thymus glabrescens Populations
Thymus pannonicus and T. glabrescens flowering shoots are gathered from wild populations. Dried aerial parts contain active compounds used in the therapy of coughing and possess strong antimicrobial activity. Eight natural habitats, involving 17 populations of the two species were found in 2010, where the essential oil characteristics of the flowering shoots and soil parameters have been determined. The highest essential oil level (1.079 mL/100 g) have been detected in the T. pannonicus sample collected near Balatongyorok. Concerning average essential oil amounts, T. pannonicus samples accumulated 0.566 mL/100 g, while those of T. glabrescens produced 0.083 ml/100 g. High thymol ratio is an important qualitative trait: fairly high levels (51.1-65.6%) were found in samples of T. pannonicus. T. pannonicus population, growing on rhyolite tuff in Bukk Mountains, had low essential oil content with sesquiterpene chief compounds and without thymol. Regarding essential oils of T. glabrescens, the major compounds were sesquiterpenes (germacrene D, β-caryophyllene, caryophyllene oxide), with low amount of thymol (<5%). Our results approve data of the previous literature, concerning generalist and pioneer characters of both species with eurytopic attitude, tolerating different soil parameters (pH, salt %, NPK and CaCO3 content). Strong positive correlation have been found between the p-cymene and γ-terpinene ratios (r=0.951), while the latter compounds were in medium positive correlation with thymol percentage (r=0.387 and 0.481, respectively). It was also proven statistically that the essential oil content correlated negatively with high ratio of sesquiterpenes.