Cadmium effects to the growth of thymes (Thymus vulgaris) and their extracts quality

Abstract

Heavy metal pollution is considered as one of the most serious problems worldwide and has significant environmental and human health impact. The aim of this study was to evaluate the effects of soil cadmium pollution to the growth and quality of medicinal herbs plant thyme (Thymus vulgaris) and their extracts. The plants were grown in soils contaminated with Cd (10 – 800 mg Cd kg-1) for seven weeks. The morphological (shoot height and root length, dry weight), physiological (content of photosynthetic pigments), biochemical (content of malondialdehyde) parameters and the content of Cd in thyme root, shoot and herbal extracts were determined. All the endpoints were measured after three, five and seven weeks of exposure. The results of this study showed that soil contamination with Cd had no adverse acute effects to the growth of thyme. Adverse effects on the growth were determined only after 7 weeks of exposure and at the highest levels of Cd in the soil. Cd amendments had no significant adverse effect on the content of photosynthetic pigments. Cd induced lipid peroxidation and slight increase in MDA content was recorded. Cadmium concentrations in the plant tissues and extracts increased along with Cd concentration in the soil and the time of exposure. It was found that Cd concentrations in thyme shoots and extracts were above the WHO limits (0.3 mg Cd kg-1). This study demonstrated that the use of thyme products may pose a risk to human health even if thymes are growing at environmentally relevant Cd soil concentration.