Variation of essential oil composition of Thymus pulegioides in relation to soil chemistry

Soil chemistry, as one of environmental factors, can influence both yield and chemical composition of essential oils, the natural industrial products, in essential oils bearing plants. Purpose of study was to evaluate effects of soil pH, humus, mobile phosphorus, mobile potassium and 14 chemical elements of soil on percentages of essential oil and their main chemical compounds in raw material of large thyme (Thymus pulegioides L.) that represents commercially important genus Thymus (Lamiaceae). Plant raw materials and soils were collected separately from spontaneous populations of T. pulegioides. Essential oils were isolated by hydrodistillation and analysed by gas chromatography/flame ionization (GC/FID) and gas chromatography/mass spectrometry (GC/MS) analytical methods. Amount of humus and mobile phosphorus in soil were estimated photoelectrocolorimetrically, mobile potassium − by flame photometry, soil pH − electrometrically, chemical elements − by energy-dispersive x-ray fluorescence analysis. Results showed that increase in amount of aluminium, copper, iron, potassium and manganese in soil of habitats was accompanied by decrease in amount of essential oils in raw material of T. pulegioides. Presence of higher amount of mobile phosphorus in soil can positively influence biosynthesis of α-terpinyl acetate. Increase of sulphur in soil was accompanied by increase in percentages of carvacrol and linalool and by decrease in percentage of p-cymene in T. pulegioides essential oils. Presence of higher amounts of manganese in soil can stimulate and inhibit the biosynthesis of main compounds in essential oils of T. pulegioides geraniol and carvacrol chemotypes, respectively.