Chemical Composition of Thymus leucotrichus var. creticus Essential Oil and Its Protective Effects on Both Damage and Oxidative Stress in Leptodictyum riparium Hedw. Induced by Cadmium

The chemical profile of the essential oil (EO) of the aerial parts of Thymus leucotrichus var. creticus (Lamiaceae), a taxon not previously studied, was investigated by GC–MS analysis, using a DB–Wax polar column. Oxygenated monoterpenes and monoterpene hydrocarbons dominate the EO, with thymol (46.97%) and p-cymene (28.64%) as the main constituent of these two classes, respectively. The ability of the EO of T. leucotrichus to reduce Cd toxicity was studied in aquatic moss Leptodictyum riparium. To study EO-induced tolerance to Cd toxicity, apex growth, number of dead cells, DNA damage and antioxidant response in gametophytes were examined. The exogenous application of the EO yields a resumption of growth rate and a reduction in the number of dead cells; it also reduces the oxidative stress induced by Cd, as demonstrated by the reduction of the ROS content (with a decrease of 1.52% and 5%) and by the increased activity of antioxidant enzymes such as superoxide dismutase (SOD) (with an increase of 1.44% and 2.29%), CAT catalase (1.46% and 2.91%) and glutathione-S-transferase GST (1.57% and 1.90%). Furthermore, the application of the EO yields a reduction of DNA damage. These results clearly indicate the protective capacity of the EO of T. leucotrichus in modulating the redox state through the antioxidant pathway by reducing the oxidative stress induced by Cd.