Trace element contents and essential oil yields from wild thyme plant (Thymus serpyllum L.) grown at different natural variable environments, Jordan

摘要

The yields of essential oils and concentrations of some heavy metals (Fe, Cu, Ni, Cd, Co, Pb and Cr) were determined in the wild thyme plant (Thymus serpyllum L.) grown at different environments in Jordan. The samples were collected from various natural climatic regions located northern (Jeresh) and southern (Al-Karak, Al-Shouback and Aqaba) regions of Jordan. Our results showed a wide variation of essential oil contents among wild thyme plants grown at different natural variable environments, Jordan. They were 5.6 and 5.4% in Aqaba and Al-Karak regions, respectively, and 3.3 and 2.5% in Jerash and Al-Shouback, respectively. The results showed different heavy metal concentrations in all investigated samples. The highest mean levels of copper (10.40 mg/kg) were recorded at the southern regions of Al-Karak and Al-Shouback but they were within the range of permissible limit for medicinal plants. The average concentrations of lead in T serpyllum were 1.45, 0.05, and 0.79, 1.26 mg/kg, in samples collected from Jerash, Al-Karak, Al-Shouback and Aqaba, respectively. The lead concentrations were below recommended levels by WHO. The iron content showed a great variation between the different plant samples that can be attributed to the place of growth, concentrations varying from 15.31 to 205.80 mg/kg. Cadmium concentration was below the guidelines toxic levels in samples collected from Jerash and Al-Karak, however, it was not detected in Aqaba and Al-Shouback. The essential oil and heavy metal contents in T serpyllum are mainly affected by variable natural climatic conditions. Moreover, the current study showed that T serpyllum species grown in Jordan are characterized by low heavy metal contents and can safely be used for pharmaceutical and edible purposes without any hazardous effect on human health.