Chemical profile and eco-safety evaluation of essential oils and hydrolates from Cistus ladanifer, Helichrysum italicum, Ocimum basilicum and Thymbra capitata

Abstract

The demand for natural-based products for industrial applications is increasing sharply and therefore the search for new alternatives to the plants traditionally used is growing. These alternative plants can be an important source of bioactive compounds under a circular economy approach. Considering the potential future use of new plant products by the industry, it is necessary to assess the risk associated with their introduction into the ecosystem. This work aims to provide an insight into the volatile profiles and evaluate the potential (eco)toxic effects of essential oils (EO’s) and hydrolates of four plant species, namely rockrose (Cistus ladanifer), curry plant (Helichrysum italicum), conehead thyme (Thymbra capitata) and basil (Ocimum basilicum). Chemical analysis were performed by GC-MS and acute toxicity tests were performed using the model organism Daphnia magna. The essential oil and the hydrolate from H. italicum, as well as all the other hydrolates caused no immobilization up to the highest concentrations tested, suggesting that all hydrolates present low to no risk towards D. magna. Similarly, the essential oil of H. italicum, presented negligible risk towards D. magna. For C. ladanifer and T. capitata essential oils, the EC50 (the concentration estimated to immobilize 50 per cent of the Daphnia) at 48 h varied between 199.7 mg/L and 12.1 mg/L, respectively. The essential oil from C. ladanifer was mainly characterised by monoterpene hydrocarbons, while the H. italicum was richer in sesquiterpene hydrocarbons. Both essential oil and hydrolate from T. capitata contained exclusively monoterpene hydrocarbons with a particularly high content of carvacrol. The higher acute toxicity of T. capitata essential oil can be attributed to the high amount of carvacrol present in the distillate. Overall, of the essential oils and hydrolates tested, all can be classified as practically non-toxic, except for T. capitata essential oil that, according to the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) of the United Nations, can be classified as moderately toxic.