Development and first evaluation of new Natural Deep Eutectic Solvents (NaDES) formulations for applications in the agronomic field

Following the concept of sustainable development, Green Chemistry is actively seeking for new solvents to replace conventional ones that present inherent toxicity, flammability and hazardous environmental fate. In this contest, Natural Deep Eutectic Solvents (NaDES) have recently emerged as new generation solvents; NaDES are eutectic mixtures of naturally occurring hydrogen bond donors (HBD, e.g choline chloride) and hydrogen bond acceptors (HBA, e.g. sugars, organic acids, amino acids) that display peculiar solubilization behaviour. In the present study, the possibility of use NaDES as eco-compatible bioactive formulations to deliver high value compounds in agricultural field was evaluated. The investigated NaDES were composed by betaine and choline chloride as HBA, and various HBD with different reactivity: acid (citric acid, lactic acid, malic acid), basic (urea) and neutral (glycerol and ethylene glycol). NaDES formulations were produced by extraction of highly-valuable macromolecules from algae biomasses (Arthrospira platensis and Phaeodactylum tricornutum) and grape by-products (grape pomace and grape seeds). Since NaDES ecotoxicological profile is poorly known, the toxicity of NaDES was investigated on soil animals (Eisenia andrei) and plants (Lepidium sativum, Avena sativa, Ocimum basilicum and Lactuca sativa) and their biodegradability were assessed. Results revealed NaDES high extraction efficiency and promising ability as antioxidants and inhibitors of the enzyme urease. NaDES formulations did not seem to produce promoting effects on plants and exhibited different toxicological profiles based on the tested organisms and the solvent composition. Overall, NaDES containing acids and urea as HBD showed a significant toxicity on the tested organisms.